Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/18—Fireproof paints including high temperature resistant paints
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
  • C09D7/40—Additives
  • C09D7/65—Additives macromolecular

Definitions

• the present invention relates to the field of flame retardant materials with a low density, in particular to materials comprising a porous substrate preferably formed by a polymeric foam.
• the present invention relates to a method for coating a superficially porous substrate in order to improve its flame reaction, comprising the following steps:
• a colloidal aqueous suspension comprising at least inorganic and/ or hybrid nanoparticles and a water-soluble polymer, wherein said nanoparticles have a concentration ranging between 0.01 and 50% by weight with respect to the water concentration, wherein said water-soluble polymer has a concentration ranging between 0.01 and 50% by weight with respect to the water concentration and wherein the total concentration of said nanoparticles and said water-soluble polymer has a value of up to 100% by weight with respect to the water concentration;
• the present invention relates to a superficially coated porous substrate having an improved flame resistance obtained according to the above method.
• the present invention relates to a flame-resistant panel comprising a superficially coated porous substrate having an improved flame resistance as provided for in the previous method.
• the present invention finds a preferred and advantageous application in the fields using polymeric materials foams, such as thermal insulation of housings, apartments and other buildings; such as the realization of upholstered furniture; such as seats for means of transport such as aircraft, public transport and the like.
• the polymeric foams are usually highly flammable, and therefore pose serious safety problems in all their applications, if subject to exposure to a flame.
• halogenated additives that act in the gas phase during the combustion of the porous material; many of these halogenated additives have been recognized as being or suspected toxic and/ or having negative impacts on the environment.
• WO 2016/123295 A2 refers to a further method for depositing electrolytes layers; this document exemplifies the methodology of deposition of complexes of anionic and cationic polyelectrolytes, also defined “one-pot" deposition.
• the object of the present invention is to overcome the drawbacks of the prior art related to the flame reaction.
• the present invention aims to solve the problem of improving the adhesion of the flame-retardant particles deposited on a porous material substrate. Still more in particular, the present invention aims to solve the problem of improving the quality/ quantity of the particle deposition.
• the method is a method for coating superficially polymeric foams in order to improve their flame reaction
• the porous substrate is a coated superficially polymeric foam, that results having a better flame reaction, such embodiment representing the optimal solution to the problem faced.
• Another aspect of the present invention relates to a flame-retardant panel comprising a superficially coated porous substrate having an improved flame resistance.
• the technical solution according to the present invention which provides a method for coating superficially a porous substrate and the related superficially coated porous flame-retardant substrates, allows to:
• the method and the porous material thus obtained can also be applied to porous materials not derived from polymeric foams, and this extends the potential application range of the present invention.
• FIG. 1 is a flowchart showing the steps of the method for coating superficially polymeric foams in order to improve their flame reaction according to the present invention
• FIG. 2 is a schematic representation of the method of FIG. 1;
• FIG. 3A shows, to a first magnification, a cell of a polymeric foam, specifically polyurethane;
• FIG. 3B shows, to a second magnification higher than the first magnification, the cell of FIG. 3A;
• FIG. 4A shows the cell of figure 3A after application of the surface coating with the method according to the present invention
• FIG. 4B shows the cell of figure 4A after application of the surface coating with the method according to the present invention
• FIG. 5 shows a diagram that summarizes in a comparative way the results of flame penetration tests on the three samples in polymeric foam, specifically polyurethane, superficially coated with the method according to the present invention
• FIG. 6A shows a sample of polyurethane foam as such at the end of the flame penetration test
• FIG. 6B shows a sample of a material according to a first embodiment of the present invention at the end of the flame penetration test
• FIG. 6C shows a sample of a material according to a second embodiment of the present invention at the end of the flame penetration test
• FIG. 6D shows a sample of a material according to a third embodiment of the present invention at the end of the flame penetration test.
• FIG. 7 shows a diagram that summarizes in a comparative way the results of flame penetration tests on two more samples in polymeric foam, specifically polyurethane, superficially coated with the method according to the present invention on a material obtained according to a further embodiment of the present invention.
• the method, porous substrate and panel of the present invention are based on the innovative concept of depositing a continuous, uniform and compact layer of inorganic and/ or hybrid particles on a porous substrate to obtain a structure capable of resisting the flame and keeping the thermal insulation properties of the original foam.
• the inventors have surprisingly and unexpectedly found the method according to the present invention that allows obtaining polymer foams capable of resisting the flame penetration, while it was - and still is - commonly believed that these foams could not/ can not resist such stress, due to their organic nature.
