Waterborne epoxy coating composition
A stable two-component waterborne coating composition comprising an epoxy component A comprising a waterborne epoxy resin, a polymeric dispersant, and pigments and/or extenders; and a component B comprising a curing agent; providing coatings made therefrom with improved anti-corrosion properties; and a method of preparing the coating composition.
1. A two-component waterborne coating composition comprising an epoxy component A and a component B,
wherein the epoxy component A comprises a waterborne epoxy resin, a polymeric dispersant, and pigments and/or extenders;
wherein the polymeric dispersant comprises (a) structural units of an ethylenically unsaturated sulfonic acid-containing monomer, a salt thereof, or a combination thereof, and (b) structural units of an ethylenically unsaturated phosphorous-containing monomer, wherein the combined amount of (a) and (b) is from 10% to 35% by weight based on the dry weight of the polymeric dispersant, and the weight ratio of (a)/(b) is from 0.3 to 20; and
wherein the component B comprises a curing agent.
2. The coating composition of claim 1 , wherein the polymeric dispersant further comprises (c) structural units of an ethylenically unsaturated nonionic monomer.
3. The coating composition of claim 1 , wherein the combined amount of (a) and (b) is from 20% to 30% by weight based on the dry weight of the polymeric dispersant.
4. The coating composition of claim 1 , wherein the weight ratio of (a)/(b) is from 0.4 to 12.
5. The coating composition of claim 1 , wherein the ethylenically unsaturated phosphorous-containing monomer is selected from the group consisting of phosphoethyl (meth)acrylate, phosphopropyl (meth)acrylate, phosphobutyl (meth)acrylate, and salts thereof.
6. The coating composition of claim 1 , wherein the ethylenically unsaturated sulfonic acid-containing monomer or a salt thereof is selected from the group consisting of sodium styrene sulfonate, sodium vinyl sulfonate, acrylamido-2-methylpropanesulfonic acid, and sodium 2-acrylamido-2-methylpropane sulfonate.
7. The coating composition of claim 1 , wherein the polymeric dispersant comprises, based on the dry weight of the polymeric dispersant,
from 10% to 15% by weight of structural units of the ethylenically unsaturated sulfonic acid-containing monomer,
from 5% to 15% by weight of structural units of the ethylenically unsaturated phosphorous-containing monomer, and
from 70% to 80% by weight of structural units of an ethylenically unsaturated nonionic monomer.
8. The coating composition of claim 1 , wherein the polymeric dispersant has a weight average molecular weight of from 300 to 50,000 Daltons.
9. The coating composition of claim 1 , wherein the polymeric dispersant is present, by dry weight based on the total dry weight of pigments and/or extenders, in an amount of from 0.01% to 10%.
10. The coating composition of claim 1 , wherein the waterborne epoxy resin is an aqueous dispersion of acrylic polymer particles imbibed with an epoxy compound.
11. The coating composition of claim 1 , wherein the weight ratio of the epoxy component A and the component B is from 90:1 to 1:1.
12. A method of preparing a two-component waterborne coating composition, comprising: admixing an epoxy component A and a component B,
wherein the epoxy component A comprises a waterborne epoxy resin, a polymeric dispersant, and pigments and/or extenders;
wherein the polymeric dispersant comprises (a) structural units of an ethylenically unsaturated sulfonic acid-containing monomer, a salt thereof, or a combination thereof, and (b) structural units of an ethylenically unsaturated phosphorous-containing monomer, wherein the combined amount of (a) and (b) is from 10% to 35% by weight based on the dry weight of the polymeric dispersant, and the weight ratio of (a)/(b) is from 0.3 to 20; and
wherein the component B comprises a curing agent.