Patent GB-1450012-A (GB)
Title: Process for the production of free-flowing hollow beads
IPC: B29C67/00
Filed: 1975-04-03
Abstract: 1450012 Coated free flowing hollow beads BAYER AG 3 April 1975 [6 April 1974] 13651/75 Heading B2E [Also in Division C3] A process for preparing free flowing hollow beads of thermoplastic plastics, e.g. ethylene/ vinyl chloride, with an apparent density of 0.005 to 3.0 g/cc, a diameter of 11 u to 6 mm and a non-perforated surface comprises mixing the hollow heads, which have a water content of 10 to 2000% based on dry hollow beads, with an aqueous solution or dispersion of adhesive and then separating the paste into a free flowing mixture by adding 0.05 to 5.0 parts of a water insoluble dry powder per part of dry hollow beads. The beads may be of polymers and copolymers of styrene, acrylic and methacrylic acid esters, acrylonitrile, methacrylonitrile. vinylidene chloride, vinyl pyrolidone, vinyl chloride, vinyl bromide, vinyl fluoride, ethylene, propylene, butene, methyl pentene, vinyl acetate, butadiene, chlorobutadiene. Other suitable polymers include alpha-olefin-SO 2  copolymers, e.g. 1:1 butene/SO 2  and copolymers of maleic anhydride or maleic acid semi-ester. Suitable adhesives include glues, ureaformaldehyde or melamine-formaldehyde condensates, ethylene polymers, e.g. polyvinyl pyrrolidone, polyvinyl alcohol, partially hydrolysed vinyl acetate polymers and copolymers, maleic anhydride copolymers, acrylic acid polymers, acrylamide polymers, cellulose derivatives such as methyl cellulose and carboxyalkyl cellulose, gelatin, starch, sugar syrup, alginates, gum arabic, vegetable mucosa, e.g. tragacanth, rape oil, molasses, agar agar, polygalactouronic acid, water soluble peptides and proteins. Waterdispersible adhesives include polyepoxide emulsions, ionic and non-ionic polyurethane emulsions, olefinic polymer emulsions, e.g. vinyl acetate polymers and copolymers, polymers of ethylene, propylene, vinyl chloride, acrylonitrile, butadiene, chlorobutadiene and acrylic acid alkyl esters. Cross linking or self cross linking groups may be present. Inorganic adhesives such as water glass may be used. Powders which may be employed in the second coating step include crushed oxidic ores, pyrogenic or precipitated silicas, precipitated chalk, magnesium carbonate, kaolin, talcum, asbestos, zinc oxide, barium sulphate, calcium sulphate, bismuth salts, cement dust, metal stearates, iron oxides, aluminium phosphate, water insoluble metal phosphates, alum, ion exchange resins, zeolites, crushed glass, ground sand, quartz, minerals, rocks, enamel frit, carbon, graphite, diamond and metal carbide. Metal powders may be used, e.g. bronzes, aluminium bronze, copper bronze, palladium, silver, gold, iron, nickel, chromium, hafrium, cobalt, platinum, irridium, zinc, cadmium, molybdenum, tungsten and manganese. Organic powders which may be used include epoxy resins, acrylates, polyesters, polyvinyl chloride, polyethylene, polyamides and ethylene/vinyl acetate copolymers. Other suitable powders include sawdust, peat, waxes, seed grains, pollens, inorganic white and coloured pigments ,such as lithopones, sulphides, titanium dioxide, phthalocyanines azo compounds, chromium and lead pigments. The powdered beads may be used in lightweight building components, packings for heat insulation, as a filler for breaking up garden soil when fertilisers, growth promoters and pesticides may be added, as in ion exchanges or molecular sieves and catalysts particularly for use in fluidised beds. They are readily kept suspended due to their large surface and low weight.