Patent ID: 7252740

Claim:
A method for conferring oleorepellence to paper substrata in wet-end and size-press applications comprising the step of sizing with compounds of the formula: T 1 —CFW 1 —O—R f—CFW 2 —T 2 (I) or salts thereof, wherein T 1 , T 2 , equal to or different from each other, are selected from the group formed of—CH 2 —B—Y—(COOH) n , —CH(CF 3 )O—Y(COOH) n , —F, —CF 3 , —C 2 F 5 , —(C 2 F 4 )C1;B=—O— or —S—; Y represents a C 1 —C 20 alkylene chain, optionally containing heteroatoms as O, N, S; n is an integer between 1 and 4; with the proviso that at least one of the two end groups T 1 , T 2 is —CH 2 —B—Y—(COOH) n , —CH(CF 3 )O—Y—(COOH) n ; W 1 , W 2 , equal to or different from each other, are —F or —CF 3 ; R f is a (per)fluoropolyoxyalkylene chain formed of one or more repeating units, statistically distributed along the chain, having the following structure: (CFXO), (CF 2 CF 2 O), (CF 2 CF 2 CF 2 O), (CF 2 CF 2 CF 2 CF 2 O), (CR 4 R 5 CF 2 CF 2 O), (CF(CF 3 )CF 2 O), (CF 2 CF(CF 3 )O), wherein X=F, CF 3 ; R 4 and R 5 , equal to or different from each other, are selected from H, C1, or perfluoroalkyl from 1 to 4 carbon atoms, said R f having a number average molecular weight in the range 500-10,000.