Report 3: Textile Processing Techniques
Ref: S5471 September 1999
SATCO Report 3: Textile Processing Techniques
In order to determine the true environmental impact of textile processing the
main types of machinery in current use together with typical processing routes
need to be described. The pollutants and waste generated by these
processes together with typical levels or concentrations emitted or discharged
help to provide a more detailed picture of the polluting nature of the textile
For convenience, the whole textile chain has been split into seven main
sections. These are fibre production, fibre to fabric, preparative treatments,
textile coloration, finishing processes, fabric aftercare and recycling and
• Fibre production – this includes details on cotton growing, sheep rearing,
sericulture and the generation of man-made fibres.
• Fibre to fabric - which contains information on the types of machinery used
in spinning, weaving, knitting and non-woven production.
• Preparative treatments - which includes details of processes such as
desizing, scouring and bleaching.
• Textile coloration – contains information on the different methods used for
dyeing and printing.
• Finishing processes – includes information on coating and lamination, wet
chemical finishing and mechanical finishing processes.
• Fabric aftercare – which contains information on the different types of
commercial laundry and dry cleaning machinery used.
• Recycling and disposal – looks at the processes involved in textile
recycling, the segregation techniques and the different end-uses.
Cotton is cultivated as a shrubby annual in temperate climates but can be
found as a perennial in tree-like plants in tropical climates. The cultivated
shrub grows from about one to two metres tall over a growing period of six to
Warm and humid climates with sandy soil are the most suitable. Although
cottton can be grown between latitudes 45 N and 30 S, yield and fibre quality
are considerably influenced by climatic conditions, and best qualities are
obtained with high moisture levels resulting from rainfall or irrigation during the
growing season and a dry, warm season during the picking period. Rain or
strong wind may cause damage to the opened bolls. Cotton producing areas
vary in climate from arid to semi-humid. Some of the biggest include parts of
the USA, China, Russia, Brazil, Mexico, Egypt, Sudan, Turkey and India.
African producers include the Ivory Coast, Nigeria, Uganda and Tanzania.
Every year, new seed is planted, the crop grown to maturity, the seeds with
their fibres harvested, the dead plants destroyed and the land prepared for the
following season. The lint or raw cotton, is shipped to textile factories all over
the world, while most of the seed is processed for its food components
(soaps, margarine and animal feed cake). Only a small quantity of seed is
retained for planting.
Cotton is a key agricultural product in the world’s economy, and is particularly
important to developing countries. Production in the Third World provides a
livelihood to 125 million people. It ensures that developing countries have an
important source of foreign exchange ($25 billion annually) and a major raw
material to develop their own textile industries.
Cotton needs a lot of water to grow, over 50cm of rain in a season. However,
cotton can be grown with less rainfall by applying supplementary water from
Pests in the cotton can be controlled by the regular application of pesticides
sprayed onto the plants. Cotton is attacked by several hundred species of
insects. Limited insect control can be achieved by proper timing of planting, or
by selective breeding of varieties with some resistance to insect damage.
Chemical insecticides, which were first introduced in the early 1900’s, require
careful and selective use because of ecological considerations but appear to
be the most effective and efficient means of control.
Cotton plants are also subject to diseases caused by fungi, bacteria and
viruses. The treatment of seeds before planting is common, as is the practice
of soil fumigation.
A really good field of cotton ready for picking will yield about 1000 kg of cotton
fibre per hectare. Yields vary, but the present world average of only 400 kg
per hectare could be improved. Crops could be increased without using any
more land in developing countries if agricultural knowledge could be applied
and supplies of pesticide and fertiliser made available to the farmers there.
Even in the more advanced countries, the improvements in seed varieties and
farming techniques give better yields per hectare almost every year. The
present world production of cotton is about 13 million metric tonnes which is
grown on about 32 million hectares.
On small farms cotton is hand picked. It is packed in loose bales and is
marketed by farmers at local seed cotton markets. The buyer then provides
the transport to national ginneries. In countries where labour costs are high
and where the terrain is suitable, machine picking is used. These machines
collect immature bolls and other vegetable matter, which is called trash. To
minimise the trash collected, the plants are sometimes sprayed with a
chemical defoliant causing the leaves to drop prior to picking.
Ginning machines are designed to separate the cotton fibres from the seed.
The separation of fibres from seed is effected by means of a row of circular
saws passing through a series of narrow grids. The saw teeth grip the fibres
and draw them through the grids. The seed is too wide to pass through and
the fibre is thus pulled from the seeds.
Cotton is then baled in loads of 220kg. The bale which is fabric or plastic
covered is secured by strong metal bands.
Wool is available in a wide range of fineness, crimp, length and colour. Types
are denoted by quality numbers on a subjective scale related to fineness,
spinnability, etc. Merino wool is usually about 60’s –64’s, crossbred wool is
There are about 1000 million sheep of nearly 500 different breeds scattered
about the world, with large concentrations in New Zealand, Australia, South
Africa, South America, China and Russia. The British share of the world’s
sheep is 3%, with a 2% share of the world’s wool, but British sheep have
made contributions to the world’s flocks out of all proportion to the story the
statistics alone tell.
In order to protect the sheep during its productive lifetime, regular treatment
with pesticides is given in the form of a sheep dip. These pesticides, some of
which are organo-phosphorus, can be harmful to humans and so great care
must be taken when the sheep are being treated. Residual pesticides also
find their way into surface and ground water supplies and are found in the
waste liquors from raw wool scouring.
The basic steps in wool processing have remained unchanged for centuries.
Wool obtained from different parts of the sheep varies in fibre fineness, length
and crimp. There are variations between locks, or cohering bunches of wool,
and between fleece from different areas of the sheep. The quality of wool
obtained from the belly is short and burry; the shoulders yield the finest wool.
Sorting is the separation of the different qualities of wool from the fleece. The
most important property is usually fibre fineness, closely related to softness of
handle. The sorter unrolls the fleece on the sorters board, usually waist high,
and cuts away any wool carrying tar or paint marks. He next removes the
coarsest wool, placing it in a separate basket, and finally reaches the fine
wool on the shoulders. A sorter can generally sort up to 4500 kgs of
Australian fleece in a week.
Flax requires a temperate climate free from heavy rains and frosts. Frequent
moist winds during the growing season are advantageous. Hot dry summers
produce a short and harsh but strong fibre; moderately moist summers
produce plants yielding fine, strong, silky linen.
Flax is difficult to grow because of the soil preparation required before sowing,
and the heavy applications of artificial fertilisers required. After a slow initial
growth, the plants grow as rapidly as one inch per day for 30 to 40 days.
Blossoms then begin to develop and stem growth ceases. Flax is normally a
three month crop, although this growing time varies with climatic and other
It is attacked by several fungal and viral diseases, usually kept under control
by chemical treatments of the seed, or by cultivation of resistant varieties.
Harvesting is usually carried out by pulling the plant from the ground. Pulling
is considered superior to cutting since flax deteriorates at the cut. Yields of
fibre per acre vary from 200 to 360 kgs.
Like other bast fibres, flax must be separated from the stalks by retting. Water
retting, which is essentially bacterial, is practised in areas such as the
Philippines, Taiwan and China; most of the crop grown in Russia and the
United States is dew retted, which is predominantly fungal. In this method the
harvested flax straw is left in the field and allowed to remain until the
combined action of the moisture from dew and micro-organisms makes
separation of the fibres possible. The process depends very much on the
temperature and chemical nature of the water, but takes only six to eight days
under controlled temperature conditions. After removal of the stalks from the
retting medium, thorough drying is necessary to prevent further fermentation.
