Spunbond nonwoven fabric, sanitary material, industrial material, hollow fiber production device, and hollow fiber production method

Abstract

SB nonwoven fabric according to the present disclosure contains a plurality of hollow fibers. The coefficient of variation of the hollowness ratios of the hollow fibers is less than 10%.

Description

Spunbond nonwoven fabric, sanitary materials, industrial materials, hollow fiber manufacturing equipment and hollow fiber manufacturing method

[0001] The present disclosure relates to a spunbond nonwoven fabric, a sanitary material, an industrial material, a hollow fiber manufacturing apparatus, and a hollow fiber manufacturing method.

[0002] Nonwoven fabrics have been widely used for various purposes due to their excellent breathability and flexibility. Therefore, nonwoven fabrics are required to have various properties according to their applications, and improvements in these properties are also required. For example, nonwoven fabrics used as agricultural covering materials are required to have a certain level of mechanical strength.

[0003] Patent Document 1 discloses an agricultural sheet. The agricultural sheet is a long-fiber nonwoven fabric (hereinafter simply referred to as a "spunbond nonwoven fabric") having a specific basis weight. The spunbond nonwoven fabric is made of polypropylene-based fibers with a fiber diameter of 25 μm or more and a specific hollow cross section.

[0004] Patent Document 1 specifically discloses a method for producing an agricultural sheet using a general spunbond nonwoven fabric manufacturing apparatus. Specifically, a polypropylene polymer was melted, and the resulting melt was spun from a specific spinneret at a single-hole output rate of 3.1 g / min. This resulted in continuous fibers with a hollow cross section (hereinafter also referred to as "hollow fibers"). The hollow fibers were then cooled in a cooling device, pulled and attenuated by a yarn suction device installed below at a take-up speed of 4,800 m / min, opened by a corona discharge means, and deposited on a moving screen. This resulted in a web on the screen. The web was then thermocompressed using an embossing roll. This resulted in a spunbond nonwoven fabric (agricultural sheet).

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 8-126440

[0006] However, the hollow fibers constituting the spunbonded nonwoven fabric disclosed in Patent Document 1 may undergo fiber cracking in some of the fibers when pulled in the fiber axis direction of the hollow fibers, and may be difficult to stretch. In other words, the mechanical strength of the spunbonded nonwoven fabric disclosed in Patent Document 1 itself may be insufficient depending on the degree to which it is pulled in the fiber axis direction. Therefore, there is a demand for a spunbonded nonwoven fabric that includes hollow fibers that are unlikely to undergo fiber cracking in some of the fibers when pulled in the fiber axis direction and that are easy to stretch (i.e., hollow fibers that have excellent tensile strength and elongation).

[0007] Furthermore, from the viewpoint of improving production efficiency, there is a demand for high-speed production of spunbonded nonwoven fabrics. However, when the production speed of hollow fibers is increased, the resulting hollow fibers may suffer from fiber cracking. Such fiber cracking tends to occur more easily in hollow fibers with a large variation in hollowness. Therefore, even when spunbonded nonwoven fabrics are produced at high speeds, there has been a demand for hollow fibers with a small variation in hollowness and for spunbonded nonwoven fabrics containing such hollow fibers.

[0008] In view of the above problems, the present disclosure aims to provide a spunbond nonwoven fabric, a sanitary material, an industrial material, a hollow fiber manufacturing apparatus, and a hollow fiber manufacturing method, each of which includes hollow fibers having excellent tensile strength and elongation.

[0009] Specific means for solving the above problems include the following aspects.

[0010] <1> A spunbond nonwoven fabric containing hollow fibers, wherein the hollow fibers have a coefficient of variation of hollowness of less than 10%. <2> A spunbond nonwoven fabric containing hollow fibers having a coefficient of variation of hollowness of less than 10%. ３ The spunbond nonwoven fabric according to <1>, wherein the coefficient of variation of the outer diameter of the hollow fibers is: ２× coefficient of variation of the hollow ratio of the hollow fibers <3> The spunbond nonwoven fabric according to <1> or <2>, wherein the average outer diameter of the hollow fibers is less than 30 μm. <4> The spunbond nonwoven fabric according to any one of <1> to <3>, wherein the average hollow ratio of the hollow fibers is 10% to 40%. <5> The spunbond nonwoven fabric according to any one of <1> to <4>, wherein the hollow fibers contain a polypropylene-based resin. <6> The spunbond nonwoven fabric according to any one of <1> to <5>, wherein the hollow fibers have a single filament linear strength of 19.0 mN / denier or more and a single filament elongation of 300% or more. <7> The spunbond nonwoven fabric according to any one of <1> to <6>, wherein the average outer diameter of the hollow fibers is 10 μm or more and less than 30 μm and an average hollow ratio of the hollow fibers is 10% to 40%. <8> A sanitary material comprising the spunbonded nonwoven fabric according to any one of <1> to <7>. <9> An industrial material comprising the spunbonded nonwoven fabric according to any one of <1> to <7>. <10> A hollow fiber manufacturing apparatus for manufacturing the hollow fiber according to any one of <1> to <7>, the manufacturing apparatus having a spinneret, wherein the ratio of the length of the spinneret slot to the width of the slot is less than 8. <11> A hollow fiber manufacturing method for manufacturing the hollow fiber according to any one of <1> to <7> by spinlay lamination, wherein the take-up speed of the hollow fiber when laminating the hollow fiber on a moving screen is 2000 m / min to 4000 m / min. <12> A method for producing hollow fibers, which comprises producing hollow fibers by spinlay lamination using a hollow fiber production apparatus, wherein the production apparatus has a spinneret, the ratio of the slot length to the slot width of the spinneret is less than 8, and the take-up speed of the hollow fibers when the hollow fibers are laminated on a moving screen is 2000 m / min to 4000 m / min.

[0011] <13> A spunbond nonwoven fabric comprising hollow fibers, wherein the hollow fibers have a coefficient of variation of hollowness of less than 10%, and the hollow fibers have an average outer diameter of 30 μm or more. <14> A spunbond nonwoven fabric comprising hollow fibers having a coefficient of variation of hollowness of less than 10%, and the average outer diameter of the hollow fibers is 30 μm or more. ３ The spunbond nonwoven fabric according to <13>, wherein the coefficient of variation of the outer diameter of the hollow fibers is: ２× coefficient of variation of the hollow ratio of the hollow fibers <15> The spunbond nonwoven fabric according to <13> or <14>, wherein the average hollow ratio of the hollow fibers is 10% to 40%. <16> The spunbond nonwoven fabric according to any one of <13> to <15>, wherein the hollow fibers contain a polypropylene-based resin. <17> The spunbond nonwoven fabric according to any one of <13> to <16>, wherein the hollow fibers have a single filament linear strength of 19.0 mN / denier or more, and a single filament elongation of 300% or more. <18> The spunbond nonwoven fabric according to any one of <13> to <17>, wherein the hollow fibers have an average outer diameter of 30 μm to 40 μm, and an average hollow ratio of 10% to 40%. <19> A sanitary material comprising the spunbonded nonwoven fabric according to any one of <13> to <18>. <20> An industrial material comprising the spunbonded nonwoven fabric according to any one of <13> to <18>. <21> A hollow fiber manufacturing apparatus for producing the hollow fiber according to any one of <13> to <18>, the apparatus having a spinneret, wherein the ratio of the length of the spinneret slot to the width of the slot is less than 8. <22> A hollow fiber manufacturing method for producing the hollow fiber according to any one of <13> to <18> by spinlay lamination, the take-up speed of the hollow fiber when the hollow fiber is layered on a moving screen is 2000 m / min to 4000 m / min. <23> A method for producing hollow fibers, which comprises producing hollow fibers by spinlay lamination using a hollow fiber production apparatus, wherein the production apparatus has a spinneret, the ratio of the slot length to the slot width of the spinneret is less than 8, and the take-up speed of the hollow fibers when laminating them on a moving screen is 2000 m / min to 4000 m / min.

[0012] According to one embodiment of the present disclosure, there are provided a spunbond nonwoven fabric, a sanitary material, an industrial material, a hollow fiber manufacturing apparatus, and a hollow fiber manufacturing method, each of which includes hollow fibers having excellent tensile strength and elongation.

[0013] Figure 1 is a schematic diagram showing a closed spunbond nonwoven fabric manufacturing apparatus according to an embodiment of the first aspect of the present disclosure. Figure 2 is a schematic diagram of an example of the hole shape of a slot of a spinneret according to an embodiment of the first aspect of the present disclosure. Figure 3 is a cross-sectional view of a spinning hole of a spinneret according to an embodiment of the first aspect of the present disclosure. Figure 4 is a schematic diagram of an example of the hole shape of a slot of a spinneret according to an embodiment of the first aspect of the present disclosure. Figure 5 is a schematic diagram of an example of the hole shape of a slot of a spinneret according to an embodiment of the first aspect of the present disclosure.

[0014] The following describes embodiments of the present disclosure. These descriptions and examples are intended to illustrate the embodiments and do not limit the scope of the embodiments. In the numerical ranges described in stages in this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. In the numerical ranges described in this disclosure, the upper or lower limit of that numerical range may be replaced with a value shown in the Examples. In this disclosure, each component may contain multiple corresponding substances. When referring to the amount of each component in a composition in this disclosure, if multiple substances corresponding to each component are present in the composition, this refers to the total amount of those multiple substances present in the composition, unless otherwise specified. In this disclosure, the term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes, as long as the purpose of the process is achieved. In this disclosure, numerical ranges indicated using "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In this disclosure, when multiple substances corresponding to each component are present in the composition, the content of each component in the composition refers to the total amount of those multiple substances present in the composition, unless otherwise specified. In this disclosure, "spunbond nonwoven fabric" refers to a nonwoven fabric made by bonding one or more bonding methods (e.g., embossing) to a spunlaid web. "Spunlaid web" refers to a web laminated by spinlaid lamination. "Spinlaid lamination" refers to a method of making a web by extruding molten or dissolved polymer through a spinneret (i.e., spinning holes) and laminating single fibers onto a moving screen.

