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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 ...
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.
Chemical pulp is used for materials that need to be stronger or combined with mechanical pulps to give a product different characteristics. The kraft process is the dominant chemical pulping method, with the sulfite process second. Historically soda pulping was the first successful chemical pulping method. Recycled pulp
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.
Tall oil, also called liquid rosin or tallol, is a viscous yellow-black odorous liquid obtained as a by-product of the kraft process of wood pulp manufacture when pulping mainly coniferous trees. The name originated as an anglicization of the Swedish tallolja ('pine oil').
The pulp and paper industry comprises companies that use wood, specifically pulpwood, as raw material and produce pulp, paper, paperboard, and other cellulose-based products. Diagram showing the sections of the Fourdrinier machine.
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, and soda pulping which is the least ecologically ...
By 1900 sulfite pulping had become the dominant means of producing wood pulp, surpassing mechanical pulping methods. The competing chemical pulping process, the sulfate or kraft process was developed by Carl F. Dahl in 1879 and the first kraft mill started (in Sweden) in 1890.
The two major classifications of pulp are chemical and mechanical. Chemical pulps formerly used a sulphite process, but the kraft process is now predominant. Kraft pulp has superior strength to sulphite and mechanical pulps and kraft process spent pulping chemicals are easier to recover and regenerate.
Northern bleached softwood kraft ( NBSK) is the paper industry's benchmark grade of pulp. Market NBSK is produced mainly in Canada and the Nordic countries. Some NBSK is also produced in north-western United States and in Russia. NBSK futures are traded on the Chicago Mercantile Exchange .