Patent ID: 7534323

Claim:
A method of conferring to paper oleorepellence, comprising sizing the paper in wet-end, size-press or coating applications with perfluoropolyethers, wherein said perfluoropolyethers are only selected from compounds having the following structure: T-O—R f -T (I) wherein T=—CF 2 —COOH or —CF 2 CF 2 —COOH, in acid or salt form; R f is a (per)fluoropolyoxyalkylene chain, having number average molecular weight in the range 500-10,000, formed of one or more repeating units, statistically distributed along the chain, selected from the group consisting of the following structures: (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), and (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 the group consisting of H, Cl, or perfluoroalkyl from 1 to 4 carbon atoms.