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Bleaching of wood pulp is the chemical processing of wood pulp to lighten its color and whiten the pulp. The primary product of wood pulp is paper , for which whiteness (similar to, but distinct from brightness) is an important characteristic. [ 1 ]
Elemental chlorine free (ECF) is a technique that uses chlorine dioxide for the bleaching of wood pulp.It does not use elemental chlorine gas during the bleaching process and prevents the formation of dioxins and dioxin-like compounds, carcinogens.
Often, the wood's color is changed by staining, bleaching, or any of a number of other techniques. Once the wood surface is prepared and stained, the finish is applied. It usually consists of several coats of wax, shellac, drying oil, lacquer, varnish, or paint, and each coat is typically followed by sanding.
A precursor to the soda pulping process was the paper making process developed by Matthias Koops in 1801 which involved washing wood shavings in limewater, adding soda crystals and then boiling the mixture. [2] Soda pulping was one of the first chemical pulping methods and was invented in 1851 by Burgess (United States) and Watts (England).
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 ...
The use of wood to make pulp for paper began with the development of mechanical pulping in the 1840s by Charles Fenerty in Nova Scotia [1] and by F. G. Keller [2] in Germany. Chemical processes quickly followed, first with Julius Roth 's use of sulfurous acid to treat wood in 1857, followed by Benjamin Chew Tilghman 's US patent on the use of ...
The Kappa number estimates the amount of chemicals required during bleaching of wood pulp to obtain a pulp with a given degree of whiteness. Since the amount of bleach needed is related to the lignin content of the pulp, the Kappa number can be used to monitor the effectiveness of the lignin-extraction phase of the pulping process.
A major source of chemical bleaching is hydrogen peroxide (H 2 O 2) that contains a single bond, (–O–O–). When the bond breaks, it gives rise to very reactive oxygen specie, which is the active agent of the bleach. Around sixty percent of the world's hydrogen peroxide is used in chemical bleaching of textiles and wood pulp. [7]
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