Vat dye
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not complete but little definition for vat dyes

not complete but little definition for vat dyes

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    Vat dye Vat dye Presentation Transcript

    • VAT DYES
      Except Deep Red
      7/2/2008
      1
    • 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
    • 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
    • Introduction
      1
      • Dyeing produced with the vat dyes have the highest overall fastness properties.
      • All of these dyes have good fastness against
      • Wet treatments
      • Crocking
      • Light fastness in the region of 6 to 7.
      • The vat dyes can also withstand oxidizing agents like
      • Hydrogen peroxide (H202)
      • Sodium Chloride (NaCl)
      • Hypochlorite (--OCl)
      7/2/2008
      4
    • Introduction
      1
      • the vat dyes are extensively used for dyeing yarn
      • THIS CLOTH can undergo the pretreatment processes like
      • Alkali Boiling
      • Bleaching
      • Mercerizing
      Without any damage to the dyed yarn.
      After the introduction of hydrogen peroxide- tolerant reactive dyes
      • Yarn dyeing has been taken over by the reactive dyes.
      • Because reactive dyes less expensive , easier to apply.
      • Vat dyes are still popular on account of the all round high fastness properties.
      • VAT DYES ARE COMMONLY USED FOR:
      • Superior Quality Shirting Material
      • Military Uniforms
      • Furnishings, Curtain, Toweling etc.
      7/2/2008
      5
    • Introduction
      1
      • there are about 60 vat dyes in the market
      • That cover the entire Gamut(range) of shades except Deep Red Colors.
      • VAT DYES ARE ESSENTIALLY Insoluble Polycyclic Aromatic Compound:
      • Containing Two or more pair of QUINONE GROUPS
      • Indigo and Tyrian Purple belongs to this family.
      • VATTING: In order to apply cellulosic Fibers
      • VAT PIGMENTS are made water soluble by reducing to HYDROQUINONE Forms in an alkaline media.This process Known as Vatting.
      • 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.
      • PRESENT VATTTING CHEMICALS ARE:
      • Sodium Hydroxide
      • 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.
      • Sodium Dithionate reduces the KETO GROUPS into the ENOL Form
      • Sodium Hydroxide forms sodium salts of the ENOL to make the DYES WATER SOLUBLE.
      7/2/2008
      6
    • Introduction
      1
      • PRESENT VATTTING / REDUCING CHEMICALS ARE:
      • Sodium Hydroxide
      • 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.
      • Sodium Dithionate reduces the KETO GROUPS into the ENOL Form
      • Sodium Hydroxide forms sodium salts of the ENOL to make the DYES WATER SOLUBLE.
      • Caustic Soda Also NEUTRALISE THE ACIDIC Decomposition products of the reducing agent ‘DITHIONITE’ produced during vatting and Dyeing.
      7/2/2008
      7
    • Introduction
      1
      • PRESENT VATTTING / REDUCING CHEMICALS ARE:
      • Quantity of Reducing Agent Depend upon
      • No. of KETO groups Present in the Dye Molecule
      • To the extent/ amount of exposure or the dye bath to AIR.
      • Reduction is Accompanied by
      • Change in Color that is due to alteration in the conjugation of DOUBLE BONDS.
      • The reduced indigo has a PALE SHADE and so it was called the LEUCO(white) dye.
      7/2/2008
      8
    • Chemical Structure of VAT Dyes
      2
      • Around 1900 Rene Bohn in GERMANY
      • accidently prepared a blue dye from ANTHRAscene, which he named as an INDANthrene dye. Soon after this breakthrough
      • Bohn and his Coworkers synthesize many other VAT DYES.
      • THE VAT DYES ARE OFTEN CLASSIFIED AS:
      7/2/2008
      9
    • DYEING Structure of VAT Dyes
      3
      • Sodium Salts (Nacl) of the Reduced or Leuco VAT Dyes behave like:
      • Direct dyes
      • As for as adsorption on the cellulose fibres is concerned
      • But the ANTHRAquinone derivatives have
      • High intrinsic substantivity
      • In spite of lack of linearity and
      • Hydrogen bonding groups attributed
      • to the molecular complexity
      • And CO-PLANARITY of the VAT dyes.
