Installation for producing a polymer melt and use of such an installation for producing a polymer melt for a porous film

Installation for producing a polymer melt for porous films having the following features:

• having a planetary roller extruder for producing a flowable polymer melt from thermoplastics;
• the planetary roller extruder has a filling opening and a discharge side for delivering the polymer melt;
• wherein:
• a melt pump is provided;
• the discharge side of the planetary roller extruder is connected to a downstream inlet side of the melt pump for further conveying the polymer melt;
• the connection is in the form of:
• a pressure line having a length longer than 5 cm and shorter than 500 cm, and shielded from the ambient atmosphere;
• the planetary roller extruder and the melt pump are designed and/or can be driven in such a manner that the polymer melt is applied or can be transferred under pressure at the melt pump on the inlet side, wherein the pressure under which the polymer melt is applied at the inlet side of the melt pump is greater than 4 bar;
• and,
• to increase the pressure under which the plastic melt is applied or can be transferred to the input side of the melt pump, the melt pump is configured to reduce its pump rotational speed, so that the plastic melt builds up from the input side of the melt pump in the direction of the output side of the planetary roller extruder, this build-up working against the continuous material flow of the further plastic melt so that it causes an increase in pressure;
• and
• a region beginning from the filling opening of the planetary roller extruder is free from air openings up to the inlet side of the melt pump, so that air dragged into the polymer melt is pushed out of said polymer melt when the pressure of the polymer melt is increased, and wherein the air is pushed in the direction of the filling opening of the planetary roller extruder and only then degassed from the planetary roller extruder.