The retted and dried fibres are removed from the woody remainder of the
stem by the process of scutching, in which the stems are first broken by
passage through a series of fluted metal rollers, and the fine pieces of the
woody portion of the straw, called shives, are beaten out. About a tenth of the
original flax stem is useful fibre.
Although the lifecycle of Bombyx mori is typical of most other silkmoth
species, domestication over the ages has deprived the moth of its ability to fly.
This feature is exploited in sericulture to introduce an orderly sequence into
the whole cycle, for the moths can be put in desired places for egg laying.
The fully grown silkworm has two silk glands each filled with a concentrated
solution of the silk proteins, fibroin and sericin, the latter forming a sheath
around the former. The two glands unite in the spinneret, a minute aperture in
the muzzle of the worm.
Immediately prior to the process of pupation the worm first attaches silk fibre
to various supports, to form a scaffolding, and then extrudes the silk thread
and deposits it layer upon layer to form a cocoon around itself. Most cocoons,
except those required for propagation purposes, are subsequently heated by
a process known as stifling to kill the chrysalis within and prevent the
emergence of the moth which otherwise would make the cocoon unreelable.
Following the stifling process the cocoons are inspected and graded,
defective ones are separated for subsequent treatment as silk waste.
Reeling consists of unwinding the fibre from several cocoons together and
reeling the baves so as to form a composite thread of the required denier. A
Bombyx silk bave is only about 15 to 25 microns thick and it is too thin and
weak to be used singly. The reeling process consists essentially of softening
the silk gum, by maceration in hot water, removing the loose outer layers until
the free end of the bave has been located and then combining it with the
baves from other cocoons.
Although much of the world’s silk is still reeled from hand operated basins,
99% of the silk produced in Japan (the world’s largest producer and
consumer) is reeled on automatic reeling machines. With these machines the
process is considerably less labour intensive.
Silk throwing involves the preparation of the raw silk into a form suitable for
knitting and weaving. The first process is that of soaking the hanks in a warm
emulsion of various oils and other softening agents in a slightly alkaline
solution. During this process the oils are taken up by the silk gum. The
objective is to make the yarns more supple and pliable. Following soaking and
drying the hanks are rewound on to bobbins or cones. It is at this stage that
twist is inserted to form different types of yarn.
Many silk fabrics are still produced on hand looms which can produce
superior goods for which the purchaser is obviously prepared to pay the extra
Some 60% of the silk extruded by the silkworm is useless for the production of
continuous filament yarns, and the spun silk process is based on the
utilisation of this material. The technique of spun silk production is quite
distinct from that of thrown silk yarns, and many of the mechanisms involved
in the process are closely related to machines used in the preparation and
production of yarns from staple fibres such as cotton, wool, flax and jute. After
degumming, cleaning and opening, the fibres are cut into short lengths and
then combed into slivers. These are made into yarns by mixing, drafting and
The basic method of viscose fibre production can be split into five stages.
Firstly, sheets of cellulose in the f rm of purified wood pulp are steeped in
caustic soda solution and then pressed to remove the excess and ground into
crumbs. The crumbs are allowed to stand for a time during which ‘ageing’
occurs, the very long cellulose molecules are thus reduced in length to allow a
satisfactory spinning solution to be prepared later.
The product ‘alkali cellulose’, is churned with the liquid carbon disulphide to
form a soluble derivative of cellulose, cellulose xanthate. The crumbs turn
orange in colour and are then dissolved in a second caustic soda solution
forming the syrupy liquid viscose.
The viscose is allowed to stand for a controlled time to ‘ripen’. The chemical
and physical character of the solution changes slowly with time until an
optimum spinning condition is reached. Meanwhile it is subjected to vacuum
to remove gas bubbles and filtered.
The viscose is extruded at a measured rate through the holes of spinnerets
that are immersed in a bath containing water, sulphuric acid and salts. The
emerging filaments are coagulated and chemically changed back to cellulose.
They are drawn from the bath at a controlled rate that involves some stretch,
Either continuously or in batches, the fibres are washed free of coagulating
bath chemicals, are treated with further chemicals and are finally washed,
lightly oiled, and dried. In its final form the fibre may be either continuous
filament or cut staple.
The raw material for the production of polyester is oil. In the first step of
production the oil is cracked to give ethylene gas. This is oxidised in air with a
catalyst to form ethylene oxide, which is then hydrated to produce ethylene
glycol. This process was already well established for the production of
antifreeze and explosives, but a new commercial process had to be
developed for the other component, terephthalic acid. This is made from para-
xylene, which is distilled from petroleum and then highly purified.
Either the acid or its ester, dimethyl terephthalate, is added to the ethylene
glycol and then polymerised in a vacuum at a temperature of about 270 C.
The polymer is extruded from the polymerisation vessel in the form of a ribbon
which, after cooling, is cut into chips ready for further processing.
The bulk polyester is formed into filaments or fibre by first drying and then
melting the chips, and then pumping the molten polymer through many holes
in a spinneret. The fine filaments solidify quickly and are wound up either at a
speed of about 1000 m/min to produce undrawn yarn, or at about 3500 m/min
to produce a partially orientated yarn.
The nylon developed at Du Pont is formed by thermal polycondensation of
hexamethylene diamine and adipic acid, each component having six carbon
atoms, hence the name nylon 6.6. The first part of the process consists of
mixing the two components in exact proportions in methanolic solution from
which the nylon salt settles out. A concentrated solution of this salt is first
heated under pressure in an inert atmosphere to about 270 C; steam is then
bled off and the residue is heated further under vacuum to complete the
The nylon developed at IG Farbenindustrie is made by thermal polymerisation
of caprolactam in an inert atmosphere at temperatures up to 270 C, followed
by the extraction with water of about 10% residual monomer before the
polymer can be used. As the repeating unit in the polymer contains 6 carbon
atoms it is called nylon 6.
Nylons are thermoplastic, i.e. they progressively soften on heating and
eventually melt, nylon 6 at 210 C and nylon 6.6 at 250 C. This enables them
to be extruded in their molten state through small holes in a plate called a
spinneret to form very fine jets of molten polymer that quickly solidify to
continuous filaments as they are transported down a cooling chimney to the
The basic material for acrylic fibre production is acrylonitrile. This is usually
produced by the so called Sohio process.
Before 1960, acrylonitrile was commercially produced by adding hydrogen
cyanide to acetylene, or by dehydration of ethylene cyanohydrin. The
discovery and development of the ammoxidation of polypropylene (Sohio
process), appreciably reduced production costs because of the lower cost of
raw materials and the single step nature of the process. In the Sohio process,
propylene, ammonia, and oxygen, react at high temperature in the presence
of catalysts such as bismuth phosphomolybdate.
The acrylonitrile monomer is then combined with other monomers to produce
co-polymers or polymerised alone to form homopolymer acrylic. In order to
qualify for the description acrylic, the final polymer must contain at least 85%
by weight of acrylonitrile units. Acrylonitrile is an addition polymer, the
monomers adding or joining end-to-end without liberating any by-product.
