Method of producing dissolving pulp, dissolving pulp and use of method

Abstract

A method of producing dissolving pulp from a recycled fibrous feedstock. The method comprises providing a fibrous material comprising cellulose, lignin and hemicellulose, said fibre source further having a lignin content of 0.1 to 7% lignin and an ash content of up to 3%; subjecting the fibrous material to an alkaline extraction at a temperature of about 0 to 25° C., to produce fibres having a reduced content of hemicellulose; subjecting the fibres thus obtained to a bleaching treatment carried out with oxidative chemical reagents in order to reduce the lignin content of the fibres; and recovering the fibres thus obtained. By means of the method, dissolving pulp can be produced from recycled paper and cardboard products.

1 . A method of producing dissolving pulp from a recycled fibrous feedstock, comprising the steps of
 providing a fibrous material comprising cellulose, lignin and hemicellulose, said fibre source further having a lignin content of 0.1 to 7% lignin and an ash content of up to 3%;   subjecting the fibrous material to an alkaline extraction at a temperature of about 0 to 25° C., to produce fibres having a reduced content of hemicellulose;   subjecting the fibres thus obtained to a bleaching treatment carried out with oxidative chemical reagents in order to reduce the lignin content of the fibres; and   recovering the fibres thus obtained.   
     
     
         2 . The method according to  claim 1 , wherein the recycled fibrous feedstock is selected from recycled paper and recycled cardboard products and combinations thereof which comprise at least 1% by weight of lignocellulosic fibre materials. 
     
     
         3 . The method according to  claim 1 , wherein the fibrous material comprises the recycled fibrous feedstock or is produced therefrom. 
     
     
         4 . The method according to  claim 1 , wherein the fibrous material comprises at least 50% by weight of cellulosic fibres. 
     
     
         5 . The method according to  claim 1 , wherein the fibrous material comprises 50 to 95% by weight of fibres of chemical pulping and 5 to 50% by weight of fibres of mechanical pulping. 
     
     
         6 . The method according to  claim 1 , wherein the cellulosic fibres are derived from deciduous tree, coniferous tree or combinations thereof. 
     
     
         7 . The method according to  claim 1 , wherein the fibres recovered after bleaching are subjected to a chemical treatment for increasing accessibility of the cellulosic fibres. 
     
     
         8 . The method according to  claim 1 , wherein the recovered fibres are subjected in an aqueous slurry to acid treatment, whereby the pH of the slurry is less than 3.5. 
     
     
         9 . The method according to  claim 1 , wherein the fibrous feedstock comprises recycled paper or recycled cardboard products or combinations thereof having an original ash content of up to 10% or more, which have been subjected to a mechanical or chemical operation for reducing the ash content to less than about 3, in order to provide said fibrous material. 
     
     
         10 . The method according to  claim 1 , wherein the fibrous feedstock comprises recycled paper or recycled cardboard products or combinations thereof having an original lignin content of up to 20% by weight, which have been subjected to chemical delignification with an alkaline cooking chemical for reducing the lignin content to less than 10% by weight in order to provide said fibrous material. 
     
     
         11 . The method according to  claim 10 , wherein the delignification is carried out by kraft pulping, soda pulping or oxygen delignification. 
     
     
         12 . The method according to  claim 1 , wherein said bleaching is carried out with oxidative chemicals selected from the group of peroxides and peracids, chlorine dioxide, hypochlorite and ozone and combinations thereof. 
     
     
         13 . The method according to  claim 1 , wherein the recycled papers are selected from office papers, and the recycled cardboard products are selected from liner clippings. 
     
     
         14 . The method according to  claim 1 , wherein the fibres recovered exhibit at least one of the following properties:
 a lignin content of less than 0.7% by weight;   a viscosity of 250 ml/g or more;   a Fock value of 55% or better;   cellulose 90% or more; and   a R18% value of 88% or better   
     
     
         15 . The method according to  claim 1 , wherein the fibres recovered exhibit a hemicellulose content of 0.1 up to 10% by weight. 
     
     
         16 . A dissolving pulp produced by a method according to the steps of:
 providing a fibrous material comprising cellulose lignin and hemicellulose, fibre source further having a lignin content of 0.1 to 7% lignin and an ash content of up to 3%;   subjecting the fibrous material to an alkaline extraction at a temperature of about 0 to 25° C., to produce fibres having a reduced content of hemicellulose;   subjecting the fibres thus obtained to a bleaching treatment carried out with oxidative chemical reagents in order to reduce the content of the fibres; and   recovering the fibres thus obtained.   
     
     
         17 . (canceled) 
     
     
         18 . (canceled) 
     
     
         19 . (canceled)