In the previous study on sulfo-acetalization of vinylon and the dyeing of the acetalized vinylon, it was pointed out that vinylon treated with sulfuric acid was dyed with basic dyes. This effect may be due to the bonding sulfuric acid, for it has tendency to adhere to C-C double bond or carbonyl group in polyvinylalcohol. It was assumed from this that the addition of sodium bisulfite to the double bond or carbonyl group originated with oxidation of vinylon may be effective for introducing acid groups to polyvinylalcohol.
The treatment of oxidized vinylon with sodium bisulfite was found to be very practicable for dyeing with basic dyes. In the case of amino-group-introduced-vinylon the same circumstance was observed for dyeing with acid dyes.
Bromine or potassium bichromate is very effective as an oxidizing agent. The latter is less efficient in oxidizing than the former. Vinylon oxidized with bromine was treated with sodium bisulfite and then dyed with some basic dyes. The dyed goods have good fastness against light such as acrylic fiber. The vinylon oxidated with potassium bichromate was treated with ammonia or mono-ethanolamine and then dyed with metal-complex, sulfide or Indanthren dyes. The dyed goods have remarkable advantages in the high yields of colours and good washing fastness.
Foundamental formula of those reactions are as follows: