NELL SERGEJ (DE)
LACHNIT PATRIZIA (DE)
KRASEMANN THOMAS (DE)
WO2007028511A2 | 2007-03-15 |
CN108727979A | 2018-11-02 | |||
US20030083453A1 | 2003-05-01 | |||
US20200199406A1 | 2020-06-25 | |||
CN108727979A | 2018-11-02 | |||
EP3546498A1 | 2019-10-02 |
Claims 1. A coating composition, comprising: (i) a silazane polymer (A); (ii) a silane coupling agent (B); and (iii) inorganic nanoparticles (C); wherein the weight ratio [A]:[B] of the silazane polymer (A) to the silane coupling (B) is in the range from 75:25 to 40:60, and the weight ratio [A+B]:[C] of the silazane polymer (A) and the silane coupling agent (B) to the inorganic nanoparticles (C) is in the range from 80:20 to 50:50. 2. The coating composition according to claim 1, wherein the weight ratio [A]:[B] of the silazane polymer (A) to the silane coupling (B) is in the range from 66:34 to 45:55, and the weight ratio [A+B]:[C] of the silazane polymer (A) and the silane coupling agent (B) to the inorganic nanoparticles (C) is in the range from 73:27 to 55:45. 3. The coating composition according to claim 1, wherein the weight ratio [A]:[B] of the silazane polymer (A) to the silane coupling (B) is in the range from 60:40 to 50:50, and the weight ratio [A+B]:[C] of the silazane polymer (A) and the silane coupling agent (B) to the inorganic nanoparticles (C) is in the range from 70:30 to 60:40. 4. The coating composition according to one or more of claims 1 to 3, wherein the silazane polymer (A) comprises a repeating unit M1 represented by Formula (1): -[SiR1R2-NR3-] Formula (1) wherein R1, R2 and R3 are the same or different from each other and independently selected from hydrogen, an organic group, or a hetero-organic group. 5. The coating composition according to claim 4, wherein R1 and R2 are the same or different from each other and independently selected from hydrogen, alkyl having 1 to 30 carbon atoms, alkenyl having 2 to 30 carbon atoms, or aryl having 2 to 30 carbon atoms, wherein one or more hydrogen atoms bonded to carbon atoms may be replaced by fluorine; and R3 is selected from hydrogen, alkyl having 1 to 30 carbon atoms, alkenyl having 2 to 30 carbon atoms, or aryl having 2 to 30 carbon atoms, wherein one or more hydrogen atoms bonded to carbon atoms may be replaced by fluorine. 6. The coating composition according to claim 4 or 5, wherein the silazane polymer (A) further comprises a repeating unit M2 represented by Formula (2): -[SiR4R5-NR6-] Formula (2) wherein R4, R5 and R6 are the same or different from each other and independently selected from hydrogen, an organic group, or a hetero-organic group. 7. The coating composition according to claim 6, wherein R4 and R5 are the same or different from each other and independently selected from hydrogen, alkyl having 1 to 30 carbon atoms, alkenyl having 2 to 30 carbon atoms, or aryl having 2 to 30 carbon atoms, wherein one or more hydrogen atoms bonded to carbon atoms may be replaced by fluorine; and R6 is selected from hydrogen, alkyl having 1 to 30 carbon atoms, alkenyl having 2 to 30 carbon atoms, or aryl having 2 to 30 carbon atoms, wherein one or more hydrogen atoms bonded to carbon atoms may be replaced by fluorine. 8. The coating composition according to one or more of claims 1 to 7, wherein the silane coupling agent (B) comprises one or more alkoxy silyl groups. 9. The coating composition according to one or more of claims 1 to 8, wherein the silane coupling agent (B) is represented by Formula (a): Formula (a) wherein Z is a structural unit comprising one or more carbon and/or silicon atoms; RI is at each occurrence independently from each other a linear alkoxy group having 1 to 20 carbon atoms, a branched alkoxy group having 3 to 20 carbon atoms, or a cyclic alkoxy group having 3 to 20 carbon atoms, which optionally contains one or more -O- and/or -Si(CH3)2- groups; RII is at each occurrence independently from each other a linear alkyl group having 1 to 20 carbon atoms, a branched alkyl group having 3 to 20 carbon atoms, or a cyclic alkyl group having 3 to 20 carbon atoms; k is 0, 1 or 2; and n is 1, 2, 3 or 4. 