| abstract |
The invention relates to a co-extruded thermoplastic foodstuff sleeve made from at least two layers, including an outer layer (Z), with a porosity of at least 5 vol. %, measured as bubbles or pores essentially in the plane at the surface. The surface of the outer layer (Z) comprises an open pore or/and a cratered surface structure and a mean roughness RZ of at least 5.0 µm. On production of the foodstuff sleeve, a propellant or propellant gas is introduced before the extrusion, or the composition is selected such that, in the plastic mass, gas is generated by chemical reaction of the components. The melt is foamed by means of pressure release on or/and after escape from the extruder, whereby at least a part of the gas forms pores or bubbles which are at least partly retained in the hardening melt or at the surface thereof. The invention further relates to a production method, whereby at least two plastic components are used for the outer layer (Z) and, optionally, for at least one further layer. The at least two plastic components comprise clearly different properties and only bond to each other with difficulty, such that at the boundary surfaces between the components pores and/or bubbles are generated, which are at least partly retained in the hardening melt, or at the surface thereof. |