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

Abstract

A SB nonwoven fabric of the present disclosure includes plural hollow fibers. The coefficient of variation of hollowness of the hollow fibers is less than 10%.

Description

Technical Field

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

[0002] Conventionally, nonwoven fabrics are widely used in various applications because of excellent air permeability and flexibility. Therefore, the nonwoven fabrics are required to exhibit various properties depending on their intended applications, and improvements in such properties are also demanded. For example, a nonwoven fabric used for an agricultural covering material is required to have predetermined mechanical strength.

[0003] Patent Document 1 discloses an agricultural sheet. The agricultural sheet is a long-fiber nonwoven fabric having a specific basis weight (hereinafter, also simply referred to as "spunbond nonwoven fabric"). The spunbond nonwoven fabric is made of a polypropylene-based fiber having 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 producing apparatus. Specifically, a polypropylene polymer is melted, and the resulting melt is spun from a specific spinneret at a single-hole discharge rate of 3.1 g / min. As a result, long fibers having a hollow cross section (hereinafter, also referred to as "hollow fibers") are obtained. Then, the hollow fibers are cooled with a cooling device, thinned by drawing at a take-up speed of 4800 m / min using a yarn suction device installed below, opened by a corona discharge means, and deposited onto a transporting screen. As a result, a web on the screen is obtained. Subsequently, the web is thermally bonded using embossing rolls. As a result, a spunbond nonwoven fabric (agricultural sheet) is obtained.

[0005] Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. H08-126440SUMMARY OF INVENTIONTechnical Problem

[0006] However, the hollow fibers constituting the spunbond nonwoven fabric disclosed in Patent Document 1 may undergo fiber breakage in part when pulled in the fiber axial direction and may exhibit poor elongation properties. That is, the mechanical strength of the spunbond nonwoven fabric itself disclosed in Patent Document 1 may not be sufficient depending on the degree of being pulled in the fiber axial direction. Therefore, there is a demand for a spunbond nonwoven fabric including hollow fibers (that is, the hollow fibers excellent in tensile strength and elongation) that are less likely to undergo fiber breakage in part of the fibers and are likely to stretch when pulled in the axial direction of the hollow fibers.

[0007] From the viewpoint of increasing production efficiency, it is required to produce a spunbond nonwoven fabric at high speed. However, when the production speed is increased in the hollow fibers, the resulting hollow fibers may undergo fiber breakage. Such fiber breakage tends to occur in hollow fibers having a large variation of hollowness. Therefore, even when a spunbond nonwoven fabric is produced at a high speed, hollow fibers having a small variation of hollowness and a spunbond nonwoven fabric including the hollow fibers have been required.

[0008] In view of the above problems, it is an object of the present disclosure to provide a spunbond nonwoven fabric, a sanitary material, and an industrial material, each including hollow fibers having excellent tensile strength and elongation, as well as a hollow fiber production apparatus and a hollow fiber production method.Solution to Problem

[0009] Specific means for solving the problems include the following aspects. <1> A spunbond nonwoven fabric containing hollow fibers, in which a coefficient of variation of hollowness of the hollow fibers is less than 10%. <2> The spunbond nonwoven fabric according to <1>, in which a value represented by the following Formula (I) is 300% 3< or less: <3> The spunbond nonwoven fabric according to <1> or <2>, in which the hollow fibers have an average outer diameter of less than 30 µm. <4> The spunbond nonwoven fabric according to any one of <1> to <3>, in which the hollow fibers have an average hollowness of from 10% to 40%. <5> The spunbond nonwoven fabric according to any one of <1> to <4>, in which the hollow fibers contain a polypropylene-based resin. <6> The spunbond nonwoven fabric according to any one of <1> to <5>, in which the hollow fibers have a single yarn tenacity of 19.0 mN / denier or more and a single yarn elongation of 300% or more. <7> The spunbond nonwoven fabric according to any one of <1> to <6>, in which the hollow fibers have an average outer diameter of from 10 µm to less than 30 µm and an average hollowness of from 10% to 40%. <8> A sanitary material, containing the spunbond nonwoven fabric according to any one of <1> to <7>. <9> An industrial material, containing the spunbond nonwoven fabric according to any one of <1> to <7>. <10> A hollow fiber production apparatus for producing the hollow fibers according to any one of <1> to <7>, the hollow fiber production apparatus containing a spinneret, in which a ratio of a length of a slot of the spinneret to a width of the slot is less than 8. <11> A hollow fiber production method, containing: producing the hollow fibers according to any one of <1> to <7> by spin-lay lamination, in which a take-up speed of the hollow fibers when the hollow fibers are laminated on a moving screen is from 2000 m / min to 4000 m / min. <12> A hollow fiber production method, containing: producing hollow fibers by spin-lay lamination using a hollow fiber production apparatus, the hollow fiber production apparatus containing a spinneret, in which: a ratio of a length of a slot of the spinneret to a width of the slot is less than 8, and a take-up speed of the hollow fibers when the hollow fibers are laminated on a moving screen is from 2000 m / min to 4000 m / min. <13> A spunbond nonwoven fabric containing hollow fibers, in which: a coefficient of variation of hollowness of the hollow fibers is less than 10%, and the hollow fibers have an average outer diameter of 30 µm or more. <14> The spunbond nonwoven fabric according to <13>, in which a value represented by the following Formula (I) is 300% 3< or less: <15> The spunbond nonwoven fabric according to <13> or <14>, in which the hollow fibers have an average hollowness of from 10% to 40%. <16> The spunbond nonwoven fabric according to any one of <13> to <15>, in which the hollow fibers contain a polypropylene-based resin. <17> The spunbond nonwoven fabric according to any one of <13> to <16>, in which the hollow fibers have a single yarn tenacity of 19.0 mN / denier or more and a single yarn elongation of 300% or more. <18> The spunbond nonwoven fabric according to any one of <13> to <17>, in which the hollow fibers have an average outer diameter of from 30 µm to 40 µm and an average hollowness of from 10% to 40%. <19> A sanitary material, containing the spunbond nonwoven fabric according to any one of <13> to <18>. <20> An industrial material, containing the spunbond nonwoven fabric according to any one of <13> to <18>. <21> A hollow fiber production apparatus for producing the hollow fibers according to any one of <13> to <18>, the hollow fiber production apparatus containing a spinneret, in which a ratio of a length of a slot of the spinneret to a width of the slot is less than 8. <22> A hollow fiber production method, containing: producing the hollow fibers according to any one of <13> to <18> by spin-lay lamination, in which a take-up speed of the hollow fibers when the hollow fibers are laminated on a moving screen is from 2000 m / min to 4000 m / min. <23> A hollow fiber production method, containing: producing hollow fibers by spin-lay lamination using a hollow fiber production apparatus, the hollow fiber production apparatus containing a spinneret, in which a ratio of a length of a slot of the spinneret to a width of the slot is less than 8, and a take-up speed of the hollow fibers when the hollow fibers are laminated on a moving screen is from 2000 m / min to 4000 m / min. Advantageous Effects of Invention

[0010] In one embodiment, the present disclosure provides a spunbond nonwoven fabric including hollow fibers excellent in tensile strength and elongation, a sanitary material, an industrial material, a hollow fiber production apparatus, and a hollow fiber production method.BRIEF DESCRIPTION OF DRAWINGS

[0011] Fig. 1 is a schematic view showing a sealed spunbond nonwoven fabric producing apparatus according to an embodiment of a first aspect of the present disclosure. Fig. 2 is a schematic view of an example of a hole shape of a slot of a spinneret according to an embodiment of a first aspect of the present disclosure. Fig. 3 is a cross-sectional view of a spinning hole of a spinneret according to an embodiment of a first aspect of the present disclosure. Fig. 4 is a schematic view of an example of a hole shape of a slot of a spinneret according to an embodiment of a first aspect of the present disclosure. Fig. 5 is a schematic view of an example of a hole shape of a slot of a spinneret according to an embodiment of a first aspect of the present disclosure. DESCRIPTION OF EMBODIMENTS

[0012] Hereinafter, embodiments of the present disclosure will be described. These descriptions and examples illustrate embodiments and do not limit the scope of the embodiments.

[0013] With regard to the stepwise numerical ranges described in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another stepwise numerical range. In the numerical range described in the present disclosure, the upper limit value or the lower limit value of the numerical range may also be replaced with a value shown in Examples.

[0014] Each component in the present disclosure may contain a plurality of corresponding substances. When a plurality of substances corresponding to each component are present in a composition, the amount of each component in the composition, to which are referred in the present disclosure, means the total amount of the plurality of substances present in the composition, unless otherwise specified.

[0015] In the present disclosure, the term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved. In the present disclosure, a numerical range indicated using "to" indicates a range including numerical values described before and after "to" as a minimum value and a maximum value, respectively. In the present disclosure, the content of each component in the composition means the total amount of a plurality of substances corresponding to each component in the composition when the plurality of substances exists in the composition, unless otherwise specified.

[0016] In the present disclosure, the "spunbond nonwoven fabric" refers to a nonwoven fabric made by one or more bonding methods (for example, embossing) on a spunlaid web. The "spunlaid web" refers to a web that is laminated by a spin-lay lamination. The "spin-lay lamination" refers to a method of extruding a molten or dissolved polymer from a spinneret (that is, the spinning hole) and laminating single fibers on a moving screen to make a web.(1) First Aspect(1.1) Spunbond Nonwoven Fabric

[0017] A spunbond nonwoven fabric (hereinafter, also referred to as "SB nonwoven fabric") according to a first aspect of the present disclosure includes a plurality of hollow fibers. The hollowness of the hollow fibers has a coefficient of variation (hereinafter, also referred to as "Cv of hollowness") of less than 10%.

[0018] The "hollow fiber" refers to a straw-like fiber. Specifically, one hollow fiber includes one or more internal hollow portions extending along the fiber axial direction.

