The Association of Plastic Recyclers
  • PP

    PP

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

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.

DETRIMENTAL

Paper labels

The PP 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 PP travels with the PP to the extruder where the material carbonizes and causes color defects. Even after melt filtering, the burned smell and discoloration remain with the recycled PP 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 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.

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 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.

BENCHMARK TEST

Full bottle sleeve labels

Full bottle sleeve labels must be tested for both bottle surface coverage and compatibility with PP.

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 PP bottle to another material stream where it is lost to the process.

BENCHMARK TEST

Compatibility:
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.

DEFINITIVE TEST

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.

DEFINITIVE TEST


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 PP 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 PP. 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 PP 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 PP and enters the extruder where it is blended with the PP. PS is not compatible with PP and may cause splay or reduce impact toughness for the recycled PP user. PS label material, when used with an adhesive that releases in the wash, detaches from the PP 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 PP where they are incompatible. When used with an adhesive that releases in the wash, the PLA detaches from the PP 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 PP where they are incompatible. PVC degrades at PP extrusion temperatures and renders large amounts of the recycled PP 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

See section above and "Requires Test Results" section

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 PP in the recycling process or be compatible with PP. Since typical PP recycling process conditions are not aggressive enough to remove all adhesive material, a certain amount of residual adhesive is to be expected in recycled PP. Such adhesive residue that is not removed from PP during the wash step is a source of contamination and discoloration when PP 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 PP, or non-wash friendly and incompatible with PP.

Non-wash friendly, incompatible adhesive is detrimental to recycling.

Label adhesives that have received APR Design® Recognition are commercially available. See APR’s list of recognized innovations. 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

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