New Antiozonants for Rubber Protection Based on Derivatives of a Naturally Occurring Molecule: Camphor

ABSTRACT Two new antiozonant molecules (for diene rubber compounds) have been synthesized using (1R,4R) (+)‐camphor as key raw material derived from the renewable source Cinnamomum camphora tree. The diimine reaction product of p‐phenylenediamine (p‐PPD) and two molecules of camphor was reduced in situ with NaBH 4 , yielding N , N ′‐dicamphyl‐p‐phenylenediamine (2Cam‐PD). Similarly, the imine reaction intermediate between ADPA (4‐aminodiphenylamine) and one molecule of camphor was reduced in situ, producing N ‐camphyl‐ N ′‐phenyl‐p‐phenylenediamine (Cam‐PPD). The two new antiozonants were characterized by FT‐IR spectroscopy and by DSC analysis in comparison to the diimine (2Cam‐PD‐diimine) and imine (Cam‐PPD‐imine) intermediates, respectively. DSC analysis was also made on the starting reagents p‐PPD, ADPA, and (1R,4R) (+)‐camphor. The properties of 2Cam‐PD and Cam‐PPD are discussed in comparison to the currently used antiozonants. Particular emphasis is addressed toward the analogies of 2Cam‐PD with the “safe” antiozonant CCPD ( N , N ′‐dicyclohexyl‐p‐phenylenediamine) and Cam‐PPD with CPPD ( N ‐cyclohexyl‐ N ′‐phenyl‐p‐phenylenediamine). The raw material fraction derived from the renewable source is 73.8% for 2Cam‐PD and 45.2% for Cam‐PPD.