US 12,065,763 B2
Method of making a phosphonated PBI fiber
Brian P. Shiels, Charlotte, NC (US); Gregory S. Copeland, Tega Cay, SC (US); and Feng Qin, Charlotte, NC (US)
Assigned to PBI Performance Products, Inc., Charlotte, NC (US)
Filed by PBI Performance Products, Inc., Charlotte, NC (US)
Filed on May 3, 2018, as Appl. No. 15/970,285.
Application 15/970,285 is a division of application No. 15/193,206, filed on Jun. 27, 2016.
Claims priority of provisional application 62/188,812, filed on Jul. 6, 2015.
Prior Publication US 2018/0251915 A1, Sep. 6, 2018
Int. Cl. D01F 6/74 (2006.01); C08G 73/18 (2006.01); D01F 1/07 (2006.01); D06M 11/70 (2006.01); D06M 11/84 (2006.01)
CPC D01F 6/74 (2013.01) [C08G 73/18 (2013.01); D06M 11/70 (2013.01); D01F 1/07 (2013.01); D06M 11/84 (2013.01); D06M 2200/30 (2013.01)] 5 Claims
OG exemplary drawing
 
1. A method of making a phosphonated polybenzimidazole (PBI) fiber comprising the steps of:
spinning an untreated PBI resin into a PBI fiber;
immersing the PBI fiber in a phosphoric acid bath, wherein the bath is maintained at 35° C.;
squeezing the phosphoric acid-treated PBI fiber to dry the fiber;
washing the squeezed-dry PBI fiber with water at room temperature;
drying the washed PBI fiber in an air non-contact oven at 350° C.; and
heat-treating the air-dried PBI fiber in a nitrogen-blanketed oven at 565° C. to fix the acid within the polymer structure;
thereby obtaining a phosphonated PBI fiber with a phosphoric acid pick-up (APU) in the range of 1-25 wt % and having a Limiting Oxygen Index (LOI) per ASTM 2863 of about ≥47%.