Two-component clear coat systems comprising polyaspartic acid ester
The present invention relates to two-component clear-coat systems comprising polyaspartic esters having primary amino groups and small amounts of dialkyl fumarates, to a process for the production thereof, and to the use thereof in the production of coatings for vehicle repair applications and to substrates coated therewith.
1. A process for producing a coating on a substrate comprising:
i) applying a two-component coating composition to at least part of a substrate to be coated; and
ii) curing the coating composition from step i),
wherein the two-component coating composition comprises
a) at least one polyaspartic ester-containing component A;
b) at least one polyisocyanate component B;
c) optionally one or more components C that are different from A and are reactive towards isocyanate groups;
d) at least one water scavenger and/or hydrolysis stabilizer (component D1); and
optionally other auxiliaries and additives (component D2),
wherein component A comprises
one or more polyaspartic esters of the general formula (I)
in which
X is an m-valent organic radical, optionally containing one or more heteroatoms, as can be obtained by removing the primary amino groups from a corresponding polyamine that has (cyclo) aliphatically or araliphatically attached primary amino groups and is in the molecular weight range from 60 to 6000 g/mol, and which may contain further functional groups that are reactive towards isocyanate groups and/or that are inert at temperatures of up to 100° C.,
R1 and R2 are identical or different organic radicals each having 1 to 18 carbon atoms,
m is an integer >1,
and one or more polyaspartic esters having a primary amino group that are of the general formula (II)
in which
n is m-1,
X and radicals R1 and R2 have the meanings defined above,
wherein a proportion of compounds of the general formula (II) corresponds to ≥4% to ≤20% of a total area measured as area % in a gas chromatogram (GC), wherein the total area corresponds to a sum of the areas in the GC of compounds of the two general formulas (I) and (II) and is equal to 100% and wherein dialkyl fumarates are present in component A in amounts from ≥0.01% to ≤1.2% by weight based on a total weight of component A, and
wherein the coating is a clear coat.
2. The process according to claim 1 , wherein the clear coat is a refinishing clear coat.
3. The process according to claim 1 , wherein the proportion of compounds of the general formula (II) is >4% of the total area in the GC (measured as area % in the gas chromatogram).
4. The process according to claim 1 , wherein the proportion of compounds of the general formula (II) is ≤15% of the total area in the GC (measured as area % in the gas chromatogram).
5. The process according to claim 1 , wherein dialkyl fumarates are present in component A in an amount from ≥0.01% to ≤1% by weight based on the total weight of component A.
6. The process according to claim 1 , wherein dialkyl fumarates are present in component A in an amount from ≥0.01% to ≤0.1% by weight based on the total weight of component A.
7. A substrate coated with a coating obtained in accordance with the process according to claim 1 .
8. The substrate coated with a coating according to claim 7 , wherein the clear coat is a refinishing clear coat.