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RESIST PRINTING UNDER REACTIVE DYES

RESIST PRINTING UNDER REACTIVE DYES. REIST PRINTING: PREVENTION OF DYE FIXATION AT THE PRINTED PORTION WHITE RESIST: WHITE PRINT AGAINST COLOURED BACKGROUND COLOURED RESIST: COLOUR PRINT AGAINST COLOUR BACKGROUND PRINCIPLE REACTIVE DYES FIXED ON COTTON UNDER ALKALINE CONDITIONS

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RESIST PRINTING UNDER REACTIVE DYES

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  1. RESIST PRINTING UNDER REACTIVE DYES REIST PRINTING: PREVENTION OF DYEFIXATION AT THE PRINTED PORTION WHITE RESIST: WHITE PRINT AGAINST COLOURED BACKGROUND COLOURED RESIST: COLOUR PRINT AGAINST COLOUR BACKGROUND PRINCIPLE • REACTIVE DYES FIXED ON COTTON UNDER ALKALINE CONDITIONS • DYE FIXATION PREVENTED UNDER ACIDIC CONDITIONS SEQUENCE: PRINT WITH RESISTING AENT > DRY > NIP PAD WITH DYE + ALKALI >DRY > STEAM > WASH > SOAP > WASH > DRY

  2. CHOICE OF ACID • INORGANIC ACID SUCH AS HCl NOT SUITABLE DUE TO DANGER OF FIBRE DEGRADATION DURING STEAMING • VOLATILE ORGANIC ACID LIKE ACETIC ACID NOT SUITABLE • NON-VOLATILE ORGANIC ACID LIKE CITRIC ACID, TARTARIC ACID SUITABLE THICKENER: SHOULD BE STABLE TO ACID e.g. MODIFIED GUAR GUM (INDALCA AGBV)

  3. PRINT PASTE COMPOSITION CITRIC ACID 50 PARTS WATER 50 ml THICKENER PASTE 900 PARTS TOTAL 1000 PARTS PRINT > DRY PAD LIQUOR COMPOSITION REACTIVE DYE 10-20 g/l RESIST SALT 10 g/l SOD. BICRBONATE 10-20 g/l NIP PAD > DRY > STEAM FOR 10-15 MIN. > WASH > SOAP > WASH > DRY

  4. COLOURED RESIST COLOURED PRINT AGAINST COLOUR BACKGROUND PRINCIPLE: • INCORPORATE DYE/PIGMENT IN RESIST PASTE WHICH CAN BE FIXED UNDER ACIDIC CONDITION • SIMULTANEOUS FIXATION OF GROUND COLOUR AND PRINT COLOUR • PIGMENT ALONG WITH BINDER MOST SUITABLE PRINT PASTE COMPOSITION PIGMENT COLOUR 20-30 PARTS BINDER 100 PARTS EMULSION THICKENER 850 PARTS CITRIC ACID 50 PARTS TOTAL 1000 PARTS PRINT > DRY > NIP PAD WITH REACTIVE DYE + ALKALI > DRY > STEAM > WASH > SOAP > WASH > DRY

  5. DISCHARGE PRINTING UNDER REACTIVE DYES PRINCIPLE • DISTRUCTION (CHEMICAL DECOMPOSITION) OF DYE AT THE PRINTED PORTION DISCHARGING AGENT • THERMALLY STABLE STRONG REDUCING AGENT COMMON DISCHARGING AGENTS • SODIUM SULPHOXYLATE FORMALDEHYDE (HSO2CH2O)Na OR • ZINC SULPHOXYLATE FORMALDEHYDE • (HSO2 CH2O) 2 Zn OR Zn(OH)(HSO2CH2O) (HSO2CH2O)Na + H2O > CH2OHSO3NA + 2 H TRADE PRODUCTS ROGALITE C (BASF), SAFOLITE (TRANSPEK), AROSIT SR (CLARIANT)

  6. DISCHARGING AGENTS • CALCIUM SULPHOXYLATE FORMALDEHYDE ( RONGALIT H) • STANNOUS CHLORIDE • THIUREA DIOXIDE

  7. SEQUENCE • UNDYED FABRIC > DYEING > DISCHARGE PRINTING > DRY > STEAM > WASH > SOAP > WASH > DRY GROUND COLOURS • CORRECT CHOICE OF DYES IS VERY IMPORTANT IN DISCHARGE PRINTING • SUITABLE DYES USUALLY CONTAIN N=N GROUP WHICH IS READILY ATTACKED BY REDUCING AGENTS GIVING COLOURLESS WATER SOLUBLE AMINES R-N==N-R’ > RNH2 + R’NH2 INFORMATION RELATED TO EASE OF DISCHARGEABILITY IS NORMALLY GIVEN IN MANUFACTURERES SHADE CARDS

  8. COLOURED DISCHARGE • DYES STABLE TO REDUCING AGENT AND THOSE CAN BE FIXED DURING STEAMING IN PRESENCE OF REDUCING AGENT ARE INCORPORATED IN DISCHARGE PASTE • VAT DYES ARE MOST SUITABLE

  9. WHITE DISCHARGE GLYCERINE 10-20 PARTS REDUCING AGENT 30-150 PARTS ZnO/TiO2 30-50 PARTS WATER 100-150 PARTS OPTICAL BRIGHTENER 10 PARTS BRITISH GUM TO MAKE 1000 PARTS THIKENER PASTE PRINT ON DYED FABRIC > DRY > STEAM FOR 30 MIN > WASH > SOAP > WASH > DRY

  10. COLOUR DISCHARGE VAT DYE 50-100 PARTS Na2CO3/K2CO3 30-40 PARTS Zn/Na SULPHOXYLATE FORMALDEHYDE 80-120 PARTS GLYCERINE 10-20 PARTS WATER 100-150 PARTS BRITISH GUM THICKENER PASTE TO MAKE 1000 PARTS PRINT ON DYED FABRIC > DRY > STEAM 30 MIN. > WASH > OXIDIZE > WASH > SOAP > WASH > DRY

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