As already explained, textile production is a complex process, and recycling requires several steps in the production chain to be traced and sometimes repeated. As a result, there is no uniform recycling strategy; Used textiles can enter the process chain again at various points (e.g. as fibers, polymers or monomers), so that at least part of the process chain has to be run through again (see Figure 2). Therefore, the recycling route should aim to go back as little as possible to minimize the repetition of process steps. Below you will find brief explanations of possible cycles.
1. Manufacturing of Cleaning and Wiping Rags (CWR):
In this process, the physical and chemical properties of the textiles are only minimally changed (e.g. cutting into pieces measuring approximately 20 x 20 cm). Producing CWR requires little energy as no further processing is required other than cutting. However, these CWR are disposable products that are subjected to thermal recycling after use. Therefore, this path does not correspond to the concept of the circular economy.
2. Recycling while preserving the fiber structure:
This breaks down the textile structure while maintaining the integrity of the fibers. Ripping machines can be used to produce fibers that are suitable for the production of yarns or nonwovens. A resulting reduction in fiber length and the associated possible loss of quality is often unavoidable. Alternatively, textiles can be processed into flock, which consists of short (non-spinnable) fibers that are suitable as additives in building materials. In both scenarios, the need to start new fiber production is eliminated, resulting in significant energy savings.
3. Recycling while retaining the underlying polymer:
Physical properties are changed (e.g. melting or dissolving) while the chemical structure is preserved. The melted or dissolved polymer is introduced into a fiber spinning process. For example, cotton textiles can serve as a raw material for the production of lyocell fibers and replace domestic wood, creating recycled fibers equivalent to those made from new raw materials. Secondary thermoplastic polymers such as PET can also be fed into a melt spinning process.
The biggest challenge in this process is the need for highly pure input streams, unlike textiles that contain multiple polymers. High-quality sorting and/or additional separation steps (mechanical, chemical, biochemical) are essential, but not yet implemented industrially. Compared to previous routes, the potential for energy savings is lower because a significant part of the processing chain needs to be renewed.
4. Recycling at the level of the underlying monomer(s):
The fiber is physically and chemically changed. For example, fibers made from PA6 can be converted into polycaprolactam, which is then used for re-polymerization into PA6. Although this approach is suitable for a wide range of input materials, it requires a reconsideration of almost the entire process chain.
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