Although acrylic polymer is thermoplastic, it does n melt sharply to give a
fluid melt suitable for melt spinning, and so must be solvent spun. This fact
delayed development of the fibre while a suitable solvent was found. Typical
solvents include dimethylformamide, dimethylacetamide, dimethyl sulphoxide,
ethylene carbonate, sodium thiocyanate (50% in water), zinc chloride (60% in
water), and nitric acid (70% in water).
Acrylic fibres are either wet or dry spun.
Principal pollutants: Emissions from oil processing, carbon disulphide
from viscose production, fertilisers in cotton and flax growing,
pesticides in cotton, flax and wool production, methane (from sheep
rearing), emissions from the transportation (fuel usage) of fibre.
Fibre to Fabric
Spinning (includes; opening, carding, combing/drawing, roving, spinning and
The fibre contained in cotton bales, for example, is first opened and cleaned.
The trash is removed and a lap or sheet of fibre is produced. Selection of
layers of cotton from different bales allows fibre blending to take place at this
early stage. Material losses can be 5% or more. Carding converts the lap to a
parallel sliver, removing more of the trash and some lint. In some modern
systems, tufts are fed through tubes directly to the card. The carding action
takes place between the surfaces of a large cylinder and a system of
overhead revolving flats, which are covered with fine wire points. This process
produces about another 4% to % in waste. The fibres collected at the end of
the card in the form of a filmy web, are condensed into a card sliver of about
25mm diameter. The sliver is then delivered into a tall can. Combing, the next
process (although optional, depending on the end use of the yarn), removes
short fibres and any remaining trash or nep. A lap forming machine is used to
combine a number of slivers into a wide ribbon of fibre which is then
presented to the comber. The total material loss up to this stage can be as
much as 15%, depending on the grade of cotton. In drawing, the card sliver is
drafted down to an intermediate roving. It is at this stage that man-made fibres
are blended into the final roving. At the speedframe a single drawframe sliver
is drafted 5 to 10 times and a slight twist added. This is wound onto a roving
bobbin. The roving is then spun into yarn. Total losses from fibre to yarn can
be large. For example 100 kgs of 50/50 polyester cotton yarn can require 56
kgs of polyester and up to 70 kgs of cotton.
In ring spinning a fine sliver of fibres is fed downwards from a roving bobbin
through a drafting zone, which drafts out the strand of fibres to the correct
thickness. The yarn is then wound onto a second package called a ring
bobbin. Twist is then inserted by the combined action of the spindle and the
traveller. The ringframe, in one form of another, is used for spinning all types
of staple fibre, wool, cotton and synthetics.
Another more recent method of yarn formation is called rotor spinning. This is
a form of open-end spinning where twist is introduced into the yarn without the
need for package rotation. Allowing for higher twisting speeds with a relatively
low power cost. In rotor spinning a continuous supply of fibres is delivered
from delivery rollers off a drafting system or from an opening unit. The fibres
are sucked down a delivery tube and deposited in the groove of the rotor as a
continuous ring of fibre. The fibre layer is stripped off the rotor groove and the
resultant yarn wound onto a package. The twist in the yarn being determined
by the ratio of the rotational speed of the rotor and the linear speed of the
yarn. The use of this system has two basic advantages. It is fed by sliver, not
as with the ringframe by roving, and so eliminates the speedframe from the
process line. It can also be modified to remove any remaining trash, thereby
improving the yarn quality.
Open-end spinning produces a different type of yarn to ringframe spinning.
Open-end yarns tend to be more uniform, lower in strength, more extensible,
bulkier, more abrasion resistant and more absorbent. It is likely then with all of
these differences, only some of which are beneficial, that open-end spinning
will not replace ringspun yarn as originally thought, but will be a
The production of worsted or woollen y arn differs from cotton in that the raw
loose fibre is first scoured, washed, dried and blended. Carding and
condensing for woollens and carding, gilling, combing (Noble or French),
gilling again, blending and drawing for worsteds. The result is what is called a
white wool top. The top is then drawn and spun into yarn. Woollen yarns are
made up of fairly short fibres, loosely spun with little twist. Worsted yarns
however, are made up of longer fibres with a higher twist. Woollen yarns have
a fuzzy appearance whilst worsted yarns are smooth.
Typically about 40 to 60% of the original raw wool is made up of wool grease,
suint (water soluble wool wax), excess water and dirt, which is removed on
scouring and drying. Oil is then added prior to carding to reduce later
breakages. A further 1 to 4% waste consists of burr which is removed at the
carding stage (alternatively it can be removed by carbonising which is an acid
Twist is inserted into the yarn at the spinning stage. If the direction of the twist
is to the left, looking up the thread, it is called S-twist. If to the right it is Z-
twist. When yarn is made of one strand of twisted fibres it is known as a
singles yarn, and when two or three singles are twisted together it is a twofold
or threefold yarn. When folded yarns are twisted together the result is a
cabled yarn. There are also a range of what are called ‘fancy yarns’ which are
obtained by variations in how yarns are twisted together. These include slub,
loop and gimp yarns.
Principal pollutants: noise and dust.
Typical noise levels found near carding machines, 84 dB(A); combing
machines, 90 dB(A); in twisting and texturing rooms, 101 dB(A); ring
spinning rooms, 92 dB(A); open end spinning, 93 dB(A); automatic cone
winding rooms, 93 dB(A).
Typical total dust levels found around these processes (opening to
spinning) vary from 0.1 to 2.5 mg/m³. With the higher levels found
around opening and carding machines. Levels depend on the type of
yarn processed, air ventilation rates and the age/ type of machine used.
Weaving ( includes; beaming, warp sizing and fabric/carpet weaving).
Before weaving can commence the warp yarns must be assembled onto a
beam. At this stage, cotton and some man-made warp yarns are sized to
improve their strength and to minimise breakages. The size is squeezed into
the threads as they pass between rollers and drying is achieved by large
steam heated cylinders. A variety of substances can be used as size, but
typically these are either polyvinyl alcohol, polyacrylic acid, carboxymethyl
cellulose or starch.
The yarn is now ready to be woven into fabric. A number of different types of
loom are available for this process, conventional shuttle, gripper shuttles,
rapier, multi-phase, air jet or water jet. Although, conventional shuttle looms
have now been replaced to a great extent by shuttleless rapier looms.
The Jacquard loom is different in that it is used for weaving elaborate fabrics
such as curtains and upholstery. Instead of the usual arrangement of healds
the jacquard is equipped with a series of cords and attachments called a
harness. This enables each warp thread in each repeat of the pattern to be
lifted independently. Movement of the harness is controlled by perforated
cards threaded together into an endless loop, in which the punched holes
correspond to the pattern.
Typical weave structures are calico or plain weave; twill weave, which
produces diagonal lines in the fabric; sateen weave, which is predominantly
weft-faced with a smooth surface; and figured patterns made on a Jacquard
A carpet is essentially a heavy pile fabric with vertical tufts or loops held in
place with a backing material. Carpet can be constructed by weaving the pile
and backing simultaneously, or by punching the pile loops into an already
prepared woven backing. The latter is called a tufted carpet and these tend to
be constructed using a nylon pile and jute or polypropylene backing. A
secondary backing with latex foam may also be applied on the cheaper tufted
The more expensive woven carpets such as Wilton and Axminster are woven
on large carpet looms, some controlled by a jacquard system, not unlike the
ones used for fabric patterning. Most Wilton type carpets are woven face to
face and then split down the middle to form two carpet pieces. Woven carpets
are generally made of a wool/nylon blend of fibres with a jute backing.
