Technology gist of producing elastic slub fabric on a ZAX-e type air-jet loom was discussed. Slub yarn was used as warp, and elastic slub yarn was used as weft. It is considered that the difficulties in production were weft stop caused by unsuccessful weft insertion and weft defects which included warp breaking, hairiness, pilling, weft detwisting and breaking et al. It is put forward that slub shape, warp and weft twists should be selected according to fabric style. Loom efficiency could reach to about 83% when air pressure of jet nozzle was set rationally, as loom tension was increased properly and one main jet nozzle was adopted et al.

 

 

Elastic slub fabric was a new product on an air-jet loom in our company according to market demands, corresponding with characteristics of both elastic fabric and slub fabric. Normal yarn or slub yarn was used as its warp. And elastic slub yarn was as its weft. It had double characteristics from both slub fabric and elastic fabric, such as excellent resilience, moisture absorption and air permeability, obvious three-dimensional sense, well feeling, comfortable wearability. So it had a widespread favor for customers and a wide market prospect.

 

1 Fabric Specification

Its fabric specification was C29.2/ C 29.2(78 dtex) 275.5/220.5 180 elastic slub plain cloths. Basin weave was plain. Selvedge weave was 2/2 weft rib. Total ends in warp was 4,980, including of 60 ends ¡Á 2 selvedge yarn. Warp was C 29.2 tex slub yarn, according to diverse repetition slubs of 6.0 cm average length, 46.7 cm average slub distance, 2.5 times thicker than normal yarn. Weft was C 29.2 (78 dtex) an elastic slub yarn which the slub was 5.3 cm and 2.5 times thicker than normal yarn, average slub distance was 29.8 cm.

 

2 Technology Difficult Points of Producing Elastic Slub on an Air-jet Loom

Wrap-wise slubby yarn had special characteristics of some thick slubs after some thin slubs so that its broken strength was obviously declined than normal yarn. In production, it was easy to break under repeated mechanical tension and abrasion so as to cause difficult production.

Because slub place was about 2.5 times thicker than normal place, its force moment was larger than the other place, as well as smaller twist. So its fiber cohesion was declined obviously. Therefore, warps were easy to cause hairiness and pulling even to unclear shed in weaving while they passed through some components including of beaming machine, expansion reed of sizing machine, drop wires of a loom, heddles, steal reed et al. Moreover, an air-jet loom had high speed so that it was strict with the clarity of warp shed. At same time, it was just easy to prevent weft insertion in a shed. So it cause weft stop to impact loom efficiency and fabric quality. Because air-jet loom inserted wefts by a fluidic method, wefts were difficult to control. Initial jet tension and stop tension were hugely enhanced while wefts were inserting, as well as hugely larger than normal insertion force especially under stop tension. In one aspect, wefts were easy to detwist while wefts were inserting by air beam in an air-jet loom. So wefts strength was decreased, even to cause weft breakage at small twist place of slubs in a weft accumulator or a cloth fell. Another aspect, weft shrinkage defects were easily presented on the cloth owing to elastic recoil of elastic yarn and slightly large twist of slubs. In addition, shell fibers and core fibers in an elastic yarn were easily peeled as air function as inserting weft, along with defects like mispick-like on the cloth.

 

3 Technical Measures before Weaving

In order to solve the above conflicts and to enhance weaving efficiency and fabric quality, we groped a series of ways in the processes of technology design and product development from initial yarn twist, warp intension, size prescription, shedding process et al. We improved techniques boldly and gained obvious effects.

 

3.1 Selection on slubby shape

For slubby fabric, length, distance and thickness of a slub would influence fabric style directly. Generally, many and thick slubs precipitated a linen-like style. And less and thick slubs were used to show a rough style. Moreover dense and thread-like slubs presented an elegant feeling. Therefore, we selected from specific purpose and operating requirements. Moreover, in order to ensure slubs scattering on a cloth evenly and naturally, we determine slub repetition according to the fabric width.

 

3.2 Selection on warp twists

Generally, C 29.2 tex yarn was 68 twists per ten centimeter. But in order to enhance warp broken strength and loom efficiency for a slub product, twist number was enhanced 5%-10% than a normal product because weak places existed in some section of slub yarn. Therefore, we design twists of C 29.2 tex slubs with 72 twists per ten centimeter. So warp tension was strengthened to ensure normal production in backward processes. At same time, steal ring weight was declined suitably to reduce breakages, as well as ensuring smooth production and enhancement on spinning quality.

 

3.3 Selection on weft twists

According to actual experiences on spinning cotton elastic core-spun yarn, cohesion force of fibers in elastic core-spun yarn was largely decreased because of its core-shell structure. In order to well cover, as well as meeting the demands of winding and weaving, twist was designed higher 10%-15% than normal yarn so as to enhance single yarn broken strength. Moreover, for special style of a slubby yarn, its twists must be enhanced to ensure the tension at small twist place. As free ends of wefts were inserted in an air-jet loom, wefts would be easy to form weft shrinkage if its twist was too many. So fabric quality would be influenced. Therefore, it was the key for loom efficiency to select a suitable twist of wefts. 

