Bleaching and dyeing; fluid treatment and chemical modification – Using enzymes – dye process – composition – or product of dyeing
Patent
1993-10-07
1994-10-18
Prescott, Arthur C.
Bleaching and dyeing; fluid treatment and chemical modification
Using enzymes, dye process, composition, or product of dyeing
25217412, C11D 3395, C11D 339
Patent
active
053564375
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to removal of excess dye from newly manufactured printed or dyed fabric or yarn.
BACKGROUND OF THE INVENTION
In printing of textiles, it is common to use a printing paste containing a dye and a thickener. Among the commonly used thickeners are biological polymers and chemically modified biological polymers, such as alginate, galactomannan, starch and carboxymethyl cellulose. But also synthetic thickeners can be used.
With most printing methods, the polymer and excess dye must be removed by washing with water after the fixation of the print. Generally, a large amount of water is required for complete removal of excess dye due to the risk of back-staining during the process, i.e. redeposit on the fabric of already dissolved dye, which may cause unwanted dye transfer during laundering by the consumer. The risk of back-staining is significant in the early stages of the rinsing and/or at high temperatures, especially when the polymer is quickly solubilized.
After dyeing of fabric or yarn, the excess dyestuff, after the fixation, has to be removed by washing with water. Generally, a large amount of water is required for complete removal of excess dye, and during washing the backstaining of released dyestuff will result in an insufficient wet fastness unless the washing is repeated several times.
When garments sewn of differently dyed fabrics are subjected to a wet treatment, e.g. for desizing or so-called "stone-washing" of denim, there is a risk of dye transfer.
In a conventional process the printed or dyed textile is first rinsed with cold water, then washed at high temperature with the addition of a suitable additive to decrease backstaining like PVP. The process is repeated until satisfactory amount of dyestuff (and thickener) have been removed. A polyvinyl pyrrolidone (PVP) can be added as a retarder to reduce backstaining during hot washing, but this compound does not bleach the dye and is relatively expensive. The waste water from a conventional process tends to be strongly coloured and may represent a disposal problem.
SUMMARY OF THE INVENTION
We have developed an improved process for removal of excess dye, wherein dye leached from dyed or printed textiles is decolourized in an aqueous solution by adding enzymes that utilize hydrogen peroxide or molecular oxygen for the oxidation of organic or inorganic substances, including coloured substances, together with a source of H.sub.2 O.sub.2 or O.sub.2. Such enzymes are usually termed peroxidases and oxidases, respectively. This treatment reduces the risk of back-staining (redeposition of dye onto textile) even when less water is used. The enzymatic bleaching of released dyestuff will decrease process time as well as the amount of energy and water needed to achieve a satisfactory quality of the textile, and the colour of the waste water is reduced.
The process of the invention can result in a decreased number of washes, thereby increasing the productivity and decreasing the consumption of water and chemicals. It can also lead to a decreased dye-load in the waste water, thus reducing water pollution. Further, the quality of the treated textile can be increased (e.g. improved dye-fastness).
Accordingly, the present invention provides a process for removal of excess dye from newly manufactured printed or dyed fabric or yarn comprising treatment with a wash liquor containing (1) an enzyme exhibiting peroxidase activity and a suitable source of H.sub.2 O.sub.2 or (2) an enzyme exhibiting a suitable oxidase activity and a source of O.sub.2.
It is well recognized in the art (cf. for instance B. C. Saunders et al., Peroxidase, London, 1964, p. 10 ff.) that peroxidases act on various amino and phenolic compounds resulting in the production of a colour. In view of this, it must be considered surprising that peroxidases (and certain oxidases) may also exert an effect on coloured substances in solution such that backstaining is inhibited.
It has been reported that peroxidases may decolorize certain natural pigments
REFERENCES:
patent: 4421668 (1983-12-01), Cox et al.
patent: 5131918 (1992-07-01), Kelley
Pedersen Gitte
Schmidt Michael
Lambiris Elias J.
Novo Nordisk A S
Prescott Arthur C.
Zelson Steve T.
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