JP7427882B2 - Nonwoven fabric using eccentric core-sheath composite short fibers - Google Patents

Description

The present invention relates to a nonwoven fabric using eccentric core-sheath composite short fibers.

Synthetic fibers made from thermoplastic resins such as polyester and polyamide have excellent properties such as strength, heat resistance, chemical resistance, and wash-and-wear properties, so they are widely used in clothing, industrial materials, and nonwoven fabrics. It is being Among these uses, fibers with high stretchability and elastic recovery are required for use in daily life materials, particularly in nonwoven fabrics for adhesive base materials, due to requirements for functionality and fit.

Patent Document 1 proposes a latent crimpable conjugate fiber made of a conjugate fiber in which two component polymers (polyester) having different viscosities are laminated side-by-side as a method of imparting stretchability to polyester fibers. Since this latent crimpable conjugate fiber is largely curved toward the high shrinkage component side after heat treatment, the continuation of this curve forms a three-dimensional spiral structure. Therefore, the structure expands and contracts like a spring, making it possible to obtain fibers with high stretchability and elastic recovery.

However, in the manufacturing method proposed in Patent Document 1, the yarn bends significantly immediately after spinneret spinning due to the difference in melt viscosity between the two types of polymers, and even a small amount of dirt on the spinneret surface may cause yarn breakage, causing the spinning operation to be interrupted. Sex is bad. In particular, short fibers need to be produced with spindles of several hundred to several thousand hours from the viewpoint of production efficiency and cost. There is a problem that thread breakage easily occurs. In non-woven fabrics, in order to make the base material thinner and to obtain a homogeneous non-woven fabric with no unevenness in thickness or thinness, it is also required to increase the fineness of the single fibers. Remarkable.

In Patent Document 1, yarn bending is suppressed by reducing the viscosity difference between two types of polymers, but since a certain viscosity difference is required to obtain sufficient latent crimp development, yarn bending is The effect of inhibition is small, and the effect of spinning stability is small. If the viscosity difference is made larger than this, the spinnability will further deteriorate, making it difficult to improve stretchability and elastic recovery. Therefore, in the example of Patent Document 1, a needle punching process is used in which the fibers are less entangled with each other, and the latent crimp-producing fibers are mixed at a high blending rate of 95% by weight, which increases the elongation rate of the nonwoven fabric. It has an easy-to-use non-woven design.

The parts where the yarn breaks during spinning or the fused parts that occur due to yarn shaking are subjected to the thermal history of the spinning process and shrink, becoming fused fibers (thicker yarns than normal fibers, or yarns made of multiple fused yarns). . In addition, in the short fiber manufacturing process, there is a step in which the undrawn yarn after spinning is stretched with hot water above the polymer glass transition temperature. It has the characteristic that it easily fuses with other fibers, increasing the risk of contamination with fused fibers. These fused fibers are exposed on the surface of the nonwoven fabric and become defects, resulting in an increase in the work required to remove the defects and an accompanying increase in waste.

Patent Document 2 proposes an actual crimpable conjugate short fiber in which, in a fiber cross section of a conjugate fiber containing a first component and a second component, the center of gravity of the second component is shifted from the center of gravity of the fiber. . Because of the core-sheath structure, yarn bending during discharge is suppressed, and excellent spinning stability is obtained, resulting in an overtly crimpable composite short fiber having wave-shaped crimp and spiral crimp. 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 for fibers that do not develop latent or overt crimps. Therefore, when crimping occurs in a simple eccentric core-sheath composite fiber, the essential stretch performance is poor, and it is difficult to say that the material has satisfactory stretch performance. In addition, when the fineness is used, there is a problem that the stretch performance is even worse.

Although the eccentric core-sheath fiber proposed in Patent Document 3 is a filament, it suppresses yarn bending directly under the spinneret and obtains good spinnability, so that fibers with a single fiber fineness of 1.0 dtex or less can be obtained, and Sufficient stretchability is obtained. However, the number of spindle holes actually used in the example of Patent Document 3 is less than 100H, which makes it easy to carry out flow straightening in the polymer cooling process after spinneret spinning, and to easily suppress yarn shaking. However, from the viewpoint of production efficiency, short fibers require production at several hundred to several thousand hours, so even with this method, it is possible to suppress yarn breakage at yarn bends. Fineness is difficult to achieve.

Japanese Patent Application Publication No. 2014-148768 JP2016-106188A WO2018/110523 publication

The present invention overcomes the problems of the prior art, improves the quality of the nonwoven fabric, and provides a nonwoven fabric with sufficient stretch performance.

In order to achieve the above object, the present invention employs the following configuration.

(1) In the cross section of a composite fiber made of two types of polyesters, component A and component B, component A is 2 to 7 mol% of 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane and isophthalic acid. A copolymerized polyester mainly composed of ethylene terephthalate units copolymerized with 5 to 13 mol% of ethylene terephthalate units, a polyester in which the B component is substantially composed of ethylene terephthalate units , the A component is completely covered with the B component, and the A component is The ratio S/D of the minimum thickness S of the covering B component to the fiber diameter D is 0.01 to 0.1, and the peripheral length of the fiber in the part where the thickness is within 1.05 times the minimum thickness S is 1/3 or more of the circumference of the whole fiber, the single fiber fineness is 0.5 to 1.8 dtex, and the number of crimps in the nonwoven fabric is 50 crimp/25 mm or more. % or more, the elongation rate is 20% or more and 85% or less, and the elongation recovery rate is 60% or more and 80% or less .

By using the eccentric core-sheath composite short fibers of the present invention, the quality of the nonwoven fabric can be improved and a nonwoven fabric having sufficient stretch performance can be obtained.

