Design, Synthesis And Characterization Of Hindered Amine Light Stabilizers

Hindered amine light stabilizers (HALS) are a new class of light stabilizers developed at the end of 1970s, which exhibited excellent light stabilizing performance much better than traditional stabilizers. Thus, the attractive research field was intensively studied during the last several decades.The two-step and three-step synthetic routes were employed for the synthesis of Cyasorb UV-3346 and Chimassorb 2020 in this paper. Cyasorb UV-3346 was successfully obtained by two-step synthetic process. The numerical average molecular weight was about 1600, the polydispersity was about 2.0, the transparency was over 95% under 425 nm and the consumption of N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl) -1,6-hexanediamine was about 0.85. Pilot scale production of it was qualified as the advanced level of the kindred products. Furthermore, Cyasorb UV-3346 has been successful according to two-step synthetic process. Chimassorb 2020 which had the numerical average molecular weight between 2600~3400 and the polydispersity lower than 1.5, was obtained by three-step synthetic process, but not by two-step synthetic route.Based on the established synthetic processes for polymeric HALS, a series of polymeric high molecular weight and multi-functional stabilizers with both of hindered amine group and hindered phenol group were designed in order to attain light stability and antioxidant functions. In this thesis, two synthetic routes for the target molecules started from 2,6-di-tert-butyl-4-methylphenol or 3,5-di-tert-butyl-4- hydroxy-benzaldehyde were studied respectively. The target molecules were successfully synthesized from 3,5-di-tert-butyl-4-hydroxy-benzaldehyde through imidation, reduction and the established two-step synthetic process. The numerical average molecular weight was between 2000 and 3000, the polydispersity was about 2.0, the transparency was lower than 60% under 425nm and the consumption of N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine was about 0.85.Additionally, several byproducts of N,N-bis-(3,5-di-tert-butyl-4-hydroxybenzyl)- N-alkylamines were obtained and determined in the reduction of 3,5-di-tert-butyl-4- ((alkylimino)-methyl)-phenol with NaBH4. Designed experimental results they were formed from the 2,6-di-tert-butyl-4-alkylaminomethyl-phenol. The possible mechanism of this transformation was proposed in the thesis.