[0015] (1) First Aspect (1.1) Spunbond Nonwoven Fabric A spunbond nonwoven fabric (hereinafter also referred to as an "SB nonwoven fabric") according to a first aspect of the present disclosure includes a plurality of hollow fibers, the hollow fibers having a coefficient of variation of hollowness (hereinafter also referred to as "Cv of hollowness") of less than 10%.

[0016] The term "hollow fiber" refers to a straw-shaped fiber. Specifically, a hollow fiber has one or more hollow portions extending along the fiber axis.

[0017] The coefficient of variation of the hollow ratio of hollow fibers quantitatively represents the degree of variation in the hollow ratio in the fiber axial direction of the multiple hollow fibers constituting the SB nonwoven fabric. A coefficient of variation of the hollow ratio of hollow fibers closer to 0 indicates that the shapes of the hollow fibers contained in the SB nonwoven fabric are relatively uniform, that the hollow ratios of the multiple hollow fibers are all approximately the same, and that there is less variation in the hollow ratio in the fiber cross-sectional direction of the hollow fibers. The "hollow ratio" refers to the ratio of the cross-sectional area of ​​the hollow portion of a hollow fiber to the cross-sectional area defined by the outer diameter of the hollow fiber in a cross-section perpendicular to the fiber axial direction of the hollow fiber taken from the SB nonwoven fabric. The method for measuring the hollow ratio Cv is the same as that described in the Examples.

[0018] The SB nonwoven fabric of the first embodiment has the above-described configuration and includes hollow fibers that are excellent in tensile strength and elongation. Therefore, the SB nonwoven fabric of the first embodiment has excellent tensile strength (hereinafter also referred to as "MD tensile strength") in the machine direction (hereinafter also referred to as "machine direction (MD)") of the SB nonwoven fabric of the first embodiment. In a preferred embodiment, the SB nonwoven fabric of the first embodiment has excellent MD tensile strength and elongation (hereinafter also referred to as "MD elongation"). This effect is presumed to be due to, but not limited to, the following reasons. A hollowness Cv of less than 10% indicates that, in the multiple hollow fibers that make up the SB nonwoven fabric, the thickness of the walls that make up the hollow portions of the hollow fibers is relatively uniform in a cross section obtained by cutting the hollow fibers along a direction perpendicular to the fiber axis (hereinafter also referred to simply as a "cross section of the hollow fibers"). Therefore, when the hollow fiber is pulled in the fiber axial direction, stress is less likely to concentrate in specific regions of the hollow fiber (particularly regions where the wall thickness of the hollow portion is thin) than in a configuration in which the wall thickness of the hollow portion of the hollow fiber is non-uniform across the cross section of the hollow fiber. As a result, the hollow fibers contained in the SB nonwoven fabric of the first aspect are presumed to have excellent tensile strength and excellent elongation. Therefore, the SB nonwoven fabric containing the hollow fibers, which includes multiple hollow fibers with a relatively uniform cross-sectional shape, has superior tensile strength compared to an SB nonwoven fabric in which the wall thickness of the hollow portion of the hollow fiber is non-uniform across the cross section of the hollow fiber.

[0019] The machine direction (MD) of an SB nonwoven fabric can be determined from the SB nonwoven fabric itself by measuring its tensile strength. Generally, in the production of SB nonwoven fabrics, the screen movement speed is set relatively fast from the viewpoint of productivity. Therefore, the monofilaments (long fibers) contained in the web tend to be oriented parallel to the machine direction (MD) when stacked on the screen. As a result, the tensile strength of an SB nonwoven fabric in the machine direction (MD) is higher than the tensile strength in the direction (CD) perpendicular to the machine direction (MD) (hereinafter also referred to as the "cross direction (CD)"). Therefore, the machine direction (MD) of an SB nonwoven fabric can be determined from the SB nonwoven fabric itself by measuring its tensile strength.

[0020] The SB nonwoven fabric is a sheet-like material and may have a single layer structure or a laminated structure.

[0021] The basis weight of the SB nonwoven fabric is not particularly limited and is appropriately selected depending on the application of the SB nonwoven fabric. The basis weight of the SB nonwoven fabric is 5 g / m ２ ~400g / m ２ and 10 g / m ２ ~50g / m ２ and 15 g / m ２ ~30g / m ２ As a sanitary material (i.e., from the viewpoint of imparting flexibility and breathability to the SB nonwoven fabric), the basis weight of the SB nonwoven fabric may be 5 g / m ２ ~30g / m ２ It is preferable that the density is 5 g / m ２ ~20g / m ２ As an industrial material (i.e., from the viewpoint of increasing tensile strength), the basis weight of the SB nonwoven fabric is preferably 30 g / m ２ ~400g / m ２ The method for measuring the basis weight of the SB nonwoven fabric is the same as the method described in the examples.

[0022] The thickness of the SB nonwoven fabric is not particularly limited and may be appropriately selected depending on the intended use of the SB nonwoven fabric. The thickness of the SB nonwoven fabric may be 0.1 mm to 2.0 mm, or 0.2 mm to 1.0 mm.

[0023] The SB nonwoven fabric may be made by a known bonding method. Known bonding methods include heat fusion methods (e.g., embossing and ultrasonic bonding), mechanical entanglement methods (e.g., needle punching and water jetting), methods using adhesives (e.g., hot melt adhesives and urethane adhesives), and extrusion lamination. These bonding methods are appropriately selected depending on the application. When the SB nonwoven fabric is made by the heat fusion method, the SB nonwoven fabric may have multiple embossed portions. The "embossed portion" refers to a non-fibrous portion where a portion of multiple hollow fibers is thermally bonded. Specifically, the embossed portion is a bonded portion having an area of ​​0.1 mm ２The ratio of the total area of ​​the embossed portions to the surface area of ​​the SB nonwoven fabric (hereinafter referred to as "embossed area ratio") is not particularly limited, but is preferably 5% to 50% from the viewpoints of tensile strength and breathability. From the viewpoint of further imparting flexibility, the embossed area ratio is preferably 5% to 25%. From the viewpoint of increasing rigidity, the embossed area ratio may be more than 25% but not more than 50%.

[0024] The SB nonwoven fabric contains a plurality of hollow fibers. The SB nonwoven fabric may be a composite material containing other fibers (e.g., solid fibers, fibers without hollow portions in the fiber cross section, and staple fibers) in addition to the hollow fibers. The staple fibers may be carded fibers, pulp fibers, cotton fibers, bamboo fibers, or the like. When the SB nonwoven fabric contains other fibers, the content of the hollow fibers can be adjusted appropriately depending on the application. The content of the hollow fibers may be 80% by mass or more and less than 100% by mass, or 90% by mass or more and less than 100% by mass, based on the total amount of the SB nonwoven fabric. The SB nonwoven fabric may be composed solely of a plurality of hollow fibers.

[0025] The MD tensile strength of an SB nonwoven fabric is not particularly limited and is selected appropriately depending on the application of the SB nonwoven fabric. The MD tensile strength of an SB nonwoven fabric is preferably 20 N / 25 mm to 40 N / 25 mm. An MD tensile strength of an SB nonwoven fabric of 20 N / 25 mm or more indicates that the SB nonwoven fabric has excellent MD tensile strength. In other words, the SB nonwoven fabric is tear-resistant. Therefore, the SB nonwoven fabric is suitable for use in sanitary materials and industrial materials (e.g., agricultural covering materials, etc.). The method for measuring the MD tensile strength of an SB nonwoven fabric is the same as that described in the examples.

[0026] The MD elongation of the SB nonwoven fabric is not particularly limited and is appropriately selected depending on the application of the SB nonwoven fabric. The MD elongation of the SB nonwoven fabric may be 30% or more, and preferably 60% to 100%. An MD elongation of the SB nonwoven fabric of 60% or more indicates that the SB nonwoven fabric has an excellent MD elongation. In other words, the SB nonwoven fabric is easy to elongate and has excellent flexibility and shape-following properties. Therefore, the SB nonwoven fabric is suitable for use in sanitary materials and industrial materials (e.g., agricultural covering materials, etc.). The method for measuring the MD elongation of the SB nonwoven fabric is the same as that described in the examples.

[0027] The air permeability of the SB nonwoven fabric is not particularly limited and is appropriately selected depending on the application of the SB nonwoven fabric. The air permeability of the SB nonwoven fabric is preferably 500 cm ３ / cm ２ ・sec~700cm ３ / cm ２ ・sec. The air permeability of SB nonwoven fabric is 500 cm ３ / cm ２ A permeability of 1 / 2 s or more indicates that air easily permeates the SB nonwoven fabric. Therefore, the SB nonwoven fabric is suitable for use in sanitary materials and industrial materials (e.g., agricultural covering materials, etc.). The method for measuring the air permeability of the SB nonwoven fabric is the same as that described in the examples.

[0028] The light transmittance of the SB nonwoven fabric is not particularly limited and is selected appropriately depending on the application of the SB nonwoven fabric. The light transmittance of the SB nonwoven fabric is preferably 93.4% to 90.0%. A light transmittance of 93.4% or less of the SB nonwoven fabric indicates that the SB nonwoven fabric adequately blocks light transmission. Therefore, the SB nonwoven fabric is suitable for use as an agricultural covering material. The method for measuring the light transmittance of the SB nonwoven fabric is the same as that described in the Examples.

