Abstract:

Objective Hollow spindle covering technology, in which a staple yarn is covered with a filament yarn as the outer wrapping, can significantly reduce hairiness and inhibit hairiness regeneration of the staple fiber yarns. However, during the covering process, the movement of the core yarn and its surface hairiness cannot be effectively controlled, which limits further improvement of the hairiness reduction effect. In this paper, an improved design of the hollow spindle mechanism is proposed to strengthen the control over core yarn movement and surface hairiness, and the technical approach to further enhance the hairiness reduction effect of staple fiber/filament covered yarn is discussed.

Method The key factors limiting the improvement of hairiness control effect of conventional covering technology were analyzed for staple fiber yarns. A compact covering hollow spindle mechanism was designed and manufactured to enhance the running stability of core yarn and the control of surface hairiness by extending the spindle rod of the hollow spindle mechanism, installing a tapered compact tube at its top with an outlet diameter matching the linear density of the core yarn, reducing the aperture of the converging guide hook to match the diameter of the composite yarn, and reasonably adjusting the distance between the compact tube and the converging guide hook. Using a HKV 141D hollow spindle covering machine, two series of conventional covered yarns and compact covered yarns with five levels of covering twist (300, 375, 500, 600, 750 twists/m) were produced, using worsted wool yarn as the core and polyamide filament as the out wrapping yarn and ramie yarn as core and polyester filament as the outer wrapping yarn. The hairiness characteristics of the samples were compared and analyzed.

Results The hairiness test results of worsted yarn/polyamide filament covered yarns showed that the compact covered yarns with the same five covering twists could further reduce the 1-2 mm short hairiness index by 10.2%, 11.4%, 36.4%, 50.8%, and 66.5%, respectively, compared with the corresponding conventional covered yarns of the same covering twists, and for hairiness longer than 3 mm, the additional reduction rates are 19.8%, 42.1%, 75.9%, 90.8%, and 97.4%, respectively. The hairiness index test results of ramie yarn/polyester filament covered yarns indicated that compared with conventional covered yarns, compact covered yarns with the same five covering twists could further reduce the 1-2 mm short hairiness index by 13.0%, 42.4%, 50.5%, 58.7%, and 67.3%, respectively, and the hairiness index of 3 mm and above by 43.2%, 67.7%, 77.8%, 86.6%, and 93.4%, respectively.

Conclusion Using an compact covering hollow spinning technology the control over the movement of the core yarn can be enhanced, and mechanical compact of core yarn hairiness can be achieved. This can further significantly reduce the hairiness of staple fiber yarns on the basis of conventional covering. Compared with ordinary covered spinning, compact covering presents a stronger synergistic effect with covering twist. Within the experimental twist range, the hairiness index decreases continuously and significantly with the increase of wrapping twist, while the effect of ordinary covered spinning in reducing hairiness is no longer significant when the covering twist level increases to a certain extent, compact covering exhibits better compact and binding effects on long hairiness. Compared with conventional covering, compact covering provides better control over long hairiness of 3 mm and above than short hairiness of 1-2 mm. Meanwhile, its hairiness control effect on ramie yarn with higher long hairiness content is superior to that on worsted yarn.

Key words: hairiness, compact covering, technological principle, worsted yarn/polyamide filament covered yarn, ramie yarn/polyester filament covered yarn, covering twist, hollow spindle covering machine