Processes to reuse plastics from end-of-life vehicles are complicated by solid contaminants — including pre-embedded metal and rubber components of different sizes and reinforcing glass fiber. Currently, recycling solids-containing waste-plastic parts is accomplished by physical sorting processes.
Honda (Tokyo, Japan; www.honda.com) recently announced that it has developed a new “chemical sorting” technology, which sorts and extracts reusable plastics from waste plastic using solvents. The new solid-contaminant separation technology dissolves plastic resin in solvents to remove solid contaminants and extract high-purity resin. Dissolution occurs at temperatures lower than the resin’s degradation point, suppressing degradation of the plastic.
Conventional separation has several challenges, including the specification and optimization of filters and sorting process for the size of each target contaminant. Since the sizes of contaminants are unpredictable, the filter mesh has to be set very fine, which often causes clogging and halts processing. Fine-mesh filters need to be replaced every few hours due to clogging, Honda says. This makes recycling feasible at the research scale, but technically challenging for a large-volume continuous process.
Honda’s chemical sorting process allows the use of coarse-mesh filters that are less prone to clogging to sort out millimeter-sized contaminants, and the use of centrifuges to physically separate micrometer-sized fine contaminants. This eliminates the need to adjust the specifications of removal filters depending on the size of each contaminant, enabling the thorough removal of contaminants of all sizes. It also minimizes the need for maintenance and filter replacement, enabling the establishment of a stable and continuous industrial-scale process.
With the new technology, Honda improved the solid-contaminant separation rate to above 99% — the conventional process had not exceeded 80%. It also reduces capital costs because there are fewer process steps.
After mechanical and chemical recycling processes, reusable plastics extracted with Honda’s chemical sorting technology have a purity of more than 99%, and can be reused as automotive materials, the company says.
By the end of 2026, Honda will build a 350-ton/yr pilot facility using the chemical sorting technology. The company says it is striving to put the chemical sorting process into practical use by 2029.
Source: Honda