Spun-bonded nonwoven fabric, sanitary material, industrial material, device for producing hollow fibers, and method for producing hollow fibers

Abstract

The SB non-woven fabric of the present disclosure comprises a plurality of hollow fibers. The coefficient of variation in the hollow ratio of the hollow fibers is less than 10%.

Description

Technical Field

[0001] This disclosure relates to apparatus for manufacturing spunbond nonwoven fabrics, sanitary materials, industrial materials, hollow fibers, and methods for manufacturing hollow fibers. Background Technology

[0002] Nonwoven fabrics have long been widely used for various applications due to their excellent breathability and softness. Therefore, various properties corresponding to their intended uses are required for nonwoven fabrics, and improvements in these properties are demanded. For example, nonwoven fabrics used as covering materials in agriculture require specified mechanical strength.

[0003] Patent Document 1 discloses an agricultural sheet. This agricultural sheet is a long-fiber nonwoven fabric (hereinafter also referred to as "spunbond nonwoven fabric") with a specific weight per unit area. The spunbond nonwoven fabric is composed of polypropylene fibers with a fiber diameter of 25 μm or more and a specific hollow cross-section.

[0004] Patent Document 1 specifically discloses a method for manufacturing agricultural sheets using a general spunbond nonwoven fabric manufacturing 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. This yields long fibers with a hollow cross-section (hereinafter also referred to as "hollow fibers"). The hollow fibers are then cooled using a cooling device, drawn and refined using a filament suction device positioned below at a traction speed of 4800 m / min, and opened using a corona discharge unit, causing them to accumulate on a moving mesh screen. This results in a fiber web on the mesh screen. The fiber web is then heat-pressed using an embossing roller. This yields a spunbond nonwoven fabric (agricultural sheet).

[0005] Patent Document 1: Japanese Patent Application Publication No. 8-126440 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, when the hollow fibers constituting the spunbond nonwoven fabric disclosed in Patent Document 1 are stretched along the fiber axis, a portion of the fibers sometimes breaks, and it may be difficult to elongate. That is, the mechanical strength of the spunbond nonwoven fabric disclosed in Patent Document 1 may sometimes be insufficient depending on the degree of stretching in the fiber axis. Therefore, there is a need for a spunbond nonwoven fabric having hollow fibers that are not prone to fiber breakage when stretched along the axial direction of the hollow fibers and are easy to elongate (i.e., hollow fibers with excellent tensile strength and elongation).

[0008] Furthermore, from the perspective of improving production efficiency, high-speed production of spunbond nonwoven fabrics is required. However, if the production speed of hollow fibers is increased, fiber breakage may sometimes occur. Such fiber breakage tends to occur more easily in hollow fibers with a large deviation in hollowness. Therefore, even in the case of high-speed manufacturing of spunbond nonwoven fabrics, hollow fibers with a small deviation in hollowness and spunbond nonwoven fabrics containing such hollow fibers are required.

[0009] In view of the above-mentioned issues, the present disclosure aims to provide spunbond nonwoven fabrics, sanitary materials, industrial materials, hollow fiber manufacturing apparatus, and hollow fiber manufacturing methods that possess excellent tensile strength and elongation.

[0010] Methods for solving problems

[0011] The specific means to solve the above problems include the following methods.

[0012] <1> A spunbond nonwoven fabric comprising hollow fibers, wherein the coefficient of variation of the hollowness of the hollow fibers is less than 10%.

[0013] <2> According to the above <1> The spunbond nonwoven fabric, wherein the value shown in formula (I) below is 300%. 3 the following.

[0014] Equation (I): (The variation coefficient of the outer diameter of the hollow fiber mentioned above) 2 × The coefficient of variation of the hollow fiber ratio mentioned above

[0015] <3> According to the above <1> or <2> The spunbond nonwoven fabric wherein the average outer diameter of the hollow fibers is less than 30 μm.

[0016] <4> According to the above <1> ~ <3> In any one of the spunbond nonwoven fabrics, the average hollowness of the hollow fibers is 10% to 40%.

[0017] <5> According to the above <1> ~ <4> The spunbond nonwoven fabric according to any one of the following methods, wherein the hollow fibers comprise a polypropylene resin.

[0018] <6> According to the above <1> ~ <5> In any one of the spunbond nonwoven fabrics, the monofilament linear strength of the hollow fiber is 19.0 mN / denier or higher, and the monofilament elongation of the hollow fiber is 300% or higher.

