Page 28 - Plastics News April 2017

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set at levels that also remove as much as 20% of the PET if present when the
(particularly the newer light-weight water bottles); in the PET re cycla t e is
case of float / sinking, the label material simply sinks with processed. While some
the PET, potentially causing the contamination impacts. applications (fiber)
can tolerate certain
Melt and Bleed:
contaminants better
The full-wrap label material tends to melt or get sticky than other applications
at temperatures of 165 degrees centigrade or lower. (packaging), the overall quality of the RPET is impacted
This results in material coating or clumping in dryers as is next-use customers’ ability to process it back into
and requires costly and unscheduled maintenance. Many products of acceptable quality. These impacts include,
labels tested also bleed ink into the wash water while but are not limited to:
being processed. While the impact of this on flake quality
is still being evaluated, there are also concerns about the - Substantial loss of intrinsic viscosity (IV)
impact of effluent discharge. - Color issues, including yellowing and/or graying
- Loss of clarity/haze
Intermediate Processing:
- Extruder drool or drip
An increasing number of Material Recovery Facilities (MRFs)
are investing in equipment that uses near infrared (NIR) - Black specks
technology to positively identify PET containers, then uses The Solution:
compressed air to sort them from the other recyclables. While “temporary” solutions have been discussed involving
Full-wrap labels tend to blind these detection systems, zippered or scored labels that would make them easier
preventing them from to remove, or a return to paper labels, clearly the most
identifying the PET, effective long--term solution is to use a label that floats
resulting in either the and is compatible with the existing label stream and PET
loss of the container recycling infrastructure. For those companies embracing
to the waste stream, the principles of sustainability, addressing this issue
o r necessitating is a priority since there is no sustainability for plastic
additional manual bottes without recycling, and no recycling without an
sortation. This added economically viable reclamation industry. Full--wrap
cost lengthens the labels that sink inwater are threatening this viability
payback of these and the overarching sustainability premise for PET—by
investments, many of which are retrofits. adversely impacting the recycling of not just the PET

Contamination Impacts: bottle,but the label itself. Continued use of full---wrap
labels that sink threaten these fledgling efforts, and once
Depending on the label material substrate, these residual again runs counter to sustainability principles.
contaminants cause a myriad of further challenges

Why can’t reclaimers remove these labels...
In a nutshell: they do not float in water, but the problems really start earlier in the process.
Most reclaimers, particularly those that process curbside material, perform a pre-wash on the bottles.
This is done to remove as many labels as possible prior to the bottles being presented to the autosort unit for identification. These pre-washers run at very hot
water temperatures, or even steam conditions, to loosen the dirt and labels by shrinking the bottle a little. Unfor tunately, the materials generally used in the
full-wrap labels – OPS, PETG, PLA and PVC – shrink even more, tightening around the bottle. They become impervious to standard agitation, or even attempts
to slice them off manually. On some occasions, labels actually melt over the bottles. If the bottles are not removed after the prewash, the labels will travel
through the granulat ion and elutriation, float/sink, wash and dry parts of the process (not necessarily in that order) and stay with the PET, resisting efforts to
be separated, either by air or water, due to their specific gravity being too similar to that of PET (greater than one). In some systems, the contaminating labels
will curl or otherwise densify making it even more difficult to remove them. In most cases, the dried RPET flake is then passed through different types of flake
sorters that remove trace contaminants, including color, metal and other resin as a final quality control step. While many flake sorters can detect most of the
offending label materials, none are wholly effective at removing the quantity of material seen at this stage if these bottles are left in the stream at the current
or increased percentages. The flake sorting technologies are meant as a final polishing step, not for primary sorting

Plastics News | April 2017 28