Improving the fire resistance of wood fiber-based materials

Abstract

The invention relates to a method for fireproofing a wood fiber-based substrate comprising applying a geopolymer composition to said substrate. It also relates to fireproofed elements obtained according to this method, which comprise at least one wood fiber-based substrate and at least one geopolymer-based coating on said substrate, and their use, particularly in the building sector, for example as interior architectural, structural, or decorative elements, or for constructing fireproof cable trays. Figure for the abstract: none

Description

Title of the invention: Improving the fire resistance of wood fiber-based materials Technical field

[0001] The present invention relates to the field of fireproofing of wood. It is more specifically concerned with the protection against fire of substrates based on wood fibers, such as those used for example in the field of construction, in particular the construction and interior decoration elements of residential buildings or premises intended to receive the public.

[0002] For the purposes of this description, the term “wood fiber-based” substrate (or also “woody” substrate) means a solid part comprising or consisting of wood fibers. This solid part may be a wooden part or a part based on agglomerated wood fibers or particles. Thus, according to one possible embodiment, a wood fiber-based substrate may be a solid wood substrate (a board for example or more generally a block of machined solid wood) or a plywood or glued laminated wood comprising several glued wooden plates.According to another possible embodiment, a wood fiber-based substrate may comprise wood particles (chips, sawdust and / or wood flour) reagglomerated together, and most often joined together using a binder, such as, for example, a particle board type material (notably OSB or MDF) based on wood particles (cut and ground wood chips in general) then agglomerated with a binder (typically a resin, for example an isocyanate resin), or a fiberboard type material obtained from compressed wood fibers with or without a binder.

[0003] The so-called "fireproofing" and "fire protection" properties sought in the context of the present invention are fire resistance properties of the substrate, which prevent it from burning under fire conditions, thus making it possible in particular to inhibit the spread of fire. Technological background

[0004] Methods for ensuring fireproofing of wood or wood fibers have been described in the past, which however prove to be quite cumbersome to implement as a general rule. For example, we can cite the method described in FR 2 358 964, where a woody material is immersed in an aqueous solution of a salt of sodium chloride type, preferably kept boiling; then dried to a humidity level of approximately 12%; then impregnated with silicate and coated with kaolin, the coated woody material then being put under pressure and at a temperature of 100 to 1400°C for about 1 minute; dried until completely dry then baked for a few seconds at about 5000°C.

[0005] Other methods use toxic or dangerous compounds such as volatile organic compounds, or even borax recommended for example in application CZ35748.

[0006] An object of the present invention is to confer fire resistance properties to a wood fiber-based substrate while avoiding the difficulties encountered with the methods described in the aforementioned documents, in particular by providing a fireproofing method that is easy to implement and without having to use toxic or delicate compounds to handle. In this context, the invention preferably aims to provide a fireproofing effect of the type defined above, while also limiting, as much as possible, the generation of smoke. Summary of the invention

[0007] To achieve these objectives, the present invention proposes coating the wood fiber-based substrate with a geopolymer composition. The composition is applied to the substrate with the same ease as a water-based paint composition and the coated substrate proves to have particularly advantageous fire resistance properties.

[0008] More specifically, according to a first aspect, the present invention relates to a method for fireproofing a wood fiber-based substrate comprising the application to said substrate of a geopolymer composition.

[0009] The application of the geopolymer composition to the substrate may be total or partial. More specifically, this application is advantageously carried out over the entire available surface of the substrate, but it may also be chosen, for example for economic reasons, to apply the geopolymer composition only to surfaces likely to be subjected to fire under fire conditions. In the case of application to only a part of the entire available surface of the substrate, it is preferable that the portion of the surface coated with the geopolymer composition comprises all of the surface areas likely to be subjected to fire in the event of a fire.

[0010] The geopolymer composition used according to the invention is an aqueous composition which has the advantage of being able to be applied to the substrate in a similar manner to a paint composition, by modifying the viscosity of the composition as needed by, for example, adjusting its water content (the viscosity decreases when the water content increases).

