Fluorination method for phosphonitrilic chloride trimer and its derivatives

This application is the national phase entry of International Application No. PCT/CN2015/093219, filed on Oct. 29, 2015, which is based upon and claims priority to Chinese Patent Application No. CN2015101758942, filed on Apr. 14, 2015, the entire contents of which are incorporated herein by reference.

This invention relates to a fluorination method for phosphonitrilic chloride trimer and its derivatives.

Phosphazenes have both the good flame retardant property of phosphorus flame retardant and flame retardant synergism of nitrogen compound. Without the need to add any other assisting flame retardants, they have advantages like good flame retardant efficiency, good thermal stability, no toxicity, less smoke and self-extinguishment and are therefore generally recognized as one of the future development directions of fire retardant. Various kinds of phosphazene flame retardants are synthesized and used in flame retardant research of various materials. At the same time, phosphazenes can also be used in preparation of high temperature resistant, low temperature resistant and oxidation resisting special rubber and elastic materials used in military and aerospace industries. Chloro-cyclotriphosphazene has good flame retardant efficiency. However, it has easy hydrolysis and chlorine is highly corrosive to battery system. Recently, it is found in research that replacing chlorine with fluorine can get a functional phosphazene derivative with hydrolysis resistance, lower viscosity and better compatibility. Fluoro-phosphazenes can also be used as an efficient flame retardant for lithium ion battery. Currently, phosphazenes are usually fluoridized in organic small molecule solvent and then make distillation and fractionation to the fluoride generated. As the organic small molecule is volatile and forms azeotrope with fluoro-cyclotriphosphazene, which makes purification difficult. It wastes solvents and increases cost.

To solve the above problem, this invention provides an efficient and non-volatile fluorination system in which ionic liquid is used as reactive system solvent to improve fluorination efficiency of cyclotriphosphazene and its derivatives and reduce purification cost.

The technical plan adopted in this invention is as follows:

A fluorination method for phosphonitrilic chloride trimer and its derivatives, characterized in that (including the following steps):

Dissolve phosphonitrilic chloride trimer or its derivatives in ionic liquid, add fluorinating agent and control the temperature to have fluorination. Then distill to prepare high-purity hexafluorocyclotriphosphazene or its derivatives.

The chemical formula of the described phosphonitrilic chloride trimer and its derivatives is:

Wherein: There is at least one chlorine in S 1 -S 6 , and S 1 -S 6 come independently from alkyl, alkoxy, fluoroalkoxy, aryl, carboxyl, hydroxy, cyanogroup, nitro, ether oxygen group and halogen.

The chemical formula of the described ionic liquid is:

Substitution in the above chemical formula is mono, binary or triple substitution, and moreover, R1, R2 and R3 are independently selected from alkyl (when the carbon atom is 0, R, R2 or R3 is hydrogen), alkoxy, aryl, carboxyl, hydroxy, cyanogroup, nitro, ether oxygen group and halogen of carbon atom in 0-20.

The optimal and substitution groups R 1, R2 and R3 are independently selected from the following groups: methyl, ethyl, propyl, butyl, vinyl, allyl, butenyl, vinylidene, phenyl or benzyl.

Wherein, the anion X is at least one from the following: F—, PF6-, BF4-, TFSI—, FSI—, BOB— and ClO4-.

The fluorinating agent described is one or multiple combinations of ammonium, lithium, sodium, potassium, rubidium, calcium, magnesium, aluminum, chromium, iron, cobalt, antimony, nickel, copper, zinc, titanium or rare earth fluorides, and the optimal fluorides are sodium fluoride and potassium fluoride.

Temperature of the described fluorination is 10-300° C., and the optimal temperature is 100-130° C. Time for the described reaction is 2-98 hours, and the optimal time is 12-15 hours. Temperature of the distillation described is 40-300° C. The optimal temperature is 10° C. higher than the boiling point of the product.

Compared with current technology, this invention uses non-volatile and pollution free ionic liquid, and just controls distillation temperature to get high-purity hexafluorocyclotriphosphazene or its derivatives. It overcomes the shortcoming that solvent of average solvent system forms azeotrope with product. The post-process is simple, product purity and production rate are high, and the ionic liquid can be used repeatedly.

Take 0.1 mole phosphonitrilic chloride trimer and add it into a flask with 100 ml 1-benzyl-3-methylpyridinium hexafluorophosphate ionic liquid and then add 1 mole sodium fluoride. Fluoridate 10 hours at 130° C. and then distill at 60° C. to get high-purity hexafluorocyclotriphosphazene.

Take 0.1 mole ethoxy pentachloride cyclotriphosphazene and add it into a flask with 100 ml 1-allyl-3-methylimidazolium tetrafluoroborate ionic liquid and then add 1 mole sodium fluoride. Fluoridate 12 hours at 130° C. and then distill at 160° C. to get high-purity pentafluoro ethoxy cyclotriphosphazene.

Take 0.1 mole pentachloride trifluoro ethoxy cyclotriphosphazene and add it into a flask with flux unit and containing 100 ml 1-phenyl-3-methylimidazolium tetrafluoroborate ionic liquid and then add 1 mole potassium fluoride and 0.5 mole sodium fluoride. Fluoridate 20 hours at 200° C. and then distill at 180° C. to get high-purity pentafluoro ethoxy cyclotriphosphazene.

Take 0.1 mole dichloro tetrabutoxy cyclotriphosphazene and add it into a flask with flux unit and containing 100 ml 1-methyl-3-methylimidazolium tetrafluoroborate ionic liquid and then add 0.5 mole potassium fluoride and 0.5 mole calcium fluoride. Fluoridate 16 hours at 280° C. and then distill at 220° C. to get high-purity difluoro tetrabutoxy cyclotriphosphazene.

Take 0.1 mole pentachloride phenoxy cyclotriphosphazene and add it into a flask with flux unit and containing 100 ml 1-ethylene-3-methylimidazolium tetrafluoroborate ionic liquid and then add 0.8 mole potassium fluoride. Fluoridate 16 hours at 50° C. and then distill at 240° C. to get high-purity pentafluoro phenoxy cyclotriphosphazene.

Take 0.1 mole pentachloride phenoxy cyclotriphosphazene and add it into a flask with 50 ml 1-phenoxy-3-methylimidazolium tetrafluoroborate and 50 ml 1-allyl-3-imethylimidazolium hexafluorophosphate ionic liquid and then add 0.8 mole potassium fluoride and 0.2 mole zinc fluoride. Fluoridate 16 hours at 50° C. and then distill at 240° C. to get high-purity pentafluoro phenoxy cyclotriphosphazene.