| 摘要 |
1501142 Hydrating silicate glass CORNING GLASS WORKS 18 Feb 1975 [25 Feb 1974] 6790/75 Heading C1M A glass body is made by: (a) hydrating a glass body comprising 3-26 mole per cent Na 2 O and/or K 2 O and 50-95 mole per cent SiO 2 , these oxides totalling at least 55 mole per cent, by exposing the glass to a H 2 O-containing gaseous environment having a relative humidity of at least 75% and a temperature of at least 100‹ C., for a period sufficient to develop at least a surface portion essentially saturated with water; and, thereafter (b) dehydrating the glass body by exposure to a gaseous environment whose relative humidity is less than 90% of that in step (a), for a period sufficient to reduce the water content at least in the surface portion, but leaving an amount therein to impart thereto the ability to flow at a lower temperature than the anhydrous glass. The glass may contain 5-35 wt. per cent water after step (a), and 1-12 wt. per cent water at the end of step (b). Step (a) is preferably conducted at from 100‹ C. to the glass softening point for “-96 hours. Step (b) preferably employs a H 2 O partial pressure of less than 100 p.s.i. and a temperature above 200‹ C. for “-72 hours. The environment in step (b) may include an acid gas (e.g. SO 2 , SO 3 ). The H 2 O- containing environment may include air or He, Ar or N 2 . The glass body may be formed with a surface layer having a lower water content than the interior, or with crystals in the surface layer, such that the surface has a lower expansion coefficient than the interior, resulting in a surface compressive layer on cooling. The glass treated may optionally include CaO, ZnO, B 2 O 3 , PbO, MgO, BaO or Al 2 O 3 . The glass produced in the above method may be provided as particles which are shaped into a body under pressure and at 0-500‹ C. The product may be a bottle or in cane form. The shaped product may be strengthened by treatment with an acid gas (e.g. SO 2 , SO 3 or CuCl) at, e.g. 170-300‹ C., or with a molten salt (e.g. LiNO 3 ) at, e.g. 300‹ C. In an alternative embodiment both steps (a) and (b) are conducted at above the glass softening point, to produce a foamed product. |
