Improvement Of The Preparation Process To Enhance The Yield And Quality Of Pigment Red 177

C.I.Pigment Red 177(4,4’-Diamino-1,1’-dianthraquinone,PR177)is a high-grade pigment with high brightness and clear red color.It can be used for coloring of coatings,colouring of raw pulp,polyolefin and PVC.At present,DAS is synthesized by bromamine acid in an organic solvent by Ullman coupling reaction.The reaction takes 7-8 h.The purity of DAS obtained by this process is 73.5 %,and the yield is 78.3 %.But the yield and purity can not meet the production requirements.In this paper,the yield and purity of intermediate DAS prepared by Ullman coupling reaction were improved,and the post-treatment of crude PR177 was studied.1.The reaction temperature was selected 55 ℃,a mixed solvent of methanol and DMF with a mass ratio of 2: 1 was used as the reaction medium,the liquid-solid ratio of 33: 1,pretreated copper powder(600 mesh),bromaminic acid sodium 5.0 g,the reaction time was 5.5 h,and the purity of DAS was 96 %.TLC was used to monitor the synthesis of DAS.2.Adding the catalyst copper powder in batches can effectively avoid the problem of partial deactivation and shorten the reaction time.Methanol and DMF with a mass ratio of 2: 1 were used as the mixed reaction solvent,the liquid-solid ratio was 33: 1,pretreated copper powder(600 mesh),bromaminic acid sodium 5.0 g,reaction time 5.5 h,copper powder was added in batches,2/3 of the total mass of catalyst added in the early stage.In the later stage,1/3 of the total mass of catalyst added.3.The p H of the reaction system directly affects the color and quality of the Pigment Red 177.The experimental results of p H = 1-3,p H = 6.5-7.5 and p H = 10-12 were studied.The better p H is 1-3.4.It was studied that adding citric acid to make copper salt mixed in DAS form copper citrate,then filtering to remove copper ion.The ratios of copper powder to citric acid(3:1,6:1,8:1 and 12:1)were studied.The content of copper in DAS was measured.After adding citric acid,the strength of copper iondecreased to about 500.The better dosage of citric acid is 0.5 g.5.The amount of filtrate remaining after distillation has a certain effect on the yield of DAS.The yield of amount of filtrate remaining at 10,20,30 and 40 m L were studied respectively.The amount of filtrate remaining after distillation is preferably controlled at 20 m L.6.During the post-treatment of PR177,a certain amount of dispersing aid(Including super-dispersant Tilo-17000,Tilo-22000,Tilo-24000,Tilo-27000,Tilo-28000,sodium diisobutyl naphthalene sulfonate,red oil,sodium dodecylbenzene sulfonate,sodium dodecyl sulfate,disproportionated rosin,polymerized rosin,hydrogenated rosin),or combination use of super-dispersant including Tilo-17000+27000,Tilo-27000+22000,Tilo-17000+22000,Tilo-22000+28000,were added.The dispersant was dissolved in water,N-methyl-pyrrolidone or DMF respectively for adsorptionand dispersion.Additionof hydrogenated rosin to DMF has the best effect.