2-component primer composition and method for producing coatings using the primer composition
The present invention relates to an aqueous two-component primer composition comprising (1) a paint base component comprising (A) at least one polyurethane resin having an OH number of 5 to 60 mg KOH/g, (B) zinc phosphate, (C) at least one pigment, and (2) a curing component comprising (D1) at least one polyisocyanate which is an isocyanurate based on hexamethylene diisocyanate, (D2) at least one polyisocyanate which is a polyether-modified isocyanurate based on isophorone diisocyanate, where the stoichiometric ratio of isocyanate groups in the curing component to the complementary hydroxyl groups in the paint base component is greater than 2. The present invention further relates to a method for producing a coating on a metallic substrate, by applying the primer composition of the invention directly to a substrate. Moreover, the present invention relates to a substrate coated by the stated method.
1. An aqueous two-component primer composition comprising
(1) a paint base component comprising
(A) at least one polyurethane resin having an OH number of 5 to 80 mg KOH/g,
(B) zinc phosphate,
(C) at least one pigment,
and
(2) a curing component comprising
(D1) at least one polyisocyanate which is an isocyanurate based on hexamethylene diisocyanate,
(D2) at least one polyisocyanate which is a polyether-modified isocyanurate based on isophorone diisocyanate,
where the stoichiometric ratio of isocyanate groups of the isocyanurates (D1) and (D2) to the hydroxyl groups present in the at least one polyurethane resin (A) is a ratio from greater than 3 to a ratio of 10.
2. The aqueous two-component primer composition as claimed in claim 1 , wherein the at least one polyurethane resin (A) has an OH number of 5 to 60 mg KOH/g.
3. The aqueous two-component primer composition as claimed in claim 2 , wherein the at least one polyurethane resin (A) has an acid number of 10 to 40 mg KOH/g.
4. The aqueous two-component primer composition of claim 1 , wherein the fraction of the at least one polyurethane resin (A) is 6% to 30% by weight, based on the total amount of the primer composition.
5. The aqueous two-component primer composition of claim 1 , wherein the fraction of the zinc phosphate (B) is 3% to 20% by weight, based on the total amount of the primer composition.
6. The aqueous two-component primer composition as claimed in claim 1 , wherein the pigments (C) are selected from the group of black pigments and white pigments.
7. The aqueous two-component primer composition as claimed in claim 1 , wherein the at least one isocyanurate (D1) has an isocyanate content of 8% to 13% and the at least one polyether-modified isocyanurate (D2) has an isocyanate content of 7% to 12%.
8. The aqueous two-component primer composition as claimed in claim 1 , wherein the fraction of the at least one isocyanurate (D1) is 1.5% to 7.5% by weight and the fraction of the at least one hydrophilically modified isocyanurate (D2) is 3% to 10% by weight, based in each case on the total amount of the primer composition.
9. The aqueous two-component primer composition as claimed in claim 1 , further comprising a filler (E).
10. The aqueous two-component primer composition as claimed in claim 1 , wherein the stoichiometric ratio of the isocyanate groups of the isocyanurates (D1) and (D2) to the hydroxyl groups present in the at least one polyurethane resin (A) is 4 to 10.
11. The aqueous two-component primer composition as claimed in claim 1 , comprising at least 25% by weight of water, based on the total weight of the primer composition, and wherein the fraction of organic solvents, based on the total weight of the primer composition, is less than 15% by weight.
12. The aqueous two-component primer composition as claimed in claim 1 , wherein the stoichiometric ratio of the isocyanate groups of the isocyanurates (D1) and (D2) to the hydroxyl groups present in the at least one polyurethane resin (A) is a ratio from 3.5 to 10.
13. A method for producing a coating by
(1) applying a primer composition as claimed in claimed in claim 1 directly to a metallic substrate, and
(2) forming a polymer film from the primer composition applied in stage (1).
14. The method as claimed in claim 13 , wherein the metallic substrate is a substrate coated with an automotive finish having regions of damage to repair the damaged regions.
15. The method as claimed in claim 13 , comprising applying at least one further coating composition which is cured together with the applied primer composition.
16. The method as claimed in claim 15 , wherein two further coating compositions are applied, the first further coating composition being a basecoat material and the second further coating composition being a clearcoat material.
17. A coated substrate coated by the method as claimed in claim 13 .