Patent ID: 8299172

Claim:
A method for the preparation of biodegradable plastics, said method consisting essentially of: (I) providing a suspension in a basic aqueous carrier of a finely divided natural material containing a saccharide selected from the group consisting of (i) polysaccharides, (ii) oligosaccharides, and (iii) a combination of (i) and (ii); (II) adding water to the suspension; (III) agitating the suspension for a period of time; (IV) subjecting the product resulting from step (III) to a modifying material that converts any pendant hydroxyl group at any carbon atom of the anhydroglucose unit of the saccharide to a carboxylate, thereby forming a polysaccharide carboxylate, without breaking carbon—carbon bonds that form the ring of the anhydroglucose units of the saccharides, such modification selected from the group consisting of: (A) acylation using a material selected from the group consisting of cyclic anhydrides selected from the group consisting of (i) maleic anhydride, (ii) succinic anhydride, (iii) glutaric anhydride, (iv) phthalic anhydride and, (v) derivatives of (i), (ii), (iii), and (iv); (B) carboxymethylation using materials selected from the group consisting of: (i) haloalkanoic acids and (ii) salts of haloalkanoic acids, and, (C) oxidation using an oxidizing agent selected from the group consisting of: (a) hypochlorites; (b) hydrogen peroxide; (c) ozone and air, to provide a solid anionic material wherein pendant hydroxyl groups on any carbon atom of the anhydroglucose units of the saccharides are carboxylated and the carbon—carbon bonds that form the ring of the anhydroglucose units of the saccharide are not broken, and thereafter, (V) combining the material resulting from (IV) with a protein and allowing the resulting material and the protein to react with each other by forming interpolymeric electrostatic bonds between the protein and polysaccharide carboxylate molecules without the formation of strong, interpolymeric covalent bonds between the protein and polysaccharide molecules.