Patent ID: 8444815

Claim:
A process for making a fibrous pulp comprising fibrillated polypyridobisimidazole fibrous structures and fibrous structures derived from another polymer, comprising: (a) combining pulp ingredients including: (1) rigid rod polypyridobisimidazole fiber having an average length of no more than 10 cm and being 3 to 40 weight percent of the total solids in the ingredients; (2) fiber derived from another polymer that is capable of being fibrillated and having an average length of no more than 10 cm and being 60 to 97 weight percent of the total solids in the ingredients; and (3) water; (b) mixing the ingredients to a substantially uniform slurry; (c) co-refining the slurry by simultaneously: (1) fibrillating, cutting and masticating the fiber in the pulp ingredients to form irregularly shaped fibrillated fibrous structures with stalks and fibrils; and (2) dispersing all solids such that the refined slurry is substantially uniform; and (d) removing water from the refined slurry, thereby producing a fibrillated pulp with the fibrillated polypyridobisimidazole fibrous structures and fibrous structures derived from another polymer, the fibrous structures having an average maximum dimension of no more than 5 mm, a length-weighted average length of no more than 1.3 mm, the fibrils and/or stalks of the polypyridobisimidazole fibrous structures being substantially entangled with the fibrils and/or stalks of the fibrous structures derived from another polymer.