The guidance considers the direct application of inks to the film package as more impactful than inks printed on a label substrate, as direct printing fulfills a decorative function whereas a label conveys more limited information. However, label technologies and printing must also conform to guidance.
Polyethylene labels with tested inks and adhesives
Labels may represent a significant fraction in weight on flexible packaging, being more critical on recyclability when compared to rigid packaging. Ideally, no label is preferable, but if a flexible film needs labelling, a PE-based substrate is preferred over paper or any other material.
Polyolefin labels that have been tested and found to be compatible with PE recycling systems
APR offers various testing protocols and options for recognition to companies striving to design and commercialize Preferred labels and printing systems for PE films. Test results demonstrating recycling compatibility can determine material classification. One company has received Critical Guidance Recognition for a compatible olefin based label system.
Printed labels with untested inks
Inks applied to the label must be minimized to prevent the same potential adverse effects listed in the “Direct Printing Inks, Primers, Coatings and Laminating Adhesives” section.
Untested label adhesives
The amount of adhesive should also be limited since heavy levels can degrade and volatize in the extruder and may cause gels and specks in the final product even if most recyclers use vented extruders. Large amounts of adhesives can overwhelm the capacity of these extruders to remove the volatile components.
Paper labels pulp and become a water filtration and contamination problem if they are processed through a wet recycling process. Individual paper fibers are very difficult to remove and attach themselves to the film creating specks and irregularities in the products made from recycled film. Furthermore, in either a wet or dry process they degrade in the extruder creating an undesirable burnt smell that cannot be removed from the recycled plastic. This significantly limits its reuse.
See "Requires Test Results" section
Metal foil labels
These labels should not be confused with metalized film. Metal foil labels are extremely problematic in two areas. First, they alarm metal detectors that are employed at the beginning of the recycling process to protect machinery. When this occurs, the entire package containing the offending part is discarded and landfilled. Secondly, if they happen to pass through the process into the extruder, they can quickly clog a melt filter causing a pressure upset which automatically shuts down the process for safety.
REQUIRES TEST RESULTS
Even though they are currently recycled commercially, there is no solid evidence available for a complete evaluation of the impact of the packaging components above on the recycling process and the recycled material. Test results or equivalent evidence need to be developed, based on which these guidelines will need to be confirmed or updated.
Label inks applied to Preferred label materials
The guidance considers the direct application of inks to the film package as more impactful than inks printed on a label substrate, as direct printing fulfills a decorative function whereas a label conveys more limited information. Labels typically feature smaller amounts of printing and limited colors. However, the impact of printed labels must still be evaluated for recycling compatibility.
Certain levels of ink components dispersed in the final polymer are thought to be responsible for the grey-green color of recycled PE pellets. While this is a noticeable quality impact, markets exist for such colored PCR pellet when the correct inks are used and there is no impact on physical or chemical properties of the PCR.
The amount of printing should be limited since heavy levels of ink may degrade and volatize in the extruder, causing gels and specks in the final product even with vented extruders. Large amounts of printing can overwhelm the capacity of these extruders to remove the volatile components.
Heavily printed labels using dark color inks can be problematic since the dark color affects a large amount of polymer, limiting its potential for reuse.
Some label inks bleed color in the reclamation process, discoloring the PE in contact with them and possibly diminishing its value for recycling. Since most recycled PE 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.
Chemically, EBeam or UV curable inks, primers and adhesives are thermoset in nature, not melting with the thermoplastic components of a flexible film, thus acting as a contaminant in the recycling process. Depending on the amount used, they may limit the potential reuse of recycled films by negatively impacting film appearance (gels, specks) and mechanical properties.
Labels with metallic inks
Inks designed for metallic appearance are not always removed in the recycling process and are melted and blended with the PE. This may cause material discoloring. In many cases a metallic ink will be detected early in the recycling process by metal detectors designed to protect machinery from catastrophic damage. Metal detectors are unable to differentiate between a metallic print and a solid metal part, so the entire package is normally discarded rather than accept the risk.
Testing must show that adhesives will wash off cleanly from the PE in the recycling process and be compatible with PE. Since typical film PE recycling process conditions are not aggressive enough to remove all adhesive material, a certain amount of residual adhesive is to be expected in recycled PE film. Adhesive residue that is not removed from PE during the wash step, for those film recyclers that use washing, is a source of contamination and discoloration when PE is recycled. Recyclers without wash systems may encounter melt filtration issues from adhesives. For these reasons, minimal adhesive usage is encouraged.
The APR is developing a screening PP/HDPE Adhesive Test to classify adhesive as compatible with PE whether reclaimed in a wet or dry process. Companies that are considering label adhesives and are unsure of their compatibility with recycling should ask their suppliers to provide APR test results.
Non-wash friendly, incompatible adhesive is detrimental to recycling.