Method of stretching films according to an overbias or overstretch stretch profile

US6303067A · kind A · utility

Assignee

• 3M INNOVATIVE PROPERTIES COMPANY · US

Inventors

• Chiu Ping Wong · Windom, US
• Thomas P. Hanschen · Windom, US
• Anthony B. Ferguson · Lake Elmo, US
• William W. Merrill · White Bear Lake, US
• Fred J. Roska · Woodbury, US
• Jeffery N. Jackson · Woodbury, US

Key dates

• Filing date: Nov 13, 1998
• Grant date: Oct 16, 2001
• Expiry date: Nov 13, 2018

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B29C55/16
• WIPO field: Other special machines
• WIPO sector: Mechanical engineering

Abstract

A method of biaxially stretching a polymeric film according to an overbias or overstretch stretch profile to a final first direction stretch parameter and a final second direction stretch parameter to provide a film having uniform properties. First, a sufficiently high temperature is imparted to the film to allow a significant amount of biaxial stretch. The film is then biaxially tenter stretched to a peak first direction stretch parameter that is at least 1.3 times the final first direction stretch parameter wherein the final first direction stretch parameter is no larger than the final second direction stretch parameter. Finally, the film is retracted in the first direction from the peak first direction stretch parameter to the final first direction stretch parameter to produce a film having uniformity of properties in the first direction.