[0019] The coefficient of variation of hollowness of hollow fibers quantitatively indicates the degree of variation of hollowness in the fiber axial direction of the plurality of hollow fibers constituting the SB nonwoven fabric. The fact that the coefficient of variation of hollowness of the hollow fibers is closer to 0 indicates that the shape of the hollow fibers included in the SB nonwoven fabric is relatively uniform, the hollowness of the plurality of hollow fibers is almost the same, and the variation of hollowness of the hollow fiber in the fiber cross-sectional direction is smaller. The "hollowness" refers to the ratio of the cross-sectional area of the hollow portion of the hollow fiber to the cross-sectional area defined by the outer diameter of the hollow fiber in the cross section perpendicular to the fiber axial direction of the hollow fiber collected from the SB nonwoven fabric. The method for measuring Cv of the hollowness is the same as the method described in Examples.

[0020] Since the SB nonwoven fabric of the first aspect has the above configuration, the SB nonwoven fabric includes hollow fibers excellent in tensile strength and elongation. Therefore, the SB nonwoven fabric of the first aspect is excellent in 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 aspect. In a preferred aspect, the SB nonwoven fabric of the first aspect is excellent in MD tensile strength and elongation in the machine direction (MD) (hereinafter, also referred to as "MD elongation").

[0021] This effect is presumed to be due to the following reason, but is not limited thereto.

[0022] A coefficient of variation (Cv) of hollowness of less than 10% indicates that, in the plurality of hollow fibers constituting the SB nonwoven fabric, the thickness of a wall forming 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 axial direction (hereinafter also simply referred to as "cross section of the hollow fiber"). Therefore, when the hollow fibers are pulled in the fiber axial direction, stress is less likely to concentrate on a specific part (in particular, a portion where a wall forming the hollow portion has a small thickness) of the hollow fibers than in a configuration in which the thickness of a wall forming the hollow portions of the hollow fibers is non-uniform in the cross section of the hollow fibers. As a result, it is presumed that the hollow fibers contained in the SB nonwoven fabric of the first aspect have excellent tensile strength and excellent elongation. Therefore, since the SB nonwoven fabric containing the hollow fibers includes a plurality of hollow fibers having a relatively uniform cross-sectional shape, the SB nonwoven fabric is superior in tensile strength to the SB nonwoven fabric in which the thickness of the wall constituting the hollow portion of the hollow fibers is non-uniform in the cross section of the hollow fibers.

[0023] The machine direction (MD) of the SB nonwoven fabric may be determined from the SB nonwoven fabric itself by measuring the tensile strength of the SB nonwoven fabric.

[0024] In general, in the production of the SB nonwoven fabric, the moving speed of the screen is set to be fast from the viewpoint of productivity. Therefore, single fibers (long fibers) contained in the web are likely to be oriented in a direction parallel to the machine direction (MD) when being laminated on a screen. As a result, the tensile strength of the SB nonwoven fabric in the machine direction (MD) is higher than the tensile strength of the SB nonwoven fabric in the cross direction (CD) (hereinafter, also referred to as "width direction (CD)"), which is perpendicular to the machine direction (MD). Thus, by measuring the tensile strength of the SB nonwoven fabric, the machine direction (MD) can be determined from the SB nonwoven fabric itself.

[0025] The SB nonwoven fabric is a sheet-like material. The SB nonwoven fabric may have a single layer structure or a laminated structure.

[0026] The basis weight of the SB nonwoven fabric is not particularly limited, and is appropriately selected according to the use of the SB nonwoven fabric. The basis weight of the SB nonwoven fabric may be from 5 g / m 2< to 400 g / m 2< , from 10 g / m 2< to 50 g / m 2< , or from 15 g / m 2< to 30 g / m 2< . As the sanitary material (that is, from the viewpoint of imparting flexibility and air permeability to the SB nonwoven fabric), the basis weight of the SB nonwoven fabric is preferably from 5 g / m 2< to 30 g / m 2< , and more preferably from 5 g / m 2< to 20 g / m 2< . As an industrial material (that is, from the viewpoint of enhancing the tensile strength), the basis weight of the SB nonwoven fabric is preferably from 30 g / m 2< to 400 g / m 2< . The method for measuring the basis weight of the SB nonwoven fabric is the same as the method described in Examples.

[0027] The thickness of the SB nonwoven fabric is not particularly limited, and is appropriately selected according to the use of the SB nonwoven fabric. The thickness of the SB nonwoven fabric may be from 0.1 mm to 2.0 mm, or may be from 0.2 mm to 1.0 mm.

[0028] The SB nonwoven fabric may be made by a known bonding method. Examples of the known bonding method include a thermal fusion method (such as embossing treatment, or ultrasonic welding), a mechanical entanglement method (such as needle punching or water jet), a method using an adhesive (such as a hot melt adhesive or a urethane-based adhesive), and extrusion lamination. These bonding methods are appropriately selected according to the application.

[0029] When the SB nonwoven fabric is formed by a thermal fusion method, the SB nonwoven fabric may have a plurality of embossed portions. The "embossed portion" refers to a non-fibrous portion in which a part of a plurality of hollow fibers is thermally bonded. Specifically, the embossed portion indicates a site where the area of the binding site is 0.1 mm 2< or more. The ratio of the total area of the embossed portion to the surface area of the SB nonwoven fabric (hereinafter, referred to as "embossed area ratio") is not particularly limited, and is preferably from 5% to 50% from the viewpoint of tensile strength and air permeability. From the viewpoint of further imparting flexibility, the embossed area ratio is preferably from 5% to 25%. From the viewpoint of enhancing the rigidity, the embossed area ratio may be more than 25% and 50% or less.

[0030] The SB nonwoven fabric includes a plurality of hollow fibers. The SB nonwoven fabric may be a composite containing other fibers (such as solid fibers, fibers having no hollow portion in the fiber cross section, and short fibers) in addition to hollow fibers. The short 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 appropriately adjusted according to 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 with respect to the total amount of the SB nonwoven fabric. The SB nonwoven fabric may be composed of only a plurality of hollow fibers.

[0031] The MD tensile strength of the SB nonwoven fabric is not particularly limited, and is appropriately selected according to the use of the SB nonwoven fabric. The MD tensile strength of the SB nonwoven fabric is preferably from 20 N / 25 mm to 40 N / 25 mm. The fact that the MD tensile strength of the SB nonwoven fabric is 20 N / 25 mm or more indicates that the MD tensile strength of the SB nonwoven fabric is excellent. That is, the SB nonwoven fabric is hardly torn. Therefore, the SB nonwoven fabric is suitably used for sanitary materials and industrial materials (such as agricultural covering materials). The method for measuring the MD tensile strength of the SB nonwoven fabric is the same as the method described in Examples.

[0032] The MD elongation of the SB nonwoven fabric is not particularly limited, and is appropriately selected according to the use of the SB nonwoven fabric. The MD elongation of the SB nonwoven fabric may be 30% or more, and is preferably from 60% to 100%. The fact that the MD elongation of the SB nonwoven fabric is 60% or more indicates that the MD elongation of the SB nonwoven fabric is excellent. That is, the SB nonwoven fabric easily stretches, and is excellent in flexibility and shape followability. Therefore, the SB nonwoven fabric is suitably used for sanitary materials and industrial materials (such as agricultural covering materials). The method for measuring the MD elongation percentage of the SB nonwoven fabric is the same as the method described in Examples.

[0033] The air permeability of the SB nonwoven fabric is not particularly limited, and is appropriately selected according to the use of the SB nonwoven fabric. The air permeability of the SB nonwoven fabric is preferably from 500 cm 3< / cm 2< ·sec to 700 cm 3< / cm 2< ·sec. The fact that the air permeability of the SB nonwoven fabric is 500 cm 3< / cm 2< ·sec or more indicates that air easily permeates the SB nonwoven fabric. Therefore, the SB nonwoven fabric is suitably used for sanitary materials and industrial materials (such as agricultural covering materials). The method for measuring the air permeability of the SB nonwoven fabric is the same as the method described in Examples.

[0034] The light transmittance of the SB nonwoven fabric is not particularly limited, and is appropriately selected according to the use of the SB nonwoven fabric. The light transmittance of the SB nonwoven fabric is preferably from 93.4% to 90.0%. The light transmittance of the SB nonwoven fabric being 93.4% or less indicates that the SB nonwoven fabric appropriately blocks light transmission. Therefore, the SB nonwoven fabric is suitably used as an agricultural covering material. The method for measuring the light transmittance of the SB nonwoven fabric is the same as the method described in Examples.(1.1.1) Hollow Fiber

[0035] The average outer diameter of the hollow fibers is not particularly limited, and is appropriately selected according to the use of the SB nonwoven fabric. In one embodiment, the hollow fibers preferably have an average outer diameter of less than 30 µm.

[0036] The hollow fibers have an average outer diameter of less than 30 µm, and the Cv of the hollow fibers may be less than 10%. From the viewpoint of imparting flexibility, the hollow fibers may have an average outer diameter of 25 µm or less or 5 µm or more. As the average outer diameter of the hollow fibers is smaller, the surface friction coefficient is smaller, and the smoothness when the hollow fibers come into contact with the skin is increased. Therefore, the SB nonwoven fabric is useful for sanitary materials, artificial leather, and the like.

[0037] From the viewpoint of enhancing the air permeability of the nonwoven fabric, the hollow fibers may have an average outer diameter of 20 µm or more. The larger the fiber diameter of the outer diameter, the higher the friction resistance. Therefore, the SB nonwoven fabric is useful in applications for suppressing fibrillation.

[0038] The method for measuring the average outer diameter of the hollow fibers is the same as the method described in Examples.