10. The coating composition according to one or more of claims 1 to 9, wherein the silane coupling agent (B) is represented by one of Formulae (b) to (e): wherein Xb is selected from the list consisting of (CH3)2N-, [HO-(CH2)m]2N-, AcO-, CH3(CH2)m-NH-, CH3-NH-, Cl-, H2C=C(CH3)-CH2-NH-, H2C=C(CH3)-CO-O-, H2C=C(CH3)-O-CH2-CH(OH)-CH2-NH-, H2C=CH-, H2C=CH-CH2-NH-, H2C=CH-CO-CH2-CH(OH)-CH2-NH-, H2C=CH-CO-O-, H2N-, H2N-(CH2)m-NH-, H2N-(CH2)m-NH-(CH2)n-, H2N-(CH2)m-NH-(CH2)n-NH-, H2N-(CH2)m-NH-C4H6-, H2N-(CH2)mNH-CH2-C4H6-, H2N-(CH2)m-O-C(CH3)2-CH=CH-, H2N-C6H4-, H2N-C6H4-O-, H3C-, H3C-(CH2)m-, H3C-(CH2)m-O-, H3CO-, HO-, HS-, NCS-, Ph2N-, Ph-CO-O-, Ph-NH-, and m is an integer from 1 to 10; n is an integer from 1 to 10; Xc is selected from the list consisting of -(CH2)p-, -NH-, -NH-(CH2)p-NH-, -O-, -S-, -S2-, -S3-, -S4-, -Si(CH3)2-, and -Si(CH3)2-O-Si(CH3)2-; p is an integer from 1 to 20; Xd is selected from the list consisting of , and Xe is selected from the list consisting of ; Y is absent or a linear alkylene group having 1 to 20 carbon atoms, a branched alkylene group having 3 to 20 carbon atoms, or a cyclic alkylene group having 3 to 20 carbon atoms; RI is at each occurrence independently from each other a linear alkoxy group having 1 to 20 carbon atoms, a branched alkoxy group having 3 to 20 carbon atoms, or a cyclic alkoxy group having 3 to 20 carbon atoms, which optionally contains one or more -O- and/or -Si(CH3)2- groups; RII is at each occurrence independently from each other a linear alkyl group having 1 to 20 carbon atoms, a branched alkyl group having 3 to 20 carbon atoms, or a cyclic alkyl group having 3 to 20 carbon atoms; and k is 0, 1 or 2. 11. The coating composition according to one or more of claims 1 to 10, wherein the silane coupling agent (B) is selected from the list consisting of: (i) monofunctional silane coupling agents selected from (3-acryloxypropyl)dimethylmethoxysilane, (3-acryloxypropyl)methyldimethoxysilane, (3-acryloxypropyl)trimethoxysilane, (aminoethylaminomethyl)phenethyltrimethoxysilane, (methacryloxymethyl)dimethylethoxysilane, 3-(2-aminoethylamino)propylmethyldiethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(3-aminopropoxy)-3,3-dimethyl-1-propenyl-trimethoxysilane, 3-(m-aminophenoxy)propyltrimethoxysilane, 3-(N-allylamino)propyltrimethoxysilane, 3-(trimethoxysilyl)-1-propanethiol, 3-aminopropyldimethylethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltris(methoxyethoxyethoxy)silane, 3-chloropropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-methacryloxypropyldimethylethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltris(methoxyethoxy)silane, 4-aminobutyltriethoxysilane, 6-ethyl-6-(2-methoxyethoxy)-2,5,7,10-tetraoxa-6-silaundecane, acetoxymethyltriethoxysilane, acetoxymethyltrimethoxysilane, acetoxypropyltrimethoxysilane, benzoyloxypropyltrimethoxysilane, hydroxymethyltriethoxysilane, m-aminophenyltrimethoxysilane, methacryloxymethyltriethoxysilane, methacryloxymethyltrimethoxysilane, N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(3-acryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane, N-(6-aminohexyl)aminopropyltrimethoxysilane, N-(n-butyl)-3-aminopropyltrimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, N1-(3-trimethoxysilylpropyl)diethylenetriamine, N-methylaminopropylmethyldimethoxysilane, N-methylaminopropyltrimethoxysilane, N-phenylaminomethyltriethoxysilane, N-phenylaminopropyltrimethoxysilane, p-aminophenyltrimethoxysilane, tetraethoxysilane, triethoxy(3-thiocyanato)propylsilane, triethoxy(octyl)silane, trimethoxymethylsilane, and vinyltriethoxysilane; (ii) difunctional silane coupling agents selected from 1-(triethoxysilyl)-2-(diethoxymethylsilyl)ethane, 1-(trimethoxysilyl)-2-(dimethylmethoxysilyl)ethane, 1-(trimethoxysilyl)-2-(methyldimethoxysilyl)ethane, 1,2-bis(dimethylmethoxysilyl)ethane, 1,2-bis(methyldimethoxysilyl)ethane, 1,2-bis(trimethoxysilyl)ethane, 1,3-bis(triethoxysilylethyl)-1,1,3,3-tetramethyldisiloxane, 1,3-bis(trimethoxysilylethyl)-1,1,3,3-tetramethyldisiloxane, 1,6-bis(triethoxysilyl)hexane, 1,6-bis(trimethoxysilyl)hexane, 1,8-bis(triethoxysilyl)octane, 1,8-bis(trimethoxysilyl)octane, bis(3-(triethoxysilyl)-1-propyl)disulfide, bis(3-(trimethoxysilyl)-1-propyl)disulfide, bis(3-(trimethoxysilyl)-1-propyl)tetrasulfide, bis[2-(triethoxysilyl)ethyl]dimethylsilane, bis[3-(triethoxysilyl)propyl]amine, bis[3-(triethoxysilyl)propyl]sulfide, bis[2-(trimethoxysilyl)ethyl]dimethylsilane, bis[3-(trimethoxysilyl)propyl]amine, bis[3-(trimethoxysilyl)propyl]sulfide, bis[3-(triethoxysilyl)propyl]ether, bis[3-(trimethoxysilyl)propyl]ether, and