Design, Synthesis And Characterization Of Hindered Amine Light Stabilizers

Hindered amine light stabilizer (HALS) is a new class of excellent light stabilizerdeveloped at the end of 1970s. They have shown excellent light stabilizing ability,application performance and synergism with ultraviolet absorbers and antioxidants.Thus, extensive attention has been paid to this area, which has become the mostattractive research field during the last several decades.According to the characteristics of cyanuric chloride, three different syntheticprocesses, namely two-step, three-step and four-step processes, for synthesis ofChimassorb 944 were designed and examined systematically in this thesis. Accordingto the two-step synthetic process, the intermediate I, which was obtained from thesubstitution of one chlorine atom on triazine ring with amine, was charged into anautoclave together with N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine. The desired polymer was obtained by programmed temperature.Three chlorine atoms on triazine ring were substituted one by one under differentreaction conditions in three-step synthetic process and the desired polymer wasobtained. However, according to the four-step synthetic process, two intermediatewere obtained by treatment of the intermediate I with N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine at low temperature and at high temperature in anautoclave respectively. Condensation of these two obtained intermediates in anautoclave afforded the target polymer. The results indicated that the two-step syntheticprocess was more efficient. The obtained Chimassorb 944 was qualified as theadvanced level of the kindred products. The numerical average molecular weight wasbetween 2000 and 3000, the polydispersity was about 2.0, the transparency was over95% under 425nm and the consumption ofN,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine was about 0.80.Similarly, qualified Cyasorb UV-3346 was successfully obtained by two-stepsynthetic process. The numerical average molecular weight was about 1600, thepolydispersity was about 2.0, the transparency was over 95% under 425nm and theconsumption of N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine wasabout 0.85. Because the polydispersity of Chimassorb 2020 was lower than 1.5, thesatisfied product could not be made by two-step synthetic route. According to thecharacteristics of Chimassorb 2020, the product, which had the numerical averagemolecular weight between 2600~3400 and the polydispersity lower than 1.5, wassuccessfully obtained by three-step synthetic process.Based on the established synthetic processes for polymeric HALS, two novelpolymeric high molecular weight and multi-functional stabilizers with hindered amineand hindered phenol as active groups together were designed in order to attain lightstability and antioxidant functions.In this thesis, two synthetic routes for the target molecules started from2,6-Di-tert-butyl-4-methylphenol or 3,5-Di-tert-butyl-4-hydroxy-benzaldehyde werestudied respectively. The designed products were successfully synthesized from3,5-Di-tert-butyl-4-hydroxy-benzaldehyde through imidation, reduction and theestablished two-step synthetic process. The numerical average molecular weight wasbetween 2000 and 3000, the polydispersity was about 2.0, the transparency was lowerthan 60% under 425nm and the consumption ofN,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine was about 0.85.Industrial production of Chimassorb 944 had already been operated according toestablished two-step synthetic process in 2004. Furthermore, Cyasorb UV-3346 isdoing trial-production according to two-step synthetic process.