Patent ID: 7323435

Claim:
A method to form films having hydro and oil repellant properties on surfaces of objects, said method comprising applying to said surfaces aqueous dispersions of fluorinated oligourethanes having a number average molecular weight lower than or equal to 9,000, determined by vapor pressure osmometry, said oligourethanes having a branched structure, optionally crosslinked, formed of the following monomers and macromers: a) aliphatic, cycloaliphatic or aromatic polyisocyanates, having NCO functionality, determined by titration with dibutylamine-HCl (ASTM D2572), higher than 2; b) bifunctional hydrogenated monomers wherein the two functions are chemically different, having formula: X 0 —(CR 1 A R 2 A ) b —Y 0 (Ib) wherein: R 1 A and R 2 A , equal to or different from each other, are H or aliphatic radicals from 1 to 10 carbon atoms, b is an integer in the range 1-20, X 0 =X A H with X A =O or S, Y 0 is SO 3 , COOH or a tertiary aminic group NR′ N R″ N , wherein R′ N and R″ N , equal to or different from each other, are a linear or branched C 1 -C 6 alkyl, or, when in the formula (Ib) X 0 =OH, b=1, R 1 A =R 2 A =H, Y 0 is a hydrophilic group having formula —CH 2 O—(CH 2 —CH 2 O) nI —CH 3 (Ib1) wherein nI is an integer in the range 3-20; and one or more of the following compounds: c) bifunctional hydroxyl (per)fluoropolyethers having a number average molecular weight in the range 400-3,000; e) monofunctional hydroxyl (per)fluoropolyethers (e 0 ) or monofunctional hydroxyl (per)fluoroalkanes (e′), said compounds (e 0 ) and (e′) having a number average molecular weight in the range 300-1,000, and optionally the following compounds: d) hydrogenated monomers capable to insert a crosslinkable chemical function in the oligourethane, having the formula (Ib), wherein R 1 A , R 2 A , b and X 0 are as above defined and Y 0 is selected from the following functional groups: wherein R I B =H, CH 3 ; R x is a saturated C 1 -C 5 ; d I ) blocking agents of the NCO group, wherein the blocking agent is one or more compounds selected from the group consisting of ketoximes, phenols, mono- di-alkyl substituted phenols with an alkylic chain from 1 to 8 carbon atoms, pyrazol, caprolactam, ethylmalonate, acetylacetone and ethylacetoacetate.