Method for obtaining an insulating coating

Abstract

The invention relates to obtaining an insulating coating on or against a support, comprising a mixing step with water of a dry composition comprising a powdery hydraulic binder but not comprising mineral wool flakes, to obtain a wet binder, then a projection step, during which mineral wool flakes are projected with said wet binder onto or against said support.

Description

Title of the invention: Method for obtaining an insulating coating

[0001] The invention relates to the field of building construction. It relates more particularly to obtaining coatings having good thermal insulation properties.

[0002] It is known to thermally insulate buildings from the outside by placing panels of insulating material, for example mineral wool or polystyrene, on the exterior walls of the buildings. Compared to interior insulation, this technique saves space for occupants and provides better thermal insulation due to the elimination of thermal bridges. Various construction systems are used for this purpose. Examples include ventilated façade systems, in which facing panels are held by frames at a certain distance from the insulation to create an air gap, and external insulation systems (EWI or ETICS), in which reinforcing and finishing renders are applied directly to the insulation. In these different techniques, the insulating panels are fixed to the wall to be insulated either by mechanical fasteners or by adhesives.

[0003] However, these techniques are complex and require significant installation time, particularly for fixing the insulation and facing panels. Furthermore, cutting the panels on site generates large quantities of waste, and poor panel joints can lead to reduced thermal insulation performance.

[0004] The invention aims to provide a construction technique that allows for more effective thermal insulation of facades, with simpler and faster implementation.

[0005] A method for projecting a composition obtained by mixing a dry composition comprising mineral wool flakes and a mineral binder with water is known from application WO2022 / 219275.

[0006] Such a process makes it possible to obtain insulating coatings with good adhesion to walls and good cohesion, even at significant thicknesses. However, this process is not without drawbacks. In particular, obtaining a homogeneous mixture of relatively large flakes with a mineral binder in the form of a very fine powder requires complex and expensive industrial equipment, and its projection generates dust.

[0007] The invention aims to overcome these drawbacks and, to this end, proposes a method for obtaining an insulating coating on or against a substrate, comprising a mixing step with water of a dry composition comprising a powdered hydraulic binder but not comprising mineral wool flakes, to obtain a binder wet, then a projection stage, during which mineral wool flakes are projected with said wet binder onto or against said support.

[0008] The invention also relates to a building element comprising a support coated on one of its surfaces with an insulating coating obtained by such a process.

[0009] Unlike the aforementioned prior process, the mineral wool flakes are not pre-mixed with the powdered binder, but with the wet binder during spraying. The process is therefore simpler to implement, as it does not require dry mixing of the binder and the mineral wool flakes. Furthermore, the use of a hydraulic binder allows for the use of larger flakes, compared to organic binders or other mineral binders such as alkali silicates. The use of hydraulic binders also results in improved mechanical strength compared to organic binders.

[0010] After mixing the composition with water and hardening the hydraulic binder, the resulting coating comprises mineral wool flakes bonded together by a hardened hydraulic binder. The powdered hydraulic binder present in the dry composition becomes fluid after mixing with water, before hardening. The term "binder" therefore covers both the powdered hydraulic binder present in the dry composition, the wet binder obtained by mixing the hydraulic binder with water, and the final hardened binder in the finished coating. The following details apply to both the dry composition and the final coating.

[0011] Mineral wool is preferably selected from glass wool, slag wool and rock wool. Mineral wool fibers preferably have a chemical composition comprising 30 to 75% by weight of SiO2, 5 to 40% CaO+MgO, 0-20% Na2O+K2O, 0-30% Al2O3 and 0-15% Fe2O3.

[0012] The use of glass wool generally allows for better thermal insulation performance, particularly due to a lower density.

[0013] Glass wool is generally formed by electric or flame melting of a mixture of powdered raw materials and cullet (recycled glass), followed by fiberization, in particular by internal centrifugation using a fiber-forming plate. The glass wool fibers preferably have a chemical composition comprising 50-75% by weight of SiO2, 12-20% Na2O+K2O, 5-20% CaO+MgO, 0-8%, in particular 0-3% Al2O3 and 2-10% B2O3.

[0014] Rock wool and slag wool are generally formed by melting raw materials in the form of blocks or briquettes in a cupola furnace, or by electric melting or by submerged burners of powdered materials, then fiberizing by external centrifugation using a plurality of rotors. Rock wool fibers preferably have a chemical composition comprising 30-50% SiO2, 10-26% Al2O3, 15-40% CaO+MgO, 0-5% Na2O+K2O and 3-15% Fe2O3. Slag wool fibers preferably have a chemical composition comprising 30-45% SiO2, 5-18% Al2O3, 30-60% CaO+MgO and 0-3% Na2O+K2O.

