Liquid kraft lignin compositions

1. A liquid kraft lignin-containing composition comprising:

water in the amount of approximately 60-89.5% by weight;

urea in the amount of approximately 5-30% by weight;

a group 1 alkaline metal hydroxide in the amount of approximately 0.5-3.0% by weight; and

kraft lignin in the amount of approximately 5-25% by weight on a dry basis;

wherein the composition is a solution; and

wherein the composition exhibits phase stability for 1-4 weeks.

2. The composition of claim 1 , wherein the pH is in the range of 8 to 12.

3. The composition of claim 1 , wherein the viscosity of the composition is 5-1,000 cps.

4. The composition of claim 3 , wherein the viscosity of the composition is 50-500 cps.

5. The composition of claim 3 , wherein the viscosity of the composition is 50-300 cps.

6. The composition of claim 1 , wherein the kraft lignin is present in the amount of approximately 15-25% by weight on a dry basis.

7. The composition of claim 1 , wherein the kraft lignin has a molecular weight greater than about 1000 Da.

8. The composition of claim 1 , wherein the group 1 alkaline metal hydroxide includes one or more of sodium hydroxide and potassium hydroxide.

9. The composition of claim 1 , wherein the water is present in the amount of about 61.5% by weight, the urea in the amount of about 14.9% by weight, the group 1 alkaline metal hydroxide in the amount of about 1.5% by weight, and the kraft lignin in the amount of about 20.6% by weight.

10. An aqueous kraft lignin-containing LPF resin produced from the composition of claim 1 .

11. A method of producing a kraft lignin-containing composition, the method comprising:

combining urea and kraft lignin in an aqueous, alkaline medium in a reaction vessel to form a mixture, wherein water is present in the mixture in the amount of approximately 60-89.5% by weight, urea in the amount of approximately 5-30% by weight, a group 1 alkaline metal hydroxide in the amount of approximately 0.5-3.0% by weight, and kraft lignin in the amount of approximately 5-25% by weight on a dry basis, and wherein the pH of the mixture is 8-13;

heating the mixture to a temperature sufficient to dissolve the kraft lignin;

maintaining the mixture at the temperature until the lignin is substantially dissolved; and

subsequently cooling the mixture containing the dissolved kraft lignin, to yield a liquid kraft lignin-containing composition, wherein the composition exhibits phase stability for 1-4 weeks.

12. The method of claim 11 , wherein the group 1 alkaline metal hydroxide includes one or more of sodium hydroxide and potassium hydroxide.

13. The method of claim 11 , wherein the temperature is approximately 95° C.

14. The method of claim 11 , wherein the cooling includes cooling to approximately 20° C.

15. The method of claim 11 , wherein the cooling is performed prior to significant urea hydrolysis occurring in the heated mixture.

16. The method of claim 11 , further comprising subsequently assaying the lignin content of the liquid kraft lignin-containing composition via UV spectroscopy.

17. The method of claim 11 , further comprising reacting the liquid kraft lignin-containing composition with phenol and paraformaldehyde in an alkaline solution to produce a kraft lignin-containing LPF resin.

18. The method of claim 11 , wherein water is present in the mixture in an amount of about 61.5% by weight, urea in the amount of about 14.9% by weight, kraft lignin in the amount of about 20.6% by weight, and a group 1 alkaline metal hydroxide in the amount of about 1.5% by weight.

19. The liquid kraft lignin-containing composition produced by the method of claim 11 .