Hydrophilic anti-fog coatings
The present invention relates to hydrophilic anti-fog coatings. In particular, the coatings use two types of nanoscale particles, colloidal silica and porous organosilicate micelles, in a polyurethane matrix. The invention is an anti-fog coating for optically clear substrates (polycarbonate, polyurethane, nylon, polyester and other clear plastics) without the need for a primer and glass or oxide substrates with an additional primer layer, comprising monosized colloidal silica nanoparticles and porous organosilicate micelles in a polyurethane matrix. The silica is preferably 1-5% by weight and the micelles are loaded at 0.1 to 10% volume percentage by volume. The polyurethane prepolymer is dissolved at 10-40% by weight in a mixture of tertiary amyl alcohol and diacetone alcohol to customize for dip, flow or spray coating processes
1. A chemical resistant, transparent anti-fog coating for optically clear surfaces comprising colloidal silica and porous organosilicate micelles in a polyurethane matrix,
a. colloidal silica having monosized nanoparticles with a particle size of 25 to 35 nanometers, the colloidal silica nanoparticles comprising 1-5% by weight of the coating;
b. porous organosilicate micelles being 5-10 nanometers in size and comprising 0.1 to 10% by volume of the coating, each micelle having a porous hydrophilic silicate shell and a hydrophilic micellar core or
a porous hydrophilic silicate shell and a hydrophobic micellar core.
2. The coating of claim 1 where the organosilicate micelles result from precursors selected from the following group: N-(Acetylglycyl)-3-aminopropyltrimethoxysilane; 2-[(Acetoxy(polyethyleneoxy)propyl]triethoxysilane; and 3-cyanopropyltrimethoxysilane.
3. An anti-fog coating with sustained water-sheeting and durability properties for plastic substrates comprising monosized colloidal silica nanoparticles and porous organosilicate micelles in a polyurethane matrix wherein,
the monosized colloidal silica nanoparticles are 25-35 nm in the coating, absorb water droplets or moisture and create a sheeting action at the coating surface to prevent fogging and are from 1-5% by weight; and,
the porous organosilicate micelles are loaded at 0.1 to 10% volume percentage by volume, are 5-10 nm in the coating and draw water or moisture to the porous micellar surface, said micelles comprising a hydrophilic core that serves as a reservoir to sustain superhydrophilic properties and fogging resistance of a coated surface.
4. The anti-fog coating of claim 3 where the polyurethane matrix is formed from a prepolymer dissolved at a concentration of 10-40% by weight in a mixture of tertiary amyl alcohol and diacetone alcohol, said mixture formulated to have a viscosity suitable for either dip, flow or spray coating of the plastic optical surface.