JP7322730B2 - Eccentric core-sheath composite staple fiber - Google Patents

Description

The present invention relates to eccentric core-sheath composite staple fibers.

Synthetic fibers using thermoplastic resins such as polyester and polyamide are widely used for clothing, industrial materials, and non-woven fabrics due to their excellent strength, heat resistance, chemical resistance, and wash and wear properties. It is

Among clothing applications, woven and knitted fabrics using spun yarn are widely used for jackets, coats, shirts, underwear, sports clothing, and the like because of their texture and natural appearance. Spun yarn is a yarn made by twisting several to several tens of short fibers with a fiber length of several tens of millimeters.Short fibers include natural fibers such as cotton, regenerated fibers such as rayon, and animal hair fibers such as wool. By using, it is possible to obtain a woven or knitted fabric featuring excellent hygroscopicity and heat retention. However, due to the properties of these fibers, they are weak in terms of strength, and when they absorb a large amount of sweat or moisture, they are taken into the interior of the fibers, so they are difficult to dry and have the drawback of causing discomfort such as stickiness.

In order to solve these problems, spun yarn made of polyester fiber, which is excellent in mechanical properties, chemical properties, water absorption and quick drying, etc., or spun yarn made by blending polyester fiber with natural fiber or recycled fiber is used. It is

In order to meet the various properties required for clothing applications, the development of spun yarns containing higher-performance polyester fibers is underway. and the demand for stretch performance is high. In particular, there is a high demand for stretchability in thin fabrics using fine count spun yarn (30 to 60 count), such as shirts, underwear, and sportswear. In general, using large fineness staple fibers (single fiber fineness of 3 dtex or more) for fine count spun yarn leads to yarn unevenness and neps in the spun yarn, which leads to a decrease in the quality of the final fabric. Fiber fineness less than 3 dtex) is being developed.

As a method of obtaining stretchability, there is a method of blending polyurethane fibers to impart stretchability. However, polyurethane-based fibers have a hard texture, which is an inherent property of polyurethane, and there is a problem that the texture and drapeability of the woven fabric are deteriorated. Furthermore, polyurethane fibers are difficult to dye with dyes for polyester, and even if they are used in combination with polyester fibers, not only is the dyeing process complicated, but it is also difficult to dye them in desired colors.

Various latent crimp-developing fibers using side-by-side compositing have been proposed as methods that do not use polyurethane fibers. Latent crimp-developing fibers refer to fibers that have the ability to develop crimps by heat treatment or to develop finer crimps than before heat treatment.

For example, Patent Literature 1 proposes a latently crimpable conjugate fiber obtained by laminating two components of polymers (polyester) having different viscosities in a side-by-side manner.

When this latently crimpable conjugate fiber is used, the fiber is largely curved toward the high-shrinkage component side after heat treatment, so that the continuation of the fiber results in a three-dimensional spiral structure. Therefore, the structure expands and contracts like a spring, so that stretchability can be imparted to the woven or knitted fabric.

However, although the single fiber fineness of the fiber proposed in Patent Document 1 is 1.0 to 1.8 dtex, the yarn bending immediately after spinneret spinning due to the difference in melt viscosity between the two types of polymers is large. Yarn breakage occurred due to contamination of the spinneret surface, resulting in poor spinning operability. In particular, from the viewpoint of production efficiency and cost, short fibers need to be produced with spinnerets of several hundred to several thousand yards. There is a problem that yarn breakage is likely to occur. These problems are more conspicuous as the fineness becomes finer.

In Patent Document 1, the viscosity difference between two types of polymers is minimized to suppress yarn bending. The effect of suppressing bending is small, and the effect of spinning stability is small. Then, the broken yarn portion and the fused portion caused by yarn shaking receive the heat history of the spinning process and shrink to become a fused fiber (a yarn thicker than a normal fiber or a yarn in which a plurality of yarns are fused together). The fused fibers can be removed to some extent in the flat part of the flat card in the spinning process, but not all of them can be removed. If it is mixed in the spun yarn, it causes defects such as neps, and lowers the quality of the spun yarn.

Patent Document 2 proposes an actual crimpable conjugate staple fiber in which the center of gravity of the second component is deviated from the center of gravity of the fiber in the fiber cross section of the conjugate fiber containing the first component and the second component. . Due to the core-sheath structure, bending of the yarn during ejection is suppressed, excellent spinning stability is obtained, and actual crimpable conjugate short fibers having wavy crimps and helical crimps are obtained. However, the number of crimps is at most 16 crimps/25 mm, which is comparable to the number of crimps in a stuffing box type crimper with fibers that normally do not develop latent or overt crimps. Therefore, the simple eccentric core-sheath composite fiber with crimp expression is inferior in terms of stretch performance, which is the key, and it is difficult to say that the material has satisfactory stretch performance. In addition, when the fineness is fine, there is a problem that the stretchability is further inferior.

Although the eccentric core-sheath fiber proposed in Patent Document 3 is a filament, it suppresses the bending of the yarn right under the spinneret and provides good spinnability, so that a fiber with a single fiber fineness of 1.0 dtex or less can be obtained, Sufficient stretchability is obtained. However, the number of spinneret holes actually used in the examples of Patent Document 3 is less than 100H, which facilitates straightening in the polymer cooling process after spinneret spinning and easily suppresses yarn swinging. Therefore, it is possible to suppress yarn breakage at the bent part, but from the viewpoint of production efficiency, short fibers need to be produced at several hundred to several thousand hours. Fineness is difficult to achieve.

JP 2014-148768 A JP 2016-106188 A WO2018/110523

The present invention overcomes the problems of the prior art and provides eccentric core-sheath conjugate staple fibers that improve the spinnability and the quality of the spun yarn, and can be used to obtain thin fabrics with sufficient stretchability.

In order to achieve the above objects, the present invention has a cross section of a conjugate fiber composed of two types of polyesters, the A component and the B component, in which the A component is completely covered with the B component, and the A component is covered. The ratio S/D of the minimum thickness S of the thickness of the B component to the fiber diameter D is 0.01 to 0.1, and the peripheral length of the fiber in the portion within 1.05 times the minimum thickness S is the entire fiber. 1/3 or more of the peripheral length of the, the number of crimps before heat treatment is 8 to 20 crests / 25 mm, the degree of crimp is 8 to 25%, and the number of crimps developed during heat treatment without load at 180 ° C. An eccentric core-sheath composite staple fiber characterized by having a latent crimpability of 50 crimps/25 mm or more and a single fiber fineness of 0.5 to 2.4 dtex is employed.