[0029] (1.1.1) Hollow Fibers The average outer diameter of the hollow fibers is not particularly limited and is appropriately selected depending on the application of the SB nonwoven fabric. In one embodiment, the average outer diameter of the hollow fibers is preferably less than 30 μm. The average outer diameter of the hollow fibers may be less than 30 μm, and the Cv of the hollow fibers may be less than 10%. From the perspective of imparting flexibility, the average outer diameter of the hollow fibers may be 25 μm or less or 5 μm or more. The smaller the average outer diameter of the hollow fibers, the smaller the surface friction coefficient and the smoother the fibers feel when touching the skin. Therefore, SB nonwoven fabrics are useful in sanitary materials, artificial leather, and the like. From the perspective of increasing the breathability of the nonwoven fabric, the average outer diameter of the hollow fibers may be 20 μm or more. The thicker the outer fiber diameter, the higher the abrasion resistance. Therefore, SB nonwoven fabrics are useful in applications where fuzzing is suppressed. The method for measuring the average outer diameter of the hollow fibers is the same as that described in the Examples.

[0030] The coefficient of variation of the outer diameter of the hollow fibers in the SB nonwoven fabric produced by spinlay lamination (hereinafter also referred to as "outer diameter Cv") is 10.0% or less. The outer diameter Cv of the multiple hollow fibers contained in the SB nonwoven fabric is preferably 2.0% to 10.0%, more preferably 3.0% to 10.0%. When the outer diameter Cv is within the above numerical range, the cross-sectional area Cv of the hollow fibers can be reduced. In other words, the fiber diameter distribution of the multiple hollow fibers contained in the SB nonwoven fabric becomes narrower. For example, an SB nonwoven fabric having an outer diameter Cv of 10.0% or less is useful as a low-basis-weight SB nonwoven fabric with reduced variation between production lots, and is useful for applications such as filter media. The outer diameter Cv can be measured using the same method as described in the Examples.

[0031] The average hollow ratio of hollow fibers is not particularly limited and is selected appropriately depending on the application of the SB nonwoven fabric. The average hollow ratio of hollow fibers is preferably 10% to 40%. The higher the average hollow ratio of hollow fibers, the greater the effect of reducing environmental impact. Furthermore, in applications requiring heat retention (e.g., hand warmers), a high average hollow ratio is required. From this perspective, the average hollow ratio of hollow fibers is preferably 10% or more. From the viewpoint of the single fiber linear strength and single fiber elongation of the hollow fibers, the average hollow ratio of hollow fibers is preferably 40% or less. The method for measuring the average hollow ratio of hollow fibers is the same as that described in the examples.

[0032] The hollow fiber has a Cv of less than 10.0%. From the viewpoint of increasing the single fiber linear strength and the MD tensile strength of the SB nonwoven fabric, the Cv of the hollow fiber is preferably 2.0% or more and less than 10.0%. When an SB nonwoven fabric containing hollow fibers is produced at high speed, fiber cracking may occur, and the Cv of the resulting hollow fiber generally tends to exceed 10%. Fiber cracking reduces the fiber strength. Therefore, the single fiber elongation of conventional hollow fibers was poor. In other words, the single fiber linear strength of conventional hollow fibers was less than 19.0 mN / denier. In the present disclosure, it has been discovered that the hollow fiber Cv can be reduced to less than 10% by the manufacturing method described below. While some of the mechanisms are unclear, the challenge to obtain such excellent hollow fibers is to produce a resin molded product that is relatively uniformly thin in the circumferential direction of the fiber while preventing the formation of extremely thin weak points that could be the starting point for fiber cracking in the hollow fiber. In order to achieve this object with fine modified cross-section fibers, it is considered useful to control the method of extruding hollow fibers.

[0033] The hollow fibers preferably have an average outer diameter of 10 μm or more and less than 30 μm, and an average hollow ratio of 10% to 40%, which improves the single filament linear strength and single filament elongation of the hollow fibers and provides the SB nonwoven fabric with excellent MD tensile strength.

[0034] The value represented by the following formula (I) (hereinafter also referred to as "Cv of the cross-sectional area of ​​the hollow fiber") is 300% ３ It is preferable that the ratio is less than 100%.３ ~300% ３ It is more preferable that ３ ~250% ３ It is more preferable that the coefficient of variation of the outer diameter of the hollow fiber is expressed by the formula (I): ２ × Coefficient of variation of hollowness of the hollow fiber

[0035] The Cv of the cross-sectional area of ​​a hollow fiber can be considered to quantitatively represent the degree of variation in the area of ​​the wall constituting the hollow portion in the cross section of the hollow fiber (hereinafter also referred to as the "cross-sectional area of ​​the hollow fiber") in the fiber axial direction of the multiple hollow fibers constituting the SB nonwoven fabric. A Cv of the cross-sectional area of ​​a hollow fiber closer to 0 indicates less variation in the cross-sectional area of ​​the hollow fiber in the fiber axial direction of the hollow fiber. In other words, a Cv of the cross-sectional area of ​​a hollow fiber closer to 0 means that the resulting SB nonwoven fabric is composed of hollow fibers with a more uniform cross-sectional shape.

[0036] Cv of the cross-sectional area of ​​the hollow fiber is 300% ３ When the cross-sectional area of ​​the hollow fiber is 300%, the linear strength and elongation of the hollow fiber are not good. ３ The cross-sectional area of ​​the hollow fiber is 300% or more. ３ When the cross-sectional area of ​​the hollow fiber is less than 1 / 2 of the cross-sectional area of ​​the hollow fiber, there are fewer extremely thin weak points that can become the starting points for fiber cracking. The mechanical strength of the SB nonwoven fabric containing such hollow fibers is superior to that of conventional nonwoven fabrics. The method for measuring the cross-sectional area Cv of the hollow fiber is the same as that described in the Examples.

[0037] The single filament linear strength of the hollow fiber is not particularly limited and is appropriately selected depending on the application of the SB nonwoven fabric. The single filament linear strength of the hollow fiber is preferably 19.0 mN / denier or more, more preferably 19.0 mN / denier to 30.0 mN / denier. A single filament linear strength of 19.0 mN / denier or more indicates that the hollow fiber has excellent single filament linear strength. In other words, SB nonwoven fabrics tend to be tear-resistant. Therefore, SB nonwoven fabrics are suitable for use in low-basis-weight sanitary materials and industrial materials (e.g., agricultural covering materials, etc.). The method for measuring the single filament linear strength of SB nonwoven fabrics is the same as that described in the examples.

[0038] The single filament elongation of the hollow fiber is not particularly limited and is appropriately selected depending on the application of the SB nonwoven fabric. The single filament elongation of the hollow fiber is preferably 300% or more, more preferably 300% to 450%. A single filament elongation of the hollow fiber of 300% or more indicates that the single filament elongation of the hollow fiber is excellent. In other words, the SB nonwoven fabric has excellent MD tensile strength. Depending on the thermoplastic resin used in the SB nonwoven fabric, the SB nonwoven fabric may not only have excellent MD tensile strength, but also be easily stretched, flexible, and excellent in shape conformability. Therefore, the SB nonwoven fabric is suitable for use in sanitary materials and industrial materials (for example, agricultural covering materials that require conformability to uneven shapes). The method for measuring the single filament elongation of the SB nonwoven fabric is the same as that described in the examples.

[0039] The hollow fiber preferably has a single filament linear strength of 19.0 mN / denier or more and a single filament elongation of 300% or more. This gives the SB nonwoven fabric excellent MD tensile strength. Therefore, the SB nonwoven fabric is suitable for use in sanitary materials and industrial materials (e.g., agricultural covering materials).

[0040] (1.1.1.1) Material The hollow fiber may be made of a thermoplastic resin composition.

[0041] (1.1.1.1.1) Thermoplastic Resin The thermoplastic resin composition contains a thermoplastic resin. Examples of thermoplastic resins include polyolefin-based resins, polyester-based resins (e.g., polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate), polyamide-based resins (e.g., nylon-6, nylon-66, and polymetaxylene adipamide), polyvinyl chloride, polyimide, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester-carbon monoxide copolymer, polyacrylonitrile, polycarbonate, polystyrene, and ionomer. "(Meth)acrylic acid" refers to acrylic acid or methacrylic acid. Examples of polyolefin-based resins include polyethylene-based resins (e.g., linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), and the like) and polypropylene-based resins. Examples of polypropylene-based resins include propylene homopolymers (i.e., homopolypropylene), propylene-α-olefin random copolymers (e.g., propylene-ethylene random copolymers), and propylene-α-olefin block copolymers. Examples of α-olefins other than propylene include ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-pentene. When an α-olefin is copolymerized, the copolymerization amount is preferably 1 mol % to 10 mol %. The term "polypropylene-based resin" refers to a polymer containing 50% by mass or more of structural units derived from propylene. These thermoplastic resins may be used alone or in combination of two or more.

[0042] The hollow fibers may be monocomponent fibers. In other embodiments, the hollow fibers may further comprise one or more polymer layers to further enhance strength, processability, and other properties. The hollow fiber structure may have a bilayer structure (e.g., a sheath-core configuration) or a multilayer structure (e.g., side-by-side, segmented pie, and islands-in-the-sea).

[0043] The hollow fibers may contain a polypropylene-based resin or may be a polypropylene-based resin. The hollow fibers may be a polypropylene-based resin or a homopolypropylene. When the main component of the thermoplastic resin of the hollow fibers is homopolypropylene, the SB nonwoven fabric can have both MD tensile strength and MD elongation. "Main component of thermoplastic resin" refers to a thermoplastic resin component whose content relative to the total amount of thermoplastic resin is 50 mass% or more.

[0044] Hereinafter, the case where the hollow fiber contains a propylene-based polymer will be described.

