Quenching of polymeric film
AssigneeImperial Chemical Industries PLC
InventorsRaymond John Latham, Arthur John Holloway
Life of this patent
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Abstract
In the electrostatic pinning of molten polymeric film, especially polyethylene terephthalate film, to a quenching drum, the insulators for those parts of the pinning electrode positioned outside the edges of the film are adjusted to follow the transverse fluctuations which may occur in the film edges so as to prevent sparking between the electrode and the margins of the quenching drum outside the film edges.
Claims5
In a process for casting a molten polymeric film upon an electrically earthed casting surface which comprises passing the film past a pinning wire electrode which extends transversely across the casting surface and is connected to a high voltage electrical source, the pinning wire being supported in spaced relation from the molten film and depositing electrostatic charges upon the molten film from the pinning wire electrode in the proximity of or prior to the region of first contact of the film and the casting surface, the pinning wire electrode being electrically insulated by dielectric insulators located beyond the film edges, the improvement which comprises monitoring the film by means of a sensor for any transverse fluctuations which may occur in the film edges and moving the dielectric insulators along the wire electrode by an amount corresponding to any such transverse fluctuations in response to said sensor whereby sparking between the wire electrode and the margins of the casting surface is impeded.
Dependencies are inferred from the claim text.