Oxidative chlorine-free methods in bleaching of paper pulp | Oksidatīvās bezhlora metodes papīrmasas balināšanā
2009
Sable, I., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Zakis, G., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Neiberte, B., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Verovkins, A., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Grinfelds, U., Latvian State Inst. of Wood Chemistry, Riga (Latvia)
A method of bleaching the pulp with ammonium persulphate in acidic medium has been worked out. The highest brightness of the pulp was achieved, using sulphuric acid in first stage of bleaching; results of mechanical strength of pulp fell behind slightly in case of use of nitric acid in bleaching; in hydrochloric and acetic acid bleaching process didn't process at all. The best reducing agent for second stage bleaching is sodium borohydride. Other reducing agents provide sufficient brightness, but noticeably decrease mechanical strength of pulp. Changes of fibre length occur in bleaching process, but fibre length doesn't affect the mechanical strength of pulp directly. The elaborated method can be recommended to obtain paper with average brightness and mechanical strength. Indicators of bleaching quality (brightness and mechanical strength) of aspen and grey alder indicate that grey alder is competitive in industrial production of pulp.
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