FIG. 1 is an example of the eccentric core-sheath composite short fiber of the present invention, and is a fiber cross section for explaining the position of the center of gravity in the fiber cross section. FIG. 2 is a fiber cross section for explaining the fiber diameter (D) and minimum thickness (S) of 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 short fiber of the present invention. FIG. 4 is an example of a fiber cross section of an eccentric core-sheath composite staple fiber other than the present invention. FIG. 5 is an example embodiment of a distribution arrangement on the final distribution plate.

The present invention will be explained in detail below.

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

The polymer mentioned here is preferably a fiber-forming thermoplastic polymer, and in view of the purpose of the present invention, a combination of polymers that causes a difference in shrinkage when subjected to heat treatment is suitable; A combination of polymers with different molecular weights or compositions such that the difference in melt viscosity is 40 Pa·s or more is suitable.

Melt viscosity as used in the present invention refers to the strain when a chip-shaped polymer is measured in a vacuum dryer with a moisture content of 200 ppm or less, the strain rate is changed stepwise, and the measurement temperature is the same as the spinning temperature. This is the value at a speed of 1216s ^-1 . If the melt viscosities of the polymers constituting the composite fibers differ by 40 Pa·s or more, stress will be concentrated on the polymer components with higher melt viscosity in the spinning line, for example. Therefore, in the case of a core-sheath type cross-section or a sea-island type cross-section, stress is concentrated on the main polymer, resulting in excellent mechanical properties, and in the case of a bonded-type cross-section, the stress is noticeable due to the orientation of the combined components. This creates a difference, and it becomes possible to develop a suitable crimp.

Suitable polymers for achieving the purpose of the present invention include polyethylenes such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyamides, polylactic acid, thermoplastic polyurethanes, polyphenylene sulfides, and co-producers thereof. Examples include polymerized polymers. It is also possible to change these molecular weights and use a high molecular weight polymer for component A and a low molecular weight polymer for component B shown in Figure 1, or use one component as a homopolymer and the other component as a copolymer. .

In addition, for combinations with different polymer compositions, for example, A component/B component may be polybutylene terephthalate/polyethylene terephthalate, polytrimethylene terephthalate/polyethylene terephthalate, thermoplastic polyurethane/polyethylene terephthalate, polytrimethylene terephthalate/polybutylene terephthalate, etc. Various combinations are possible.

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. The polyester mentioned here includes polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, those copolymerized with a dicarboxylic acid component, diol component, or oxycarboxylic acid component, or a blend of these polyesters.

Among the above-mentioned polymers, component A is a copolymerized polyester having ethylene terephthalate units as a main structural unit, and the copolymerized component is 2,2-bis[4- Polyethylene terephthalate copolymer modified using (2-hydroxyethoxy)phenyl]propane (BHPP) or its ester-forming derivative (hereinafter, ester-forming derivatives may also be referred to as BHPP) and isophthalic acid (IPA). It is preferable that the polyester (hereinafter also referred to as polyester (A)) is a polyester in which component B is substantially an ethylene terephthalate unit. In the present invention, the copolymerization ratio of BHPP in the polyester (A) is preferably 2 to 7 mol%. If the copolymerization ratio of BHPP is less than 2 mol %, the shrinkage properties will be insufficient, and when made into a nonwoven fabric, the elongation rate and elongation recovery rate will be small and sufficient elastic function may not be obtained. On the other hand, if it exceeds 7 mol %, the melting point of the polymer decreases, which tends to impair thermal stability.

The copolymerization ratio of IPA in the polyester (A) is preferably 5 to 13 mol%. If the copolymerization ratio of IPA is less than 5 mol %, it is difficult to obtain substantially large crimp, while if it exceeds 13 mol %, the melting point of the polymer decreases, so thermal stability tends to be impaired.
In addition, as the copolymerized polyester of component A, a copolymerized polyester containing 5-sodium isophthalic acid (5-SIPA) as a copolymerization component instead of IPA or in combination with IPA can also be mentioned as a preferred embodiment.

The polyester consisting essentially of ethylene terephthalate units as component B is a polyester mainly composed of ethylene terephthalate units, and preferably contains 85 mol% or more of ethylene terephthalate units. In order to have lower heat shrinkage than the above-mentioned copolymerized polyester, it is preferable that it does not contain components that significantly inhibit crystallinity, BHPP, IPA, sulfonic acid base compounds, etc. It is.

In addition, when the A component/B component is a combination of polybutylene terephthalate/polyethylene terephthalate or polytrimethylene terephthalate/polyethylene terephthalate, a sufficient elongation rate and elongation recovery rate can be obtained when processed into a nonwoven fabric, and it has excellent stretch performance. However, the combination of a polyethylene terephthalate copolyester modified with BHPP and IPA as the A component and a polyester that is substantially ethylene terephthalate units as the B component has a better elongation recovery rate. This is a more preferable form.

However, the combination of polytrimethylene terephthalate/polyethylene terephthalate has low rigidity and has a soft texture, so it is suitable for applications that require a soft texture.

Furthermore, the composite short fibers in the present invention are composed of a combination of polymers that cause a difference in shrinkage when heat treated, so they develop crimps during heat treatment. It is preferable to have a latent crimp ability such that the number of crimp developed during heat treatment under no load is 50 crimp/25 mm or more. If the number of developed crimps is less than 50 crimps/25 mm, the stretchability of the nonwoven fabric will be significantly reduced, resulting in low stretchability. There is no particular upper limit to the number of expressed crimps. The above-mentioned developed crimp number (potential crimp ability) can be achieved by adjusting the types of polymers to be combined, their area ratios (described later), the cross-sectional structure of the eccentric core-sheath, and the like.

Regarding the composite area ratio of the A component and B component in the fiber cross section in the composite short fiber in the present invention, from the viewpoint of crimp development, a fine spiral structure can be achieved by increasing the ratio of the high shrinkage component, which is the A component. In addition, since it is necessary to have excellent physical properties as an eccentric core-sheath composite short fiber, the ratio of both components is in the range of A component: B component = 70:30 to 30:70 (area ratio). is preferable, and the range of 65:35 to 45:55 is more preferable.

