lecture 01 to 06 intridution to dyes & dyeing
TRANSCRIPT
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INTRODUCTION TO
DYESAND DYEING
Lecture# 01 & 06
Mujahid Mehdi Ar! I"du U"i$erit% arachi'
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Dye: A coloured organic compound or mixture that may be
used for imparting colour to a substrate such as cloth, paper,
plastic or leather.
Requirements of a Dye:
Suitable colour Attractive colour.
Able to attach itself.
Must be ater soluble Substrates must be affinity to dye.
After fixation of dye, it must be good !properties" ashing,
cleaning etc.
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GENERAL INTRODUCTION TO T(E C(EMISTRY O) DYES
Dyes possess colour because
1) Absorb light in the visible spectrum (400–700 nm)
2) Have at least one chromophore (colour-bearing group)
!) Have a con"ugate# system i$e$ a structure %ith alternating #ouble
an# single bon#s$
4) &'hibit resonance o electrons %hich is a stabiliing orce in
organic compoun#s$
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GENERAL INTRODUCTION TO T(E C(EMISTRY O) DYES
Dyes possess colour because
#rganic dyes, hether natural or synthetic, are complex
unsaturated compounds having certain substituent groups. $heunsaturated part of the molecule is called the chromophore,
hich, ultimately, is responsible for the colour. %n textile dyes,
the chromophore usually consists of aromatic rings e.g.
anthraquinone and triphenylmethane or A&o groups e.g. A&o
ben&ene.
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GENERAL INTRODUCTION TO T(E C(EMISTRY O) DYES
Although these chromophores do give characteristic colours,
these colours tend to be very ea' because most of the lightthey absorb is at avelengths in the ultraviolet region, hich
is invisible. $he final colour, hoever, is influenced by the
presence of substituent groups 'non as auxochromes,
hich shift the avelengths of the light absorbed into the
visible region. $ypical auxochromes are (#, #) and *)+.
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*ost #yes also contain groups +no%n as auxochromes (colour
helpers), examples of which are carboxylic acid, sulonic aci#
amino an# hy#ro'yl groups$
,hile these are not responsible or colour their presence can
shit the colour o a colourant an# they are most oten use# to
inluence #ye solubility$
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(lassification Systems for Dyes
1$ Che*ica+ C+ai,icati!"-
$he most appropriate system for the classification of dyes is
by chemical structure,
Advantages:
it readily identifies dyes as belonging to a group that has
characteristic properties.
-. A&o dyes !strong, good all/round properties, cost/
effective" and anthraquinone, dyes !ea', expensive".
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2$ Ua.e C+ai,icati!"-
(lassification by usage or application is the principal system
adopted by the (olour %ndex. 0ecause the most important
textile fibers are cotton and polyester.
$he most important dye types are those used for dyeing these
to fibers, including polyester. cotton blends.
#ther textile fibers include nylon, polyacrylonitrile, and
cellulose acetate.
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)A/RIC COLORATION
$here are to methods fabric coloration:
1. Dyeing
+. 2rinting
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DYEING
DYES Substances that add color to
textiles.
$hey are incorporated into the
fiber by chemical reaction,
absorption, or dispersion.
Dyes differ in their resistance to
sunlight, perspiration, ashing,gas, al'alis, and other agents3
their affinity for different fibers3
their reaction to cleaning agents
and methods3 and their solubilityand method of a lication.
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T%e !, D%e
1. *atural Dyes
#btained from plants
#btained from animals
#btained from minerals+. Synthetic Dyes
0asic Dyes
Reactive Dyes
Sulfur Dyes A&oic Dyes
Mordant Dyes etc.
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DYEING
Dyeing is the process of imparting colors to a textile material
through a dye !color".
(olor is applied to fabric by different methods of dyeing for
different types of fiber and at different stages of the textile
production process. $hese methods include
1. Direct dyeing
+. Stoc' dyeing
4. $op dyeing
5. 6arn dyeing7. 2iece dyeing
8. Solution pigmenting or dope dyeing
9. arment dyeing etc.
#f these Direct dyeing and 6arn Dyeing methods are the most popular ones.
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Direct D%ei".
;hen a dye is applied
directly to the fabric ithout
the aid of an affixing agent,
it is called direct dyeing.
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St!c D%ei".
Stoc' dyeing refers to the dyeing
of the fibers, or stoc', before it is
spun in to yarn. %t is done by
putting loose fibers in to large vats
containing the dye bath, hich isthen heated to the appropriate
temperature required for the dye
application and dyeing process.
Stoc' dyeing is usually suitable foroolen materials hen heather
li'e color effects are desired.