By using the eccentric core-sheath composite short fibers of the present invention, it is possible to improve the spinnability and the quality of the spun yarn, and obtain a thin fabric with sufficient stretchability.

FIG. 1 is an example of the eccentric core-sheath composite staple fiber of the present invention, and is a cross section of the fiber for explaining the position of the center of gravity in the cross section of the fiber. FIG. 2 is a fiber cross section for explaining the fiber diameter (D) and the minimum thickness (S) in the eccentric core-sheath composite staple fiber of the present invention. FIG. 3 is a fiber cross section for explaining the IFR (curvature radius of the interface between the A component and the B component in the fiber cross section) in the fiber cross section of the eccentric core-sheath composite staple fiber of the present invention. FIG. 4 is an example of a fiber cross-section of an eccentric core-sheath composite short fiber not according to the present invention. FIG. 5 is an example embodiment of a distribution arrangement in the final distribution plate.

The present invention will be described in detail below.

The eccentric core-sheath composite staple fiber of the present invention has a fiber cross section composed of two types of polymers, the A component and the B component.

The polymer referred to here is preferably a fiber-forming thermoplastic polymer. In view of the object of the present invention, a combination of polymers that cause a difference in shrinkage when heat-treated is preferable. Combinations of polymers with different molecular weights or compositions that result in a difference in melt viscosity of 40 Pa·s or more are suitable.

The melt viscosity referred to in the present invention is measured by changing the strain rate stepwise with a chip-shaped polymer having a moisture content of 200 ppm or less in a vacuum dryer, and the strain when the measurement temperature is the same as the spinning temperature. This is the value at a speed of 1216s ^-1 . A difference of 40 Pa·s or more in the melt viscosities of the polymers constituting the conjugate fiber means, for example, stress is concentrated on the polymer components with high melt viscosities in the spinning line. Therefore, in the case of a core-sheath type cross section or a sea-island type cross section, stress is concentrated in the main polymer, resulting in excellent mechanical properties. A difference is generated, and it becomes possible to develop a suitable crimp.

Suitable polymers for the purposes of the present invention include polyethylenes such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyamides, polylactic acid, thermoplastic polyurethanes, polyphenylene sulfides, and combinations thereof. Polymerized polymers are mentioned. By changing the molecular weights of these components, it is possible to use a high-molecular-weight polymer for component A and a low-molecular-weight polymer for component B shown in FIG. 1, or to use a homopolymer for one component and a copolymer for the other component. .

Further, for combinations with different polymer compositions, for example, component A/component B includes polybutylene terephthalate/polyethylene terephthalate, polytrimethylene terephthalate/polyethylene terephthalate, thermoplastic polyurethane/polyethylene terephthalate, polytrimethylene terephthalate/polybutylene terephthalate, and the like. Various combinations are mentioned.

In particular, as the polymer, polyester, polyamide, polyethylene, polypropylene, etc. are preferably used, and among them, polyester is more preferable because it also has mechanical properties and the like. The polyester referred to here includes polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, copolymers thereof with a dicarboxylic acid component, diol component or oxycarboxylic acid component, and blends of these polyesters.

Among the above polymers, as an example of a suitable polymer combination for the conjugate staple fiber of the present invention, component A is a copolymerized polyester having ethylene terephthalate units as main structural units, and 2,2-bis[ 4-(2-Hydroxyethoxy)phenyl]propane (BHPP) or its ester-forming derivatives (hereinafter sometimes referred to as BHPP including ester-forming derivatives) and polyethylene terephthalate modified with isophthalic acid (IPA) It is preferably a copolymerized polyester, and the B component is preferably a polyester substantially composed of ethylene terephthalate units. In the present invention, the copolymerization ratio of BHPP in polyester (A) is preferably 2 to 7 mol %. If the copolymerization ratio of BHPP is less than 2 mol %, the shrinkage property becomes insufficient, and when spun yarn is formed, the elongation rate and elongation recovery rate are small, and sufficient stretchability may not be obtained. On the other hand, when it exceeds 7 mol %, the melting point of the polymer is lowered, so that the thermal stability tends to be impaired.

The copolymerization ratio of IPA in polyester (A) is preferably 5 to 13 mol %. If the IPA copolymerization ratio is less than 5 mol%, it is difficult to obtain substantially large crimps.
Further, as the copolymerized polyester of the A component, a copolymerized polyester containing 5-sodium isophthalic acid (5-SIPA) as a copolymerization component instead of or in combination with IPA can also be cited as a preferred embodiment.

The combination of polyethylene terephthalate-based copolymerized polyester modified with BHPP and IPA as component A and polyester substantially composed of ethylene terephthalate units as component B is polybutylene terephthalate/polyethylene terephthalate as component A/component B, Compared with the combination of polytrimethylene terephthalate/polyethylene terephthalate, when processed into a fabric, it has good elasticity and is suitable for thin fabrics such as shirts. This is because polybutylene terephthalate and polytrimethylene terephthalate are less rigid than polyethylene terephthalate.

The polyester substantially composed of ethylene terephthalate units as the component B is a polyester mainly composed of ethylene terephthalate units, and the ethylene terephthalate units are preferably 85 mol % or more. In addition, in order to make the heat shrinkability lower than that of the copolyester described above, it is preferable not to contain a component that greatly inhibits crystallinity, BHPP, IPA, or a sulfonic acid group compound. is.

On the other hand, when it is desired to obtain a soft and soft dough, it is preferable to use polybutylene terephthalate and polytrimethylene terephthalate as the A component, so it is preferable to use them properly according to the required properties.

The combination of polytrimethylene terephthalate/polyethylene terephthalate as component A/component B is superior in fabric elongation rate and fabric elongation recovery rate when processed into fabric, compared to the combination of polyethylene terephthalate for both A component and B component. It is possible to obtain a fabric with excellent stretch performance.

Furthermore, since the composite short fibers of the present invention are composed of a combination of polymers that cause differential shrinkage when heat-treated, they develop crimps during heat treatment. It is necessary to have latent crimp ability such that the number of developed crimps at the time of heat treatment under no load is 50 crimps/25 mm or more. When the number of developed crimps is less than 50 crimps/25 mm, the stretchability of the fabric is remarkably lowered, resulting in low stretchability. There is no particular upper limit for the number of crimps expressed. The number of crimps to be developed (latent crimp ability) can be achieved by adjusting the polymer species to be combined, their area ratio (described later), the cross-sectional structure of the eccentric core sheath, and the like.

Regarding the composite area ratio of the A component and the B component in the fiber cross section in the composite staple fiber of the present invention, a fine spiral structure can be realized by increasing the ratio of the high shrinkage component, which is the A component, in view of the appearance of crimp. Also, since it is necessary to have excellent physical properties as eccentric core-sheath composite staple fibers, the ratio of both components is in the range of A component: B component = 70: 30 to 30: 70 (area ratio) is preferred, and a range of 65:35 to 45:55 is more preferred.