N,N’-bis[3-(trimethoxysilyl)propyl]ethylenediamine; (iii) trifunctional silane coupling agents selected from tris(triethoxysilylethyl)methylsilane, tris(triethoxysilylethyldimethylsiloxy)methylsilane, tris(triethoxysilylpropyl)amine, tris(triethoxysilylpropyl)methylsilane, tris(trimethoxysilylethyl)methylsilane, tris(trimethoxysilylethyldimethylsiloxy)methylsilane, tris(trimethoxysilylpropyl)amine, and tris(trimethoxysilylpropyl)methylsilane; and (iv) tetrafunctional silane coupling agents selected from tetrakis(triethoxysilylethyl)silane, tetrakis(triethoxysilylpropyl)silane, and tetrakis(trimethoxysilylpropyl)silane. 12. The coating composition according to one or more of claims 1 to 11, wherein the inorganic nanoparticles (C) are selected from the list consisting of carbides, diamond, nitrides, oxides, silicates, sulfates, sulfides, sulfites, and titanates which are optionally surface-modified with a capping agent. 13. The coating composition according to one or more of claims 1 to 12, wherein the inorganic nanoparticles (C) are selected from the list consisting of boron carbide, silicon carbide, titanium carbide, tungsten carbide, diamond, boron nitride, silicon nitride, titanium nitride, aluminum oxide, molybdenum oxide, silica, titania and zirconia. 14. The coating composition according to one or more of claims 1 to 13, wherein the inorganic nanoparticles (C) have a particle diameter in the range from 1 to 100 nm, more preferably from 5 to 60 nm, even more preferably from 10 to 40 nm, and most preferably from 10 to 25 nm. 15. The coating composition according to one or more of claims 1 to 14, wherein the coating composition further comprises one or more solvents. 16. A method for preparing a coated article, wherein the method comprises the following steps: (a) applying a coating composition according to one or more of claims 1 to 15 to a surface of an article; and (b) curing said coating composition to obtain a coated article. 17. A coated article, obtainable by the method according to claim 16. 18. Use of a coating composition according to one or more of claims 1 to 15 for forming a hard coating on a surface of a base material. |
Formula (d) Formula (e) wherein X b is selected from the list consisting of (CH 3 ) 2 N-, [HO-(CH 2 ) m ] 2 N-, AcO-, CH 3 (CH 2 ) m -NH-, CH 3 -NH-, Cl-, H 2 C=C(CH 3 )-CH 2 -NH-, H 2 C=C(CH 3 )-CO-O-, H 2 C=C(CH 3 )-O-CH 2 -CH(OH)-CH 2 -NH-, H 2 C=CH-, H 2 C=CH-CH 2 -NH-, H 2 C=CH-CO-CH 2 -CH(OH)-CH 2 -NH-, H 2 C=CH-CO-O-, H 2 N-, H 2 N-(CH 2 ) m -NH-, H 2 N-(CH 2 ) m -NH-(CH 2 ) n -, H 2 N-(CH 2 ) m -NH-(CH 2 ) n -NH-, H 2 N-(CH 2 ) m -NH-C4H6-, H 2 N-(CH 2 ) m NH-CH 2 -C 4 H 6 -, H 2 N-(CH 2 ) m -O-C(CH 3 ) 2 -CH=CH-, H 2 N-C 6 H 4 -, H 2 N-C 6 H 4 -O-, H 3 C-, H 3 C-(CH 2 ) m -, H 3 C-(CH 2 ) m -O-, H 3 CO-, HO-, HS-, NCS-, Ph 2 N-, Ph-CO-O-, Ph-NH-, and ; m is an integer from 1 to 10, preferably 1 to 6, more preferably 1 to 3; n is an integer from 1 to 10, preferably 1 to 6, more preferably 1 to 3; X c is selected from the list consisting of -(CH 2 ) p -, -NH-, -NH-(CH 2 ) p -NH-, -O-, -S-, -S 2 -, -S 3 -, -S 4 -, -Si(CH 3 ) 2 -, and -Si(CH 3 ) 2 -O-Si(CH 3 ) 2 -; p is an integer from 1 to 20, preferably 1 to 12, more preferably 1 to 8; X d is selected from the list consisting of , and X e is selected from the list consisting of ; Y is absent or a linear alkylene group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, a branched alkylene group having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms, or a cyclic alkylene group having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 6 carbon atoms; R I is at each occurrence independently from each other a linear alkoxy group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, a branched alkoxy group having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms, or a cyclic alkoxy group having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 6 carbon atoms, which optionally contains one or more -O- and/or -Si(CH 3 ) 2 - groups; R