[0045] The melting point of the propylene polymer is preferably 140°C or higher, more preferably 150°C or higher, even more preferably 155°C or higher, and particularly preferably 157°C to 165°C. The melting point (Tm) can be measured using differential scanning calorimetry (DSC) as follows. Using a Perkin-Elmer DSC Pyris1 or SII NanoTechnology DSC7020 as a differential scanning calorimeter (DSC), a sample (approximately 5 mg) is heated from room temperature to 200°C at 10°C / min under a nitrogen atmosphere (20 ml / min), held at that temperature for 5 minutes, cooled to -50°C at 10°C / min, held at -50°C for 5 minutes, and heated a second time to 200°C at 10°C / min. The melting point (Tm) is calculated from the peak top of the crystalline melting peak during this second heating process. Note that if multiple crystalline melting peaks are observed, the peak on the higher temperature side is taken as the melting point (Tm).

[0046] The melt flow rate (MFR) of the polypropylene-based resin is not particularly limited as long as it is melt-spinnable, and may be 1 g / 10 min to 1000 g / 10 min, 5 g / 10 min to 500 g / 10 min, or 10 g / 10 min to 100 g / 10 min. The MFR of the polypropylene-based resin is measured in accordance with ASTM D-1238 under the measurement conditions of 230°C and a load of 2.16 kg.

[0047] The content of the polypropylene resin may be 80.0% by mass to 100.0% by mass, 90.0% by mass to 100.0% by mass, or 100.0% by mass, relative to the total amount of the thermoplastic resin composition.

[0048] The thermoplastic resin (e.g., polypropylene-based resin, etc.) used in the first embodiment may be a biomass-derived raw material. Because biomass-derived raw materials are carbon-neutral, the environmental impact of producing an SB nonwoven fabric using the hollow fibers of the present disclosure can be further reduced. Monomers serving as raw materials for biomass-derived thermoplastic resins can be obtained by cracking biomass naphtha or synthesizing them from biomass-derived ethylene. Biomass-derived thermoplastic resins can be obtained by polymerizing the biomass-derived monomers synthesized in this manner using a method similar to that used for conventionally known petroleum-derived thermoplastic resins. A thermoplastic resin polymer synthesized using bio-derived monomers as raw materials is a biomass-derived thermoplastic polymer. The content of the bio-derived thermoplastic polymer in the raw material monomers may be greater than 0% by mass, 100% by mass, or less, relative to the total amount of raw material monomers. The "biomass content" indicates the content of biomass-derived carbon and is calculated by measuring radiocarbon (C14). Atmospheric carbon dioxide contains a certain proportion of C14 (approximately 105.5 pMC). Therefore, it is known that the C14 content in plants (e.g., corn) that grow by absorbing carbon dioxide from the atmosphere is about 105.5 pMC. It is also known that fossil fuels contain almost no C14. Therefore, by measuring the proportion of C14 carbon in the total carbon atoms in the polymer, the content of biomass-derived carbon in the raw material can be calculated.

[0049] In a preferred embodiment, the thermoplastic polymer used as the raw material in the first embodiment includes a thermoplastic polymer obtained by recycling, i.e., a so-called recycled polymer. "Recycled polymer" includes polymers obtained by material recycling or chemical recycling of waste polymer products, and can be produced, for example, by the method described in DE 102019127827 (A1). The recycled polymer may contain a marker that identifies it as having been obtained by recycling. By including a recycled polymer in the thermoplastic resin used in the SB nonwoven fabric, the amount of virgin petrochemical raw materials used can be reduced, and the environmental impact during the production of the SB nonwoven fabric using hollow fibers can be further reduced.

[0050] (1.1.1.1.2) Additives The thermoplastic resin composition may contain additives, such as antioxidants, heat stabilizers, weather stabilizers, antistatic agents, softeners, slip agents, anti-fogging agents, lubricants, dyes, pigments, natural oils, synthetic oils, waxes, compatibilizers, and fatty acid amides.

[0051] (1.1.3) Method for producing hollow fibers In the method for producing hollow fibers of the first embodiment, the hollow fibers of the first embodiment are produced by spin-lay lamination. In the method for producing hollow fibers of the first embodiment, the take-up speed of the hollow fibers when they are layered on a moving screen (hereinafter simply referred to as the "take-up speed") is 2000 m / min to 4000 m / min.

[0052] In the method for producing hollow fibers of the first embodiment, the take-up speed is set to 2000 m / min to 4000 m / min, whereby the hollow fibers of the first embodiment can be stably formed. Therefore, it is easy to make the hollow ratio Cv of the obtained hollow fibers less than 10%. In addition, it is easy to make the cross-sectional area Cv of the obtained hollow fibers less than 300%. ３ It can be the following:

[0053] The method for producing the hollow fiber of the first embodiment may include known steps, except that the take-up speed is 2000 m / min to 4000 m / min.

[0054] The hollow fibers of the first embodiment may be produced as a spunbond web (hereinafter also referred to as "SB web"). The SB web is a web formed by laminating a plurality of hollow fibers. When the SB web is subjected to the above-mentioned bonding method (e.g., embossing), an SB nonwoven fabric is obtained. The method for producing the hollow fibers of the first embodiment may be the same as the method for producing an SB nonwoven fabric, except that the bonding method (e.g., embossing) is not performed. An example of a method for producing an SB nonwoven fabric will be described with reference to FIGS. 1 to 5.

[0055] (1.1.4) Hollow Fiber Manufacturing Apparatus The hollow fiber manufacturing apparatus of the first embodiment is an apparatus for manufacturing hollow fibers according to the first embodiment. The manufacturing apparatus has a spinneret. The ratio of the slot length (hereinafter also referred to as "slot length L") to the slot width (hereinafter also referred to as "slot width W") of the spinneret (hereinafter also referred to as "slot ratio (length / width)") is less than 8. The slot ratio (length / width) is synonymous with "the ratio of the length to width" described in Patent Document 2 (WO 2016 / 100057). The slot has a nozzle hole through which a melt of a thermoplastic resin composition, which is a raw material for the hollow fiber, is discharged. The slot length L indicates the length of the nozzle hole in the thickness direction of the spinneret. The slot width W and slot length L will be described below with reference to Figures 2 to 5.

[0056] Patent Document 2 discloses a method for producing hollow fibers using a hollow fiber production apparatus. Specifically, an example of Patent Document 2 discloses the production of an SB nonwoven fabric consisting of multiple hollow fibers using a spinneret with a slot ratio (length / width) of 8. However, because the slot ratio (length / width) is 8, the void ratio Cv of the hollow fibers contained in the SB nonwoven fabric is 10% or more, and the tensile strength and elongation of the hollow fibers may be insufficient. In other words, Patent Document 2 does not disclose or suggest any technical idea of ​​improving the tensile strength and elongation of hollow fibers by reducing the void ratio Cv of the hollow fibers to less than 10%. It has been conventionally believed that the larger the slot ratio (length / width), the more uniformly the single fibers discharged from the spinning holes can be drawn, resulting in stable spinning. The present inventors have found that, in the hollow fiber manufacturing apparatus of the first aspect, by setting the slot ratio (length / width) to less than 8, the hollow ratio Cv of the obtained hollow fiber can be made less than 10% even in high-speed production (for example, take-up speed: 2000 m / min to 4000 m / min). In addition, the cross-sectional area Cv of the obtained hollow fiber can be made less than 300%. ３ The reason for this is not clear, but by setting the slot ratio (length / width) to less than 8, the deformation in the thickness direction of the hollow fibers from extrusion to cooling and solidification can be made gentle. Therefore, it is thought that hollow fibers having a uniform cross-sectional shape can be produced in high-speed production (take-up speed: 2000 m / min to 4000 m / min).

[0057] The spinneret has multiple spinnerets. The spinnerets spin a melt of a thermoplastic resin composition to form hollow fibers (hereinafter also referred to as "continuous fiber groups"). Unlike multifilament spinnerets, spinlay lamination uses a spinneret with multiple spinnerets (e.g., 100 or more than 1000 spinnerets) arranged at equal intervals. In conventional spinlay lamination, it is difficult to uniformly cool the hollow fibers extruded from the center of the spinneret and the hollow fibers extruded from the end of the spinneret. As a result, temperature unevenness occurs between the hollow fibers extruded from the center of the spinneret and the hollow fibers extruded from the end of the spinneret, which tends to cause variations in the hollow ratio of the hollow fibers.

[0058] The spinneret has spinneret-wide spinning holes. The spinneret has at least one slot. A melt of a thermoplastic resin composition, which is a raw material for the hollow fiber, flows through the slot. The melt of the thermoplastic resin composition that passes through the slot forms a hollow fiber. The shape of the slot (hereinafter also referred to as "hole shape") is not particularly limited, and examples thereof include a C-shape, an arc-shape, a circle, a triangle, a square, a star-shape (e.g., a four-pointed star, a five-pointed star, a six-pointed star, or a star with seven or more points), a flat ellipse-shape, a T-shape, an M-shape, an S-shape, a Y-shape, an H-shape, and a dumbbell-shape. Among these, from the viewpoint of reducing the hollowness Cv of the hollow fiber, the hole shape is preferably a single C-shape, more preferably a shape in which multiple C-shapes are combined, and even more preferably a shape in which two to six C-shapes are combined. A hole shape in which six C-shapes are combined is one preferred embodiment. When the slot is not symmetrical, the slot width W can be calculated using the largest width of the slot. This is because the thicker the wall constituting the hollow portion of the hollow fiber discharged from the spinning hole, the longer it takes for the hollow fiber to cool and solidify, and the more difficult it is for the cross-sectional shape of the hollow fiber to become uniform.

