Dyeing cellulose-containing textile material with hydrogenated indigo
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A process for dyeing celluose-containing textile material with indigo comprises using an aqueous solution of leuco indigo prepared by catalytic hydrogenation and, after the leuco indigo has gone onto the textile material, converting it back into the pigment form in a conventional manner by air oxidation.
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1. A process for dyeing cellulose-containing textile material with indigo which comprises
a) introducing into a dyebath an aqueous solution of leuco indigo prepared by catalytic hydrogenation;
b) contacting the textile material with the dyebath; and, after the leuco indigo has gone onto the textile material,
c) converting said leuco indigo back into the pigment form in a conventional manner by air oxidation.
2. A process as claimed in claim 1 wherein the leuco indigo solution contains from 10 to 35% by weight of leuco indigo.
3. A process as claimed in claim 1 wherein the leuco indigo solution contains from 2 to 10% by weight of alkali.
4. A process as claimed in claim 1 wherein the leuco indigo solution contains from 2 to 10% by weight of sodium hydroxide.
5. A process for dyeing cellulose-containing textile material with indigo which comprises using an aqueous solution of leuco indigo prepared by catalytic hydrogenation and, after the leuco indigo has gone onto the textile material, converting the leuco indigo back into the pigment form by air oxidation, wherein the leuco indigo oxidized during dyeing by air contact is electrochemically reduced in the dyeing liquor using a mediator system.
7. A process as claimed in claim 5 wherein the mediator used is an organic redox system which is substantially reversible under the dyeing conditions.
Comments from the community
One comment has been received for United States Patent No. 5,586,992. Want to add another?
#1|FizzMaster comments:
In Dystar Textilfarben v. C.H. Patrick, the Court of Appeals for the Federal Circuit ruled Claims 1 through 4 of United States Patent No. 5,586,992 invalid as being unpatentably obvious. The Court reasoned that "an ordinar artisan, with knowledge of [the cited prior art references], would have realized that, by stabilizing catalytic hydrogenated leuco indigo solution in oxygen-excluding containers, he could devise a 'cheaper, faster, and more convenient indigo dyeing process." (citations omitted)
Dystar is actually chock full of obviousness goodness, including commentary on the relationship between the motivation/suggestion test, the implicit motivation to combine that exists for certain improvement-type inventions, the importance of determining proper person of ordinary skill in the art for method/process claims, what doesn't constitute a teaching away, and what doesn't qualify as a failed attempt of others as a secondary consideration in a Graham analysis.
View and/or download a .pdf of the Dystar opinion.
Read the full fedcirc.us review of the Dystar opinion