US 11,725,338 B2
Method for producing bleached wood fibre material
Stefan Erren, Ludwigshafen am Rhein (DE); Dieter Schönhaber, Ludwigshafen am Rhein (DE); Martin Schachtl, Ludwigshafen am Rhein (DE); and Pavel Vassilievitch Osipov, Ludwigshafen am Rhein (DE)
Assigned to BASF SE, Ludwigshafen am Rhein (DE)
Filed by BASF SE, Ludwigshafen am Rhein (DE)
Filed on May 4, 2021, as Appl. No. 17/307,060.
Application 17/307,060 is a continuation of application No. 15/128,755, granted, now 11,015,290, previously published as PCT/EP2015/055275, filed on Mar. 13, 2015.
Claims priority of application No. 14161583 (EP), filed on Mar. 25, 2014.
Prior Publication US 2021/0254280 A1, Aug. 19, 2021
This patent is subject to a terminal disclaimer.
Int. Cl. D21B 1/02 (2006.01); D21B 1/14 (2006.01); D21C 9/10 (2006.01)
CPC D21B 1/021 (2013.01) [D21B 1/14 (2013.01); D21C 9/1005 (2013.01); D21C 9/1057 (2013.01); D21C 9/1063 (2013.01); D21C 9/1089 (2013.01)] 3 Claims
 
1. A process for producing bleached mechanical woodpulp, said process comprising the steps of
a) delaminating large particles of wood, which have optionally been pretreated with chemicals and/or water, into modified particles of wood,
b) grinding the modified particles of wood from a) in one or more refiners,
c) optionally treating a stock obtained in step b) with oxidative or reductive bleaching agents,
wherein a composition Z is present during step a) and/or step b), said composition Z comprising a component (Z1): a salt of dithionous acid H2S2O4 (Z1), and also additives (Z4) wherein additive (Z4) is a carbonate or hydrogencarbonate of alkali or alkaline earth metal,
wherein the salt of dithionous acid H2S2O4 is sodium dithionite, and
wherein step a) comprises the large, optionally pretreated particles of wood being first (i) exposed to mechanical pressure and/or shearing forces and then (ii) ground in a refiner, wherein refiner stage a) (ii) pressure and/or energy consumption are lower than the corresponding parameters for the refiner step b) and wherein Z is metered into the refiner stage a) (ii), stage b) or both stage a) (ii) and b), and
said large particles of wood are a size of about (15-50) mm×(15-50) mm×about (6-12) mm.
 
3. A process for producing wood-base materials, which comprises producing a bleached mechanical woodpulp by the process defined in claim 1, resinating the bleached mechanical woodpulp to form resinated wood pulp, optionally under addition of white pigments, and compression molding the resinated woodpulp into wood-base materials.