In the present invention, it is necessary to have a composite cross section formed by bonding two different polymers, and two polymers with different polymer properties are present in a bonded state without being substantially separated, It is necessary to have an eccentric sheath-core type in which the A component completely covers the B component.

Here, the eccentricity referred to in the present invention means that the position of the center of gravity of the A component polymer in the cross section of the composite short fiber is different from the center of the cross section of the composite short fiber, which will be explained with reference to FIG.

In FIG. 1, the horizontal hatching is the B component, the 30 deg hatching (slanting line rising to the right) is the A component, the center of gravity of the A component in the cross section of the composite short fiber is the center of gravity point a, and the center of gravity of the cross section of the composite short fiber is It is the center of gravity point C.

In the present invention, it is important that the center of gravity point a of the A component and the center of gravity point C of the cross section of the conjugate short fiber be apart, so that the fiber is greatly curved toward the high-shrinkage component after the heat treatment. For this reason, the conjugate fiber continues to bend in the direction of the fiber axis, thereby forming a three-dimensional spiral structure and exhibiting excellent crimps. Here, the further apart the center of gravity is, the better the crimp is developed and the better the stretching performance is obtained.

In the present invention, since the A component is completely covered with the B component, even if the fiber or fabric is subjected to friction or impact, whitening or fluffing does not occur, so that the quality of the fabric can be maintained. In addition, high-molecular-weight polymers, high-elasticity polymers, etc., which are exposed on the surface of the conjugate fibers in the conventional simple bonded structure, can be used as one of the components of the conjugate short fibers.

In addition, since the A component on one side is completely covered with the B component on the other side, even if a polymer with low heat resistance or abrasion resistance or a hygroscopic polymer is used, the fiber characteristics can be maintained well. can do

In the conjugate staple fiber of the present invention, the ratio S/D of the minimum thickness S of the B component covering the A component and the fiber diameter (diameter of the conjugate fiber) D must be 0.01 to 0.1. be. Preferably, it is between 0.02 and 0.08. Within this range, abrasion resistance and the like are excellent, and sufficient crimp development force and stretchability can be obtained.

Originally, good stretchability can be obtained by contacting each polymer only at the bonding interface, and if the high-shrinkage component is completely covered with the low-shrinkage component, the stretchability decreases. However, by setting the thickness of the B component within the range of the present invention, it has become possible to obtain a composite short fiber that satisfies both properties of stretchability and abrasion resistance.

A more detailed description will be given using the fiber cross section shown in FIG. Here, the minimum thickness S is the thinnest portion of the B component in the core-sheath composite staple fiber.

Furthermore, it is important that the portion having a thickness within 1.05 times the minimum thickness S occupies 1/3 or more of the entire peripheral length of the composite short fibers. This means that the A component exists along the contour of the fiber, and compared with the conventional eccentric core-sheath composite fiber with the same area ratio, the present invention has the center of gravity of each component in the fiber cross section. The positions are farther apart, forming fine spirals and developing good crimps. More preferably, the perimeter of the thickness within 1.05 times the minimum thickness S is set to 2/5 or more of the perimeter of the entire fiber to obtain good stretchability without crimp unevenness.

Furthermore, it is preferable that the curvature radius IFR of the interface between the A component and the B component in the cross section of the fiber satisfies the following formula 1 when the value R obtained by dividing the fiber diameter D by 2 is used. The curvature radius IFR referred to here is a circle (dashed line ).
(IFR/R)≧1 (Formula 1)
This means that the interface is more straight. In the present invention, by making the interface between the A component and the B component a curve close to a straight line in a form close to the cross section of a conventional laminated crimped fiber, a high crimp that could not be achieved with a conventional eccentric core-sheath composite fiber can be achieved. It is preferable because it can be expressed. More preferably, it is 1.2 or more.

The minimum thickness S at which the thickness of the B component covering the A component is the minimum, the fiber diameter D, the curvature radius IFR of the interface, and the area ratio of the A component and the B component are obtained as follows.

That is, an eccentric core-sheath composite staple fiber is embedded in an embedding agent such as an epoxy resin, and an image of this cross-section is taken with a transmission electron microscope (TEM) at a magnification that allows observation of 10 or more fibers. At this time, if metal dyeing is applied, the difference in dyeing between polymers can be used to clarify the contrast at the junction between the A component and the B component. A value obtained by measuring the diameter of 10 circumscribed circles randomly extracted from each photographed image corresponds to the fiber diameter D referred to in the present invention. If 10 or more fibers cannot be observed, a total of 10 or more fibers including other fibers may be observed. The circumscribed circle diameter as used herein means the diameter of a perfect circle that circumscribes the cross section perpendicular to the fiber axis from a two-dimensionally photographed image and circumscribes this cut plane at two or more points. do.

In addition, the minimum thickness of the B component covering the A component for 10 or more fibers is measured using the image obtained by measuring the fiber diameter D, which corresponds to the minimum thickness S referred to in the present invention. Further, the fiber diameter D, the minimum thickness S, and the radius of curvature IFR are measured in units of μm and rounded off to the third decimal place. A simple numerical average value of the measured values and their ratio (S/D) is calculated for 10 images photographed during the above operation.

In addition, the area ratio of the A component and the B component is obtained by using the image taken above and the image analysis software "WinROOF2015" manufactured by Mitani Shoji Co., Ltd. After obtaining the area of the entire fiber and the area of the A component and the B component, the area Find the ratio.

The single fiber fineness of the composite short fibers of the present invention must be 0.5 dtex or more and 2.4 dtex or less. If it is less than 0.5 dtex, card passability is poor, leading to winding around the card cylinder and occurrence of card neps. As the fineness increases, the number of constituent single yarns per spun yarn decreases, resulting in unevenness in the thickness of the spun yarn and NEP. to 60), when the yarn is 2.5 dtex or more, the unevenness in the thickness of the spun yarn and neps are extremely increased. It is more preferably 0.8 dtex or more and 1.8 dtex or less, and still more preferably 1.0 dtex or more and 1.5 dtex or less.

The conjugate staple fiber of the present invention can be produced by the following spinning method.

