Impregnated corrugated sheets for packing boxes and method of manufacture

Abstract From the Canadian patent

The medium and liners of a water resistant containerboard are each essentially completely impregnated by a liquid water resistant agent which also uniformly coats the surfaces of the medium and liners with a layer sufficiently thick to cover the outer extremities of fibers protruding from such surfaces. The coating and impregnation is accomplished by feeding a flat untreated corrugated containerboard in the direction of its open flutes and in a continuous movement into and out of a hot melt bath of the water resistant agent at a controlled speed sufficient to force the liquid agent through the flutes of the containerboard to as to assure exposure of all surface portions of the board to the …