• the present invention provides an innovative method for the production of thin coatings (indicatively defined between 10 nm 100 microns) to confer flame- retardant properties to organic porous polymeric substrates, without influencing substantially their deformability properties.
• the coating is made with a limited number of depositions (preferably ⁇ 5).
• Substrates are considered having at least partially open porosity and densities in the range of 0.1-500 g/dm 3 (as a non-limiting example, polyurethanes, polyesters, polyolefins, polyamides, phenolic resins are mentioned).
• flame-retardant properties are defined as conferring one or more of the specific properties to the coated substrate:
• the product structural properties include:
• to surface coat/ surface coating means the application by means of sagging, spreading, spraying a substance that, as a result of the application, settles on every surface available of the substrate and preferably, but not necessarily, covers its surface evenly and continuously.
• porous substrate means a material whose cells are least partially open.
• polymeric foam means a porous polymeric material, having an at least partially open porosity, with a density ranging between 0,1-500 g/dm 3 .
• nanoparticles means the portions of inorganic or hybrid organic/ inorganic substance, the dimensions of which are less than 100 nm in at least one of the directions.
• colloidal suspension means a water-based mixture in which nanoparticles are dispersed.
• stabilizer means any additive suitable for stabilizing the colloidal suspension over time.
• binder means an additive, preferably polymeric, suitable to consolidate and stabilize the deposition of nanoparticles over time.
• the method for superficially coating a porous substrate 1 in order to improve its flame reaction comprises the steps of:
• step 100 exposing the substrate to a solution of a positive electrolyte 2
• step 101 exposing the substrate to a solution of a negative electrolyte 4
• step 102 drying the substrate treated in the previous steps
• a colloidal aqueous suspension 6 comprising at least inorganic and/ or hybrid nanoparticles
• step 103 said nanoparticles have a concentration ranging between 0.01 and 50% by weight with respect to the water concentration, wherein said water-soluble polymer has a concentration ranging between 0.01 and 50% by weight with respect to the water concentration and wherein the total concentration of said nanoparticles and said water-soluble polymer has a value of up to 100% by weight with respect to the water concentration (step 103);
• said at least one water-soluble polymer 61 acts as a stabilizer of the colloidal aqueous suspension and/ or as a binder among the deposited nanoparticles (step 104).
• the quantities of water, nanoparticles and water-soluble polymer are in a variable ratio between 2:1:1 and 10,000:1:1 by weight.
• the method according to the present invention provides for that the order of said steps 100 and 101 is reversed, namely that step 101 takes place before step 100.
• the method according to the present invention further comprises the following steps:
• the method according to the present invention provides for that steps 103 and 104 are cyclically repeated in a number equal to or less than 5.
• the method in accordance with the present invention provides for that the superficially coated porous substrate 1 is an organic polymeric foam substrate, having at least a partially open porosity and a density ranging between 0.1-500 g/dm 3 .
• the substrate in organic polymeric foam is polyurethane, polyester, polyolefin, polyamide, phenolic resin.
• the inorganic and/ or hybrid nanoparticles 60 are electrolytes or non- electrolytes.
• the inorganic and/ or hybrid nanoparticles 60 are lamellar or needle- shaped or isodimensional, and more preferably are selected from graphene, graphene oxide, nanographite, boron nitride, natural or synthetic clays, zirconium phosphate and derivatives, molybdenum disulphide or other dichalcogenides, sepiolites, carbon nanotubes, halloysites, carbon or silica or alumina nanofibers, metal oxides, polyhedral oligomeric silsesquioxane (POSS), metal-organic clusters and the like.
• the water-soluble polymer 61 is an ionic or non-ionic surfactant; more preferably, the water-soluble polymer 61 is an organic compound.
• the polymer 61 is natural or synthetic; more preferably, the polymer 61 is selected from alginates, carboxymethyl cellulose and other cellulose derivatives, chitosan, gelatin, DNA, lignin, polyacrylic acid, poly diallyl dimethyl ammonium chloride, branched polyethylene imine, ammonium polyphosphate, polyphosphoric acid and the like.
• the method according to the present invention provides for that the colloidal aqueous suspension 6 further comprises at least one salt 62, wherein said at least one salt has a concentration ranging between 0.01 and 50% by weight with respect to the water concentration and wherein the total concentration of the nanoparticles, water-soluble polymer and salt has a value of up to 150% by weight with respect to the water concentration.
• the quantities of water, nanoparticles, water-soluble polymer and salts are in a variable ratio between 2:1:1:1 and 10,000:1:1:1 by weight.
