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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 ]
Paper chemicals designate a group of chemicals that are used for paper manufacturing, or modify the properties of paper. These chemicals can be used to alter the paper in many ways, including changing its color and brightness , or by increasing its strength and resistance to water. [ 1 ]
The procedure is the same for paper processing except that the EDTA and thiosulfate are mixed in 'bleachfix'. In reversal processing, residual silver in the emulsion after the first development is reduced to a soluble silver salt using a chemical bleach, most commonly EDTA. A conventional fixer then dissolves the reduced silver but leaves the ...
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.
Since dissolving pulp is highly refined, it is a product of high whiteness with few impurities making it suitable in specialty paper-related products such as filter paper and vulcanized fibre. Cellulose powder is dissolving pulp that has undergone acid hydrolysis, been mechanically disintegrated and made into fine powder.
The pulp produced up to this point in the process can be bleached to produce a white paper product. The chemicals used to bleach pulp have been a source of environmental concern, and recently the pulp industry has been using alternatives to chlorine, such as chlorine dioxide, oxygen, ozone and hydrogen peroxide.
2 - Bleached chemical pulp 1 - Coating Not drawn to scale. Solid bleached board (SBB) or solid bleached sulphate (SBS) is a virgin fibre grade of paperboard. This grade is made purely from bleached chemical pulp and usually has a mineral or synthetic pigment [1] coated top surface in one or more layers (C1S) and often also a coating on the ...
Recycled pulp can be bleached with the same chemicals used to bleach virgin pulp, but hydrogen peroxide and sodium hydrosulfite are the most common bleaching agents. Recycled pulp, or paper made from it, is known as PCF (process chlorine free) if no chlorine-containing compounds were used in the recycling process. [20]