Method for preparing cellulose dope

Abstract

The invention relates to a method for preparing a cellulose dope comprising mixing and dissolving the cellulosic raw material in dilute and concentrated aqueous organic solvent in a two-stage process to form a homogeneous slurry, followed by heating the homogeneous slurry to obtain a cellulose dope containing 11% to 20% cellulose by weight. The invention also relates to a cellulose dope comprising 11% to 20% cellulose by weight and 73% to 79% aqueous organic solvent wherein the concentration of the cellulosic and metallic impurities in the cellulose dope shows a percent reduction of 20% to 50% from the cellulosic raw material.

We claim: 
     
         1 ) A method for preparing a cellulose dope comprising the steps of:
 a) mixing cellulosic raw material and an anti-oxidant with 10% to 65% aqueous organic solvent to obtain a slurry of 3% to 7% cellulose by weight;   b) pressing the slurry obtained in step (a) to obtain a cellulose cake containing 30% to 65% cellulose by weight;   c) shredding the cellulose cake obtained in step (b) and mixing the shredded cellulose cake and anti-oxidant with 76% to 88% aqueous organic solvent to prepare a homogeneous slurry containing 9% to 20% cellulose by weight; and   d) heating the homogeneous slurry obtained in step (c) at a temperature of 90 to 120 degree Celsius under vacuum to obtain cellulose dope containing 11% to 20% cellulose by weight.   
     
     
         2 ) The method as claimed in  claim 1 , wherein the aqueous organic solvent is selected from aqueous N-methylmorpholine-N-oxide or aqueous imidazolium based ionic liquids. 
     
     
         3 ) The method as claimed in  claim 1 , wherein the concentration of cellulosic impurities shows a percent reduction of 20% to 25% and metallic impurities shows a percent reduction of 20% to 50% in the cellulose cake of step (b). 
     
     
         4 ) The method as claimed in  claim 1 , wherein the anti-oxidant is propyl gallate. 
     
     
         5 ) The method as claimed in  claim 1 , wherein cellulosic raw material and aqueous organic solvent are mixed at a temperature of 50 to 70 degree Celsius. 
     
     
         6 ) The method as claimed in  claim 1 , wherein the pressing of slurry is carried out using a press selected from screw press, drum press or hydraulic press. 
     
     
         7 ) The method as claimed in  claim 1 , wherein the cellulosic dope obtained in step (d) comprises 73% to 79% aqueous organic solvent. 
     
     
         8 ) A cellulosic dope comprising:
 11 to 20% cellulose by weight; and   73% to 79% aqueous organic solvent, wherein the concentration of the cellulosic and metallic impurities in the cellulose dope shows a percent reduction of 20% to 50% from the cellulosic raw material.   
     
     
         9 ) The cellulose dope as claimed in  claim 8 , wherein the aqueous organic solvent is selected from aqueous N-methylmorpholine-N-oxide or aqueous imidazolium based ionic liquids. 
     
     
         10 ) The cellulose dope as claimed in  claim 8 , wherein the concentration of cellulosic impurities shows a percent reduction of 20% to 25% and metallic impurities shows a percent reduction of 20% to 50% in the cellulose dope from the cellulosic raw material.