[0015] Mineral wool is generally made up of interwoven vitreous fibers. As a rule, the mineral wool used does not contain an organic binder. However, it may contain one when the loose fill comes from recycled construction or factory waste, for example, obtained by grinding mineral wool panels. The loose fill may be blown-in wool flakes, which do not normally contain an organic binder, but may nevertheless contain organic additives, for example, silicone or an antistatic agent. These additives are notably sprayed onto the mineral wool during the fiber-laying process.

[0016] The term "flakes" refers to pieces formed from agglomerates (or clusters) of intertwined fibers of a certain size or dimension. It is essential that the composition and coating include the fibers in flake form and not as dispersed individual fibers or as fibers organized into sheets, grids, fabrics, or nonwovens, in order to achieve good thermal insulation properties. The coating is therefore distinct from a fiber-reinforced plaster or mortar, which does not exhibit insulating properties.

[0017] Mineral wool flakes preferably have a size between 1 and 10 cm, particularly between 2 and 8 cm, or even between 3 and 7 cm. Flakes that are too small result in denser coatings, and therefore less thermally insulating ones. Obtaining the flakes and adjusting their size can be achieved, in particular, using a carding machine, which can be integrated into the projection machine. This size can be determined by sieving.

[0018] The hydraulic binder preferably comprises at least one compound selected from the group formed by Portland cements, belitic cements, aluminous cements, sulfoaluminous cements, pozzolanic mixture cements, slags, fly ash, calcined clays, hydraulic lime, calcium sulfate sources and mixtures of two or more of these compounds.

[0019] The hydraulic binder may in particular consist of Portland cement, in particular of type CEM I or CEM IL

[0020] According to another embodiment, the hydraulic binder comprises (in particular consists of) a mixture of Portland cement and a source of calcium sulfate. The presence of a source of calcium sulfate particularly improves the fire resistance properties and accelerates the setting of the binder. Its carbon footprint is also reduced compared to Portland cement. The proportion of the calcium sulfate source calcium in this hydraulic binder is preferably between 2 and 20% by weight, in particular between 5 and 15% by weight.

[0021] According to another embodiment, the hydraulic binder comprises (in particular consists of) a mixture of sulfoaluminate cement and a calcium sulfate source. The binder then preferably comprises a setting accelerator, for example a lithium salt. The proportion of calcium sulfate source in this binder is preferably between 2 and 20% by weight, in particular between 5 and 15% by weight.

[0022] According to yet another embodiment, the hydraulic binder comprises (or consists of) a mixture of Portland cement, aluminous cement, and a source of calcium sulfate. The binder may also include a setting accelerator, for example, a lithium salt. Such a binder allows for faster final hardening. In this embodiment, the weight proportions of the constituents in the binder are preferably as follows: 65 to 90% Portland cement, 5 to 20% aluminous cement, and 2 to 15% of a source of calcium sulfate.

[0023] In general, the presence of Portland cement allows for good mechanical performance, particularly in terms of compressive strength. The addition of a lime source to the aforementioned binders has also proven beneficial in this respect.

[0024] Slags include, in particular, ground granulated blast furnace slag or steelmaking slag, for example, ladle slag. Slags, especially ground granulated blast furnace slag, are latent hydraulic binders and therefore generally require activation. The hydraulic binder preferably comprises an activation system including at least one compound selected from Portland cement, lime, finely ground slags, finely ground calcium and / or magnesium carbonates, CSH seeds, alkali silicates, phosphate salts, and a calcium sulfate source. Fly ash and calcined clays (in particular metakaolin) are pozzolanic compounds that require a calcium source to develop hydraulic properties. In this case, the hydraulic binder therefore includes a calcium source.

[0025] The dry composition preferably comprises a cellulose ether, in particular a carboxymethylcellulose. These compounds make it possible to achieve coatings of greater thickness. The total cellulose ether content in the dry composition is preferably between 0.1 and 3.0%, in particular between 0.5 and 1.8% by weight.

[0026] The dry composition preferably comprises redispersible polymer powders. The polymer is preferably based on one or more monomers selected from vinyl esters (in particular C1-C15 vinyl esters of carboxylic acids such as vinyl acetate), (meth)acrylates (in particular C1-C10 alcohols), vinyl aromatics, alkenes (e.g., ethylene), dienes, and vinyl halides. These polymers improve the coating's mechanical strength without affecting its thermal insulation properties.

[0027] The dry composition may also include surfactants, particularly to facilitate the wetting of the fibers by the wet binder during the coating application process. Sodium dodecyl sulfate is one advantageous surfactant.

