From rigid to foam sheet on the fly…

From rigid to foam sheet on… Gneuss PET sheet extrusion lines are well known for their flexibility with regard to input material and the finished product. With over 30 years of experience, Gneuss has no shortage of expertise with regard to the specific properties of this material and the special aspects of processing it.

Initially known for its unique Rotary Filtration Systems which have helped to improve the efficiency of PET extrusion lines for decades now, Gneuss introduced its revolutionary MRS Multi Rotation System extruder 10 years ago and which immediately became a success. The MRS extruder offers dryerless processing or PET and offers unparalleled devolatilisation / decontamination performance. The MRS extruder is complemented by a low maintenance vacuum system, a rugged and accurate Online Viscometer and of course the Gneuss Rotary Filtration System. These units combined form the core of the Gneuss Processing Unit (GPU).

The machinery company from Bad Oeynhausen, Germany supplies tailor made PET sheet extrusion lines worldwide. Thanks to the Gneuss Processing Unit, these lines are extremely flexible. They will operate with both virgin and/or recycled material (post-consumer bottle flake, edge trim / skeletal waste regrind). Practically all types of PET input material can be used without the need for drying or crystallising and the sheet manufactured on these lines is suitable for food contact.

PET sheet extrusion lines with the Gneuss Processing Unit can be quickly and flexibly switched to producing physically foamed PET sheet. Thanks to the extremely good mixing properties of the MRS extruder, the nucleating and foaming agents are distributed completely and homogeneously in the melt. The Online Viscometer ensures that the viscosity is maintained at the required level. After extrusion and filtration, the melt is conditioned so that it has the optimum viscosity and strength. This ensures that as the polymer emerges from the die, it foams with the required density reduction.

Thanks to the MRS foam module, foam sheet with a weight reduction of over 50 % can be manufactured (depending on the process) with a consistent foam structure and mechanical properties. And this from 100 % post-consumer material, edge trim / skeletal waste regrind and combinations of these. Foam PET sheet is an ideal material for economically manufacturing thermoformed containers for the food industry such as meat trays, egg boxes, cups and pots.

The effect of foaming sheet is to reduce the weight and therefore the raw material costs compared with rigid sheet. Depending on the requirements, this weight reduction can also permit an increase in the linear sheet output rate or can permit a thicker sheet to be made from the same amount of material.