Strengthening of thin-walled, light glass containers
AssigneeYamamura Glass Co., Ltd.
InventorMuneo Watanabe
Life of this patent
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Abstract
Thin-walled, light glass containers formed by the press and blow process may be strengthened by (1) exposing the internal surface of said containers to the action of an agent capable of decreasing the amount of extractable alkali from said surface at an elevated temperature immediately after the blowing process but before the annealing process; (2) passing the containers through the annealing station; and (3) subjecting the external and internal surfaces of said glass containers to a treatment of exchanging sodium ions in the surface portion with potassium ions to form a compressive stress layer in said surface portion.
Claims6
In a process for strengthening thin-walled, light containers made of soda-lime glass comprising the steps of molding said containers by the press-and-blow process, annealing the glass containers and thereafter exchanging sodium ions present in the surface portion of the external surface and the internal surface of said containers with potassium ions to form a compressive stress layer in said surface portion, the improvement which comprises the pretreatment step of placing a compound selected from the group consisting of elemental sulfur, sulfur dioxide, ammonium chloride, ammonium sulfate, aluminum chloride, water, a fluorine-containing substance and a mixture thereof into the interior of said containers immediately after the molding step but before the annealing step at an elevated temperature so that only said internal surface of said containers reacts with the gas generated from said compound at said elevated temperature to decrease the amount of extractable alkali on said internal surface.
Dependencies are inferred from the claim text.