Use of a vinylidene fluoride copolymer for providing a film with properties of adhesion

Abstract

The present invention relates to the use of a fluorinated copolymer in the manufacture of a solid polymer film, to give said film properties of adhesion to a metal surface or to glass. It also relates to a process for improving the adhesion of a fluoropolymer to a metal, polymer or glassy substrate, and also to a composite part comprising a solid polymer film in direct contact with at least one metal or glassy element.

We claim: 
     
         1 . A process of preparing a film-forming polymer with adhesion properties to metal, polymer or glass surfaces, consisting of synthesizing a fluorinated copolymer by:
 (a) radical copolymerizing monomers comprising: (i) vinylidene fluoride (VDF), (ii) trifluoroethylene (TrFE), (iii) optionally at least one other fluoromonomer and (iv) an adhesion-promoting monomer, said adhesion-promoting monomer being a non-perfluorinated vinyl or vinylene monomer bearing at least one weak acid or weak acid precursor function other than carboxyvinyl, carboxyvinylene, 1-alkylcarboxyvinyl, and 1-alkylcarboxyvinyl ene monomers and precursors thereof, wherein the molar proportion of the moieties derived from said adhesion-promoting monomer is less than 1% of the copolymer, and   (b) conversion of the weak acid precursor functions into weak acid functions.   
     
     
         2 . The process according to  claim 1 , wherein the molar proportion of the moieties derived from said adhesion-promoting monomer is from 0.2% to 0.9%. 
     
     
         3 . The process according to  claim 1 , wherein the molar proportion of the moieties derived from said adhesion-promoting monomer is from 0.5% to 0.8% of the copolymer. 
     
     
         4 . The process according to  claim 1 , wherein said other fluoromonomer is selected from the group consisting of: tetrafluoroethylene (TFE), chlorofluoroethylene (CFE), chlorotrifluorethylene (CTFE), hexafluoropropylene (HFP), trifluoropropene, tetrafluoropropene, chlorotrifluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, perfluoroethers. 
     
     
         5 . The process according to  claim 1 , wherein the weak acid function is selected from the group consisting of a carboxylic acid function and a phosphonic acid function. 
     
     
         6 . The process according to  claim 1 , wherein the precursor of a weak acid function is selected from the group consisting of carboxylic acid salts, carboxylic acid alkyl esters, phosphonic acid salts and phosphonic acid alkyl esters. 
     
     
         7 . The process according to  claim 6 , wherein the precursor of the weak acid function is the phosphonic acid alkyl ester and conversion comprises reaction with a halogenated silane, in an organic solvent followed by hydrolysis in methanol. 
     
     
         8 . The process according to  claim 1 , wherein the adhesion-promoting monomer is selected from the group consisting of a vinylphosphonic acid dialkyl ester, vinylphosphonic acid and (2-trifluoromethyl)acrylic acid. 
     
     
         9 . A process for forming a fluoropolymer for improved adhesion, to a metal, polymer or glassy substrate, consisting of: radical copolymerizing vinylidene fluoride (VDF), trifluoroethylene (TrFE) and optionally at least one other fluoromonomer, and a non-perfluorinated vinyl or vinylene monomer bearing at least one weak acid or weak acid precursor function other than carboxyvinyl, carboxyvinylene, 1-alkylcarboxyvinyl and 1-alkylcarboxyvinylene monomers and precursors thereof; wherein the molar proportion of the moieties derived from said adhesion-promoting monomer is less than 1% of the copolymer, and conversion of the weak acid precursor function into a weak acid, when it is present.