Tetrafluoroethylene-ethylene copolymers with a core-shell particle structure

摘要

Aq. dispersions (I) contain colloidal particles of a melt-processing copolymer, comprising (a) a core consisting of a copolymer (IIA) of 32-60 mole-% tetrafluoroethylene (TFE), 40-60 mole-% ethylene (E) and 0-8 mole-% fluoro-olefinic comonomer (FM), and (b) a shell consisting of a melt-processable polymer (IIB) with a m.pt. 20 degrees C lower than that of (IIA) and constituting 1-26 vol.% of the total particle vol.. Also claimed are (a) coagulated powder or spray dried powder from (I), contg. sec. particles with a mean particle size of 5 mu to 2 mm and 1-100 mu respectively; and (b) a process for the prodn. of (I) by (i) making a seed dispersion by copolymerisation of the above monomers and (ii) continuing polymerisation in the presence of the seed dispersion by adding the monomers for the shell.