[0011] The application of the geopolymer composition on the surface can advantageously be accompanied by more or less marked phenomena of impregnation of the substrate by the geopolymer composition. According to a particular embodiment, a portion of the geopolymer composition may be used to act as a binder within the substrate, in particular when the substrate is based on reagglomerated wood fibers or particles based on reagglomerated wood fibers.

[0012] According to another particular aspect, the present invention relates to fireproofed elements based on wood fibers of the type obtained using the method of the invention. These fireproofed elements comprise at least one substrate based on wood fibers, preferably of the aforementioned type, and at least one coating based on a geopolymer material on said substrate.

[0013] As used in the present description, the term "geopolymer material" designates a solid obtained by hardening a geopolymer composition. The method of the invention generally comprises, following the application of the geopolymer composition, a step of converting the geopolymer composition (initially liquid) into a geopolymer material (forming a solid deposit, in particular on the surface, and generally more or less in depth), in particular by drying.

[0014] In the context of the work which led to the present invention, the inventors have now shown that the fireproofed elements as obtained according to the invention have very interesting fire resistance properties, which makes them, for example, particularly well suited as architectural, structural or decorative elements, in particular inside residential dwellings or more generally inside buildings intended to receive the public. By way of illustration and not limitation, a fireproofed element according to the invention may, for example, be any structural element such as a beam, a joist, a door, a door or window frame, all or part of a partition, all or part of a piece of furniture (cupboard, shelf, worktop, etc.), all or part of a decorative element. These particular applications of the aforementioned fireproofed elements constitute, according to yet another aspect, another object of the present invention.

[0015] In addition to the advantages they present in terms of their own fire resistance, the coated elements obtained according to the invention also provide a thermal barrier effect capable of thermally insulating two spaces by placing them at their interface: an element coated according to the invention thus proves capable of inhibiting the propagation of thermal energy and can, for example, protect thermally sensitive elements by interposing itself between them and a heat source. According to a particular embodiment, an element coated according to the invention may be a cable tray, intended to contain electrical cables for the transport of energy or information. In this case, the substrate is typically in the form of a part provided with at least one groove for the passage of a cable or several cables on one of its faces, the opposite face, more or less decorative, making it possible to mask the wires. The application of a geopolymer composition according to the invention on one and / or the other of the faces of a cable tray of this type induces protection of the cables in the event of fire by thermal barrier effect or, conversely, limits the start of a fire which would originate in the cable (under the effect of an overvoltage or electric arcs for example).

[0016] The inventors have also demonstrated that in addition to the aforementioned advantages, the geopolymer applied according to the invention allows an improvement in the mechanical resistance of the substrate: the geopolymer composition applied tends in fact to penetrate the structure of the substrate (particularly in the case of a porous substrate of the particle board type for example) and the geopolymer is therefore formed not only on the surface (where it plays the aforementioned role of protection against fire) but also within the structure of the substrate, where it provides a role of mechanical binder which improves the mechanical properties of the substrate.

[0017] Furthermore, the geopolymer composition applied to the substrate proves to have fungicidal and bactericidal properties, and to induce resistance to insects. Thus, in addition to an improvement in the mechanical properties, the coating applied according to the invention induces an inhibition of the degradation of the substrate by living organisms, in particular by inhibiting the formation of molds or fungi or attacks by termites or other wood-boring insects.

[0018] Furthermore, the geopolymer layer applied to the substrate can be advantageously used as a bonding layer for depositing a second coating layer from an aqueous composition. In particular, the applied geopolymer layer can, if necessary, serve as a bonding layer for a second geopolymer layer if it is desired to increase the thickness of the layer obtained and therefore increase the aforementioned effects. The geopolymer layer can also serve as a primer layer before applying a water-based paint, or even a water-based varnish or adhesive, which is particularly interesting in the field of housing and the development of premises intended to receive the public.In this context, the method of the invention further comprises a step of applying an aqueous composition, preferably of the water-based paint, varnish or adhesive type, to the layer of geopolymer material obtained on the substrate from the geopolymer composition. According to an interesting embodiment, the aqueous composition deposited on the geopolymer material is chosen so as to obtain an insulating coating against water or humidity above the geopolymer composition.

