Process for forming an aramid copolymer

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

a) forming a slurry of DAPBI in a solvent system comprising an organic solvent and an inorganic salt;

b) adding terephthaloyl dichloride to the slurry in an amount of up to one-half mole for every mole of DAPBI in the slurry;

c) agitating the slurry to react the DAPBI and terephthaloyl dichloride to form an oligomeric solution;

d) adding PPD to the oligomeric solution and agitating until substantially all of the PPD is dissolved,

e) adding terephthaloyl dichloride in an amount of greater than one mole for every mole of PPD in the solution to form a prepolymer solution; and

e) agitating the prepolymer solution to form a polymer.

2. The process of claim 1 , wherein said solvent system is NMP/CaCl 2 .

3. The process of claim 2 , further comprising isolating said polymer.

4. The process of claim 3 , further comprising the step of comminuting the polymer.

5. The process of claim, further comprising treating the polymer with one or more washing and/or neutralizing steps.

6. The process of claim 5 , further comprising the step of dissolving the polymer in a solvent comprising sulfuric chloride to form a solution suitable for spinning fibers.

7. The process of claim 6 , wherein the DAPBI and phenylene diamine are present in a molar ratio in the range of from 0.25 to 4.