ijftr 21(1) 41-49.pdf
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Indian Journal
of
Fibre Textile Resea rch
Vol.
21, March 1996, pp
. 41-49.
.
New developments in dyeing process control
M
DTeli
Department
of C hemical Techn9logy, University of Bombay, Ma
tung
a . Bombay 400 019, India
Present textile market is buyers' market. The con
su
mer dictates
the
term as
far
as the quality quantity and
delivery schedule are concerned. To withstand such competition . the manufacturers/processors have to
adopt total quality management approach so th at not only they ge t the o n ~ processed
ri
ght at the first time,
but quality is ensured. Increas
in
g environmental pollution a\l4areness has thrown new challenges before the
textile technocrat
s.
The pre
se nt
paper reviews the
new
developments
in
the
field
of dyes manufactured,
methods
of
application and machinery
used
.
t
al
so
takes into account the impact
of
advent of microfibres and
specihc developments in process
in
g of terry-towels, garments. etc. The future trend is al
so
pre
di
ct
ed
based on
all
th
e above factors.
Keywords: Dyei ng . Di sperse dyes. Reacti ve dyes. Polyester fibre. Cellulosic fibre. Wool fibre , Silk fibre.
Dye ing machinery
1 Introduction
The globalization has widen the scope of the textile
business
with the
inevitable entry of international
co
mpetition . The challenges
and
opportunities are incr
easing
and
the appropriate response
has
to
be evoked
.
in terms
of technological advancement and
on-time
delivery . Such
quality and quantity
supply has
to
be
done on the
basis of
right-
first-time, right-every
time,
quick
response
approach.
While
this is
being
attempted, it is also incumbent to consider reduction
in energy and production cost.
The
challenges
posed
by this decade revolve
around the
conservation of
environment, an issue which has aroused the attent
ion
at
global level
and
will
direct
th
future chemical
technological adva
ncements
predominantly.
The emergence of new materials such as polyester
microfibres, increasing applications ofcomputer tec
hnology for recipe
pr
ediction as we
ll
as for expert
systems
of
dyeing and fini shing, and the increasing
use
of
microprocessor-based process monitoring
and control equipment will stimulate the fine tuning
of our production
efficiency
and
effectiveness
as
well
,\seconomy. The opportunities placed
before
us, of
course
with
a package
of challenges
, in po s
t-GATT
period need to be exploited and it is
the
technological
advances which will be playing major role in shaping
the
destiny of thi s industry .
When one talks about technological
advance
ments in dyeing process control it is natural
th
a t the
majority of these advances are concentrated on dye
ing of woven fabric. However, dyeing of garment,
terry-towel, microfibre and hosiery
or
knit
goods
also account for a sizable production and some e v e ~
lopments in this res
pect
need to be also summarized.
The advancements in dyeing processes have bea rin g
on the developments
n dyes and newer
applications.
Th
e
colouration and
finishing are
the
key stages in
imparting fas
hion
a
ppeal
to
the
textile apparels.
Th
e
timing and po sitioning ofcolouration in the handling
of
textile are essential factors in ensuring
that
a chosen
ma rket is supplied with the
right
product at the right
time and in
ri
ght quantities as well as
at the
right
pnce
.
The
first aspect
of
Quick Response
(QR)
to consi
der
is the shortening of
the
traditional pipeline
l
by
e
liminating
unnecessary inventories and optimiza
tion of process times. Learning to
operate
with signifi
cantly
lower s
tocks
of raw materia ls and finished go
ods
is
no
simple ma
tter
because so many new discipli
nes must permeate
the
organization. One
such
new
discipline is the
Right-First-Tim
e concept in wet
processing. The objective is to avoid unnecessary act
ivity
and complexity
-
wasted
time,
wasted energy
,
wasted material and correction
of
errors. Thi s in posi
tive terms means
quality managementz
(QM).
As far as the recent
trends
in dyeing process contr
o ls are concerned, they
are
the result of developments
in d yes, fibres, application conditions
and machin
e
ry3.
2 Developments in Dyes
The technological developments in the dyestuff in
du st ry are taking place from the point of view of:
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42
INDIAN 1. FIBRE TEXT. RES., MARCH 1996
i) High-performance products
Concentrated brands
:
To
minimize neutral cutt·
ing agents
and
to
incorporate
useful additives.
Non-dusting brands:
Granulated
and liquid
brand
s.
The use
of
non-dustinggrains or powders
and
liq
uid brands of dyes help in minimizing air/water pollu
tion and in application
of
automated dye dispensing
systems.
ii) Cost effectiveness
Increased
automation,
advanced
instrumentation
and
controls,
and computerization
for the manufact
uring
operations
with the objectives of high
quality
standards help in cost reduction
and
increasing profi
tability with Quality
production.
iii) Health , safety
nd
ecology
t
has
good
fastness
to heat-setting
/wet
treatments
too.
Navy Blue··CF: t is an extension to the Palanil
CF
(Controlled Fastness) series and is suitable for all dye
ing
processes.
Brilliant Blue BGM-CF: t can be readily thermo
fixed and has good light fastness even at i ~ t
m p r -
ture. It is particularly suitable for automotive
textiles.
• Dispersol SF
Super Fast),
a new
range
from
ICI
which inCludes black, navy, rubine, yellow, blue
and brown dyes specifically targeted for dull tern
ary shades, a very difficult
area
fo r most dyers .
They are alkali clearable dyes and exhibit extre
mely low cross-staining.
•
The
Dispersol XF range complements the ICI Di
spersol SF (Super Fast) dyes which are benzodifu
ranone
ba6ed
4
.
Selection
of
dyes is necessary from the points of
view of: • A fascinating area
of
disperse dye chemistry has
been the development of high-value speciality co
lours giving brilliant fluorescent dyes. These are
complicated, expensive
structures
involving sop
histicatd organic chemistry yielding brilliant sha
des with acceptable fastness
properties
s
.