[0028] The dry composition may further include a water-repellent agent to improve the coating's resistance to aging. Its presence helps to limit undesirable interactions between the hydraulic binder, which is generally highly alkaline, and the mineral wool fibers, which are sensitive to alkaline environments. Preferably, the water-repellent agent comprises (or consists of) an organosilicon compound, in particular one containing silane and / or siloxane groups, which may be monomeric, dimeric, oligomeric, or polymeric. Such water-repellent agents have proven to be far more effective than other known water-repellent agents such as sodium, potassium, or calcium fatty acid salts, for example, calcium stearate or sodium oleate. The water-repellent agent is preferably in powder form. It may, for example, comprise the organosilicon compound and an inorganic or organic solid carrier.Possible inorganic supports include, for example, silica-based (such as precipitated or fumed silica), carbonates, or talc. They are preferably porous, with a BET surface area of ​​at least 50 m² / g, or even at least 100 m² / g. The water-repellent agent can also be a redispersible powder. It may then include polymers, in addition to the organosilicon compound. These polymers are, for example, based on one or more monomers selected from the group comprising vinyl esters (in particular, vinyl esters of unbranched or branched alkylcarboxylic acids having 1 to 15 carbon atoms), methacrylates and acrylates (in particular, (meth)acrylates of alcohols having 1 to 10 carbon atoms), methacrylic acid, acrylic acid, vinylaromatics, olefins, dienes, and vinyl halides. The powder may also contain water-soluble protective colloids, fatty acids, and / or antiblocking agents.

[0029] The dry composition may further comprise other compounds, in particular selected from biocides, pigments, rheological agents, plasticizing or superplasticizing agents, dispersing agents and accelerators and / or retarders of setting or hardening.

[0030] The dry composition may further comprise lightweight fillers, in particular selected from perlite, vermiculite, expanded glass beads, beads expanded polystyrene, cenospheres, expanded silicates, aerogels and their mixtures.

[0031] Preferably, the weight ratio between the powdered hydraulic binder and the water in the wet binder is between 0.10 and 0.40, in particular between 0.20 and 0.30, especially around 0.25. Such ratios make it possible in particular to obtain a wet binder which allows for good projection and good mixing with the mineral wool flakes during projection.

[0032] The weight ratio between the mineral wool flakes and the powdered hydraulic binder is preferably between 1.0 and 3.0, particularly between 1.5 and 2.5, especially around 2. Such ratios make it possible to achieve coatings that combine both good mechanical strength and good thermal insulation. Given the low density of the mineral wool flakes relative to the binder, the mineral wool is clearly the dominant component by volume, allowing for good thermal insulation properties.

[0033] The weight ratio of powdered hydraulic binder: mineral wool flakes: water is preferably 1:1.0-3.0:3.0-5.0, in particular 1:1.5-2.5,3.5-4.5. A ratio of 1:2:4 has proven to be particularly advantageous.

[0034] The substrate is preferably vertical, in particular an exterior wall of a building, with the coating being applied to the exterior surface of said wall. An "exterior wall" is defined as a wall separating the interior of the building from the exterior. An "exterior surface" is defined as the surface facing the exterior of the building. Thanks to its insulating, mechanical, and aging resistance properties, the coating can then replace insulating material panels in the ventilated facade and external thermal insulation systems described in the introduction. Advantageously, the wall is manufactured using an additive manufacturing technique (also known as "3D printing"). In such a case, the texture created by this technique (due to the fact that layers of mortar are successively deposited one on top of the other) improves the adhesion of the coating.The process according to the invention is also well suited to the formation of insulating coatings on substrates with complex shapes, for example obtained by additive manufacturing of mortar. The process is also amenable to automation, so that it can easily be used to produce prefabricated elements.

[0035] The building element then comprises an exterior wall clad on its outer surface with insulating material. The element may further comprise a frame (wood or metal) for fixing and holding a facing material at a distance, while maintaining an air gap between the insulating material and the facing material. The facing material may be of any type: glass, metal, wood, PVC, ceramics, etc. Alternatively, the element may include directly on the insulating coating a reinforcing coating, generally including a reinforcing grid, and a finishing coating or facing.

[0036] The invention is not limited to this application, however, and the coating can also be deposited on a horizontal support, for example to insulate a ceiling from below.

[0037] The application of the wet binder / mineral wool flake mixture onto or against the substrate is carried out by spraying. Preferably, the mineral wool flakes are fed into a spray nozzle, and the wet binder is added as soon as possible after the nozzle outlet. The wet binder is preferably obtained in a hopper or in a mixer integrated into the spraying machine. Mixing preferably takes place immediately before spraying, for example, at most 10 minutes, and in particular at most 5 minutes before spraying. The wet binder is then conveyed to a spray lance using a pump or compressed air.

