EP4656781A1

EP4656781A1 - Polyamide composite cross-section fiber, polyamide multifilament, and polyamide composite cross-section false-twisted yarn

Info

Publication number: EP4656781A1
Application number: EP24747223.6A
Authority: EP
Inventors: Yudai WATANABE; Taisuke Kishida
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 2023-01-27
Filing date: 2024-01-19
Publication date: 2025-12-03
Also published as: TW202447011A; CN120603999A; JPWO2024157895A1; JP7648000B2; KR20250137596A; WO2024157895A1

Abstract

The present invention addresses the problem of providing, by appropriately controlling alignment characteristics of fibers, polyamide composite cross-section fibers having both excellent crimp characteristics and abrasion resistance which have been difficult to be achieved by conventional technologies. The present invention pertains to polyamide composite cross-section fibers containing two types of polyamide satisfying the following terms A-C. A. The form of composite of the fiber cross-section of the polyamide composite cross-section fibers is a side-by-side type or an eccentric core-sheath type. B. The absolute value of the difference in an alignment parameter between the two types of polyamide is 0.20 or more. C. The range of the alignment parameter of the polyamide on the less aligned side is 1.50-3.00.

Description

TECHNICAL FIELD

The present invention relates to a polyamide conjugated fiber that has crimpability and excellent soft stretchability when formed into a fabric, and provides a polyamide conjugated fiber that has crimpability and greatly improved abrasion resistance.

BACKGROUND ART

Polyamide fibers typified by polycaproamide and polyhexamethylene adipamide are excellent in mechanical properties and dimensional stability, and thus are widely used not only for clothing applications but also for interior, vehicle interior, industrial applications, and the like.
Among them, in particular, a false-twisted yarn or the like obtained by imparting crimpability to a polyamide fiber is suitably used for an application of woven or knitted fabric having stretchability, but it is difficult to obtain a woven or knitted fabric having good stretchability by subjecting a polyamide single fiber to false twisting or the like. In the related art, there has been proposed a method of imparting crimpability to a polyamide fiber by forming a polyamide conjugated fiber in which two kinds of polyamides having compositions different from each other are bonded in a side-by-side manner or conjugated into an eccentric core-sheath type in a fiber cross-section, and obtaining a woven or knitted fabric having stretchability.
For example, there have been proposed a polyamide conjugated fiber (Patent Literature 1) in which two kinds of crystalline polyamides having different compositions are conjugated in an eccentric core-sheath type and a water absorption rate and a heat shrinkage stress are defined, and a polyamide conjugated fiber (Patent Literature 2) in which two kinds of polyamides having different viscosities are conjugated in a side-by-side type or an eccentric core-sheath type and a CF value is defined.

CITATION LIST

PATENT LITERATURE

Patent Literature 1: WO2021/020354
Patent Literature 2: JP2018-3190A

SUMMARY OF INVENTION

TECHNICAL PROBLEM

However, in the polyamide conjugated fiber in which two kinds of crystalline polyamides having different compositions are conjugated in an eccentric core-sheath type as described in Patent Literature 1, since orientation properties of the fiber necessary for abrasion resistance are not appropriately controlled, there is a problem that the abrasion resistance in the case of forming the fiber into a fabric is poor. In particular, as compared with a polyamide single fiber, although the same crystalline polyamide is used, since the polyamides having different compositions are simply bonded to each other, peeling off or the like is likely to occur, which is a cause of a remarkable decrease in abrasion resistance.
The polyamide conjugated fiber in which two kinds of polyamides having different viscosities are conjugated in a side-by-side type or an eccentric core-sheath type as described in Patent Literature 2 also has a problem that the abrasion resistance is poor as in the polyamide conjugated fiber described in Patent Literature 1. The abrasion resistance may be improved by bonding the polyamides having the same composition only with different viscosities, but this only applies to the polyamide conjugated fiber, and the abrasion resistance is inevitably poorer than that of the polyamide single fiber.
An object of the present invention is to provide a polyamide conjugated fiber excellent in both abrasion resistance and crimpability, which has been difficult to achieve by techniques in the related art, by appropriately controlling orientation properties of a fiber necessary for abrasion resistance.

SOLUTION TO PROBLEM

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

(1) A polyamide conjugated fiber, the conjugated fiber including two kinds of polyamides, and satisfying the following A to C,
1. A. a cross-sectional morphology in a fiber cross-section of the polyamide conjugated fiber is a side-by-side type or an eccentric core-sheath type,
2. B. a difference in orientation parameter between the two kinds of polyamides is 0.20 or more in terms of absolute value, and
3. C. a low-orientation-side polyamide has an orientation parameter in a range of 1.50 to 3.00.
(2) The polyamide conjugated fiber according to the above (1), in which the low-orientation-side polyamide has a crystallinity in a range of 10.0% to 40.0%.
(3) A polyamide multifilament including the polyamide conjugated fiber according to the above (1) or (2), and having a stretch elongation rate of 1.0% or more.
(4) A polyamide conjugated false-twisted yarn, the yarn including two kinds of polyamides, and satisfying the following D to G,
- D. a cross-sectional morphology in a fiber cross-section of the polyamide conjugated false-twisted yarn is a side-by-side type or an eccentric core-sheath type,
- E. the polyamide conjugated false-twisted yarn has a stretch elongation rate of 30.0% or more,
- F. a difference in orientation parameter between the two kinds of polyamides is 0.05 or more in terms of absolute value, and
- G. a low-orientation-side polyamide has a crystallinity in a range of 10.0% to 40.0%.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a polyamide conjugated fiber excellent in both abrasion resistance and crimpability by appropriately controlling orientation properties of a fiber.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] FIG. 1 illustrates an example of a cross section of a polyamide conjugated fiber according to the present invention, and (A) to (C) are schematic views of a side-by-side type.
[FIG. 2] FIG. 2 illustrates an example of a cross section of the polyamide conjugated fiber according to the present invention, and is a schematic view of an eccentric core-sheath type.
[FIG. 3] FIG. 3 is a schematic view illustrating a degree of eccentricity of the eccentric core-sheath type in an example of the cross section of the polyamide conjugated fiber according to the present invention.
[FIG. 4] FIG. 4 illustrates a conjugated interface of yarns to be discharged and a direction of yarn cooling air in an example of a method for producing a polyamide conjugated fiber according to the present invention, in which (A) is a schematic view showing an example of the present invention, and (B) is a schematic view showing an example of a production method described in JP3769434B ( JP2000-328349A ).

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present invention will be described in detail.
A polyamide conjugated fiber according to an embodiment of the present invention (hereinafter also referred to as "the present embodiment") includes two kinds of polyamides. From the viewpoint of abrasion resistance, it is important to prevent interfacial peeling by increasing affinity at a conjugated interface between the two kinds of polyamides.
The polyamide in the present embodiment is a polymer in which a so-called hydrocarbons are linked via an amide bond in the main chain. Examples of the polyamide include polycaproamide, polyundecanamide, polydodecanamide, polytetramethylene adipamide, polypentamethylene adipamide, polypentamethylene sebacamide, polyhexamethylene adipamide, polyhexamethylene sebacamide, polyhexamethylene dodecanamide, polyhexamethylene tridecanamide, and a copolymer containing these as a main component. Here, the main component means 50 parts by mass or more in 100 parts by mass of the copolymer.
The two kinds of polyamides are not limited as long as there is a difference in orientation degree, that is, a difference in orientation parameter. The two kinds of polyamides may have the same composition or different compositions, but in order to obtain desired crimpability, polyamides having different compositions are preferred. Examples thereof include a polyamide composed of an aminocaproic acid unit, such as polycaproamide, and a polyamide composed of a dicarboxylic acid and diamine unit, such as polyhexamethylene sebacamide. In the case of forming a conjugated fiber by using polyamides having the same composition, polymerization degrees of the two kinds of polyamides may be made different in order to obtain a desired crimping performance.
Examples of a cross-sectional morphology in the fiber cross-section include a side-by-side type, an eccentric core-sheath type, a double core-sheath type, a sea-island type, and a multilayer laminated type, and from the viewpoint of obtaining desired crimpability, the polyamide conjugated fiber according to the present embodiment is either a side-by-side type or an eccentric core-sheath type. As the cross-sectional morphology of the polyamide conjugated fiber according to the present embodiment, the side-by-side type refers to a cross-sectional morphology as shown in FIG. 1, and the eccentric core-sheath type refers to a cross-sectional morphology as shown in FIG. 2. When the two kinds of polyamides are a polyamide (A) and a polyamide (B), for the side-by-side type, a conjugated interface (bonding surface) between a polyamide (A) 1 and a polyamide (B) 2 may be a straight line as shown in (A) of FIG. 1, or may be curved as shown in (B) and (C) of FIG. 1. In either the side-by-side type or the eccentric core-sheath type, a composite ratio is preferably such that a component ratio of the two kinds of polyamides is in a range of 2:1 to 1:2 in terms of area ratio of cross sections. For the eccentric core-sheath type, regarding a degree of eccentricity of an eccentric core-sheath type including a polyamide (A) 3 as a core component and a polyamide (B) 4 as a sheath component as shown in FIG. 2, when a line segment between a center 6 of a conjugated fiber and a center 5 of a core component as shown in FIG. 3 is defined as L and a line segment between two intersection points of the extended line segment L and an outer periphery of the conjugated fiber is defined as M, L/M is preferably in a range of 1/8 to 1/2.
In the polyamide conjugated fiber according to the present embodiment, it is extremely important to appropriately control orientation properties from the viewpoint of the abrasion resistance. Since the orientation properties of the polyamide conjugated fiber described in Patent Literature 1 or Patent Literature 2 are not appropriately controlled, even when the crimping performance is good, the abrasion resistance is poor. There are various methods for measuring the orientation properties of fibers. The orientation properties in the polyamide conjugated fiber according to the present embodiment refer to an orientation parameter measured and normalized by laser Raman spectroscopy, and the gist thereof will be described later.
A Raman band of a polyamide at around 1640 cm^-1 belongs to a stretching vibration mode of C=O, a stretching vibration direction of which is perpendicular to a molecular chain, and indicates a polarizability changes in a direction perpendicular to a molecular chain direction. Since strong Raman scattering is obtained in the case where the stretching vibration direction of the molecular chain coincides with a polarization direction of incident light, a Raman scattering intensity I₁₆₄₀ at the stretching vibration mode of C=O changes in correlation with an orientation degree. That is, a ratio between a Raman scattering intensity in vertical polarization and a Raman scattering intensity in parallel polarization is used as a parameter for evaluating the orientation degree. In addition, by using a Raman scattering intensity I₁₄₅₀ in a C-H deformation band (around 1450 cm^-1) having small anisotropy with respect to orientation as a reference for each of the vertical polarization and the parallel polarization, the Raman scattering intensity under each polarization condition (vertical/parallel) can be normalized as an orientation parameter. The orientation parameter shows a larger value as the orientation degree in a fiber axis direction increases, and is 1.0 (minimum value) in the case of non-orientation (uniform orientation). The equation thereof is shown below. $Orientation parameter = (I_{1640} {/ I}_{1450}) vertical polarization / (I_{1640} {/ I}_{1450}) parallel polarization$
The above equation satisfies the following definitions.

