ABSTRACT
Abstract A process for the hydrogenation of adiponitrile and 6-aminocapronitrile to hexamethylenediamine in streams of depolymerized Nylon-6,6 or a blend of Nylon-6 and Nylon-6,6 has been described. Semi-batch and continuous hydrogenation reactions of depolymerized (ammonolysis) products were performed to study the efficacy of Raney® Ni 2400 and Raney® Co 2724 catalysts. The study showed signs of deactivation of Raney® Ni 2400 even in the presence of caustic, whereas little or no deactivation of Raney® Co 2724 was observed for the hydrogenation of the ammonolysis product. The hydrogenation products from the continuous run using Raney® Co 2724 were subsequently distilled and the recycled hexamethylenediamine (HMD) monomer was polymerized with adipic acid. The properties of the polymer prepared from recycled HMD were found to be identical to that obtained from virgin HMD. Introduction Recycling of waste carpets has become an increasingly important problem in recent years. Carpet waste generally includes both industrial carpet waste and post-consumer carpet waste. Currently, landfill capacity is nearing maximum utilization. In the United States, a minimum of 25% recycle content is required in government carpet installations, and customer mills are also asking for fibers with a high recycle content. A critical problem of recycling Nylon-6, and -6,6 is the capability of converting the polyamide in carpet waste to monomeric components, which can subsequently be reused as pure spinnable Nylon. Costeffective recovery processes in which the monomers are available for reuse without further conversion reactions are especially important.