[0019] Various aspects and possible embodiments of the invention are described in more detail below.

[0020] The geopolymer material and the geopolymer composition allowing it to be obtained

[0021] For the purposes of the present description, the term "geopolymer material" denotes a solid material comprising silicon (Si), aluminum (Al), oxygen (O) and at least one element chosen from potassium (K), sodium (Na), lithium (Li), cesium (Cs) and calcium (Ca), and preferably chosen from potassium (K) and sodium (Na).

[0022] The geopolymer material may in particular be an alumino-silicate geopolymer material. Where appropriate, this aluminosilicate geopolymer material may be chosen from poly(sialates) corresponding to the formula (I) Mn(-Si-O-Al-O-)n [(M)-PS] and having a Si / Al molar ratio equal to 1, poly(sialate-siloxos) corresponding to the formula (II) Mn(-Si-O-Al-O-Si-O-)n [(M)-PPS] and having a Si / Al molar ratio equal to 2, poly(sialate-disiloxos) corresponding to the formula (III) Mn(-Si-O-Al-O-Si-O-Si-O)n [(M)-PSDS] and having a Si / Al molar ratio equal to 3, and other poly(sialates) with a Si / Al ratio > 3, the aforementioned poly(sialates) comprising an alkali cation M chosen from K, Na, Li, Cs and one of their mixtures, and n denotes the degree of polymerization.

[0023] The geopolymer material is obtained from a geopolymer composition, generally by drying, geopolymerization and / or polycondensation of said geopolymer composition (processes referred to herein as "curing" of the geopolymer composition).

[0024] A “geopolymer composition”, as used herein, is a composition, generally liquid, capable of forming a solid geopolymer material upon hardening. The ingredients of the geopolymer composition may therefore undergo polycondensation to form said geopolymer material.

[0025] The formation of the geopolymer material from the geopolymer composition is carried out by an internal reaction and is generally not the result of simple drying, as is generally the case for binders based on alkali silicates. Indeed, geopolymer materials result from a mineral polycondensation reaction by alkaline activation, called geosynthesis, as opposed to traditional hydraulic binders in which hardening is the result of hydration of calcium aluminates and calcium silicates.

[0026] The geopolymer composition used in the context of the present invention is preferably an aluminosilicate geopolymer composition.

[0027] The geopolymer composition of the invention is particularly preferably a geopolymer composition comprising water, silicon (Si), aluminum (Al), oxygen (O), and at least one element chosen from potassium (K), sodium (Na), lithium (Li), cesium (Cs), and calcium (Ca), and preferably chosen from potassium (K) and sodium (Na).

[0028] The geopolymer composition may in particular comprise at least one aluminosilicate, at least one alkali silicate, water, and optionally an alkaline base.

[0029] Aluminosilicate

[0030] The aluminosilicate(s) present in the geopolymer composition may be chosen from metakaolins (i.e. calcined kaolins), fly ash (well known by the Anglicism "fly ash"), blast furnace slag (well known by the Anglicism "blast furnace slag"), swelling clays such as bentonite, calcined clays, any type of compound comprising aluminum and silica fume, zeolites, and mixtures thereof.

[0031] Among these compounds, metakaolins are preferred, in particular those marketed by the company Imérys.

[0032] In the invention, the expression "metakaolin" means a calcined kaolin or a dehydroxylated aluminosilicate. It is preferably obtained by dehydration of a kaolin or a kaolinite.

[0033] The geopolymer composition may comprise from 5 to 50% by weight approximately of aluminosilicate, and preferably from 10 to 35% by weight approximately of aluminosilicate, relative to the total weight of the geopolymer composition.

[0034] The aluminosilicate content relative to the weight of the dry matter of the geopolymer composition is typically between 10 and 50%, for example between 15 and 30%.

[0035] Preferably, the geopolymer composition used according to the present invention comprises a mixture of two distinct aluminosilicates, namely at least one first aluminosilicate and at least one second aluminosilicate distinct from the first aluminosilicate.

