Feeding solutions for plastics recycling applications



Feeding solutions for plastics recycling applications

Brabender Technologie and its special feeders used for recycling synthetic fibers from plastic waste are contributing to a high-tech circular or recycling economy.

The circular (or recycling) economy is a new type of economic system aimed at reducing consumption of resources, and is considered a key element in climate protection strategy. In the last several years Brabender Technologie has demonstrated how new processes and products can originate from innovative ideas. Bernhard Hüppmeier, Head of Business Development at Brabender Technologie, reports: “In the last few years, demand for feeding solutions, focused on recycling synthetic fibers, has increased steadily.” Equipment for feeding components derived from used tires, fabrics and PET bottles is in demand. “Some materials like rubber pellets are already processed to the extent that they can be fed using a normal feeder. In contrast, others require a feeding concept specifically matched to their material properties,” says Bernhard Hüppmeier.

Used tire recycling

The rubber crumb obtained from recycling used tires can be processed in extruders, kneaders or mixers along with additives and crosslinkers to produce new products like insulation materials, road surfacing, floor coverings, rubber mats or new tires. A key consideration is not to dispose of used tires like normal waste, because they are made of India rubber, bulking agents like carbon black, silica and carbon, plasticizers and reinforcement materials like steel and nylon and other chemicals like sulfur. Used tires are reduced to palm-sized pieces in shredders and then ground down to small pellets in pellet plants. All residual metal is then removed, leaving pure rubber crumb at the end of this process. Used tires also contain woven fibers like polyester and polyamide fibers, which can be vacuumed off during the shredding or grinding phases. In extrusion processes, these fibers then serve as reinforcement or bulking agents for new polymer blends and can be processed into fiber-reinforced polymer compounds by mixing in additives.

PE/aluminum recycling of used beverage cartons

Beverage cartons also consist of valuable raw materials: a combination of cardboard, plastic and often aluminum. The cellulose fibers reclaimed during recycling have a significantly longer fiber length and better strength properties than most other types of waste paper. This makes these fibers particularly suitable for producing sturdy corrugated cardboard packaging. In the so-called Palurec, method the remaining PE/aluminum foil remnants and closures are separated using a zigzag sifter, due to their very uneven ‘particle’ sizes, poor pourability properties and tendencies towards severe bridging. A special Brabender Technologie feeding solution is used when LDPE (low density polyethylene) is being processed. Bernhard Hüppmeier explains: “Our special fiber feeder is particularly suitable for fibers of different lengths, which easily get entangled. For pelletizing purposes, the FiberXpert feeds the reclaimed LDPE into a twin screw extruder. This enables it to be reused for various applications.

Recycling of carpets made of PA fibers

In the European Union an estimated 1.6 million tonnes of carpet are disposed of annually. According to a very recent study by market research institute Goldstein Market Intelligence, around 95 percent of this carpet ends up at disposal sites or incinerator plants. An alternative to incineration is recycling waste carpets made of high-grade synthetic fibers like polyamide (PA) or polypropylene (PP). Waste carpets or PA carpet remnants, which consist of the texturized carpet continuous filament yarn BCF (bulk continuous filament), can be chemically recycled into polyamide or mechanically processed into secondary plastics. To this end, PA carpets are sorted according to their fiber components PA6 or PA 6.6 and then shredded. After separation, they are fed via silos into a depolymerization process. The FiberXpert FX225 loss-in-weight feeder, which can handle long, uneven fibers, is particularly suited for this task. Bernhard Hüppmeier puts it in concrete terms: “Synchronous conical twin screws in combination with a large feed section, which can be fitted with a stuffing unit, and a high feeding rate of 1000 kilograms per hour ensure that pelletized Polyamide 6 features excellent melting properties and superior quality.” The FX225 is also well suited for feeding PA, PET as well as PE fibers obtained from woven textiles, which contain textile fiber borders from the weaving process and silicon-coated or non-silicon coated textile fabrics, that can be recycled.

PET is transformed into rPET

In order to optimize the versatility and sustainability of plastic in its various applications and to manage this material within the cycle, plastic waste needs to be utilized even more efficiently - in the form of valuable secondary raw materials. Brabender Technologie provides appropriate feeding technology to process ground PET flakes into recycled rPET. In the subsequent extrusion process, the PET flakes are treated with additives and the molten mass is sent on to the liquid state polycondensation phase. After the molten mass has been cooled, pelletized or foamed up using physical expanding agents, it reaches the downstream film extrusion stage, which produces fully recyclable rPET foam film.

(published in FLUX 1/2021)