Fluoropolymer non-stick coatings
View Patent ↗A coating composition is provided comprising (a) an aqueous medium, (b) melt-fabricable perfluoropolymer dispersed in said aqueous medium and having a melting temperature of at least 290° C., (c) melt-fabricable perfluoropolymer dispersed in said aqueous medium and having a melting temperature of no greater than 270° C., and (d) water miscible organic liquid having a boiling temperature of at least 280° C. and optionally (e) filler, the combination of (c) and (d) providing sloughing resistance to said composition applied to a non-horizontal substrate and baked, component (d) being unnecessary when component (a) is not present in the coating composition, and when filler is present the amount of (c) being present in an effective amount to increase the cohesive strength of the baked layer of the coating composition.
1. Metal substrate having a non-stick coating comprising a primer layer and an overcoat layer on said primer layer, said overcoat layer comprising melt-fabricable perfluoropolymer (b) having a melting temperature of at least 290° C. and an effective amount of melt-fabricable perfluoropolymer (c) having a melting temperature of no greater than 270° C. to improve the rapid decompression adhesion between said primer layer and said overcoat layer, wherein melt-fabricable perfluoropolymer (b) is a copolymer of tetrafluoroethylene and perfluoro(alkyl vinyl ether) and wherein melt-fabricable perfluoropolymer (c) is a copolymer of tetrafluoroethylene and hexafluoropropylene and wherein the amount of said perfluoropolymer of (c) present is 2 to 10 wt % based on the sum of the weights of said perfluoropolymers (b) and (c).
2. The metal substrate of claim 1 wherein said layer of baked composition further comprises about 4 to 20 wt % of filler (e) particles, based on the sum of (b), (c) and (e), for increasing the impermeability of said overcoat layer.
3. The metal substrate of claim 2 wherein said filler (e) particles are platelet in shape.
4. The metal substrate of claim 1 as down-hole oil pipe or heat exchanger tube, said non-stick coating forming the interior surface thereof.
5. The metal substrate of claim 1 , said overcoat layer further comprising filler particles for increasing the impermeability of said lining.