Single sided sealable biaxially oriented coextruded polyester film useful for flexible packaging, has at least one base layer polyester thermoplastic, sealable top layer, and matt top layer with specific properties

摘要

A single sided, sealable biaxially oriented coextruded polyester film having at least one base layer (B) containing at least 80 wt.% thermoplastic polyester, a sealable top layer (A), and a matt top layer (C), where: (a) layer A has a starting sealing temperature of less than 120 deg C, a seal seam strength of at least 1.0 N/25 mm of film width, a maximum Ra value of 100 nm, and a surface gas flow measurement value of 20-4000 s is new. A single sided, sealable biaxially oriented coextruded polyester film having at least one base layer (B) containing at least 80 wt.% thermoplastic polyester, a sealable top layer (A), and a matt top layer (C), where: (a) layer A has a starting sealing temperature of less than 120 deg C, a seal seam strength of at least 1.0 N/25 mm of film width, a maximum Ra value of 100 nm, and a surface gas flow measurement value of 20-4000 s; (b) the matt top layer C has a maximum glaze of 100, a minimum Ra value of 150 nm, and a surface gas flow measurement value of 0-80 s; and (c) ess than 50% turbidity. An Independent claim is also included for: preparation of the film by coextrusion, where the individual A, B, and C layers of polymer or polymer mixture are compressed and liquefied in an extruder, if necessary with addition of additives, pressing of the melt simultaneously through a flat nozzle, feeding of the multilayer melt to one or more rollers, with cooling of the melt and fixing of the melt to a prefilm, which is biaxially prestretched, heat fixed, and, if necessary, corona or flame treated. The film is stretched longitudinally at 80-130 deg C, and transversely at 90-150 deg C, at a preferred longitudinal stretching ratio of 3:1 to 5,5:1, and a preferred transverse stretching ratio of 3.5:1 to 4.5:1.