II is at each occurrence independently from each other a linear alkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, a branched alkyl group having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms, or a cyclic alkyl group having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 6 carbon atoms; and k is 0, 1 or 2, preferably 0. The serpentine line in the above structures for X d and X e denotes a binding site. Preferred silane coupling agents (B) of Formula (b) are selected from the list consisting of: (3-acryloxypropyl)dimethylmethoxysilane, (3-acryloxypropyl)methyldimethoxysilane, (3-acryloxypropyl)trimethoxysilane, (aminoethylaminomethyl)phenethyltrimethoxysilane, (methacryloxymethyl)dimethylethoxysilane, 3-(2-aminoethylamino)propylmethyldiethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(3-aminopropoxy)-3,3-dimethyl-1-propenyl-trimethoxysilane, 3-(m-aminophenoxy)propyltrimethoxysilane, 3-(N-allylamino)propyltrimethoxysilane, 3-(trimethoxysilyl)-1-propanethiol, 3-aminopropyldimethylethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltris(methoxyethoxyethoxy)silane, 3-chloropropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-methacryloxypropyldimethylethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltris(methoxyethoxy)silane, 4-aminobutyltriethoxysilane, 6-ethyl-6-(2-methoxyethoxy)-2,5,7,10-tetraoxa-6-silaundecane , acetoxymethyltriethoxysilane, acetoxymethyltrimethoxysilane, acetoxypropyltrimethoxysilane, benzoyloxypropyltrimethoxysilane, hydroxymethyltriethoxysilane, m-aminophenyltrimethoxysilane, methacryloxymethyltriethoxysilane, methacryloxymethyltrimethoxysilane, N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(3-acryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane, N-(6-aminohexyl)aminopropyltrimethoxysilane, N-(n-butyl)-3-aminopropyltrimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, N 1 -(3-trimethoxysilylpropyl)diethylenetriamine, N-methylaminopropylmethyldimethoxysilane, N-methylaminopropyltrimethoxysilane, N-phenylaminomethyltriethoxysilane, N-phenylaminopropyltrimethoxysilane, p-aminophenyltrimethoxysilane, tetraethoxysilane, triethoxy(3-thiocyanato)propylsilane, triethoxy(octyl)silane, trimethoxymethylsilane, and vinyltriethoxysilane. Preferred silane coupling agents (B) of Formula (c) are selected from the list consisting of: 1-(triethoxysilyl)-2-(diethoxymethylsilyl)ethane, 1-(trimethoxysilyl)-2-(dimethylmethoxysilyl)ethane, 1-(trimethoxysilyl)-2-(methyldimethoxysilyl)ethane, 1,2-bis(dimethylmethoxysilyl)ethane, 1,2-bis(methyldimethoxysilyl)ethane, 1,2-bis(trimethoxysilyl)ethane, 1,3-bis(triethoxysilylethyl)-1,1,3,3-tetramethyldisiloxane, 1,3-bis(trimethoxysilylethyl)-1,1,3,3-tetramethyldisiloxane, 1,6-bis(triethoxysilyl)hexane, 1,6-bis(trimethoxysilyl)hexane, 1,8-bis(triethoxysilyl)octane, 1,8-bis(trimethoxysilyl)octane, bis(3-(triethoxysilyl)-1-propyl)disulfide, bis(3-(trimethoxysilyl)-1-propyl)disulfide, bis(3-(trimethoxysilyl)-1-propyl)tetrasulfide, bis[2-(triethoxysilyl)ethyl]dimethylsilane, bis[3-(triethoxysilyl)propyl]amine, bis[3-(triethoxysilyl)propyl]sulfide, bis[2-(trimethoxysilyl)ethyl]dimethylsilane, bis[3-(trimethoxysilyl)propyl]amine, bis[3-(trimethoxysilyl)propyl]sulfide, bis[3-(triethoxysilyl)propyl]ether, bis[3-(trimethoxysilyl)propyl]ether, and N,N’-bis[3-(trimethoxysilyl)propyl]ethylenediamine. Preferred silane coupling agents (B) of Formula (d) are selected from the list consisting of: tris(triethoxysilylethyl)methylsilane, tris(triethoxysilylethyldimethylsiloxy)methylsilane, tris(triethoxysilylpropyl)amine, tris(triethoxysilylpropyl)methylsilane, tris(trimethoxysilylethyl)methylsilane, tris(trimethoxysilylethyldimethylsiloxy)methylsilane, tris(trimethoxysilylpropyl)amine, and tris(trimethoxysilylpropyl)methylsilane. Preferred silane coupling agents (B) of Formula (e) are selected from the list consisting of: tetrakis(triethoxysilylethyl)silane, tetrakis(triethoxysilylpropyl)silane, and tetrakis(trimethoxysilylpropyl)silane. Particularly preferred silane coupling agents (B) are 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, bis[3-(trimethoxysilyl)propyl]amine, bis[3-(triethoxysilyl)propyl]amine, tris(trimethoxysilylpropyl)amine and tris(triethoxysilylpropyl)amine. It