Patent GB-1497659-A (GB)
Title: Thermal protecting process and composition
IPC: C09K21/14
Filed: 1974-11-14
Abstract: 1497659 Endothermic flame retardancy T S I INC 14 Nov 1974 49336/74 Heading DIP [Also in Division B2] A substrate is protected from flame or other extreme thermal conditions by coating, impregnating or incorporating therein a protective composition comprising one or more components at least one of which has the property of undergoing an endothermic phase change from solid to vapour below the temperature of the thermal extreme, the composition and proportions of components being such that the composition forms a continuously porous open cell matrix with the vapour at the thermal extreme temperature, allowing the vapour to pass to the ambient atmosphere. The composition contains a binder, which may be the same ingredient as the vapour-forming component, which preferably softens at the flame temperature. The components and their proportions are selected so as to ensure that the required open cell structure is formed on heating. They may be used for fire proofing wood, paper or fabric. The preferred compositions comprise a reaction product of a silicate, e.g. alkali metal silicate or aluminosilicates or silicotitanates, with an amine salt. The amine salt is preferably that of a primary aromatic amine and sulphuric or phosphoric acid. The reaction is effected in aqueous solution to give a slightly viscous product containing excess silicate, which may itself, preferably with the addition of alkali metal hydroxide, be used as the protective composition. Other compositions may include many different vapour-forming components such as organic amines, quinones, aromatic acids, phenols, halogenated organic compounds, antimony halides and oxyhalides. ammonium salts and many others. The binder component may be inorganic e.g. alkali metal silicate. or an organic resin e.g. nitrocellulose, phenolic modified acrylonitrile-butadiene rubber. nolysulphide polymer with epoxy resin, nolysiloxane and other silicon polymers, acrvlics, polyesters and nolyvinyl chloride. Other ingredients include fibres e.g. silica. and materials to improve the thermal reflectivity of the composition, e.g. magnesia, zirconia and alumina. These reflective materials may alternatively be applied (e.g. spraved) as a further coating on top of the protective coating: The Examples illustrate the following matter: Compositions of p-nitroaniline sulphate in excess sodium silicate, with and without sodium hydroxide, are applied to a wooden panel; the composition is also applied to a polyvinyl chloride backing strip, cured by heating, a further coating of contact adhesive is applied and the strip is wound onto an iron pipe. A similar strip is made up by impregnating a woven fibre-glass tape with the said composition, and wound onto a copper pipe. A porous sintered steel disc is impregnated with the above composition. Compositions of p-nitroaniline phosphate in excess aqueous sodium aluminosilicate, containing potassium hydroxide, boric acid, antimony trisulphide and potassium permanganate are coated onto a steel wall. A further composition is made by drying the preceding said composition, grinding it and mixing with an epoxy resin binder, the composition then being coated onto wood. Other resins i.e. polyurethanes. silicones, phenolic resins and proteins may be used in place of the epoxy binder. A composition of p-nitroaniline phosphate in sodium silicotitanate, with potassium hydroxide, boric acid, antimony trisulphide and potassium permanganate is coated onto corrugated cardboard sheet. A similar composition in which p-phenylenediamine replaces the pnitroaniline is injected into the corrugations of a corrugated cardboard sheet and also coated onto its surface. A p-nitroaniline composition as before, to which ammonium chloride has been added is blended with asbestos fibres and foamed; the foam is cast into slabs. Compositions of molybdenum hexacarbonyl or ammonium p-nitroaniline orthosulphonate, and epoxy resin, polysulphide polymer, silica or glass fibres,: epoxy resin and curing agent are coated onto steel panels. An analogous composition of ammonium fluoroborate or potassium fluoroborate, epoxy resin, polyester resin, quartz fibres and magnesium oxide is coated onto steel. The coating may be subsequently sprayed with powdered alumina while still tacky. A similar composition wherein the fluoroborate and magnesium oxide are replaced by ammonium hypophosphate and bentonite is also used to coat steel.