Method to produce high-quality carbon fiber using lignin

Abstract

The present application is directed to a method of producing a lignin-based carbon fiber. This method comprises providing a lignin-containing material; producing a lignin fiber from the lignin-containing material; stabilizing the lignin fiber under tension, where the tension is adjusted during said stabilizing such that the maximum bearable tension is applied to the lignin fiber; and carbonizing the lignin fiber under tension to produce a carbon fiber, where said carbonizing is carried out at a temperature below 1200° C. and where the tension during said carbonizing is adjusted to avoid shrinkage. The present application is also directed to a lignin-based carbon fiber and molded articles containing such fibers.

What is claimed: 
     
         1 . A method of producing a lignin-based carbon fiber, said method comprising:
 providing a lignin-containing material;   producing a lignin fiber from the lignin-containing material;   stabilizing the lignin fiber under tension, wherein the tension is adjusted during said stabilizing such that a maximum bearable tension is applied to the lignin fiber; and   carbonizing the lignin fiber under tension to produce a carbon fiber, wherein said carbonizing is carried out at a temperature below 1200° C. and wherein the tension during said carbonizing is adjusted to avoid shrinkage.   
     
     
         2 . The method of  claim 1 , further comprising:
 purifying the lignin-containing material prior to said producing a lignin fiber.   
     
     
         3 . The method of  claim 1 , wherein said producing a lignin fiber is carried out by spinning the lignin-containing material. 
     
     
         4 . The method of  claim 3 , wherein the lignin-containing material is spun using melt-spinning, wet-spinning, dry-spinning, or gel-spinning techniques. 
     
     
         5 . The method of  claim 3 , wherein the lignin-containing material is spun at a temperature from about −60° C. to about 250° C. 
     
     
         6 . The method of  claim 1 , wherein said stabilizing the lignin fiber is carried in an inert environment. 
     
     
         7 . The method of  claim 1 , wherein said stabilizing the lignin fiber is carried in an oxidative environment. 
     
     
         8 . The method of  claim 1 , wherein the tension applied during said stabilizing stretches fibers to a length greater than its length prior to said stabilizing. 
     
     
         9 . The method of  claim 1 , wherein, during said stabilizing, the fiber is heated from a temperature of about 25° C. to a temperature of about 300° C. over 2-28 hours. 
     
     
         10 . The method of  claim 1 , wherein said stabilizing is carried out while subjecting the lignin fiber to thermal treatment, plasma treatment, UV light treatment, or microwave radiation. 
     
     
         11 . The method of  claim 1 , wherein said stabilizing is carried out at a tension of about 1.5 kPa to about 1250 kPa per fiber. 
     
     
         12 . The method of  claim 1 , wherein said stabilizing is carried out at a temperature of about 105° C. to about 300° C. 
     
     
         13 . The method of  claim 1 , wherein said carbonizing is carried out at a temperature of about 500° C. to about 1200° C. 
     
     
         14 . The method of  claim 13 , wherein said carbonizing is carried out at a temperature of about 500° C. to about 1000° C. 
     
     
         15 . The method of  claim 1 , wherein the carbon fiber has an average diameter of 2 μm to about 20 μm. 
     
     
         16 . The method of  claim 1 , wherein the carbon fiber has an average tensile strength of about 2.0 GPa to about 4.0 GPa. 
     
     
         17 . The method of  claim 1 , wherein the carbon fiber has an average tensile modulus of about 200 GPa to about 400 GPa. 
     
     
         18 . The method of  claim 1 , wherein the carbon fiber has inner pores having an average radius of about 0.2 nm to about 4.0 nm. 
     
     
         19 . A carbon fiber prepared by the method of  claim 1 . 
     
     
         20 . The carbon fiber of  claim 19 , wherein the carbon fiber has an average diameter of 2 μm to about 20 μm. 
     
     
         21 . The carbon fiber of  claim 19 , wherein the carbon fiber has an average tensile strength of about 2.0 GPa to about 4.0 GPa. 
     
     
         22 . The carbon fiber of  claim 19 , wherein the carbon fiber has an average tensile modulus of about 200 GPa to about 400 GPa. 
     
     
         23 . The carbon fiber of  claim 19 , wherein the carbon fiber has inner pores having an average radius of about 0.8 nm to about 2.2 nm. 
     
     
         24 . A lignin-based carbon fiber comprising:
 an elemental oxygen content of at least 1 wt %;   an elemental carbon content of at least 65 wt %;   an average diameter of about 0.1 μm to about 20 μm;   an average tensile strength of from about 2.0 GPa to about 4.0 GPa; and   an average tensile modulus of from about 200 GPa to about 400 GPa.   
     
     
         25 . The lignin-based carbon fiber of  claim 24 , wherein the elemental oxygen content is from about 1 wt % to about 30 wt %. 
     
     
         26 . The lignin-based carbon fiber of  claim 24 , wherein the elemental carbon content is from about 65 wt % to about 88 wt %. 
     
     
         27 . A molded article for a machine part, electric and electronic part, or automotive part, said article comprising:
 a matrix material; and   the carbon fiber of  claim 24  dispersed in said matrix material.   
     
     
         28 . The molded article of  claim 27 , wherein the molded article is an automotive part. 
     
     
         29 . The molded article of  claim 28 , where the automotive part is selected from the group consisting of a hood, a pillar, a panel, a structural panel, a door panel, a door component, an interior floor, a floor pan, a roof, an exterior surface, an underbody shield, a wheel component, a storage area, a glove box, a console box, a trunk, a trunk floor, a truck bed, a lamp pocket, a shock tower cap, a control arm, a suspension component, a crush can, a bumper, a structural rail, a structural frame, a cross car beam, an undercarriage component, a drive train component, and combinations thereof. 
     
     
         30 . The method of  claim 1 , wherein the carbon fiber has an average tensile modulus of about 50 GPa to about 500 GPa. 
     
     
         31 . The carbon fiber of  claim 19 , wherein the carbon fiber has an average tensile modulus of about 50 GPa to about 500 GPa.