Vat dye

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not complete but little definition for vat dyes

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Vat dye

  1. 1. VAT DYES<br />Except Deep Red<br />7/2/2008<br />1<br />
  2. 2. Introduction<br />1<br />Chemical Structure of Vat Dyes<br />2<br />Dyeing Structure of Vat Dyes<br />Treatments After Exhaustion of Vat Dyes<br />Semi and Fully Continuous Method<br />3<br />5<br />6<br />Method of Dyeing<br />4<br />Overview<br />7/2/2008<br />2<br />
  3. 3. Wet on Wet Process<br />7<br />Fixation Process<br />8<br />Package Dyeing<br />Correction of Faulty Dyeing<br />Indigo Dyeing for Denim<br />Solublised VAT Dyes<br />9<br />11<br />12<br />13<br />Dyeing of Knit Goods<br />10<br />Overview<br />7/2/2008<br />3<br />
  4. 4. Introduction<br />1<br /><ul><li> Dyeing produced with the vat dyes have the highest overall fastness properties.
  5. 5. All of these dyes have good fastness against
  6. 6. Wet treatments
  7. 7. Crocking
  8. 8. Light fastness in the region of 6 to 7.
  9. 9. The vat dyes can also withstand oxidizing agents like
  10. 10. Hydrogen peroxide (H202)
  11. 11. Sodium Chloride (NaCl)
  12. 12. Hypochlorite (--OCl)</li></ul>7/2/2008<br />4<br />
  13. 13. Introduction<br />1<br /><ul><li> the vat dyes are extensively used for dyeing yarn
  14. 14. THIS CLOTH can undergo the pretreatment processes like
  15. 15. Alkali Boiling
  16. 16. Bleaching
  17. 17. Mercerizing </li></ul>Without any damage to the dyed yarn.<br />After the introduction of hydrogen peroxide- tolerant reactive dyes<br /><ul><li>Yarn dyeing has been taken over by the reactive dyes.
  18. 18. Because reactive dyes less expensive , easier to apply.
  19. 19. Vat dyes are still popular on account of the all round high fastness properties.
  20. 20. VAT DYES ARE COMMONLY USED FOR:
  21. 21. Superior Quality Shirting Material
  22. 22. Military Uniforms
  23. 23. Furnishings, Curtain, Toweling etc.</li></ul>7/2/2008<br />5<br />
  24. 24. Introduction<br />1<br /><ul><li> there are about 60 vat dyes in the market
  25. 25. That cover the entire Gamut(range) of shades except Deep Red Colors.
  26. 26. VAT DYES ARE ESSENTIALLY Insoluble Polycyclic Aromatic Compound:
  27. 27. Containing Two or more pair of QUINONE GROUPS
  28. 28. Indigo and Tyrian Purple belongs to this family.
  29. 29. VATTING: In order to apply cellulosic Fibers
  30. 30. VAT PIGMENTS are made water soluble by reducing to HYDROQUINONE Forms in an alkaline media.This process Known as Vatting.
  31. 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.
  32. 32. PRESENT VATTTING CHEMICALS ARE:
  33. 33. Sodium Hydroxide
  34. 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.
  35. 35. Sodium Dithionate reduces the KETO GROUPS into the ENOL Form
  36. 36. Sodium Hydroxide forms sodium salts of the ENOL to make the DYES WATER SOLUBLE.</li></ul>7/2/2008<br />6<br />
  37. 37. Introduction<br />1<br /><ul><li>PRESENT VATTTING / REDUCING CHEMICALS ARE:
  38. 38. Sodium Hydroxide
  39. 39. Sodium Dithionate(Na2 S2 O4) a strong reducing agent one with high reduction potential.
  40. 40. Commonly termed in Industry as Sodium Hydro Sulphite or Simply HYDROS.
  41. 41. Sodium Dithionate reduces the KETO GROUPS into the ENOL Form
  42. 42. Sodium Hydroxide forms sodium salts of the ENOL to make the DYES WATER SOLUBLE.
  43. 43. Caustic Soda Also NEUTRALISE THE ACIDIC Decomposition products of the reducing agent ‘DITHIONITE’ produced during vatting and Dyeing.</li></ul>7/2/2008<br />7<br />
  44. 44. Introduction<br />1<br /><ul><li>PRESENT VATTTING / REDUCING CHEMICALS ARE:
  45. 45. Quantity of Reducing Agent Depend upon
  46. 46. No. of KETO groups Present in the Dye Molecule
  47. 47. To the extent/ amount of exposure or the dye bath to AIR.
