Patent ID: 8772545

Claim:
A method of preparing a rinsable dye, comprising the following steps: (a) providing an organic sulfonic acid, comprising sulfonic acid molecules which each contain one or more sulfonic groups and an aryl-aldehyde functional group; (b) providing a polyalkyleneoxylated tertiary aryl amine, comprising polyalkyleneoxylated tertiary aryl amine molecules; (c) reacting the polyalkyleneoxylated tertiary aryl amine with the organic sulfonic acid so as to attach two of the polyalkyleneoxylated tertiary aryl amine molecules to each of the sulfonic acid molecules, thereby forming triarylmethane molecules; (d) oxidizing the triarylmethane molecules so that one or more of the sulfonic groups become sulfonic ions (SO 3 − ); and (e) capping the sulfonic ions in the triarylmethane molecules with an amine or amine salt group.