CPC technology class · D21

D21D - Treatment Of The Materials Before Passing To The Paper-ma…

Treatment of the materials before passing to the paper-making machine. 314 US utility patents granted 2015–2025, with the leading assignees and year-by-year grant trajectory.

Compiled by PlainPatent · May 15, 2026

314
US patents granted: #6/7
in D21: 3.8%
D21 class share: +59%
5-yr velocity

The verdict

According to USPTO PatentsView, Treatment Of The Materials Before Passing To The Paper-ma… ranks #581 of 670 CPC technology areas - 314 US patents granted since 2015, with recorded grant volume up 59% over five years.

#581
of 670 CPC technology areas: 314
US patents granted, 2015–2025: Andritz
leading assignee (35): +59%
grant velocity, last 5 yrs

How D21D's grant cadence moved

Between 2020–2024, D21D recorded 175 grants versus 110 in 2015–2019 (+59% equal-window velocity). Across complete years, output peaked in 2024 at 41 grants and bottomed in 2016 at 17 (+141% peak-over-trough). Lead assignee Andritz Inc. holds 11.1% of the class ; the top three share 25.8%.

Leaderboard read

D21D concentration, lead at 11.1%

Andritz Inc. leads this historical grant record at 11.1% of D21D - foreign corporation assignees hold 66% of class grants (125 of 188). Figures describe granted US utility patents in this CPC subclass, not current investment or legal strength.

Leader's share: 11.1%
Top three share: 25.8%
Lead over #2: 5

Where D21D sits inside D21

Among 7 subclasses in D21 (PAPER-MAKING; Production OF Cellulose), D21D ranks #6 and holds 3.8% of the parent class's 8,169 recorded grants. Sibling chips below are the other subclasses in the same parent class, not the nationwide volume/lead-share peers further down.

D21H 4,080 D21C 1,427 D21F 1,255 D21B 452 D21G 371 D21J 270

Rising assignees active in D21D

Company-wide grant multiples (2022–2024 vs 2019–2021) among assignees with ≥5 patents in this subclass. Growth is company-wide; class patent counts are subclass-specific.

#1 Domtar Paper Company, LLC 2.00x 4 → 8 company-wide · 9 in D21D
#2 Valmet AB 1.96x 22 → 43 company-wide · 30 in D21D
#3 Valmet Technologies Oy 1.52x 29 → 44 company-wide · 16 in D21D
#4 Valmet Technologies, Inc. 1.25x 8 → 10 company-wide · 13 in D21D
#5 Aikawa Fiber Technologies OY 1.00x 2 → 2 company-wide · 5 in D21D

D21D grants by year, peak 2024 (41)

US utility-patent grants per year in D21D, 2015–2025 - recent five years are up 59% versus 2015–2019.

Andritz

35
Valmet Ab

30
Valmet Oy

16
Valmet

13
Fiberlean

12
Voith Patent

10
Domtar Paper

9
International Paper

8
Aikawa Fiber Oy

5
Andritz Oy

4
Andritz Fiedler

4
Westrock Mwv

3

What this shows Andritz is the most active filer in D21D, holding 35 of the 314 patents in this class. Concentration at the top signals how contestable this technology area is for new entrants.

View data table

Top patent holders in CPC subclass D21D
Rank	Company	Patents in D21D
#1	Andritz Inc.	35
#2	Valmet AB	30
#3	Valmet Technologies Oy	16
#4	Valmet Technologies, Inc.	13
#5	Fiberlean Technologies Limited	12
#6	Voith Patent GmbH	10
#7	Domtar Paper Company, LLC	9
#8	International Paper Company	8
#9	Aikawa Fiber Technologies OY	5
#10	Andritz OY	4
#11	Andritz Fiedler GMBH	4
#12	WestRock MWV, LLC	3
#13	Qilu University of Technology	3
#14	Billerudkorsnas AB	3
#15	Suzano S.A.	3
#16	Valmet Aktiebolag	2
#17	Packaging Corporation of America	2
#18	Mercer International Inc.	2
#19	Borregaard AS	2
#20	Kadant Black Clawson LLC	2

Footprint here vs. claim strategy

Each dot is a leading D21D 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 D21D assignees by class footprint. Bubble size = patents in D21D. Source: USPTO PatentsView (claim depth is company-wide across all classes).

Questions about D21D

Which company holds the most patents in D21D?

Andritz Inc. leads D21D with 35 patents (11.1% of the subclass). By PatentsView assignee type, foreign corporations account for 66% of class grants.

Which D21D assignees grew fastest recently?

Among assignees with ≥5 grants in D21D, Domtar Paper Company, LLC shows the highest company-wide grant multiple (2.00x: 4 grants in 2019–2021 → 8 in 2022–2024) while holding 9 patents in this subclass. Growth is company-wide, not class-only.

How does D21D compare inside parent class D21?

Inside D21 (PAPER-MAKING; Production OF Cellulose), D21D ranks #6 of 7 subclasses by grant volume and holds 3.8% of the parent class total. The largest sibling is D21H (4,080 grants).

What to do with this data

D21D in context - here's where to go next.

Andritz Inc. leads D21D with 35 grants in this class. See full portfolio
D21D ranks #581 of 670 by grant volume among all tracked CPC technology areas. See the ranking
Inside parent class D21, the largest sibling subclass is D21H with 4,080 grants. Explore D21H

Figures reflect USPTO PatentsView grant data through 2026-05-15; pending applications not yet granted are not counted.

Methodology - D21D figures are USPTO PatentsView granted-utility totals for this subclass (314 grants in the tracked window).

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.