a dye mordant composition containing a polymer comprising repeating units with at least 20 mol % of the repeating units having the general formula : ## str1 ## wherein r 1 represents an alkyl group containing 1 to 12 carbon atoms , an aralkyl group , an aryl group or an allyl group ; r 2 and r 3 , which may be the same or different , each represents a hydrogen atom , an alkyl group , an aralkyl group , an aryl group or an allyl group , where the total number of carbon atoms contained in the main chain and / or ring of r 2 and r 3 is less than 16 ; n represents an integer from 2 to 20 ; and x . sup .⊖ represents an anion .