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

Here, the eccentricity referred to in the present invention refers to the fact that the center of gravity of the component A polymer in the cross section of the composite short fiber is different from the center of the cross section of the composite short fiber, and will be explained using FIG. 1.

In Fig. 1, the horizontal hunting is the B component, the 30 degree hunting (slanted line upward 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 the center of gravity of the A component in the cross section of the composite short fiber. The center of gravity is C.

In the present invention, it is important that the center of gravity point a of component A and the center of gravity point C of the cross section of the composite short fibers are apart from each other, so that the fibers are largely curved toward the high-shrinkage component after heat treatment. Therefore, by continuing to curve the composite fiber in the fiber axis direction, it takes on a three-dimensional spiral structure and exhibits good crimp. Here, the further apart the center of gravity is, the better the crimp will be, and the better the stretch performance will be.

In the present invention, since component A is completely covered by component B, the quality of the nonwoven fabric can be maintained because no whitening phenomenon or fluffing occurs even when friction or impact is applied to the fibers or nonwoven fabric. In addition, high molecular weight polymers, high elasticity polymers, etc., which are exposed on the surface and are a disadvantage of composite fibers in conventional simple bonded structures, can also be used as one component of composite short fibers.

In addition, since one component A is completely covered with the other component B, it also has the effect of retaining fiber properties well even if a polymer with low heat resistance or abrasion resistance, or a hygroscopic polymer is used. I can do it.

The composite short fibers in the present invention must have a ratio S/D of the minimum thickness S of the B component covering the A component and the fiber diameter (diameter of the composite fiber) D of 0.01 to 0.1. be. Preferably it is 0.02 to 0.08. Within this range, it is possible to obtain excellent abrasion resistance and sufficient crimp development power and stretch performance.

Originally, good stretch performance can be obtained by having the respective polymers in contact only at the bonding interface, and if the high shrinkage component is completely covered with the low shrinkage component, the stretch performance will deteriorate. However, by setting the thickness of component B within the range of the present invention, it became possible to obtain a composite staple fiber that satisfies both stretch performance and abrasion resistance.

This will be explained in more detail using the fiber cross section shown in FIG. Here, the thinnest part of component B in the core-sheath composite staple fiber is the minimum thickness S.

Furthermore, it is important that the portion having a thickness within 1.05 times the minimum thickness S accounts for 1/3 or more of the total circumference of the composite staple fiber. This means that the A component exists along the contour of the fiber, and compared to 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 further apart, forming a fine spiral and exhibiting good crimp. More preferably, by setting the circumference of a thickness within 1.05 times the minimum thickness S to 2/5 or more of the circumference of the entire fiber, good stretch performance without crimp spots can be obtained.

Further, when the radius of curvature IFR of the interface between the A component and the B component in the fiber cross section is a value R obtained by dividing the fiber diameter D by 2, it is preferable that the following formula 1 is satisfied. The radius of curvature IFR referred to here is a circle (dashed line ) refers to the radius.
(IFR/R)≧1...(Formula 1)
This means that the interface is closer to a straight line. The present invention has a cross-sectional shape similar to that of conventional bonded crimped fibers, and the interface between A component and B component is a curved line close to a straight line, thereby achieving high crimping that could not be achieved with conventional eccentric core-sheath composite fibers. It is preferable because it can be expressed. More preferably, it is 1.2 or more.

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

That is, an eccentric core-sheath composite short fiber is embedded in an embedding agent such as an epoxy resin, and an image of this cross section is photographed using 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 contrast at the junction between component A and component B can be made clear by utilizing the difference in dyeing between the polymers. The value obtained by measuring the diameters of 10 circumscribed circles randomly extracted within the same image from each photographed image corresponds to the fiber diameter D in the present invention. Here, if it is impossible to observe 10 or more fibers, it is sufficient to observe 10 or more fibers in total including other fibers. The circumscribed circle diameter referred to here means the diameter of a perfect circle that is most circumscribed at two or more points on a cross section perpendicular to the fiber axis from a two-dimensionally photographed image. do.

Further, the value obtained by measuring the minimum thickness of the B component covering the A component for 10 or more fibers using the image obtained by measuring the fiber diameter D corresponds to the minimum thickness S as referred to in the present invention. Furthermore, the fiber diameter D, minimum thickness S, and radius of curvature IFR are measured in μm and rounded to the third decimal place. A simple numerical average value of the measured values and their ratios (S/D) is determined for the 10 images taken during the above operations.

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

The single fiber fineness of the composite short fibers in the present invention is preferably 0.5 dtex or more and 2.5 dtex or less. When it is less than 0.5 dtex, the card passing property is poor, which may lead to winding around the card cylinder and generation of card nep. If it exceeds 2.5 dtex, it may lead to uneven basis weight of the nonwoven fabric. More preferably, it is 0.8 detx or more and 1.8 dex or less, and still more preferably 1.0 T detx or more and 1.5 dex or less.

The composite staple fiber in the present invention can be produced by the following spinning method.

After melting the polymers of component A and component B and forming a composite stream at a predetermined mass ratio using a composite melt spinning device, the mixture is passed through a spinneret having 100 to 2000 discharge holes with a hole diameter of 0.2 to 0.6 mm. Melt spinning is performed at a spinning temperature higher than 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 at least +20°C higher than the polymer melting point, it is possible to prevent the polymer from solidifying and clogging in the spinning machine piping, and by setting the temperature higher to +60°C or less, excessive polymer buildup can be prevented. This is preferable because thermal 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 employ a melting method using an extruder from the viewpoint of uniform melting and prevention of stagnation. The molten polymer passes through the piping, is metered, and then flows into the cap pack. At this time, in order to suppress thermal deterioration, it is preferable that the passage time through the pipe is 30 minutes or less. The molten polymer that has flowed into the pack is spun out from a spinneret.

