Process for preparation of yellow shade modification of gamma quinacridone
AssigneeCiba-Geigy Corporation
InventorEdward E. Jaffe
Life of this patent
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Abstract
Process for preparing yellow shade modification of gamma quinacridone whereby the .gamma..sub.II form is converted to the .gamma..sub.I form (1) by milling in an alcohol and in the presence of a base or (2) by premilling the .gamma..sub.II form to the .gamma..sub.I form and then refluxing or milling the resulting .gamma..sub.I form in an alcohol in the presence of a base, the resulting product being a highly crystalline, bright, yellow shade, ready dispersable .gamma..sub.I quinacridone pigment.
Claims16
A process for converting crude gamma-phase II quinacridone to gamma-phase I quinacridone having an average particle size in excess of 0.1 .mu.m and a surface area less than 30 square meters per gram which comprises milling the crude quinacridone in the presence of a converting system consisting essentially of effective converting amounts of a lower alcohol or glycol and a base and isolating the yellow-shade gamma-phase I quinacridone.
A process for converting crude gamma-phase II quinacridone to gamma-phase I quinacridone having an average particle size in excess of 0.1 .mu.m and a surface area less than 30 square meters per gram which comprises the steps of dry premilling the crude quinacridone for conversion to the gamma I form, contacting said premilled quinacridone with a system consisting essentially of a lower alcohol or glycol and a base, refluxing the resulting quinacridone dispersion and isolating the yellow shade gamma-phase I quinacridone.
A process for converting crude gamma-phase II quinacridone to gamma-phase I quinacridone having an average particle size in excess of 0.1 .mu.m and a surface area less than 30 square meters per gram which comprises the steps of dry premilling the crude quinacridone for conversion to the gamma I form, milling the premilled quinacridone in the presence of a system consisting essentially of effective particle growth promoting amounts of a lower alcohol or glycol and a base and isolating the yellow shade gamma-phase I quinacridone.
Dependencies are inferred from the claim text.