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Sustainable raw material for sustainable
textile production
by DyStar Ecology
Solutions.
Background With
sustainability being the current buzz word, the question remains
as to how far the industry can go to achieve measurable
improvements in sustainability with the existing choices of raw
materials like dyestuffs, chemicals, eco-friendly textile
fibers.
One important aspect is to identify the key elements and
areas in the textile production chain which could contribute the
most towards improved sustainability, if managed in the correct
manner. With our first paper of the sustainability series, we
gave an elaborate introduction and insight into the most
important elements of sustainability in the textile supply
chain. We looked into the economic, social and environmental
aspects of sustainability and identified the key challenges in
the chain. We emphasized the importance of sustainable design,
informed selection of dyes and chemicals, accurate color
communication and controlled coloration by Best Available
Technology.
In this paper we will deal with individual fibers to give you
an insight into their basic features and how DyStar expertise in
textile coloration and finishing can help our customers meet the
requirements and challenges of processing sustainable textiles.
Sustainable textile fibers
Recently, with the increase in consumer interest and the
establishment of third party certification systems a greater
focus has been given by the textile companies to the production
of sustainable fibers. New alternatives have been investigated,
developed and introduced to the market. Challenges arise when
these fibers have to be processed in the industry using the
available dyestuffs, auxiliaries, and chemicals. The Best
Available Technology has to be identified in order to maintain
the sustainable nature of the fiber and to achieve
sustainability in processing in order to deliver the sustainable
end product. DyStar anticipated these challenges well ahead due
to its network of contacts with innovative fiber producers and
started its research on the applicability of our dyestuff ranges
for the various sustainable fiber bases. With environmentally
compliant dyestuffs, highly experienced process expertise and a
solid foundation of textile industry knowledge, DyStar can help
its customers face the upcoming challenges of the new eco fibers
and contribute towards realizing sustainability in the textile
supply chain.
Organic cotton
Organic cotton has gone a long way to becoming the most
sustainable choice of today’s fashion world. With well
researched globally established standards and certification
systems this fiber has made its place in the textile world. This
is definitely a first choice for the brands and retailers when
coming to introduce a sustainable line. However the questions
related to its processing are still there among manufacturers.
DyStar’s efforts toward organic sustainability
Under our econfidence® program DyStar has co-operated with
organizations like the Institute of Market Ecology – (IMO) which
was instrumental in developing and implementing the global
organic textile standard (GOTS).
DyStar is the leading global supplier of dyes for cellulosic
fibers and has always been committed to
environmentally-responsible dyestuff production and optimized
application processes using best available technology to
minimize resource use and waste.
DyStar was one of the first companies to get its dyestuffs
approved to the GOTS standard for the specific use on organic
cotton. These low impact dyes from DyStar meet the demanding
requirements of the organic textile standard and provide the
basis for achieving a wide range of shades by all application
methods (exhaust dyeing, continuous dyeing, cold pad batch
dyeing and printing).
DyStar is currently preparing a manual for organic cotton
processing where the optimum processing technology by exhaust
and continuous pretreatment and dyeing methods can be shared
with the industry. DyStar takes a holistic approach towards
achieving sustainability. We believe in not only developing
suitable products but also advising our customers on the most
efficient recipes and processes to achieve efficient and
sustainable results.
Bamboo
Bamboo's eco-friendly positioning in the market has been
based on the following properties:
- A natural (that is, non-synthetic) fiber.
- A quick-growth plant (it belongs to the grass family) that
sequesters greenhouse gases.
- A renewable plant that can grow back after its three to
five year harvesting period.
- A plant that doesn't need pesticides or fertilizers during
its growth phase.
The manufacturing of bamboo fiber is where the debate really
gets heated. There are three methods by which bamboo may be
processed into fiber for fabric production.
The first is a mechanical process similar to that used to
process flax or hemp; the stalks are crushed and natural enzymes
break them down further, allowing fibers to be combed out. This
is an expensive process but it is eco friendly. The second other
method follows the process by which rayon is made where the
fibers are broken down with aggressive chemicals and extruded
through mechanical spinnerets. A third method follows the closed
solvent spinning loop which is used for the production of
Lyocell fibres (see further below).
