Chemical modification of lignin and lignin derivatives
A method for producing a trans-esterified hydroxypropyl lignin (HPL) is provided in one example embodiment and includes precipitating a lignin, dissolving the precipitated lignin in a solution, adding a reagent to the solution, adjusting the pH of the solution, allowing reactions in the solution to occur for a predetermined amount of time, precipitating the solution to produce a precipitate, and washing, filtering, and drying the precipitate to produce the trans-esterified HPL. In one example, a thermoplastic may be added to produce a trans-esterified HPL/thermoplastic blend.
1. A method for producing a biodegradable plastic, the method comprising:
extruding a trans-esterified lignin/thermoplastic blend, the trans-esterified lignin/thermoplastic blend comprising:
a trans-esterified hydroxypropyl lignin (HPL), wherein the trans-esterified HPL is created by:
precipitating a lignin;
dissolving the precipitated lignin in a solution;
adding a reagent to the solution;
adjusting a pH of the solution;
allowing reactions in the solution to occur for a predetermined amount of time such that the lignin has undergone transesterification with a nearby polyester macromolecule from a polyester, thereby transferring a segment of the polyester onto the lignin;
precipitating the solution to produce a precipitate; and
washing, filtering, and drying the precipitate to produce the lignin/thermoplastic polyester blend.
2. The method of claim 1 , wherein an alkyl ester of the HPL exchanges carboxylic acid groups with an alcohol terminated segment of a polyester chain such that long chain polyester segments are covalently-bond to the HPL.
3. The method of claim 1 , wherein the extent of transesterification of the lignin/thermoplastic blend is controlled such that extensive crosslinking does not occur in order to retain thermoplastic properties.
4. The method of claim 1 , wherein the biodegradable plastic is a film product, a formed and molded product, an injection molded product, or an extruded product that biodegrades over a period of time into humus through an oxidative process.
5. The method of claim 4 , wherein polylactide is added to the lignin/thermoplastic blend to extend the period of time that the biodegradable plastic biodegrades.