Chemical Finishing of NonWovens

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					CHEMICAL FINISHING
OF NONWOVEN

                 R.Senthil Kumar,
             sen29iit@yahoo.co.in

   R.Senthil Kumar
Washing (scouring)
   The fabric is treated in an aqueous media, usually containing a detergent.
    Synthetic detergents have largely replaced natural soaps and non-ionics are
    widely used.

   Non-ionic detergents have good fibre compatibility and stability to
    variations in water supply. Washing can have a softening effect as
    contaminants are removed and strain induced during fabric formation is
    relaxed.

   Temperature, processing time, mechanical action and the addition of
    detergent are key factors influencing washing efficiency.

   The detergent creates a separating layer between the fibre and the
    contaminant, coating the contaminant with detergent. The contaminant
    collects into a globule, which detaches from the fibre.

   Ionic charges help prevent re-deposition of contaminants onto the fabric; the
    contaminant held in a scouring emulsion is usually stabilised by the
    presence of alkali.
                                   R.Senthil Kumar
Washing (scouring)




      R.Senthil Kumar
    Washing (scouring)
   Removal of contaminants is also facilitated by mechanical action such as
    squeeze rollers, which mechanically separate the contaminants from the fabric.

   Washing is followed by rinsing, with attention to gradual dilution of the
    washing emulsion, to maintain emulsion stability.

   Washing machines are normally open width and continuous. The fabric may
    pass around guide rollers and through a series of vats containing scouring
    and rinsing liquors.

   The fabric is squeezed at intervals to promote a scouring and liquor interchange
    minimising transfer of liquor from the scouring to the rinsing baths.

   Nonwoven fabrics composed of dope dyed fibre or bonded by
    hydroentanglement are normally sufficiently clean and may not require further
    wet processing. It is known that hydroentanglement is capable of removing a
    large proportion of the wax on cotton even at low specific energy inputs.
                                     R.Senthil Kumar
Coloration
   Coloration is undertaken with either dyestuffs or pigments. For nonwoven materials,
    fabric coloration is performed in open width to avoid the creasing that results in rope
    dyeing.

Several coloration methods are available, principally:
 In dope dyeing (producer coloration or melt dyeing) the dye or pigments
  are added to the molten polymer (spinning dope) prior to melt extrusion.

    Dope dyeing has the disadvantage that colour commitment is made at an
    early stage but excellent colour fastness can be achieved.

    Pigments have little fibre substantivity (or solubility) and are applied
    along with a suitable binder resin. Pigments are often applied by printing
    onto the nonwoven fabric along with a binder or added to the binder
    resin in chemical bonding processes.

   The bonding agent fixes the pigment to the fibre surfaces during drying and thermal
    curing. Pigments must be finely ground and sufficiently well dispersed in the binder
    dispersion,

                                       R.Senthil Kumar
    Coloration
   Liquor flow in the beam (generally in-to-out and out-to-in flow directions are available)
    can lead to flattening of low density nonwovens, if not lateral collapse of the nonwoven
    structure.

   One advantage of dyeing on the beam is that at elevated temperatures there is a thermal
    stabilising effect, which imparts additional dimensional stability and fabric surface
    integrity. Dye flow directions and time influence dye levelness and must be adjusted to
    prevent the possibility of moiré effects.

   Nonwoven fabrics composed of conventional fibres tend to dye to a deeper shade than
    woven or knitted fabrics of the same composition and have a greater accessible fibre
    surface area because of the high permeability and absence of twisted yarns and yarn
    intersections in the fabric structure.

   In general, heavy or high-loft fabrics are dyed continuously, as batch dyein
				
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Description: Chemical Finishing of NonWovens
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PARTNER senthil kumar
i did m.tech in IIT delhi.Atpresent working as senior lecturer in KCT coimbatore.I am having 6 years of industrial experience in areas such as production,R & D and maintenance departments of yarn manufacturing unit.