CPC Definition - Subclass D21C
This place covers:
Production of cellulose by removing non-cellulose substances from cellulose containing material. This subclass also embraces the after treatment of cellulose pulp and the regeneration of pulp liquors. It further also covers different aspects of digesters for pulping cellulosic material.
D21B covers fibrous raw material or their mechanical treatment.
D21D covers treatment of materials before passing to the paper-making machine.
D21F covers papermaking machines and methods for producing paper thereon.
This place does not cover:
The main aspect(s) of the invention is/are given a class according to the classification scheme. The invention per se should be classified in the last appropriate class(es), if possible. Ideally, one class should be given for covering the main aspect of the invention per se. Exceptionally, the core of the invention may also be classified by using several classes (up to three)
Classification of additional information
In this subclass, it is highly desirable to add Indexing Codes for secondary aspects of the invention (e.g. the features of the dependent claims) or for additional information, which is not considered to form the claimed invention per se, but which might be of interest for the search. For the Indexing Codes the "D" is replaced with an "N", e.g. to classify the additional information that the pulp is treated by an enzyme (or microorganisms ) should read D21C 5/005 (instead of D21C 5/005).
In this place, the following terms or expressions are used with the meaning indicated:
Pulp | A dispersion [e.g. a aqueous suspension] comprising cellulosic fibres and optional additives; it may also be referred to as "stock", furnish" or "slurry". |
Lignocellulosic material | Cellulosic material which also comprises lignin. |
Delignification | Treatment of the lignocellulosic material to remove a part of the lignin. |
Bleaching | Treatment of the lignocellulosic material to obtain a pulp/paper having an increased brightness. |
In patent documents, the following words/expressions are often used with the meaning indicated:
both "fibres" | "fibers". |
This place covers:
Different pre-treatments (e.g. impregnation) of finely divided cellulosic containing material using e.g. water, steam, acids, alkaline compounds, oxygen generating compounds or physical methods for facilitating impregnation.
Attention is drawn to the following places, which may be of interest for search:
Pre-treatment of the raw material by physical or chemical means |
This place covers:
Pulping with inorganic bases or alkaline reacting compounds, e.g. the sulphate process
Pulping with acid, acid salts or acid anhydrides
Pulping with sulphur dioxide, sulphurous acid, bisulphites or sulphites
Pulping with nitrogen oxides, nitric acid, nitrates or nitrites
Pulping with organic solvents or in solvent environment
Other features of the pulping process
This place does not cover:
Digesters |
This place covers:
Other processes for obtaining cellulose such as:
- cooking cotton linters
- processes characterised by the choice of cellulose-containing starting material
- treatment of cellulose-containing material with microorganisms or enzymes
- working-up waste paper
- working-up waste paper, e.g.de-inking
This place does not cover:
Mechanical part of working up waste paper |
Attention is drawn to the following places, which may be of interest for search:
Enzymes (generally) | |
De-inking of waste paper using flotation | |
Pulp from non-woody plants or crops, e.g. cotton, flax, straw, bagasse | |
Pulp from secondary fibres | |
Microorganisms or enzymes added to the pulp or as a paper impregnating material |
This place covers:
This group refers to structural features of the digester, i.e. defining different types or parts of the digester, e.g. rotary digesters, linings, feeding devices, discharge devices, heating devices, devices for regulating or controlling, means for circulating the lye (e.g. white or black liquor) or safety devices.
Attention is drawn to the following places, which may be of interest for search:
Continuous (pulping) processes | |
Multistage (pulping) processes | |
Processes or apparatuses for adding material to the pulp or paper; controlling or regulating not limited to any particular process or apparatus |
This place covers:
Modification of pulp properties
Washing
Displacing cooking or pulp-treating liquors contained in the pulps by fluids, e.g. wash water or other pulp treating agents
Removal of fats, resin pitch or waxes
Chemical or physical purification i.e. refining of crude cellulose by removing non-cellulose contaminants, optionally in combination with bleaching
Bleaching, e.g with halogen or halogen containing compounds, with ClO2 or chlorites, with oxygen or its allotropic modifications, with ozone, with per compounds such as peroxides or peracids
Apparatus for bleaching
De-watering
Elimination of cooking or pulp-treating liquors from the pulp
Attention is drawn to the following places, which may be of interest for search:
Hemicellulose | |
Natural resins | |
Purification by mechanical means | |
Modification of the pulp properties by a particular after treatment | |
Agents for preventing deposition on paper mill equipment, e.g. pitch or slime control | |
De-watering in general |
This place covers:
Aspects concerning the production and the treatment of green and white liquors, e.g. causticizing green liquor
Combustion of pulp liquors
Concentration spent liquors by evaporation
Deodorisation or elimination of malodorous compounds, e.g. sulphur compounds such as hydrogen sulphide and mercaptans, for gas streams
Introduction of auxiliary substances into the regenerating system in order to improve the performance of certain steps of the latter, the presence of these substances being confined to the regeneration cycle
Recovery of by-products, i.e. compounds other than those necessary for pulping
Regeneration of alkali lye, of pulp liquors or effluent waste waters, of acid, neutral or alkaline sulphite lye
Treatment of pulp gases or of gases arising from various sources in pulp and paper mills
Recovery of the heat content in the gases
Regeneration of gaseous SO2, e.g. arising from liquors containing sulphur compounds
Wet combustion
Treatment of pulp liquor without previous evaporation, by oxidation of liquors remaining at least partially in the liquid phase, e.g. by application of pressure
This place does not cover:
Water treatment |
Attention is drawn to the following places, which may be of interest for search:
Evaporation in general | |
Hemicellulose | |
Macromolecular compounds derived from lignin | |
Macromolecular compounds derived from lignocellulosic material | |
Production of biofuel, i.e. ethanol |