EP4640933A1

EP4640933A1 - Textile

Info

Publication number: EP4640933A1
Application number: EP23906635.0A
Authority: EP
Inventors: Yutaro Suzuki
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 2022-12-22
Filing date: 2023-11-30
Publication date: 2025-10-29
Also published as: CN120380209A; JPWO2024135267A1; WO2024135267A1

Abstract

To provide a water-repellent woven fabric having excellent water repellency, low water retention rate, and buoyancy, and capable of maintaining these properties, a woven fabric of the present invention is a woven fabric including a synthetic fiber multifilament yarn and an elastic fiber, wherein at least a part of the synthetic fiber multifilament used in the woven fabric includes a synthetic fiber including a single fiber having, on a surface of the single fiber, a plurality of grooves continuous in a fiber length direction, the grooves of the single fiber have a wide part wider than an inlet in a cross section, a depth of 1.0 to 10.0 µm, and an inlet width of 0.5 to 10.0 µm, a width of a top of a protrusion is 10.0 µm or less, a porosity of the woven fabric is 75% or less, a porosity resulting from a fiber cross-section shape of the single fiber having the plurality of grooves on the surface is 3 to 30%, and a water repellent film is provided on a front surface, inside of the woven fabric, and a back surface.

Description

TECHNICAL FIELD

The present invention relates to a woven fabric.

BACKGROUND ART

Water repellency is an important factor in fabric used for clothing intended to be worn in water, such as swimsuits. This is to prevent an increase in the underwater weight of fabric to hinder movement in water when the fabric absorbs or retains water.
Particularly in competitive swimming to compete on speed, development of fabric that enables easy movement and has a light underwater weight is the most important issue in order to further establish a new record, and improvements have been made from various viewpoints.
Water repellency is particularly important for preventing an increase in the underwater weight of a swimsuit, and a swimsuit has been proposed that is highly compatible with water repellents and has high water repellency by using a specific polyurethane elastic yarn containing 0.5 to 10 mass% of a cationic high-molecular compound having a number-average molecular weight of 2000 or more (Patent Document 1). It is true that the swimsuit has high water repellency, but this is merely a feature obtained by improvement in the water repellency performance of the yarn, and required properties such as high water repellency and low water retention rate cannot be satisfied depending on the structure of fabric. For example, in a material having large voids between yarns, it is inferred that water is retained in the voids to cause an increase in underwater weight even if a raw yarn having excellent water repellency is used.
In addition, it has been proposed to obtain buoyancy from a hollow part by using a raw yarn having a C-shaped hollow cross section (Patent Document 2). It is true that the C-shaped hollow cross section has high hollowness and can provide excellent buoyancy, but the water repellency performance of the hollow part is deteriorated due to repeated wearing, and in a case where water enters the inside of the hollow part, the C-shaped hollow cross section conversely acts to increase the underwater weight of a swimsuit. In addition, the effect of improving water repellency by the raw yarn structure cannot be expected, and the feature is insufficient from the viewpoint of water repellency.
In addition, there has been proposed a method for reducing flowing water resistance by forming a weave structure with a large number of float yarns in the body length direction of a woven fabric for swimsuits (Patent Document 3). Furthermore, this prior art document mentions that the flowing water resistance can be effectively reduced by using, as the float yarn, a raw yarn having a specific cross-section shape with an inlet constriction type groove. This method is only intended to reduce the flowing water resistance, and an increase in the number of float yarns makes inter-structure voids larger in the fabric structure, so that the fabric has excellent buoyancy in the short term. However, water is retained in the inter-structure voids over time or due to a crumpling effect on the fabric by exercise to cause an increase in underwater weight.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

Patent Document 1: Japanese Patent No. 7138071
Patent Document 2: Japanese Patent Laid-open Publication No. 6-228820
Patent Document 3: International Publication No. 2021/100810

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

As described above, a water-repellent woven fabric intended to be worn in water has various required properties such as stretchability, water repellency, low water retention rate, and buoyancy. Among them, it is desirable to form a dense structure in which the porosity of the fabric is lowered for a low water retention rate. Conversely, since buoyancy is improved by containing air in the fabric, it is desirable that the porosity of the fabric is high, and a structure incompatible with the low water retention rate is required. In addition, in order to obtain buoyancy, air contained in the fabric is required to remain in the fabric in spite of the crumpling effect by exercise or even after wearing for a long time.
An object of the present invention is to provide a water-repellent woven fabric that satisfies these conflicting required properties, has excellent water repellency, low water retention rate, and buoyancy, and can maintain these properties.

SOLUTIONS TO THE PROBLEMS

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

(1) A woven fabric including a synthetic fiber multifilament yarn and an elastic fiber, wherein at least a part of the synthetic fiber multifilament used in the woven fabric includes a synthetic fiber including a single fiber having, on a surface of the single fiber, a plurality of grooves continuous in a fiber length direction, the grooves of the single fiber have a depth of 1.0 to 10.0 µm, and an inlet width of 0.5 to 10.0 µm, a width of a top of a protrusion is 10.0 µm or less, a porosity in the fabric is 75% or less, a porosity resulting from a fiber cross-section shape of the single fiber having the plurality of grooves on the surface is 3 to 30%, and a water repellent film is provided on a front surface, inside of the woven fabric, and a back surface.
(2) The woven fabric according to (1), wherein the number of grooves of the single fiber having the plurality of grooves continuous in the fiber length direction on the surface is 2 to 32.
(3) The woven fabric according to (1) or (2), wherein the synthetic fiber filament is a non-crimped multifilament.
(4) The woven fabric according to any of (1) to (3), wherein a water repellency in a spray test in accordance with JIS L 1092: 2009 is grade 4 or higher.
(5) The woven fabric according to any of (1) to (4), wherein a water retention rate after 60 minutes is 50 mass% or less of a mass of the woven fabric.
(6) The woven fabric according to any of (1) to (5), wherein a buoyancy per 1 g of the woven fabric is 0.017 N or more.
(7) The woven fabric according to any of (1) to (6), wherein a cross-section shape of the synthetic fiber satisfies (Formula 1) and (Formula 2) below. $W 2 / W 1 \geq 1.3$ $0.15 \leq H / D \leq 0.25$
- W1: groove inlet width (µm)
- W2: groove wide part width (µm)
- H: groove depth (µm)
- F: fiber diameter (µm)

EFFECTS OF THE INVENTION

According to the present invention, the synthetic fiber multifilament yarn having a specific cross-section shape with the plurality of grooves continuous in the fiber length direction, and the elastic fiber are mix-woven and subjected to water repellent finish, so that excellent stretchability is provided by the elastic fiber, and in addition, a water repellent penetrates into the grooves of the synthetic fiber multifilament yarn to provide a lotus effect, and exhibit high water repellency and durability thereof. Furthermore, it is possible to provide a water-repellent woven fabric having high buoyancy by entrapping air into the grooves of a raw yarn of the synthetic fiber multifilament yarn while preventing deterioration of a water retention rate by water entering the structure by performing high-density weaving so as to make inter-structure voids smaller.
As a result, the woven fabric of the present invention can provide excellent buoyancy when used in water.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is an outline view for explaining a transverse sectional shape of a single fiber example used in the present invention.
Fig. 2 is a groove enlarged schematic view for explaining a groove of the single fiber example used in the present invention.
Fig. 3 is a protrusion enlarged schematic view of the single fiber example used in the present invention.
Fig. 4 is a schematic explanatory view illustrating a buoyancy measurement method.
Fig. 5 is a partially enlarged view of one embodiment of the arrangement of distribution holes in a final distribution plate.