Today the majority of bamboo on the market is processed as
rayon. As long as it is manufactured by the rayon process,
Bamboo fibre and fabrics will not be more sustainable than
Conventional rayon method. Retailers have sold both end products
as "bamboo fabric" to cash in on bamboo's current eco-friendly
image. However, the US Federal Trade Commission is cracking down
on the practice of labeling bamboo rayon as natural bamboo
fabric. Under their guidelines these products must be labeled as
rayon with the optional qualifier "from bamboo". True bamboo
fabric is known for its softness and boasts strong absorbency
and anti-microbial properties, but the chemical process in
bamboo rayon destroys this anti-microbial effect.
Bamboo fiber can be dyed with all dyes recommended for
cellulosic fibres. As usual, the dye class selection depends
mainly on fastness requirements. But as always when producing a
sustainable fibre, sustainable products in pre-treatment, dyeing
and finishing should also be selected.
DyStar offers a full range of GOTS 2.0 approved dyes and
auxiliaries which should be the first choice. In reactive dyeing
high fixation Levafix® CA dyes, with outstanding retailer
fastness performance in the pale to medium shade area, are
highly recommended. Remazol® RGB / Ultra RGB are the economical
and ecological solution for medium to ultra deep shades. Under
critical dyeing conditions (e.g. high density of yarn bobbins)
Procion® H-EXL hot reactive dyes keeps you on the safe side.
If the highest overall fastness levels are required,
Indanthren® vat dyes are the solution. On the other end of the
fastness scale, Sirius® direct dyes are highly suitable if only
a moderate wash fastness level is necessary.
Lyocell (Tencel™)
The manufacturing process for lyocell is different from that
of other regenerated cellulosic’s such as rayon, in that it
proceeds without the formation of intermediate compounds and
there is no curing or ripening stage, therefore the whole
process is complete in 3 hours. The use of minimal chemicals
means that the pure cellulose pulp used to feed the lyocell
process remains chemically unchanged by processing. No
aggressive chemicals are used for this spinning process only an
organic solvent. Therefore no regeneration of the cellulose is
necessary. The average polymerisation value (DP value) of the
cellulose used for the Lyocell process is the same at the
beginning and at the end.
Additionally the production process for lyocell is
characterized by an almost completely closed solvent cycle. The
spinning bath is cleaned, the excess water is removed by
evaporation and the solvent is then recovered for re-use. The
water generated during evaporation is used in the washing
process. On account of the closed-loop process, the solvent
necessary for the production process is recovered almost
completely. The remaining minimal emissions are treated before
disposal.
According to DyStar experts, the unique properties of the
DyStar’s Remazol Ultra RGB reactive dyes on lyocell fibers leads
to a significantly reduced impact in the effluent discharge and
in the total environmental load calculation.
Because of the higher build-up and fixation yield with the
Remazol Ultra RGB dyes, the lower amount of dye required to
achieve a given depth also means reduced quantities of
electrolyte resulting in lower TDS values in effluent.
Additionally the build-up of the Remazol Ultra RGB dyes is
higher on lyocell than on unmercerised cotton leading to
significant further reduction of unfixed colour, Chemical Oxygen
Demand and Total Dissolved Solids.
A full story about the sustainability of Tencel fibre in
cooperation with Remazol Ultra RGB dyes can be found on Dystar
homepage (www.dystar.com).
PLA (Ingeo™)
Ingeo is a polylactide acid fibre (PLA fibre) made from 100%
annually renewable resources and was introduced by Cargill Dow
LLC in January 2003 to the textile market. In 2003 out of
Cargill Dow LLC the company NatureWorks LLC was formed. The name
Ingeo literally means “ingredients from the earth”.
Ingeo is produced by fermentation of dextrose obtained in
this case from corn starch. Other potential feedstock could be
rice and potatoes and even grass or straw. The fermentation
products are subsequently transformed by condensation and vacuum
extraction into a high-performance polymer called polylactic
acid from which the branded Ingeo fibres and filament yarns are
extruded.
