Aqueous compositions containing starch ester dispersants

A process for preparing aqueous coating compositions which comprises dispersing in an aqueous medium about 25 to 95 parts by volume of a polymeric resin binder and about 5 to 75 parts by volume of pigment with an effective amount of dispersant consisting of mixed esters of starch characterized as having an average degree of substitution ranging from 0.5 to 3.0 wherein at least about 0.1 of the total degree of substitution consists of ester groups having pendant carboxylic acid groups and at least about 10 mole percent of said pendant carboxylic acid groups are neutralized;

• said mixed esters of starch derived from
• a. low molecular weight hydrolyzed starch having a plurality of anhydroglucose units with average molecular weights ranging up to about 100,000 or a derivative of said hydrolyzed starch having a degree of substitution below about 0.1 and
• b. at least about 0.5 mole by acylating agent for each anhydroglucose unit of the hydrolyzed starch or the derivative thereof;
• said acylating agent consisting of (i) from about 0.1 to 2.9 moles of at least one anhydride of a polycarboxylic acid and (ii) from about 0.1 to 2.9 moles of at least one agent selected from the class consisting of anhydrides of monocarboxylic acids and the acyl halides of monocarboxylic acids.