Emulsion polymerization of vinyl fluoride

Emulsion Polymerization of Vinyl Fluoride in the Presence of Ammonium Iodide 344... 

The surfactants usually used in the emulsion polymerizations of nonfluorine-containing monomers appear to be unsatisfactory in the case of vinyl fluoride polymerizations [6]. Salts of the higher perfluorinated carboxylic acids are more suitable emulsifiers. Cationic surfactants based on perfluoroalkylpropylamines are used in a recent patent for the emulsion polymerization of vinyl fluoride [36]. 

In another patent [53], a seeded emulsion polymerization is described. The seed polymer is prepared by emulsion polymerization of vinyl fluoride using tert-butyl peroxypivalate as initiator and ammonium G>-hydroperfluoronona-noate as emulsifier. The process required 9 hr at 40 kg/cm (0.4 MPa). The resultant particles were described as having an average diameter of 18/an (which we would consider a a bit large for emulsion particles) and are said to be present in a concentration of 2.26 X lo particles/dm. In the second stage of the process, this seed latex (400 ml in a total volume of 1.8 dm ) was subjected to the same reaction conditions a second time. 

Considerable work has been done on the initiation of the vinyl fluoride by ionizing radiation much as y-radiation from a °Co source. A selection of references on this research includes Usmanov and other authors [4,48-62], Of these, Usmanov et al. [4] deal with the graft copolymerization of vinyl fluoride to some natural and synthetic polymers. Usmanov et al. [53] discuss the formation of branched polymers during radiation-induced polymerization. Gubareva et al. [54] deal with solution polymerizations. Nakamura et al. [58, 59, 61] deal with emulsion polymerizations of vinyl fluoride by radiation initiations. Usmanov et al. [60,61] discuss the effects of chain-transfer agents during radiation-initiated polymerization. Some copolymerization studies are described in Usmanov et al. [55]. 

As mentioned before, the monomer has a low boiling point ( - 72.2°C) and a relatively low critical temperature (54.7°C). For comparison, vinyl chloride has a boiling point of - 13.8°C and a critical temperature of 147°C (cf. this series, Vol. 11, 2nd ed., p. 358). Therefore the polymerization of vinyl fluoride is usually carried out under high-pressure conditions which probably resemble the polymerization of ethylene more than that of the other vinyl halides. The monomer is soluble in a variety of solvents. At room temperature, the homopolymer is insoluble. Therefore the neat subdivision of polymerization techniques into bulk, solution, suspension, and emulsion procedures which we have used in many other sections in this series becomes blurred. Most procedures seem to lead to blocks of polymer or some sort of dispersions from which... 

The earliest reported polymerization of vinyl fluoride involved heating a saturated solution of VF in toluene at 67°C at 600 MPa for a period of 16 hours. In another study, benzoyl peroxide was the polymerization initiator. A polymer was produced with a density of 1.39 g/cm which could be dissolved in hot dimethylformamide, chlorobenzene, and other polar solvents. A great many initiators and vinyl fluoride polymerization conditions have been studied. Examples ofbulk f ] and solution[ ][ F[i04] pp lymerizations have been reported. Aqueous suspension or emulsion techniques have been generally preferable over other methods.Vinyl fluoride volatility required the use of moderately high pressures during the polymerization. Photopolymerization of VF, aided by a free-radical initiator, has also been accom-... 

The resulting complexes can be effectively employed as single component catalysts to homopolymerize ethylene or copolymerize ethylene with acrylates [50, 51] and a variety of other polar monomers including vinyl ethers, [51,52] vinyl fluoride [53], iV-vinyl-2-pyrrolidinone, and AMsopropylacrylamide [54], In fact, the resulting catalysts are so robust that they can be used as single component catalysts in aqueous emulsion homo-polymerization of ethylene and copolymerization of ethylene with norbomenes and acylates [55]. 

Vinyl fluoride imdergoes free-radical polymerization.The first polymerization involved heating a saturated solution of VF in toluene at 67° C under 600 MPa for 16 hr. A wide variety of initiators and polymerization conditions have been explored. Examples of bulk and solution polymerizations exist however, aqueous suspension or emulsion method is generally preferred. Copolymers of VF and a wide variety of other monomers have been prepared. More recently, interpolymers of VF have been reported with tetrafluoroethylene and other highly fluorinated monomers, such as hexafluoropropylene, perfluorobuty-lethylene, and perfluoroethylvinylether. 

Copolymers from tetrafluoroethylene and 40% perfluorovinyl methyl ether are also elastomers (glass-transition temperature — 12°C). The copolymerization is carried out in aqueous emulsion with ammonium perfluoro-octanoate as emulsifier. Vulcanization is possible with hexamethylene diamine via the small amount of perfluoro(4-carboxy methyl butyl vinyl ether) also polymerized into the copolymer. This ether is produced from perfluoroglutaryl fluoride and hexafluoropropylene oxide. 

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