Novel substituted diarylamines and use of same as antioxidants

Antioxidant molecules stable in air and effective at both high and low temperatures, interesting for the protection of petroleum, employed in engineering industry, including the automotive industry, as well as in the protection of polymers and plastics.

Title of the patent Substituted diarylamines and use of same as antioxidants
Thematic area Chemistry and biotechnology
Ownership Alma Mater Studiorum - Università di Bologna and Queen’s University
Inventors Luca Valgimigli, Derek A. Pratt, Jason J. Hanthorn
Protection USA
Licensing status Available for licensing agreement
Keywords Antioxidants, regenerable, diarylamines, pyridine-containing antioxidant, pyrimidine-containing antioxidants
Filed on Jun 03, 2011

Aromatic amines and particularly diphenylamines are among the most employed antioxidant compounds in the antioxidant protection of lubricant oils and other petrol-derived products at high temperatures (100°-220°C). In such systems and experimental settings (temperature) diphenylamines have considerably better performance compared to phenolic antioxidants,  both due to their higher stability and particularly to the longer extension of their antioxidant protection. However diphenylamines are considerably less efficient at low temperature (10-40°C) due to a much lower (and modest) reactivity with chain-carrying peroxyl radicals. Therefore they are rather useless as antioxidants at these temperatures. Furthermore they also have a modest reactivity with alkyl radicals (as compared to phenols, catechols and nitroxides), which makes them poorly effective as inhibitors of radical polymerization. Clearly they can rarely be employed as inhibitors of polymerization or stabilizers/antioxidants for reactive monomers, both at high or low temperature. Structural modifications, such as the introduction of electron donating substituents or ring-closure to form phenothiazine-like compounds, significantly increase the reactivity toward peroxyl radicals at low temperature and, to some extent, also improve the reactivity toward alkyl radicals. However these modifications dramatically impair their stability toward air or molecular oxygen, thereby verifying their usefulness, both as antioxidants or as inhibitors of radical polymerization under most conditions.

Thanks to a specific molecular design, also associated with “classical” structural modifications inventors have developed novel amino antioxidants with largely improved air–stability both at high and low temperatures. At the same time the compounds possess a higher reactivity toward peroxyl radicals (both at high and low temperatures), thereby being more efficient antioxidants, compared to diphenylamines, both in typical applications (e.g. the antioxidant protection of lubricant engine oils) and in novel extended applications where diphenylamines would be inefficient or unstable. This opens completely new fields of application. Furthermore the novel compounds have largely increased reactivity toward alkyl radicals, which makes them excellent inhibitors of free radical polymerization and excellent stabilizers/antioxidants for reactive monomers, both at high or low temperature.

  • Increased antioxidant efficacy both at high and low temperatures, as compared to diphenylamines
  • Increased efficacy as inhibitors of radical polymerization both at high and low temperature, as      compared to diphenylamines or phenothiazines
  • Increased air-stability and shelf life as compared to reference competing compounds.