Further, since the present invention relates to short fibers, from the viewpoint of production efficiency, a multi-hole ferrule is usually used, and it is necessary to use a ferrule of 100H or more. Considering the market price of short fibers, it is more preferable that it is 300H or more, and even more preferable that it is 600H or more.

Generally, as the number of holes increases, it becomes more difficult to uniformly cool the spun yarn, and in addition, turbulent flow occurs directly under the spinneret, making stable spinning difficult. Furthermore, in eccentric core-sheath composite spinning and side-by-side composite spinning using two components, yarn bending occurs after the polymer is discharged, making stable spinning more difficult. However, by creating a cross section like that of the present invention, it is possible to suppress yarn bending that occurs due to the difference in flow velocity between the two types of polymers when they are discharged from the nozzle. In other words, the presence of the sheath component generates a force in the direction opposite to the bending direction of the polymer flow, which suppresses the force in the direction perpendicular to the spinning line caused by the difference in flow speed between the two types of polymers during discharge from the spinneret. be able to. In addition, by controlling the cooling of the yarn and the convergence position of the yarn from the discharge surface of the spinneret as described below, it becomes possible to perform stable spinning even if a spinneret with a large number of spindle holes is used.

Regarding the method of cooling the yarn, it is preferable to rapidly cool it directly below the cap, using a cold air blowing device with an air temperature of 10 to 50°C, a cooling start position at a position of 0 to 200 mm directly below the cap, and a cooling length of 10 to 400 mm. It is preferable to cool down at a rate of 30 to 120 m/min. A more preferable range of the cooling start position is a position of 20 mm to 100 mm, where the mouth surface is less likely to get cold and yarn shaking can be suppressed more effectively. This cooling process suppresses the turbulent flow that occurs directly under the spinneret and suppresses yarn shaking.Also, by rapidly cooling the yarn, the solidification position of the polymer is raised, making it difficult to cause yarn breakage due to yarn shaking. . By creating a cross section like that of the present invention, it was possible to suppress yarn bending after polymer discharge, so even when spinning with a spindle of 100H or more, cooling can be started directly under the spinneret. This made it possible to manufacture composite fibers using a die. A method for achieving the same effect by rapid cooling directly below the cap is to use a suction cooling device with a suction start position 0 to 200 mm directly below the cap and a suction length of 10 to 400 mm, and perform suction at a rate of 30 to 120 m/min. It is also possible to carry out cooling.

In addition, it is preferable to rectify the flow immediately after rapid cooling directly under the cap, 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, and cooling at a rate of 20 to 90 m/min. It is preferable to perform cooling under conditions of a wind speed of or less than . If the speed is higher than the wind speed of the cooling air directly under the nozzle, the yarn sways will become large, causing yarn breakage and yarn fusion, and stable spinning may not be possible.

The distance from the discharge surface of the nozzle to the convergence position of the threads is preferably 2000 mm or less. By setting the distance from the nozzle discharge surface to the yarn convergence point to 2000 mm or less, the width of yarn sway due to cooling air can be suppressed, and accompanying airflow until the yarn converges can be suppressed, resulting in stable yarn breakage with less yarn breakage. It is preferable because it is easy to obtain yarn spinning properties. A more preferable range of the convergence position of the threads in the spinning process is 1600 mm or less.

In the step of drawing the spun undrawn yarn, the undrawn yarn is bundled into a bundle of 30 to 300 ktex and stretched 2 to 5 times in steam or hot water at a temperature equal to or higher than the glass transition temperature. Thereafter, a tension heat treatment is performed, and crimping is applied using a push-in crimper or the like.

Next, the stretched tow after being crimped is dried, an aqueous finishing oil solution is applied to the tow by spraying, and the tow is cut to produce the composite staple fiber of the present invention.

In the case of latent crimp composite fibers that are laminated side-by-side, the process of drawing the spun undrawn yarn has the characteristic that it tends to fuse with adjacent fibers due to the drawing heat, increasing the risk of contamination with fused fibers. . This is a problem that is conspicuous in the production process of short fibers, and the composite fiber of the present invention solves this problem unique 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 component A is completely covered by component B, this reduction in fusion is alleviated, and It is possible to suppress the contamination of fused fibers. Since the lower the melting point, the easier the fibers are to fuse together, it is expected that the number of fused fibers will further decrease when a component with a lower melting point is used as component B compared to component A.

In addition, by drawing the undrawn yarn while preheating it to 40 to 60° C. before drawing, it is possible to further suppress the formation of fused fibers.

During the nonwoven fabric processing process, the fused fibers are exposed on the surface of the nonwoven fabric and become defects, which increases the work required to remove the defects and increases the resulting amount of waste. Therefore, the number of fused fibers contained in 20 kg of short fibers of the present invention is preferably 7 or less, more preferably 4 or less.

It is preferable that the number of crimps of the composite fiber in the present invention (the number of crimps before heat treatment) is 8 to 24 crimps/25 mm, and the degree of crimp is 8 to 30%. The number of crimp and the degree of crimp mentioned here refer to the numerical values after cutting the stretched tow.

If the number of crimps is less than 8/25 mm or the degree of crimp is less than 8%, card passing properties will be extremely poor. Also, if the number of crimp is higher than 24 threads/25 mm or the degree of crimp is higher than 30%, the card passing performance will be extremely poor, and after the card passes, neps will occur frequently or the fabric weight will be uneven. This will significantly reduce the quality of the nonwoven fabric.

A more preferable range of the number of crimps is 10 to 20 crimps/25 mm, and an even more preferable range is 12 to 17 crimps/25 mm.

The degree of crimp is more preferably in the range of 9 to 25%, and even more preferably in the range of 14 to 20%.

