Aqueous emulsion polymerization of fluorinated monomers using a perfluoropolyether surfactant

Abstract

The invention relates to an aqueous emulsion polymerization of fluorinated monomers using perfluoropolyethers of the following formula (I) or (II). In particular, the perfluoropolyether surfactants correspond to formula (I) or (II)

CF₃—(OCF₂)_m—O—CF₂—X  (I)

wherein m has a value of 1 to 6 and X represents a carboxylic acid group or salt thereof,

CF₃—O—(CF₂)₃—(OCF(CF₃)—CF₂)_z—O-L-Y  (II)

wherein z has a value of 0, 1, 2 or 3, L represents a divalent linking group selected from —CF(CF₃)—, —CF₂— and —CF₂CF₂— and Y represents a carboxylic acid group or salt thereof. The invention further relates to an aqueous dispersion of a fluoropolymer having the aforementioned perfluoropolyether surfactant(s).

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims priority to Great Britain Patent Application No. GBO514387.0, filed on Jul. 15, 2005, herein incorporated by reference in its entirety. [0002] The present invention relates to the aqueous emulsion polymerization of fluorinated monomers to produce fluoropolymers. BACKGROUND OF THE INVENTION [0003] Fluoropolymers, i.e. polymers having a fluorinated backbone, have been long known and have been used in a variety of applications because of several desirable properties such as heat resistance, chemical resistance, weatherability, UV-stability etc. The various fluoropolymers are for example described in “Modern Fluoropolymers”, edited by John Scheirs, Wiley Science 1997. Commonly known or commercially employed fluoropolymers include polytetrafluoroethylene (PTFE), copolymers of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) (FEP polymers), perfluoroalkoxy copolymers (PFA), ethylene-tetrafluoroethylene (ETFE) cop...

AI Technical Summary

Benefits of technology

[0021] Since the aqueous emulsion polymerization can be carried out without the need for using a perfluoroalkanoic acid, dispersions can be readily obtained that are free of such perfluoroalkanoic acids or salts thereof. Thus, in a further aspect, the present invention relates to an aqueous dispersion of a fluoropolymer comprising a perfluoropolyether selected from the group consisting of perfluoropolyethers according to above formula (I), perfluoropolyethers according to above formula (II) and mixtures of perfluoropolyethers according to formula (I) and / or (II) as an emulsifier and wherein the aqueous dispersion is free of perfluorinated alkanoic acids or salts thereof.

Problems solved by technology

However, environmental concerns have been raised against these surfactants and moreover these surfactants are generally expensive.

It is taught that the perfluoropolyether surfactants on their own are not very powerful surfactants.