DYE CONSUMPTION (TONNE)

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• DYE CONSUMPTION (TONNE)

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

• CONSUMPTION (1000 TONNE)

YEAR COTTON REGENERATED WOOL SYNTHETIC TOTAL
1990 18700 (49) 2700 2000 14900 (39) 39300
1995 20700 (49) 2500 2000 17300 (41) 42600
2000 23400 (49) 2400 2200 20500 (42) 48500
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DYEING OF COTTON WITH DIRECT DYES

• TYPICAL DYE STRUCTURE
• CONGO RED

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DIRECT DYES

• 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

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DIRECT 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.

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CLASSIFICATION

• 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

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EFFECT OF VARIOUS PARAMETERS ON DYEING

• 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 ML RATIO. HOWEVER, UNIFORMITY OF
  DYEING IS IMPROVED.

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EFFECT OF VARIOUS PARAMETERS ON DYEING

• ELECTROLYTE
• ELECTROLYTE IS ESSENTIAL FOR DYEING WITH
  DIRECT DYES
• COMMON ELECTROLYTE USED COMMON SALT (NaCl) OR
  GLAUBERS SALT (Na2SO4)
• 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

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ROLE OF ELECTROLYTE

• 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

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BATCHWISE DYEING OF COTTON

• 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 ML 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 10OWM AND HEAVY SHADE 20 OWM.
• ENTER THE FABRIC AT 40-500C
• 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.

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CLASS B DYES

• 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

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CLASS C DYES

• 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.

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AFTER TREATMENT

• 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 1-3OWM CATIONIC AGENT
  AT 600C FOR 30 MIN AT pH 5 WITH ACETIC ACID.
• NO RISING AFTER TREATMENT

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CATIONIC DYE FIXING AGENT