Process for preparing a carbon fiber precursor

Abstract

A process for preparing a carbon fiber precursor is hereby disclosed, wherein the precursor is selected from a series of solid PAN (polyacrylonitrile) fibers, wherein each member of the series contains about 0.5 mole % to about 8 mole % ammonium salt of 2-acrylamido-2-methyl propane sulfonic acid.

1 . A process for preparing a carbon fiber precursor, the process comprising:
 (a) obtaining a series of monomer mixtures, wherein each mixture of monomers comprises acrylonitrile and an ammonium salt of 2-acrylamido-2-methyl propane sulfonic acid;   (b) individually polymerizing the monomer mixtures to obtain a PAN polymer;   (c) individually spinning the PAN polymer to obtain PAN filaments;   (d) individually bundling the filaments to obtain a PAN fiber;   (e) individually analyzing the PAN fiber for a physical property, wherein the property is a member selected from the group consisting of: number of surface defects, interior homogeneity, degree of orientation, tenacity, number and size of micro voids, arrangement of crystallites on the surface, compactness of structure, and combinations thereof; and   (f) ranking the PAN fiber, wherein a most highly ranked solid PAN fiber is the carbon fiber precursor.   
     
     
         2 . The process according to  claim 1  wherein the acrylonitrile monomer is present in an amount of about 92 mole % to about 99.5 mole %, and the ammonium salt of 2-acrylamido-2-methyl propane sulfonic acid monomer is present in an amount of about 0.5 mole % to about 8 mole %. 
     
     
         3 . A carbon fiber prepared according to the process of:
 (a) obtaining a series of monomer mixtures, wherein each mixture of monomers includes acrylonitrile and an ammonium salt of 2-acrylamido-2-methyl propane sulfonic acid;   (b) individually polymerizing the monomer mixtures to obtain a PAN polymer;   (c) individually spinning the PAN polymer to obtain PAN filaments;   (d) individually bundling the filaments to obtain a PAN fiber;   (e) individually analyzing the PAN fiber for a physical property, wherein the property is a member selected from the group consisting of: number of surface defects, interior homogeneity, degree of orientation, tenacity, number and size of micro voids, arrangement of crystallites on the surface, compactness of structure, and combinations thereof;   (f) ranking the PAN fiber, wherein a most highly ranked solid PAN fiber is the carbon fiber precursor;   (g) heating the carbon fiber precursor in a first heating step to obtain PANOX fiber; and   (h) heating the PANOX fiber in a second heating step to obtain carbon fiber.   
     
     
         4 . The carbon fiber according to  claim 3  wherein the acrylonitrile monomer is present in an amount of about 92 mole % to about 99.5 mole %, and the ammonium salt of 2-acrylamido-2-methyl propane sulfonic acid monomer is present in an amount of about 0.5 mole % to about 8 mole %. 
     
     
         5 . An apparatus for preparing a carbon fiber precursor, the apparatus comprising:
 (a) a polymerization zone for obtaining a series of solid PAN polymers, wherein each solid PAN polymer in the series contains a different ratio of monomers, and wherein the monomers are acrylonitrile and an ammonium salt of 2-acrylamido-2-methyl propane sulfonic acid;   (b) a first transfer means for removing the PAN polymer to a spinning zone;   (c) a spinning zone for obtaining PAN filaments:   (d) a second transfer means for removing the PAN filaments to a bundling zone;   (e) a bundling zone for obtaining PAN fiber;   (f) a third transfer means for removing the PAN fiber to an analysis zone;   (g) an analysis zone, wherein the analysis zone includes measurement devices for obtaining a physical property of the PAN fiber, and wherein the physical property is a member selected from the group consisting of: number of surface defects, interior homogeneity, degree of orientation, tenacity, number and size of micro-voids, arrangement of crystallites on the surface of the fiber, compactness of structure and combinations thereof; and   (h) a ranking zone, wherein a most highly ranked PAN fiber is the carbon fiber precursor.   
     
     
         6 . The apparatus according to  claim 5  wherein the acrylonitrile monomer is present in an amount of about 92 mole % to about 99.5 mole %, and the ammonium salt of 2-acrylamido-2-methyl propane sulfonic acid monomer is present in an amount of about 0.5 mole % to about 8 mole %. 
     
     
         7 . A mixture of monomers useful in preparing a carbon fiber precursor, wherein the mixture is obtained from a process comprising:
 obtaining a series of monomer mixtures, wherein the monomer mixtures comprise acrylonitrile in an amount of about 92 mole % to about 99.5 mole % and an ammonium salt of 2-acrylamido-2-methyl propane sulfonic acid in an amount of about 0.5 mole % to about 8 mole %;   polymerizing the monomer mixtures to obtain a series of PAN polymers;   spinning the PAN polymers to obtain a series of PAN fibers;   analyzing the series of PAN fibers to obtain a set of analysis results, wherein a physical property of the PAN fibers is analyzed, wherein the property is a member selected from the group consisting of: number of surface defects, interior homogeneity, degree of orientation, tenacity, number and size of micro voids, arrangement of crystallites on the surface, compactness of structure, and combinations thereof; and   ranking the PAN fibers based on the set of analysis results; and wherein the mixture of monomers yielding the most highly ranked PAN fiber is employed as starting material for the preparation of the carbon fiber precursor.