GB1136498A - Manufacture of sealing glasses - Google Patents

Abstract

1,136,498. Sealing glass. OWENS-ILLINOIS Inc. 25 Aug., 1966 [17 Nov., 1965],No. 38167/66. Heading C1M. A glass comprising 70-80% PbO; 10-15% ZnO; 7-10% B 2 O 3 ; 1-3% BaO and 1-3% SiO 2 , for sealing glass to glass for cathoderay tubes is produced by blending a glass batch comprising lead oxide, zinc oxide, boric acid, barium carbonate and silica sand or compounds containing oxides of the said elements; melting and fining the batch constituents into a uniform homogeneous molten mass under oxidizing conditions in a substantially enclosed noble metal lined melting chamber; continuously discharging and air dividing a stream of molten glass so produced into discrete individual droplets; pressing the droplets between a pair of cooled rolls into flattened chips; grinding the chips into powder form; screening, regrinding and rescreening oversize particles and intimately blending and rescreening the powder form into a uniform sealing glass product having a fineness less than 100 U.S. mesh. The sealing glass batch may be melted in a closed-system platinum alloy melter to reduce volatile loss; the oxidizing atmosphere may be produced by introducing oxygen into the batch and fining zones of the melting chamber; the discharging molten sealing glass may be air-cooled, rolled, maintained dry and out of contact with water; the chips may be water-free and have a thickness of 0À02 to 0À03 inch; the screened powder may be magnetically separated to remove metallic constituents and the melting chamber may comprise a platinum -rhodium vessel having an external alumina wash followed by alumina silica fibrous layers which is then cast in a refractory.