Process for production of cellulose nanofibers from miscanthus x. giganteus and composites therefrom

Abstract

A process for the isolation of cellulose nanofibers, in particular carboxylic acid functionalized cellulose nanofibers (MxG-CNF-CO2H) from the sustainable grass hybrid Miscanthus x. giganteus (MxG). The process includes the steps of performing bleach treatment on a quantity of MxG followed by ammonium persulfate oxidation. The resulting MxG-CNF-CO2Hs have good dispersibility in aqueous and polar organic solvents. They are also able to form gels at relatively low concentrations. The MxG-CNF-CO2H show significantly higher reinforcement effect when compared to carboxylic acid functionalized cellulose nanocrystals at the same weight percent in a composite composition.

What is claimed is: 
     
         1 . A process for preparing cellulose nanofibers from  Miscanthus  x.  giganteus  (MxG), comprising the steps of:
 performing a bleaching step on a quantity of the MxG; and   thereafter subjecting a solid material obtained from the bleaching step to ammonium persulfate oxidation and obtaining carboxylic acid functionalized cellulose nanofibers, MxG-CNF-CO 2 H.   
     
     
         2 . The process according to  claim 1 , further including the step of obtaining the quantity of the MxG and reducing a particle size thereof to a smaller average particle size. 
     
     
         3 . The process according to  claim 2 , wherein the reduced average particle size is less than 500 μm. 
     
     
         4 . The process according to  claim 1 , wherein the bleaching step comprises contacting the MxG with a bleaching solution comprising an oxidizing agent and one or more of an acid and an acid liberating agent. 
     
     
         5 . The process according to  claim 4 , wherein the oxidizing agent comprises one or more of sodium chlorite, sodium hypochlorite, calcium hypochlorite and hydrogen peroxide. 
     
     
         6 . The process according to  claim 5 , wherein the concentration of the oxidizing agent ranges from about 2 wt. % to about 4 wt. % based on the total weight of the bleaching solution. 
     
     
         7 . The process according to  claim 4 , wherein the pH of the bleaching solution is between about 4 and about 6. 
     
     
         8 . The process according to  claim 6 , wherein the bleaching step is performed at a temperature between 60° C. and 80° C. for an amount of time sufficient to convert lignins present in the MxG. 
     
     
         9 . The process according to  claim 1 , wherein after the bleaching step has been performed, the MxG-containing bleaching solution is filtered, washed and dried prior to subjecting the solid material obtained from the bleaching step to ammonium persulfate oxidation. 
     
     
         10 . The process according to  claim 1 , wherein the ammonium persulfate oxidation step includes contacting the solid material obtained from the bleaching step with an ammonium persulfate solution having a concentration from about 0.5 M to about 2.0 M. 
     
     
         11 . The process according to  claim 10 , wherein the ammonium persulfate solution containing the solid material is mixed fora suitable period of time in order to oxidize the solid material to form the MxG-CNF-CO 2 H. 
     
     
         12 . The process according to  claim 11 , wherein the mixing is performed at a temperature between about 50° C. to about 90° C. 
     
     
         13 . The process according to  claim 12 , wherein the oxidation process is performed for about 8 hours to about 24 hours.