Patent ID: 11858191
Assignee: KUHNE ANLAGENBAU GMBH
Field: Surface technology, coating (Chemistry)
Classification: CPC B | IPC B

Claim 0:
1. A method for producing a multilayered composite film, the method comprising at least the following steps:
a step of coextruding at least three layers, including a first layer, a second layer and a third layer, wherein:
the first layer forms an outward surface of the composite film;
the third layer forms a surface of the composite film facing or coming in contact with a good to be packaged; and
the second layer is disposed between the first layer and the third layer;
wherein the second layer consists of a single layer or a plurality of the second layers;

a step of stretching the coextruded composite film; and
a step of relaxing the stretched composite film;
wherein the stretching is bi-axial;
wherein a stretch factor in the machine direction or longitudinal direction is at least 2.0;
wherein a stretch factor in the transversal direction is at least 2.0;
wherein the sum of the stretch factor in the machine direction and the stretch factor in the transversal direction is at least 5.0;
wherein the composite film has a temperature of 70 to 130° C. during stretching;
wherein a relaxation factor in the machine direction is more than 0.00;
wherein a relaxation factor in the transversal direction is more than 0.00;
wherein the sum of the relaxation factor in the machine direction and the relaxation factor in the transversal direction is at least 0.05;
wherein the composite film has a temperature of 60 to 180° C. during relaxation;
wherein a dwell time during relaxation, is at least 2 seconds;
wherein a dwell time during relaxation is at most 30 seconds, or the duration of relaxation is at most 30 seconds;
wherein a residual stretch factor in the machine direction is at most 5.0;
wherein a residual stretch factor in the transversal direction is at most 5.0;
wherein the first layer comprises a thermoplastic resin having a density of greater than 1.00 g/cm3;
wherein the second layer or the plurality of the second layers each comprises a thermoplastic resin having a density of greater than 1.00 g/cm3; and
wherein the third layer comprises a thermoplastic resin having a density of less than 0.95 g/cm3.