In order to obtain the number of crimps and the degree of crimp of the present invention, the tension heat treatment temperature, tension heat treatment time, temperature of the tow when entering the push-type crimper, pushing pressure of the push-type crimper, and crimping It is important to set the drying temperature of the tow after application.

Tension heat treatment is performed by heat setting while maintaining tension, and then cooling to below the glass transition temperature with cooling water to fix the structure of the molecular chains. Crimp development can be suppressed, and high crimp development ability can be exhibited by heat treatment in higher-order processing steps such as spinning and nonwoven fabrics.

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, crimp development may occur excessively in the subsequent drying step of the tow after crimping, and the latent crimp characteristics may deteriorate. Furthermore, 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 upon entering the push-in crimper is preferably 20 to 60°C. If the temperature is less than 20°C, the degree of crimp will be low and the degree of crimp of the present invention may not be obtained, and if it is higher than 60°C, the degree of crimp will be high and the degree of crimp of the present invention may not be obtained. Sometimes.

The pushing pressure of the pushing type crimper is preferably 1 to 3 kg/cm ² G. When it is less than 1 kg/cm ² G, the number of crimp or the degree of crimp becomes low, and when it is higher than 3 kg/cm ² G, the number of crimp or the degree of crimp tends to become high.

The drying temperature of the tow after crimping is preferably 80 to 120°C. If the temperature is lower than 80℃, it may not be possible to dry the tow sufficiently, and if the temperature is higher than 120℃, crimp will occur during the drying process, and heat treatment in higher processing steps such as spinning and non-woven fabrics may not dry the tow sufficiently. In some cases, proper crimp expression may not be obtained.

By having the cross-sectional shape of the present invention, crimp development in the yarn spinning process is moderately suppressed, and the crimp of the present invention can be obtained relatively easily. Although the detailed mechanism has not been elucidated, it is thought that the thin part of the B component that covers the A component can appropriately suppress the shrinkage of the A component. When the A component is exposed in a cross section such as a side-by-side type cross section, especially when the difference in melt viscosity between the two component polymers is large, crimp occurs during the spinning process, for example, when the tow dries after being crimped, and stretching Since the number of crimps and the degree of crimping after cutting the tow tend to increase, it is relatively difficult to control crimps during the spinning process.

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

The cutting strength of the composite short fibers in the present invention is preferably 1.5 to 5.0 cN/dtex, more preferably 2.5 to 4.0 cN/dtex, and if the cutting strength is lower than 1.5. , the strength of the nonwoven fabric is extremely reduced. Moreover, if the cutting strength is higher than 5.0 cN/dtex, the cuttability will be significantly reduced in the process of cutting the nonwoven fabric.

The cutting elongation of the composite staple fiber in the present invention is preferably 10 to 50%, more preferably 20 to 40%. If the cutting elongation is less than 10%, fries occur frequently during the carding process and workability deteriorates. If it is higher than 50%, the cuttability will be significantly reduced in the nonwoven fabric cutting process.

It is preferable to precisely control the sheath thickness and the circumference of the thin skin part of the composite staple fiber in the present invention, and examples thereof are shown in JP-A No. 2011-174215, JP-A No. 2011-208313, and JP-A No. 2012-136804. A method using a distribution plate is preferably used. When manufacturing a fiber having an eccentric core-sheath type cross section using a conventionally known composite die, 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, if the sheath thickness becomes thinner and the core component is exposed, friction and impact may cause whitening of the fabric or fluffing, while conversely, if the sheath thickness becomes thicker, crimping may occur. As a result, a problem such as a decrease in stretch performance may occur.

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

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

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

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

Here, although the composite short fibers in the present invention are as described above, it is preferable that the B component completely covers the A component as shown in FIG. By having a cross section like that of the present invention, it is possible to suppress the bending of the discharge line (kneeing phenomenon) that occurs due to the difference in flow velocity between the two types of polymers during discharge from the nozzle. In other words, the presence of the sheath component generates a force in the direction opposite to the direction in which the polymer flow curves, and as a result, the force in the direction perpendicular to the spinning line, which is generated from the difference in flow speed between the two types of polymers when they are discharged from the spinneret, is It can be suppressed.

In addition, in the case of a conventional simple bonded structure (bimetal structure), there is a difference in the stress balance applied to each polymer during thinning on the spinning line after discharge from the spinneret, causing uneven elongation deformation, which causes uneven fineness. In some cases, it manifested as This tendency is very noticeable when finer fineness is achieved by combining polymers with a large viscosity difference or by reducing the discharge amount, but in the present invention, it is possible to As a result, the stress balance is balanced within the fiber cross section, and uneven fineness can be suppressed.

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

This dramatically increases the degree of freedom in selecting polymers for improving added value other than improving stretch performance and improving spinning stability even in fine-grained yarns, which also contributes to improved productivity.

Furthermore, from the viewpoint of suppressing the bending of the discharge line, the difference in melt viscosity of the polymers used in the composite short fibers of the present invention is also important. When the two types of melted polymers forming the composite fiber are contracted, the cross-sectional area is changed in the cross section perpendicular to the polymer flow direction in order to match the pressure loss of the two types of polymers, thereby reducing the flow velocity difference. These particles are discharged with a biased center of gravity, resulting in a curved discharge line.

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

In this way, when the bending of the discharge line is suppressed, interference between single fibers on the spinning line can be suppressed, thereby increasing the discharge hole density on the spinneret, that is, the number of discharge holes per spinneret. This makes it possible to achieve sophistication and improve production efficiency by increasing the number of threads.

At this time, it is preferable to set the spinning draft to 300 times or less because homogeneous fibers with suppressed variations in physical properties among yarns can be obtained.