is preferred that the coating composition according to the present invention comprises one of the above-mentioned silane coupling agents or two, three or more of the above-mentioned silane coupling agents in combination. Inorganic nanoparticles (C) In a preferred embodiment of the present invention, the inorganic nanoparticles (C) are selected from the list consisting of carbides, diamond, nitrides, oxides, silicates, sulfates, sulfides, sulfites, and titanates which are optionally surface-modified with a capping agent. In a more preferred embodiment of the present invention, the inorganic nanoparticles (C) are selected from the list consisting of boron carbide, silicon carbide, titanium carbide, tungsten carbide, diamond, boron nitride, silicon nitride, titanium nitride, aluminum oxide, molybdenum oxide, silica, titania and zirconia. In a most preferred embodiment of the present invention, the inorganic nanoparticles (C) are silica (SiO 2 ). The coating composition according to the present invention may comprise one, two or more types of the above-mentioned inorganic nanoparticles (C). Preferably, the inorganic nanoparticles (C) have a particle diameter of ≤ 100 nm, more preferably ≤ 60 nm, even more preferably ≤ 40 nm, and most preferably ≤ 25 nm. Preferably, the inorganic nanoparticles (C) have a particle diameter in the range from 1 to 100 nm, more preferably from 5 to 60 nm, even more preferably from 10 to 40 nm, and most preferably from 10 to 25 nm. The particle diameter can be determined by any standard method known to the skilled person such as e.g. dynamic light scattering. Devices and methods for determining the size of nanoscale particles are available, for example, from Malvern Panalytical (https://www.malvernpanalytical.com/en/products/product-rang e/zetasizer- range/zetasizer-advance-range/zetasizer-pro). Weight ratios In the coating composition according to the present invention the weight ratio [A]:[B] of the silazane polymer (A) to the silane coupling (B) is in the range from 75:25 to 40:60, and the weight ratio [A+B]:[C] of the silazane polymer (A) and the silane coupling agent (B) to the inorganic nanoparticles (C) is in the range from 80:20 to 50:50. It is preferred that the weight ratio [A]:[B] of the silazane polymer (A) to the silane coupling (B) is in the range from 66:34 to 45:55, and the weight ratio [A+B]:[C] of the silazane polymer (A) and the silane coupling agent (B) to the inorganic nanoparticles (C) is in the range from 73:27 to 55:45. It is more preferred that the weight ratio [A]:[B] of the silazane polymer (A) to the silane coupling (B) is in the range from 60:40 to 50:50, and the weight ratio [A+B]:[C] of the silazane polymer (A) and the silane coupling agent (B) to the inorganic nanoparticles (C) is in the range from 70:30 to 60:40. Further components It is preferred that the coating composition according to the present invention comprises one or more solvents. Suitable solvents are organic solvents such as, for example, aliphatic and/or aromatic hydrocarbons, which may be halogenated, such as 1-chloro-4-(trifluoromethyl)benzene, esters such as ethyl acetate, n-butyl acetate, propylene glycol methyl ether acetate, or tert-butyl acetate, ketones such as acetone or methyl ethyl ketone, ethers such as tetrahydrofuran or dibutyl ether, and also mono- or polyalkylene glycol dialkyl ethers (glymes), or alpha alkyl omega alkyl carbonyl mono or poly glycols such as for example butyldiglycol acetate, or mixtures thereof. Moreover, the coating composition according to the present invention may comprise one or more additives, preferably selected from the list consisting of additives influencing evaporation behavior, additives influencing film formation, adhesion promoters, anti-corrosion additives, crosslinking agents, dispersants, fillers, functional pigments (e.g. for providing functional effects such as electric or thermal conductivity, magnetic properties, etc.), optical pigments (e.g. for providing optical effects such as color, refractive index, pearlescent effect, etc.), particles reducing thermal expansion, primers, rheological modifiers (e.g. thickeners), surfactants (e.g. wetting and leveling agents or additives for improving