The combed process is a standard process which is widely used in the industry to improve the quality of virgin cotton. It enables the spinning of finer yarns with a higher tenacity as well as lower imperfections and unevenness. With the potential of reducing the short-fiber content and the number of neps, it is a very interesting process to be also used for recycled cotton blends. Rieter conducted several trials which show the successful use of the combed process for spinning ring and compact yarns from blends of mechanically recycled and virgin cotton.
- Better yarn quality
- Higher recycling ratio
- Using the noil for rotor yarn
Characteristics of mechanically recycled fibers
Recycled fibers are going to play an important role in the fiber mix of the future. Despite extensive research, mechanically recycled fibers are still challenging to be re-spun into yarns due remaining yarn and fabric pieces, a high short-fiber content and a high number of neps. These parameters become particularly problematic when virgin cotton is used as a blending fiber. Depending on the cotton quality, the virgin cotton can already have a high content of short fibers and neps. This can quickly limit the additional amount of recycled fibers that can be added to the blend.
Improving quality with the combed process
Recycled fibers affect yarn quality. In the Rieter trial the carded sample containing 25% recycled cotton has high unevenness values as well as many thick places and neps. Combing helps to get rid of the very short and disturbing fibers and improves the yarn quality. This can be seen when comparing the carded and combed sample: Although the share of recycled fibers is twice as high in the combed sample, the unevennness and imperfection level is better compared to the carded sample.
Share of recycled fibers left in the yarn
A main question of the trial was how many recycled fibers are removed during the combed process and how this affects the overall recycling ratio in the final yarn. The results show that after combing, the share of recycled fibers in the blend is reduced from 50% to around 40%. However, not only recycled fibers are combed out but also short fibers of the virgin cotton. This means that there is still a considerable amount of recycled fibers remaining in the blend. The noil resulting from the combed process is ideal for processing on a rotor spinning system.
Detailed results in technology publication
An extensive technological publication on the trial is available in the download section. It contains details about the trial set-up and further results. It also answer the question how the additional process steps of the combed process are impacting the process cost.
Field test with Recover and Polopiqué
It is important to validate the combed process for recycling also on an industrial level. For this reason, a similar trial as in the Rieter spincenter was conducted at Portuguese textile manufacturer Polopiqué. A green recycled fiber from post-industrial origin provided by Spanish recycled fiber-producer Recover was used for the trial. The results at Polopiqué confirm the results of the spincenter. The yarn quality can be improved significantly with the combed process, while maintaining a high share of green recycled fibers in the blend. Polopiqué - as a vertically integrated textile company – produced polo shirts from the combed recycled ring yarns. The quality of the garment is comparable to a virgin product.
Com4recycling Spinning Systems
Rieter’s technology know-how enables the use of recycled fibers to spin ring, compact and rotor yarns. By pushing the technological boundaries of recycling, Rieter systems contribute to closing the loop in the textile sector.