Modification of temperature dependence of pitch viscosity for carbon article manufacture

Abstract

Methods are provided for reducing or minimizing the temperature dependence of a pitch feed or fraction for use in carbon fiber production, such as a mesophase pitch feed or fraction or an isotropic pitch feed or fraction. A pitch sample can be characterized to determine a characteristic temperature and a characteristic viscosity for the sample. One or more solvent extraction processes can also be performed on the pitch and/or the extract and raffinate fractions formed by the solvent extraction(s). The resulting raffinate and extract fractions are then used to form a modified pitch fraction with a T0 value that is lower than the T0 value of the original pitch. The modified pitch fraction can optionally also have a different ηinf value relative to the original pitch.

1 . A method for forming a modified pitch, comprising:
 performing solvent extraction on a pitch comprising a T 0  value to form an extract comprising a first fraction of the pitch and a raffinate comprising a second fraction of the pitch; and   blending at least a portion of the first fraction with at least a portion of the second fraction to form a modified pitch having a modified T 0  value less than the T 0  value of the pitch.   
     
     
         2 . The method of  claim 1 , wherein the first fraction and the second fraction comprise a first volume ratio, and wherein a volume ratio comprising the at least a portion of the first fraction and the at least a portion of the second fraction is greater than the first volume ratio. 
     
     
         3 . The method of  claim 1 , wherein the at least a portion of the first fraction is formed from the extract without performing an additional solvent extraction step; or wherein the at least a portion of the second fraction is formed from the raffinate without performing an additional solvent extraction step; or a combination thereof. 
     
     
         4 . The method of  claim 1 , wherein the at least a portion of the second fraction is formed by a method comprising:
 performing a second solvent extraction on at least a portion of the raffinate to form a second extract comprising a third fraction of the pitch and a second raffinate comprising a fourth fraction of the pitch, the fourth fraction comprising the at least a portion of the second fraction.   
     
     
         5 . The method of  claim 4 , wherein the modified pitch further comprises at least a portion of the third fraction, a volume ratio of the at least a portion of the first fraction, the at least a portion of the third fraction, and the at least a portion of the fourth fraction being different from a volume ratio of the first fraction, the third fraction and the fourth fraction in the pitch. 
     
     
         6 . The method of  claim 4 , wherein the modified pitch does not include a portion of the third fraction. 
     
     
         7 . The method of  claim 4 , wherein performing a solvent extraction comprises performing an extraction with a first solvent, wherein performing a second solvent extraction comprises performing an extraction with a second solvent, and wherein the first solvent has a solubility parameter that is different from a solubility parameter of the second solvent by 1.0 or more. 
     
     
         8 . The method of  claim 1 , wherein the at least a portion of the first fraction is formed by a method comprising:
 performing a third solvent extraction on at least a portion of the first fraction to form a second extract comprising a fifth fraction of the pitch and a second raffinate comprising a sixth fraction of the pitch, the fifth fraction comprising the at least a portion of the first fraction.   
     
     
         9 . The method of  claim 8 , wherein the modified pitch further comprises at least a portion of the fourth fraction, a volume ratio of the at least a portion of the second fraction, the at least a portion of the fourth fraction, and the at least a portion of the third fraction being different from a volume ratio of the second fraction, the fourth fraction and the third fraction in the pitch; or wherein the modified pitch does not include a portion of the fourth fraction. 
     
     
         10 . The method of  claim 8 , wherein performing a solvent extraction comprises performing an extraction with a first solvent, wherein performing a third solvent extraction comprises performing an extraction with a second solvent, and wherein the first solvent has a solubility parameter that is different from a solubility parameter of the second solvent by 1.0 or more. 
     
     
         11 . The method of  claim 1 , wherein the pitch comprises a mesophase pitch and wherein the modified pitch comprises a modified mesophase pitch; or wherein the pitch comprises an isotropic pitch and wherein the modified pitch comprises a modified isotropic pitch. 
     
     
         12 . The method of  claim 11 , wherein the mesophase pitch comprises 10 vol % or more of an optically active fraction. 
     
     
         13 . The method of  claim 1 , wherein the pitch comprises a glass transition having a width of 40° C. or less; or wherein the pitch comprises a softening point of 100° C. to 300° C.; or wherein the pitch comprises a coke value of at least 50 wt. % or more; or a combination thereof. 
     
     
         14 . The method of  claim 1 , wherein the pitch comprises a viscosity at 280° C. of 20 Pa-sec or less; or wherein the pitch comprises a T5 distillation point of 350° C. or more; or wherein the pitch comprises a T50 distillation point of 500° C. or more; or a combination thereof. 
     
     
         15 . The method of  claim 1 , wherein the modified pitch comprises a modified T 0  value that is at least 5.0° C. less than the T 0  value of the pitch, or wherein the modified pitch comprises a modified η inf  value that is greater than a η inf  value of the pitch, or a combination thereof. 
     
     
         16 . A method for forming a modified pitch, comprising:
 performing solvent extraction on a pitch comprising a T 0  value to form an extract comprising a first fraction of the pitch and a raffinate comprising a second fraction of the pitch;   performing a second solvent extraction on a) at least a portion of the first fraction or b) at least a portion of the second fraction, to form a second extract comprising a third fraction of the pitch and a second raffinate comprising a fourth fraction of the pitch,   wherein the second solvent extraction is performed on the at least a portion of the first fraction, a T 0  of the fourth fraction being less than the T 0  value of the pitch, the modified pitch corresponding to at least a portion of the fourth fraction, or   wherein the second solvent extraction is performed on the at least a portion of the second fraction, a T 0  value of the third fraction being less than the T 0  value of the pitch, the modified pitch corresponding to at least a portion of the third fraction.   
     
     
         17 . The method of  claim 16 , further comprising separating an extract product fraction and a solvent fraction from the extract, the extract product fraction comprising the at least a portion of the first fraction. 
     
     
         18 . The method of  claim 16 , further comprising separating a solvent recovery fraction from the raffinate; or further comprising separating a second solvent recovery fraction from the second raffinate; or a combination thereof. 
     
     
         19 . The method of  claim 16 , wherein performing a solvent extraction comprises performing an extraction with a first solvent, wherein performing a second solvent extraction comprises performing an extraction with a second solvent, and wherein the first solvent has a solubility parameter that is different from a solubility parameter of the second solvent by 1.0 or more. 
     
     
         20 . The method of  claim 16 , wherein the pitch comprises a mesophase pitch and wherein the modified pitch comprises a modified mesophase pitch.