[0036] Preferably, the geopolymer composition comprises two distinct calcined kaolins, having different calcination temperatures, preferably a first metakaolin chosen from kaolins calcined at a temperature Tci of at least approximately 650°C, and a second metakaolin chosen from kaolins calcined at a temperature Tc2 such that Tc2 - Tci > 100°C.

[0037] According to a particularly preferred embodiment of the invention, the geopolymer composition comprises a first metakaolin chosen from kaolins calcined at a temperature Tci of at least approximately 650°C, and a second metakaolin chosen from kaolins calcined at a temperature Tc2 such that Tc2 - Tci > 100°C, at least one first alkali silicate, water, and optionally an alkali base. The geopolymer composition can then have improved mechanical properties, in particular in terms of flexibility and durability, while guaranteeing good reaction and fire resistance properties.

[0038] According to one embodiment of the invention, the first metakaolin is a kaolin calcined at a temperature Tci of at least approximately 700°C, and preferably of at least approximately 725°C.

[0039] According to a preferred embodiment of the invention, the first metakaolin is a kaolin calcined at a temperature Tci of at most approximately 875°C, and preferably of at most approximately 825°C.

[0040] The first metakaolin may comprise at least about 20 mol%, and preferably at least about 30 mol% of aluminum oxide (A12O3), relative to the total number of moles of the first metakaolin.

[0041] The first metakaolin may comprise at most approximately 60 mol%, and preferably at most approximately 50 mol% of aluminum oxide (A12O3), relative to the total number of moles of the first metakaolin.

[0042] The first metakaolin may comprise at least about 35 mol%, and preferably at least about 45 mol% of silicon oxide (SiO2), relative to the total number of moles of the first metakaolin.

[0043] The first metakaolin may comprise at most approximately 75 mol%, and preferably at most approximately 65 mol% of silicon oxide (SiO2), relative to the total number of moles of the first metakaolin.

[0044] As examples of first metakaolin, we can cite the metakaolins sold by the company Imérys, in particular that marketed under the reference PoleStar® 450.

[0045] The first metakaolin may be chosen from kaolins calcined at Tci as defined above, for at least approximately 1 min, preferably for at least approximately 10 min, particularly preferably for a duration ranging from approximately 30 min to 8 h, and more particularly preferably for a duration ranging from approximately 2 h to 6 h.

[0046] The second metakaolin is preferably chosen from kaolins calcined at a temperature Tc2 such that Tc2 - Tci > approximately 150°C, particularly preferably such that Tc2 - Tci > approximately 200°C, and more particularly preferably such that Tc2 - Tci > approximately 250°C.

[0047] According to one embodiment of the invention, the second metakaolin is a kaolin calcined at a temperature Tc2 of at least approximately 800°C, preferably at least approximately 850°C, and particularly preferably at least approximately 900°C.

[0048] According to a preferred embodiment of the invention, the second metakaolin is a kaolin calcined at a temperature Tc2 of at most approximately 1200°C, and preferably of at most approximately 1150°C.

[0049] The second metakaolin may comprise at least about 20 mol%, and preferably at least about 30 mol% of aluminum oxide (A12O3), relative to the total number of moles of the second metakaolin.

[0050] The second metakaolin may comprise at most approximately 60 mol%, and preferably at most approximately 50 mol% of aluminum oxide (A12O3), relative to the total number of moles of the second metakaolin.

[0051] The second metakaolin may comprise at least about 35 mol%, and preferably at least about 45 mol% of silicon oxide (SiO2), relative to the total number of moles of the second metakaolin.

[0052] The second metakaolin may comprise at most approximately 75 mol%, and preferably at most approximately 65 mol% of silicon oxide (SiO2), relative to the total number of moles of the second metakaolin.

[0053] As examples of second metakaolin, we can cite the metakaolins sold by the company Imérys, in particular that marketed under the reference PoleStar® 200R.

[0054] The second metakaolin may be chosen from calcined kaolins at Tc2 as defined in the invention, for at least approximately 1 min, preferably for at least approximately 5 min, particularly preferably for a duration ranging from approximately 10 min to 2 h, and more particularly preferably for a duration ranging from approximately 15 min to 1 h.