[0019] <7> According to the above <1> ~ <6> In any one of the spunbond nonwoven fabrics, the average outer diameter of the hollow fibers is 10 μm or more and less than 30 μm, and the average hollowness of the hollow fibers is 10% to 40%.

[0020] <8> A sanitary material comprising the above <1> ~ <7> The spunbond nonwoven fabric described in any one of the following statements.

[0021] <9> An industrial material comprising the above <1> ~ <7> The spunbond nonwoven fabric described in any one of the following statements.

[0022] <10> A hollow fiber manufacturing apparatus for manufacturing the above-mentioned... <1> ~ <7> The hollow fiber according to any one of the above-mentioned manufacturing apparatus has a spinneret, wherein the ratio of the length of the slot of the spinneret to the width of the slot is less than 8.

[0023] <11> A method for manufacturing hollow fibers, which involves spinning and layering to produce the aforementioned... <1> ~ <7> The hollow fiber as described in any one of the following, wherein the traction speed (Haul-off speed) of the hollow fiber when it is stacked on the moving mesh curtain is 2000 m / min to 4000 m / min.

[0024] <12> A method for manufacturing hollow fibers involves producing hollow fibers by spinning and stacking using a hollow fiber manufacturing apparatus having a spinneret. The length of the slot of the spinneret is less than 8 times the width of the slot, and the traction speed (Haul-off speed) of the hollow fibers when stacked on a moving mesh curtain is 2000 m / min to 4000 m / min.

[0025] <13> A spunbond nonwoven fabric comprising hollow fibers, wherein the coefficient of variation of the hollowness of the hollow fibers is less than 10%, and the average outer diameter of the hollow fibers is 30 μm or more.

[0026] <14> According to the above <13> The spunbond nonwoven fabric, wherein the value represented by the following formula (I) is 300%. 3 the following.

[0027] Equation (I): (The variation coefficient of the outer diameter of the hollow fiber mentioned above) 2 × The coefficient of variation of the hollow fiber ratio mentioned above

[0028] <15> According to the above <13> or <14> The spunbond nonwoven fabric wherein the average hollowness of the hollow fibers is 10% to 40%.

[0029] <16> According to the above <13> ~ <15> The spunbond nonwoven fabric according to any one of the following methods, wherein the hollow fibers comprise a polypropylene resin.

[0030] <17> According to the above <13> ~ <16> In any one of the spunbond nonwoven fabrics, the monofilament linear strength of the hollow fiber is 19.0 mN / denier or higher, and the monofilament elongation of the hollow fiber is 300% or higher.

[0031] <18> According to the above <13> ~ <17> In any one of the spunbond nonwoven fabrics, the average outer diameter of the hollow fibers is 30 μm to 40 μm, and the average hollowness of the hollow fibers is 10% to 40%.

[0032] <19> A sanitary material comprising the above <13> ~ <18> The spunbond nonwoven fabric described in any one of the following statements.

[0033] <20> An industrial material comprising the above <13> ~ <18> The spunbond nonwoven fabric described in any one of the following statements.

[0034] <21> A hollow fiber manufacturing apparatus for manufacturing the above-mentioned... <13> ~ <18> The hollow fiber according to any one of the above-mentioned manufacturing apparatus has a spinneret, wherein the ratio of the length of the slot of the spinneret to the width of the slot is less than 8.

[0035] <22> A method for manufacturing hollow fibers, which involves spinning and layering to produce the aforementioned... <13> ~ <18> The hollow fiber as described in any one of the following, wherein the traction speed of the hollow fiber when it is stacked on the moving mesh curtain is 2000 m / min to 4000 m / min.

[0036] <23> A method for manufacturing hollow fibers involves producing hollow fibers by spinning and stacking using a hollow fiber manufacturing apparatus. The manufacturing apparatus has a spinneret, the length of which is less than 8 relative to the width of which is less than 8. The traction speed of the hollow fibers when stacked on a moving mesh curtain is 2000 m / min to 4000 m / min.

[0037] Invention Effects

[0038] According to one aspect of this disclosure, spunbond nonwoven fabrics, sanitary materials, industrial materials, an apparatus for manufacturing hollow fibers, and a method for manufacturing hollow fibers are provided, all possessing excellent tensile strength and elongation. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of a closed spunbond nonwoven fabric manufacturing apparatus illustrating a first embodiment of the present disclosure.

