RFT in Reactive Dyeing

A Journey towards

RFT (Right First Time) Processing

Industry Trends

Number of fashion Trends

Garment Manufacturers and Retailers

Consumers

Range of fabrics Colour changes Environmental pressure Order size Repeat orders Lead times Choice Fabric performance Colour fastness Value for money

D ec re as ing In cr ea sing In cr ea sing

Which ultimately trends in increasing Production Cost and reducing Profit margins

Colour Fastness Requirements

Incr

eas

ing

Effects on Dyehouse

Energy costs

Water and effluent costs Labour costs

Number of Competitors

Create additional pressure on Production Costs

Retailer’s knowledge of process costs

‘Performance for Profit’

q

How much is performance affecting the profitability? -Impact of Right First Time performance

-Benefits of true dyestuffs & user friendly Processes -Achieving high standards of process control

q

Can we meet retailer needs with cost-effective approaches?

-Optimize dyestuffs Selection to meet exactly customer needs

Aiming at Blind Dyeing in Dye-houses

1. Review Industry Trends 2. Impact of RFT

3. Dyeing Performance 4. Optimizing dye selection

5. Process Technology for different Substrates 6. Process Selection

7. Process Control 8. Control Parameters 9. Test procedures

10. Determine effectiveness with ‘on-line’ control 11. Usage of software to make technology user friendly

q

Assignable variables

Measurable factors that influence dye performance can be controlled: 1. Liquor ratio

2. Internal fabric pH 3. Fixation temperature

4. Specific gravity (salt concentration) 5. Addition profile

6. Fixation pH 7. Time

q

Random variables

Factors that require intervention of management to effect control of Impurities in:

1.

Cotton

2.

Water supply

3.

Chemicals eg QC of raw materials

4.

Controlled Coloration concept

Control Options

The Benefits Of Right-first-time

Financial

Lower Costs per Batch Increased Output Improved Profit Margin

Non-financial

Enhanced Customer Service Improved Quality of Goods Reduced Effluent Load

RFT (Right First Time) Performance & Setting Specifications

q

Measures of performance

Shade Reproducibility

- Lab to bulk CMC 2:1 delta E 1.0 - Bulk to bulk CMC 2:1 delta E 1.0 Level Dyeing

- Average throughout batch, piece to piece CMC 2:1 delta E 0.3 Colour Fastness

- Customer specific

- Washing, Repeat Washing, Rubbing, Light

q

Non-conformance

- Off shade-Lab to Bulk-needs shading addition - Off shade-Bulk to Bulk-needs shading addition - Unleveled-side to side variation, shading or patchy - Fails in Q.C Test-staining, fading

Process

Cost

Productivity

Profit

Blind Dyeing

100

100

100

Small Addition

110

80

48

Large Addition

135

64

-45

Stripping & Re-dying

206

48

-375

Cost of Non-conformance-for Cotton Exhaust Processing

RFT Rate %

50

70

80

90

100

Cost

167

143

125

111

100

Additional Cost

12

9

6

3

0

Total Cost

179

152

131

114

100

Batches

7.0

8.4

9.8

11.2

14

Cost of Shading (30% of original batch cost)

Increasing Productivity

Increase in Productivity

10%

20%

30%

40%

Reduction in total cost %

9

17

23

29

Additional batches/week

1.4

2.8

4.2

5.6

Reducing dye costs

% dye costs

-10

-20

-30

-40

Saving on total cost %

2.5

5.0

7.5

10

1. Dyes 25%

2. Chemicals 15%

3. Wage & Salary 15%

4. Capital Investment

& Other Overhead 13%

5. Energy 15%

6. Water 10%

7. Depreciation 7%

Model of costing for average colour Cotton Knit Processing

Capacity :

2 batches/day working 7 days a week

Cost control comes from optimization & profit comes from improved performance

Number of batches/week at % utilization 9.8

New Total Cost at % utilization 80.5

Actual number of RFT batches 8.8

Additional cost at 90% RFT rate 9.0

Total cost 89.3%

70% Plant Utilization @ 90% RFT

70% Plant Utilization @ 70% RFT

Number of batches/week at % utilization 9.8

New Total Cost at % utilization 80.5

Actual number of RFT batches 6.9

Additional cost at 70% RFT rate 12.0

Total cost 92.5%

Summary

q

Increasing RFT from 70 to 90 % reduces costs by 32%

q

Increasing Productivity by 30% reduces cost by 23%

q

Reducing dye costs by 30% only saves 7%

q

Combined effect of increasing RFT from 70 to 90% with increase in Productivity of 30%,

even with 30% higher dye costs reduces total cost of production by 44%

q

As a bonus additional ‘opportunity’ margin can be generated from increase in productivity.