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T! D%ei".
$op dyeing is also the dyeing of the fiber
before it is spun in to yarn and serves the
same purpose as stoc' dyeing < that is,
to produce soft, heather li'e color effects.
$he term top refers to the fibers of oolfrom hich the short fibers have been
removed.
$op is thus selecting long fibers that are
used to spin orsted yarn.
$he top in the form of sliver is dyed and
then blended ith other colors of dyed
top to produce desired heather shades.
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S!+uti!" 2i.*e"ti". Or D!e D%ei".
$his is a method applied for
dyeing the synthetic fibers.
Dye is added to the solution
before it is extruded through
the spinnerets for ma'ingsynthetic filaments. $his gives
a colorfast fiber as the
pigments are used hich are
the fastest 'non colors.
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Yar" D%ei".
6arn dyeing is the dyeing of the yarns before they have been
oven or 'nitted into fabrics.
6arn dyeing is used to create interesting chec's, stripes and
plaids ith different/colored yarns in the eaving process.
%n yarn dyeing, dyestuff penetrates the fibers in the core of theyarn.
$here are many forms of yarn dyeing/ S'ein !)an'" Dyeing,
2ac'age Dyeing, ;arp/beam Dyeing, and Space Dyeing.
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A' Sei" 3(a"4 D%ei".
S'ein dyeing consists of
immersing large, loosely
ound han's !s'eins" of yarn
into dye vats that are
especially designed for thispurpose.
Soft, lofty yarns, such as hand
'nitted yarns are usually s'ein
dyed. S'ein dyeing is the mostcostly yarn/dye method.
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/' 2aca.e D%ei".
%n pac'age dyeing the yarn is ound
on a small perforated spool or tube
called a pac'age.
Many spools fit into the dyeing
machine in hich the flo of the dyebath alternates from the center to the
outside, and then from the outside to
the center of the pac'age.
2ac'age dyed yarns do not retain the
softness and loftiness that s'ein/dyedyarns do.
$hey are hoever satisfactory and
very idely used for most types of
yarns that are found in 'nitted and
oven fabrics.
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C' 5ar /ea* D%ei".
0eam dyeing is the much larger
version of pac'age dyeing.
An entire arp beam is ound on to
a perforated cylinder, hich is then
placed in the beam dyeing machine,here the flo of the dye bath
alternate as in the pac'age dyeing.
0eam dyeing is more economical
than s'ein or pac'age dyeing, but it
is only used in the manufacture ofoven fabrics here an entire arp
beam is dyed.
=nitted fabrics, hich are mostly
produced from the cones of the yarn,
are not adaptable to beam dyeing.
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D' Sace D%ei".
%n this method, the yarn is dyed at
intervals along its length. >or this 'nit/
de'nit method is adopted.
;here the yarn is 'nitted on either a
circular or flat/bed 'nitting machine
and the 'nitted cloth is then dyed and
subsequently it is de'nitted.
Since the dye does not readily
penetrate the areas of the yarn hereit crosses itself, alternated dyed and
undyed spaces appear.
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2iece D%ei".
$he constructed fabrics are piece dyed for the flexibility they provide. $he
textile manufacturer can dye the hole fabric in batches according to the
fashion demands of the time thus avoiding astage and resultantly loss.
$here are several methods prevalent or piece dyeing.
/ec d%ei". / >abric is in rope form i. d%ei". / $he fabric in ?ig dyeing is held on rollers at full idth rather
than in rope
2ad d%ei". / 2adding is also done hile holding the fabric at full idth.
$he fabric is passed through a trough having dye in it. $hen it is passed
beteen to heavy rollers hich force the dye into the cloth and squee&eout the excess dye. $hen it is passed through a heat chamber for letting the
dye to set. After that it is passed through asher, rinser and dryer for
completing the process.
et d%ei". / >abric is placed in a heated tube here ?ets of dye solution
are forced through it at high pressures.
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A. 0ec' Dyeing
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0. @ig Dyeing
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(. 2ad Dyeing
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D. @et Dyeing
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0eam Dyeing
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Gar*e"t d%ei".
;hen the finished textile product
such as hosiery or seaters are
dyed, it is called garment dyeing. A
number of garments are pac'ed
loosely in a nylon net and put into adyestuff filled tub ith a motor driven
paddle. $he dye is thron upon the
garments by the moving paddles
effect.
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a# .atch Dyeing machine is one o the %i#ely use# techni/ue or semi-continuous#yeing process$ t is mainly use# in the #yeing o cellulosic ibre li+e cotton or viscose
(+nit an# %oven abric) %ith reactive #yes$ he characteristics o this machine is simple
an# le'ible an# a substantial re#uction in capital investment or e/uipment.