[0059] From the viewpoint of making the hollowness Cv less than 10%, the slot ratio (length / width) is preferably less than 8, more preferably less than 6, and even more preferably not more than 5. From the viewpoint of reducing the hollowness of the hollow fiber, the slot ratio (length / width) is preferably 3.0 or more.

[0060] The slot width W may be, for example, 0.05 mm to 0.2 mm, and the slot length L may be, for example, 0.3 mm to 1.2 mm. The slot length L is selected appropriately depending on the slot ratio (length / width) and the slot width W.

[0061] The apparatus for producing hollow fibers of the first embodiment may be similar to known apparatus for producing hollow fibers, except that the slot ratio (length / width) is less than 8. An example of an apparatus for producing hollow fibers will be described with reference to Figures 1 to 5.

[0062] (1.1.5) An embodiment as an example of a method for producing an SB nonwoven fabric In this embodiment, an SB nonwoven fabric is obtained by producing a spunbond web (hereinafter also referred to as an "SB web") by spinlay lamination using a spinneret for hollow fibers, and then embossing the SB web.

[0063] An example of a method for producing an SB nonwoven fabric according to the first embodiment will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing a closed-type SB nonwoven fabric production apparatus according to an embodiment of the first embodiment. In the closed-type SB nonwoven fabric production apparatus, a plurality of continuous fibers extruded from a spinneret (spinning holes) for hollow fibers are stretched while being cooled in a sealed space. The closed-type SB nonwoven fabric production apparatus is an example of an apparatus for producing hollow fibers. The hollow fibers of the present disclosure can be produced not only by a closed-type SB nonwoven fabric production apparatus, but also by an open-type SB nonwoven fabric production apparatus or a general-purpose SB nonwoven fabric production apparatus.

[0064] The method for producing an SB nonwoven fabric according to the first embodiment is carried out using a closed SB nonwoven fabric production apparatus 100 shown in Figure 1. The method for producing an SB nonwoven fabric includes a melting step, a spinning step, a cooling and drawing step, a collecting step, and an embossing step. The melting step, spinning step, cooling and drawing step, a collecting step, and an embossing step are carried out in this order. The melting step, spinning step, cooling and drawing step, and a collecting step are an example of a method for producing hollow fibers.

[0065] (1.1.5.1) Manufacturing Apparatus As shown in Figure 1, the closed SB nonwoven fabric manufacturing apparatus 100 includes a spinning section 10. The spinning section 10 includes an extruder 11, a spinneret 12, a cooling chamber 13, a spinning air supply section 14, a spinning air supply section 15, and a drawing section 16.

[0066] The extruder 11 melts the thermoplastic resin composition and extrudes the molten thermoplastic resin composition into the spinneret 12 .

[0067] The spinneret 12 spins a melt of the thermoplastic resin composition to form a group of continuous fibers 1. The spinneret 12 is for hollow fibers. Specifically, the spinneret 12 forms a melt of the thermoplastic resin composition into a group of continuous fibers. The spinneret 12 has a large number of spinning holes 120. As shown in FIG. 3, the spinning holes 120 penetrate from the surface S12A of the spinneret 12 to the surface S12B of the spinneret 12 (i.e., along the thickness direction D of the spinneret 12). In the spinneret 12, as shown in FIG. 2, the spinning hole 120 for producing one hollow fiber has four slots 121A. A melt of the thermoplastic resin composition, which is a raw material for the hollow fiber, flows through the slots 121A. The hole shape of the slots 121A is a modified hole as shown in FIG. 2. The slots 121A have a slot width W (see FIG. 2). As shown in Figure 3, the spinneret 12 has a guide hole 1201 and a nozzle hole 1202 connected continuously to the guide hole 1201. The slot length L (see Figure 3) indicates the length of the nozzle hole 1202 in the thickness direction D of the spinneret 12. The slot ratio (length / width) is less than 8. The "slot ratio (length / width)" indicates the ratio of the slot length L (see Figure 2) to the slot width W (see Figure 2).

[0068] In the first embodiment, the radiation hole 120 for producing one hollow fiber is the slot 121A shown in Fig. 2, but the present disclosure is not limited to this. In the present disclosure, the radiation hole 120 for producing one hollow fiber may be the slot 121B shown in Fig. 4 or the slot 121C shown in Fig. 5.

[0069] The cooling chamber 13 cools the continuous fiber mass 1 spun from the spinning holes of the spinneret 12. The spinning air supply section 14 and the spinning air supply section 15 supply spinning air A into the cooling chamber 13 and the drawing section 16.

[0070] In the drawing section 16, the continuous fiber flock 1 is drawn by the spinning air A. The drawing section 16 has a narrow passage section 16a and a cylindrical section 16b. The cylindrical section 16b is formed at the end of the narrow passage section 16a on the lower side (i.e., on the screen 21 side) in the vertical direction (i.e., in the direction of gravity). The narrow passage section 16a is narrow. The cylindrical section 16b is cylindrical. The hollow section of the cylindrical section 16b widens downward as shown in FIG. 1. The suction unit 22 collects the continuous fiber flock 1 on the screen 21.

[0071] In the method for producing a multifilament, the thread (multifilament) eluted from the spinning holes is drawn using a drawing machine consisting of one or more pairs of rollers. Specifically, in general, for fibers made of a melt-spinnable thermoplastic resin, the thread (multifilament) is produced by drawing the fiber in the fiber axis direction depending on the peripheral speed ratio between the first roller and the second roller, heat-setting the fiber, and then winding it up. The temperature of the first roller is set to a temperature equal to or higher than the glass transition temperature of the thermoplastic resin and equal to or lower than the melting point of the thermoplastic resin. The temperature of the second roller is set to a temperature equivalent to the crystallization temperature of the thermoplastic resin. From the viewpoint of increasing the draw ratio and improving the mechanical properties of the thread, this drawing process may be carried out in multiple stages. Another method for drawing a multifilament involves two-stage drawing in a drawing liquid bath at a temperature of 60°C to 120°C to a predetermined total draw ratio without winding.

[0072] The suction unit 22 is disposed below the collecting surface of the screen 21 .

[0073] (1.1.5.2) Melting Step In the melting step, the thermoplastic resin composition is melt-kneaded using the extruder 11, and the molten thermoplastic resin composition is extruded from the extruder 11.

[0074] The melting temperature of the thermoplastic resin composition (hereinafter also referred to as "extrusion temperature") is not particularly limited as long as it is equal to or higher than the softening temperature and melting temperature of the thermoplastic resin composition and lower than the thermal decomposition temperature of the thermoplastic resin composition, and is appropriately set depending on the physical properties of the thermoplastic resin composition, etc. When the thermoplastic resin composition contains a polypropylene-based resin, the extrusion temperature is preferably 180°C to 260°C, more preferably 190°C to 250°C.

[0075] (1.1.5.3) Spinning Step In the spinning step, a melt of the thermoplastic resin composition is extruded from the spinning holes of the spinneret 12 using the spinneret 12. This forms a group of continuous fibers 1 consisting of a plurality of hollow fibers.

[0076] The shape of the spinning holes of the spinneret 12 is not particularly limited, and the above-mentioned slot shapes, slot widths W, slot lengths L, etc. can be combined and used.

[0077] The output rate per spinning hole of the spinneret 12 is preferably 0.1 g / min to 3.0 g / min, more preferably 0.2 g / min to 1.0 g / min.

[0078] The temperature of the spinneret 12 is adjusted appropriately depending on the physical properties of the thermoplastic resin composition, etc. When the thermoplastic resin composition contains a polypropylene-based resin, the temperature of the spinneret 12 is preferably 180°C to 260°C, more preferably 190°C to 250°C.

[0079] (1.1.5.4) Cooling and Drawing Step In the cooling and drawing step, the continuous fibers 1 are cooled and drawn by the spinning air A. Specifically, the spinning air A is supplied from the spinning air supply section 14 and the spinning air supply section 15 into the cooling chamber 13 and the drawing section 16. As a result, the continuous fibers 1 extruded from the spinning holes of the spinneret 12 are cooled in the cooling chamber 13. The cooled continuous fibers 1 are then introduced into the drawing section 16 located downstream of the cooling chamber 13. The continuous fibers 1 introduced into the drawing section 16 are drawn by increasing the speed of the spinning air in the narrow passage section 16a. The continuous fibers 1 that have passed through the tubular section 16b are dispersed and collected on the screen 21. The dispersed continuous fibers 1 are efficiently collected on the screen 21 by the suction unit 22. In this way, the SB web 2 is formed.

[0080] The wind speed of the spinning air A supplied from each of the spinning air supplying section 14 and the spinning air supplying section 15 is determined by the cross-sectional area (m ２ ) to the flow rate of cooling air (Nm ３ That is, the wind speed of the spinning air A indicates the speed at the narrow passage portion 16a of the drawing section 16, and is the same value as the "take-up speed" mentioned above.

[0081] The take-up speed of the continuous fiber group 1 (i.e., a plurality of hollow fibers) when the continuous fiber group 1 is layered on the moving screen 21 is 2000 m / min to 4000 m / min. The "take-up speed" refers to the cross-sectional area (m ２ ) to the flow rate of cooling air (Nm ３ That is, the take-up speed indicates the speed of the spinning air A at the edge of the tubular portion 16b of the drawing section 16 on the screen 21 side.

[0082] The temperature of the spinning air A supplied from each of the spinning air supply units 14 and 15 is not particularly limited as long as it is a temperature at which the thermoplastic resin composition solidifies. The temperature of the spinning air A is preferably 5°C to 50°C, more preferably 10°C to 40°C.

[0083] (1.1.5.5) Embossing Step In the embossing step, the SB web 2 is embossed. As a result, the hollow fibers contained in the SB web 2 are bonded to each other, resulting in an SB nonwoven fabric.