[0055] The mass ratio [first metakaolin / second metakaolin] corresponding to the total mass of first metakaolin in the geopolymer composition relative to the total mass of second metakaolin in the geopolymer composition preferably ranges from about 0.1:1 to about 2:1, particularly preferably from about 0.5:1 to about 1.0:1, and more particularly preferably is about 1:1.

[0056] The geopolymer composition may comprise from 5 to 50% by weight approximately, and preferably from 10 to 35% by weight approximately of first and second metakaolins, relative to the total weight of the geopolymer composition.

[0057] Alkali silicate

[0058] The alkali silicate(s) present in the geopolymer composition may be chosen from sodium silicates, potassium silicates, and mixtures thereof.

[0059] Alkali silicates marketed by Silmaco or PQ corporation are preferred.

[0060] Advantageously, the geopolymer composition used according to the invention comprises at least one sodium silicate.

[0061] An alkali silicate useful according to the invention may have a SiO2 / M2O molar ratio ranging from about 1.1 to 35, preferably from about 1.3 to 10, and particularly preferably from about 1.4 to 5, with M being a sodium or potassium atom, and preferably a sodium atom.

[0062] The geopolymer composition may comprise from 5 to 80% by weight approximately, and preferably from 10 to 50% by weight approximately of alkali silicate, relative to the total weight of the geopolymer composition.

[0063] According to an interesting embodiment, the geopolymer composition used according to the invention comprises an alkali silicate of the aforementioned type, preferably a sodium silicate, and two distinct aluminosilicates which are preferably two metakaolins. distinct from the aforementioned type, with an alkali silicate content which is preferably between 70% and 90%, preferably between 75% and 85% (for example of the order of 80%) relative to the total mass of silicate and aluminosilicates. The aluminosilicate content is between 10% and 70%, preferably between 15% and 25% (for example of the order of 20%) relative to the total mass of silicate and aluminosilicates.

[0064] The geopolymer composition may optionally comprise several alkali silicates, namely at least one alkali silicate of the aforementioned type and a second alkali silicate different from the first.

[0065] The second alkali silicate may be chosen from sodium silicates, potassium silicates, and one of their mixtures. The alkali silicates marketed by Silmaco or by PQ Corporation are preferred. The second alkali silicate is preferably a sodium silicate.

[0066] The first and second alkali silicates may respectively have molar ratios SiO2 / M2O and SiO2 / M'2O such that M and M', which are identical, are chosen from a sodium atom and a potassium atom, and preferably a sodium atom, and said ratios have different values, preferably values ​​such that their difference is at least 0.3, particularly preferably such that their difference is at least 0.5, and more particularly preferably such that their difference is at least 1.0.

[0067] According to a possible embodiment of the invention, the geopolymer composition comprises: - a first alkali silicate having a SiO2 / M2O molar ratio ranging from approximately 1.5 to 2.6, and - a second alkali silicate having a SiO2 / M'2O molar ratio greater than 2.6, preferably ranging from approximately 2.8 to 4.5, and particularly preferably ranging from approximately 3.0 to 4.0, it being understood that M' is identical to M.

[0068] The geopolymer composition may comprise from about 10 to 60% by weight, and preferably from about 20 to 50% by weight of first and second alkali silicates, relative to the total weight of the geopolymer composition.

[0069] The mass ratio [first alkali silicate / second alkali silicate] in the geopolymer composition preferably ranges from 0.5 to 2.5, and particularly preferably from 0.8 to 2.0.

[0070] The alkaline base

[0071] The alkaline base typically used in the geopolymer composition useful according to the invention may for example be sodium hydroxide, or potassium hydroxide, and preferably sodium hydroxide.

[0072] The geopolymer composition may be free of alkaline base. This thus allows to improve the handling of the geopolymer composition, particularly when applying to the substrate.

[0073] Water content

[0074] The mass ratio of solids to water in said geopolymer composition determines the solidification (setting) kinetics of the composition, as well as the viscosity of the geopolymer composition during its application.

