Yamamura Glass Kabushiki Kaisha

Yamamura Glass Co., Ltd.

Muneo Watanabe

In a method of strengthening chemically a glass container comprising applying an aqueous solution of potassium salts to a soda-containing glass container to form a potassium salt adhered layer, holding at an ion exchange treatment temperature for a period of time sufficient, then cooling to room temperature and removing the residual potassium salts, the feature consists in using, as the aqueous solution of potassium salts, a concentrated aqueous solution containing a small amount of surfactant and a high concentration of mixed potassium salts consisting of potassium nitrate having a relatively low melting point and at least one potassium salt having a relatively high melting point selected from the group consisting of potassium chloride and potassium sulfate in such a proportion that 10 to 80% by weight of the potassium salts be present in solid phase, when heated at the ion exchange treatment temperature, to prevent the fused potassium salts from flowing off from the surfaces of the glass container, applying the concentrated aqueous solution to the outer surface and inner surface of the glass container at a temperature of lower than that of the concentrated aqueous solution, causing the potassium salts to deposit on the outer surface and inner surface of the glass container by virtue of the temperature difference, then drying and holding the glass container having the mixed potassium salt adhered layer 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 form a compressive stress layer on the outer surface and inner surface of the glass container.

Method of strengthening chemically a glass container

Thin-walled, light glass containers formed by the press and blow process may be strengthened by

Strengthening of thin-walled, light glass containers

This invention relates to a chemical method of strengthening glass articles subjected to abrasion resistance treatment, which comprises (1) a first step of applying a metal oxide-forming compound to the surface of a heated glass article to form the corresponding metal oxide coating having a thickness of 50 to 130 Angstrom on the surface of the glass article, (2) a second step of causing to adhere, to the outer and inner surfaces of the glass article, a mixed solution of potassium chloride and potassium nitrate, having a potassium chloride to potassium nitrate ratio by weight of 85 to 45:15 to 55, or a mixed solution of potassium sulfate and potassium nitrate, having a potassium sulfate to potassium nitrate ratio by weight of 30 to 100:70 to 0, (3) a third step of holding the glass article 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 obtain a compressive stress layer having a depth of at least 10 microns and a compressive stress of at least 700 kg/cm.sup.2 and (4) a fourth step of cooling the glass article to room temperature and then washing the glass article to remove the mixture of the potassium salts remaining on the outer surface and inner surface of the glass article.

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Nishinomiya, Japan

Muneo Watanabe