Transcript 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
• DYE FIXATION PREVENTED UNDER ACIDIC CONDITIONS
SEQUENCE: PRINT WITH RESISTING AENT > DRY > NIP PAD
WITH DYE + ALKALI >DRY > STEAM > WASH > SOAP > WASH >
DRY
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)
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
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
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)
DISCHARGING AGENTS
• CALCIUM SULPHOXYLATE
FORMALDEHYDE ( RONGALIT H)
• STANNOUS CHLORIDE
• THIUREA DIOXIDE
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
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
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
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