Patent ID: 8048353
Filing Date: 2011-11-01
Classification: B32B,E04C,Y10T

Abstract:
1. A process for the production of a multilayer polymeric product which comprises a coextruded internal central layer of a first blend of polyethylene terephthalate (PET) copolymer, in a quantity ranging from 80 to 90% by weight with respect to the total weight of the internal layer, mixed with polycarbonate (PC), in a quantity ranging from 10 to 20% by weight with respect to the total weight of the layer, and two outer, side layers, of a second blend of PET, in a quantity ranging from 15 to 25% by weight with respect to the total weight of the outer layers, and PC, in a quantity ranging from 75 to 85% by weight with respect to the total weight of said outer layers, said process comprising the following phases: i) subjecting PET, optionally containing additives, to crystallization drying and regradation; ii) subjecting PC, optionally containing additives, to drying; iii) blending the PET and PC at a temperature ranging from 80 to 140° C. to form the blends; iv) drying the first blend, optionally containing additives; v) charging the first blend into the main extruder and extruding said first blend to give the internal layer at a pressure ranging from 70 to 450 atm and a temperature ranging from 250 to 350° C.; vi) drying the second blend, optionally containing additives; vii) extruding the second blend to give the two outer layers; viii) converging and stabilizing the three layers in a coextruder where they are coextruded at an increasing pressure from 70 to 450 atm and a temperature varying from 230 to 270° C. to give a multilayer product; ix) calendering and thermoforming the multilayer product using by-step thermal cycles within a range from 10 to 140° C.