[0038] The spray lance advantageously has a central conduit through which the mineral wool flakes are sprayed, around which is arranged at least one orifice, or in particular a plurality of orifices, through which the wet binder is sprayed. The mixing of the flakes and the wet binder is then carried out at the nozzle outlet, before the mixture reaches the substrate. The spraying machine can be a machine conventionally used for spraying mortars and exterior plasters.

[0039] The density of the coating after hardening of the hydraulic binder (and possibly drying of excess water) is preferably not more than 250 kg / m³, in particular not more than 150 kg / m³, and in particular between 50 and 100 kg / m³. The thermal conductivity of the coating is preferably between 35 and 60 mW / mK. When the mineral wool is rock wool or slag wool, this density is preferably between 100 and 200 kg / m³, with a thermal conductivity ranging in particular from 37 to 60 mW / mK. When the mineral wool is glass wool, the density of the coating is preferably between 50 and 100 kg / m³, in particular between 60 and 80 kg / m³, for thermal conductivities ranging in particular from 35 to 40 mW / mK.

[0040] The thickness of the coating after hardening of the hydraulic binder is preferably between 5 and 25 cm, in particular between 8 and 16 cm.

[0041] The mechanical resistance of the coating is excellent, with resistances ranging in particular from 5 to 20 kPa in tension, from 5 to 60 kPa in bending (in particular from 40 to 60 kPa with slag or rock wool) and from 20 to 110 kPa in compression (in particular from 90 to 110 kPa with slag or rock wool).

[0042] The following examples illustrate the invention in a non-limiting manner.

[0043] Two dry compositions were tested, one (composition 1) consisting of Portland cement (CEM I 52.5 N) and the other (composition 2) comprising 98.8% by weight of Portland cement and 0.12% by weight of carboxymethylcellulose (Tylose). The weight ratio of powdered hydraulic binder to water was 0.25. After mixing for a few minutes, the wet binder was conveyed to a spray lance where it was sprayed against a gypsum board at a flow rate of 20 L / min via three nozzles (5 mm diameter) surrounding the spray nozzle of the mineral wool flakes. The latter was blown glass wool, marketed by the Applicant under the reference Comblissimo. The weight ratio of mineral wool to powdered hydraulic binder was 2. The spray machine was equipped with a carding device.

[0044] For both compositions studied, a 16 cm thick insulating coating could be obtained in a single pass, with a low density. However, the coating obtained using composition 2 exhibited better mechanical cohesion. The density in the wet state (before drying and hardening of the binder) was 152 kg / m³ for composition 1 and 168 kg / m³ for composition 2. After drying and hardening, the density was 80 to 100 kg / m³ and the thermal conductivity was 38 to 40 mW / mK for both compositions. The tensile strength of the coating was better in the case of composition 2.

Claims

Demands

1. A method for obtaining an insulating coating on or against a support, comprising a mixing step with water of a dry composition comprising a powdered hydraulic binder but not comprising mineral wool flakes, to obtain a wet binder, then a projection step, during which mineral wool flakes are projected with said wet binder onto or against said support.

2. Method according to claim 1, wherein the support is vertical, in particular is an exterior wall of a building, the projection step being carried out on the exterior surface of said wall.

3. A method according to any one of the preceding claims, wherein the mineral wool is selected from glass wool, slag wool and rock wool.

4. A method according to any one of the preceding claims, wherein the mineral wool flakes have a size between 1 and 10 cm, in particular between 2 and 8 cm.

5. A method according to any one of the preceding claims, wherein the hydraulic binder comprises at least one compound selected from the group consisting of Portland cements, belitic cements, aluminous cements, sulfoaluminous cements, pozzolanic mixture cements, slags, fly ash, calcined clays, hydraulic lime, calcium sulfate sources and mixtures of two or more of these compounds.

6. A process according to any one of the preceding claims, wherein the dry composition comprises a cellulose ether.

7. A method according to any one of the preceding claims, wherein the weight ratio between the powdered hydraulic binder and the water in the wet binder is between 0.10 and 0.40, in particular between 0.20 and 0.

30.

8. A method according to any one of the preceding claims, wherein the weight ratio between the mineral wool flakes and the powdered hydraulic binder is between 1.0 and 3.0, in particular between 1.5 and 2.

5.

9. A method according to any one of the preceding claims, wherein the density of the coating after hardening of the binder 10 hydraulic is at most 250 kg / m3, in particular at most 150 kg / m3

10. A method according to any one of the preceding claims, wherein the thickness of the coating after hardening of the hydraulic binder is between 5 and 25 cm, in particular between 8 and 16 cm.

11. Building element comprising a support coated on one of its surfaces with an insulating coating obtained by a process according to one of the preceding claims.