The Dow Chemical Company

Carl W Hurtig

Thomas D Gregory

Steven Rosenberg

Harvey D Ledbetter

Kenneth J Quackenbush

Ying Hung So

The invention is a condensation polymerization reaction in which functionally terminated polybenzazole ligomers are reacted in a solvent acid at a temperature of at least 150.degree. C. and a shear of at least about 10 sec..sup.-1 under conditions so that the desired molecular weight is reached in no more than about 4 hours. The oligomers may be, for example, derived from the reaction of 4,6-diaminoresorcinol bis(hydrochloride) and terephthalic acid. The concentration of oligomers is high enough so that the reaction mixture contains liquid crystalline domains.

Rapid advancement of molecular weight in polybenzazole oligomer dopes

Polybenzazole polymers can be synthesized rapidly in large quantities at high molecular weight and high concentration by a two-step process of forming oligomers in a batch reactor and advancing the molecular weight of the polymer in an extruder.

Semi-continuous process for synthesis of polybenzazole polymers

It is advantageous to prepare oligomers of polybenzazole polymers by reaction of AA-PBZ monomer with an excess of BB-PBZ monomer. The resulting oligomer dopes may be stored at a temperature at which they remain pumpable until such time as the dope can be advanced to higher molecular weight by adding additional AA-PBZ monomer. The molecular weight of the polymer may be adjusted by controlling the amount of chain extender and/or chain terminator added to oligomer mixtures as they are advanced to final molecular weight.

Staged polymerization of polybenzazole polymers

Polybenzazole polymers can be advanced rapidly to high molecular weight at relatively high temperatures and high shear in a dehydrating solvent acid.

Growing community of inventors

Stade, Germany

Carl W Hurtig