The polymers of component A and component B are melted and made into a composite flow at a predetermined mass ratio using a composite melt spinning device, and then passed through a spinneret having 100 to 2000 discharge holes with a hole diameter of 0.2 to 0.6 mm, Melt spinning at a spinning temperature above the melting point. The spinning temperature is preferably set at +20 to +60° C. higher than the melting point of the polymer. By setting the temperature higher than the melting point of the polymer by +20 ° C. or more, it is possible to prevent the polymer from solidifying and clogging in the spinning machine pipe, and by setting the temperature to be higher than +60 ° C., excessive polymer It is preferable because heat deterioration can be suppressed.

Examples of the melting method include a pressure melter method and an extruder method, and although there is no problem with either method, it is preferable to adopt a melting method using an extruder from the viewpoint of uniform melting and prevention of retention. Molten polymer is passed through a pipe, metered, and then flowed into the mouth pack. At this time, in order to suppress heat deterioration, it is preferable that the piping passage time is 30 minutes or less. Molten polymer flowing into the pack is spun from a spinneret.

Further, since the present invention relates to short fibers, from the viewpoint of production efficiency, a spinneret with multiple holes is usually used, and it is necessary to use a spinneret of 100H or more. Considering the market price of staple fibers, it is more preferably 300H or more, and even more preferably 600H or more.

In general, as the number of holes increases, it becomes more difficult to uniformly cool the yarn after spinning, and in addition, turbulent flow occurs immediately below the spinneret, making stable spinning difficult. In addition, in eccentric core-sheath conjugate spinning and side-by-side conjugate spinning using two components, yarn bending occurs after the polymer is discharged, making stable spinning more difficult. However, by making the cross section as in the present invention, it is possible to suppress yarn bending caused by the difference in flow velocity between the two types of polymers during discharge from the spinneret. In other words, the presence of the sheath component causes a force in the direction opposite to the direction in which the polymer flow bends. be able to. In addition, by controlling the cooling of the yarn and the convergence position of the yarn from the spinneret discharge surface as follows, it is possible to perform stable spinning even when using a spinneret with a large number of spinneret holes.

Regarding the method of cooling the yarn, it is preferable to rapidly cool it immediately below the spinneret. It is preferable to use and cool at 30 to 120 m/min. A more preferable range of the cooling start position is a position of 20 mm to 100 mm. This cooling process suppresses the turbulent flow that occurs directly under the spinneret and suppresses yarn swaying.In addition, the rapid cooling of the yarn raises the solidified position of the polymer, making it difficult for yarn breakage due to yarn swaying to occur. . By making the cross section as in the present invention, it was possible to suppress the yarn bending after discharging the polymer. This made it possible to manufacture composite fibers using a spinneret. As a method for obtaining the same effect by rapid cooling directly below the nozzle, a suction cooling device with a suction start position at a position of 0 to 200 mm directly below the nozzle and a suction length of 10 to 400 mm is used, and suction is performed at 30 to 120 m/min. may be performed and cooled.

In addition, it is preferable to rectify after quenching directly under the nozzle, using a cold air blowing cooling device with an air temperature of 10 to 50 ° C. and a cooling length of 100 to 700 mm, cooling at 20 to 90 m / min, and cooling the cooling air directly under the nozzle. It is preferable to cool at a wind speed of less than or equal to . If the speed of the cooling air is higher than that of the cooling air just below the spinneret, yarn swaying becomes large, causing yarn breakage and yarn fusion, which may hinder stable spinning. If there are many yarn breakages and yarn fusions, they may be mixed into the spun yarn, resulting in deterioration of the quality of the spun yarn.

It is preferable that the distance from the spinneret discharge surface to the yarn convergence position is 2000 mm or less. By setting the distance from the ejection surface of the spinneret to the convergence point of the yarn to 2000 mm or less, the fluctuation width of the yarn caused by the cooling air can be suppressed, and the accompanying air current until the yarn converges can be suppressed. It is preferable because it is easy to obtain spinning properties. A more preferable range of the yarn convergence position in the spinning process is 1600 mm or less.

In the step of drawing the spun undrawn yarn, the undrawn yarn is bundled to 30 to 300 ktex and drawn 2 to 5 times under steam or in hot water. Thereafter, tension heat treatment is performed, and crimping is applied using a press-type crimper or the like.

Next, the stretched tow after crimping is dried, an aqueous finishing oil solution is sprayed on the tow, and the tow is cut to produce the composite short fibers of the present invention.

In the case of latently crimpable conjugate fibers laminated in a side-by-side fashion, the process of drawing spun undrawn yarns has the characteristic of being easily fused with adjacent fibers due to the heat of drawing, increasing the risk of contamination of fused fibers. . This problem is conspicuous in the production process of short fibers, and the composite fiber of the present invention solves this problem specific to short fibers.

Although the detailed mechanism has not been elucidated, in the present invention, by applying an eccentric core-sheath type composite short fiber in which the A component is completely covered with the B component, this decrease in fusion bonding is alleviated and It is possible to suppress the contamination of the fusible fibers into. The lower the melting point, the easier it is for the fibers to fuse together. Therefore, when a component with a lower melting point than the A component is used as the B component, the number of fused fibers is expected to further decrease. If the number of fused fibers is reduced, the risk of contamination of the fused fibers into the spun yarn can be reduced, and the quality of the spun yarn can be improved.

In addition, by stretching the undrawn yarn in a state of being preheated to 40 to 60° C. before drawing, the fused fibers can be further suppressed.

The number of crimps (the number of crimps before heat treatment) of the composite fiber of the present invention should be 8 to 20 crimps/25 mm, and the crimp degree should be 8 to 25%. The number of crimps and the degree of crimping referred to herein refer to numerical values after cutting the stretched tow.

If the number of crimps is less than 8 crimps/25 mm, or the degree of crimping is less than 8%, cardability will be extremely poor. Also, when the number of crimps is higher than 20 crimps/25 mm or the degree of crimp is higher than 25%, card passability is extremely poor, and neps occur frequently after passing through the card, and the thickness of the spun yarn is uneven. is extremely increased, significantly degrading the high-order workability and the quality of the spun yarn.

A more preferable range of the number of crimps is 10 to 17 crests/25 mm, and a still more preferable range is 11 to 15 crimps/25 mm.

A more preferable range of crimp degree is 9 to 20%, and a further preferable range is 10 to 16%.

In order to obtain the number of crimps and the degree of crimping of the present invention, the tensioning heat treatment temperature, the tensioning heat treatment time, the temperature of the tow when entering the tucking crimper, the tucking pressure of the tucking crimper, and the crimp Setting the drying temperature of the tow after application is important.

In the tension heat treatment, heat setting is performed while tension is maintained, and then cooling is performed with cooling water to a temperature below the glass transition temperature to fix the structure of the molecular chains. The crimp expression can be suppressed, and a high crimp expression ability can be exhibited by heat treatment in a high-order processing step such as spinning or nonwoven fabric.

