Meaning
Quantitative measurements of the percentage of ink removed from printed polymer substrates during recycling processes define the performance of wash and flotation stages. In the reclamation of post-consumer plastic packaging, de-inking efficiency determines the purity and color quality of the recycled resin. The evaluation is conducted by comparing the color and reflectance of the washed polymer flakes against unprinted virgin material.
The process achieves maximum performance when all printed ink layers are completely stripped without degrading the base polymer.
Process Chemistry
Chemical wash solutions use surfactants and alkaline agents to detach ink binders from the plastic surface. The wash temperature must be kept below the softening point of the polymer to prevent the flakes from sticking together. Proper surfactant selection ensures that the freed ink particles remain suspended in the water.
Mechanical Separation
Turbulence within the washing chamber assists the chemical action by providing friction between the plastic flakes. High-shear washing units strip stubborn inks but generate fine particles that must be filtered out. Centrifugal separation then removes the contaminated wash water from the cleaned polymer.
Recycling Economics
Contaminants remaining after washing limit the market value of the output material. Low ink removal leads to grey or discolored pellets that cannot be used in high-value packaging applications. Enhancing this wash step unlocks higher pellet pricing.
