Main factors affecting the covering effect of core spun nylon yarn

The ring spun core spun yarn of nylon filament is one of the most popular composite yarns in the market in recent years, but in the actual production, there are some quality problems such as uneven elasticity poor covering effect. This paper points out the main factors that affect the covering effect of the ring spun core spun yarn of nylon filament, analyzes these factors, puts forward the measures to improve the covering effect of the core spun yarn according to the production practice in the factory.

Factors affecting core spun yarn wrapping rate

In order to improve the strength elasticity of the core spun yarn, the nylon filament is usually located in the core of the yarn; in order to improve the hand feel of the fabric improve the comfort of the fabric, it is required to wrap the short wrapped fiber evenly on the surface of the core spun yarn. The correct technology good mechanism are beneficial to spinning high quality core spun nylon yarn on ring spinning frame.

Core content

In actual production, when spinning fine tex yarn core wire is thick, it is easy to have bad covering, because the number of fibers in the cross section is small, the fiber cohesion is reduced, it is easy to break in drafting. When the content of nylon fiber exceeds 30%, the quality of yarn is obviously poor. For the core spun yarn with fixed count, if the core content is high, the content of the outer fiber is low, the hollowness degree of the outer fiber is large, the cohesion of the fiber is weakened, it is easy to produce broken ends, open core yarn defects, even bare silk, which reduces the wrapping fastness affects the covering effect, thus leading to the reduction of the appearance quality.

Theoretically, the small coverage of core spun yarn is:

Small package coverage = [small linear density of outer fiber / (small linear density of outer fiber + denier number of core fiber / 9)] x 100%

In the actual cladding, the outer fibers are randomly distributed around the core wire, uniformly arranged around the core wire. Therefore, the actual coverage should be greater than the theoretical value, the content of the outer fiber, on the premise of ensuring that the core fiber is exposed, to ensure that the core yarn fabric has the style of the outer fiber, there is no color difference on the surface of the fabric. In a word, the content of nylon filament should be too high. According to the yarn specification use, the content of - is generally controlled at 25% - 30%. For example, the coverage of 23tex core spun yarn is about 72%, the content of nylon filament is about 28%.

Pre draft ratio of core wire

If the core yarn is drawn, the core spun yarn will have elasticity. If the drafting ratio is too low, it is suitable to give full play to the advantage of elasticity. If it is too high, it will make spinning difficult. When the outer fiber is changed, the larger the pre draft ratio is, the thinner the core wire is. When the core wire leaves the front roller, the more the retraction is, the higher the coverage is.

The selection range of drafting multiple of different specifications of nylon filament is different, but the selection of drafting multiple of different brands, even the same brand, different batch number of nylon filament is also different. In actual production, the inherent quality index spinning performance of each batch of nylon fiber raw materials are tested before feeding, then the reasonable pre drafting ratio is selected. Generally, the core pre draft ratio of high elastic nylon filament is 1.03 ~ 1.35. In the drafting system design, if two three change gears are designed, the selection range of drafting ratio is wider more accurate, which is conducive to the selection of reasonable pre drafting ratio.

Structure properties of the outer fiber

When the yarn is twisted, the centripetal pressure of the edge fiber located in the twisting triangle area is large, which will overcome the resistance between the fibers transfer to the inside of the yarn; while the fiber located in the inner layer will transfer outwards due to extrusion, some fibers will transfer to the vicinity of the filament, encounter the obstruction of the filament, change the direction of rotation, then wrap around the filament. The short fiber wrapped in the yarn is a conical helix, the fiber is wound inside outside, the nylon filament is wrapped in the yarn.

When the fiber transfers inside outside, it will be affected by tension resistance between fibers, the internal external transfer degree of each fiber is different. The longer fiber will have multiple internal external transfers; the shorter fiber will have less internal external transfers, tend to the outer layer of the yarn; the short fiber is floating fiber in the drafting process, generally does have internal external transfers. Therefore, it is necessary to the raw materials optimize the pre spinning process. For example, the pre spinning of the cotton fiber should be combed to remove the short fiber to a large extent. The chemical short fiber is long thin, its length fineness are in good order.

Spinning technology of outer fiber

the cross section, the structure of core spun yarn should take core spun yarn as the core, the outer fiber should be evenly distributed around it. the longitudinal view, the core spun yarn should be located on the axis, the outer fiber should be spirally wrapped outside. The results show that the long thin fibers are easy to transfer to the inner part of the yarn, the thick short fibers tend to the outer part of the yarn, the upper part of the roller output fiber strip is more located in the inner part of the yarn.

On the one hand, the outer fiber the fibers on both sides of the fiber bundle clamped by roller constantly extrude the middle fiber to form a transfer due to the spinning tension, the transfer efficiency is high; on the other hand, because of the role of the geometric mechanism of the fiber, the fiber transfer caused by the formation of the ring twist of the initially twisted fiber bundle is low. The internal external transfer of fiber is the result of coexistence of spinning tension fiber geometry. Moreover, with the increase of the width of the strand, the number of fibers along the edge of the twist triangle increased, the number of fibers involved in the transfer increased in the same time; with the increase of the height of the triangle, the area of the twist triangle increased, the number of fibers involved in the internal external transfer increased. If the area of the twisting triangle area of the same yarn count is large, the thickness of the sliver is small, the resistance of the fiber transfer is small, the probability of the outer fiber transfer to the core is large, which is conducive to improving the covering effect of the core spun yarn. Therefore, on the premise of ensuring that other quality indexes of yarn are deteriorated obviously, the following measures can be taken for spinning processing:

(1) The distance between the anterior roller the epithelium is increased, but the length of the floating area is increased, generally 15 mm;