• the at least one salt 62 is a phosphorus, nitrogen, sulphur or boron salt.
• the residual water after removal by evaporation is less than 10% by weight with respect to the water present before removal by evaporation.
• 1 has a thickness ranging from 10 nm to 100 microns.
• the flame retardancy is defined as having at least one of the following characteristics:
• Example 1 The method according to the present invention is described below in greater detail with reference to the following Examples, which have been developed on the basis of experimental data and which are meant to be illustrative, but not limitating, of the present invention.
• Example 1 The method according to the present invention is described below in greater detail with reference to the following Examples, which have been developed on the basis of experimental data and which are meant to be illustrative, but not limitating, of the present invention.
• Polyurethane foams used to make the porous substrate 1 are a commercial product with a density equal to 15 g/ dm 3 .
• Graphene oxide was provided by the company Avanzare (Spain) as a 1% by weight suspension in water.
• Sodium montmorillonite MMT was purchased from Southern Clays (USA).
• Sepiolite SEP was purchased from Tolsa (Spain).
• Polyacrylic acid PAA, Mw ⁇ 100,000, 35% by weight in H 2 O
• PDAC poly diallyl dimethyl ammonium chloride
• Na alginate Al
• SHMP sodium hexametaphosphate
• PAA and PDAC have been used to prepare aqueous solutions at 1% by weight.
• the used water (18.2 ⁇ ) was taken from a Q20 water purification system by Millipore (Italy).
• step 103 and 104 the water-soluble polymer and the nanoparticles penetrate the porous substrate 1 and coat the individual cells of the latter with a continuous, uniform coating that does not alter the open cell structure of substrate 1, as shown in FIG.s 4A-4B (FIG.s 3A-3B illustrate some of the cells before steps 102, 104). Flammability Test
• reaction to a flame exposure was assessed by means of a flammability test in a horizontal configuration.
• a sample of porous material obtained according to the method of the present invention having a size of 5x15x1.8 cm 3 is placed on a metal grid, the 5 cm side is exposed to a 2 cm-high natural gas blue flame for 3 seconds.
• the samples were conditioned in a climate chamber (23 °C, 50% R.H.) for 24 hours before the test.
• An oxygen-consumption cone calorimeter is used to perform a test according to ISO
• Flame penetration tests were conducted by placing the sample (5x5x1.8 cm 3 ) into a vertical ceramic structure and exposing one side of the sample to the flame of a torch powered by butane (150 W), placed 10 cm apart. During the test, the temperatures of the side exposed to the flame and the opposite side were monitored using 1 mm armoured thermocouples of type K. The test was performed twice for each of the six formulations. The samples were conditioned in a climate chamber (23 °C, 50% R.H.) for 24 hours before the test.
• the non-modified PU polyurethane immediately ignites, and the flame propagates to the whole sample causing a conspicuous dripping that propagates the flames also to the cotton wool.
• the sample burns out completely leaving a 13% residue.
• the coated porous materials after application of the flame, a self-extinguishing behaviour is observed: the flame remains confined within the first 2-3 cm of the sample and is extinguished after a few seconds. Only in the case of MMT/ alginate sample, a small flame remains confined and propagates only on the edge of the sample, reaching the side not exposed to methane flame. All tested coatings were able to stop the dripping phenomenon.
• the cone calorimeter allows assessing the exact behaviour of materials when exposed to a heat flow typical of fires under development. Normally, when exposed to heat flow, the material melts and then begins to release products of decomposition; when the volatile products exceed the limit of flammability, ignition and combustion of the material occur. During the combustion of the sample, the cone calorimeter measures the oxygen consumption and calculates the rate of heat release. The non-modified polyurethane ignites after just 4 seconds. During the combustion, the foam collapses losing its original shape, giving rise to a mass of molten polymer that burns out completely reaching a pkHRR of 304 kW/ m 2 .
• modified samples do not collapse, but retain the original shape of the foam; the ignition is delayed on average of a few seconds and the combustion takes place with flames of smaller size than those observed for the reference. All formulations showed to be capable of reducing the pkHRR of at least 50% . The best performances were obtained with GO/ alginate/ SHMP and SEP/ alginate/ SHMP samples. Unlike other samples, the set of GO/ alginate foams did not ignite during the test; consequently, the degradation products did not reach the limit of flammability. The instrument has measured in any case an HRR signal which can be traced back to the sample oxidation without flame.
• FIG. 5 shows temperature diagrams of both the surface exposed to the flame and the opposite surface.
• FIG.s 6B to 6D show sample images at the end of the test.