[0084] "Embossing" refers to a process in which an SB web is sandwiched between an embossing roll and a flat roll, and some of the fibers contained in the SB web are thermally compressed. The embossing roll has a plurality of protrusions arranged in a regular pattern on its surface. The embossing roll transfers the shape of the top surfaces of the plurality of protrusions to some of the fibers contained in the SB web. In this way, the embossing roll forms a plurality of embossed portions arranged in a regular pattern on the SB web. The ratio of the area of ​​the plurality of protrusions on the embossing roll to the surface area of ​​the embossing roll (hereinafter also referred to as the "embossed area ratio") is appropriately selected depending on the application of the SB nonwoven fabric. The embossed area ratio of the embossing roll is the same as the embossed area ratio of the SB nonwoven fabric described above.

[0085] The surface temperature of the embossing roll (hereinafter also referred to as "embossing temperature") can be set appropriately depending on the application. For example, in applications requiring flexibility, the surface temperature is preferably (resin melting point - 20°C) to (resin melting point + 20°C), more preferably (resin melting point - 15°C) to (resin melting point + 10°C), and even more preferably (resin melting point - 15°C) to the resin melting point. If the embossing temperature is (resin melting point - 10°C) to the resin melting point, the multiple hollow fibers in the embossed portion are sufficiently fused together.

[0086] Before the embossing process, the SB web 2 may be pressed and compacted using a nip roll.

[0087] In the method for producing an SB nonwoven fabric according to the first aspect, an SB nonwoven fabric containing hollow fibers having a hollowness Cv of less than 10% can be produced by adjusting the extrusion temperature of the extruder 11, the single-hole output rate of the spinning holes of the spinneret 12, and the spinning air speed of the spinning air supply unit 14 and the spinning air supply unit 15. Specifically, methods for adjusting the hollowness Cv of the hollow fibers to less than 10% include, for example, adjusting the single-hole output rate of the molten thermoplastic resin composition within an appropriate range and reducing the air velocity of the spinning air. The appropriate range of the single-hole output rate varies depending on the type, viscosity, and melting point of the resin used. However, when using the propylene-based resin used in the first aspect and the production method and production apparatus of the first aspect, the single-hole output rate is preferably in the range of 0.2 g / min to 1.0 g / min. Furthermore, by reducing the air velocity of the spinning air, unevenness in the stretching and cooling of the hollow fibers due to turbulence in the air flow can be suppressed, thereby lowering the hollowness Cv. Cv of the cross-sectional area of ​​the hollow fiber is 300% ３ Examples of methods for making the following adjustments include adjusting the single-hole output rate of the melted thermoplastic resin composition within an appropriate range and reducing the wind speed of the spinning air. Examples of methods for making the average outer diameter of the hollow fibers 10 μm to 30 μm and the average hollow ratio of the hollow fibers 10% to 40% include adjusting the extrusion temperature, single-hole output rate, and spinning air speed within appropriate ranges. The appropriate ranges for the extrusion temperature and single-hole output rate vary depending on the type, viscosity, and melting point of the resin used. When the propylene-based resin used in the first embodiment is used, the extrusion temperature is preferably 190°C to 250°C, and the single-hole output rate is preferably 0.2 g / min to 1.0 g / min.

[0088] (1.2) Sanitary Material The sanitary material of the first embodiment includes the SB nonwoven fabric of the first embodiment.

[0089] The hygienic material of the first aspect has the above-described configuration, and therefore has excellent mechanical strength (e.g., MD tensile strength) and is tear-resistant. Furthermore, hollow fibers can reduce the amount of thermoplastic resin composition used compared to solid fibers of the same fiber diameter. This allows nonwoven fabrics using hollow fibers to have a lower basis weight, thereby reducing the environmental impact.

[0090] Examples of sanitary materials include absorbent articles (e.g., disposable diapers, disposable pants, sanitary products, urine absorption pads, and pet sheets), medical sanitary materials (e.g., bandages, medical gowns, medical drapes, sterilized sheets, medical gauze, towels, sheets, body warmers, cell culture sheets, and compresses), and masks (e.g., industrial masks and sanitary masks). Sanitary materials are not limited to these, and other sanitary materials may also be used. The sanitary material may include a nonwoven fabric laminate. The nonwoven fabric laminate may be composed of two or more layers of the SB nonwoven fabric of the first embodiment, or may include the SB nonwoven fabric of the first embodiment and a layer other than the nonwoven fabric according to the first embodiment.

[0091] (1.3) Industrial Material The industrial material of the first embodiment includes the SB nonwoven fabric of the first embodiment.

[0092] Because the industrial material of the first aspect has the above-mentioned configuration, it has excellent mechanical strength and is resistant to tearing. When the industrial material is used as an agricultural covering material, the industrial material of the first aspect is less likely to break than conventional mulch sheets. The industrial material of the first aspect is suitable for use on uneven ground surfaces (e.g., gravel, etc.). The industrial material of the first aspect can reduce the number of times the industrial material needs to be replaced due to breakage. When the industrial material is used as an industrial material, it can be made lighter than conventional materials while maintaining the same mechanical strength as conventional materials. Lightweight industrial materials can also be expected to reduce transportation costs and energy consumption related to transportation. When the industrial material is a sound-absorbing material, the sound-absorbing material is suitable for use on curved or uneven installation surfaces.

[0093] The industrial material of the first embodiment may have a single-layer structure consisting of only SB nonwoven fabric, or may have a laminated structure. Since SB nonwoven fabric is composed of long fibers, it is less likely to lose fibers during transportation and use than nonwoven fabrics containing short fibers, and is therefore useful from the perspective of reducing environmental impact.

[0094] Examples of industrial materials include agricultural covering materials (e.g., sheets for open-field cultivation, sheets for tunnel cultivation, sheets for greenhouse cultivation, sheets for covering plants, and sheets for seedbeds), clothing (e.g., interlinings and adhesive interlinings), construction (e.g., roofing materials and tufted carpet substrates), civil engineering (e.g., drain materials and filtration materials), vehicles (e.g., automobile interiors, automobile parts, seat cushion substrates, and sound-absorbing materials), hygiene (e.g., first aid supplies and cleaning supplies), interiors (e.g., carpets, furniture components, building materials, wall coverings, and decorative items), bedding (e.g., futon bags, pillowcases, and sheets), leather (e.g., artificial leather base fabrics and synthetic leather base fabrics), daily necessities (e.g., storage supplies, packaging materials, and bags), and industrial materials. Industrial materials include abrasives, oil absorption mats, piping ducts, papermaking felt, cushioning materials, drain materials for concrete forms, water-repellent materials, heat insulation materials, soundproofing materials, buffer materials, vibration-proofing materials, marine materials (e.g., interiors, parts, seat cushion substrates, and sound-absorbing materials), wipes (e.g., cleaning sheets and decorative sheets), electrical materials (e.g., electrical insulating materials for printed wiring boards, electromagnetic wave shielding materials, electric wire pressure winding tapes, and battery separators), product substrates (e.g., substrates for fiber-reinforced plastics, substrates for printing, substrates for synthetic paper, electrostatic recording media, substrates for adhesive tapes, thermal transfer sheets, and radiation shielding mats, etc.), materials for office automation equipment (for example, floppy disk liners and floppy disk packaging materials, etc.), materials for audiovisual equipment (for example, speaker diaphragms and sound-absorbing boards, etc.), rolls (for example, buff rolls, squeezing rolls, and oiling rolls, etc.), equipment components (for example, V-belts, conveyor belts, and timing belts, etc.), and materials for musical instruments (for example, piano key cushions and hammer rails, etc.).

[0095] The industrial material of the first embodiment may be a laminate in which a film, an adhesive layer, and an SB nonwoven fabric are laminated in this order.

[0096] The industrial material of the first embodiment may be an SMS laminate or an SMMS laminate. The SMS laminate is formed by laminating a spunbond nonwoven fabric, a meltblown nonwoven fabric, and a spunbond nonwoven fabric in this order. The SMMS laminate is formed by laminating a spunbond nonwoven fabric, a meltblown nonwoven fabric, a meltblown nonwoven fabric, and a spunbond nonwoven fabric in this order. The basis weight of the SMS laminate or the SMMS laminate is adjusted depending on the application, and is 10 g / m or less. ２ ~1500g / m ２ It may be.

[0097] The industrial material of the first embodiment may be a laminate of the SB nonwoven fabric of the present disclosure and a film. Examples of the film include a film that is liquid-impermeable and vapor-permeable, or a film that is vapor-impermeable. A film that is liquid-impermeable and vapor-permeable has breathability. Therefore, by combining the SB nonwoven fabric of the present disclosure, which has excellent breathability, with a film that is liquid-impermeable and vapor-permeable, the breathability of the industrial material of the first embodiment is excellent. The vapor permeability of the film is 500 g / m or more. ２ / 24 hours ~ approx. 20000g / m ２ / 24 hours. The breathable film may be a microporous film or a monolithic film.

[0098] Examples of films include films made of thermoplastic synthetic resins commonly used in agriculture (e.g., polyethylene resins, polypropylene resins, polyurethane resins, polyvinyl chloride resins, etc.). The film may be single-layer or multi-layer. The film may be colored or uncolored. The film may be a breathable film (i.e., a perforated film) or a non-breathable film. When the film is a perforated film, the agricultural covering material can appropriately release humidity and heat from the covered ground surface. When the film is a non-breathable film, the agricultural covering material functions as a water barrier and can prevent rainwater from suddenly leaking into the soil. In fruit cultivation, covering the ground surface with such a non-breathable film can reduce the water supply for several months before fruit harvest and improve the sugar content of the fruit.