Reducing dye costs and lower RFT (70 to 60%)

%Cost Reduction 10 20 30 40

Saving on total cost % 2.5 5.0 7.5 10

Additional cost at 60% RFT 24 25 28 29 0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 5 0 5 5 6 0 6 5 7 0 7 5 8 0 8 5 9 0 9 5 1 0 0 R F T P e rf o rm a n ce E ff ec t o n C o st S e rie s 1

Impact of RFT on Cost

q

Performance of dyestuff combinations is critical to cost and profitability of dyeing operation.

q

Selection of the most suitable combination is essential for success.

Audit and Trials Equipment

1. Hardness Test Papers 2. pH Meter or pH Papers

3. Thermometer preferably an Infra Red one. 4. Peroxide Test Papers

5. Hydrometer 1.000-1.100 6. Universal Indicator Solution

Fibre pH

A simple & quick spotting test with pH indicator solution is done. A slightly acidic state avoids premature fixation during migration phase of dye application. So, Ideal pH of fibre after neutralization is to be 5.0-6.0

Hydrogen Peroxide in dyebath can reduce dye yields and result in poor shade reproducibility. So, carry over of residual Hydrogen Peroxide to Zero.

Residual Hydrogen Peroxide

Fibre absorbency

Simple drop test with any temporary colouring liquid (i.e Potassium Permanganate Solution) can confirm fibre absorbency property.

Scouring and Bleaching Process

80°C X 10’ overflow 40°C Acetic Acid 95-105°C 80°C 10’

Pre-dyeing Check:

Ø

Fabric temperature should be lower than dyeing temperature.

Ø

No H₂O₂ is left in fabric.

Ø

pH of fabric should be within 5.0-6.0. 30’

10’ 10’

Peroxide Killer-Enzymatic (Catalase based)

Chemicals

1.0 g/l Anionic Detergent ( Remove dirt ) 0.5 g/l Nonionic Detergent ( Remove Oil & Fat ) 1.0 g/l Sequestrant-High alkali stable

1.0g/l H₂O₂Stabilizer-Organic 3.0 g/l Hydrogen Peroxide(50%)

3.0 g/l Caustic Soda 38°Bé ( NaOH 38°Bé )

Salt Concentration

Confirm Salt concentration with a Hydrometer & SG Charts. Specific gravity is influenced by temperature, so always confirm with a thermometer with Tolerance +/- 5% from target SG

Controlling Liquor Ratio and Salt concentration optimizes shade reproducibilty ensuring highest RFT production performance.

Accurate control of dyebath temperature ensures best possible shade reproducibility. Every after certain period calibrate controller, adjustment needed with an Infra-red one if required.

Dye-bath Temperature

q

Same fabric ?

q

Same pretreatment (weight loss, ...) ?

q

Same liquor ratio ?

q

Same salt quality and concentration at same temperature ?

q

Soda ash quality ok ?

q

Same caustic soda concentration ?

q

Temperature indicator at lab equipment and dyeing machine ok or regularly calibrated?

q

Right lab method for simulating the bulk process

Reproducibility between lab and bulk

a) Fabric GSM

b) Whiteness value of Scoured fabric depending on shade depth. c) Absorbency grade of Scoured fabric of specific GSM.

d) Different metal ions contents & total hardness.

As per different impurities content in greige cotton, scouring recipe to be adjusted to achieve required scoured fabric. For this reason, depending on shade depth, required specification for scoured fabrics (ready for dyeing) to be numerically pre-determined. Such as:

Water quality & Standard Textile Process water

Ø

pH: 6 - 8

Ø

Hardness: max. 5 °dH

Ø

Suspended matter: < 1 mg/l

Ø

Organic load: < 20 mg/l

Ø

Residue on ignition: < 50 mg/l

Ø

Iron: < 0.1 mg/l

Ø

Manganese: < 0.05 mg/l

Ø

Copper: < 0.01 mg/l

Ø

Nitrate: < 50 mg/l

Ø

Nitrite: < 5 mg/l

Ø

Free CO₂ 0 if possible (risk of corrosion)

Water contamination is constantly varying, so check it timely. Is water treatment effective? Is water free from vegetable, suspended solids & other mineral impurities? Hardness contaminants in dyehouse water can adversely effect level dyeing, shade reproducibility & wash off performance.

