PlainPatent

CPC technology class · D21

D21C - Production OF Cellulose BY Removing Non-cellulose Substan…

Production of cellulose by removing non-cellulose substances from cellulose-containing materials; regeneration of pulping liquors; apparatus therefor. 1,427 US utility patents granted 2015–2025, with the leading assignees and year-by-year filing trajectory.

1,427
US patents granted
D21
Parent CPC class
20
Active assignees
+6%
5-yr velocity

The verdict

Production OF Cellulose BY Removing Non-cellulose Substan… ranks #413 of 670 CPC technology areas - 1,427 US patents granted since 2015, with filing up 6% over five years.

#413
of 670 CPC technology areas
1,427
US patents granted, 2015–2025
Valmet Ab
leading assignee (58)
+6%
filing velocity, last 5 yrs
Top assignee: Valmet AB (58 patents)

CPC subclass D21C - PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR - covers 1,427 US utility patents granted between 2015 and 2025 according to USPTO PatentsView records, within the broader CPC class D21 (PAPER-MAKING; PRODUCTION OF CELLULOSE). See our CPC classification guide for how the system works.

The competitive landscape in D21C is shaped by 20 distinct companies actively filing in this space. Valmet AB leads with 58 patents, followed by Xyleco, Inc. at 47 grants and Andritz Inc. at 40.

Filing activity in D21C is up 6% over the past five years versus 2015-2019, a relatively steady filing pace. All counts come directly from USPTO PatentsView and reflect US granted utility patents only.

Is D21C innovation accelerating?

US utility-patent grants per year in D21C, 2015–2025 - recent five years are up 6% versus 2015–2019.

90100110120130140 20152016201720182019202020212022202320242025 102

Who leads D21C?

The 12 most active assignees in PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR - wider bars mean more grants

patents

What this shows Valmet Ab is the most active filer in D21C, holding 58 of the 1,427 patents in this class. Concentration at the top signals how contestable this technology area is for new entrants.

Source USPTO PatentsView, granted utility patents As of 2015–2025 grant years
View data table
Top patent holders in CPC subclass D21C
Rank Company Patents in D21C
#1 Valmet AB 58
#2 Xyleco, Inc. 47
#3 Andritz Inc. 40
#4 GP Cellulose Gmbh 33
#5 International Paper Company 31
#6 Upm-kymmene Corporation 31
#7 Stora Enso OYJ 30
#8 Andritz OY 29
#9 Unicharm Corporation 25
#10 Shell OIL Compny 23
#11 Sixring Inc. 23
#12 Kemira OYJ 20
#13 Granbio Intellectual Property Holdings, Llc 20
#14 Fiberlean Technologies Limited 17
#15 Virdia, Llc 17
#16 Nippon Paper Industries Co., Ltd. 16
#17 Valmet Technologies Oy 16
#18 Solenis Technologies, L.p. 14
#19 Lenzing Aktiengesellschaft 11
#20 API Intellectual Property Holdings, Llc 11

About This Class

CPC subclass D21C belongs to class D21.

1,427 patents were granted in this class between 2015 and 2025.

20 companies actively patent in this space.

Classification System

Cooperative Patent Classification (CPC) is a hierarchical patent classification system used by the USPTO and EPO.

← All Technology Classes Technology Rankings →

Footprint here vs. claim strategy

Each dot is a leading D21C assignee, placed by how many patents it holds in this class (horizontal) against its company-wide average claims per patent (vertical) - a read on whether the class is led by broad-but-shallow filers or focused deep-claim players.

Top 14 D21C assignees by class footprint. Bubble size = patents in D21C. Source: USPTO PatentsView (claim depth is company-wide across all classes).

Top 14 D21C assignees by class footprint. Bubble size = patents in D21C. Source: USPTO PatentsView (claim depth is company-wide across all classes). Scatter plot of 14 data points (bubble-sized by third dimension). 10152025 10203040506070 Patents in D21C Avg claims / patent (company-wide) Valmet AbXylecoAndritzGp CelluloseInternational PaperUpm-kymmeneStora Enso OyjAndritz OyUnicharmShell Oil CompnySixringKemira OyjGranbio Intellectual…Fiberlean
Top 14 D21C assignees by class footprint. Bubble size = patents in D21C. Source: USPTO PatentsView (claim depth is company-wide across all classes).

Frequently Asked Questions

What is CPC class D21C?
CPC subclass D21C covers PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR. It belongs to CPC class D21 (PAPER-MAKING; PRODUCTION OF CELLULOSE), with 1,427 US utility patents granted since 2015.
How many patents have been filed in D21C?
1,427 US utility patents were granted in CPC subclass D21C between 2015 and 2025, based on USPTO PatentsView data.
Which company holds the most patents in D21C?
Valmet AB leads D21C with 58 patents, making it the most active assignee in this technology area.
How is patent data for D21C collected?
Patent data comes from USPTO PatentsView, a public research dataset maintained by the United States Patent and Trademark Office. It covers all US granted utility patents and assigns CPC codes based on the technology described in each patent.
What is the difference between CPC class and subclass?
A CPC class (e.g., D21) is a broad technology category. Subclasses like D21C provide finer granularity within that category. PlainPatent organizes data at the subclass level (4-character codes) for the most useful view of technology domains.

Read our methodology - how this data is sourced, computed, and verified.

Data sourced from USPTO PatentsView - official U.S. government patent data. See our methodology for computation details. Retrieved and formatted by PlainPatent Editorial

Every figure on PlainPatent is rendered directly from USPTO source data, no number is typed in by an editor. This page draws directly on USPTO source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.