[0075] The geopolymer composition may comprise from 35% to 80% by weight approximately, and particularly preferably from 40% to 70% by weight approximately, of solid materials (alkali silicate(s), aluminosilicate(s) and alkaline base), relative to the total weight of said geopolymer composition.

[0076] Optional additives

[0077] The geopolymer composition useful according to the invention may optionally comprise one or more additives chosen from: - at least one colorant, - mineral fibers, in particular chosen from alumina fibers, - a polymer structure additive, in particular chosen from polyolefin fibers such as polypropylene fibers, high density polyethylene (HDPE), aramids, and technical glass fibers coated with silicone or an organic polymer of the polyethylene type; a styrene-butadiene copolymer (SBR); a styrene-butadiene-ethylene copolymer (EBS); derivatives of styrene-ethylene copolymers, in particular those marketed by Kraton such as a styrene-ethylene-butylene-styrene copolymer (SEBS), a styrene-butadiene-styrene copolymer (SBS), a styrene-isoprene-styrene copolymer (SIS), a styrene-propylene-ethylene copolymer (EPS) or a styrene-ethylene-propylene-styrene copolymer (SEPS); an ethylene vinyl acetate copolymer (EVA), a crosslinked polyorganosiloxane (egusing a peroxide); polyethylene possibly in powder form; lignosulfonates; cellulose acetate; other cellulose derivatives; a low viscosity silicone oil (eg of the order of 12500 cPo); and a polyethylene oil, . - a compound accelerating the setting in mass, in particular chosen from aluminum sulfate, alums (e.g. double aluminum and potassium sulfate), calcium chloride, calcium sulfate, hydrated calcium sulfate, sodium aluminate, sodium carbonate, sodium chloride, sodium silicate, sodium sulfate, iron (III) chloride, and sodium lignosulfonates, - a setting retarding agent, in particular chosen from ammonium, alkali metals, alkaline earth metals, borax, lignosulfonates and in particular metal salts of calcium lignosulfonates, celluloses such as carboxymethyl hydroethyl cellulose, sulfoalkylated lignins such as, for example: sulfomethylated lignin, hydroxycarboxylic acids, copolymers of salts of 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid or maleic acid, and saturated salts, - an inert filler, notably chosen from talc, micas, dehydrated clays, and calcium carbonate, - a starch, - a starch plasticizer, in particular chosen from a metal stearate, a polyethylene glycol, an ethylene glycol, a polyol such as glycerol, sorbitol, mannitol, maltitol, xylitol or an oligomer of one of these polyols, a sucrose such as glucose or fructose, a plasticizer containing amide groups, and any type of plasticizer based on modified polysaccharide(s), - a cellulose derivative, - an expanded carbon material such as expanded graphite.

[0078] When a colorant is present, it is preferably a colorant that is liquid at room temperature (i.e. 18-25°C).

[0079] The geopolymer composition may comprise from 0.01 to 15% by weight approximately of additive(s), and preferably from 0.5 to 8% by weight approximately of additive(s), relative to the total weight of the geopolymer composition.

[0080] Preparation of the geopolymer composition

[0081] A geopolymer composition useful according to the invention can typically be prepared according to a step (E) of mixing the aluminosilicate, or the mixture of aluminosilicates when several aluminosilicates are used, with the alkali silicate, or the mixture of alkali silicates where appropriate, water, and optionally the alkaline base and / or the additives.

[0082] This mixing step is generally carried out at a high pH, ​​in particular varying from 10 to 13.

[0083] This mixing step preferably comprises the following sub-steps: (EJ preparation of an aqueous solution of a first alkali silicate; and (E2) mixing a first aluminosilicate in powder form with the aqueous alkali silicate solution prepared in sub-step (EJ.

[0084] The aqueous solution of the first alkali silicate can be prepared by mixing silicon dioxide SiO2 or an alkali silicate with a base MOH in which M is K or Na.

[0085] Silicon dioxide SiO2 can be chosen from silica fume (i.e. pyrogenic silica), quartz, and mixtures thereof.

