GB917453A - Improvements relating to synthetic textile fibres - Google Patents

Abstract

The invention comprises highly oriented nodular fibres of a synthetic organic polymer of uniform chemical composition having an oriented surface and closely spaced intermittent regions of enlarged diameter, the ratio of the diameter of the enlarged regions to that of the remainder of the fibre being between 1,1 and 2,5 and the regions of enlarged diameter occurring along the thread line with a frequency of at least 10 per inch, particularly between 50 and 500 per inch. Such fibres are produced by subjecting fibres of a synthetic organic orientable fibre-forming polymer to a first drawing step while the fibres are in contact with a surface-crack-promoting agent, in which step the fibres are crack-drawn to at least 1,01 and preferably from 1,01 to 2,5 times theeir undrawn length, but insufficiently to orient them completely, and then to a second drawing step carried out under conditions such that further crack-drawing is avoided, e.g. by removing the agent before the second step or by carrying out the latter at a temperature sufficiently high to plasticize the fibres. "Crack-drawing" is defined as drawing under conditions such that the small surface cracks produced on the fibre by the agent are considerably enlarged by sharp-neck drawing which is initiated at the surface cracks. Crack-drawing is suitably carried out at room temperature. The suitability of an agent for producing cracks may be determined by observing whether the placing of the fibre in the agent under slight tension causes cracks. The agents are preferably liquids, but may be vapours. If liquids, they should not be solvents or string swelling agents for the polymer. They preferably have a surface tension relative to air not greater than 60 dynes per cm. measured at the crack-drawing temperature and are preferably non-aqueous. The fibre polymers may be polyamides, polyesters, polyurethanes, acrylic and vinyl polymers and polyhydrocarbons such as linear polypropylenes. In examples, undrawn polyethylene terephthalate continuous filament yarn soaked in narrow boiling-range kerosene, undrawn polyhexamethylene adipamide monofil and poly(m-phenylene isophthalamide) yarn, both soaked in methyl isobutyl ketone, are treated to impart a nodular configuration to them. Acetone, dimethylformamide, dimethylsulphoxide, methyl ethyl ketone, and methylene chloride are other suitable cracking agents. Ethanol and ethanol-water mixtures are suitable cracking agents for most polyesters and polyamides, but carbon tetrachloride and kerosene are unsuitable for polyamides. Nodular fibres according to the invention have a delustered appearance. Specification 905,833 is referred to.