Process for forming an aramid copolymer

1. A polymer comprising residues of 2-(4-amino phenyl)-5(6) amino benzimidazole (DAPBI), paraphenylene diamine (PPD) and terephthaloyl dichloride (TCL), made by a process comprising the steps of:

i) forming a slurry of b mole percent DAPBI in a solvent system comprising organic solvent and c weight percent of an inorganic salt, wherein the inorganic salt is present in an amount of at least 5 weight percent of the organic solvent;

ii) contacting the slurry with a less than stoichiometric amount of terephthaloyl chloride, based on the amount of DAPBI in step i), to form an prepolymer solution; and

iii) contacting the prepolymer solution with y mole percent of PPD and additional TCL to form a polymer solution;

wherein the total amount of TCL added in steps ii) and iii) is a stoichiometric amount based on the total amount of DAPBI added in step i) and PPD added in step iii);

wherein the DAPBI and PPD are added in an amount sufficient for providing a polymer solution having a weight percent solids of 12 percent or greater on a polymer basis; and

wherein the sum of y+b is 100 and the product of b×c is 225 or greater.

2. The polymer of claim 1 wherein the product of (b×c) is equal to 300 or greater.

3. The polymer of claim 2 wherein the product of (b×c) is equal to 350 or greater.

4. The polymer of claim 1 wherein the DAPBI and PPD are present in a molar ratio in the range of from 0.25 to 4.

5. The polymer of claim 1 wherein the polymer has an inherent viscosity of 4 dl/g or greater.

6. The polymer of claim 1 in the form of a crumb.