| 摘要 |
1,025,656. Heat treating oriented films. IMPERIAL CHEMICAL INDUSTRIES Ltd. Sept. 24, 1964 [Oct. 7, 1963], No. 39403/63. Heading B5B. An oriented film of a synthetic organic thermoplastic crystallizable polymeric material is heat-treated in a continuous manner to render it substantially sag-free by causing the film to travel around and in contact with the peripheral surface of a first rotating roll which is maintained at a temperature (below the melting point of the film) which would cause the film to shrink laterally in the absence of any lateral restraint, applying lateral restraint to the film over at least part of its travel round the surface of said first roll whereby the width of the film remains constant, then permitting the film to relax by a controlled amount in at least the longitudinal direction by passing it around at least one second heated roll rotating at a peripheral speed less than that of the first roll and quenching the heat-treated film. The term " oriented film " is defined as a film which has been drawn in one direction to induce molecular orientation in that direction or biaxially in the longitudinal and transverse directions simultaneously or in sequence. Lateral restraint may be applied to the film by holding the edges of the film against the roll by means of two elastomeric surfaces moving in the same direction and at the same speed as the film, the surface being spaced apart laterally with respect to the longitudinal axis of the film. They preferably do not have an independent drive and are driven by the roll via the film. The surfaces may be provided by endless rubber belts of Vee or rectangular cross-section travelling around pulleys. Alternatively lateral restraint may be applied to the film by electrically earthing the peripheral surface of the roll and to deposit an electrostatic charge on the surface of the film which does not contact the roll. The charge may be deposited along the edges of the film at least over the initial part of its travel around the roll, or it may be deposited along a line extending across the width of the film at or near the line where the film first contacts the roll. After passing over the roll, the charged surface of the film is discharged by contacting it with earthing means (or causing it to pass very near to earthing means) before passing it to the next stage of the process. |
