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Solid structure formation in the drying step for wet spinning of poly(1-oxotrimethylene) using as a solvent an aqueous solution of complex metal salts of calcium chloride/zinc chloride was studied. Because the degree of structural densification and the crystal structure both differ depending on the drying temperature, the drying temperature had a major effect on the drawing behavior and the strength achieved after drawing. With higher drying temperature, the denseness increased due to smaller voids in the dried undrawn fiber, while there was also a tendency toward higher strength with respect to the draw ratio. However, an excessively high drying temperature altered the crystal structure from a rough crystalline form to a dense crystalline form and reduced both the maximum draw ratio and strength. Mechanical cleavage of the molecular chains occurred between the ethylene groups and carbonyl groups of the main chains in the drawing step. This cleavage made it possible to suppress the inhibition of drawing due to entanglement of the molecular chains, thereby enabling superdrawing to afford a high performance fiber. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 446 -452, 2004

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Poly(1-oxotrimethylene), obtained by the perfectly alternating polymerization of ethylene and carbon monoxide, was successfully dissolved in composite metal salt solutions such as zinc chloride and calcium chloride aqueous solutions. Certain poly(1-oxotrimethylene) solutions exhibited a phase-separation point of 0°C or greater; the different phase-separation temperatures depended on the metal salt composition ratio, the polymer molecular weight, and the polymer concentration. When a solution with a phase-separation point was used for wet spinning, a coagulation temperature below the phase-separation point resulted in gelation of the filament, which was caused by a temperature jump during the coagulation process; this yielded a coagulated filament with a dense and homogeneous cross-sectional structure. The hot drawing of the coagulated fiber produced a high-performance polyketone fiber with high strength and high elastic modulus [tenacity ϭ 18.5 cN/dtex (2.4 GPa); elongation ϭ 5%; elastic modulus ϭ 450 cN/dtex (59 GPa)].With a solution that exhibited no phase-separation temperature, coagulation proceeded as the coagulant penetrated from the fiber surface into the filament inside, yielding a coagulated filament with a skin-core structure. The maximum tenacity achieved with this skincore coagulated filament was as low as 15 cN/dtex (1.9 GPa).