Melt spinning lignin/acrylic fibers

Abstract

Methods of preparing melt-spun polyacrylonitrile (PAN) fibers are described. The fibers can be used as carbon fiber precursors and/or carbonized and graphitized to provide carbon fibers. The methods can include melt-spinning mixtures of PAN and a meltable solvent, such as dimethyl sulfone. In some methods, the mixtures also include lignin and/or can include waste PAN or PAN copolymers prepared from bio-derived monomers. Carbon fibers and carbon fiber composites prepared from the melt-spun fibers are also described.

1 . A method of preparing a fiber, wherein the method comprises:
 (a) preparing a mixture of solids comprising polyacrylonitrile (PAN), lignin, and a meltable solvent; and   (b) melt-spinning said mixture of solids; thereby preparing the fiber.   
     
     
         2 . The method of  claim 1 , wherein the mixture of solids comprises up to about 30 weight (wt) % lignin, optionally about 10 wt % lignin and/or wherein the lignin comprises or consists of kraft softwood lignin. 
     
     
         3 . The method of  claim 1 , wherein the meltable solvent comprises or consists of dimethyl sulfone (DMSO-2), optionally wherein the mixture of solids comprises about 40 wt % to about 60 wt % DMSO-2. 
     
     
         4 . The method of  claim 1 , wherein the PAN comprises a copolymer of acrylonitrile (AN) and up to about 15 mole (mol) % of one or more comonomers, optionally wherein the one or more comonomers are selected from the group consisting of methyl acrylate (MA), vinyl acetate, ethyl vinyl ether, vinyl bromide, vinylidene chloride, and vinyl chloride. 
     
     
         5 . The method of  claim 4 , wherein the copolymer is a copolymer of AN and MA, optionally wherein the copolymer comprises about 8 mole (mol) % MA. 
     
     
         6 . The method of  claim 1 , wherein the PAN has a viscosity average molecular weight (M v ) of about 50 kilograms per mole (kg/mol) to about 250 kg/mol, optionally about 80 kg/mol. 
     
     
         7 . The method of  claim 1 , wherein the PAN is a polymer or copolymer of biomass-derived AN and/or wherein the PAN is derived from pre- or post-consumer waste. 
     
     
         8 . The method of  claim 1 , wherein the mixture of solids further comprises one or more additives, optionally comprising at least one antiplasticizer. 
     
     
         9 . The method of  claim 1 , wherein the melt-spinning of step (b) is performed at a temperature of about 150° C. to about 220° C. and/or wherein the melt-spinning is performed using a take-up speed of about 40 meters per minute (m/min) to about 100 m/min. 
     
     
         10 . The method of  claim 1 , wherein the melt-spinning of step (b) is performed by melt-spinning a melt prepared from pellets, wherein said pellets are provided by melt-compounding the mixture of solids to provide a melt of the mixture of solids, optionally at a temperature of 90° C. to about 180° C.; extruding the melt to provide a rod; and chopping the rod to provide the pellets. 
     
     
         11 . The method of  claim 1 , wherein the method further comprises washing the fiber to remove the meltable solvent, optionally wherein the washing comprises submerging the fiber in water at a temperature up to about 100° C., further optionally wherein the water has a temperature of about 95° C. and/or wherein the fiber is submerged in the water for a period of time between about 10 seconds to about 300 seconds. 
     
     
         12 . The method of  claim 1 , wherein the fiber is a carbon fiber precursor and the method further comprises carbonizing the fiber to provide a carbonized fiber, optionally wherein the method further comprises graphitizing the carbonized fiber to provide a carbon fiber. 
     
     
         13 . A fiber prepared according to  claim 1 , optionally wherein said fiber is a carbon fiber or wherein said fiber is a carbon fiber precursor comprising about 30 wt % to about 50 wt % lignin and/or having a diameter of about 15 micrometers or less. 
     
     
         14 . A carbon fiber composite comprising a carbon fiber of  claim 13 . 
     
     
         15 . A method of preparing a fiber, wherein the method comprises:
 (a) preparing a mixture of solids comprising polyacrylonitrile (PAN) and a meltable solvent, wherein said mixture is substantially free of water or a PAN hydrate; and   (b) melt-spinning said mixture of solids; thereby preparing the fiber.   
     
     
         16 . The method of  claim 15 , wherein the meltable solvent comprises or consists of dimethyl sulfone (DMSO-2), optionally wherein the mixture of solids comprises about 40 wt % to about 60 wt % DMSO-2. 
     
     
         17 . The method of  claim 15 , wherein the PAN comprises a copolymer of acrylonitrile (AN) and up to about 15 wt % of one or more comonomers, optionally wherein the one or more comonomers are selected from the group consisting of methyl acrylate (MA), vinyl acetate, ethyl vinyl ether, vinyl bromide, vinylidene chloride, and vinyl chloride, further optionally wherein the copolymer is a copolymer of AN and MA. 
     
     
         18 . The method of  claim 15 , wherein the method further comprises washing the fiber to remove the meltable solvent, optionally wherein the washing comprises submerging the fiber in water at a temperature up to about 100° C., further optionally wherein the water has a temperature of about 95° C. and/or wherein the fiber is submerged in the water for a period of time between about 10 seconds to about 300 seconds. 
     
     
         19 . The method of  claim 15 , wherein the fiber is a carbon fiber precursor and the method further comprises carbonizing the fiber to provide a carbonized fiber, optionally wherein the method further comprises graphitizing the carbonized fiber to provide a carbon fiber. 
     
     
         20 . A fiber prepared according to  claim 15 .