Recycling of UF-bonded fibreboards

Thermo-mechanical pulps (TMP) from UF-bonded fibreboards (MDF) can be obtained using the refiner technique at high temperature (170-180 °C) and pressure (7-8 bar) or far more optimally under mild conditions (100 °C) using a twin-screw extruder. The pulps obtained in both cases still contain substantial amounts of the UF-binder originally used in making MDF. Nevertheless, TMP from MDF can be used to partially substitute TMP from wood in making MDF under conventional gluing and pressing conditions without, if any, significant deterioration of the physical-mechanical properties of the boards or any adverse effects on their formaldehyde release, as assessed by the perforator test (EN 120). A new concept is presented to insert pulps made using the twin-screw extruder into the conventional production line of MDF. The new technology envisions the independent optimal pulping of wood and recycling UF-bonded boards.