Process of impregnating an assembled corrugated container board

Claim 1

THE PROCESS OF IMPREGNATING AND ASSEMBLED CORRUGATED CONTAINER BOARD HAVING A FIBROUS OUTER LINER ELEMENT, A FIBROUS CORRUGATED INNER ELEMENTS, AND OIL-INSOLUBLE ADHESIVE UNITING SAID ELEMENTS, WHICH PROCESS COMPRISES FIRST DISTRIBUTING ONLY OVER THE OUTER SURFACE OF THE FIBROUS OUTER LINER ELEMENT A LIMITED AMOUNT OF THERMOPLASTIC COATING MATERIAL, SAID AMOUNT NOT BEING IN EXCESS OF THAT FREE OUTER SURFACE ON SAID NOARD, SAID THERMOPLASTIC MATERIAL CONTAINING A MAJOR PERCENTAGE OF COATING MATERIAL WHICH BECOMES FLUID AT TEMPERATURES BELOW THE BURNING TEMPERATURE OF THE BOARD AND WHICH IS SOLID AT AMBIENT TEMPERATURE, AND THEN SUBJECTING THE COATED BOARD IN AIR TO A TEMPERATURE ABOVE THE MELTING POINT OF THE FLUIDIZABLE COATING MATERIAL SO AS TO LIQUIFY THE SAME, MAINTAINING THE BOARD AT SAID ELEVATED TEMPERATURE IN AIR FOR A PERIOD OF TIME SUFFICIENT TO ENABLE THE FLUIDIZED COATING MATERIAL TO MIGRATE FROM THE OUTER SURFACE OF SAID LINER ELEMENT THROUGH THE ADHESIVE AND INTO THE CORRUGATED INNER ELEMENT TO PROVIDE A FINISHED CORRUGATED CONTAINER BOARD HAVING A UNIFORM DISTRIBUTION OF SAID FLUIDIZABLE COATING MATERIAL THERETHROUGH, THE OUTER SURFACE OF SAID OUTER LINER ELEMENT BEING ESSENTIALLY FREE OF A COATING OF SAID COATING MATERIAL.