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

By setting the spinning draft to 50 or more, the polymer flow discharged from the spinneret hole is prevented from remaining directly under the spinneret for a long time, and staining of the spinneret surface can be suppressed, resulting in stable yarn reeling properties. Further, by setting the spinning draft to 300 or less, yarn breakage due to excessive spinning tension can be suppressed, and eccentric core-sheath composite staple fibers can be obtained with stable spinnability, which is preferable. More preferably it is 80-250.

The nonwoven fabric of the present invention needs to contain 70% by mass or more of the composite short fibers. If the content of the composite short fibers is less than 70% by mass, a nonwoven fabric with excellent stretchability cannot be obtained.

That is, in addition to the composite short fibers of the present invention, ordinary polyester fibers, heat-adhesive binder fibers, natural fibers such as cotton, wool, hemp, and the like can be appropriately blended into the nonwoven fabric of the present invention.

The nonwoven fabric of the present invention is obtained by carding the raw cotton (short fibers) made of the composite short fibers alone or blending them with ordinary polyester fibers or heat-adhesive binder fibers as necessary to create a fiber web. After applying needle punching or spunlace processing to the fibrous web as necessary, it is heat-treated in a free state to reveal latent crimp, thereby creating entanglement between the fibers, which has excellent elastic recovery properties. A nonwoven fabric can be obtained.

In the nonwoven fabric of the present invention, the composite short fibers must be developed by heat treatment, and the number of crimps in the nonwoven fabric must be 50 crimp/25 mm or more. If the number of crimps is less than 50 crimps/25 mm, the stretchability when made into a nonwoven fabric is significantly reduced, resulting in low stretchability. There is no particular upper limit to the number of expressed crimps.

The elongation rate of the nonwoven fabric of the present invention is preferably 20% or more. If the elongation rate is less than 20%, it may not be applicable to applications requiring elasticity.

Further, the elongation recovery rate of the nonwoven fabric of the present invention is preferably 60% or more. If the elongation recovery rate is less than 60%, it may become easily deformed by external force.

The basis weight of the nonwoven fabric of the present invention is preferably 20 to 300 g/m ² . If the basis weight is less than 20 g/m ² , it is difficult to obtain sufficient strength of the nonwoven fabric, and if the basis weight exceeds 300 g/m ² , the desired elasticity may not be obtained. In order to obtain more appropriate strength and elasticity, the basis weight is preferably 50 to 150 g/m ² .

The elongation rate was determined using a tensile testing machine for a nonwoven fabric test piece (5 cm width x 60 cm length), with one end of the test piece fixed with an upper clamp and an initial load of 29 mN applied to the other end. Next, marks are made at 20 cm intervals, the initial load is removed, and a load (A) of 0.98 N per 1 cm width of the specimen is gently applied. After standing for 1 minute, the length between the marks was measured, and the elongation rate (%) was calculated using the following formula, and expressed as the average value of 3 times.
・Elongation rate (%) = {(L1-L0)/L0}×100
However, L0 is the original length between the marks (20 cm), and L1 is the length (cm) between the marks after applying the load (A) and leaving it for 1 minute.

The elongation recovery rate was determined using a tensile tester using a test piece similar to that used for measuring the elongation rate described above. One end of the test piece was fixed with an upper clamp, and an initial load of 29 mN was applied to the other end. Next, marks are made at 20 cm intervals, the initial load is removed, and a load (A) of 0.98 N per 1 cm width of the specimen is gently applied. After leaving it for 1 minute, measure the length between the marks, immediately remove the load (A), and leave it for another 3 minutes. After repeating this operation five times, the length between the marks was measured again under the initial load, and the elongation recovery rate (%) was calculated using the following formula, and expressed as the average value of the three measurements.
・Recovery growth rate (%) = {(L01-L02)/(L01-L00)}×100
However, L00 is the original length between the marks (20 cm), L01 is the length between the marks after applying the load (A) and leaving it for 1 minute (cm), and L02 is the length between the marks after removing the load (A). This is the length (cm) between the marks under the initial load after being left for a minute.

In the nonwoven fabric of the present invention, by using eccentric core-sheath composite short fibers with a fineness of 1.8T or less, more preferably 1.5T or less, a thin nonwoven fabric with excellent flexibility can be obtained.

Moreover, the lower the melt viscosity of the B component used in the eccentric core-sheath composite short fibers in the nonwoven fabric of the present invention, the more excellent the flexibility of the nonwoven fabric can be obtained. When the melt viscosity of component B is 60 Pa·s or less, more preferably 45 Pa·s or less, a nonwoven fabric with better flexibility can be obtained. Moreover, even if polybutylene terephthalate or polytrimethylene terephthalate is used as the A component, a soft nonwoven fabric can be obtained. This is because eccentric core-sheath composite short fibers using polymers with low melt viscosity or polybutylene terephthalate or polytrimethylene terephthalate have low bending rigidity.

<Evaluation method>
<Polymer melt viscosity>
The chip-shaped polymer was reduced to a moisture content of 200 ppm or less using a vacuum dryer, and the melt viscosity was measured by changing the strain rate stepwise using Capillograph 1B manufactured by Toyo Seiki. The measurement temperature was the same as the spinning temperature, and the examples and comparative examples have a melt viscosity of 1216 s ^-1 . Incidentally, the time from the time the sample was placed in the heating furnace to the start of measurement was 5 minutes, and the measurement was performed under a nitrogen atmosphere.

<Silking stability>
Each example was spun for 8 hours, and a relative evaluation was made based on the number of spun yarn breaks, and the results were evaluated in four stages.
◎ (Extremely good): Number of thread breakages: 0 to 1 times ○ (Good): Number of thread breaks: 2 to 5 times Δ (Slightly poor): Number of thread breaks: 6 to 10 times × (Poor): Number of thread breaks: 11 More than once.

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

<Number of crimps (crest/25mm)>
It was measured according to the method of JIS-L1015 (2010).

