Abstract:

Objective Sirospun is only suitable for two sets of rovings with similar fiber length, while fibers with different lengths require different gauges during the drafting process. In this study, cotton and wool rovings were fed into a double apron drafting device, and segment colored yarn and AB yarn were produced by intermittent and continuous feeding separately. In this research, cotton/wool segment colored yarns and AB yarns were prepared based on the double apron drafting ring spinning machine. However, when spinning conditions were the same, the CV and strength of cotton/wool segment colored yarn were worse than those of AB yarns. This paper reports on the development of a method for reducing the performance gap between two types of yarns.

Method Aiming at the unevenness caused by the retraction of the roving at the front roller nip, the principle of alternating advance-feeding of two rovings was proposed in such a way that when the front middle roller stopped feeding the cotton roving, and the back middle roller kept feeding the wool roving. When the cotton roving broke at the front roller nip, the gripping force by the front roller would disappear. The cotton roving was held by apron on the front middle roller, and the fore-end of the roving retracted from the front roller nip. Before the wool roving stopped feeding, the cotton roving was fed into the front roller nip in advance, so that when the cotton roving resumed feeding, they are perfectly connected to the wool roving, avoiding weak points in the yarn due to the shrinkage of the roving. The advance-feeding of wool roving was carried out in the same way as for the cotton roving.

Results Cotton/wool segment colored yarn showed pure color segments as well as mixed color segments. The lengths of the mixed color segment of the yarns with advance-feeding of 0, 0.1, 0.2, 0.3, 0.4, and 0.5 mm were 28.5, 30.9, 32.7, 35.1, 37.1, and 39.8 mm, respectively. As the advance-feeding amount increased, the length of the cotton/wool mixed color segment gradually increased too, but the lengths of the mixed color segment of the yarns were only below 17% of that of the yarns produced by coaxial back roller method. As the advance-feeding amounts increased, the unevenness, coarse and fine knots, breaking strength, and harmful hairness of cotton/wool segment colored yarns were improved firstly but then deteriorated. When the advance-feeding amount was 0.3 mm, the CV and coarse/fine knots were found minimized. The shrinkage of the rovings during the spinning process was compensated by the advance-feeding amount, thereby improving the evenness of the yarn. When the advance-feeding amount is above 0.4 mm, the advance amount exceeds the shrinkage amount, and the evenness of cotton/wool segment colored yarn became worse. As the advance-feeding amount was increased from 0 to 0.3 mm, breaking strength of the yarn was increased, but when the advance feeding amount was increased from 0.4 mm to 0.5 mm, the breaking strength of the yarn was decreased. When the advance-feeding amount wasis 0.3 mm, the breaking strength of cotton/wool segment colored yarn was 1.38 times than that of yarn made without advance-feeding, reaching 96% of the breaking strength of AB yarn with cotton/wool 30/70. The number of harmful hairiness in cotton/wool segment colored yarn was found higher than that of pure cotton, cotton/wool AB, and pure wool yarns, indicating that the two rovings can easily form harmful hairiness when breaking alternately at the front roller nip.

Conclusion Cotton/wool segment colored yarns with shorter mixing color segments can be produced by proper advance-feeding amounts. The unevenness of cotton/wool segment colored yarn can be reduced by applying an appropriate advance-feeding amount, hence improving the breaking strength and reducing harmful hairiness. The three indexes of the segment colored yarns are improved to match those of the cotton/wool 30/70 AB yarns. Due to higher distribution of wool fibers in the outer layer, the yarn has a strong wool appearance, thereby improving grading of the fabric. Cotton components in the yarn can improve the breaking strength, save usage of wool fibers, and reduce costs. The cotton/wool segment colored yarns has potential application in the field of fancy yarns. In the future, the performance of segment colored yarn can be further increased by improving the mechanical accuracy of the cotton/wool intermittent feeding transmission.

Key words: fancy yarn, cotton/wool segment colored yarn, cotton/wool AB yarn, yarn structure, yarn property, advance-feeding amount