EMBODIMENTS OF THE INVENTION

Hereinafter, the present invention will be described in detail.
A woven fabric of the present invention is a woven fabric including a synthetic fiber multifilament yarn and an elastic fiber. The woven fabric is a stretch woven fabric having stretchability by including the elastic fiber. Therefore, hereinafter, the above woven fabric may be referred to as a stretch woven fabric.
At least a part of the synthetic fiber multifilament yarn used in the present invention includes, as a constituent single fiber, a synthetic fiber including a single fiber having, on its surface, a plurality of grooves continuous in the fiber length direction. As illustrated in Fig. 1, which is an outline view for explaining a transverse sectional shape of an example of the single fiber used in the present invention, the single fiber is a fiber having a transverse sectional shape in which a plurality of grooves 12 each having a wide part on its outer circumference are present with a protrusion 11 interposed therebetween (hereinafter, the cross-section shape may be referred to as a "specific cross-section shape", and the fiber having the specific cross-section shape may be referred to as a "specific cross-section fiber").
In addition, a depth (H) of each groove in the above specific cross-section shape is preferably 1.0 µm to 10.0 µm. Water droplets adhering to the fiber surface enter the groove due to their own weights or a crumpling effect, and when reaching the bottom surface of the groove, the water droplets adhere thereto and the fiber gets wet, resulting in deterioration of a water retention rate and buoyancy. However, in a case where the groove is deep, the water droplets are pushed up to the toward the upper part of the groove by surface tension of water droplets, and the fiber exhibits water repellency without being wet. On the other hand, in a multifilament having a single fiber fineness of 2.5 to 5 dtex, which is typically used for this application, the diameter of a single fiber filament is 12 to 26 µm. Thus, in a case where the groove is designed to be excessively deep, there is a concern that raw yarn strength may decrease. Therefore, the depth of the groove is 10.0 µm or less, and more preferably 8.0 µm or less. In a case where the diameter of the single fiber filament is small, it is preferable to control, within the above range, the depth of the groove to such an extent that the raw yarn strength does not excessively decrease, preferably a relationship between the diameter and the depth of the groove to a range to be described later. In addition, in a case where the depth of the groove is too small, the droplets reach the bottom surface of the groove, and sufficient water repellency cannot be obtained. Therefore, in order to exhibit water repellency performance by utilizing the surface tension of water droplets, the depth of the groove is preferably 1.0 µm or more as described above, and more preferably 2.0 µm or more. The depth (H) of the groove in the specific cross-section fiber is defined as a distance on a perpendicular line 22 from an intersection of a straight line 21 connecting the ends of the protrusions 11 present with the groove interposed therebetween in Fig. 2 (the distance of the straight line 21 is defined as a width (W1) of an inlet of the groove) and the perpendicular line 22, to a contact point 23 between the perpendicular line 22 and a fiber polymer portion by drawing the perpendicular line 22 from the straight line 21 to a center point 13 (not shown in Fig. 2) of a cross section in a direction perpendicular to the length direction of the synthetic fiber filament (a center point of a circumcircle circumscribing most tops of the protrusions). In addition, the center point 13 is defined as a center point of a circle circumscribing most tops of the protrusions (hereinafter referred to as a circumcircle) in the fiber polymer cross section, and the diameter of the circumcircle is defined as a fiber diameter (D) 14.
The width (W1) of the inlet of the groove is preferably 0.5 µm to 10.0 µm. When the width of the inlet of the groove is in the above preferable range, high water repellency performance can be exhibited by obtaining surface tension by the surface tension of water droplets. In a case where the width of the inlet of the groove is too small, a water repellent does not penetrate into the groove and it is difficult to obtain water repellency. Thus, the width is preferably 0.5 µm or more, and more preferably 1.0 µm or more. In addition, in a case where the width of the inlet of the groove is too large, water enters the inside of the groove, resulting in deterioration of a water retention rate and buoyancy. Therefore, the width of the inlet of the groove is desirably 10.0 µm or less, and more preferably 8.0 µm or less.
Preferred ranges of the width (W1) of the inlet of the groove, a width (W2) 24 of the wide part of the groove, and the depth (H) of the groove with respect to the fiber diameter (D) 14 in the specific cross-section fiber used in the present invention will be described below. For the width (W2) of the wide part of the groove, the width (W2) 24 of the wide part of the groove is the maximum section when the length orthogonal to the center line of the groove is measured toward the center of the fiber from the outer circumference along the center line. A ratio W2/W1 of the width (W2) of the wide part of the groove to the width (W1) of the inlet of the groove is set to 1.3 or more, which is preferable in that more air can be entrapped inside the groove, and the buoyancy and the water repellency can be improved. W2/W1 is more preferably 1.5 or more, and still more preferably 1.8 or more. In addition, to inhibit splitting of the protrusion due to abrasion in wearing and provide excellent shape maintenance of the inlet of the groove, W2/W1 is 3.0 or less. The shape of the inlet of the groove is maintained, so that it is possible to maintain the feature.
In addition, it is preferable that a ratio (H/D) of the groove depth (H) to the fiber diameter (D) is 0.15 or more to 0.25 or less. As a result, it is possible to exhibit features such as water repellency performance and high buoyancy by forming a sufficient air layer inside, and on the other hand, there is little risk of deterioration in the performance due to deformation or destruction when the protrusion forming the groove receives an external force. H/D is more preferably 0.17 or more to less than 0.22.
As the single fiber filament having the grooves on its surface used in the present invention, a single fiber filament in which a protrusion top width 31 (Pout), the width (W1) of the inlet of the groove, and a width (Pmin) 32 of the bottom surface of the grooves adjacent to the protrusion top width (Pout) 31 satisfy the following formula can be more preferably used. The above width (Pout) 31 of the top of the protrusion is a shortest distance connecting one end and the other end of the protrusion, and is a distance indicated by reference numeral 31 in Fig. 3. In addition, the above protrusion bottom surface width 32 (Pmin) is, in other words, a distance connecting contact points of an inscribed circle of the grooves adjacent to each other with the protrusion interposed therebetween, and is a distance indicated by reference numeral 32 in Fig. 3. $Pout / W 1 = 2 to 10$ $Pout / Pmin \geq 1.3$
The shape of the groove in the specific cross-section fiber is preferably a shape (such as a teardrop shape or a hexagonal shape) in which, when the groove is observed in the cross section in the direction perpendicular to the length direction of the fiber, the wide part wider than the width of the inlet is provided in a range from the inlet of the groove to the bottom surface of the groove, and the width of the groove gradually becomes narrower from the wide part toward the bottom surface of the groove.
It is preferable that the plurality of grooves are provided in the specific cross-section fiber. In a case where only one groove is present, the groove may not be present at a boundary surface with water depending on the orientation of the fiber, and the effect of improving the water repellency cannot be obtained. The number of grooves is preferably 2 to 32, and more preferably 4 to 16. When the number of grooves is in the above preferred range, the width of the top of the protrusion in the fiber cross-section shape is not too small, and fibrils and fluffs are not generated on a product surface in a processing step or at the time of using a product.
In the present invention, it is desirable to use a core-sheath conjugate fiber as a raw material fiber in order to obtain the above specific cross-section shape. Here, the core-sheath conjugate fiber includes two types of polymers, the cross section of a core component has the above-described shape, and the specific cross-section 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, polyamide such as nylon 6, or the like can be used. From the viewpoint of simplifying the step of eluting the sheath component, the sheath component is preferably a copolymerized polyester, polylactic acid, polyvinyl alcohol, or the like that is soluble in an aqueous solvent, hot water, or the like. Particularly, it is preferable to use a polyester copolymerized singly or in combination with polyethylene glycol or sodium sulfoisophthalic acid, or polylactic acid, from the viewpoint of handleability and easy dissolution in an aqueous solvent. In addition, the mass ratio of the core component and the sheath component is preferably in a range of 50 : 50 to 90 : 10. As the ratio of the sheath component, which is an eluted component, is larger, a larger air layer can be formed in the cross section of the raw yarn, which is preferable for improving the buoyancy. However, since the raw yarn strength is deteriorated and the elution step is prolonged, the above range is preferable, and a range of 60 : 40 to 80 : 20 is more preferable.
At least a part of the synthetic fiber multifilament yarn used in the present invention is the above specific cross-section fiber, and the entire synthetic fiber multifilament yarn may be the above specific cross-section fiber or another multifilament may be used. The other multifilament may be a multifilament having a fiber cross section other than the above specific cross-section 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 addition, the synthetic fiber multifilament is preferably a non-crimped multifilament as described below. In a case where the entire synthetic fiber multifilament yarn is the specific cross-section fiber, it is also preferable to be non-crimped. In a case where the other multifilament is used in combination, using non-crimped multifilament is also 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 impart crimps to the synthetic fiber multifilament by yarn processing represented by false twisting to improve the elongation properties of the synthetic fiber multifilament. However, in a case where crimps are formed in the synthetic fiber filament, the crimps make inter-structure voids larger. In the present invention, it is important to prevent deterioration of the water retention rate and the buoyancy over time in water or by crumpling in wearing by minimizing the inter-structure voids (reduce coarse voids). Therefore, as the synthetic fiber multifilament, it is preferable to use a so-called non-crimped multifilament (hereinafter, also referred to as a non-crimped fiber) having substantially no crimp. As a result, the inter-structure voids can be further made smaller. Here, the term "substantially no crimp" or "non-crimped" means that crimps are not actively imparted as in crimping such as false twisting or in an actualized crimped conjugate fiber (weave crimp inevitably generated by weaving is not regarded as crimp).
As a means for making the inter-structure voids smaller other than using the non-crimped fiber, there is a method of forming a high-density woven fabric by mix-weaving an elastic fiber. As the elastic fiber used here, a polyurethane spandex or a polyether/ester-based elastic fiber, a polybutylene terephthalate fiber or a polytrimethylene terephthalate fiber, and a conjugate fiber obtained by bonding the above-mentioned polymer having different shrinkage properties in a side-by-side or eccentric core-sheath shape can be used. Such an elastic fiber is also preferably a non-crimped fiber for the same reason as the above synthetic fiber multifilament yarn. In addition, a covering coated thread using such an elastic fiber as a core yarn may be used. A covering coated thread formed by using, particularly, the polyurethane spandex among the elastic fibers as a core yarn and the synthetic fiber multifilament as a sheath yarn is superior in elongation rate and elongation recovery rate, and is preferably used for a swimsuit, particularly a swimsuit for competitive swimming.
The specific cross-section fiber used in the present invention can be woven, dyed, and functionally processed by a normal method.
In addition, the weave structure is not specifically limited as long as it satisfies the porosity of the woven fabric defined in the present invention. Examples thereof include plain weave, modified plain weave such as ripstop structure, twill weave, satin weave, modified twill weave, modified satin weave, variable weave, crest weave, one-ply weave, double weave structure, multiple weave structure, warp pile weave, weft pile weave, and gauze weave, and among these, plain weave and modified plain weave such as ripstop structure are preferable in that the number of interlace points is easily secured.
In addition, a material woven at a high density is preferable in order to achieve a low water retention rate, and a total cover factor (Cf) is preferably 2300 or more. When the total cover factor becomes small, the number of interlace points is reduced, and the restraint of the weaving yarn is reduced, whereby not only the problems of distortion and slippage of yarn and snag occur, but also the inter-structure voids become large due to a loose weave structure, and there is a concern that the water retention rate may be deteriorated at the time of wearing, that is, the water retention rate may be increased. From this, the Cf is more preferably 2500 or more, and still more preferably 2700 or more. In addition, in a case where the Cf is too high, tear strength and productivity are likely to deteriorate, and therefore the Cf is preferably 3500 or less, and more preferably 3000 or less from the viewpoint of obtaining the woven fabric excellent in tear strength.
Furthermore, in order to prevent deterioration of the water retention rate, the porosity of the woven fabric is 75% or less, preferably 70% or less. The porosity here is a 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 (volume measured)
v: true volume of woven fabric (volume of synthetic fiber calculated from densities of components constituting synthetic fiber)

