Shrinkproofing of Wool with Reducing Agents

Wool can be shrinkproofed by treatment with ethanolic or aqueous solutions of ammonium thioglycollate or of mixtures of thioglycollic acid and organic bases. Preliminary extraction of the fabric with ethanol greatly increases the effectiveness of aqueous solutions of ammonium thioglycollate. Extracted fabric can also be shrinkproofed by treatment with aqueous solutions of sodium bisulphite, which are without effect on unextracted fabric. However, the shrink resistance, which withstands washing in hot water, is largely lost on washing in soap solution. Shrinkproofing with reducing agents can be achieved under conditions where reaction very probably occurs only with disulphide bonds. Re‐building of disulphide, or formation of new covalent, bonds after the shrinkproofing reaction does not destroy the unshrinkability. Treatment with aqueous solutions of reducing agents leads to unshrinkability without the reaction being confined to the surface of the fibre, and without affecting the difference between the with‐scale and anti‐scale coefficients of friction. The effect cannot be explained in terms of the conventional theories of shrinkproofing.