Building a better wood-composite extruder

A new conical twin-screw extruder, which can take on challenging wood-fiber/plastic composites (WPC), allows outputs of 2600 lb/hr with fiber loadings as high as 70% thanks to unique compression and low-shear mixing of materials. The TC96 promises a homogenous melt of the multitude of materials that can go into WPC, including natural and synthetic fibers; virgin and recycled resin; coupling and nucleating agents; as well as other additives. Moving beyond decking and rail applications, the machine's manufacturer, Cincinnati Milacron, is envisioning applications in profiles and structural components.

The TC96 features 202-mm screws that taper to 96 mm, creating a 30:1 L/D ratio on the basis of the discharge meter. The tapered screw allows for a larger feed zone that can accept fluffy material and apply natural compression during processing so that wood flour is more effectively wetted out. Deep flights and tight clearances between the screws create optimized mixing without shear. With high torque at a screw speed of 34 rpm, the system creates low-shear melting and mixing so that fibers are distributed without breaking up.

The barrel has five zones for heating with a total barrel-heating capacity of 100 kW, and four cooling zones using a heat-transfer fluid or water-cooling to dissipate thermal energy. The extruder has an individual temperature control zone for screws that provides a heat capacity of 12 kW, and there are eight die zones for a maximum heating capacity of 51 kW. All machines come with the PC-based Xtreem XP touch-screen controls and a 15-inch LCD monitor, self-diagnostics, and Ethernet TCP/IP connectivity.

Cincinnati has also announced a partnership with B&P Process Equipment (Saginaw, MI) to create a corotating parallel twin-screw extruder with an output of 4000 lb/hr (1818 kg/hr). Dubbed the TimberEx TE125-33, the extruder is slated for the red-hot decking and outdoor composite industry, and features a low price in terms of investment/lb of output as well as a modular, segmented barrel for easier maintenance. The system, which has a 125-mm bore diameter, 200-rpm maximum screw speed, and a 32.5:1 L/D ratio, is the first in a series of WPC extruders to be offered by the Milacron/B&P partnership. Milacron, Cincinnati, OH, USA; +1 888-645-2276; www.milacron.com