about 10 of the diester of formula iiic more typically the blend typically comprises by weight of the blend i from about 6 to about 12 of the diester of formula iiia ii from about 86 to about 92 of the diester of formula iiib and iii from about 0 5 to about 4 of the diester of formula iiic most typically the blend comprises by weight of the blend i about 9 of the diester of formula iiia ii about 89 of the diester of formula iiib and iii about 1 of the diester of formula inc the blend is generally characterized by a flash point of 98 u00b0 c a vapor pressure at 20 u00b0 c of less than about 10 pa and a distillation temperature range of about 200 275 u00b0 c in some embodiments the polar solvent blend comprises by weight of the solvent blend up to 100 wt or 99 9 wt of the ketone in one embodiment the polar solvent blend comprises by total weight of the polar solvent blend up to 80 wt of the ketone in one embodiment the polar solvent blend comprises by total weight of the polar solvent blend up to 90 wt of the ketone in one embodiment the polar solvent blend comprises by total weight of the polar solvent.