Chemical Technology in the Pre-Treatment Processes of Textiles

521 Pages·1999·45.66 MB·English

by  S.R. Karmakar

TEXTILE SCIENCE AND TECHNOLOGY 12
CHEMICAL TECHNOLOGY
IN THE PRE-TREATMENT
PROCESSES OF TEXTILES
TEXTILE SCIENCE AND TECHNOLOGY
Volume 1 Open-end Spinning by V.Rohlena et al.
Volume 2 Processing of Polyester Fibres by O. Pajgrt and B. Reichst~dter
Volume 3 Shuttleless Weaving Machines by O. Talava~,ek and V. Svat~/
Volume 4 Fluorescent Brightening Agents by R. Williamson
Volume 5 Polypropylene Fibres - Science and Technology by M. Ahmed
Volume 6 Production and Applications of Polypropylene Textiles by O. Pajgrt et al.
Volume 7 Absorbency edited by P.K. Chatterjee
Volume 8 Needle Punching Textile Technology by V. Mr~tina and F. Fejgl
Volume 9 Industrial Textiles edited by J. Sv6dova
Volume 10 Modified Polyester Fibres by J. Militk~ et al.
Volume 11 Textile Processing and Properties: Preparation, Dyeing, Finishing
and Performance by T.L. Vigo
Volume 12 Chemical Technology in the Pre-treatment Processes
of Textiles by S.R. Karmakar
TEXTILE SCIENCE AND TECHNOLOGY 12
CHEMICAL
TECHNOLOGY IN
THE PRE-TREATMENT
PROCESSES OF
TEXTILES
BY
S.R. KAR MAKAR
Professor of Textile Chemistry
College of Textile Technology
Serampore, Hooghly, West Bengal
India
1999
i
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First edition 1999
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PREFACE
Textile chemical processing today, particularly the pre-treatment processes require
a highly sophisticated technology and engineering to achieve the well known concepts
of"Right first time, Rigtht everytime and Right on time" processing and production.
Chemical pre-treatment may be broadly defined as a procedure mainly concerned
with the removal of natural as well as added impurities in fabric to a level necessary
for good whiteness and absorbancy by utilismg minimum time, energy and chemical
as well as water.
This book discusses the fundamental aspects of chemistry, chemical technology
and machineries involved in the various pre-treatment process of textiles before
subsequent dyeing, printing and finishing. With the introduction of newer fibres,
specialty chemicals, improved technology and sophisticated machineries developed
during the last decade, all attempts have been made to fill a gap in this area of
technology. New chapters are integrated and introduced to upgrade the information
and the subject matter and contents are so chosen that it will permit the teacher to
rearrange units to suit the needs of individual groups of students. Efforts are also
made to provide an in-depth exposition of the topic with a review of the most
exciting recent developments in the rapidly moving field. But the real strength of
this book is its clear perception of ample background description, which will enable
to understand most current journals empowering the reader to stay abreast of the
latest advances in the field.
The interplay between fibre structure, morphlogy and chemistry is an integral
part of all pre-treatment processes and in Chapter 1 an attempt is made to cover the
most up-to-date information regarding all the principal classes of fibres, viewed in
the light of research and commercial exploitation. Chapter 2 is devoted to mechanical
fabric preparation before chemical processing commences to achieve smooth and
trouble free results in subsequent dyeing and finishing. Chapter 3 discusses the
chemistry of different sizing agents with respect to their removal from the fabrics.
Chapter 4 covers a purifying treatment of textiles to reduce the amount of natural
impurities sufficiently to enable level and reproducible dyeings and finishing to be
produced. Specialty chemicals have very high value in the chemical processing of
textiles and the applications of chemical auxiliaries are included in the relevent
processes. Chapter 5 describes the various machineries that have been developed
vi Preface
for the purifying operations. Chapter 6 deals with the detailed understanding of
various bleaching agents and their mechanisms or mode of action on various fibres.
The chemistry, technology and care guides are included seperately for each fibre
and blended fiber fabrics. New machineries have been developed for the bleaching
of textiles and Chapter 7 looks at the machineries involved in such process. Recent
technological advances of mercerizing and heat-setting of textiles are included in
Chapters 8 and 9 respectively. Textile fibres do not appear perfectly white even
after chemical bleaching and Chapter 10 describes the chemistry and mechanism
of optical brightening agents as well as their applications to various kinds of fibers.
All serious efforts have been directed in Chapter 11 towards shortened or combined
