Thermoplastic polyesters containing perfluoropolyoxyalkylene sequence

A process for the preparation of fluorinated thermoplastic polyesters having a block structure:

• --[--R.sub.f --H.sub.1 --H.sub.2 --H.sub.1 --]-- (I)
• wherein:
• --R.sub.f --is a perfluoropolyoxyalkylene unit of formula:
• --CF.sub.2 O--(CF.sub.2 CF.sub.2 O).sub.m --(CF.sub.2 O).sub.n --CF.sub.2 --(II)
• wherein m and n are numbers such that the ratio m/n is between 0.2 and 5;
• --H.sub.1 -- and --H.sub.2 --, equal or different from each other, are bivalent radicals having arylene, alkylarylene, alkylene, or cycloalkylene structure, optionally containing fluorine and/or heteroatoms selected from oxygen, sulfur, and nitrogen;
• the --R.sub.f --, --H.sub.1 --, and --H.sub.2 -- units being linked to each other by ester groups;
• the fluorinated thermoplastic polyesters being obtained from perfluoropolyoxyalkylene diols having the formula:
• HO--Z--CF.sub.2 O--(CF.sub.2 CF.sub.2 O).sub.m --(CF.sub.2 O).sub.n --CF.sub.2 --Z--OH (III)
• wherein m and n are numbers such that the m/n ratio is between 0.2 and 5, and Z is a bivalent organic group, the perfluoropolyoxyalkylene diols having a functionality of at least 1.97 and a number average molecular weight from 500 to 10,000;
• the process comprising:
• (a) reacting (1) a perfluoropolyoxyalkylene diol with a functionality at least equal to 1.97 and a molecular weight from 500 to 10,000, having the formula
• HO--Z--CF.sub.2 O--(CF.sub.2 CF.sub.2 O).sub.m --(CF.sub.2 O).sub.n --CF.sub.2 --Z--OH (III)
• where m and n are numbers such that the ratio m/n is between 0.2 and 5 and Z is a bivalent organic group;
• with (2) a dicarboxylic acid of formula:
• HO--CO--H.sub.1 --CO--OH (IV)
• or a derivative thereof, to form a pre-polymer;
• wherein H.sub.1 has the meaning given above and the molar ratio between the dicarboxylic acid (IV) or the derivative thereof and the diol (III) is between 2 and 50;;
• (b) reacting the prepolymer from step (a) with a diol of formula:
• HO--H.sub.2 --OH (V)
• wherein H.sub.2 has the meaning given above and the molar ratio between the diol (V) and the prepolymer is between 0.9 and 2.