Avoiding the use of dyes which can fonn on reduc
tion carcinogenic amines,
and
Selection
of
high exhaustion/ fixation dyes, parti
cularly among reactives.
Most of the product development has been concen
trated in the field
of
disperse and reactive dyes. Some
of the new dyes
of
these classes introduced in the mar
ket in recent years
are
briefly reviewed here .
2.1
Disperse Dyes
Disperse dyes are used to colour polyester. Anthra
quinone
dyes have much lower
colour
values
and are
more expensive although they give valuable bright
red, blue and turquoise shades whereas azo dyes offer
a full shade range
and
high
colour
values. With the
advent of
et
dyeing
and
tHermosol application , the
search for new
chromophores
has led to the develop
ment ofbenzodifuranone
dyes of high
colour
value,
brightness of shade, good substantivity
and
low ther
momigration. Some of the new disperse dyes availa
ble are:
• Resoline Brilliant Red F 3GS (Bayer) has
good
fastness to
dry
heat
fixation
and
high brilliance
which
is
required for fashion polyester
and
poly.e-
ster/
cotton
sports
and
leisure wear. '
• BASF has introduced a new series of Palani dyes
in its Palanil disperse range- Palanil Black
G,
Red FF B , Navy Blue GN, Navy Blue-CF, Brilli
ant
Blue
BGFN
and Brilliant Blue
BGM-CF.
These dyes are available as low-dusting powders/
liquids .
Palanil Bue
BGFN
: Suitable for polyester blend
dyeing, it
is
insensitive to dyebath pH
and
reduct ion.
• Zeneca (previously ICI) has introduced diester,
thiophene and
benzod
'
ifuranone
based high fast
ness Dispersol dyes. They obviate the need for
reduction clearing and are used in
both
exhaust
and continuous
dyeing.
•
Marlow-Van Loan Corp
. offers a new disperse
bfack which claims excellent
colour
yield
and
ex
haustion properties in dyeing
of
polyester
6
.
Black ASB Extra exhibits superior sublimation ,
light, wash and perspiration fastness properties
and
high alkaline stability, thus enabling to acco
mplish single
bath
dyeing of polyester/cellulosics
with minimum staining.
2.2 Reactive O V 'S
Ofall the classes of dyes used for cellulose, reactive
dyes account for
2 % of
total consumption
of
dyes in
the world and show upward trend in their application
for obvious reasons.
Recently, a new
generation
of bi-
and
poly
functional dyes have been
introduced
which
consist
of
homo or
het
ero
reactive systems.
As
a result, exha
ustion, fixa tion
and
migration can be controlled, lea
ding to much impr oved dye fixation and better repro
ducibility. Some
of
the recent additions are reviewed
here.
• Sumifix Supra range (bifunctional) has a high de
gree
of
exhaustion
and
fixation, resulting in less
wl:lshi
ng-off (hence less dye in the effluent), high
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TELl: DEVELOPMENTS IN DYEING PROCESS CONTROL
43
fa s
tn
ess
to
lig
ht
,
perspiration
,
peroxide washing
and chlorinated
water,
and
high
stability to acid
hydrol ysi
s?
• K
ayace lon
r
eact
ive
dye
s
are high-temperature
neutr
al -d yeing
dyes
which a re especially
suitable
for fast
processing
of cotton
and
one-
bath
dyeing
of cotton / nylon ,
o t t o n ~ r y l i
and co tton /poly
ester blends
•
Cibacron
C
rangedyes (Ciba-Geigy) are bifunct
ional reactive dyes which have
an
aliphatic vinyl
s
ulphon
e gro
up combined with
eith er a
monoflu
orotriazine
group or
an aromatic
vinyls
ulph
o ne
group
with following
features:
Suitable for
pad application
and
exhaust
dyeing
at
low
liquor
ra tios,
Very
goo
d solubility a nd hi gh
to ve
ry high degrees
of fixation ,
- Excellent
wash-off
,
and
High fastness leve ls
8
The environmental
benefits
include
:
No urea needed fo r disso lving the dye,
- Less dye in effluent
due
to high fixati on, a
nd
- W
ate
r
and
e
nerg
y
saving
s
du
e to
easy
\vash-
ofT
• Zencca s Pr oc ion H-EXLexh a ust dyes (hifuncti
o nal) ha ve been
engineered to
produce
hi
gh per
formance le vel d ye ing, migration , diffusio n a'nd
exceptional build-up properties.
Of the rea ctive dyes available toda y, new
Rema
zo l
EF d yes significantly reduce waste in e fflu ent , cla im s
Hoechst. These
dye
s
Re
quir
e
33-70%
le
ss salt
than conventional
reac
tive d yes,
Pr
ov ide higher fix a tion under low salt
conditions
as compared to
conventional
reac ti ve
dy
es, and
Arc available
in env
ironrnental
safe
packag
ing
(l
ow-
du st
powd
ers or
liquid
s).
•
Rite Indu
stri es Inc.
ha
s
launch
ed
the Rite Reac
tive B se ries
of
dyes whi ch a llow
to
reduee the
a
mount
of salt to
e
used in the d ye
in
g with similar
advantages
.
•
BASF
hi l S introduced f
ive
new r
eac
tive d yes into
the
. Bas
il
en
rang
e. Th ese
are
Basilen Blue
E-FRN . Blue E- BG F ,
.Red
F-RM,
Red
F-3BM
and
Ye
ll
ow
f ~ R
Ba silen Blue
E-FRN
is a
double anchor
type mon
Qc
hlo ro tri zine
dye
free
of heavy metal
which
pr
o
du
ces a
unique royal
blue s
had
e
and
ca n be used on polyester/cellul
os
ic
blends by the
BASF
reco
mm
e
nded
process. Bas
i-
len Blue E- BGF is a brilliant blue d ye free of he
avy meta ls and
sta
ble under
hi
gh-temperature
dyeing conditions
(e.g. pol yes
ter
/cellul
os
e
blend
d ye ing) . Th e o ther three
Ha si
len FM dyes
ha
ve
hi gh
exhaustion and easy
wash o ut
propertics to
decrea
se
water
usag.e
and wate
r contamination.
