Patent ID: 6025307
Filing Date: 2000-02-15
Classification: C10M

Abstract:
Fluorinated greases comprising at least:15%-50% by weight of a polytetrafluoroethylene or tetrafluoroethylene copolymers with other ethylenically unsaturated monomers totally or partially fluorinated;30%-84.5% by weight of perfluoropolyether oil having a viscosity comprised between 20 and 4000 cSt at 20.degree. C.;0.5%-10% by weight of surfactant or dispersant having perfluoropolyether or perfluoroalkylic chain;0%-10% by weight of an anticorrosion and/or antiwear additive,said fluorinated greases being obtained by a process comprising at least the following steps:a) obtaining a TFE-based (perfluoropolymer by polymerization in an aqueous phase;b) adding surfactants in an amount from 50 to 500 mg per gram of polymer to the TFE-based (per)fluoropolymer in the aqueous phase;c) adding to the aqueous phase of b) a perfluoropolyether oil having a viscosity lower than 5 cSt at 25.degree. C. and a boiling point not greater than 150.degree. C., or to a fluorocarbon with a boiling point lower than 150.degree. C., so that the ratio by weight of polymer/oil is lower than 0.5;d) adding a perfluoropolyether oil having a viscosity between 20 and 4000 cSt at 20.degree. C. in amounts such as to obtain in the final grease a polymer percentage by weight of between 15% and 50%;e) evaporating completely under vacuum the low boiling components at a temperature between 50.degree. C. and 90.degree. C.such that the (per)fluoropolymer particles based on TFE or their aggregates have average sizes smaller than a micron.