Lignin/polyacrylonitrile-containing dopes, fibers, and methods of making same
The invention relates to a process for preparing a composition comprising 10 to 45% of the total solids weight lignin, polyacrylonitrile or a polyacrylonitrile copolymer, and a solvent to form a lignin-based polyacrylonitrile-containing dope and the resulting products. The dope can be processed to produce fibers, including precursor, oxidized and carbonized fibers. The oxidized fibers are of value for their flame resistant properties and carbonized fibers are suitable for use in applications requiring high strength fibers, or to be used to form composite materials.
1. A fiber dope solution comprising lignin, and polyacrylonitrile or polyacrylonitrile copolymer, in an organic solvent that dissolves both the lignin and the polyacrylonitrile or polyacrylonitrile copolymer, wherein the solution has a solids content of from 10 to 35% of the total weight of the solution, wherein the lignin is 5 to 45% of the total weight of solids in the solution and wherein solution has a viscosity of 20 to 1500 poise at a temperature of 20° C. to 80° C.
2. The fiber dope solution of claim 1 wherein the solution has a viscosity of 20 to 1000 poise at a temperature of 20° C. to 80° C.
3. The fiber dope solution of claim 1 wherein the solution has a viscosity of 20 to 500 poise at a temperature of 20° C. to 80° C.
4. The fiber dope solution of claim 1 wherein the solution has a viscosity of 20 to 100 poise at a temperature of 20° C. to 80° C.
5. The fiber dope solution of claim 1 wherein the lignin is 10 to 45% of the total weight of the solids in the solution.
6. The fiber dope solution of claim 1 wherein the lignin is 30 to 45% of the total weight of the solids in the solution.
7. A method of producing a fiber dope solution comprising combining lignin, and polyacrylonitrile or polyacrylonitrile copolymer, and an organic solvent that dissolves both the lignin and the polyacrylonitrile or polyacrylonitrile copolymer, to produce a fiber dope solution having a viscosity of about 20 to about 1500 poise at a temperature of about 20° C. to about 80° C., wherein the total solids in the solution is 10 to 35% of the total weight of the solution, and wherein the weight of the lignin in the solution is 5 to 45% of the weight of the solids in the solution.
8. The method of claim 7 further comprising forming a fiber from the dope by spinning, coagulating and extracting the solvent to form a fiber, wherein the spinning is one of solution spinning or dry jet wet spinning.
9. The method of claim 8 further comprising stretching the fiber to decrease the diameter of the fiber and further increase molecular orientation.
10. The method of claim 9 further comprising washing the fiber to remove residual solvent from the fiber.
11. The method of claim 8 further comprising heating the fiber in air atmosphere at a temperature in the range of 200 to 300° C.
12. The method of claim 11 further comprising carbonizing the fiber in an inert atmosphere at a temperature of 600 to 2000° C.
13. The product of the process of claim 11 .
14. The product of the process of claim 12 .