Liquor Ratio

Confirming Liquor Ratio

Assumed volume X Expected salt Concentration Actual Volume =

Common Observations in Bangladeshi Dye-houses:

Usual phenomena :

q

Cold water temperature about 40°C-50°C =All in method needs 25°C-30°C

q

Bicarbonates in water about 0.3-0.5 g/l up to 1.0 g/l =Bad reproducibility in Exhaust method

=Alteration of final shade after wash-off (Chromophore sentitivity)

q

Poor quality Common & Glauber’s salt : high presence of impurity and Ca, Mg : =Bad reproducibility in Exhaust method

=Big problems with Turquoise (Phthalocyanine) & Royal Blue (Anthra-quinone)

q

Low quality auxiliaries with insufficient Wetting & Cleaning property

In pretreatment phases :

=Incomplete oil, fat, dirt elimination, consequently lead to bad leveled dyeing

q

No controls after bleaching :

=Peroxide residuals destroy dyestuffs

=Out of right pH range (=6.5-8) gives bad reproducibility =Hardness neutralize alkali (NaOH)

q

Large use of non-ionic auxiliaries agents in high amount :

=These kinds of auxiliaries are difficult to be washed out.

=Levelling problem especially with Phthalo-cyanine dyestuffs(Turquoise type)

q

Insufficient knowledge about microprocessors in dye machinery :

=People often have new technologies but do not accurately know how to use. =A program mistake means a bad dyeing e.g. during alkali dosing.

Check List in Exhaust Dyeing-Reactive

1. Water Hardness Test : With Hardness Test-strips.

2. Bicarbonate in dye-bath :Can be tested with Methyl-Orange + HCI Test. Sodium

bicarbonate presence in dye-bath water can work as a buffer; increase caustic soda 38°Bé at 0.1 ml/l for each 0.1 g/l sodium bicarbonate.

3. Salt Hardness Test :With Hardness Test-strips and NaOH Test

If total amount of hardness from water, salt & material is more than 10°dH, try to reduce. For water : Increase Sequestrant

For salt : Change salt to good quality For material : Demineralization can solve it. If not possible, try to dye with Only Soda ash method.

4. Residual Peroxide :With Peroxide test-strips ( if just bleached material )

5. Alkali Concentration :Correct concentration to be used ( if different, convert it)

6. Recipe Calculation :Should be done for dyes & auxiliaries, Control workman

-To measure weight, he has to use a balance.

-To measure volume, he has to to use a cylinder or pipette.

7. Material quality Checking :

- pH with pH test paper

-Hardness with Hardness test-strips

8. Machine parameters :

-Dependability of thermometer

-Circulation pump’s pressure (in package dyeing of yarn) -Winch speed (in rope dyeing for knit goods)

9. Dyeing Liquor Ratio :The amount of water in Dyeing machine,

Determination of Fibre contamination

Simple extraction technique enables fibre hardness level can be determined after pretreatment. Effective pretreatment reduces carrying over of alkaline earth element contamination of dye-bath.

Ø

Extract fibre sample at liquor ratio 20:1, 95°C for 30mins in 100g/l Analytical Salt (Pure NaCl)

Ø

Cool solution and test with hardness paper

Ø

Calculate approximate hardness level:

1°German Hardness = 17ppm Calcium/Magnesium So, 5° German Hardness = 85ppm Calcium/Magnesium Fabric contamination = 85 X 20 ( LR 20:1 )

= 1700ppm

Being a natural fibre, cotton’s contamination levels can vary. So, check regular basis & accordingly dematerialize, if needed & adjust Sequestrant dosing in pretreatment.

Determination of hardness from salt

Ø

Make a solution about 80 g/l Salt( Salt dosing that is used in dye-bath)

Ø

Check solution hardness with Hardness Test strip or by titration.

Ø

To confirm, add some ml. of NaOH 38°Bé to solution. If there is any hardness in salt, an opal white snow of Mg(OH)2Ca(OH)2can be seen.

Ø

Consequently in dye bath from 1_/

2to approximately same hardness is found from salt.

Determination of total amount of Bicarbonate in water

Ø

Put 100 ml of water (the same water to be used in dyeing) in a beaker.

Ø

Add 1-2 drops of Methyl-orange and mix.

Ø

The water will turn to a pale yellow solution.

Ø

Start adding drops of 0.1 N of HCl (never stop shaking) till last drop that changes solution colour from yellow to orange-red.

Ø

Stop immediately

Ø

Write down the amount of HCl solution used and put it in the calculation bellow:

Ø

Bicarbonate in water(gm/l) =(ml) of 0.1N HCl X0.084

Soda Ash pH to be able to reach pH 10.8 to 11.2 in salt solution to reach optimum fixation conditions.

Check Soda Ash Quality

q

Hardness adversely effects level dyeing, shade reproducibility and wash off

q

Fibre, salt and water contamination all contribute to dyebath hardness

q

Measuring levels of contamination of the above allows us to determine required sequestrant concentration to protect & overcome it’s adverse effects

Hardness contamination

Calculating required concentration of dye-bath Sequestrants

Hardness from prepared Fabric

+

Hardness from process Water +

Hardness fro Salt

Total dyebath Hardness

Required Amount of Dye-bath Sequestering agent

Conversion of Caustic soda soln. with Sodium Bicarbonate

Temporary hardness and it’s neutralization :

NaHCO₃ + NaoH = Na₂CO₃ + H₂O Mg 84 40 106 18 1° dH = 0.03 g/l NaHCO₃ 10° dH = 0.30 g/l NaHCO₃ 16.7° dH = 0.50 g/l NaHCO₃ 20° dH = 0.60 g/l NaHCO₃ 33.4° dH = 1.00 g/l NaHCO₃ + 0.48 g/l Caustic soda

1 g/l NaHCO3 + 1.09 g/l Caustic soda 1.26 g/lNa₂CO₃ + 0.62 g/l Caustic soda

Note: Sodium Bicarbonate is generated only by the components in water that cause temporary hardness, not by total hardness of water.

