Reactive Extrusion of Post-Consumer Carpet into Thermoplastic Resins

Abstract

Monsanto has developed and patented a process to recycle all the components of a nylon face fiber carpet. Using compatibilizers, fillers, and/or additives, post consumer carpets can be extruded into thermoplastic pellets which have a variety of properties useful for injection molding. Research was carried out on a 20mm and 2" counter rotating, non-intermeshing (CRNI) twin screw extruders. Optimization of the formulation led to the development of several polymers having a wide variety of material properties. The approach developed here offers a low cost method to recycle nylon carpets. The technology reported is applicable to carpets made from nylon 6 and 6,6 face fiber, polypropylene backing, and SBR latex filled with CaC03. additional work was done with polyester and polypropylene carpets with similar success. The objective is to use the complete carpet to minimize processing costs. No fiber separation or latex removal steps are required however preparation to feed to the extruder results in some removal. Reactive extrusion and compatibilization offers a way to alloy these different components into useful products for injection molding.