      • As a High Concentration of SODIUM IONS from Caustic Soda(NaoH) and Sodium Dithionate(Na2 S2O4)
      • Already exist in the Reduced Bath.
      • The VAT dye tend to have HIGH RATE of adsorption
      • And EXHAUSTION in the initial stage of Application.
      • The RAPID ADSORPTION of dye in the first few minutes:
      • Technically termed as “HIGH STRIKE” value.
      • This tendency require a careful attention as well as ADDITION of RETADING agents to obtained level dyeing.
      7/2/2008
      10
    • DYEING Structure of VAT Dyes
      3
      • After the adsorption of the LEUCO DYES
      • AN OXIDIZING AGENT IS ADDED TO THE BATH
      • That regenerates the VAT PIGMENT inside the fibres.
      • Finally, to achieve full fastness properties and to develop the proper shade, the dyed goods are
      • THOROUGHLY SOAPED AT BOIL.
      • VAT dyes three main classes for APPLICATION PUPOSES.
      7/2/2008
      11
    • DYEING Structure of VAT Dyes
      3
      7/2/2008
      12
      • Where I stands for Indanthrene and N for Normal
      • In their Leuco forms Have High substantively for the cellulosic fibres.
      • These needs High Alkalinity for Dissolution
      • And are dyed at about 75o c.
      • Where I stands for Indanthrene and W for Warm
      • In their MODERATE substantivity for cellulosic fibres.
      • These needs MEDIUM Alkalinity for Dissolution
      • And are dyed at about 45o c TO 75o c.
      • Needs Electrolytes for complete EXHAUSTION of the dye.
    • DYEING Structure of VAT Dyes
      3
      7/2/2008
      13
      • Where I stands for Indanthrene and K for KALT / COLD
      • Have LOW substantivity for the cellulosic fibres.
      • These needs moderate Alkalinity for Dissolution
      • And are dyed at low temperature about 20o c to 30o c..
      • Needs in a Higher concentration Electrolytes than class II for complete EXHAUSTION of the dye.
      • Dyes of the IK Group other than the Indigo, are Not much used now a days.
      • Some vat dyes like BLACKS do NOT into the above mentioned three groups and are dyed by a special method
    • METHOD DYEING
      4
      • In Batch dyeing of fabric, VAT dyes are normally applied in the
      • Reduced in a JIGGER.
      • For continuous processes,
      • Fabric is PADDED in stable dispersion of very finely divided vat pigments often termed as MICRO-DISPERSIONS.
      • 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
      • LEUCO FORM diffuses into the fibre.
      7/2/2008
      14
    • METHOD DYEING
      4
      • REDUCED VAT DYEING:
      • This process is applicable for
      • Batch wise dyeing WOVEN and KNIT fabrics
      • Also for YARNs in hank or package form.
      • REDUCTION OF the dye is faster in the STOCK VAT
      • BECAUSE
      • 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
    • METHOD DYEING
      4
      • REDUCED VAT DYEING:
      • THE MORE Difficult to reduced CLASS I dyes:
      • Vatted by the STOCK VAT method.
      • This dispersion at optimum temperature
      • Stirred for 10 minutes. When reduction is COMPLETE.
      • SOFT WATER must for dissolving and as far as dyeing.
      • 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.
    • METHOD DYEING REDUCED VAT DYEING:
      4
      7/2/2008
      17
    • METHOD DYEING REDUCED VAT DYEING
      4
      • THE FOLLOWING TABLE WILL GIVE A
      • GENERAL IDEA OF CONCENTRATION
      • OF rducing and exhausationchemicalsrequired in the bath at a liquor ratio of 10:1
      7/2/2008
      18
    • METHOD DYEING REDUCED VAT DYEING
      4
      • For the Class I dyes,
      • a nonionic retarding agent (ALKO-Xylated type)
      • Is often added that forms a complex with the REDUCED dye and release it gradually as the bath is exhausted,
      • addition of the Retarding or LEVELLING agent is more necessary
      • When dyeing mercerized COTTON, Regenerated RAYON
      • And for PALE SHADES
      • And also in LOW LIQUOR ratios.
