One assignee leads the ranked field with 1,344 records, well ahead of fifth place at 183 and tenth at 136. That said, the top 5 assignees combined represent only 21.7% of the 13,521 total records in scope, and the top 10 only 27.0%, so no single company or small group controls the field outright. A freedom-to-operate review should still start with the leader's portfolio given the size of the gap, but should not stop there.

Filings peaked at 575 in 2017 and have generally declined since, with 2021 at 380 falling to 311 by 2024 -- an 18% drop over that three-year span. Figures for 2025 and 2026 look lower still, but publication typically lags filing by around 18 months, so those recent years are undercounted rather than necessarily reflecting a real slowdown. The safest reading is that filing activity cooled after 2017 through at least 2024.

Separation-process claims under IPC class B01D appear on 63.2% of the 13,521 records, and water/wastewater treatment under C02F appears on 33.0%, making these the most heavily claimed areas. Polymer-synthesis-focused classes such as C08G (condensation polymers, 4.4%) and C08J (polymer processing, 5.5%) see far less filing density, which is worth noting since a record can carry multiple IPC codes. Anyone drafting new claims in the core separation-membrane space should expect dense prior art there.

The technology classes with the lowest record shares -- C08G condensation polymers at 4.4%, B01J catalytic processes at 4.3%, and A23L food applications at 4.1% -- point to branches that are comparatively under-claimed relative to the dominant separation and water-treatment classes. This does not mean these areas are unimportant, only that fewer filings currently occupy them. A new claim built around condensation-polymer backbone chemistry or catalytic feedwater pre-treatment would face less crowded prior art than one filed squarely in B01D.

US20170197182A1, filed by LG NanoH2O and published 2017-07-13, covers a process for treating the backside of a TFC membrane with a pore-protection agent -- specifically a tertiary amine salt of camphorsulfonic acid -- applied before or during frontside coating to improve water flux. It is a process claim tied to that specific backside-treatment chemistry and sequencing, not a claim over TFC membranes generally. Work using different pore-protection chemistries or a different treatment sequence would sit outside its scope, though a full claim-chart comparison is needed before relying on that distinction.