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

<Number of fused fibers (ko/20kg)>
Pass 20 kg of short fibers through a roller card (SC-300RT, manufactured by Daiwa Kiko Co., Ltd.), observe the web discharged from the card, and visually count the number of fused fibers that stand out on the front and back sides of the web. A relative evaluation was made based on the number of , and a five-level evaluation was made from A to E. The conditions of the roller card were as follows: cylinder rotation speed: 357 rpm, doffer rotation speed: 11 rpm, taker-in rotation speed: 300 rpm, feed roller rotation speed: 3 rpm, and fly comb rotation speed: 1500 rpm. Here, the fused fiber refers to a fiber in which a plurality of yarns are fused together, or a fiber in which a single yarn is shrunk and is thicker than a normal yarn (a single yarn with a target fineness).
A (very good): Number of fused fibers: 1 piece/20 kg or less B (good): Number of fused fibers: 4 pieces/20 kg or less C (slightly good): Number of fused fibers: 7 pieces/20 kg or less D (slightly Defective): Number of fused fibers: 10 pieces/20 kg or less E (Defective): Number of fused fibers: 11 pieces/20 kg or more.

<Basic weight of nonwoven fabric (g/m ² )>
The weight of a 20 cm x 20 cm sample was measured according to the method of JIS-L1085 (1998), and the weight was determined as the mass per m ² .

<Number of crimp in nonwoven fabric (crest/25mm)>
A nonwoven fabric test piece (10cm x 10cm) was magnified 100 times with a microscope (manufactured by Keyence Corporation, VHS-900F), and when focusing from the top to the bottom of the nonwoven fabric, the fibers focused from the top The length per crimp was measured in order, converted to the number of crimp per 25 mm, and expressed as the average value of 20 different crimp lengths.

<Extension rate>
For a nonwoven fabric test piece (5 cm width x 60 cm length), one end of the test piece is fixed with an upper clamp using a tensile tester, and an initial load of 29 mN is applied to the other end. Next, marks are made at 20 cm intervals, the initial load is removed, and a load (A) of 0.98 N per 1 cm width of the specimen is gently applied. After standing for 1 minute, the length between the marks was measured, and the elongation rate (%) was calculated using the following formula, and expressed as the average value of 3 times.
・Elongation rate (%) = {(L1-L0)/L0}×100
However, L0 is the original length between the marks (20 cm), and L1 is the length (cm) between the marks after applying the load (A) and leaving it for 1 minute.

<Elongation recovery rate>
Using a tensile tester, one end of the test piece is fixed with an upper clamp, and an initial load of 29 mN is applied to the other end of the test piece similar to that used for measuring the elongation rate described above. Next, marks are made at 20 cm intervals, the initial load is removed, and a load (A) of 0.98 N per 1 cm width of the specimen is gently applied. After leaving it for 1 minute, measure the length between the marks, immediately remove the load (A), and leave it for another 3 minutes. After repeating this operation five times, the length between the marks was measured again under the initial load, and the elongation recovery rate (%) was calculated using the following formula, and expressed as the average value of the three measurements.
・Recovery expansion rate (%) = {(L01-L02)/(L01-L00)}×100
However, L00 is the original length between the marks (20 cm), L01 is the length between the marks after applying the load (A) and leaving it for 1 minute (cm), and L02 is the length between the marks after removing the load (A). This is the length (cm) between the marks under the initial load after being left for a minute.

<Thickness of nonwoven fabric>
The thickness of the nonwoven fabric was measured in accordance with JIS L 1908 (2010 edition). A presser foot with an area of 2500 mm ² is prepared. After applying a pressure of 2 kPa for a certain period of time, the thickness of a test piece whose size is 1.75 times or more the diameter of the presser foot is measured. The average value of 10 test pieces was calculated, and this value was taken as the thickness.

<Flexibility of nonwoven fabric>
It was measured in accordance with the Handle-ohmeter method of JIS L 1913 (2010 edition). Three samples with a size of 200 mm x 200 mm are taken. Place the sample on the sample stand so that the measurement direction is perpendicular to the slot (20 mm), lower the blade adjusted so that it is 8 mm below the sample stand surface, press the sample, and calculate the maximum pressure value at that time. read. For each sample, measurements are taken at different locations on the front and back in both the vertical and horizontal directions at a position 67 mm (1/3 of the sample width) from either side. For each sample, measure at 4 locations in the vertical direction and 4 locations in the horizontal direction, calculate the average value in the vertical direction and the horizontal direction of the values measured for a total of 3 samples, and add up the average values in the vertical direction and the horizontal direction. The lower the number, the better the flexibility.

[Example 1]
Polyethylene terephthalate (melt viscosity: 110 Pa・s, melting point: 225°C), which is a copolymerization of 7.0 mol% IPA and 4.0 mol% BHPP, was used as the polymer for component A, and polyethylene terephthalate (melt viscosity: 70 Pa・s) was used as the polymer for component B. , melting point: 260°C), and both the polymer of component A and the polymer of component B were melted at 280°C using an extruder, and then measured using a pump, and the melting temperature was set at 290°C, while maintaining the temperature. I let it flow into my account. The area ratio of the A component and the B component was set to 50/50, and they were flowed into a spinneret for eccentric core-sheath composite fibers having 600 holes. The respective polymers were combined inside the nozzle to form an eccentric core-sheath composite in which the polymer of component A was included in the polymer of component B, and was discharged from the nozzle. In addition, in the spinning of Example 1, a distribution plate-type die was used to obtain the eccentric core-sheath composite fiber shown in FIG. 1. The spun yarn was cooled while being taken off at a speed of 1300 m/min. The yarn was cooled from a position 20 mm from the spinneret using a cold air blowing device with an air temperature of 20°C, a wind speed of 70 m/min, and a cooling length of 30 mm, and then an air temperature of 20°C, a wind speed of 40 m/min, and a cooling length of 600 mm. It was cooled by a cold air blowing cooling device. After cooling the yarn, 0.1% by mass of process oil was applied, and 20 other spinning spindles were combined using a free roller and a converging 0.1% guide to obtain an undrawn yarn. The distance from the discharge surface of the nozzle to the yarn convergence position was 1600 mm. Thereafter, while keeping the temperature of the undrawn yarns at 50°C, the 20 undrawn yarns were brought into hot water at a temperature of 90°C, and the drawn yarns were drawn at a draw ratio of 2.8 times. The stretched tow was subjected to tension heat treatment for 5 seconds with a heated roller at ℃, then introduced to a crimper, and then mechanically crimped at a temperature of 30℃ and a tow pressing pressure of 1.5 kg/cm ² G, resulting in 12 crimps. A crimped tow with a diameter of /25 mm and a degree of crimp of 12% was obtained. After drying the obtained crimped tow at 80° C., 0.2% by weight of finishing oil was applied, and the fiber length was cut to 51 mm using a rotary cutter. Eccentric core-sheath composite staple fibers with an elongation of 32%, a number of crimps of 15/25 mm, and a crimp degree of 16% were obtained.

