Coextrusion processes for making multilayer films and films made thereby

• Main Authors: VINCK MICHAEL, TIERENS MARC, BASTIAENS MARIO
• Format: Patent
• Language: Chinese; English
• Published: 22.07.2009
• Subjects: AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING; PERFORMING OPERATIONS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDEDFOR; SHAPING OR JOINING OF PLASTICS; TRANSPORTING; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL

The invention relates to a blown film coextrusion process. The process involves melting and extruding a core layer and a pair of core contact layers adjacent both sides of the core layer through a die exit at a linear speed Vo cm/s and cooling, orienting and crystallizing the multi-layer film formed at a deformation rate until a the frost line is reached at a distance FLH from the die exit by withdrawing film at a take up speed Vf in cm/s at the frost line. The core and core contact layers are of a film forming polymer composition comprising at least 90 wt% of ethylene based polymer. The ethylene based polymer of the core layer has an average density of ethylene based polymers equal to or higher than that of ethylene based polymer of the core contact layers. The invention specifically concerns the feature that the core layer composition contains at least 5 wt% of LDPE having an I2.16 ldpe-core of less than 1.5 g/10 min and the composition of the core contact layers contains at least 75 wt% of a linear polyeth