Patent ID: 8268122

Claim:
A process for preparing a high-yield pulp for papermaking selected from mechanical pulp (MP), refiner mechanical pulp (RMP), pressurized refiner mechanical pulp (PRMP), thermomechanical pulp (TMP), thermomechanical chemical pulp (TMCP), high-temperature TMP (HT-TMP) RTS-TMP, Thermopulp, groundwood pulp (GW), stone groundwood pulp (SGW), pressure groundwood pulp (PGW), super pressure groundwood pulp (PGW-S), thermo groundwood pulp (TGW), thermo stone groundwood pulp (TSGW), chemimechanical pulp (CMP), chemirefinermechanical pulp (CRMP), chemithermomechanical pulp (CTMP), high-temperature CTMP (HT-CTMP), sulphite-modified thermomechanical pulp (SMTMP), reject CTMP (CTMP R ), groundwood CTMP (G-CTMP), high-yield sulphite pulp (HYS), biomechanical pulp (BRMP), pulps produced according to the OPCO process, Bi-Vis process, dilution water sulfonation process (DWS), sulfonated long fibres process (SLF), chemically treated long fibres process (CTLF), long fibre CMP process (LFCMP) or any modifications and combinations thereof comprising a) treating a lignocellulose containing material selected from wood particles and/or fibers chemically by means of an oxidising system comprising at least one non-enzymatic oxidant selected from inorganic or organic peroxy compounds or hydrogen peroxide generating compounds substantially free from ozone and chlorine dioxide in an amount from about 0.1 to about 5 wt % based on the weight of the lignocellulose containing material and an activator in an amount from about 0.0001 to about 1 wt % based on the weight of the lignocellulose containing material at a pH from about 2 to about 6.5; and b) treating the lignocellulose containing material mechanically in at least two or more stages for a time sufficient to produce a high-yield pulp, wherein the energy input to said at least two or more stages is at least 1150 kWh/bdmt and up to about 5000 kWh/bdmt, wherein the lignocellulose containing material is chemically treated by adding the non-enzymatic oxidant and activator to the lignocellulose containing material prior to and/or during any mechanical treatment stage, and wherein the lignocellulose containing material is not chemically treated at a pH from about 11.5 to about 14 between stages a) and b), wherein the activator is selected from transition metal ions and wherein the lignocellulosic containing material is treated at a temperature from 80 to 180° C.