FIELD: polymer materials.
SUBSTANCE: invention, in particular, relates to preparation of concentrated aqueous polytetrafluoroethylene dispersion comprised of following stages: (i) sedimentation of polytetrafluoroethylene particles by adding from 2 to 20% (based on the weight of polytetrafluoroethylene) of nonionic surfactant with mean molecular mass between 450 and 800 and ratio of inorganic to organic residues 1.07 to 1.50 and from 10 to 800% by weight of water to aqueous polytetrafluoroethylene emulsion containing 10 to 50% of polytetrafluoroethylene obtained by emulsion polymerization of tetrafluoroethylene in presence of anionic surfactant based on perfluorocarboxylate to form aqueous polytetrafluoroethylene dispersion with 1 to 40% by weight of polytetrafluoroethylene; (ii) concentration of aqueous polytetrafluoroethylene dispersion thus obtained to form polytetrafluoroethylene-enriched aqueous polytetrafluoroethylene dispersion wherein content of polytetrafluoroethylene varies between 30 and 70 % by weight and which contains supernatant; and (iii) separation of polytetrafluoroethylene-enriched aqueous dispersion from supernatant. Content of above-indicated perfluorocarboxylate-based anionic surfactant is below 500 ppm of the weight of polytetrafluoroethylene.
EFFECT: significantly reduced content of perfluorocarboxylate-based anionic surfactant in aqueous polytetrafluoroethylene dispersion.
4 cl, 3 tbl, 12 ex
