EP4732697A1

EP4732697A1 - Swimsuit

Info

Publication number: EP4732697A1
Application number: EP24825936.8A
Authority: EP
Inventors: Hiroyuki Tanaka; Kenji Ootake; Ryosuke Kimura; Miyoko Kamei; Yutaro Suzuki
Original assignee: Mizuno Corp; Toray Industries Inc
Current assignee: Mizuno Corp; Toray Industries Inc
Priority date: 2023-06-21
Filing date: 2024-06-19
Publication date: 2026-04-29
Also published as: TW202507103A; WO2024262535A1; CN121194719A; JPWO2024262535A1

Abstract

Provided is a swimsuit that has excellent water repellency/low water retention rate/buoyancy and contributes to enhanced athletic ability. The present invention comprises a woven fabric in which a covering-covered yarn having a polyurethane elastic yarn as a core yarn and a synthetic fiber filament as a sheath yarn is disposed in at least a portion of warp and weft yarns, the polyurethane elastic yarn containing 0.5 to 10 mass% of a cationic high-molecular-weight compound having a number average molecular weight of 2,000 or more and an inorganic chlorine degradation inhibitor, the mass ratio of the cationic high-molecular-weight compound and the inorganic chlorine degradation inhibitor being 0.3 to 3, and the polyurethane elastic yarn including silicone, the synthetic fiber filament being constituted from synthetic fibers including single fibers having a plurality of grooves continuous in the fiber length direction, the depth of the grooves being 1.0-10.0 µm, the width of an inlet being 0.5-10.0 µm, the width of the tip of a protruding part being 10.0 µm or less, the porosity due to the fiber cross-sectional shape of the grooves being 5-30%, and the woven fabric including a flat woven fabric having a porosity of 75% or less and a weft double woven fabric, including a portion in which the flat woven fabric and the weft double woven fabric are repeated at a position covering the buttocks, and being subjected to a water repellent treatment.

Description

TECHNICAL FIELD

The present invention relates to a swimsuit.

BACKGROUND ART

In a swimming competition in which a player competes for less than one second, improvement of buoyancy, reduction of water flow resistance, stretchability and low water retention rate for securing ease of movement in water, and high water repellency of a competition swimsuit to be worn are important problems in addition to improvement of a skill of the player, and improvement of a cloth for a swimsuit has been advanced.
For example, for the purpose of improving buoyancy, it has been proposed to obtain buoyancy by a hollow part by using a raw yarn having a C-shaped hollow cross section (for example, see Patent Literature 1). Accordingly, excellent buoyancy can be obtained by a high hollow ratio of the C-shaped hollow cross section.
In addition, there has been proposed a method of reducing water flow resistance by forming a woven fabric for a swimsuit into a weave texture having many floating yarns in a body length direction (for example, see Patent Literature 2). It is described that the water flow resistance can be effectively reduced by using a raw yarn having a special cross-sectional shape and having an inlet narrowing type groove as a floating yarn.
From the viewpoint of reducing the water flow resistance, also there has been proposed a swimsuit including a woven fabric in which a plain weave part and a double weave part are alternately repeated (for example, see Patent Literature 3).

CITATION LIST

PATENT LITERATURE

Patent Literature 1: JPH06-228820A
Patent Literature 2: WO2021/100810A
Patent Literature 3: WO2015/151820A

SUMMARY OF INVENTION

TECHNICAL PROBLEM

As described above, a water-repellent woven fabric intended to be worn in water has various required characteristics such as stretchability, water repellency, low water retention rate, buoyancy, and water flow resistance. Among them, the buoyancy and the water flow resistance are particularly important elements in a competition swimsuit for improving the athletic ability. One of solutions for the water flow resistance is to increase the number of floating yarns. In this case, voids become large and initial buoyancy is excellent, but the voids retain water over time or due to kneading in water, and the buoyancy is conversely reduced. Further, in a material having a large void, the void generates a turbulent flow, which also leads to an increase in surface water flow resistance. That is, it has been difficult to implement both durable buoyancy and water flow resistance.
For example, in the technique of Patent Literature 1, although the initial buoyancy is excellent, the water repellency of the hollow part decreases due to repeated wearing, the hollow part acts in a direction of increasing a weight of the swimsuit in water when immersed in water, and thus the durability of the buoyancy decreases. In addition, an effect of improving water repellency by a raw yarn structure cannot be expected, and the water repellency is also insufficient.
In addition, although the technique of Patent Literature 2 described above is excellent in reducing the water flow resistance, since voids in texture of a cloth structure are enlarged by increasing the number of floating yarns, the technique has excellent buoyancy in a short period of time, but water is retained in the voids in the texture due to a kneading effect on the cloth over time or by motion, the weight in water is increased, and the buoyancy is reduced.
Similarly, the technique of Patent Literature 3 is also effective in reducing the water flow resistance, but no consideration is given to the buoyancy.
In view of the above, an object of the present invention is to reduce water flow resistance and improve buoyancy and durability thereof.

SOLUTION TO PROBLEM

In order to solve the above problems, the present invention has the following configurations.

(1) A swimsuit partially including:
- a woven fabric in which a covered yarn is disposed in at least a part of a warp yarn and a weft yarn, the covered yarn including a polyurethane elastic yarn as a core yarn and a synthetic fiber filament as a sheath yarn, in which
- the polyurethane elastic yarn includes 0.5 mass% to 10 mass% of a cationic high-molecular-weight compound A having a number average molecular weight of 2,000 or more and an inorganic chlorine degradation inhibitor B,
- a mass ratio (A/B) of the cationic high-molecular-weight compound A and the inorganic chlorine degradation inhibitor B is 0.3 to 3,
- the polyurethane elastic yarn includes silicone,
- at least a part of the synthetic fiber filament comprises a synthetic fiber comprising a single fiber comprising a plurality of grooves on a surface of the single fiber,
- the grooves are continuous in a fiber longitudinal direction,
- each of the grooves has a depth of 1.0 µm to 10.0 µm, a width of an inlet of 0.5 µm to 10.0 µm, a width of a tip of a protruding part of 10.0 µm or less, and a porosity due to a fiber cross-sectional shape of 5% to 30%,
- the woven fabric includes a plain woven fabric and a weft double woven fabric and has an internal porosity of 75% or less,
- the swimsuit further includes a part in which the plain woven fabric and the weft double woven fabric are alternately repeated at a position covering at least a buttock, and
- the swimsuit is subjected to water repellent processing.
(2) The swimsuit according to (1), in which
the part in which the plain woven fabric and the weft double woven fabric are alternately repeated is disposed in at least a part of a region covering from a navel to above a knee.
(3) The swimsuit according to (1) or (2), in which
the part in which the plain woven fabric and the weft double woven fabric are alternately repeated is disposed in the entire swimsuit.
(4) The swimsuit according to any of (1) to (3), in which
a main body cloth of the swimsuit includes the woven fabric.
(5) The swimsuit according to any of (1) to (4), in which
a lining of the swimsuit includes the woven fabric.
(6) The swimsuit according to any of (1) to (5), in which
- the swimsuit is for covering only an upper body, and
- a mass ratio of the woven fabric in the swimsuit is 35% or more.
(7) The swimsuit according to any of (1) to (6), in which
- the swimsuit is for covering only an upper body, and
- a mass ratio of the woven fabric in the swimsuit in a front body region and a rear body region is front body region: rear body region = 4 to 50: 50 to 96.
(8) The swimsuit according to any of (1) to (5), in which
- the swimsuit is for covering an upper body and a lower body, and
- a mass ratio of the woven fabric in the swimsuit is 28% or more.
(9) The swimsuit according to any of (1) to (5) and (8), in which
- the swimsuit is for covering an upper body and a lower body, and
- a mass ratio of the woven fabric in the swimsuit in a front body region and a rear body region is front body region: rear body region = 7 to 45: 55 to 93.
(10) The swimsuit according to any of (1) to (5), (8), and (9), in which
- the swimsuit is for covering an upper body and a lower body, and
- a mass ratio of the woven fabric in the swimsuit in an upper body region covering from a head to a body center of gravity and a lower body region covering from the body center of gravity to above a knee is upper body region: lower body region = 2 to 45: 55 to 98.
(11) The swimsuit according to any of (1) to (10), in which
the polyurethane elastic yarn has a fluorine/carbon (F/C) ratio of 0.030 or more in an element mass concentration determined by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX).
(12) The swimsuit according to any of (1) to (11), in which
the number of the grooves of the synthetic fiber filament is 2 to 32.
(13) The swimsuit according to any of (1) to (12), in which
the synthetic fiber filament is a non-crimped multifilament.
(14) The swimsuit according to any of (1) to (13), in which
the woven fabric achieves grade four or higher in a spray test described in JIS L 1092:2009.
(15) The swimsuit according to any of (1) to (14), in which
the woven fabric has a water retention rate after 60 minutes of 50 mass% or less relative to a weight of the fabric.
(16) The swimsuit according to any of (1) to (15), in which
a buoyancy per 1 g of the woven fabric is 0.0170 N or more.
(17) The swimsuit according to any of (1) to (16), in which
- a cross-sectional shape of the synthetic fiber of the woven fabric satisfies the following Expression 1 and Expression 2. $W 2 / W 1 \geq 1.3$ $0.15 \leq H / D \leq 0.25$
- W1: width (µm) of inlet of grooves
- W2: width (µm) of wide width part of grooves
- H: depth (µm) of grooves
- F: diameter (µm) of fiber

