Tetraphenyl phosphonium salts are stable at high temperature and have been reported for several PTC reactions including fluoride halex reactions and polymerizations based on nucleophilic aromatic substitution. Alkyl triphenyl phosphonium salts are used to build molecular weight for epoxy resins after benzyl trimethyl ammonium chloride is used to form bisphenol A diglycidyl ether (“BAGDE”).
The reaction shown in the diagram is not a phase-transfer catalysis reaction, it’s a reaction catalyzed by organic soluble chloride or bromide. The halide opens the epoxide rings of BADGE and the resulting alkoxide attacks the isocyanate (MDI) that ring closes to the oxazolidone, liberating the halide for another cycle. In a second step, molecular weight is built by adding more MDI. A monofunctional epoxide, para-t-butyl phenyl glycidyl ether is used to cap (terminate) the polymer, performed in two steps.
The reaction conditions described in the patent application publication provides several advantages. This catalyst system produces a polyoxazolidinone product with low polydispersity, and high chemical selectivity. In particular it reduces the amount of unwanted side products like isocyanurates (formed from isocyanates) that cause unwanted cross-linking of the reaction product and negatively impact the thermoplastic properties.
About Marc Halpern
Dr. Halpern is founder and president of PTC Organics, Inc., the only company dedicated exclusively to developing low-cost high-performance green chemistry processes for the manufacture of organic chemicals using Phase Transfer Catalysis. Dr. Halpern has innovated PTC breakthroughs for pharmaceuticals, agrochemicals, petrochemicals, monomers, polymers, flavors & fragrances, dyes & pigments and solvents. Dr. Halpern has provided PTC services on-site at more than 260 industrial process R&D departments in 37 countries and has helped chemical companies save > $200 million. Dr. Halpern co-authored five books including the best-selling “Phase-Transfer Catalysis: Fundamentals, Applications and Industrial Perspectives” and has presented the 2-day course “Practical Phase-Transfer Catalysis” at 50 locations in the US, Europe and Asia.
Dr. Halpern founded the journal “Industrial Phase-Transfer Catalysis” and “The PTC Tip of the Month” enjoyed by 2,100 qualified subscribers, now beyond 130 issues. In 2014, Dr. Halpern is celebrating his 30th year in the chemical industry, including serving as a process chemist at Dow Chemical, a supervisor of process chemistry at ICI, Director of R&D at Sybron Chemicals and founder and president of PTC Organics Inc. (15 years) and PTC Communications Inc. (20 years). Dr. Halpern also co-founded PTC Interface Inc. in 1989 and PTC Value Recovery Inc. in 1999. His academic breakthroughs include the PTC pKa Guidelines, the q-value for quat accessibility and he has achieved industrial PTC breakthroughs for a dozen strong base reactions as well as esterifications, transesterifications, epoxidations and chloromethylations plus contributed to more than 100 other industrial PTC process development projects.
Dr. Halpern has dedicated his adult life to his family and to phase-transfer catalysis (in that order!).