Principal pollutants: noise, dust and high effluent COD from residual
Typical noise levels found in shuttle loom weaving rooms, 100 dB(A);
gripper shuttle loom weaving rooms, 95 dB(A); rapier looms 92 dB(A).
Typical total dust levels found in weaving sheds vary from 0.1 to 6.0
mg/m³. Levels depend on the type of fabric processed, air ventilation
rates and the type of loom used.
Knitting (includes; texturing, winding, warping and knitting).
Man-made yarn is textured by twisting the yarn and heat setting it into place
before cooling and untwisting. On relaxing the yarn has a bulky, elastic
property suitable for knitted fabrics. Air texturing, an alternative process, uses
high velocity air instead of heat. The yarn is then wound onto cones.
Knitted fabrics are made by interlacing loops of yarn. Weft knitting is when
successive loops of a single yarn form a row running across the width of the
fabric. Warp knitting is when successive loops of yarn run along the length of
the fabric. Weft knitting produces a more extensible fabric and tends to be
used for producing items such as stockings, tights and socks.
Knitting machines are either circular or flat bed. There are many types of
circular knitting machines. A single jersey type utilises one set of needles for
knitting, disposed around the circumference of the machine. Yarns are fed in
from numerous bobbins in creels at each side of the machine and delivered to
the needles at various feeder points around the circumference. Cloth
produced by this method is tubular and is collected on a cloth roller at the
base of the machine. Another type of knitting machine is the flat V-bed type
which uses a single yarn supply which moves backwards and forwards on a
carriage. Fabric produced by this machine is flat, rather than tubular, and is
usually employed for making heavier fabrics suitable for garment blanks for
pullovers and cardigans.
Raschel or tricot warp-knitting machines are used for knitting coarse and fine
gauge fabrics. Coarse gauge raschel is used for outerwear, furnishings and
industrial purposes, whilst fine gauge tricot is used for lingerie, sheets and
Warp knitting is also used in the production of lace, net and elasticated net
(which used as a backing or lining material for stretch garments).
Circular Weft Knitting Machine
Principal pollutants: noise and dust.
Typical noise levels found in a warp knitting room (compound needles)
Typical total dust levels found in knitting rooms vary from 0.2 to 1.2
Non-wovens (includes; needlepunching, adhesive bonding, stitch bonding,
spun bonding, spun laced and wet laid).
Needlepunching, the first of six methods used to form a non-woven, produces
an interlocking of the fibres in a fleece. The fleece is usually derived from a
carding machine. The action of the needles pushes some of the fibres down
through the fleece effectively holding it together. In adhesive bonding,
adhesive is impregnated or sprayed onto the fleece. It is then dried in an
oven. Stitch bonding is a process by which the fleece is held together by a
knitted structure based on interlooping tufts of fibre from the fleece. Spun-
bonded materials are based on a continuous filament being randomly
deposited onto a porous belt with suction. The web is then heated or
chemically bound, producing a more traditionally textile-like non-woven fabric.
Spun lacing is similar to needle punching but uses a high velocity jet of air
instead of a needle, whilst wet laid, a process with limited success, is very
similar to the paper making process.
Principal pollutants: Noise (to a lesser degree than spinning, weaving
Typical noise levels in adhesive bonding are 83 dB(A), whilst in needle
punching, levels are about 85 to 86 dB(A).
Cotton is prepared for dyeing by removing the surface fibres. This is done by
singeing the surface of the fabric with a gas flame. The equipment used for
this process is very simple and has changed little in design over the years.
Both flat and tubular knitted fabrics as well as woven fabrics can be singed.
Desizing units are sometimes used in conjunction with the singeing process.
Principal pollutants: dust and fume.
Typically levels of dust in the process emissions from singeing are of
the order of 10 to 40 mg/m³, whilst in the workroom levels vary from 2 to
The size added to the yarn prior to weaving must now be removed. This is
achieved by either an enzyme treatment or by dilute acid and a simple
washing off procedure. If starch is the size on the fabric then it can contribute
up to 50% of the total BOD loading from the processing of a typical woven
fabric. Other sizes such as PVA are recoverable and so have less of an
impact on effluent BOD.
Principal pollutants: High BOD/COD in effluent.
The chemical oxygen demand (COD) of a desizing effluent varies
between mg/l and mg/l. Water usage for this process is of the
order of litres per kg of textile.
Scouring (including; loose stock, yarn, fabric scouring and milling)
Scouring of cotton or man-made fibres to remove oils or lubricants, is done at
either the hank, yarn or fabric stage, prior to dyeing. This is not the case for
wool, where the large quantity of impurities present means that it is always
necessary to scour the fibre in its raw state. Cotton and flax scouring is
usually done at high temperature using a caustic liquor, whilst wool goods
require a milder soap and soda, or detergent scour at low temperature. Raw
wool scouring, washing and drying is usually done in a single continuous
operation prior to blending.
The milling of woollen fabrics is a process, which effectively compacts the
textile structure producing a change in handle from a slight to a dense matting
or felting. The process is undertaken at low temperature using soap and soda
or detergent. The process was originally undertaken on old open topped
wooden milling machines, some of which are still in use because of their
gentleness in processing and hence better fabric finish that they can provide.
More modern milling machines resemble winches in shape and basic design,
they may not be as gentle as the old machines, but they can be used for a
wider range of processing.
Traditional Raw Wool Scouring
Principal pollutants: High effluent BOD (biochemical oxygen
demand)/COD and solids. Pentachlorophenol residues from cotton
scouring and pesticide residues from wool scouring .
Wool scouring effluent has a pH of between 8-10, with a COD of between
5000 and 35000 mg/l and a suspended solids content of anything up to
20000 mg/l. Cotton scouring effluent and wool milling effluent are
considerably less polluting with respective COD’s of about 200 mg/l and
1000 mg/l and suspended solids contents of 100 mg/l and 150 mg/l.
Severe limitations are placed on the concentration of PCP and
pesticides in textile effluent. The cost of treating effluent containing
these substances is usually high. The introduction of bans on the use of
PCP and certain pesticides has led to a significant improvement.
However, the problem still exists.
Water usage for these processes varies considerably. Typical values are
10 to 20 litres of water per kg of scoured wool, and 10 to 30 litres per kg
of scoured cotton.
This process is used predominantly on cotton or cotton blend fabrics or yarn,
although it may also be required on wool and acrylic where a white yarn is
needed. The whiteness of the goods (cotton or linen) is improved by treating
with hypochlorite or peroxide. Nowadays, it is predominantly the latter that is
used, at least for cotton goods. Hypochlorite bleaching can cause
environmental problems due to the presence of chlorine breakdown products,
but it still is the preferred method when bleaching linen goods due to the
better level of whiteness that can be achieved. Absorbable organo-halogens
(AOX) which are produced by hypochlorite bleaching, amongst other
processes, are consented for discharge in some European countries. Notably,
Sweden and Germany.
Desizing, scouring and bleaching, or more commonly just scouring and
bleaching can also be achieved in a single continuous process. Washing
ranges associated w continuous preparation invariably have countercurrent
flow, lidded tanks and heat recovery systems to help minimise water and
Principal pollutants: Effluent pH, residual chlorinated organics (AOX)
and chemical oxygen demand (COD).
Effluent from bleaching operations contain the residues of oxidising
agents, as well as alkalis or acids. Residual peroxide is not a problem,
but other oxidising agents may reduce the effectiveness of some at
effluent treatment plants.
