Finishing Targets for Knit Fabric Dyeing

Name : MAZADUL HASAN SHESHIR
ID: 2010000400008
Batch: 13th Batch (Session 2009-2013)
Department: Wet Processing Technology
Email: mazadulhasan@yahoo.com
Blog: www. Textilelab.blogspot.com
Southeast University
Department of Textile Engineering
PREPARED BY ©right

Special Instruction:
1. Fabric shrinkage must keep within ±5%
2. Color fastness should be 4-5 range
3. Pilling range 3 to 5
4. pH range 5.5 to 7
5. Fabric weight will be allowed ±02%
6. Fabric quality should be s per approved swatches & Lab-Dips.
7. Batch to batch color matching should be 4-5
8. Batch to batch “Shade Band Swatch” must be submitted for approval.
Special Instruction:

Process Temp(▫C) pH Time min M : L ratio
Scouring - Bleaching 98 10-11 30 1:8
Enzyme Wash 55 4.5-5 30 1:8
Reactive Dyeing
(Light Shade)
60 10-11 60 1:8
Reactive Dyeing
(Dark Shade)
60 11-12 60 1:8
White Shade 98 10.5-11.5 30 1:8
Turquish color dyeing 80-90 11-12 60 1:8
Polyester dyeing 130 4-4.5 45 1:8
Production Parameters

pH:
 Bleaching bath pH : 10.5 – 11
 Neutralization or after bleaching pH : 5.5 – 6.5
 Bio polishing bath pH : 4.5
 Initial dye bath pH : 5.5-6.5
 After alkali addition pH : 10.5 – 11
 After dyeing pH : 5.0 – 6.0
 Fixation bath pH : 4.5 – 5.5
 Softener bath pH : 4.0 – 5.0 ( For color )
Dyeing Parameter:

Temperature:
 For cotton Pretreatment : 98C
 For Cotton Biopolishing : 55C
 Cotton Dyeing: : (50-60)C
 During Turquise :80C
 During Isothermal :60C
 Red special : 60 C
 White dyeing : 80 C
 For Polyester Dyeing :130C
 For Cotton soaping : 98C
 Temperature during softening & fixing : 40C
 For cotton hot wash : (70-90)C
 For cotton acid wash : (50-60)C
Dyeing Parameter:

A. pH
During peroxide bleaching & scouring 9-11
During enzyme treatment 4.5-5
Before addition of leveling agent 6-6.5
Before addition of color softener 6-6.5
Before addition of white softener 4.5-5
Softener at stenter& de-watering 5.5-6
Silicon softener 5.5-6
Reactive dyeing 10.5-12
Disperse dyeing 4.5-5.5
Dyeing Parameter:

C. Time
For scouring and bleaching 60-90 mins
For reactive dyeing 60-90 mins
For disperse dyeing 60-90 mins
B. Temperature
For cotton scouring 95-100˚C
For cotton bleaching 50-60˚C
For cotton hot wash 70-80˚C
For cotton acid wash 60-70˚C
For cotton dyeing 80˚C ( For hot brand)/60˚C(For cold brand)
Dyeing Parameter:

Amount Of Salt , Alkali & Fixation time On The Basis Of Shade%:
Shade % Salt(g/l) Alkali(g/l) Fixing time(min)
0-0.1 30 10 20
0.1-0.5 30 15 30
0.5-01 40 20 40
1-1.5 50 20 50
1.51-2 60 20 60
2-2.5 70 20 60
2.5-5 80 20 60
Above 6 100 25 70
Black shade 100 10+0.5g/l NaOH 70

QUALITY ASSURANCE SYSTEM
Quality is always a vital parameter for customers’ satisfaction. No matter what is the
job you perform, but your contribution is also a matter of fact. Here the top management
is concerned about that & thus build up a reasonable “Quality Control” department.
Task(s) of Q.C. Department
1. Initial check (checking of yarn quality)
2. Final check (checking of yarn properties after dyeing, finishing & hard
winding)
3. Initial check
4. Strength
5. Count (specially of melange)
6. T.P.I (specially of melange)
Final Check
1. Strength
2. Shade (both of yarn & fabric)
3. Fastness (wash & rubbing)
4. Evenness of dyeing
5. Layer check
6. Waxing check

