A method for the separation of linear polydichlorophosphazene of cyclic poly dichlorobenzene phosphazene oligomers

摘要

1506365 Linear (NPCL 2 ) n ; polyphosphazenes HORIZONS RESEARCH Inc 22 June 1976 [23 June 1975] 25995/76 Heading C1A Linear (PNCl 2 ) n are separated from cyclic (PNCl 2 ) n which have a degree of polymerization of 3 to 7 by (i) thermally polymerizing cyclophosphazene (NPCl 2 ) 3 or (NPCl 2 ) 4 , or mixtures thereof, (ii) contacting the mixed product of linear and cyclic (PNCl 2 ) n with a solvent or solvent mixture selected from aliphatic hydrocarbons of boiling point at least 65‹ C., and (iii) separating a solution of the cyclic species from the insoluble linear polydichlorophosphazenes. The amount of solvent used may be 2-6 the weight of the product of the thermal polymerization. In particular, a process is described wherein linear polyphosphazenes of general formula where n is 50 to 20,000, and each R represents an alkyl, substituted alkyl, aryl or arylalkyl, with at least some of the R groups possessing unsaturation, the process comprising (a) thermally polymerizing at least one polydichlorophosphazene (NPCl 2 ) m in which m is 3 to 7, yielding a product of linear (NPCl 2 ) q where q is greater than 7 and cyclic (PNCl 2 ) x where x is 3 to 7, (b) extracting the cyclic species from the product using an aliphatic hydrocarbon with a boiling point of at least 65‹ C. to produce a solution of cyclic, polydichlorophosphazenes and recovering and reacting a solid residue containing linear species with an alkali metal alkoxide (e.g. NaOR) to yield the polyphosphazene. The hydrocarbon solvent is removed from the solution and the residual cyclic polydichlorophosphazenes are recycled to the polymerizing step. The solvent, purified if necessaary, may be re-used.