[0039] The coefficient of variation (hereinafter, also referred to as "Cv of outer diameter") of the outer diameter of the hollow fibers of the SB nonwoven fabric produced by spin-lay lamination is 10.0% or less. The Cv of the outer diameter of the plurality of hollow fibers included in the SB nonwoven fabric is preferably 2.0% to 10.0%, and more preferably 3.0% to 10.0%. When Cv of the outer diameter is within the above numerical range, Cv of the cross-sectional area of the hollow fibers can be reduced. That is, the fiber diameter distribution of the plurality of hollow fibers included 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 for an SB nonwoven fabric having a low basis weight in which variation between production lots is suppressed, and is useful for applications such as a filter medium. The method for measuring Cv of the outer diameter is the same as the method described in Examples.

[0040] The average hollowness of the hollow fibers is not particularly limited, and is appropriately selected according to the use of the SB nonwoven fabric. The average hollowness of the hollow fibers is preferably from 10% to 40%.

[0041] The higher the average hollowness of the hollow fibers is, the higher the effect of reducing environmental load is. In an application where heat retention performance is required (such as a warmer), the average hollowness is required to be high. From this viewpoint, the average hollowness of the hollow fibers is preferably 10% or more.

[0042] The average hollowness of the hollow fibers is preferably 40% or less from the viewpoint of single yarn tenacity and single yarn elongation of the hollow fibers.

[0043] The method for measuring the average hollowness of the hollow fibers is the same as the method described in Examples.

[0044] The Cv of hollowness of the hollow fibers is less than 10.0%. The Cv of hollowness of the hollow fibers is preferably 2.0% or more and less than 10.0% from the viewpoint of enhancing the single yarn tenacity and the MD tensile strength of the SB nonwoven fabric.

[0045] When an SB nonwoven fabric containing hollow fibers is produced at a high speed, fiber breakage may occur, and the Cv of hollowness of the resulting hollow fibers generally tends to be more than 10%. When fiber breakage occurs, the strength of the fiber decreases. Therefore, the single yarn elongation of the conventional hollow fibers was not excellent. In other words, the single yarn tenacity of the conventional hollow fibers was less than 19.0 mN / denier. In the present disclosure, it has been found that the Cv of hollowness of the hollow fibers can be less than 10% by the production method described below. Although some mechanisms are unknown, in order to obtain such excellent hollow fibers, it is a problem to form a thin resin molded body which is relatively uniform in the circumferential direction of the fibers while preventing formation of extremely thin fragile points as starting points of fiber breakage of the hollow fibers. In fine-denier fibers having irregular cross sections, it is considered useful to control a discharge method of the hollow fibers in order to achieve the object.

[0046] The average of the outer diameters of the hollow fibers is preferably 10 µm or more and less than 30 µm, and the average hollowness of the hollow fibers is preferably 10% to 40%. Accordingly, the single yarn tenacity and the single yarn elongation of the hollow fibers are improved, and the SB nonwoven fabric is excellent in the MD tensile strength.

[0047] The value represented by the following Formula (I) (hereinafter, also referred to as "Cv of the cross-sectional area of the hollow fibers") is preferably 300% 3< or less, more preferably from 100% 3< to 300% 3< , and still more preferably from 100% 3< to 250% 3< .

[0048] The Cv of the cross-sectional area of the hollow fibers can be regarded as quantitatively indicating the degree of variation of the area (hereinafter, also referred to as "cross-sectional area of hollow fibers") of the wall constituting the hollow portion in the cross section of the hollow fibers in the fiber axial direction of the plurality of hollow fibers constituting the SB nonwoven fabric. The fact that the Cv of the cross-sectional area of the hollow fibers is closer to 0 indicates that the variation of the cross-sectional area of the hollow fibers in the fiber axial direction of the hollow fibers is smaller. In other words, the fact that the Cv of the cross-sectional area of the hollow fibers is closer to 0 means that the resulting SB nonwoven fabric is composed of hollow fibers having a more uniform cross-sectional shape.

[0049] When Cv of the cross-sectional area of the hollow fibers is 300% 3< or less, the single yarn tenacity and the single yarn elongation of the hollow fibers tend to be superior to the configuration in which Cv of the cross-sectional area of the hollow fibers is more than 300% 3< .

[0050] When the hollow fibers have a Cv of the cross-sectional area of 300% 3< or less, there are few extremely thin fragile points that become starting points of fiber breakage of the hollow fibers. The mechanical strength of the SB nonwoven fabric containing such hollow fibers is superior to the conventional one. The method for measuring Cv of the cross-sectional area of the hollow fibers is the same as the method described in Examples.

[0051] The single yarn tenacity of the hollow fibers is not particularly limited, and is appropriately selected according to the use of the SB nonwoven fabric. The single yarn tenacity of the hollow fibers is preferably 19.0 mN / denier or more, and more preferably from 19.0 mN / denier to 30.0 mN / denier. The fact that the single yarn tenacity of the hollow fibers is 19.0 mN / denier or more indicates that the hollow fibers have excellent single yarn tenacity. That is, the SB nonwoven fabric tends to be hardly broken. Therefore, the SB nonwoven fabric is suitably used for sanitary materials having a low basis weight and industrial materials (such as agricultural covering materials). The method for measuring the single yarn tenacity of the SB nonwoven fabric is the same as the method described in Examples.

[0052] The single yarn elongation of the hollow fibers is not particularly limited, and is appropriately selected according to the use of the SB nonwoven fabric. The single yarn elongation of the hollow fibers is preferably 300% or more, and more preferably from 300% to 450%. A single yarn elongation of the hollow fibers of 300% or more indicates that the single yarn elongation of the hollow fibers is excellent. That is, the SB nonwoven fabric is excellent in MD tensile strength. Depending on the thermoplastic resin used for the SB nonwoven fabric, the SB nonwoven fabric is excellent in MD tensile strength, is easy to stretch, and is also excellent in flexibility and shape followability. Therefore, the SB nonwoven fabric is suitably used for sanitary materials and industrial materials (such as an agricultural covering material required to follow an uneven shape). The method for measuring the single yarn elongation of the SB nonwoven fabric is the same as the method described in Examples.

[0053] The single yarn tenacity of the hollow fibers is preferably 19.0 mN / denier or more, and the single yarn elongation of the hollow fibers is preferably 300% or more. Thus, the SB nonwoven fabric is excellent in MD tensile strength. Therefore, the SB nonwoven fabric is suitably used for sanitary materials and industrial materials (such as agricultural covering materials).(1.1.1.1) Material

[0054] The hollow fibers may be made of a thermoplastic resin composition.(1.1.1.1.1) Thermoplastic Resin

[0055] The thermoplastic resin composition contains a thermoplastic resin. Examples of the thermoplastic resin include polyolefin-based resins, polyester-based resins (such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate), polyamide-based resins (such as nylon-6, nylon-66, and polymetaxylylene adipamide), polyvinyl chloride, polyimide, ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid ester-carbon monoxide copolymers, polyacrylonitrile, polycarbonate, polystyrene, and ionomers. The "(meth)acrylic acid" refers to acrylic acid or methacrylic acid.

[0056] Examples of the polyolefin-based resin include polyethylene-based resins (such as linear low density polyethylene (LLDPE) and high density polyethylene (HDPE)) and polypropylene-based resins.

[0057] Examples of the polypropylene-based resin include a propylene homopolymer (that is, homopolypropylene), a propylene-α-olefin random copolymer (such as a propylene / ethylene random copolymer), and a propylene-α-olefin block copolymer. Examples of the α-olefin other than propylene include ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-pentene. When the α-olefin is copolymerized, the copolymerization amount is preferably from 1 mol% to 10 mol%. The "polypropylene-based resin" refers to a polymer containing 50 % by mass or more of a propylene-derived structural unit.

[0058] These thermoplastic resins may be used singly or in combination of two or more kinds thereof.

[0059] The hollow fibers may be one-component fibers. In other embodiments, the hollow fibers may further include one or more polymer layers as components that further improve strength, processability, and other properties. The hollow fibers may have a two-layer structure (such as a sheath-core arrangement) or a multilayer structure (such as a parallel type, a segmented pie-type, or a sea-island type).

[0060] 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 homopolypropylene. Since 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. The "main component of the thermoplastic resin" refers to a thermoplastic resin component having a content of 50% by mass or more with respect to the total amount of the thermoplastic resin.

[0061] Hereinafter, a case where the hollow fibers contain a propylene-based polymer will be described.

[0062] The melting point of the propylene-based polymer is preferably 140°C or higher, more preferably 150°C or higher, still more preferably 155°C or higher, and particularly preferably 157°C to 165°C.

[0063] The melting point (Tm) can be measured by differential scanning calorimetry (DSC) as follows. Using DSC Pyris1 manufactured by Perkin Elmer or DSC7020 manufactured by SII NanoTechnology Inc. as a differential scanning calorimeter (DSC), a sample (about 5 mg) is heated from room temperature to 200°C at a rate of 10°C / min in a nitrogen atmosphere (20 ml / min), held at the temperature for 5 minutes, then cooled to -50°C at a rate of 10°C / min, held at -50°C for 5 minutes, and heated for the second time to 200°C at a rate of 10°C / min, and a melting point (Tm) is calculated from a peak top of a crystal melting peak in the second heating process. When a plurality of crystal melting peaks are observed, the high temperature side peak is taken as the melting point (Tm).

[0064] The melt flow rate (MFR) of the polypropylene-based resin is not particularly limited as long as it can be melt spun, and may be from 1 g / 10 min to 1000 g / 10 min, from 5 g / 10 min to 500 g / 10 min, or from 10 g / 10 min to 100 g / 10 min. The method for measuring the MFR of the polypropylene-based resin is in accordance with ASTM D-1238, and the measurement conditions are 230°C and a load of 2.16 kg.

[0065] The content of the polypropylene-based resin may be from 80.0% by mass to 100.0% by mass, from 90.0% by mass to 100.0% by mass, or 100.0% by mass with respect to the total amount of the thermoplastic resin composition.