 

For selection on twists of elastic slub wefts, we did a lot of experiments. Weft twist was set as 73 twists/10 cm, 75 twists/10cm, 78 twists/10 cm and 81 twists/10 cm. Then they were respectively trial in an air-jet loom, according with experimental data in Table 1.

It was analyzed according to last experiences, special characteristics of air-jet loom and weaving principle. Large scale weft breakages at the pick storer and H2 place was because of less weft twist, inadequate yarn strength and too large air pressure. And stop at H1 place was relative with unclear shed, too length hairiness of wefts, small air pressure and unsuccessful weft insertion. After comparison on loom, we found that weft breakages at pick storer and H2 place was gradually reduced, along with gradually increase of weft twists. But at same time, weft stop at H1 was increasing little by little. Moreover, while twists were up to 81 twists/10 cm, some kinked weft shrinkage was presented on the cloth dispersedly. Even to adjust air pressure and shedding time, it was not obviously improved. It indicated that twist was more. Hence, we determined to adopt 78 twists/10 cm.

 

At the same time, wefts were storing for over 24 h after winding so as to stabilize weft twists and reduce defects of weft shrinkage. In addition, weft strength and hairiness were improved largely by optimizing steal ring, process of ring, adjustments on spinning path.

 

3.4 Technical measures in preparation process

In order to overcome weak link at slub place of warps and also to reduce hairiness, we applied the principle of slow speed and small tension to decline warp breakage, ensuring smooth production. In order to control coincide warp tension strictly, warping halfhitch was equipped as an arc shape, along with slightly light. Sucker sizing machine which could control size strength precisely was applied in sizing process. PVA and phosphatestarch were used as main size, adding with a spot of smoothness agent. And wet dividing rod and after-waxing process were also adopted. So sizing quality was enhanced obviously, as well as decrease of hairiness, increase of shed clarity and loom efficiency. Its specific size prescription was 100 kg phosphatestarch, 25 kg PVA, 12.5 kg crylic acid, 2 kg smooth agent, 10.3% solid content, 12.5% sizing percentage.

 

4 Chief Technical Measures in Weaving Process

ZAX-e type air-jet loom was applied. It was equipped with two jet nozzles, along with speed at 700 r/min. Weft stop was too much mainly because air pressure was difficult to control under elastic slub yarn with slightly large twists. If air pressure was smaller, it was easy to cause weft stop in shedding, along with H1 stop. Whereas air pressure was bigger, wefts were easily broken by air, along with H2 stop. In two jet nozzles, wefts in the intermittent nozzle were easily broken at slub place obviously. It seriously affected production efficiency and product quality. After repeated experiments, better effects were got under the followed measures.

 

(1) To adjust jet pressure and find an optimum range of air pressure. As it was determined, jet pressure was kept never change normally.

(2) Closing one nozzle, another one was used to jet yarn in order to reduce staying time of wefts in chief jet nozzle. So weft breakage by air jet was reduced. (3) To increase weave tension suitably and also keep a well shed, then to enhance chief jet nozzle and enlarging the chief jet nozzle and the angle of yarn stop pin, reducing tractive force on wefts.

Chief on-loom processes were that 76¡ã-109¡ã yarn stop pin, 86¡ã-107¡ãchief jet nozzle, auxiliary jet nozzles of 80¡ã-160¡ã, 100¡ã-180¡ã, 120¡ã-210¡ã, 140¡ã-240¡ã, 160¡ã-260¡ã and 180¡ã-280¡ã, weaving tension of 3 kN, back rest height of six, stop warps frame height of 2.5.     

After our repeated analysis and relative measures application, better effects were gained. Product quality was enhanced largely. And loom efficiency could reach up to 83%.

 

5 Conclusions

(1) The key to produce elastic slub fabric was to overcome the weak link of yarn, as possible as reducing the loss of tension at slub place.

(2) On selection yarn twists, it was considered not only to increase strength so as to weave smoothly, but also to ensure no weft shrinkage, mispick and other defects on a cloth.

(3) It was an important aspect for an air-jet loom to reduce yarn hairiness. As slub yarns had more hairiness, it was helpful for enhancement on loom efficiency to reduce hairiness regeneration and decrease hairiness.  

(4) To control jet pressure, it was necessary to minimize the weft stop, as well as to ensure the cloth quality.

 

References

[1] Zhu Baolin. Manufacturing Experience on Weft Slub Fabric in Air-jet Loom [J]. Cotton Textile Technology, 2008, 36(3): 56-58.

[2] Liu Lixia. Production Techniques Gist of Weft Elastic Fabric with Spandex Core-spun Yarn [J]. Cotton Textile Technology, 2008, 36 (1): 54-56. 

Cotton Textile Technology English Version - 2010 / 3

(2010-07-28)