[0040] Figure 2 This is a schematic diagram of an example of the orifice shape of the slot of the spinneret according to a first embodiment of the present disclosure.

[0041] Figure 3 This is a cross-sectional view of the spinning orifice of the spinneret according to a first embodiment of the present disclosure.

[0042] Figure 4 This is a schematic diagram of an example of the orifice shape of the slot of the spinneret according to a first embodiment of the present disclosure.

[0043] Figure 5 This is a schematic diagram of an example of the orifice shape of the slot of the spinneret according to a first embodiment of the present disclosure. Detailed Implementation

[0044] The embodiments of this disclosure will now be described. These descriptions and examples illustrate the embodiments but do not limit the scope of the embodiments.

[0045] In the numerical ranges described in this disclosure, the upper or lower limit of one numerical range can be replaced by the upper or lower limit of another numerical range described in other stages. In the numerical ranges described in this disclosure, the upper or lower limit of that numerical range can be replaced by the values ​​shown in the embodiments.

[0046] In this disclosure, each component may comprise multiple corresponding substances. When referring to the amount of each component in the composition, if multiple substances equivalent to each component are present in the composition, unless otherwise specified, it refers to the total amount of the multiple substances present in the composition.

[0047] In this disclosure, the term "process" is not limited to independent processes; even when it is difficult to distinguish them from other processes, they are included as long as the purpose of the process is achieved. The numerical range indicated by "~" in this disclosure represents the range of minimum and maximum values, respectively, before and after the "~". In this disclosure, when multiple substances equivalent to each component are present in the composition, unless otherwise specified, the content of each component in the composition refers to the total amount of the multiple substances present in the composition.

[0048] In this disclosure, "spunbond nonwoven fabric" refers to a nonwoven fabric made by combining spunbond fiber webs using one or more bonding methods (e.g., embossing). "Spunbond fiber web" refers to a fiber web formed by spinning lamination. "Spin-lay lamination" refers to a method of creating a fiber web by extruding molten or dissolved polymer from a spinneret (i.e., a spinning orifice) and laminating single fibers onto a moving mesh screen.

[0049] (1) First method

[0050] (1.1) Spunbond nonwoven fabric

[0051] The spunbond nonwoven fabric (hereinafter also referred to as "SB nonwoven fabric") of the first aspect of this disclosure comprises a plurality of hollow fibers. The coefficient of variation of the hollowness ratio of the aforementioned hollow fibers (hereinafter also referred to as "Cv of hollowness ratio") is less than 10%.

[0052] "Hollow fiber" refers to a straw-like fiber. In more detail, a hollow fiber has one or more hollow sections extending along the fiber axis inside.

[0053] The coefficient of variation (Cv) of the hollow fiber hollow ratio quantitatively represents the deviation of the hollow ratio along the fiber axis of the multiple hollow fibers constituting the SB nonwoven fabric. A Cv closer to 0 indicates that the hollow fibers in the SB nonwoven fabric have a more uniform shape, the hollow ratios of multiple hollow fibers are approximately the same, and the deviation in the hollow ratio along the fiber cross-section is less. "Hollow ratio" represents 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 a cross-section orthogonal to the fiber axis of the hollow fiber collected from the SB nonwoven fabric. The method for determining the hollow ratio Cv is the same as that described in the examples.

[0054] The SB nonwoven fabric of the first embodiment, having the above-described structure, possesses hollow fibers with excellent tensile strength and elongation. Therefore, the SB nonwoven fabric of the first embodiment exhibits excellent tensile strength (hereinafter also referred to as "MD tensile strength") in the mechanical direction (hereinafter also referred to as "mechanical direction (MD)"). In a preferred embodiment, the SB nonwoven fabric of the first embodiment exhibits excellent MD tensile strength and elongation (hereinafter also referred to as "MD elongation") in the mechanical direction (MD).

[0055] This effect is speculated to be based on the following reasons, but is not limited to these.

[0056] A hollowness ratio (Cv) of less than 10% indicates that, among the multiple hollow fibers constituting the SB nonwoven fabric, the wall thickness of the hollow portion constituting the hollow fiber in the cross-section (hereinafter also referred to as the "hollow fiber cross-section") obtained by cutting the hollow fiber in a direction perpendicular to its fiber axis is relatively uniform. Therefore, when the hollow fiber is stretched along the fiber axis, stress is less likely to concentrate in specific parts of the hollow fiber (especially in parts where the wall thickness of the hollow portion is thinner) compared to a structure where the wall thickness of the hollow portion is uneven in the cross-section of the hollow fiber. As a result, it is presumed that the hollow fiber contained in the SB nonwoven fabric of the first type has excellent tensile strength and excellent elongation. Therefore, the SB nonwoven fabric containing this hollow fiber has multiple hollow fibers with a relatively uniform cross-sectional shape, and thus has excellent tensile strength compared to SB nonwoven fabrics where the wall thickness of the hollow portion constituting the hollow fiber is uneven in the cross-section of the hollow fiber.