Vertical condition: fiber longitudinal direction is orthogonal to polarization direction
Parallel condition: fiber longitudinal direction is parallel to polarization direction
I₁₆₄₀ vertical: intensity of Raman band at 1640 cm^-1 under vertical condition
I₁₄₅₀ vertical: intensity of Raman band at 1450 cm^-1 under vertical condition
I₁₆₄₀ parallel: intensity of Raman band at 1640 cm^-1 under parallel condition
I₁₄₅₀ parallel: intensity of Raman band at 1450 cm^-1 under parallel condition

The orientation parameter will be described in detail in Examples.
In the polyamide conjugated fiber according to the present embodiment, a difference in orientation parameter between the two kinds of polyamides is 0.20 or more, and preferably 0.30 or more in terms of absolute value. Within such a range, the crimping performance of the fiber is improved, and a fabric or a fiber product rich in soft stretchability can be obtained. In the case where the difference in orientation parameter between the two kinds of polyamides is less than 0.20 in terms of absolute value, or in the case where the difference in orientation parameter between the two kinds of polyamides is less than 0.05 in terms of absolute value in a polyamide conjugated false-twisted yarn according to the present embodiment to be described later, the crimpability of the fiber is not exhibited, and a fabric or a fiber product rich in soft stretchability cannot be obtained. The difference in orientation parameter between the two kinds of polyamides is preferably high as long as the effect of the present embodiment is not impaired, and is preferably 2.00 or less in view of a stable process of producing the polyamide conjugated fiber. When the difference in orientation parameter between the two kinds of polyamides is more than 2.00, defects of a wound package form, fluff, and the like may occur.
Here, the absolute value of the difference in orientation parameter between the two kinds of polyamides can be calculated according to the following equation. Absolute value of difference in orientation parameter = (orientation parameter of high-orientation-side polyamide) - (orientation parameter of low-orientation-side polyamide)
In the present description, the high-orientation-side polyamide is a polyamide having a higher value of the orientation parameter among the two kinds of polyamides, and the low-orientation-side polyamide is a polyamide having a lower value of the orientation parameter among the two kinds of polyamides.
In the polyamide conjugated fiber according to the present embodiment, the orientation parameter of the low-orientation-side polyamide is in a range of 1.50 to 3.00. Within such a range, the abrasion resistance of the fiber is improved, and it is possible to obtain a fabric or a fiber product rich in soft stretchability with greatly improved abrasion resistance, which has been difficult to achieve by techniques in the related art. In the case where the orientation parameter of the low-orientation-side polyamide is less than 1.50, the strength and the elongation of the fiber remarkably decrease, and therefore, only a fabric or a fiber product poor in abrasion resistance can be obtained even though the crimping performance is excellent, as in the related art. In the case where the orientation parameter of the low-orientation-side polyamide is more than 3.00, the fiber is rigid, and therefore, only a fabric or a fiber product poor in abrasion resistance can be obtained even though the crimping performance is excellent.
In this manner, in the polyamide conjugated fiber according to the present embodiment, it is possible to obtain a polyamide conjugated fiber excellent in both abrasion resistance and crimping performance not only by simply conjugating two kinds of polyamides but also by focusing on the orientation properties of the polyamide conjugated fiber and appropriately controlling the orientation parameters of the two kinds of polyamides. For controlling the orientation parameters of the two kinds of polyamides, it is important to optimize a spinning draft and a draw ratio, to be described in detail later.
There are various methods for measuring a crystallinity of the fiber. A crystallinity in the polyamide conjugated fiber according to the present embodiment refers to a crystallinity obtained by converting a Raman band half width from calibration data obtained by laser Raman spectroscopy and X-ray diffraction, and the gist thereof will be described later.
The Raman band of the polyamide at around 1640 cm^-1 belongs to the stretching vibration mode of C=O, and is also used for analysis of crystalline nature. When the crystallinity increases, the molecular arrangement is uniform, and thus peak positions of a molecular vibration frequency is uniform. As a result, a band width becomes sharp, and thus, by analyzing the band width, a parameter related to the crystalline nature is obtained. Here, in the polyamide species, the crystallinity is calculated based on a band half width of the Raman band in non-polarized light at around 1640 cm^-1 and a peak area ratio of a broad peak indicating amorphous and a sharp peak indicating a crystal obtained by X-ray diffraction, and calibration data of the band width and the crystallinity is created. Accordingly, the crystallinity of each component in the polyamide conjugated fiber according to the present embodiment can be calculated using laser Raman spectroscopy capable of local measurement. The crystallinity will be described in detail in Examples.
In the polyamide conjugated fiber according to the present embodiment, the low-orientation-side polyamide has a crystallinity preferably in a range of 10.0% to 40.0%, and more preferably in a range of 20.0% to 35.0%. When the crystallinity of the low-orientation-side polyamide is 10.0% or more, a crystal structure of the polyamide conjugated fiber is stabilized, and thus stable textile-processing process such as false twisting, weaving, knitting, and dyeing can be performed even after long-term storage. When the crystallinity of the low-orientation-side polyamide is 40.0% or less, it is possible to further improve the abrasion resistance while maintaining the crimping performance.
The polyamide multifilament including the polyamide conjugated fiber according to the present embodiment preferably has a stretch elongation rate of 1.0% or more.
Examples of the polyamide multifilament including the polyamide conjugated fiber according to the present embodiment include a so-called drawn yarn obtained by a one-step method, a two-step method, or the like, and a partially oriented yarn (POY). Preferred ranges of the stretch elongation rate thereof are different from each other. The preferred stretch elongation rate of the drawn yarn is 20.0% to 100.0%, and the preferred stretch elongation rate of the POY is 1.00% to 100.0%. Since a stretch elongation rate of 20.0% or more is preferred for obtaining a fabric or fiber product rich in soft stretchability with maintaining the crimping performance, the drawn yarn to be directly subjected to product processing such as weaving preferably has a stretch elongation rate of 20.0% or more. A stretch elongation rate of 20.0% or more is not necessary for the POY to be subjected to false twisting, but when the stretch elongation rate is 1.0% or more, a stretch elongation rate of 30.0% or more, which is even higher than that of the drawn yarn, is easily exhibited when false twisting is performed. The POY having a stretch elongation rate of 1.0% or more has, for example, a coil crimp that enables stretch elongation. The stretch elongation rate is preferably high as long as the effect of the present embodiment is not impaired, and is preferably 100.0% or less in view of a stable process of producing the polyamide conjugated fiber. When the stretch elongation rate is more than 100.0%, defects of a wound package form, fluff, and the like may occur.
The stretch elongation rate of the polyamide multifilament according to the present embodiment is a value measured in accordance with JIS L 1013 (Method C) (2010 version).
A single yarn fineness of the polyamide conjugated fiber according to the present embodiment is not particularly limited as long as the effect of the present embodiment is not impaired. When the single yarn fineness is in a range of 1.0 dtex to 6.0 dtex, the polyamide conjugated fiber can be suitably used for innerwear, outerwear, and the like. A total fineness of the polyamide multifilament is preferably in a range of 20.0 dtex to 200.0 dtex in consideration of clothing applications.
The polyamide conjugated fiber according to the present embodiment may include various additives as long as the effect of the present embodiment is not impaired. Examples of the additives include pigments such as titanium oxide and carbon black, light resistant agents such as a manganese compound, antioxidants such as hindered phenol and a phosphorus compound, heat resistant agents, flame retardants, conductivity-imparting agents, and fibrous reinforcing agents.
A section shape such as a cross section of the polyamide conjugated fiber according to the present embodiment may be appropriately selected within a range where the effect of the present embodiment is not impaired, as long as the cross-sectional morphology is a side-by-side type or an eccentric core-sheath type. In the case of the eccentric core-sheath type as shown in FIG. 2, the polyamide (A) 3 as the core component may be a low-orientation-side polyamide and the polyamide (B) 4 as the sheath component may be a high-orientation-side polyamide, or the polyamide (A) 3 as the core component may be a high-orientation-side polyamide and the polyamide (B) 4 as the sheath component may be a low-orientation-side polyamide. Preferably, the polyamide (A) 3 as the core component is a high-orientation-side polyamide and the polyamide (B) 4 as the sheath component is a low-orientation-side polyamide. Examples thereof include a perfect circular, elliptical, trilobate, quatrefoil, cross, hollow, and flat cross section, and a perfect circular cross section is preferred from the viewpoint of melt spinnability and ease of spinning.
As described above, examples of the polyamide multifilament including the polyamide conjugated fiber according to the present embodiment include a drawn yarn and a partially oriented yarn (POY), and by further subjecting these yarns to false twisting, it is possible to further greatly improve both the abrasion resistance and the crimpability. In the false twisting, it is preferred to use the POY from the viewpoint of processability, but the drawn yarn can also be subjected to the false twisting to further increase the stretch elongation rate.
In the case where the cross-sectional morphology in the fiber cross-section of the polyamide conjugated fiber according to the present embodiment is a side-by-side type, a cross-sectional morphology in a fiber cross-section of the polyamide conjugated false-twisted yarn obtained by subjecting this polyamide conjugated fiber to false twisting is also a side-by-side type. In the case where the cross-sectional morphology in the fiber cross-section of the polyamide conjugated fiber according to the present embodiment is an eccentric core-sheath type, the cross-sectional morphology in the fiber cross-section of polyamide conjugated false-twisted yarn obtained by subjecting this polyamide conjugated fiber to false twisting is also an eccentric core-sheath type.
In addition, in the polyamide conjugated false-twisted yarn according to the present embodiment, the difference in orientation parameter between the two kinds of polyamides is 0.05 or more, and preferably 0.09 or more in terms of absolute value. When the difference in orientation parameter between the two kinds of polyamides is less than 0.05 in terms of absolute value, crimping is poor and the soft stretchability cannot be obtained. That is, two kinds of polyamides (high-orientation-side polyamide and low-orientation-side polyamide) form a polyamide conjugated false-twisted yarn including a conjugated fiber in either a side-by-side type or an eccentric core-sheath type.
A method for calculating the orientation parameter and a method for calculating the absolute value of the difference in orientation parameter for the polyamide conjugated false-twisted yarn according to the present embodiment are the same as the method for calculating the orientation parameter and the method for calculating the absolute value of the difference in orientation parameter for polyamide conjugated fiber according to the present embodiment.
The polyamide conjugated false-twisted yarn according to the present embodiment has a stretch elongation rate of 30.0% or more, and preferably 50.0% or more. A stretch elongation rate of 20.0% or more is preferred for maintaining the crimping performance and obtaining a fabric or fiber product rich in soft stretchability, and in order to obtain ultimate soft stretchability, it is important to make the stretch elongation rate 30.0% or more by subjecting, to false twisting, the polyamide multifilament including the polyamide conjugated according to the present embodiment. In the polyamide conjugated false-twisted yarn according to the present embodiment, the orientation properties of the polyamide conjugated fiber as a precursor are appropriately controlled, and by subjecting this polyamide conjugated fiber to false twisting, a false-twisted yarn having a higher stretch elongation rate can be obtained. A method for measuring the stretch elongation rate of the polyamide conjugated false-twisted yarn according to the present embodiment is the same as the method for measuring the stretch elongation rate of the polyamide multifilament according to the present embodiment.
In the polyamide conjugated false-twisted yarn according to the present embodiment, the low-orientation-side polyamide has a crystallinity in a range of 10.0% to 40.0%, and preferably in a range of 20.0% to 35.0%. When the crystallinity of the low-orientation-side polyamide is 10.0% or more, a crystal structure of the false-twisted yarn is stabilized, and thus stable textile-processing process such as weaving, knitting, and dyeing can be performed even after long-term storage. When the crystallinity of the low-orientation-side polyamide is 40.0% or less, it is possible to further improve the abrasion resistance while maintaining the crimping performance. A method for measuring the crystallinity of the low-orientation-side polyamide of the polyamide conjugated false-twisted yarn according to the present embodiment is the same as the method for measuring the crystallinity of the low-orientation-side polyamide of the polyamide conjugated fiber according to the present embodiment.
The polyamide conjugated fiber and the polyamide conjugated false-twisted yarn according to the present embodiment can be woven and knitted according to a known method. The texture of the woven or knitted fabric is not limited. In the case of a woven fabric, the texture thereof may be any of a plain weave, a twill weave, a sateen weave, a changed weave thereof, or a mixed weave depending on the application to be used, and a plain texture having a large number of constraint points, or a ripstop weave obtained by combining a plain weave with a rough weave or a mat weave is preferred in order to obtain a woven fabric having a firm woven fabric texture and a fluffy feeling. In the case of a knitted fabric, the texture thereof may be any of a plain stitch of a circular knitted fabric, an interlock stitch, a half stitch of a warp knitted fabric, a satin stitch, a jacquard stitch, a changed stitch thereof, and a mixed stitch depending on the application to be used, and a half stitch fabric of a single tricot knitted fabric is preferred from the viewpoint that the knitted fabric is thin, stable, and excellent in elongation rate.
The application of the woven or knitted fabric in the present embodiment is not limited, and the woven or knitted fabric is preferably used for clothing applications, and more preferably used for sportswear, casual wear, and woman's and men's clothing represented by down jackets, windbreaker, golf wear, rain wear, and the like.
