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The kraft process (also known as kraft pulping or sulfate process) is a process for conversion of wood into wood pulp, which consists of almost pure cellulose fibres, the main component of paper. The kraft process involves treatment of wood chips with a hot mixture of water, sodium hydroxide (NaOH), and sodium sulfide (Na 2 S), known as white ...
After the cellulose fibers are separated from the lignin, a pulp is created which can then be treated to create durable paper, boxes, and corrugated cardboard. Chemical pulping can be characterized by two main methods: sulfate (Kraft process) pulping and sulfite pulping, and these two methods have different benefits. Sulfate pulping can be ...
Chemical pulping involves dissolving lignin in order to extract the cellulose from the wood fiber. The different processes of chemical pulping include the Kraft process, which uses caustic soda and sodium sulfide and is the most common; alternatively, the use of sulfurous acid is known as the sulfite process, the neutral sulfite semichemical is treated as a third process separate from sulfite ...
Kraft paper or kraft is paper or paperboard (cardboard) produced from chemical pulp produced in the kraft process. Sack kraft paper (or just sack paper ) is a porous kraft paper with high elasticity and high tear resistance, designed for packaging products with high demands for strength and durability.
The kraft process does less damage to the cellulose fibers than the sulfite process, thereby producing stronger fibers, but the sulfite process makes pulp that is easier to bleach. The chemical pulping processes use a combination of high temperature and alkaline (kraft) or acidic (sulfite) chemicals to break the chemical bonds of the lignin.
Mechanical pulping process [25] Thermomechanical pulp is pulp produced by processing wood chips using heat (thus "thermo-") and a mechanical refining movement (thus "-mechanical"). It is a two-stage process where the logs are first stripped of their bark and converted into small chips. These chips have a moisture content of around 25–30 percent.
Mechanical pulping is the process in which wood is separated or defibrated mechanically into pulp for the paper industry.. The mechanical pulping processes use wood in the form of logs or chips that are mechanically processes, by grinding stones (from logs) or in refiners (from chips), to separate the fibers.
The kraft process, due to the alkali and sulphur compounds used, tends to minimize attack on the cellulose and the non-crystalline hemicellulose, which promotes bonding, while dissolving the lignin. Acidic pulping processes shorten the cellulose chains. Kraft pulp makes superior linerboard and excellent printing and writing papers.