Tuesday 2 October 2007

Raw Material and Manufacturing Trends.

The theme of the last 35 years has been the progressive replacement of fibres and absorbents obtained from biomass with fibres and absorbents obtained from fossil reserves. Within that megatrend we’ve seen:
  • Polyester replacing viscose rayon and cotton in blends, initially as a cost saving measure.
  • Embossed latex-bonded 100% polyester coverstocks for improved surface dryness (and lower cost).
  • Conulated film replacing fibrous coverstocks on femcare and adult incontinence products.
  • 100% PP staple nonwovens, thermally bonded and embossed – for even drier coverstock and lower cost.
  • Polyacrylic superabsorbents replacing fluff pulp.
  • 100% PP Spunbonds replacing staple in coverstock and backsheets.
  • Air-Laid pulps replacing latex bonded fibres in wipes.
  • Hydroentangled fibres replacing air-laid in wipes.
Nonwovens Manufacturing Trends
The move to synthetic polymers allowed spunbonding to develop and started the “arms race” between dry laying and spunbonding that has transformed the economics and quality of both processes. Leaving aside the early history of spunbonding when it was restricted to the inventors, e.g. Dupont, ICI and Freudenberg, the technology began to transform the industry when machines first from Lurgi and later from Reifenhauser and others began to replace the traditional card and bond processes. These machines which effectively by-passed fibre producers and allowed the nonwovens producer to convert polymer chips directly into nonwovens were initially slow, relatively narrow, and incapable of making a lightweight coverstock to match the carded product. However in the last 25 years, driven by the expanding market for disposables, they have become the low cost producer of quality lightweights. Along the way, melt-blowing heads positioned between the fibre spinnerets have allowed improvements in opacity, cover and barrier properties. Today’s machines are up to 7 metres wide run up to 700 m/min at basis weights down to 10 gsm with fibre counts down to 1 denier - and below with a melt-blow capability. Bicomponent fibres, usually PP/PE can be spun with little loss of output once the extra polymer handling kit and special spinnerets are added.
Spunbonding was transformed by German engineers and carding followed, again being re-engineered in Germany and Italy. Wide fast carding systems were developed to allow the thermal bonded staple coverstocks to be produced ever more economically, and these systems were later adapted to feed cellulosic blends into the newer hydroentanglement bonding systems. Up to the development of high productivity lines with hydroentanglement bonding in the 1990’s, almost all nonwoven machinery developments had been for the synthetic fibres: the earlier development of calendar bonding having led to the industry being largely re-equipped with systems that could no longer handle the natural polymer fibres efficiently.
Hydroentanglement on the other hand is perfect for inherently wettable, water swellable fibres of the cellulosic variety, and for the first time lightweight cellulosic nonwovens could be made where the softness of the cellulose could be properly perceived in a binder-free construction. Hydroentanglement, like spunbonding, was transformed, initially by one engineering firm (Perfojet) into a wide, fast, highly efficient bonding system which in turn allowed disposable wipes to be transformed from a nice-to-have product to an essential of everyday life.

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