GB1533686A - Method of chemically strengthening glass containers - Google Patents

Abstract

1533686 Chemically strengthening glass containers YAMAMURA GLASS KK 18 April 1977 [4 June 1976] 16006/77 Heading C1M A method of chemically strengthening a glass container comprises applying to the outer surface and inner surface of the glass container an aqueous solution of mixed potassium salts consisting of potassium nitrate and at least one potassium salt selected from potassium chloride and potassium sulphate, the temperature of the glass being lower than that of the aqueous solution thereby depositing out the potassium salts on the outer surface and inner surface of the glass container by virtue of the temperature difference to form a potassium salt adhered layer, then drying the container, holding the glass container at an elevated temperature below the strain point of the glass but as near the strain point as possible for a period of time sufficient to cause replacement by ion exchange of cations in the glass container by potassium ions so that a compressive stress layer is formed on the outer surface and inner surface of the glass container, the proportion of potassium nitrate to at least one potassium salt selected from potassium chloride and potassium sulphate used to form the potassium salt adhered layer being such that when the layer is heated at the aforementioned elevated temperature 10-80% by weight of the potassium salts are present in the solid phase, thereby preventing the fused potassium salts from flowing from the surfaces of the glass container, cooling the glass container to room temperature and removing the residual potassium salts. The glass container may previously have been subjected to a coating of a metal oxide having a high abrasion resistance, e.g. tin oxide and titanium oxide.