This is the treatment of cotton or linen yarn or fabric with concentrated caustic
alkali. It has the effect of swelling the fibres, increasing their strength and dye
affinity and altering the lustre and handle of the material. Mercerisers are
either chain or chainless and consist of three sections, impregnation,
stabilisation and washing off.
Most mercerisation units have their own caustic recovery systems to help
Principal pollutants: Alkaline effluent from washing and rinsing
rom mercerising operations consists mainly of mildy caustic
rinsewater. Typically the pH of this effluent is about 10 to 12. Water
usage for this process is about 20 litres per kg of cloth.
The fabric, yarn or loose stock is now ready to receive colour. Dyestuffs can
be applied by many different techniques to give shades which are fast to
washing and light. Dyeing can be carried out at almost every stage of
manufacture. Yarn dyeing is quite common, to obtain coloured yarns with
which the weaver can produce a wide range of coloured striped or check
designs for such fabrics as shirtings, bedding and dress materials.
Dyeing (includes: atmospheric, pressure and pad dyeing systems)
There are a wide range of machines and processes available for dyeing fibre,
yarns, staple, tow, fabric and garments. Dyeing can be done continuously or
batchwise, at pressure or in open vessels. The process chosen depends on
the nature of the textile, the type of dyestuff and the end use.
Yarn dyeing is done at pressure on a package dyeing machine, with the
cheeses or cones of yarn being mounted onto vertical hollow spindles. The
spindles are lowered into the cylindrical vessel and the lid bolted down. Heat
is applied via a steam coil and the dye liquor is forced through the package in
a two-way flow pattern until the correct shade has been achieved. This is
confirmed by testing a package held in a sample pot on the side of the main
vessel. Liquor ratios vary from 3:1 to 10:1 depending on the nature of the dye
and package .The liquor is then cooled using a heat exchanger before it is
dropped to drain.
An alternative way of dyeing heavier yarns is the hank dyeing machine. Hanks
of yarn are threaded onto horizontal poles and the poles are lowered into the
dyebath. These machines tend to take up a lot of floorspace and are
nowadays only used for dyeing bulky wool or acrylic yarns.
Machines used for dyeing loose stock are similar to those used for dyeing
yarn except that the textile is placed in a basket or perforated cage instead of
being placed on a spindle.
The continuous dyeing of yarns and tow is much less common. Machines are
used for dyeing polyester and acrylic tow where the tow is padded through
dye liquor and then through a tunnel for fixation and washing.
Fabric dyeing in batches is done on one of four basic types of machine. The
jig, winch, beam or jet type. The jig is the oldest and simplest type of machine
for dyeing woven fabric. It is suitable for fabrics which cannot be creased
during processing. The fabric is wound on to a roll. This then passes through
the dye liquor and onto a second roll. The process is repeated back and forth
until the desired shade is achieved. These machines are very versatile and
can also be used for the batchwise preparation of fabric (scouring and
bleaching) prior to dyeing. Heating is through steam coils although direct
steam injection is usually also provided for rapid heating up of the dye bath.
The exhausted liquor is dropped hot directly to drain.
Jig Dyeing Machine
Winches are used for fabrics that can withstand creasing when in rope form. It
is ideal for loosely woven cottons, woollens and some knitted and man-made
materials. The fabric circulates, in a continuous rope of between 50 to 100
metres, over reels and rollers and down into a dyebath. Old winch dyebaths
were constructed using wood, but these have been largely replaced with more
versatile modern steel vessels.
Jigs and winches are atmospheric machines. There is a requirement however,
for dyeing certain types of fabric at high temperature and pressure. These
lightweight, delicate and knitted fabrics suffer creasing, damage and poor dye
uptake on jigs and winches. The answer is to dye using a pressure beam or
jet type machine.
Pressure beams consist of a roll of fabric wound around a perforated beam.
This is placed in a horizontally orientated dyeing vessel and the door bolted
shut. The liquor is heated using steam coils and circulated through the fabric.
Dyeing temperatures are typically 120 to 130°C. On completion of the dye
cycle the liquor is cooled using an integrated water cooling system. The
warmed cooling water can then be stored at temperatures of about 40 to
50°C, as an alternative to passing it through a cooling tower, and used for
The final class of machine used for batchwise dyeing of fabric is the jet or jet
type machine. Fabric is circulated in a rope form with a vigorous circulation of
liquor, at temperatures of between 120 to 130°C . Variations on this type of
machine include fully flooded and Softflow machines useful for delicate and
sensitive fabrics. As with the pressure beams these high temperature jets are
fitted with cooling systems with the potential for reuse of the warmed water on
the next dyeing cycle.
The continuous dyeing of fabric is preferred where large quantities of woven
fabric have to be dyed one colour. It is therefore a more common process in
American mills where orders tend to be much larger. The fabric is fed through
a pad bath then nipped through rollers to remove excess liquor. It is then dried
and the dye fixed. Fixation can be done at high temperature as with the
Thermosol process for dyeing fabrics containing polyester, or it can be done
using a steamer (saturated steam) as with the v sulphur and direct dyeing
Principal pollutants: residual colour in effluent.
The pollutant load of discharged dye liquor is generally low, although
reactive dyes still have relatively poor exhaustion rates. Where these
dyes are used coloured effluent is still a problem.
Typical colour absorbances of reactive dye effluent over the visible
range from 400nm to 700nm can be as high as 1 to 1.5AU (using a 10mm
cell). This is considerably higher than consent levels, which can be as
low as 0.01 to 0.06 AU for discharge to river.
Water usage in dyeing is relatively high since it not only includes the
dye liquor, but also all the preparative, rinsing and finishing stages
involved in the application of colour. Typically, from 4 to 50 litres of
water is used to dye each kg of textile. This ratio is highly dependent on
the type of dye machine, the fabric to be dyed and the class of dyestuff
used to match the customer’s requirements.
In a typical process involving the pre-treatment, dyeing and rinsing of a cotton
fabric a whole host of chemicals will be used. These include sequestrants,
alkalis, bleaching agents, stabilisers, catalysts, crease resisting agents, acids,
levelling agents, dyes, exhausting agents, soaping agents and softeners.
Probably 20 to 30 chemicals, contained in 10 to 15 individual treatment
baths/systems. The total effluent from these processes will have a COD of
about 1000 to 1500 mg/l, a BOD of 300 to 500 mg/l, suspended solids of 200
to 400 mg/l, a pH of 6 to 8, a temperature of 35 to 45°C and will probably also
contain traces of heavy metals and PCP.
Printing (includes; rotary, flatscreen and transfer printing)
In rotary and flatscreen printing, colour is applied to a fabric by passing it
under a series of rollers of screens where a part of the pattern is exposed,
allowing the colour through to the fabric on the stroke of a squeegee. The
printed fabric is then dried in an oven. In flat screen printing the colour passes
through a screen onto the cloth, the pattern being produced by masking out
parts of the screen. Each colour used in the design requires a separate
screen. Well designed, mechanised flat bed machines give precise prints and
are suitable for wide fabrics or large pattern repeats.
For roller, or rotary screen printing the required design is cut into the surface
of copper rollers. Again, each colour in the pattern requires a separate roller.
If a large pattern is used then the roller must have a bigger circumference.
This is why large patterns are avoided in roller printing. By varying the depth
of the engraving on the roller the shade depth can be altered. A characteristic
of engraved roller printing is the sharpness of line and the very fine detail
which can be obtained.
