Carboxy-functional, polyether-based reaction products and aqueous basecoat materials comprising the reaction products
The present invention relates to a pigmented aqueous basecoat material comprising a polyether-based reaction product which is preparable by reaction of (a) at least one cyclic carboxylic anhydride comprising a free carboxylic acid group and/or the halide of a carboxylic acid group with (b) at least one polyether of the general structural formula (I) in which R is a C 3 to C 6 alkylene radical and n is selected accordingly such that the polyether (b) possesses a number-average molecular weight of 800 to 4000 g/mol, the components (a) and (b) being used in the reaction in a molar ratio of 0.7/2.3 to 1.6/1.7 and the resulting reaction product possessing an acid number of 10 to 50 mg KOH/g.
1. A pigmented aqueous basecoat material, comprising
a polyether-based reaction product prepared by reacting
(a) trimellitic anhydride
with
(b) at least one polyether of formula (I)
wherein
R is a C 4 alkylene radical and n is selected accordingly such that the polyether (b) possesses a number-average molecular weight of from 1000 to 2900 g/mol,
wherein a molar ratio of (a) to (b) ranges from 0.45/1 to 0.55/1 and the polyether-based reaction product has an acid number of 10 to 30 mg KOH/g.
2. The basecoat material of claim 1 , wherein the polyether (b) possesses a number-average molecular weight of 1200 to 2900 g/mol.
3. The basecoat material of claim 1 , wherein R in the formula (I) comprises a tetramethylene radical.
4. The basecoat material of claim 1 , wherein the polyether-based reaction product possesses a number-average molecular weight of 1500 to 15,000 g/mol.
5. The basecoat material of claim 1 , wherein a sum total of weight-percentage fractions, based on a total weight of the basecoat material, of all polyether-based reaction products is 0.1 to 20 wt %.
6. The basecoat material of claim 1 , further comprising
a melamine resin and
a polyurethane resin that is grafted with olefinically unsaturated monomers and comprises hydroxyl groups.
7. A polyether-based reaction product, obtained by reacting
(a) trimellitic anhydride
with
(b) at least one polyether of formula (I)
wherein
R is a C 4 alkylene radical and n is selected accordingly such that the polyether (b) possesses a number-average molecular weight of from 1000 to 2900 g/mol,
wherein a molar ratio of (a) to (b) ranges from 0.45/1 to 0.55/1 and the polyether-based reaction product has an acid number of 10 to 30 mg KOH/g.
8. A method for improving adhesion and stonechip resistance of a paint system produced from a pigmented aqueous basecoat material, the method comprising:
introducing the polyether-based reaction product of claim 7 into the basecoat material.
9. A method for producing a multicoat paint system, the method comprising
(1) applying the basecoat material of claim 1 to a substrate,
(2) forming a basecoat from the basecoat material,
(3) applying a clearcoat material to the basecoat, and subsequently
(4) curing the basecoat together with the clearcoat.
10. The method of claim 9 , wherein the substrate is a metallic substrate coated with a cured electrocoat, and all coats applied to the electrocoat are cured jointly.
11. The method of claim 9 , wherein the substrate is a multicoat paint system which possesses defects.
12. A multicoat paint system, produced by the method of claim 9 .
13. A multicoat paint system with defects, produced by forming the defects on the multicoat paint system of claim 12 as a result of external mechanical influences.