In addition, the porosity calculated by the above parameter includes inter-structure voids of the weaving yarn such as the synthetic fiber multifilament yarn constituting the weave structure, voids between single fiber strands constituting the synthetic fiber multifilament yarn, and voids due to hollow parts such as the grooves in the specific cross-section fiber. In order to prevent a decrease in the water retention rate, it is necessary to control the porosity to 75% or less. For example, the porosity can be controlled to 75% or less by weaving the non-crimped fiber with less expansion of a yarn bundle with a Cf of 2500 or more to 3500 or less where a high density is obtained within a range not causing problems in tear strength and productivity by using a structure such as plain weave having many interlace points to easily obtain a high density within a range not leading to deterioration of tear strength and productivity as described above. For example, by weaving a covering thread obtained by covering polyurethane (PU) having a strong shrinkage force with the non-crimped fiber at a high density, a denser and higher-density woven fabric can be obtained by the shrinkage force of PU. In addition, in a case where the specific cross-section fiber having the hollow parts 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 conflicting properties of a low water retention rate and high buoyancy at a high level, and thus it is desirable that many fine air layers are present in the structure.
Therefore, in the present invention, as the degree of the voids formed by the grooves of the specific cross-section fiber included in the woven fabric, the porosity resulting from the fiber cross-section shape of the single fiber having the plurality of grooves on the surface is set to a range of 3 to 30%. Within the range, the porosity is preferably 10 to 30%. The porosity resulting from the fiber cross-section shape of the single fiber having the plurality of grooves on the surface here is a value calculated by the following method.
That is, a value obtained by subtracting the area (actual area) of the cross section of the actual specific cross-section fiber from the area of the circumcircle in greatest contact with the outer circumference of the cross section in the direction perpendicular to the fiber length direction of the specific cross-section fiber is taken as the area of the voids, and the ratio to the area of the above circumcircle is taken as the porosity. In a case where the fiber cross-section shape is a round cross section and the fiber is a solid fiber (hereinafter referred to as a solid round cross-section fiber), the outer circumference thereof theoretically coincides with the circumcircle, and the porosity is 0%. On the other hand, in the case of the specific cross section, the area of the circumcircle is larger than the area of the specific cross-section fiber itself. In the present invention, the area of a difference therebetween divided by the area of the circumcircle and expressed as a percentage is the "porosity resulting from the fiber cross-section shape of the single fiber having the plurality of grooves on the surface" (hereinafter referred to as a "porosity resulting from the cross-section shape of the specific cross-section fiber) per single fiber of the specific cross-section fiber. $Vcs = \{(Ac - a) / Ac\} \times 100 %$

Vcs: porosity (%) resulting from cross-section shape of specific cross-section fiber per single fiber
Ac: area of circumcircle in greatest contact with cross section of specific cross-section fiber
a: actual area of cross section of specific cross-section fiber