Pad Batch Dyeing machine
(Semi-continuous)
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Schematic layout of a pad-batch:
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a#-steam process
(continuous)
hermosol process
(continuous)
a#-#ry process
(continuous)
Pad Batch Dyeing machine
(Continuous)
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igniicant cost an# %aste re#uction as compare# to other conventional #yeing
processes$
&'cellent %et astness properties$
A uniorm #ye /uality is achieve# %ith even color absorbency an# color astness$
As compare# to rope #yeing a# batch #yeing pro#uces much lo%er #eect levels
n pa# batch #yeing /ualities li+e high sha#e reliability an# repeatability are
common$ his is because o high reactivity #yes %ith rapi# i'ation rate an#stability$
Special Features of Pad Batch
Dyeing Process:
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2ad7atch 3Se*i c!"ti"u!u4
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2ad7 tea* 3C!"ti"u!u4
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The !ii+it% !, c!*i"i".
d%ei". a"d ,i"ihi". e8it 9ithi.*e"t c!+!rati!"' 2r!duct
*ut e e+ected ! that ,i"ih
a"d i"der react u"der a*e
c!"diti!" !, ( a"d:!rte*erature'
2i.*e"t D%ei".
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2i.*e"t c!+!rati!" i ec!"!*ica+ ecaue !,+i*ited "u*er !, r!cei". te'
/+e"d ca" e d%ed a u"i,!r* hade 9ith !"e
!erati!" a+ica+e t! a++ ,ier'
2i.*e"t c!+!rati!" ha a" e8te"i$e c!+!rra".e a"d hi.h +i.ht ,at"e'
2i.*e"t c!+!rati!" ha ati,act!r% 9ah
,at"e'
2i.*e"t D%ei".
Ad$a"ta.e
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(ea$% hade cr!c ad+%' Li.ht hade *a%
9et cr!c'
2i.*e"t c!+!rati!" i "!r*a++% a+ied %
addi".'
2i.*e"t ad$ere+% a,,ect ha"d' The +ar.e
a*!u"t !, i"der
re;uired *a% ti,,e" ,aric' Thi i *!t
"!ticea+e !" $er% thi" ,aric'
2i.*e"t c!+!rati!" *a% ha$e tici". !r
ui+du !" ad r!++'
Mi.rati!" 3u"e$e" c!+!rati!"4 *a% !ccur i,
dr%i". i $aria+e !r icu i hi.h'
2i.*e"t D%ei".
Diad$a"ta.e
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Otica+ ri.hte"er< a+! ca++ed )+u!rece"t /ri.hte"er !r
)+u!rece"t /ri.hte"i". A.e"t 3)/A4 are c!+!r+e d%e
that 9!r % e*itti". $ii+e +i.ht 9he" e8!ed t! i"$ii+e
u+tra7$i!+et +i.ht'
The% are ued t! *ae 9hite !r +i.ht7c!+!red ,aric aear
ri.hter'
M!t+% +eached 9hite ,aric are treated 9ith thee
ri.hte"er'
)aric a"d .ar*e"t that are tru+% reared ,!r d%ei".
h!u+d "!t c!"tai" ri.hte"er' Otica+ ri.hte"er ca"
i"ter,ere 9ith !*e d%e % c!*eti". ,!r the =d%e ite= !"
the ,ier'
Otica+ /ri.hte"er
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Otica+ ri.hte"er ha$e the r!ert% !, a!ri".u+tra$i!+et U>4 +i.ht a"d re7e*itti". e"er.% i" the ,!r* !,
9eaer e"er.%< i'e' $ii+e +i.ht 3$i!+et7+ue +i.ht4 ! that the
%e++!9 c!+!r !, the *ateria+ 9i++ aear 9hite'
The che*ica+ tructure !, thee a.e"t c!"tai" a" a+ihatic
car!"7car!" d!u+e !"d< 9hich i e"iti$e t! u"+i.ht<!8idati!"< 9eatheri".< etc'
There,!re< thee c!*!u"d d! "!t ha$e .!!d ,at"e
r!ertie< a"d te"d t! +!!e their ai+it% t! a!r U> +i.ht
!$er h!rt eri!d !, ti*e i" ue'
The ree"ce !, hi.h c!"ce"trati!" !r i*r!er
a+icati!" !r cheaer ;ua+it% !, ,+u!rece"t ri.hte"er
c!u+d +ead t! %e++!9i". !, the *ateria+ i"tead !, 9hite"i".'
Otica+ /ri.hte"er