In Indian
mark
et t
oo,
a number of
co mpanie
s have
co
me out w
ith high-exhaustion
a
nd
m
ed ium-exhau
s
tion
bir
eact
i
ve
dyes
which
a re finding increasi ng
ap
plica tions.
3 Developments n pplication Methods
3 1
Pol) ester Fibres
Durin
g the d
ye
ing
of
po
ly
ester fibre. the
conventio
nal dyeing liquor co ntains la rge a1Tlounts of di s
per
s
ing agents
a
nd
s
urfactants which are
used
to
ge t rea
so na ble ra tes of dyeing,
ensuri
ng levelne ss.
Thi
s leads
to
an
effluent loa ded with
dye
an d dis
persing
agent s
which is to be treated with
an
ever increasing cost.
On
e
radically
n
ew
a
pproach
is to use s
up
ercritical
CO
med ium for dyeing PET with dis
per
se dyes
9
.
Afte r the
dyeing
o
perati
o n is
conwlete,
dr y dye
powder
, which
h
as
not been used
up
. de
posit
s
at
th
e
bottom
.
There
is
no necessit y of
dispersing agent
or
carrier.
However.
this dyeing requires disperse dyes of spec ial s
tructur
al
features. free from
dispersing
agents. Also.
the co
st of
eq
uipmcnt
an d
pipings
is hi gh.
B l ~ t th
e
operational
costs are very low
as compared
to
that
in conventional
dyeing method
(re
quire
s
only
1/
5th of the
ene rgy) .
Ther
e is
also
no re
quirement
fo r r
ed uction
clearing
trea
tment
s, washings,
dryin
gs, etc.,
thereb
y saving
time a
nd en
ergy
and providing protecti
o n
to environ
ment. Thi
s
method
loo ks
to
se t
further the cause of
QR and hence QM .
Rece ntl y, H
oec
hst
Mit
subi shi K
ase
i (HMK)
ha
s
made
possible
the
dyeing
of
pol yes
ter
in
an alkalinc
me
dium
.
thereb
y
makin
g
the
e
ntire
wet
proce
ssi ng
simple
and
reproducible. The
quality of
dyed materi
als is
also improve
d. In
addition
,
th
e
problem
s
due
to
the presence
of
pol
yes
ter oligomers
in
acidic
dyei ng
conditions are
also
minimized 10.
The HMK
sys tem
involves
both
alkali-resistant
dyes
and
a newly deve
loped stabilizer JPH95 for
dyes
fo r
alkaline conditions. The
stabilizer
has many
func
ti o ns such
as
buffering
the
dyebath
pH to
around
9.0-9.5
during
dye
ing
,
stabilizing dyes. chelating
me
tal ions and dis so lving oligomers.
The
small variation
in
pH during
the
dyeing
cycle promotes excelle
nt
re
producibility.
3.2 Cellulosic· Fibres
Many ideas surround the concept of blind colorati
o n,
ranging
from a simple no addition
dyeing to
the
management
of
all those factors that affect the colora
tion o fa textile, resulting in a right-firs t-time
dyeing
.
The latter definiti o n implies the total control of all
factors
(including
the
human ones) that can
influence
coloration
and
ca use a shade
to
de viate fro
the
stan
da rd .
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44 INDIAN J.
FIBRE TEXT
RES
MA
RCH 1996
The beneflts of blind dyeing can be summarized as
follows: cost sav
in g
improved
planning
, better qua li
ty. increased
productivity
, customer sa tisfaction .
etc . I
Dyeing with monofunctional reactive dyes is
known to be rather sensitive to changes in dyei ng
con
ditions such as temperature, liquor ratio, addition of
salt and a lkal
i. A
low se nsitivity to dyeing
parameters
using dyes with two differen t reactive groups is
parti
cu lar ly advantageous in
continuous
dyeing operati
ons as it helps
to
achieve reproducibility of shades, i.e.
right-first-time and every time.
The key factors influencing th e rates
of ri
ght-first
time production are dye selection, co ntrol of raw mat
eria ls and on- line process control. In it self,
improv
ing the
rate
of right-first-time production can
impr
ove
productivity
by 20% and the ret
urn on
sa les to
a round 13 % (ref. 12).
Right-first-time
production
will
be
maximized if
these fundamental measures of performance within
the
reactive
dye
compatibi
lit y
matrix
R
CM are
set
a t:
Substantivity
Migration Index
LDF
Tso
a minimum of 10 min
70-80%
> 90%
> 70 %
A comparison ofRCM of individual dyes will pro
vide a measure of the compatibility ofdyes when they
are
used in combination. Dyes wit h similar performa
nce and with s
ub
stantivity,
migration ind
ex, LDF,
and so
values within the target specification will offer
robustness to
small
var
iat i
ons
in
processing condi
tions, sh
ade reproducibility
and level
dyeing perfor
mance
l
.
Newer developments controlling
ad d ition a l para
meters relati ng to the physical characteristics of the
substrate
take
into account
the influence of mechan
ca l and hydraulic forces exercised by the machine
du
ring the process
l3
.
The control eq uipment a llow the
hydraulic and
mechanical action
of the
dyeing mach
ine to be
adjusted, not only
for th e
entire
process but
also for each period in the dyeing pcocess. This princi
ple is utilized in the sync
hron dyeing control
system,
whic h sy
nchroni
zes
liquor circulation
,
fabric speed
and process cycle
l 4
The alka li
dosing
proces s is
becoming
popular as a
rationalized dyeing
method
for
reacti ve
dyes
6
-
s
.
Many types
of
reactive dye can be used , but the
opti
mum
pH
range
will depend on the nature
of
the dye
employed . To
control
the rate
of
exhaustion, it
is
desi
rable to use a
dye
that reacts
over
a wide pH r
ange so
that the
co
nditions can easily be controlled during
dyeing. The Sumifix
Supra
range of dyes
contain
both
a vinyl su lphone
group
a nd a monochlorotriazi ne rea
ct ive
group.