The fibrous web obtained by passing the eccentric core-sheath composite short fibers obtained above through roller carding twice was punched into a needle punch processing machine (Organ Co., Ltd., FELTING NEEDLES FPD-1 36) at a rate of 40 pieces/cm. ² , one side was processed using a water jet machine under the conditions of water pressure 6 Barrr, speed 10 m/min, nozzle shape 0.1 mmφ, 0.6 mm pitch, 834 holes, and 500 mm effective width, and then further processed at a temperature of 180 ° C. After drying, a nonwoven fabric with a basis weight of 50 g/m ² was obtained. The obtained eccentric core-sheath composite short fibers and nonwoven fabric were evaluated by the method described above, and the evaluation results are shown in Table 2.

[Examples 2 to 6, Reference Example 7, Examples 8 to 13]
Examples 2 to 5 are combinations of the polymer of component A and the polymer of component B, Example 6, and Reference Example 7
is the single fiber fineness, Examples 8 to 10 are the S/D size, Examples 11 to 13 are the composite ratio, Table 1
Eccentric core-sheath composite short fibers were obtained in the same manner as in Example 1 except for the following changes.

[Example 14]
Separately, polyethylene terephthalate fiber (number of crimps: 14 threads/25 mm, degree of crimp: 14%) with a single fiber fineness of 1.45 dtex and a cut length of 51 mm was produced as an extender. On the other hand, the same eccentric core-sheath composite short fibers as in Example 2 were produced, and the eccentric core-sheath composite short fibers and the above-mentioned filler were passed twice through roller carding at a ratio of 80:20 (mass ratio). The fiber web was punched through a needle punch processing machine (Organ Co., Ltd., FELTING NEEDLES FPD-1 36) at a rate of 40 pieces/cm ² once, and then passed through a water jet machine with a water pressure of 6 Barr, a speed of 10 m/min, and a nozzle shape of 0. After single-sided processing under the conditions of .1 mmφ, 0.6 mm pitch, 834 holes, and 500 mm effective width, it was further dried at a temperature of 180° C. to obtain a nonwoven fabric with a basis weight of 50 g/m ² .

[Example 15]
Separately, as heat bonding fibers, heat bonding binder fibers (crimps number: 14 A ridge of 25 mm and a crimp degree of 14% was created. On the other hand, the same eccentric core-sheath composite short fibers as in Example 2 were produced, and the eccentric core-sheath composite short fibers and the above-mentioned filler were passed through a roller-type carding twice at a ratio of 95:5 (mass ratio) to give a basis weight of 70 g. /m ² of the fiber web was heat-shrinked for 5 minutes in an oven at a temperature of 160°C, and then heat-treated for 1 minute using a hot roll with a surface temperature of 160°C to obtain a nonwoven fabric.

[Comparative Examples 1 to 5]
As shown in Table 1, Comparative Examples 1 to 3 were composite fibers laminated side-by-side using the die described in JP-A-09-157941 (the fineness was changed in Comparative Example 2, and the B component was also changed in Comparative Example 3). In Comparative Example 4, the composite form was as shown in FIG. 4 (however, a thin skin was present and the core component was not exposed), and in Comparative Example 5, concentric core-sheath fibers were made using a conventional core-sheath composite die. Other than that, each was produced in the same manner as in Example 1.

a: Center of gravity point of A component in the composite fiber cross section C: Center of gravity point of the composite fiber cross section S: Minimum thickness of B component D: Fiber diameter IFR: Radius of curvature of the interface between A component and B component in the composite fiber cross section 5 - (a ): Among the distribution holes in the final distribution plate, distribution holes 5-(b) for the B component forming the thin skin: Among the distribution holes in the final distribution plate, distribution holes 5-( for the B component other than 5-(a) c): Of the distribution holes in the final distribution plate, distribution holes for component A

Claims (1)

In the cross section of a composite fiber made of two types of polyesters, component A and component B, component A contains 2 to 7 mol% of 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane and 5 to 13% of isophthalic acid. A copolymerized polyester mainly composed of ethylene terephthalate units copolymerized with mol%, a polyester in which the B component is substantially composed of ethylene terephthalate units , and the A component is completely covered with the B component, which covers the A component. The ratio S/D of the minimum thickness S of the thickness of the B component and the fiber diameter D is 0.01 to 0.1, and the peripheral length of the fiber in the part where the thickness is within 1.05 times the minimum thickness S is the entire fiber. Contains 70% by weight or more of eccentric core-sheath composite short fibers having a circumferential length of 1/3 or more, a single fiber fineness of 0.5 to 1.8 dtex, and a number of crimp in the nonwoven fabric of 50 threads/25 mm or more. , a nonwoven fabric having an elongation rate of 20% or more and 85% or less , and an elongation recovery rate of 60% or more and 80% or less .