Colines, Gneuss and ExxonMobil collaborate on LLDPE stretch film with recycled content

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 Italian machinery maker Colines, US materials firm ExxonMobil Signature Polymers and auxiliary equipment supplier 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 minimised with the appropriate materials from ExxonMobil  and a pressure-constant screen changer from Gneuss on a cast film line from Colines.

ExxonMobil adds that its 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, according to the partners. 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).

Gneuss’s patented RSFgenius self-cleaning screen changer is a fully automatic filtration system that renews the screen surface with no measurable pressure fluctuations and can be adapted to the material in question, with screen finenesses typically ranging from 30–75 microns, even during full operation.

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.

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