Pulping and Bleaching Patents: Leaders, Trends & White Space 2026
- Filing has cooled since its 2021 peak. Annual filings rose to 69 in 2021 then declined toward single digits by 2026, a pattern consistent with a maturing, already-claimed core rather than an expanding one.
- D21C dominates the classification mix by a wide margin. 1,616 of 1,650 records sit in D21C (pulp production & treatment), while adjacent water-treatment and separation classes (C02F, B01D) carry only 65 and 44 records respectively — a visible gap between core chemistry and downstream process integration.
- No assignee shows momentum in the latest year. Every tracked assignee in the recent-momentum data, including established filers, recorded zero filings in the most recent year — a signal that active prosecution has moved to smaller or unlisted entrants, or paused.
Filing growth compares 2021 (69 records) with 2024 (17) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field. Top-5 share is the combined record count of the five largest assignees divided by all 1,650 records in scope (CR5), not by the ranked leaders only.
What this landscape covers
This review covers patent families filed or published against kraft pulping, pulp bleaching and related delignification processes, filtered to IPC subclasses D21C (pulp production and treatment), D21C9-adjacent bleaching routes, and D21B1 pulp preparation. The dataset spans 2015 to mid-2026, with 1,650 patent families forming the base for every ranking and trend in this page. Because publication typically lags filing by around eighteen months, the most recent one to two years of the trend line will always understate true filing activity.
The technology composition is heavily weighted toward the core D21C pulp-treatment class, with secondary density in D21B pulp preparation and D21H pulp-and-paper compositions. Peripheral classes touching water treatment, inorganic chemistry and separation processes appear at much lower volume, marking them as areas of lighter claim coverage rather than technical irrelevance.
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Filing trends and classification spread
Annual filing counts and IPC distribution for the pulping and bleaching corpus, drawn directly from the 1,650-family dataset.
A peak in 2021, then decline
Filings climbed from 33 in 2017 to a peak of 69 in 2021, sat at 21 by the 2022 midpoint, and fell toward 3 by 2026 (partial year). That trajectory reads as flat-to-declining rather than growth, though the final one to two years are undercounted due to publication lag.
Concentration in D21C, with a long secondary tail
D21C accounts for 1,616 of 1,650 records — effectively the entire dataset — while D21B (203) and D21H (202) form a secondary tier. Water treatment (C02F, 65), paper stock treatment (D21D, 63), inorganic chemistry (C01B, 55), specialty materials (C09K, 48) and separation processes (B01D, 44) each appear at low volume, marking these as adjacent, lightly claimed zones rather than core territory.
Shares are the percentage of the 1,650 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Pulping and Bleaching Processes with Eureka
This page is one run against one query. Ask Eureka your own question about pulping and bleaching processes and every answer comes back with the patent numbers behind it.
Try EurekaMost-cited prior art in the corpus
Kraft Pulping Process (CA2259109A1, FPInnovations)
Sodium chloride is removed from pulping chemicals used in a Kraft pulping process using a snake-cage polyelectrolyte ion exchange resin, coupled with sulfide removal prior to treatment. Dust collected from black liquor recovery exhaust gases is dissolved in water to produce a sodium chloride and sodium sulfate solution, which is filtered and fed to an ion exchange unit that removes chloride and yields a purified sodium sulfate product.Filed by FPInnovations; illustrates the recovery-cycle chemical purification route common to this dataset's core claims.
View full filing| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US4952277A | Process for producing kraft pulp for paper using nonionic surface active agents to improve pulp yield | 141 |
| 2 | US4100016A | Solvent pulping process | 135 |
| 3 | US5788812A | Method of recovering furfural from organic pulping liquor | 123 |
| 4 | US5179021A | Pulp bleaching process comprising oxygen delignification and xylanase enzyme treatment | 120 |
| 5 | US3969201A | Electrolytic production of alkaline peroxide solutions | 91 |
| 6 | US4619733A | Pollution free pulping process using recycled wash effluent from multiple bleach stages to remove black liquo… | 77 |
| 7 | US6682923B1 | Thermostable alkaliphilic xylanase | 75 |
| 8 | US20040256065A1 | Method for producing corn stalk pulp and paper products from corn stalk pulp | 70 |
| 9 | US20030102094A1 | Method in the bleaching of pulp and a device for the bleaching of pulp | 70 |
| 10 | US20040112555A1 | Bleaching stage using xylanase with hydrogen peroxide, peracids, or a combination thereof | 68 |
Citation counts reflect influence within the searched corpus and skew toward older filings; they are a signal of foundational status, not of current commercial relevance.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Browse MCP servers →What the numbers indicate
Three patterns stand out once filing volume, classification spread and citation weight are read together.
Activity has cooled from its 2021 high
The rise to 69 filings in 2021 followed by a steady drop through 2022 (21) and into single digits by 2026 suggests the core kraft and bleaching chemistry claim space filled up rather than kept expanding. Some of the 2025-2026 dip owes to publication lag, but the multi-year downward slope predates that window.
