Trimethyl borate → Boric Acid

Temperature

60 °C

Then, 207.6 g (2.0 mols) of trimethyl borate was added to 618 g (3.0 mols) of tripropylene glycol monomethyl ether. The mixture was heated to 60° C. with stirring in a dry nitrogen atmosphere. After the mixture was kept at 60° C. for 1 hour, it was heated to 120° C. over a period of 1 hour. After the temperature reached 120° C., the pressure in the system was gradually reduced. The system was kept at a pressure of 2.67 kPa (20 mmHg) or lower for 3 hours to remove volatile matters produced with progress of ester interchange reaction of boric acid and excess trimethyl borate, followed by filtration to obtain 610 g of a polymerizable boron-containing compound G (an esterification product of boric acid with tripropylene glycol monomethyl ether) represented by the formula (3). An infrared absorption spectrum of the resulting polymerizable boron-containing compound G was measured to confirm that the absorption band originating from hydroxyl group at 3300 cm−1 disappeared.