Ingeo combines the comfort properties of natural fibers with
the performance of man-made fibers like breathability, moisture
management, crease resistance, no support of bacterial growth,
inherent flame retardancy and UV resistance. In addition, the
fibres have environmental benefits that result from using
renewable resources as their feedstock, including reduced CO2
emissions and less fossil fuel usage than other materials
(estimated at up to 50%). In textile application Ingeo is used
for fibre fill, knitted apparel, furnishings, carpets and denim.
For successful processing of Ingeo fibres in the textile
mill, the following aspects need to be considered:
The melting point is 170°C – this is important for
determining the heat setting conditions, and fabrics can be
stabilized at 125 – 130°C for 30 seconds.
Hydrolytic degradation of the polymer can occur, particularly
under combined high temperature and alkaline conditions. The
degree of hydrolysis is influenced by time, temperature and pH,
and can be influenced by the modification of the dyeing and
finishing process.
The Dianix® range of disperse dyes are the preferred dye
class for exhaust dyeing of Ingeo fibers. Intelligent dye
selection on Ingeo is crucial, as individual dye behavior is
quite different from dyeing polyester. Disperse dyes should be
chosen for:
- High levels of dye bath exhaustion: to optimize
batch-to-batch shade reproducibility, reduce dye costs and to
minimize effluent pollution.
- Compatible dye combinations: to optimize Right-First-Time
dyeing performance and to reduce the production costs.
- Good color fastness: to washing, perspiration, light and
rubbing
More detailed information about preparation and dyeing of
Ingeo fibres and their blends is available in DyStar’s “Ingeo™
Fiber Coloration Pack.”
Recycled polyester
Two kinds of recycled PET are available on the market: One is
mechanically recycled PET (only melting of PET) which has a
strong yellowish shade and is not suitable for white or pale
shades. To get a better degree of whiteness a bleaching process
has to be carried out and even then the OBA has to be tinted
with some dyes to get close to the required level of white. The
bleaching process is not eco friendly at all and adds additional
cost to the process. This kind of recycled PET should only be
used for dark shades (mainly Navy + Black).
The other type of recycled polyester is a full chemical
recycled PET. This has a similar shade to “virgin PET" and can
be used without any problem for all shades. It is claimed that
the cost of recycled PET can be twice the cost of virgin PET.
Regarding dyeing, both recycled PETs behave the same as
"virgin PET" but careful dye selection is necessary to ensure
highest levels of exhaustion compatibility and fastness. As part
of its econfidence program DyStar has recently launched a range
of “green” Dianix dyes which are ideally suited for the
processing of recycled PET. A comprehensive screening program
covering raw materials and intermediates as well as
sophisticated dye manufacturing controls ensure that no harmful
chemicals are carried through onto the fiber.
Organic wool
Organic wool is different from conventional wool in at least
two major ways: (1) sheep cannot be dipped in insecticides to
control external parasites such as ticks and lice, and (2)
organic wool farmers are required to ensure that they do not
exceed the natural carrying capacity of the land on which their
animals graze.
The term “organic” doesn’t only cover management of the
livestock according to organic or holistic management principles
but also (1) processing of the raw wool, using newer, more
benign processes rather than harmful scouring and descaling
chemicals; and (2) wastewater treatment from scouring and
processing according to Global Organic Textile Standard (GOTS).
DyStar recommends its GOTS-approved Realan® EHF reactive dyes
for organic wool and a complementary range of GOTS-approved wool
auxiliary chemicals are available.
Dye and Chemical selection for eco
fibres
As for all eco fibers it is important that the Best Available
Technology (BAT) is used for coloration and finishing in order
to preserve as far as possible the eco credentials of the
fabrics produced. Using dyes and chemicals covered by DyStar’s
econfidence commitment gives both the dyer and the retailer
peace of mind that top quality products have been used and
confidence in the ecological qualities of the articles produced.
For more details please visit www.dystar.com.
The next article will be published in April 2010 issue of
Pakistan Textile Journal will highlight sustainable
methods/measures of colour communication.
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