Nanosilica coating for retarding dew formation

Patent metadata

Field	Value
Publication number	US-10508202-B2
Application number	US-201314404973-A
Country	US
Kind code	B2
Filing date	May 30, 2013
Priority date	Jun 11, 2012
Publication date	Dec 17, 2019
Grant date	Dec 17, 2019

Abstract

The present disclosure relates to silica nanoparticle coatings and articles, such as in particular retro-reflective devices, bearing silica nanoparticle coatings thereon. The present disclosure is also directed to a method for retarding dew formation on the surface of an article, in particular an article comprising a retro-reflective support.

First claim

The invention claimed is:

1. A method for retarding dew formation on the surface of an article comprising a retro-reflective support, the method comprising:
providing a substrate;
applying a primer coating composition free of silica particles to the surface of the substrate, wherein the primer coating composition comprises a hydrophilic organofunctional silane and a multifunctional acrylic-based additive, wherein the hydrophilic organofunctional silane is 3-(acryloyloxy)propyl trimethyoxysilane, 3-(methacryloyloxy)propyl trimethoxysilane, or a combination thereof, wherein the multifunctional acrylic-based additive is trimethylolpropane trimethacrylate, wherein a weight ratio of the hydrophilic organofunctional silane to the trimethylolpropane trimethacrylate is 95:5 to 60:40;
contacting at least part of the surface of said substrate with a silica nanoparticle coating composition comprising:
an aqueous dispersion of a mixture of silica nanoparticles having an average particle diameter of 40 nanometers or less and silica nanoparticles having an average particle diameter greater than 40 nanometers, said aqueous dispersion having a pH of less than 5, and
an acid having a pKa of less than 5;

drying said coating composition so as to provide a silica nanoparticle coating onto said substrate, and thereby forming a coating assembly; and

applying said coating assembly onto at least part of said retro-reflective support.

2. A method for retarding dew formation on the surface of an article comprising a retro-reflective support, the method comprising the steps of:
providing a substrate;
applying a primer coating composition free of silica particles to the surface of the substrate, wherein the primer coating composition comprises a hydrophilic organofunctional silane and a multifunctional acrylic-based additive, wherein the hydrophilic organofunctional silane is 3-(acryloyloxy)propyl trimethyoxysilane, 3-(methacryloyloxy)propyl trimethoxysilane, or a combination thereof, wherein the multifunctional acrylic-based additive is trimethylolpropane trimethacrylate, wherein a weight ratio of the hydrophilic organofunctional silane to the trimethylolpropane trimethacrylate is 95:5 to 60:40;
contacting at least part of the surface of said substrate with a silica nanoparticle coating composition comprising:
an aqueous dispersion of a mixture of acicular silica nanoparticles and spherical silica nanoparticles, said aqueous dispersion having a pH of less than 5, and
an acid having a pKa of less than 5;

drying said coating composition so as to provide a silica nanoparticle coating onto said substrate, and thereby forming a coating assembly; and

applying said coating assembly onto at least part of said retro-reflective support.

3. A method for retarding dew formation on the surface of an article comprising a retro-reflective support, the method comprising the steps of:
providing a substrate;
applying a primer coating composition free of silica particles to the surface of the substrate, wherein the primer coating composition comprises a hydrophilic organofunctional silane and a multifunctional acrylic-based additive, wherein the hydrophilic organofunctional silane is 3-(acryloyloxy)propyl trimethyoxysilane, 3-(methacryloyloxy)propyl trimethoxysilane, or a combination thereof, wherein the multifunctional acrylic-based additive is trimethylolpropane trimethacrylate, wherein a weight ratio of the hydrophilic organofunctional silane to the trimethylolpropane trimethacrylate is 95:5 to 60:40;
contacting at least part of the surface of said substrate with a silica nanoparticle coating composition comprising:
an aqueous dispersion of core-shell particles, each core-shell particle comprising a polymer core surrounded by a shell consisting essentially of silica nanoparticles disposed on said polymer core, said aqueous dispersion having a pH of less than 5, and

an acid having a pKa of less than 5;
drying said coating composition so as to provide a silica nanoparticle coating onto said substrate, and thereby forming a coating assembly; and
applying said coating assembly onto at least part of said retro-reflective support.

4. A method according to claim 3 , wherein the substrate comprises a material selected from the group consisting of polymeric materials, glass, ceramic, organic and inorganic composite material, metal, and any mixtures or combinations thereof.

5. A method according to claim 4 , wherein the substrate comprises an organic polymeric material that is a poly(meth)acrylate, polyurethane, polyester, polycarbonate, polyolefin, polymethylmethacrylate, or any combination or mixture thereof.

6. The method according to claim 3 , wherein the substrate comprises a material that is transparent or translucent to visible light.

7. The method according to claim 3 , wherein the silica nanoparticles are free of surface modification or free of surface functionalization.

8. The method according to claim 3 , wherein the acid is nitric acid, wherein the aqueous dispersion has a pH of less than 3.

9. The method according to claim 3 , wherein the weight ratio of the hydrophilic organofunctional silane to the trimethylolpropane trimethacrylate is 90:10 to 80:20.

10. The method according to claim 3 , wherein the dried silica nanoparticle coating composition has a thickness of 500 angstroms to 2500 angstroms.

11. The method according to claim 3 , wherein the primer coating composition further comprises tetraethoxysilane.

12. The method according to claim 11 , wherein the hydrophilic organofunctional silane is 3-(acryloyloxy)propyl trimethoxysilane, wherein the weight ratio of the 3-(acryloyloxy)propyl trimethoxysilane and the trimethylolpropane trimethacrylate is 98:2 to 80:20.

13. The method according to claim 12 , wherein the weight ratio of the 3-(acryloyloxy)propyl trimethoxysilane and the trimethylolpropane trimethacrylate is 96:4 to 92:8.

Assignees

• 3M Innovative Properties Co

Inventors

• Jing Naiyong
• Strerath Christiane
• Jost Michael R

Classifications

• C08J7/065

  Low-molecular-weight organic substances, e.g. absorption of additives in the surface of the article · CPC title

• C08K3/36

  Silica · CPC title

• C08J7/06

  with compositions not containing macromolecular substances · CPC title

• Y10T428/259

  Silicic material · CPC title

• C09D1/00 Primary

  Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances · CPC title