The technical hurdles to recycling clothing made of cotton have been too high in the past, but now a team of researchers at the Fraunhofer Institute for Applied Polymer Research IAP, Potsdam-Golm/Germany, together with re:newcell, Stockholm/Sweden, have cleared that obstacle.
They are the first to produce a viscose filament yarn made of recycled cotton and have found a way to turn cotton clothes into new high-quality garments rather than lowly cleaning rags.
Old clothes often end up as inferior products such as cleaning cloths rather than new garments. This is because they are often made of blends rather than a single type of fabric. To date, it has been impossible to separate these intertwined fibers. Researchers were able to extract the foreign fibers from the pulp by setting the right parameters for both the dissolving and spinning processes, for example, with effective filtration stages. This yielded a filament yarn, a continuous strand of fiber several km long consisting of 100% cellulose, the quality of which is comparable to that of wood-based regenerated cellulosic fiber. Compatible with the standard industrial process for making viscose rayon, the new fibers spun from this cotton pulp are suitable for mass manufacturing.
The pulp is first activated with lye and then chemically derivatized. This yields a very pure alkaline viscose solution. Spinnerets riddled with several thousand 55 μm diameter holes then spin this solution in an acidic bath. The thousands of liquid jets emerging from the polymeric solution enable the derivatized cellulose to regenerate and continuously precipitate in the spinning bath to form a filament. The next step is to steadily reverse the chemical derivatization, and then wash and dry the filament for it to be wound onto a spool. Made of pure cellulose, this filament is eco-friendly. Rather than adding to the mountains of microplastics that pollute the oceans, it readily decomposes. This is a huge advantage over petroleum-based polyester fibers, which still predominate on the global market with a share of some 60%.