      • These LEVELLING Agent reduce the ultimate dye- uptake slightly,
      7/2/2008
      19
    • METHOD DYEING REDUCED VAT DYEING
      4
      7/2/2008
      20
    • METHOD DYEING REDUCED VAT DYEING
      4
      • Some Dyes during dyeing
      • OVER – REDUCED
      • Their SHADES becomes LIGHTER or even ALTERED.
      7/2/2008
      21
    • METHOD DYEING REDUCED VAT DYEING
      4
      Dyeing is started at temperature of 20o C.
      • Which is gradually raised to the optimum.
      • Dyes of IN and IW groups temperature
      • can be raised to 80o C
      • The Dyeing Continued for 45 TO 60 minutes.
      • ELECTROLYTE is added in portions about 20 Minutes
      After the dye Liquor reaches the MAXimum Temperature.
      In case or CLASS III
      • ELECTROLYTE added at beginning
      • And dyeing is carried out in a cooling BATH after attaining TEMP of 45o C.
      • 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
    • TREATMENTS AFTER EXHAUSTION OF DYES
      5
      AFTER EXHAUSTION OF THE VAT DYES
      7/2/2008
      23
    • TREATMENTS AFTER EXHAUSTION OF DYES
      5
      AFTER EXHAUSTION OF THE VAT DYES
      7/2/2008
      24
    • TREATMENTS AFTER EXHAUSTION OF DYES
      5
      AFTER EXHAUSTION OF THE VAT DYES
      7/2/2008
      25
    • TREATMENTS AFTER EXHAUSTION OF DYES
      5
      AFTER EXHAUSTION OF THE VAT DYES
      7/2/2008
      26
    • TREATMENTS AFTER EXHAUSTION OF DYES
      5
      AFTER EXHAUSTION OF THE VAT DYES
      7/2/2008
      27
    • Semi and Fully Continuous Dyeing Method
      6
      THE PRINCIPLE OF THIS TECHNIQUE
      • TO pad the well prepared fabric
      • With a very fine dispersion (PARTICLE SIZE 0.5 – 1 um) of VAT PIGMENT.
      • Then to convert the absorb pigment into LUECO FORM
      • This is followed by
      • OXIDATION
      • SOAPING in a Washing Range
      • The MAIN ADVANTAGE of this process over the reduced-VAT method are as under.
      • A) HIGH PRODUCTIVITY
      • B) BETTER LEVELLING
      • C) GOOD PENETRATION
      7/2/2008
      28
    • Semi and Fully Continuous Dyeing Method
      6
      Different steps involve in the APPLICATION are:
      PADDING:
      Padder should be mechanically perfect
      And exert even pressure throughout the
      Width of the fabric.
      The pigment dispersion normally contains
      • a migration inhibitor and
      • a wetting agent.
      • The latter is added for quick wetting of the fabric.
      7/2/2008
      29
    • Semi and Fully Continuous Dyeing Method
      6
      Different steps involve in the APPLICATION are:
      2. DRYING:
      It is not necessary for Light Shades
      But it HELPS IN LEVELLING and improving colour yield.
      It may be done at
      • Combination of INFRA- RED
      • HOT FLUE or
      • CYLINDER DRYER
      • Incase the cylinder are used
      • The IR-predryer is must
      • First few cylinder Teflon Coated as to reduce staining.
      • Temp 100oC first few cylinders to minimize Migration and two sided effect.
      7/2/2008
      30
    • Semi and Fully Continuous Dyeing Method
      6
      Different steps involve in the APPLICATION are:
      3. DEVELOPMENT:
      Method are used for both Development of the DYE PIGMENT:
      • BOTH the batch and continuous.
      • In the BATCH PROCESS
      • Reduction and
      • Adsorption
      Of the dye can be carried out on a Jigger.
      • DONE in the reduced dyeing method, after ADDING
      • Alkali and Reducing Agent
      • IF variation in SHADE due to BLEEDING in not totally eliminated
      • In the CHEMICAL PADDER 5 – 10 % of the bath is made with the pad liquor
      7/2/2008
      31
    • Semi and Fully Continuous Dyeing Method
      6
      Different steps involve in the APPLICATION are:
      3. DEVELOPMENT: CONTINUOUS PROCESS
      7/2/2008
      32
    • 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:
    • 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.