Dissolution-based purification process for recycled HDPE suitable for blow molding

Overview

Polystyvert has developed a patented dissolution-based purification process originally scaled for polystyrene and now being adapted for HDPE recycling. The technology addresses a key challenge in plastics circularity: recovering high-purity recycled HDPE from complex post-consumer resin streams contaminated with mixed polymers, additives, colors, odors, fillers, flame retardants, and VOCs. By selectively dissolving HDPE and precipitating it back as clean resin, the process yields recycled HDPE with quality comparable to virgin material, making it suitable for demanding blow molding applications.

Technical specifications

The purification process relies on the differing polarity of polymers, enabling selective dissolution of HDPE from polar polymers such as polyesters and polyamines, as well as separation of HDPE from PP and LDPE through tuning of thermodynamic variables. The full process sequence includes:

• Selective dissolution of the target polymer in a tailored solvent
• Filtration to remove macro-contaminants
• Deep purification using flocculation to agglomerate and separate fine particles
• Precipitation by adding a non-solvent
• Washing to extract soluble contaminants such as colorants
• Drying and extrusion with devolatilisation to eliminate residual solvent traces and produce recycled pellets

The technology is already proven at commercial scale for polystyrene in continuous mode and is at pilot stage for ABS, demonstrating scalability potential.

Technology readiness level

Laboratory-scale validation has confirmed that HDPE can be selectively extracted from feedstock containing LDPE, PP, PS, and ABS with quantitative yield. The purification step via flocculation has been validated and patented. The current research plan targets TRL 3-4 through laboratory feasibility tests on representative post-consumer resin, producing 10-50 gram samples with purity analysis and extensional rheology testing for blow molding. A second milestone aims to scale up to pilot plant production of 20-50 kg of recycled HDPE, validating scalability and end-product quality for blow molding applications.