They react with cellulose ove r a wide
pH
range and are, therefore , suitable for use in such opti
mized dyeing processes I 5 .
Thesc
dyes
ha
ve bee n
ad a
pted
both
fo r
exhau
st
dyeing and semi -continuous operations. High fixati
on, low sub stanti vity
and
good diffusio n, effect ing
rapid and efTicient rcmoval
of sma
ll amounts
of
unfix
cd dye, are the sa lient fea tures of these dyes. To i ncre
ase the fixation of d ye, the
one
of the
most popular
alternat
i
ve
energy sources which could he used is rad
io -fr
equency
(RF) energy.
Heatin
g of the
batch
with
radio-frequency
energy
during
the
batching
stage grea ly accelerated the rate
of
fixa ti on. Fixa tion leve ls
ac
hie ved usi ng
opti mi
zed
R F-assisted methods were approximately equival
ent to
those achieved in co nventional
pad-batch
dye
ing
l
.
Dawson
International , in 1978, patented a process
and the
equipmen
t design used for fixing dyes or che
micals with RF energyl6.
Th
e process involved conti
nuous conveying of
treated
fibres through closely co
nfin ed tube located between flat parallel electrodes.
By gener
ating
RF energy field within the tube, a se lf-
sealing
pressure
chamber was created by the format
ion of steam from
the wetted
fibres. The advantage
claimed was an increase in the reaction rate ofthe dye
on
the fi bre.
The
semi-continuous pad-batch process using
RF
energy
has also been
recognized
as one of
the
mo st
efficient
methods
ofapplying reactive
dyes to
cellulo
sics with exce
ll
ent reproducibility
,
leading to
ri
ght
first-time every time concept.
Laser
fixati
on
is a feasible
low-heat
tre a tment met
hod
for fine-line dye fixation . A comparison of wash
fastness of ha
nd-ironed
and l
aser-treated
specimens
showed that the specimens
treated
with a n argon
-ion
l
aser
at 129°C and
23YC maintained
color significan
tly bcttcr
than
thc specimens trcatcd with a lowcr lascr
heat
(94°C) and hand
iron
( 190°C).
This
was
true
for
10 , 20 and 30 washes. A laser
tempera
ure of 129°C
was as effective in setting fibre reactive d
ye in
cotton as
was a la
ser
te
mperature
of 23°C, ind ica ting that a
lower energy laser would be as
usef
ul in setting dye as
higher
power
models
17
Electromagnetic hea ti ng produces dyei ngs of si mi
lar shades to
those
obtained by conventional heating
when pressure and temperature conditions are
kept
the same for both treatme nt s.
However,
e lectromag
netic heating allows
smoother
and more homogene
ous boiling tha n do cs conventional heating and can
be u
se f
ul
indu
stria
ll
y 18 .
Lewis
and
eoworkers
l 9
ca rri ed
out
fibre pretreat
ments aimed a t dyeing with reactive dyes under neut-
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TEll
: DEVELO
PM
ENTS IN DYEING PROCESS CONTROL
45
ral to sli g
ht
Iy acid ic conditions
in
the absence
of
elec t
rolyt
es. All
of
these treatments introduce cationic
(bas ic) resid u
es
in the form
of
quarternary, tertiary
and secondary am
in
es.
One
of
the most conve
ni
ent pretreatments wa s to
app ly polyamide epic
hl
orohyd rin r
es in
to the ce llul o
s
ic
fab ric usin g pad-dry system. Selection
of
highl y
reac tive dyes gave good co lour yield on thi s type
or
fabr ic and the fixation
of
dyes proceeded si mply by
ap ply
in
g them from a dyebath se t a t pH 5 and raising
the tempera ture to boil. Unfortunately. ring d
ye
ing
of tb e fibre a
nd
ya
rn
s was clearly evident and as a
result , light
fas
tness red uced by 1-2 points. These dra
wbacks, however, have been overcome by the use
or
low molecular we ight speci
es
and pretrea ting the co t
ton fabric usin g a pad-thermollxa tion technique.
Another adva ntage
is
th e need fo r sho rter washing
olfp rocess to remove the unfixed dye because
of
high
level or dye -libre fixation ac
hi
eved.
In
eoloura tion of ce llul osic fibres. vat dyes (includ
ing Indigo) and sulphur dyes ho ld a la r
ge
part of the
dyestuO mark e
t.
Vat dyes give exce ll ent fa stness,
whereas sulphur d
yes
a rc economical with good deg
ree of fastness properties . The
red
uction process emp
loyed here req uires reducing age i1t s and it has
ye
t not
been possible to regenera te these co nven tiona I ag
ents, except in th e standing dyeba th procedure .
In rec
ent inves tigations, an el
ec
tro lytic process was
u
sed
to <lchieve dye
reel
uction I n eli rect electrolysis,
the dye
it
self has to be rcduced
at
the surface
of
the
ca th ode , while
in
indirect elec tro lys is the reducing
power of the cathode is transferred to the solution by a
soluble redox system (mediator). This reversible re
dox system
is
continuously rege nera ted at th e cath
ode so th a t a renewal
of
the reducing agent is achiev
ed. Thi s technique offers th e poss ibility
of
full dye
bath recyeling, including the reuse of reducing ag
ents.
Co tton may readily be modified by pret reatment
with N-methylolacrylamide to introd uce pendant
ac
tiva ted double bonds. These have been
ex
ploited in
tw o ways to improve the reac ti
ve
dyeing of co tton.