39.37 1000
.
Machine Capacity
Winch speed
GSM fabric width no of Nozzle Cycle Timt
 

  
39.37 10000
.
Machine Capacity
Cycle Time
Fabric GSM Fabric width No of Nozzle Winch speed
 

  
Re ( ) %quired Dye kg Shade Fabric weight in Kg 
/
Re
1000
g l required Total liquor
quired Chemicals


Calculation realted to dyeing floor:

There are some reasons related to arise those problem, are mentioned below:
1. More rejection of garments items due to fabric faults (lack of adequate and improper
inspection.)
2. Short quantity production due to lack of full quantity finished fabric.
3. Dyeing & finishing department unable to supply full quantity finish fabric to garment
section according to “Time and action” plan due to facing problem on batch to batch
shade variation (out of tolerance limits); fabric width; GSM; shrinkage; spirality, dyeing
faults.
4. More dyeing and finishing faults appear due to follow incorrect dyeing & finishing
recipe & procedure.
5. Knitting section fail “Time and action” plan.
6. Grey GSM problem due to improper yarn count; stitch length, machine selection.

Dyeing Parameter & Calculation:
The things which influence the effective coloration of textile materials with reactive
dye are called as parameters of dyeing. These include –Temperature, Time, Liquor
ratio, pH of the bath etc. A brief description about them is given below
Effects of Temperature:
Temperature of the dye bath plays vital role for dyeing. Rise in temperature has a large
effect on an increase in the diffusion rate of dyes into fabrics. Increasing of
temperature increases the rate of dyeing & of the dye migration. Higher dyeing
temperature ensures the good leveling & better penetration of dye in to the fibers. But
the temperature depends on the types of dyes adapted in the dye bath.
For Example-in case of hot brand dyestuff the dosing temperature of dye is 80ºC and
for cold brand dye temperature is kept 60ºC.

Effects of pH:
In the case of most popular fiber reactive dyes, a high PH actually activates the
cellulose (cot-ton) fiber, forming a cellulosed anion, which can then attack the
dye molecule, leading to a reaction that produces a strong, permanent covalent
bond. Without a high pH, the dye will not fix permanently to the cellulose fiber.
For this reason Sodium Carbonate (Na2CO3) [Some time mixed alkali such as
(NaOH + Na2CO3)] is used for no other reason than to increase the PH of the
dye reaction, so that the fiber will react with the dye. Basically during the color
addition, the PH of the bath remains at near about 6, but after adding alkali it
goes rise to pH 11.4 & this is the critical stage in which the dye molecules fix up
with the fiber.
Effects of Time:
The time for dyeing also the vital one. A specific Time adjusted with the
temperature, very much needed for better dyeing. For this reason color dosing
takes place in 20 minutes (may vary process to process) & Specific run time is
set for dyeing.

Effects of Material:
Liquor Ratio (M:L): Dye bath exhaustion increases with the decreasing of liquor
ratio. Dyeing at low liquor ratio decreases the amount of waste dyes &
chemicals in the effluent. Because higher the liquor ratio greater the amount of
g/l of chemicals which increases the volume of effluent. To get rid from this
problem Then Air flow Dyeing machine is getting popular in our country which
can dyeing at 1:3 Materials: Liquor ratio. But in case of Thies Jet Dyeing
machine it can possible up to 1: 5 Materials: liquor ratio.
Shrinkage:
A dimensional change resulting in a decrease in the length or width of a
specimen subjected to specified condition is known shrinkage.
Spirality:
If the Wales of the knitted fabric are not perpendicular to the course and skew
to the right or left spirality occurs in the fabric. This creates serious problem,
especially in the apparel industry.

