US Patent 7141537 Mixture of fluorinated polyethers and use thereof as surfactant

The present invention provides the use of a fluorinated polyether composition as a surfactant, said fluorinated polyether composition comprising a mixture of fluorinated polyethers of the formula:(Rf)n—Xw—Z   (I)wherein n is 1 or 2, w is 0 or 1, X is a divalent or trivalent organic linking group, Z is a polar group selected from the group consisting of an acid group or a salt thereof, an ammonium group, an amine-oxide group and an amphoteric group, and Rf represents a perfluorinated polyether group of the formula:CF3CF2CF2—O—[CF(CF3)CF2O]k—CF(CF3)—wherein k is at least 1;said mixture of fluorinated polyethers having a weight average molecular weight between 750 g/mol and 5000 g/mol and the amount of perfluorinated polyether groups in said mixture where k is 2 or less, is not more than 10% by weight of the total amount of perfluorinated polyether groups in said mixture.