Firstly,
by
introducing amino r
es
idues at these new
site
s,
exce llent dyeings with reactive dyes can be achi
eved at pH 5-7
in
absence
of
an electrolyte, coupled
with a
ve
ry
hi
gh degree
of
fixation. Secondl
y,
it is
pos
si
ble to dye the cellulose, modified o
nl
y with
N-methylolac rylamide, with d
ye
s co ntaining pend
ant aliphatic amino residues. In thi s case, it is necess
ary to
dye
in the pr
ese
nce oran elec trolyte under alkal
ine condi tions but ve ry high colour yield s are obtain
ed, thanks to the elimin a tion of the h
yd
rolytic s
id
e
reactions nOrilla
ll
y associated wit h n:ac ti vc dye ing.
Such amino-containing dyes can be readily prepared
rrom all
l l l m e
i a l ranges
of
reactive dyes
2 1
Prdreatment or cotton wi th pol
ye
pichlorohydrin
dilllethylamine prod uces a mod i
i
ed
cotto
n that can
he
d
ye
d un der neutr al conditions with se lected low
reactivit y dyes wi thou t sa lt. The d
yei
ngs
of
trea ted
colton ex hibit improved co lour yield and
hi
gh wash
r; lstness ..Bot h ex haust dye ing and continuous dye ing
l)f trea ted cotton gi
ve hi
gh co lou r yield
22
Pretreatment of co
tt
on with higher molecu l
ar
mass
polye pic
hl
oroh ydrin dimethylamine co uld intro
duce more cationic sites onto the modified cotton.
This would increase the ex tent of complexing with the
dye and thu s improve the dyeability with direct and
reactive s ~ 3
Eth ylened iami ne tetra(methylene
ph
osphonic)
acid when adso rb
ed by cotton fibres prior to
th
e appli
ca ti
on of the direc t dye Solamine
I-
ast R
ed
4BL causes
a marked
in
crease in rat e
of
dye in
g. It
also improves
the wet fastne ss properties
of
the dyed eotton
4
.
3.3 Wool Fibres
. Due to the increasing enviro nm enta l problems
of
dy
eing with heavy metal containing dyes as we ll as
wi th reac ti
ve
dyes, the dye ing behaviour
of pl
asma
trea ted wool towa rd s the
se
dyes was recently in vesti
ga
ted
by
Hocker and eoworkers2 . Plasma treatmen t
on wool have shown th
at
it leads to, apa rt
fr
om an
improvement in the mechanical properties
of
the
fibre , improved dyeability with ac id dyes, reactive
dyes and metal-containing dyes, and reduced felting
tendenc
y.
Low- te l)1perature glow discharge trea tm
ent
of
wool opens up the follo win g possibilities to the
wool dyer:
IInproved utili zation
of
the ex isting plant due to
reduced dye ing times,
Savings in cost and maintenance
of
intens
iv
e wa
ter purifica tion plants as well as possibilities for
recycling the dye effl uent s due to reduced di scha
rg
e of toxic
components
,
Cos t savings by reduc
tion
in
the amounts of dyes
and aux
ili
a ries,
and
I mproveel market prospects due to environment
friendly process man agement.
It
has also been obse
rv
ed by Fibre Resea rch Insti
tut
e,
Israel, h ~ t wool on treatment with enzymes loo
ses its felting property. At the same time, libre seems
to acquire much enhanced ac
id
dyeability.
3.4 Silk Fibres
As fa r as the dyeing of silk fibre is concerned, the
low-tempera
tur
e dye ing has been attempted using
va rious redo x systems. These sy stems ca use an incre
ase in the number ofd
ye
ing si
e
s on the silk, through
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46
IND IAN
J.
FIBRE TEXT
RE
S. M
AR
CH 19<. 6
th e ac ti on
offree radicals
which might be
assisting
in
covalent fi
xa
ti on of
th e
dye
in
ad
diti
on to
usua l i
on
ic
links, hy
dr o
gen
bonds
a nd van der
Waals'
fo rces.
Th
e
use
of
bufTers lik e
so
d i
um
ace
ta t
e-acet ic
acid ha
s al
so
been fo
und
to be
quite
pr
omis
in
g
as
far as the
fi
xati o n
an
d the
fastness properties
of th e
ac
id dye
on
silk a re
concerned
6 7
.
Developments
n
Machinery
As
the
textile
wet pr ocesso
rs r
ea li
ze
that the
y
mu
st
a
dapt
to the cha ng
ing
nee
ds of
th e ma rket , the m
ac
hi
ner
y
manufacturer
s
mu
st
tak
e
ap pr
o
priat
e
actions
through
extensive re
search
and
deve lo
pment to
deve
lop
a
new
ge
ner
a
tion of dyein ,
m
ac hineri
es
that
are
able
to meet
th
e
changing market
co nditi
o ns.
Th
e
ma
chin e ry deve lo
pm
ent s
are
t
owards
achi ev-
ing o ne o r
mor
e
of
the following o
bje
c tives :
Reducing th e labo
ur complement,
Increas
ing th e
pr
od
uctivit y,
Minimi
zing th e req uireme nt s
of
Iltilities,
Simplifying the machin e
operations,
S
av
in g in mac hine s
pac
e,
Reducin
g th e efflu en ts,
thu
s minimi zin g
po
ssibl e
po llutio n,
R
ecove
ry
of heat
e
ne r
gy a
nd water, and
Eco n
omizing
th e
cos
t s
tructur
e.
In
batch piec
e a
nd
ya
rn
d ye ing , it is essential
that
the
fi nisher ha s
machin
es
at
hi s di sp
osa
l
that operate
cos
t e
fT
ectivel
y. At
the sa me time, th e finished
prod
uct
mu
st meet the
qualit
y de
mand
s
of
the
consumer.
Th
e
introducti
o n
of
new
technology and
the modifi ca
tion
of
design
that
entails
ar
e the moves in the right directi
on
. M o re
economic
a l d ye in g
pr ocesses can
be
ac
hie
ve
d in the pi ece
and yarn dye
ho use applying the s
hort
and ultn
i-s
hort
liqu
o r t
ec hn
o l
ogy,
liquor
fl
ow cont
rol
and
finishing by
th
e Sync
hron
D y
ein
g Sys te m.
