Study on the transformation of metal-free phthalocyanine polymorph crystals by organic solvent treatment

摘要

Five organic solvents,sulfolane,N,N-dimethylethanolamine,iso-propanol,N,N-dimethylformamide (DMF),and acetone have been used to precipitate the sulfuric acid slurry paste of metal-free phthalocyanine and the pigments were analyzed by the X-ray powder diffraction method.The morphology was investigated by scanning electron microscopy.The organic solvents provided certain influences on the formation of the polymorphs.The alpha-form metal-free phthalocyanine was obtained by precipitation of the phthalocyanine acid-paste in DMF,iso-propanol,and 2-dimethylethanolamine.The beta-form of the metal-free phthalocyanine was obtained by direct synthesis in 2-dimethylethanolamine or by precipitation of the phthalocyanine acid-paste in sulfolane.Finally the gamma-form of metal-free phthalocyanine was obtained in acetone.The dispersibility of the metal-free phthalocyanine was improved after the solvent treatment process.These results gave an interesting and potentially commercially important improvement for polymorph transformation of metal-free phthalocyanine.