Label selection should be considered carefully to find the solution most compatible with the recycling process that also provides the necessary performance characteristics. At a minimum, labels must be designed so NIR sorting machinery can identify the bottle polymer with the label attached, and labels should use adhesives that release from the bottle. Removing adhesives is a significant component to the cost of recycling so the packages using the lowest quantity of appropriate adhesive are the most compatible.
Since these are the same material as the target polymer they will be recycled with it and add to the material yield.
Polymers with a density < 1.0 that float in water, specifically polypropylene or polyethylene
If a PLA label is not available or suitable, then PP or PE labels are preferred since they float in water and separate from the PLA in the float-sink tank with the closures. Since they are the same general polymer as most of the closures they do not contaminate or devalue this stream. Care should be taken to ensure that any modifiers to the label material do not increase its density above 0.95. Minimizing label size is advantageous to both processes.
The PLA reclamation process involves a hot caustic wash that removes glue and other label components to the levels required to render the RPLA usable. Paper, when subjected to these conditions, becomes pulp which is very difficult to filter from the liquid, thereby adding significant load to the filtering and water treatment systems. Individual paper fibers making up pulp are very small and difficult to remove so some travel with the PLA. Paper fibers remaining in the RPLA carbonize when the material is heated and re-melted, causing quality degradation and a burnt smell to the polymer. Non-pulping paper labels that resist the caustic wash process sink in the float-sink tank, thereby causing RPLA contamination. These, although removed when the polymer is melt filtered, carbonize causing the same effect.
Also see "Requires Test Results" Section
PET and PETG
Both materials are extremely difficult to remove in the recycling process due to their similarity in density to PLA which causes them to sink in the float/sink tank along with the PLA. Both cause severe quality degradation in the final recycled PLA stream even in very small amounts.
This material is extremely difficult to remove in the recycling process due to its similarity in density to PLA. The recycled PLA process is very intolerant of even minute amounts of PVC.
REQUIRES TEST RESULTS
Laminated label substrate
Labels that break into small, very thin pieces of material are more difficult to manage in the recycling process because they behave erratically in a float-sink tank. Therefore, labels that stay intact are preferred. Carry-over of delaminated labels into the recycled PLA can result in contamination.
*Under Development - Definitive Test: New Delamination
Full container sleeve labels
Full container sleeve labels cover a large amount of the container surface with a polymer that is not the same as the container body. Because of this, a sleeve label designed without considering recycling may cause a false reading on an automatic sorter and direct a PLA container to another material stream where it is lost to the process. Furthermore, some sleeve label materials cannot be removed in the recycling process and contaminate the RPLA produced. Sleeve labels that have been found compliant with the APR test protocols should be selected.
Metal foil, metalized and metallic printed labels
Sortation testing for metal components will result in either a Detrimental or a Renders Non-Recyclable ruling. Metal components cannot be Preferred at this time.
Sorting equipment in the recycling process is designed to detect and eliminate metal from PLA. Even very thin metallized labels may be identified as metal by the sorting equipment and cause the entire package to be rejected as waste, thereby creating yield loss. If not detected, they pass through the process with the PLA and cause contamination issues in the final product.
Pressure sensitive labels and adhesives
Pressure sensitive labels generally require complete adhesive coverage which is greater than other typical label methods. This raises the importance of the compatibility of the type of adhesive with the recycling process. Adhesives resistant to washing in the recycling process allow labels to remain on the container and become contaminants in the final product. Adhesives that have been found compliant with the APR test protocols should be selected.
Screening Test: TBD
Direct printing other than date coding
Historically, inks used in direct printing tend to bleed or otherwise discolor the polymer during the recycling process or introduce incompatible contaminants. In either case, the value of the recycled polymer is diminished. Some inks used in direct printing do not cause these problems. The specific ink must be tested to determine its effect.
No test methods currently exist for PLA. However, HDPE Bleeding Label Test (HDPE-S-01) may be adapted substituting PLA for HDPE.
Adhesives that wash off cleanly from PLA and remain adhered to the label are preferred. Label adhesive that is not removed from PLA, or which re-deposits on the PLA during the wash step, is a source of contamination and discoloration when PLA is recycled.
The recycling process is designed to remove reasonably expected contamination from the surface of the container to a degree necessary to render the polymer economically reusable in further applications. In practice, some adhesives are resistant to this process so are detrimental to recycling. In extreme cases, an adhesive and label cannot be separated from the PLA and may render a package not recyclable.
Screening Tests: TBD
Some label inks bleed color in the reclamation process, discoloring the polymer in contact with them and significantly diminishing its value for recycling. Label inks must be chosen that do not bleed color when tested under this protocol.
Screening Tests: TBD