Production of fiberboard containing mineral fiber

Claim 1

IN THE METHOD OF FORMING A FIRE-RETARDANT MINERAL FIBER BOARD BONDED BY A BINDER CONSISTING ESSENTIALLY OF DRIED GELATINIZED STARCH BY CONTINUOUSLY DEWATERING AN AQUEOUS SLURRY CONTAINING SAID STARCH AS RAW STARCH GRAIN SYNTHETIC MINERAL FIBERS AND A SMALL QUANTITY OF ASBESTOS FIBERS AND THEREBY FORMING A WET FIBER MAT, THE IMPROVEMENT IN WICH SAID SLURRY CONTAINS SOLIDS CONSISTING ESSENTIALLY OF FROM 5 TO 20 PARTS OF SAID RAW STARCH GRAINS AND FROM 77 TO 100 PARTS OF FELTABLE FIBERS OF WHICH 77 TO 90 PARTS ARE MINERAL FIBERS, IN TURN CONSISTING OF 75 TO 80 PARTS OF SYNTHETIC MINERAL FI BERS AND FROM 2 TO 15 PARTS OF ASBESTOS FIBERS FOR RETAINING AT LEAST 80% OF SAID STARCH GRAINS IN DEWATERING, ANY REMAINDER BEING SUBSTANTIALLY UNHYDRATED CELLULOSE FIBERS, GELATINIZING THE STARCH GRAINS IN SITU IN THE WET MAT BY HEATING THE WET MAT THROUGHOUT TO AT LEAST THE GELATINIZNG TEMPERATURE FOR THE STARCH, AND DRYING THE RESULTING WET MAT CONTAINING SAID GELATINIZED STARCH AS BINDER FOR THE FIBERS.