Synthesis of trimethylolpropane fatty acid triester as a high performance electrical insulating oil

The trimethylolpropane esters (TME) based high performance electrical insulating oil was synthesized by esterification of the mixture of C-6, C-8 and C-10 acids blend with trimethylolpropane (TMP). The conversion yields of TME is maximized at catalyst (SnCl2) dosage of 0.8 wt.% and the TMP:acid molar ratio of 3.2:1 at 140 degrees C. The electrical performance is significantly improved by a purpose-oriented purification process which is structured by washing with ultrapure water and absorption with molecular sieve. The obtained insulating oil shows much reduced viscosity (23.3 mm(2) s(-1)) and much enhanced AC breakdown voltage (72.6 kV) comparing with the commercial natural ester insulating oil FR3 (R) (34 mm(2) s(-1) and 63 kV). The high performance of the insulating oil is also manifested by quite low pour point (-45 degrees C) and high flash point (248 degrees C) which are superior to those values of mineral insulating oil (-30 degrees C and 170 degrees C). The remarkable oxidation stability of the insulating oil is metered by the oxidation induction time (OIT) 2275 min at 130 degrees C which should be attributed to the elimination of C=C double bonds and beta-H atoms.