Method of preparing crosslinked starch esters
AssigneeNational Starch and Chemical Investment Holding Corporation
InventorsDennis Neigel, Lawrence J. Scotchie, Martin M. Tessler
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Abstract
A process for preparing biodegradable, high humidity resistant crosslinked starch esters comprising reacting starch with monocarboxylic acid anhydride in a caustic catalyzed system to a DS of about 1.3 to 2.7 and crosslinking the starch ester in the same reaction mixture with polyfunctional acid and/or anhydride.
Claims19
A process for preparing crosslinked starch esters having a degree of substitution (DS) of about 1.3 to 2.7 comprising:
- a) slurrying starch in a monocarboxylic acid anhydride selected from anhydrides having carboxylic groups of 2 to 4 carbon atoms;
- b) adding a polyfunctional acid or anhydride to the above formed slurry, wherein said polyfunctional acid is selected from the group consisting of polycarboxylic acids having one of the following formulas:
- ##STR5## wherein R is selected from the group consisting of alkylene, unsaturated alkylene, bis alkylene ether, cycloalkylene and arylene containing from 1 to 42 carbon atoms;
- and R.sub.1 is selected from the group consisting of trivalent paraffin radicals, and trivalent aromatic hydrocarbon radicals containing from 6 to 20 carbon atoms.
- and said polyfunctional anhydride is selected from the group of anhydrides having the following general formula:
- ##STR6## wherein R.sub.2 is a divalent organic group, --O--, --S--, SO.sub.2, or ##STR7## and y is O or 1;
- c) activating the slurry by the addition of aqueous caustic solution;
- d) heating the slurry to its boiling point and holding until greater than about 95% conversion of the monoanhydride is reached and a crosslinked starch paste is formed;
- and
- e) isolating and recovering the crosslinked starch ester product.
A biodegradable, high humidity resistant crosslinked starch ester having a degree of substitution (DS) of about 1.3 to 2.7 which is prepared by:
- a) slurrying starch in a monocarboxylic acid anhydride selected from anhydrides having carboxylic groups of 2 to 4 carbon atoms;
- b) adding a polyfunctional acid or anhydride to the above formed slurry, wherein said polyfunctional acid is selected from the group consisting of polycarboxylic acids having one of the following formulas:
- ##STR8## wherein R is selected from the group consisting of alkylene, unsaturated alkylene, bis alkylene ether, cycloalkylene and arylene containing from 1 to 42 carbon atoms;
- and R.sub.1 is selected from the group consisting of trivalent paraffin radicals, and trivalent aromatic hydrocarbon radicals containing from 6 to 20 carbon atoms.
- and said polyfunctional anhydride is selected from the group of anhydrides having the following general formula ##STR9## wherein R.sub.2 is a divalent organic group, --O--, --S--, SO.sub.2, or ##STR10## and y is 0 or 1;
- c) activating the slurry by the addition of aqueous caustic solution;
- d) heating the slurry to its boiling point and holding until greater than about 95% conversion of the monoanhydride is reached and a crosslinked starch paste is formed;
- and
- e) isolating and recovering the crosslinked starch ester product.
Dependencies are inferred from the claim text.