A tube is formed by pressing the extruded polymer through a circular die, cooling it in a water bath and then cutting it or winding it up. The twin screw extruder is used when the production of medical tubes requires a compound. An example is the incorporation of silver salts. These help to prevent sepses when placing a catheter or stent. Anticoagulants can be incorporated as well to reduce blood coagulation around the appliances.
The production of the tubes on a twin screw extruder enables the modification of the metering and the reduction of raw material stocks. The tubes can be extruded either directly from the twin screw extruder by means of a downstream melt pump, or the twin screw extruder can be used as a second extruder in a co-extrusion system. The material containing the active ingredient can be produced either as the outer layer or within the tube.