DYE CLASS 1988 a 1992 2004 b
SULPHUR
DIRECT
VAT
INDIGO
AZOIC
REACTIVE
90 000
74 000
36 000
12 000
28 000
60 000
70 000
60 000
21 000
12 000
18 000
109 000
70 000
68 000
22 000
12 000
13 000
178 000
TOTAL 300 000 290 000 354 000

CONSUMPTION (1000 TONNE)
YEAR COTTON REGENERATED WOOL SYNTHETIC TOTAL
1990 18700
(49%)
1995 20700
(49%)
2000 23400
(49%)
2700
2500
2400
2000 14900
(39%)
2000 17300
(41%)
2200 20500
(42%)
39300
42600
48500

• TYPICAL DYE STRUCTURE
NH
2 NH
2
N N
N N
Na
2
SO
3
Na
2
SO
3
CONGO RED

FEATURES
• PRESENCE OF SULPHONIC ACID GROUPS
•
WATER SOLUBLE
•
ANIONIC IN NATURE
• SUBSTANTIVITY/AFFINITY TO COTTON
• APPLIED FROM AQUEOUS DYEBATH CONTAINING
ELECTROLYTE
• SIMPLE DYEING OPERATION
•
LOW WASH FASTNESS
• WASH FASTNESS IMPROVED TO SOME EXTENT AFTER
TREATMENT WITH CATIONIC DYE FIXING AGENT
• WASH FASTNESS STILL NOT ADEQUATE COMPARED TO OTHER
DYE CLASSES SUCH AS REACTIVE DYES

USES
•
USED FOR DYEING OF LOW PRICED COTTON OR
VISCOSE FABRIC, CUTAIN, FURNISHING OR
CARPETS WITH GOOD LIGHT FASTNESS AND
MODERATE WASH FASTNESS
• CHEAP COTTON DRESSING GOWNS AND BED
SPREADS WHICH ARE NOT WASHED REGULARLY
• DUE TO LOW WASH FASTNESS, LIMITED USE.
• BEING REPLACED TO GREAT EXTENT WITH
REACTIVE DYES WHICH HAVE BETTER WASH
FASTNESS AND PRODUCE BRIGHT SHADES.

• CLASSIFIED ACCORDING TO DYEING BEHAVIOUR
CLASS A SELF LEVELLING
• DYES WITH GOOD MIGRATION OR LEVELLING
PROPERTIES i.e. DYES WHICH PRODUCE UNIFORM
SHADE. NOT SENSITIVE TO DYEING CONDITIONS.
CLASS B SALT CONTROLLABLE
• UNIFORM SHADE PRODUCD ON CONTROLLED
ADDITION OF SALT DURING DYEING
CLASS C TEMPERATURE CONTROLLABLE
• UNIFORM SHADE PRODUCED ON CAREFUL
CONTROL OF DYEING TEMPERATURE AND SALT
ADDITION

TEMPERATURE
•
RATE OF DYEING AND PENETRATION INCREASES
TEMPERATURE. DYES BEING HIGH MOLECULAR WEIGHT
DYEING CARRIED OUT AT BOIL FOR GOOD PENETRATION.
DYEING TIME
• PRODUCTION OF LEVEL AND WELL PENETRATED DYEING IS
FAVOURED BY INCREASED DYEING TIME. HOWEVER,
PROLONGED BOILING CAUSES DECOMPOSITION OF MANY
DIRECT DYES. THE DYEING TIME IS USUALLY 1 hr. AT BOIL
LIQUOR RATIO
• DYEBATH EXHAUSTION IS USUALLY DECREASED WITH
INCREASE IN M:L RATIO. HOWEVER, UNIFORMITY OF
DYEING IS IMPROVED.

ELECTROLYTE
•
ELECTROLYTE IS ESSENTIAL FOR DYEING WITH
DIRECT DYES
•
COMMON ELECTROLYTE USED COMMON SALT
(NaCl) OR GLAUBER’S SALT (Na
2
SO
4
)
•
CONCENTRATION OF ELECTROLYTE IS GOVERNED
•
DYE CONCENTRATION: LESS SALT FOR LOW DYE
CONCENTRATION
•
No OF SULPHONIC ACID GROUPS IN DYE
MOLECULE: HIGH SALT WITH MORE No. OF
SULPHONIC ACID GROUPS

