The document discusses vat dyes, which are insoluble aromatic compounds containing quinone groups. Vat dyes are reduced to a soluble hydroquinone form using reducing agents like sodium dithionite and sodium hydroxide for application to cellulosic fibers. The reduced dyes are then oxidized back to the insoluble pigment form within the fibers. Vat dyes provide excellent fastness properties and can withstand various treatments. Common application methods include reduced vat dyeing in jigs or stock vats, and continuous padding and developing processes. Post-dyeing treatments may include oxidation, soaping, leveling, or partial stripping to correct any faults.
2. Introduction 1 Chemical Structure of Vat Dyes 2 Dyeing Structure of Vat Dyes Treatments After Exhaustion of Vat Dyes Semi and Fully Continuous Method 3 5 6 Method of Dyeing 4 Overview 7/2/2008 2
3. Wet on Wet Process 7 Fixation Process 8 Package Dyeing Correction of Faulty Dyeing Indigo Dyeing for Denim Solublised VAT Dyes 9 11 12 13 Dyeing of Knit Goods 10 Overview 7/2/2008 3
30. VAT PIGMENTS are made water soluble by reducing to HYDROQUINONE Forms in an alkaline media.This process Known as Vatting.
31. Vatting Term referring to a historical link with the vegetable Indigo Dye that used to reduced in WOODEN VATS with natural reducing agents like sugar.
34. Sodium Dithionate(Na2 S2 O4) a strong reducing agent one with high reduction potential. Commonly termed in Industry as Sodium Hydro Sulphite or Simply HYDROS.
103. Concentration of the dye and reducing chemicals is higher than LONG BATH.7/2/2008 15 The dye is first reduced into SOLUBLE FORM. In the bath(long liquor) Or in the stock vat Before bringing it in contact with substrate
110. Dyeing in HARD WATER causes precipitation (useless product) COUNTER THIS PROBLEM by use of SQUEStering AGENT.7/2/2008 16 Dye is pasted with the dispersing agent. And soft water And then the required quantities of Caustic Soda(NaoH) And DI-THIONATE(S2O4) Are added as per manufacturer literature.
132. And dyeing is carried out in a cooling BATH after attaining TEMP of 45o C.
133. However SPECIAL REDUCING AGENTS of the HYDROXY-Alkyl-Sulphinate type may have to be used that can withstand decomposition at these HIGH Temperature.7/2/2008 22
134. TREATMENTS AFTER EXHAUSTION OF DYES 5 AFTER EXHAUSTION OF THE VAT DYES 7/2/2008 23
135. TREATMENTS AFTER EXHAUSTION OF DYES 5 AFTER EXHAUSTION OF THE VAT DYES 7/2/2008 24
136. TREATMENTS AFTER EXHAUSTION OF DYES 5 AFTER EXHAUSTION OF THE VAT DYES 7/2/2008 25
137. TREATMENTS AFTER EXHAUSTION OF DYES 5 AFTER EXHAUSTION OF THE VAT DYES 7/2/2008 26
138. TREATMENTS AFTER EXHAUSTION OF DYES 5 AFTER EXHAUSTION OF THE VAT DYES 7/2/2008 27
139.
140. With a very fine dispersion (PARTICLE SIZE 0.5 – 1 um) of VAT PIGMENT.
164. IF variation in SHADE due to BLEEDING in not totally eliminated
165. In the CHEMICAL PADDER 5 – 10 % of the bath is made with the pad liquor7/2/2008 31
166. Semi and Fully Continuous Dyeing Method 6 Different steps involve in the APPLICATION are: 3. DEVELOPMENT: CONTINUOUS PROCESS 7/2/2008 32
167. 7/2/2008 33 Semi and Fully Continuous Dyeing Method 6 OXIDATION AND SOAPING In the Continuous Process, In a WASHING RANGE In which fabric is treated in the following different sequences:
168. 7/2/2008 34 CORRECTION OF FAULTY DEING 7 Fauls are usually corrected by Levelling Out Partial Stripping or Cross Dyeing However kept in mind LEUCO VATS have a very high affinity with cotton fibers and so difficult to strip off the dyed goods.