| 摘要 |
Synthetic polymer films are stretched lengthways by applying tension to the film as it moves forward continuously, over a stretching zone determined as to its length, by adjacent, cntrariwise-running cylinders, rotating on parallel axes at right angles to the line of motion; the length of the stretching zone measured at right angles to the cylinders being less than the sum of their radii. When the film is heated to its stretching temp., the first contrariwise-running cylinder is also raised to this temp., whilst the second is held at a lower temp. Each cylinder has a surface coating to which the film will not adhere. Longitudinal stretching takes place at high speed without any significant reduction in the film width. |
