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Abstract

The present invention relates to a method of production of a paper fibre composition, comprising the steps of: a) Providing a vessel, b) Providing Na₂S0₃ in the range of 12-122 kg/bdt combined with NaOH in the range of 0-97 kg/bdt, or NaHSO₃ in the range of 10-100 kg/bdt combined with NaOH in the range of 10-100 kg/bdt to said vessel, c) Providing wood, preferably softwood chips to said vessel for pre-treatment, d) Providing heat and pressure to said vessel in order be able control the vessel to have a temperature T comprised in the range of 160° C.-184° C., e) Controlling the retention time t for the wood chips, in relation to the temperature T of the content of the vessel, wherein T is controlled to be within the range of step d) and t is controlled to be in the range of 2-27 min, preferably in the range of 2-25 min, more preferred in the range of 5-20 min, f) Providing a defibration device coupled to the outlet of said vessel, the defibriation device being a refiner, mill, defibrator, fiberizer, or the like, g) Providing the pre-treated wood chips to the defibration device, h) Providing an energy consumption of 75-1000 kWh/bdt in said defibration device. The invention also relates to a paper fibre composition prepared by the method and a paper or paperboard or molded pulp made from the paper fibre composition.

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First Claim