The tension heat treatment temperature is preferably 100 to 190° C., and the tension heat treatment time is preferably 3 to less than 20 seconds. If the treatment temperature is less than 100° C. or the treatment time is less than 3 seconds, the crimp may be excessively expressed in the subsequent drying process of the tow after crimping, and the latent crimp property may be lowered. Also, if the treatment temperature is higher than 190° C. or the treatment time is longer than 20 seconds, the latent crimp properties may deteriorate.

The temperature of the tow as it enters the tucking crimper is preferably 20-60°C. If the temperature is lower than 20°C, the degree of crimping is low and the degree of crimping of the present invention may not be obtained. Sometimes.

The pressing pressure of the pressing type crimper is preferably 1 to 3 kg/cm ² G. When it is less than 1 kg/cm ² G, the number of crimps or the degree of crimping tends to be low, and when it is more than 3 kg/cm ² G, the number of crimps or the degree of crimping tends to be high.

The drying temperature of the tow after crimping is preferably 50 to 120°C. If it is lower than 50°C, the tow may not be sufficiently dried, and if it is higher than 120°C, crimps will appear in the drying process, and heat treatment in high-order processing such as spinning and nonwoven fabrics may cause insufficient drying. sufficient crimp expression cannot be obtained.

Due to the cross-sectional shape of the present invention, the appearance of crimps in the spinning process is moderately suppressed, and the crimps of the present invention can be obtained relatively easily. Although the detailed mechanism has not been elucidated, it is considered that the thin portion of the B component covering the A component can moderately suppress the shrinkage of the A component. In the case of a cross section in which the A component is bare, such as a side-by-side type cross section, especially if the melt viscosity difference between the two-component polymers is large, during the spinning process, for example, when the tow is dried after crimping, crimps are developed and stretched. Since the number of crimps after cutting the tow and the degree of crimping tend to increase, it is relatively difficult to control crimping during the spinning process.

The fiber length of the conjugate fiber of the present invention is preferably 20 to 120 mm, more preferably 30 to 90 mm, from the viewpoint of process passability in higher processing steps.

The conjugate staple fiber of the present invention preferably has a breaking strength of 1.5 to 5.0 cN/dtex, more preferably 2.5 to 4.0 cN/dtex. , yarn breakage and process troubles occur in the spinning process. Moreover, when the cutting strength is higher than 5.0 cN/dtex, the softness and pilling resistance become poor.

The conjugate staple fiber of the present invention preferably has a breaking elongation of 10 to 50%, more preferably 20 to 40%. If the elongation at break is less than 10% or more than 50%, yarn breakage and process troubles occur in the spinning process.

In the composite staple fiber of the present invention, it is preferable to precisely control the sheath thickness and the peripheral length of the thin skin portion. A method using a distributed plate is preferably used. When a fiber having an eccentric core-sheath type cross section is produced using a conventionally known composite spinneret, it is often very difficult to precisely control the position of the center of gravity of the core and the thickness of the sheath. For example, when the thickness of the sheath becomes thin and the core component is exposed, it causes whitening and fluffing of the fabric due to friction and impact, and conversely, when the thickness of the sheath increases, crimping occurs. As a result, there may be a problem that the stretching performance is deteriorated.

In the method using such distribution plates, the cross-sectional form of the single yarn can be controlled by arranging the distribution holes in the final distribution plate installed furthest downstream among the plurality of distribution plates.

The cross-sectional shape of the conjugate staple fiber of the present invention can be controlled by arranging the distribution holes of the polymer (component A) forming the core component and the polymer (component B) forming the sheath component. Specifically, as illustrated in FIG. 5, the polymer (B By arranging distribution holes 5-(a) and 5-(b) of component), it is possible to form an eccentric core-sheath type composite cross-section, which is necessary in the present invention, which is preferable.

Here, the number of distribution holes 5-(a) for the polymer (component B) forming the skin is preferably 6 or more from the viewpoint of complete coverage of the core component and uniform thickness of the skin. In addition, by adjusting the number of distribution holes 5-(a) that form the thin skin and the discharge rate of the polymer around the distribution holes, the S/D and the length of the minimum thickness in the cross section of the composite fiber It is possible to control the

In this way, the polymer flow cross-sectionally formed by the distribution plate is constricted and discharged from the discharge holes of the spinneret. At this time, the purpose of the discharge holes is to re-meter the flow rate of the composite polymer stream, that is, to control the draft on the spinning line (=take-up speed/line speed of discharge). The pore size and pore length are preferably determined in consideration of the viscosity and discharge rate of the polymer. When producing the composite staple fiber of the present invention, the ejection hole diameter can be selected in the range of 0.1 to 2.0 mm, and the L/D (ejection hole length/ejection hole diameter) can be selected in the range of 0.1 to 5.0. can.

As described above, the conjugate short fibers of the present invention preferably completely cover the A component with the B component as shown in FIG. By making the cross section as in the present invention, it is possible to suppress ejection line bending (kneeing phenomenon) caused by the difference in flow velocity between the two types of polymers during ejection from the die. That is, the presence of the sheath component causes a force in the direction opposite to the bending direction of the polymer flow. It can be suppressed.

In addition, in the case of the conventional simple bonding structure (bimetal structure), there is a difference in the stress balance applied to each polymer when thinning on the spinning wire after ejection from the spinneret, and unevenness occurs in extensional deformation, which is the fineness unevenness. was sometimes manifested as This tendency appears very conspicuously when combining polymers with a large difference in viscosity or when reducing the fineness by restricting the discharge rate, etc., but in the present invention, the polymer is covered with one polymer. As a result, the stress balance is balanced within the cross section of the fiber, and fineness unevenness can be suppressed.

Furthermore, when a high-molecular-weight polymer is used as the A component and a low-molecular-weight polymer is used as the B component, it has been found that the high-speed spinning stability is excellent because the B component is completely covered. This is because the low-molecular-weight polymer is placed on the outside, making it easier for the high-molecular-weight polymer to follow the elongation deformation after ejection from the nozzle.

As a result, even in fine fineness yarn, the degree of freedom in polymer selection for improving added value other than improving stretch performance and improving spinning stability increases dramatically, contributing to improved productivity.

In addition, from the viewpoint of suppressing discharge line bending, the difference in melt viscosity of the polymer used for the composite staple fiber of the present invention is also important. When the two melted polymers forming the conjugate fiber are contracted, in order to match the pressure loss of the two polymers, the cross-sectional area is changed in the polymer flow direction and the vertical cross section, resulting in a flow velocity difference. Since these particles are ejected with the center of gravity biased, ejection line bending occurs.

