Patent ID: 7385019

Claim:
A polymer fluid, the polymer comprising: non-ionic hydrosoluble functional groups corresponding to one or more of the following monomers: acrylamide, N substituted acrylamide derivatives and N-vinylamides; ionic functional groups corresponding to one or more of the following monomers: acrylic acid, methacrylic acid, maleic anhydride, acrylamidomethylpropylsulphonate, styrene sulphonic acid, vinyl sulphonic acid, vinylpyridine, quaternary ammonium salts of vinylpyridine, N-vinylimidazole, quaternary ammonium salts of N-vinylimidazole, and monomers of general formulae: where R 1 =H or CH 3 , A=O or NH, R 2 =(CH 2 ) n where n=1 to 3, R 3 and R 5 =H or CH 3 , and R 4 =H to C m H 2m+1 , where m is less than 22, or perfluorinated derivatives thereof; and hydrophobic functional groups corresponding to one or more of the following monomers: monomers of general formula —(CH 2 ) m —(CF 2 ) n —X wherein X=H or F, m+n<19, m<19 if n=0, and n<12 if m=0, and monomers of general formula: where R 1 =H or CH 3 , A=O or NH, R 4 =C n H 2n+1 or perfluorinated derivatives thereof, and n≧8, a hydrophobic silane, or a silicone; the viscosity of the fluid increasing when the fluid is subjected to shear, wherein the ionic monomers comprise at least one of vinylpyridine with a pH of less than 2 or quaternary ammonium salts thereof, and N-vinylimidazole having a pH of less than 7 or quaternary ammonium salts thereof and wherein the proportion of ionic monomer units in the polymer is more than 0.1 mol %.