Comparison of ring-spun and siro-spun core-spun yarn

For high-strength and durable, non-iron, dimensionally stable and anti-pilling, moisture-absorbing and breathable, beautiful and comfortable textiles, such as sewing threads and military uniforms, core-spun yarns are superior to ordinary pure spinning and blended yarns and can better meet the requirements. However, the traditional ring-spun core-spun yarn has poor covering effect. Sometimes its structure is like a strand in which filaments and outer fiber strands are twisted together, and there is no peel strength suitable for subsequent machining, thus reducing the added value of the core spun yarn limits the potential use of the core spun yarn.

Siro-spun core-spun yarn is a single yarn with strand properties, its strength, elongation, and uniformity are better than ring-spun core-spun yarn, and it is soft to the touch and has a good covering effect. In order to economically produce core-spun yarns with good quality and meet customer requirements, the production equipment and yarn-forming properties of traditional and siro-spun nylon filament core-spun yarns were compared based on the actual production of our factory, and the performance of the two was analyzed. Differences, pointed out the reasonable spinning process that should be adopted.

1 Equipment modification

1.1 Equipment modification of ring-spun core-spun yarn

Conventional ring-spun core-spun yarns can be produced on ordinary converted spinning frames. First, a core wire feeding mechanism and a pre-drafting mechanism are installed on the general spinning frame. The bobbin filament is unwound under the traction of the wire guide roller, not through the drafting mechanism of the spinning frame, but through the pre-drafting mechanism and the V-groove guide wheel installed, and is fed from the collector behind the front roller top roller. It is combined with the drafted whiskers, and then passes through the front roller and the yarn guide hook, and is rotated and twisted by the ring spindle to form a filament core-spun yarn.

Then refit the roving frame. Since the size of the nylon filament used is larger than 200mm×500mm, a roving frame is changed from six rows of single-layer hanging spindles to four-row single-layer hanging spindles, and the spindle pitch is changed from the original 210mm to 130mm. The core feeder is located above the roving creel, so the creel is lowered by 30mm to make room for the addition of filament columns, brackets and thread insertion spindles. Considering the maneuverability, only two rows of filament brackets and spindles are installed on the column, and one row of filament brackets and spindles is installed using the space in front of the roving. In this way, the rovings and filaments can be distributed reasonably. The filaments are drawn out by the guide rod and fed into the front jaw of the drafting area, and the rovings are drawn out through the yarn guide rod and the yarn splitting rod and fed into the post-drafting area.

The traverse rod is fixed to ensure that the roving sliver fed from the bell mouth and output through the drafting area does not move. A godet wheel is installed at the position of the cradle to effectively control the filament to be always in the center of the roving sliver when the front roller is output, reduce defects such as exposed core yarn, and improve the wrapping effect. The pre-drafting of the filament is controlled by the changing drafting gear, which can change the drafting ratio between the wire guide roller and the front roller.

1.2 Equipment modification of siro spinning core spun yarn

Siro core yarns can be spun on spinning frames equipped with siro spinning and core yarn devices. The core yarn of the siro core-spun yarn is fed into the front roller jaws through the godet, and the two parallel outer fiber rovings enter the three-roller long and short apron drafting device through the collector, and are laid flat in the drafting area, and the short fibers are wrapped. When passing through the front roller, the core yarn is between the two rovings, always in the middle, and the three are combined and twisted and wound onto the spun yarn bobbin.

Addition of siro spinning components to the spinning frame with the core spun yarn device installed. Install the roving feed divider, change the single-end yarn guide in the post-draft area and the drafting area to a double-end yarn guide, and change the single-end collector at the front roller to a double-end collector. The spacing between the rovings is equal to the roving spacing, and the centerlines of the front and rear three horns are on a straight line. In this way, it is ensured that the two fed rovings are always separated parallel to each other in the drafting zone.

A self-stopping device is installed between the front roller and the yarn guide hook. When one of the whiskers breaks, the other yarn can be automatically interrupted to prevent single yarn from appearing. The interrupter is required to be sensitive. It will not be mistaken.

Refit the roving frame, lengthen the cross bar bracket on the original hanging spindle roving frame, install the roving bracket, etc. to make the hanging spindle roving frame higher and wider, and the center distance of the hanging spindle is changed from 155mm, 350mm, 510mm to 100mm, 315mm, 480mm, respectively. The center distance of the yarn guide rod was changed from 240mm and 140mm to 230mm and 130mm respectively, the height from the car surface was changed from 1130mm, 775mm and 450mm to 1030mm, 675mm and 390mm respectively, and the roving frame was raised from 50mm to 150mm. Thereby, the roving capacity is doubled, so that the original roving creel, which can only hold 420 rovings, can be increased to 840 rovings, and the accidental drafting of the roving sliver can also be reduced.

