DYE CONSUMPTION (TONNE)
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DYE CONSUMPTION (TONNE). WORD FIBRE CONSUMPTION. CONSUMPTION (1000 TONNE). NH 2. NH 2. Na 2 SO 3. Na 2 SO 3. N. N. N. N. DYEING OF COTTON WITH DIRECT DYES. TYPICAL DYE STRUCTURE CONGO RED. DIRECT DYES. FEATURES PRESENCE OF SULPHONIC ACID GROUPS WATER SOLUBLE ANIONIC IN NATURE

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Word fibre consumption
WORD FIBRE CONSUMPTION

CONSUMPTION (1000 TONNE)


Dyeing of cotton with direct dyes

NH2

NH2

Na2SO3

Na2SO3

N

N

N

N

DYEING OF COTTON WITH DIRECT DYES

  • TYPICAL DYE STRUCTURE

    CONGO RED


Direct dyes
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


Direct dyes1
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.


Classification
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


Effect of various parameters on dyeing
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 M:L RATIO. HOWEVER, UNIFORMITY OF DYEING IS IMPROVED.


Effect of various parameters on dyeing1
EFFECT OF VARIOUS PARAMETERS ON DYEING

ELECTROLYTE

  • ELECTROLYTE IS ESSENTIAL FOR DYEING WITH DIRECT DYES

  • COMMON ELECTROLYTE USED COMMON SALT (NaCl) OR GLAUBER’S 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


Role of electrolyte
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


Batchwise dyeing of cotton
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 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 40-500C

  • 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.


Class b dyes
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


Class c dyes
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.


After treatment
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 1-3%OWM CATIONIC AGENT AT 600C FOR 30 MIN AT pH 5 WITH ACETIC ACID.

  • NO RISING AFTER TREATMENT



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