Process for preparing a lignin-based resin
The present invention relates to an improved process for preparing an aqueous dispersion of lignin and the use of said suspension in the preparation of a resin.
1. A method for preparing a resin comprising the steps of
a) providing an aqueous medium having a pH of 6;
b) adding lignin to the aqueous medium;
c) mixing until a dispersion of lignin in the aqueous medium has been obtained;
d) adding alkali, phenol and formaldehyde to the dispersion to form a mixture; and
e) maintaining the mixture at a temperature of from 30° C. to 95° C. for at least 30 minutes.
2. A method according to claim 1 , wherein steps a), b) and c) are carried out without actively heating the aqueous medium.
3. A method according to claim 1 , wherein the amount of lignin in the dispersion in step c) is 5-60 wt %.
4. A method according to claim 1 , wherein the amount of lignin in the dispersion in step c) is 35-60 wt %.
5. A method according to claim 1 , wherein the pH of the aqueous medium in step a) is pH 2 to 5.
6. A method according to claim 1 , wherein the pH of the aqueous medium in step a) is pH 2 to 6.
7. A method according to claim 1 , wherein the dispersion of lignin is stored or shipped to a different location before step d) is carried out.
8. A method according to claim 7 , wherein after the dispersion of lignin is stored or shipped to a different location, the dispersion of lignin is stirred before step d) is carried out.
9. A method according to claim 1 , wherein the aqueous medium further comprises up to 10 wt % of a solvent.
10. A method according to claim 9 , wherein the solvent comprises an alcohol.
11. A method according to claim 1 , wherein the aqueous medium further comprises up to 10 wt % of an additive.
12. A method according to claim 11 , wherein the additive comprises urea, a thickener, or a tenside.
13. A method according to claim 1 , wherein steps a), b), and c) are carried out at a temperature in a range of 15° C. to 40° C.
14. A method for preparing a resin comprising the steps of
a) providing an aqueous medium having a pH of 1 to 6;
b) adding lignin to the aqueous medium;
c) mixing until a dispersion of lignin in the aqueous medium has been obtained, wherein the amount of lignin in the dispersion in step c) is 5-60 wt %;
d) adding alkali, phenol and formaldehyde to the dispersion to form a mixture; and
e) maintaining the mixture at a temperature of from 30° C. to 95° C. for at least 30 minutes;
wherein steps a), b), and c) are carried out at a temperature in a range of 15° C. to 40° C.
15. A method according to claim 13 , wherein the amount of lignin in the dispersion in step c) is 35-60 wt %.
16. A method according to claim 13 , wherein the pH of the aqueous medium in step a) is pH 2 to 5.
17. A method according to claim 13 , wherein the pH of the aqueous medium in step a) is pH 5 to 6.
18. A method according to claim 13 , wherein the dispersion of lignin is stored or shipped to a different location before step d) is carried out.
19. A method according to claim 17 , wherein after the dispersion of lignin is stored or shipped to a different location, the dispersion of lignin is stirred before step d) is carried out.
20. A method according to claim 13 , wherein the aqueous medium further comprises up to 10 wt % of a solvent.
21. A method according to claim 13 , wherein the aqueous medium further comprises up to 10 wt % of an additive.