Coated polymeric thermoplastic sheet material

Claim 1

A STRONG, FLEXIBLE, DIMENSIONALLY STABLE SHEET MATERIAL WHICH IS CAPABLE OF WITHSTANDING REPEATED CREASING EVEN AT EXTREMELY LOW TEMPERATURES AND WHICH HAS A GRAPHITE- AND INK-RECEPTIVE SURFACE FROM WHICH GRAPHITE MARKS CAN BE ERASED WITHOUT SUBSTANTIAL INJURY THERETO, SAID SHEET METAL BEING CAPABLE OF RETAINING ITS DESIRABLE PROPERTIES EVEN WHEN EXPOSED TO ULTRAVIOLET LIGHT, WATER, ALCOHOLS, HYDROCARBONS, ESTERS, AND KETONES AT A WIDE RANGE OF TEMPERATURES, SAID SHEET MATERIAL COMPRISING A POLYALKYLENE TEREPHTHALATE FILM COATED ON AT LEAST ONE SURFACE WITH A FILM-FORMING PIGMENT-CONTAINING RESIN COMPRISING THE FLEXIBLE CURED REATION PRODUCT OF REACTANTS CONSITING ESSENTIALLY OF A POLYFUNCTIONAL ISOCYANATE AND A POLYOL SELECTED FROM THE GROUP CONSISTING OF POLYESTERS AND POLYESTER, SAID POLYOL HAVING AN ALIPHATIC HYDROXYL CONTENT OF BETWEEN 0.1% AND 8% AND AN ACID NUMBER LESS THAN 5, SAID POLYOL BEING PRESENT IN AMOUNTS SUFFICIENT TO PROVIDE UP TO ABOUT 0.5 HYDROXYL GROUP PER ISOCYANATE GROUP SUPPLIED BY SAID POLYFUNCTIONAL ISOCYANATE.