In a case where the core-sheath conjugate fiber is used as the raw material fiber of the specific cross-section fiber, and where the cross-section shape of the core-sheath conjugate fiber before elution of the sheath component is a solid round cross section, the specific cross-section shape is developed by elution of the sheath component, and there is no large difference in density between the eluted component and the non-eluted component (for example, as a guide, in a case where the ratio of the absolute value of a difference between two densities to the density of the component having a larger density is 10% or less, or the like), an elution rate in the elution treatment for eluting the sheath component from the core-sheath conjugate fiber may be substituted for the porosity resulting from the cross-section shape of the specific cross-section fiber per single fiber in the specific cross-section fiber (hereinafter referred to as a "substitution method"). When the elution rate is determined, a fabric (may be a woven fabric or a knitted fabric) including 100 mass% of the core-sheath conjugate fiber is used, and the ratio of the absolute value of a mass difference before and after the elution treatment to the mass of the fabric before the elution treatment is calculated as a percentage. However, in a case where determination as to whether or not the porosity satisfies the above range varies depending on whether or not the evaluation is performed by this substitution method, the formula for obtaining Vcs is used to perform the determination.
Furthermore, in a case where the specific cross-section fiber and another fiber are mixedly used, a value obtained by multiplying the porosity resulting from the cross-section shape of the specific cross-section fiber per single fiber by the mixing ratio of the solid cross-section fiber (corresponding to the mixing ratio of the core-sheath conjugate fiber in a case where the above substitution method can be used), supposing that the cross section of the specific cross-section fiber is the solid cross section having the above circumcircle as its outer circumference, can be defined as the porosity resulting from the cross-section shape of the specific cross-section fiber in the woven fabric. That is, when 80 mass% of the specific cross-section fiber having a porosity of 20% resulting from the cross-section shape of the specific cross-section fiber per single fiber and 20 mass% of the other fiber are included, the mass ratio of the solid cross-section fiber having the circumcircle as its cross section and the other fiber is 100 : 20, and therefore the assumed mixing ratio of the solid cross-section fiber is calculated as 100/120 = 0.83 (83 mass%). Thus, the porosity resulting from the cross-section shape of the specific cross-section fiber in the woven fabric is calculated as 20% × (100/120) = 16.7%.
In the case of determining the porosity from the woven fabric in which the other fiber is mixed, the porosity derived from the cross-section shape of the specific cross-section fiber can be determined by extracting the specific cross-section fiber from the woven fabric, determining the porosity derived from the cross-section shape of the specific cross-section fiber per single fiber, and multiplying the porosity by the above assumed mixing ratio of the solid cross-section fiber. In a case where the woven fabric includes only the specific cross-section fiber, the porosity derived from the cross-section shape of the specific cross-section fiber is determined by multiplying the porosity derived from the cross-section shape of the specific cross-section fiber per single fiber of the specific cross-section fiber by the above assumed mixing ratio of 100 mass% of the solid cross-section fiber.
As described above, the specific cross-section fiber used in the present invention desirably uses the core-sheath conjugate fiber as the raw material fiber, and the specific cross-section fiber can develop the specific cross-section shape by elution of the sheath component of the core-sheath conjugate fiber. In elution and dyeing/finishing steps required therefor, a gray fabric is scoured, relaxed, and dried, and then the width in intermediate set is thermally fixed, and the sheath component is eluted. Thereafter, the fabric is dyed, and is subjected to reduction cleaning if the fabric is a polyester material, and is subjected to fixing treatment if the fabric is a nylon material, washed with hot water, and dried. Then, a finishing set step is desirably performed by subjecting the fabric to water repellent treatment and various functional processes as necessary.
In order to exhibit a water repellency feature in the woven fabric of the present invention, water repellent finish is performed to obtain a woven fabric having a water repellent film on the front surface, the inside of the woven fabric, and the back surface, or a woven fabric having a water repellency of grade 4 or higher in a spray test in accordance with JIS L 1092: 2009.
The water repellent used in the water repellent finish may be any one of fluorine-based, silicone-based, paraffin-based water repellents. Among them, a fluorine-based water repellent is preferable from the viewpoint of water repellency performance. Particularly, a fluorine-based water repellent having 8 or more carbon atoms (so-called C8 water repellent) is preferable in terms of performance. More preferred is a PFOA-free fluorine-based water repellent having 6 carbon atoms (C6 water repellent) in which there is no possibility of generating perfluorooctanoic acid (PFOA) from the viewpoint of environmental load. Furthermore, in view of a market environment in which fluorine-free is desired, it is more preferable to use a non-fluorine-based water repellent (C0 water repellent) by using a hydrocarbon-based water repellent such as paraffin-based and acryl-based water repellents, or a silicone-based water repellent alone or in combination.
In order to improve the durability of the water repellency performance, the water repellent is preferably used in combination with a cross-linker. As the cross-linker, at least one type of a melamine-based resin, a blocked isocyanate-based compound, a glyoxal-based resin, and an imine-based resin can be used, and the cross-linker is not particularly limited.
In the present invention, the woven fabric having the water repellent film on the front surface, the inside of the woven fabric, and the back surface is obtained by performing the water repellent finish. Specifically, it is preferable to perform the water repellent finish by a method such as Pad-Dry-Cure (Pad-Dry-Cure).
In addition, for the water repellent film on the front surface of the woven fabric, the inside of the woven fabric, and the back surface, the presence or absence of the water repellent film on the fiber surface can be confirmed for each fiber present on the front surface of the woven fabric, the inside of the woven fabric, and the back surface by observing the cross section of the woven fabric in the thickness direction with a scanning electron microscope (SEM). For the determination of the presence or absence of the water repellent film, it is not essential that the film is continuously formed inside the groove or on the outer circumference of the fiber, and it is determined that the film is present if the film can be confirmed to adhere to the entire outer circumference of the fiber even supposing that there is partially a resin missing part in the observed visual field.
In the woven fabric of the present invention, the water repellency (grade) is preferably grade 4 or higher in accordance with Spray Method of JIS L 1092: 2009. In addition, it is desirable to maintain grade 3 or higher after washing 20 times in accordance with Method 103 of JIS L 0217: 1995. In general, the water repellency performance of a water-repellent material deteriorates with washing. In particular, in a case where a non-fluorine-based water repellent is used as the water repellent, the durability of water repellency to washing is inferior to the case where a fluorine-based water repellent is used. However, in the present invention, the deterioration of the water repellency can be compensated by using the specific cross-section fiber, and excellent water repellency can also be maintained after washing.
In addition, in a case where the woven fabric retains water, water is heavier than air, and thus the buoyancy decreases, leading to deterioration of a wearing feeling in water. Therefore, the woven fabric of the present invention preferably has a water retention rate after 60 minutes of 50 mass% or less, more preferably 40 mass% or less, and still more preferably 30 mass% or less with respect to the mass of the woven fabric. The water retention rate is most preferably 0 mass%, but in practice, 3 mass% is assumed as the lower limit. Regarding an initial water retention rate, a low water retention rate can be achieved depending on the water repellency even in a material having many coarse inter-structure voids. However, in order to maintain the low water retention rate, it is necessary to make a design to reduce the coarse voids as in the present invention. Therefore, as the water retention rate, the water retention rate after 60 minutes assuming actual use is evaluated.
Furthermore, in competitive swimming or the like to severely compete on the speed of swimming, the mass of a material at the time of wearing is preferably as light as possible even by 0.1 g from the viewpoint of improving competitive ability, and the woven fabric has a buoyancy of preferably 0.0170 N or more, more preferably 0.0185 N or more, and still more preferably 0.0200 N or more per 1 g of the woven fabric. In addition, since excessive buoyancy impairs ease of movement in water, the buoyancy is preferably 0.0300 N or less.
In addition, the buoyancy per 1 g of the woven fabric after the elapse of 20 minutes is preferably 0.0165 N or more, more preferably 0.0180 N or more, and still more 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 desirably 0.0300 N or less. The reason why the buoyancy after the elapse of 20 minutes decreases as compared with the initial buoyancy is that coarse inter-structure voids retain water over time. In a material having many fine voids as in the present invention, the decrease in buoyancy can be minimized.
The woven fabric preferably has a tear strength of 8 N or more, more preferably 10 N or more, and still more preferably 12 N or more as measured in accordance with JIS L 1096: 1999. As an example of the method of producing the woven fabric having the above tear strength, the woven fabric can be obtained by using a yarn of a single yarn of 1.5 dtex or more and setting the total cover factor to 3000 or less as described above.
Furthermore, the woven fabric preferably has a burst strength of 200 kPa or more, more preferably 300 kPa or more, and still more preferably 400 kPa or more as measured in accordance with JIS L 1096: 1999. As an example of the method of producing the woven fabric having the above burst strength, the woven fabric can be obtained by using a yarn having a large single yarn fineness and weaving the yarn with a high total cover factor. Specifically, the woven fabric can be obtained by using a yarn of a single yarn of 1.5 dtex or more and setting the total cover factor to 2500 or more.
By satisfying these strengths, it is possible to prevent splitting or tearing when the woven fabric is worn as a sewn product, and to maintain high durability.
The woven fabric of the present invention thus obtained is a water-repellent woven fabric having excellent water repellency, low water retention rate, and buoyancy, and capable of maintaining these properties, and thus can be preferably used for a swimsuit, particularly for a swimsuit for competitive swimming.

EXAMPLES

Hereinafter, the woven fabric of the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. Each evaluation in Examples was obtained by the following method.

(1) Various cross-section parameters in specific cross-section fiber

A part of the woven fabric was cut perpendicularly to the fiber axis direction so as to be able to observe the transverse sectional shape of the specific cross-section fiber. The specific cross-section fiber was extracted with a scanning electron microscope (SEM), manufactured by Hitachi High-Tech Corporation, and the groove inlet width (W₁), the groove wide part width (W₂), the groove depth (H), and the fiber diameter (D) were measured using image processing software (ImageJ). Furthermore, regarding the protrusion of the specific cross-section fiber, the protrusion top width (P_out) and the protrusion bottom surface width (P_min) were also measured in a similar manner as described above. The same operation was performed on five specific cross-section fibers, and the average value was used as each value. Note that these values were calculated to two decimal places in units of µm and rounded off to one decimal place.

(2) Cover factor

(2-1) Apparent fineness of yarns obtained by unweaving woven fabric

A warp yarn and a weft yarn were taken out from the woven fabric, and the apparent density thereof was measured in accordance with "Method for Measuring the Apparent Fineness of Fibers Taken from the Fabric" in JIS L 1096: 2010, Appendix H. In the case of a processed article laminated with a resin coating or a film, measurement was performed by the method described in "Chapter 3: Measurement of the Apparent Fineness of Fibers Taken from the Fabric after Removal of Non-Fibrous Substance" for removing a non-fibrous substance by the method described in ISO1833-1. In the case of a processed article subjected to dyeing finishing (including water repellent finish and softening) without resin processing, measurement was performed by the method described in "Chapter 2: Measurement of the Apparent Fineness of Fibers Taken from the Fabric without Removal of Non-Fibrous Substance".
In this regard, the mass of the yarn was measured by adjusting the yarn to a moisture equilibrium in a standard state (20°C and 65% RH) and measuring it by Method A, and the apparent fineness was calculated by the following formula. The number n of measured yarns was 40 or more. $Ld = [Ws / L \times n] \times 1000$

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

When the yarns were pulled straight, the following initial load was applied for the measurement.
Non-crimped synthetic fiber filament: initial load $(cN) = fineness (tex) \times 0.5$
In the case of the covering thread, the apparent fineness was measured in a state where the yarn extracted from the fabric was covered without being separated into a core yarn: elastic fiber and a sheath yarn: synthetic fiber filament.

(2-2) Density of woven fabric

The density of the woven fabric was converted to the density per inch (2.54 cm) by measuring the number of yarns per cm by Method B (Lunometer) of JIS L 1096: 2010, Appendix F. The number of measurements was an average of warp and weft measurements at three times.

(2-3) Cover factor

Calculation was performed by substituting the measurement results of the apparent fineness and the density of the woven fabric described above into the following formula: $Cf = Cfw + Cff$ $Cfw = Nw \times \sqrt Dw$ $Cff = Nf \times \sqrt Df$

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

(3) Weight per unit area

As the weight per unit area, the mass per unit area in a standard state (20°C and 65% RH) was measured in accordance with Method A of 8.3.2 of JIS L 1096: 2010. Specifically, three test pieces of 200 mm × 200 mm were taken, and the mass (g) after allowing each of the test pieces in each standard state to stand for 1 day was weighed, the mass (g/m²) per 1 m² was determined by the following formula, and the average value thereof was calculated and rounded off to an integer value. $Sm = W / A$

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

(4) Thickness

The thicknesses at 5 different points of a sample subjected to humidity conditioning by Method A were measured under constant pressure after applying a pressure of 23.5 kPa for 10 seconds using a thickness measuring instrument, in accordance with 8.4 of JIS L 1096: 2010, and the average value was calculated.