Nearly the entire corpus sits in one subclass
D21C's dominance means most competitive filing activity is contesting the same pulp production and treatment ground. Adjacent classes such as water treatment (C02F) and separation processes (B01D) appear at a fraction of that volume, pointing to less-crowded integration points around effluent handling and recovery.
Foundational patents cluster in yield and delignification
The highest-cited records address pulp yield improvement, solvent pulping, furfural recovery and oxygen delignification with enzyme treatment — all filed well before the 2021 peak. Their citation weight reflects age and foundational status within the corpus rather than current filing priority.
No tracked assignee is actively filing right now
Every assignee surfaced in the recent-momentum data shows zero filings in the latest tracked year, including firms with substantial historical volume. That pattern is consistent with a lull in disclosed activity or a shift toward filers too new or too small to yet appear in the ranking.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to pulping and bleaching processes, with the prior art for and against each one.
Who holds the claim space
Assignee activity in this dataset is measured across 1,650 families, with co-filing pairs and recent-year momentum layered in to separate historical volume from live prosecution.
A small number of tight collaborations
Only 10 co-assignee pairs appear in the dataset, with the strongest pairing (Akzo Nobel and Ecolab-affiliated entities) sharing 12 families. Most other pairs sit in the single digits, indicating that joint filing is the exception rather than the norm in this field.
Established filers have gone quiet
Assignees including Andritz, Nalco, Eurochem Biosciences and Akzo Nobel all show zero filings in the most recent tracked year. That does not necessarily mean withdrawal from the space — it may reflect publication lag or a shift to filing under new entities not yet ranked.
Filing is spread across major offices, not concentrated in one
The United States, Canada and the European Patent Office each receive over 200 filings, with China (191), WIPO/PCT (142) and Australia (126) not far behind. That spread suggests assignees are pursuing multi-jurisdiction protection rather than relying on a single home market.
| Assignee | Recent year | YoY |
|---|---|---|
| Yolimp Patent Holdings Ltd. | 0 | — |
| Nalco Company | 0 | — |
| Liuhuan Co., Ltd. | 0 | — |
| Eurochem Biosciences Inc. | 0 | — |
| Akzo Nobel N.V. | 0 | — |
| Andritz AG | 0 | — |
| Solutia Inc. | 0 | — |
| Pulp and Paper Research Institute of Canada (FPInnovations) | 0 | — |
Where to take this analysis
The filing data points to a crowded core and a quiet recent period — the next step is deciding what that means for a specific filing or freedom-to-operate question.
Map a specific claim against the D21C core
With 1,616 of 1,650 records sitting in one subclass, a new filing in core kraft or bleaching chemistry needs a tight novelty check against that density before drafting.
Explore claim mapping in Eureka →Watch for re-emergence after the momentum lull
Zero latest-year filings across major assignees may reverse once publication catches up; tracking this space over the next filing cycle will clarify whether it is a pause or a real slowdown.
Set up monitoring in Eureka →Test the under-claimed branches
Effluent load reduction, chlorine-free enzyme co-treatment and energy recovery integration all show lighter classification density than the D21C core and may offer more open claim space.
Run a white space search in Eureka →Common questions on pulping and bleaching patents
The dataset's most-cited records address pulp yield improvement using nonionic surfactants, solvent-based pulping, furfural recovery from pulping liquor, and oxygen delignification combined with xylanase enzyme treatment. These sit at the foundational end of the corpus, cited well above average, and mostly predate the 2021 filing peak. Newer filings tend to build on these same mechanisms — yield improvement, delignification chemistry and recovery-cycle purification — rather than introducing entirely new routes.
Assignee activity in this dataset spans historically active filers such as Andritz, Akzo Nobel, Nalco and International Paper, alongside research bodies like FPInnovations. However, the recent-momentum data shows every tracked assignee at zero filings in the latest year, which likely reflects a mix of genuine slowdown and publication lag rather than exit from the field. A current freedom-to-operate check should not rely solely on the top-ranked historical filers.
Filings rose from 33 in 2017 to a peak of 69 in 2021, then fell steadily to 21 by 2022 and into single digits by 2026. Part of that decline is an artifact of publication lag, since recent filings take roughly eighteen months to appear in the record. But the multi-year downward trend predates the most recent lag window, which points to the core D21C claim space becoming increasingly occupied rather than actively expanding.
The IPC composition shows a stark gap between the crowded D21C core (1,616 of 1,650 records) and adjacent classes like water and wastewater treatment (65 records) and separation processes (44 records). That gap suggests under-claimed territory around effluent load reduction, membrane-based liquor separation and energy recovery integration from black liquor — areas that touch pulping chemistry but are not saturated by it.
Citation counts here favour older filings simply because they have had more time to accumulate citations within the searched corpus; the top-cited record (US4952277A) dates from well before the recent filing peak. Treat high citation counts as a marker of foundational or influential status, not as evidence that a technique is still the most commercially relevant one. Recent, lower-cited filings may be more representative of current design-around strategies.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.