Of
co urse, an increase in
pr
oductivity and
qu
a lity is
today
in
co
nceiva ble
without
a n elec
tronic
a
ll
y
-cont
rol l
ed process
seq
uenc
e.
It
is, the refo re, important for th e fini s
her
when inv
es tin g in new
equipment
or
impro
ving
old
machine
plant
to
ge t familiar with the la test
advancement
in
dyeing
machi ne ma l1Lifacture a nd the lates t
proc
ess
tech no l
ogy
28 .
T he
adve
nt
of
meterin
g tec
hn
o l
ogy
h
as
mad
e th e
s
hort
liquo r
dyeing
a re liable process.
Th
e
mo d
e rn
meteri ng sys tem- M
ulti-pr
od uct
J
ec
tion
(M
PI)
-
permits co
nt r
o lled di s
pensin
g
of
so
lid s o r li
quids such as dyes, sal ts, alkalies, acids or o ther tex tile
a uxili a
ri
es.
M lIlti-product injec
tion (MPI)
meterin g sys tem in
conjunction with
the
application
of
sho rt
and ultra
sho rt
liqu
o r
technolo
gy h
as
th e foll
ow
ing
ad
va
nt
ag
es:
A ut o ma t ion or the d yei ng process avoiding in
co rrect a ddi ti o ns of dye
so
lutio n,
auxiliaries
a nd
che
mical s: mo r
eove
r,
th
ere
are
no idl e times .
Reliabilit y
of the
pro
cess,
because
th ere is a l
wa
ys
an
o
ptimum
r
eac ti
o n
medium
a v
ailable for
th e
d ye in g
proces
s.
-
Increas
ed
repr
o
du
c ibility by ex act
rcp
etiti
on
of
the
d ye ing
pr
ocess.
Optimi
za
tion
of
the
leve lness .
Co
st sa v
ing
s
by
usin g
caustic
as fixation
alkali
in s
tead of soda
(e.g. in r
ea c ti
ve
dyeing).
Cost sav
ings by using
acid (acetic
o r fo rmic ) in
wo o
l/po lya
mid
e d ye ing.
- Simplil ica
tion
of the
rinsing
a nd
washing pr
oces
ses in r
eac ti
ve d ye ing,
owing to
less hy
drol yzate
fo
rmati
o n
during th
e d
yei.
ng
pr
ocess.
Ort
e n it is
po
ss ible
to reduce
th e d ye ing time.
Mo re re li a ble sho rt
liquo
r dyei ng, especially wit h
dark
colours.
By meterin g-in
the
d ye, th e
co
nce n
tr a ti o n
of
d ye in the dyebath is re
du
ced
so
th a t n o
ag glo me
ration
can
occur.
Incr
eas
ing
automation
in
application
o f dyes to the
fibre substrate ha s been o ne m o re guid ing principle in
th e d eve lo
pment of the machin
e ry
as
desc
rib
ed
aho
ve.
One
of
th e typi
ca
l
examples
in
exhaust
d yeing is
ADC-200,
a me
tering devic
e
de ve
lo p
ed
by
Ho
ec hs t
a nd
ADCON.
Th
e
proc
ess, mo re
known
as Ra m
aza
l-
automat,
me
te r
s
the supply
o f a lkal i for
the
li
xat
io n
o f
th
e re
ac
t ive d yes a ut o ma ticall y
and pr og
ressiv
el
y
in
order
to o
btain the
hi ghes t leve lness in sho rtes t
dye ing
tim
e.
The
eme rge nce
or
short
liq uo r je ts fo r dye
ing
cot
to n
and it
s ble
nd
s h
as
bee n
mark
ed
over
recent yea rs.
Not only
d ocs thi s
proce
ss offe r the
po
ss ibility of
more
eco
no lllical d ye
ing
but
it
also
r
edu
ces
the
l
oad
inflect ed o n the env
ironment
to the
tun
e or 30% (
rd
.
29).
On-line
con
trol s in
continuou
s dye ing
are
ro
und to
be elTective in improvin g th e
cos
t e llicie ncy
and
rep ro
ducibi ity. Forexample , on - line liqu o r
pi
ck-up mea
s
urement
wit h level
co rr
ecti o n
and
co nt r
o l e n:lblcs
precise calculation of the
vo
lum
e o f
li
qu
o r Ileelled
and conse
q ucntl y sav
in
gs in the
cos
t
of
dyes a nd auxi
l
iarie
s. On-line colourimctry
orthe p;ldJed r
ab
ri c im
pr
ove
s
th
e
contro
l
ov
er
th e
pr od
uc tio n
pr oce
ss wit h
reliability
and
im p
ro
ved
quality
· o .
4 J igg('r Dye ing
Jigg
er is th e m
os
t
stable ma
c hin e in dye ho use
and
f
uture
d y
eingjiggers
w
ill
ha
ve a
v
er
y mo
dern
l
ook and
will
be chara
c teri zed
with
use ful aspec ts vvhich a re
sUlllmari zed
und
er
Futur
e
Trend<'
in this JXlpc r.
4.2
J(
Dyeing
Th
e utilit y, s pecific
appli
c
ati
o n
and pre
ss
ur
e
con-
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TEll:
DEVELOPMENTS IN DYEING PROCESS.CONTROL
47
dition inside th e vessel as
well
as the shape of the vessel
have been, for quite some time, under constant exami
nation
. Some
manufacturer
s have finalized designs
for a
ll
typ es of material s and dyes, which claim all the
important
features such as :
Dyeing.tempe
ratures
up to 140 °C when desired ,
Soft flow or ove rflow,
Low
liquor
ra tio
up
to 1:5,
Automatic
co ntrols by
microprocessors
,
Suitability for light weight
as
well as heavy fab
rics, say 50-500 g/m
2
High fabric speeds at the lowest possible
pressure,
Tangle-free operation,
High quality dye ing results with reduced tension
and surface abrasion,
Minimum
operator involvement ,
and
Economy of energy, water
and
chemical auxiliary
ingredients
3 1.