That is, a polymer with a high melt viscosity has a large cross-sectional area, resulting in a slow flow rate, while a polymer with a low melt viscosity has a small cross-sectional area, resulting in a high flow rate. Therefore, by reducing the melt viscosity difference between the polymers to be used, the flow velocity difference between the polymers can be alleviated, and the ejection line bending can be suppressed. From this point of view, it is preferable that the melt viscosity difference between the polymers to be combined is smaller. However, in the composite staple fiber of the present invention, it is preferable that the melt viscosity difference between the polymers to be combined is larger in consideration of the occurrence of crimping. is.

When the bending of the discharge line is suppressed in this way, the interference between the single fibers on the spinning line can be suppressed, so the density of the discharge holes on the spinneret can be increased, that is, the number of discharge holes per spinneret can be increased. is possible, and it is possible to achieve sophistication and improvement in production efficiency by increasing the number of yarns.

At this time, it is preferable to set the spinning draft to 300 times or less to obtain a homogeneous fiber in which variations in physical properties between yarns are suppressed.

The spinning draft represented by the following formula of the conjugate staple fiber of the present invention is preferably 50 to 300.
Spin draft = Vs/V0
Vs: Spinning speed (m/min)
V0: Ejection linear velocity (m/min).

By setting the spinning draft to 50 or more, it is possible to prevent the polymer flow discharged from the spinneret hole from staying directly under the spinneret for a long time and to suppress the spinneret surface contamination, thereby stabilizing the spinning property. Further, by setting the spinning draft to 300 or less, it is possible to suppress yarn breakage due to excessive spinning tension, and eccentric core-sheath composite short fibers can be obtained with stable spinning properties, which is preferable. More preferably 80-250.

The eccentric core-sheath composite staple fiber of the present invention can be used to make a spun yarn, but the types of other fibers constituting the spun yarn are not particularly limited, and polyester fiber, acrylic fiber, polyamide fiber, rayon. , cotton, hemp, wool, and silk are preferable because the effect of the present invention can be exhibited, and the composite staple fiber of the present invention may be used alone. Particularly preferred are 100% composite staple fibers of the present invention, composite staple fiber/cotton blends of the present invention, and composite staple fiber/wool blends of the present invention.

When making the conjugate staple fiber of the present invention into a spun yarn, the spun yarn can be produced by a normal spinning method. The count of the spun yarn is preferably 30 to 60, which is often used for thin fabrics such as shirts, underwear and sportswear. If the number is less than 30, the desired material cannot be obtained due to the thickness of the fabric, and if the number is higher than 60, there is a problem of workability, and it is hardly used for existing applications. The twist coefficient of the spun yarn is preferably in the range of 2.5 to 4.5. If the twist coefficient is less than 2.5, there is a tendency that sufficient yarn strength cannot be obtained, and yarn breakage during spinning and weaving may occur. It tends to cause a decrease in strength when made into a knitted fabric. On the other hand, if the twist coefficient exceeds 4.5, there is a tendency that the fabric tends to be warped due to twisting, and a woven or knitted fabric tends to have a rough and stiff feeling. In addition, since the fibers are strongly bound to each other and the fibers are difficult to contract, the essential stretchability cannot be obtained.

As a method for evaluating the stretchability of the fabric by the spun yarn using the composite staple fiber of the present invention, there are the fabric elongation rate and the fabric elongation recovery rate. When you put on the fabric, you can feel the stretchability and it is difficult to feel the feeling of restraint. When the count, twist coefficient, and fabric composition of the spun yarn are the same, the thicker the fineness, the fewer the number of constituent yarns, the less binding between fibers, and the improvement in the elongation rate of the fabric can be expected. quality is reduced.

In addition, the elongation rate is measured by first making a spun yarn with a count of 45S (single yarn) and a twist coefficient of 3.5 from the composite staple fiber of the present invention, using it as a weft yarn in a fabric, and polyester ( Toray Co., Ltd., product name: T403-1.45T×38mm) and cotton are mixed to use spun yarn with a count of 45S and a twist coefficient of 3.5. A 1/3 twill fabric was produced using an air jet loom with a warp yarn density of 110 / inch (2.54 cm) and a weft density of 76 / inch (2.54 cm). After heat treatment for 10 minutes in a moist and hot atmosphere, the fabric is cut into 30 cm x 5 cm samples so that the weft threads are oriented in the longitudinal direction, and 3 samples are cut out. Next, using a constant speed extension type tensile tester with an automatic recording device (manufactured by INSTRON: MODEL 5566), the grip interval is set to 20 cm, an initial load equivalent to the mass of a 5 cm x 1 m size is applied, and fixed to the grip. The grip interval at this time is assumed to be L0. Elongate to 14.7 N (1.5 kg) at a tensile speed of 20 cm/min, measure the gripping distance (L1) at that time, determine the elongation rate (%) from the following formula, and express the average value of three sheets.
Fabric elongation rate (%) = {(L1-L0) / L0} x 100
L0: Grip interval under initial load (mm)
L1: Grip interval (mm) when stretched to 14.7 N (1.5 kg).

As in the measurement of the elongation recovery rate, the fabric was heat-treated for 10 minutes in a moist and hot atmosphere of 130 ° C under no load and cut into a size of 30 cm x 5 cm so that the weft thread is in the longitudinal direction. Cut out as 3 samples. A tensile tester is used with a grip interval of 20 cm, and an initial load equivalent to the mass of a sample measuring 5 cm x 1 m is fixed to the grip. After stretching to 80% of the previously obtained elongation rate at a tensile speed of 20 cm/min (L3) and leaving for 1 minute, return to the original position at the same speed and leave for 3 minutes. After repeating these operations 10 times, the sheet is stretched again at the same speed to the initial load condition, the residual elongation (L4) at that time is measured, and the elongation recovery rate is calculated by the following formula, and is expressed as the average value of three sheets.
Elongation recovery rate (%) = {(L3-L4) / L3} × 100
L3: 80% length of fabric elongation (mm)
L4: Length of residual elongation after 10 repeated elongations (mm).

The spun yarn using the composite staple fibers of the present invention is suitable for thin fabrics such as shirts, underwear, and sports clothing, but can also be used for thick fabrics such as pants and suits, and has sufficient stretchability. Obtainable.

<Evaluation method>
<Melt viscosity of polymer>
The moisture content of the chip-shaped polymer was reduced to 200 ppm or less by a vacuum dryer, and the melt viscosity was measured by changing the strain rate stepwise using Capilograph 1B manufactured by Toyo Seiki Co., Ltd. The measurement temperature is the same as the spinning temperature, and a melt viscosity of 1216 s ⁻¹ is described in Examples and Comparative Examples. Incidentally, the measurement was performed in a nitrogen atmosphere with 5 minutes from the time the sample was put into the heating furnace to the time the measurement was started.