Hereinafter, a method for producing the polyamide conjugated fiber according to the present embodiment and the polyamide multifilament formed therefrom will be described.
The two kinds of polyamides used in the polyamide conjugated fiber according to the present embodiment may have the same composition or different compositions, but in order to obtain desired crimpability, it is preferred that the two kinds of polyamides have different compositions, and for example, polycaproamide and polyhexamethylene sebacamide are one of preferred combinations. In the case of forming a conjugated fiber by using polyamides having the same composition, polymerization degrees of the two kinds of polyamides may be made different. On the other hand, for example, a difference in composition may be caused by mixing titanium oxide into only one of the two kinds of polyamides. In the polyamide conjugated fiber described in Patent Literature 1 or Patent Literature 2, a difference in polymerization degree and a difference in melt viscosity are defined between two kinds of preferred polyamides, but these are not very important. Even when the polymerization degree and the melt viscosity of the two kinds of polyamides are completely the same, a combination of polyamides that cause a difference in orientation behavior or crystal structure in a subsequent step may be used, and it is more important to appropriately control the spinning draft and the draw ratio to be described later.
A melting portion in a production step will be described. When two kinds of polyamides are melted, a pressure melter method or an extruder method may be used, but the method is not particularly limited. A melting temperature may be appropriately determined in consideration of the melting point of the polyamide resin, and it is preferred to separately melt the two kinds of polyamides at a temperature 20°C to 60°C higher than the melting point the polyamide resin.
Similar to the melting temperature, a spinning temperature may be appropriately determined in consideration of the melting point of the polyamide resin. Note that, the spinning temperature here is a so-called heat retention temperature (spin block temperature) at which a polymer pipe, a metering pump, a spinneret, and the like are kept warm.
In the method for producing the polyamide conjugated fiber according to the present embodiment and the polyamide multifilament formed therefrom, it is important to appropriately control the spinning draft and the draw ratio. From the viewpoint of controlling these, a direct spinning-and-drawing method is excellent, and a production method in terms of the direct spinning-and-drawing method will be exemplified below.
As shown in FIG. 4, the two kinds of polyamides separately melted are weighed and supplied to a composite spinneret 9 forming a side-by-side type or an eccentric core-sheath type. Here, the two kinds of polyamides are merged and discharged through spinneret discharge holes 10 as a side-by-side type or eccentric core-sheath type polyamide conjugated fiber. In the case of a side-by-side type in which the conjugated interface is a straight line, as shown in (A) of FIG. 4, it is preferred to arrange the two kinds of polyamides such that a conjugated interface 11 is parallel to a direction of yarn cooling air 8 to be described later from a yarn cooling device such as a chimney 7, and to discharge a yarn, that is, the polyamide conjugated fiber. It is preferred to arrange the two kinds of polyamides such that a straight line connecting two end portions of the conjugated interface is parallel to the direction of the yarn cooling air in the case of a side-by-side type in which the conjugated interface is a curved line, and to discharge the yarn. It is preferred to arrange the two kinds of polyamides such that the longitudinal direction of the polyamide as the core component is parallel to the direction of the yarn cooling air in the case of an eccentric core-sheath type, and to discharge the yarn. Regarding the arrangement of the two kinds of polymers, for example, as described in JP3769434B ( JP2000-328349A ) and the like, as shown in (B) of FIG. 4, it is general from the viewpoint of exhibiting the crimping performance that a high shrinkable (high orientation side) polymer 14 is arranged on a windward side of the yarn cooling air 8 and a low shrinkable (low orientation side) polymer 15 is arranged on a leeward side of the yarn cooling air 8, but in this method, since the low shrinkable polymer 15 is not easily cooled, a spinning stress may concentrate only on the high shrinkable polymer 14, and yarn breakage may occur, which is not preferred from the viewpoint of spinning operability. Here, the high shrinkable (high orientation side) polymer 14 corresponds to the high orientation side in the present embodiment, and the low shrinkable (low orientation side) polymer 15 corresponds to the low orientation side in the present embodiment.
In the present embodiment, improvement of the crimping performance and the abrasion resistance is realized by appropriately controlling the spinning draft and the draw ratio to be described later, and in this system, as shown in (A) of FIG. 4, it is preferred that the two kinds of polyamides are arranged and discharged such that the conjugated interface 11 is parallel to the direction of the yarn cooling air 8, and the two kinds of polyamides are uniformly cooled from the viewpoint of spinning operability.
The discharged yarns are cooled to room temperature by blowing cooling air from a yarn cooling device such as a chimney after a gaseous low polymer component coming out from the yarns are sucked and removed (MO suction), and the yarns are oiled by an oil supplying device, bundled, and entangled by a fluid treatment device. If necessary, the yarns are oiled by the oil supplying device and bundled again, and the bundled yarns are given an appropriate spinning draft by a take-up roller, pass through a drawing roller, and are appropriately drawn according to a ratio of peripheral speeds of the take-up roller and the drawing roller. The fiber after drawing is preferably heat-set as much as possible regardless of whether the fiber is a drawn yarn or a partially oriented yarn (POY), and is wound by a winding device thereafter.
In the method for producing the polyamide conjugated fiber according to the present embodiment and the polyamide multifilament formed therefrom, the spinning draft is preferably in a range of 100 to 300, and more preferably in a range of 150 to 250. Note that, the "spinning draft" here is a value obtained by dividing the take-up roller peripheral speed by a spinneret discharge linear speed. The "spinneret discharge linear speed" here is a value obtained by dividing a discharge capacity (volume), which is calculated by dividing a discharge mass per spinneret discharge hole by a molten polymer density, by a cross-sectional area of the spinneret discharge hole. By setting the spinning draft within such a range, the orientation properties of the two kinds of polyamides in the present embodiment can be appropriately controlled, and therefore a polyamide conjugated fiber excellent in both abrasion resistance and crimping performance can be obtained, and a fabric or a fiber product rich in soft stretchability can be obtained. In the case where the spinning draft is less than 100, there is no difference in orientation parameter between the two kinds of polyamides, and thus the crimpability of the fiber is not exhibited, and there is a tendency that a fabric or a fiber product rich in soft stretchability cannot be obtained. In the case where the spinning draft is more than 300, the orientation parameter of the low-orientation-side polyamide is increased, and thus the fiber is rigid, and there is a tendency that only a fabric or a fiber product poor in abrasion resistance can be obtained even though the crimping performance is excellent, as in the related art.
The draw ratio is preferably in a range of 1.05 times to 2.40 times, and more preferably in a range of 1.07 times to 2.00 times. Note that, the "draw ratio" here is a value obtained by dividing the drawing roller peripheral speed by the take-up roller peripheral speed. By setting the draw ratio within such a range, the orientation properties of the two kinds of polyamides in the present embodiment can be appropriately controlled, and therefore a polyamide conjugated fiber excellent in both abrasion resistance and crimping performance can be obtained, and a fabric or a fiber product rich in soft stretchability can be obtained. In the case where the draw ratio is less than 1.05 times, orientation does not proceed and the orientation parameter decreases, and thus the crimpability of the fiber is not exhibited, and there is a tendency that a fabric or a fiber product rich in soft stretchability cannot be obtained. In addition, since the orientation parameter of the low-orientation-side polyamide also decreases, the strength and the elongation of the fiber decrease, and practical durability when the fiber is formed into a fabric or a fiber product tends to greatly decrease. In the case where the draw ratio is more than 2.40 times, the orientation parameter of the low-orientation-side polyamide is increased, and thus the fiber is rigid, and there is a tendency that only a fabric or a fiber product poor in abrasion resistance can be obtained even though the crimping performance is excellent, as in the related art.
Regarding the heat setting, it is preferred to perform the heat setting regardless of whether the yarn is a draw yarn or a partially oriented yarn (POY). A heat setting temperature is preferably in a range of 100°C to 200°C, and more preferably in a range of 130°C to 190°C. When the heat setting temperature is 100°C or higher, the orientation parameter obtained by appropriately controlling the spinning draft and the draw ratio is not relaxed, and as a result, the difference in orientation parameter between the two kinds of polyamides can be maintained, the crimpability of the fiber is exhibited, and a fabric or a fiber product rich in soft stretchability can be obtained. In addition, since the crystallinity of the low-orientation-side polyamide is also increased, the crystal structure is stabilized, and stable textile-processing process (false twisting, weaving, knitting, dyeing, and the like) can be performed even after long-term storage. When the heat setting temperature is 200°C or lower, the orientation parameter of the low-orientation-side polyamide is lowered, and thus flexibility of the fiber can be maintained, and a fabric or a fiber product excellent in both soft stretchability and abrasion resistance can be obtained.
As described above, examples of the polyamide multifilament including the polyamide conjugated fiber according to the present embodiment include a drawn yarn and a partially oriented yarn (POY), and it is preferred that the POY is also heat-set as described above. Usually, a polyamide POY is not heat-set in many cases. This is because, when the fiber is heat-set at the stage of POY, crystallization of the fiber proceeds and an amorphous strain portion subjected to twist deformation is reduced, and thus the crimping performance of the obtained false-twisted yarn decreases. However, in the two kinds of polyamides in the present embodiment, it is more important to control the orientation parameter, and it is preferred to also heat-set the POY in order to appropriately control the orientation parameter.
As for the heat setting method, in the case of a direct spinning-and-drawing method, the heat-set is performed by bringing the yarn and a heating body into contact with each other after drawing. A method is preferably used in which a heater is provided inside the drawing roller, and the yarn held by (brought into contact with) the drawing roller is heat-set.
A winding speed may be appropriately set within a range in which various parameters such as the orientation parameter, the crystallinity, and the stretch elongation rate of the two kinds of polyamides in the present embodiment are in desired ranges and stable production is possible, and is preferably in a range of 3000 m/min to 5000 m/min.
The polyamide conjugated false-twisted yarn according to the present embodiment can be obtained by a known false twisting method, and preferably by subjecting yarns to false twisting with a drawing friction false twisting device.
An example is as follows. For example, a polyamide yarn for false twisting according to the present embodiment supplied to the drawing friction false twisting device is fed to a supply roller via a desired yarn guide or a fluid treatment device. Thereafter, the polyamide yarn for false twisting is guided to the drawing roller through a heated false twisting heater, a cooling plate, and a twisting body that performs drawing friction false twisting, and wound as a false-twisted yarn. As the drawing friction false twisting, friction false twisting may be performed after drawing the polyamide yarn for false twisting using a heat pin or a hot plate before the polyamide yarn for false twisting is fed to the supply roller of the drawing friction false twisting device, or the friction false twisting may be performed while the polyamide yarn for false twisting is drawn between the supply roller and the orienting roller.
The twisting body is not limited to a pin type, a friction type, or a belt nip type. When it is desired to increase a crimp strength, a pin type is preferably used, and when it is desired to increase a processing speed to reduce a production cost, a friction type or a belt nip type is preferably used.
Examples of a heating method include, but are not limited to, a high-temperature contact type heater and a high-temperature non-contact type heater. In order to obtain a high crimping performance, it is necessary to apply heat firmly to the yarn using the high-temperature contact type heater to rearrange molecules in the fiber and to relax a strain. Therefore, the high-temperature contact type heater is preferred, and a processing temperature, that is, a heater setting temperature of a contact type hot plate is preferably 170°C to 200°C.
Examples of a cooling method include, but are not limited to, a method using a cooling plate, and a method using air cooling or water cooling. In the method using a cooling plate and the method using air cooling or water cooling, the method using water cooling has the highest cooling efficiency but has large damage to the yarn, and the method using air cooling has the lowest cooling efficiency but has little damage to the yarn. Note that, the method using water cooling tends to be complicated in step and poor in productivity. In consideration of the efficiency and the damage to the yarn, it is preferred to use a cooling plate.
A ratio (T2/T1) of an untwisting tension T2 to a twisting tension T1 is preferably 0.7 to 1.0. In the case where T2/T1 is 1.0 or less, that is, the untwisting tension T2 is small, occurrence of fluff, that is, single yarn breakage can be prevented, so that yarn breakage after the twisting body is reduced, stable drawing friction false twisting can be performed, and the obtained false-twisted yarn also has an excellent quality. When T2/T1 is 0.7 or more, untwisting failure can be prevented, so that high crimp can be obtained. Here, the twisting tension is a tension at a portion where twisting is applied upstream of the twisting body, and the untwisting tension is a tension at a portion where twisting is removed downstream of the twisting body. The twisting tension and the untwisting tension can be measured by using a tension meter.
A ratio (D/Y ratio) of a surface speed D of the twisting body to a speed Y of the drawing roller, which is a yarn running speed, is preferably 1.0 to 2.0. When the D/Y ratio is 1.0 or more, the twisting tension T1 and the untwisting tension T2 are well balanced, and drawing friction false twisting without fluff or yarn breakage can be performed. In addition, when the D/Y ratio is 2.0 or less, surface wear of the twisting body is prevented, the quality in the yarn longitudinal direction is stabilized even in continuous operation over several tens of hours, and drawing friction false twisting without fluff or yarn breakage is realized.