[0066] The thermoplastic resin (such as polypropylene resin or the like) used in the first aspect may be made from a biomass-derived raw material. Since the biomass-derived raw material is a carbon-neutral material, the environmental load in the production of the SB nonwoven fabric using the hollow fibers of the present disclosure can be further reduced.

[0067] Monomers serving as raw materials for the biomass-derived thermoplastic resin are obtained by cracking of biomass naphtha or synthesis from biomass-derived ethylene. The biomass-derived thermoplastic resin is obtained by polymerizing the biomass-derived monomer synthesized in this way by the same method as in the case of using a conventionally known petroleum-derived thermoplastic resin.

[0068] A polymer of a thermoplastic resin synthesized using a biomass-derived monomer as a raw material is a biomass-derived thermoplastic polymer. The content of the bio-derived thermoplastic polymer in the raw material monomers is more than 0% by mass, and may be 100% by mass or less with respect to the total amount of the raw material monomers.

[0069] The "biomass degree" indicates the content of carbon derived from biomass, and is calculated by measuring radioactive carbon (C14). Carbon dioxide in the atmosphere contains a certain proportion (about 105.5 pMC) of C14. Therefore, it is known that the content of C14 in a plant (for example, corn) that grows by taking in carbon dioxide in the atmosphere is also about 105.5 pMC. It is also known that fossil fuels contain little C14. Therefore, the content of biomass-derived carbon in the raw material can be calculated by measuring the ratio of C14 contained in all carbon atoms in the polymer.

[0070] In a preferred aspect, the thermoplastic polymer used as the raw material of the first aspect contains a thermoplastic polymer obtained by recycling, a so-called recycled polymer. The "recycled polymer" includes a polymer obtained by material recycling, chemical recycling, or the like of a waste polymer product, and can be produced, for example, by the method described in DE102019127827 (A1). The recycled polymer may contain a marker capable of identifying the polymer as having been obtained through recycling. When the thermoplastic resin used for the SB nonwoven fabric contains a recycled polymer, the amount of virgin petrochemical raw material used can be reduced, and the environmental load at the time of producing the SB nonwoven fabric using hollow fibers can be further reduced.(1.1.1.1.2) Additive

[0071] The thermoplastic resin composition may contain an additive. Examples of the additive include an antioxidant, a heat stabilizer, a weathering stabilizer, an antistatic agent, a softener, a slipping agent, an antifogging agent, a lubricant, a dye, a pigment, a natural oil, a synthetic oil, a wax, a compatibilizer, and a fatty acid amide.(1.1.3) Hollow Fiber Production Method

[0072] In the hollow fiber production method according to the first aspect, the hollow fibers according to the first aspect are produced by spin-lay lamination. In the hollow fiber production method according to the first aspect, a take-up speed of the hollow fibers when the hollow fibers are laminated on a moving screen (hereinafter, also simply referred to as "take-up speed") is from 2000 m / min to 4000 m / min.

[0073] In the hollow fiber production method according to the first aspect, the hollow fibers according to the first aspect can be stably formed by setting the take-up speed to 2000 m / min to 4000 m / min. Therefore, the Cv of hollowness of the resulting hollow fibers is likely to be less than 10%. Further, the resulting hollow fibers may have a Cv of cross-sectional area of 300% 3< or less.

[0074] The hollow fiber production method according to the first aspect may include a known step except that the take-up speed is from 2000 m / min to 4000 m / min.

[0075] The hollow fibers of the first aspect may be made 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. The SB nonwoven fabric is obtained when the SB web is subjected to the bonding method described above (for example, embossing). The hollow fiber production method of the first aspect may be the same as the SB nonwoven fabric production method except that the bonding method (for example, embossing) is not performed. An example of the SB nonwoven fabric production method will be described with reference to Figs. 1 to 5.(1.1.4) Hollow Fiber Production Apparatus

[0076] The hollow fiber production apparatus according to a first aspect is for producing hollow fibers according to the first aspect. The production apparatus includes a spinneret. A ratio (hereinafter, also referred to as "slot ratio (length / width)") of a length of the slot (hereinafter, also referred to as "slot length L") of the spinneret to a width of the slot (hereinafter, also referred to as "slot width W") 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 A). The slot has a nozzle hole for discharging a melt of the thermoplastic resin composition as a raw material of the hollow fibers. The slot length L indicates a length of the nozzle hole in the thickness direction of the spinneret. The slot width W and the slot length L will be described later with reference to Figs. 2 to 5.

[0077] Patent Document 2 discloses a hollow fiber production method using a hollow fiber production apparatus. Specifically, Patent Document 2 discloses in Examples that an SB nonwoven fabric composed of a plurality of hollow fibers is produced using a spinneret having a slot ratio (length / width) of 8. However, since the slot ratio (length / width) is 8, the coefficient of variation (CV) of hollowness (void fraction) of the hollow fibers contained in the SB nonwoven fabric is 10% or more, which may result in insufficient tensile strength and elongation of the hollow fibers. That is, Patent Document 2 does not disclose nor suggest a technical idea of improving the tensile strength and the elongation of the hollow fibers by adjusting the coefficient of variation (CV) of hollowness (void fraction) of the hollow fibers to less than 10%.

[0078] Conventionally, it has been considered that the single fibers discharged from spinning holes can be uniformly stretched and stably spun as the slot ratio (length / width) is larger. The discloser of the present disclosure has found that, in the hollow fiber production apparatus according to the first aspect, by setting the slot ratio (length / width) to less than 8, the Cv of hollowness of the resulting hollow fibers can be less than 10% even in high-speed production (for example, the take-up speed: from 2000 m / min to 4000 m / min). The resulting hollow fibers had a Cv of the cross-sectional area of 300% 3< or less. The reason for this is not clear, but when the slot ratio (length / width) is less than 8, deformation of the hollow fibers in the thickness direction from discharge to cooling and solidification can be made gentle. Therefore, it is considered that hollow fibers having a uniform cross-sectional shape can be produced in high speed production (take-up speed: from 2000 m / min to 4000 m / min).

[0079] The spinneret has a plurality of spinning holes. The spinning holes spin the melt of the thermoplastic resin composition to form hollow fibers (hereinafter also referred to as "continuous fiber group"). Unlike a spinneret of a multifilament, a spinneret in which a plurality of spinning holes (for example, 100 or more than 1000 spinning holes) are disposed at equal intervals is used in spin-lay lamination. In the conventional spin-lay lamination, it is difficult to uniformly cool the hollow fibers extruded from the central portion of the spinneret and the hollow fibers extruded from the end portion of the spinneret. As a result, temperature unevenness occurs between the hollow fibers extruded from the central portion of the spinneret and the hollow fibers extruded from the end portion of the spinneret, and the hollowness of the hollow fibers tends to vary.

[0080] The spinning holes of the spinneret penetrates the spinneret. Each spinning hole has at least one slot. A melt of the thermoplastic resin composition as a raw material of the hollow fibers flows through the slots. Hollow fibers are formed with the melt of the thermoplastic resin composition that has passed through the slots. 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 circular shape, a triangular shape, a square shape, a star shape (for example, four-pointed star, five-pointed star, six-pointed star, or star shapes having seven or more points), a flat elliptical shape, a T shape, an M shape, an S shape, a Y shape, an H shape, and a dumbbell shape. Among them, from the viewpoint of reducing the Cv of hollowness of the hollow fibers, the hole shape is preferably one C-shape, more preferably a shape in which a plurality of C-shapes are combined, and more preferably a shape in which two to six C-shapes are combined. One of preferable aspects is that the hole shape is a shape in which six C-shapes are combined.

[0081] When the slot is not line-symmetric, the slot width W may be calculated using the largest width of the slot. This is because the thicker the thickness of the wall constituting the hollow portion of the hollow fibers discharged from the spinning holes, the longer it takes for the hollow fibers to be cooled and solidified, and the cross-sectional shape of the hollow fibers is less likely to be uniform.

[0082] From the viewpoint of setting the Cv of hollowness to less than 10%, the slot ratio (length / width) is preferably less than 8, more preferably less than 6, and still more preferably 5 or less. The slot ratio (length / width) is preferably 3.0 or more from the viewpoint of reducing the hollowness of the hollow fibers.

[0083] The slot width W may be, for example, from 0.05 mm to 0.2 mm, and the slot length L may be, for example, from 0.3 mm to 1.2 mm. The slot length L is appropriately selected according to the slot ratio (length / width) and the slot width W.

[0084] The hollow fiber production apparatus according to the first aspect may be similar to a known hollow fiber production apparatus except that the slot ratio (length / width) is less than 8. An example of a hollow fiber production apparatus will be described with reference to Figs. 1 to 5.(1.1.5) Embodiment Illustrating One Example of SB Nonwoven Fabric Production Method

[0085] In the present embodiment, the SB nonwoven fabric is obtained by preparing a spunbond web (hereinafter, also referred to as "SB web") by spin-lay lamination using a spinneret for hollow fibers and embossing the SB web.

[0086] Hereinafter, an example of the SB nonwoven fabric production method of the first aspect will be described in detail with reference to the drawings. Fig. 1 is a schematic view illustrating a sealed SB nonwoven fabric production apparatus according to an embodiment of a first aspect. In the sealed SB nonwoven fabric production apparatus, a plurality of continuous fiber groups extruded from a spinneret (spinning holes) for hollow fibers are stretched while being cooled in a closed space. The sealed SB nonwoven fabric production apparatus is an example of a hollow fiber production apparatus. The hollow fibers of the present disclosure are not limited to the sealed SB nonwoven fabric production apparatus, and may be produced with an open SB nonwoven fabric production apparatus or a general-purpose SB nonwoven fabric production apparatus.

