Patent GB-712184-A (GB)
Title: Improvements in or relating to a process for the production of polymeric perhalo olefines
IPC: C08F14/24
Filed: 1951-04-11
Abstract: <PICT:0712184/IV (a)/1> Perhalo olefines, e.g. trifluorochloroethylene, are polymerized under conditions of temperature, residence time, and initially selected concentration of peroxide promotor to produce either (a) a solid polymer having a softening point above 200 DEG C., using a solvent for the promotor and not permitting the concentration of the monomer to vary more than 10 per cent. for more than 10 per cent. of the time; or (b) a polymer in the oil, grease or soft wax range with a softening point up to 200 DEG C., by using a chain transfer solvent and not permitting the promotor and monomer concentrations therein to vary more than 10 per cent. of the initial concentration for more than 10 per cent. of the time.  A thermoplastic polymer is produced at a temperature between -20 DEG  and 150 DEG C., at a pressure in excess of the vapour pressure of the monomer and a residence time sufficient to polymerize a major portion of the monomer, using bis-trichloro-acety-peroxide as catalyst in a concentration of between 0.1 and 0.5 per cent.  At a temperature between -20 DEG  and 25 DEG C. a polymer having a no-strength temperature between 240 and 340 DEG C. is formed.  A normally liquid, grease or wax polymeric trifluorochloroethylene is formed at a temperature of between 0 DEG C. and 300 DEG C. in the presence of benzoyl peroxide and chloroform.  Organic peroxides such as trifluoroacetyl, difluorochloroacetyl, 2, 4-dichlorobenzoyl, chloracetyl, bis-trifluorodichloro - propionyl, and dichlorofluoroacetyl peroxides, may be used and for liquid polymers, acetyl, monochloro-, dichloro- and trichloroacetyl, fluoroacetyl, p-bromobenzoyl, difluorochloroacetyl, chlorodifluoroacetyl, diethyl and di-t-butyl peroxides, and t-butyl and cumene hydroperoxides, together with other chain transfer solvents such as carbon tetrachloride, bromo - trichloromethane, trichlorotrifluoroethane, 1,1,2,2-tetrachloroethane, ethylene and saturated halogenated aliphatic compounds preferably those containing bromide or chlorine are suitable.  Inorganic promotors such as persulphates, perborates, peroxides and perphosphates, e.g. ammonium or potassium persulphates may also be used, preferably in aqueous suspension methods, in which inert diluents such as water or hydrocarbon oils are used. Polymerization may be carried out batchwise or continuously and the components may be added continuously or intermittently.  In an example, a plastic polymer of trifluorochloroethylene is prepared from a monomer prepared from trichlorofluoroethane.  The promotor is added as a solution to the monomer in a reactor which may also be in the form of tubes, coils, an elongated zone, or a reactor having an inner annular chamber around which the solution is circulated.  A slurry of monomer and solid polymer is removed, preferably continuously, by raking, passed to coolers and the polymer separated by conventional filtering or settling methods, separated monomer being purified and recycled.  The solid polymer may be further treated by fluorination, pyrolysis or by drying.  Intermediate boiling polymers of trifluorochloroethylene may be prepared in a polymerization chamber 112, Fig. 6. at a temperature preferably between 70 DEG  and 200 DEG C. under a pressure to maintain the liquid phase, passed to a stripper 118, the top products from which are condensed and recycled, and the polymer passed to a cracking chamber 141 operating at between 330 DEG  and 450 DEG C. and 25 to 200 mm. pressure, which yields a product with lower melting and boiling points.  Free chlorine and/or fluorine with antimony pentachloride, may be present during the cracking process to give a more stable oil.  The product is fractionated at 143 to yield oils of various boiling points, which may be stabilized by fluorination, separately or together, in successive steps, in a fluorinator 168 up which passes a mixture of 90 per cent. nitrogen and 10 per cent. chlorine trifluoride, and in a fluorinator 178 in which it is flowed over cobalt trifluoride granules.  The vapours are absorbed, caustic washed, stripped at 188 with an inert gas and further separated by fractional distillation if necessary. Specification 712,152 is referred to.ALSO:<PICT:0712184/IV (b)/1> Trifluorochloroethylene is prepared by dehalogenating trichlorotrifluoroethane.  A suitable apparatus comprises a dehalogenator 6 containing the trichlorotrifluoroethane in solution in, for example, methyl, ethyl, n-propyl, and n-butyl alcohols, dioxane, glycerol, butyl carbitol, the "Cellosolves" (Registered Trade Mark) and water.  A metallic dechlorinating agent, e.g. zinc, tin, magnesium, and iron is added continually or intermittently, together with a small amount of metallic halide, e.g. zinc chloride, as a promotor.  The temperature may be between 0 DEG  and 200 DEG  C. at a pressure between atmospheric and 400 pounds per square inch and preferred conditions are 115 DEG  C. at 180 pounds per square inch.  The olefine vapours pass to a rectification column 11, are liquefied in a cooler 14 and fractionally distilled in two columns 16, 26 having top temperatures of -20 DEG  and -26 DEG  C. respectively, and kettle temperatures of 15 DEG  and -20 DEG  C. respectively at atmospheric pressure. Coolers 19, 29 and accumulators 21, 30 are in the circuit.  The liquid bottoms product from column 26 is passed to a third column 34, the top product from which goes to cooler 47 and accumulator 48. Treaters 39, 41, 53, 54 used alternately contain phosphorus pentoxide, silica gel, active carbon or mixtures thereof or, preferably, alternate layers of phosphorus pentoxide and silica. Stabilizers, e.g. a t.-amine or terpene may be added to the monomer. Alternative methods of purification include treating the monomer containing stream 13 with phosphorus pentoxide prior to the fractional distillation and treating with silica gel after distillation.  The stream may be treated with phosphorus pentoxide and silica gel without a distillation stage or alternatively a water wash prior to or instead of the distillation step may be used. Bis-trichloracetyl peroxide is prepared by reacting sodium peroxide with trichloracetyl chloride at about -15 DEG  C. and extracting with trichlorofluoromethane and recovering by crystallization. Specification 712,152, [Group IV (a)], is referred to.