SYNTHESIS AND PERFORMANCE OF NEW BIFUNCTIONAL STABILIZERS

Six new bifunctional stabilizers have been synthesized by a two-step c ontrolled isocyanation. In the first step a compound containing a stab ilizing functional group, 2,4-dihydroxy benzophenone (DHBP) or 2,2,6,6 -tetramethyr-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 s uch 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 dicarba mate (A, MW=540); 2-hydroxy-4-benzophenonyl, 3,5-di-tert-butyl-4-hydro xyl benzyl hexamethylene dicarbamate (B, MW=619); 3,5-di-tert-butyl-4- hydroxyl benzyl, 2,2,6,6-tetramethyl-4-piperidinyl hexamethylene dicar bamate (C, MW=562); 2,2,6,6-tetramethyl-4-piperidinyl, 2-hydroxy-4-ben zophenonyl toluene 2,4-dicarbamate (D, MW= 546); 3,5-di-tert-butyl-4-h ydroxyl 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 (E, MW = 568). Their structures have been characterized by IR, NMR, UV and elemental analysis. The ph otostabilizing and thermal stabilizing effectiveness of these new stab ilizers for polypropylene (PP) had been examined. Experimental results show that these new bifunctional stabilizers are effective in protect ing PP against photo-oxidation and thermal-oxidation. The effectivenes s in relation to the structures of these new bifunctional stabilizers is discussed. (C) 1998 Elsevier Science Limited. All rights reserved.