| 摘要 |
601038 Disclosed is a heat-shrinkable multilayer film adapted for deep draw forming, comprising: a surface layer (a) comprising a thermoplastic resin (such as PET), an intermediate layer (b) comprising a polyamide resin, and a surface layer (c) comprising a sealable resin (such as a polyolefin), wherein, (A) the intermediate layer (b) comprises a mixture of an aliphatic polyamide having a melting point of at least 180oC (such as nylon 6 or nylon 6-66), and an amorphous aromatic polyamide comprising a polycondensation product of an aliphatic diamine with isophthalic acid and terephthalic acid as main acid components (such as nylon 6I-6T), including 25-45 wt.% of the amorphous aromatic polyamide, and has a thickness exceeding 25% and at most 50 % of a total thickness of whole layers , and the multilayer film exhibits: (B) tensile stresses at an elongation of 100% as measured in a tensile test at 100oC, including 3-22 MPa in at least one of a longitudinal direction (MD) and a transverse direction (TD) and an average of MD and TD values of 3-20 MPa, and (C) a shrinkage in hot water at 90oC of 3 to 20% in each of MD and TD. Further disclosed is a method for preparing the above film which includes a step of vertically pulling a tubular product while introducing a fluid into the tubular product to stretch the tubular product 2.1 - 2.4 times in the vertical direction and 2.1 - 2.6 times in the circumferential direction to form a biaxially stretched tubular film, folding the tubular film, again introducing a fluid into the folded tubular film to form a tubular film, heat-treating the tubular film from its surface layer (a) side with steam or warm water to provide a relaxation ratio of 20 - 35 % in each of the vertical direction and the circumferential direction, and cooling the heat-treated tubular film to obtain a stretch-oriented multilayer film. |
