Wipes from hydroentangled Nonwovens
Nonwovens have several merits over woven textiles. They have
higher filtration efficiency, better absorbancy and
permiability, non directional properties compared to wovens; the
process is also cheaper because of ability to process recycled
and waste fibres and make composites using wood pulp for making
wipes. Among the various methods of making nonwovens,
hydroentanglement has the merit that it is ideally suited for
cotton, translates the characteristics of fibres into fabric and
retains textile character. Chemical bonding polymerises the
binder with the fibre to create bonds. Thermal bonding welds the
fibres. So with both methods, inter-fibre movement is
restricted. The resultant fabrics are therefore stiff, lack
drape and textile character. Chemical bonding covers the
material with binder and so masks the soft feel and absorbancy
of cellulosic fibre. It also causes allergy problems to skin.
Thermal boding reduces the strength because of melting of fibre.
Hydroentanglement, on the other hand, is free from these
drawbacks. Fibre characteristics are fully translated into
fabric in this system. Further, products have a high durability
and do not easily disintegrate. This is because the entanglement
is similar to that achieved by twisting of fibres into yarn. The
nonwoven made by hydroentanglement has a textile character
similar to knits or wovens.Strength of hydroentangled fabrics
are also close to that of woven and knitted materials. Fibres
are first opened and carded.Entanglement is achieved by
directing fine water jets on to a web emerging from card and
supported by a transporting belt. As the water strikes the web,
fibres are deflected and entanglement occurs. Very high water
pressure of the order of 100-160 bars is used. Production rates
are very high with delivery speeds up to 400-500 m/min.
Hydroenglement has the merit that it can make cheap wipes by
making a sanwich of nonwoven with wood pulp. 3 layer sandwich
with wood pulp sanwiched between 2 layers of staple fibre and
cosolidated by hydroentanglement, represents an attractive
proposition for making cost effective wipes and medical
products. Web made from a card is transported on a conveyer
lattice. On this a pulp forming unit sprays wood pulp uniformly.
Over this a layer of carded web from a second card is laid. The
sandwich material then passes through a hydroentanglement unit
where entanglement of top and bottom layer of web occurs. the
material is then taken through a dryer. Wood pulp thus
sandwiched and hydroentangled with a staple fibre web is cheaper
compared to 100% staple fibre nonwoven wipes, has a higher
thickness and absorbancy and comparable strength. Further, the
product has more uniformity as pulp levels out card web
irregularities. Production rates upto 400 m/min are possible.
Though higher investment is involved in this technology, it pays
back rapidly because of low raw material cost, higher
productivity and improved properties.