Method of producing mechanical pulp and the mechanical pulp thus produced

Abstract

A method of producing mechanical pulp, comprising impregnation of fiber material with an enzyme-containing aqueous liquid prior to defibration and refining of the fiber material to produce a mechanical pulp. According to the invention, said enzyme-containing aqueous liquid is a pectinase-containing aqueous liquid. The invention is also related to the mechanical pulp thus produced.

1 . A method of producing mechanical pulp, comprising impregnation of fiber material with an enzyme-containing aqueous liquid prior to defibration and refining of the fiber material to produce a mechanical pulp, characterised in said enzyme-containing aqueous liquid being a pectinase-containing aqueous liquid and in initial compression of the fiber material.  
   
   
       2 . A method according to  claim 1 , characterised in that said initial compression of the fiber material is a mechanical compression, preferably combined with a thermal pretreatment of the fiber material, preferably by steaming, before the impregnation.  
   
   
       3 . A method according to  claim 2 , characterised in that steaming is carried out, preferably at atmospheric pressure, for 1 to 30 min, preferably 10 to 20 min.  
   
   
       4 . A method according to  claim 2 , characterised in that compression is performed by a compression screw or a twin roll press, with a compression ratio of 1:1 to 8:1, preferably 2:1 to 5:1.  
   
   
       5 . A method according to  claim 1 , characterised in that the pectinase-containing liquid comprises an enzymatic preparation with pectolytic activity for both pectins and esterified pectins.  
   
   
       6 . A method according to  claim 1 , characterised in that the aqueous liquid comprises two or more enzymatic preparations wherein at least one of the preparations has pectinase activity.  
   
   
       7 . A method according to  claim 1 , characterised in that the pectinase is added as a biological agent comprising one or more fungi or bacteria, at least one of which having pectolytic activity.  
   
   
       8 . A method according to  claim 1 , characterised in that the pectinase arises from a group of microorganisms containing  Aspergillus aculeatus  and  Aspergillus oryzae.    
   
   
       9 . A method according to  claim 1 , characterised in that the charge of pectinase is 2,000,000 to 200,000,000 polygalacturonase units/ton fiber material, preferably 10,000,000 to 50,000,000 polygalacturonase units/ton.  
   
   
       10 . A method according to  claim 1 , characterised in that the aqueous liquid comprises at lease one chelating agent, preferably deithylenetetraminepentaacetic acid at a charge of 1 to 10 kg/ton and/or sulfite at a charge of 5 to 50 kg/ton.  
   
   
       11 . A method according to  claim 1 , characterised in that a retention time after uptake of the impregnation liquid is 3 min to 24 hours, preferably 15 to 240 min, and more preferably 30 to 120 min.  
   
   
       12 . A method according to  claim 11 , characterised in that a temperature in the retention after uptake of the impregnation liquid is 20 to 100° C., preferably 35 to 70° C., and more preferably about 50° C..  
   
   
       13 . A method according to  claim 1 , characterised in that a pH in the impregnation liquid is 3 to 10, preferably 4 to 7, and more preferably about 5.  
   
   
       14 . A method according to  claim 1 , characterised in that the defibration and refining of the fiber material is performed by use of single disc, double disc or conical refiners in one or multi stages.  
   
   
       15 . A method according to  claim 14 , characterised in that a refiner rotation speed is 1000 to 3000 rpm, preferably 1500 to 2600 rpm.  
   
   
       16 . A method according to  claim 14 , characterised in that the fiber material is preheated for 2 to 10 min before refining, that a refiner pressure is from atmospheric up to 5 bar, preferably up to 4 bar and that a refiner rotation speed preferably is 1200 to 1800 rpm.  
   
   
       17 . A method according to  claim 14 , characterised in that the fiber material is preheated for 3 to 30 sec before refining, that a refiner pressure is from 4 to 8 bar, preferably 5 to 8 bar and that a refiner rotation speed preferably is above 2000 rpm.  
   
   
       18 . A method according to  claim 1 , characterised in that said fiber material is softwood chips or hardwood chips.  
   
   
       19 . A method according to  claim 1 , characterised in that the fiber material is non-wood fiber material including bagasse, bamboo, reed and straw.  
   
   
       20 . A method according to  claim 1 , characterised in that the pulp obtained after defibration and refining is bleached, preferably with alkaline peroxide, to obtain bleached pulp having high brightness.  
   
   
       21 . Mechanical pulp, characterised in that it has been produced according to  claim 1.