Recycled Plastic Coloring Made Easy: EFFICIENTLY COLOR ALL TYPES OF RECYCLED PLASTIC WITH ROWASOL LIQUID PIGMENTS

It has been proven time and again that liquid pigment dispersions offer added value in many applications due to their high color strength and uniform incorporation during plastics processing. But the benefits don’t stop there: When it comes to the hot topic of recycling, liquid pigments score points in several key areas.

The use of recycled plastics is becoming increasingly important, while at the same time, the requirements for their properties are rising. In addition to mechanical properties, color is also playing an increasingly important role, as recycled materials are being used more and more in consumer goods and food packaging—a trend that is certain to continue gaining relevance.

Post-Industrial Recycled (PIR) plastics are processed by type and color and can be dyed with relatively little effort. Although post-consumer recycled (PCR) materials are also sorted by type, they contain foreign materials and are always a mix of colors that typically results in a shade of gray without the addition of colorants. Dyeing these efficiently and uniformly is a challenge that liquid dyes are perfectly suited for. This is because the liquid concentrate wets the recycled chips as soon as they enter the feed zone, ensuring that the dye is evenly distributed even before melting in the extruder. Furthermore, it does not matter whether the recycled material contains different fractions—for example, in terms of melt index and plastic type—since the universal carrier is compatible with all materials. And because it is based on renewable raw materials, this approach also reduces the proportion of fossil-based components in the product.

The accompanying figure shows examples of PCR flakes made from HD-PE that were directly injection-molded using various liquid colors. The pellet in the foreground of the image shows the original color of the recycled material, from which four attractive earth tones were produced despite the dark green base color. Even greater potential can be realized when the user mixes liquid monopigment concentrates to create the final color. In this way, the color formulation can be quickly and efficiently adapted to the PCR’s iridescent natural color with minimal effort. And in the case of upstream regranulation of the recycled material—for example, in a twin-screw extruder—inline color correction is even possible through the separate feeding of the “monos.”