 Achieving finishing target of knit fabric means to achieve the finished fabric with
all the quality or parameters that is required by the customer. In case of knit
fabric, target quality refers to the shade, GSM, shrinkage, spirality, color fastness
etc.
 When order is placed, at first fabric structure, GSM, shade is considered.
Depending on the parameters yarn count, m/c gauge, stitch length, machine dia,
yarn type are selected all those factors are related with target quality.
 Grey fabric gsm should be lower than finished gsm. In case of knitting fabric at
least 15% weight will increase during wet processing.
 Grey gsm will depend on the shade percentage, lycra %, type of yarn used and
type of finishing pequired for that particular fabric. For light shade stitch length
will be more than deep shade.
 In case of spirality, it will depend on the yarn count, compactness, feeder no. of
the knitting machine.
 If count (Ne) is high, compactness of the fabric is more and feeder no. of the m/c
is lower than fabric spirality and shrinkage will be less.
Finishing & Finishing Target:

 Yarn count and m/c gauge are related to each other and if those two factors are
not matched then faults will be occurred on the fabric. For example, 20’s for
20G/18G, 30’s for 24G, 40’s/28G will yield lower spirality and shrinkage.
 In case of wet processing, shade must be developed in the dyeing laboratory and
should be approved by the buyer. The recipe that is developed in lab is used by
reducing in quantity for bulk production. Because dye pick up percentage is
always high in dyeing m/c.
 Shade should be kept in deeper condition before dropping of dye liquor from
dyeing m/c. because shade could be lighter during soaping. In case of finishing
process, padder pressure, temperature, fabric speed, chemicals and finishing line
should be determine by considering the finishing target because, all those
factors may affect fabric shade.
 But in case of open line, stenter machine is used, which may control most of the
parameters in knit fabric. But fabric should be in open form. Thus open squeezer
is used to slitting the fabric. Then the fabric is feed on stenter where chemicals
can also be applied.

 When fabric is unloaded from m/c water content is about 200% in case of knit
fabric. Thus hydro-extractor, de-watering m/c are used before drying the fabric.
Otherwise heat consumption for drying process will be huge and that is not
cost effective. In this section finishing chemicals can be applied to the fabric.
 Drying machine is used to evaporate water remaining in the fabric after de-
watering process and to obtain fully dried fabric. Fabric dia will reduce during
relax drying process and tube fabric is finished in this machine. Thus tubular
fabric dia should be kept more than the required finished dia in de-watering
machine. This dia will be reduced in drying machine. After that tube compactor
is finally used to achieve target quality of the fabric. gsm can be controlled up
to 10%.
 Fabric shrinkage, spirality, Gsm, shade, bowing effect, slanting etc can be
controlled by stenter m/c. Maximum 20% gsm can be controlled by stenter
m/c. Fabric shade can be controlled by maintaining temp. if shade is dark then
temp.

 should be high and 15-20% light shade can be obtained. If shade is light in fabric
then temp. should be lowered and silicon softener is used in large quantity.Then
the fabric is finally finished with open compactor m/c.
 Maximun 14% gsm of the fabric can be controlled.
 If ultra-soft fabric is required by the buyer, then gsm of the fabric should be kept
at least 5% more after finishing process. Softening action is done on the back side
of the fabric and the fabric is again finished on stenter m/c.
 In case of brushing, the back side of the fabric is brushed. Loops of the fleece
fabric are brushed. Fabric may feed on the m/c for 5-8 times until the target
brushing action is achieved.

 After all those operations, quality control process of the fabric is done in
online and off-line process. In online process gsm, shade, shade variation,
hole patta, bowing, slanting, oil mark, chemical spot etc are checked and
graded with 4 points system. In off-line QC shrinkage, spirality, gsm, color
fastness, wash fastness etc are done which are required by the buyer.
 Sometimes problem can appear such as shrinkage, spirality, gsm of the fabric
which cannot be controlled by those finishing process. In this case fabric is
wetted and tumble dried to overcome those problems.
 By this process, sample fabric is finished at first then required tests are done on
the fabric. Sometimes it is not possible to control shrinkage, gsm, spirality, and
other knitting faults due to knitting m/c and yarn. In this situation, the knitting
department should take necessary actions to overcome those problems.

 If any faults or quality problem is appeared due to dyeing or finishing the
fabric should be reprocessed, such as re-dyeing, topping, stripping are done
and finished again. But target should be to finish the fabric without re-
processing.
 Above all those factors, target finished date must not exceed to finish the
fabric. If the fabric is achieve with all the required quality within the target
finished date then that will be said that we have achieved the finishing target
of knit fabric for a particular batch.

