摘要:
A method and apparatus particularly adapted for impregnating corrugated paperboard with wax, the percentage wax pickup being variable within limits as desired. In operation, a plurality of boards is vertically positioned side-by-side, but slightly separated one from the other, into separate lines of travel. The group of vertically positioned boards is then passed underneath a free-falling, unrestrained cascade of molten wax at a controlled rate to obtain complete flooding or coating of all exterior board surfaces. The cascade is developed in a plane transverse to the boards'' lines of travel. Such flooding also occurs within the boards'' flutes if the flutes are vertical as the boards pass trough the cascade. A first air knife then directs hot air onto the top edges of the vertical boards to remove excess wax from the exterior faces or liners of the boards, as well as from the boards'' interior if the corrugations or flutes are also vertical. The boards then move through a temperature-controlled conditioning section the section being maintained at an elevated temperature, where impregnation takes place. Thereafter, a second air knife directs air onto the bottom edges of the vertical boards to remove excess wax in the form of beads or drips that may be formed toward the bottom of or at the bottom edge of the board. Finally, cool air is blown up through the vertical boards to set the wax and cool the boards for handling and stacking. Depending on the wax used, the temperature of the molten wax, the temperature of the environment immediately after waxing but prior to cooling, and the throughput speed of the board, the board will be either dry waxed or wet waxed. The wax pickup percentage of the boards is controlled mainly by varying wax temperature and board exposure time in the wax-flooding step. The wax distribution in the board is controlled mainly by varying environment temperature and board exposure time in the conditioning step. Thus, the method and apparatus can be controlled to obtain either dry-waxed or wet-waxed paperboard at a desired wax pickup level.
摘要:
Tandem coating of paper web on one side with a clay coat and on the other side with a coating of pressure-rupturable encapsulated materials with the clay coat applied first and with a calender immediately before the coating with the encapsulated materials.