Editing Lyocell (section)

==Manufacturing process==
The Lyocell process uses a direct solvent rather than indirect dissolution such as the xanthation-regeneration route in the viscose process. Lyocell fibre is produced from [[dissolving pulp]], which contains [[cellulose]] in high purity with little [[hemicellulose]] and no [[lignin]]. Hardwood logs (such as [[oak]] and [[birch]]{{better source needed|date=May 2024}}<ref name="madehow" />) are chipped into squares about the size of postage stamps. The chips are digested chemically, either with the prehydrolysis-[[kraft process]] or with [[sulfite process]], to remove the [[lignin]] and hemicellulose. The pulp is bleached to remove the remaining traces of lignin, dried into a continuous sheet and rolled onto spools. The pulp has the consistency of thick [[posterboard]] paper and is delivered in rolls weighing some 500&nbsp;lb (230&nbsp;kg).

:[[File:NMO.png|thumb|left|148px|[[N-Methylmorpholine N-oxide|''N''-Methylmorpholine ''N''-oxide]] is a key solvent in the Lyocell process ]]

At the Lyocell mill, rolls of pulp are broken into one-inch squares and dissolved in [[N-Methylmorpholine N-oxide|''N''-methylmorpholine ''N''-oxide]] (NMMO<ref name=brief/>), giving a solution called "dope". The filtered cellulose solution is then pumped through [[Spinneret (polymers)|spinnerets]], devices used with a variety of synthetic fibres. The spinneret is pierced with small holes rather like a shower head; when the solution is forced through it, continuous strands of filament come out. The fibres are drawn in air to align the cellulose molecules, giving the Lyocell fibres its characteristic high strength. The fibres are then immersed into a water bath, where desolvation of the cellulose sets the fibre strands. The bath contains some dilute amine oxide in a steady state concentration. Then the fibres are washed with demineralised water. Next, the Lyocell fibre passes to a drying area, where the water is evaporated from it.

Manufacture then follows the same route as with other kinds of fibres such as viscose. The strands pass to a finishing area, where a lubricant, which may be a soap or silicone or other agents, depending on the future use of the fibre, is applied. This step is a detangler, prior to carding and spinning into yarn. At this stage, the dried, finished fibres are in a form called tow, a large, untwisted bundle of continuous lengths of filament. The bundles of tow are taken to a crimper, a machine that compresses the fibre, giving it texture and bulk. The crimped fibre is then carded by mechanical carders, which perform a combing action to separate and order the strands. The carded strands are then cut and baled for shipment to a fabric mill. The entire manufacturing process, from unrolling the raw cellulose to baling the fibre, takes roughly two hours. After this, the Lyocell may be processed in many ways. It may be spun with another fibre, such as cotton or wool. The resulting yarn can be woven or knitted like any other fabric, and may be given a variety of finishes, from soft and suede-like to silky.{{sfn|Kadolph|Langford|2001|p={{pn|date=April 2025}}}}

The [[amine oxide]] used to dissolve the cellulose and set the fibre after spinning (NMMO) is recycled. Typically,<ref name="madehow">{{Cite web |title=How lyocell is made - material, manufacture, making, used, processing, steps, industry, machine |url=http://www.madehow.com/Volume-5/Lyocell.html |access-date=28 July 2022 |website=www.madehow.com}}</ref> 99 per cent of the amine oxide is recovered.<ref name="good">{{Cite web|date=27 July 2018|title=Material Guide: How Ethical is Tencel?|url=https://goodonyou.eco/how-ethical-is-tencel/|access-date=21 July 2020|website=Good On You|language=en}}</ref> NMMO biodegrades without producing harmful products.<ref name=brief/> Since there is little waste product, this process is relatively eco-friendly, though it is energy-intensive.<ref name="good" />

===Future research===
Lyocell's lack of antibacterial properties limits its uses in the medical field. Due to its biodegradability, low toxicity, and comfort, Lyocell would become a useful material for antibacterial garments. Several approaches have been tested to introduce antibacterial capabilities. Three general approaches have been studied to achieve this: physical blending, chemical reaction, and post-treatment. Physical blending methods introduce antibacterial agents into the spinning dope. In chemical reaction methods, antibacterial additives are crosslinked into the Lyocell fibres and therefore giving antimicrobial properties. In post-treatment methods, antibacterial additives are being deposited on Lyocell fibre surfaces through physical coating, padding, or impregnation processes. Physical blending and post-treatment methods appear to be the most promising for large-scale manufacturing. Careful consideration of cost, preparation time, and antibacterial effectiveness is required to select the best method. Creating successful modification of Lyocell fibres to enhance antibacterial properties would allow to manufacture products for health care (such as lab coats, caps, gowns), hygiene products (scrubs, sanitary napkins), and clothing (socks, underwear).<ref>{{cite journal |last1=Edgar |first1=Kevin J. |last2=Zhang |first2=Huihui |date=December 2020 |title=Antibacterial modification of Lyocell fiber: A review |journal=Carbohydrate Polymers |volume=250 |pages=116932 |doi=10.1016/j.carbpol.2020.116932 |pmid=33049845 }}</ref>