Patent ID: 7572399

Claim:
A process for producing cylindrical-shaped polyvinyl butyral interlayer rolls comprising the steps: (a) extruding a polyvinyl butyral interlayer sheet such that the extreme edges of the polyvinyl butyral interlayer sheet are thicker than the middle section of the polyvinyl butyral interlayer sheet; (b) forming a roll from the extruded polyvinyl butyral interlayer sheet by taking up the extruded polyvinyl butyral interlayer sheet onto a wind-up roll such that the edges of the roll initially have a larger circumference than the middle of the roll; (c) allowing the polyvinyl butyral interlayer roll to remain on the wind-up roll for a time sufficient for the circumference of the polyvinyl butyral interlayer roll at the edges to be within 10% of the circumference of the middle of the polyvinyl butyral interlayer roll.