1°dH = 10 mg/l CaO

= 22.5 mg/l Ca(HCO₃)₂ = 30 mg/l NaHCO₃

Scouring & Bleaching chemicals:

q

Anionic detergent - To remove dirt

q

Nonionic detergent - To remove FAT & OIL

Caustic soda:

q

Proper amount of caustic soda should be used aiming at avoiding oxycellulose

Hydrogen Peroxide:

q

Cotton should not be over bleached

Hydrogenperoxide Killer:

q

Good Peroxide killer to be selected that has no effect on both dyestuffs & environment.

Fabric condition to be ensured before dyeing that:

q

pH on fabric is about be 5.0-6.0 & must be bellow 7.

q

No Hydrogen peroxide left in the fabric.

q

Fabric temperature is lower than dyeing temperature.

A brief idea about different types of Textile Colourants

Many years of research have been put into the development and synthesis of dyes. Based on research, there are eight general classes of dyes used to colour different textile fibres. As per their chemical structures & application, they’re described shortly as in the following ways:

1. Acid dyes:

It is referred to as anionic dyes, are applied under acidic conditions. Acid dyes are typically used for polyamides (nylon), wool, and silk.

2. Azoic dyes:

They are known as developed dyes because they are built from two smaller molecules. They are used for dyeing and printing cellulose fibres.

3. Basic dyes:

Due to a net positive ion that is active anchoring portion of dye, they are referred to as cationic dyes. Acrylic and cationic-dye-able polyester fibres are main targets for these dyes, but they were originally designed for silk and wool.

4. Direct dyes:

The first dyes to color fibres directly, used without a mordant. They are used for cellulose fibres.

5. Disperse dyes:

Disperse dye class does not contain water-solublizing groups & so remains as finely-dispersed particles, were developed for synthetic fibres & are used mainly for polyester, but are also used for acetate, polyamide & acrylic fibres.

6. Reactive dyes:

Fibre-reactive dyes are the only dyes that form a covalent bond with fibre. Are primarily used for cellulose fibres, but some of them can also be used for polyamide and wool.

7. Sulfur dyes:

These are sulfur-containing dyes with high molecular weights. They are normally insoluble dyes but become soluble & form leuco compound by reduction. Once applied to the fibre, they are oxidized to become insoluble again. They are used for cellulose fibres.

8. Vat dyes:

Vat dyes are similar to sulfur dyes as they start as insoluble, become soluble upon reduction, & are oxidized to become insoluble after application. They are used for cellulose dyeing & printing.

9. Pigment

One additional colourant class for fibres is pigments-are not soluble & do not dye fibres; are normally applied in printing process along with a binder which fix the pigment particles on the fabrics & show colour effects. Used on all fibre types, but are only attached to the surface of fibre.

Group

Type

Brand

Vinylsulfone

Monochlorotriazine

Dichloroquinoxaline

Diflourochlorpyrimidine

Monofluorotriazine

Company

ICI

Hoechst

Bayer

Name

Monochlorotriazine & Vinyl sulfone

Monofluorotriazine

&

Vinylsulfone

Bi-functional

Bayer & Sandoz

Year

Sumitomo

Ciba Geigy

Ciba Geigy

Ciba Geigy 2000

Cibacron L-S

MFT/MFT

Cibacron S

Bi-functional

Monofluorotriazine

&

Monofluorotriazine

1960

1970

1990

1970

1970

1960

1950

2000

Ciba Geigy

Monofluorotriazine

+

Monochlorotriazine

+

Vinylsulfone

Multi-functional

MFT/MCT/VS

Mono-functional

Bi-functional

Procion H-E

Remazol

Levafix E

Levafix E-A

Sumifix Supra

Cibacron F

Cibacron FN

Mono-functional

Mono-functional

Mono-functional

Mono-functional

BIS-MCT

VS

DCC

DFCP

MCT/VS

MFT

MFT/VS

Drimarene K

Reactive Dyestuffs Details-with it’s major historical landmarks

New Chemical Structure Leading to Higher Colour Value & Fastness

Cibacron S

Multi-functional

2000

C (Chromophores) : 2-3

R (Reactive group) : 3

Features of new structure

q

High fixation rate (>90%)

q

Medium-high affinity

q

Flexible molecules

q

Good wash-off property

q

Excellent build-up ability

Insertion of two Chromophores & more than two Functional Groups in Dye molecular

structures leads to increasing of both Colour value & all round fastness.

