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US 8,557,990 B2Granted
2,5-di(methoxyanilino) terephthalic acid polymorphs and quinacridones realized therefrom
AssigneeSun Chemical Corporation
InventorsBrian Thompson, Daphne Rice, Tracie Tibbs, Wengan Wu, John Britanak, Edward H. Sung
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Abstract
2,5-di(p-methoxyanilino)terephthalic acid crystal types I and II are made by controlling the pH during the recovery of the oxidized product of the condensation of dimethylsuccinyl succinate with p-methoxyaniline. The resulting 2,5-di(p-methoxyanilino)-terephthalic acid can be converted into 2,9-dimethoxyquinacridone or a solid solution thereof having controlled characteristics.
Claims5
A method for preparing 2,5-di(p-methoxyanilino)terephthalic acid crystal type II, comprising:
- dissolving 2,5-di(p-methoxyanilino)terephthalic acid crystal type I in a solvent with a basic pH;
- and
- precipitating 2,5-di(p-methoxyanilino)terephthalic acid crystal type II by adjusting the pH of the solvent to about 5.5 or lower, wherein:
- crystal type I is brown and has an x-ray diffraction pattern that exhibits the strongest peak at d=6.3 angstroms (2θ=13.9 via CuKα);
- and
- crystal type II is violet and has an x-ray diffraction pattern that exhibits the strongest peak at d=16.1 angstroms (2θ=5.5 via CuKα).
3 more elements
Dependencies are inferred from the claim text.