Totally chlorine-free bleaching of flax pulp

• Published in: Bioresource technology 2002-10, Vol.85 (1), p.79-85
• Main Authors: Khristova, P., Tomkinson, J., Valchev, I., Dimitrov, I., Lloyd Jones, G.
• Format: Article
• Language: English
• Subjects: Acetamides - pharmacology; Alkaline-sulphite pulp; alkalinity; Anions - chemistry; Applied sciences; Biotechnology; bleaching; bleaching agents; Brightness; cellulose; Chelating Agents - pharmacology; Chlorine - chemistry; delignification; Edetic Acid - pharmacology; Ethylenediamines; Exact sciences and technology; flax; Flax - chemistry; Flax - drug effects; Hydrogen Peroxide - chemistry; Hydrogen-Ion Concentration; Multistage peroxide bleaching; Oxygen; Oxygen delignification; oxygen pulping; Paper, paperboard, non wovens; Peracetic Acid - chemistry; Polymer industry, paints, wood; pulp; Pulp manufacturing; Sonication; Sulfites - chemistry; TAED; Tamlin flax; Temperature; Time Factors; ultrasonics; Viscosity; Wood. Paper. Non wovens
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/S0960-8524(02)00022-6

Alkaline-sulphite Tamlin flax mill pulp of 34–41% brightness has been bleached with different totally chlorine-free (TCF) sequences (oxygen delignification, pressurised peroxide, peroxide without and with activator (TAED, tetraacetylethylenediamine) and with and without pre-treatment with ultrasound to 82% ISO brightness of the mill conventional CEH bleaching. Although the best results after oxygen delignification were obtained with pressurised peroxide, activated peroxide caused lower cellulose degradation and gave a higher pulp strength. The effects of temperature, retention time, chemical charge, TAED/peroxide ratio and alkalinity have been studied in order to maximise the brightness gain at lower viscosity loss. The chemistry and flexibility of TAED made it possible to activate the peroxide under conditions for which the peroxide alone is ineffective as a bleach, such as low alkalinity or low temperature. The presence of shives hindered the bleaching, but the bleached non-screened pulp was stronger than the screened one. Pre-treatment with ultrasound for 4 min of 1% pulp consistency gave 3–4% gain in ISO brightness for non-screened pulp and 2% for screened pulp and facilitated further delignification and peroxide bleaching.