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.
PREFERRED
Polypropylene or polyethylene labels
HDPE labels are the same polymer as the final product and PP at the very small levels expected from label residue has a very minimal negative impact. Therefore, these labels that remain with the HDPE 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 HDPE and be blended with the recycled HDPE. 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 HDPE 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 HDPE bottle to another material stream where it is lost to the process. Furthermore, some incompatible sleeve materials that cannot be separated from the HDPE in the float-sink tank can contaminate the recycled HDPE 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 HDPE 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.
DETRIMENTAL
Paper labels
The HDPE reclamation process involves water and agitation. The paper that detaches from the container when subjected to these conditions becomes pulp, which does not sink intact but remains suspended in the liquid, adding load to the filtering and water treatment systems. Paper remaining adhered to the HDPE travels with the HDPE to the extruder where the material carbonizes and causes color defects. Even after melt filtering, the burned smell and discoloration remain with the recycled HDPE thereby negatively affecting its potential reuse. Non-pulping paper labels used with non-releasing adhesives compound the problem since the entire label enters the extruder. Non-pulping labels, heavy enough to sink and durable enough to withstand the washing process that are used with releasing adhesives may alleviate this issue.
RENDERS NON-RECYCLABLE
None Specified
REQUIRES TEST RESULTS
Label inks
Some label inks bleed color in the reclamation process, discoloring the HDPE in contact with them and possibly diminishing its value for recycling. Since most recycled HDPE 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 HDPE 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.
SCREENING TEST
DEFINITIVE TEST
Metal foil, metalized and metallic printed labels
Sorting equipment in the recycling process is designed to detect and eliminate metal from HDPE. 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 HDPE 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 HDPE.
Surface area: 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 HDPE bottle to another material stream where it is lost to the process.
Compatibility: Some sleeve label materials have a density of <1.0, and thus float in the float/sink tank and remain with the HDPE. This material cannot be removed in the recycling process and can contaminates the recycled HDPE produced if not compatible with HDPE.
Direct printing other than date coding
Inks used in direct printing may bleed or otherwise discolor the HDPE during the recycling process or introduce incompatible contaminants that reduce the value of the recycled HDPE. The specific ink must be tested to determine its effect. Companies that are considering direct printing technologies and are unsure of their compatibility with recycling should ask their suppliers to provide APR test results.
Direct printing technologies for HDPE 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.
LABEL/ADHESIVE COMBINATIONS
The classification and recyclability of label substrates is dependent on the type of adhesive that is used with them. In general, a label substrate that sinks in water and is used with an adhesive that releases in the reclaimers wash system is preferred since the substrate will be removed in the float-sink tank. A label substrate that is compatible with HDPE is also preferred no matter what the adhesive. Therefore, recyclability of certain label substrates is conditional upon the type of adhesive used with them.
CONDITIONALLY PREFERRED
Metal foil labels that pass sorting requirements are preferred when used with an adhesive that releases in the wash and detrimental to recycling when used with an adhesive that does not release in the wash.
Even very thin metallized labels may be identified as metal by the sorting equipment and cause the entire bottle to be directed to the metal stream, thereby creating yield loss. Sorting equipment in the reclaiming process is designed to detect and eliminate metal from HDPE. If small, not detected, or allowed to pass, these labels, when used with an adhesive that does not release in the wash, either cause the attached HDPE to sink where it is lost in the float-sink tank or pass into the extruder where they can blind melt filters. When used with an adhesive that releases in the wash, these labels quickly sink in the float sink tank where they are removed
Polystyrene labels are preferred when used with an adhesive that releases in the wash and detrimental to recycling when used with an adhesive that does not release in the wash.
PS, when used with an adhesive that does not release in the wash, remains with the HDPE and enters the extruder where it is blended with the HDPE. PS is not compatible with HDPE and may cause splay or reduce impact toughness for the recycled HDPE user. PS label material, when used with an adhesive that releases in the wash, detaches from the HDPE before the float sink tank where it sinks and is removed.
PLA labels are preferred when used with an adhesive that releases in the wash and render the package non-recyclable per APR when used with an adhesive that does not release in the wash.
PLA label material, when used with an adhesive that does not release in the wash, enters the extruder with the HDPE where they are incompatible. When used with an adhesive that releases in the wash, the PLA detaches from the HDPE before the float-sink tank where it sinks and is removed. Even though the float-sink process is imperfect, the small amounts of PLA entering the extrusion process are not catastrophic.
CONDITIONALLY DETRIMENTAL
PVC labels are detrimental to recycling when used with an adhesive that releases in the wash and render the package non-recyclable per APR when used with an adhesive that does not release in the wash.
PVC, when used with an adhesive that does not release in the wash, enters the extruder with the HDPE where they are incompatible. PVC degrades at HDPE extrusion temperatures and renders large amounts of the recycled HDPE unusable. When used with an adhesive that releases in the wash, these labels sink in the float-sink tank where they are removed. But because the float-sink tank is imperfect, and even a very small amount of PVC entering the extruder causes severe quality and yield problems, this material is detrimental.
RENDERS NON-RECYCLABLE
None specified
REQUIRES TEST RESULTS
Label/Adhesive combinations where adhesive release and substrate float/sink behavior are not known.
Testing must show that adhesives will either wash off cleanly from the HDPE in the recycling process or be compatible with HDPE. Since typical HDPE recycling process conditions are not aggressive enough to remove all adhesive material, a certain amount of residual adhesive is to be expected in recycled HDPE. Such adhesive residue that is not removed from HDPE during the wash step is a source of contamination and discoloration when HDPE is recycled. For these reasons, minimal adhesive usage is encouraged.
The APR is developing a screening PP/HDPE Adhesive Test to classify adhesive as either wash friendly, non-wash friendly and compatible with HDPE, or non-wash friendly and incompatible with HDPE. Non-wash friendly, incompatible adhesive is detrimental to recycling. Label adhesives 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 label adhesives and are unsure of their compatibility with recycling should ask their suppliers to provide APR test results.
DEFINITIVE TEST
