Coextrusion film and method of mixing
AssigneeMondi Consumer Packaging Technologies GmbH
InventorsHenner SOLLMANN, Matthias Perick, Marcel Grossmann, Herbert Bader
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Abstract
A coextrusion film has a core layer made of thermoplastic elastomer, and first and second outer layers sandwiching the core layer. The outer layers are each formed from a polymer having a lower elasticity than the thermoplastic elastomer of the core, each have a layer thickness of less than 15 μm, each have a density of less than 0.800 g/cm3, and each have more than 500 gas-filled cells per 1 cubic millimeter of volume.
Claims16
A coextrusion film comprising:
- a core layer made of thermoplastic elastomer;
- and
- first and second outer layers sandwiching the core layer, each formed from a polymer having a lower elasticity than the thermoplastic elastomer of the core, each having a layer thickness of less than 15 μm, each having a density of less than 0.800 g/cm3, and each having more than 500 gas-filled cells per 1 cubic millimeter of volume.
The coextrusion film defined in claim 8, wherein the polyolefin is a mixture of polyethylene and polypropylene.
A method of making a coextrusion film comprising:
- a core layer made of thermoplastic elastomer;
- and
- a first outer layer formed from a polymer having a lower elasticity than the thermoplastic elastomer of the core, having a layer thickness of less than 15 μm, having a density of less than 0.800 g/cm3, and having more than 500 gas-filled cells per 1 cubic millimeter of volume,
- the method comprising the steps of:
- extruding a first plastic melt of the thermoplastic elastomer for the core layer from a first extruder;
- adding a liquid or gaseous propellant to a thermoplastic base substance in a second extruder at a propellant pressure between 35 and 75 bar;
- extruding a second plastic melt of the thermoplastic base substance and propellant for the first outer layer from the second extruder;
- combining the first and second plastic melts in a coextrusion nozzle while maintaining the propellant at the propellant pressure;
- and
- emitting the combined first and second melts from the coextrusion nozzle at ambient pressure such that the propellant expands on exiting the coextrusion nozzle and brings about a homogeneous distribution of the cells in the first outer layer.
The coextrusion method defined in claim direction by a first stretching by 150% and a subsequent second stretching is smaller than 2:1.
Dependencies are inferred from the claim text.