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a swimsuit having buoyancy with excellent durability and capable of reducing surface water flow resistance.
The present invention has been briefly described above. Further, the details of the present invention will be further clarified by reading modes for carrying out the invention described below (hereinafter referred to as "embodiments") with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] FIG. 1 is a schematic diagram illustrating a cross-sectional shape of an example of a single fiber used in the present invention.
[FIG. 2] FIG. 2 is a schematic enlarged diagram of a groove illustrating a groove of an example of the single fiber used in the present invention.
[FIG. 3] FIG. 3 is an enlarged schematic diagram of a protruding part of an example of the single fiber used in the present invention.
[FIG. 4] FIG. 4 is a schematic diagram illustrating a buoyancy measurement method.
[FIG. 5] FIG. 5 is a partially enlarged diagram of one embodiment of distribution hole arrangement in a final distribution plate.
[FIG. 6] (A), (B), and (C) of FIG. 6 are a front view, a side view, and a rear view of a swimsuit (male swimsuit for racing) according to a first embodiment, respectively.
[FIG. 7] (A), (B), and (C) of FIG. 7 are a front view, a side view, and a rear view of a swimsuit (male swimsuit for racing) according to a second embodiment, respectively.
[FIG. 8] (A), (B), and (C) of FIG. 8 are a front view, a side view, and a rear view of a swimsuit (male swimsuit for racing) according to a third embodiment, respectively.
[FIG. 9] (A), (B), and (C) of FIG. 9 are a front view, a side view, and a rear view of a swimsuit (female swimsuit for racing) according to a fourth embodiment, respectively.
[FIG. 10] (A), (B), and (C) of FIG. 10 are a front view, a side view, and a rear view of a swimsuit (female swimsuit for racing) according to a fifth embodiment, respectively.
[FIG. 11] (A), (B), and (C) of FIG. 11 are a front view, a side view, and a rear view of a swimsuit (female swimsuit for racing) according to a sixth embodiment, respectively.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present invention will be described in detail. "To" in a numerical range includes numerical values before and after it. For example, "1.0 to 10.0" means a range of 1.0 or more and 10.0 or less.
A covering-coated yarn in the present invention includes a synthetic fiber multifilament as a sheath yarn. At least a part of the synthetic fiber multifilament yarn includes, as a constituent single fiber, a synthetic fiber including a single fiber including, on a surface thereof, a plurality of grooves continuous in a fiber longitudinal direction. As illustrated in FIG. 1, which is a schematic diagram illustrating a cross-sectional shape of an example of the single fiber used in the present invention, the fiber has a cross-sectional shape in which a plurality of grooves 12 each having a wide width part in an outer circumferential part are present with a protruding part 11 interposed therebetween (hereinafter, above-described cross-sectional shape may be referred to as "special cross-sectional shape", and fiber having special cross-sectional shape may be referred to as "special cross-sectional fiber").
A depth (H) of the groove in the special cross-sectional shape is 1.0 µm to 10.0 µm. A water droplet adhering to a fiber surface enters the groove due to its own weight or a kneading effect, and adheres to a bottom surface of the groove when reaching the bottom surface, and the fiber gets wet, which leads to deterioration of a water retention rate and buoyancy. However, when the groove is deep, the water droplet is pushed up to an upper part of the groove by a surface tension of the water droplet, and thus the fiber does not get wet and water repellency is exhibited. On the other hand, in a multifilament having single fiber fineness of 2.5 dtex to 5 dtex, which is generally used in a swimsuit, since a diameter of a single fiber filament is 12 µm to 26 µm, there is a concern that strength of a raw yarn may decrease when the groove is designed to be excessively deep. Therefore, the depth of the groove is preferably 10 µm or less, and more preferably 8 µm or less.
When the diameter of the single fiber filament is small, it is preferable to control the depth of the groove, preferably a relation between the diameter and the depth of the groove to such an extent that the strength of the raw yarn does not excessively decrease within the above range. In addition, when the depth of the groove is too small, the droplet reaches the bottom surface of the groove, and sufficient water repellency cannot be obtained. Therefore, in order to exhibit water repellency by utilizing the surface tension of the water droplet, the depth of the groove is preferably 1 µm or more, and further preferably 2 µm or more, as described above.
The depth (H) of the groove in the special cross-sectional fiber is defined as a distance from an intersection point of a perpendicular line 22 and a straight line 21 connecting ends of the protruding part on a line of the perpendicular line 22 to a contact point 23 of a fiber polymer part with the perpendicular line 22 by connecting the perpendicular line 22 to a center point 13 (not illustrated in FIG. 2) (center point of circumscribed circle circumscribing tip of protruding part most frequently) of a cross section in a direction perpendicular to a longitudinal direction of the synthetic fiber filament from the straight line 21 (distance of this straight line 21 is defined as width of inlet of groove (W1)) connecting the ends of the protruding part 11 existing across the groove in FIG. 2. In addition, as illustrated in FIG. 1, the center point 13 of the fiber is defined as a center point of a circle that circumscribes the tip of the protruding part most frequently in a fiber polymer cross section (hereinafter, referred to as circumscribed circle), and a diameter of the circumscribed circle is defined as a fiber diameter (D) 14.
The width of the inlet of the groove (W1) in the special cross-sectional shape is 0.5 µm to 10.0 µm. When the width of the inlet of the groove is within the above preferable range, high water repellency can be exhibited by obtaining a surface tension due to the surface tension of the water droplet. When the width of the inlet of the groove is too small, a water repellent agent does not penetrate into the groove and it is difficult to obtain the water repellency, and thus the width is preferably 0.5 µm or more, and further preferably 1.0 µm or more. In addition, when the width of the inlet of the groove is too large, water enters the inside of the groove, and thus the water retention rate and the buoyancy deteriorate. Therefore, the width is preferably 10 µm or less, and further preferably 8 µm or less.
In the above-described special cross-sectional shape, preferable ranges of the width of the inlet of the groove (W1), the width 24 of the wide width part of the groove (W2), and the groove depth (H) with respect to the fiber diameter (D) 14 will be described below. The width of the wide width part of the groove (W2) is the width 24 of the wide width part of the groove (W2) that is maximum when a length orthogonal to a center line of the groove is measured from an outer circumferential part toward a fiber center along the center line. It is preferable that a ratio W2/W1 of the width of the wide width part of the groove (W2) to the width of the inlet of the groove (W1) be set to 1.3 or more because more air can be mixed inside and the buoyancy and the water repellency can be improved. W2/W1 is more preferably 1.5 or more, and further preferably 1.8 or more. In addition, W2/W1 is 3.0 or less in order to prevent cracking of the protruding part due to rubbing caused by wearing and to be excellent in maintaining a shape of the inlet of the groove. The functions can be maintained by maintaining the shape of the inlet of the groove.
A ratio (H/D) of the depth (H) of the groove to the fiber diameter (D) is preferably 0.15 or more and 0.25 or less. Accordingly, it is possible to exhibit functions such as water repellency and high buoyancy by forming a sufficient air layer inside, and on the other hand, there is no possibility that performance deterioration occurs due to deformation or breakage when the protruding part forming the groove receives an external force. H/D is more preferably 0.17 or more and less than 0.22. In summary, the special cross-sectional shape preferably satisfies the following expression. $W 2 / W 1 \geq 1.3$ $0.15 \leq H / D \leq 0.25$

W1: width (µm) of inlet of grooves
W2: width (µm) of wide width part of grooves
H: depth (µm) of grooves
F: diameter (µm) of fiber