R

Chemical structure of Cellulose & Dyestuffs-Fibre bonding

O H O C H₂O H H O H H H O H H O O H H C H₂O H H O H H O H H O H O C H₂O H H O H H H O H H H O H C H₂O H H O H H O H H O C₆H₁₀O₅

Mechanisms of Reactive Dye Fixation

F -SO

₂

-CH

₂

-CH

₂

-OSO

₃

Na

+ Alkali

F -SO

₂

-CH=CH

₂

+ HO-Cellulose

+ H

₂

O

F -SO

2

-CH

2

-CH

2

-O-Cell

F -SO

₂

-CH

₂

-CH

₂

-OH

Ether Bond

Additions mech.

VS Dyes

Fibre Reaction 70-95% Hydrolysis 5-30%

Hydrolysis

Resistant to Acid

Sensitive to Alkali

F

Vinyl Sulphone Based:

Chloro Triazine Based:

F -HN-

-NH-R

+ Alkali

+ HO-Cellulose

+ H

₂

O

Ester Bond

Substitutions mech.

N

N

N

Cl

F -HN-

N

-NH-R

N

_N

O

H

F- HN-

N

- NH-R

N

N

O

Cell

Hydrolysis

MCT Dyes

Resistant to Alkali

Sensitive to Acid

F

Reactive Dyes-Cellulose Reaction in brief

-SO₂-CH₂-CH₂-OSO₃Na

ß-sulphato ethyl sulphone

F

-SO₂-CH=CH₂

Reactive vinyl sulphone

-SO₂-CH₂-CH₂-O-Cell

Fibre Reaction

F F

Hydrolysis

-SO₂-CH₂-CH₂-OH + Alkali F

O N N H O O O N N O O H O O N N+ O H

l

Singulet-O

₂

reacts with Hydrazone-tautomer of Azo Dye

Griffiths & Hawkins JCS Perkin II 1977, 747

i) Photo Oxidation

Destruction of Chromophores group (Azo Group) resulting in affecting Light or Light

Perspiration Fastness of Reactive Dyestuffs in following two ways:

N N + H - D o n o r H N _N. H N N H N H 2 N H 2 •

ii) Photo Reduction

Light Perspiration Fastness of Reactive Dyestuffs

Reactive dyes Fixation

pH value

Temperature

Time

Reactive Dyestuffs Fixation Parameters

OH HOH₂C O CH₂ O O O O HOH₂C OH OH O O H O H O N N N Cl O HN NaO₃S N SO₃Na O H N SO₃Na

Lower Temperature Sensitivity

Dependence of Colour Strength on Different Dyeing Parameters for Different Anchor Systems

110 100 90 80 70 60 50 40 30 40 50 60 70 80

Dyeing Temperature in °C

R

el

a

ti

ve

C

ol

ou

r

S

tr

eng

th

i

n

%

MCT MCT-VS VS

Temperature Sensitivity of Different Functional Groups

Acid

Alkali

Stability of

dye-fibre bond

pH

VS

MCT/MFT

Bi-functional SYSTEM - BALANCE MCT / VS Dyeing-Temperature

Relative Fixing Rate

MCT Dyeing-Temperature

Relative Fixing Rate VS 65 °C 65 °C 60 °C 55 °C 60 °C 55 °C

Dyeing Parameters in Reactive Dyeing

Liq

uor

rat

io

Dyeing

tem

peratu

_re

Electrolyte C

_{oncerntration}

Alkali Concerntration

All reactive dyestuffs are sensible to the above parameters & show differences, more or

less. Dyestuffs selection of showing same behaviour can reduce sensitivity to different dye

parameters, but decisive for a good reproducibility is a conscientious working method !

Influence of diffusion, substantivity as a function of temperature in fastness washing

Rel. diffusion

40 50 60 70

°

80 90 100

C

Temperature

D

S

Substantivity

Ø

The ‘right profile’ represents the best balance of cost and performance

Ø

Preservation of Standardized dye quality

Ø

Protection from decomposition Reactions

Ø

Reasonable recipe cost according to buyers price

Ø

Higher Solubility

Ø

Higher Acid & Alkali stability

Ø

Excellent dyebath stability

Ø

Shade, tinctorial strength, viscosity

Ø

Good technical performance to meet the most tailor made requirements 1. Substantivity in neutral electrolyte

