Studies in Wool Yellowing

Abstract

The use of thiourea-formaldehyde resin for retarding the rate of yellow ing of wool by sunlight has been examined. This method provides considerable protection against yellowing, particularly of wet fabrics. It has been found that treatment with thioureaformaldehyde mixtures. which does not give rise to resin, provides similar protection against yellowing. This modification has the advantages that the handle and color of the wool are unaffected, As for the resin treatment, initial rinsing reduces the protective effect, although this is not further reduced by subsequent washing. . ~ -~---

Studies in Wool Yellowing. Part XVIII: Processes for Retardation of Sunlight Yellowing of Fluorescent-Brightened Wool

“…An investigation into the problem has commenced in these laboratories, and initial findings are now reported. These mainly confirm and extend the work of previous investigators [3,4,5].. -An attempt was first made to compare 20 of the various brighteners currently available with respect to lightfastness, when applied to wool, and to find which particular chemical class of brightener is more suitable for application to wool. Information as to the exact structure of a brightener was not always available from the manufacturer, but we were usually informed of the class [9, 10] to which the brightener belonged, such as stilbene, coumarin, or pyrazoline.…”

“…The thiourea-formaldehyde treatment also gave added whiteness to the wool. A similar treatment with thiourea and formaldehyde was suggested by Milligan and Tucker [5] for retarding the yellowing of unbrightened wool. For brightened wool, the treatment was carried out as follows.…”

“…A product of markedly improved whiteness, but of reduced lightfastness, was obtained when wool was bleached with peroxide, either before or after brightening. 5. A slight improvement in whiteness with no loss in lightfastness was obtained when wool was bleached with hydrosul6te or sodium formaldehyde sulfoxylate, ether °b efore, with, or after brightening.…”

Wool: Structure, Properties, and Processing

“…Treatment of wool with a FWA, followed by post-treatment with thiourea/ formaldehyde by a pad/cure method, confers a high level of protection against photoyellowing and also improves the initial fabric whiteness (171). Unfortunately, this process is not commercially viable, partly because of environmental concerns about thiourea and formaldehyde and also because much of the benefit is lost after laundering.…”

Studies in Wool Yellowing

“…Such substances may function in a variety of ways, such as by absorbing the active wave bands in the ultraviolet radiation and, hence, &dquo;screening&dquo; the wool or by physical or chemical bonding with sensitive sites in the wool protein., Although several yellowing inhibitors have already been reported. [2,3,5,6), no generalizations can be drawn about the chemical types which are effective.…”