Perfluoropolyether carboxylic acids and use thereof for the oleo-repellent paper sizing

摘要

Carboxylic acids comprising perfluoropolyether chains, of formula:        T₁-CFW₁-O-R_f-CFW₂-T₂     (I)wherein T₁, T₂, equal to or different from each other, are selected from the group formed of -CH₂-B-Y-(COOH)_n, -CH(CF₃)O-Y(COOH)_n, -F, -CF₃, -C₂F₅, -(C₂F₄)Cl, wherein B = -O- or -S-; Y = C₁-C₂₀ alkylene chain, n = 1-4; with the proviso that at least one of the two end groups T₁, T₂ be -CH₂-B-Y-(COOH)_n, - CH(CF₃)O-Y(COOH)_n; W₁, W₂, equal to or different from each other, are -F or -CF₃; R_f is a (per)fluoropolyoxyalkylene chain formed of one or more repeating units, statistically distributed along the chain, having a number average molecular weight in the range 500-10,000.