2. Exhaustion after the addition of alkali 3. Fixation efficiency

4. Migration Index 5. Level Dyeing Factor

6. Unfixed dye to be removed in the first hot rinse bath

70 – 80% Above 90% 80 - 90% Above 90% Above 70% Above 60%

Target Profiles for Dyestuffs Selection

Influence of dye compatibility

Level dyeing factor : LDF = S/E X MI

Standard Requirements for Selection of Dyestuff:

Lower Substantivity + Moderate Reactivity + Lower dye-hydrolysate & Rapid washing-off

An Ideal Orange Combination Reactive Orange 107 Reactive Red 198 Reactive Blue 220 Reactive Yellow 176 Reactive Red 238 Reactive Black 5

Yellow component very low substantivity

Yellow very high secondary exhaustion – unlevel risk Exhaustion in alkali ‘on tone’

Rapid fixation of yellow and slow of blue

Yellow and red medium substantivity, blue low Red slow to fix

Exhaustion in alkali ‘on tone’

Final fixation of yellow low, fixation greener paler when compared to final exhaustion

Increased compatibility during salt exhaustion

Exceptional ‘on tone’ exhaustion and fixation in alkali Final exhaustion and fixation ‘on tone’

Compatibility Study a Trichromate Dyestuffs

Robustness Study

Reactive Orange 107

Reactive Red 198 Reactive Blue 220 Reactive Yellow 176 Reactive Red 238 Reactive Black 5 An Ideal Orange Combination 20% Underfill/20% Overfill -10% Salt/+10% Salt -10% Alkali/+10% Alkali

45 mins Fix/75 mins Fix

-Temperature/+Temperature

-2:1 Liquor Ratio/+2:1Liquor Ratio _{V.Yellower Redder}

V.Yellow Bluer Yellower Stable Stable Stable Stable Yellower Yellower Redder Redder Bluer Bluer V.Yellow

Stable Less Blue

Bluer Yellower Less Blue Bluer Less Blue Redder

Stable Stable Stable Stable

Change in Hue

Stable Stable Little Stable Redder Stable Stable Stable Stable

Migration and Compatibility studies : Orange – Red - Navy

Migration

D1 D2 B1 Final

Migration index 93.4%

Orange : 1.41% Red : 0.60% Navy : 0.65% Salt : 80 g/l Soda ash : 15 g/l LR : 10 : 1 Fixation temperature : 60°C 30°C 40°C 50°C 60°C 15’ 15’ 15’ 5’ 5’ 5’ 5’ 20’ 20’ 20’ 1 2 3 4 5 6 7 8 9 10 11 12

10% Alkali 20% Alkali 70% Alkali

Exhaustion

Fixation

Compatibility

Compatibility Study a Trichromate Dyestuffs

Combinations in Ternary Shade (Olive)

CIELab Color Difference

DE*

C.I. Yellow 145 C.I. Red 195 C.I. Blue 222

Compatibility Study a Trichromate Dyestuffs

STD. A B C D STD. A B C D E F G HE F G H A : Alkali -20% B : Alkali +20% C : Salt -20% D : Salt +20% E : Temp. 50 F : Temp. 70 G : L.R. 1:8 H : L.R. 1:12

Standard. Recipe

Chemicals Requirement : Glauber’s salt 60g/l, Soda ash 20g/l Liquor ratio : 1:10

Dyeing Temp. : 60

Performance of a Standard Trichromatic Dyestuffs

Compatibility

Ø‘On Tone’ exhaustion in salt

ØMedium substantivity with high migration in neutral exhaustion conditions ØGood levelling ability

ØLower E-S leading to better levelling on alkali addition ØExhaustion remains ‘on tone’ after alkali add

ØExhaustion and fixation are the same shade through out

Robustness

Ø

Most stable only small variations in hue and depth

For Production of Deep and Color fast Blacks

q

Mixture of Soda Ash/Caustic Soda gives highest fixation

q

60’C application ensures good diffusion and penetration

q

Highest fixation and diffusion reduce ‘bronzing’ effect

q

Best process for fixation and reproducibility is automet

Conclusion

Traditional combinations are sensitive with large changes in hue, especially to time & temperature

Influence of Chemicals, Processes & Substrates:

For Production of Bright Greens and Turquoise

q

Best preparation – fibre hardness contamination needs to be minimized

q

Migration (Temperature raising) Method would give better levelling.

q

Avoid using non-ionic chemicals in dyebath

q

Good anticreasant with emulsifying properties

q

Best quality (pH lower than 8 & zero hardness) Glauber’s Salt

q

Use clean Machine

Possible problems and causes

Potential problems

Ø

Unlevelness, Shade Variation-Long variation/Short Variations

Ø

Poor penetration

Ø

Surface deposition

Possible causes

Ø

Wrong or poor quality ancillary equipment (e. g. pumps)

Ø

Problems due to improper synchronization of winch speed & fabric string speed

Ø

Sub-optimized dyeing process

Ø

Incorrect dye selection

Ø

Improper Auxiliaries selection & Inefficient pretreatment

For Production of ready for dis-charge print fabric

q

Required dischargeable plus highly pure Reactive dyes to be selected

q

Cationic Finishes to be avoided for white dis-chargeability

Rubbing fastness affected by the following factors:

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Substrate

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Dye concentration

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Water hardness

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Improper finishing of the dyeing

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Inadequate liquor flow rate

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Lower colour yield

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Poor reproducibility of the dyeings

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Dusting of the yarn, particularly when rewinding onto another bobbin

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Poor fastness properties

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Harsh handle

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Poor wettability

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Deposits on the machines

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Poor levelling-out properties, particularly with wound packages

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Formation of spots

These problems can be avoided by Good pretreatment of the fabric

Proper usage of sequestering and complexing agents in the dyeing process These problems can be avoided by

Good pretreatment of the fabric

Proper usage of sequestering and complexing agents in the dyeing process

Possible Problems with hardness

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Poor liquor circulation-Too low circulation results in-Unlevelness due to insufficient liquor flow

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Poor temperature control

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Contaminated addition tanks or dyeing equipments (dyes, O.B.A, Softeners, oligomer)

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Flooded seals at reduced liquor levels

By Dyeing Machine

In Reactive Dyeing

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Inefficient pretreatment.

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Inefficient rinsing after pretreatment.

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Inappropriate dosing cycle times for the dyes used.

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Inefficient rinsing after dyeing.

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Unleveled application of cationic products to the goods (especially in pale shades).

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Inappropriate dye selection for down-stream processes (eg., post-bleach, post-merc.).

Potential Problems-In Processing

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Lack of heat-setting of Yarn or fabric leads to shrinkage on dyeing

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Unevenly heat set of the substrate

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Poor temperature control

- Dispersion stability problems - Unleveled dyeing

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Incorrect dye selection

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Insufficient dispersing agent with highly concentrated dyestuffs

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Too much auxiliary (less is better)

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Waxes, oils, hydrocarbons on the substrates.

In Polyester Dyeing

Wash Off

Main items before start

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Is the dyeing process ok?

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Is the dyestuff properly desolved?

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Is the dyeing machine & other used vessels clean or free from any technical problem?

Check-list before starting a Winch/Batch dyeing machine

Main vessel

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Inside or outside lying pump with engine control or not.

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Different kind of level control making variable kind of liquor levels possible or not.

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Overpressure devices.

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Overpressure devices, different kind of valves, heating & cooling device.

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Different kind of sealings.

Peripheral vessels

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Expansion vessel with heating, automatic dosing system to regulate pH & stirrer.

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Preparation vessel with heating and stirrer.

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Dosing system for solid material.

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Dosing or cycle pump.

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Connection to an automatic dosing system for bulk chemical and auxiliaries.

Precautions for Finishing of different shades to achieve required quality

Carefulness to be needed to ensure for achieving better wet rubbing, staining or wash

fastness of the darkest Shades:

Cotton:

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As required Dye amount is very high, dye selection is to be optimized between Quality & Prices.

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Total Shade depth should not exceed total standard depth of it’s different dye components. i.e try to use as less dyestuffs% as possible.

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Any sort of “Micro or Nano” Silicon finish adversely affect wet rubbing, staining or wash fastness of the finished RMG.

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Be sure of removing maximum hydrolyzed dyes from the substrates with efficient wash off process. Specially for dischargeable dyeing as hydrolyzed dyes do not leave white ground.

Polyester:

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Proper Pre-heat set needed to evenly rearrange the fibre structure.

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For polyester-filament, lower filament no. containing substrates give better wash, sublimation & other fastness.

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A non-ionic wetting agent to be used with other reduction cleaning recipe.

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A post-heat set with subsequent further reduction cleaning may ensure the best wash, sublimation & other fastness of polyester apart from dyestuffs quality.

Conclusion

Pre-cautions to be ensured for achieving required light fastness, shades changes

possibilities & other pale shade related fastness:

Cotton:

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As dyestuffs amount is very low, usually the best quality dyestuffs to be chosen.

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Avoid matching any light shades without dyestuffs-mostly by scouring as colour fastness of natural Chromophores & different contamination of scoured fabrics change in time & do not give permanent effect.

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Select equal light & other fast dyes components for on tone fading.

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Avoid using any “Cationic finish” or Fixatives as they adversely affect Light fastness

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Removal of maximum hydrolyzed dyestuffs from substrates with efficient wash off process.

Polyester:

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Proper Pre-heat set needed to evenly rearrange the fibre structure.

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For polyester-filament, applicable dyes energy level is inversely proportionate to filament no.

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A non-ionic wetting agent to be used with other reduction cleaning recipe.

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A post-heat set is not always necessary.

