Method for increasing the reactivity of lignin
The present invention relates to a method for increasing the reactivity of lignin, wherein the method comprises the following steps: a) forming, under heating at a temperature of 30-70° C., an aqueous dispersion comprising alkali and lignin, wherein the alkali comprises a hydroxide of an alkali metal; and b) heating the dispersion formed in step a) at a temperature of 50-95° C. for producing alkalated lignin.
1. A method for increasing the reactivity of lignin, wherein the method comprises the following steps:
a) forming, under heating at a temperature of 30-70° C., an aqueous dispersion consisting of alkali and lignin and water, wherein the alkali comprises a hydroxide of an alkali metal, and wherein the concentration of the lignin is 10-50 weight-% based on the total weight of the aqueous dispersion in step a); and
b) heating the aqueous dispersion formed in step a) at a temperature of 50-95° C. thereby producing alkalated lignin, wherein the alkalated lignin has increased reactivity relative to the lignin.
2. The method of claim 1 , wherein the concentration of alkali is 5-50 weight-% based on the total weight of the aqueous dispersion in step a).
3. The method of claim 1 , wherein the concentration of the lignin is 20-50 weight-%, based on the total weight of the aqueous dispersion in step a).
4. The method of claim 1 , wherein the temperature in step a) is 50-65° C.
5. The method of claim 1 , wherein the temperature in step b) is 60-75° C.
6. The method of claim 1 , wherein step b) is carried out for 15 minutes-24 hours.
7. The method of claim 1 , wherein the method comprises, before step a), a step i) of reacting the lignin with a compound selected from the class of phenols.
8. The method of claim 7 , wherein step i) is carried out at a temperature of 100-140° C. for 1-3 hours in the presence of a catalyst.
9. The method of claim 1 , wherein the method comprises, after step b), a step ii) of adding an aldehyde to the aqueous dispersion formed in step b).
10. The method of claim 9 , wherein the weight ratio of the aldehyde to the lignin in the aqueous dispersion from step b) is 0.2-0.7.
11. The method of claim 9 , wherein the aldehyde is formaldehyde.
12. The method of claim 1 , wherein the concentration of alkali is 10-25 weight-% based on the total weight of the aqueous dispersion in step a).
13. The method of claim 1 , wherein the concentration of the lignin is 20-45-weight-% based on the total weight of the aqueous dispersion in step a).
14. The method of claim 1 , wherein step b) is carried out for no longer than 5 hours.
15. The method of claim 1 , wherein step b) is carried out for 0.5-1.5 hours.
16. The method of claim 9 , wherein the weight ratio of the aldehyde to the lignin in the aqeuous dispersion from step b) is 0.3-0.6.
17. The method of claim 1 , wherein the alkalated lignin is a product, and the alkalated lignin product is added to a subsequent reaction process.
18. The method of claim 17 , wherein the subsequent reaction process comprises binder production.