EXAMPLES

Next, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples. Note that, methods for measuring the property values in Examples are as follows.

A. Orientation Parameter

The measurement was performed by Raman spectroscopy using T-64000 manufactured by Jobin Yvon/Atago Bussan Co., Ltd. under the conditions of measurement mode: microscopic Raman, objective lens: ×100, beam diameter: 1 µm, light source: Ar + laser/514.5 nm, laser power: 100 mW, diffraction grating: Single 600, 1800 gr/mm, slit: 100 µm, detector: CCD 1024 × 256 manufactured by Jobin Yvon.
As a measurement sample, one single yarn was taken out from the multifilament and fixed in a curled state in accordance with crimping of the single yarn. The analysis was performed by vertically irradiating each component with polarized light, with the high-orientation-side polyamide being on the curled inner side and the low-orientation-side polyamide being on the curled outer side. The polarized light for irradiation is parallelly polarized light (||) which coincides with the fiber longitudinal direction and vertically polarized light (⊥) which is orthogonal to the fiber longitudinal direction, and a Raman band at about 1640 cm^-1 which belongs to the stretching vibration mode of C=O of the polyamide and a Raman band at about 1450 cm^-1 which belongs to the C-H deformation angle band are read for each component and each polarized light, which are used for calculation according to the following equation. Note that, the measurement was performed on five single yarns randomly taken from the multifilament, and calculation was made using an average value of three measurements for each component (the high-orientation-side polyamide and the low-orientation-side polyamide) in each single yarn. $Orientation parameter = (I_{1640} {/ I}_{1450}) vertical polarization / (I_{1640} {/ I}_{1450}) parallel polarization$ Absolute value of difference in orientation parameter = (orientation parameter of high-orientation-side polyamide) - (orientation parameter of low-orientation-side polyamide).

B. Crystallinity

The measurement was performed by Raman spectroscopy using T-64000 manufactured by Jobin Yvon/Atago Bussan Co., Ltd. under the conditions of measurement mode: microscopic Raman, objective lens: ×100, beam diameter: 1 µm, light source: Ar + laser/514.5 nm, laser power: 100 mW, slit: 100 µm, detector: CCD 1024 × 256 manufactured by Jobin Yvon.
As a measurement sample, one single yarn was taken out from the multifilament and fixed in a curled state in accordance with crimping of the single yarn. The analysis was performed by vertically irradiating the component on the curled outer side with light, with the curled outer side being the low orientation side. A half width of the Raman band at about 1640 cm^-1 which belongs to the stretching vibration mode of C=O of the polyamide was read and converted into the crystallinity of the low-orientation-side polyamide. The conversion from the half width to the crystallinity was performed by preparing single yarns of polyamides having different crystallinity in advance, and creating a calibration curve by measuring the half width and XRD. Note that, the measurement was performed on five single yarns randomly taken from the multifilament, and calculation was made using an average value of three measurements for the low-orientation-side polyamide component of each single yarn.

C. Stretch Elongation Rate

The stretch elongation rate was measured in accordance with JIS L 1013 (method C) (2010 version). The heat treatment method was performed for 20 minutes without applying a load in warm water at a temperature of 90°C.

D. Total Fineness and Single Yarn Fineness

A yarn sample was set in a sizing reel having a circumferential length of 1 m, and rotated 250 times to prepare a loop-shaped hank. The hank was dried using a hot air dryer (105 ± 2°C × 60 minutes), then the hank mass was measured using a weighing balance, and the total fineness was calculated based on a value obtained by multiplying the hank mass by an official moisture regain. Note that, the official moisture regain was uniformly 4.5%. The single yarn fineness was a value obtained by dividing the calculated total fineness by the number of filaments.

E. 98% Sulfuric Acid Relative Viscosity

A sample (0.25 g) was dissolved in 100 ml of sulfuric acid having a concentration of 98 mass% to be 1 g, and a flow-down time T1 at 25°C was measured using an Ostwald viscometer. Subsequently, a flow-down time T2 of only sulfuric acid having a concentration of 98 mass% was measured. A ratio of T1 to T2, that is, T1/T2, was defined as a 98% sulfuric acid relative viscosity.

F. Fabric Stretching

In accordance with JIS L 1096 (method A) (constant-speed elongation method: 2010 version), a tensile tester manufactured by Instron was used to measure an elongation rate when a sample having a width of 50 mm × 300 mm was elongated in the warp direction and the weft direction to 14.7 N at a grip interval of 200 mm and a tensile speed of 200 mm/min. The measurement results were categorized into the following levels, with A and B indicating pass.

A: 25.0% or more
B: 15.0% or more and less than 25.0%
C: 10.0% or more and less than 15.0%
D: less than 10.0%.

G. Fabric Abrasion Resistance (Martindale Method)

The abrasion resistance was measured in accordance with JIS L 1096 (method A) (friction strength: 2010 edition) method E. The measurement results were categorized into the following levels, with A and B indicating pass.

A: Grade 5
B: Grade 4 or higher to lower than Grade 5
C: Grade 3 or higher to lower than Grade 4
D: lower than Grade 3.

