D21C PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE- CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
Introduced: September 1968
Classification Context
- Section:
- TEXTILES; PAPER
- Class:
- PAPER-MAKING; PRODUCTION OF CELLULOSE
- Subclass:
- PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE- CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
Description
D21C covers pulping processes that isolate cellulose fibers by chemically or mechanically removing lignin, hemicellulose, and other non-cellulose constituents from raw cellulose-containing feedstocks such as wood, straw, or recycled paper. This subclass encompasses major pulping methods including kraft, sulfite, soda, and mechanical pulping, along with their associated chemical recovery systems for regenerating and recycling pulping liquors. Included are apparatus, equipment, and process control technologies for delignification, cooking, washing, and liquor circulation throughout pulp production facilities. Adjacent classes cover downstream pulp bleaching and paper sheet formation rather than the primary pulp production stage.
Additional Content
Glossary
bagasse fibre remaining after the extraction of the sugar-bearing juice from sugarcane cellulose structural component of the primary cell wall of green plants. It is an organic compound with the formula (C 6 H 10 O 5 ) n and is the major constituent of paper, paper-board, and of textiles made from cotton, linen, and other plant fibres. linings material that covers the inner surface of something. cotton linters fine, silky fibres which adhere to the seeds of the cotton plant after ginning and are traditionally used in the manufacture of paper and as a raw material in the manufacture of cellulose. pulp a dispersion (e.g. aqueous suspension) comprising cellulosic fibres and optional additives; it is prepared by chemically or mechanically separating cellulose fibres from wood, fibre crops or waste paper.
Limiting references
Mechanical treatment of waste paper by dry methods Mechanical treatment of waste paper by wet methods, by the use of steam or other means
Application references
Evaporating Distillation Drying solid materials or objects by removing liquid therefrom
Related Keywords
6 direct subcodes
Child Classifications
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- D21C 1/00 Pretreatment of the finely-divided materials before digesting
- D21C 11/00 Regeneration of pulp liquors
- D21C 3/00 Pulping cellulose-containing materials
- D21C 5/00 Other processes for obtaining cellulose, e.g. cooking cotton linters
- D21C 7/00 Digesters
- D21C 9/00 After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters
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