Patent GB-865722-A (GB)
Title: Process for the manufacture of poly-fluoro-chloro carboxylic acids
IPC: C07C51/093
Filed: 1957-10-17
Abstract: Polyfluorochlorocarboxylic acids are obtained by hydrolizing an oil or wax of low molecular weight as hereinafter defined, or a polymeric oil containing fluorine and chlorine, at raised temperature with sulphuric acid of at least 98% strength or oleum containing up to about 60% by weight of free sulphur trioxide and in the presence of 0,05 to 10% by weight of nitrosyl-sulphuric acid calculated on the quantity of 100% sulphuric acid.  The oils and waxes of low molecular weight are obtained by the thermal decomposition of polymers of perfluorochloro-olefines and consist of mixtures of olefines and paraffins containing about 20% carbon, about 30% chlorine and about 50% fluorine and having average molecular weights between 400 and 1,000.  The nitrosyl-sulphuric acid may be formed during the reaction by the addition of absolute nitric acid or a nitrate to the reaction mixture.  Preferred temperatures for the hydrolysis are about 150 DEG to about 300 DEG C. The alkali metal salts of the resultant acids are used as emulsifying agents and the diacyl peroxides of the acids are used as initiators in olefine polymerizations.  In Examples: (1) an oil obtained by the thermal cracking of polytrifluorochloroethylene is heated with a mixture of absolute sulphuric acid, kieselguhr and nitroyl sulphuric acid, the mixture made alkaline with potassium hydroxide, the aqueous layer separated and the acids precipitated with hydrochloric acid; (2) a polymer oil obtained from trifluorochlor-ethylene as described in Example 2 of Specification 744,256 is heated with absolute sulphuric acid and nitric acid is added dropwise during the reaction.  Specification 758,419 also is referred to.ALSO:Polyfluorochlorocarboxylic acids are obtained by hydrolysing an oil or wax of low molecular weight as hereinafter defined, or a polymeric oil containing fluorine and chlorine, at raised temperature with sulphuric acid of at least 98% strength or oleum containing up to about 60% by weight of free sulphur trioxide and in the presence of 0,05 to 10% by weight of nitrosyl-sulphuric acid calculated on the quantity of sulphuric acid of 100% strength. The oils and waxes of low molecular weight are obtained by the thermal decomposition of polymers of per-fluoro-chloro-olefines and consist of mixtures of olefines and paraffins containing about 20% carbon, about 30% chlorine and about 50% fluorine and having average molecular weights between 400 and 1000.  The nitrosyl-sulphuric acid may be formed during the reaction by the addition of absolute nitric acid or a nitrate to the reaction mixture.  Preferred temperatures for the hydrolysing are about 150 DEG  to about 300 DEG C.  The alkali metal salts of the resultant acids are used as emulsifying agents and the diacylperoxides of the acids are used as initiators in olefin polymerisations.  In examples: (1) an oil obtained by the thermal cracking of polytrifluorochloroethylene is heated with a mixture of absolute sulphuric acid, kieselguhr and nitrosyl-sulphuric acid, the mixture rendered alkaline with potassium hydroxide, the aqueous layer separated, and the acids precipitated with hydrochloric acid; (2) a polymer oil obtained from trifluorochloroethylene as described in Example 2 of Specification 744,256 is heated with absolute sulphuric acid and nitric acid is added dropwise during the reaction.  Specification 758,419 also is referred to.