[0086] Sub-step (Ei) can be carried out by dissolving the base in water, resulting in the release of heat (exothermic reaction), and then adding the silica (or alkali silicate). The heat released then accelerates the dissolution of the silica (or alkali silicate) during sub-step (EJ, and the first aluminosilicate during sub-step (E2).

[0087] When a second aluminosilicate and / or a second alkali silicate is used, step (E) of preparing the geopolymer composition may comprise mixing said first aluminosilicate and optionally said second aluminosilicate, with said first alkali silicate, optionally said second alkali silicate, water, and optionally the alkali base.

[0088] Step (E) preferably comprises mixing the first and second meta-takaolins, with the first alkali silicate and optionally the second alkali silicate, water, and optionally an alkali base.

[0089] According to a preferred embodiment, step (E) comprises the following sub-steps: (Ea) mixing the first and second alkali silicates, in particular with stirring; (Eb) optional addition of an alkaline base, in particular while maintaining stirring; and (Ec) adding the first and second metakaolins, in particular while maintaining stirring.

[0090] At the end of step (E), in particular at the end of sub-step (E2) or (E c) when they are implemented, a fluid and homogeneous solution is preferably obtained.

[0091] At the end of step (E), the geopolymer composition may comprise from 35% to 80% by weight approximately, and particularly preferably from 40% to 70% by weight approximately, of solid materials (alkali silicate(s), aluminosilicate(s) and alkaline base), relative to the total weight of said geopolymer composition.

[0092] Such a mass ratio makes it possible to have a geopolymer composition that is fluid enough to allow its handling, and whose solidification kinetics are slow enough to allow application to the substrate.

[0093] The solids / water mass ratio in said geopolymer composition can make it possible to determine the solidification kinetics of said geopolymer composition.

[0094] After step (E) of preparing the geopolymer composition, and before its impregnation onto the fibrous material, the geopolymer composition may optionally be heated, in particular to a temperature ranging from approximately 55°C to 95°C, for example between approximately 70°C and 90°C. This heating may facilitate the impregnation step. Where appropriate, it is nevertheless advisable to control the heating conditions, which, if they are too drastic, may induce polymerization and solidification phenomena.

[0095] Application of the geopolymer composition on the wood fiber-based substrate

[0096] In the fireproofing method of the present invention, the geopolymer composition polymer, by its liquid and aqueous nature, lends itself to application to the substrate using the techniques usually used to apply a water-based paint. Thus, without limitation, the application of the geopolymer composition to the wood fiber-based substrate can, for example, be carried out: - by roller; - with a brush; - using a tampon - by spraying, in particular using a paint gun type device; - by immersion of the substrate in the geopolymer composition.

[0097] According to an interesting embodiment which is illustrated in the example given at the end of the present description, the geopolymer composition is applied by roller to the substrate.

[0098] The viscosity of the composition can be adjusted according to the chosen application method, in particular by modulating the quantity of water present in the composition, with viscosities preferably quite low for spraying or immersion methods, and higher for applications by brush or roller.

[0099] Obtaining the geopolymer material from the geopolymer composition is typically obtained by simple drying in the open air, without applying heat treatment (generally in the open air and at room temperature for a duration of around 24 hours makes it possible to obtain the geopolymer material).

[0100] In the aforementioned embodiments, the application of the geopolymer composition occurs after the manufacture of the substrate. According to a more particular embodiment, concerning substrates consisting of wood fiber base particles and / or reagglomerated wood fibers, the application of the geopolymer composition can however take place during the preparation of the substrate: in this context, the geopolymer of the invention can be used as all or part of the binder used to secure the wood fiber base particles and / or wood fibers together, whereby part of the geopolymer is applied to the surface.However, unlike the aforementioned methods where the application takes place on a preformed substrate, the penetration of the geopolymer into the structure of the substrate is total in this more particular mode, which increases the aforementioned effects in particular with regard to the mechanical reinforcement of the material: the reinforcement provided, in the mass, by the geopolymer opposes even more clearly a collapse of the structure of the substrate, in particular under the conditions of a fire. In the embodiment where the geopolymer is used as a binder, the substrate is typically obtained from a mixture comprising the geopolymer composition and the fibers or particles dispersed in said composition, this composition leading to the desired substrate following the pro- transformation. progressive setting of the geopolymer composition into the geopolymer material (setting). Typically, this setting of the mixture takes place in a mold, possibly under pressure, the molding making it possible to obtain a substrate of predetermined shape.