Examples 1 to 4, 6, and 7, and Comparative Examples 3 to 5
Polycaproamide (98% sulfuric acid relative viscosity: 3.25, chip moisture content: 100 ppm) as the polyamide (A) as a core component, and polyhexamethylene sebacamide (98% sulfuric acid relative viscosity: 2.70, chip moisture content: 1500 ppm) as the polyamide (B) as a sheath component were melted at 290°C and 270°C, respectively, using a pressure melter, and the molten polyamides were discharged using an eccentric core-sheath composite spinneret (24 holes × 2 groups, round holes). In the present description, polycaproamide is also referred to as N6, and polyhexamethylene sebacamide is also referred to as N610.
Note that, the area ratio of the polyamide (A) to the polyamide (B) (polyamide A/polyamide B), L/M where L is a line segment between the center of the entire conjugated fiber and the center of the core portion, and M is a line segment between two intersection points of a straight line extending from the line segment L and the outer periphery of the conjugated fiber having a cross-sectional morphology, and the spinning draft are as shown in Table 1.
In addition, the polyamide (A) and the polyamide (B) were arranged and discharged such that the direction of the yarn cooling air and the direction of the conjugated interface were parallel to each other. The discharged yarn was MO sucked, and the yarn was cooled and solidified to room temperature by blowing cooling air (air speed: 30 m/min, air temperature: 20°C) by a uniflow chimney. The cooled and solidified yarn was subjected to supplying a water-containing oil agent with the oil supplying device, then entanglement was applied by the fluid treatment device, and the water-containing oil agent was supplied again with the oil supplying device.
The take-up roller peripheral speed, the drawing roller peripheral speed, and the draw ratio in the drawing are as shown in Table 1. The heat setting was performed by providing a heater inside the drawing roller and bringing the yarn into contact with the drawing roller, and the surface temperature of the drawing roller (heat setting temperature) is as shown in Table 1. After the drawing and the heat setting, winding was performed using a winder to obtain a multifilament including a 66-dtex and 24-filament polyamide fiber having an eccentric core-sheath type cross section.
The obtained polyamide fiber having an eccentric core-sheath type cross section was measured in terms of the orientation parameters of the low-orientation-side polyamide and high-orientation-side polyamide, the difference (absolute value) in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, the total fineness, and the single yarn fineness. In addition, the number of times of yarn breakage when 1 ton of the polyamide fiber having an eccentric core-sheath type cross section was produced was also counted. The results are shown in Table 1.
The obtained multifilament was subjected to simultaneous drawing and false-twisting at a processing temperature (heater setting temperature of contact type hot plate) of 160°C, a draw ratio of 1.25, a D/Y ratio of 1.95, and T2/T1 = 0.81 in a friction type drawing friction false twisting device to obtain a false-twisted yarn having about 56 dtex and 24 filaments. The obtained false-twisted yarn was measured in terms of the difference in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, and the total fineness. The results are shown in Table 1.
Note that, the cross-sectional morphology of the false-twisted yarn was the same as the cross-sectional morphology of the polyamide conjugated fiber used in the production of the false-twisted yarn.

With the obtained false-twisted yarn, a fabric including plain weave having a warp density of 116 yarns/2.54 cm and a weft density of 84 yarns/2.54 cm was prepared, refined and dyed by a liquid flow, and dry heat setting of the fabric was appropriately adjusted. The obtained fabric was measured in terms of the fabric stretching and the fabric abrasion resistance (Martindale method). The results are shown in Table 1.

[Table 1]

		Example	Example	Example	Comparative Example	Comparative Example
		1	2	3	3	4
Cross-sectional morphology	Cross-sectional morphology	Eccentric core-sheath	Eccentric core-sheath	Eccentric core-sheath	Eccentric core-sheath	Eccentric core-sheath
	Polyamide (A)	Core: N6	Core: N6	Core: N6	Core: N6	Core: N6
	Polyamide (B)	Sheath: N610	Sheath: N610	Sheath: N610	Sheath: N610	Sheath: N610
	Sulfuric acid relative viscosity of polyamide (A)	3.25	3.25	3.25	3.25	3.25
	Sulfuric acid relative viscosity of polyamide (B)	2.70	2.70	2.70	2.70	2.70
	Area ratio (polyamide A/polyamide B)	1/1	1/1	1/1	1/1	1/1
	(L/M)	0.18	0.18	0.18	0.18	0.18
Conjugated fiber	Orientation parameter (low orientation side)	2.49	2.03	2.94	1.97	3.02
	Orientation parameter (high orientation side)	2.86	2.25	3.50	2.14	3.63
	Difference in orientation parameter	0.37	0.22	0.56	0.17	0.61
	Crystallinity (low orientation side) (%)	30.2	24.6	35.7	23.9	36.6
	Stretch elongation rate (%)	18.1	8.4	33.5	6.3	37.9
	Total fineness (dtex)	66.2	66.1	66.0	66.1	66.2
	Number of filaments	24	24	24	24	24
	Single yarn fineness (dtex)	2.8	2.8	2.8	2.8	2.8
False-twisted yarn	Difference in orientation parameter	0.09	0.05	0.13	0.04	0.14
	Crystallinity (low orientation side) (%)	33.4	27.2	39.5	26.4	40.5
	Stretch elongation rate (%)	70.0	42.0	98.7	29.4	110.6
	Total fineness (dtex)	56.1	56.0	55.9	56.0	56.1
Melt spinning step	Direction of conjugated interface with respect to varn cooling air	Parallel	Parallel	Parallel	Parallel	Parallel
	Spinning draft	200	105	295	90	310
	Take-up roller peripheral speed (mpm)	3500	3100	3900	2900	4100
	Drawing roller peripheral speed (mpm)	4025	3565	4485	3335	4715
	Draw ratio	1.15	1.15	1.15	1.15	1.15
	Heat setting temperature (°C)	170	170	170	170	170
	Winding speed (mpm)	4005	3565	4481	3342	4709
	Number of times of yarn breakage (per ton)	1	0	2	1	3
Evaluation	Fabric stretching	25.2	15.1	35.5	10.6	39.8
	Fabric stretching rating	A	B	A	C	A
	Fabric abrasion resistance (Martindale method)	A	A	B	A	C

		Example	Comparative Example	Example	Example
		4	5	6	7
Cross-sectional morphology	Cross-sectional morphology	Eccentric core-sheath	Eccentric core-sheath	Eccentric core-sheath	Eccentric core-sheath
	Polyamide (A)	Core: N6	Core: N6	Core: N6	Core: N6
	Polyamide (B)	Sheath: N610	Sheath: N610	Sheath: N610	Sheath: N610
	Sulfuric acid relative viscosity of polyamide (A)	3.25	3.25	3.25	3.25
	Sulfuric acid relative viscosity of polyamide (B)	2.70	2.70	2.70	2.70
	Area ratio (polyamide A/polyamide B)	1/1	1/1	1/1	1/1
	(L/M)	0.18	0.18	0.18	0.18
Conjugated fiber	Orientation parameter (low orientation side)	2.78	3.06	2.54	2.39
	Orientation parameter (high orientation side)	3.05	3.28	2.92	2.75
	Difference in orientation parameter	0.27	0.22	0.38	0.36
	Crystallinity (low orientation side) (%)	33.7	37.1	27.5	31.4
	Stretch elongation rate (%)	14.1	12.3	19.0	16.9
	Total fineness (dtex)	66.2	66.0	66.2	66.0
	Number of filaments	24	24	24	24
	Single yarn fineness (dtex)	2.8	2.8	2.8	2.8
False-twisted yarn	Difference in orientation parameter	0.06	0.05	0.09	0.08
	Crystallinity (low orientation side) (%)	37.3	41.0	30.4	34.7
	Stretch elongation rate (%)	56.0	42.0	73.3	65.4
	Total fineness (dtex)	56.1	55.9	56.1	55.9
Melt spinning step	Direction of conjugated interface with respect to yarn cooling air	Parallel	Parallel	Parallel	Parallel
	Spinning draft	200	200	250	250
	Take-up roller peripheral speed (mpm)	2800	2100	3500	3500
	Drawing roller peripheral speed (mpm)	4480	4410	4100	4100
	Draw ratio	1.60	2.10	1.15	1.15
	Heat setting temperature (°C)	170	170	100	200
	Winding speed (mpm)	4390	4190	4075	4100
	Number of times of yarn breakage (per ton)	1	1	1	1
Evaluation	Fabric stretching	20.2	15.1	26.4	23.5
	Fabric stretching rating	B	B	A	B
	Fabric abrasion resistance (Martindale method)	B	C	A	A

Example 5

The polymer composition, the temperature, and the cross-sectional morphology were the same as in Example 1, except that heat setting after drawing was not performed, and other conditions were as shown in Table 2. Melt spinning was performed to obtain a 66-dtex and 24-filament polyamide fiber having an eccentric core-sheath type cross section. The obtained polyamide fiber having an eccentric core-sheath type cross section was measured in terms of the orientation parameters of the low-orientation-side polyamide and high-orientation-side polyamide, the difference (absolute value) in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, the total fineness, and the single yarn fineness. In addition, the number of times of yarn breakage when 1 ton of the polyamide fiber having an eccentric core-sheath type cross section was produced was also counted. The results are shown in Table 2.
The obtained polyamide fiber having an eccentric core-sheath type cross section was subjected to false twisting in the same manner as in Example 1 to obtain a false-twisted yarn having about 56 dtex and 24 filaments. The obtained false-twisted yarn was measured in terms of the difference in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, and the total fineness. The results are shown in Table 2.
The obtained false-twisted yarn was subjected to textile-processing process in the same manner as in Example 1 to obtain a fabric. The obtained fabric was measured in terms of the fabric stretching and the fabric abrasion resistance (Martindale method). The results are shown in Table 2.

Comparative Example 1

An about 66-dtex and 24-filament polyhexamethylene adipamide fiber was obtained by melt spinning in the same manner as in Example 1 except that polyhexamethylene adipamide (98% sulfuric acid relative viscosity: 2.63, chip moisture content: 1100 ppm) was melted at 290°C using a pressure melter, the molten polyhexamethylene adipamide was discharged using a spinneret (24 holes × 2 groups, round holes), and the heat setting after drawing was not performed. In the present description, polyhexamethylene adipamide is also referred to as N66.
The obtained polyhexamethylene adipamide fiber was measured in terms of the stretch elongation rate, the total fineness, and the single yarn fineness. In addition, the number of times of yarn breakage when 1 ton of the polyhexamethylene adipamide fiber was produced was also counted. The results are shown in Table 2.
The obtained polyhexamethylene adipamide fiber was subjected to false twisting in the same manner as in Example 1 except that the processing temperature was changed to 195°C to obtain a false-twisted yarn having about 56 dtex and 24 filaments. The obtained false-twisted yarn was measured in terms of the stretch elongation rate and the total fineness. The results are shown in Table 2.
The obtained false-twisted yarn was subjected to textile-processing process in the same manner as in Example 1 to obtain a fabric. The obtained fabric was measured in terms of the fabric stretching and the fabric abrasion resistance (Martindale method). The results are shown in Table 2.

Comparative Example 2

An about 66-dtex and 24-filament polyamide fiber having a double core-sheath (concentric circle) cross section was obtained by melt spinning in the same manner as in Example 1 except that polycaproamide (98% sulfuric acid relative viscosity: 3.25, chip moisture content: 100 ppm) as the polyamide (A) as a core component and polyhexamethylene sebacamide (98% sulfuric acid relative viscosity: 2.70, chip moisture content: 1500 ppm) as the polyamide (B) as a sheath component were melted at 290°C and 270°C, respectively, using a pressure melter, and the molten polyamides were discharged using a double core-sheath (concentric circle) composite spinneret (24 holes × 2 groups, round holes).
The obtained polyamide fiber having a double core-sheath (concentric circle) cross section was measured in terms of the stretch elongation rate, the total fineness, and the single yarn fineness. In addition, the number of times of yarn breakage when 1 ton of the polyamide fiber having a double core-sheath (concentric circle) cross section was produced was also counted. The results are shown in Table 2.
The obtained polyamide fiber having a double core-sheath (concentric circle) cross section was subjected to false twisting in the same manner as in Example 1 to obtain a false-twisted yarn having about 56 dtex and 24 filaments. The obtained false-twisted yarn was measured in terms of the stretch elongation rate and the total fineness. The results are shown in Table 2.
The obtained false-twisted yarn was subjected to textile-processing process in the same manner as in Example 1 to obtain a fabric. The obtained fabric was measured in terms of the fabric stretching and the fabric abrasion resistance (Martindale method). The results are shown in Table 2.

