| 摘要 |
1,057,110. Polyvinyl fluoride filaments. DIAMOND ALKALI CO. April 30, 1965 [May 4, 1964], No. 18354/65. Heading B5B. In a process for the preparation of an extruded structure from a vinyl fluoride polymer, the polymer is extruded without sufficient tension on the extrudate to result in molecular orientation, essentially all the latent solvent in the extrudate is removed, without added molecular orientation, and the extrudate is then drawn with a sharp neck. A " latent solvent " is defined as an organic liquid boiling above 100‹ C., which has no significant swelling or solvent action on polyvinyl fluoride at room temperature, but is capable, at elevated temperature, of sufficient solvent action to cause polyvinyl fluoride particles to coalesce. Many latent solvents are specified. The composition extruded is a dispersion of vinyl fluoride polymer in latent solvent and may be a powder, paste or liquid containing 5-90% by weight of latent solvent. The polymer, of particle size preferably less than 20 Á, may be polyvinyl fluoride homopolymer or a copolymer containing at least 75-80% vinyl fluoride. In one embodiment, Fig. 1 (not shown), a dispersion of polymer in hopper 8 is heated by means 10 to coalesce the polymer particles. The fluid composition is filtered at 11 and extruded through orifice 4 placed close to or in quenching liquid bath 6 to prevent molecular orientation by tension of the resulting monofilament. The cooled filament is passed through heater 16 (120-190‹ C.) to remove latent solvent, stretched with a sharp neck between godets 18, 20 and 22, and heatset at 24 (150-190‹ C.). The speed of godet 26 may be varied to permit heat-setting with or without tension. The quenching liquid, e.g. water or brine, may be maintained below 100‹ C. Alternatively, the polymer-latent solvent system may be extruded into air. Examples describe the formation of filaments of tensile strength at least 5 g./den. from dispersions of polyvinyl fluoride in dimethyl formamide.
|
