Analysis of the synthesis of fluorescent whitener DT

The uses and synthetic processes were summarized. The new theory for the Reaction mechanism of DT synthesis by Ladenburg Reaction of malic acid was investigated. The selection of the 8 Reaction conditions was discussed on this basis, and the essential controls and the resolution of the principal problems were proposed. The following process was believed to have many advantages: Reaction of o-amino-p-cresol with malic acid in xylene solvent with boric acid as the catalyst, followed by dewatering, distn., purifn. etc. The optimal mol. ratio of o-amino-p-cresol and malic acid was 2∶1 ~ 2∶1.05. The Reaction temps. after the initial temp. rising could be divided into 3 stages: 140 ℃ for the first, 170 ℃ for the second and above 190 ℃ for the third stage. The product was of high whiteness and the yield surpassed 85%. The future research directions and methods were also proposed.