[0087] The SB nonwoven fabric production method of the embodiment of the first aspect is performed using a sealed SB nonwoven fabric production apparatus 100 shown in Fig. 1. The SB nonwoven fabric production method includes a melting step, a spinning step, a cooling and stretching step, a collecting step, and an embossing step. The melting step, the spinning step, the cooling and stretching step, the collecting step, and the embossing step are performed in this order. The melting step, the spinning step, the cooling and stretching step, and the collecting step are examples of a method for producing hollow fibers.(1.1.5.1) Production Apparatus

[0088] As illustrated in Fig. 1, the sealed SB nonwoven fabric production 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 supplying unit 14, a spinning air supplying unit 15, and a stretching section 16.

[0089] The extruder 11 melts the thermoplastic resin composition and extrudes a melt of the thermoplastic resin composition to the spinneret 12.

[0090] The spinneret 12 spins a melt of the thermoplastic resin composition to form a continuous fiber group 1. The spinneret 12 is for hollow fibers. Specifically, the spinneret 12 forms a melt of the thermoplastic resin composition into a continuous fiber group. The spinneret 12 includes a large number of spinning holes 120. As illustrated in Fig. 3, each spinning hole 120 penetrates from a surface S12A of the spinneret 12 to a surface S12B of the spinneret 12 (that is, along the thickness direction D of the spinneret 12). In the spinneret 12, as shown in Fig. 2, a spinning hole 120 for producing one hollow fiber has four slots 121A. A melt of the thermoplastic resin composition as a raw material of the hollow fibers flows through the slots 121A. The hole shape of the slots 121A is the deformed hole illustrated in Fig. 2. Each slot 121A has a slot width W (see Fig. 2). As illustrated in Fig. 3, the spinneret 12 includes guide holes 1201 and nozzle holes 1202 continuously connected to the guide holes 1201. The slot length L (see Fig. 3) indicates the length of each 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 a ratio of the slot length L (see Fig. 2) to the slot width W (see Fig. 2).

[0091] In the first embodiment, each spinning hole 120 for producing one hollow fiber is the slots 121A shown in Fig. 2, but the present disclosure is not limited thereto. In the present disclosure, each spinning hole 120 for producing one hollow fiber may be slots 121B shown in Fig. 4 or slots 121C shown in Fig. 5.

[0092] The cooling chamber 13 cools the continuous fiber group 1 spun from the spinning holes of the spinneret 12. The spinning air supplying unit 14 and the spinning air supplying unit 15 supply the spinning air A into the cooling chamber 13 and the stretching section 16.

[0093] In the stretching section 16, the continuous fiber group 1 is stretched by the spinning air A. The stretching section 16 includes a bottleneck portion 16a and a cylindrical portion 16b. The cylindrical portion 16b is formed at a lower end (that is, the screen 21 side) of the bottleneck portion 16a in the vertical direction (that is, the gravity direction). The bottleneck portion 16a has a narrow path shape. The cylindrical portion 16b is a cylindrical object. As illustrated in Fig. 1, the hollow portion of the cylindrical portion 16b expands downward. The suction unit 22 collects the continuous fiber group 1 on the screen 21.

[0094] In the production method of the multifilaments, the yarn (multifilament) eluted from the spinning hole is stretched using a stretching machine including one or more pairs of rollers. Specifically, in the case of fibers made of a thermoplastic resin that can be generally melt-spun, the yarns (multifilaments) are produced by being stretched in the fiber axial direction by the peripheral speed ratio between the first roller and the second roller, and thermally set and wound. 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 corresponding to the crystallization temperature of the thermoplastic resin. From the viewpoint of increasing the draw ratio and improving the mechanical characteristics of the yarn, this drawing step is performed in multiple stages. As another stretching method of the multifilament, the multifilament is not wound, and is subjected to two-stage stretching in a stretching liquid bath at a temperature of from 60°C to 120°C, and the total ratio thus becomes a predetermined ratio.

[0095] The suction unit 22 is disposed below the auxiliary collecting surface of screen 21.(1.1.5.2) Melting Step

[0096] In the melting step, the thermoplastic resin composition is melt-kneaded using an extruder 11, and a melt of the thermoplastic resin composition is extruded from the extruder 11.

[0097] The melting temperature (hereinafter, also referred to as "extrusion temperature") of the thermoplastic resin composition 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 according to the physical properties and the like of the thermoplastic resin composition. When the thermoplastic resin composition contains a polypropylene-based resin, the extrusion temperature is preferably from 180°C to 260°C, and more preferably from 190°C to 250°C.(1.1.5.3) Spinning Step

[0098] In the spinning step, the melt of the thermoplastic resin composition is extruded from the spinning holes of the spinneret 12 using the spinneret 12. Accordingly, the continuous fiber group 1 including a plurality of hollow fibers is formed.

[0099] The hole shape of the spinning holes of the spinneret 12 is not particularly limited, and the above-described shapes of the slot, the slot width W, the slot length L, and the like can be used in combination.

[0100] The single-hole discharge rate of the spinning holes of the spinneret 12 is preferably from 0.1 g / min to 3.0 g / min, and more preferably from 0.2 g / min to 1.0 g / min.

[0101] The temperature of the spinneret 12 is appropriately adjusted according to the physical properties and the like of the thermoplastic resin composition. When the thermoplastic resin composition contains a polypropylene-based resin, the temperature of the spinneret 12 is preferably from 180°C to 260°C, and more preferably from 190°C to 250°C.(1.1.5.4) Cooling and Stretching Step

[0102] In the cooling and stretching step, the continuous fiber group 1 is cooled and stretched by the spinning air A. Specifically, the spinning air A is supplied from the spinning air supplying unit 14 and the spinning air supplying unit 15 into the cooling chamber 13 and the stretching section 16. Thus, the continuous fiber group 1 extruded from the spinning holes of the spinneret 12 is cooled in the cooling chamber 13. Next, the cooled continuous fiber group 1 is introduced into the stretching section 16 disposed on the downstream side of the cooling chamber 13. The continuous fiber group 1 introduced into the stretching section 16 is stretched by increasing the speed of the spinning air at the bottleneck portion 16a. The continuous fiber group 1 having passed through the cylindrical portion 16b is dispersed and collected on the screen 21. The dispersed continuous fiber group 1 is efficiently collected on the screen 21 by the suction unit 22. Thus, the SB web 2 is formed.

[0103] The wind speed of the spinning air A supplied from each of the spinning air supplying unit 14 and the spinning air supplying unit 15 indicates the ratio of the flow rate (Nm 3< / min) of the cooling air to the cross-sectional area (m 2< ) of the bottleneck portion 16a of the stretching section 16. That is, the wind speed of the spinning air A indicates the speed at the bottleneck portion 16a of the stretching section 16, and is the same value as the above-described "take-up speed".

[0104] The take-up speed of the continuous fiber group 1 when the continuous fiber group 1 (that is, a plurality of hollow fibers) is laminated on the moving screen 21 is from 2000 m / min to 4000 m / min. The "take-up speed" indicates the ratio of the flow rate (Nm 3< / min) of the cooling air to the cross-sectional area (m 2< ) of the edge of the cylindrical portion 16b of the stretching section 16 on the screen 21 side. That is, the take-up speed indicates the speed of the spinning air A at the edge of the cylindrical portion 16b of the stretching section 16 on the screen 21 side.

[0105] The temperature of the spinning air A supplied from each of the spinning air supplying unit 14 and the spinning air supplying unit 15 is not particularly limited as long as the temperature is a temperature at which the thermoplastic resin composition is solidified. The temperature of the spinning air A is preferably from 5°C to 50°C, and more preferably from 10°C to 40°C.(1.1.5.5) Embossing Step

[0106] In the embossing step, the SB web 2 is embossed. Thereby, the hollow fibers contained in the SB web 2 are bonded together, resulting in an SB nonwoven fabric.

[0107] The "embossing" refers to a process of sandwiching the SB web between an embossing roll and a flat roll and thermocompression-bonding a part of the plurality of fibers included in the SB web. The embossing roll has a plurality of protrusions arranged in a regular pattern on a surface thereof. The embossing roll transfers the shape of the top surface of the plurality of protrusions to a part of the plurality of fibers included in the SB web. As a result, the embossing roll forms a plurality of embossed portions arranged in a regular pattern on the SB web. The ratio of the area of a plurality of protrusions of the embossing roll to the surface area of the embossing roll (hereinafter, also referred to as "embossed area ratio") is appropriately selected according to 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.

[0108] The surface temperature (hereinafter, also referred to as "emboss temperature") of the embossing roll can be appropriately set according to the application. For example, in applications requiring flexibility, the emboss 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 still more preferably (resin melting point: -15°C) to the resin melting point. When the emboss temperature is (resin melting point: -10°C) to the resin melting point, the plurality of hollow fibers in the embossed portion are sufficiently welded.

[0109] Before embossing, the SB web 2 may be compacted using nip rolls.

[0110] In the SB nonwoven fabric production method according to the embodiment of the first aspect, by adjusting the extrusion temperature of the extruder 11, the single-hole discharge rate of the spinning holes of the spinneret 12, and the spinning air speeds of the spinning air supplying unit 14 and the spinning air supplying unit 15, an SB nonwoven fabric containing hollow fibers having a Cv of hollowness of less than 10% can be manufactured.

[0111] Specifically, examples of the method for adjusting Cv of the hollowness of the hollow fibers to less than 10% include adjusting the single-hole discharge rate of the melt of the thermoplastic resin composition to an appropriate range and lowering the wind speed of the spinning air. The range of the appropriate single-hole discharge rate varies depending on the type, viscosity, resin melting point, and the like of the resin to be used, but when the propylene-based resin used in the first aspect is used and the production method and production apparatus of the first aspect are used, the single-hole discharge rate is preferably in the range of from 0.2 g / min to 1.0 g / min. In addition, by lowering the wind speed of the spinning air, unevenness in stretching and cooling of the hollow fibers due to the turbulence of the air flow can be suppressed, and the Cv of hollowness can be lowered.