  48. 48. Reduction is Accompanied by
  49. 49. Change in Color that is due to alteration in the conjugation of DOUBLE BONDS.
  50. 50. The reduced indigo has a PALE SHADE and so it was called the LEUCO(white) dye.</li></ul>7/2/2008<br />8<br />
  51. 51. Chemical Structure of VAT Dyes<br />2<br /><ul><li>Around 1900 Rene Bohn in GERMANY
  52. 52. accidently prepared a blue dye from ANTHRAscene, which he named as an INDANthrene dye. Soon after this breakthrough
  53. 53. Bohn and his Coworkers synthesize many other VAT DYES.
  54. 54. THE VAT DYES ARE OFTEN CLASSIFIED AS:</li></ul>7/2/2008<br />9<br />
  55. 55. DYEING Structure of VAT Dyes<br />3<br /><ul><li>Sodium Salts (Nacl) of the Reduced or Leuco VAT Dyes behave like:
  56. 56. Direct dyes
  57. 57. As for as adsorption on the cellulose fibres is concerned
  58. 58. But the ANTHRAquinone derivatives have
  59. 59. High intrinsic substantivity
  60. 60. In spite of lack of linearity and
  61. 61. Hydrogen bonding groups attributed
  62. 62. to the molecular complexity
  63. 63. And CO-PLANARITY of the VAT dyes.
  64. 64. As a High Concentration of SODIUM IONS from Caustic Soda(NaoH) and Sodium Dithionate(Na2 S2O4)
  65. 65. Already exist in the Reduced Bath.
  66. 66. The VAT dye tend to have HIGH RATE of adsorption
  67. 67. And EXHAUSTION in the initial stage of Application.
  68. 68. The RAPID ADSORPTION of dye in the first few minutes:
  69. 69. Technically termed as “HIGH STRIKE” value.
  70. 70. This tendency require a careful attention as well as ADDITION of RETADING agents to obtained level dyeing.</li></ul>7/2/2008<br />10<br />
  71. 71. DYEING Structure of VAT Dyes<br />3<br /><ul><li>After the adsorption of the LEUCO DYES
  72. 72. AN OXIDIZING AGENT IS ADDED TO THE BATH
  73. 73. That regenerates the VAT PIGMENT inside the fibres.
  74. 74. Finally, to achieve full fastness properties and to develop the proper shade, the dyed goods are
  75. 75. THOROUGHLY SOAPED AT BOIL.
  76. 76. VAT dyes three main classes for APPLICATION PUPOSES.</li></ul>7/2/2008<br />11<br />
  77. 77. DYEING Structure of VAT Dyes<br />3<br />7/2/2008<br />12<br /><ul><li>Where I stands for Indanthrene and N for Normal
  78. 78. In their Leuco forms Have High substantively for the cellulosic fibres.
  79. 79. These needs High Alkalinity for Dissolution
  80. 80. And are dyed at about 75o c.
  81. 81. Where I stands for Indanthrene and W for Warm
  82. 82. In their MODERATE substantivity for cellulosic fibres.
  83. 83. These needs MEDIUM Alkalinity for Dissolution
  84. 84. And are dyed at about 45o c TO 75o c.
  85. 85. Needs Electrolytes for complete EXHAUSTION of the dye.</li></li></ul><li>DYEING Structure of VAT Dyes<br />3<br />7/2/2008<br />13<br /><ul><li>Where I stands for Indanthrene and K for KALT / COLD
  86. 86. Have LOW substantivity for the cellulosic fibres.
  87. 87. These needs moderate Alkalinity for Dissolution
  88. 88. And are dyed at low temperature about 20o c to 30o c..
  89. 89. Needs in a Higher concentration Electrolytes than class II for complete EXHAUSTION of the dye.
  90. 90. Dyes of the IK Group other than the Indigo, are Not much used now a days.
  91. 91. Some vat dyes like BLACKS do NOT into the above mentioned three groups and are dyed by a special method</li></li></ul><li> METHOD DYEING<br />4<br /><ul><li>In Batch dyeing of fabric, VAT dyes are normally applied in the
  92. 92. Reduced in a JIGGER.
  93. 93. For continuous processes,
  94. 94. Fabric is PADDED in stable dispersion of very finely divided vat pigments often termed as MICRO-DISPERSIONS.
