Improved electrostatic pinning method

摘要

A process for improving adhesion of a thermoplastic polymeric resin on a casting surface by using an electrostatic pinning wire in conjunction with a conductive shield. The method includes the steps of extrusion casting a sheet of molten polymer from a die, directing the cast sheet onto a moving, chilled and electrically grounded casting surface to solidify the polymer and extending a conductive wire transverse to a longitudinal axis of the sheet with the sheet between the wire and the chilled surface before the sheet contacts the chilled surface. An elongated conductive uninsulated shield parallel to the wire with the wire between the shield and the sheet is provided and a bias voltage is applied to the wire and the shield. The bias voltage of the wire is in the range of 6 to 15 kV, and the bias voltage of the shield is adjusted to be at least 5 kV lower than the voltage of the wire to maintain a desired current flowing from the wire and the shield to the sheet.