Lecture 2 preparatory processes
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Lecture 2 preparatory processes

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Lecture 2 preparatory processes Presentation Transcript

  • 1. PREPARATORY PROCESSES FOR COTTON R.B.CHAVAN Department of Textile Technology Indian Institute of Technology Hauz-Khas, New Delhi 110016 E-mail rbchavan@hotmail.com
  • 2. Composition of cotton
    • Natural impurities
    8.0 Moisture 1.0 Mineral Matter 0.5 Colouring matter 1.1 Proteins 0.7 Pectins 0.5 Oils, Fats and Waxes 88 Cellulose % Constituent
  • 3. Fats and Waxes
    • Fatty acids
    • Stearic acid
    • Palmitic acid
    • Oleic acid
    • Fatty alcohols
    • Gossipyl alcohol (C30H61OH)
    • Ceryl alcohol (C26H53OH)
    • Montanyl alcohol (C28H57OH)
  • 4. Pectins
    • Derivatives of pectic acid
    • Polymer of high molecular weight
    • Composed of Galactouronic acid
    Some COOH groups are present as Ca and Mg salts Free acid and Ca and Mg salts are insoluble in water
  • 5. Proteins
    • Nitrogenous compounds
    • Present in primary wall and Lumen
    • Some of the amino acids identified are
    • Leucine
    • Valine
    • Proline,
    • Alanine etc.
    • Yellowish (Creamish) colour of cotton is related to Proteins and
    • Colouring matter
  • 6. Colouring matter
    • Colour pigments present are
    • 3,5,7,2’, 4’ Penta hydroxy flavone (Morrin)
    • 3,5,7,8,3’,4’ Hexa hydroxy flavone (Gossypetine)
  • 7. Mineral Matter
    • Depends on soil composition
    • Can be determined by ash analysis
    5.0 Aluminium oxide 3.0 Ferric oxide 8.4 Magnesium sulphate 10.3 Calcium carbonte 9.0 Calcium sulphate 9.3 Potassium sulphate 9.9 Potassium chloride 44.8 Potassium carbonate
  • 8. Added Impurities
    • Sizing agents:
    • Agents used to give protective coating to warp threads
    • Minimize the breaking of warp threads during weaving
    • Improve weaving productvity.
    • The operation is known as sizing.
    • Starch is one of the most important sizing agent for cotton
  • 9. PREPARATORY PROCESSES
    • Purpose
    • To remove added and natural impurities from textile material
    • Removal impurities to the maximum extent possible with minimum effect on fibre strength.
    • To impart desirable properties to textile material
  • 10. Principle of preparatory processes
    • The impurity is insoluble in water
    • Conversion of water insoluble impurity to its water soluble form.
    • Chemical reactions involved are
    • Hydrolysis
    • Oxidation
    • The choice of chemicals depends on chemical nature of impurity.
  • 11. Desizing
    • Process of removal of size is known as desizing
    • Facilitates penetration of chemicals and dyes applied during subsequent processing operations
    • Starch is the main ingredient for sizing of cotton warp
    • Chemically starch is
    Chemically it is Amylose: Linear polymer of low mol. Wt. Amylopectin: High molecular wt. Branched polymer Water insoluble
  • 12. Desizing methods
    • Starch solubilization
    • Hydrolysis
  • 13. Oxidation
  • 14. Ref: http://www3.itv-denkendorf.de/itv2/downloads/d0003602/WG3BarcPosner.pdf
  • 15. SCOURING TREATMENT OF COTTON WITH ALKALINE SOLUTION
    • PURPOSE
    • REMOVE NATURAL IMPURITIES : FATS AND WAXES,
    • PECTIC SUBSTANCES, PROTINES
    • REMOVE ADDED IMPURITY : OIL STAINS
    • SEED COAT FRAGMENTS
    • IMPROVE WATER ABSORBENCY FOR UNIFORM DYEING,
    • PRINTING AND FINISHING .
    • PRINCIPLE
    • Hydrolysis of impurities
  • 16.
    • BLEACHING
    • Removal of colouring matters by Oxidation
    • BLEACHING AGENTS
    • sodium and calcium hypochlorite
    • Hydrogen peroxide
    • Sodium Hypochlorite
    • Peracetic acid
    • HYDROGEN PEROXIDE MOST POPULAR ON INDUSTRIAL SCALE
    • It is environment friendly
  • 17. INDUSTRIAL PRACTICES EQUIPMENT USED
    • BATCH WISE OPERATION
    • KIER ( ROPE FORM )
    • JIGGER (OPEN WIDTH )
    • WINCH (ROPE FORM, PARTICULARLY FOR KNITS )
    • JET DYING (ROPE FORM, PARTICULARLY FOR KNITS )
    • CONTINUOUS
    • J – BOX ( ROPE FORM )
    • VARIOUS PAD STEAM PROCESSES (OPEN WIDTH )
    • SEMI-CONTINUOUS
    • 1. PAD – ROLL (OPEN WIDTH)
  • 18. Kier(Rope Form) Winch (Rope Form) Jet machine (Rope form) Jigger (Open width form)
  • 19. Continuous Processing J-Box (Rope Form) Continuous (Open width) Saturator, Steamer, Washer.
  • 20. Semi-Continuous Pad-Batch (Open Width form)
  • 21.
    • PRESENT PRACTICE
    • COMBINED (OPEN WIDTH)
    • DESIZING - SCOURING
    • SCOURING – BLEACHING
    • DESIZING – SCOURING – BLEACHING
    • EQUIPMENT
    • SATURATOR – PADDER – STEAMER - WASHER
  • 22. ENVIRONMENTAL ISSUES
    • DESIZING
    • the wash water from desizing may contain up to 70 % of the total COD load in the final effluent ,
    • Neither enzymatic nor oxidative desizing allows size recovery .
    • H2O2 BLEACHING
    • H2O2 decomposition forms water and oxygen
    • some stabilzers may from complexes with metal in the effluent, releasing them in the receiving waters
    • effluents containing inorganic chlorides (e.g. NaCI from dyeing can be oxidised to their chlorites/hypochlorites when they are mixed with hydrogen peroxide bleach waste water.
    • In this way AOX may be found in waste water even if bleaching is carried out without chlorine-based bleaching agents.