US Patent 7490486 Method for producing borosilicate glasses

Patent 7490486 was granted and assigned to Schott AG on February, 2009 by the United States Patent and Trademark Office.

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Is a

Patent

Patent attributes

Current Assignee

Schott AG

Patent Jurisdiction

United States Patent and Trademark Office

Patent Number

7490486

Date of Patent

February 17, 2009

Patent Application Number

10480183

Date Filed

June 7, 2002

Patent Primary Examiner

‌

Steven P. Griffin

Patent abstract

The process of producing a refined borosilicate glass includes preparing a glass batch with a composition in wt. % on the basis of oxide content of SiO2, 65-82; Al2O3, 2-8; B2O3, 5-13; MgO+CaO+SrO +BaO+ZnO, 0-7; ZrO2, 0-2; and Li2O+Na2O+K2O, 3-10; adding 0.05 wt. % to 0.6 wt. % of sulfate(s) expressed as SO3 to the glass batch as the refining agent; melting the glass batch including the refining agent to form melted glass; and then hot-shaping the borosilicate glass. The refining agent may also include from 0.01 wt. % to 0.6 wt. % of F− or from 0.015 wt. % to 0.6 wt. of Cl−. The sulfate is preferably an alkali metal and/or alkaline earth metal sulfate or sulfates.