(5-1) Porosity

The area of the test piece prepared in (3) was multiplied by the thickness obtained in (4) to determine the apparent volume (V) of the test piece. Furthermore, the true volume (v) of the fiber structure was determined from the mass (Wc) of this test piece, the densities of the components constituting the synthetic fiber used, and the mixing ratios thereof by the following formula. Regarding the density and the mixing ratio, known values may be used, but when the values are unknown and evaluated from the 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 performed by JIS L 1030-2: 2021, release method or dissolution method, as necessary. v = Wc × 100/{(ra × da} + (rb × db) + ... + (rz × dz)}

v: true volume
Wc: test piece mass
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 applies to component c and the subsequent components.
Furthermore, the apparent volume and the true volume determined by the above method were substituted into the following formula, and rounded off to the first decimal place 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 (volume measured)
v: true volume of woven fabric (volume of synthetic fiber calculated from densities of components constituting synthetic fiber as described above)

(5-2) Porosity resulting from fiber cross-section shape of single fiber having a plurality of grooves on surface

In view of the density of each component constituting the core-sheath conjugate fiber used in Examples and Comparative Examples, it has been obvious that the evaluation may be performed by the substitution method, and thus in the present Examples, the evaluation was performed using the substitution method.
A knitted fabric using a core-sheath conjugate fiber having a round cross section before elution produced in Examples and Comparative Examples was produced using a 28G circular knitting machine, and after 24 hours of humidity conditioning in a standard state (20°C, 65% RH), the mass (Wb) before elution was measured.
Furthermore, after elution treatment at a bath ratio of 1 : 30 at 100°C for 60 minutes in a sodium hydroxide aqueous solution having a concentration of 10 g/L, line dry was performed in a standard state (20°C, 65% RH) for 24 hours, then the mass (Wa) after elution of the sheath component was measured, and the elution rate was calculated from the following formula. From the elution rate, it has been confirmed that 100% of the sheath component was eluted as compared with a fiber designed value. This elution rate was defined as the porosity resulting from the cross-section shape of the specific cross-section fiber per single fiber of the specific cross-section fiber. $Elution rate (%) = (Wa - Wb) \times 100 / Wb$
Furthermore, the porosity resulting from the fiber cross-section shape of the single fiber having the plurality of grooves on the surface (the porosity resulting from the cross-section shape of the specific cross-section fiber) was determined by multiplying the mixing ratio of the core-sheath conjugate fiber in the woven fabric before elution by the elution rate.

(6) Water repellency

The water repellency was measured in accordance with Water Repellency Test (Spray Test) of JIS L 1092: 2009, 7.2. Three samples of about 200 mm × 200 mm were collected, a water repellency tester was used, 250 ml of water was poured into a funnel so that the warp direction of the samples was parallel to the flow of water, and the water was sprayed onto the samples in 20 to 25 seconds. Next, a sample holding frame was removed from the tester and held horizontally at one end thereof. With the front side of the test piece being directed downward, the other end thereof was once lightly pressed against a hard object to drop water droplets. One end thereof was rotated through 180° and held, and the same operation as described above was performed to drop extra water droplets. The wet state of the sample while the sample was attached to the holding frame was compared with the comparative sample and determined.
As the method of washing the water-repellent woven fabric, Method 103 described in JIS L 0217: 1995 "Textiles-Care labelling code using symbols" was used. The number of times of washing was set to 20 times, and the water repellency performance after washing was evaluated by the above spray test.

(7) Water retention rate (%)

On the center of the woven fabric cut into 20 cm long and 20 cm wide, a circle having a diameter of 11.2 cm was drawn, the woven fabric was stretched so that the area of the circle was increased by 80%, the woven fabric was attached to the test piece holding frame used in the water repellency test (JIS L 1092: 2009), the spray test (JIS L 1092: 2009) was performed, and then the woven fabric was detached from the holding frame and dried with wind under an environment of 20°C × 53% RH. 10 sheets of the same woven fabric were prepared, and the mass was measured in each woven fabric to obtain a "mass before treatment".
30 L of water (water temperature; 25 to 29°C) was poured into a washing machine (JIS C 9606: 2007), the 10 woven fabrics were put in the water and rotated for a predetermined time (10 min, 60 min) under "strong conditions", and then taken out one by one from the water. After waiting for 10 seconds with an inclination of about 15° in a spread state, water droplets attached to the woven fabrics were dropped, the mass was measured as a "mass after treatment", and the water retention rate was measured by the following formula. Water retention rate (%) = ((mass after treatment - mass before treatment)/mass before treatment) × 100

(8) Buoyancy test

First, the load (W1) of the sample in air was measured with an electronic balance, model: AUY220, manufactured by Shimadzu Corporation. Next, the load (W2) in water was measured using the buoyancy measurement method illustrated in Fig. 4. Fig. 4 is a schematic explanatory view illustrating the buoyancy measurement method. In a buoyancy tester 40, water 42 was poured into a container 41, a test sample 48 was placed therein, and a suspension-type balance (electronic balance AUY220 manufactured by Shimadzu Corporation) as a weight scale 43 was fixed thereon. In the tester, the weight scale 43 was held between a support 44 and a plate 46, and a support rod 45 and a metal mesh 47 were attached. As illustrated in Fig. 4, the metal mesh 47 was put in the water, the test sample 48 was hung from the weight scale 43 (not illustrated) with the metal mesh 47 interposed therebetween, and the load (value measured by the suspension-type balance) (W2) in water was measured. The buoyancy was calculated by W1 - W2. Five samples of 3 cm long and 4 cm wide were randomly taken from the woven fabric, the measurement was performed for each sample, and the average value was obtained. For the woven fabric sample at the time of the measurement of W1, the load when the sample was dry was measured.

(9) Tear strength

Evaluation was performed by Pendulum method defined in JIS L 1096 "Testing methods for woven and knitted fabrics" (1999).

(10) Burst strength

Evaluation was performed by Mullen method defined in JIS L 1096 "Testing methods for woven and knitted fabrics" (1999).

[Example 1]

A drawn yarn of a core-sheath conjugate fiber (33 dtex/10 filaments) was obtained by using a spinneret designed such that nylon 6 (N6) (density: 1.14 g/cm³) was disposed in the core part and polyethylene terephthalate (copolymerized PET1) (density: 1.26 g/cm³) in which 8.0 mol% of 5-sodium sulfoisophthalic acid and 10 wt% of polyethylene glycol having a molecular weight of 1000 were copolymerized was disposed in the sheath part, separately melting the core part and the sheath part at 270°C, then allowing the core part and the sheath part to flow into the spinneret, and discharging a composite polymer flow from a discharge hole. In a distribution plate immediately above a discharge plate, a portion located at an interface between the core component and the sheath component was set to the arrangement pattern illustrated in Fig. 5, and eight teardrop-shaped grooves with wide parts were formed on one single fiber filament surface. A distribution hole 52 for sheath component was disposed between distribution holes 51 for core component, whereby the sheath component was disposed so as to be sandwiched between the core components discharged from the distribution holes for core component, resulting in formation of a polymer flow complexed to a core-sheath type in which the specific groove shape was controlled. In addition, the core-sheath composition ratio was adjusted so as to be 80 : 20 in terms of a mass ratio.
Then, a sheath yarn: the obtained core-sheath conjugate fiber (non-crimped fiber) and a core yarn: chlorine-resistant LYCRA "LYCRA 176E" (polyurethane-based resin (PU), solid fiber) 44 dtex, manufactured by TORAY OPELONTEX CO., LTD. as an elastic fiber were used to produce a single covering thread with a draft ratio of the core yarn of 3.5 (times).
The single covering thread was used for a warp yarn and a weft yarn to produce a plain woven fabric, and the same gray fabric in a spread state was subjected to relaxation and scouring, and then preset according to a conventional method. Subsequently, by performing treatment at a bath ratio of 1 : 30 at 100°C for 60 minutes in 1 mass% of a sodium hydroxide aqueous solution using jet dyeing, 100% of the sheath component was eluted, and the core-sheath conjugate fiber in the woven fabric was formed into the specific cross-section fiber.
After the elution treatment, the resulting woven fabric was dyed black with an acidic dye by a conventional method using a jet dyeing machine. Then, soaping treatment using an aqueous surfactant solution and fixing treatment were each performed according to a conventional method.
Thereafter, the resulting woven fabric was immersed in a non-fluorine water repellent finishing solution with the following formulation, squeezed with a mangle at a squeezing rate of 60%, dried at 130°C for 2 minutes, and further subjected to final setting at 160°C for curing as well.

