Using counter-bore and capillary geometry to control mesophase pitch-based carbon fiber filament micro and macro structure

Abstract

A spinning die for spinning mesophase pitch into carbon fibers. The die includes a central cavity having a bottom and at least one side wall which intersects the bottom. At least one capillary for forming a fiber is in fluid communication with the cavity, the capillary having a first open end, a second open end, an axis and a diameter (d). A flow disruption shoulder is positioned at the juncture of the bottom of the central cavity and the first open end of the capillary to create turbulence at the capillary entrance.

What is claimed is:  
     
         1 . A spinning die for spinning mesophase pitch into carbon fibers comprising: 
 a central cavity having a bottom and at least one side wall which intersects said bottom;    at least one capillary for forming a fiber in fluid communication with said cavity, said capillary having a first open end, a second open end, an axis and a diameter (d); and    a flow disruption shoulder positioned at the juncture of said bottom of said central cavity and said first open end of said capillary.    
     
     
         2 . The spinning die of  claim 1  wherein said flow disruption shoulder is essentially perpendicular to the axis of said capillary.  
     
     
         3 . The spinning die of  claim 1  wherein the ratio of the length of said capillary to the diameter of said capillary (L:d) ranges from about 2:1 to about 10:1.  
     
     
         4 . The spinning die of  claim 1  wherein the ratio of the length of said capillary to the diameter of said capillary (L:d) ranges from about 3:1 to about 4:1.  
     
     
         5 . The spinning die of  claim 1  wherein the side wall and the bottom of said central cavity meet at an angle ranging from 0 degrees to less than 90 degrees relative to the axis of said capillary.  
     
     
         6 . The spinning die of  claim 1  wherein the side wall and the bottom of said central cavity meet at an angle ranging from about 10 degrees to about 30 degrees relative to the axis of said capillary.  
     
     
         7 . The spinning die of  claim 1  wherein the distance between the axis of said capillary and the intersection of the nearest side wall with the bottom of said central cavity is at least one radius plus one mil.  
     
     
         8 . The spinning die of  claim 1  wherein there is more than one said capillary and the distance between the axes of adjacent said capillaries is at least one diameter plus one mil.  
     
     
         9 . A spinning die as set forth in  claim 1  wherein said flow disruption shoulder comprises a sharp edge.  
     
     
         10 . The spinning die of  claim 1  wherein said die is a slot or annular die.  
     
     
         11 . A blow spinning die for spinning mesophase pitch into carbon fibers comprising: 
 a die body having at least one central cavity, said cavity having a bottom and at least one side wall which intersects said bottom;    a die tip, said die tip containing at least one capillary for forming a fiber, said capillary being in fluid communication with said central cavity, said capillary having a first open end, a second open end, an axis and a diameter (d), said capillary exiting said die body at the terminus of said die tip;    a flow disruption shoulder positioned at the juncture of said bottom of said central cavity and said first open end of said capillary; and    means for directing at an attenuating gas stream at an acute angle to said diameter (d) to the region adjacent to said terminus of said die tip.    
     
     
         12 . The blow spinning die of  claim 11  wherein said flow disruption shoulder is perpendicular to the axis of said capillary.  
     
     
         13 . The blow spinning die of  claim 11  wherein said acute angle is less than 45°.  
     
     
         14 . The blow spinning die of  claim 11  wherein the ratio of the length of said capillary to the diameter (L:d) ranges from about 2:1 to about 10:1.  
     
     
         15 . The blow spinning die of  claim 11  wherein the ratio of the length of said capillary to the diameter (L:d) ranges from about 3:1 to about 4:1.  
     
     
         16 . The blow spinning die of  claim 11  wherein the angle of intersection between the side wall and the bottom of said central cavity ranges from 0 degrees to less than 90 degrees relative to the axis of said capillary.  
     
     
         17 . The blow spinning die of  claim 11  wherein the angle of intersection between the side wall and the bottom of said central cavity ranges from about 10 degrees to about 30 degrees relative to the axis of said capillary.  
     
     
         18 . The blow spinning die of  claim 11  wherein the distance between the axis of said capillary and the intersection of the nearest side wall with the bottom of said central cavity is at least one radius plus one mil.  
     
     
         19 . The blow spinning die of  claim 11  wherein there is more than one said capillary and the distance between the axes of adjacent capillaries is at least one diameter plus one mil.  
     
     
         20 . The blow spinning die of  claim 11  wherein said flow disruption shoulder comprises a sharp edge.  
     
     
         21 . The blow spinning die of  claim 11  wherein said die is a slot or annular die.  
     
     
         22 . A process for spinning carbon fibers from mesophase pitch, said fibers having a round cross-section and a non-radial structure comprising: 
 heating a spinnable pitch to a temperature sufficient to allow the pitch to flow; and    passing the pitch into a spinning die, said die having a central cavity and at least one capillary in fluid communication therewith; and    drawing said pitch past a flow disruption shoulder positioned at the juncture of said central cavity and said capillary; and    drawing said pitch from said capillary by force of an attenuating gas to form a fiber.    
     
     
         23 . A process for spinning carbon fibers as set forth in  claim 22  wherein said mesophase pitch is a solvated mesophase pitch.  
     
     
         24 . A process for spinning carbon fibers as set forth in  claim 22  including the step of contacting said attenuating gas with said pitch at an angle less than 45°.  
     
     
         25 . A process for spinning carbon fibers as set forth in  claim 22  including disrupting said pitch by said shoulder through the complete length of said capillary.  
     
     
         26 . A process for spinning carbon fibers as set forth in  claim 22  wherein said flow disruption shoulder is perpendicular to the axis of said capillary.