GB864130A - Improvements in and relating to polymers - Google Patents

Abstract

864,130. Perfluorocarbon polymers. DU PONT DE NEMOURS & CO., E. I. June 12, 1958 [June 12, 1957], No. 18750/58. Class 2(6). A process for preparing perfluorocarbon polymers comprises contacting, at at least 0‹C., tetrafluoroethylene, or a mixture of at least 20 molar per cent thereof with a C 3-10 perfluoroolefine having a terminal difluoromethylene group, with a catalytic amount of a metal fluoride wherein the metal has a higher oxidization potential than mercury and is present in its highest valency state. Such metals (and their fluorides) are chromium (trifluoride), manganese (trifluoride), cerium (tetrafluoride), lead (tetrafluoride), bismuth (pentafluoride), cobalt (trifluoride) and silver (difluoride). The amount of catalyst may be 0À1 to 50, preferably 0À5 to 5 molar percent. The preferred temperature range is 15 to 150‹C. The reaction may be carried out with the monomer and catalyst alone in a sealed vessel at the autogeneous pressure e.g. up to 200 atmospheres but it is preferred to use an inert diluent which is a solvent for at least one of the monomer and catalyst to an extent of at least 5% at 25‹C. Suitable diluents are fluorine containing liquids e.g. hydrogen fluoride, arsenic trifluoride, antimony pentafluoride and fluorocarbons containing an aliphatic radical and free from aliphatic unsaturation such as perfluoro-dimethylcyclohexane, -toluene, -ethylcyclopentane, -n-octane, and -n-decane. The diluents may be used in amounts of 0À5 to 20 parts by weight per part of catalyst. The perfluoroolefins which may be copolymerized with the tetrafluoroethylene have the general formula CnF 2 n, where n is at least 3 and not more than 10, especially those of the formula F-(CF 2 )m-CF=CF 2 where m is an integer from 1 to 8 e.g. hexafluoropropene-1, octafluorobutene-1, dodecafluorohexene-1, hexadecafluoroheptene-1 and eicosafluorodecene-1. Examples describe the polymerization of tetrafluoroethylene with lead, silver and cobalt fluorides in arsenic trifluoride; with cobalt trifluoride in liquid hydrogen fluoride and in perfluorodimethylcyclohexane; and the copoperfluorodimethylcyclohexane; and the copolymerization of tetrafluoroethylene and hexaflucropropene with silver difluoride in arsenic trifluoride. The products were purified by extraction with acetic, hydrochloric and nitric acids.