Patent GB-881726-A (GB)
Title: Producing foamed or porous coatings
IPC: B29C44/00
Filed: 1958-11-11
Abstract: A substrate is provided with a foamed coating by immersing it in a fluidized bed of particles while heated to at least the softening temperature of the particles so as to form a softened mass of material on the surface, producing gaseous material within the resultant melt, and allowing the melt to set with the gaseous material therein.  More than one coating may be applied, and the surface may subsequently be re-heated.  The gaseous material may be produced by adding a blowing agent to the particles, by using a volatile liquid, or by applying a vacuum or an excessively high temperature, or it may consist of gaseous reaction products.  The particles may be of polyvinyl chloride, polystyrene, polyethylene, plasticized cellulose ethers and esters, phenolic resins, polyamides, epoxy resins, urea- or melamine-aldehyde resins, acetal resins, polyvinyl acetate, polyurethanes, silicone resins or shellac, or mixtures thereof.  The components of a polyurethane may be applied separately, the carbon dioxide evolved acting as foaming agent. Blowing agents which may be added include N, N1-dinitroso-pentamethylene-tetramine, diazoaminobenzene, azodicarbonamide, 2, 21-azo-isobutyronitrile, azohexahydrobenzonitrile, benzene sulphonylhydrazide p, p1-oxy-bis-benzene sulphonylhydrazide, p-tert-butyl benzoyl azide, a mixture of urea and biuret, ammonium bicarbonate, sodium bicarbonate, sodium nitrate or mixtures thereof.  Other additives may include carbon black, graphite, molybdenum sulphide, titanium dioxide and zinc oxide.  Surfaces which may be coated include metal, paper, wood, glass, hardboard, plasterboard, and textiles.  Examples are given of (1) coating copper tubing with polythene containing diazoaminobenzene; (2) coating a steel rod with a silicone resin containing a foaming agent; (3) coating a steel rod with polyvinyl chloride containing stabilizer, plasticizer, pigment and azodicarbonamide; (4) applying two successive coats as in (3); (5) coating a sandblasted aluminium rod with polythene and applying a partial vacuum to cause the formation of bubbles; (6) coating steel rods and sheets with a phenol-formaldehyde resin containing water and in which water was evolved as a result of polymerization-depolymerization reactions, said water acting as foaming agent; (7) aluminium foil heated much above the softening point of polyvinyl chloride and passed continuously through a fluidized bed of that polymer; (8) a continuous web of fibreglass cloth, heated and passed through polythene containing a blowing agent.  Specification 759,214 is referred to.ALSO:A substrate is provided with a foamed coating by immersing it in a fluidized bed of particles while heated to at least the softening temperature of the particles so as to form a softened mass of material on the surface, producing gaseous material within the resultant melt, and allowing the melt to set with the gaseous material therein.  More than one coating may be applied, and the surface may subsequently be re-heated.  The gaseous material may be produced by adding a blowing agent to the particles, by using a volatile liquid, or by applying a vacuum or an excessively high temperature, or it may consist of gaseous reaction products.  The particles may be of polyvinyl chloride, polystyrene, polyethylene, plasticized cellulose ethers and esters, phenolic resins, polyamides, epoxy resins, urea- or melamine-aldehyde resins, acetal resins, polyvinyl acetate, polyurethanes, silicone resins or shellac, or mixtures thereof.  The components of a polyurethane may be applied separately, the carbon dioxide evolved acting as foaming agent.  Blowing agents which may be added include N,N1-dinitroso pentamethylene tetramine, diazoaminobenzene, azodicarbonamide, 2,21-azoisobutyronitrile, azo-hexahydrobenzonitrile, benzene sulphonylhydrazide, p,p1,oxy-bis-benzene sulphonylhydrazide, p-tert-butyl benzoyl azide, a mixture of urea and biuret, ammonium bicarbonate, sodium bicarbonate, sodium nitrate or mixtures thereof.  Other additives may include carbon black, graphite, molybdenum sulphide, titanium dioxide and zinc oxide.  Surfaces which may be coated include metal, paper, wood, glass, hardboard, plasterboard, and textiles.  Examples are given of (1) coating copper tubing with polythene containing diazoaminobenzene; (2) coating a steel rod with a silicone resin containing a foaming agent; (3) coating a steel rod with polyvinyl chloride containing stabilizer, plasticizer, pigment and azodicarbonamides; (4) applying two successive coats as in (3); (5) coating a sandblasted aluminium rod with polythene and applying a partial vacuum to cause the formation of bubbles; (6) coating steel rods and sheets with a phenol-formaldehyde resin containing water and in which water was evolved as a result of polymerization-depolymerization reactions, said water acting as foaming agent; (7) aluminium foil-heated much above the softening point of polyvinyl chloride was passed continuously through a fluidized bed of that polymer; (8) a continuous web of fibreglass cloth was heated and passed through polythene containing a blowing agent.  Specification 759,214 is referred to.ALSO:A substrate is provided with a foamed coating by immersing it in a fluidised bed of particles while heated to at least the softening temperature of the particles so as to form a softened mass of material on the surface, producing gaseous material within the resultant melt, and allowing the melt to set with the gaseous material therein.  More than one coating may be applied, and the surface may subsequently be re-heated.  The gaseous material may be produced by adding a blowing agent to the particles, by using a volatile liquid, or by applying a vacuum or an excessively high temperature, or it may consist of gaseous reaction products.  The particles may be of polyvinyl chloride, polystyrene, polyethylene, plasticised cellulose ethers and esters, phenolic resins, polyamides, epoxy resins, urea or melamine-aldehyde resins, acetal resins, polyvinyl acetate, polyurethanes, silicone resins or shellac, or mixtures thereof.  The components of a polyurethane may be applied separately, the carbon dioxide evolved acting as foaming agent.  Blowing agents which may be added include N,N1-dinitroso pentamethylene tetramine, diazoaminobenzene, azodicarbonamide, 2,21-azo-iso butyronitrile, azohexahydrobenzonitrile, benzene sulphonylhydrazide, p.p1-oxybis-benzene sulphonylhydrazide, p-tert-butyl benzoyl azide, a mixture of urea and biuret, ammonium bicarbonate, sodium bicarbonate, sodium nitrate or mixtures thereof.  Other additives may include carbon black, graphite, molybdenum sulphide, titanium dioxide and zinc oxide.  Surfaces which may be coated include metal, paper, wood, glass, hardboard, plasterboard, and textiles.  Examples are given of (1) coating copper tubing with polythene containing diazoaminobenzene; (2) coating a steel rod with a silicone resin containing a foaming agent; (3) coating a steel rod with polyvinyl chloride containing stabiliser, plasticiser, pigment and azodicarbonamide; (4) applying two successive coats as in (3); (5) coating a sandblasted aluminium rod with polythene and applying a partial vacuum to cause the formation of bubbles; (6) coating steel rods and sheets with a phenol-formaldehyde resin containing water and in which water was evolved as a result of polymerisation-depolymerisation reactions, said water acting as foaming agent; (7) aluminium foil heated much above the softening point of polyvinyl chloride was passed continuously through a fluidised bed of that polymer; (8) a continuous web of fibreglass cloth was heated and passed through polythene containing a blowing agent.  Specification 759,214 is referred to.