Plastic Recycling Innovation: Evidence from Patent Portfolios and Convergence

Plastic recycling technologies are rapidly being reoriented toward process, operations, and quality-centered innovation, driven by the circular economy and digital transformation. Using 64,639 triadic patents (2005–2024), this study applies International Patent Classification (IPC) portfolio, co-occurrence network, and BERTopic analyses to compare technological structures before and after 2015. Since 2015, data- and AI-enabled sorting and process optimization (IPC class G06), tracking and connectivity (IPC class H04), collection and logistics (IPC class B65), water treatment (IPC class C02), and quality modification/compounding (IPC class C09) have expanded, while organic chemistry (IPC class C07), signal-processing circuitry (IPC class H03), and petroleum/fuel conversion (IPC class C10) have declined. G06 and H04 together account for approximately 29% of the total portfolio and record the largest share increases (+1.63 and +1.28 percentage points); water treatment (C02F) and quality correction (C09K) expand by 0.62 and 0.38 percentage points, while organic chemistry (C07) shows the largest decline (−2.16 percentage points). Topic modeling identifies 10 topics in 2005–2014 and 11 in 2015–2024, with the later period newly featuring reverse logistics for reusable packaging, remanufacturing, chemical recycling for packaging, and data sources. Cross-domain network linkages rise from 49 to 68, with processing–logistics and post-treatment–standardization combinations showing the strongest structural strengthening. Industrially, these findings offer reference signals for firms aligning R&D and IP portfolios with domains of concentrated innovation, particularly AI-enabled sorting, digital connectivity, and feedstock quality correction. For policy, the strengthening of cross-domain linkages suggests that support for sorting infrastructure, traceability and data standards, and quality certification frameworks targets where R&D effort is most concentrated.