  95. 95. After drying the dye padded fabric, it is reacted with an ALKALINE REDUCING SOLUTION in a padder to VAT PIGMENT into water-soluble LEUCO FORM
  96. 96. LEUCO FORM diffuses into the fibre.</li></ul>7/2/2008<br />14<br />
  97. 97. METHOD DYEING<br />4<br /><ul><li>REDUCED VAT DYEING:
  98. 98. This process is applicable for
  99. 99. Batch wise dyeing WOVEN and KNIT fabrics
  100. 100. Also for YARNs in hank or package form.
  101. 101. REDUCTION OF the dye is faster in the STOCK VAT
  102. 102. BECAUSE
  103. 103. Concentration of the dye and reducing chemicals is higher than LONG BATH.</li></ul>7/2/2008<br />15<br />The dye is first reduced into SOLUBLE FORM.<br />In the bath(long liquor)<br />Or in the stock vat<br />Before bringing it in contact with substrate<br />
  104. 104. METHOD DYEING<br />4<br /><ul><li>REDUCED VAT DYEING:
  105. 105. THE MORE Difficult to reduced CLASS I dyes:
  106. 106. Vatted by the STOCK VAT method.
  107. 107. This dispersion at optimum temperature
  108. 108. Stirred for 10 minutes. When reduction is COMPLETE.
  109. 109. SOFT WATER must for dissolving and as far as dyeing.
  110. 110. Dyeing in HARD WATER causes precipitation (useless product) COUNTER THIS PROBLEM by use of SQUEStering AGENT.</li></ul>7/2/2008<br />16<br />Dye is pasted with the dispersing agent. And soft water<br />And then the required quantities of <br />Caustic Soda(NaoH)<br />And<br />DI-THIONATE(S2O4) <br />Are added as per manufacturer literature.<br />
  111. 111. METHOD DYEING REDUCED VAT DYEING:<br />4<br />7/2/2008<br />17<br />
  112. 112. METHOD DYEING REDUCED VAT DYEING<br />4<br /><ul><li>THE FOLLOWING TABLE WILL GIVE A
  113. 113. GENERAL IDEA OF CONCENTRATION
  114. 114. OF rducing and exhausationchemicalsrequired in the bath at a liquor ratio of 10:1</li></ul>7/2/2008<br />18<br />
  115. 115. METHOD DYEING REDUCED VAT DYEING<br />4<br /><ul><li>For the Class I dyes,
  116. 116. a nonionic retarding agent (ALKO-Xylated type)
  117. 117. Is often added that forms a complex with the REDUCED dye and release it gradually as the bath is exhausted,
  118. 118. addition of the Retarding or LEVELLING agent is more necessary
  119. 119. When dyeing mercerized COTTON, Regenerated RAYON
  120. 120. And for PALE SHADES
  121. 121. And also in LOW LIQUOR ratios.
  122. 122. These LEVELLING Agent reduce the ultimate dye- uptake slightly,</li></ul>7/2/2008<br />19<br />
  123. 123. METHOD DYEING REDUCED VAT DYEING<br />4<br />7/2/2008<br />20<br />
  124. 124. METHOD DYEING REDUCED VAT DYEING<br />4<br /><ul><li>Some Dyes during dyeing
  125. 125. OVER – REDUCED
  126. 126. Their SHADES becomes LIGHTER or even ALTERED.</li></ul>7/2/2008<br />21<br />
  127. 127. METHOD DYEING REDUCED VAT DYEING<br />4<br />Dyeing is started at temperature of 20o C.<br /><ul><li>Which is gradually raised to the optimum.
  128. 128. Dyes of IN and IW groups temperature
  129. 129. can be raised to 80o C
  130. 130. The Dyeing Continued for 45 TO 60 minutes.
  131. 131. ELECTROLYTE is added in portions about 20 Minutes</li></ul>After the dye Liquor reaches the MAXimum Temperature.<br />In case or CLASS III<br /><ul><li>ELECTROLYTE added at beginning
  132. 132. And dyeing is carried out in a cooling BATH after attaining TEMP of 45o C.
