GB1244832A - Strengthening glassware - Google Patents

Abstract

1,244,832. Surface-treating glass. UNITED GLASS Ltd. 26 Sept., 1968 [4 Oct., 1967], No. 45235/67. Heading C1M. A glass article is treated, on at least one surface, at a temperature between the strain and softening points of the glass, with an acid gas (e.g. HCl, SO 2 , SO 3 ) to remove Na ions from the glass and deposit a sodium salt on the glass surface, then causing the glass at and adjacent the surface to undergo dehydration, treating with an organo-metallic compound of high decomposition temperature and then causing the organo-metallic or a decomposition product thereof to diffuse into the surface of the article, and finally annealing and cooling. Thus an article is formed wherein there is an outer layer richer in SiO 2 than the interior of the glass, and a surface layer containing a metal dispersed through it. The acid gas may be applied as a solid which decomposes at the temperature used, e.g. NH 4 Cl (NH 4 ) 2 SO 4 . The organo-metallic is preferably of tin or titanium, and is preferably formed from SnCl 4 and lower alcohols, e.g. isopropyl alcohol, or other organic liquids, e.g. butyl acetate. Triethanolamine titanate, titanium lactate, butyl hexylene glycol titanate or the reaction product of TiCl 4 or TiBr 4 and an alkoxide of titanium, e.g. Ti(OR) 4 , may also be used. The sodium salt deposit may be removed prior to the dehydration, preferably by maintaining at the required temperature in a dry, chloride-free atmosphere. The dehydration is carried out by keeping in a dry atmosphere. Similarly, the organo-metallic is caused to diffuse into the glass by maintaining for at least 5 minutes at the process temperature. A surface layer of metal oxide may be provided by exposing the article, after treatment with the organo-metallic, at a temperature above 450‹ C. or the strain point, whichever is the greater, to the vapour of a metal compound which will deposit as the metal oxide, e.g. SnCl 4 , TiCl 4 .