Patent ID: 7468142

Claim:
A composition comprising 1,1,1,3,3-pentafluorobutane and a perfluoropolyether of the formula (I), CF 3 —[(OCF(CF 3 )—CF 2 ) a —(O—CF 2 ) b ]O—CF 3 (I) wherein a and b independently denote integers greater than 0, and said perfluoropolyether has a boiling point of about 57° C. at 101.3 kPa and an average molecular mass of about 340, in proportions for which they form an azeotrope or a pseudo-azeotrope, the said azeotrope or pseudo-azeotrope consisting of about 52% by weight to about 83% by weight of 1,1,1,3,3-pentafluorobutane and about 17% by weight to about 48% by weight of said perfluoropolyether of the formula (I) at a pressure of 100.1 kPa.