2 Comparison of yarn performance

Using 60% combed cotton and 40% Modal blended roving as the outer covering fiber, and using 80 denier nylon filament as the core yarn, the traditional core spun yarn of 23.5 tex was produced on the above modified FA506S spinning frame respectively. and siro corespun yarn. The spinning process used by the two spinning frames is: the draft ratio in the rear area is 1.394, the roller gap in the front and rear areas is 18 mm and 40 mm, and the pressure on the front, middle and rear rollers is 18, 10 and 14 kg/double spindle, respectively. The twist coefficient is 350, the speed of the front roller is 163 rpm, the speed of the spindle is 10067 rpm, and the pre-draft ratio of the core yarn is 1.06, but the feeding roving weight of the traditional core yarn is 5.6 g/10m. The basis weight of the incoming roving is 3.1 g/10m, and the distance between the two rovings is 4 mm. The following is the performance comparison of JC/M (60/40) 23.5tex/N80D nylon filament core-spun yarn.

2.1 Strong

The main factors affecting the strength of the core-spun yarn are fiber raw material, twist coefficient, roving quantitative, draft in the rear area, and spacing between two rovings. Traditional core-spun yarns obtain strength through twisting and fiber transfer, while siro-spun yarns mainly obtain strength through intertwining of single yarns. Siro spinning feeds finer rovings with narrower fiber strands, which effectively bind the surface fibers to the yarn body. The intertwining of the two single yarns makes the internal and external transfer of the fibers only half of the traditional spinning, and the inclination angle between the fibers and the yarn axis is small. When the yarn is stretched, the fiber strength utilization rate is higher.

2.2 Coating effect

The coverage rate testing method can use a computer image analysis system to scan the surface of the core-spun yarn or the surface of the knitted fabric, input the scanned area into the computer, and calculate the coverage rate of the core-spun yarn. If only the outer fibers are dyed, the core fibers and the outer fibers can be clearly distinguished.

The peel strength of a core-spun yarn can be indirectly determined by two different methods. The first method is to weave a small piece of knitted fabric on the loom, and then use the computer image analysis system to test its covering effect. The second method is to install a knitting needle on the yarn friction tester, give the core-spun yarn a certain degree of friction or imitate the knitting process, so that the core-spun yarn is subjected to certain wear, and then wind the worn core-spun yarn on the yarn plate in parallel. , the coating effect was tested and calculated by a computer image analysis system. The wrapping effect of the core spun yarn tested by these two methods is obviously lower than that before processing, and the reduced percentage shows the degree of damage to the core spun yarn by peeling during machining.

The main factors affecting the covering effect of the core spun yarn are the content of the outer fiber and the content of the core fiber, the pre-draft ratio of the core fiber, the structural properties of the core fiber and the outer fiber, the design and installation of the godet, and the spinning process of the outer fiber. , yarn twist coefficient, spindle speed, and distance between two rovings. The internal and external transfer of fibers is the result of the coexistence of spinning tension and fiber geometry. The width of the whisker increases, the number of fibers at the edge of the twisting triangle area increases, and the number of fibers involved in the transfer increases at the same time, which increases the probability of the transfer of the outer fibers to the core wire. In order to make the two rovings fed in parallel transfer and hug each other better in the pre-drafting area, the siro spinning feeding horn enables the two rovings to be fed in parallel at a close distance, and the covering effect of the core-spun yarn is greatly improved.

2.3 Fluff

The main factors affecting the hairiness of the core-spun yarn are the roving spacing, twist and spindle speed. The single sliver of siro yarn contains a small amount of twist. Due to the double twisting, the fiber output from the front roller is not subjected to a sudden strong twisting force, and the two ends of the fiber will not protrude. , many fiber ends are brought into the sliver by the adjacent single yarn strips, and the surface fibers are bound to a certain extent. The hairiness of the siro-spun core-spun yarn is relatively less than that of the traditional ring-spun core-spun yarn.

2.4 Dry

The combined effect of the double roving feeding, plus the distance between the two rovings is much less than 12-14mm, the fibers in the sliver will not produce large slippage, so the siro-spun core-spun yarn has better evenness.

2.5 Wear resistance

The Siro core-spun yarn is evenly even, the cross section is round, the hairiness is less, the surface is smooth, and the friction with various yarn guides and heald reeds is small. Even if the surface fibers are partially rubbed, the internal fibers still maintain a certain connection and will not be damaged immediately. Ply yarn structure, so the wear resistance is better.