[0057] The mechanical orientation (MD) of SB nonwoven fabric can be determined by measuring the tensile strength of SB nonwoven fabric itself.

[0058] In the manufacture of SB nonwoven fabrics, the moving speed of the mesh curtain is typically set to be relatively fast from a productivity perspective. Therefore, the single fibers (long fibers) contained in the web tend to align parallel to the mechanical direction (MD) when layered on the mesh curtain. As a result, the tensile strength of the SB nonwoven fabric in the mechanical direction (MD) is higher than the tensile strength in the direction orthogonal to the mechanical direction (MD) (hereinafter also referred to as the "width direction (CD)"). Therefore, by measuring the tensile strength of the SB nonwoven fabric, the mechanical direction (MD) can be determined from the SB nonwoven fabric itself.

[0059] SB nonwoven fabric is a sheet-like material. SB nonwoven fabric can be a single-layer structure or a multi-layer structure.

[0060] There is no specific limit to the area weight of SB nonwoven fabric; it can be selected appropriately based on its intended use. The area weight of SB nonwoven fabric can be 5 g / m². 2 ~400g / m 2 It can also be 10g / m 2 ~50g / m 2 It can also be 15g / m 2 ~30g / m 2 As a sanitary material (i.e., from the viewpoint of imparting softness and breathability to SB nonwoven fabric), the preferred area weight of SB nonwoven fabric is 5 g / m². 2 ~30g / m 2 More preferably 5g / m 2 ~20g / m 2 As an industrial material (i.e., from the viewpoint of improving tensile strength), the preferred area weight of SB nonwoven fabric is 30 g / m². 2 ~400g / m 2 The method for determining the unit area weight of SB nonwoven fabric is the same as the method described in the examples.

[0061] There is no particular limitation on the thickness of SB nonwoven fabric; it can be selected appropriately according to its intended use. The thickness of SB nonwoven fabric can be 0.1mm~2.0mm or 0.2mm~1.0mm.

[0062] SB nonwoven fabrics can also be manufactured using known bonding methods. These known bonding methods include thermal bonding (e.g., embossing and ultrasonic bonding), mechanical weaving (e.g., needle punching and hydroentangling), methods using adhesives (e.g., hot melt adhesives and polyurethane-based adhesives), and extrusion lamination. These bonding methods can be appropriately selected depending on the application.

[0063] When SB nonwoven fabric is manufactured using a thermal bonding method, the SB nonwoven fabric can also have multiple embossed sections. An "embossed section" refers to a non-fibrous area where a portion of multiple hollow fibers has been thermally bonded. Specifically, an embossed section refers to a bonded area with an area of ​​0.1 mm. 2 The ratio of the total area of ​​the embossed portion to the surface area of ​​the SB nonwoven fabric (hereinafter referred to as "embossing area ratio") is not particularly limited, but from the viewpoint of tensile strength and breathability, it is preferably 5% to 50%. Furthermore, from the viewpoint of imparting softness, the embossing area ratio is preferably 5% to 25%. From the viewpoint of improving rigidity, the embossing area ratio can exceed 25% and be less than 50%.

[0064] SB nonwoven fabric comprises multiple hollow fibers. SB nonwoven fabric can also be a composite material containing other fibers besides hollow fibers (e.g., solid fibers, fibers without hollow sections in their cross-section, and short fibers). Short fibers can be carded fibers, pulp fibers, cotton fibers, or bamboo fibers, etc. When SB nonwoven fabric contains other fibers, the hollow fiber content can be adjusted appropriately according to the intended use. The hollow fiber content relative to the total amount of SB nonwoven fabric can be 80% by mass or more but less than 100% by mass, or 90% by mass or more but less than 100% by mass. SB nonwoven fabric can also consist solely of multiple hollow fibers.

