Patent ID: 7045016

Claim:
A method for removing stains from a ceramic material, comprising (a) applying to said ceramic material a (per)fluoropolyether derivative having the following structures: (O − Z + ) 2 P(O)[O-L-YFC—O—R f —CFY-L-O—P(O)(O − Z + )] m′ -[O-L-YFC—O—R f —CFY-L-O]P(O)(O 31 Z + ) 2 (B) R f —CFY-L-W (C) W-L-YFC—O—R f —CFY-L-W (D) wherein m′ is an integer from 0 to 20; L is a moiety selected from —CH 2 —(OCH 2 CH 2 ) n — and —CO—NR′—(CH 2 ) q —, the R′ group being H or a C 1 –C 4 alkyl group; n=0–8, q=1–8; Z=H, alkaline metal or NR 4 group with R=H or C 1 –C 4 alkyl group; Y=F, CF 3; m=1,2,3; W is a —Si(R 1 ) α (OR 2 ) 3-α group with α=0, 1, 2, R 1 and R 2 equal to or different from each other are C 1 –C 6 alkyl groups, containing and non containing one or more ether O and substituents selected from C 6 –C 10 aryl and C 7 –C 12 alkyl-aryl or aryl-alkyl; R f has a number average molecular weight in the range 350–8,000 and comprises repeating units having at least one of the following structures, statistically placed along the chain: (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, Cl, or perfluoroalkyl from 1 to 4 carbon atoms; (b) treating said ceramic material with a solvent based staining agent and allowing for complete solvent evaporation from said staining agent; (c) applying a water system to remove the stain.