Crosslinkable vinyl fluoride copolymer coated film and process for making same

A process for forming a fluoropolymer coated film comprising:

• coating a polymeric substrate film with a liquid fluoropolymer coating composition, wherein said liquid fluoropolymer coating composition comprises a liquid medium, cross-linking agent, and dispersed or dissolved vinyl fluoride copolymer comprised of about 50 to about 69.9 mole % of repeat units derived from vinyl fluoride and about 30 to about 50 mole % of repeat units derived from monomer selected from a mixture of (a) and (b) below, with the proviso that at least about 30 mole % of repeat units in said copolymer are derived from (a), and about 0.1 mole % to about 20 mole % of repeat units in said copolymer are derived from monomer selected from (b):
• (a) tetrafluoroethylene;
• and
• (b) fluorinated vinyl monomer containing at least one functional group selected from the group consisting of hydroxyls, thiols, carbonyls, carboxylic acids, carboxylic esters, acid anhydrides, sulfonyls, sulfonic acids, sulfonic esters, phosphoric acids, phosphoric esters, boric acids, boric esters, epoxies, isocyanates, thiocyanates, amines, amides, nitriles and halogen selected from bromide and iodide, wherein the functional groups of the vinyl fluoride copolymer provide crosslinkable reaction sites, and wherein said polymeric substrate film comprises functional groups that interact with the functional groups of the vinyl fluoride copolymer to promote bonding of the fluoropolymer coating to the polymeric substrate film, and
• removing the liquid medium from the fluoropolymer coating and cross-linking said vinyl fluoride copolymer.

A backsheet for a photovoltaic module comprising:

• a polymeric substrate film;
• and
• a fluoropolymer coating on said polymeric substrate film, said fluoropolymer coating comprising a vinyl fluoride copolymer comprised of about 50 to about 69.9 mole % of repeat units derived from vinyl fluoride and about 30 to about 50 mole % of repeat units derived from monomer selected from a mixture of (a) and (b) below, with the proviso that at least about 30 mole % of repeat units in said copolymer are derived from (a), and about 0.1 mole % to about 20 mole % of repeat units in said copolymer are derived from monomer selected from (b):
• (a) tetrafluoroethylene;
• and
• (b) fluorinated vinyl monomer containing at least one functional group selected from the group consisting of hydroxyls, thiols, carbonyls, carboxylic acids, carboxylic esters, acid anhydrides, sulfonyls, sulfonic acids, sulfonic esters, phosphoric acids, phosphoric esters, boric acids, boric esters, epoxies, isocyanates, thiocyanates, amines, amides, nitriles and halogen selected from bromide and iodide,
• wherein the functional groups of the vinyl fluoride copolymer provide crosslinkable reaction sites, and wherein said polymeric substrate film comprises functional groups that interact with the functional groups of the vinyl fluoride copolymer to promote bonding of the fluoropolymer coating to the polymeric substrate film, and wherein said vinyl fluoride copolymer coating is cross-linked.