Low molecular weight cellulose mixed esters and their use as low viscosity binders and modifiers in coating compositions

Abstract

Cellulose mixed esters are disclosed having low molecular weights and low degrees of polymerization. These new cellulose mixed esters include cellulose acetate propionate and cellulose acetate butyrate. The esters exhibit solubility in a wide range of organic solvents with minimal viscosity increase, are compatible with a wide variety of resins, and are useful in coatings and inks compositions as binder resins and rheology modifiers.

1 . A cellulose mixed ester having the following properties:
 a total degree of substitution per anhydroglucose unit of from 3.08 to 3.50, having the following substitutions:
 a degree of substitution per anhydroglucose unit of hydroxyl of no more than about 0.70, 
 a degree of substitution per anhydroglucose unit of C 3 -C 4  esters from about 0.80 to about 1.40, and 
 a degree of substitution per anhydroglucose unit of acetyl of from about 1.20 to about 2.34; 
   an inherent viscosity of from 0.05 to 0.12 dL/g, as measured in a 60/40 (wt./wt.) solution of phenol/tetrachloroethane at 25° C.;   a number average molecular weight (M n ) of from about 1,000 to about 5,600;   a weight average molecular weight (M w ) of from about 1,500 to about 10,000; and   a polydispersity of from about 1.2 to about 3.5.