[Formulation of Water Repellent Finishing Solution]

"NEOSEED (registered trademark)" NR-158 (manufactured by NICCA CHEMICAL CO., LTD.) ... 5.0 mass%
"AMIDIR (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 ... 93.5 mass%

The resulting woven fabric had a warp density of 196 yarns/2.54 cm and a weft density of 179 yarns/2.54 cm, and a mixing ratio of 69 mass% of nylon 6 (Ny) and 31 mass% of PU. In addition, the weight per unit area was 103 g/m² and the thickness was 0.30 mm, and when the porosity of the woven fabric was calculated from these values, and the density 1.14 g/cm³ of the component constituting the nylon fiber and the density 1.0 g/cm³ of the PU fiber, the porosity was 68.8%. In addition, 20% of voids are generated by the elution treatment in comparison with the core-sheath conjugate fiber of the round cross section before elution, and since the mixing ratio of the core-sheath conjugate fiber before elution is 73 mass%, the porosity resulting from the cross-section shape of the specific cross-section fiber is 14.6%.
In addition, as a result of observing the grooves in the fiber cross section of the core-sheath conjugate fiber after elution of the sheath component with a scanning electron microscope, there were eight grooves in the fiber circumference, the inlet width of each groove was 0.6 µm, the wide part of the groove was 1.1 µm (W2/W1 = 1.8), and the specific cross-section shape having the teardrop-shaped grooves with the wide parts was developed. The fiber had a diameter of 9.97 µm and a groove depth of 1.9 µm (H/D = 0.19), and had a desired shape capable of sufficiently maintaining the air layer. The width of the top of the protrusion was 4.9 µm, and peeling or collapse of the protrusion did not occur in the processing step.
Furthermore, the resulting woven fabric was used to evaluate the water repellency by the spray method, water retention rate, and buoyancy. The evaluation results are shown in Table 1. In the water-repellent woven fabric obtained by this method, the water repellent film was formed on the fiber surface on all of the front surface, the inside of the woven fabric, and the back surface, and the water-repellent woven fabric had a low water retention rate and high buoyancy at the initial stage and over time, and was suitable for wearing in water.

[Example 2]

A sheath yarn: a semi-dull/round cross-section drawn yarn of nylon 6 of 33 dtex and 10 filaments (solid fiber) and a core yarn: chlorine-resistant LYCRA "LYCRA 176E" 44 dtex, manufactured by TORAY OPELONTEX CO., LTD. were used to produce a single covering thread with a draft ratio of the core yarn of 3.5 (times). The single covering thread using the round cross section was used for a warp yarn, a single covering thread using a core-sheath conjugate fiber similar to that in Example 1 was used for a weft yarn, and elution treatment, dyeing, and water repellent finish were performed by steps similar to those in Example 1.
The resulting woven fabric had a warp density of 194 yarns/2.54 cm and a weft density of 181 yarns/2.54 cm, and a mixing ratio of 71 mass% of Ny and 29 mass% of PU. In addition, the weight per unit area was 113 g/m² and the thickness was 0.31 mm, and when the porosity of the woven fabric was calculated by a calculation method similar to that in Example 1, the porosity was 66.9%. In addition, 20% of voids are generated by the elution treatment in comparison with the core-sheath conjugate fiber of the round cross section before elution, and since the mixing ratio of the core-sheath conjugate fiber before elution is 36.5 mass%, the porosity resulting from the cross-section shape of the specific cross-section fiber is 7.3%.
As a result of observing the grooves in the fiber cross section of the core-sheath conjugate fiber after elution of the sheath component with a scanning electron microscope, the parameters representing the groove shape were similar to those in Example 1.
Furthermore, the resulting woven fabric was used to evaluate the water repellency by the spray method, water retention rate, and buoyancy. The evaluation results are shown in Table 1. In the water-repellent woven fabric obtained by this method, the water repellent film was formed on the fiber surface on all of the front surface, the inside of the woven fabric, and the back surface, and the water-repellent woven fabric had a low water retention rate and high buoyancy at the initial stage and over time, and was suitable for wearing in water.

[Example 3]

A drawn yarn of a core-sheath conjugate fiber (84 dtex/24 filaments) was obtained by using a spinneret designed such that nylon 6 (N6) was disposed in the core part and polyethylene terephthalate (copolymerized PET1) in which 8.0 mol% of 5-sodium sulfoisophthalic acid and 10 wt% of polyethylene glycol having a molecular weight of 1000 were copolymerized was disposed in the sheath part, separately melting the core part and the sheath part at 270°C, then allowing the core part and the sheath part to flow into the spinneret, and discharging a composite polymer flow from a discharge hole. In addition, the arrangement of a distribution plate was similar to that in Example 1, and the core-sheath composition ratio was adjusted so as to be 80 : 20 in terms of a mass ratio.
Then, a sheath yarn: the obtained core-sheath conjugate fiber and a core yarn: chlorine-resistant LYCRA "LYCRA 176E" (polyurethane-based resin (PU), solid fiber) 78 dtex, manufactured by TORAY OPELONTEX CO., LTD. as an elastic fiber were used to produce a single covering thread with a draft ratio of the core yarn of 3.5 (times).
The single covering thread was used for a warp yarn and a weft yarn to produce a plain woven fabric, and elution treatment, dyeing, and water repellent finish were performed by steps similar to those in Example 1.
The resulting woven fabric had a warp density of 150 yarns/2.54 cm and a weft density of 112 yarns/2.54 cm, and a mixing ratio of 76 mass% of Ny and 24 mass% of PU. In addition, the weight per unit area was 201 g/m² and the thickness was 0.56 mm, and when the porosity of the woven fabric was calculated by a calculation method similar to that in Example 1, the porosity was 70.9%. In addition, 20% of voids are generated by the elution treatment in comparison with the core-sheath conjugate fiber of the round cross section before elution, and since the mixing ratio of the core-sheath conjugate fiber before elution is 80 mass%, the porosity resulting from the cross-section shape of the specific cross-section fiber is 16.0%.
In addition, as a result of observing the grooves in the fiber cross section of the core-sheath conjugate fiber after elution of the sheath component with a scanning electron microscope, there were eight grooves in the fiber circumference, the inlet width of each groove was 0.9 µm, the wide part of the groove was 1.6 µm (W2/W1 = 1.8), and the specific cross-section shape having the teardrop-shaped grooves with the wide parts was developed. The fiber had a diameter of 15.9 µm and a groove depth of 3.1 µm (H/D = 0.19), and had a desired shape capable of sufficiently maintaining the air layer. The width of the top of the protrusion was 7.8 µm, and peeling or collapse of the protrusion did not occur in the processing step.
Furthermore, the resulting woven fabric was used to evaluate the water repellency by the spray method, water retention rate, and buoyancy. The evaluation results are shown in Table 1. In the water-repellent woven fabric obtained by this method, the water repellent film was formed on the fiber surface on all of the front surface, the inside of the woven fabric, and the back surface, and the water-repellent woven fabric had a low water retention rate and high buoyancy at the initial stage and over time, and was suitable for wearing in water.

[Example 4]

The same single covering thread as that produced in Example 1 was used for a warp yarn and a weft yarn to produce a woven fabric of ripstop structure, and elution treatment, dyeing, and water repellent finish were performed by steps similar to those in Example 1.
The resulting woven fabric had a ripstop interval with a pitch of 3 mm in both warp and weft, a warp density of 192 yarns/2.54 cm and a weft density of 174 yarns/2.54 cm, and a mixing ratio of 68 mass% of Ny and 32 mass% of PU. In addition, the weight per unit area was 105 g/m² and the thickness was 0.35 mm, and when the porosity of the woven fabric was calculated by a calculation method similar to that in Example 1, the porosity was 72.7%. In addition, 20% of voids are generated by the elution treatment in comparison with the core-sheath conjugate fiber of the round cross section before elution, and since the mixing ratio of the core-sheath conjugate fiber before elution is 73 mass%, the porosity resulting from the cross-section shape of the specific cross-section fiber is 14.6%.
The fiber cross-section shape of the core-sheath conjugate fiber after elution of the sheath component was similar to that in Example 1.
Furthermore, the resulting woven fabric was used to evaluate the water repellency by the spray method, water retention rate, and buoyancy. The evaluation results are shown in Table 1. In the water-repellent woven fabric obtained by this method, the water repellent film was formed on the fiber surface on all of the front surface, the inside of the woven fabric, and the back surface, and the water-repellent woven fabric had a low water retention rate and high buoyancy at the initial stage and over time, and was suitable for wearing in water.