hydro- or oleophobicity and anti-graffiti effects), viscosity modifiers, and other kinds of resins or polymers. It is possible to accelerate the curing of the coating composition by the addition of one or more catalysts. Examples of useful catalysts are Lewis acids such as boron-, aluminum-, tin- or zinc-alkyls, aryls or carboxylates, Brönsted acids such as carboxylic acids, bases such as primary, secondary or tertiary amines or phosphazenes, or metal salts such as Pd, Pt, Al, B, Sn or Zn salts of carboxylates, acetylacetonates or alkoxylates. If silazanes having both Si-H and Si-CH=CH 2 groups are used, well known hydrosilylation catalysts such as Pt or Pd salts or complexes can be used. If silazanes having only Si-CH=CH 2 or both Si-H and Si-CH=CH 2 groups are used, UV or thermal radical initiators like peroxides or azo compounds can be used. In a preferred embodiment, the coating composition according to the present invention comprises one or more of the above-mentioned catalysts. It is to be understood that the skilled person can freely combine the above- mentioned preferred, more preferred, particularly preferred and most preferred embodiments relating to the coating composition and definitions of its components in any desired way. Method The present invention further relates to a method for preparing a coated article, wherein the method comprises the following steps: (a) applying a coating composition according to the present invention to a surface of an article; and (b) curing said coating composition to obtain a coated article. Preferably, the coating composition, which is applied in step (a), is a homogeneous liquid having a viscosity in the range from 0.5 to 1,000 mPas, more preferably from 1 to 250 mPas. The viscosity of the composition may be adjusted by the type and content of solvent as well as the type, ratio and/or molecular weight of the silazane polymer (A), the silane coupling agent (B) and inorganic nanoparticles (C). It is preferred that the coating composition is applied in step (a) by an application method suitable for applying liquid compositions to a surface of an article. Such methods include, for example, wiping with a cloth, wiping with a sponge, dip coating, spray coating, flow coating, roller coating, slit coating, slot coating, spin coating, dispensing, screen printing, stencil printing or ink-jet printing. Dip coating and spray coating are particularly preferred. The coating composition of the present invention may be applied to the surface of various articles such as, for example, buildings, dentures, furnishings, furniture, sanitary equipment (toilets, sinks, bathtubs, etc.), signs, signboard, plastic products, glass products, ceramics products, metal products, wood products and vehicles (road vehicles, rail vehicles, watercrafts and aircrafts). It is preferred that the surface of the article is made of any one of the base materials as described for the use below. Typically, the coating composition is applied in step (a) as a layer in a thickness of 0.1 µm to 100 µm, preferably 0.5 µm to 50 µm, to the surface of the article. In a preferred embodiment, the coating composition is applied as a thin layer having a thickness of 1 to 30 µm. The curing of the coating in step (b) may be carried out under various conditions such as e.g. by ambient curing, thermal curing and/or irradiation curing. The curing is optionally carried out in the presence of moisture, preferably in the form of water vapor. For this purpose, a climate chamber may be used. Ambient curing preferably takes place at temperatures in the range from 10 to 40°C. Thermal curing preferably takes place at t emperatures in the range from 100 to 200°C, preferably from 120 to 180°C. Ir radiation curing preferably takes place with IR irradiation or UV irradiation. Preferred IR irradiation wavelengths are in the range from 7 to 15 µm or from 1 to 3 µm for substrate absorption. Preferred UV irradiation wavelengths are in the range from 300 to 500 nm. Preferably, the curing in step (b) is carried out in a furnace or climate chamber. Alternatively, if articles of very large size are coated (e.g. buildings, vehicles, etc.), the curing is preferably carried out under ambient conditions. Preferably, the curing time for step (b) is from 0.01 to 24 h, more preferably from 0.10 to 16 h, still more preferably from 0.15 to 8 h, and most preferably from 0.20 to 5 h, depending on the coating composition and coating thickness. Other preferred curing conditions are: 1. Thermal curing in the presence of a catalyst such as, e.g. peroxides or sulfur compounds (vulcanization). 