Thursday, January 3, 2013

Early Tencel History from "Regenerated Cellulose Fibres"

Regenerated Cellulose Fibres published by Woodhead Publishing Ltd in 2001 contains a history of the Tencel development, the first extract of which appears below. (see the original for references)

Direct Dissolution in Amine Oxide: Lyocell
Lyocell technology was pioneered in the USA by Eastman Kodak and American Enka, but it was Courtaulds in the UK who persisted with development until a commercially viable fibre process emerged. Furthermore, Courtaulds did it at a time in its history when the very wisdom of continued involvement, not just in cellulosics but in any fibre or textile activity, was being called into question.

As early as the mid 1950's, Courtaulds believed the future of viscose to be so unattractive that it started to divert viscose profits not only into other fibres, but also into totally unrelated businesses.

By the late fifties, despite accounting for 80-90% of Courtaulds earnings, the reality of viscose's decline was becoming apparent. The usual remedies, reducing costs, improving quality, selling more aggressively and internationally were yielding diminishing returns so the Board's reaction was a new strategy involving:
  • Developing new internal sources of profit i.e. utilising the viscose wet-spinning expertise to move into wet-spun acrylic fibres ("Courtelle"), and opening up a vast, and with hind-sight, transient, new market for a coarse and tough viscose in tufted carpets. ("Evlan")
  • Developing new external sources of profit by acquisitions in "related but different" products, in reality British Celanese (Cellulose acetate fibres and related products) and Pinchin Johnson Paints (Later renamed International Paint)
  • Developing greater market power by acquiring key elements of the rest of the fibre value-chain - "Verticalisation" - resulting most notably in the acquisition of the Lancashire Cotton Corporation Ltd and Fine Spinners and Doublers. (representing about 35% of the entire Lancashire cotton industry.)
Of these three, a) was least favoured with funds. Furthermore, little emphasis was placed on modernisation of regenerated cellulose fibre production methods
to counteract the intertwined problems of synthetic fibre expansions, rising costs and diminishing returns. The demise of viscose thus became a self-fulfilling prophecy. The leading exponent of the technology (then Courtaulds) turned it's back on cellulose at a crucial time in it's history, a time in fact when new ways of dissolving cellulose were already evident in the research work of other organisations.

Reviews of this early work on direct dissolution are provided by Turbak , who records the efforts to dissolve cellulose directly as a base using phosphoric, sulphuric and nitric "protonic" acids, or using zinc chloride, thiocyanates, iodides, and bromides as Lewis acids. However, despite early promise, the problems of developing fibre production routes using these systems, have, with the single exception of the amine oxide route, so far proved insurmountable.

The amine-oxide solvent, later to become the focus of Courtaulds most costly development project, and the most acrimonious patent battle since the dispute over the Müller bath in 1910, had in fact been discovered back in 1939 by a pair of Swiss chemists Charles Graenacher and Richard Sallman. But it was not until 1969 that Dee Lynn Johnson of Eastman Kodak described the use of cyclic mono(N-methylamine-N-oxide) compounds as a solvent-size for strengthening paper by partially dissolving the cellulose fibres.

N-methyl morpholine-n-oxide

Other Johnson patents , covered the preparation of cellulose solutions using NMMO and speculated about their use as dialysis membranes, food casings (sausage skins), fibres, films, paper coatings, and nonwoven binders.

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