<Thinning stability>
Spinning was carried out for 8 hours for each example, and relative evaluation was made based on the number of spinning breakages, and evaluation was made on a 4-point scale.
◎ (Extremely good): 0 to 1 thread breakage ○ (Good): 2 to 5 thread breakages Δ (slightly poor): 6 to 10 thread breakages × (Poor): 11 thread breakages more than once.

<Fineness, fiber length>
The fineness and fiber length were measured by the method shown in JIS L1015 (2010).

<Number of crimps before heat treatment (peak/25 mm), crimp degree (%)>
It was measured according to the method of JIS-L1015 (2010).

<Number of crimps expressed (peak/25mm)>
The number of developed crimps was obtained by dry-heating the short fibers at a temperature of 180° C. for 5 minutes under no load, and then using an optical microscope (manufactured by Keyence, VHX-900F) to observe one single yarn at a magnification of 100. . After counting the number of crimps per 200 μm using the scale measurement function of the optical microscope, the observation results were converted to the number of crimps per 25 mm. This operation was repeated 10 times, and the average value was calculated as the number of developed crimps.

<Breaking strength (cN/dtex) and breaking elongation (%)>
It was measured according to the method of JIS-L1015 (2010).

<Spun Yarn Quality>
A spun yarn with a count of 45S (single yarn) and a twist coefficient of 3.5 is produced from 100% of the short fibers to be measured, and 1000 m of the spun yarn is detected by a yarn defect detector (USTER (Switzerland) Evenese Tester (Tester 5)). The number of unevenness and neps was measured and evaluated relatively.
⊚ (extremely good): less than 100 ∘ (good): 100 or more and less than 200 Δ (slightly poor): 200 or more to less than 500 × (defective): 500 or more.

<Fabric elongation rate>
A spun yarn with a count of 45S (single yarn) and a twist coefficient of 3.5 is prepared from the short fibers to be measured, and used as a weft yarn for fabrics. 1.45T x 38 mm) and cotton are used. A 1/3 twill fabric was produced using an air jet loom with a warp yarn density of 110 / inch (2.54 cm) and a weft density of 76 / inch (2.54 cm). After heat treatment for 10 minutes in a moist and hot atmosphere, the fabric is cut into 30 cm x 5 cm samples so that the weft threads are oriented in the longitudinal direction, and 3 samples are cut out. Next, using a constant speed extension type tensile tester with an automatic recording device (manufactured by INSTRON: MODEL 5566), the grip interval is set to 20 cm, an initial load equivalent to the mass of a 5 cm x 1 m size is applied, and fixed to the grip. The grip interval at this time is assumed to be L0. Elongate to 14.7 N (1.5 kg) at a tensile speed of 20 cm/min, measure the gripping distance (L1) at that time, determine the elongation rate (%) from the following formula, and express the average value of three sheets.
Fabric elongation rate (%) = {(L1-L0) / L0} x 100
L0: Grip interval under initial load (mm)
L1: Grip interval (mm) when stretched to 14.7 N (1.5 kg).

<Fabric elongation recovery rate>
As in the measurement of the elongation rate, the fabric is heat-treated for 10 minutes in a moist and hot atmosphere of 130°C under no load, cut into 30 cm x 5 cm pieces so that the weft threads are in the longitudinal direction, and three samples are cut out. A tensile tester is used with a grip interval of 20 cm, and an initial load equivalent to the mass of a sample measuring 5 cm x 1 m is fixed to the grip. After stretching to 80% of the previously obtained elongation rate at a tensile speed of 20 cm/min (L3) and leaving for 1 minute, return to the original position at the same speed and leave for 3 minutes. After repeating these operations 10 times, the sheet is stretched again at the same speed to the initial load condition, the residual elongation (L4) at that time is measured, and the elongation recovery rate is calculated by the following formula, and is expressed as the average value of three sheets.
Elongation recovery rate (%) = {(L3-L4) / L3} × 100
L3: 80% length of fabric elongation (mm)
L4: Length of residual elongation after 10 repeated elongations (mm).

<Strong feeling of fabric>
A spun yarn with a count of 45S (single yarn) and a twist coefficient of 3.5 is produced from 100% of the short fibers to be measured, and used as warp and weft yarns in fabrics, and the warp yarn density is 110 / inch (2.54 cm). , and a weft density of 76 lines/inch (2.54 cm) to obtain a plain weave using an air jet loom. The produced fabric was cut to 20 cm × 20 cm, the sample was touched by 10 subjects, and the average score was calculated after scoring according to the following criteria, and ranked A to D according to the average score. .

(evaluation score)
3 points: There is a feeling of stiffness 2 points: There is a feeling of stiffness a little 1 point: There is no feeling of stiffness (Evaluation based on average points)
A: 3.0 to 2.6 points B: 2.5 to 2.1 points C: 2.0 to 1.6 points D: 1.5 to 1.0 points.

<Soft feel of fabric>
A spun yarn with a count of 45S (single yarn) and a twist coefficient of 3.5 is produced from 100% of the short fibers to be measured, and used as warp and weft yarns in fabrics, and the warp yarn density is 110 / inch (2.54 cm). , and a weft density of 76 lines/inch (2.54 cm) to obtain a plain weave using an air jet loom. The produced fabric was cut to 20 cm × 20 cm, the sample was touched by 10 subjects, and the average score was calculated after scoring according to the following criteria, and ranked A to D according to the average score. .

(evaluation score)
4 points: very soft feeling 3 points: soft feeling 2 points: slightly soft feeling 1 point: no soft feeling (evaluation based on average score)
S: 4.0-3.3 points A: 3.2-2.6 points B: 2.5-2.1 points C: 2.0-1.6 points D: 1.5-1.0 points .

