Process for preparing polymeric colorants having a poly(vinylamine) backbone

Claim 1

The process for preparing a poly(vinylamine)-based polymeric colorant which comprises the steps of (a) reacting at a temperature of from 20° C. to 100° C. acetaldehyde and from two to four stoichiometric equivalents of acetamide in the presence of from 0.001 to 1 mole per mole of acetamide of an aqueous mineral acid catalyst to yield--a vinylacetamide and--ethylidene-bis-acetamide containing reaction product; (b) neutralizing the aqueous mineral acid catalyst and heating the ethylidene-bis-acetamide containing reaction product to 70° C. to 250° C. for from 0.2 to 5 hours in the presence of an inorganic nonacidic silicious oxide surface catalyst having a surface area of at least about 1 m 2 /g to yield a decomposition product; (c) separating vinylacetamide from said decomposition product--by vacuum volatilization--; (d) contacting a solution of said vinylacetamide with a catalytically effective amount of free radical initiator polymerization catalyst at a temperature of from 25° C. to 125° C. for from 4 to 8 hours to yield poly(vinylacetamide); (e) hydrolyzing said poly(vinylacetamide) by contacting it with--from 1.05 to 3--stoichiometric--equivalents--of a mineral acid per equivalent of poly(vinylacetamide)--at a temperature of from 60° C. to 175° C. for from 1 to 36 hours to yield the poly(vinylamine) salt of said mineral acid,--and precipitating and recovering said poly(vinylamine) salt--; (f) contacting said poly(vinylamine) salt with not less than a stoichiometric amount of an aqueous solution of a strong base selected from the alkali and alkaline earth metal hydroxides, thereby forming poly(vinylamine); and (g) coupling, in solution, chromophoric groups to the amine functionalities of said poly(vinylamine).