• COTTON IN WATER : NEGATIVE SURFACE POTENTIAL
• ANIONIC DYES DISSOLVED IN WATER : NEGATIVE CHARGE
DUE TO IONOIZATION OF WATER SOLUBILIZING SO3Na
GROUPS
• DUE TO SIMILAR CHARGES: REPULSION BETWEEN DYE AND
FIBRE SURFACE
•
FOR THE DYE TO GO ON FIBRE: NECESSARY TO REDUCE –Ve
CHARGE OF FIBRE
• ACHIEVED BY ADDITION OF ELECTROLYTE
• ELECTROLYTE DISSOCIATE IN WATER, RELEASE +Ve CHARGE
Na +
• Na + ACCUMULATE AT THE –Ve CHARGED FIBRE SURFACE
• NEUTRALIZE –Ve SURFACE POTENTIAL OF FIBRE
•
FACILITATE –Ve DYE MOLECULE ATTRACTION/ADSORPTION
ON FIBRE

DYE DISSOLUTION
• USE SOFT WATER FOR DYE DISSOLUTION AND DYEING. PASTE WITH
COLD WATER. ADD SUFFICIENT QUANTITY OF BOILING WATER.
STIRR. FILTR TO REMOVE ANY INSOLUBLE DYE PARTCLES
•
ADDITION OF 0.5-1 g/l WETTING AGENT HELPS TO WET OUT THE FIBRE
DURING DYEING.
GENERAL DYEING PROCEDURE
CLASS A DYES
•
THE DISSOLVED DYE IS ADDED TO DYEING MACHINE
•
MAKE TO TOTAL VOLUME ACCORDING TO M:L RATIO
• IF DYE IS SENSITIVE TO HARDNESS OF WATER, ADD 1-2 g/l SODIUM
HEXAMETA PHOSPHATE OR SODA ASH
• ADD SODIUM CHLORIDE, FOR PALE SHADE 5% OWM, MEDIUM SHADE
10%OWM AND HEAVY SHADE 20% OWM.
•
ENTER THE FABRIC AT 40-50 0 C
•
RAISE THE TEMPERATURE TO BOIL IN 30-40 MIN.
• CONTINUE DYEING AT BOIL FOR 30-45 MIN
•
RINSE WITH COLD WATER
•
AFTER TREAT WITH CATIONIC DYE FIXING AGENT.
• DRY WITHOUT RINSING.

SALT SENSITIVE DYES
•
ADD SALT IN INSTALMENTS DURING RAISING THE
TEMP. TO BOIL
•
IF DESIRED SALT ADDITION MAY BE CONTINUED
AFTER THE DYEBATH HAS REACHED TO BOIL.
• ADDITION OF DISSOLVED SALT BY DRIP FEED
METHOD IS PREFERRED

TEMPERATURE SENSITIVE DYES
• LOW ELECTROLYTE CONC. ADDED AT THE START
•
RAISE TEMP TO BOIL AT VERY LOW RATE
•
DYEING CONTINUED AT BOIL FOR 45-60 MIN.
• SALT ADDITION SHOULD BE DONE IN INSTALMENTS AT BOIL.
COMPOUND SHADES
• PRODUCED BY USING TWO OR THREE DYES TAKEN
TOGETHER
• TAKE MIX DYES BELONGING TO THE SAME CLASS
• DYES IN MIXTURE SHOULD HAVE SIMILAR RATE OF
EXHAUSTION
•
DYE MANUFACTURER SHADE CARD GIVES INFORMATION ON
DYE CLASS AND DYEING CONDITIONS
• FOLLOW THE INSTRUCTIONS CAREFULLY AND FAITHFLLY.

• INADEQUATE WASH AND PERSPIRATION FASTNESS
OF DIRECT DYES
•
CAN BE IMPROVED BY AFTERTREATMENT AFTER
DYEING
• DIAZOTIZATION AND DEVELOPMENT
•
COPPER SULPHATE AND POTASSIUM DICHROMATE
TREATMENT
• FORMALDEHYDE TREATMENT
•
CATIONIC DYE FIXING AGENT: MOST POPULAR
• FORMS COMPLEX WITH ANIONIC DYE. DECREASE
IN DYE SOLUBILITY
•
TRETMENT CARRIED OUT USING 1-3%OWM
CATIONIC AGENT AT 60 0 C FOR 30 MIN AT pH 5 WITH
ACETIC ACID.
•
NO RISING AFTER TREATMENT