Melt filtration system for single, twin screw extruders

The new RSFgenius 75 melt filtration system from Gneuss provides superior thickness tolerances in the manufacture of sheet and strapping tape when used with either a single or twin screw extruder.

The film thickness is monitored using an ultrasonic scanner. The maximum deviation from the target thickness is on average +/-3 microns, which represents a relative deviation of on average +/-0.9 per cent.

Even during filter element changes, which represents the biggest potential for variations — performed usually every three months — there are no quality variations in the film.

Similar results are also obtained on PET applications.

The characteristic feature of this system is the rotary disk, located between the inlet and outlet block, on which the filter media is arranged in a ring pattern. The polymer flows across the disk and contamination is collected in the filter medium. This creates a small increase in the differential pressure, causing an instant reaction by the control system: the disk rotates by an angle of approximately 1. In this way, contaminated filter area is moved out of the melt flow and fresh, clean filter medium is introduced at the same rate.

The self-cleaning system ensures that the filter medium is cleaned shortly before re-entry into the polymer melt. The dirt cake is removed by means of a high-pressure segmental back flushing system. This system ensures that the filter medium is practically 100 per cent clean and can be re-used up to 400 times.

Gneuss Inc. (Matthews, N. C.); www.gneuss.com; 704-841-7251