2. UV curing in the presence of UV active photoinitiators. After the curing in step (b), the coating composition is chemically crosslinked to form a hard coating on the surface of the article. The coating obtained by the above method is a hard coating with maximum mechanical resistance and durability such as maximum surface hardness, scratch resistance and abrasion resistance. Moreover, adverse behavior such as formation of turbid films and wetting problems is avoided. Article Moreover, a coated article is provided, which is obtainable or obtained by the above-mentioned preparation method. Use The present invention further relates to the use of the coating composition according to the present invention for forming a hard coating on the surface of a base material. Preferred base materials, to which the coating composition according to the present invention is applied, include a wide variety of materials such as, for example, metals (such as iron, steel, silver, zinc, aluminum, nickel, titanium, vanadium, chromium, cobalt, copper, zirconium, niobium, molybdenum, ruthenium, rhodium, silicon, boron, tin, lead or manganese or alloys thereof provided, if necessary, with an oxide or plating film); plastics (such as polymethyl methacrylate (PMMA), polyurethane, polyesters (PET), polyallyldiglycol carbonate (PADC), polycarbonate, polyimide, polyamide, epoxy resin, ABS resin, polyvinyl chloride, polyethylene (PE), polypropylene (PP), polythiocyanate, or polytetrafluoroethylene (PTFE)); glass (such as fused quartz, soda-lime-silica glass (window glass), sodium borosilicate glass (Pyrex®), lead oxide glass (crystal glass), aluminosilicate glass, or germanium-oxide glass); and construction materials (such as brick, cement, ceramics, clay, concrete, gypsum, marble, mineral wool, mortar, stone, or wood and mixtures thereof). The base materials may be treated with a primer to enhance adhesion of the hard coating. Such primers are, for example, silanes, siloxanes, or silazanes. If plastic materials are used, it may be advantageous to perform a pretreatment by flaming, corona or plasma treatment which might improve the adhesion of the functional coating. If construction materials are used, it may be advantageous to perform a precoating with lacquers, varnishes or paints such as, for example, polyurethane lacquers, acrylic lacquers and/or dispersion paints. The present invention is further illustrated by the examples following hereinafter which shall in no way be construed as limiting. The skilled person will acknowledge that various modifications, additions and alternations may be made to the invention without departing from the spirit and scope of the present invention. Examples Used raw materials In the examples described herein, the following raw materials were used: • DBU [1,8-Diazabicyclo[5.4.0]undc-7-ene], available from Sigma- Aldrich. • n-Butyl acetate in water-free quality, available from Sigma-Aldrich. • Nanopol ® C 784, 50 wt.-% in butyl acetate, average particle size 20 nm, colloidal silica, available from Evonik. • 3-Aminopropyltriethoxysilane (AMEO), available from Sigma-Aldrich: • Bis[3-(trimethoxysilyl)propyl]amine (AMEO-Dimer), available from Sigma-Aldrich: • Durazane ® 1000: n:m = 0:100, Durazane ® 1033: n:m = 33:67, Durazane ® 1066: n:m = 66:34, Durazane ® 1085: n:m = 85:15, all available from Merck KGaA: I. Preparation of formulations comprising Durazane® as silazane polymer (A) and AMEO as silane coupling agent (B) Formulations comprising Durazane® as silazane polymer (A) and AMEO as silane coupling agent (B) were prepared according to the following general procedure. The exact amounts used are shown in Table 1: First, AMEO was mixed with the solvent n-butyl acetate. Then Durazane® was added. The formulation was intensively stirred for 8 h and finally a clear solution was obtained.