[Example 5]

A drawn yarn of a core-sheath conjugate fiber (84 dtex/24 filaments) was obtained by using a spinneret designed such that polyethylene terephthalate (PET) (density: 1.38 g/cm³) was disposed in the core part and copolymerized PET1 similar to that in Example 1 was disposed in the sheath part, separately melting the core part and the sheath part at 290°C, then allowing the core part and the sheath part to flow into the spinneret, and discharging a composite polymer flow from a discharge hole. The distribution plate and the core-sheath composition ratio are similar to those in Example 1.
Then, a sheath yarn: the obtained core-sheath conjugate fiber and a core yarn: chlorine-resistant LYCRA "LYCRA 176E" 78 dtex, manufactured by TORAY OPELONTEX CO., LTD. were used to produce a single covering thread with a draft ratio of the core yarn of 3.5 (times).
The single covering thread was used for a warp yarn and a weft yarn to produce a plain woven fabric. Elution treatment was performed after relaxation and scouring in a manner similar to that in Example 1, and the core-sheath conjugate fiber in the woven fabric was formed into the specific cross-section fiber.
After the elution treatment, the resulting woven fabric was dyed black with a disperse dye by a conventional method using a jet dyeing machine. Then, soaping treatment using an aqueous surfactant solution and RC treatment were each performed according to a conventional method, and water repellent treatment was subsequently performed with the same formulation as in Example 1.
The resulting woven fabric had a warp density of 153 yarns/2.54 cm and a weft density of 115 yarns/2.54 cm, and a mixing ratio of 77 mass% of PET and 23 mass% of PU. In addition, the weight per unit area was 186 g/m² and the thickness was 0.49 mm, and when the porosity of the woven fabric was calculated from these values, and the density 1.38 g/cm³ of the component constituting the PET fiber and the density 1.0 g/cm³ of the component constituting the PU fiber, the porosity was 70.9%. In addition, 20% of voids are generated by the elution treatment in comparison with the core-sheath conjugate fiber of the round cross section before elution, and since the mixing ratio of the core-sheath conjugate fiber before elution is 81 mass%, the porosity resulting from the cross-section shape of the specific cross-section fiber is 16.2%.
In addition, as a result of observing the grooves in the fiber cross section of the core-sheath conjugate fiber after elution of the sheath component with a scanning electron microscope, there were eight grooves in the fiber circumference, the inlet width of each groove was 0.7 µm, the wide part of the groove was 1.8 µm (W2/W1 = 2.6), and the specific cross-section shape having the teardrop-shaped grooves with the wide parts was developed. The fiber had a diameter of 15.9 µm and a groove depth of 3.0 µm (H/D = 0.19), and had a desired shape capable of sufficiently maintaining the air layer. The width of the top of the protrusion was 7.9 µm, and peeling or collapse of the protrusion did not occur in the processing step.
Furthermore, the resulting woven fabric was used to evaluate the water repellency by the spray method, water retention rate, and buoyancy. The evaluation results are shown in Table 1. In the water-repellent woven fabric obtained by this method, the water repellent film was formed on the fiber surface on all of the front surface, the inside of the woven fabric, and the back surface, and the water-repellent woven fabric had a low water retention rate and high buoyancy at the initial stage and over time, and was suitable for wearing in water.

[Comparative Example 1]

A single covering thread similar to that in Example 1 was used for a warp yarn and a weft yarn to produce a gray fabric of plain weave having a lower density than that of Example 1, and elution, dyeing, and water repellent finish were performed by steps similar to those in Example 1.
The resulting woven fabric had a warp density of 168 yarns/2.54 cm and a weft density of 159 yarns/2.54 cm, and a mixing ratio of 68 mass% of Ny and 32 mass% of PU. In addition, the weight per unit area was 100 g/m² and the thickness was 0.44 mm, and when the porosity of the woven fabric was calculated by a calculation method similar to that in Example 1, the porosity was 79.3%. In addition, 20% of voids are generated by the elution treatment in comparison with the core-sheath conjugate fiber of the round cross section before elution, and since the mixing ratio of the core-sheath conjugate fiber before elution is 73 mass%, the porosity resulting from the cross-section shape of the specific cross-section fiber is 14.6%.
As a result of observing the grooves in the fiber cross section of the core-sheath conjugate fiber after elution of the sheath component with a scanning electron microscope, the parameters representing the groove shape were similar to those in Example 1.
Furthermore, the resulting woven fabric was used to evaluate the water repellency by the spray method, water retention rate, and buoyancy. The evaluation results are shown in Table 2. In the water-repellent woven fabric obtained by this method, the water repellent film was formed on the fiber surface on all of the front surface, the inside of the woven fabric, and the back surface, but the water retention rate after 60 minutes was deteriorated, and accordingly, the buoyancy after 20 minutes was also greatly reduced as compared with the initial value. It is inferred that a wearing feeling in water is deteriorated over time or by a crumpling effect.

[Comparative Example 2]

The single covering thread used in Example 3 was used for a warp yarn and a weft yarn to produce a woven fabric of 1/2 weft twill structure, and elution treatment, dyeing, and water repellent finish were performed by steps similar to those in Example 1.
The resulting woven fabric had a warp density of 138 yarns/2.54 cm and a weft density of 144 yarns/2.54 cm, and a mixing ratio of 76 mass% of Ny and 24 mass% of PU. In addition, the weight per unit area was 173 g/m² and the thickness was 0.69 mm, and when the porosity of the woven fabric was calculated by a calculation method similar to that in Example 1, the porosity was 77.4%. In addition, 20% of voids are generated by the elution in comparison with the core-sheath conjugate fiber of the round cross section before elution, and since the mixing ratio of the core-sheath conjugate fiber before elution is 80 mass%, the porosity resulting from the fiber cross-section shape is 16.0%.
As a result of observing the grooves in the fiber cross section of the core-sheath conjugate fiber after elution of the sheath component with a scanning electron microscope, the parameters representing the groove shape were similar to those in Example 3.
Furthermore, the resulting woven fabric was used to evaluate the water repellency by the spray method, water retention rate, and buoyancy . The evaluation results are shown in Table 2. In the water-repellent woven fabric obtained by this method, the water repellent film was formed on the fiber surface on all of the front surface, the inside of the woven fabric, and the back surface, but the water retention rate after 60 minutes was deteriorated, and accordingly, the buoyancy after 20 minutes was also greatly reduced as compared with the initial value. It is inferred that a wearing feeling in water is deteriorated over time or by a crumpling effect.

[Comparative Example 3]

A single covering thread using a sheath yarn: a semi-dull/round cross-section drawn yarn of nylon 6 of 33 dtex and 10 filaments (solid fiber) similar to that used for a warp yarn in Example 2 was used for a warp yarn and a weft yarn to produce a plain woven fabric, and scouring relaxation, dyeing, and water repellent finish were performed by steps excluding elution treatment from the steps in Example 1.
The resulting woven fabric had a warp density of 197 yarns/2.54 cm and a weft density of 176 yarns/2.54 cm, and a mixing ratio of 73 mass% of Ny and 27 mass% of PU. In addition, the weight per unit area was 108 g/m² and the thickness was 0.30 mm, and when the porosity of the woven fabric was calculated by a calculation method similar to that in Example 1, the porosity was 67.3%. Since all the used raw yarns have a round cross section, the porosity resulting from the fiber cross-section shape is 0%.
Furthermore, the resulting woven fabric was used to evaluate the water repellency by the spray method, water retention rate, and buoyancy. The evaluation results are shown in Table 2. In the water-repellent woven fabric obtained by this method, the water repellent film was formed on the fiber surface on all of the front surface, the inside of the woven fabric, and the back surface. Although the water retention rate is excellent, the buoyancy is poor, and it is considered that the woven fabric is insufficient in performance required for wearing in water.

[Comparative Example 4]

A sheath yarn: a semi-dull/round cross-section false-twisted yarn of nylon 6 of 84 dtex and 24 filaments (solid fiber) and a core yarn: chlorine-resistant LYCRA "LYCRA 176E" (PU) 78 dtex, manufactured by TORAY OPELONTEX CO., LTD. as an elastic fiber were used to produce a single covering thread with a draft ratio of the core yarn of 3.5 (times). The single covering thread using the round cross section was used for a warp yarn and a weft yarn to produce a woven fabric of 1/2 weft twill structure similar to that in Comparative Example 2, and scouring relaxation, dyeing, and water repellent finish were performed by steps excluding elution treatment from the steps in Example 1.
The resulting woven fabric had a warp density of 120 yarns/2.54 cm and a weft density of 124 yarns/2.54 cm, and a mixing ratio of 80 mass% of Ny and 20 mass% of PU. In addition, the weight per unit area was 168 g/m² and the thickness was 0.88 mm, and when the porosity of the woven fabric was calculated by a calculation method similar to that in Example 1, the porosity was 66.9%. Since all the used raw yarns have a round cross section, the porosity resulting from the fiber cross-section shape is 0%.