Parameter Setting
Pump Speed (Load) 70%
Pump Speed (Next all) 80%
Winch Speed (Load) 100m/min
Winch Speed (Next all) 220m/min
Nozzle Speed (For all) 50%

Table : GSM achievement for Elastane Single Jersey (Chocolate Color) By ISO Standard.
Stenter GSM Compactor/ Actual GSM Target GSM Variation (%) Remarks
160 173 180 -3.89% Pass
160 171 180 -4.35% pass
163 176 180 -2.25% Pass
158 172 180 -4.15% pass

Table : Achievent of colorfastness to wash for Chocolate Color By ISO Standard.
Target grade Actual Variation Remarks
4 – 5 4 – 5 No Pass
4 – 5 4 – 5 No Pass
4 – 5 3 - 4 1 Fail
4 – 5 4 – 5 No Pass

Table : Achievent of colorfastness to rubbing for Chocolote Color By ISO Standard.
Target grade Actual Variation Remarks
Dry Wet Dry Wet Dry Wet
Pass4 – 5 3 to 5 4 3 0.5 No
4 – 5 3 to 5 5 4 No No Pass
4 – 5 3 to 5 4 3 0.5 No Pass
4 – 5 3 to 5 4 4 0.5 No Pass

Table : Achievement of shrinkage for Es. Single Jersey (Chocolate Color) By ISO Standard.
Target Actual Variation Remarks
Length Width Length Width Length Width
Pass± 5% ± 5% -5% -2% No No
± 5% ± 5% -4% -3% No No Pass
± 5% ± 5% -4.5% -2% No No Pass
± 5% ± 5% 5% -2.5% No No Pass

Table 4-24: Physical test report for Navy color
(Buyer: S.Oliver)

GSM Achievement
Sample Stenter
GSM
Finish
GSM
Target
GSM
Variation
(%)
Remarks
Elastane Single Lacoste
(Aqua color)
168 185 200 -7.5 Pass(Speci
al Case)
Elastane Single
Lacoste(Chocolate color)
160 173 180 -3.89 pass
Elastane Single
Lacoste(Black color)
185 193 200 -3.5 pass
Single Jersey(Navy color) 158 160 160 0 pass

Color Fastness Wash Achievement
Sample Target
grade
Actual Variation Remarks
Elastane Single Lacoste(Aqua color) 4 - 5 4 - 5 No Pass
Elastane Single Lacoste(Chocolate color) 4 - 5 4 - 5 No Pass
Elastane Single Lacoste(Black color) 4 - 5 4 - 5 No Pass
Single Jersey(Navy color) 4 - 5 4 0.5 Pass

Color Fastness to Rubbing Achievement
Sample Target grade
Dry Wet
Actual
Dry
Wet
Variation
Dry
Wet
Remarks
Elastane Single
Lacoste(Aqua color)
4 – 5 3 - 5 4 – 5 3 No
No
Pass
Elastane Single
Lacoste(Chocolate color)
4 – 5 3 - 5 4 3 0.5 No Pass
Elastane Single
4 – 5 3 - 5 4 3 0.5
No
Pass
Single Jersey(Navy color) 4 – 5 3 - 5 4 3 0.5 No Pass

Shrinkage Achievement
Sample
Target
Length Width
Actual
Length Width
Variation
Length Width
Remarks
(Aqua color)
±5% ±5% -6.3% -2% -1.3% No Pass(spec
ial case)
(Chocolate color)
±5% ±5% -5% -2% No No Pass
Elastane Single
±5% ±5% -2.4% -2.9% No No Pass
Single Jersey(Navy color) ±5% ±5% -5% -3% No No Pass

Control parameters
1. Liquor ratio by analogue control or electromagnetic flow meter
2. Time/temperature profile
3. pH measurement, monitoring and adjustment using retractable electrode
4. Rate of change of pH
5. Conductivity
6. Specific gravity
7. Redox potential
8. Liquor flow rate
9. Rope circulation time
10.Addition time and profile for dyes, auxiliaries and chemicals

Control functions in continuous processing
1. Bath temperature control
2. Fabric temperature control
3. Steamer pressure
4. Water and chemical flow
5. Liquor pH control
6. Conductivity of liquor or fabric
7. Specific gravity of process liquor
8. Pad pressure and nip expression
9. Compensator pressure
10. Liquor level
11. Fabric speed
12. Chemical dosing
13. Automatic filling of baths
14. Data for steam, water, chemical and electricity consumption
15. Process visualisation/schematics
16. Automated mangle rinsing
17. Automated I R predryer heat control to speed up batch changeover
18. Control of oxidation baths
19. Control of final fabric pH
20. Rapid substitution of operating process details to cope with changes in substrate quality
being processed