Rotary Screen Printing
Transfer printing differs from the other two methods in that the printed pattern
is transferred from printed transfer paper onto the fabric by passing both over
a heated roller.
The paper, which is printed with volatile dyes, is heated for 30 seconds at
temperatures of up to 200°C. The dyestuff transfers to the textile by
sublimation. The advantage of this type of printing is that no other chemicals
are used and no other processes are required to finish the cloth. This helps to
minimise energy and water usage. The quality of print however, does not tend
to be as good as that achieved with flat screen or rotary printing.
Principal pollutants: colour in effluent from washing down. Low level
VOC’s, formaldehyde and ammonia in fumes from the drying ovens.
After each printing run the rollers, squeegees, screens and print paste
containers that have been used must be cleaned out thoroughly ready
for the next print run. This is achieved using water spray guns and tub
cleaning machines. Wherever possible water is recycled. However there
is still a lot of water consumed by this process. For example, it takes 100
litres of water just to clean one screen or squeegee, and on average
about 250 litres of water to process one kg of printed textile (transfer
Coating and Laminating
Coating processes were, in the past, large consumers of solvents. Solvent
based coating formulations produced significant VOC (volatile organic
compound) emissions. More recently, with increased environmental
legislation, companies have gone over to water based, or low solvent
formulations. Where alternatives are not available then recovery and
abatement systems have had to be installed. Coatings are applied using a
doctor blade on a roller, by padding techniques or by spraying. The textile is
then air or oven dried and cured at a controlled rate.
Laminating, or the formation of a layered textile, is a common process used in
the production of such items as internal trim panels for the automobile
industry. Lamination can be achieved by either the use of solvent based
formulations or hot-melt cured polyurethanes followed by low temperature
curing through an oven, or by flame lamination where the component textiles
are brought together and passed rapidly over a flame. This effectively seals
Principal pollutants: Fume, volatile organic compounds (VOC’s), and
A wide range of solvent types are still used, although in much lower
volumes, in coating and lamination processing. Where emissions
exceed consent, which in the UK varies between 50mg/m³ and 150mg/m³
(as carbon), then process modification, such as solvent replacement or
if this is not possible then some form of abatement is required. This can
be done using carbon absorption or thermal oxidation/incineration,
usually with heat recovery.
The formulations used in lamination and some coating processes
commonly include isocyanate. The health implications of inhaling
significant levels of this chemical are severe, and so strict limits are set
on both workroom exposure and process emission concentrations to
Wet Chemical Finishing (includes; FR treatment, enzyme treatment, resin
finishing, steam treatment)
A variety of finishes such as Proban and resin finishes can be applied by
padding liquor onto the fabric prior to stenter drying/baking. The concentration
of the liquor, the fabric speed and the moisture retention after mangling
determines the level of pick-up on the fabric.
The application of an easy-care finish is one such process. Easy-care
finishing reduces the tendency of the fabric to crease in wear and makes it
much easier to iron after laundering. The same finish also prevents shrinkage
during washing. These types of finish have greatly reduced the maintenance
which cotton in everyday use requires, and have increased its suitability for
apparel of all types.
Principal pollutants: Formaldehyde and ammonia emissions from curing
Formaldehyde concentrations during resin curing processes are
typically 5 to 15 mg/ m³ in the process emissions from the stenter and
0.2 to 0.5 mg/m³ in the workroom . Ammonia concentrations during
ammonia curing of cotton fabrics can result in process emissions of the
order of 4000 mg/m³. It is essential therefore that some form of
abatement, such as a wet scrubber, is fitted to this process so that
emissions can comply with legal requirements.
Mechanical Finishing (includes; raising, shearing, calendaring, schreinering
Mechanical finishing involves the modification of the fabric by means of
mechanical action. Raising is achieved by passing a fabric over a series of
wire rollers. This has the effect of pulling the surface fibres to give a brushed
or raised effect. Shearing is almost the opposite, where protruding fibres are
removed from the surface of a fabric by cropping the surface.
A calendar or schreiner consists of two heated rollers through which the fabric
is passed. This has the effect of smoothing and flattening the surface,
conferring a glaze, lustre or pattern on the fabric.
Sanforising is the shrinkage of cotton fabric, and is achieved by controlled
dampening and drying of the relaxed fabric to remove any tensions and
distortions which have appeared as a result of earlier processing.
Principal pollutants: Dust from raising and shearing.
Dust levels found near raising machines are usually in the range from 1
to 3 mg/m³, whilst near shearing machines they reach about half of this
Fabric Finishing (includes; water extraction, drying, pulling to width and heat
After preparation, washing or colouration, textiles require drying. This is
usually carried out in two stages. The first stage is mechanical dewatering
using centrifuges, mangles and vacuum slots. Mangling is the most cost
effective way of removing water mechanically but water retention levels are
still quite high. Centrifuging can only be used for relatively small batches of
fabric. It is more effective than mangling but costs almost twice as much in
terms of the energy required per kg of water removed. It is a method more
commonly associated with the woollen industry. Suction or vacuum slots are
the most effective way of mechanical dewatering (except for woollen fabrics
where water removal under suction is poor) but they are the most expensive.
Improved drying rates alone may not be sufficient to justify the expense. An
alternative use of vacuum slots is the recovery of chemicals from pad finishing
operations. It is sometimes the case that they are bought for the chemical
The second stage involves heating the textile and removing the remaining
water by evaporation. This is done using cylinder dryers, stenters, batch
drying ovens, infra-red or RF dryers.
The traditional way of drying yarn or loose stock textiles was by a warm air
drying oven. A large batch drying oven which when full takes up to 24 hours to
dry the textile load. More recently, radio-frequency (RF) drying has become
widely used, as it produces a rapid and uniform drying of the textile goods,
even though it is a relatively expensive process.
The latest RF drying systems use a combined vacuum arrangement and RF
drying capability, enabling drying to be achieved at much lower temperatures.
This helps to save energy and improve product quality.
Diagram of Stenter
Fabric drying is usually carried out on either drying cylinders (intermediate
drying) or on stenters (final drying). Drying cylinders are basically a series of
steam heated drums over which the fabric passes. It has the drawback of
pulling the fabric and effectively reducing its width. For this reason it tends to
be used for intermediate drying. The stenter is a gas fired oven, with the fabric
passing through on a chain drive, held in place by either clips or pins. Air is
circulated above and below the fabric, before being exhausted to atmosphere.
As well as for drying processes, the stenter is used for pulling fabric to width,
chemical finishing and heat setting and curing. It is a very versatile piece of
Modern stenters are designed with improved air circulation, which helps to
improve drying performance, and with integrated heat recovery and
environmental abatement systems.
Infra-red drying is used for both curing and drying. It is used as either a stand
alone piece of equipment, or as a pre-dryer to increase drying rates and
hence fabric speed through a stenter.
In the carpet industry there are a number of different types of drying/curing
machine used. Wool wash dryers at the end of scouring machines for drying
the loose stock wool; wool drying ranges for drying wool hanks prior to
weaving; and wide 4 and 5-metre latexing or backing machines used to apply
and dry/cure the latex backing on to carpets. Low level VOC emissions are
produced by this process.
Principal pollutants: Oily fume during setting of man-made
Typically the setting of a man-made fabric on a stenter produces oil
mist/fume emissions in the exhaust ducts at concentrations ranging
from 20 to 200 mg/m³, whilst in the workroom levels may reach 10 to 20
Stenter manufacturers now make abatement systems that can be bought with
a new machine or retro-fitted to an old one, these systems usually comprise of
a heat recovery section followed by an electrostatic precipitator. Provided the
unit is cleaned on a regular basis then removal efficiencies can be as high as
85%. More simple heat recovery and filtration systems are also available,
these tend to be cheaper but they require more maintenance than those
based on electrostatic precipitators.
Garment or Product Making-up
The final production process, at least in the garment or domestic textile
sectors, is the cutting up and sewing of the fabric. Cutting up is achieved by
placing layers of the same fabric on a long table, and then automatically
cutting through all the layers using a computer controlled system capable of
organising the patterns so that there is minimal fabric loss. The sections are
then sewn up on industrial sewing machines. Where required the final product
may be pressed or ironed or passed through a garment finishing oven before
being packaged for final delivery.
Principal pollutants: Dust and noise from cutting up and sewing
operations and residual formaldehyde from garment finishing ovens.
The noise from sewing machines can be quite high, especially when
there are forty or fifty machines all operating in close proximity. As is
usually the case. Levels have been recorded in the range from 80 to
Dust is also produced around a sewing machine by the action of the
needle on the fabric. It of course depends on the nature of the textile,
but again levels have been recorded as high as 5 – 10 mg/m³. More
typically levels are in the region of 1 - 3 mg/m³.
Formaldehyde can also be a problem in some cutting and sewing rooms,
where resin treated cotton or polyester/cotton fabrics are being used,
especially around garment finishing ovens.
Inspection and Quality Control
Inspection and quality control is probably the only relatively clean stage, in
terms of environmental pollution, of the whole textile chain. It plays an
important role however, in terms of helping to reduce waste (seconds are sold
on at much lower cost and so need to be eliminated) both of the product and
of the raw materials, and to improve the quality of the product. The garment or
item produced must wear well, must not contain any banned chemicals and
must not affect the wearer or user in any way that may be detrimental to
Certain dyestuffs are known to trigger dermatitis, whilst formaldehyde is a well
known irritant. It is therefore important to keep monitoring the processes in the
textile chain and to test samples periodically to ensure that they comply with
any quality or environmental standards.
Principal pollutants: none.
Fabric Care (includes; washer extractors, tunnel washing, tumble drying,
tunnel finishing, dry cleaning and calendaring)
The typical laundry usually consists of a number of washer extractors, which
are card controlled industrial batch washing machines ; a tunnel washer,
which is a counterflow continuous washer based on the principal of the
Archimedian screw ; a number of tumble dryers, with programmable drying
cycles for different catagories of textile ; a couple of calendars, which are
large presses ; and a collection of smaller presses and ironing tables.
Laundries that process a lot of garments may also have a tunnel dryer, a long
steam heated drying tunnel through which garments pass suspended on
hangers. There are also specialised machines for cleaning such items as
roller towels and hire mats used by the fabric care rental sector.
Design of Typical 13-Stage Batch Continuous Tunnel Washer
Dry cleaning machines use recoverable solvent, usually perchloroethylene,to
clean woollen garments and the more delicate fabrics that cannot be cleaned
in a normal washing machine, due to problems with shrinkage and distortion
at the seams. Apart from residual losses from machine venting, solvent used
in this process is, cleaned and reused.
Bans on the use of certain halogenated solvents have led to more research
into the use of alternatives, such as mixtures of hydrocarbons or even
aqueous based formulations based on limonene.
Principal pollutants: High COD, poor detergent BOD and high solids
content in effluent. Fume around garment drying tunnels. Residual
VOC’s around dry cleaning machines.
Historically, the reclamation and fibre re-cycling industry became an integral
part of the UK woollen industry. Recovered material from worsted production
and other materials of lower value were used as a source of fibre for lower
quality cloths, and machinery was therefore developed alongside this need to
regenerate the used fibre. The industry continued in this traditional way until
the larger scale introduction of synthetic fibres after the Second World War.
Re-processing became more complex especially with the increased use of
multi-component blends. During the 1960’s and 70’s the house to house
collection of worn garments gradually disappeared and the onus was put on
the householder to take these items to a charity shop or more recently to the
local recycling points/clothing banks.
The organised recovery of textiles can be traced back as far as the old
clothiers, many of whom were farmers involved in all stages of textile
production. However, the practice of recovering this used material is probably
as old as the art of spinning and weaving itself.
The clothiers would buy rags and convert them into a state where they could
be turned back into yarn and eventually cloth. The rags were collected by
horse and cart or by packhorse and deposited in a yard. They were then
sorted and pulled. The fibres were then ready for reprocessing. At this stage
the industry was still a cottage industry with people working where they lived.
Benjamin Law invented shoddy and mungo, as such, in 1813. He was the first
to organise, on a larger scale, the activity of taking old clothes and grinding
them down into a fibrous state that could be re-spun into yarn. The shoddy
industry was centred on the towns of Batley, Morley, Dewsbury and Ossett in
West Yorkshire, and concentrated on the recovery of wool from rags. The
importance of the industry can be gauged by the fact that even in 1860 the
town of Batley was producing over 7000 tonnes of shoddy. At the time there
were 80 firms employing a total of 550 people sorting the rags. These were
then sold to shoddy manufacturers of which there were about 130 in the West
Picture of used textile collection (late 19th Century)
The shades of recovered wool produced by the shoddy trade, especially in the
early days, tended because of the nature of the process, and the source of
the garments, to be dull. There were lots of greys, blues, and blacks obtained
from old uniforms. A lot of this went back into uniforms producing a complete
cycle of use.
As more and more fibre blends and cotton appeared, and competition from
the Italian recycling industry became stiffer, there was a tendency for the
English rag trade to move towards garment sorting and the selling of second
hand clothing to the third world. Today there are only about ten rag pulling
companies left in the UK, even so, there are still a lot of recoverable textiles
Typical figures for the textile material ‘lost’ during each stage of processing,
and use, gives an idea of the potential for the minimisation and the re-use of
what is essentially a feedstock material.
Fibrous/Fabric Re-useable Material
Typical Material Losses %
Raw Fibre and/or Reuse:
Prep’n/Blending 2 - 10
Loose Stock Prep’n Secondary Fibres
Synthetics 1 -7 Spinning
Natural fibres 1 - 20
Texturing 0 -2
Weaving 3 -8 Fabric Production Losses:
Knitting 2 -6 or Assembly Condenser/fibre.
Finishing 3 - 10 Finishing
Making/up 5 - 20 Product/Garments Losses:
Yarn, Fabric, Garments
Sorting and Reuse
Export Wiping Cloths
It is worth noting t at even in these days of increased environmental
awareness, about a million tonnes of textiles are landfilled each year in
the UK. Only when a textile has reached this stage can it be truly
classified as a waste.
Recoverable material, a bi-product of processing and use, is generated at all
stages of the life cycle of a fibre. Wherever possible in the early stages of
processing, that is from the raw fibre up to spinning, what is essentially ‘lost’
fibre is collected and reused in the process. Once the yarn is woven or knitted
up into a fabric the options for reuse become more limited. Wool and synthetic
recovered material (yarn and fabric) can be pulled apart and recycled, but
cotton and cotton blend recovered material is a more difficult proposition since
the cotton fibre length after pulling is too short for reuse. Historically this bi-
product of the industry has been used for wiping rags and filling materials.
There is also a significant trade in acrylic and hosiery clip off-cuts from the
clothing industry and acrylic jumpers from the clothing recycling sector.
The average lifetime of a garment is probably about 3 years. At the end of this
period it is either thrown into a dustbin or if in better condition passed on to a
charity shop or clothing recycling bank. Throughout Europe the collection of
worn clothing is a well-organised industry. Sorters either collect clothing
directly from networks of clothing banks, or increasingly, in the UK, organise
house to house collections or buy surplus clothing from charity shops and
jumble sales. The charity shop first removes the cream of the clothes that they
receive from the public and then sells the rest on at prices which can vary
from nothing up to £250 per tonne (1999). This depends on the state of the
market for second hand clothes in the developing world as well as that for
Across the whole of Europe the total sorting output is probably in the range
675000 – 750000 tonnes per year. About half of this total is produced by
Holland and Germany, whilst UK sorting levels are at about 250000 tonnes
Typically, the clothing sorted by the garment reclamation industry can be
broken down into the following categories :-
Cream – as new 5%
Second-hand clothing 45%
Fibre reclamation 25%
Wiping cloths 15%
Oddments and rubbish 10%
The cream percentage accounts for the garments that have hardly been used.
These are sold through charity and ‘second-hand’ shops throughout Europe
and can command prices ranging from £2-3 per item up to even £100 or
more, this equivalates to £1,000 - £10,000 per tonne (1999).
Sequence of photographs –
Opening bags of donated clothes
Sorting into different types from a moving conveyer
Checking shirts for wear
Grading jackets and trousers for quality
Bales of clothes awaiting shipment to other countries
The second-hand quality accounts for the largest proportion of sorted clothing,
and this finds its way to the developing third world markets. Second-hand
handbags, belts and shoes also find their way to these developing countries.
Most of us when recycling clothes tend to forget to recycle underclothes for
many reasons, but these are in great demand too.
The sorting of the clothes is a very labour intensive procedure and requires a
significant amount of specialist knowledge. Today the specialist textile
recycler will sort into about 140 different grades. Typically Africa probably
takes well over 100000 tonnes per year of this quality of clothing.
There are many countries involved in this trade. The main markets for
European sorters are the African states, Pakistan and Estonia, Latvia and
Lithuania. The USA and Canada tend to supply South America, Africa and
Pakistan, whilst Australasia concentrates on trading with Vietnam, Thailand
Fibre reclamation, which accounts for about a quarter of the clothing sent for
sorting consists mainly of woollens and single shade synthetics. This sector
has somewhat stagnated over the past few years. A significant market for
reclaimed fibre is India. It is interesting to note that because of the Indian
Government’s ban on the import of second-hand clothing all clothing sent for
fibre reclamation must be mutilated so that it does not find its way into the
second-hand trade. These import restrictions are designed to stimulate the
domestic industry which processes woollen jackets back into blankets and
other useful items of clothing at prices that the ‘home’ market, that is Indian,
The remaining fabric can then be utilised as industrial wiping cloths and
flocking rags. Wiping cloths are produced after the removal of buttons, zips,
seams and other ‘appendages’, which could scratch or cause damage. They
are graded from white cotton wipers down to synthetics for use in various
industries. Flocking rags are shredded and then sold on for industrial usage
as filling materials, ending up in mattress or upholstery felts, automotive
sound absorbency panelling as well as carpet underlay.
More recently, different more cost-effective strategies have been introduced to
minimise the large amounts of unwanted material generated. Synthetic fibre
production from non-fibre sources such as polyethylene bottle waste and from
polypropylene waste, and the depolymerisation of consumer waste back to
the polyester and nylon monomer are two of the more important
The need to minimise all waste is more apparent when you consider that :-
More than 80% of materials are consumed and waste generated by
less than 20% of the world’s population.
The growth in the world’s population and the spread of wealth is
rapidly exacerbating the problem.
In order to sustain human life under the present system, global
environmental efficiency will have to increase by as much as 50 times.
The whole concept of product life cycle, design, fashion and the
responsibility for re-use have to be reassessed. A culture built on the
idea of wastage needs to be dismantled and a new way introduced.
There is always a trend towards increased automation, control and speed,
and a reduction in labour and manual intervention. Most developments in
textile machinery tend to be in this direction. Here are just a few of the more
recent developments and trends, which will help to reduce the overall
environmental impact of the textile industry.
Spinning: Recent developments include improved mini-carding sets to help
provide more flexibility at lower cost, and carding machines designed
specifically for re-cycled fibres. There are also more cutting, pulling and
opening machines available, with a wider range of uses. For example in the
recycling of carpet waste.
Machinery for the moth proofing of woollen yarn has also been improved so
that much less liquor is used and wasted. Instead of using 1000’s of litres at a
time these machines use only 10’s of litres, and virtually all of it ends up on
Weaving: The on-loom automatic inspection of fabric enables faults to be
detected immediately and so helps to minimise waste. Quick style change
systems are also more in evidence, providing greater flexibility in product
The ordering of spare parts via the Internet has also just been introduced by
some machinery manufacturers.
Reduced air consumption, energy and noise on air jet looms and lower weft
waste on rapier looms are two more examples of recent improvements which
could have an effect on the environmental impact of weaving. Highly
productive multi-phase weaving machines, with very low noise production and
energy usage, is also another development worth mentioning.
Knitting: Multi-effect garments can now be more easily produced, with the
introduction of automatic needle changing. This should replace the slower
manual cam changing required on conventional machines. Reduced noise,
raschel and tricot knitting machines have also been developed.
Pretreatment: New developments here include turbo-rollers for increasing
penetration through fabrics during preparation and washing. Liquor passes
through a perforated outer shell with an inner fluted roller. Another
development is hot steam washing which helps to remove contaminants more
rapidly than conventional washing. There are even new designs in circular
singeing machines to improve the quality of tubular knitted fabric preparation.
For wool scouring, high solids or dyehouse effluent, evaporative treatment
followed by a secondary polishing stage such as reverse osmosis are
becoming an option for those wishing to recycle virtually all of their process
water. Recycling rates of up to 99.5% have been achieved by some wool
Dyeing and Printing: In dyeing, or at least drying after yarn/loose stock
dyeing, there are more developments in combined RF and hot air drying
machines. These help to improve the speed and uniformity of drying.
There is also a move towards integrated dyeing/heat recovery systems, which
use less water and energy and help to reduce dye cycle times. Pump
powered fill and drain mechanisms, reel-less jet dyeing machines and jigs
with built in padder mangles, low liquor usage, additional spray bars and
vacuum slots for more effective dyeing and rinsing are now becoming options
Fully automated yarn and package dyeing plants, which monitor and control
the use of water and energy have also recently been introduced.
In printing there is more of an emphasis on improving productivity with digital
processing of designs and digital printing being the next major goal.
Finishing: Stenters are now sold with heat recovery and abatement systems
as part of a complete package. Revolutionary stenter air circulation systems
are also coming on to the market to help reduce the overall energy use in
fabric drying. RF and air/vacuum dryers which allow drying to take place at
only 60 C, produce significant energy savings for the drying of packages and
Steam agers are also now available with non-uniform steam concentration
(low at the front and high at the back), which saves up to 30% on steam
Improved bearing systems, to help reduce energy usage, together with more
efficient dust removal have helped to reduce the environmental impact of