Abstract: A method of winding a polymer film web around a cylindrical core, where the core is heated by blowing hot-air against the core prior to winding the polymer film web, and the polymer film web is wound around the heated core while blowing hot-air against the polymer film web. In another embodiment of the winding method, the polymer film is wound while knurled along both edge parts in the width direction of the film to form knurls so as to gradually decrease in the thickness thereof from one end of the film that contacts with the core toward the other end of the film. Furthermore, a heat treating method for annealing a film roll and a heat treating apparatus therefor are disclosed, which method comprises the steps of surrounding the film roll with heat insulating panels and blowing hot-air against the film roll in the direction along the core axis while rotating the core intermittently or continuously at a rotary speed of from 0.04 to 4 revolutions per hour.

Abstract: The present invention provides a method for recovering flatness of a web material which comprises heating a side edge portion of the web material at a temperature in a range from a glass transition temperature minus 40.degree. 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 for conveying the web material and a side edge portion heating means 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.

Abstract: A core for winding a web of plastic film prior to heat treatment of the film is provided with annular collars having a height of 1 to 10 times the thickness of the film.The core includes a rigid cylindrical member of GFRP, CFRP, or a composite structure of metal or heat-resistant resin material and fiber reinforced plastics, and the annular collars provided at the ends of the cylindrical member. The annular collars protect the film from a cut end mark which may be caused by the end edge of the web, degradation of flatness, and slipping with the core while the web wound around the core accepts the heat treatment.