| 摘要 |
1,038,738. Polyimide filaments. E:I. DU PONT DE NEMOURS & CO. March 29, 1965 [March 30, 1964], No. 13200/65. Heading B5B. Polyimide filaments are made by spinning into a gaseous atmosphere a solution of a polyamide-acid of pyromellitic dianhydride and a diamine of formula wherein X is O or S to form a filament, and converting the filament to the pyromellitimide under a tension of 0À0-0À5 g./d., the filament being drawn before and/or after conversion to pyromellitimide, the total draw ratio being at least 1À4 times. The spinning solution comprises a solution of the polyamide-acid in an organic solvent, e.g. N,N-dimethylacetamide or pyridine. The solution contains e.g. 15-25% by weight solids and is desirably maintained below 80‹ C. prior to spinning. The solution is extruded into a column containing a cocurrent flow of dry gas, e.g. nitrogen at 200-280‹ C. to form polyamide filaments in which 8-16% of the amide linkages are converted to imide during their residence in the column. The as-spun filaments are then drawn and completely converted to polyimide. Drawing before conversion may be effected in air or in water at 50-90‹ C., or concurrently with washing the filaments in distilled or deionized water. Drawing after conversion may be carried out during a tempering step, which may comprise heating the filaments to at least 380‹ C. The tempered filaments may then be annealed. Conversion of polyamide to polyimide may be effected chemically, e.g. by immersing the polyamide filaments in a dehydrating agent such as an acid anhydride or a carbodiimide, or by thermal means, as by heating to at least 200‹ C. for 1 to 120 minutes, while being supported to avoid tension. The polyimide filaments have a straight tenacity of at least 3À0 g./d., a transverse tenacity of at least 1 g./d. and a flex life of at least 1000 cycles. |
