Patent ID: 8613824

Claim:
A method of producing a multi-layer composite foil, said method comprising: providing a cover layer comprising at least one sub-layer; extruding a material including at least one of acrylonitrile butadiene styrene copolymers, acrylonitrile butadiene styrene copolymers with admixtures, polystyrene, polystyrene with admixtures, high-impact polystyrene, polyester, amorphous polyester copolymer so as to form at least two carrier layers; arranging the at least two carrier layers under the cover layer to form the composite foil; and ensuring that the composite foil has a tensile strength sufficient to achieve a maximum tensile force between 30 Newton and 280 Newton in a single-axis tensile testing procedure using the composite foil as a testing body, wherein said ensuring comprises performing the single-axis tensile testing procedure using the following sub-steps: a) storing the test body according to type 1 B as set forth in ISO 527-2: 1996 Section 6 having a thickness corresponding to a desired thickness of the composite foil to be tested for 24 hours prior to the beginning of the testing at 23° C. and 50% relative air humidity; b) clamping the previously-stored test body into a testing apparatus according to ISO 527-1:1996 Section 5, wherein the longitudinal axis of the test body is parallel to the direction of extrusion or calendaring direction of the composite foil, and applying pre-stressing according to ISO 527-1:1996 Section 9.2 and 9.5; c) subsequently implementing the single-axis tensile testing procedure according to ISO 527-1:1996 at a constant testing speed of 800 mm/min and at a constant temperature of 80° C., wherein immediately prior to the beginning of said implementing of the single-axis tensile testing procedure, keeping the clamped test body in a climatic chamber temperature-controlled at 80° C. for a period of 10 minutes; and d) recording tensile forces which occur during said implementing of the single-axis tensile testing procedure depending on a test time measured from a beginning of the testing procedure in a range of nominal stretch ε t (according to ISO 527-1:1996 Section 10.2) of between 0% and 100%.