Dark Shades:

Details for Silicon Based Product application-with Types

Silicon emulsion is of three kinds according to its molecular size:

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Nano Type :

Amino Silicon Nano-emulsion, having particle size up to 10nm, is physically water like transparent. Because of their finest particle size, they can easily penetrate right in to the core of fibre very easily and after cross-linking; they make the fabrics soft handled and elastomeric. Due to their penetration in side the core of fibres & cross-linking there, they push out the rest hydrolyzed dyestuffs particles resulting in negatively affect the rubbing, staining, washing & other fastness properties of fabrics. So, it is advisable to avoid using comparatively loser particles sized silicone emulsion in darker shaded fabrics.

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Micro Types:

Amino Silicon Micro Emulsion, containing particle size above 10nm & up to 50-100nm, is also physically transparent looking. Because of their smaller particle size, they can penetrate into the inner parts of the fabrics and with the effect of the temperature; the silicon particles cross-link themselves with the presence of amino-based emulsifier and hence impart permanent elastomeric type softness. This type of silicone particle sized emulsion also contributes to the deteriorations of rubbing, staining, washing & other fastness properties due to the same reason as nano type silicones sized particles do.

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Semi-Micro Types:

Silicon Emulsion containing particle size above 100nm & up to 150nm, are physically translucent looking. Because of their comparatively smaller particle size than the macro emulsion but larger than the nano & micro-emulsion, they cannot fully penetrate into the inner part of the substrate and hence remain submerged in the fabric surface and get cross-linked there. That’s why they impart both elastomeric and slippery type softness on the surface of the fabrics. They deteriorate the fastness of dyed fabrics to a few extent.

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Macro Type:

Amino Silicon Macro Emulsion, containing particle size above 150nm, is physically opaque looking. Usually, they’re less shear force stable and emulsion can easily break. So, they can’t be applied in exhaust process. Because of their comparatively larger particle size, they cannot penetrate into the inner parts of the fabrics and remain on the surface of the fabrics and then during drying they cross-link and impart permanent slippery type smooth softness effect on the surface of the fabrics. So, it also helps in developing rubbing fastness of the substrate.

Ionic Characteristics:

Silicon Emulsions are made by Silicon particles with amine-based emulsifiers and are given either Anionic or Cationic or Non-ionic nature during manufacturing. So, all kinds of silicon can be usually of two kinds according to the ionic nature:

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Cationic:

Has more affinity towards the substrate and thus more reactive to the fabrics. It leaves some yellowing effect after application and so is not suitable for use in the white/light shades.

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Non-ionic:

Has less affinity towards the substrate and thus are less reactive to the fabrics. Leaves no yellowing effect after application and thus does not make any change in white/light shades application.

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Besides, there are some other silicones of different kind, which impart cotton like hydrophilic nature of different hydrophobic fabrics, creating some capillary pores on the surface of the fabrics. There are also some other silicones which are more robust towards alkali i.e remains active in pH of above 7 and thus make it user friendly.

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Because of lower stability of Silicon emulsion i.e, easily breakable emulsion, they should not be given high sheer-force which might result in breaking of silicone emulsion & thus it is usually not suitable for use in Exhaust application but in Padding application. While using in Padding, the concentration of pad-liquor is to be kept constant to avoid “Tailing effect”. If it is used in Winch, the nozzle pressure is to be reduced remarkably to avoid silicon emulsion breakage.

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As it is very sensitive to alkali, specially cationic one, here padding liquor pH should never exceed 6.5.

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As cationic silicone emulsion reacts with different radicals like Ca++, Mg++ and specially Fe+++, the presence of any kind of the above radicals might make some precipitation & so water to be softened carefully before applying silicon.

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Usually the Cross-linking Temperature of Silicone emulsion is about 45-50°C so, to avoid Pre-mature cross-linking, the cross linking of silicone emulsion is to let happen in the next subsequent processes, i.e.. Drying/Calendaring period, not during application.

Over-coming problems of Silicon Spot (pre-matured cross-linking of Silicones):

Using of both silicon emulsion and fatty acid based softener:

Carefulness in Silicon based product application:

If accidentally any premature cross-linking happens, there creates some silicon spot on the fabrics surface & it is very hard to remove. Only some Organic solvent type emulsions (mostly organic solvent based) can dissolve these spot. So, if these types of problems occur accidentally during application, some AEPO/NEPO free organic solvent-based detergent can be applied (with temp. 80-90°C) to overcome it.

For special softness, combination of both silicon & fatty acid softener can be applied. Some manufacturers have developed some products of this kind readily usable for this purpose. But while using combination, it is suitable to use them in padding application:

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Making combination of Fatty acid stock solution+ Silicon Emulsion→Applying in padding

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Silicon Emulsion to be applied first and then Fatty acid softener but because of coating & washibility nature, fatty acid softener should not be used first.