Pulp extrusion: A new processing method for recycling recovered wastepaper and papermill sludge and its application for building materials

Fibers recovered from recycled paper products have desirable mechanical properties and can be used for the manufacture of composite materials. Contrary to their use in papermaking, recycled wood pulp fibers used for composites may require only minimal cleaning and de-inking, thus greatly reducing manufacturing costs. In addition, waste fiber sources which are not used presently could be exploited. In the research presented it is shown that extrusion processing of highly concentrated, aqueous pulp fiber suspensions offers a way to manufacture composite materials which make use of the inherent strength and bonding potential of wood fibers. With this process, fiber composites with mechanical properties comparable to those found in medium density-fiberboard and hardboard can be produced continuously. Stiffness loss due to moisture can be controlled by addition of crosslinkable resins, thus offering the possibility to manufacture structural materials with consistent and predictable properties. Tolerance of the extrusion process toward the addition of inorganic materials make it a suitable process for recycling contaminated fibers and papermill sludges.