3M Patents Highly Water Repellent Fluoropolymer Coating

U.S. 8,632,856 B2
3M Innovative Properties Company has been granted a patent for a method for making a coated article, which method is comprised of providing a substrate; providing microparticles of a partially or fully fluorinated polymer and providing a partially fluorinated binder soluble in one or more of butyl acetate, ethyl acetate, methanol, dimethylacetamide, dimethylformamide, dimethylsulfoxide, acetone, methyl ethyl ketone, sulfolane or tetrahydrofuran, wherein the partially fluorinated binder is a fluorothermoplastic comprising a terpolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride; applying to at least a portion of the substrate a coating comprising the microparticles and a solution of the binder in a nonfluorinated solvent that dissolves the binder and does not dissolve the microparticles, wherein prior to applying the binder solution to the substrate the microparticles are dispersed in the binder solution, or after applying the binder solution to the substrate the microparticles are sprinkled or otherwise deposited on the applied binder; and heating the coating sufficiently to bond the microparticles to the binder but not so much as to cause the receding water contact angle for the coating to fall below 80°, wherein the coating comprises 70 to 95 weight percent microparticles based on a total weight of the microparticles plus the partially fluorinated binder.