Formation of foamed silicate articles

Claim 1

A method for making an alkali metal silicate glass foam which comprises the steps of: Step (a) subjecting anhydrous glass consisting essentially, in mole percent on the oxide basis, of about 8-23% Na 2 O and/or K 2 O, 1.5-11.5% Al 2 O 3 and/or B 2 O 3 and/or Fe 2 O 3 and/or ZnO, and 65-90% SiO 2 , to a H 2 O-containing gaseous environment having a relative humidity of at least about 75% at a temperature in excess of 100° C., but less than the softening point of the anhydrous glass, for a sufficient length of time to hydrate said glass wherein the amount of water therein will be in excess of 10% by weight; Step (b) exposing fine-dimensioned bodies of said hydrated glass to a temperature in excess of 100° C., but below that of the softening point of the anhydrous glass, and a relative humidity less than 75% of that employed in the hydration process of Step (a) for a sufficient length of time to reduce the water content therein at least 50% and yield individual foam bodies; Step (c) subjecting said foamed bodies to a H 2 O-containing environment having a relative humidity of at least about 50% at a temperature at or below about 250° C., but above about 100° C., for a sufficient length of time to hydrate said glass to a water content in excess of 10% by weight and tightly bond said bodies into an integral mass; Step (d) exposing said integral mass to a temperature in excess of 100° C., but below that of the softening point of the anhydrous glass, and a relative humidity less than 75% of that employed in the hydration process of Step (c) for a sufficient length of time to reduce the water content therein at least 50% and foam said mass.

Claim 2

A method for making an alkali metal silicate glass foam which comprises the steps of: Step (a) subjecting anhydrous glass consisting essentially, in mole percent on the oxide basis, of about 8-23% Na 2 O and/or K 2 O, 1.5-11.5% Al 2 O 3 and/or B 2 O 3 and/or Fe 2 O 3 and/or ZnO, and 65-90% SiO 2 , to a H 2 O-containing gaseous environment having a relative humidity of at least about 75% at a temperature in excess of 100° C., but less than the softening point of the anhydrous glass, for a sufficient length of time to hydrate said glass wherein the amount of water therein will be in excess of 10% by weight; Step (b) exposing fine-dimensioned bodies of said hydrated glass to a temperature in excess of 100° C., but below that of the softening point of the anhydrous glass, and a relative humidity less than 75% of that employed in the hydration process of Step (a) for a sufficient length of time to reduce the water content therein at least 50% and yield individual foam bodies; Step (c) subjecting said foamed bodies to a H 2 O-containing environment having a relative humidity of at least about 50% at a temperature at or below about 250° C., but above about 100° C., for a sufficient length of time to hydrate said glass to a water content in excess of 10% by weight and tightly bond said bodies into an integral mass; Step (d) exposing said integral mass to a temperature in excess of 100° C., but below that of the softening point of the anhydrous glass, and a relative humidity less than 75% of that employed in the hydration process of Step (c) for a sufficient length of time to reduce the water content therein at least 50% and foam said mass.