Process for preparing lubricating greases

Claim 1

A process for preparing a lubricating grease based on polytetrafluoroethylene and on a liquid dispersant selected from oligomers of trifluorochloroethylene or from perfluoropolyethers of the classes of the general formula : wherein: X and Y are a terminal -CF 3 or -C 2 F 5 group; m and n are integers, and m + n = 10-100, and m/n = 10-50; A and B are terminal -CF 3 , -C 2 F 5 , -CF 2 Cl or - C F 2 CF 2 Cl groups; p and g are integers, and p + q = 10-200, and p/q = 0.1-10; r, s and u are integers, and r + s + u = 10-3000, u r+s = 0.01-0.3, and r/s = 0.1-10; and t ≥ 3; characterized in that polytetrafluoroethylene having a molecular weight in the range of from 500,000 to 1,000,000, comprising particles of the aggregated type, previously heated under vacuum to remove volatile products which may be contained therein, is mixed, under reduced pressure and at a temperature higher than room temperature, with an oligomer of CF 2 CFC1 having a viscosity, at 20°C, from 100 to 1000 cst, or with a perfluoropolyether selected from the Classes (I), (II) or (III) and having a viscosity, at 20°C, from 20 to 4000 cs if belonging to Class (I), from 40 to 6000 cs if belonging to Class (II), and from 40 to 30,000 cs if belonging to Class (III), and also with a perfluorinated surfactant of the anionic type, characterized by a perfluoroalkylene chain or by a perfluorooxyalkylene chain, the amount of polytetrafluoroethylene being from 15% to 40% by weight of the total mix, the amount of perfluoropolyether or of oligomer of CF 2 CFCl being from 60% to 85% by weight of the total mix, and the amount of surfactant being from 0.1% to 0.4% by weight of the polytetrafluoroethylene.