Bio-based starch mixed ester biodegradable and/or compostable compositions and methods for making the same

Abstract

A bio-based starch mixed ester biodegradable and/or compostable composition includes a mixed starch mixed ester having a total degree of substitution of at least 1.0, wherein the ester substituents include a mixture of (a) acetate and (b) one or more C 10 to C 24 ester residues, wherein the degree of substitution of (a) is greater than (b). A method of preparing a bio-based starch mixed ester biodegradable and/or compostable composition having a degree of substation of at least 1.0 includes reacting starch with a mixed acid anhydride in the presence of an esterification catalyst to form a starch mixed ester composition wherein the mixed acid anhydride is formed from (a) an acid anhydride and (b) a carboxylic acid having 10 to 24 carbon atoms.

1 . A bio-based starch mixed ester biodegradable and/or compostable composition comprising a mixed starch mixed ester having a total degree of substitution of at least 1.0, wherein the ester substituents include a mixture of (a) acetate and (b) one or more C 10  to C 24  ester residues, wherein the degree of substitution of (a) is greater than (b). 
     
     
         2 . The composition of  claim 1  wherein the one or more C 10  to C 24  ester residues are selected from the group consisting of laurate, stearate, oleate, or mixtures thereof. 
     
     
         3 . The composition of  claim 2  wherein the composition has a glass transition temperature between about 125° C. to about 165° C. 
     
     
         4 . The composition of  claim 1  wherein the starch mixed ester has a total degree of substitution between 1.5 to about 2.9. 
     
     
         5 . A method of preparing a bio-based starch mixed ester biodegradable and/or compostable composition having a total degree of substation of at least 1.0 comprising reacting starch with a mixed acid anhydride to form a starch mixed ester composition, wherein the mixed acid anhydride results from a reaction of an acid anhydride and a carboxylic acid having 10 to 24 carbon atoms. 
     
     
         6 . The method of  claim 5  wherein the acid anhydride is acetic anhydride. 
     
     
         7 . The method of  claim 6  wherein the carboxylic acid is selected from the group consisting of lauric, stearic, oleic, or mixtures thereof. 
     
     
         8 . The method of  claim 4  wherein the starch is reacted with a mixed acid anydride in the presence of an esterification catalyst. 
     
     
         9 . The method of  claim 8  wherein the esterification catalyst is an alkaline metal hydroxide or amino compound. 
     
     
         10 . The method of  claim 5  further comprising;
 a. reacting sodium hydroxide, acetic anhydride and starch in a first reactor; 
 b. reacting stearic acid and acetic anhydride in a second reactor to form a mixed acid anhydride; 
 c. reacting the contents of the first reactor with the contents of the second reactor to esterify the starch and form the starch mixed ester composition. 
 
     
     
         11 . The method of  claim 5  wherein the starch is a high amylose content starch. 
     
     
         12 . The method of  claim 5  further comprising water washing the starch mixed ester composition and thereafter drying to form a water-washed starch mixed ester composition. 
     
     
         13 . The method of  claim 12  further comprising, subsequent to the water washing, washing the water-washed starch mixed ester with an alcohol to from an alcohol-washed starch mixed ester composition. 
     
     
         14 . The method of  claim 5  comprising mixing an acid anhydride, starch, and sodium hydroxide to form a mixture and to dehydrate the starch and, thereafter adding a fatty acid containing from 10 to 24 carbons and additional acid anhydride to the mixture to esterify the starch and to form the starch mixed ester composition. 
     
     
         15 . The method of  claim 14  wherein the starch is a high amylose content starch. 
     
     
         16 . The method of  claim 14  further comprising water washing the starch mixed ester composition and thereafter drying to form a water-washed starch mixed ester composition. 
     
     
         17 . The method of  claim 16  further comprising, subsequent to the water washing, washing the water-washed starch mixed ester with an alcohol to from an alcohol-washed starch mixed ester composition.