Synthesis and performance of new bifunctional stabilizers

Abstract

Six new bifunctional stabilizers have been synthesized by a two-step controlled isocyanation. In the first step a compound containing a stabilizing functional group, 2,4-dihydroxy benzophenone (DHBP) or 2,2,6,6-tetramethyl-4-piperidinol (TMP), reacts with toluene-2,4-diisocyanate (TDI) or hexamethylene diisocyanate (HMDI) at a mole ratio of 1 to 1 to form an intermediate I. In the second step I was directly added to another compound containing a different stabilizing functional group such as TMP or 2,6-di-tert-butyl-4-hydroxy methyl phenol (DBHMP) at a 1 to 1 mole ratio at a given temperature in the presence of dibutyltin dilaurate (DBTDL) catalyst. These six new stabilizers are 2-hydroxy-4-benzophenonyl, 2,2,6,6-tetramethyl-4-piperidinyl hexamethylene dicarbamate ( A, MW=540); 2-hydroxy-4-benzophenonyl, 3,5-di- tert-butyl-4-hydroxyl benzyl hexamethylene dicarbamate ( B, MW=619); 3,5-di- tert-butyl-4-hydroxyl benzyl, 2,2,6,6-tetramethyl-4-piperidinyl hexamethylene dicarbamate ( C, MW=562); 2,2,6,6-tetramethyl-4-piperidinyl, 2-hydroxy-4-benzophenonyl toluene 2,4-dicarbamate ( D, MW=546); 3,5-di- tert-butyl-4-hydroxyl benzyl, 2-hydroxy-4-benzophenonyl toluene 2,4-dicarbamate ( E, MW=625) and 3,5-di- tert-butyl-4-hydroxyl benzyl, 2,2,6,6-tetramethyl-4-piperidinyl toluene 2,4-dicarbamate ( F, MW=568). Their structures have been characterized by IR, NMR, UV and elemental analysis. The photostabilizing and thermal stabilizing effectiveness of these new stabilizers for polypropylene (PP) had been examined. Experimental results show that these new bifunctional stabilizers are effective in protecting PP against photo-oxidation and thermal-oxidation. The effectiveness in relation to the structures of these new bifunctional stabilizers is discussed.