[0112] Examples of the method for adjusting Cv of cross-sectional area of the hollow fibers to 300% 3< or less include adjusting the single-hole discharge rate of the melt of the thermoplastic resin composition to an appropriate range, and lowering the wind speed of the spinning air.

[0113] As a method for adjusting the average outer diameter of the hollow fibers to from 10 µm to 30 µm and the average hollowness of the hollow fiber to from 10% to 40%, for example, the extrusion temperature, the single-hole discharge rate, and the wind speed of the spinning air are adjusted to appropriate ranges. The range of the appropriate extrusion temperature and single-hole discharge rate varies depending on the type, viscosity, resin melting point, and the like of the resin to be used. When the propylene-based resin used in the first aspect is used, the extrusion temperature is preferably from 190°C to 250°C, and the single-hole discharge rate is preferably from 0.2 g / min to 1.0 g / min.(1.2) Sanitary Material

[0114] The sanitary material of the first aspect includes the SB nonwoven fabric of the first aspect.

[0115] Since the sanitary material of the first aspect has the above configuration, the sanitary material is excellent in mechanical strength (for example, MD tensile strength) and is resistant to tearing. In addition, the hollow fibers can reduce the amount of the thermoplastic resin composition used as compared with solid fibers having the same fiber diameter. As a result, the nonwoven fabric using the hollow fibers can reduce the basis weight and reduce the environmental load.

[0116] Examples of the sanitary material include absorbent articles (such as disposable diapers, disposable pants, sanitary products, urine absorbing pads, or pet sheets), medical sanitary materials (such as bandage, medical gown, medical drape, sterile sheet, medical gauze, towel, sheet, warmer, cell culture sheet, and poultice), and masks (such as an industrial mask and a sanitary mask).

[0117] The sanitary material is not limited thereto, and may be suitably used for other sanitary materials. The sanitary material may include a nonwoven fabric laminate. The nonwoven fabric laminate may include two or more layers of the SB nonwoven fabric of the first aspect, or may include the SB nonwoven fabric of the first aspect and layers other than the nonwoven fabric according to the first aspect.(1.3) Industrial Material

[0118] The industrial material of the first aspect includes the SB nonwoven fabric of the first aspect.

[0119] The industrial material of the first aspect has the above configuration, and is thus excellent in mechanical strength and 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 be damaged than the conventional multi-sheet. The industrial material of the first aspect is suitably used for a ground surface having an irregular shape (for example, gravelly soil). The industrial material of the first aspect can reduce the number of times of replacement of the industrial material due to occurrence of damage.

[0120] When an industrial material is used as an industrial material, it is possible to reduce the weight compared to the related art while maintaining the same mechanical strength as the related art. The reduced weight industrial material can also be expected to reduce transportation cost and energy consumption related to transportation.

[0121] When the industrial material is a sound absorbing material, the sound absorbing material is suitably used for a curved installation surface or an installation surface having an uneven shape.

[0122] The industrial material of the first aspect may have a single-layer structure made of only SB nonwoven fabric or a laminated structure. Since the SB nonwoven fabric is composed of long fibers, the SB nonwoven fabric can reduce fall-off of fibers during transportation and use as compared with a nonwoven fabric containing short fibers, and is also useful from the viewpoint of reducing the environmental load.

[0123] Examples of the industrial materials include agricultural covering materials (such as an open-field cultivation sheet, a tunnel cultivation sheet, a plastic greenhouse cultivation sheet, a solid covering sheet, and a nursery-bed sheet), clothing (such as a core fabric or an adhesive core fabric), construction (such as a roofing material or a tuft carpet substrate), civil engineering (such as a drain material or a filter material), vehicles (such as an automobile interior, an automobile component, a cushion base material of a seat, and a sound absorbing material), hygiene (such as emergency supplies or cleaning supplies), interior (such as carpets, furniture members, fittings, wall coverings, or decorative articles), sleeping (such as a mattress bag, a pillow cover, or a sheet), leather (such as a base fabric for artificial leather or a base fabric for synthetic leather), living materials (such as a storage article, a packaging material, and a bag), and industrial materials.

[0124] Examples of industrial materials include abrasives, oil-absorbing mats, ducts, papermaking felts, cushioning materials, drain materials for concrete formwork, drainage materials, thermal insulation materials, soundproofing materials, shock-absorbing materials, vibration-damping materials; ship materials (such as interior materials, parts, seat cushion base materials, and sound-absorbing materials; wipes (such as cleaning sheets and cosmetic sheets); electrical materials (such as electrical insulating materials for printed circuit boards, electromagnetic shielding materials, wire-holding tapes, and battery separators); product base materials (such as base materials for fiber-reinforced plastics, printing base materials, synthetic paper base materials, electrostatic recording base materials, adhesive tape base materials, thermal transfer sheet base materials, and radiation-shielding mat base materials); office automation equipment materials (such as floppy disk liners and floppy disk packaging materials); audiovisual equipment materials (such as speaker diaphragms and sound-absorbing panels); rolls (such as buff rolls, liquid-squeezing rolls, and oil-coating rolls); equipment components (such as V-belts, conveyor belts, and timing belts); and musical instrument materials (such as piano key cushions and hammer rails).

[0125] The industrial material of the first aspect may be a laminate in which a film, an adhesive layer, and an SB nonwoven fabric are laminated in this order.

[0126] The industrial material of the first aspect may be an SMS laminate or an SMMS laminate. The SMS laminate is formed by laminating a spunbond nonwoven fabric, a melt-blown nonwoven fabric, and a spunbond nonwoven fabric in this order. The SMMS laminate is formed by laminating a spunbond nonwoven fabric, a melt-blown nonwoven fabric, a melt-blown nonwoven fabric, and a spunbond nonwoven fabric in this order. The basis weight of the SMS laminate or the SMMS laminate is adjusted according to the application, and may be from 10 g / m 2< to 1500 g / m 2< .

[0127] The industrial material of the first aspect may be a laminate of the SB nonwoven fabric of the present disclosure and a film. Examples of the film include a film having liquid impermeability and vapor permeability, and a film having vapor impermeability. The film having liquid impermeability and vapor permeability has air permeability. Therefore, by combining the SB nonwoven fabric having excellent air permeability of the present disclosure with a film having liquid impermeability and vapor permeability, the air permeability of the industrial material of the first aspect is excellent. The vapor permeability of the film may be from 500 g / m 2< / 24 hours to about 20,000 g / m 2< / 24 hours. The breathable film may be a microporous film or a monolithic film.

[0128] Examples of the film include films of thermoplastic synthetic resins (such as a polyethylene-based resin, a polypropylene-based resin, a polyurethane-based resin, and a polyvinyl chloride-based resin) generally used in agriculture and the like. The film may be a single layer or a multilayer. The film may be colored or uncolored.

[0129] The film may be a breathable film (That is, the porous film) having breathability or a non-breathable film having no breathability. When the film is a porous film, the agricultural covering material can appropriately release the humidity and hot air of the covered ground surface. When the film is an non-breathable film, the agricultural covering material functions as a water shielding layer, and can prevent rainwater from rapidly leaking into the soil. In fruit cultivation, by covering the ground surface with such an non-breathable film, the supply of water for several months before harvest of the fruit can be reduced, and the sugar content of the fruit can be improved.

[0130] The adhesive layer is formed of 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 singly or may be used in combination of two or more kinds thereof.

[0131] In the agricultural covering material of the first aspect, the hollow fibers of the first aspect are excellent in single yarn tenacity and single yarn elongation, and the SB nonwoven fabric containing the hollow fibers is excellent in MD tensile strength and also excellent in light transmittance. Therefore, the agricultural covering material of the first aspect is used by being laid on a ground surface for growing crops, for example. When the agricultural covering material of the first aspect has the above-described laminated structure, the agricultural covering material of the first aspect is preferably laid so that the SB nonwoven fabric is on the ground surface side.(2) Second Aspect

[0132] The hollow fiber production method of the second aspect includes producing a hollow fibers by spin-lay lamination using a hollow fiber production apparatus. The production apparatus includes a spinneret. The slot ratio (length / width) of the spinneret is less than 8. The take-up speed (hereinafter, also simply referred to as "take-up speed") of the hollow fibers when the hollow fibers are laminated on a moving screen is from 2000 m / min to 4000 m / min.

[0133] Since the hollow fiber production method according to the second aspect has the above configuration, the Cv of hollowness of the obtained hollow fibers can be less than 10% by forming a stable spinning line. In addition, the Cv of the cross-sectional area of the hollow fibers can be 300% 3< or less.

[0134] The hollow fiber production method according to the second aspect is the same as the hollow fiber production method according to the first aspect except that it is not essential to produce the hollow fibers according to the first aspect, but it is essential to have a slot ratio (length / width) of less than 8 and a take-up speed of from 2000 m / min to 4000 m / min. Therefore, in the description of the second aspect, the description of the first aspect is cited, and the description overlapping with the description of the first aspect in the description of the second aspect is omitted.(3) Modification(3.1) SB Nonwoven Fabric

[0135] An SB nonwoven fabric (hereinafter, also referred to as "SB nonwoven fabric") of a modification is an SB nonwoven fabric including hollow fibers, in which: a coefficient of variation of hollowness (hereinafter, also referred to as "Cv of hollowness") of the hollow fibers is less than 10%, and the hollow fibers have an average outer diameter of 30 µm or more.

[0136] Since the SB nonwoven fabric of the modification has the above configuration, the SB nonwoven fabric includes hollow fibers excellent in tensile strength and elongation as in the first aspect. Therefore, the SB nonwoven fabric of the modification is excellent in the MD tensile strength and the MD elongation of the SB nonwoven fabric of the modification.

