Bleaching and dyeing; fluid treatment and chemical modification – Using enzymes – dye process – composition – or product of dyeing
Patent
1996-09-04
1998-01-20
Einsmann, Margaret
Bleaching and dyeing; fluid treatment and chemical modification
Using enzymes, dye process, composition, or product of dyeing
8125, D06M 1140, D06M 1600, D06P 1673, D06P 360
Patent
active
057097160
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention is concerned with methods of improving the visual appearance of lyocell fabrics.
It is known that man-made cellulose fibre can be made by extrusion of a solution of cellulose in a suitable solvent into a coagulating bath. One example of such a process is described in U.S. Pat. No. 4,246,221, the contents of which are incorporated herein by way of reference. Cellulose is dissolved in a solvent such as an aqueous tertiary amine N-oxide, for example N-methylmorpholine N-oxide. The resulting solution is then extruded through a suitable die into an aqueous bath to produce an assembly of filaments which is washed in water to remove the solvent and is subsequently dried. This process is referred to as "solvent-spinning", and the cellulose fibre produced thereby is referred to as "solvent-spun" cellulose fibre or as lyocell fibre. Lyocell fibre is to be distinguished from cellulose fibre made by other known processes, which rely on the formation of a soluble chemical derivative of cellulose and its subsequent decomposition to regenerate the cellulose, for example the viscose process.
As used herein, the term "lyocell fibre" means a cellulose fibre obtained by an organic solvent spinning process, wherein the organic solvent essentially comprises a mixture of organic chemicals and water, and wherein solvent spinning involves dissolving cellulose in the organic solvent to form a solution which is spun into fibre without formation of a derivative of the cellulose. As used herein, the terms "solvent-spun cellulose fibre" and "lyocell fibre" are synonymous. As used herein, the term "lyocell yarn" means a yarn which contains lyocell fibre, alone or in blend with other type(s) of fibre. As used herein, the term "lyocell fabric" means a fabric woven or knitted from yarns, at least some of which are lyocell yarns.
Fibres may exhibit a tendency to fibrillate, particularly when subjected to mechanical stress in the wet state. Fibrillation occurs when fibre structure breaks down in the longitudinal direction so that fine fibrils become partially detached from the fibre, giving a hairy appearance to the fibre and to fabric containing it, for example woven or knitted fabric. Dyed fabric containing fibrillated fibre tends to have a "frosted" visual appearance, which may be aesthetically undesirable. Such fibrillation is believed to be caused by mechanical abrasion of the fibres during treatment in a wet and swollen state. Wet treatment processes such as dyeing processes inevitably subject fibres to mechanical abrasion. Higher temperatures and longer times of treatment generally tend to produce greater degrees of fibrillation. Lyocell fibres appear to be particularly sensitive to such abrasion in comparison with other types of cellulose fibre, in particular cotton which has an inherently very low fibrillation tendency.
It is an object of the present invention to provide dyed lyocell fabric which does not exhibit a "frosted" appearance and which does not develop such a "frosted" appearance after repeated laundering. This improvement is referred to hereinafter as improving the colour properties of the lyocell fabric. This term "colour properties" is to be distinguished from the terms "uniform dyeability" and "level dyeing" commonly used in the art. In general, the levelness of dyeing of a fabric does not change on repeated laundering. Cotton is a natural fibre, and its dyeability varies from fibre to fibre. In contrast, lyocell fibres are made by a controlled manufacturing process and exhibit uniform dyeability. Cotton does not fibrillate, and so its colour properties do not change during processing or laundering. The colour properties of known lyocell fabric may change depending on the type of treatment to which it is subjected. For example, repeated laundering commonly induces fibrillation and worsens the colour properties of lyocell fabric, whereas enzyme (cellulase) treatment removes fibrils and generally improves the colour properties of the fabric.
BACKGROUND ART
It has been known for
REFERENCES:
patent: 3148106 (1964-09-01), Mitchell
patent: 4246221 (1981-01-01), McCorsley, III
patent: 4399275 (1983-08-01), Sears
patent: 5580354 (1996-12-01), Taylor
"Enzymatic and Acid Hydrolysis of Cotton Cellulose After Slack and Tension Mercerization", Textile Chemist and Colorist, vol. 26, No. 4, pp. 17-24, pbl 4-94 (Entire Article in the English language).
"Properties and Structure of Lyocell and Viscose-Type Fibres in the Swollen State", Lenzinger Berichte, pp. 19-25, publ. 9-94 (Entire article provided in the English language).
"Bio-Polishing--Ein Neuer Alternativer Veredelungsprozess Fur Cellulosefasern", Lenzinger Berichte, pp. 95-97, publ. Sep. 1994 (Article in the German Language, English language abstract provided on p. 95 of the article).
"Die Veredlung Von Lyocellfasern--Ein Erfahrungsbericht", Lenzinger Berichte, pp. 99-101, publ. Sep. 1994 (Article in the German language, English language abstract provided on p. 99 of the article).
Courtaulds Fibres (Holdings) Limited
Einsmann Margaret
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