In other words, more air, less liquor and gentle han
dling have been the key factors behind the develop
ment
of
jet dyeing machines.
Then s
Air-Flow ASF machine
uses
the
liqu
or
ra
tio about 1:2 and it is found to give high productivity
and low consumption of water and chemica1. Th e dye
solution is automatized with the air stream which is pro
duced by the blower for application on the fabric.
The
Italian machinery
maker
Laip
ha
s
brought out
air
water-flow Mod 800, a l
atest
rope dyeing
machine
,
for both knitted a nd woven fabrics .
The
air-injection
is not simply used to accelerate the fabric to high speed
but
in some cases to
open the
fabric.
Apollon Twin
Soft Flow machine manufactured by a Greek mach
inery ma
nufacturer make
s use of micro
wash
system,
using clean hot water which is introduced through the
double-
ove
rflow of the
machine
to ac hieve very high
cleani ng effici
ency
32.
4.3 Continuous Dyeing
The component units
of
the contin
.u
ous dyeing ran
ges are being modified from time to time
to
minimize
the possible imperfections in the final dyed product.
Development work regarding these component units
is s till .in progress. The points which have been a nd
which will still be considered
during
such work inclu
de:
Co mposition and formation
of
pad rollers,
Pre-drying by infra -red ra
diation
to
avoid
possi
ble mig
ration
, with vertical fa bric passage, and
Well-designed and evenly
impinging hot
flue or
high-te
mperature dry
ers for
thermo
so l dyeing.
With the
advent
of synthetics and blends, the ther
mosol system is
bound
to achieve a very
promising
position .
Th
e FD 45
pad-stream
machine from Rami sch
Kleinewefers for the
continuous
dyeing of
cotton
and
its blends with viscose
rayon or
polyester has been
reported. In
addition
to a Bicoflex
padding arrange
ment, the machine has system for feeding in single
doses ofchemicals
and
storage
programmable
contr
ol. This contro l system ha s a modem whidi permits
continuous dialogue between the supplier and the cu
stomer. t
cou
ld be prefera bly used for vat and sulp
hur
dyes
33
.
5 Garment Dyeing
.Whil st garment dyeing has an in-built le
ad
time
advantage for
producing
comparatively sm'all tot s,
the com
bined effect of
cu
s
tomers wanting
larger lo t
sizes quicker
and
more e p r o d ~ c i b i l i t y and the adva
nces in response time
made
by the
colouration
routes
has driven development in gannent dyeing technolo
gy.
5.1 Dyes
Proper selection
of
dyes a nd finishing chemicals is
quite important for dyeing of
gaments
made
of
cott
on, wool, nylon, polyester, acrylic and .their blends.
The range
of
articles include socks, sportswear ,
shirts, T-shirts, etc. Of the dyes available in the mark ·
et, reactive dyes
are
the
most
popular dyes used in
garment
dyeing . Newly
introduced
bireactive dyes
are finding increasing
application and are
preferred
to direct dyes
3
,, . Subsequent trea tment with dye fixing
agent is also recommended t o improve fastness prop
erties.
Other
dyes used for
garment
include acid and
reactive dyes for woollen gannents , cationic dyes for
acrylic , and sulphur
and vat
dyes for cellulosic gar
men t
s.
The chlorine fastness
of
sulphur and reactive
dyes is poor whereas vat dyes have the best perfonna
nce properties although they a re quite expensive.
5.2 Dyeing Methods
Exhau
st dyeing is carried
out
using special dyeing
111achines for garments.
5.3 Machinery
Th
e
mo
st recent development from
Gilwood (Fab
rica tors) Co. Ltd , a British machine maker, is an oval,
double
side-paddle
machine
for dyeing readymade
knitwear.
Machine capacity
ranges frum 150 to 6800
litres. Positive dye
penetr
a tion is achieved by specia
lly designed paddles fitted with synchronised dri ve
for enhanced liquor circulation .
An
innovati
ve
recir
culation system delivers heated
liquor
i m u l t n e ~ u -
sly to the two-paddle a rea, significantly improving
the overall tempe
rature
controp5.
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48
IND I N 1. FIBRE TEXT RES..M RCf 1 1996
The recent innova ti on in convcntional drum dye
ing machine is
th
e one with liquor circu lation through
the drum centre. Thi s helps impart ing an extremel y
gentle treatment to the goods even at low liquor rati
os.
i.e.
I
6.
This kind
of
machinery has the advantage
of dyeing
all
kinds of hosiery. The goods dyed can al
so
be cent,:ifuged in the same machi
ne
which means in ve
stm ent costs ["or centrifugers a re a voided. The techni
cal advanta ges include:
Level dyei ng due to rapid liquor interchang
e.
Reduced water eilluent and less steam and chemi
cal
consumption because of operations at low liq
lI
or rati o
s.
and
- In-built hydroex traction · .
The newer machinery for garment dyeing are based
on the fo llowin g feature s: (i) Low liq uor ratio, (ii)
Microprocessors- for improved lot-to -I ot reprod
ucibility, (iii) Hea t exchan
ge
rs - for rapid heating
uJ1dcoo lin g. (iv) ....int
filte
rs) (v) Centrifugal hydroex
traction , (vi) Ea sy
sa
mpling with out
dr
oping dye
l
iq
uo
r.
(vii) Tilting- f
or
ease of loading/unloa din
g,
(vi ii ) Cushioned suspension, (ix) Variable drum
sp
ee
d, and
(x)
Automatic balancing drum.
What is important in garment dye in g is to achieve
level dyeing, with exce
ll
en t penetration in short dye
ing cycle. The deve lopments a rc thus directed tow
ards these aspects.
