Process for the preparation of silica gel and silica aerogels

Claim 2

A PROCESS OF PREPARING A SILICA GEL WHICH COMPEISES INCORPORATING A WATER-SOLUBLE, SUBSTANTIALLY NEUTRAL, THERMALLY DECOMPOSABLE ORGANIC AMMONIA LIBERATING COMPOUND IN AN ACIDIC SILICA SOL HAVING A SILICA CONTENT OF ABOUT 4 TO 15% BY WEIGHT AS A DISPERSED PHASE, A CONTINUOUS LIQUID PHASE COMPRISING WATER AND ABOUT 0.001 TO 3% BY WEIGHT OF A SALT DISSOLVED IN SAID LIQUID PHASE, SAID COMPOUND BEING HOMOGENEOUSLY DISSOLVED IN SAID LIQUID PHASE ON THE SOL, RAISING THE TEMPERATURE OF BY WEIGHT BASED ON THE SOL, RAISING THE TEMPERATURE OF SAID SOL UNIT SAID SOL FORMS A GEL BUT BELOW THE TEMPERATURE AT WHICH SAID COMPOUND DECOMPOSES AND HEATING SAID GEL TO LIBERATE AMMONIA FROM SAID COMPOUND.

Claim 3

A PROCESS OF PREPARING SILICA AEROGELS WHICH COMPRISES INCORPORATING FROM ABOUT 0.005 TO ABOUT 0.15% BY WEIGHT OF A WATER-SOLUBLE, SUBSTANTIALLY NEUTRAL, THERMALLY DECOMPOSABLE ORGANIC AMMONIA LIBERATING COMPOUND IN AN ACIDIC SILICA AQUASOL HAVING A PH OF ABOUT 1.5 TO 4.5, A SILICA CONTENT OF ABOUT 5 TO 15% BY WEIGHT AND CONTAINING LESS THAN 0.001% BY WEIGHT OF METALLIC CATIONS, SAID COMPOUND BEING HOMOGENEOUSLY DISSOLVED IN SAID AQUASOL HEATING SAID SOL IN A CLOSED SYSTEM TO CONVERT IT TO AN AQUAGEL IN SITU BUT AT A TEMPERATURE BELOW THAT AT WHICH SAID COMPOUND DECOMPOSES, HEATING SAID AQUAGEL TO A TEMPERATURE SUFFICIENTLY HIGH TO LIBERATE AMMONIA FROM SAID COMPOUND AND WITHOUT SUBJECTING SAID AQUAGEL TO A SUBSTANTIAL COMPRESSIVE LIQUID-SOLID INTERFACE UNTIL ALL OF THE WATER PHASE OF THE GEL HAS BEEN CONVERTED TO A VAPOR AND SEPARATING SAID VAPOR FROM THE RESULTING GEL.

Claim 4

A PROCESS OF PREPARING SILICA AEROGELS WHICH COMPRISES INCORPORATING FROM ABOUT 0.005 TO ABOUT 0.15% BY WEIGHT OF A WATER-SOLUBLE, SUBSTANTIALLY NEUTRAL, THERMALLY DECOMPOSABLE ORGANIC AMMONIA LIBERATING COMPOUND IN AN ACIDIC SILICA AQUASOL HAVING A PH OF ABOUT 1.5 TO 4.5, A SILICA CONTENT OF ABOUT 5 TO 15% BY WEIGHT AND CONTAINING LESS THAN 0.001% BY WEIGHT OF METALLIC CATIONS, SAID COMPOUND BEING HOMOGENEOUSLY DISSOLVED IN SAID AQUASOL HEATING SAID SOL IN A CLOSED SYSTEM TO CONVERT IT TO AN AQUAGEL IN SITU BUT AT A TEMPERATURE BELOW THAT AT WHICH SAID COMPOUND DECOMPOSES, HEATING SAID AQUAGEL TO A TEMPERATURE SUFFICIENTLY HIGH TO LIBERATE AMMONIA FROM SAID COMPOUND AND WITHOUT SUBJECTING SAID AQUAGEL TO A SUBSTANTIAL COMPRESSIVE LIQUID-SOLID INTERFACE UNTIL ALL OF THE WATER PHASE OF THE GEL HAS BEEN CONVERTED TO A VAPOR AND SEPARATING SAID VAPOR FROM THE RESULTING GEL.