USE OF POLYSILAZANES FOR COATING METAL STRIPS
A coating for coating a metal or a metal strip by the coil coating process comprising a solution of a polysilazane or a mixture of polysilazanes of the formula 1 —(SiR′R″-NR′″) n — (1) where R′, R″ and R′″ are identical or different and independently of one another are hydrogen or an unsubstituted or substituted alkyl, aryl, vinyl or (trialkoxysilyl)alkyl radical, n being an integer such that the polysilazane or mixture of polysilazanes has a number-average molecular weight of 150 to 150 000 g/mol, in at least one solvent and at least one catalyst and the solution of a polysilazane or a mixture of polysilazanes contains 1% to 50% by weight of the polysilazane or mixture of polysilazanes.
1 . A coating for coating a metal or a metal strip by the coil coating process comprising a solution of a polysilazane or a mixture of polysilazanes of the formula 1
—SiR′R″-NR′″) n — (1)
where R′, R″ and R′″ are identical or different and independently of one another are hydrogen or an unsubstituted or substituted alkyl, aryl, vinyl or (trialkoxysilyl)alkyl radical, n being an integer such that the polysilazane or mixture of polysilazanes has a number-average molecular weight of 150 to 150 000 g/mol, in at least one solvent and at least one catalyst and the solution of a polysilazane or a mixture of polysilazanes contains 1% to 50% by weight of the polysilazane or mixture of polysilazanes.
2 . The coating as claimed in claim 1 , wherein R′, R″, and R′, R′″ independently of one another are a radical selected from the group consisting of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tertbutyl, phenyl, vinyl, 3-(triethoxysilyl)propyl, and 3-(trimethoxysilyl)propyl.
3 . The coating as claimed in claim 1 wherein the solution of a polysilazane or mixture of polysilazanes is a perhydropolysilazane of formula 2
4 . The coating as claimed in claim 1 , wherein the solution of a polysilazane or mixture of polysilazanes is of the formula (3)
—SiR′R″-NR′″) n —(SiR*R**-NR***) p — (3)
where R′, R″, R′″, R*, R** and R*** independently of one another are hydrogen or an unsubstituted or substituted alkyl, aryl, vinyl or (trialkoxysilyl)alkyl radical, n and p being integers.
5 . The coating as claimed in claim 4 , wherein R′, R′″, and R*** are hydrogen and R″, R*, and R** are methyl.
6 . The coating as claimed in claim 1 , wherein the solution of a polysilazane or mixture of polysilazanes is of the formula (4)
—SiR′R″-NR′″) n —(SiR*R**-NR***) p —(SIR 1 ,R 2 -NR 3 ) q — (4)
where R′, R″, R′″, R*, R**, R***, R 1 , R 2 , and R 3 independently of one another are hydrogen or an unsubstituted or substituted alkyl, aryl, vinyl or (trialkoxysilyl)alkyl radical, n, p and q being integers.
7 . The coating as claimed in claim 6 , wherein R′, R′″, and R*** are hydrogen, R″, R*, R**, and R 2 are methyl, R 3 is (triethoxysilyl)propyl, and R 1 is alkyl or hydrogen.
8 . The coating as claimed in claim 3 , wherein the perhydropolysilazane solution contains 0.001 to 10% by weight of at least one catalyst.
9 . The coating as claimed in claim 1 , wherein the at least one catalyst is selected from the group consisting of organic amines, acids, metals, metal salts and mixtures thereof.
10 . The coating as claimed in claim 1 , wherein the at least one solvent is anhydrous organic solvent containing no reactive groups.
11 . A metal or a metal strip coated with a coating as claimed in claim 1 .
12 . The metal or metal strip as claimed in claim 11 , wherein the metal or metal strip is selected from the group consisting of alloys of aluminum, steel, galvanized steel, zinc, magnesium and titanium.
13 . The coating as claimed in claim 4 , wherein R′, R′R″, and R*** are hydrogen, R″ and R* are methyl, and R** is vinyl.
14 . The coating as claimed in claim 4 , wherein R′, R′″, R*, and R*** are hydrogen and R″ and R** are methyl.
15 . A metal or metal strip having at least one surface, wherein the at least one surface is coated with a coating as claimed in claim 1 .