Extremely scratch-resistant, highly elastic coating agents based on alkoxysilanes
The invention relates to coating agents, containing (A) at least 50 wt. %, (in relation to the content of non-volatile substances in said coating agent), of at least one compound (A1) and/or (A1′) comprising at least two reactive groups of formula (I): —X—SiR″x(OR′)3-x, in which R′=hydrogen, alkyl or cycloalkyl, whereby the carbon chain can be interrupted by non-adjacent oxygen, sulphur or NRa groups, Ra=alkyl, cycloalkyl, aryl or aralkyl, X=a linear and/or branched alkene or cycloalkene group comprising between 2 and 20 carbon atoms, R″=alkyl, cycloalkyl, aryl or aralkyl, whereby the carbon chain can be interrupted by non-adjacent oxygen, sulphur or NRa groups, and x=0 to 2, (B) a catalyst for cross-linking the —Si(OR′)3-x units, and (C) an organic solvent or a mixture of organic solvents. According to the invention, during the curing of the coating agents, the reactive groups (I) are cross-linked in such a way, that the following characteristics are noted during the nanoindentation test on the cured coating: elastic recovery of volume >86.5%; plastic deformation <3.5%; brittle deformation <10.0%.
1. A coated article comprising a substrate having thereon a cured layer of a coating material comprising
(A) at least 50% by weight, based on the amount of nonvolatile substances in the coating material, of at least one compound (A1′) comprising an adduct of polyisocyanate and alkoxysilane, and further wherein (A1′) comprises at least one reactive group of the formula II:
—NR—C(O)—N—(X—SiR″ x (OR′) 3-x ) n (X′—SiR″ y (OR′) 3-y ) m (R′″) o (II)
where
R is a hydrogen, alkyl, cycloalkyl, aryl or aralkyl, the carbon chain being uninterrupted or interrupted by nonadjacent oxygen, sulfur or NRa groups, where Ra is an alkyl, cycloalkyl, aryl or aralkyl,
X is a linear and/or branched alkylene or cycloalkylene radical of 2 to 20 carbon atoms,
X′ is a linear and/or branched alkylene or cycloalkylene radical of 2 to 20 carbon atoms,
R′ is hydrogen, alkyl or cycloalkyl, wherein the carbon chain of the alkyl cycloalkyl is uninterrupted or interrupted by nonadjacent oxygen, sulfur or NRa groups,
R″ is an alkyl, cycloalkyl, aryl or aralkyl, wherein the carbon chain of the alkyl, cycloakyl or aralkyl is uninterrupted or interrupted by nonadjacent oxygen, sulfur or NRa groups,
R′″ is an alkyl, cycloalkyl, aryl or aralkyl, wherein the carbon chain of the alkyl, cycloakyl or aralkyl is uninterrupted or interrupted by nonadjacent oxygen, sulfur or NRa groups,
n=0 to 2,
m=0 to 2,
o=0 or 1,
x=0 to 2,
m+n+o=2, and
y=0 to 2,
(B) a catalyst for the crosslinking of the —Si(OR′) 3-x units selected from the group consisting of boron chelates, boron alkoxides, boron esters, aluminum chelates, aluminum alkoxides, aluminum esters, titanium chelates, titanium alkoxides, titanium esters, zirconium chelates, zirconium alkoxides, zirconium esters and nanoparticles of compounds of the elements aluminum, silicon, titanium or zirconium, and
(C) an aprotic solvent or a mixture of aprotic solvents,
wherein the reactive groups (II) are crosslinked in the course of curing the coating material,
and further wherein said cured layer has a thickness of at least 40 μm and exhibits properties upon nanoindentation testing as follows:
a. elastic volume recovery >86.5%,
b. plastic deformation <3.5%,
c. brittle deformation <10.0%.
2. The coated article of claim 1 , wherein X is alkylene of 2 to 4 carbon atoms.
3. The coated article of claim 1 , wherein m+n=2 in formula II.
4. The coated article of claim 1 , wherein the aprotic solvent (C) has a water content of not more than 1% by weight, based on the solvent.
5. The coated article of claim 1 , wherein the coating material further comprises up to 40% by weight of a component (D), based on the amount of nonvolatile substances, wherein component (D) is able to form network nodes with the Si(OR′) 3 groups of component (A), with itself and/or with a further reactant.
6. The coated article of claim 1 wherein said cured layer is a clearcoat layer, and further comprising
a cured pigmented basecoat layer comprising a polymeric binder and a pigment between said clearcoat layer and said substrate.
7. A coated article comprising a substrate having thereon a cured layer of a coating material comprising
(A) at least 50% by weight, based on the amount of nonvolatile substances in the coating material, of at least one compound (A1′) comprising an adduct of polyisocyanate and alkoxysilane, and further wherein (A1′) comprises at least one reactive group of the formula II:
—NR—C(O)—N—(X—Si x (OR′) 3-x ) n (X′—SiR″ y (OR′) 3-y ) m (R′″) o (II)
where
R is a hydrogen, alkyl, cycloalkyl, aryl or aralkyl, the carbon chain being uninterrupted or interrupted by nonadjacent oxygen, sulfur or NRa groups, where Ra is an alkyl, cycloalkyl, aryl or aralkyl,
X is a linear and/or branched alkylene or cycloalkylene radical of 2 to 20 carbon atoms,
X′ is a linear and/or branched alkylene or cycloalkylene radical of 2 to 20 carbon atoms,
R′ is hydrogen, alkyl or cycloalkyl, wherein the carbon chain of the alkyl cycloalkyl is uninterrupted or interrupted by nonadjacent oxygen, sulfur or NRa groups,
R″ is an alkyl, cycloalkyl, aryl or aralkyl, wherein the carbon chain of the alkyl, cycloakyl or aralkyl is uninterrupted or interrupted by nonadjacent oxygen, sulfur or NRa groups,
R′″ is an alkyl, cycloalkyl, aryl or aralkyl, wherein the carbon chain of the alkyl, cycloakyl or aralkyl is uninterrupted or interrupted by nonadjacent oxygen, sulfur or NRa groups,
n=0 to 2,
m=0 to 2,
o=0 or 1,
x=0 to 2,
m+n+o=2, and
y=0 to 2,
(B) a catalyst, selected from the group consisting of boron chelates, boron alkoxides, boron esters, aluminum chelates, aluminum alkoxides, aluminum esters, titanium chelates, titanium alkoxides, titanium esters, zirconium chelates, zirconium alkoxides, zirconium esters and nanoparticles of compounds of the elements aluminum, silicon, titanium or zirconium, for the crosslinking of the —Si(OR′) 3-x units, and
(C) an aprotic solvent or a mixture of aprotic solvents,
wherein the reactive groups (II) are crosslinked in the course of curing the coating material,
and further wherein said cured layer has a thickness of at least 40 μm and exhibits properties upon nanoindentation testing as follows:
a. elastic volume recovery >86.5%,
b. plastic deformation <3.5%,
c. brittle deformation <10.0%.