Study On The Synthesis Process Of Heat-sensitive And Pressure-sensitive Dye ODB-2

2-phenylamino-3-methyl-6-dibutylaminofluorane（ODB-2）is the most widely used and highest yield fluorescent black dye in the world for its high color density,high sensitivity and good stability.In recent years,with the development of take-away and express industry,the demand for ODB-2 which is used to colouring agent of thermal paper and pressure-sensitive paper has been increased greatly.There are many synthetic routes of ODB-2,such as long route,low yield,high waste,high cost.So it is of great significance to develop a synthetic process with low cost,less waste and stable quality.In this thesis,based on the existing synthetic route,a suitable route for industrial production was designed.ODB-2 was prepared from o-nitrotoluene by three steps of catalytic hydrogenation,condensation with phenol and condensation ring closing,the synthesis route is short,high atomic utilization rate,low production cost,high yield,fewer three wastes.2-methyl-4-methoxyaniline（MMA）was synthesized from o-nitrotoluene by Pt/C catalysis and Bamberger rearrangement.The 3%Pt/C catalyst was selected,and 98%sulfuric acid was selected to provide an acidic environment.According to orthogonal experiments,the reaction temperature was 50℃,the amount of catalyst was 5%（w/w）.The optimal molar ratio of o-nitrotoluene,98%sulfuric acid,H₂O and methanol was 1:2.7:3.8:47.5.The yield of MMA was 71.30%,and the purity was 99.35%.The catalyst was treated by refluxing with methanol and water,and MMA yield was still 67.50%after repeating 30 times of the Pt/C catalyst,solving the problem of large cost ratio of precious metal catalyst in catalytic hydrogenation process.The purity of MMA was increased from 95.05%to 99.35%using rectification instead of vacuum distillation.2-methyl-4-methoxy diphenylamine（DPA）was synthesized by condensation of MMA and phenol in the presence of Pd/C.Cyclohexanone was selected as organic auxiliary agent and 5%Pd/C was used as catalyst,the optimal reaction conditions were as follows:at 230℃,the molar ratio of MMA,cyclohexanone,phenol was 1.0:0.1:5.0,the reaction time was 3 h,the yield of DPA was 96.35%and the purity of product was 99.78%.At the same time,the recycle of Pd/C catalyst was studied.The DPA yield was reduced to 35.58%after using three times if the catalyst wasn’t treated.After treatment,the catalyst could be repeated more than25 times,and the yield of DPA was still 85.12%.The catalyst accounted for the largest proportion in the production cost of this step,and the recycling technology reduced the cost by 88.32%.The target product ODB-2 was synthesized from DPA and BBA via PHT synthesis,PHT water washing curing and base-catalyzed closed-loop reaction.The effects of sulfuric acid concentration,dosage and feeding mode on the synthesis of intermediate PHT were studied.100%sulfuric acid was selected as solvent and catalyst,and the feeding mode of one-time addition was adopted.When the molar ratio of BBA,DPA,100%sulfuric acid was 1:1:14,the content of PHT was 95.13%.In addition,a unique impurity 2-methoxy-4-methyl-5-phen-ylamino-benzenesulfonic acid was successfully synthesized by High-performance liquid chromatography analysis of the product ODB-2.The impurity content is reduced from 0.62%to 0.16%by lowering the temperature of the reaction liquid when DPA was added.In the stage of PHT washing and solidification,the acid waste water was neutralized by sodium carbonate.The waste water could be recycled more than 30 times,and the waste water was reduced by 96.67%.In the closed-loop reaction catalyzed by base,the p H value of the reaction is slowly increased to 12～13 by using the two-step-adjusting-base method instead of the one-step method,thus avoiding the thermal decomposition of the raw material PHT produced during the one-step addition of base.The purity and yield of ODB-2 was increased remarkably,reaching 99.84%,91.56%,respectively.The total yield was 62.90%,the cost was reduced by 63.86%and the waste water was reduced by 96.67%.The product was identified and characterized by nuclear magnetic resonance,High-performance liquid chromatography,gas chromatography,mass spectrometry,and infrared spectroscopy.