Functionalized lignin and method of producing the same
In this study, commercially available softwood lignin was esterified with tall oil fatty acid (TOFA) and tested as barrier material in fiber-based packaging material. The modified lignin samples were applied with a bar coater forming an even coating on the paperboard substrate. A significant decrease in WVTR and OTR value was observed for paperboard coated with the modified lignin as well as pure TOFA used as a reference. In contrast to the TOFA coating, the modified lignin coatings exhibited a high and stable contact angle. The coating material did not affect the tensile strength of the paperboard. According to the results, the demonstration of the conversion of lignin into a value added product has been shown. Furthermore, the novel coating material shows promising properties for the development as sustainable barrier material in fiber-based packaging material to replace oil-placed barriers.
1. Modified lignin obtained by modifying lignin derived from: a kraft process, a soda cooking process, a polysulphide cooking process or an organosolv process comprising esterifying at least a part of the hydroxyl groups present in the lignin with a tall oil fatty acid composition, wherein the tall oil fatty acid composition contains at least 80% by mass, calculated from the total solid matter, of fatty acids having 18 carbon atoms.
2. The modified lignin according to claim 1 , wherein at least a part of the tall oil fatty acids contains unsaturation.
3. Method of modifying lignin comprising esterifying at least a part of the hydroxyl groups present in the lignin with a tall oil fatty acid composition, wherein the lignin is derived from a kraft process, a soda cooking process, a polysulphide cooking process or an organosolv process and wherein the tall oil fatty acid composition contains at least 80% by mass, calculated from the total solid matter, of fatty acids having 18 carbon atoms.
4. The method according to claim 3 , wherein the tall oil fatty acid composition comprises mixtures of unsaturated C18 fatty acids.
5. The method according to claim 3 , wherein at least a part of the hydroxyl groups present in lignin are esterified with acids present in the tall oil fatty acid fraction (TOFA).
6. The method according to claim 3 , wherein the hydroxyl groups are esterified with fatty acids and optionally rosin acids.
7. The method according to claim 3 , wherein at least a part of the acids used for esterification contain unsaturation.
8. The method according to claim 3 , wherein a tall oil fatty acid composition is used for esterification, comprising C 16 to C 20 fatty acids, at least a part of which are formed by fatty acids containing 2 and optionally 3 double bonds.
9. The method according to claim 3 , wherein the lignin comprises phenolic hydroxyl groups, aliphatic hydroxyl groups or a combination thereof.
10. The method according to claim 3 , wherein at least 50% of the hydroxyl groups are esterified.
11. The method according to claim 3 , wherein the tall oil fatty acid composition contains 0.1 to 10% rosin acids calculated by weight of the solid matter of the composition.