Furthermore, the resulting woven fabric was used to evaluate the water repellency by the spray method, water retention rate, and buoyancy. The evaluation results are shown in Table 2. In the water-repellent woven fabric obtained by this method, the water repellent film was formed on the fiber surface on all of the front surface, the inside of the woven fabric, and the back surface. However, the water retention rate is low from the initial stage, and the buoyancy is also greatly reduced over time. From this, it is considered that the woven fabric has a poor wearing feeling in water and is insufficient for required performance.

[Table 1]

		Example 1	Example 2	Example 3	Example 4	Example 5
Use of yarn	Warp	Ny: 33T - 10⁽⁺¹⁾ × PU: 44T	Ny: 33T-10 (round cross section) × PU: 44T	Ny: 84T - 24 ^(*1) × PU78T	Ny: 33T - 10^(*1) × PU: 44T	PET: 84T - 24^(*1) × PU78T
Use of yarn	Weft	Ny: 33T - 10^(*1) × PU: 44T	Ny: 33T - 10^(*1) × PU: 44T	Ny: 84T - 24^(*1) × PU78T	Ny: 33T - 10^(*1) × PU: 44T	PET: 84T - 24^(*1) × PU78T
Mixing ratio	(Mass basis)	Core-sheath conjugate fiber 73%/PU 27%	Core-sheath conjugate fiber 36.5%/Ny 36.5%/ PU 27%	Core-sheath conjugate fiber 80%/PU 20%	Core-sheath conjugate fiber 73%/PU 27%	Core-sheath conjugate fiber 81%/PU 19%
Mixing ratio ^(*2)	(Mass basis)	Ny68%/PU32%	Ny71%/PU29%	Ny76%/PU24%	Ny68%/PU32%	PET77%/PU23%
Specific cross-section fiber	Warp	Present	Absent	Present	Present	Present
Specific cross-section fiber	Weft	Present	Present	Present	Present	Present
Number of grooves of specific cross-section fiber		8	8	8	8	8
Presence or absence of crimp of synthetic fiber multifilament yarn	Warp	Absent	Absent	Absent	Absent	Absent
	Weft	Absent	Absent	Absent	Absent	Absent
Presence or absence of crimp of elastic of crimp of elastic fiber	Warp	Absent	Absent	Absent	Absent	Absent
	Weft	Absent	Absent	Absent	Absent	Absent
Stitch		Plain weave	Plain weave	Plain weave	Ripstop	Plain weave
Weave density (yarns/2.54 cm)	Warp	196	194	150	192	153
Weave density (yarns/2.54 cm)	Weft	179	181	112	174	115
Cover factor		2531	2538	2701	2471	2763
Weight per unit area	g/m²	103	113	201	105	186
Thickness	mm	0.3	0.31	0.56	0.35	0.49
Porosity of woven fabric	%	68.8	66.9	70.9	72.7	70.9
Porosity resulting from cross-section shape of specific cross-section fiber	%	14.6	7.3	16.0	14.6	16.2
Water repellency (spray method)	Grade	4-5	4-5	4-5	4-5	4
Burst strength	kPa	405	415	430	430	370
Tear strength	N	12.2	12.5	11.3	13.5	8.6
Water retention rate (10 min)	%	8.3	9.5	10.6	8.9	12.3
Water retention rate (60 min)	%	12.5	13.0	13.1	13.1	15.3
Buoyancy (initial)	N	0.026	0.023	0.025	0.025	0.020
Buoyancy (after 20 min)	N	0.025	0.021	0.023	0.022	0.017

*1: Core-sheath conjugate fiber for forming specific cross section
*2: The mixing ratio in the case of elution using the core-sheath conjugate fiber indicates the mixing ratio of the specific cross-section fiber after elution.

[Table 2]

		Comparative Example 1	Comparative Example 2	Comparative Example 3	Comparative Example 4
Use of yarn	Warp	Ny: 33T - 10^(*1) × PU: 44T	Ny: 84T - 24^(*1) × PU78T	Ny: 33T-10 (round cross section) × PU: 44T	Ny: 84T-24 (round cross section) × PU 78T
Use of yarn	Weft	Ny: 33T - 10^(*1) × PU: 44T	Ny: 84T - 24^(*1) × PU78T	Ny: 33T-10 (round cross section) × PU: 44T	Ny: 84T-24 (round cross section) × PU 78T
Mixing ratio	(Mass basis)	Core-sheath conjugate fiber 73%/PU 27%	Core-sheath conjugate fiber 80%/PU 20%	Ny73%/PU27%	Ny80%/PU20%
Mixing ratio ^(*2)	(Mass basis)	Ny68% /PU31%	Ny76%/PU24%	Ny73%/PU27%	Ny80%/PU20%
Specific cross-section fiber	Warp	Present	Present	Absent	Absent
Specific cross-section fiber	Weft	Present	Present	Absent	Absent
Number of grooves of specific cross-section fiber		8	8	0	0
Presence or absence of crimp of synthetic fiber multifilament yarn	Warp	Absent	Absent	Absent	Present
	Weft	Absent	Absent	Absent	Present
Presence or absence of crimp of elastic fiber	Warp	Absent	Absent	Absent	Absent
Presence or absence of crimp of elastic fiber	Weft	Absent	Absent	Absent	Absent
Stitch		Plain weave	1/2 weft twill weave	Plain weave	1/2 weft twill weave
Weave density (yarns/2.54 cm)	Warp	168	138	197	120
Weave density (yarns/2.54 cm)	Weft	159	144	176	124
Cover factor		2207	3738	2525	3228
Weight per unit area	g/m²	100	173	108	168
Thickness	mm	0.44	0.69	0.30	0.88
Porosity of woven fabric	%	79.3	77.4	67.3	82.8
Porosity resulting from cross-section shape of specific cross-section fiber	%	14.6	16.0	0	0
Water repellency (spray method)	Grade	4-5	4-5	3-4	4
Burst strength	kPa	180	425	400	400
Tear strength	N	18.4	9.6	12.7	11.2
Water retention rate (10 min)	%	32.6	39.2	8.6	52.3
Water retention rate (60 min)	%	58.2	61.1	13.1	81.6
Buoyancy (initial)	N	0.018	0.022	0.013	0.022
Buoyancy (after 20 min)	N	0.004	0.006	0.008	0.003

DESCRIPTION OF REFERENCE SIGNS

11:: Protrusion
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 portion
24:: Groove wide part width (W2)
31:: Protrusion top width (Pout)
32:: Protrusion bottom surface width (Pmin)
40:: Buoyancy tester
41:: Container
42:: Water
43:: Weight scale
44:: Support
45:: Support rod
46:: Support plate
47:: Metal mesh
48:: Test sample
51:: Distribution hole for core component
52:: Distribution hole for sheath component

Claims

A woven fabric comprising a synthetic fiber multifilament yarn and an elastic fiber, wherein at least a part of the synthetic fiber multifilament used in the woven fabric comprises a synthetic fiber including a single fiber having, on a surface of the single fiber, a plurality of grooves continuous in a fiber length direction, the grooves of the single fiber have a wide part wider than an inlet in a cross section, a depth of 1.0 to 10.0 µm, and an inlet width of 0.5 to 10.0 µm, a width of a top of a protrusion is 10.0 µm or less, a porosity of the woven fabric is 75% or less, a porosity resulting from a fiber cross-section shape of the single fiber having the plurality of grooves on the surface is 3 to 30%, and a water repellent film is provided on a front surface, inside of the woven fabric, and a back surface.
The woven fabric according to claim 1, wherein the number of grooves of the single fiber having the plurality of grooves continuous in the fiber length direction on the surface is 2 to 32.
The woven fabric according to claim 1 or 2, wherein the synthetic fiber multifilament is a non-crimped multifilament.
The woven fabric according to claim 1 or 2, wherein a water repellency in a spray test in accordance with JIS L 1092: 2009 is grade 4 or higher.
The woven fabric according to claim 1 or 2, wherein a water retention rate after 60 minutes is 50 mass% or less of a mass of the woven fabric.
The woven fabric according to claim 1 or 2, wherein a buoyancy per 1 g of the woven fabric is 0.017 N or more.
The woven fabric according to claim 1 or 2, wherein a cross-section shape of the synthetic fiber satisfies (Formula 1) and (Formula 2) below. $W 2 / W 1 \geq 1.3$ $0.15 \leq H / D \leq 0.25$
W1: groove inlet width (µm)

W2: groove wide part width (µm)

H: groove depth (µm)

F: fiber diameter (µm)