Patent ID: 10767072

Abstract:
The current invention relates to a process for preparing an aqueous binder composition free of organic solvent, the process comprising at least the following steps: A) preparing a hydrophilic vinyl polymer (Polymer A) by polymerisation of a monomer composition A that contains: Ai) at least one carboxylic acid functional olefinically unsaturated monomer; and Aii) at least one olefinically unsaturated monomer different than Ai); and Aiii) optionally at least one wet adhesion promoting olefinically unsaturated monomer different than Ai and Aii); where Polymer A has an acid value (AV) from 32 to 98 mg KOH/g of solid Polymer A; B) preparing a hydrophobic vinyl polymer (Polymer B) by emulsion polymerization of a monomer composition B in the presence of Polymer A where the monomer composition B contains: Bi) at least one olefinically unsaturated monomer; Bii) optionally carboxylic acid functional olefinically unsaturated monomer different than Bi); and Biii) optionally wet adhesion promoting olefinically unsaturated monomer different than Bi); where Polymer B has an acid value (AV) of no more than 23.4 mg KOH/g of solid polymer B, wherein at least a part of the carboxylic acid groups that are present in Polymer A and Polymer B are neutralized during or following the steps A and/or B to form a (partially) neutralized polymer emulsion; where the weight average molecular weight (Mw) of Polymer A is lower than the weight average molecular weight (Mw) of polymer B; and wherein the process is further characterized by the presence of a further step C) reacting at least 10 mol % of the carboxylic acid and/or carboxylate salt groups of the (partially) neutralized polymer emulsion with an iminating agent to produce an iminated polymer C; wherein the total amount of surfactant applied in steps A, B and C is at most 0.5 wt. %, based on the total weight of monomers charged for the preparation of polymer A and polymer B.