Aqueous coating composition for applying a basecoat film, comprising a mixture of a polyester and a polyamide with low acid number as rheological assistant
The present invention relates to an aqueous coating composition comprising at least one mixture (M) of at least one polymeric resin (P1) and at least one polymeric resin (P2), different therefrom, where (P1) is a polyamide and (P2) is a polyester which is at least obtainable by reaction of at least one polymerized aliphatic C 12 -C 24 -monocarboxylic acid with at least one diol and/or polyol, at least one binder (A) comprising at least one polymeric resin (A1), which is different from the polymeric resins (P1) and (P2), at least one pigment (B), where the polyamide used as polymeric resin (P1) has an acid number <10 mg of KOH per g of polyamide and the mixture (M) is obtainable by dispersing of the polymeric resin (P1) in water or an aqueous medium in the presence of the polymeric resin (P2), to a method for at least partly coating a substrate with a basecoat film by means of the aqueous coating composition, and to a use of the mixture (M) as a rheological assistant in aqueous coating compositions.
1. An aqueous coating composition, comprising:
at least one mixture (M) of at least one polymeric resin (P1) and at least one polymeric resin (P2), different from (P1),
wherein
the polymeric resin (P1) is a polyamide, and
the polymeric resin (P2) is a polyester which is at least obtainable by reaction of at least one polymerized aliphatic C 12 -C 24 -monocarboxylic acid with at least one diol and/or polyol,
at least one binder (A) comprising at least one polymeric resin (A1), which is different from the polymeric resins (P1) and (P2), and optionally at least one crosslinking agent (A2), and
at least one pigment (B),
wherein the polyamide used as polymeric resin (P1) has an acid number <10 mg of KOH per g of polyamide and
the mixture (M) is obtainable by dispersing of the polymeric resin (P1) in water or an aqueous medium in the presence of the polymeric resin (P2).
2. The coating composition as claimed in claim 1 , wherein the polyamide used as polymeric resin (P1) has an acid number in a range from 0.01 to 8.0 mg of KOH per g of polyamide.
3. The coating composition as claimed in claim 1 , wherein the relative weight ratio of the polymeric resins (P2) and (P1) to one another, based in each case on their solids content, in the coating composition is in a range from 10:1 to 1.5:1.
4. The coating composition as claimed in claim 1 , wherein the coating composition is obtainable by the steps (1) and (2), succeeding one another in this order, specifically
(1) dispersing the polymeric resin (P1) in water or an aqueous medium in the presence of the polymeric resin (P2), to give an aqueous dispersion of the mixture (M), and
(2) mixing the aqueous dispersion of the mixture (M) obtained by step (1) with the further components used for preparing the coating composition.
5. The coating composition as claimed in claim 1 , wherein the mixture (M) of the at least one polymeric resin (P1) and the at least one polymeric resin (P2), different from (P1), is present in the coating composition in an amount in a range from 0.5 to 15 wt %, based on the total weight of the coating composition.
6. The coating composition as claimed in claim 1 , which comprises the polyamide used as polymeric resin (P1) in an amount in a range from 0.05 to 5 wt %, based on the total weight of the coating composition.
7. The coating composition as claimed in claim 1 , wherein the polyester used as polymeric resin (P2) has an acid number in a range from 20 to 50 mg of KOH per g of polyester and/or a hydroxyl number in a range from 20 to 300 mg of KOH per g of polyester.
8. The coating composition as claimed in claim 1 , wherein the polyester used as polymeric resin (P2) is at least obtainable by reaction of at least one dimerized and/or trimerized aliphatic C 12 -C 24 monocarboxylic acid with at least one aliphatic C 2 -C 20 polyol and/or C 2 -C 20 diol.
9. The coating composition as claimed in claim 1 , wherein to prepare the polyester used as polymeric resin (P2) use is made additionally of at least one dicarboxylic acid and/or at least one tricarboxylic acid selected from the group consisting of aliphatic C 3 -C 12 dicarboxylic acids, cycloaliphatic C 5 -C 12 dicarboxylic acids, aromatic C 8 -C 12 dicarboxylic acids, aliphatic C 5 -C 12 tricarboxylic acids, cycloaliphatic C 6 -C 12 tricarboxylic acids, and aromatic C 9 -C 12 tricarboxylic acids, and optionally at least one aliphatic C 12 -C 24 monocarboxylic acid.
10. The coating composition as claimed in claim 1 , wherein the binder (A) comprises at least one polyurethane and/or at least one poly(meth)acrylate and/or at least one polyester as at least one polymeric resin (A1).
11. The coating composition as claimed in claim 1 , which comprises the polymeric resin (A1) in an amount in a range from 5 to 40 wt %, based on the total weight of the coating composition, and the pigment (B) in an amount in a range from 0.1 to 25 wt %, based on the total weight of the coating composition.
12. An aqueous coating composition, comprising:
a rheological assistant which is a mixture (M) of at least one polymeric resin (P1) and at least one polymeric resin (P2), different therefrom, wherein
the polymeric resin (P1) is a polyamide which has an acid number <10 mg of KOH per g of polyamide, and
the polymeric resin (P2) is a polyester which is at least obtainable by reaction of at least one polymerized aliphatic C 12 -C 24 monocarboxylic acid with at least one diol and/or polyol.
13. A substrate coated at least partly with the aqueous coating composition as claimed in claim 1 .
14. A method for at least partly coating an optionally coated substrate with a basecoat film, comprising:
(a) at least partly coating at least one optionally coated substrate with a basecoat film by the aqueous coating composition as claimed in claim 1 .
15. A basecoat film which is obtainable by the method as claimed in claim 14 .
16. A substrate coated at least partly with the basecoat film as claimed in claim 15 .