Method for recovering flatness of web material and apparatus therefor

摘要

The present invention provides a method for recovering flatness of a web material (20) which comprises heating a side edge portion (21) of the web material at a temperature in a range from a glass transition temperature minus 40 DEG C to a melting point of the web material for a period of from 1 to 600 seconds, and an apparatus for recovering flatness of a web material which comprises a plurality of conveying rollers (31,32) for conveying the web material and a side edge portion heating means (40,50) which surrounds and heats the side edge portion of the web material traveling through conveying rollers. According to the method and apparatus, the side edge portion(s) elongated by the previous heat treatment is recovered to a state similar to the central portion by reheating to correct the side edge portion(s), and thereby, flatness of the web material can be improved.