Gneuss Recycling Line for PET Nonwoven Waste. Image: Gneuss

Recycling of PET nonwoven fibre waste

| Recycling machines | Gneuss Kunststofftechnik | Bad Oeynhausen | Germany

In the manufacture of PET nonwovens, waste of various types and amounts occurs at different points in the process. Waste is for example created during start up, as edge trim and also as waste when technical parts are cut out of the web. This can be a relatively high proportion of the production. Ideally, this material should all be put back into the process as a complete replacement for virgin material.

Gneuss Recycling Lines, consisting of the Gneuss Processing Unit with the MRS extruder, Rotary Melt Filteration System, Online Viscometer and Polyreactor “JUMP” enable the complete nonwoven fibre waste to be put directly back into the extrusion process. This is done without any compromises with regard to quality (including mechanical properties) regardless as to whether the fibers have been treated with spin finish oils or other treatments. Additionally, in the “JUMP” reactor, the molecular weight of the polymer is accurately adjusted to the required level for reprocessing to fibers.

The compact and especially efficient Gneuss Recycling Line is specifically designed for direct processing of voluminous waste with a low bulk density and which may include spin finish oils or other processing aids. In the first processing step, the bulky production waste is put into a shredder and is fed via a conveyor belt (with metal detection) into an intermediate container with an agitator and is fed subsequently with an augur and crammer feeder into the extruder. The MRS extruder plasticises the material and decontaminates the polymer, removing spin finish oils etc. in the special MRS devolatilising section.

The MRS extruder, with its special Multi Rotation System provides an intensive devolatilisation (and decontamination) of the melt.

It is based on the conventional and robust single screw extruder but has a central section with multiple screws. The barrel is open over the full length of the devolatilising section and this whole section is kept under vacuum. The rugged and simple vacuum system is equipped with a system for separating solid particles. Downstream of the MRS extruder, the Gneuss Rotary Filtration System removes contaminants from the devolatilised polymer melt. The viscosity is monitored during the process with the Online Viscometer and adjusted via a control loop with the MRS extruder. Subsequently, the purified polymer melt is fed by means of a booster pump into the compact IV boosting system “JUMP”. This reactor is equipped with various stirring elements, which create a large surface area exchange under vacuum so that a pre-set viscosity boost is accurately achieved. There is no contact between the polymer and oxygen so yellowing of the material is avoided. After a stabilising stage, the polymer melt is discharged from the reactor by means of a polymer vacuum discharge pump to a pelletising system. The PET pellets are made can be used for fibre spinning as a 1:1 replacement for virgin material.

For IV boosting, the „JUMP “system represents an extremely efficient alternative to a solid state polymerisation (SSP) system. The reaction time in the JUMP is much shorter (for the same IV boost: approximately 10 % of the time needed in an SSP) and the energy input is vastly reduced as the material does not need to be heated up (the melt only needs to be maintained at temperature). The space requirement of the JUMP system is also far smaller than that of an SSP. With the Gneuss Recycling System for nonwovens, inhouse production waste can be re-used up to 100 %. This means that not only are the costs for disposing of waste avoided, the recycled material can replace virgin material 1:1, thereby saving on raw material costs. The result is an extremely short return on investment.