Patent ID: 8901237

Claim:
A method for making an aqueous coating composition, which confers stain and penetration resistance when applied to a substrate and dried and/or cured, comprising mixing together at least one pigment, at least one film-forming polymer in the form of an aqueous polymer dispersion, and at least one anionic surfactant of formula (Ia), to obtain the aqueous coating composition; wherein said aqueous coating composition comprises: at least one pigment, an aqueous polymer dispersion containing at least one film-forming polymer, and at least one anionic surfactant (S) of formula (Ia); wherein the at least one film-forming polymer, in polymerized form, consists of: (M1a) 40 to 59.4% by weight of methyl methacrylate or a mixture thereof with styrene, (M1b) 40 to 55% by weight of at least one C 2 -C 10 alkyl ester of acrylic acid, (M2) 0.1 to 3% by weight of itaconic acid, acrylic acid, methacrylic acid, or a mixture thereof, (M3a) 0.5 to 3% by weight of acrylamide, methacrylamide, hydroxyethyl acrylate, or a mixture thereof, and (M3b) 0 to 2% by weight of N-(2-methacryloxyethyl) imidazolin-2-one, provided that a total amount of (M1a), (M1b), (M2), (M3a), and (M3b) is 100% by weight and a total amount of (M2), (M3a), and (M3b) is from 0.7 to 5% by weight, based on the total amount of (M1a), (M1b), (M2), (M3a), and (M3b); and wherein the at least one surfactant (S) is of formula (Ia): M 3-n [O 4-n P—(O-(Alk-O) m R) n ] (Ia), wherein n is 1 or 2, m is an integer from 0 to 15, M is hydrogen, an alkali metal ion, or an ammonium ion, Alk is C 2 -C 3 -alkylene, and R is C 8 -C 30 alkyl or C 4 -C 30 alkylphenyl; wherein a weight ratio of the at least one pigment to the at least one film-forming polymer ranges from 4:1 to 1:5; and wherein the amount of the at least one surfactant (S) of formula (Ia) constitutes at least 85% of the total amount by weight of anionic surfactants in the aqueous coating composition.