[0065] The tensile strength (MD) of SB nonwoven fabric is not particularly limited and can be appropriately selected according to its intended use. The preferred tensile strength (MD) of SB nonwoven fabric is 20 N / 25 mm to 40 N / 25 mm. A tensile strength (MD) of 20 N / 25 mm or higher indicates excellent tensile strength, meaning the SB nonwoven fabric is less prone to tearing. Therefore, SB nonwoven fabric is suitable for use in sanitary materials and industrial materials (e.g., agricultural covering materials). The method for determining the tensile strength (MD) of SB nonwoven fabric is the same as that described in the examples.

[0066] The MD elongation of SB nonwoven fabric is not particularly limited and can be appropriately selected according to its intended use. An MD elongation of 30% or higher is acceptable, preferably 60% to 100%. An MD elongation of 60% or higher indicates excellent MD elongation of the SB nonwoven fabric. That is, the SB nonwoven fabric is easily stretched, exhibiting excellent softness and shape conformability. Therefore, SB nonwoven fabric is suitable for use in hygiene materials and industrial materials (such as agricultural covering materials). The method for determining the MD elongation of SB nonwoven fabric is the same as the method described in the examples.

[0067] There is no specific limitation on the air permeability of SB nonwoven fabric; it can be selected appropriately based on the intended use. The preferred air permeability of SB nonwoven fabric is 500 cm⁻¹. 3 / cm 2 ·sec~700cm 3 / cm 2 •sec. The air permeability of SB nonwoven fabric is 500cm. 3 / cm 2 A permeability of sec or higher indicates that air can easily permeate the SB nonwoven fabric. Therefore, SB nonwoven fabric is suitable for use in hygiene materials and industrial materials (such as agricultural covering materials). The method for measuring the air permeability of SB nonwoven fabric is the same as that described in the examples.

[0068] The light transmittance of SB nonwoven fabric is not particularly limited and can be appropriately selected according to its intended use. The preferred light transmittance of SB nonwoven fabric is 90.0% to 93.4%. A light transmittance of SB nonwoven fabric below 93.4% indicates that the SB nonwoven fabric moderately blocks light transmission. Therefore, SB nonwoven fabric is suitable for use as a covering material in agriculture. The method for measuring the light transmittance of SB nonwoven fabric is the same as the method described in the examples.

[0069] (1.1.1) Hollow fiber

[0070] The average outer diameter of the hollow fibers is not particularly limited and can be appropriately selected according to the application of the SB nonwoven fabric. As one embodiment, the average outer diameter of the hollow fibers is preferably less than 30 μm.

[0071] The average outer diameter of hollow fibers can be less than 30 μm, and the Cv of hollow fibers can be less than 10%. From the viewpoint of imparting softness, the average outer diameter of hollow fibers can be less than 25 μm or more than 5 μm. The smaller the average outer diameter of hollow fibers, the lower the surface friction coefficient, and the greater the smoothness when in contact with skin. Therefore, SB nonwoven fabric is useful for hygiene materials, artificial leather, etc.

[0072] From the perspective of improving the air permeability of nonwoven fabrics, the average outer diameter of hollow fibers can be above 20 μm. The coarser the outer diameter of the fibers, the higher the abrasion resistance. Therefore, SB nonwoven fabric is useful for suppressing fuzzing.

[0073] The method for determining the average outer diameter of the hollow fibers is the same as that described in the examples.

[0074] The coefficient of variation (hereinafter also referred to as "Cv of outer diameter") of the hollow fibers in the SB nonwoven fabric manufactured by spinning and laminating is 10.0% or less. The Cv of the outer diameter of the plurality of hollow fibers contained in the SB nonwoven fabric is preferably 2.0% to 10.0%, more preferably 3.0% to 10.0%. When the Cv of the outer diameter is within the above-mentioned range, the 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 contained in the SB nonwoven fabric becomes narrower. For example, SB nonwoven fabrics with an outer diameter Cv of 10.0% or less are useful for SB nonwoven fabrics with low unit area weight that suppresses batch-to-batch variations, and are useful for applications such as filter materials. The method for measuring the Cv of the outer diameter is the same as the method described in the examples.

[0075] There is no particular limitation on the average hollow fiber ratio, which can be appropriately selected according to the application of SB nonwoven fabric. The preferred average hollow fiber ratio is 10% to 40%.

[0076] The higher the average hollow ratio of hollow fibers, the greater the reduction in environmental impact. Furthermore, for applications requiring thermal insulation (such as hand warmers), a high average hollow ratio is desirable. From this perspective, an average hollow ratio of 10% or higher is preferably preferred for hollow fibers.

