Preparation of starch esters

Claim 1

A process for preparing esters of a starch having free reactive hydroxyl groups comprising the steps of: a. reacting said starch with a N,N'-disubstituted imidazolium salt selected from the group consisting of ##STR3## wherein R is selected from the group consisting of lower alkyl (C 1 -C 4 ) and lower alkenyl (C 2 -C 4 ); R 1 is selected from the group consisting of alkyl, substituted alkyl, alkenyl, cycloalkyl, aryl, substituted aryl, and arylalkyl; R 2 is selected from the group consisting of alkylene, substituted alkylene, bisalkylene ether, cycloalkylene, arylene and substituted arylene; and R 3 is selected from the group consisting of lower alkyl or H; R 1 and R 2 may each contain between 1 and 20 carbons; and X is Br - or Cl -; wherein the reaction with the starch is conducted in an aqueous medium at a pH level of from about 5.0 to 12.5 at temperatures of from 5° to 55° C. for a period of from about 10 minutes to 20 hours, employing the N,N'-disubstituted imidazolium salt in an amount of 0.10 to 100 percent on the weight of dry starch; and b. isolating the resultant starch derivative.