  133. 133. However SPECIAL REDUCING AGENTS of the HYDROXY-Alkyl-Sulphinate type may have to be used that can withstand decomposition at these HIGH Temperature.</li></ul>7/2/2008<br />22<br />
  134. 134. TREATMENTS AFTER EXHAUSTION OF DYES<br />5<br />AFTER EXHAUSTION OF THE VAT DYES<br />7/2/2008<br />23<br />
  135. 135. TREATMENTS AFTER EXHAUSTION OF DYES<br />5<br />AFTER EXHAUSTION OF THE VAT DYES<br />7/2/2008<br />24<br />
  136. 136. TREATMENTS AFTER EXHAUSTION OF DYES<br />5<br />AFTER EXHAUSTION OF THE VAT DYES<br />7/2/2008<br />25<br />
  137. 137. TREATMENTS AFTER EXHAUSTION OF DYES<br />5<br />AFTER EXHAUSTION OF THE VAT DYES<br />7/2/2008<br />26<br />
  138. 138. TREATMENTS AFTER EXHAUSTION OF DYES<br />5<br />AFTER EXHAUSTION OF THE VAT DYES<br />7/2/2008<br />27<br />
  139. 139. Semi and Fully Continuous Dyeing Method<br />6<br />THE PRINCIPLE OF THIS TECHNIQUE<br /><ul><li>TO pad the well prepared fabric
  140. 140. With a very fine dispersion (PARTICLE SIZE 0.5 – 1 um) of VAT PIGMENT.
  141. 141. Then to convert the absorb pigment into LUECO FORM
  142. 142. This is followed by
  143. 143. OXIDATION
  144. 144. SOAPING in a Washing Range
  145. 145. The MAIN ADVANTAGE of this process over the reduced-VAT method are as under.
  146. 146. A) HIGH PRODUCTIVITY
  147. 147. B) BETTER LEVELLING
  148. 148. C) GOOD PENETRATION</li></ul>7/2/2008<br />28<br />
  149. 149. Semi and Fully Continuous Dyeing Method<br />6<br />Different steps involve in the APPLICATION are:<br />PADDING:<br />Padder should be mechanically perfect<br />And exert even pressure throughout the <br />Width of the fabric.<br />The pigment dispersion normally contains <br /><ul><li> a migration inhibitor and
  150. 150. a wetting agent.
  151. 151. The latter is added for quick wetting of the fabric.</li></ul>7/2/2008<br />29<br />
  152. 152. Semi and Fully Continuous Dyeing Method<br />6<br />Different steps involve in the APPLICATION are:<br />2. DRYING:<br />It is not necessary for Light Shades<br />But it HELPS IN LEVELLING and improving colour yield.<br />It may be done at<br /><ul><li>Combination of INFRA- RED
  153. 153. HOT FLUE or
  154. 154. CYLINDER DRYER
  155. 155. Incase the cylinder are used
  156. 156. The IR-predryer is must
  157. 157. First few cylinder Teflon Coated as to reduce staining.
  158. 158. Temp 100oC first few cylinders to minimize Migration and two sided effect.</li></ul>7/2/2008<br />30<br />
  159. 159. Semi and Fully Continuous Dyeing Method<br />6<br />Different steps involve in the APPLICATION are:<br />3. DEVELOPMENT:<br />Method are used for both Development of the DYE PIGMENT:<br /><ul><li>BOTH the batch and continuous.
  160. 160. In the BATCH PROCESS
  161. 161. Reduction and
  162. 162. Adsorption</li></ul>Of the dye can be carried out on a Jigger.<br /><ul><li>DONE in the reduced dyeing method, after ADDING
  163. 163. Alkali and Reducing Agent
  164. 164. IF variation in SHADE due to BLEEDING in not totally eliminated
  165. 165. In the CHEMICAL PADDER 5 – 10 % of the bath is made with the pad liquor</li></ul>7/2/2008<br />31<br />
  166. 166. Semi and Fully Continuous Dyeing Method<br />6<br />Different steps involve in the APPLICATION are:<br />3. DEVELOPMENT: CONTINUOUS PROCESS<br />7/2/2008<br />32<br />
  167. 167. 7/2/2008<br />33<br /> Semi and Fully Continuous Dyeing Method<br />6<br />OXIDATION AND SOAPING<br />In the Continuous Process, <br />In a WASHING RANGE<br />In which fabric is treated in the following different sequences:<br />
  168. 168. 7/2/2008<br />34<br />CORRECTION OF FAULTY DEING<br />7<br />Fauls are usually corrected by<br />Levelling Out<br />Partial Stripping or Cross Dyeing<br />However kept in mind LEUCO VATS have a very high affinity with cotton fibers and so difficult to strip off the dyed goods.<br />

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