Method of eliminating defects while extrusion coating film using speed control of the nip roll
Assignee3M Innovative Properties Company
InventorsRandy S. Bay, Todd G. Pett, Brent R. Hansen
Life of this patent
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Abstract
It has now been determined that an internal optical defect can be eliminated by controlling the relative speed mismatch between the resilient roll and the casting roll in a film extrusion coating process. In particular, slowing down the surface speed of the resilient roll relative to the casting roll when coating a biaxially orientated film was found to remove the optical defect. Conversely, speeding up the surface speed of the resilient roll relative to the casting roll when coating a uniaxially orientated film was found to remove the optical defect.
Claims7
A method of eliminating an optical defect in an extrusion coated film, comprising:
- conveying a film that is uniaxially or biaxially oriented to a coating station comprising an elastomeric roll nipped with a casting roll and an extrusion coating die adjacent to the nip, in which the surface speed of the elastomeric roll is controlled independently of the surface speed of the casting roll;
- contacting the film with the elastomeric roll while extruding a polymeric material into the nip, in which nip pressure is at least 100 pounds/linear inch (175N/cm), to make a coated film comprising a coated layer of polymeric material on the film;
- and
- adjusting the surface speed of the elastomeric roll to be different from the surface speed of the casting roll to eliminate optical defects in the coated film, such that:
- for uniaxially oriented film, surface speed of the elastomeric roll is adjusted to be greater than the surface speed of the casting roll by no more than 5%;
- and
- for biaxially oriented film, surface speed of the elastomeric roll is adjusted to be less than the surface speed of the casting roll by no more that 5%.
Dependencies are inferred from the claim text.