Coating material with high scratch resistance
View Patent ↗The present invention relates to a coating material comprising at least one aliphatic or cycloaliphatic polyisocyanate having an NCO functionality of at least 2, preferably 2.8 to 6, optionally at least one binder, preferably a hydroxyl-containing binder, at least one adduct of an isocyanatotrialkoxysilane and a polyhydric alcohol, with more than 90, more preferably more than 95, most preferably more than 99 percent of the hydroxyl groups in the polyhydric alcohol having been converted by reaction with the isocyanatotrialkoxysilane, and less than 0.1 wt % of the isocyanate groups from the isocyanatotrialkoxysilane being reactive in the adduct, at least one catalyst selected from the group consisting of Lewis acids, phosphoric acid or phosphorous acid and esters thereof, blocked or non-blocked sulphonic acids, sulphuric acid, carboxylic acids having a melting point >60° C. and tetraalkylammonium carboxylates, optionally at least one auxiliary, preferably at least one further crosslinker, and/or adjuvant, and optionally organic solvents, and also to a process comprising providing, applying to a surface and curing the coating material, to a coating obtainable by curing the coating material, and to use of the coating material for coating a metal, glass, plastic or wood surface.
1. A coating material, comprising:
an aliphatic or cycloaliphatic polyisocyanate having an NCO functionality of at least 2,
optionally, a binder,
an adduct of an isocyanatotrialkoxysilane and a polyhydric alcohol,
wherein more than 99 percent of the hydroxyl groups in the polyhydric alcohol have been converted by reaction with the isocyanatotrialkoxysilane, and less than 0.1 wt % of the isocyanate groups from the isocyanatotrialkoxysilane are reactive in the adduct,
a catalyst selected from the group consisting of a Lewis acid, phosphoric acid, phosphorous acid and an ester thereof, blocked or non-blocked sulphonic acids, sulphuric acid, carboxylic acids having a melting point >60° C. and tetraalkylammonium carboxylates,
optionally, an auxiliary selected from the group consisting of an isocyanate-free crosslinker, an additive, a stabilizer and an adjuvant, and
optionally, an organic solvent.
2. The coating material according to claim 1 , wherein the fraction of the aliphatic or cycloaliphatic polyisocyanate, based on the sum of the aliphatic or cycloaliphatic polyisocyanate, the binder and the adduct is 15 to 40 weight percent.
3. The coating material according to claim 1 , wherein the fraction of the binder, based on the sum of the aliphatic or cycloaliphatic polyisocyanate, the binder and the adduct is 20 to 60 weight percent.
4. The coating material according to claim 1 , wherein the fraction of the adduct, based on the sum of the aliphatic or cycloaliphatic polyisocyanate, the binder and the adduct is 10 to 70 weight percent.
5. The coating material according to claim 1 , wherein the aliphatic or cycloaliphatic polyisocyanate is prepared by oligomerization of a diisocyanate.
6. The coating material according to claim 1 , which contains the binder, and wherein the binder is selected from the group consisting of a hydroxyl-containing polyester, a hydroxyl containing polyether, a hydroxyl-containing polyacrylate, a hydroxyl-containing polyurethane and mixtures thereof, and
wherein the binder has an OH number of 20 to 500 mg KOH/g.
7. The coating material according to claim 1 , wherein the adduct of an isocyanatotrialkoxysilane and polyhydric alcohol is an adduct from the reaction of an isocyanatotrialkoxysilane, which represents an alkyl radical substituted by at least one Si(OR 1 )(OR 2 )(OR 3 ) group and an isocyanate group, and a polyhydric alcohol,
wherein the alkyl radical substituted by the at least one Si(OR 1 )(OR 2 )(OR 3 ) group and an isocyanate group is a linear or branched alkane comprising 1 to 4 carbon atoms,
and wherein R 1 , R 2 and R 3 , in each case and independently of one another, are selected from the group consisting of methyl, ethyl, propyl and butyl.
8. The coating material according to claim 7 , wherein the isocyanatotrialkoxysilane is a compound of the formula (I),
OCN—(CH 2 ) n —Si(OR 1 )(OR 2 )(OR 3 ) (I),
wherein
n is 1, 2, 3, 4, 5 or 6, and
R 1 , R 2 and R 3 , in each case and independently of one another, are selected from the group consisting of methyl, ethyl and propyl.
9. The coating material according to claim 1 , wherein the polyhydric alcohol in the adduct is a non-cyclic polyhydric alcohol to an extent of at least 75%.
10. A process of coating a surface, comprising:
(1) applying the coating material of claim 1 to a surface, and
(2) curing the coating material.
11. The process according to claim 10 , wherein curing the coating material is carried out at a temperature of 10 to 200° C.
12. A coating obtained by the process according to claim 10 .
13. The coating material according to claim 1 , which consists essentially of:
the aliphatic or cycloaliphatic polyisocyanate,
optionally, the binder,
the adduct of an isocyanatotrialkoxysilane and a polyhydric alcohol,
the catalyst,
optionally, the auxiliary, and
optionally, the organic solvent.
14. The coating material according to claim 1 , which consists of:
the aliphatic or cycloaliphatic polyisocyanate,
optionally, the binder,
the adduct of an isocyanatotrialkoxysilane and a polyhydric alcohol,
the catalyst,
optionally, the auxiliary, and
optionally, the organic solvent.
15. The coating material according to claim 1 , wherein the catalyst consists of a component selected from the group consisting of a Lewis acid, phosphoric acid, phosphorous acid and an ester thereof, blocked or non-blocked sulphonic acids, sulphuric acid, carboxylic acids having a melting point >60° C., tetraalkylammonium carboxylates, and mixtures thereof.
16. The coating material according to claim 1 , wherein the catalyst consists of (1) a first component selected from the group consisting of a Lewis acid, phosphoric acid, phosphorous acid and an ester thereof, blocked or non-blocked sulphonic acids, sulphuric acid, carboxylic acids having a melting point >60° C., tetraalkylammonium carboxylates, and mixtures thereof, and, optionally, (2) a second component selected from the group consisting of metal complexes with chelate ligands, aluminium, zirconium, titanium and/or boron alkoxides and/or esters thereof, organic Sn(IV), Sn(II), Zn and Bi compounds, substituted phosphonic diesters and diphosphonic diesters, amine-blocked phosphoric esters, amine-blocked phosphoric acid catalysts, amine-blocked partial esters of phosphoric acid, and mixtures thereof.
17. The coating material according to claim 1 , which comprises
15 to 40 weight percent of the aliphatic or cycloaliphatic polyisocyanate having an NCO functionality of at least 2,
20 to 60 weight percent of the binder, and
10 to 70 weight percent of the adduct of an isocyanatotrialkoxysilane and a polyhydric alcohol,
based on the total weight of the aliphatic or cycloaliphatic polyisocyanate having an NCO functionality of at least 2, the binder and the adduct of an isocyanatotrialkoxysilane and a polyhydric alcohol.
18. The coating material according to claim 1 , which has a water content of at most 3 weight percent.