[Example 1]
Polyethylene terephthalate (melt viscosity: 110 Pa s) obtained by copolymerizing IPA 7.0 mol% and BHPP 4.0 mol% as the A component polymer, and polyethylene terephthalate (melt viscosity: 70 Pa s) as the B component polymer. Both the polymer of (1) and the polymer of component (B) were melted at 280°C using an extruder, weighed by a pump, and flowed into a nozzle while maintaining the temperature at 290°C. The area ratio of the A component and the B component was set to 50/50, and the components were flowed into a spinneret for eccentric core-sheath composite fibers having 600 spinneret holes. The respective polymers joined together inside the die to form an eccentric core-sheath composite form in which the polymer of component A was included in the polymer of component B, and the polymer was discharged from the die. In addition, in the spinning of Example 1, a spinneret of a distribution plate type was used so as to obtain the eccentric core-sheath composite fiber shown in FIG. The spun yarn was cooled while being taken up at a speed of 1300 m/min. The yarn is cooled from a position 20 mm from the spinneret by a cold air blowing device with an air temperature of 20°C, an air velocity of 70 m/min, and a cooling length of 30 mm. was cooled by a cold air blowing cooling device. After the yarn was cooled, 0.1% by mass of a process oil was applied, passed through a free roller, and 20 other spindles were combined with a convergence 0.1% guide to obtain an undrawn yarn. The distance from the ejection surface of the spinneret to the convergence position of the yarn was set to 1600 mm. After that, while pulling 20 undrawn yarns together, they are led to hot water at a temperature of 90°C, and the drawn yarns drawn at a draw ratio of 2.8 are tension-heat treated with a heating roller at 160°C for 5 seconds and sent to a crimper. A crimped tow with 10 crimps/25 mm and a degree of crimping of 11% is obtained by mechanical crimping at a drawn tow temperature of 30° C. and a tow pressing pressure of 1.5 kg/cm ² G. rice field. The resulting crimped tow was dried at 80° C., applied with 0.2% by weight of a finishing oil, and cut into fibers of 38 mm in fiber length by a rotary cutter. A polyester staple fiber having an elongation of 32%, a number of crimps of 12 crimps/25 mm, and a degree of crimp of 14% was obtained. The obtained polyester short fibers were evaluated by the method described above.

Table 2 shows the evaluation results of the obtained eccentric core-sheath composite short fibers. The S/D in the fiber cross section was 0.02, and the minimum thickness portion occupied 45% of the fiber circumference. The spinnability and the quality of the spun yarn of the eccentric core-sheath composite short fibers were good, and the elongation ratio, which is a stretch performance index, was 24%, and a fabric with elasticity could be obtained.

[Examples 2 to 5]
Examples 2-5 varied the combination of the A component polymer and the B component polymer. For Example 2, the tow drying temperature was changed to 70°C, and for Example 4, the tow drying temperature was changed to 50°C. This is because when the drying temperature is high, crimps appear, the number of crimps and the degree of crimping increase, and the quality of the spun yarn tends to deteriorate, so the drying temperature was changed in consideration of the quality of the spun yarn. Otherwise, in the same manner as in Example 1, an eccentric core-sheath composite staple fiber was obtained.

[Comparative Examples 1 to 3]
As shown in Table 1, Comparative Examples 1 to 3 are conjugate fibers bonded side-by-side using the die described in JP-A-09-157941 (Comparative Examples 2 and 3 also change component B). , 3 was dried at 70°C. Otherwise, the procedure was the same as in Example 1. The obtained short fibers were inferior in spinning stability and contained many broken yarns and fused yarn portions. In addition, in the case of latently crimpable conjugate fibers laminated side-by-side, in the process of drawing spun undrawn yarn, there is a characteristic that it is easy to fuse with adjacent fibers due to the heat of drawing, and the fused fibers are mixed. bottom. The quality of the spun yarn deteriorated due to the effects of these yarn breaks and fused portions.

[Examples 6-8]
In Examples 6 to 8, the single fiber fineness was changed, and in Example 8, the tow drying temperature was changed to 50°C. Otherwise, in the same manner as in Example 1, an eccentric core-sheath composite staple fiber was obtained.

[Comparative Examples 4 and 5]
In Comparative Examples 4 and 5, eccentric core-sheath composite staple fibers were obtained in the same manner as in Example 1 except that the single fiber fineness was changed. The staple fibers obtained in Comparative Example 4 had poor spinning stability, and as a result, the spun yarn quality deteriorated. In Comparative Example 5, there was no problem in terms of spinning stability, but the quality of the spun yarn deteriorated due to the large single fiber fineness.

[Examples 9 to 14]
Eccentric core-sheath conjugate short fibers were obtained in the same manner as in Example 1 except that the S/D size was changed in Examples 8-10 and the composite ratio in Examples 11-13 as shown in Table 1.

[Comparative Examples 6-7]
In Comparative Example 6, the composite form was as shown in Fig. 4 (however, the thin skin was present and the core component was not exposed). Except for this, the same procedure as in Example 1 was carried out.

[Examples 15-17]
In Example 15, the tow drying temperature was 80°C. In Example 16, the tow drying temperature was 90°C. In Example 17, a crimped tow having a number of crimps of 8 crimps/25 mm and a degree of crimping of 8% was obtained by mechanically crimping the tow at a pressing pressure of 1.0 kg/cm ² G. was performed at 60°C. Others were the same as in Example 2.

[Comparative Examples 8 and 9]
In Comparative Example 8, the tow was dried at a temperature of 100°C. In Comparative Example 9, a crimped tow having a number of crimps of 5 crimps/25 mm and a degree of crimping of 5% was obtained by mechanically crimping the tow at a pressing pressure of 0.7 kg/cm ² G. was performed at 55°C. Others were the same as in Example 2. Since the staple fibers obtained in Comparative Example 8 had a high number of crimps and a high degree of crimping, the quality of the spun yarn was poor, and crimps were developed during the drying process of the tow. gave inferior results. Since the staple fibers obtained in Comparative Example 9 had a low number of crimps and a low degree of crimping, the cardability was poor and the quality of the spun yarn was lowered.

a: Gravity center point of A component in conjugate fiber cross section C: Gravity point of conjugate fiber cross section S: Minimum thickness of B component D: Fiber diameter IFR: Curvature radius of interface between A component and B component in conjugate fiber cross section 5-(a ): Of the distribution holes in the final distribution plate, the distribution holes for the B component that form the thin skin
5-(b): Among the distribution holes in the final distribution plate, distribution holes for the B component other than 5-(a) 5-(c): Among the distribution holes in the final distribution plate, the distribution holes for the A component

Claims (1)

In the cross section of a composite fiber composed of two types of polyesters, the A component and the B component, the A component is completely covered with the B component, and the minimum thickness S and the fiber diameter D of the B component covering the A component ratio S/D is 0.01 to 0.1, and the peripheral length of the fiber in the portion whose thickness is within 1.05 times the minimum thickness S is 1/3 or more of the peripheral length of the entire fiber, and heat treatment The number of crimps before is 8 to 20 crimps/25 mm, the crimp degree is 8 to 25%, and the number of crimps is 50 crimps/25 mm or more when heat treated at 180°C without load. An eccentric core-sheath composite short fiber characterized by having a single fiber fineness of 0.5 to 2.4 dtex.