As the single fiber filament having a groove on the surface thereof used in the present invention, it is more preferred to use a single fiber filament in which a width 31 of the tip of the protruding part (Pout) and the width of the inlet of the groove (W1) as well as a width 32 of a bottom surface (Pmin) of a groove adjacent to the width 31 of the tip of the protruding part (Pout) satisfy the following expressions. The width 31 of the tip of the protruding part (Pout) is a shortest distance connecting one tip and the other tip of the protruding part, and is a distance represented by a reference numeral 31 in FIG. 3. The width 31 of the tip of the protruding part (Pout) is preferably 10.0 µm or less. When the width of the tip of the protruding part (Pout) exceeds 10.0 µm, the water droplet may come into contact with only the tip of the protruding part without coming into contact with the air layer formed in the groove, and thus the effect of improving the water repellency cannot be sufficiently obtained. In addition, the width 32 of the bottom surface of the protruding part (Pmin) is a distance connecting contact points of inscribed circles of adjacent grooves sandwiching the protruding part, and is a distance represented by a reference numeral 32 in FIG. 3. $Pout / W 1 = 2 to 10$ $Pout / Pmin \geq 1.3$
The shape of the groove in the special cross-sectional fiber is preferably a shape which has a wide width part having a width wider than the width of the inlet in a range from the inlet of the groove having a teardrop shape, a hexagonal shape, or the like to the bottom surface of the groove when the groove is observed in a cross section in a direction perpendicular to the fiber longitudinal direction, and in which the width of the groove gradually decreases from the wide width part toward the bottom surface of the groove.
The number of the grooves in the special cross-sectional fiber is preferably plural, and when only one groove is present, the groove may not be present on a boundary surface with water depending on an orientation of the fiber, and the effect of improving the water repellency cannot be obtained. The number of the grooves is preferably 2 to 32, and more preferably 4 to 16. When the number of the grooves is within the above preferable range, the width of the protruding part in the fiber cross-sectional shape does not become too small, and fibrils and fluff are not generated on a product surface during a processing step or use of the product.
In the present invention, in order to obtain the above-described special cross-sectional shape, it is desirable to use a core-sheath composite fiber as a raw material fiber. Here, the core-sheath composite fiber is composed of two types of polymers, where a cross section of a core component has the above-described shape, and the special cross-sectional fiber can be obtained by eluting a sheath component with a solvent or the like. As the core component, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polyamide such as nylon 6 can be used. The sheath component is preferably a copolymerized polyester, polylactic acid, polyvinyl alcohol, or the like that exhibits easy elution in an aqueous solvent, hot water, or the like from the viewpoint of simplifying an elution step, and is particularly preferably polyester or polylactic acid in which polyethylene glycol or sodium sulfoisophthalic acid is copolymerized alone or in combination with each other from the viewpoint of handleability and easy solubility in an aqueous solvent. A mass ratio of the core component to the sheath component is preferably in a range of 50:50 to 90:10. The larger the core component ratio, which is an elution component, is, the larger the air layer can be formed in the cross section of the raw yarn, which is preferable for improving the buoyancy, but the above range is preferable, and a range of 60:40 to 80:20 is further preferable for causing deterioration of the strength of the raw yarn and prolongation of the elution step.
At least a part of the synthetic fiber multifilament yarn used in the present invention is the special cross-sectional fiber, and all of the synthetic fiber multifilament yarn may be the special cross-sectional fiber, or may be another multifilament. The other multifilament may be a multifilament having a fiber cross section other than the special cross-sectional fiber. As a material constituting such a multifilament, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyamide such as nylon 6, or the like can be used. In this case, a non-crimped multifilament is preferable from the viewpoint of reducing the porosity of the woven fabric.
In order to impart stretchability to the woven fabric, it is common to improve elongation properties of the synthetic fiber multifilament by imparting crimps by yarn processing represented by false twisting in the synthetic fiber multifilament, and when the crimps are formed in the synthetic fiber filaments, voids in the texture become large due to the crimps. In the present invention, it is important to prevent deterioration of the water retention rate and buoyancy due to aging in water or kneading during wearing by minimizing the voids in the texture (reducing coarse voids). Therefore, as the synthetic fiber multifilament, it is preferable to use a so-called non-crimped multifilament (hereinafter, sometimes referred to as non-crimped fiber) having substantially no crimp. Accordingly, the voids in the texture can be further reduced. Here, the term "non-crimped", which has substantially no crimp, is intended to mean that positive crimps are not imparted unlike crimping processing such as false twisting or actually-crimped conjugate fibers (woven crimps inevitably generated by weaving are not regarded as crimps).
As a means for reducing the voids in the texture other than the use of non-crimped fibers, there is a method of forming a high-density woven fabric by interweaving elastic fibers.
The covering-coated yarn in the present invention includes a polyurethane elastic yarn as a core yarn. The polyurethane elastic yarn contains a cationic high-molecular-weight compound A having a number average molecular weight of 2,000 or more in a range of 0.5 mass% to 10 mass% and an inorganic chlorine degradation inhibitor B, and a mass ratio of A/B satisfies a range of 0.3 to 3. Accordingly, a large synergistic effect can be exhibited, and excellent chlorine deterioration resistance effect and water repellent processability can be exhibited. Further details of the polyurethane elastic yarn are disclosed, for example, in JP2020-169400A .
The cationic high-molecular-weight compound used in the present invention is not particularly limited as long as it is a compound having an amino group in the structure, but a compound having only a tertiary amino group among primary to tertiary amino groups in the molecule is particularly preferable from the viewpoint of chlorine deterioration resistance and yellowing resistance of the polyurethane elastic yarn. When the number average molecular weight of the cationic high-molecular-weight compound is less than 2,000, the water repellent processability is deteriorated by falling off due to abrasion with a guide or a knitting needle during knitting of the polyurethane elastic yarn or by outflow during processing in a bath such as dyeing, and thus it is necessary that the number average molecular weight be 2,000 or more. In view of solubility in a polyurethane spinning solution, the range of the number average molecular weight is preferably 2,000 to 10,000. More preferably, the range of the number average molecular weight is 2,000 to 4,000. The number average molecular weight of the cationic high-molecular-weight compound can be measured by gel permeation chromatography (GPC) in terms of polystyrene.
By containing the cationic high-molecular-weight compound described above, the water repellent processability of the polyurethane elastic yarn can be enhanced. From the viewpoint of making this effect sufficient and not adversely affecting the physical properties of the fiber, the cationic high-molecular-weight compound is contained in an amount of preferably 0.5 mass% or more and 10 mass% or less, and more preferably 0.5 mass% or more and 4 mass% or less, based on a mass of the fiber.
The polyurethane elastic yarn in the present invention contains silicone. Preferably, silicone in a specific range of 0.5 mass% or more and 20 mass% or less is applied to the polyurethane elastic yarn in the form of an oil agent, for example. The silicone is originally intended to reduce a tension fluctuation at the time of unwinding of the polyurethane elastic yarn at the time of producing a fabric to be small and to prevent yarn breakage or the like due to a unwinding force fluctuation even in the case of an elastic fiber having fine fineness, but in the present case, the silicone significantly contributes to the improvement of the water repellent processability. A content of the silicone in a treatment agent is preferably 0.5 mass% to 10 mass%, and more preferably 1 mass% to 6 mass% in terms of dry mass. Accordingly, affinity with a water repellent treatment agent can be improved. For example, when silicone is contained in the oil agent, surface energy of a fabric surface is reduced, and diffusion performance of a water repellent processing agent is significantly improved when it is spread on the fabric surface. In the present invention, any water repellent processing agent may be used, and it is preferable to use a treatment agent having an F/C ratio of 0.030 or more in an element mass concentration of SEM-EDX on the polyurethane elastic yarn. The F/C ratio in the element mass concentration of SEM-EDX on the polyurethane elastic fiber being 0.030 or more indicates that an adhesion amount of a fluorine-based water repellent agent is large, and when the F/C ratio is less than 0.030, the adhesion amount of the fluorine-based water repellent agent is small, and there is a tendency that sufficient low wettability cannot be obtained. The F/C ratio is further preferably 0.045 or more.
The covering-coated yarn in the present invention includes the polyurethane elastic fiber as a core yarn and the synthetic fiber filament as a sheath yarn, but a covering method is not particularly limited, and the covering-coated yarn may be in a form in which the polyurethane elastic fiber is covered with the synthetic fiber filament by a method such as single covering or double covering. A draft rate of the polyurethane elastic fiber used for the core yarn is preferably 1.5 times to 5 times, and is preferably 2 times to 4 times from the viewpoint of productivity and stretchability of the woven fabric to be obtained.
In the woven fabric according to the present invention, the covering-coated yarn is disposed in at least a part of the warp yarn and the weft yarn. The covering-coated yarn may be used for either of the warp yarn and the weft yarn, or may be used for both of the warp yarn and the weft yarn. In addition, the covering-coated yarn may be used for a part of the warp yarn or the weft yarn. From the viewpoint of further exerting the effect of the present invention, it is preferable that the covering-coated yarn be used for all the warp yarns and the weft yarns. In addition, the texture is not particularly limited, such as plain weave, twill weave, and multilayer structure woven fabric, but it is preferable to include at least a plain woven fabric and a weft double woven fabric in terms of water flow resistance reduction and buoyancy.
In addition, a high-density woven fabric is preferable for implementing a low water retention rate, and a total cover factor (Cf) is preferably 2,300 or more. When the total cover factor is small, the number of intersections is small, and the constraint of the woven yarn is small, so that not only problems of displacement and snag occur, but also the weave texture is loose, so that the voids in the texture are large, and there is a concern that the water retention rate at the time of wearing decreases. Therefore, the Cf is more preferably 2,500 or more, and further preferably 2,700 or more. When the Cf is too high, the tearing strength and the productivity are likely to deteriorate, and therefore, the Cf is preferably 3,500 or less, and more preferably 3,000 or less from the viewpoint of obtaining a woven fabric excellent in tearing strength.
Further, in order to prevent a decrease in water retention rate, the porosity of the woven fabric is 75% or less, and preferably 70% or less. The porosity as used herein is porosity per volume and refers to a parameter represented by the following formula. $Vall = \{(V - v) / (V)\} \times 100$

Vall: porosity of woven fabric (%)
V: apparent volume of woven fabric (actually measured volume)
v: true volume of woven fabric (volume of synthetic fiber calculated based on density of component constituting synthetic fiber)

In addition, the porosity calculated by the above parameters includes voids in texture of a woven yarn such as a synthetic fiber multifilament yarn constituting a weave texture, voids among yarns of a single fiber constituting a synthetic fiber multifilament yarn, and voids due to a hollow part such as a groove in the special cross-sectional fiber. When a special cross-sectional fiber having a hollow part is used, many fine air layers are formed as compared with a round cross section. By forming such fine air layers, it is possible to exhibit contradictory characteristics of a low water retention rate and high buoyancy at a high level, and thus it is desirable that the fine air layers be present in a large amount in the texture.
Therefore, in the present invention, as the degree of the voids formed by the grooves of the special cross-sectional fibers contained in the woven fabric, the porosity due to the fiber cross-sectional shape of the single fiber having a plurality of grooves on the surface thereof is set in the range of 5% to 30%. Among these, the porosity is preferably 10% to 30%. The porosity due to the fiber cross-sectional shape of the single fiber having a plurality of grooves on the surface thereof is a value calculated by the following method.
That is, a value obtained by subtracting an actual area of the cross section of the special cross-sectional fiber (actual area) from an area of the circumscribed circle that is in largest contact with an outer circumference of the cross section of the special cross-sectional fiber in a direction perpendicular to the fiber longitudinal direction is set as an area of the void, and a ratio thereof to the area of the circumscribed circle is set as the porosity. When the fiber cross-sectional shape is a round cross section and the fiber is a solid fiber (hereinafter referred to as solid round cross-sectional fiber), the outer circumference thereof theoretically coincides with the circumscribed circle, and the porosity is 0%. On the other hand, in the case of the special cross section, the area of the circumscribed circle is larger than the area of the special cross-sectional fiber itself. In the present invention, an area of a difference therebetween is divided by the area of the circumscribed circle and expressed as a percentage, which is referred to as "porosity due to fiber cross-sectional shape of single fiber having plurality of grooves on surface thereof" (hereinafter, referred to as "porosity due to cross-sectional shape of special cross-sectional fiber") per single fiber of the special cross-sectional fiber. $Vcs = \{(Ac - a) / Ac\} \times 100 %$