Example 8

An about 66-dtex and 24-filament polyamide fiber having an eccentric core-sheath type cross section was obtained by melt spinning in the same manner as in Example 1 except that the polyamide (A) and the polyamide (B) were arranged such that the direction of the yarn cooling air and the direction of the conjugated interface were perpendicular to each other (the polyamide (A) was on the windward side of the cooling air and the polyamide (B) was on the leeward side of the cooling air).
The obtained polyamide fiber having an eccentric core-sheath type cross section was measured in terms of the orientation parameters of the low-orientation-side polyamide and high-orientation-side polyamide, the difference (absolute value) in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, the total fineness, and the single yarn fineness. In addition, the number of times of yarn breakage when 1 ton of the polyamide fiber having an eccentric core-sheath type cross section was produced was also counted. The results are shown in Table 2.
The obtained polyamide fiber having an eccentric core-sheath type cross section was subjected to false twisting in the same manner as in Example 1 to obtain a false-twisted yarn having about 56 dtex and 24 filaments. The obtained false-twisted yarn was measured in terms of the difference in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, and the total fineness. The results are shown in Table 2.
The obtained false-twisted yarn was subjected to textile-processing process in the same manner as in Example 1 to obtain a fabric. The obtained fabric was measured in terms of the fabric stretching and the fabric abrasion resistance (Martindale method). The results are shown in Table 2.

Example 9

An about 66-dtex and 24-filament polyamide fiber having an eccentric core-sheath type cross section was obtained by melt spinning in the same manner as in Example 1 except that polycaproamide (98% sulfuric acid relative viscosity: 3.25, chip moisture content: 100 ppm) as the polyamide (A) as a core component and polyhexamethylene adipamide (98% sulfuric acid relative viscosity: 2.63, chip moisture content: 1100 ppm) as the polyamide (B) as a sheath component were melted at 290°C and 290°C, respectively, using a pressure melter.
The obtained polyamide fiber having an eccentric core-sheath type cross section was measured in terms of the orientation parameters of the low-orientation-side polyamide and high-orientation-side polyamide, the difference (absolute value) in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, the total fineness, and the single yarn fineness. In addition, the number of times of yarn breakage when 1 ton of the polyamide fiber having an eccentric core-sheath type cross section was produced was also counted. The results are shown in Table 1.
The obtained polyamide fiber having an eccentric core-sheath type cross section was subjected to false twisting in the same manner as in Example 1 to obtain a false-twisted yarn having about 56 dtex and 24 filaments. The obtained false-twisted yarn was measured in terms of the difference in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, and the total fineness. The results are shown in Table 2.
The obtained false-twisted yarn was subjected to textile-processing process in the same manner as in Example 1 to obtain a fabric. The obtained fabric was measured in terms of the fabric stretching and the fabric abrasion resistance (Martindale method). The results are shown in Table 2.

Example 10

An about 66-dtex and 24-filament polyamide fiber having an eccentric core-sheath type cross section was obtained by melt spinning in the same manner as in Example 1 except that polycaproamide (98% sulfuric acid relative viscosity: 3.25, chip moisture content: 100 ppm) as the polyamide (A) as a core component and polycaproamide (98% sulfuric acid relative viscosity: 2.10, chip moisture content: 100 ppm) as the polyamide (B) as a sheath component were melted at 290°C and 270°C, respectively, using a pressure melter.
The obtained polyamide fiber having an eccentric core-sheath type cross section was measured in terms of the orientation parameters of the low-orientation-side polyamide and high-orientation-side polyamide, the difference (absolute value) in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, the total fineness, and the single yarn fineness. In addition, the number of times of yarn breakage when 1 ton of the polyamide fiber having an eccentric core-sheath type cross section was produced was also counted. The results are shown in Table 2.
The obtained polyamide fiber having an eccentric core-sheath type cross section was subjected to false twisting in the same manner as in Example 1 to obtain a false-twisted yarn having about 56 dtex and 24 filaments. The obtained false-twisted yarn was measured in terms of the difference in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, and the total fineness. The results are shown in Table 2.

The obtained false-twisted yarn was subjected to textile-processing process in the same manner as in Example 1 to obtain a fabric. The obtained fabric was measured in terms of the fabric stretching and the fabric abrasion resistance (Martindale method). The results are shown in Table 2.

[Table 2]

		Example	Comparative Example	Comparative Example
		5	1	2
Cross-sectional morphology	Cross-sectional morphology	Eccentric core-sheath	Single yarn	Double core-sheath
	Polyamide (A)	Core: N6	N66	Core: N6
	Polyamide (B)	Sheath: N610	-	Sheath: N610
	Sulfuric acid relative viscosity of polyamide (A)	3.25	2.63	3.25
	Sulfuric acid relative viscosity of polyamide (B)	2.70	-	2.70
	Area ratio (polyamide A/polyamide B)	1/1	-	1/1
	(L/M)	0.18	-	-
Conjugated fiber	Orientation parameter (low orientation side)	2.58	-	-
	Orientation parameter (high orientation side)	2.97	-	-
	Difference in orientation parameter	0.39	-	-
	Crystallinity (low orientation side) (%)	24.8	-	-
	Stretch elongation rate (%)	19.8	0.20	0.30
	Total fineness (dtex)	66.1	66.5	66.0
	Number of filaments	24	24	24
	Single yarn fineness (dtex)	2.8	2.6	2.6
False-twisted yarn	Difference in orientation parameter	0.09	-	-
	Crystallinity (low orientation side) (%)	27.4	-	-
	Stretch elongation rate (%)	76.7	28.9	29.6
	Total fineness (dtex)	56.0	56.6	56.1
Melt spinning step	Direction of conjugated interface with respect to varn cooling air	Parallel	-	-
	Spinning draft	250	250	250
	Take-up roller peripheral speed (mpm)	3500	3750	3750
	Drawing roller peripheral speed (mpm)	4100	4100	4100
	Draw ratio	1.15	1.09	1.09
	Heat setting temperature (°C)	Room temperature	Room temperature	170
	Winding speed (mpm)	4069	4000	4000
	Number of times of yarn breakage (per ton)	1	0	0
Evaluation	Fabric stretching	27.6	8.4	9.5
	Fabric stretching rating	A	D	D
	Fabric abrasion resistance (Martindale method)	A	B	B

		Example	Example	Example
		8	9	10
Cross-sectional morphology	Cross-sectional morphology	Eccentric core-sheath	Eccentric core-sheath	Eccentric core-sheath
	Polyamide (A)	Core: N6	Core: N6	Core: N6
	Polyamide (B)	Sheath: N610	Sheath: N66	Sheath: N6
	Sulfuric acid relative viscosity of polyamide (A)	3.25	3.25	3.25
	Sulfuric acid relative viscosity of polyamide (B)	2.70	2.63	2.10
	Area ratio (polyamide A/polyamide B)	1/1	1/1	1/1
	(L/M)	0.18	0.18	0.18
Conjugated fiber	Orientation parameter (low orientation side)	2.44	2.51	2.29
	Orientation parameter (high orientation side)	2.92	2.83	2.92
	Difference in orientation parameter	0.48	0.32	0.63
	Crystallinity (low orientation side) (%)	29.6	33.2	29.9
	Stretch elongation rate (%)	23.8	10.6	6.0
	Total fineness (dtex)	66.2	66.0	66.0
	Number of filaments	24	24	24
	Single yarn fineness (dtex)	2.8	2.8	2.8
False-twisted yarn	Difference in orientation parameter	0.11	0.07	0.14
	Crystallinity (low orientation side) (%)	32.7	36.7	33.1
	Stretch elongation rate (%)	92.0	49.7	42.0
	Total fineness (dtex)	56.1	55.9	55.9
Melt spinning step	Direction of conjugated interface with respect to yarn cooling air	Vertical (windward, N6)	Parallel	Parallel
	Spinning draft	250	200	200
	Take-up roller peripheral speed (mpm)	3500	3500	3500
	Drawing roller peripheral speed (mpm)	4025	4025	4025
	Draw ratio	1.15	1.15	1.15
	Heat setting temperature (°C)	170	170	170
	Winding speed (mpm)	4005	4005	4005
	Number of times of yarn breakage (per ton)	5	1	1
Evaluation	Fabric stretching	33.1	17.9	15.1
	Fabric stretching rating	A	B	B
	Fabric abrasion resistance (Martindale method)	A	B	A

Examples 11 to 15 and Comparative Examples 6 to 8

An about 63-dtex and 24-filament polyamide fiber having a side-by-side type cross section was obtained by melt spinning in the same manner as in Example 1 except that the melt spinning step shown in Table 3 was performed, for example, polycaproamide (98% sulfuric acid relative viscosity: 2.63, chip moisture content: 100 ppm) as the polyamide (A) and polyhexamethylene sebacamide (98% sulfuric acid relative viscosity: 2.70, chip moisture content: 1500 ppm) as the polyamide (B) were melted at 275°C and 260°C, respectively, using a pressure melter, and the molten polyamides were discharged using a side-by-side composite spinneret (24 holes × 2 groups, round holes).
The obtained polyamide fiber having a side-by-side type cross section was measured in terms of the orientation parameters of the low-orientation-side polyamide and high-orientation-side polyamide, the difference (absolute value) in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, the total fineness, and the single yarn fineness. In addition, the number of times of yarn breakage when 1 ton of the polyamide fiber having a side-by-side type cross section was produced was also counted. The results are shown in Table 3.
The obtained polyamide fiber having a side-by-side type cross section and the obtained multifilament were subjected to simultaneous drawing and false twisting at a processing temperature (heater setting temperature of contact type hot plate) of 190°C, an draw ratio of 1.20, a D/Y ratio of 1.95, and T2/T1 = 0.81 in a pin type drawing friction false twisting device to obtain a false-twisted yarn having about 56 dtex and 24 filaments. The obtained false-twisted yarn was measured in terms of the difference in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, and the total fineness. The results are shown in Table 3.

The obtained false-twisted yarn was subjected to textile-processing process in the same manner as in Example 1 to obtain a fabric. The obtained fabric was measured in terms of the fabric stretching and the fabric abrasion resistance (Martindale method). The results are shown in Table 3.

