High-solids binder combinations for scratch-resistant topcoats

1. Binder compositions comprising

A) one or more hydroxy-functional polyacrylate resins,

B) one or more ε-caprolactone-based polyols having an average hydroxy functionality ≧2 and a number-average molecular weight of from 119 to 2000 g/mol, and

C) one or more crosslinkers reactive with OH groups and having an average functionality>1,

wherein the polyacrylate resins of component A) are prepared by copolymerizing:

a) 0.4–10 parts by weight of one or more, optionally functional, polybutadienes having a number-average molecular weight of from 500 to 10 000 g/mol and containing at least 10 mol % of 1,2-pendant vinylic double bonds, based on all of the vinylic double bonds present in the polybutadiene,

b) 1–30 parts by weight of one or more unsaturated aromatic monomers selected from the group consisting of styrene, α-methylstyrene and vinyltoluene,

c) 30–80 parts by weight of one or more hydroxyalkyl esters of acrylic or methacrylic acid having primary hydroxyl groups,

d) 0–30 parts by weight of one or more cycloaliphatic esters of acrylic or methacrylic acid and C 3 to C 12 monoalcohols,

e) 10–60 parts by weight of one or more aliphatic esters of acrylic or methacrylic acid and C 1 to C 8 monoalcohols,

f) 0.1–5 parts by weight of one or more α,β-unsaturated C 3 –C 7 monocarboxylic or dicarboxylic acids or of one or more monoesters of maleic acid or fumaric acid and C 1 to C 14 monoalchols, and

g) 0–30 parts by weight of other copolymerizible compounds different from the compounds of components a)–f),

the sum of the parts by weight of components a) to g) being in each case 100.

2. The binder compositions according to claim 1 , wherein the copolymers of component A) are composed of:

a) 0.4–5 parts by weight of one or more, optionally functional, polybutadienes having a number-average molecular weight of from 500 to 2000 g/mol and containing at least 40 mol % of 1,2-pendant vinylic double bonds, based on all the vinylic double bonds present in the polybutadiene,

b) 5–20 parts by weight of styrene,

c) 40–60 parts by weight of hydroxyethyl acrylate, hydroxyethyl methacrylate or mixtures thereof,

d) 0–15 parts by weight of one or more compounds from the group consisting of isobornyl acrylate, isobornyl methacrylate, cyclohexyl (meth)acrylate, 3,5,5-trimethylcyclohexyl (meth)acrylate and 4-tert-butylcyclohexyl (meth)acrylate,

e) 25–45 parts by weight of one or more esters of acrylic or methacrylic acid and aliphatic C 1 to C 4 monoalcohols,

f) 0.5–2 parts by weight of acrylic acid, methacrylic acid or mixtures thereof, and

g) 0–15 parts by weight of one or more compounds from the group consisting of hydroxypropyl (meth)acrylate, vinyl esters of aliphatic, optionally branched C 1 to C 9 monocarboxylic acids, dialkyl or dicycloalkyl esters of maleic or fumaric acid and C 3 to C 6 monoalcohols, the sum of the parts by weight of components a) to g) being 100.

3. The binder compositions according to claim 1 , wherein the ε-caprolactone-based polyols of component B) have an average OH functionality of 3–8, a number-average molecular weight of 119 to 1500 g/mol and a hydroxyl content of 9.0 to 36% by weight.

4. The binder compositions according to claim 1 , wherein the ε-caprolactone-based polyols of component B) have been modified by reaction with diphenyl carbonate or dimethyl carbonate.

5. The binder compositions according to claim 1 , wherein the crosslinker(s) of component C) include polyisocyanates containing urethane, uretdione, allophanate, biuret, iminooxadiazindione and/or isocyanurate groups and having an NCO group content of 5 to 25% by weight, an average NCO functionality of 2.5 to 5.0, the NCO groups being free or wholly or partly blocked.

6. The binder compositions according to claim 1 , wherein the mixture of components A) to C) is composed of 40 to 60 parts by weight of A), 2 to 20 parts by weight of B) and 30 to 50 parts by weight of C), the stated amounts adding up to 100.

7. A method of producing coatings, adhesive bonds or mouldings comprising adding one or more auxiliaries and/or additives selected from the group consisting of plasticizers, pigments, fillers, catalysts, levelling agents, thickeners, stabilizers, adhesion promoters, light stabilizers and UV absorbers to the binder composition according to claim 1 .

8. Coatings obtainable from binder compositions according to claim 1 .

9. Substrates coated with coatings according to claim 8 .

10. The binder composition according to claim 1 further comprising one or more solvents selected from the group consisting of aliphatic hydrocarbons, cycloaliphatic hydrocarbons, aromatic hydrocarbons, esters, ethers, and ketones.

11. The binder composition according to claim 10 , wherein the solvents are selected from toluene, xylene, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, n-hexyl acetate, 2-ethylhexyl acetate, ethyl propionate, butyl propionate, pentyl propionate, ethylene glycol monoethyl ether acetate, ethylene glycol monomethyl ether acetate, ethylene glycol acetate monomethyl ether, ethylene glycol acetate monoethyl ether, ethylene glycol acetate monobutyl ether, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl n-amyl ketone, and mixtures thereof.

12. The binder composition according to claim 1 further comprising one or more auxiliaries and/or additives selected from the group consisting of plasticizers, pigments, fillers, catalysts, levelling agents, thickeners, stabilizers, adhesion promoters, light stabilizers and UV absorbers.

13. The binder composition according to claim 12 , wherein the auxiliaries and/or additives are selected from the group consisting of tricresyl phosphate, phthalic diesters, chlorinated paraffins, titanium dioxide, barium sulfate, chalk, carbon block; catalysts, N,N-dimethylbenzylamine, N-methylmorpholine, zinc octoate, tin(II) octoate, dibutyltin dilaurate, substituted phenols; silanes with organic functional groups, sterically hindered amines, bis(1,2,2,6,6-pentamethylpiperid-4-yl) sebacate, bis(2,2,6,6-tetramethylpiperid-4-yl) sebacate, bis(1,2,2,6,6-pentamethylpiperid-4-yl) n-butyl(3,5-di-tert-butyl-4-hydroxybenzyl)malonate and mixtures thereof.

14. The binder compositions according to claim 2 , wherein the ε-caprolactone-based polyols of component B) have an average OH functionality of 3–8, a number-average molecular weight of 119 to 1500 g/mol and a hydroxyl content of 9.0 to 36% by weight.

15. The binder compositions according to claim 2 , wherein the ε-caprolactone-based polyols of component B) have been modified by reaction with diphenyl carbonate or dimethyl carbonate.

16. The binder compositions according to claim 2 , wherein the crosslinker(s) of component C) include polyisocyanates containing urethane, uretdione, allophanate, biuret, iminooxadiazindione and/or isocyanurate groups and having an NCO group content of 5 to 25% by weight, an average NCO functionality of 2.5 to 5.0, the NCO groups being free or wholly or partly blocked.

17. The binder compositions according to claim 2 , wherein the mixture of components A) to C) is composed of 40 to 60 parts by weight of A), 2 to 20 parts by weight of B) and 30 to 50 parts by weight of C), the stated amounts adding up to 100.

18. A method of producing coatings, adhesive bonds or mouldings comprising adding one or more auxiliaries and/or additives selected from the group consisting of plasticizers, pigments, fillers, catalysts, levelling agents, thickeners, stabilizers, adhesion promoters, light stabilizers and UV absorbers to the binder composition according to claim 2 .

19. Coatings obtainable from binder compositions according to claim 2 .

20. Substrates coated with coatings according to claim 19 .