Tuesday, January 1, 2013

Early Tencel History from "Regenerated Cellulose Fibres" (part 2)

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

NMMO emerged as the best of the amine-oxides and a team at American Enka demonstrated its commercial potential in the late '70's. In their laboratories in Enka, North Carolina, Neil Franks and Julianna Varga, developed a way of making a more concentrated, and hence economical, solution of cellulose, by carefully controlling the water content of the system.

In this Figure from USP41926282 the concentrations of water and cellulose where complete dissolution of the cellulose occurs (at 95C), lie between lines B and C. Between lines A and B there can be 95% confidence that the solution would be free from undissolved cellulose fibres, and to the right of Line A, undissolved cellulose fibres are bound to be present. Similarly, between C and D there is a 95% chance that crystals of undissolved NMMO will be present, and such crystals will always be present to the left of line D.

Clarence C. McCorsley III, also at Enka, developed the key elements of several possible commercial processes. In one, cellulose pulp sheets were soaked in NMMO solution, and after mild heat and vacuum treatment to adjust the water content, the ground-up sheet was fed to an extruder from which fibres could be spun. In another, the solution was made in a large mixer prior to casting it as thick film, freezing it solid, and grinding up into chips for later extrusion. In a continuous process, a vented extruder fed directly with the ground-up wood-pulp and NMMO, mixes the ingredients, creates the solution by removing excess water and volatiles through the vent, and feeds the spinning pumps.

Both American Enka and Courtaulds set up pilot plant work in the early eighties with the objectives of developing the fibre spinning and solvent recovery operations. Courtaulds commercialized first and this, and the continuing development of lyocell is dealt with by White , who from the outset of practical work in 1979, led the lyocell development effort at Courtaulds.

(more to come)

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