Abstract: A process for manufacturing heat-sealed proofed paper solely using a Fourdrinier machine for paper or card with one or more layers, wherein the paper or card leaving the dry section of the Fourdrinier machine, forms a continuous layer with heat-sealing and impermeable properties, by utilizing polyolefin synthetic fibers in a layer scattered uniformly and heated at the top surface of the layer to around melting temperature of the polyolefin fibers in a further heating step after a drying step. Then the polyolefin layer while close to the melting temperature of the polyolefin fibers is pressed between calender rollers until interpenetration and contact has taken place, and then cooled at the exit of the calender rollers.