Cellulose material plasticization and viscosity controlled cellulosic material

Abstract

The invention relates to method for producing viscosity controlled cellulosic material having a viscosity value in a range between 150 ml/g and 500 ml/g in a continuous process, the method comprising the following steps: i) forming a cellulose-water mixture (15) comprising water and chemically treated wood-based cellulosic material, the cellulose-water mixture (15) having a dry matter content between 3% and 20%, ii) treating the formed cellulose-water mixture (15) in a plasticization step (100) at a temperature between 130° C. and 200° C., and a pressure between 3 bars and 15 bars, at least 5 minutes and 120 minutes at the most, while mixing the cellulose-water mixture (15), and feeding hot water and/or water steam to the cellulose-water mixture, thereby obtaining a treated mixture (18), and iii) depressurizing the treated mixture (18) in a depressurizing step (105) in a controlled manner, thereby obtaining the viscosity controlled cellulosic material (20). This invention further relates to a viscosity controlled cellulosic material and a system for producing viscosity controlled cellulosic material.

1 - 14 . (canceled) 
     
     
         15 . A viscosity controlled cellulosic material having a viscosity value in a range between 150 ml/g and 500 ml/g, and an R18 solubility between 60% and 87%, wherein the viscosity controlled cellulosic material comprises wood-based cellulosic material. 
     
     
         16 . The viscosity controlled cellulosic material according to  claim 15 , wherein ISO Brightness of the viscosity controlled cellulosic material is between 75% and 90%. 
     
     
         17 . The viscosity controlled cellulosic material according to  claim 15 , wherein the viscosity value of the viscosity controlled cellulosic material is between 170 ml/g and 350 ml/g. 
     
     
         18 . The viscosity controlled cellulosic material according to  claim 15 , wherein a crystallinity index of the viscosity controlled cellulosic material is at least 74%, preferably at least 76%. 
     
     
         19 . The viscosity controlled cellulosic material according to  claim 15 , wherein a content of fibers having length below 0.6 mm, measured from the viscosity controlled cellulosic material, is between 10% and 30%. 
     
     
         20 . The viscosity controlled cellulosic material according to  claim 15 , wherein alpha cellulose content of the viscosity controlled cellulosic material is between 67% and 99.5%. 
     
     
         21 . The viscosity controlled cellulosic material according to  claim 15 , wherein hemicellulose content of the viscosity controlled cellulosic material is between 0.5 dry wt. % and 30 dry wt. %. 
     
     
         22 . The viscosity controlled cellulosic material according to  claim 15 , wherein the R18 solubility value of the viscosity controlled cellulosic material is at least 70% and 87% at the most. 
     
     
         23 . A system for producing viscosity controlled cellulosic material having a viscosity value in a range between 150 ml/g and 500 ml/g in a continuous process, the system comprising:
 means for forming a cellulose-water mixture ( 15 ),   a continuous reactor ( 101 ) for treating the cellulose-water mixture in a plasticization step ( 100 ) at a temperature between 130° C. and 200° C.,   mixing means for mixing the cellulose-water mixture during the plasticization step,   heating means for increasing temperature of the cellulose-water mixture in the continuous reactor, such as a feeder to feed water steam to the continuous reactor,   means for depressurizing the treated mixture ( 18 ) in a controlled manner without a steam explosion after the plasticization step ( 100 ), and   optionally, means for conveying at least part of a filtrate ( 102 ) obtained from the plasticization step to the continuous reactor ( 101 ).   
     
     
         24 . The viscosity controlled cellulosic material according to  claim 15 , wherein the material is cold alkali soluble. 
     
     
         25 . The viscosity controlled cellulosic material according to  claim 16 , wherein the material is dissolvable to an aqueous alkaline having NaOH content of solution between 5% and 10% at a temperature from −10° C. to +5° C. 
     
     
         26 . The viscosity controlled cellulosic material according to  claim 15 , wherein the viscosity controlled cellulosic material is manufactured from chemically treated wood-based cellulosic material comprising bleached kraft pulp and/or bleached sulfite pulp and/or bleached soda pulp. 
     
     
         27 . The viscosity controlled cellulosic material according to  claim 15 , wherein a length weighted fiber length Lc(l) of the viscosity controlled cellulosic material measured according to standard ISO 16065-N is at least 0.9 mm. 
     
     
         28 . The viscosity controlled cellulosic material according to  claim 21 , wherein the hemicellulose content of the viscosity controlled cellulosic material is at least 5 dry wt. %. 
     
     
         29 . The viscosity controlled cellulosic material according to  claim 22 , wherein the R18 solubility value of the viscosity controlled cellulosic material is 84% at the most. 
     
     
         30 . The viscosity controlled cellulosic material according to  claim 15 , wherein a sodium (Na) content of the viscosity controlled cellulosic material is in a range between 200 mg/kg and 1500 mg/kg based on the dry weight of the chemically treated wood-based cellulosic material fibers. 
     
     
         31 . The viscosity controlled cellulosic material according to  claim 15 , wherein a curliness of the viscosity controlled cellulosic material is between 25% and 90%. 
     
     
         32 . The viscosity controlled cellulosic material according to  claim 15 , wherein a water retention value (WRV) of the viscosity controlled cellulosic material is between 1 g/g and 2 g/g. 
     
     
         33 . The viscosity controlled cellulosic material according to  claim 15 , wherein a lignin content of the viscosity controlled cellulosic material is less than 1.5%. 
     
     
         34 . The viscosity controlled cellulosic material according to  claim 15 , wherein an extractive content of the viscosity controlled cellulosic material is less than 0.2%. 
     
     
         35 . A regenerated cellulosic material comprising the viscosity controlled cellulosic material according to  claim 15 . 
     
     
         36 . A method for producing viscosity controlled cellulosic material having a viscosity value in a range between 150 ml/g and 500 ml/g in a continuous process, the method comprising the following steps:
 i) forming a cellulose-water mixture ( 15 ) comprising
 water and 
 chemically treated wood-based cellulosic material comprising bleached kraft pulp, bleached sulfite pulp and/or bleached soda pulp, the cellulose-water mixture ( 15 ) having a dry matter content between 3% and 20%, 
   ii) treating the formed cellulose-water mixture ( 15 ) in a plasticization step ( 100 ) at
 a temperature between 130° C. and 200° C., and 
 a pressure between 3 bars and 15 bars, 
 at least 5 minutes and 120 minutes at the most, 
   while
 mixing the cellulose-water mixture ( 15 ), and 
 feeding hot water and/or water steam to the cellulose-water mixture, 
   thereby obtaining a treated mixture ( 18 ),   and   iii) depressurizing the treated mixture ( 18 ) after the plasticization step ( 100 ) in a depressurizing step ( 105 ) in a controlled manner without a steam explosion to maintain fiber integrity,   thereby obtaining the viscosity controlled cellulosic material ( 20 ).