[0137] The SB nonwoven fabric of the modification is the same as the SB nonwoven fabric of the first aspect except that the hollow fibers have an average outer diameter of 30 µm or more. Therefore, in the description of the modification, the description of the first aspect is cited, and the description overlapping with the description of the hollow fiber production method of the first aspect in the description of the hollow fiber production method of the modification is omitted.

[0138] The hollow fibers have an average outer diameter of 30 µm or more. Even when the hollow fibers have an average outer diameter of 30 µm or more, the Cv of hollowness of the hollow fibers of the present disclosure can be less than 10%. Since the Cv of hollowness is less than 10%, even when the hollow fibers have an average outer diameter of 30 µm or more, the single yarn elongation is superior to a configuration in which the hollow fiber has an average outer diameter of less than 30 µm. Thus, SB nonwoven fabrics containing hollow fibers of 30 µm or more are useful in industrial materials requiring relatively high mechanical strength.

[0139] The method for measuring the average outer diameter of the hollow fibers is the same as the method described in Examples.

[0140] In the modification, as in the first aspect, the value represented by the following Formula (I) (hereinafter, also referred to as "Cv of the cross-sectional area of the hollow fibers") is preferably from 300% 3< or less, preferably from 100% 3< to 300% 3< , and preferably from 100% 3< to 250% 3< .

[0141] In the modification, as in the first aspect, the hollow fibers preferably have an average hollowness of from 10% to 40%.

[0142] In the modification, as in the first aspect, the hollow fibers preferably contain a polypropylene-based resin.

[0143] In a modification, the hollow fibers preferably have a single yarn tenacity of 19.0 mN / denier or more and a single yarn elongation of 300% or more, and the hollow fibers preferably have a single yarn tenacity of 22.0 mN / denier or more and a single yarn elongation of 360% or more.

[0144] In a modification, the hollow fibers preferably have an average outer diameter of from 30 µm to 40 µm and an average hollowness of from 10% to 40%.

[0145] The sanitary material of the modification is a sanitary material including the SB nonwoven fabric of the modification. The sanitary material of the modification is the same as the sanitary material of the first aspect except that the SB nonwoven fabric of the modification is included instead of the SB nonwoven fabric of the first aspect.

[0146] The industrial material of the modification is an industrial material including the SB nonwoven fabric of the modification. The industrial material of the modification is the same as the industrial material of the first aspect except that the SB nonwoven fabric of the modification is included instead of the SB nonwoven fabric of the first aspect.

[0147] Since the fiber diameter is larger than that of the industrial material of the first aspect, it is useful for applications in which higher mechanical strength is required and applications in which high air permeability is required. In addition, since the larger the fiber diameter, the larger the amount of air contained in the hollow fibers, a higher heat retaining effect can be expected.

[0148] The hollow fiber production apparatus according to a modification is a hollow fiber production apparatus for producing hollow fibers according to the modification, the hollow fiber production apparatus including a spinneret, in which a ratio of a length of a slot to a width of the slot of the spinneret is less than 8.

[0149] The hollow fiber production apparatus according to the modification is the same as the hollow fiber production apparatus according to the second aspect except for producing a SB nonwoven fabric according to the modification instead of the SB nonwoven fabric according to the first aspect.

[0150] The hollow fiber production method according to the modification includes producing hollow fibers according to the modification by spin-lay lamination, in which a take-up speed of the hollow fibers when the hollow fibers are laminated on a moving screen is from 2000 m / min to 4000 m / min.

[0151] The hollow fiber production method of the modification is the same as the hollow fiber production method of the first aspect except that the SB nonwoven fabric of the modification is produced instead of the SB nonwoven fabric of the first aspect. It is a preferable aspect in the hollow fiber production method according to the modification that the slot ratio (length / width) of the spinneret is less than 8 and the take-up speed is necessarily from 2000 m / min to 4000 m / min.EXAMPLES

[0152] Hereinafter, the present disclosure will be described in more detail based on Examples, but the present disclosure is not limited to the following Examples. Materials, amounts used, proportions, processing procedures, and the like shown in the following Examples can be appropriately modified without departing from the gist of the present disclosure. Note that "parts" means "parts by mass" unless otherwise specified.[1] Measurement Method[1.1] Collection of Fiber Sample for Measurement

[0153] Fiber samples for measuring the outer diameter, hollowness, single yarn tenacity, and single yarn elongation of hollow fibers were collected as follows. Using tweezers, 100 single fibers having a length of 100 mm were randomly selected from the SB nonwoven fabric so as not to be stretched. The midpoint of each of these single fibers was cut with a razor blade in a direction perpendicular to the fiber axial direction of the hollow fibers to prepare two sets of 10 single fibers having a length of 50 mm. One set was used for measuring the outer diameter, the single yarn tenacity, and the single yarn elongation. The remaining one set was used for the measurement of hollowness.[1.2] Average Outer Diameter [µm] and Cv Value [%] of Outer Diameter

[0154] Using an optical microscope (ECLIPSE E-400 manufactured by Nikon Corporation), the outer diameter of a single fiber to be measured was measured at 10 arbitrary points in the fiber axial direction. This operation was performed on 100 single fibers. The average of the measured values of the outer diameters of 1000 pieces was taken as the "average outer diameter" of the single fibers. A value obtained by multiplying the standard deviation of the measured values of the outer diameters of 1000 pieces by 100 and dividing the product by the average of the outer diameters was defined as the "Cv value of the outer diameter" of the single fiber.[1.3] Average Hollowness [%] and Cv Value [%] of Outer Diameter

[0155] The single fiber to be measured was embedded in an epoxy resin, and subsequently 10 arbitrary portions of the single fiber were cut in the fiber axial direction using a microtome to obtain 10 test pieces. These tests pieces were observed using an optical microscope (ECLIPSE E-400, manufactured by Nikon Corporation], and the hollowness of the fiber cross sections at 10 arbitrary portions was measured in the fiber axial direction of the tests pieces. This operation was performed on 10 test pieces. The average of the measured values of the hollowness of 100 points was taken as the "average hollowness" of the single fiber. A value obtained by multiplying the standard deviation of the measured values of the hollowness of 100 points by 100 and dividing the product by the average hollowness was taken as the "Cv value of hollowness" of the single fiber.[1.4] Fineness [denier]

[0156] The fineness of a single fiber was determined from the following Formula (A) using the average of the measured values of the outer diameter and the average of the measured values of the hollowness. In Formula (A), "0.91" is the density (g / cm 3< ) of polypropylene. In Comparative Example 7 (solid fiber), the fineness was calculated by assuming the average hollowness to be 0. [1.5] Single Yarn Tenacity [N / denier] and Single Yarn Elongation [%]

[0157] In accordance with JIS L 1095 (Method 9.5.1 ), the single fiber used for the measurement of the outer diameter was subjected to a tensile test, and the tensile load and the elongation were measured. A tensile tester (Instron 5564 type, manufactured by Instron Japan Co., Ltd.) was used for the tensile test. Conditions of the tensile test were that a distance between chucks was 20 mm, and a tensile speed was 20 mm / min. The measured value of the tensile load was defined as "single yarn tenacity". The measured value of elongation was defined as "single yarn elongation". Using the measured value of the single yarn tenacity, the single yarn tenacity was evaluated according to the following criteria. Using the measured value of the single yarn elongation, the single yarn elongation was evaluated according to the following criteria. An acceptable evaluation of single yarn tenacity is "A1". An acceptable evaluation of single yarn elongation is "A2".[1.5.1] Evaluation Criteria of Single Yarn Tenacity

[0158] "A1": Single yarn tenacity ≥ 19.0 mN / denier "B1": Single yarn tenacity < 19.0 mN / denier [1.5.2] Evaluation Criteria of Single Yarn Elongation

[0159] "A2": Single yarn elongation ≥ 300% "B2": single yarn elongation < 300% [1.6] Basis Weight [g / m 2< ]

[0160] From the SB nonwoven fabric, 10 test pieces of 100 mm (machine direction (MD)) ×100 mm (width direction (CD)) were sampled. The test pieces were sampled at the center in the width direction (CD). Next, under an environment of 20°C and a relative humidity of 50%RH, the mass [g] of each collected test piece was measured using an upper pan electronic balance (manufactured by KENSEI KOGYO Co., Ltd.). The average mass of the test pieces was converted to a mass [g] per 1 m 2< and rounded off to the first decimal place. The resulting value was taken as the "basis weight" of the nonwoven fabric.[1.7] MD Tensile Strength [N / 25 mm] and MD Elongation [%]

[0161] 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] (shifted to JIS L 1913:2010, corresponding to ISO 9073-3:1989). From the SB nonwoven fabric, 10 test pieces of 200 mm (machine direction (MD)) × 25 mm (width direction (CD)) were sampled. The test pieces were sampled at 10 arbitrary points along the width direction (CD) of the SB nonwoven fabric. Using a tensile tester, the test pieces were pulled in the machine direction (MD) at a distance between chucks of 100 mm and a head speed of 100 mm / min to determine the maximum tensile strength [N / 25 mm] and the elongation percentage [%] at that time. The average of the 10 measured values of the maximum tensile strength was taken as the "MD tensile strength". The average of the measured values of the maximum elongation at 10 points was taken as "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.[1.7.1] Evaluation Criteria of MD Tensile Strength

[0162] "A3": MD tensile strength ≥ 20.0 N / 25 mm "B3": MD tensile strength < 20.0 N / 25 mm [1.7.2] Evaluation Criteria of MD Elongation

[0163] "A4": MD elongation ≥ 60% "B4": MD elongation < 60% [1.8] Air Permeability [cm 3< / cm 2< ·sec]

[0164] From the SB nonwoven fabric, 10 test pieces of 100 mm (machine direction (MD)) ×100 mm (width direction (CD)) were sampled. The airflow volume at a pressure difference of 125 Pa was measured in accordance with JIS L1096 using a Frazier-type tester. The average of 10 measured values of air permeability was taken as "air permeability". Using the measured values of air permeability, air permeability was evaluated according to the following criteria.[1.8.1] Evaluation Criteria of Air Permeability

[0165] "A5": Air permeability ≥ 500 cm 3< / cm 2< ·sec "B5": Air permeability < 500 cm 3< / cm 2< ·sec [1.9] Light Transmittance [%]

[0166] Light transmittance was measured at 10 arbitrary points of the SB nonwoven fabric using a formation tester FMT-MIII (manufactured by Nomura Shoji Co., Ltd.). The average of the 10 measured values of light transmittance was taken as "light transmittance". Using the measured value of the light transmittance, the light transmittance was evaluated according to the following criteria.[1.9.1] Evaluation Criteria of Air Permeability

[0167] "A6": Light transmittance ≤ 93.4% "B6": Light transmittance > 93.4% [2] Examples and Comparative Examples[2.1] Example 1

[0168] The following raw material was prepared. hPP: homopolypropylene (melting point: 163°C, MFR (temperature: 230°C, load: 2.16 kg): 60 g / 10 min)

[0169] An SB nonwoven fabric was produced as follows using a sealed SB nonwoven fabric producing apparatus 100 shown in Figs. 1 and 2.

