Development of a Regeneration Process for Nylon-6 and Nylon-6,6 from Felt Wastes

Nylon felts used in the paper manufacturing process are constructed of Nylon-6 and Nylon-6,6 and most of the 1100 t/year of felt produced is disposed of. In this study, a new process was proposed for regeneration of Nylon-6 and Nylon-6,6 from Nylon felts discarded by the paper mill industry. The process consists of dissolution-separation of Nylon into a solvent, reprecipitation of Nylon using a non-solvent, and recycling of waste solvent from the above two steps by distillation. The mixed solution of methanol with calcium chloride dihydrate (CaCl2-MeOH solution) used in the previous work was again used as solvent for dissolution of Nylons. The experimental results on the selective separation of Nylon-6 or Nylon-6,6 showed that both were possible by adjusting the concentration of calcium chloride dihydrate in the solvent. The results of X-ray diffraction analysis suggested that the solubility of Nylons was affected by their crystalline structures. The experimental results on solvent recovery indicated that methanol, water and calcium chloride dihydrate could be recycled by double distillation. By the proposed process, Nylons were regenerated in a high recovery rate 92.8% from felt wastes, and the purities of Nylon-6 and Nylon-6,6 were almost 100% and 81.4% respectively. This process is thus considered applicable for regeneration of Nylon-6 and Nylon-6,6 from Nylon wastes in chemical industries.