[0077] From the perspective of the monofilament strength and monofilament elongation of hollow fibers, the average value of the hollow fiber hollowness is preferably below 40%.

[0078] The method for determining the average hollowness ratio of hollow fibers is the same as that described in the examples.

[0079] The hollow fiber has a hollowness ratio (Cv) of less than 10.0%. From the viewpoint of improving the strength of monofilaments and the tensile strength of SB nonwoven fabric, the hollow fiber's hollowness ratio (Cv) is preferably 2.0% or more and less than 10.0%.

[0080] When manufacturing SB nonwoven fabrics containing hollow fibers at high speeds, fiber breakage sometimes occurs, and the hollowness ratio (Cv) of the resulting hollow fibers tends to exceed 10%. Fiber breakage reduces fiber strength. Therefore, the monofilament elongation of conventional hollow fibers is not excellent. In other words, the monofilament linear strength of conventional hollow fibers is less than 19.0 mN / denier. In this disclosure, it has been discovered that the hollowness ratio (Cv) of hollow fibers can be less than 10% using the manufacturing method described later. While some mechanisms are not yet fully understood, preventing the formation of extremely fine, fragile points that could become the starting point for fiber breakage and producing a relatively uniformly fine resin molded body in the circumferential direction of the fiber are crucial for obtaining such superior hollow fibers. Controlling the discharge method of hollow fibers is considered useful for achieving this in fine-grained, irregularly shaped cross-section fibers.

[0081] The preferred hollow fiber has an average outer diameter of 10 μm or more and less than 30 μm, and an average hollowness of 10% to 40%. As a result, the monofilament strength and monofilament elongation of the hollow fiber are improved, and the SB nonwoven fabric has excellent MD tensile strength.

[0082] The value shown in the following formula (I) (hereinafter also referred to as "Cv of the cross-sectional area of ​​the hollow fiber") is preferably 300%. 3 The following is preferred to be 100%. 3 ~300% 3 Further optimized to 100% 3 ~250% 3 .

[0083] Equation (I): (The variation coefficient of the outer diameter of the hollow fiber mentioned above) 2 × The coefficient of variation of the hollow fiber ratio mentioned above

[0084] The cross-sectional area Cv of hollow fibers can be considered as a quantitative representation of the deviation in the area of ​​the walls constituting the hollow portion (hereinafter also referred to as "cross-sectional area of ​​hollow fibers") in the cross-section of the hollow fibers along the fiber axis of the multiple hollow fibers constituting the SB nonwoven fabric. A Cv that is closer to 0 indicates less deviation in the cross-sectional area of ​​the hollow fibers along the fiber axis. In other words, a Cv that is closer to 0 means that the resulting SB nonwoven fabric is composed of hollow fibers with a more uniform cross-sectional shape.

[0085] If the cross-sectional area Cv of the hollow fiber is 300% 3 The following states that the monofilament strength and elongation of hollow fibers exceed 300% of the cross-sectional area (Cv) of the hollow fiber. 3 The composition tends to be more superior.

[0086] If the cross-sectional area Cv of the hollow fiber is 300%3 The following results in fewer extremely fine, fragile points that could become the starting point for fiber breakage in the hollow fibers. SB nonwoven fabrics containing such hollow fibers exhibit superior mechanical strength compared to previous types. The method for determining the cross-sectional area (Cv) of the hollow fibers is the same as that described in the examples.

[0087] The monofilament strength of the hollow fibers is not particularly limited and can be appropriately selected according to the application of the SB nonwoven fabric. Preferably, the monofilament strength of the hollow fibers is 19.0 mN / denier or higher, more preferably 19.0 mN / denier to 30.0 mN / denier. A monofilament strength of 19.0 mN / denier or higher indicates excellent monofilament strength. That is, the SB nonwoven fabric has a tendency to be less prone to tearing. Therefore, SB nonwoven fabric is suitable for use in sanitary materials and industrial materials (such as agricultural covering materials) with low unit area weight. The method for determining the monofilament strength of the SB nonwoven fabric is the same as the method described in the examples.

[0088] The elongation of the hollow fiber monofilament is not particularly limited and can be appropriately selected according to the application of the SB nonwoven fabric. The elongation of the hollow fiber monofilament is preferably 300% or more, more preferably 300% to 450%. An elongation of 300% or more indicates excellent elongation of the hollow fiber monofilament. That is, the SB nonwoven fabric has excellent MD tensile strength. