Lecture presented at Introduction of Textiles course held among ITEX CAIRO 2020 activities. ITEX CAIRO is the leading textiles digital printing event in Egypt.

1. Pretreatment Process
of Textiles
for
Dyeing & Finishing
By
Ahmed Saad Montaser
Researcher at Pretreatment and finishing for cellulosic fabrics
Textile research Division
National Research Center
Dokki, Giza, Egypt

2. Bibliography
Research Scientist in Polymer and Textile
Chemistry, with a deep understanding in polymer
chemistry and its applications that is shared in
many national and international projects.
Designed and Implemented research projects in
several areas; including, Polymer Synthesis,
Biopolymers Modifications, Porous Polymer,
Antimicrobial and UV Protection, Fiber
Extrusion, and Textile Chemistry.
Ahmed Saad Montaser
Researcher
Pretreatment and
finishing for cellulosic
fabrics
Textile research Division
National Research
Center
Dokki, Giza, Egypt

3. Introduction
The textile industry is one of the oldest in the
world. The oldest known textiles, which date
back to about 5000 BC, are scraps of linen
cloth found in Egyptian caves. The industry
was primarily a family and domestic one until
the early part of the 1500s, when the first
factory system was established. Today, the
textile sector in Egypt consists of well over
3,000 companies, ranging from the very small
(employing less than 8 labourers) to the very
large (greater than 20,000 labourers). These are
both public and private sector companies.

4. The textiles industry is the fifth largest source of foreign
earnings; after oil, remittances, tourism and earnings from
the Suez Canal. It is the second largest manufacturing sector
in Egypt after food processing and represents 25% of total
industrial output (excluding petroleum products). Egypt
produces 25-30% of the worlds cotton, although there is
strong competition from USA, China, India and Israel. Egypt
also produces the some of the highest quality Extra Fine
cotton in the world, having a 35% share of the world market.
The Egyptian textile industry is dominated by 31 large
public enterprises. The majority of these are primarily
engaged in spinning and weaving, although many also carry
out dyeing, knitting, finishing and the production of ready-
made garments. These public companies account for 100%
of spinning, 70% of weaving, 40% of knitting and 30% of
the finished goods. They also dominate in terms of labour,
volume of production and owned resources. For instance,
Misr for Spinning and Weaving is the largest enterprise in the
country and generates more than 25% of

5. There are over 2,300 private sector factories which
are members of the Egyptian Textile
Manufacturers Federation (ETMF). There are also
many small factories and workshops who are not
ETMF members, as well as informal workers
which are not included in any of these groups. The
private sector currently dominates the market in
terms of knitted fabrics and ready-made goods.
Products commonly consist of T-shirts, beach
towels, sports and casual wear, targeting Discount
Shops in the USA and Europe.

6. Pretreatment Processes

9. Sizing and Desizing
• Sizing is carried out before the weaving process to increase the
strength and smoothness of the yarn, to reduce yarn breakages.
Desizing, either with acid or enzymes then removes size from the
fabric, so that chemical penetration of the fabric in later stages is not
inhibited. Desizing effluents have very high organic concentrations,
contributing 40-50% of the total organic load from the preparatory
sequences. Gums and PVA may be removed by a simple hot wash but
starch and its derivatives have to be made soluble by soaking with
acids, enzymes or oxidants before being removed by a hot wash

11. Desizing techniques

12. Desizing methods

14. Scouring
• Scouring is carried out to remove impurities that are present in cotton,
both natural (e.g. waxes, fatty acids, proteins, etc.) and acquired
(such as size, dirt and oil picked up during
• processing). This is usually done at high temperatures (above 100°C)
with sodium hydroxide and produces strongly alkaline effluents
(around pH 12.5) with high organic loads. They tend to
• be dark in colour and have high concentrations of Total Dissolved
Solids (TDS), oil and grease.
• The scouring is normally done either on a Kier, a J Box, or an open
width pad roll system, or on open width continuous plant. Common
scouring agents include detergents, soaps, alkalis, anti- static agents,
wetting agents, foamers, defoamers and lubricants.

17. Bleaching
• Bleaching is used to whiten fabrics and yarns, using sodium
hypochlorite or hydrogen peroxide. Many cotton processing
factories in Egypt use sodium hypochlorite as it is cheaper than
hydrogen peroxide. However, this is highly toxic and is now
strictly limited or banned in many countries. It can also break
down to form absorbable organo-halogen compounds, which
are both toxic and carcinogenic. Bleaching generates
effluents with a low organic content, high TDS levels and
strong alkalinity (pH 9-12).
• Once bleaching is complete, the bleaching agent must be
completely removed, either by a thorough washing or using
enzymes.

20. Mercerising
In this process, the cotton yam or fabric is treated with an alkali
(sodium hydroxide, NaOH) to improve lustre, strength and dye uptake.
It also removes immature fibres. The process is normally carried out
on dry fabric; wet mercerisation reduces the steam consumption, but
requires stringent control of the operational parameters, such sodium
hydroxide concentration.
Excess sodium hydroxide is normally recovered for reuse in either the
scouring or other mercerisation stages. The rinse wastes are alkaline,
high in inorganic solids and caustic alkalinity, and low in BOD. With the
increasing trend toward cotton-polyester blends, much less
mercerising is being carried out.
Combined mercerising, where scouring is carried out simultaneously
with the mercerisation in hot conditions, is now becoming popular, as
the mercerisation increases the rate of scouring. This combined
process reduces capital cost, space requirements, energy costs, labour
requirement and chemical costs.

22. The effect of mercerization