Synthesis Of Perfluoropolyether By Anionic Polymerization And Its Application

Perfluoropolyether(PFPE)is widely used in modified specialty chemicals and high performance lubricant oils because of chemical inertness,non-combustibility,and low surface tension.Most of PFPE products in China is imported at present.Mature production technology is needed.In this paper,the synthesis technology of PFPE by anionic polymerization was developed and the high quality vacuum pump oil was obtained.The purifying performances and capacityies of different combinations of purification agents on removing HF,water and hexafluoroacetone were investigated.The experimental results showed that the contents of HF,water and hexafluoroacetone were dropped to 500?g/g,2?g/g and 300?g/g with anhydrous Calcium chloride-3A molecular sieve-Calcium oxide-Activated alumina.The reaction mechanism of hexafluoropropylene oxide polymerization was analyzed.The result showed that the control step of reaction rate was chain growth,while the chain transfer and chain regeneration controlled the degree of polymerization.From the viewpoint of reaction engineering,the effects of single feed reactor,batch feed reactor and continuous reactor on polymerization process were investigated.In the continuous reactor,low monomer content,high dormant chain conten tand low active chain content increased the degree of polymerization.Under the optimum conditions with the catalyst of CsF and diethylene glycol dimethyl ether,the residence time of 72 h,the reaction temperature of-60? and CsF:HFPO=1:60,the average degree of polymerization was 20.0 and average molecular weight reached 3325 g/mol.The yield of PFPE was 99.2%.The polymerization kinetics model of hexafluoropropylene oxide was established.Different polymerization processes for PFPE synthesis were simulated.The stable PFPE oil was obtained by alkali hydrolysis.Under the conditions with potassium hydroxide solution:PFPE=1:3,the reaction temperature of 100?,the reaction time of 6h,the PFPE oil was obtained by adding 2%A1F3 at temperature of 250? for 8 h.PFPE oil with different degree of polymerization was separated by vacuum distillation.The oil properties and vacuum performance showed that the fractions of 200-250? and>250?can be used as high performance vacuum pump oil.