Research Authorised and Development begins (1979)

On 4/10/79 a meeting took place in DF&VL "to decide whether to recommend that R&D work on alternative solvents for cellulose should be started".  Mike Welch (Head of DF&VL), Roger Lund (Deputy Head), Bill Brook (Head of Patent Dept), Jeff Branston, Fred Weymouth, Andy Hopkins, Dennis Woodward and Pat White were present.  If the answer was yes, then this group would decide the aims of the work and identify key areas to start.

At this meeting, the vulnerabilities of the viscose process versus a successful non-polluting solvent spinning development were listed as:

• Pollution and hazards.  Tightening environmental legislation would, if changes were made to comply, increase the costs of viscose by around 10p/kg in the USA, rather less in Europe.
• High spinning chemicals and recovery costs.
• High capital costs.  The US costs for an automated viscose plant using the latest technology would be 40% higher than a new polyester staple plant.

The combined chemical consumption, services and pollution control costs for any future viscose plant would be about 3x those of Courtaulds solvent spinning processes making acrylic and cellulose acetate fibres.

The wording of the conclusion was revealing: "if a recoverable solvent system could be found for cellulose it would be a serious threat" [to Courtaulds' viscose business]

Three potentially viable competitors for viscose were listed:

• The cuprammonium cellulose process where recent advances in ion-exchange solvent recovery had reduced energy costs and improved the viability of the technology.
• The ITT Rayonier DMF/N2O4 was too expensive by the published route due to solvent recovery difficulties.  However if Dupont's process for making anisotropic solutions with 30% cellulose content could be applied instead of ITT's 8% cellulose route, substantial reduction in costs would result.
• The AKZO amine-oxide process could be viable if a solvent recovery system could be developed, but it's costs were impossible to determine in the absence of any practical experience.  (Samples of amine-oxides had been made in the lab. and proved to be solvents for cellulose.)

The meeting agreed to undertake work on each of these systems to provide better information to decide future action:

• A range of amine-oxides would be made and screened and the most promising investigated in depth for solvent stability, potential hazards, recovery possibilities, spinning speeds, fibre properties, process costs, and capital costs.
• The solvating power of a range of known solvents would be investigated with the aim of finding anisotropic systems capable of yielding dopes with very high concentrations of cellulose.
• Because the cuprammonium system was showing no potential for growth, practical work would be avoided but contacts with the producers would be made to ascertain current pros and cons.

This work would be carried out by 2 graduates and would be reviewed after 6 months.

Geoffrey Owen's Tencel lyocell history extracts (part 2)

Geoffrey Owen of the Department of Management, London School of Economics presented a paper at SPRU in October this year entitled "Innovation in the man-made fibres industry: corporate strategy and national institutions." It is based on unpublished material made available to the author by Akzo Nobel, Lenzing and Courtaulds (amongst others) and is available in full here on the web as a PDF file.  It contains excellent sections on Tencel lyocell development history, the second extract of which is reproduced below:

Courtaulds and Tencel
Courtaulds was aware of what American Enka had been doing and their researchers saw that the solvent spinning process, if it could be made to work, might have important advantages. In 1979 a research team was set up in Coventry under Pat White, who had earlier worked on carbon fibre, to examine the process in detail; the programme was subsequently called the Genesis project. Although Courtaulds was under financial pressure at that time and several research programmes were cancelled, senior managers could see that the new process might be a way of reinvigorating the cellulosic fibres business (see Appendix 2 for a description of the solvent spinning process.)
The first laboratory-scale production began in 1981, and it was scaled up to a small pilot plant in 1983.  A note to the Board from the research department commented that the process looked extremely promising “in the sense that we believe it should be possible to produce a fibre with properties superior to viscose at lower cost…If we can succeed, this project could confound the conventional wisdom that there will be no new high volume fibre before the end of the century. It offers the possibility of transforming the prospects of our cellulosic fibre business”.

Courtaulds hired American Enka’s former research director, Bill Mathis, as a consultant. He confirmed that Courtaulds had taken a different approach to that taken by Enka and had solved some of the scaling-up problems. Courtaulds subsequently decided not to acquire an American Enka licence; it was regarded as expensive and unnecessary since White and his team were making good progress without it. Yet there were still many technical issues to be resolved.  One was to achieve a high recovery rate for the solvent which was much more expensive than the chemicals used for viscose. Another was to find a stabiliser to prevent the solvent from degrading and discolouring the cellulose. There were also difficulties in developing machinery that could dissolve the cellulose in a reliably continuous way. The published Enka route using extruders proved unsuitable for volume production. Courtaulds found an alternative route, using a Kraus Maffei horizontal mixer, and this was used in the pilot plant. It was later discovered that a more suitable machine was a vertical mixer, known as a filmtruder.

(more to come)

Could this be the Z-blade mixer mentioned in Iain Jack's post?

Iain Jack: Tencel Pilot Plant Design (1979)

The process and mechanical design for the original pilot plant was carried out by myself and Mike Perry respectively. I have many memories of the money-no object approach at the time. Particularly trying to modify an old demin water plant with Pete Laity to form the first solvent purification plant, disinterring the world's oldest Z-blade mixer for premix production, and the very "hands on" approach to pulp shredding (sheets torn up during lab tea breaks) and premix feeding (snowballs drop into an airlock by Ruth). Also went to Switzerland with Pat to carry out the first continuous dope making trial at List (but that's a whole other story!)

Stewart Alsop

I worked on the project from '79 to 82, and carried out all the early spinning work, up to commissioning the first pilot plant. We started air-gap spinning and soon realised the spin bath had to run co-curently with the fibre flow. We experimented with draw ratios to alter tenacity, and I wrote a Basic program on an Apple IIe(!) to determine the spinning settings, since everything was linked back to the cellulose content of the dope, which we could only make in small batches, courtesy of the resurrected z-blade mixer Ian referred to. We also had a few incidents making the amine oxide, and fires wre an occasional feature. It was my idea to try ion exchange resins to purify the spin bath, and I was delighted to see that was one secret Lenzing never discovered, until they bought the Tencel plant.

After leaving Courtaulds Research I move to Leek Chemicals, which under the inspirational leadership of Ian Roxburgh, quickly led to the set-up of Courtaulds Chemicals. I left there in December 88, to become the technical director of the country's last commercial high temperature coal tar distiller. The company was progressively taken over by Koppers Inc., and I was made redundant in 2004. I then worked in a specialist foundry for a few years, and led their efforts in Lean Manufacturing. 

I was headhunted for my current job, technical manager for the world's first company to recycle carbon fibre on a commercial scale. As a dedicated aviator and F1 enthusiast it is a dream job. I made all the technical input into the patenting process, and am currently leading a £multi-million project to expand and de-bottleneck the facility in Coseley, which will then be the model for new plants around the world. In the background, I'm working on the next-generation design, which should have a negative carbon foot-print.

Regards

Stewart