Antioxidants for overcoat layers and methods for making the same

摘要

Antioxidants used for overcoat layers and processes for making the same. The present process for making the antioxidant has proven to be repeatable, cheaper, faster and safer than conventional processes. In particular, the present process uses a different solvent system where crude bis(4-diethylamino-2-methylphenyl)-(4-diethylaminophenylmethane) is dissolved in methylethyl ketone at room temperature, followed by product precipitation in a warm mixture of ethanol and water.

主权项

1. A process for making purified bis(4-diethylamino-2-methylphenyl)-(4-diethylaminophenylmethane) comprising:
dissolving crude bis(4-diethylamino-2-methylphenyl)-(4-diethylaminophenylmethane) in a first solvent room temperature to form dissolved crude bis(4-diethylamino-2-methylphenyl)-(4-diethylaminophenylmethane); heating a mixture of a second solvent and a third solvent to a temperature of about 50° C. or higher to form a warm co-solvent mixture; adding the dissolved crude bis(4-diethylamino-2-methylphenyl)-(4-diethylaminophenylmethane) to the warm co-solvent mixture in a drop-wise manner to form a precipitate mixture; mixing the precipitate mixture; cooling the precipitate mixture; and drying the precipitate mixture to obtain the dried product comprising purified bis(4-diethylamino-2-methylphenyl)-(4-diethylaminophenylmethane), wherein the first, second and third solvents are not isopropanol.