6 M icrofibre Dyeing
The microfibres are th e lates t entrant in textile mar
ke
t a
nd ha
ve
inherent adva nta
ges
for which their co
n
sumption is increasing day by day. However, becau se
the microlibre has in creased surface area , the rate
of
dye ing is tremendously enhanced and it becomes ess
en
ti al to control the dyeing of microfibres to avoid
unev
en
dye ing. The dyeings obtained are also appare
ntly lighter as compared to the ones with the normal
denier polyester yarn and it is difficult to
ge
t the deep
shades in microdenier varieties. The fastness to
wa
s
h
ing. rubbing and light is inferior to th at of normal
denier polyester. This necessita tes the selection of
proper range of disperse dyes specially suited for mic
rofi bres.
The Foron
RD
dyes of Sandoz
see
m to be perfo
rm
in g favo ur abl y. To improve the
li
gh t
fa
stness
of
the
dyed microllbres, use ofF adex RF liquid
is
recommc
nded since
thi
s acts as a kind of UV -absorber. A num
ber of dyes manufacturers are making the
se
lection of
d
yes
fr om the pont of view of their appl ication on
micro
i
bre
fa
bric .
7 D)leing
of
Hosiery/Knits
In dyeing of kn ilted fabri cs. co ld bran d as well as
hot brand reac
ti
ve dyes
and
also the dir
ec
t dy
es
are
used
I'or 100 ce llulosic fabrics. The dyei
ng
is carried
out in tensionless form
in
w
in
ch and sin ce the wi n
ch
dyeing machine doesn' t allow uniform temperature
Illaintelwnce. the reactive dyes
of
HE and ME
cl
ass
arc increasingly being preferred.
8 D)'eing of
Terr
y-Towels
The dye ing of terry-t owel is more conlined to dye
in
g
of ya
rn s which are then subsequen tly use d for
producing jacqua rd designs. The asr ects of d
ye
in g
and the se lec tion of dyes rema in
sa
me as in the case of
hosiery. However, when no tinting of the' gro und
is
e.\ pec ted, th e
va
t dye d ya
rn
s are used in manufact ure
of terry-towels rather than azo , sulphur, reactive and
direct dyes.
A two
-s
tep dyeing technique is available by which
cross
-d ye
in g of 100 colton te rry cloth can
be
ach ie
ve
d with fibre reactive dyes. The
fir
st step
in
vol
ves
co ntinu ously dyeing of the fa bric, usi ng an aux
il
iary
that promotes colora
ti
on of the tips of
th
e terry cloth .
Subsequent dye ing is carried out in a beck with contr
asting colour fibre-reactive d
ye.
An a
tt
rac
ti
ve tow
toned appearance re sults
J
o.
9 Future Trends
The
manufactur
ers
wou.ld
co ncentrate on re
sea rch acti viti
es
to develop new chrolllophores and
dyes offering wider shade gamuts, higher co lour fa st
ne ss, improved environme ntal impact and higher ov
erall cos t
elTic
iency in the coloura ti on process.
I n future , the
di
sper
se
d
yes
based on ben
zo
dif
ura
n
on
es
w
ilLenc
ourage
m<1re
resea rch to deal with struc
tural
and
ph
ys
ical
fOnll
modifications designed to im
prove build
-u
p, and also encourage resea rch for
ne
w
e
hr
omogens that are particularly s
uit
ab le for polyes
ler in
ge
nera l and microfibres
in
part icular.
The future development s
in
reac
ti ve
d yes
ar
e likely
to
be
co
nc
entr ated on:
• H
igh
application flexibilit y: A broad spectrum of
~ h d e s
h
t uld be d
yea ble
by widely dilkringappl
ica tion
/.
,'l hods with a sma
ll
number of dyes.
• G
oo l reproducibility and good le ve lling proper
ties.
•
Out
standing protecti on to environment.
• Maximum productivity.
Apart from the
se,
the dye ing process with dyes con
taining no reactive group (in the usual sense) but cap
ab le of being crosslinked to cellulose via a suitable
reagent will find its pl ace in industrial applicatiun .
For dyei ng cellulosic fibres, high-fastness direct
d
yes will be
se lected
0
avoid usc of corper or chrom
ium sa lts. In reac
ti
ve dyeing, use of urea will be mini
mi zed . For dyeing with sulphur dyes, the hi ghl y po ll
uting sod iulll sulphide will be replaced by other ag-
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TELl: DEVELOPMENTS IN DYEING PROCESS
CONTROL
49
ents such as reducing byproduct from maize sta rch
indust ry or hydroxy acetone
37
•
38
• For
oxidation
of
vat and
sulphur
dyes, hydrogen pero
xi
de ,
sodium pe
rbor
ate and 1, 3-dinitrobenzene s
ulphonic
acid wi
ll
be used in place
of
dichrom
a te.
Durin
g po lyester dyeing,
chlorinated or phenolic
carriers will be avoided. Acetic acid used for
pH
adju
stment h
av
ing
hi
gh
BOD
will be replaced by
other
agents .
In case
of
d
ye
ing machineries, the jiggers
oftomor
row will be
characterized
by
the
following u
sef
ul
as
pects:
• Excellent clo sing and opening.
•
Heat
ed
hook
for
drip-proof
working.
•
One
way flap-opening chimney for re
le
as ing un
wanted
hot
and wet flue .
• Internal m
ac
hine
li
ghting to offer a
goo
d view
of
the fabric
un d
er
pr
ocess.
•
Pump
for recirculating the d
ye
liquo r.
• Safety devices and emergency switches for
avo
id
ing damage owing to sudden
br
ea kd
ow
n.
•
Automatically controlled
dr ain valve.
•
Autom
a tic reve rsa l, delay
-r
elay fabric di rection
indicator as well as speed indica to r
s.
• Effective crease removing expa
nder
s and m ot
or
i
ze d se
lv
edge aligning and continuous ce
nt
ering
system.
Development s in winch d
ye
ing m
ac
hinery with
better te
mp
era
tur
e. di stribution a nd liquor m ove m
ent are ex pected, mainly for dyeing knitted fabrics.
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