Study On The Reaction Crystallization Process Of Pigment Red 146

Pigment Red 146 is a medium-to-high-grade red organic pigment,belonging to azo pigments,mainly used in printing and dyeing,coatings and inks.At present,the domestic Pigment Red 146 product has problems such as unsatisfactory crystal habit and poor particle size distribution,which affects the performance of the pigment.At the same time,with the rapid development of inkjet printing technology,it is of great significance to prepare nanoscale pigment red 146 products to meet the needs of inkjet printing.In this paper,the crystallization thermodynamic properties of Pigment Red 146 were first studied.The static method and UV-visible absorption spectroscopy were used to determine the solubility of Pigment Red 146 in N,N-dimethylformamide,dimethyl sulfoxide,dimethylacetamide and tetrahydrofuran at different temperatures from 293.15 to 328.15 K.Group contribution method were used to calculate the melting point and melting enthalpy.The solubility data was fitted by the NRTL equation and the Apelblat simplified equation.And the dissolution enthalpy,dissolution Gibbs free energy and dissolution entropy were calculated to analyze its dissolution law.Then,a new reaction crystallization process to produce Pigment Red 146 was successfully developed.The process conditions such as solvent type and ratio,reaction crystallization temperature and stirring rate were optimized to prepare Pigment Red 146 product with a complete needle-like habit and good particle size distribution.Next,this paper proposed a preparation method of a nano-scale Pigment Red 146 product,in which the emulsion droplets are used as a soft template to carry out the reaction crystallization process of the Pigment Red 146.The principle of product synthesis was described,and the effects of surfactant type and ratio,oil-water ratio,ultrasonic treatment duration,stirring rate and reaction time on emulsion droplets and products were explored.A product with a particle size of about 400 nm was prepared.Finally,based on the above research,combined with the new fine emulsion technology in recent years,the template method was optimized and improved.The kinetically stable miniemulsion system further enhances the space-limiting effect on the product reaction crystallization process,and successfully prepares Pigment Red 146 nm particles with a maximum particle size below 500 nm and an average particle size of 172.5 nm.