Compositions of cellulose esters and layered silicates and process for the preparation thereof

#This application was funded by NSF-2001 TSE ##0124789 and NSF-2002 NER#0210681.

#Not Applicable

#(1) Field of the Invention

#FIG. 1 is a graph of FTIR analysis of compatibilizer CAB-g-MA and CA/CAB-g-MA/organoclay nanocomposites: a) CAB-g-MA (MA 0.8 wt.-% grafted), b) CAB-g-MA/organoclay nanocomposites (90/10 wt.-%) (Note: 1766 cm−1 is C═O of CAB, 1786, 1782 cm−1 is C═O of MA).

#FIG. 2 is a schematic representation: mechanism of compatibilized CA/TEC/Organoclay hybrid nanocomposites.

#FIGS. 3A, 3B and 3C are microscope photos of the CA/TEC/clay hybrid nanocomposites with different the sequential processing methods: a) CA/TEC plasticized pellet+clay mixing, b) CA/TEC melting+clay mixing, c) pre-plasticized CA/TEC powder+clay mixing;−80×.

#As the number of processing steps required to process a material increases, the more cost will be added to the finished product. Reduction in the processing complexity also makes for more Greener technology—known as “Cascade Engineering Principle”. One of the major targets of this invention is to adopt a reduced number of steps in designing the green nanocomposites. The cellulose acetate powder being mixed with clay powder, maleated compatibilizer and liquid plasticizer are fed into the extruder. In the prior art, cellulose acetate powder along with plasticizer and additives are extruded to make commercial cellulose plastic pellets. In the present invention, the cellulose acetate powder is used and thus avoiding one step of extrusion. Another advantage of this processing is achieved thorough mechanical mixing of matrix polymer and clay before extruding in presence of compatibilizer and liquid plasticizer. The schematic representation of the process for preparing green nanocomposite pellets (to be further injection molded to make test bars) from cellulose acetate powder (micron size), clay particles, liquid plasticizer (citrate/citrate+epoxidized vegetable oil), maleated cellulose acetate butyrate (powder form, prepared previously through reactive extrusion) is depicted in FIG. 2. This processing approach is a unique aspect of this invention. The cellulose acetate powder, clay, and maleated cellulose acetate butyrate compatibilizer are mechanically mixed and are fed through the powder feeder, whereas liquid plasticizer is fed through a pump into the extruder. The extrudate pellets are injection molded into test specimens.

#Compatibilization Mechanism

#In this invention organically modified montmorillonite commercial clay was used (methyl dihydroxyethyl hydrogenated tallow ammonium modified) i.e. Nanocor 1.34 TCA or CLOISITE 30B clay. Further modification of clay is avoided under this invention. Through maleated cellulose ester compatibilizer the improved adhesion of clay and cellulosic bioplastic is produced here. In comparison to maleated polypropylene (MAPP) for clay-PP nanocomposites, the maleated cellulose ester is more efficient because cellulose ester is polar while PP is nonpolar. In the case of cellulose ester-clay nanocomposites the maleated cellulose ester enters into clay gallery and also reacts with the free —OH group of the cellulose ester and clay thus improving the overall compatibilization of the entire system. The proposed reaction mechanism of compatibilization is schematically represented in FIG. 2.