Method of treating, corrugating and laminating a flexible absorbent sheet material

Claim 1

IN A METHOD OF TREATING AN ELONGATED PIECE OF FIBERBOARD FROM A PLURALITY OF FLEXIBLE ABSORBENT SHEETS OF CELLULOSIC MATERIAL, THE STEPS WHICH COMPRISE CONTINUOUSLY MOVING ONE OF SAID SHEETS OVER A GENERALLY CYLINDRICAL SUPPORTING SURFACE HAVING A CORRUGATED FORMATION, PROVIDING A LIQUID TREATING BATH CONTAINING AN AQUEOUS UNREACTED MIXTURE OF (1) A SUBSTANCE OF THE GROUP CONSISTING OF UREA AND GELATIN AND (2) FORMALDEHYDE, SAID COMPOSITION BEING KEPT AT A PH BETWEEN 2.2 AND 4.5 WHEN SAID SUBSTANCE IS GELATIN AND BETWEEN ABOUT 4.0 AND 6.8 WHEN SAID SUBSTANCE IS UREA, WHEREBY SAID SUBSTANCE AND FORMALDEHYDE REMAIN UNREACTED IN THE PRESENCE OF WATER, FLOWING A STREAM OF STEAM PAST SAID BATH AND CONSTRICTING THE FLOW OF STEAM TO CREATE A VENTURI EFFECT THEREIN; WITHDRAWING MIXTURE FROM SAID BATH AND UNIFORMLY ENTRAINING SAME IN SAID STEAM FLOW BY MEANS OF SAID VENTURI EFFECT, THE AMOUNT OF COMPOSITION WITHDRAWN FROM SAID BATH AND ENTRAINED IN SAID STEAM BEING AUTOMATICALLY REGULATED BY THE AMOUNT OF STEAM PASSING THROUGH SAID CONSTRICTED FLOW; DIRECTING A JET OF STEAM CONTAINING SAID MIXTURE AGAINST SAID SHEET WHILE SAID SHEET IS SUPPORTED BY SAID CORRUGATED SURFACE, SAID STEAM BEING UNDER PRESSURE AND FLOWING AT A HIGH VELOCITY AGAINST THE SURFACE OF SAID SHEET, WHEREBY THE SHEET IS IMPREGNATED WITH A SUBSTANTIALLY UNIFORM ESSENTIALLY UNREACTED MIXTURE OF SAID SUBSTANCE AND FORMALDEHYDE, CONTINUOUSLY ADHERING SUBSTANTIALLY FLAT SHEETS TO OPPOSITE SIDES OF THE SHEET CONTACTED BY SAID STEAM, SUBSTANCE AND FORMALDEHYDE, AND THEN HEATING SAID SHEET TO DRY SAME AND CONTINUING SAID HEATING IN THE DRY CONDITION TO CAUSE A CONDENSATION REACTION OF SAID SUBSTANCE AND FORMALDEHYDE TO FORM A RESIN IN SITU UNIFORMLY DISPERSED IN SAID SHEET.