Vcs: porosity (%) due to cross-sectional shape of special cross-sectional fiber per single fiber
Ac: area of circumscribed circle in largest contact with cross section of special cross-sectional fiber
a: actual area of cross section of special cross-sectional fiber

In a case where the core-sheath composite fiber is used as a raw material fiber of the special cross-sectional fiber, the cross-sectional shape of the core-sheath composite fiber before elution of the sheath component is a solid round cross section, the special cross-sectional shape is expressed by the elution of the sheath component, and there is no large difference in density between an elution component and a non-elution component (for example, as a guideline, in case where ratio of absolute value of difference in density between the elution component and the non-elution component to the higher density component is 10% or less), an elution rate at the time of an elution treatment of eluting the sheath component from the core-sheath composite fiber may be substituted for the porosity due to the cross-sectional shape of the special cross-sectional fiber per single fiber in the special cross-sectional fiber (hereinafter, referred to as "alternative method"). At the time of obtaining the elution rate, a fabric formed of 100 mass% of the core-sheath composite fiber (which may be woven fabric or knitted fabric) is used, and a ratio of an absolute value of a mass difference before and after the elution treatment to a mass of the fabric before the elution treatment is calculated in percentage. However, when determination on whether the porosity satisfies the above range varies depending on whether evaluation is performed by the alternative method, it is obtained using an equation for obtaining Vcs.
Further, the elution rate can be defined as the porosity due to the cross-sectional shape of the special cross-sectional fiber in the woven fabric by multiplying the porosity due to the cross-sectional shape of the special cross-sectional fiber per single fiber in the case where another fiber is mixed with the special cross-sectional fiber by a mixing ratio of a solid cross-sectional fiber when it is assumed that the cross section of the special cross-sectional fiber is a solid cross section having the circumscribed circle as the outer circumference (corresponding to mixing ratio of core-sheath composite fiber when above-described alternative method may be used). That is, when 80 mass% of the special cross-sectional fibers having porosity of 20% due to the cross-sectional shape of the special cross-sectional fiber per single fiber and 20 mass% of the other fiber are included, since a mass ratio of the solid cross-sectional fiber having the circumscribed circle thereof as a cross section to the other fiber is 100:20, the mixing ratio of the assumed solid cross-sectional fiber is calculated as 100/120 = 0.83 (83 mass%), and thus the porosity due to the cross-sectional shape of the special cross-sectional fiber in the woven fabric is calculated as 20% × (100/120) = 16.7%.
In a case where the porosity is obtained from a woven fabric mixed with another fiber, the porosity derived from the cross-sectional shape of the special cross-sectional fiber per single fiber can be obtained by extracting the special cross-sectional fiber from the woven fabric, and the obtained porosity is multiplied by the assumed mixing ratio of the solid cross-sectional fiber to obtain the porosity derived from the cross-sectional shape of the special cross-sectional fiber. When the woven fabric is composed of only the special cross-sectional fiber, the porosity derived from the cross-sectional shape of the special cross-sectional fiber is obtained by multiplying the porosity due to the cross-sectional shape of the special cross-sectional fiber per single fiber of the special cross-sectional fiber by the assumed mixing ratio of 100 mass% of the solid cross-sectional fiber.
As described above, the special cross-sectional fiber used in the present invention preferably includes a core-sheath composite fiber as a raw material fiber, and the special cross-sectional fiber can express a special cross-sectional shape by elution of the sheath component of the core-sheath composite fiber. In the elution, dyeing, and finishing steps necessary for this purpose, a gray fabric is refined, relaxed, and dried, and then a width thereof is thermally fixed in the intermediate set to elute the sheath component. Thereafter, dyeing is performed, when it is a polyester material, it is subjected to reduction cleaning, and when it is a nylon material, it is subjected to fixing treatment, washed with hot water, and dried. Next, it is desirable to perform a step of performing finishing set by performing a water repellent treatment and, if necessary, various types of functional processing.
In the swimsuit of the present invention, it is essential to perform water repellent processing. The water repellent processing may be performed at any stage such as a yarn, a woven fabric, and a swimsuit. The water repellent agent used in the water repellent processing may be any water repellent such as a fluorine-based water repellent agent, a silicone-based water repellent agent, or a paraffin-based water repellent agent, and among these, a fluorine-based water repellent agent is preferable in terms of water repellent performance. In particular, a fluorine-based water repellent agent having eight or more carbon atoms (so-called C8 water repellent agent) is preferable in terms of performance, and a PFOA-free fluorine-based water repellent agent having six carbon atoms (C6 water repellent agent) in which perfluorooctanoic acid (PFOA) is not likely to be generated is preferable from the viewpoint of environmental load. Further, in view of a market environment in which fluorine free is desired, it is more preferable to use a non-fluorinated water repellent agent (C0 water repellent agent) of a hydrocarbon-based water repellent agent such as a paraffin-based water repellent agent or an acrylic-based water repellent agent, a silicone-based water repellent agent alone, or in combination.
In order to improve the durability of the water repellency, a crosslinking agent is preferably used in combination with the water repellent agent. As the crosslinking agent, at least one of a melamine resin, a blocked isocyanate compound, a glyoxal resin, and an imine resin can be used, and the crosslinking agent is not particularly limited.
In order to perform the water repellent processing on a front surface of a woven fabric, and inside and a back surface of a cloth woven fabric, it is preferable to perform the water repellent processing by a method such as pad-dry-cure.
In addition, the fact that the water repellent processing is performed on the front surface of the woven fabric, the inside and the back surface of the woven fabric can be confirmed by observing a cross section of the woven fabric in a thickness direction with a scanning electron microscope (SEM) and confirming presence or absence of water repellent agent coating on the fiber surface for each of the fibers present on the front surface of the woven fabric, the inside and the back surface of the woven fabric. Regarding determination on the presence or absence of the water repellent agent coating, it is not essential that the coating is continuously formed inside the groove or on the outer circumferential part of the fiber, and it is determined that the coating is present when it is confirmed that there is adhesion over the entire outer circumferential part of the fiber even when a resin defect part is partially present in the observed field of view.
In the woven fabric according to the present invention, it is desirable that the water repellency (grade) be grade four or higher according to the spray method of JIS L1092:2009, and it is desirable that the water repellency (grade) be maintained at grade three or higher even after washing is performed for 20 times according to the method of JIS L0217:1995 103. In general, water repellency of a water repellent material decreases with washing, and in particular, when a non-fluorinated water repellent agent is used as the water repellent agent, the washing durability of the water repellency is inferior to that when a fluorine-based water repellent agent is used. However, in the present invention, a decrease in water repellency can be compensated by using the special cross-sectional fiber, and excellent water repellency can be maintained even after washing.
In addition, when the woven fabric retains water, the buoyancy decreases since water is heavier than air, and the feeling of wearing in water deteriorates. Therefore, the water retention rate of the woven fabric in the present invention after 60 minutes is preferably 50 mass% or less, more preferably 40 mass% or less, and further preferably 30 mass% or less of the mass of the woven fabric. The water retention rate is most preferably 0 mass%, and actually 3 mass% is assumed as a lower limit thereof. The initial water retention rate can be a low water retention rate depending on the water repellency even in a material having many coarse voids in the texture, and in order to maintain the low water retention rate, a design for reducing the coarse voids as in the present invention is required. Therefore, regarding the water retention rate, the water retention rate after 60 minutes assuming actual use is evaluated.
Further, in swimming or the like in which competition of swimming speed is severe, the mass of the material at the time of wearing is preferably as small as 0.1 g from the viewpoint of improving athletic ability, and as for the woven fabric, the buoyancy per 1 g of the woven fabric is preferably 0.0170 N or more, more preferably 0.0185 N or more, and further preferably 0.0200 N or more. Since excessive buoyancy impairs the ease of movement in water, the buoyancy is preferably 0.0300 N or less.
The buoyancy per 1 g of the woven fabric after elapse of 20 minutes is preferably 0.0165 N or more, more preferably 0.0180 N or more, and further preferably 0.0195 N or more. For the same reason as the initial buoyancy, the buoyancy per 1 g of the woven fabric after the elapse of 20 minutes is preferably 0.0300 N or less. The reason why the buoyancy after the elapse of 20 minutes is lower than that in the initial stage is that coarse voids in the texture retain water with elapse of time, and the material having many fine voids as in the present invention can minimize the decrease in buoyancy.
The tearing strength of the woven fabric in the present invention measured according to JIS L1096:1999 is preferably 8 N or more, more preferably 10 N or more, and further preferably 12 N or more. As an example of a method for obtaining a woven fabric having the above tearing strength, a yarn having a single yarn fineness of 1.5 dtex or more is used, and the total cover factor is 3,000 or less as described above.
Further, the busting strength of the woven fabric measured according to JIS L1096:1999 is preferably 200 kPa or more, more preferably 300 kPa or more, and further preferably 400 kPa or more. As an example of a method for obtaining a woven fabric having the above busting strength, a woven fabric having a high total cover factor can be obtained by using a yarn having large single yarn fineness. Specifically, the woven fabric having the above busting strength can be obtained by using a yarn having a single yarn fineness of 1.5 dtex or more and setting the total cover factor to 2,500 or more.
When the strengths are satisfied, it is possible to prevent tearing or busting when worn as a sewn product, and it is possible to maintain high durability.
The swimsuit according to the present invention includes a part of the woven fabric in which a plain woven fabric and a weft double woven fabric are alternately repeated in a part at least covering a buttock. The water flow resistance can be reduced by an effect of preventing generation of turbulent flow by periodic riblets formed on the cloth surface. Further, in the swimsuit according to the present invention, the buoyancy is improved by using the above-described woven fabric according to the present invention, and a synergistic effect of further improving the buoyancy can be obtained by forming an air layer not only inside the cloth or between raw yarns but also on the cloth surface because the riblet structure of the woven fabric contains bubbles.
Hereinafter, the woven fabric according to the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. Each evaluation in the examples is obtained by the following method.