Table 1: Composition of formulations 1-A1 to 1-D6. II. Preparation of formulations comprising Durazane® as silazane polymer (A), AMEO-Dimer as silane coupling agent (B) and DBU Formulations comprising Durazane® as silazane polymer (A), AMEO-Dimer as silane coupling agent (B) and DBU were prepared according to the following general procedure. The exact amounts used are shown in Table 2: First, AMEO-Dimer was mixed with the solvent n-butyl acetate, then DBU was added and the formulation was intensively stirred for 4h. Then Durazane® was added and the formulation was intensively stirred for another 8h. Finally, a clear solution was obtained.
Table 2: Composition of formulations 2-A1 to 2-D6. III. Preparation of formulations comprising Durazane® as silazane polymer (A), AMEO-Dimer as silane coupling agent (B) and inorganic nanoparticles (C) Formulations comprising Durazane® as silazane polymer (A), AMEO as silane coupling agent (B) and inorganic nanoparticles (C) were prepared according to the following general procedure. The exact amounts used are shown in Table 3: First, AMEO was mixed with the solvent n-butyl acetate, then inorganic nanoparticles were added and the formulation was intensively stirred for 4h. Then Durazane® was added and the formulation was intensively stirred for another 4h. Finally, a clear to slightly opalescent solution was obtained. Table 3: Composition of formulations 3-A1 to 3-C5. IV. Application All formulations were spin coated on 10 cm x 10 cm glass plates. The rotation speed of the spin coater was adjusted between 250 and 2,000 rpm to achieve a film thickness of 2.0 – 2.5 µm. All coated glass plates were cured under ambient conditions at a temperature of 25°C and a relative humidity of 50% for 14 days. Measurement and evaluation of the coatings performance: After curing for 14 days all coatings were analyzed visually with the bare eye on turbidity, inhomogeneity, cracks, delamination and other obvious film defects. The hardness of the coating was analyzed with a Nanoindenter [Nanoindenter model Helmut Fisher FISCHERSCOPE HM2000 S, Vickers diamond pyramid] according to DIN EN ISO 14577-1 / ASTM E 2546. The results are shown in Tables 4, 5 and 6.
Table 4: Analytical results Exp.1-A1 – Exp.1-D6 of coatings derived from formulations 1-A1 to 1-D6. The results in Table 4 and Figure 1 show an almost linear increase in hardness with increasing amount of AMEO. However, if the amount of AMEO reaches 60 wt.-%, the coatings show wetting defects and do not form a closed film anymore. Regarding the type of Durazane®, the higher the amount of -[Si(H)CH 3 -NH]- monomer units in the polymer is, the higher is the Nanoindenter Martens hardness.
Table 5: Analytical results Exp.2-A1 – Exp.2-D6 of coatings derived from formulations 2-A1 to 2-D6. Similar to Table 4 / Figure 1, Table 5 / Figure 2 show an almost linear increase in hardness with increasing amount of AMEO-Dimer. In contrast to AMEO, the dimeric AMEO-Dimer has a higher effect when used in lower amounts. However, if the amount of AMEO reaches 60 wt.-%, the coatings show wetting defects and do not form a closed film anymore. When mixed with Durazane® containing higher amount of -[Si(CH 3 ) 2 -NH]- monomer units (Durazane® 1066 and Durazane® 1085), turbid films are formed. Regarding the type of Durazane®, again the higher the amount of -[Si(H)CH 3 -NH]- monomer units in the polymer is, the higher is the Nanoindenter Martens hardness. Table 6: Analytical results Exp.3-A1 – Exp.3-C5 of coatings derived from formulations 3-A1 to 3-C5. Table 6 and Figure 3 show an almost linear increase in hardness with increasing amount of Nanoparticles for all the three Durazane® 1033 : AMEO ratios. However, if the amount of Nanoparticles reaches 60 wt.-%, the coatings form cracks after curing. In summary, the following general conclusions can be drawn: 1. A higher ratio of -[Si(H)CH 3 -NH]- monomer units in the Durazane® polymer results in harder coatings. 2. A higher amount of silane coupling agent relative to the Durazane® polymer results in harder coatings. However, if the amount of silane coupling agent exceeds, the coating shows film defects. 3. A higher amount of Nanoparticles relative to the sum of the Durazane® polymer and the silane coupling agent results in harder coatings. However, if the amount of Nanoparticles exceeds 60%, the coating shows film defects.