Patent GB-1002786-A (GB)
Title: Process of producing foamed glass and foamed glass and insulating material produced by this process
IPC: C04B38/00
Filed: 1963-10-01
Abstract: A composition comprises foamed glass particles and bitumen or artificial resin foam.  In the glass particles, micropores extend through the cell walls separating the macropores. Moisture-tight and gas-tight foamed glass particles comprising porous inorganic particles, e.g. perlite or vermiculite, may be mixed with bitumen. Spheroidal foamed glass particles, of diameter, e.g. 1-10 mm., may be embedded in an artificial resin foam, e.g. of polystyrene, phenolic resin, polyester or polyether; either the resin or the glass particles may form a major part of the material.  The material formed may be used for thermal or acoustic insulation.ALSO:Foamed glass is made by moistening ground glass with an aqueous solution or suspension containing alkali metal silicate and an organic substance, drying or roasting the mixture at below 600 DEG  C., and inflating and cooling in known manner.  In the foamed glass, microcells extend through the cell walls separating the macrocells.  The diameter of the microcells is up to 1/10 of the macrocell diameter.  Suitable organic substances are: polyhydric alcohols or carbohydrates, e.g. sugar, glycol, glycerol, cellulose, starch and wood flour; or precondensates of urea-formaldehyde or phenol-formaldehyde; or bitumen emulsions: 0.3-10 parts by weight organic substance may be used per 100 parts ground glass.  The alkali metal silicate is preferably water-glass solution which may contain 0.01-0.5% by weight of alkaliresisting wetting agent, e.g. oxydiphenyldisulphonate; 4-30 parts by weight concentrated water-glass solution may be used per 100 parts ground glass.  Solid, inflated alkali metal silicate may be added, up to e.g. 5 parts by weight per 100 parts ground glass. If less than 1 part organic substance and less than 10 parts alkali metal silicate are employed per 100 parts ground glass, a white to light grey foamed glass results; in this case, heat-resisting inorganic pigments, e.g. oxides of Co, Cr and Ti, may be added.  If more than 2 parts organic substance and more than 15 parts alkali metal silicate are employed, a dark grey to black foamed glass results; the ground waste of which may be used instead of the pregranulate, i.e. the ground glass moistened and roasted as above, for repeated inflation, for which purpose the inflating temperature must be 10-20 DEG  C. above the first inflating temperature.  The ground glass may have grain size of up to 0.1-1 mm. mixed with at least 10% particles of 0.035 mm.  Roasting may be performed at 300-600 DEG  C., e.g. in a rotary kiln.  On cooling, the resultant pregranulate consists of agglomerated ground glass particles covered by a crust containing water-glass and carbon. Before further processing, this pregranulate may be ground, e.g. to particle size of less than 0.5 mm., or crushed, e.g. to particle size of 1-2 mm. Inflation may be performed by rapid heating to 660-760 DEG  C., followed by slow cooling.  The roasting and inflating steps may be separate or combined.  Before the inflating step, to the pretreated, roasted, ground glass may be added up to 30% by weight of untreated ground glass, ground foamed glass waste, ground basalt or ground slag, or up to 60% by volume of lightweight, heat-resisting admixtures, e.g. expanded mica or perlite, or inflated clay; such admixtures are preferably previously wetted with dilute water-glass solution.  Shaped bodies of foamed glass may be obtained without closed moulds or pressure. They may be obtained in continuous blocks, or formed without moulds. Particles with predetermined size may be obtained by wetting porous inorganic particles stable at inflating temperature, e.g. perlite or vermiculite, with the aqueous solution of alkali metal silicate and organic substance, followed by dusting with ground glass.  The products are moisture-tight and gas-tight, and may be mixed with bitumen for thermal insulation purposes.  The initial mixture may be pressed, e.g. by extrusion, in the moist state to form uniform small compacts, e.g. of diameter 1-2 mm.  The pre-granulate formed from these compacts is then inflated to form spheroidal foamed glass particles.  Before roasting, compacts may be covered with fine, dry, ground glass, e.g. by tumbling.  Any dust obtained may be wetted with 5-20% of water-glass solution deleted 1: 1, reformed into compacts and roasted.  Heating to inflation is preferably performed by contact with a liquid bath surface at 800-900 DEG  C.  The bath liquid may be a metal, e.g. lead or aluminium. To prevent agglomeration, the compacts may be dusted with or embedded in a powder incompatible with both the glass and the bath liquid, e.g. graphite, petroleum coke, Portland cement, sintered corundum, bentonite or a mixture thereof.  The compacts may be conveyed along the bath by a conveyer belt above the bath surface by a periodically emerging submerged screen, or by electrically induced circulation of the bath metal through a furnace zone.  The compact layer preferably has a height of one particle; if the particles are dusted, however, the layer may have a greater height; in this case, motion within the layer is preferably provided.  If piling-up of particles on inflation is to be avoided, the particles should not initially cover the entire bath surface. The particles may then be passed through a zone to cool them 20-30 DEG  C. below the strain point of the glass.  The particles may then be introduced into moulds with or without previous quenching.  The outer skin of the particles is not thicker than an internal cell wall and may contain microcells.  The diameter of the particles may be e.g. 1-10 mm.  The spheroidal foamed glass particles may be used in bulk as thermal and sound insulating filler for cavities, or in the form of heat insulating slabs or blocks.  They may be embedded in glass foam, by placing them in open or closed moulds with or without wetting with a solution of alkali metal silicate and an organic substance followed by dusting with ground glass, and are then reheated so that they are inflated and agglomerate to form a moulded body.  Or the particles may be embedded in artificial resin foam, e.g. of polystyrene, phenolic resin, polyester or polyether; either resin or particles may form a major part of the insulating material.