(1) Various Cross Section Parameters of Special Cross-Sectional Fiber

A part of the woven fabric was cut perpendicular to a fiber axis direction such that the cross-sectional shape of the special cross-sectional fiber could be observed, the special cross-sectional fiber was extracted with a scanning electron microscope (SEM) manufactured by Hitachi High-Technologies Corporation, and the width of the inlet of the groove (W₁), the width of the wide width part of the groove (W₂), the depth of the groove (H), and the fiber diameter (D) were measured using image processing software (ImageJ). Further, regarding the protruding part of the special cross-sectional fiber, the width of the tip of the protruding part (P_out) and the width of the bottom surface of the protruding part (P_min) were also measured in the same manner. The same operation was performed on five special cross-sectional fibers, and an average value thereof was defined as respective values. The values were determined to a second decimal place in units of µm, and second and subsequent decimal places were rounded off.

(2) Cover Factor

(2-1) Apparent Fineness of Woven Fabric Decomposition Yarn

Warp yarns and weft yarns were extracted from the woven fabric, and the apparent density thereof was measured in accordance with "Method for measuring apparent fineness of fiber extracted from cloth" of Appendix H of JIS L1096:2010. In the case of a processed product on which a resin coating or a coating film was laminated, the apparent fineness was measured by the method described in "Chapter 3 Measurement on apparent fineness of fibers taken from cloth after removal of non-fibrous substance" in which a non-fibrous substance was removed by the method described in ISO1833-1, and in the case of a dyed and finished processed product without resin processing (including water repellent processing and softening processing), the apparent fineness was measured by the method described in "Chapter 2 Measurement on apparent fineness of fibers taken from cloth without removal of non-fibrous substance".
Measurement on a mass of the yarn was performed (method A) by the following formula by adjusting to moisture equilibrium in a standard state (20°C and 65% RH). The number of measurements n was 40 or more. $Ld = Ws / L \times n$

Ld: apparent fineness (tex) of yarn adjusted in standard state
Ws: mass (g) of yarn taken out from woven fabric
L: average value (m) of straight length
n: number of weighed yarns

The apparent fineness was measured by applying the following initial load when the yarn is pulled straight.
Non-crimped synthetic fiber filament: initial load (cN) = fineness (tex) × 0.5
In the case of a covering yarn, the apparent fineness was measured in a state where the yarn extracted from the cloth was covered without being separated into the elastic fiber of the core yarn and the synthetic fiber filament of the sheath yarn.

(2-2) Density

The density of the woven fabric was obtained by measuring the number of yarns per 1 cm by a method B (woven fabric decomposition mirror) of Appendix F of JIS L1096:2010 and converting the number of yarns per 1 cm into the number of yarns per 1 inch (2.54 cm). The number of measurements was an average of three measurements for both the warp yarns and the weft yarns.

(2-3) Cover Factor

Results of the measurement on the apparent fineness and the density were substituted into the following formulas for calculation. $Cf = Cfw + Cff$ $Cfw = Nw \times \sqrt Dw$ $Cff = Nf \times \sqrt Df$

Cf: total cover factor
Cfw: cover factor in warp yarn direction
Cff: cover factor in weft yarn direction
Nw: weaving density in warp yarn direction
Nf: weaving density in weft yarn direction
Dw: warp yarn fineness (dtex)
Df: weft yarn fineness (dtex)

(3) Basis Weight

Regarding the basis weight, the mass per unit area in a standard state (20°C, 65% RH) was measured in accordance with Method A in 8.3.2 of JIS L1096:2010. That is, three test pieces of 200 mm × 200 mm were collected, the mass (g) of each test piece after being left for one day in the standard state was measured, the mass per 1 m² (g/m²) was obtained by the following formula, and an average value thereof was calculated and was rounded to an integer. $Sm = W / A$

Sm: mass per unit area in standard state = basis weight (g/m²)
W: mass (g) of test piece in standard state
A: area (m²) of test piece

(4) Thickness

Regarding the thickness, thicknesses of five different portions of a sample whose moisture was conditioned by the method A in accordance with 8.4 of JIS L1096: 2010 were measured at a pressure of 23.5 kPa for 10 seconds using a thickness measuring instrument, and an average value thereof was calculated.

(5-1) Porosity

An apparent volume (V) of the test piece was determined by multiplying the area of the test piece prepared in (3) by the thickness calculated in (4). Further, a true volume (v) of the fiber structure was obtained by the following formula based on the mass (Wc) of the test piece, the density of the components constituting the synthetic fiber to be used, and the mixing ratio thereof. Regarding the density and the mixing ratio, values thereof may be used in a case where the density and the mixing ratio were known, but in a case where the density and the mixing ratio were unknown, when evaluation is performed from a woven fabric, the density is measured in accordance with JIS L 1013:2021 8.17.2 (density gradient tube method), and the mixing ratio is measured by a raveling method or a dissolving method of JIS L 1030-2:2021 as necessary. $v = Wc \times 100 / \{(ra \times da\} + (rb \times db) + \dots + (rz \times dz)\}$

v: true volume
Wc: mass of test piece
ra: mixing ratio of component a
da: density of component a (g/cm³)
rb: mixing ratio of component b
db: density of component b (g/cm³)

The same method as above can be used for a component c and subsequent components.
Further, the apparent volume and the true volume obtained by the above method were substituted into the following formula to obtain the porosity Vall of the woven fabric. $Vall = \{(V - v) / (V)\} \times 100$

Vall: porosity of woven fabric (%)
V: apparent volume of woven fabric (actually measured volume)
v: true volume of woven fabric (as described above, volume of synthetic fiber calculated based on density of components constituting synthetic fiber)

(5-2) Porosity due to Fiber Cross-sectional Shape of Single Fiber Having Plurality of Grooves on Surface thereof

In view of the density of each of components constituting the core-sheath composite fiber to be used in examples and comparative examples, it was clear that evaluation may be performed by an alternative method, and therefore, evaluation was performed using the alternative method in the present examples.
A knitted fabric including a core-sheath composite fiber having a round cross section before elution produced in each of examples and comparative examples was prepared using a 28G cylinder knitting machine, and the mass (Wb) before elution was measured after humidity conditioning in the standard state (20°C, 65% RH) for 24 hours.
Further, hang-drying was performed in the standard state (20°C, 65% RH) for 24 hours after an elution treatment at 100°C for 60 minutes at a bath ratio of 1:30 in an aqueous sodium hydroxide solution having a concentration of 10 g/L, then the mass (Wa) after elution of the sheath component was measured, and the elution rate was calculated based on the following formula. It was confirmed from the elution rate that the sheath component was eluted by 100% as compared with the design value of the fiber. The elution rate was defined as the porosity due to the cross-sectional shape of the special cross-sectional fiber per single fiber of the special cross-sectional fiber. $Elution rate (%) = (Wa - Wb) \times 100 / Wb$
Further, the porosity due to the fiber cross-sectional shape of the single fiber having a plurality of grooves on the surface thereof (porosity due to cross-sectional shape of special cross-sectional fiber) was obtained by multiplying the mixing ratio of the core-sheath composite fiber in the woven fabric before elution by the elution rate.

(6) Water Repellency

Regarding the water repellency, three samples of about 200 mm × 200 mm were collected in accordance with a water repellency test (spray test) of JIS L1092:2009, 7.2, and 250 ml of water was poured into a funnel such that the warp direction of the sample was parallel to the flow of water using a water repellency tester, and sprayed on the sample for 20 seconds to 25 seconds. Next, a sample holding frame was removed from the tester, one end of the sample was held horizontally, a front side of the test piece was directed downward, the other end of the test piece was once lightly pressed against a hard object to drop a water droplet. One end of the test piece rotated through 180° was taken and subjected to the same operation as described above to drop extra water droplets. A wet state of the sample while the sample is attached to the holding frame was determined by comparison with a comparative sample.
As a washing method of a water-repellent woven fabric, a method 103 described in JIS L0217:1995 "Handling Indication Symbols of Fiber Products and Indication Methods thereof' was used. The number of times of washing was 20, and the water repellency after washing was evaluated by the above-described spray test.

(7) Water Retention Rate

A circle having a diameter of 11.2 cm was drawn at a center of a woven fabric cut into a length of 20 cm and a width of 20 cm, and the woven fabric is stretched such that an area of the circle is enlarged by 80%, attached to a test piece holding frame used in a water repellency test (JIS L1092:2009), removed from the holding frame after a spray test (JIS L1092:2009), and air-dried in an environment of 20°C × 53% RH. Ten pieces of the same woven fabric were prepared, and the mass of each piece was measured as the "mass before treatment".
Water (30 L) (water temperature: 25°C to 29°C) was filled in a washing machine (JIS C9606:2007), ten pieces of the woven fabric were immersed into water and rotated for a predetermined time (10 minutes and 60 minutes) under "strong conditions", thereafter the woven fabrics were taken out one by one from the water, and inclined at about 15 degrees in a spread state for 10 seconds to remove water droplets attached to the woven fabrics, each was defined as the "mass after treatment" to measure the water retention rate by the following formula.
Water retention rate (%) = ((mass after treatment - mass before treatment)/mass before treatment) × 100

(8) Buoyancy Test

First, a load (WA1) of the sample in the air was measured with an electronic balance of model: AUY220 manufactured by Shimadzu Corporation. Next, a load (WA2) of the sample in water was measured using a buoyancy measurement method illustrated in FIG. 4. FIG. 4 is a schematic diagram illustrating the buoyancy measurement method. In a buoyancy test device 40, water 42 was filled in a container 41, a test sample 48 was placed therein, and a suspension type balance (electronic balance AUY220 manufactured by Shimadzu Corporation) which served as a gravimeter 43 was fixed thereon. In the test device, the gravimeter 43 was held between a support body 44 and a plate 46, and a support rod 45 and a wire mesh 47 were attached. As illustrated in FIG. 4, the wire mesh 47 was immersed under water, and the test sample 48 was suspended from the gravimeter 43 with the wire mesh 47 interposed therebetween to measure a load of the test sample 48 in water (value measured by suspension type balance) (WA2). The buoyancy was calculated by WA1-WA2. For the measurement, five samples having a length of 3 cm and a width of 4 cm were randomly taken from the woven fabric and averaged. For the woven fabric sample in the measurement on WA1, a load of a dry sample was measured.