Anticipated benefits from investment in control technology
Factor Benefit
Shade reproducibility
Levelness
Minimal damage of the substrate
Improved quality
RFT dyeing
Low liquor ratios
Water recovery and reuse Low-
temperature dyeing Controlled
equipment
Savings in resources (steam, water,
effluent, power)
Consistent dye and chemical weighing
and dispensing Reliable recipe
calculation
Elimination of errors
Shorter cycle times
Less downtime and less cleaning through
scheduling
Reduced manning levels
Productivity increases
Rationalised/standard products
Better stock control
Savings in dyes and chemicals
Instrumental colour measurement Improvements in productivity and
reproducibility

Control functions for dyeing machine
Function Requirement
Machine fill Actuated valve and level sensor
Raise to initial temperature at rapid
rate of rise
Actuated steam valve and temperature sensor
Circulate material or liquor Controlled electric motor or pump
Raise to top temperature at
controlled ramp
Flow reversal sequence
Holding time at top temperature
Controlled cooling ramp Actuated valve on cooling water
Drain Actuated valve on drain

Most important factors for polyester fabric dyeing
1. Substrate dyeability
2. Heat treatments above 150°C before dyeing
3. Fabric preparation
4. Dyebath pH
5. Metal-ion content of the dyebath
6. Dye concentration

Factors requiring control in the dyeing of sewing thread
Factors of prime importance  Dyeability of substrate
 Heat-setting conditions (polyester):
 time, temperature and tension
 Dry weight of substrate Colour value of
dyes Weight of dye
 Moisture content of dye
 Accuracy of dissolving or dispersing dye
 Dyebath temperature
Factors of major importance  Liquor-to-goods ratio
 Weight of electrolyte (cotton dyeing) Weight of
auxiliary product
 Time of dyeing pH of dyeing
Factors of minor importance Yarn construction (e.g. twist) Degree of bleaching
(cotton) Degree of mercerisation (cotton) Size
content
 Temperature of drying before dyeing
 Water quality

Summary of important factors in dyeing processes requiring control to minimise variability in
colour difference
Factor Variability ∆E(CMC)
Visual limit of trained colourist 0.6
Substrate variability up to 4.0
Water supply variation up to 3.0
Instability of dye solutions and dispersions 3.0 to 5.0
Variations in dye weighing of 2.5% 2.5
Quality control assessment of dyeings 0.15
Batch levelness 0.2
Reproducibility in bulk 0.2
Laboratory dyeing reproducibility 0.12
Laboratory to bulk reproducibility 0.3

 pH range
 Formaldehyde levels
 Extractable heavy metals
 Chlorinated phenols
 Pesticides
 Chlorinated Organic carriers
 Biocide finishes
 Flame retardant finishes
 Colour fastness to Water
 Colour fastness to acid & alkali perspiration
 Colour fastness to wet & dry rubbing
 Colour fastness to saliva
 Emission of volatile chemicals
 Other specific parameters as required by the customers
Ecological parameters:
Now all the Customers are asking for Ecological Parameters. Now European Buyers are
stressing this. Following are main Ecological Parameters to be considered.
Ecological parameters:

Process Temp. (C) P Time(min) M:L ratio
Scouring-
bleaching
100 10.5 30 1:8
Enzyme wash 50
70
5 30
10
1:8
Reactive
dyeing light
shade
60 10.5 60 1:6
Reactive
dyeing med.
to dark shade
60-65 10.5 60 1:6
Turquise color
dyeing
70-80 10.5 90 1:6
Polyester
stripping
90 4.5 30-45 1:8
Cotton
stripping
100 11 30 1:8
Polyester
dyeing
130 4.5-5.5 60 1:8
Cotton
whitening
100 30 1:6
H

Finishing Targets for Knit Fabric Dyeing

Finishing Targets for Knit Fabric Dyeing

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Finishing Targets for Knit Fabric Dyeing