Process for manufacturing form board for casting concrete

Claim 1

A PROCESS FOR THE MANUFACTURE OF OIL-HARDENED WOOD FIBRE BOARD SUITABLE FOR USE AS FORM BOARD IN THE CASTING OF CONCRETE WHEREIN THE WOOD FIBRE MATERIAL AFTER IT IS FORMED INTO A FIBRE FELT AND IS STILL WET IS TREATED WITH AN IMPREGNATING AGENT AND IS THEN SUBJECTED TO A PRESSING AGAINST A POLISHED PLATE, WHICH COMPRISES: (A) APPLYING TO ONE FACE ONLY OF THE WET FIBRE FELT AN IMPREGNATING AGENT CONSISTING OF A DISPERSION OF A HARDENABLE OIL AND AN ALKALI RESISTANT THERMOSETTING PLASTIC, (B) HOT PRESSING THE IMPREGNATED FELT AGAINST A POLISHED PLATE ON THE SIDE OF THE FELT PROVIDED WITH SAID AGENT AT A TEMPERATURE SUFFICIENTLY ELEVATED TO HARDEN THE IMPREGNATED PRESSED BOARD, (C) THE SIDE OF THE FELT FACING THE POLISHED PLATE BEING MADE ACID IN REACTION AT LEAST PRIOR TO COMPLETION OF THE PRESSING STEP, (D) THE VISCOSITY OF THE HARDENABLE OIL IN THE DISPERSION BEING FROM ABOUT 200 TO 800 CP. AT 20*C., (E) THE VISCOSITY OF THE THERMOSETTING PLASTIC BEING OVER5000 CP. AT 20*C., (F) WHEREBY THE HARDENABLE OIL IN SAID DISPERSION PENETRATES THE FELT AND IS DISTRIBUTED SUBSTANTIALLY HOMOGENEOUSLY THROUGHOUT WHILE THE THERMOSETTING PLASTIC FORMS A COHESIVE WATER-IMPERMEABLE ALKALI-RESISTANT COATING ON THE POLISHED FACE OF THE FIBRE BOARD, THEREBY PRODUCING A BOARD CONTAINING FROM ABOUT 3 TO 12% OF THE HARDENABLE OIL AND FROM ABOUT 0.5 TO 10.0% OF THE THERMOSETTING PLASTIC BASED ON THE WEIGHT OF THE DRY FIBRE MATERIAL IN THE FINISHED FIBRE BOARD.