Fire retardant safety glass

US5656558A · kind A · utility

Assignee

• Schott Glaswerke · DE

Inventors

• Peter Brix · Mainz, DE
• Werner Kiefer · Ingelheim am Rhein, DE
• Roland Leroux · Stadecken-Elsheim, DE

Key dates

• Filing date: Aug 1, 1994
• Grant date: Aug 12, 1997
• Expiry date: Aug 1, 2014

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C03C3/093
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

Hard glass fire retardant glasses can be tempered in a conventional air tempering plant having heat transmission values of approximately 200-500 W/(m.sup.2 .times.K) yielding in the tempered state a fire resistance period of at least 30 minutes according to DIN 4102 and the safety properties according to DIN 1249 (safe break). In order to achieve the combination of fire resistance period and safety properties, the glasses must have a coefficient of thermal expansion .alpha..sub.20/300 of between 3 and 6.times.10.sup.-6 K.sup.-1, a specific thermal stress .psi. of between 0.3 and 0.5N/(mm.sup.2 .times.K) , a glass transitione temperature Tg of between 535.degree. and 850.degree. C., a product of specific thermal stress .psi. multiplied by (Tg -20.degree. C.) of between 180 and 360N/mm.sup.2, an upper annealing temperature (temperature at a viscosity of 10.sup.13 dPas) of over 560.degree. C., a softening temperature (temperature at a viscosity of 10.sup.7.6 dPas) of over 830.degree. C. and a working temperature (temperature at a viscosity of 10.sup.4 dPas) of below 1300.degree. C.