[0099] The adhesive layer is formed by an adhesive. The adhesive is not particularly limited, and examples thereof include olefin-based adhesives, olefin-based pressure-sensitive adhesives, vinyl-based adhesives, vinyl-based pressure-sensitive adhesives, styrene-based adhesives, styrene-based pressure-sensitive adhesives, (meth)acrylic adhesives, (meth)acrylic pressure-sensitive adhesives, polyester-based adhesives, polyester-based pressure-sensitive adhesives, urethane-based adhesives, and urethane-based pressure-sensitive adhesives. The adhesive may be a known adhesive. These adhesives may be used alone or in combination of two or more.

[0100] The agricultural covering material of the first aspect is used, for example, by laying it on the ground surface for growing crops, because the hollow fibers of the first aspect have excellent single-filament linear strength and single-filament elongation, and the SB nonwoven fabric containing the hollow fibers has excellent MD tensile strength and good light transmittance. When the agricultural covering material of the first aspect has the above-mentioned laminated structure, it is preferably laid so that the SB nonwoven fabric faces the ground surface.

[0101] (2) Second Aspect A method for producing hollow fibers according to a second aspect produces hollow fibers by spin-lay lamination using a hollow fiber production apparatus. The production apparatus has a spinneret. The spinneret has a slot ratio (length / width) of less than 8. The take-up speed of the hollow fibers when they are layered on a moving screen (hereinafter also simply referred to as "take-up speed") is 2000 m / min to 4000 m / min.

[0102] The method for producing a hollow fiber according to the second embodiment has the above-mentioned configuration, and thus a stable spinning line can be formed, making it possible to make the hollow ratio Cv of the obtained hollow fiber less than 10%. ３ It can be the following:

[0103] The method for producing a hollow fiber of the second embodiment is similar to the method for producing a hollow fiber of the first embodiment, except that it does not necessarily involve producing the hollow fiber of the first embodiment, and it essentially requires that the slot ratio (length / width) be less than 8 and that the take-up speed be 2000 m / min to 4000 m / min. Therefore, the description of the first embodiment is incorporated into the description of the second embodiment, and any description of the second embodiment that overlaps with the description of the first embodiment will be omitted.

[0104] (3) Modified Examples (3.1) SB Nonwoven Fabric A modified SB nonwoven fabric (hereinafter also referred to as "SB nonwoven fabric") is an SB nonwoven fabric that contains hollow fibers, the coefficient of variation of the hollow ratio of the hollow fibers (hereinafter also referred to as "Cv of hollow ratio") is less than 10%, and the average outer diameter of the hollow fibers is 30 μm or more.

[0105] The SB nonwoven fabric of the modified example has the above-described configuration and includes hollow fibers that are excellent in tensile strength and elongation, similar to the first embodiment. Therefore, the SB nonwoven fabric of the modified example is excellent in MD tensile strength and MD elongation.

[0106] The SB nonwoven fabric of the modified example is similar to the SB nonwoven fabric of the first embodiment, except that the hollow fibers must have an average outer diameter of 30 μm or more. Therefore, the description of the modified example will be taken from the description of the first embodiment, and any description of the method for producing hollow fibers of the modified example that overlaps with the description of the method for producing hollow fibers of the first embodiment will be omitted.

[0107] The average outer diameter of the hollow fibers is 30 μm or more. Even when the average outer diameter of the hollow fibers is 30 μm or more, the hollow fiber of the present disclosure can achieve a hollowness Cv of less than 10%. When the hollowness Cv is less than 10%, even when the average outer diameter of the hollow fibers is 30 μm or more, the single fiber elongation is superior to that of a configuration in which the average outer diameter of the hollow fibers is less than 30 μm. This makes SB nonwoven fabrics containing hollow fibers of 30 μm or more useful in industrial materials that require relatively high mechanical strength. The method for measuring the average outer diameter of the hollow fibers is the same as that described in the Examples.

[0108] In the modified example, similarly to the first embodiment, the value represented by the following formula (I) (hereinafter also referred to as "Cv of the cross-sectional area of ​​the hollow fiber") is 300%３ It is preferable that the ratio is less than 100%. ３ ~300% ３ It is preferable that ３ ~250% ３ It is preferable that the coefficient of variation of the outer diameter of the hollow fiber is expressed by the formula (I): ２ × Coefficient of variation of hollowness of the hollow fiber

[0109] In the modified example, similarly to the first embodiment, the hollow fiber preferably has an average hollow ratio of 10% to 40%.

[0110] In the modified example, similarly to the first embodiment, the hollow fibers preferably contain a polypropylene-based resin.

[0111] In a modified example, the hollow fiber preferably has a single filament linear strength of 19.0 mN / denier or more and a single filament elongation of 300% or more, and the hollow fiber preferably has a single filament linear strength of 22.0 mN / denier or more and a single filament elongation of 360% or more.

[0112] In a modified example, it is preferred that the hollow fibers have an average outer diameter of 30 μm to 40 μm and an average hollow ratio of 10% to 40%.

[0113] The sanitary material of the modified example is a sanitary material containing the SB nonwoven fabric of the modified example. The sanitary material of the modified example is the same as the sanitary material of the first example, except that it contains the SB nonwoven fabric of the modified example instead of the SB nonwoven fabric of the first example.

[0114] The modified industrial material is an industrial material containing the modified SB nonwoven fabric. The modified industrial material is similar to the industrial material of the first embodiment, except that it contains the modified SB nonwoven fabric instead of the SB nonwoven fabric of the first embodiment. Because the fiber diameter is larger than that of the industrial material of the first embodiment, it is useful for applications requiring higher mechanical strength or high breathability. Furthermore, the larger the fiber diameter, the greater the amount of air encapsulated in the hollow fibers, and therefore a higher heat retention effect can be expected.

[0115] The hollow fiber manufacturing apparatus of the modified example is a hollow fiber manufacturing apparatus for manufacturing the hollow fiber of the modified example, the manufacturing apparatus having a spinneret, wherein the ratio of the slot length to the slot width of the spinneret is less than 8. The hollow fiber manufacturing apparatus of the modified example is similar to the hollow fiber manufacturing apparatus of the second example, except that the modified SB nonwoven fabric is manufactured instead of the SB nonwoven fabric of the first example.

[0116] A modified hollow fiber manufacturing method is a hollow fiber manufacturing method in which the modified hollow fiber is manufactured by spinlay lamination, and the take-up speed of the hollow fiber when the hollow fiber is laminated on a moving screen is 2000 m / min to 4000 m / min. The modified hollow fiber manufacturing method is similar to the hollow fiber manufacturing method of the first embodiment, except that the modified SB nonwoven fabric is manufactured instead of the SB nonwoven fabric of the first embodiment. In a preferred embodiment of the modified hollow fiber manufacturing method, the slot ratio (length / width) of the spinneret must be less than 8, and the take-up speed must be 2000 m / min to 4000 m / min.

[0117] The present disclosure will be described in more detail below based on examples, but the present disclosure is not limited to the following examples. The materials, amounts used, ratios, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present disclosure. Unless otherwise specified, "parts" means "parts by mass."

[0118] [1] Measurement Method [1.1] Collection of Fiber Samples for Measurement Fiber samples for measuring the outer diameter, hollowness, single fiber linear strength, and single fiber elongation of hollow fibers were collected as follows. Using tweezers, 100 single fibers, each 100 mm long, were randomly selected from an SB nonwoven fabric without stretching. These single fibers were cut at their midpoints with a razor blade in a direction perpendicular to the fiber axis of the hollow fibers, to create two sets of 10 single fibers, each 50 mm long. One set was used to measure the outer diameter, single fiber linear strength, and single fiber elongation. The other set was used to measure the hollowness.

[0119] [1.2] Average value of outer diameter [μm], Cv value of outer diameter [%] Using an optical microscope [Nikon ECLIPSE E-400], the outer diameter of the single fiber to be measured was measured at 10 arbitrary points in the fiber axis direction. This operation was performed on 100 single fibers. The average value of the measured outer diameters at 1,000 points was taken as the "average value of outer diameter" of the single fiber. The standard deviation of the measured outer diameters at 1,000 points was multiplied by 100 and the result was divided by the average value of the outer diameters, and the resulting value was taken as the "Cv value of outer diameter" of the single fiber.

[0120] [1.3] Average hollowness [%], Cv value of outer diameter [%] The single fiber to be measured was embedded in epoxy resin, and then cut at 10 arbitrary locations in the fiber axis direction of the single fiber using a microtome to obtain 10 sample pieces. These were observed using an optical microscope (Nikon ECLIPSE E-400) to measure the hollowness of the fiber cross section at 10 arbitrary locations in the fiber axis direction of the sample piece. This procedure was performed on 10 sample pieces. The average value of the hollowness measurements at 100 points was taken as the "average hollowness" of the single fiber. The standard deviation of the hollowness measurements at 100 points was multiplied by 100 and divided by the average hollowness to obtain the "Cv value of hollowness" of the single fiber.

[0121] [1.4] Fineness [denier] The fineness of a single fiber was calculated from the average value of the measured outer diameter and the average value of the measured hollowness according to the following formula (A). In formula (A), "0.91" represents the density of polypropylene (g / cm ３ In Comparative Example 7 (solid fiber), the average hollow ratio was set to 0. Formula (A): Fineness = 3.14 × (average outer diameter / 2 / 10,000) ２ × (100 - average hollowness) ÷ 100 × 0.91 × 900000

[0122] [1.5] Single filament linear strength [N / denier], single filament elongation [%] According to JIS L 1095 (9.5.1 method), a tensile test was performed on the single filament used to measure the outer diameter, and the tensile load and elongation were measured. A tensile tester (Instron 5564 model, manufactured by Instron Japan Co., Ltd.) was used for the tensile test. The tensile test conditions were a distance between chucks of 20 mm and a pulling speed of 20 mm / min. The measured value of the tensile load was defined as the "single filament linear strength." The measured value of the elongation was defined as the "single filament elongation." The single filament linear strength was evaluated using the measured value of the single filament linear strength according to the following criteria. The single filament elongation was evaluated using the measured value of the single filament elongation according to the following criteria. An acceptable rating for the single filament linear strength is "A1." An acceptable rating for the single filament elongation is "A2."

