Study On The Synthesis Of Pigment Red 146

Pigment as a colorant,it is difficult to dissolve in ordinary solvents,but in the form of particles dispersed in the solvent for coloring matter.In people's daily life,the application of pigments can be seen everywhere,involving clothing,food,housing,transportation and other aspects,so researchers have carried out extensive research on pigments.Pigment red 146 is a kind of azo pigments,which is mainly used in pigment printing paste,ink,water-based paint and so on.In the industry,pigment red 146 is usually produced by batch operation in a stirred tank.Due to the large volume of the stirred tank,the materials can not be fully mixed in a short time,the pigment particles agglomerate and the particle size becomes larger.The diazotization reaction and coupling reaction are strong exothermic reactions,and the diazonium salt produced by diazotization reaction is thermally unstable,so it is easy to cause the local temperature in the stirred tank to be high,which will lead to the explosion of diazonium salt.In addition,the batch operation mode will also cause the quality difference between batches.Therefore,it is necessary to develop new reactors and study continuous production process to improve the safety of production process and product quality.As a new type of reactor,rotating packed bed(RPB)can greatly enhance the mass transfer and micro mixing process by simulating the high gravity environment,and realize continuous production.Therefore,the RPB was used for the synthesis of pigment red 146 to explore the continuous production process.In this paper,the optimal synthesis process of pigment red 146 was investigated in a stirred tank.Then,as a reference,the continuous synthesis of pigment red 146 was studied in the RPB.UV spectrometer(UV),infrared spectrometer(IR),X-ray diffraction(XRD),elemental analyzer and scanning electron microscope(SEM)were used to analyze and characterize.Optimal process conditions in the stirred tank:1.Diazotization reaction:reaction temperature of 3?;reaction time of 40 min;molar ratio of Red base KD to hydrochloric acid was 1:2.6;molar ratio of Red base KD to sodium nitrite was 1:1.05;stirring speed of 500 rpm.The highest yield was 97.7%.2.Coupling reaction:reaction temperature of 10?;reaction time of 60 min;pH=5;stirring speed of 400 rpm.The highest yield was 96.5%,and the average particle size was 190 nm.Optimal process conditions in the RPB(the ratio of reactants and pH value were the same as those in the stirred tank):1.Diazotization reaction:reaction temperature of 15?;feed flow rate of 200 ml/min;the rotation speed of the high gravity reactor was 1600 rpm;circulation time of 0 min.The highest yield was 95%.2.Coupling reaction:circulation time of 0 min;feed flow rate of 150 ml/min;the rotation speed of the high gravity reactor was 1200 rpm;the surfactant was op-10.The average particle size was about 70 nm.Under the optimum conditions,the yield is about 93%.In conclusion,the RPB can make the temperature of diazotization reaction rise,shorten the reaction time of diazotization reaction and coupling reaction,and the particle size of the product can reach nanometer level under the condition of ensuring the yield,so it has a good industrial application prospect.