As interest in recycling has grown in importance in recent years, a wide variety of plastic waste streams are being evaluated for their recyclability potential. Important criteria are the expected annual volume, potential contamination and the material composition of the streams.
LDPE/LLDPE film has existing collection systems in many European countries that have been in place for many years to provide this type of material for recycling. As markets demand recycled content in a broader range of applications, a challenge is to produce clear shrink, stretch or blown film that maintains properties while incorporating recycled content.
In this context, new capacities have been built in Europe and worldwide or existing plants have been retrofitted with improved sorting, washing steps or additional melt filtration systems in order to be able to offer high-quality polyethylene (rPE) streams for recycling. However, even LDPE/LLDPE that has undergone extensive mechanical processing, can be difficult to convert into new film on conventional production lines, which is why the companies Colines, ExxonMobil Signature Polymers and Gneuss have joined forces in a development project to develop a viable film production process with potential cost savings.
In particular, the so-called gels and black dots are disruptive factors that could be minimized with the appropriate materials from ExxonMobil Signature Polymers and a pressure-constant screen changer from Gneuss on a highly flexible cast film line from Colines.
ExxonMobil Signature Polymers´s technical experts have conducted trials using PCR material (Post Consumer Recycle) derived from stretch film in combination with Exceed Tough m 3812 high performance polyethylene and observed a reduction in the size of the larger polymer gels.
With most of the commercial PCR grades available on the European market today, extrusion lines often cannot run continuously. Continuous filtration can help to run extrusion lines for longer production periods. Filtration removes a significant proportion of the impurities present in the melt, but not all the gels," says Bart Lauwers, Principal Extrusion Customer & Application Development at ExxonMobil Technology Group.
Nevertheless, the project has demonstrated quality and process consistency. All tests carried out demonstrated the ability to consistently produce film that incorporated 30% PCR content for automatic use with a consistency of 180-200% without the need to stop the line, except for routine operations unrelated to recyclate use (e.g. lip die cleaning, chill roll cleaning, resin or format changes).
A key component in this process was the patented Gneuss RSFgenius self-cleaning screen changer. This fully automatic filtration system renewed the screen surface with no measurable pressure fluctuations and can be adapted to the material in question, with screen finenesses typically ranging from 30 - 75μm, even during full operation.
Colines is a renowned manufacturer of cast and blown film lines based in Novara, Italy. Colines has demonstrated exceptional flexibility in meeting the individual needs of its customers. Not only with the full integration of Gneuss screen changers, but also in terms of fully customizable line set-ups for the production of any type of film.
The collaboration between Colines, Gneuss and ExxonMobil Signature Polymers has already led to the creation of several large-scale production lines specifically dedicated to recycled content incorporation with many more in progress for various global markets.
In the early months of 2025, the project partners will again invite interested professionals to Novara (Italy) to simulate their own requirements for such a production line in individual demonstrations. A Colines line with a fully integrated RSFgenius 150 will be available to achieve film thicknesses of up to 10μm consistently without quality fluctuations. ExxonMobil' Signature Polymers expertise in material and additive selection will also be available for these trials.