[Table 3]

		Example	Example	Example	Comparative Example
		11	12	13	6
Cross-sectional morphology	Cross-sectional morphology	Side-by-side	Side-by-side	Side-by-side	Side-by-side
	Polyamide (A)	N6	N6	N6	N6
	Polyamide (B)	N610	N610	N610	N610
	Sulfuric acid relative viscosity of polyamide (A)	2.63	2.63	2.63	2.63
	Sulfuric acid relative viscosity of polyamide (B)	2.70	2.70	2.70	2.70
	Area ratio (polyamide A/polyamide B)	1/1	1/1	1/1	1/1
	(L/M)	-	-	-	-
Conjugated fiber	Orientation parameter (low orientation side)	2.75	2.35	2.97	2.04
	Orientation parameter (high orientation side)	3.20	2.62	3.56	2.23
	Difference in orientation parameter	0.45	0.27	0.59	0.19
	Crystallinity (low orientation side) (%)	33.4	28.5	36.0	24.7
	Stretch elongation rate (%)	21.0	10.3	30.6	6.2
	Total fineness (dtex)	63.2	63.8	63.5	63.9
	Number of filaments	24	24	24	24
	Single yarn fineness (dtex)	2.6	2.7	2.6	2.7
False-twisted yarn	Difference in orientation parameter	0.10	0.06	0.14	0.04
	Crystallinity (low orientation side) (%)	36.4	31.1	39.3	27.0
	Stretch elongation rate (%)	109.0	53.5	159.0	23.9
	Total fineness (dtex)	56.3	56.8	56.6	56.2
Melt spinning step	Direction of conjugated interface with respect to varn cooling air	Parallel	Parallel	Parallel	Parallel
	Spinning draft	250	105	295	90
	Take-up roller peripheral speed (mpm)	3500	3100	3900	2900
	Drawing roller peripheral speed (mpm)	4025	3565	4485	3335
	Draw ratio	1.15	1.15	1.15	1.15
	Heat setting temperature (°C)	170	170	170	170
	Winding speed (mpm)	4005	3565	4481	3342
	Number of times of yarn breakage (per ton)	1	0	2	1
Evaluation	Fabric stretching	23.8	17.8	29.2	14.6
	Fabric stretching rating	B	B	A	C
	Fabric abrasion resistance (Martindale method)	B	A	B	A

		Comparative Example	Example	Example	Comparative Example
		7	14	15	8
Cross-sectional morphology	Cross-sectional morphology	Side-by-side	Side-by-side	Side-by-side	Side-by-side
	Polyamide (A)	N6	N6	N6	N6
	Polyamide (B)	N610	N610	N610	N610
	Sulfuric acid relative viscosity of polyamide (A)	2.63	2.63	2.63	2.63
	Sulfuric acid relative viscosity of polyamide (B)	2.70	2.70	2.70	2.70
	Area ratio (polyamide A/polyamide B)	1/1	1/1	1/1	1/1
	(L/M)	-	-	-	-
Conjugated fiber	Orientation parameter (low orientation side)	3.09	2.77	2.89	3.11
	Orientation parameter (high orientation side)	3.72	3.23	3.29	3.39
	Difference in orientation parameter	0.63	0.46	0.40	0.28
	Crystallinity (low orientation side) %	37.5	37.1	35.1	37.7
	Stretch elongation rate (%)	34.2	21.0	21.0	13.8
	Total fineness (dtex)	63.5	63.2	63.2	63.2
	Number of filaments	24	24	24	24
	Single yarn fineness (dtex)	2.6	2.6	2.6	2.6
False-twisted yarn	Difference in orientation parameter	0.14	0.11	0.09	0.06
	Crystallinity (low orientation side) %	40.9	36.4	38.3	41.2
	Stretch elongation rate (%)	177.4	109.0	76.3	65.4
	Total fineness (dtex)	56.3	56.3	56.3	56.3
Melt spinning step	Direction of conjugated interface with respect to varn cooling air	Parallel	Parallel	Parallel	Parallel
	Spinning draft	310	250	250	250
	Take-up roller peripheral speed (mpm)	4100	3500	2800	2100
	Drawing roller peripheral speed (mpm)	4715	4095	4480	4410
	Draw ratio	1.15	1.17	1.60	2.10
	Heat setting temperature (°C)	170	170	170	170
	Winding speed (mpm)	4709	4000	4390	4190
	Number of times of yarn breakage (per ton)	3	1	1	1
Evaluation	Fabric stretching	31.2	23.8	17.3	15.0
	Fabric stretching rating	A	B	B	B
	Fabric abrasion resistance (Martindale method)	C	B	B	C

Examples 16 to 21 and Comparative Examples 9 to 11

An about 56-dtex and 24-filament polyamide fiber having an eccentric core-sheath type cross section was obtained by melt spinning in the same manner as in Example 1 and the melt spinning step shown in Table 4. The obtained polyamide fiber having an eccentric core-sheath type cross section was measured in terms of the orientation parameters of the low-orientation-side polyamide and high-orientation-side polyamide, the difference (absolute value) in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, the total fineness, and the single yarn fineness. In addition, the number of times of yarn breakage when 1 ton of the polyamide fiber having an eccentric core-sheath type cross section was produced was also counted. The results are shown in Table 4.

The obtained polyamide fiber having an eccentric core-sheath type cross section was not subjected to false twisting, and the raw yarn was subjected to textile-processing process in the same manner as in Example 1 to obtain a fabric. The obtained fabric was measured in terms of the fabric stretching and the fabric abrasion resistance (Martindale method). The results are shown in Table 4.

[Table 4]

		Example	Example	Example	Comparative Example	Comparative Example
		16	17	18	9	10
Cross-sectional morphology	Cross-sectional morphology	Eccentric core-sheath	Eccentric core-sheath	Eccentric core-sheath	Eccentric core-sheath	Eccentric core-sheath
	Polyamide (A)	Core: N6	Core: N6	Core: N6	Core: N6	Core: N6
	Polyamide (B)	Sheath: N610	Sheath: N610	Sheath: N610	Sheath: N610	Sheath: N610
	Sulfuric acid relative viscosity of polyamide (A)	3.25	3.25	3.25	3.25	3.25
	Sulfuric acid relative viscosity of polyamide (B)	2.70	2.70	2.70	2.70	2.70
	Area ratio (polyamide A/polyamide B)	1/1	1/1	1/1	1/1	1/1
	(L/M)	0.18	0.18	0.18	0.18	0.18
Conjugated fiber	Orientation parameter (low orientation side)	2.85	2.74	2.96	2.71	3.01
	Orientation parameter (high orientation side)	3.10	2.95	3.30	2.86	3.40
	Difference in orientation parameter	0.25	0.21	0.34	0.15	0.39
	Crystallinity (low orientation side) (%)	34.8	36.9	39.5	36.5	40.1
	Stretch elongation rate (%)	18.5	16.8	27.8	11.2	33.0
	Total fineness (dtex)	56.2	56.3	56.1	56.1	55.9
	Number of filaments	24	24	24	24	24
	Single yarn fineness (dtex)	2.3	2.3	2.3	2.3	2.3
Melt spinning step	Direction of conjugated interface with respect to yarn cooling air	Parallel	Parallel	Parallel	Parallel	Parallel
	Spinning draft	200	105	295	90	310
	Take-up roller peripheral speed (mpm)	3200	3000	3400	2900	3500
	Drawing roller peripheral speed (mpm)	4480	4200	4760	4060	4900
	Draw ratio	1.40	1.40	1.40	1.40	1.40
	Heat setting temperature (°C)	170	170	170	170	170
	Winding speed (mpm)	4390	4137	4641	3991	4768
	Number of times of yarn breakage (per ton)	0	0	2	1	3
Evaluation	Fabric stretching	16.8	15.6	23.5	11.6	27.2
	Fabric stretching rating	B	B	B	C	A
	Fabric abrasion resistance (Martindale method)	B	B	B	B	C

		Example	Comparative Example	Example	Example
		19	11	20	21
Cross-sectional morphology	Cross-sectional morphology	Eccentric core-sheath	Eccentric core-sheath	Eccentric core-sheath	Eccentric core-sheath
	Polyamide (A)	Core: N6	Core: N6	Core: N6	Core: N6
	Polyamide (B)	Sheath: N610	Sheath: N610	Sheath: N610	Sheath: N610
	Sulfuric acid relative viscosity of polyamide (A)	3.25	3.25	3.25	3.25
	Sulfuric acid relative viscosity of polyamide (B)	2.70	2.70	2.70	2.70
	Area ratio (polyamide A/polyamide B)	1/1	1/1	1/1	1/1
	(L/M)	0.18	0.18	0.18	0.18
Conjugated fiber	Orientation parameter (low orientation side)	2.97	3.15	2.89	2.77
	Orientation parameter (high orientation side)	3.19	3.29	3.16	3.01
	Difference in orientation parameter	0.22	0.14	0.27	0.24
	Crystallinity (low orientation side) (%)	39.7	41.9	32.4	36.9
	Stretch elongation rate (%)	18.8	13.0	22.5	19.0
	Total fineness (dtex)	55.9	56.3	56.3	56.1
	Number of filaments	24	24	24	24
	Single yarn fineness (dtex)	2.3	2.3	2.3	2.3
Melt spinning step	Direction of conjugated interface with respect to yarn cooling air	Parallel	Parallel	Parallel	Parallel
	Spinning draft	250	250	250	250
	Take-up roller peripheral speed (mpm)	2600	1900	3200	3200
	Drawing roller peripheral speed (mpm)	4810	4750	4480	4480
	Draw ratio	1.85	2.50	1.40	1.40
	Heat setting temperature (°C)	170	170	100	200
	Winding speed (mpm)	4618	4418	4368	4413
	Number of times of yarn breakage (per ton)	0	1	1	1
Evaluation	Fabric stretching	17.0	12.9	19.7	17.2
	Fabric stretching rating	B	C	B	B
	Fabric abrasion resistance (Martindale method)	B	D	B	B

Example 22

An about 56-dtex and 24-filament polyamide fiber having an eccentric core-sheath type cross section was obtained by melt spinning in the same manner as in Example 1 except that the polyamide (A) and the polyamide (B) were arranged such that the direction of the yarn cooling air and the direction of the conjugated interface were perpendicular to each other (the polyamide (A) was on the windward side of the cooling air and the polyamide (B) was on the leeward side of the cooling air). The obtained polyamide fiber having an eccentric core-sheath type cross section was measured in terms of the orientation parameters of the low-orientation-side polyamide and high-orientation-side polyamide, the difference (absolute value) in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, the total fineness, and the single yarn fineness. In addition, the number of times of yarn breakage when 1 ton of the polyamide fiber having an eccentric core-sheath type cross section was produced was also counted. The results are shown in Table 5.
The obtained polyamide fiber having an eccentric core-sheath type cross section was not subjected to false twisting, and the raw yarn was subjected to textile-processing process in the same manner as in Example 1 to obtain a fabric. The obtained fabric was measured in terms of the fabric stretching and the fabric abrasion resistance (Martindale method). The results are shown in Table 5.

