Patent GB-1173567-A (GB)
Title: Coated Porous Structures and method for forming them
IPC: C04B35/524
Filed: 1966-09-27
Abstract: 1,173,567. Coated porous structures. SCOTT PAPER CO. 27 Sept., 1966 [30 Sept., 1965], No. 43182/66. Addition to 1,112,896. Heading B2E. [Also in Divisions B5 and, C4] A porous structure comprises a plurality of cells, all of which are open to the atmosphere, the elements which form the cells comprising a central core of a material which is selfsupporting and a contiguous solid exterior coating of a fused organic resin over the entire surface of the core material. The porous structure may be formed by temporarily attaching particulate organic resin to the entire atmospherically exposed surface of a core material having a plurality of cells which are open to the atmosphere and which is self-supporting and capable of maintaining a given shape at a temperature above the fusing temperature of resin, and subjecting the resulting coated structure to a temperature above the fusing temperature of the resin and below the fusion and decomposition temperatures of the core material so as to melt-flow the resin into a smooth contiguous coating over the entire atmospherically exposed surface of the core material. The core material may have a honeycomb structure, or may have a framework formed by. a plurality of strands integrally interconnected by thickened nexae. The organic resin may be a thermoplastic or thermosetting resin. The contiguous coating may include fibres of a different material, a granular filler material and/or a pigment material embedded within the resin, or fibres or particulate material may be adhered to the surface of the exterior coating. Materials which can be employed for the manufacture of the core materials are steel plate, steel wire, glass, wood, galvanised steel, steel screen, steel wool, cotton gabardine, nylon, cotton and rayon scrim fabrics. Advantageously the substrates are structures fabricated of or coated with other organic materials such as polyurethane and phenolic resins. The powdered coating material may be temporarily attached to the structure by initially coating a binding liquid, e.g. water by dipping or spraying. Adhesives, wetting agents, may be incorporated in the binding liquid. An adhesive which has dry tack on the surface of the porous structure may be employed. Organic resin coating materials mentioned are thermosetting resins such as phenolic resins, epoxy resins, polyamides, polyimides, polyazines, polyoxazoles and polypyrones, thermoplastic resins such as polyolefines made from ethylene, propylene, 1-butene or mixtures thereof. Other coating materials mentioned are nylons, polyesters, chlorinated polyethers, cellulose acetate, acetate butyrate, polyvinyl chloride, polyisobutylmethacrylate, mineral wax, phenol-aldehyde resins, copolymers of epoxy resins with the phenolic resins, with urea resins, the melamine resins, with polyamides, with butadieneacrylonitrile rubbers, furane. resins, polybenzimidazoles, arylene polyimides, poly Schiff bases. Additives mentioned for the organic resin coating are reinforcing fibres such as glass or asbestos fibres, fillers such as clays, pigments such as the metal oxides and copper phthalocyanines, carbon black, pumice, aluminium powder, hollow glass beads, hollow phenolic beads, silica. Additives to the surface of the coated structure may comprise feldspar, pumice, nylon flock, hollow glass beads, hollow phenolic beads, steel wool flock and polytetrafluoroethylene. The structures may be heat-formed into various shapes and may be bonded to other materials to form a variety of sand#ich structures or laminated panels. The configuration of the cellular structure may be changed after coating and while the coating material is in the molten stage such as by compression so as to densify the structure and produce a fine-pored structure. The structures are useful as heating plant filters, humidifier and evaporative cooler pads, scrubber pads, carburator air filters, cushions, mattresses or upholstery. In the Examples (1) reticulated polyurethane foam is coated with. an epoxy resin using an ethylene vinyl acetate copolymer emulsion as the binding liquid; (2) a reticulated polyurethane foam is coated as in (1), the epoxy resin containing glass fibres; (3) reticulated polyurethane foam was coated as in (1) with a phenolic resin; (4) reticulated polyurethane foam was coated as in (1) with a polyester resin; (5) an explosion-reticulated polyurethane foam was coated with polyethylene; (6) a sandwich structure was made by laminating a layer of reticulated polyurethane foam coated with an epoxy resin between two sheets of aluminium; (7) reticulated polyurethane foam was coated with an epoxy resin and disposed between two metal sheets each coated on their faces directly towards the foam with the same epoxy resin; (8) a phenolic coated, fibreglass reinforced honeycomb is coated with epoxy resin using a dry tack adhesive; (9) samples of fibreglass mat of the type used for furnace filters are coated with nylon, epoxy resin, polyester resin; (10) samples of oil-free steel wool are coated with epoxy resin, nylon, polyester and polyethylene; (11) samples : of steel screen were coated with ethylene-vinyl acetate copolymer, polypropylene, polyethylene, nylon, epoxy resin; (12) reticulated polyurethane foam was coated with epoxy resin, heated at 572‹F. to pyrolize the structure, and the structure then triple-coated with an ethylene-propylene copolymer. powder; (13) a reticulated polyurethane foam was coated with a mixture of epoxy resin and graphite.