METHOD OF PRODUCING BLEACHED HEMPEN CELLULOSE Russian patent published in 2020 - IPC D21C5/00 D21C9/16 

FIELD: pulp and paper industry.

SUBSTANCE: invention relates to pulp and paper industry, in particular to production of cellulose intended for production of cardboard, paper of various purposes from annual vegetal raw materials. Method involves pre-hydrolysis of hemp fiber, delignification in an alkaline medium, bleaching in an alkaline solution of hydrogen peroxide, intermediate washing, squeezing and drying. Prehydrolysis of raw material is carried out at temperature 85–95 °C in solution containing 0.5–2.0 wt% sodium hydroxide, 0.2–0.3 wt% synthanol and 0.3 wt% sodium thiosulphate for 60 min. Delignification is carried out in solution containing 1.5–3 wt% sodium hydroxide, 0.25–0.5 wt% sodium sulphide, 0.6–1.0 wt% sodium thiosulphate and 0.05–0.06 wt% synthanol, at temperature 125–140 °C for 90–130 minutes. Bleaching is carried out at temperature 85–95 °C in an alkaline solution of hydrogen peroxide, additionally containing 0.3–0.5 wt% sodium metasilicate, 0.02–0.05 wt% triethanolamine and 0.05–0.1 wt% chelating agent Trilon B at concentration of hydrogen peroxide of 0.5–0.6 wt%, for at least 90 minutes.

EFFECT: proposed method ensures production of bleached hemp cellulose with high molecular weight (medium degree of polymerization), lower content of lignin, satisfactory content of α-cellulose, ash and whiteness; obtained cellulose can be used for production of paper for various purposes, cardboard, as well as for chemical processing.

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