(9) Tearing Strength

Evaluation was performed by the pendulum method specified in JIS L1096: "Cloth testing methods for woven and knitted fabrics" (1999).

(10) Busting Strength

Evaluation was performed by the Mullen method specified in JIS L1096: "Cloth testing methods for woven and knitted fabrics" (1999).

(11) Preparation of Cloth A

Using a spinneret designed such that nylon 6 (N6) (density: 1.14 g/cm³) was placed in a core part and polyethylene terephthalate (copolymerized PET1) (density: 1.26 g/cm³) obtained by copolymerizing 8.0 mol% of 5-sodium sulfoisophthalic acid and 10 wt% of polyethylene glycol having a molecular weight of 1,000 was placed in a sheath part, the core part and the sheath part were separately molten at 270°C and then flowed into the spinneret, and a composite polymer flow was discharged from a discharge hole to obtain a core-sheath composite fiber drawn yarn (33 dtex/10 filaments). In a distribution plate immediately above a discharge plate, a part located at an interface between the core component and the sheath component had the arrangement pattern illustrated in FIG. 5, and teardrop-shaped grooves having eight wide width parts were formed on the surface of one single fiber filament. Sheath component distribution holes 52 were disposed between core component distribution holes 51, so that the sheath component was disposed to be sandwiched between the core components discharged from the core component distribution holes, and a composite polymer flow was formed on a core-sheath type composite fiber in which a special groove shape was controlled. In addition, a core-sheath composite ratio was adjusted to 80:20 in terms of a mass ratio.
Next, in order to obtain a polyurethane elastic yarn, PTMG having a number average molecular weight of 1,800 and MDI were charged into a container such that MDI/PTMG = 1.58/1 in terms of a molar ratio, and reacted at 90°C to dissolve the obtained reaction product in N,N-dimethylacetamide (DMAc). Next, a DMAc solution containing ethylenediamine and diethylamine was added to the solution in which the reaction product was dissolved to prepare a polyurethane urea solution in which a solid content in the polymer was 35 mass%. Further, a condensation polymer of p-cresol and divinyl benzene ("Metacrol" (registered trademark) 2390, manufactured by DuPont) as an antioxidant and 2-[4,6-bis(2,4-dimethylphenyl]-1,3,5-triazine-2-yl]-5-(octyloxy)phenol ("CYASORB" (registered trademark) 1164, manufactured by CYTEC Co., Ltd.) as an ultraviolet absorber were mixed at a mass ratio of 3:2 to adjust a DMAc solution (concentration: 35 mass%), which was used as an additive solution (35 mass%). The polyurethane urea solution and the additive solution were mixed at a ratio of 98 mass% and 2 mass% to prepare a polymer solution (X1). As a cationic high-molecular-weight compound, a cationic high-molecular-weight compound having a number average molecular weight of 2,600 was produced by a reaction between t-butyldiethanolamine and methylene-bis-(4-cyclohexyl isocyanate).
The number average molecular weight of the cationic high-molecular-weight compound was measured by gel permeation chromatography (GPC) under the following measurement conditions.

(Measurement Conditions)

Standard substance: polystyrene
Column: two columns of SHODEX KF-806M manufactured by Showa Denko K.K..
Solvent: 1 ml/min of N,N-dimethylacetamide (DMAc)
Temperature: 40°C
Detector: differential refractometer (RI detector)

The produced cationic high-molecular-weight compound was dissolved in DMAc to prepare a solution (A1) having a concentration of 35 mass%. A 35 mass% DMAc dispersion was adjusted using calcium carbonate Hakuenka A (CaCO₃, average primary particle size: 1.0 µm) manufactured by Shiraishi Kogyo Kaisha, Ltd. as a chlorine degradation inhibitor. For the adjustment, a horizontal mill DYNO-MILKDL manufactured by WILLYA. BACHOFEN AG was used, and 85% zirconia beads were filled and subjected to fine dispersion under the condition of a flow rate of 80 g/min to obtain a DMAc dispersion B1 of synthetic carbonate (35 mass%). Further, as a partially hindered phenol compound, ethylene-1,2-bis(3,3-bis[3-t-butyl-4-hydroxyphenyl]butyrate ("Hostanox" (registered trademark) O3, manufactured by Clariant Corporation) was dissolved in DMAc to prepare a solution (C1) having a concentration of 35 mass%. The polymer solutions X1, A1, B1, and C1 were mixed at ratios of 97 mass%, 1 mass%, 3 mass%, and 1 mass, respectively, to prepare a spinning solution Y1. In addition, a mass ratio (A/B) of the cationic high-molecular-weight compound to the inorganic chlorine degradation inhibitor was 0.33 based on input amounts thereof. The spinning solution Y1 was dry-spun at a winding speed of 580 m/min to produce polyurethane elastic yarns (44 dtex, 55 dtex, and 78 dtex) (Z1), and the yarns were wound while being coated with a silicone oil agent as a treatment agent. The silicone oil agent was applied at 6% by dry weight, which was a treatment agent (oil agent) containing 96% of silicone (polydimethylsiloxane), 3% of St-Mg, and 1% of a dispersant.
The core-sheath composite fiber drawn yarn obtained as described above was used as a sheath yarn that were not subjected to yarn processing such as false twisting and was a non-crimped yarn, and a polyurethane elastic yarn was used as a core yarn to produce a single covering yarn. The following three types of yarns were obtained according to the fineness of the polyurethane elastic yarn.

Yarn A: core-sheath composite fiber drawn yarn (33 dtex) × polyurethane elastic yarn (78 dtex)
Yarn B: core-sheath composite fiber drawn yarn (33 dtex) × polyurethane elastic yarn (55 dtex)
Yarn C: core-sheath composite fiber drawn yarn (33 dtex) × polyurethane elastic yarn (44 dtex)

The yarn A was used as a warp yarn, the yarn B was used as a weft yarn, the yarn C was used as a weft back yarn, and a gray fabric of a stretch woven fabric in which a plain weave part and a weft double weave part were alternately repeated was woven. The obtained woven fabric had a mixing ratio of 65 mass% of nylon and 35 mass% of polyurethane. The same gray fabric was relaxed and refined in a spread state according to a method in the related art, and then preset. Next, 100% of the sheath component was eluted by carrying out a treatment with a sodium hydroxide aqueous solution (1 mass%) at 100°C for 60 minutes at a bath ratio of 1:30 using liquid flow dyeing, and the core-sheath composite fiber in the woven fabric was made into a special cross-sectional fiber. After the elution treatment was performed, a black dyeing treatment was performed to dye the special cross-sectional fiber in black with an acid dye by a method in the related art using a liquid flow dyeing machine. Then, a soaping treatment using an aqueous surfactant solution and a fixing treatment were performed according to a method in the related art.
Subsequently, the fiber was immersed into a non-fluorinated water repellent processing liquid having the following formulation, squeezed at a squeezing ratio of 60% using a mangle, then dried at 130°C for two minutes, and cured to be subjected to final setting at 160°C.

[Formulation of Water Repellent Processing Liquid]

·"Neoceed (registered trademark)" NR-158 (manufactured by Nicca Chemical Co., Ltd.): 5.0 mass%
·"Amidia (registered trademark)" M-3 (manufactured by DIC Corporation): 0.3 mass%
"Catalyst" ACX (manufactured by DIC Corporation): 0.3 mass%
·Isopropyl alcohol: 1.0 mass%
·Water: 93.4 mass%

The obtained woven fabric had a warp density of 198 fibers/2.54 cm, a weft density of 205 fibers/2.54 cm, and a mixing ratio of 60 mass% of nylon 6 (Ny) and 40 mass% of PU after elution. In addition, the woven fabric had a basis weight of 115 g/m² and a thickness of 0.32 mm, and the porosity of the woven fabric was calculated based on the basis weight, the thickness, the density of 1.14 g/cm³ of the components constituting the nylon fiber, and the density of 1.0 g/cm³ of the PU fiber and found to be 67.1%. In addition, due to the elution treatment, voids of 20% were generated as compared with the core-sheath composite fiber of the round cross section before elution, and the mixing ratio of the core-sheath composite fiber before elution is 65 mass%, so that the porosity due to the cross-sectional shape of the special cross-sectional fiber is 13.0%.
In addition, as a result of observing the grooves of the fiber cross section after elution of the sheath component of the core-sheath composite fiber with a scanning electron microscope, eight grooves were present in a fiber circumference, the width of the inlet of the groove was 0.6 µm, and the wide width part of the groove was 1.1 µm (W2/W1 = 1.8), and a special cross-sectional shape having a teardrop-shaped groove having a wide width part was exhibited. In addition, a desired shape having a diameter of the fiber of 9.97 µm and a depth of the groove of 1.9 µm (H/D = 0.19), and capable of sufficiently maintaining an air layer, was obtained. The width of the tip of the protruding part was 4.9 µm, and the protruding part was not peeled off or collapsed in the processing step. Further, when the fluorine/carbon (F/C) ratio on the polyurethane elastic fiber was measured in the element mass concentration of SEM-EDX, F/C = 0.048 was obtained.
Further, the water repellency, the water retention rate, and the buoyancy of the obtained woven fabric were evaluated by a spray method, and the evaluation results were shown in Table 1. The water-repellent woven fabric obtained by the present method had water repellent agent coating formed on the fiber surface on all of the front surface, the inside of the woven fabric and the back surface, had a low water retention rate and a high buoyancy at the initial stage and with elapse of time, and was suitable for use in water.