[0101] The following Example illustrates the invention.

[0102] EXAMPLE

[0103] A geopolymer composition was prepared from a solid mixture containing by mass: 78% sodium silicate 11% of a PoleStar® 450 metakaolin 11% of a PoleStar® 200R metakaolin.

[0104] The composition obtained was applied by roller to the entire two surfaces of an MDF panel (type EN 13986 - 2015) measuring 30 cm x 150 cm and 10 mm thick, and then dried in open air for 24 hours at room temperature.

[0105] Tests according to standard EN50399 (2022) were carried out on the coated panel thus obtained. For comparison purposes, the same tests were carried out on an identical control panel (panel of the same MDF and of the same dimensions) but not coated with the geopolymer composition. The results obtained are reported below: Heat peak fPHRR): 9.0 kW versus 245.7 kW for the control (reduction by a factor of 25)

[0106] Total heat released (THR): 7.1 MJ versus 81.1 MJ for the control (decrease by a factor of 11)

[0107] Fire growth rate (FIGRA): 24.0 W / s versus 271.5 W / s for the control (decrease by a factor of 10) Flame spread (FS): 0.7 m versus 3.0 m for the control (total propagation - the entire sample is destroyed)

[0108] Smoke development peak (SPR peak):

[0109] 0.0 m2 / s versus 0.2 m2 / s for the control Total Smoke Production (TSP) 11.5 m2 compared to 55 m2 for the control (reduction by a factor of 5)

Claims

Claims

1. A method of fireproofing a wood fiber-based substrate comprising applying to said substrate a geopolymer composition.

2. A fireproofing method according to claim 1, wherein the geopolymer composition comprises at least one aluminosilicate, at least one alkali silicate, water, and optionally an alkali base.

3. A fireproofing method according to claim 2, wherein the geopolymer composition comprises a mixture of two distinct aluminosilicates, namely at least one first aluminosilicate and at least one second aluminosilicate distinct from the first aluminosilicate.

4. A fireproofing method according to claim 3, wherein the first aluminosilicate is a first metakaolin selected from kaolins calcined at a temperature Tci of at least about 650°C, and the second aluminosilicate is a second metakaolin selected from kaolins calcined at a temperature Tc2 such that Tc2 - Tci > 100°C.

5. A fireproofing method according to one of claims 2 to 4 wherein the alkali silicate is a sodium silicate.

6. A fireproofing method according to one of claims 1 to 5, wherein the application of the geopolymer composition to the wood fiber-based substrate is carried out by roller; by brush; using a pad; by spraying; or by immersing the substrate in the geopolymer composition.

7. A fireproofing method according to one of claims 1 to 5, wherein the substrate comprises particles based on wood fibers reagglomerated with each other or wood fibers reagglomerated with each other, and wherein the application of the geopolymer composition takes place during the preparation of the substrate, said substrate is obtained from a mixture comprising the geopolymer composition and the fibers or particles dispersed in said composition.

8. Fireproofing method according to one of claims 1 to 7, which comprises, following the application of the geopolymer composition, a step of converting the geopolymer composition into a geopolymer material, in particular by drying.

9. A fireproofing method according to claim 8, which further comprises a step of applying an aqueous composition, preferably of the water-based paint, varnish or adhesive type, to the layer of geopolymer material obtained on the substrate from the geopolymer composition.

10. Fireproof element comprising at least one substrate based on wood fibers, and at least one coating based on a geopolymer material on said substrate.

11. Use of a fireproof element according to claim 10, as architectural, structural or decorative elements, in particular inside residential dwellings or inside buildings intended to receive the public.

12. Use of a fireproof element according to claim 10, as a cable tray intended to contain electric cables for the transport of energy or information.