BIAXIALLY STRETCHED POLYAMIDE FILM AND PREPARATION THEREOF

摘要

PURPOSE:To obtain a film hard to generate distortion when a prepared bag product is heat- treated by hot water by a method wherein the hot water shrinkage factor of a film at 100 deg.C after heat-setting in all of planar directions is made specific with respect to all of the positions of the film in the lateral direction thereof and the anisotropy H(%) of the specific hot water shrinkage factor is set to 30% or less over the total width of the film. CONSTITUTION:When a biaxially stretched film low in blowing is thermally set in a flat state, said film is closely adhered to the surface of a body heated to temp. lower by 10-40 deg.C than the m.p. of the film in such a state that both ends of the film are grasped to be heated to a proper temp. range and immediately brought into contact with a cooling roll to be quenched to the Tg of the film or less. The obtained film has characteristics such that the hot water shrinkage factor of the film at 100 deg.C in all of planar directions is 5.0% or less with respect to all of positions in the lateral direction of the film and the anisotropy H(%) of the hot water shrinkage factor calculated according to formula is 30% or less over the total width of the film. A packing bag formed by using a film whose anisotropy H(%) exceeds 30% is large in distortion and not pref. practically because the appearance of the film is extremely damaged. A bag wherein H(%) is 20% or less is low in distortion and pref. because there is no trouble practically. In the formula, S45 and S135 show hot water shinkage factors at 100 deg.C in the directions of 45 deg. and 135 deg. to the left from MD.