Ring and Rotor Spinning of Recycled
importance of recycled fiber processing.
With barely one percent of garments
being recycled and three quarters of the world’s clothing ending
up in landfill, the textile industry is actively seeking ways to
make production patterns more sustainable and pay more attention
to the entire life cycle of items of clothing. Rieter is
offering solutions for the integration of recycled raw material
into yarn production to help close the textile loop. The results
of the latest study show that it is possible to spin not only
rotor, but also ring yarns of different quality with a
considerable amount of recycled raw material on a Rieter system.
In recent years, better use of raw
materials has become very important in the textile sector due to
growing environmental awareness, legal requirements for more
sustainability, and the cost of raw materials. As a result, more
research and development is being carried out in the various
areas of textile recycling.
Coordination and cooperation between the
different industrial sectors, from the procurement of raw
materials through to the new final product, will be vital. Only
then will it be possible to expand and optimize the entire
recycling process to help it grow into a larger market. In the
next few years, the realistic market potential for the staple
fiber industry for recycled raw materials amounts to around 7.6
million tons annually if the current trend continues.
Classify the raw
To help spinners in the area of recycled
fibers, Rieter has established a classification system for the
typical recycled raw material quality available on the market
(Fig. 1). The Rieter Recycling Classification makes it easier
for spinners to estimate what targets can be reached depending
on the material.
Fig. 1: The Rieter Recycling
Classification allows a very good estimation of
processability and yarn quality of the used material.
The short-fiber content, the mean fiber
length and the 5% fiber length are important parameters after
the tearing process because they help to determine which
subsequent spinning process (ring or rotor) should be used and
which quality (uniformity) and maximum spinning fineness (yarn
count) can be achieved in this context.
optimal spinning process for recycled materials
A very interesting recycling example is the
re-spinning of used cotton clothes, e.g. T-shirts. Typically,
the recycled raw material is blended with virgin cotton. This
application was also used in the Rieter trial to determine the
optimum spinning process. Both the requirements for raw-material
preparation and the best machine configuration for spinning
staple fibers were considered. The raw material in the trial was
a blend of virgin cotton from Chad and bleached cotton recycled
fibers which were mixed in varying proportions. The graph shows
the process sequences within the spinning process (Fig. 2).
Fig. 2: Process sequences for
Rotor yarn has the
In essence, the rotor spinning machine is
well suited for processing fibers with a high short-fiber
content (>30%), which is reflected in better evenness (Fig. 3).
This is due to better fiber feeding of the opened fibers in the
closed fiber feed channel and the doubling of the individual
fibers in the rotor groove. For acceptable yarn quality and
operational reliability, a blend containing up to 75% recycled
content is possible in this raw material configuration.
Fig. 3: The rotor spinning machine is well suited for
processing fibers with a high short-fiber content, which
is reflected in better evenness.
Ring yarn has the
Ring yarn, by contrast, has the highest
yarn tenacity on account of more intensive fiber integration
(Fig. 4). This opens a wider range of applications, namely the
increased use of these yarns in weaving mills. It is important
to note that tenacity reduces as the recycled and short-fiber
Fig. 4: The ring spinning process achieves significantly
higher yarn tenacities than rotor spinning.
Is it economical
to produce yarn from recycled fibers?
The economic efficiency depends on the
proportion of recycled material in the yarn, as this has an
influence on the yarn conversion costs and the yarn sale price.
In the Rieter trial a yarn count between Ne 12 and Ne 20 was
used and the yarn conversion costs were calculated for ring
yarns and rotor yarns in Turkey. (Fig. 5).
Fig. 5: The Return on Investment (ROI) is best for blends
containing 25% to 50% recycled material.
The economic analysis assumes a slightly
cheaper recycled raw material price compared to a medium-quality
virgin cotton. The calculation is also based on the realistic
view that trade will accept a higher price for yarn made of
recycled fibers. Depending on the amount of recycled fibers
there is little loss of yarn or fabric quality, but raw material
resources are better utilized and meet the need of many
companies to become more sustainable. A blend containing 25 to
50% recycled raw material should therefore achieve a yarn sales
price which is at least 0.1 to 0.2 cents per kg higher than that
of virgin cotton raw material, depending on the end-spinning
process and yarn count. Graph 5 shows that the Return on
Investment (ROI) is best for blends containing 25% to 50%
There will be greater or lesser scope for
the economic viability of the staple-fiber yarn production
process depending on whether it is a case of yarn trading or a
fully integrated process. In any case, the economic analysis
shows interesting opportunities for processing recycled cotton
raw materials using staple-fiber yarn production.
information on spinning recycled
fibers can be found here: