D21D TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
Introduced: September 1968
Last revised: January 1990
Classification Context
- Section:
- TEXTILES; PAPER
- Class:
- PAPER-MAKING; PRODUCTION OF CELLULOSE
- Subclass:
- 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.
Additional Content
Hollander traditional equipment for beating fibrous suspensions, being a device using at least one wheel like beating rotor (roll) equipped with beaters revolving in a trough having a beating stator (bed plate), also equipped with beaters, in which trough the suspension is circulated to pass multiple times through the beating zone formed between the rotor and the stator. beating treatment of fibrous suspensions in Hollander type equipment in order to fibrillate, shorten or soften fibres. refining treatment of fibrous suspensions for the same purpose in all other types of equipment. Jordan Jordans refiner having a frusto-conical rotor revolving inside a complimentary stator. bed plate bed plates stator of Hollander or Jordan devices. paper stock a term used to define pulp after mechanical (refining or beating) and/or chemical treatment (sizing, loading, dyeing etc.) in the paper making process, e.g. the pulp ready to make paper.
Related Keywords
3 direct subcodes
Child Classifications
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- D21D 1/00 Methods of beating or refining; Beaters of the Hollander type
- D21D 5/00 Purification of the pulp suspension by mechanical means; Apparatus therefor
- 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 1,809
- STORA ENSO FI 1,467
- KEMIRA FI 1,086
- KIMBERLY-CLARK CORPORATION US 935
- VALMET TECHNOLOGIES FI 924
- VALMET SE 904
- P&G (PROCTER & GAMBLE COMPANY) US 862
- OJI HOLDINGS CORPORATION 696
- OMYA INTERNATIONAL CH 584
- SOUTH CHINA UNIVERSITY OF TECHNOLOGY 571