Fluorinated polyurethane composition

1. An aqueous composition comprising:

(A) 3-25 wt %, with respect to the total weight of the composition, of at least one functional fluorinated polymer [polymer (F)] selected from the group consisting of:

fluorinated ionisable polyurethane polymers [polymer (PUR)] comprising:

at least one fluorinated block comprising a (per)fluoropolyoxyalkylene chain [chain (R OF )], wherein chain (R OF ) comprises one or more repeating units R, said repeating units R, randomly distributed along the (per)fluoropolyoxyalkylene chain, being selected from the group consisting of:

(i) —CFXO—, wherein X is F or CF 3 ,

(ii) —CF 2 CFXO—, wherein X is F or CF 3 , and

(iii) —CF 2 CF 2 CF 2 O—; and

at least one functional block comprising a hydrocarbon chain [chain (R H )], wherein chain (R H ) is selected from the group consisting of carboxylic-containing chains (R′ HC ) of formula:

wherein T is a trivalent hydrocarbon, linear or branched, cyclic or not, aliphatic or aromatic, comprising from 2 to 12 carbon atoms,

said at least one functional block being linked by urethane moieties having formula (I):

wherein E is a divalent hydrocarbon group selected from the group consisting of:

and mixtures thereof;

wherein:

R C , equal or different at each occurrence, is independently selected from a halogen atom, a C 1 -C 6 hydrocarbon group, —OR H , —NR H′ R H″ , and —C(O)—R H′″ , wherein R H , R H′ , R H″ and R H′″ , equal to or different from each other, are independently at each occurrence selected from a hydrogen atom or a C 1 -C 6 hydrocarbon group; and

n C is an integer comprised between 0 and 10,

(B) 1-15 wt %, with respect to the total weight of the composition, of at least one functional hydrogenated polymer [polymer (H)] selected from the group consisting of polyacrylic polymers, polyurethane polymers and mixtures thereof, said polymer (H) comprising at least one functional group; and

(C) 1-15 wt %, with respect to the total weight of the composition, of at least one cross-linking agent selected from polyaziridine cross-linking agents;

wherein the weight ratio of the polymer (F) to the polymer (H) is greater than 0.75.

2. The aqueous composition of claim 1 , wherein chain (R OF ) comprises one or more repeating units R, said repeating units R, randomly distributed along the (per)fluoropolyoxyalkylene chain, being selected from the group consisting of:

(i) —CF 2 O— and

(ii) —CF 2 CF 2 O—.

3. The aqueous composition of claim 2 wherein the molar ratio of recurring units of type (ii) and recurring units of type (i) ranges from 0.1 to 10.

4. The aqueous composition of claim 1 , wherein -T(COOH)— is selected from:

5. A process for the manufacture of the aqueous composition of claim 1 .

6. A method of coating a substrate comprising contacting the substrate with the aqueous composition of claim 1 .

7. The method according to claim 6 , wherein the aqueous composition is a varnish or a paint.

8. A substrate coated with the aqueous composition of claim 1 .