Process for manufacturing high-yield, high-strength pulp at low energy

Abstract

A low energy process for the manufacture of high yield pulp that involves the processing of chemically-treated chips or wood fiber at high stresses or intensity.

We claim:  
     
         1 . A process for producing a high yield pulp comprising: 
 chemically treating a pulp precursor selected from wood chips or wood fibre to develop wood fibre of said precursor while maintaining fibre integrity, and    refining the chemically treated pulp precursor at a high refining intensity.    
     
     
         2 . A process according to    claim 1    wherein said refining intensity is in a range of 200 to 2,000 J/kg/impact.  
     
     
         3 . A process according to    claim 1    wherein said intensity is in a range of 300 to 700 J/kg/impact.  
     
     
         4 . A process according to    claim 1    wherein said high refining intensity is one which establishes a high stress in said chemically treated pulp precursor in a range of 0.1 to 30 MPa at peak strain rates ranging from 50 to 100 s −1 .  
     
     
         5 . A process according to    claim 1    wherein the chemical treatment comprises sulfonating the precursor to provide a content of SO 3  on wood fibre of 1 to 3%, by weight, based on weight of oven dry wood fibre.  
     
     
         6 . A process according to    claim 5    wherein said content is 1 to 2.5% by weight.  
     
     
         7 . A process according to    claim 3    wherein the chemical treatment comprises sulfonating the precursor to provide a content of SO 3  on wood fibre of 1 to 2.5%, by weight, based on weight of oven dry wood fibre.  
     
     
         8 . A process according to    claim 2    wherein the chemical treatment comprises sulfonating the precursor with charge of alkali metal sulphite at a charge of 6 to 25%, by weight of sulphite, based on the oven dry wood fibre.  
     
     
         9 . A process according to    claim 2    wherein the chemical treatment comprises contacting said precursor with a charge of alkali metal carbonate or alkali metal hyroxide at a charge of 0.5 to 10%, by weight, based on weight of oven dry wood fibre.  
     
     
         10 . A process according to    claim 2    wherein said precursor comprises wood chips and the chemical treatment softens said wood chips for separation of wood fibres in said wood chips, and develops surface characteristics of the wood fibres of said wood chips, while maintaining fibre integrity.  
     
     
         11 . A process according to    claim 2    wherein said precursor comprises wood fibres and the chemical treatment and the refining develop surface characteristics of the wood fibres, while maintaining fibre integrity.  
     
     
         12 . A process according to    claim 2    wherein said precursor comprises wood chips and the chemical treatment swells the chips to facilitate separation of wood fibres in the chips, and develops surface characteristics of the wood fibres.