(12) Preparation of Cloth B

A plain woven fabric was prepared using single covered yarns for the warp yarn and the weft yarn, using a nylon 6 drawn yarn (solid fiber) of 33 dtex, 10 filaments, semi-dull, and round cross section as the sheath yarn which is the same as that used for the warp yarn of the cloth A, and was then subjected to refining, relaxation, dyeing, and water repellent processing in a step with the elution treatment being removed from the step of the cloth A.
The obtained woven fabric had a warp density of 197 fibers/2.54 cm, a weft density of 176 fibers/2.54 cm, and a mixing ratio of 73 mass% of Ny and 27 mass% of PU. In addition, the woven fabric had a basis weight of 108 g/m² and a thickness of 0.30 mm, and the porosity of the woven fabric was calculated by the same calculation method as that for the cloth A and found to be 67.3%. Since all raw yarns used had a round cross section, the porosity due to the cross-sectional shape of the fiber was 0%.

Further, the water repellency, the water retention rate, and the buoyancy of the obtained woven fabric were evaluated by a spray method, and the evaluation results were shown in Table 1. Since the water-repellent woven fabric obtained by the present method has the water repellent agent coating formed on the fiber surface on all of the front surface, the inside of the woven fabric and the back surface, the water retention rate is excellent, but the buoyancy is low, and it is considered that the performance required for wearing in water is insufficient. Table 1 also shows the evaluation results of the cloth C prepared by replacing only the warp yarn of the cloth A with a round cross section. Although the cloth C is slightly inferior to the cloth A, the cloth C also has a low water retention rate and a high buoyancy at the initial stage and with elapse of time, and is suitable for wearing in water.

Table 1

		Cloth A	Cloth B	Cloth C
Usage of yarn	Length	Ny: 33T-10^(1) × PU: 78T^(2)	Ny: 33T-10 (round cross section) × PU: 44T	Ny: 33T-10 (round cross section) × PU: 78T
Usage of yarn	Width	Ny: 33T-10^(1) × PU: 55T, 44T^(2)	Ny: 33T-10 (round cross section) × PU: 44T	Ny: 33T-10(1) × PU: 55T, 44T(2)
Mixing ratio	(On mass basis)	Core-sheath composite fiber 65%/PU 35%	Ny 73%/PU 27%	Core-sheath composite fiber 32.5%/Ny 32.5%/PU 35%
Mixing Ratio^(*3)	(On mass basis)	Ny 60%/PU 40%	Ny 73%/PU 27%	Ny 60%/PU 40%
Special cross-sectional fiber	Length	Present	Absent	Absent
Special cross-sectional fiber	Width	Present	Absent	Present
Number of grooves of special cross-sectional fiber		8	0	8
Presence or absence of crimping of synthetic fiber multifilament yarn	Length	Absent	Absent	Absent
	Width	Absent	Absent	Absent
Presence or absence of crimping of elastic fiber	Length	Absent	Absent	Absent
Presence or absence of crimping of elastic fiber	Width	Absent	Absent	Absent
Texture		Weft double alternating weave	Plain weave	Weft double alternating weave
Weaving density (fibers/2.54 cm)	Length	198	197	194
Weaving density (fibers/2.54 cm)	Width	205	176	208
Cover factor		2,882	2,525
Basis weight	g/m²	115	108	118
Thickness	mm	0.32	0.30	0.31
Porosity of woven fabric	%	67.1	67.3	70.5
Porosity due to cross-sectional shape of special cross-sectional fiber	%	13.0	0	6.5
Water repellency (spray method)	Grade	4 to 5	3 to 4	4 to 5
Busting strength	kPa	430	400	450
Tearing strength	N	13.8	12.7	14.0
Water retention rate (10 minutes)	%	8.8	8.6	8.8
Water retention rate (60 minutes)	%	13.2	13.1	13.5
Buoyancy (initial)	N	0.027	0.013	0.024
Buoyancy (after 20 minutes)	N	0.024	0.008	0.021

(13) Application to Swimsuit

(13-1) Relation between Buoyancy Center and Center of Gravity in Swimming Posture

In order to swim fast, it is required to maintain a posture with little resistance to keep a swimming posture horizontal to the water surface. However, when a player gets tired in a latter half of the race, the abdomen and the lower limbs sink, and the player tends to have a posture that is prone to receive water resistance. As a solution to this problem, there is a swimsuit supporting a hamstring or a swimsuit provided with a foam such that the lower limb does not sink, but there has been no swimsuit for racing in which the buoyancy effect of only the cloth is optimally provided.
The inventors have created a cloth of a weft double weave by using an FTY (raw yarn) in which a synthetic fiber filament having voids in a fiber cross section is used as a sheath yarn and a polyurethane elastic yarn to which a water repellent agent easily adheres is used as a core yarn as in the cloth A, and have confirmed that the buoyancy effect is higher than that of a cloth without voids. Further, the inventors have also confirmed that a surface friction resistance due to a weave texture is reduced as compared with a plain weave texture.
Based on the above results, the inventors have developed a swimsuit in which this cloth is partially disposed from the center of gravity to the lower limb. Normally, since the buoyancy center during the swimming operation is closer to the head than the center of gravity, a moment in the direction of gravity is applied to the lower limb. By disposing the cloth having a high buoyancy effect from the center of gravity to the lower limbs, the player can easily take a horizontal posture with respect to the water surface, can obtain a feeling that the lower limbs float, and can maintain a posture with less resistance.

(13-2) Preparation of Swimsuit

The cloth A is used such that a stripe shape is along a height direction of the body. This leads to a reduction in surface friction resistance with the water flow. Further, in order to reduce the surface friction resistance, it is desirable to use the cloth A for the waist to the buttocks having many irregularities of the body shape, and a large effect of preventing a turbulent flow can be obtained. Further, it is desirable that the cloth A is used in a part or all of the area located on the leg side relative to the center of gravity (close to leg approximately 2 cm to 3 cm from navel). Since it is necessary to cover a part or all of the area located on the leg side relative to the center of gravity in the case of a male swimsuit and to cover the upper body in the case of a female swimsuit, it is preferable that the area of the cloth A used from the center of gravity to the leg is larger than the area used from the upper body to the center of gravity. The cloth A may be used not only as a main body material but also as a lining of the swimsuit. The racing swimsuit is preferably prepared in a pattern of being about 20% to 40% smaller than the human body.

(13-3) Measurement on Buoyancy by Swimsuit

A load (WA1) of the swimsuit in the air was measured with an electronic balance of model: AUY220 manufactured by Shimadzu Corporation. Next, a load (WA2) of the swimsuit in water was measured using the buoyancy measurement method illustrated in FIG. 4. FIG. 4 is a schematic diagram illustrating the buoyancy measurement method. In the buoyancy test device 40, the water 42 was filled in the container 41, a swimsuit as a test material 48 was placed therein, and a suspension type balance (electronic balance AUY220 manufactured by Shimadzu Corporation) which served as the gravimeter 43 was fixed thereon. In the test device, the gravimeter 43 was held between the support body 44 and the plate 46, and the support rod 45 and the wire mesh 47 were attached. As illustrated in FIG. 4, the wire mesh 47 was immersed under water, and the test sample 48 was suspended from the gravimeter 43 with the wire mesh 47 interposed therebetween to measure a load of the test sample 48 in water (value measured by suspension type balance) (WA2). The buoyancy was calculated by WA1-WA2.

(13-4) Examples of Swimsuit

Examples of the swimsuit will be described below. The present invention is not limited to the following examples. In addition, in Tables 2 and 3, A means optimum, B means suitable, and C means unsuitable.

The cloth A and the cloth B were used to sew a male swimsuit for racing according to Examples 1 to 3 and Comparative Example 1 shown in Table 2. In each of examples and comparative examples, the mass ratio of the cloth A and the cloth B is a ratio shown in the tables. Each of the swimsuits is subjected to a wear test, and it was confirmed that the swimsuit according to each of Examples 1 to 3 was suitable for racing because the buoyancy effect could be perceived, stability of a kick and stretch posture and ease of movement could be obtained, as compared with the swimsuit according to Comparative Example 1 in which the cloth A was not used.

Table 2

	Example 1	Example 2	Example 3	Comparative Example 1
Cloth configuration	Cloth A: 100	Cloth A: 65	Cloth A: 50	Cloth A: 0
Cloth configuration	Cloth B: 0	Cloth B: 35	Cloth B: 50	Cloth B: 100
Buoyancy	Large	Medium	Small	C
Kick and stretch posture	A	B	B	C
Ease of movement	A	B	A	A

Similarly, the cloth A and the cloth B were combined to sew a female swimsuit for racing according to Examples 4 to 6 and Comparative Example 2 shown in Table 3. The "center of gravity" in the table is a so-called body center of gravity and corresponds to a position below the navel. In addition, in each example, a weight ratio of the cloth A with the position of the center of gravity as a boundary is expressed as head to center of gravity: center of gravity to leg, and is 10:90 in Example 4, 30:70 in Example 5, and 4:96 in Example 6. The swimsuit was subjected to a wear test, and it was confirmed that the swimsuit according to Examples 4 to 6 was a swimsuit suitable for racing because the buoyancy effect could be perceived, stability of a kick and stretch posture and ease of movement could be obtained, as compared with Comparative Example 2 in which the cloth A was not used.

