Method of calendering sheet material

Claim 1

IN A METHOD OF FORMING A SHEET FROM A THERMOPLASTIC MASS, THE STEPS COMPRISING DELIVERING TO THE NIP BETWEEN A PAIR OF CALENDERING ROLLS A MASS OF THERMOPLASTIC MATERIAL HEATED TO A TEMPERATURE ABOVE 212*F., AT WHICH SAID HEATED MASS IS PLASTIC AND MAY BE SHEETED BY CALENDARING, THE FACE-FORMING ROLL OF SAID CALENDAR BEING MAINTAINED AT A TEMPERATURE AT WHICH SAID HEATED MASS WOULD NORMALLY ADHERE UNDER CONSOLIDATING PRESSURE IN SHEET FORMATION, INTERPOSING A FILM OF AN AQUEOUS WAX EMULSION BETWEEN THE SURFACE OF THE FACE-FORMING ROLL AND SAID HEATED MASS UNDER TREATMENT, SAID HEATED MASS BEING NONADHERENT TO SAID FACE-FORMING ROLL WITH SAID INTERPOSED FILM UNDER CONSOLIDATING PRESSURE IN SHEET FORMATION, CONSOLIDATING SAID MASS INTO A SHEET BETWEEN SAID ROLLS WITH SAID FILM OF AQUEOUS WAX EMULSION INTERPOSED BETWEEN SAID FACE-FORMING ROLL AND SAID HEATED MASS, REMOVING WATER FROM SAID WAX EMULSION FILM BY THE APPLICATION OF HEAT THERETO FROM SAID HEATED MASS UNDER CONSOLIDATION, AND REMOVING THE FORMED AND WAX COATED SHEET FROM SAID CALENDAR, ROLLS SUBSTANTIALLY FREE OF CRACKS OR BREAKS IN THE FACE THEREOF.