Back to results
US 5,292,469 AGranted
Process for coagulation, washing and leaching of shaped polybenzazole articles
AssigneeThe Dow Chemical Company
InventorsReid H. Bowman, Willie E. Rochefort, Ming-Biann Liu, Peter E. Pierini
Life of this patent
Estimating the term…
Abstract
Articles (other than fiber) made from polybenzazole dopes can quickly be washed to remove polyphosphoric acid by a combination of initially washing with an acidic liquid and second washing with a hot leaching fluid at at least about 60.degree. C. The process can reach acceptable residual phosphorous levels (1500-2000 ppm) in as little as about 2 or 3 minutes.
Claims23
A process to coagulate, wash and leach a shaped polybenzazole article, comprising the steps of:
- (1) contacting a shaped article, other than a fiber, that contains a dope containing polybenzazole polymer and polyphosphoric acid, with a acidic liquid coagulant, and
- (2) contacting the shaped article, before substantial drying, with a leaching fluid, that is capable of removing residual phosphorous compounds, at a temperature of at least about 60.degree. C.,
- for a combined residence time in steps (1) and (2) of no more than about 35 minutes, whereby a polybenzazole article containing no more than about 2000 ppm phosphorus is formed.
A process to coagulate, wash and leach a shaped polybenzazole article, comprising the steps of:
- (1) contacting a shaped article, other than a fiber, that contains a dope containing polybenzazole polymer and polyphosphoric acid, with an aqueous solution containing 10 to 50 weight percent acid, and
- (2) contacting the shaped article, before substantial drying, with steam, water at a temperature of at least about 75.degree. C., or an organic solvent that is capable of removing residual phosphorous compounds at a temperature of at least about 75.degree. C.,
- for a combined residence time in steps (1) and (2) of no more than about 5 minutes, whereby a polybenzazole article containing no more than about 2000 ppm phosphorus is formed.
Dependencies are inferred from the claim text.