Date of this Version
United States Patent No.: US 10,533,031 B2
Date of Patent: Jan. 14,2020
Materials and methods for preparing reactive lignin and for preparing a bio-based adhesive are described herein.
This disclosure generally relates to methods of making and using reactive lignin. This disclosure also generally relates to methods of making and using bio-based adhesives. Lignin is the second most abundant natural polymer behind cellulose, yet lignin has very little commercial value despite years of research. Lignin is one of the major components of the cell wall in wood and other plant based materials such as hemp or crop wastes. It is produced in enormous quantities each year, primarily as a by-product in the pulp and paper industries. Lignin has little economic value and the majority of lignin is burned as a low grade fuel or is discharged into the aquatic ecosystem as waste, causing a significant impact on the environment. For example, the majority of the Biological Oxygen Demand (BOD) from pulp mill effluents is due to waste lignin. In addition, an increase in the production of cellulosic ethanol from corn stalk and other biomass resources will add significantly to this glut of lignin. This tremendous oversupply of lignin presents an enormous opportunity for the development of renewable biomaterials to replace non-biodegradable petroleum-based products, and the present disclosure provides for commercially-viable and inexpensive methods of making reactive lignin that can be used to make a wide variety of lignin-based products. In a similar vein, there is a growing demand for developing non-petroleum-based materials to replace traditional plastics. There is a critical need to replace the commonly used formaldehyde-based resins found in many building materials such as plywood and particle boards. Formaldehyde-based resins have raised alarming health concerns because formaldehyde is highly toxic, allergenic and a classified carcinogenic. The off-gassing of formaldehyde-based resins is a significant source of indoor air pollution, particularly from formaldehyde pressed-wood products. Thus, this disclosure also describes the development of a class of formaldehyde-free, bio-based reactive adhesives for binding renewable biodegradable material such as lignin, cellulose, wood chips and crop waste to fabricate useful solid materials and composites.