Example 23

An about 66-dtex and 24-filament polyamide fiber having an eccentric core-sheath type cross section was obtained by melt spinning in the same manner as in Example 1 except that polycaproamide (98% sulfuric acid relative viscosity: 3.25, chip moisture content: 100 ppm) as the polyamide (A) as a core component and polyhexamethylene adipamide (98% sulfuric acid relative viscosity: 2.63, chip moisture content: 1100 ppm) as the polyamide (B) as a sheath component were melted at 290°C and 270°C, respectively, using a pressure melter.
The obtained polyamide fiber having an eccentric core-sheath type cross section was measured in terms of the orientation parameters of the low-orientation-side polyamide and high-orientation-side polyamide, the difference (absolute value) in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, the total fineness, and the single yarn fineness. In addition, the number of times of yarn breakage when 1 ton of the polyamide fiber having an eccentric core-sheath type cross section was produced was also counted. The results are shown in Table 5.

Example 24

An about 66-dtex and 24-filament polyamide fiber having an eccentric core-sheath type cross section was obtained by melt spinning in the same manner as in Example 1 except that polycaproamide (98% sulfuric acid relative viscosity: 3.25, chip moisture content: 100 ppm) as the polyamide (A) as a core component and polycaproamide (98% sulfuric acid relative viscosity: 2.10, chip moisture content: 100 ppm) as the polyamide (B) as a sheath component were melted at 290°C and 270°C, respectively, using a pressure melter.
The obtained polyamide fiber having an eccentric core-sheath type cross section was measured in terms of the orientation parameters of the low-orientation-side polyamide and high-orientation-side polyamide, the difference (absolute value) in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, the total fineness, and the single yarn fineness. In addition, the number of times of yarn breakage when 1 ton of the polyamide fiber having an eccentric core-sheath type cross section was produced was also counted. The results are shown in Table 5.
The obtained polyamide fiber having an eccentric core-sheath type cross section was not subjected to false twisting, and the raw yarn was subjected to textile-processing process in the same manner as in Example 1 to obtain a fabric. The obtained fabric was measured in terms of the fabric stretching and the fabric abrasion resistance (Martindale method). The results are shown in Table 5.

Examples 25 to 28 and Comparative Examples 12 to 14

An about 56-dtex and 24-filament polyamide fiber having a side-by-side type cross section fiber was obtained by melt spinning in the same manner as in Example 1 except that the conditions shown in Table 6 were used, for example, polycaproamide (98% sulfuric acid relative viscosity: 2.63, chip moisture content: 100 ppm) as the polyamide (A) and polyhexamethylene sebacamide (98% sulfuric acid relative viscosity: 2.70, chip moisture content: 1500 ppm) as the polyamide (B) were melted at 275°C and 260°C, respectively, using a pressure melter, and the molten polyamides were discharged using a side-by-side composite spinneret (24 holes × 2 groups, round holes).
The obtained polyamide fiber having a side-by-side type cross section was measured in terms of the orientation parameters of the low-orientation-side polyamide and high-orientation-side polyamide, the difference (absolute value) in orientation parameter, the crystallinity of the low-orientation-side polyamide, the stretch elongation rate, the total fineness, and the single yarn fineness. In addition, the number of times of yarn breakage when 1 ton of the polyamide fiber having a side-by-side type cross section was produced was also counted. The results are shown in Table 6.

The obtained polyamide fiber having a side-by-side type cross section was not subjected to false twisting, and the raw yarn was subjected to textile-processing process in the same manner as in Example 1 to obtain a fabric. The obtained fabric was measured in terms of the fabric stretching and the fabric abrasion resistance (Martindale method). The results are shown in Table 6.

[Table 5]

		Example	Example	Example
		22	23	24
Cross-sectional morphology	Cross-sectional morphology	Eccentric core-sheath	Eccentric core-sheath	Eccentric core-sheath
	Polyamide (A)	Core: N6	Core: N6	Core: N6
	Polyamide (B)	Sheath: N610	Sheath: N66	Sheath: N6
	Sulfuric acid relative viscosity of polyamide (A)	3.25	3.25	3.25
	Sulfuric acid relative viscosity of polyamide (B)	2.70	2.10	2.10
	Area ratio (polyamide A/polyamide B)	1/1	1/1	1/1
	(L/M)	0.18	0.18	0.18
Conjugated fiber	Orientation parameter (low orientation side)	2.79	2.88	2.62
	Orientation parameter (high orientation side)	3.16	3.09	3.16
	Difference in orientation parameter	0.37	0.21	0.54
	Crystallinity (low orientation side) (%)	37.5	38.3	34.5
	Stretch elongation rate (%)	27.9	18.3	16.3
	Total fineness (dtex)	55.9	66.0	66.0
	Number of filaments	24	24	24
	Single yarn fineness (dtex)	2.3	2.8	2.8
Melt spinning step	Direction of conjugated interface with respect to yarn cooling air	Vertical (windward: N6)	Parallel	Parallel
	Spinning draft	250	200	200
	Take-up roller peripheral speed (mpm)	3200	3500	3500
	Drawing roller peripheral speed (mpm)	4480	4025	4025
	Draw ratio	1.40	1.15	1.15
	Heat setting temperature (°C)	170	170	170
	Winding speed (mpm)	4390	4005	4005
	Number of times of yarn breakage (per ton)	5	1	1
Evaluation	Fabric stretching	23.6	15.1	13.5
	Fabric stretching rating	B	B	B
	Fabric abrasion resistance (Martindale method)	B	B	A

[Table 6]

		Example	Example	Example	Comparative Example
		25	26	27	12
Cross-sectional morphology	Cross-sectional morphology	Side-by-side	Side-by-side	Side-by-side	Side-by-side
	Polyamide (A)	N6	N6	N6	N6
	Polyamide (B)	N610	N610	N610	N610
	Sulfuric acid relative viscosity of polyamide (A)	2.63	2.63	2.63	2.63
	Sulfuric acid relative viscosity of polyamide (B)	2.70	2.70	2.70	2.70
	Area ratio (polyamide A/polyamide B)	1/1	1/1	1/1	1/1
	(L/M)	-	-	-	-
Conjugated fiber	Orientation parameter (low orientation side)	2.87	2.78	2.98	2.72
	Orientation parameter (high orientation side)	3.18	3.02	3.37	2.91
	Difference in orientation parameter	0.31	0.24	0.39	0.19
	Crystallinity (low orientation side) (%)	36.1	35.0	37.5	34.3
	Stretch elongation rate (%)	25.5	19.3	33.4	15.2
	Total fineness (dtex)	56.3	56.1	55.9	56.1
	Number of filaments	24	24	24	24
	Single yarn fineness (dtex)	2.3	2.3	2.3	2.3
Melt spinning step	Direction of conjugated interface with respect to yarn cooling air	Parallel	Parallel	Parallel	Parallel
	Spinning draft	250	105	295	90
	Take-up roller peripheral speed (mpm)	3200	3000	3400	2900
	Drawing roller peripheral speed (mpm)	4480	4200	4760	4060
	Draw ratio	1.40	1.40	1.40	1.40
	Heat setting temperature (°C)	170	170	170	170
	Winding speed (mpm)	4390	4137	4641	3991
	Number of times of yarn breakage (per ton)	1	0	2	1
Evaluation	Fabric stretching	16.7	15.0	18.8	13.9
	Fabric stretching rating	B	B	B	C
	Fabric abrasion resistance (Martindale method)	B	A	B	A

		Comparative Example	Example	Comparative Example
		13	28	14
Cross-sectional morphology	Cross-sectional morphology	Side-by-side	Side-by-side	Side-by-side
	Polyamide (A)	N6	N6	N6
	Polyamide (B)	N610	N610	N610
	Sulfuric acid relative viscosity of polyamide (A)	2.63	2.63	2.63
	Sulfuric acid relative viscosity of polyamide (B)	2.70	2.70	2.70
	Area ratio (polyamide A/polyamide B)	1/1	1/1	1/1
	(L/M)	-	-	-
Conjugated fiber	Orientation parameter (low orientation side)	3.05	2.99	3.19
	Orientation parameter (high orientation side)	3.48	3.25	3.36
	Difference in orientation parameter	0.43	0.26	0.17
	Crystallinity (low orientation side) (%)	38.3	37.6	40.1
	Stretch elongation rate (%)	37.7	22.2	15.6
	Total fineness (dtex)	55.9	56.3	56.0
	Number of filaments	24	24	24
	Single yarn fineness (dtex)	2.3	2.3	2.3
Melt spinning step	Direction of conjugated interface with respect to yarn cooling air	Parallel	Parallel	Parallel
	Spinning draft	310	250	250
	Take-up roller peripheral speed (mpm)	3500	2600	1900
	Drawing roller peripheral speed (mpm)	4900	4810	4750
	Draw ratio	1.40	1.85	2.50
	Heat setting temperature (°C)	170	170	170
	Winding speed (mpm)	4768	4618	4418
	Number of times of yarn breakage (per ton)	3	0	1
Evaluation	Fabric stretching	20.0	15.8	14.0
	Fabric stretching rating	B	B	C
	Fabric abrasion resistance (Martindale method)	C	B	D

As is clear from the results in Tables 1 to 6, it can be said that the polyamide conjugated fiber according to the present embodiment exhibits an extremely remarkable effect from the viewpoint of being excellent in both abrasion resistance and crimpability as compared with the polyamide conjugated fiber in the related art.
Although the present invention has been described in detail with reference to specific embodiments, it is apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. Note that, the present application is based on Japanese Patent Application No. 2023-010788 filed on January 27, 2023 , and the content thereof is incorporated herein by reference. All references cited herein are incorporated as a whole.

REFERENCE SIGNS LIST

1: polyamide (A)
2: polyamide (B)
3: polyamide (A) as core component
4: polyamide (B) as sheath component
5: center of core component
6: center of conjugated fiber
7: chimney
8: yarn cooling air
9: composite spinneret
10: spinneret discharge hole
11: conjugated interface
12: polyamide (A)
13: polyamide (B)
14: high shrinkable (high orientation side) polymer
15: low shrinkable (low orientation side) polymer

Claims

A polyamide conjugated fiber, the conjugated fiber comprising two kinds of polyamides, and satisfying the following A to C,
A. a cross-sectional morphology in a fiber cross-section of the polyamide conjugated fiber is a side-by-side type or an eccentric core-sheath type,

B. a difference in orientation parameter between the two kinds of polyamides is 0.20 or more in terms of absolute value, and

C. a low-orientation-side polyamide has an orientation parameter in a range of 1.50 to 3.00.
The polyamide conjugated fiber according to claim 1, wherein the low-orientation-side polyamide has a crystallinity in a range of 10.0% to 40.0%.
A polyamide multifilament comprising the polyamide conjugated fiber according to claim 1 or 2, and having a stretch elongation rate of 1.0% or more.
A polyamide conjugated false-twisted yarn, the yarn comprising two kinds of polyamides, and satisfying the following D to G,
D. a cross-sectional morphology in a fiber cross-section of the polyamide conjugated false-twisted yarn is a side-by-side type or an eccentric core-sheath type,

E. the polyamide conjugated false-twisted yarn has a stretch elongation rate of 30.0% or more,

F. a difference in orientation parameter between the two kinds of polyamides is 0.05 or more in terms of absolute value, and

G. a low-orientation-side polyamide has a crystallinity in a range of 10.0% to 40.0%.