Photocatalytic hydrophilic coating compositions
First Claim
1. A photocatalytic hydrophilic coating composition comprising(A) a coat-forming element comprising an organopolysiloxane of the average compositional formula:
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space="preserve" listing-type="equation">R.sup.1.sub.p Si(OR.sup.2).sub.q O.sub.(4-p-q)/2 wherein R1 is independently a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, R2 is independently a hydrogen atom or a monovalent organic group having 1 to 4 carbon atoms, and letters p and q are numbers in the range;
0.7≦
p≦
1.6, 0<
q<
3.3, and 0.7<
p+q<
4, said coat-forming element capable of the forming a coating of silicone resin when cured, and(B) a particulate photocatalyst dispersed in said coat-forming element which exerts photocatalysis upon photo excitation such that at least some of organic groups attached to silicon atoms of silicone molecules at the surface of said coating are replaced by hydroxyl groups in the presence of water, thereby rendering the coating surface hydrophilic.
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Abstract
A photocatalytic coating composition comprising (A) a coat-forming element capable of forming a coating of silicone resin when cured and (B) a photocatalyst dispersed therein. The coat-forming element is comprised of an organopolysiloxane having a monovalent organic C1 -C18 group and a C1 -C4 alkoxy group. The coating composition is applied to an article and cured to form a silicone coating thereon. When the coating is exposed to light, typically UV, the photocatalyst is excited to provide photocatalysis permitting organic groups attached to silicon atoms of silicone molecules at the coating surface to be replaced by hydroxyl groups in the presence of water, thereby rendering the coating surface hydrophilic. Thereafter, the coating maintains water affinity semi-eternally and has improved weather resistance.
144 Citations
19 Claims
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1. A photocatalytic hydrophilic coating composition comprising
(A) a coat-forming element comprising an organopolysiloxane of the average compositional formula: -
space="preserve" listing-type="equation">R.sup.1.sub.p Si(OR.sup.2).sub.q O.sub.(4-p-q)/2wherein R1 is independently a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, R2 is independently a hydrogen atom or a monovalent organic group having 1 to 4 carbon atoms, and letters p and q are numbers in the range;
0.7≦
p≦
1.6, 0<
q<
3.3, and 0.7<
p+q<
4, said coat-forming element capable of the forming a coating of silicone resin when cured, and(B) a particulate photocatalyst dispersed in said coat-forming element which exerts photocatalysis upon photo excitation such that at least some of organic groups attached to silicon atoms of silicone molecules at the surface of said coating are replaced by hydroxyl groups in the presence of water, thereby rendering the coating surface hydrophilic. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A photocatalytic hydrophilic coating composition comprising
(a) 0 to 60 mol % of a silane of the general formula: - R12 SiX2 wherein R1 is independently a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms and X is chlorine, bromine or an alkoxy group having 1 to 4 carbon atoms,
(b) 10 to 100 mol % of a silane of the general formula;
R1 SiX3 wherein R1 and X are as defined above,(c) 0 to 30 mol % of a silane of the general formula;
SiX4 wherein X is as defined above, and(d) a particulate photocatalyst, wherein said composition, when applied to a substrate, forms a coating of silicone resin through hydrolysis of the silanes in the presence of water and dehydrating polycondensation, and said photocatalyst exerts photocatalysis upon photo excitation such that at least some of the organic groups attached to silicon atoms of silicone molecules at the surface of said coating are replaced by hydroxyl groups in the presence of water, thereby rendering the coating surface hydrophilic. - View Dependent Claims (15)
- R12 SiX2 wherein R1 is independently a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms and X is chlorine, bromine or an alkoxy group having 1 to 4 carbon atoms,
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16. A photocatalytic hydrophilic coating composition of the two part type comprising
(A) a first liquid part having dispersed in a dispersing medium an organopolysiloxane of the average compositional formula: -
space="preserve" listing-type="equation">R.sup.1.sub.p Si(OR.sup.2).sub.q O.sub.(4-p-q)/2wherein R1 is independently a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, R2 is independently a hydrogen atom or a monovalent organic group having 1 to 4 carbon atoms, and letters p and q are numbers in the range;
0.7≦
p≦
1.6, 0<
q<
3.3, and 0.7<
p+q<
4, said first liquid part capable of forming a coating of silicone resin when cured in the presence of water, and(B) a second liquid part having dispersed in an aqueous dispersing medium a particulate photocatalyst which exerts photocatalysis upon photo excitation such that at least some of the organic groups attached to silicon atoms of silicone molecules at the surface of said coating are replaced by hydroxyl groups in the presence of water, thereby rendering the coating surface hydrophilic. - View Dependent Claims (17)
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18. A photocatalytic hydrophilic coating composition of the two part type comprising
(A) a first liquid part having dispersed in a non-aqueous dispersing medium (a) 0 to 60 mol % of a silane of the general formula: - R12 SiX2 wherein R1 is independently a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms and X is chlorine, bromine or an alkoxy group having 1 to 4 carbon atoms,
(b) 10 to 100 mol % of a silane of the general formula;
R1 SiX3 wherein R1 and X are as defined above, and(c) 0 to 30 mol % of a silane of the general formula;
SiX4 wherein X is as defined above,said first liquid part capable of forming a coating of silicone resin when cured in the presence of water, and (B) a second liquid part having dispersed in an aqueous dispersing medium a particulate photocatalyst which exerts photocatalysis upon photo excitation such that at least some of the organic groups attached to silicon atoms of silicone molecules at the surface of said coating are replaced by hydroxyl groups in the presence of water, thereby rendering the coating surface hydrophilic. - View Dependent Claims (19)
- R12 SiX2 wherein R1 is independently a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms and X is chlorine, bromine or an alkoxy group having 1 to 4 carbon atoms,
Specification