| 摘要 |
PROBLEM TO BE SOLVED: To obtain a polyester film improved in impact cracking resistance, thermal embrittlement resistance, retorting resistance, rustpreventive properties and flavor retention by biaxially orienting an aromatic polyester. SOLUTION: An aromatic polyester prepared by using an acid component based on an aromatic dicarboxylic acid, a glycol component based on ethylene glycol and containing at most 5mol% diethylene glycol as a comonomer component and a polycondensation catalyst being a germanium compound and having a melting point of 210-245 deg.C, a secondary transition point of 60 deg.C or above and an intrinsic viscosity of 0.52-1.50 is mixed with fine inert particles having an aspect ratio of 1.0-1.2 to obtain a composition. This composition is thoroughly dried, fed into an extruder and melt-extruded onto a casting drum to obtain an unoriented film. This film is biaxially oriented at a draw ratio of 2.5-4.0 to obtain a polyester film for lamination with metallic sheets or plates, having the following properties: the total amount of the alkali metals in the film is equal to or larger than 5ppm, 20<=M+P<=55 (wherein M is the concentration (mmol%) of the catalyst metals in the film; and P is the concentration (mmol%) of phosphorus atoms in the film); and 1<=M/P<=5. |