[0170] The raw material hPP was melted using an extruder 11 having a diameter of 75 mm. The melt of hPP was introduced into a die with spinneret 12. The spinneret 12 was for hollow fibers. The slot ratio (length / width) of slot 121A of the spinneret 12 was a numerical value shown in Table 1. The number of slots of hole shaped 121A of the spinning hole 120 was 6. The set extrusion temperature of the extruder 11 was 200°C. The introduction amount of the melt of hPP into the die was adjusted so that the resin discharge rate (single-hole discharge rate) per one place of the spinneret 12 was 0.8 g / min. The hollow fibers discharged from the spinneret 12 were cooled with spinning air A and stretched to obtain single fibers. The temperature of the spinning air A was 20°C. The wind speed of the take-up speed was a numerical value shown in Table 1.

[0171] The single fibers spun as described above were deposited on the screen 21 to obtain a web. The web was embossed with embossing rolls (embossed area ratio: 18%, Emboss 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.[2.2] Examples 2 to 7 and Comparative Examples 1 to 6

[0172] An SB nonwoven fabric was obtained in the same manner as in Example 1 except that the extrusion temperature, the single-hole discharge rate, and the wind speed of the spinning air were changed as shown in Tables 1 and 2.[2.3] Examples 8 and 9

[0173] An SB nonwoven fabric was obtained in the same manner as in Example 1 except that hPP was changed to the following rPP and the extrusion temperature, the single-hole discharge rate, and the wind speed of the spinning air were changed as shown in Table 1. rPP: propylene / ethylene random copolymer (melting point: 138°C, MFR (temperature: 230°C, load: 2.16 kg): 60 g / 10 min) [2.4] Comparative Example 7

[0174] An SB nonwoven fabric was obtained in the same manner as in Example 1 except that the extrusion temperature, the single-hole discharge rate, and the wind speed of the spinning air were changed as shown in Table 2, and the spinneret 12 for hollow fibers was changed to a spinneret for solid fibers.[3] Results

[0175] [Table 1]Example 1Example 2Example 3Example 4Example 5Example 6Example 7Example 8Example 9Spinning conditionExtrusion temperature°C200200220240250240220220240Resin-h PPh PPh PPh PPh PPh PPh PPr PPr PPSingle-hole discharge rateg / min0.80.40.40.40.40.30.80.40.4Slot ratio (length / width)-444444444Take-up speedm / min235329413529352936853122242135293529Fiber configurationStructure-HollowHollowHollowHollowHollowHollowHollowHollowHollowOuter diameterAverageµm34.025.620.520.016.515.033.020.819.4Cv%5.14.44.05.55.35.45.35.44.9HollownessAverage%26.626.326.219.315.412.125.323.419.4Cv%8.89.07.97.87.26.98.38.19.5(Cv of outer diameter) 2< ×Cv of hollowness% 3< 229174126236184211212236228Finenessdenier6.12.82.12.02.01.56.22.32.1Fiber evaluationSingle yarn tenacityMeasured valuemN / denier22.921.119.324.420.121.624.119.520.0Evaluation-A1A1A1A1A1A1A1A1A1Single yarn elongationMeasured value%395354302329331312381301311Evaluation-A2A2A2A2A2A2A2A2A2Nonwoven fabric configurationEmbossed area ratio%181818181818181818Basis weightg / m 2< 202020202020202020Nonwoven fabric evaluationMD tensile strengthMeasured valueN / 25 mm21.025.023.222.420.921.522.220.221.1Evaluation-A3A3A3A3A3A3A3A3A3MD elongationMeasured value%72.565.168.470.174.364.469.145.135.3Evaluation-A4A4A4A4A4A4A4B4B4Air permeabilityMeasured valuecm 3< / cm 2< ·sec622518490481477465610501497Evaluation-A5A5B5B5B5B5A5A5B5Light transmittanceMeasured value%92.593.492.893.192.391.892.492.993.2Evaluation-A6A6A6A6A6A6A6A6A6 [Table 2] Comparative Example 1Comparative Example 2Comparative Example 3Comparative Example 4Comparative Example 5Comparative Example 6Comparative Example 7Spinning conditionExtrusion temperature°C200200220240200230200Resin-h PPh PPh PPh PPh PPh PPh PPSingle-hole discharge rateg / min0.80.40.40.40.40.50.4Slot ratio (length / width)-1212121248-Take-up speedm / min2647317638823882468935293176Fiber configurationStructure-HollowHollowHollowHollowHollowHollowSolidOuter diameterAverageµm33.925.220.119.918.218.325.2Cv%8.07.86.24.59.58.88.2HollownessAverage%20.126.724.319.622.217.8-Cv%12.011.218.315.319.117.2-(Cv of outer diameter) 2< × Cv of hollowness% 3< 76868170431017241332-Finenessdenier5.92.82.61.61.51.52.8Fiber evaluationSingle yarn tenacityMeasured valuemN / denier18.015.714.117.417.917.315.6Evaluation-B1B1B1B1B1B1B1Single yarn elongationMeasured value%290293293299282276289Evaluation-B2B2B2B2B2B2B2Nonwoven fabric configurationEmbossed area ratio%18181818181818Basis weightg / m 2< 20202020202020Nonwoven fabric evaluationMD tensile strengthMeasured valueN / 25 mm16.919.015.518.117.817.219.1Evaluation-B3B3B3B3B3B3B3MD elongationMeasured value%53.453.951.552.952.250.241.2Evaluation-B4B4B4B4B4B4B4Air permeabilityMeasured valuecm 3< / cm 2< ·sec626501489492488478467Evaluation-A5A5B5B5B5B5B5Light transmittanceMeasured value%92.192.892.292.492.192.493.5Evaluation-A6A6A6A6A6A6B6

[0176] The SB nonwoven fabrics of Comparative Examples 1 to 6 contained only a plurality of hollow fibers. The Cv of hollowness of the hollow fibers of Comparative Examples 1 to 6 was more than 10%. Therefore, in Comparative Examples 1 to 6, the single yarn tenacity was evaluated as "B1", and the single yarn elongation was evaluated as "B2".

[0177] The SB nonwoven fabric of Comparative Example 7 did not contain hollow fibers. Therefore, in Comparative Example 7, the single yarn tenacity was evaluated as "B1", and the single yarn elongation was evaluated as "B2".

[0178] As a result, it was found that the SB nonwoven fabrics of Comparative Examples 1 to 7 were not "SB nonwoven fabrics including hollow fibers excellent in tensile strength and elongation".

[0179] The SB nonwoven fabrics of Examples 1 to 9 contained only a plurality of hollow fibers. The Cv of hollowness of the hollow fibers of Examples 1 to 9 was less than 10%. Therefore, in Examples 1 to 9, the single yarn tenacity was evaluated as "A1", and in the SB nonwoven fabrics of Examples 1 to 7, the single yarn elongation was evaluated as "A2".

[0180] As a result, it was found that the SB nonwoven fabrics of Examples 1 to 9 were "SB nonwoven fabrics including hollow fibers excellent in tensile strength and elongation".

[0181] The disclosure of Japanese Patent Application No. 2023-167879 filed on September 28, 2023 is incorporated herein by reference in its entirety.

[0182] All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

Claims

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

2. The spunbond nonwoven fabric according to claim 1, wherein a value represented by the following Formula (I) is 300%3 or less:

3. The spunbond nonwoven fabric according to 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 hollowness of from 10% to 40%.

5. The spunbond nonwoven fabric according to 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 yarn tenacity of 19.0 mN / denier or more and a single yarn elongation of 300% or more.

7. The spunbond nonwoven fabric according to claim 1, wherein the hollow fibers have an average outer diameter of from 10 µm to less than 30 µm and an average hollowness of from 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. A hollow fiber production apparatus for producing the hollow fibers according to any one of claims 1 to 7, the hollow fiber production apparatus comprising a spinneret, wherein a ratio of a length of a slot of the spinneret to a width of the slot is less than 8.

11. A hollow fiber production method, comprising: producing the hollow fibers according to any one of claims 1 to 7 by spin-lay lamination, wherein a take-up speed of the hollow fibers when the hollow fibers are laminated on a moving screen is from 2000 m / min to 4000 m / min.

12. A hollow fiber production method, comprising: producing hollow fibers by spin-lay lamination using a hollow fiber production apparatus, the hollow fiber production apparatus comprising a spinneret, wherein: a ratio of a length of a slot of the spinneret to a width of the slot is less than 8, and a take-up speed of the hollow fibers when the hollow fibers are laminated on a moving screen is from 2000 m / min to 4000 m / min.

Images