[0123] [1.5.1] Evaluation criteria for single filament line strength "A1": Single filament line strength ≧19.0 mN / denier "B1": Single filament line strength <19.0 mN / denier

[0124] [1.5.2] Evaluation criteria for single yarn elongation "A2": Single yarn elongation ≧ 300% "B2": Single yarn elongation < 300%

[0125] [1.6] Basis weight [g / m ２ Ten test pieces measuring 100 mm (machine direction (MD)) x 100 mm (cross direction (CD)) were taken from the SB nonwoven fabric. The test pieces were taken from the center of the cross direction (CD). Then, the mass [g] of each test piece was measured using a top-pan electronic balance (manufactured by Kensei Kogyo Co., Ltd.) in an environment of 20°C and 50% RH. The mass of the test pieces was measured by 1 m from the average mass of the test pieces. ２ The value obtained was taken as the "basis weight" of the nonwoven fabric.

[0126] [1.7] MD Tensile Strength [N / 25 mm] and MD Elongation [%] The MD tensile strength and MD elongation of the SB nonwoven fabric were measured in accordance with JIS L 1906, 6.12.1 [Method A] (transitioned to JIS L 1913:2010, corresponding to ISO 9073-3:1989). Ten test pieces measuring 200 mm (machine direction (MD)) x 25 mm (cross direction (CD)) were taken from the SB nonwoven fabric. The test pieces were taken at 10 random locations along the cross direction (CD) of the SB nonwoven fabric. Using a tensile tester, the fabric was pulled in the machine direction (MD) with a chuck distance of 100 mm and a head speed of 100 mm / min, and the maximum tensile strength [N / 25 mm] and the elongation [%] at that time were determined. The average of the 10 maximum tensile strength measurements was taken as the "MD tensile strength." The average value of the ten maximum elongation measurements was taken as the "MD elongation." Using the measured values ​​of MD tensile strength, the MD tensile strength was evaluated according to the following criteria. Using the measured values ​​of MD elongation, the MD elongation was evaluated according to the following criteria.

[0127] [1.7.1] Evaluation criteria for MD tensile strength "A3": MD tensile strength ≧ 20.0 N / 25 mm "B3": MD tensile strength < 20.0 N / 25 mm

[0128] [1.7.2] Evaluation criteria for MD elongation "A4": MD elongation ≧ 60% "B4": MD elongation < 60%

[0129] [1.8] Air permeability [cm ３ / cm ２ Ten test pieces measuring 100 mm (machine direction (MD)) x 100 mm (cross direction (CD)) were taken from the SB nonwoven fabric. Using a Frazier type testing machine, the air permeability was measured at a pressure difference of 125 Pa in accordance with JIS L1096. The average value of the measured air permeability values ​​at the 10 points was taken as the "air permeability." The measured air permeability values ​​were used to evaluate the air permeability according to the following criteria.

[0130] [1.8.1] Air permeability evaluation criteria “A5”: Air permeability ≧ 500 cm ３ / cm ２ ・sec “B5”: Air permeability < 500 cm ３ / cm ２ ・sec

[0131] [1.9] Light transmittance [%] Using a Nomura Shoji Co., Ltd. firmation tester "FMT-MIII," the light transmittance of SB nonwoven fabric was measured at 10 random locations. The average value of the measured light transmittance values ​​at the 10 locations was taken as the "light transmittance." The measured light transmittance values ​​were used to evaluate the light transmittance according to the following criteria.

[0132] [1.9.1] Evaluation criteria for breathability "A6": Light transmittance ≦ 93.4% "B6": Light transmittance > 93.4%

[0133] [2] Examples and Comparative Examples [2.1] Example 1 The following raw materials were prepared: hPP: homopolypropylene (melting point 163°C, MFR (temperature 230°C, load 2.16 kg) 60 g / 10 min)

[0134] An SB nonwoven fabric was produced using the closed-type SB nonwoven fabric manufacturing apparatus 100 shown in Figures 1 and 2 as follows. The raw material hPP was melted using a 75 mmφ extruder 11. The molten hPP was introduced into a die having a spinneret 12. The spinneret 12 was designed for hollow fibers. The slot ratio (length / width) of the slot 121A of the spinneret 12 was the value shown in Table 1. The number of slots in the hole shape 121A of the spinning hole 120 was six. The extrusion temperature of the extruder 11 was set to 200°C. The amount of the molten hPP introduced into the die was adjusted so that the resin output per point of the spinneret 12 (single-hole output rate) was 0.8 g / min. The hollow fibers extruded from the spinneret 12 were cooled and drawn with spinning air A to obtain single fibers. The temperature of the spinning air A was 20°C. The wind speed for the take-up speed was the value shown in Table 1.

[0135] The spun monofilaments were deposited on a screen 21 to obtain a web. The web was embossed with an embossing roll (embossed area ratio: 18%, embossing temperature: 135°C) to produce an SB nonwoven fabric. The basis weight of the SB nonwoven fabric was 20 g / m ２ In Example 1, the single fibers constituting the SB nonwoven fabric were hollow fibers.

[0136] [2.2] Examples 2 to 7 and Comparative Examples 1 to 6 SB nonwoven fabrics were obtained in the same manner as in Example 1, except that the extrusion temperature, single-hole discharge rate, and spinning air velocity were changed as shown in Tables 1 and 2.

[0137] [2.3] Examples 8 and 9 SB nonwoven fabrics were obtained in the same manner as in Example 1, except that hPP was changed to the following rPP, and the extrusion temperature, single-hole output rate, and spinning air velocity were changed as shown in Table 1.

[0138] rPP: Propylene-ethylene random copolymer (melting point 138°C, MFR (temperature 230°C, load 2.16 kg) 60 g / 10 min)

[0139] [2.4] Comparative Example 7 An SB nonwoven fabric was obtained in the same manner as in Example 1, except that the extrusion temperature, single-hole output rate, and spinning air velocity were changed as shown in Table 2, and the spinneret 12 for hollow fibers was changed to a spinneret for solid fibers.

[0140] [3] Results

[0141] The SB nonwoven fabrics of Comparative Examples 1 to 6 contained only a plurality of hollow fibers. The hollow ratio Cv of the hollow fibers of Comparative Examples 1 to 6 exceeded 10%. Therefore, the single filament linear strength of Comparative Examples 1 to 6 was evaluated as "B1" and the single filament elongation was evaluated as "B2." The SB nonwoven fabric of Comparative Example 7 did not contain hollow fibers. Therefore, the single filament linear strength of Comparative Example 7 was evaluated as "B1" and the single filament elongation was evaluated as "B2." These results demonstrate that the SB nonwoven fabrics of Comparative Examples 1 to 7 are not "SB nonwoven fabrics having hollow fibers with excellent tensile strength and elongation."

[0142] The SB nonwoven fabrics of Examples 1 to 9 contained only a plurality of hollow fibers. The hollow ratio Cv of the hollow fibers of Examples 1 to 9 was less than 10%. Therefore, the single filament linear strength of Examples 1 to 9 was evaluated as "A1," and the single filament elongation of the SB nonwoven fabrics of Examples 1 to 7 was evaluated as "A2." These results demonstrate that the SB nonwoven fabrics of Examples 1 to 9 are "SB nonwoven fabrics comprising hollow fibers that are excellent in tensile strength and elongation."

[0143] The disclosure of Japanese Patent Application No. 2023-167879, filed on September 28, 2023, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A spunbond nonwoven fabric comprising hollow fibers, the hollow fibers having a coefficient of variation of hollowness of less than 10%.

2. The value represented by the following formula (I) is 300% ３ The spunbond nonwoven fabric of claim 1, wherein the coefficient of variation of the outer diameter of the hollow fibers is: ２ × Coefficient of variation of hollowness of the hollow fiber 3. The spunbond nonwoven fabric of claim 1, wherein the hollow fibers have an average outer diameter of less than 30 μm.

4. The spunbond nonwoven fabric according to claim 1, wherein the hollow fibers have an average hollow ratio of 10% to 40%.

5. The spunbond nonwoven fabric of claim 1, wherein the hollow fibers comprise a polypropylene-based resin.

6. The spunbond nonwoven fabric according to claim 1, wherein the hollow fibers have a single filament linear strength of 19.0 mN / denier or more, and a single filament elongation of 300% or more.

7. The spunbond nonwoven fabric according to claim 1, wherein the average outer diameter of the hollow fibers is 10 μm or more and less than 30 μm, and the average hollow rate of the hollow fibers is 10% to 40%.

8. A sanitary material comprising the spunbond nonwoven fabric according to any one of claims 1 to 7.

9. An industrial material comprising the spunbond nonwoven fabric according to any one of claims 1 to 7.

10. An apparatus for producing the hollow fibers according to any one of claims 1 to 7, the apparatus having a spinneret, the ratio of the length of the spinneret slot to the width of the slot being less than 8.

11. A method for producing hollow fibers, comprising the steps of: producing the hollow fibers according to any one of claims 1 to 7 by spinlay lamination; wherein the take-up speed of the hollow fibers as they are laid on a moving screen is between 2000 m / min and 4000 m / min.

12. A method for producing hollow fibers by spinlay lamination using a hollow fiber production apparatus, the production apparatus having a spinneret, the ratio of the length of the spinneret slot to the width of the slot being less than 8, and the take-up speed of the hollow fibers as they are laid on a moving screen being between 2000 m / min and 4000 m / min.

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