3 Spinning process comparison

The process parameters that have a great influence on the quality of the core spun yarn are the pre-draft multiple of the core yarn, the weight of the traveler, the twist of the spun yarn, as well as the feeding distance of the roving, the spindle speed, the roller pressure, and the draft multiple.

3.1 The same process

The process of roving draft multiple, core wire pre-draft multiple, roller gap, roller pressing and other processes are similar for both ring-spun core-spun yarn and siro-spun core-spun yarn.

3.2 Roving spacing

In the process of siro spinning, the twist direction of the two single yarns above the convergence point is the same as the twist direction of the lower yarns, and the twist is less up and down. The sinking effect hinders the transfer of twist, so that the twist of the single sliver on the upper side of the convergence point is smaller than the twist of the lower sliver, the height of the twist triangle decreases, the twist of the sliver on the lower side of the convergence point increases, and the twist of the single sliver also increases. After two twisted single yarns are twisted into a ply, the number of times that the fibers on the surface of the single yarn are looped into the ply is equal to the number of twists on the single yarn.

The roving spacing affects the size of the twisting triangle, the spacing between the two rovings increases, the length of the single sliver on the upper side of the convergence point increases, the twist on the single sliver also increases, the strands have less hairiness and good wear resistance. However, due to the instantaneous wrapping of each other, the wrapped beard must be output longer, so the spinning tension of the single yarn is relatively large, resulting in instantaneous tension drafting, which increases the number of slip fibers in the single yarn. The fibers in the sliver have a large slip, and the sliver details will appear when the slip is small, and the whisker will break when the slip is large. Therefore, the distance between the two rovings should not be too large, otherwise, the breakage will increase. However, the distance between the two rovings is small, the weak-twisted whiskers in the twisting triangle area are long, and the twist is low, which is prone to accidental drafting, which affects the yarn evenness and spinning ends. It can be seen that by changing the distance between the two rovings, the twisting triangle can be adjusted, so that the two slivers fed at the same time meet in the pre-drafting area, realize the mutual transfer and cohesion between the fibers, optimize the yarn evenness, and reduce the yarn hairiness. , rough details, rungs and other defects.

The distance between the two rovings should be determined according to the length of the outer covering fiber and the covering effect. In order to improve the covering effect of the finished yarn, the distance between the two rovings should be 3-5mm, which can accommodate one core wire. The core yarn is fed from the middle of the angle between the two yarns, and the core yarn is always in the center of the stranded yarn during twisting, so that the Siro core-spun yarn has a good covering effect.

3.3 Yarn twist coefficient

The twisting action produces centripetal pressure between the fibers in the yarn, which increases the friction force between the fibers. Within a certain twist range, the twist coefficient increases, the centripetal pressure of the outer fiber is large, the fibers transfer more inside and outside, the friction force and cohesion between the fibers increase, and the outer fiber wraps the core wire more tightly and firmly. The stronger the peel resistance, the higher the hairiness of the yarn. The strength and covering effect of siro-spun core-spun yarn are better than those of traditional core-spun yarn. Therefore, for the same purpose yarn, the twist coefficient of siro-spun core-spun yarn can be lower than that of similar ring-spun core-spun yarn.

3.4 Spindle speed

When the spindle speed increases, the centrifugal force of the yarn increases, the fibers will be thrown out of the yarn surface, the traveler will be accelerated, and the scraping effect will be enhanced. At this time, the spinning tension increases and the yarn hairiness increases. The quality of siro spun core yarn is better, and its spindle speed can be higher than that of traditional core spun yarn.

4 Conclusion

(1) The traditional core-spun yarn is spun on a spinning frame equipped with a core-spun yarn device, while the siro-spun core-spun yarn is spun on a spinning frame equipped with a core-spun yarn device and a siro spinning device.

(2) The outer fiber density of the traditional ring-spun core-spun yarn is relatively uniform, and the appearance has hairiness.

(3) The outer fibers of siro-spun core-spun yarn have two dense areas. The core yarn is always located in the center of the ply yarn. The surface of the yarn is smooth and clean. The strength is increased, the elongation is increased, and the evenness is also better than that of the traditional core-spun yarn. The yarn is soft to the touch, less hairiness, and good wear resistance.

(4) In addition to the advantages of siro yarn and core-spun yarn, siro-spun core-spun yarn also greatly improves the covering effect of core-spun yarn and reduces exposed core and empty sheath. However, in the spinning process, if the core yarn or one of the two rovings breaks, sometimes the automatic stop device for broken ends cannot cut off the other rovings or filaments in time, effectively preventing yarn defects such as hollow cores, poor covering and details.