• a reference material was also tested in the polyurethane PU (FIG. 6A) that, due to the low density and the high flammability of the foam, is penetrated immediately by the flame without therefore showing any relevant performance of resistance to the flame penetration.
• the materials according to the present invention as shown by the images of the residues at the end of the test (FIG.s 6B-6D), all tested formulations had been able to resist the flame penetration for more than three minutes, while maintaining the original size and isolating the side not exposed to the flame.
• the degree of insulation obtained is similar to the formulations containing GO and MMT, for which it has obtained a temperature gradient of about 600 °C through a thickness of 18 mm.
• the flame penetration test was also performed on a substrate of open cell polyurethane, with activation of 1 BL PAA/PDAC, followed by sagging and evaporation of a colloidal suspension containing nanoparticles of graphene (GNP), and carboxymethyl cellulose (CMC) with the optional addition of SHMP, as described in Example 1.
• GNP graphene
• CMC carboxymethyl cellulose
• porous material of this example was subjected to the flame penetration test as described above, and the results are illustrated in FIG. 7.
• polyurethane modified foams with the formulation that contains the three components have been able to resist the flame penetration for more than 5 minutes.
• the GNP/carboxymethyl cellulose/ SHMP formulation scored the best performance of all tested samples (including those of Example 1) reaching a temperature gradient of 685 °C.
• a superficially coated porous substrate 11 having an improved flame resistance represents an independent aspect that can be used autonomously with respect to other aspects of the invention and comprises:
• said surface coating 3 has at least one layer and is deposited in a continuous manner and with a homogeneous orientation in the direction parallel to the inner walls 10 of the porous substrate 1 by exposure to a colloidal aqueous suspension 6 comprising at least inorganic and/ or hybrid nanoparticles 60 and a water-soluble polymer 61, wherein said nanoparticles have a concentration ranging between 0.01 and 50% by weight with respect to the water concentration, wherein said water-soluble polymer has a concentration ranging between 0.01 and 50% by weight with respect to the water concentration and wherein the total concentration of said nanoparticles and said water-soluble polymer has a value of up to 100% by weight with respect to the water concentration.
• the surface coating 3 has a number of layers equal to or lower than 5.
• the superficially coated porous substrate 1 is an organic polymeric foam substrate, having at least a partially open porosity and a density ranging between 0.1-500 g/ dm 3 .
• the substrate in organic polymeric foam is polyurethane, polyester, polyolefin, polyamide, phenolic resin.
• the nanoparticles 60 are electrolytes or non-electrolytes.
• the inorganic or hybrid nanoparticles 60 are lamellar or needle-shaped or isodimensional, and more preferably are selected from graphene, graphene oxide, nanographite, boron nitride, natural or synthetic clays, zirconium phosphate and derivatives, molybdenum disulphide or other dichalcogenides, sepiolites, carbon nanotubes, halloysites, carbon or silica or alumina nanofibers, metal oxides, polyhedral oligomeric silsesquioxane (POSS), metal-organic clusters and the like.
• the water-soluble polymer 61 is an ionic or non-ionic surfactant; more preferably, the water-soluble polymer 61 is an organic compound.
• the water-soluble polymer 61 is natural or synthetic; more preferably, the polymer 61 is selected from alginates, carboxymethyl cellulose and other cellulose derivatives, chitosan, gelatin, DNA, lignin, polyacrylic acid, poly diallyl dimethyl ammonium chloride, branched polyethylene imine, ammonium polyphosphate, polyphosphoric acid and the like.
• the superficially coated porous substrate 11 having an improved flame resistance provides that the colloidal aqueous suspension 6 further comprises at least one salt 62, wherein said at least one salt has a concentration ranging between 0.01 and 50% by weight with respect to the water concentration and wherein the total concentration of the nanoparticles, water-soluble polymer and salt has a value of up to 150% by weight with respect to the water concentration.
• the at least one salt 62 is a phosphorus, nitrogen, sulphur or boron salt.
• the surface coating 3 deposited on the inner walls 10 of the porous substrate I has a thickness ranging from 10 nm to 100 microns.
• a flame-resistant panel including a superficially coated porous substrate

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Wood Science & Technology (AREA)
• Organic Chemistry (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
• Paints Or Removers (AREA)

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Citations (3)

• 2017
  • 2017-09-21 IT IT102017000105762A patent/IT201700105762A1/it unknown
• 2018
  • 2018-06-21 WO PCT/IB2018/054571 patent/WO2019058186A1/en unknown
  • 2018-06-21 EP EP18738380.7A patent/EP3684866A1/en active Pending

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