LABELS AND INKS
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.
Polypropylene or polyethylene labels
PP labels are the same polymer as the final product and PE at the very small levels expected from label residue has a very minimal negative impact. Therefore, these labels that remain with the PP throughout the recycling process, whether they detach or not, increase yield and have minimal negative quality impact for the reclaimer.
In-mold labels of a compatible polymer
In-mold labels are not removed in the recycling process since they are bonded with the wall of the package. They will flow though the recycling process with the PP and be blended with the recycled PP. The lack of adhesive is beneficial to recycling since it cannot affect color or other mechanical properties. The label polymer and ink should be compatible with PP so as not to negatively affect its properties.
Full bottle sleeve labels designed for sorting
A positive aspect of sleeve labels is the lack of adhesive requiring removal in the recycling process. However, full bottle sleeve labels cover a large amount of the bottle surface with a polymer that is not the same as the bottle body. Because of this, a sleeve label designed without considering sorting may cause an automatic sorter to direct a PP bottle to another material stream where it is lost to the process. Furthermore, some incompatible sleeve materials that cannot be separated from the PP in the float-sink tank can contaminate the recycled PP produced. Sleeve labels that are designed for automatic sorting and sink in water are preferred, with the exception of PVC, where even small residual amounts that make it through the float-sink process will destroy the recycled PP in the extrusion process. Polyolefin sleeve labels that are designed for automatic sorting are also preferred since the small levels of completely incompatible material expected from label residue has a very minimal negative impact.
REQUIRES TEST RESULTS
Some label inks bleed color in the reclamation process, discoloring the PP in contact with them and possibly diminishing its value for recycling. Since most recycled PP is colored, the impact of bleeding inks may not be significant; however, since the end use is not known beforehand, label inks should be chosen that do not bleed color when recycled. If inks redeposit on natural PP flake, this discoloring may diminish its value for recycling. Inks should remain adhered to the label and not bleed into wash water to avoid this potential discoloration.
The APR test protocol should be consulted to determine if an ink bleeds.
Companies that have developed new, innovative laminated label substrates are encouraged to pursue APR Design® Recognition for their materials as well. Companies that are considering label inks and are unsure of their compatibility with recycling should ask their suppliers to provide APR test results.
Metal foil, metalized and metallic printed labels
Sorting equipment in the recycling process is designed to detect and eliminate metal from PP. Even very thin metallized labels may be identified as metal by the sorting equipment and cause the entire bottle to be rejected as waste, thereby creating yield loss. If not detected, metals may go into grinding equipment, causing damage and premature wear.
Metal foil labels that pass through sorting and remain with the PP are Detrimental, and the package is considered Recyclable with Detrimental Features. Very thin vacuum-deposited metal layers may pass through sortation and be considered Preferred. If a bottle is lost in the metal sortation process, it is rendered non-recyclable as it does not enter the stream and is discarded as waste.
Full bottle sleeve labels
Full bottle sleeve labels must be tested for both bottle surface coverage and compatibility with PP.
Some sleeve labels cover a large amount of the bottle surface with a polymer that is not the same as the bottle body. The label may then cause a false reading on an automatic sorter and direct a PP bottle to another material stream where it is lost to the process.
Some sleeve label materials have a density of <1.0, and thus float in the float/sink tank and remain with the PP. This material cannot be removed in the recycling process and can contaminates the recycled PP produced if not compatible with PP.
Direct printing other than date coding
Inks used in direct printing may bleed or otherwise discolor the PP during the recycling process or introduce incompatible contaminants that reduce the value of the recycled PP. The specific ink must be tested to determine its effect.
Direct printing technologies for PP bottles that have received APR Design® Recognition are commercially available. Companies that have developed new, innovative laminated label substrates are encouraged to pursue APR Design® Recognition for their materials as well.
Companies that are considering direct printing technologies and are unsure of their compatibility with recycling should ask their suppliers to provide APR test results.