Chromatically creative – Hot-washing process for shredded plastic

More and more new colors and qualities are becoming possible with Systalen.

The recycling of used plastic packages from the Yellow Sack and the Yellow Bin has in recent years made another significant advance – thanks not least to Systalen, Der Grüne Punkt’s plastic recyclates, developed at the group’s plastics pilot plant in Cologne. Here, too, an innovative process has been created that enables a granulate to be produced from which packages for private consumers can be manufactured.

The extruder emits a deep humming noise, and raises the room temperature appreciably. Sascha Frings fills the machine with small shreds of plastic through a funnel, and checks the temperature. He’s a qualified process mechanic for plastics and rubber, and together with Philipp Neumann, a state-qualified technician for plastics and rubber, plus chemical engineer Dr. Ines Schwarz, belongs to the team of the pilot plant in Cologne, which in the laboratory creates recipes for polypropylene and polyethylene granulates. While Sascha is monitoring the extruder, two heated worms inside the machine are melting the plastic shreds and homogenizing the plasticized mass. Sascha enters blue-gray as the color in the extruder. The melt is micro-filtered in the rear section of the machine, extruded through apertures as strands, and cooled under water before the granulator cuts the strands into small plastic grains, the regranulates, using a rotating blade. Der Grüne Punkt markets the products concerned (both regranulates and regrinds) under the brandname of Systalen.

Translucent, odorless materialDSD_Systalen_HDPE_Granulat_natur_hw_dekon_006
The raw material used here comes from the Yellow Sack and the Yellow Bin. The lightweight packages made of metal and plastic collected in these are first of all sorted in special plants. Once the plastics have been sorted, Der Grüne Punkt shreds and washes them in its recycling lines, and then color-sorts them with the aid of cameras that detect each individual shred of plastic. Washing and color-sorting are crucial to the quality of the regranulates. “Plastic parts are hot-washed in order to remove odors,” explains Dr. Ines Schwarz, Head of Product Development in the pilot plant. For a long time, you see, because of odors, but also due to the very limited choice of colors available, plastics couldn’t be reused in the private-consumer segment. Until quite recently, the only option was producing new sales packages made of polyethylene terephthalate (PET), meaning primarily beverage bottles. Now, though, bottles and other containers made of high-quality, translucent, odorless high-density polyethylene (HDPE) can be produced from Systalen.

New granulate, new colors
The hot-washing process removes unwanted odors and soiling that are deleterious to quality. By admixing dyestuffs, stabilizers or other additives, the HDPE Systalen acquires different properties as the process continues: like a higher density for stable containers or also a special color mixture – to match the color scheme of the company concerned and its products. In recent months, for example, the pilot plant’s team has additionally developed some new colors: light-yellow, mauve, dark-blue, gold and orange.

Der Grüne Punkt is working on industrial-scale implementation

Some major manufacturers have already begun to use the HDPE Systalen for bottles that are filled with detergents or cleaning agents. This newly developed option is for Der Grüne Punkt a trail-blazing step, and was nominated for the 2016 German Raw Material Efficiency Prize of the Federal Ministry for Economic Affairs and Energy, which was awarded in February 2017. This project is still in the test phase. Der Grüne Punkt, however, is planning a larger line, able to produce 8,500 tons of granulate per year. In a next step, industrial-scale implementation for up to 30,000 tons of HDPE Systalen a year is conceivable.

From regrind to a new bottle: the pilot plant paves the way (see photos below).

1. Sascha Frings and his colleagues use the injection-molding machine to produce samples from the regranulates, enabling color and surface properties to be assessed.
2. The extruder is used to create sample quantities, which the customers can test on their own machines.
3. The team in the pilot plant examines various physical and chemical properties of the regranulates, like the flowability of the melt.
4. Der Grüne Punkt’s pilot plant utilizes leading-edge analytical technology.