Lecture 01 to 06 Intridution to Dyes & Dyeing

8/19/2019 Lecture 01 to 06 Intridution to Dyes & Dyeing

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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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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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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

Documents

Lecture 01 to 06 Intridution to Dyes & Dyeing