Table 3

	Example 4	Example 5	Example 6	Comparative Example 2
Cloth configuration	Cloth A: 56	Cloth A: 52	Cloth A: 47	Cloth A: 0
Cloth configuration	Cloth B: 44	Cloth B: 48	Cloth B: 53	Cloth B: 100
Buoyancy	Large	Medium	Small	C
Kick and stretch posture	A	B	B	C
Ease of movement	A	B	A	A

(13-5) Embodiments

FIGS. 6 to 11 illustrate swimsuits according to a first embodiment to a sixth embodiment, respectively, and (A), (B), and (C) of FIGS. 6 to 11 are a front view, a side view, and a rear view, respectively. The first embodiment to the third embodiment are male swimsuits for racing, and the fourth embodiment to the sixth embodiment are female swimsuits for racing.

A first part 3 colored in gray is formed of the cloth A, and a second part 5 not colored is formed of the cloth B. Table 4 shows a usage ratio (mass ratio) of the cloth A in each embodiment. A boundary between an upper body region and a lower body region is the body center of gravity (below navel), the upper body region corresponds to a region from the head to the body center of gravity, and the lower body region corresponds to a region from the body center of gravity to above the knee. A boundary between a front body region and a rear body region is a side line.

Table 4

	Usage ratio of cloth A
	Entire swimsuit	Upper body: Lower body	Front body: Rear body
First embodiment (FIG. 6)	77%	-	12:88
Second embodiment (FIG. 7)	100%	-	50:50
Third embodiment (FIG. 8)	35%	-	4:96
Fourth embodiment (FIG. 9)	56%	45:55	45:55
Fifth embodiment (FIG. 10)	52%	2:98	10:90
Sixth embodiment (FIG. 11)	28%	4:96	7:93

Each of the swimsuits according to the examples and the embodiments described above is a swimsuit partially including a woven fabric in which a covered yarn having a polyurethane elastic yarn as a core yarn and a synthetic fiber filament as a sheath yarn is disposed in at least a part of a warp yarn and a weft yarn.
Here, the polyurethane elastic yarn contains a cationic high-molecular-weight compound A having a number average molecular weight of 2,000 or more in a range of 0.5 mass% to 10 mass%, contains an inorganic chlorine degradation inhibitor B, and a mass ratio (A/B) of the cationic high-molecular-weight compound A to the inorganic chlorine degradation inhibitor B is in a range of 0.3 to 3, and the polyurethane elastic yarn further contains silicone. In addition, at least a part of the synthetic fiber filament is constituted from a synthetic fiber including, on a surface thereof, a single fiber including a plurality of grooves continuous in a fiber longitudinal direction, the grooves have a depth of 1.0 µm to 10.0 µm, a width of an inlet of 0.5 µm to 10.0 µm, and a width of a tip of a protruding part of 10.0 µm or less, and porosity due to a fiber cross-sectional shape of the grooves of 5% to 30%.
The woven fabric includes a plain woven fabric and a weft double woven fabric having an internal porosity of 75% or less, and the swimsuit includes a part in which a plain woven fabric and a weft double woven fabric are alternately repeated at a position at least covering the a buttock, and is subjected to water repellent processing.
Under the above-described assumption, in the swimsuit, a part in which the plain woven fabric and the weft double woven fabric are alternately repeated is disposed in at least a part of a region covering from the navel to above the knee, as shown in each embodiment. Accordingly, high buoyancy can be obtained.
The part in which the plain woven fabric and the weft double woven fabric are alternately repeated may be disposed on the entire swimsuit as in Example 1 and the second embodiment. Accordingly, higher buoyancy can be obtained.
The woven fabric described above may be used as a main body cloth of a swimsuit or may be used as a lining of a swimsuit.
In particular, for a swimsuit which covers only the upper body, such as a male swimsuit for racing, a mass ratio of the woven fabric in the swimsuit is preferably 35% or more as shown in Table 4. Similarly, in the case of the swimsuit which covers only the upper body, it is preferable that in the front body region and the rear body region, the mass ratio of the woven fabric in the swimsuit be set to a range of front body region: rear body region = 4 to 50: 50 to 96 as shown in Table 4.
In a swimsuit which covers the upper body and the lower body, such as a female swimsuit for racing, the mass ratio of the woven fabric in the swimsuit is preferably 35% or more as shown in Table 4. Similarly, in the case of a swimsuit which covers the upper body and the lower body, it is preferable that in the front body region and the rear body region, the mass ratio of the woven fabric in the swimsuit be set to a range of front body region: rear body region = 7 to 45: 55 to 93 as shown in Table 4.
Similarly, in the case of a swimsuit which covers the upper body and the lower body, it is preferable that in an upper body region covering from the head to the body center of gravity and a lower body region covering from the body center of gravity to above the knee, the mass ratio of the woven fabric described above in the swimsuit be set to a range of upper body region: lower body region = 2 to 45: 55 to 98 as shown in Table 4.
Although various embodiments have been described above, the present invention is not limited to these examples. It is apparent to those skilled in the art that various changes or modifications can be conceived within the scope described in the claims, and it should be naturally understood that these changes or modifications also belong to the technical scope of the present invention. In addition, the components described in the above embodiments may be freely combined without departing from the spirit of the invention.
The present application is based on a Japanese patent application ( JP2023-101977A) filed on June 21, 2023 , and the contents thereof are incorporated herein by reference.

REFERENCE SIGNS LIST

11: protruding part
12: groove
13: center point
14: fiber diameter (D)
21: straight line
22: perpendicular line
23: contact point between perpendicular line 22 and fiber polymer part
24: width of wide width part of groove (W2)
31: width of tip of protruding part (Pout)
32: width of bottom surface of protruding part (Pmin)
40: buoyancy test device
41: container
42: water
43: gravimeter
44: support body
45: support rod
46: support plate
47: wire mesh
48: test sample
51: core component distribution hole
52: sheath component distribution hole

Claims

A swimsuit partially comprising:
a woven fabric in which a covered yarn is disposed in at least a part of a warp yarn and a weft yarn, the covered yarn comprising a polyurethane elastic yarn as a core yarn and a synthetic fiber filament as a sheath yarn, wherein

the polyurethane elastic yarn comprises 0.5 mass% to 10 mass% of a cationic high-molecular-weight compound A having a number average molecular weight of 2,000 or more and an inorganic chlorine degradation inhibitor B,

a mass ratio (A/B) of the cationic high-molecular-weight compound A and the inorganic chlorine degradation inhibitor B is 0.3 to 3,

the polyurethane elastic yarn comprises silicone,

at least a part of the synthetic fiber filament comprises a synthetic fiber comprising a single fiber comprising a plurality of grooves on a surface of the single fiber,

the grooves are continuous in a fiber longitudinal direction,

each of the grooves has a depth of 1.0 µm to 10.0 µm, a width of an inlet of 0.5 µm to 10.0 µm, a width of a tip of a protruding part of 10.0 µm or less, and a porosity due to a fiber cross-sectional shape of 5% to 30%,

the woven fabric comprises a plain woven fabric and a weft double woven fabric and has an internal porosity of 75% or less,

the swimsuit further comprises a part in which the plain woven fabric and the weft double woven fabric are alternately repeated at a position covering at least a buttock, and

the swimsuit is subjected to water repellent processing.
The swimsuit according to claim 1, wherein
the part in which the plain woven fabric and the weft double woven fabric are alternately repeated is disposed in at least a part of a region covering from a navel to above a knee.
The swimsuit according to claim 1 or 2, wherein
the part in which the plain woven fabric and the weft double woven fabric are alternately repeated is disposed in the entire swimsuit.
The swimsuit according to claim 1 or 2, wherein
a main body cloth of the swimsuit comprises the woven fabric.
The swimsuit according to claim 1 or 2, wherein
a lining of the swimsuit comprises the woven fabric.
The swimsuit according to claim 1 or 2, wherein
the swimsuit is for covering only an upper body, and

a mass ratio of the woven fabric in the swimsuit is 35% or more.
The swimsuit according to claim 1 or 2, wherein
the swimsuit is for covering only an upper body, and

a mass ratio of the woven fabric in the swimsuit in a front body region and a rear body region is front body region: rear body region = 4 to 50: 50 to 96.
The swimsuit according to claim 1 or 2, wherein
the swimsuit is for covering an upper body and a lower body, and

a mass ratio of the woven fabric in the swimsuit is 28% or more.
The swimsuit according to claim 1 or 2, wherein
the swimsuit is for covering an upper body and a lower body, and

a mass ratio of the woven fabric in the swimsuit in a front body region and a rear body region is front body region: rear body region = 7 to 45: 55 to 93.
The swimsuit according to claim 1 or 2, wherein
the swimsuit is for covering an upper body and a lower body, and

a mass ratio of the woven fabric in the swimsuit in an upper body region covering from a head to a body center of gravity and a lower body region covering from the body center of gravity to above a knee is upper body region: lower body region = 2 to 45: 55 to 98.
The swimsuit according to claim 1 or 2, wherein
the polyurethane elastic yarn has a fluorine/carbon (F/C) ratio of 0.030 or more in an element mass concentration determined by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX).
The swimsuit according to claim 1 or 2, wherein
the number of the grooves of the synthetic fiber filament is 2 to 32.
The swimsuit according to claim 1 or 2, wherein
the synthetic fiber filament is a non-crimped multifilament.
The swimsuit according to claim 1 or 2, wherein
the woven fabric achieves grade four or higher in a spray test described in JIS L 1092:2009.
The swimsuit according to claim 1 or 2, wherein
the woven fabric has a water retention rate after 60 minutes of 50 mass% or less relative to a weight of the fabric.
The swimsuit according to claim 1 or 2, wherein
a buoyancy per 1 g of the woven fabric is 0.0170 N or more.
The swimsuit according to claim 1 or 2, wherein
a cross-sectional shape of the synthetic fiber of the woven fabric satisfies the following Expression 1 and Expression 2: $W 2 / W 1 \geq 1.3$ and $0.15 \leq H / D \leq 0.25$

where W1 represents the width (µm) of the inlet of the grooves, W2 represents a width (µm) of a wide width part of the grooves, H represents a depth (µm) of the grooves, and F represents a diameter (µm) of the fiber.