pre-treatment processing in order to minimize energy consumption. Chemical
degradation or damages caused by improper application of processes, erroneous
concept of procedure, faulty operation of machines and chemicals are critically
reviewed in Chapter 12. A changing concern in matters relating to environmental
pollution from pre-treatment processes involved in textile mills and processing
house in particular is increasingly demanded and thus all these varied developments
in legislation, in analysis and standards and in treatments are included in Chapter
13. Pre-treatment or surface modification of textiles with low temperature glow-
discharges or plasma is of great interest in near future and Chapter 14 discusses its
application as an alternative to conventional techniques. Enzymatic pre-treatment
( a biological approach) is becoming an important commercial process and Chapter
15 contains the development in the field of enzyme treatments for textiles. Testing,
analyses and evalutation of the efficiency of processes present the time domain
approach to modem process control, which allows for the formation of precise
performance objectives that can be examined. Thus, Chapter 16 will be a valuable
resource for practicing process control technologists and students.
I hope the reader will find the book interesting and useful with suggested
references in each chapter along with simplified flow diagrams showing various
processes and machineries involved in pre-treatment technology of textiles. No
single text can be sufficient unto itself. Any constructive suggestions and comments
are therefore welcome for future revesions and corrections.
Serampore,Hooghly, West Bengal, Samir Ranjan Karmakar
(India), April 1999.
CONTENTS
Preface
Chapter 1 Kinds of fibres 1
1.1 Introduction 1
1.2 Classification of fibres 1
1.3 Chemical composition, morphology and structure of cotton 3
1.3.1 Cotton impurities 5
1.4 Natural protein fibres 8
1.4.1 Molecular structure of wool fibres 8
1.4.2 Impurities in raw wool 13
1.4.3 Morphology and chemical structure of silk 14
1.5 Long vegetable fibres 16
1.5.1 Flax (linen) 17
1.5.2 Remie 18
1.5.3 Hemp 19
1.5.4 Jute 19
1.6 Regenerated natural fibres 22
1.6.1 Cuprammonium rayon 22
1.6.2 Viscose rayon 22
1.6.3 Acetate fibres 25
1.6.4 Regenerated protein fibres 26
1.7 Synthetic fibres 27
1.7.1 Polyester 27
1.7.2 Nylon 29
1.7.3 Acrylic fibres 34
1.7.4 Olefin fibres 37
1.8 Miscellaneous synthetic fibres 38
1.8.1 Chlorofibres 39
1.8.2 Poly(vinyl alcohol) fibres 39
1.8.3 Elastomeric fibres 40
1.8.4 Carbon fibres 41
1.8.5 PTO fibres (Enkatherm) 42
viii Contents
1.8.6 Other synthetic fibres 42
References 44
Chapter 2 Preparation before chemical processes 49
2.1 Introduction 49
2.2 Inspection 49
2.3 Sewing 51
2.4 Mechanical cleaning of fabrics 52
2.4.1 Brushing 52
2.4.2 Cropping and shearing 52
2.5 Singeing 55
2.5.1 Singeing different kinds of fibres fabrics 56
2.5.2 Plate singeing machine 57
2.5.3 Rotary cylinder machine 58
2.5.4 Gas singeing machine 58
2.5.5 Singeing circular knit fabrics 63
2.6 Process sequence 65
2.6.1 Cotton fabric on kier 65
2.6.2 Cotton fabric on J-Box 66
2.6.3 Cotton fabric on pad-roll/thermoreaction chamber
(T.R.C.) 66
2.6.4 Cotton fabric on Jumbo jigger 66
2.6.5 Knitted cotton goods 66
2.6.6 Woollen fabrics 67
2.6.7 Silk fabrics 67
2.6.8 Polyester fabrics 67
2.6.9 Nylon fabrics 67
2.6.10 Polyester/cotton blends 67
2.6.11 Polyester/viscose blends 68
2.6.12 Polyester/wool blends 68
2.6.13 Diacetate/viscose blends 68
Chapter 3 Desizing 69
3.1 Introduction 69
3.2 Methods of desizing 71
3.2.1 Rot steeping 72
Contents ix
3.2.2 Acid desizing 72
3.2.3 Enzymatic desizing 72
3.2.4 Desizing with oxidising agents 75
3.3 Desizing of synthetic fabrics and their blends 77
3.4 Desizing machineries 79
References 84
Chapter 4 Scouring 86
4.1 Introduction 86
4.2 Mechanism of removal of impurities 87
4.3 Scouting of cotton in alkaline agents 89
4.3.1 The lime-soda boil 89
4.3.2 The caustic soda boil 89
4.3.3 The soda-ash boil 90
4.3.4 The mixture of caustic soda and soda-ash boil 90
4.3.5 The soap/detergent-soda-ash boil 90
4.3.6 Sequestering agents 91
4.3.7 Builders 93
4.3.8 Fibre protecting reducing agents 94
4.3.9 Mild oxidising agents 94
4.3.10 Water insoluble solvents 94
4.4 Surfactants 94
4.4.1 Anionic surfactants 95
4.4.2 Cationic surfactants 96
4.4.3 Non-ionic surfactants 97
4.4.4 Amphoteric surfactants 98
4.4.5 Blends of surfactants 99
4.4.6 Surfactants as wetting agent 99
4.4.7 Surfactants as detergent (scouting agent) 101
4.4.8 Emulsion scouting 103
4.5 Solvent scouting 106
4.6 Scouting of raw wool 107
4.6.1 Emulsion scouting 108
4.6.2 Suint scouring 109
4.6.3 Solvent extraction scouring 109
4.6.4 Refrigeration process 109