D21D TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
Description
D21D covers pre-treatment processes and equipment used to prepare fibrous materials for the paper-making machine itself. This includes pulping methods, bleaching, screening, cleaning, and chemical treatment of cellulose fibers to achieve desired quality and consistency. The classification encompasses both mechanical and chemical processing steps that occur in the preparation stage, prior to the actual formation of paper on the paper machine. Related downstream processes occurring on or in the paper machine itself are classified separately under D21H and other subsequent sections.
Filing statistics
CPC subclass D21D recorded 5,357 patent applications worldwide between 2013 and 2023. Annual filings grew from 322 in 2013 to 372 in 2023 (+16%), peaking at 703 applications in 2020. The most active applicants in class D21 are VOITH PATENT (1,857 applications), STORA ENSO (1,552 applications) and KEMIRA (1,173 applications).
Source: EPO PATSTAT, worldwide filings
3 direct subcodes
Child Classifications
Navigate with arrow keys, Enter to open
- D21D 1/00 Methods of beating or refining; Beaters of the Hollander type (knotter screens D21F)
- D21D 5/00 Purification of the pulp suspension by mechanical means; Apparatus therefor (centrifuges, cyclones B04)
- D21D 99/00 Subject matter not provided for in other groups of this subclass
Top Applicants
Top 10 applicants by patent filingsfor class D21, 2013–2023, worldwide · Source: EPO PATSTAT
- VOITH PATENT DE 1,857
- STORA ENSO FI 1,552
- KEMIRA FI 1,173
- KIMBERLY-CLARK CORPORATION US 1,107
- VALMET TECHNOLOGIES FI 965
- VALMET SE 943
- P&G (PROCTER & GAMBLE COMPANY) US 941
- OMYA INTERNATIONAL CH 821
- UPM-KYMMENE CORPORATION FI 512
- SEIKO EPSON CORPORATION JP 501