Bleaching and dyeing; fluid treatment and chemical modification – Using enzymes – dye process – composition – or product of dyeing
Patent
1995-09-18
1999-07-06
Redding, David A.
Bleaching and dyeing; fluid treatment and chemical modification
Using enzymes, dye process, composition, or product of dyeing
8102, 81161, 435263, C09B 6700
Patent
active
059192720
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to processes of providing localized variation in the colour of dyed fabrics.
BACKGROUND OF THE INVENTION
The most usual method of providing a "stone-washed" look (localized abrasion of the colour) in dyed fabrics, in particular cellulose-containing fabrics, is by washing cellulose-containing fabrics or clothing made from such fabrics in the presence of pumice stones to provide the desired localized lightening of the colour of the fabric. Using pumice for this purpose has the disadvantage that pumice particles have to be washed from the fabric or clothing subsequently to treatment, and that the pumice stones and particles cause a significant wear of the machines used in the process. Also, handling large amounts of stones may be a problem.
Other approaches to providing a "stone-washed"appearance to fabrics have therefore been suggested. For instance, enzymes, in particular cellulytic enzymes, have been suggested for this purpose, either alone (4,832,864 or together with a smaller amount of pumice than required in the traditional process.
SUMMARY OF THE INVENTION
The present invention is based on the surprising finding that it is possible to obtain improved utilization of the ability of cellulytic enzymes to provide localized colour variations in dyed fabrics either by adding a chelating agent to a wash liquor containing calcium ions and other di- or trivalent cations, or by carrying out the process in soft water.
Accordingly, the present invention relates to a process for providing improved localised variation in the colour density of the surface of dyed fabrics, the process comprising treating a dyed fabric with a cellulytic enzyme in an aqueous liquor comprising a di- or trivalent cation and a chelating agent in a molar ratio of 1:0.1-50.
In another aspect, the present invention relates to a process for providing improved localised variation in the colour density of the surface of dyed fabrics, the process comprising treating a dyed fabric with a cellulytic enzyme in an aqueous liquor comprising less than 20 mg/l of Ca.sup.2+ and Mg.sup.2+.
In the present context, the expression "improved localized variation" is intended to indicate that the differences between lighter and darker areas of the fabrics is more pronounced than in fabrics treated by the enzymatic process described in, e.g. U.S. Pat. No. 4,832,864. It has been found that in the known enzymatic "stone-washing" processes for obtaining localized colour variations, at least some (though not all) of the dye washed from the fabric is redeposited thereon so that the difference between darker and lighter shades on the fabric is somewhat obscured (this phenomenon is known as backstaining to people skilled in the art). It has surprisingly been found that by reducing the amount of free calcium or other di- or trivalent cations in the liquor in which the fabric is treated (e.g. by the addition of a chelating agent to calcium-containing water or by using soft water), such redeposition of dye may be significantly reduced.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 illustrates the effects of backstaining at various concentrations of cations in the wash liquor.
DETAILED DESCRIPTION OF THE INVENTION
The di- or trivalent cations present in the wash liquor may be alkaline earth metal ions, in particular Ca.sup.2+ or Mg.sup.2+. According to the invention, the molar ratio between di- or trivalent ions and chelating agent depends on the nature of the chelating agent. However, a currently preferred ratio of di- or trivalent cations (such as Ca.sup.++) to chelating agent is 1:0.1-10, more preferably, 1:0.2-5.
The process of the invention is most beneficially applied to cellulose-containing fabrics, such as cotton, viscose, rayon, ramie, linen, Tencel or mixtures thereof, or mixtures of any of of these fibres with synthetic fibres. In particular, the fabric is denim. The fabric may be dyed with vat dyes such as indigo, direct dyes such as Direct Red 185, sulphur dyes such as Sulfur Green 6, or reactive dyes fixed
REFERENCES:
patent: 4912056 (1990-03-01), Olson
patent: 5213581 (1993-05-01), Olson et al.
patent: 5290474 (1994-03-01), Clarkson et al.
patent: 5538648 (1996-07-01), Buchelet et al.
Gregg, Esq. Valeta
Novo Nordisk A S
Redding David A.
Zelson Esq. Steve T.
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