PROTECTION OF FE PIGMENTS WITH AMINE-QUINONE POLYMERS

High magnetization iron pigments, protected by amine-quinone polymers are described. The amine-quinone polyurethanes were prepared by melt polymerization of 2,5-bis(N-2-hydroxyethyl-N-methylamino)-1,4- benzoquinone, AQM-1, tolylene diisocyanate, and an oligomeric polyether diol; either poly(1,2-butylene glycol) or poly(1,4-butylene glycol). Depending on the choice of polyether and the relative amount of AQM-1, the polyurethanes were elastomeric or thermoplastic; the thermal and mechanical properties being systematically controlled by the polymer structure. Hydrogen reduction of acicular iron oxide pigments gave pyrophoric Fe pigments with an initial sigma(s) approximate to 195 emu/g. Treatment with a THF solution of the amine-quinone polymer AQPU-8, under an inert atmosphere, gave stabilized Fe pigments with sigma(s) approximate to 160 to 180 emu/g; a value significantly higher than 140 emu/g for the best ceramic coated pigments. The treated pigments were exposed to the ambient laboratory atmosphere for more than 3000 hours with no loss in sigma(s). This demonstration that quinone polymers can replace the ceramic coatings used to protect iron pigments provides a means of significantly enhancing the performance of metal particle tape.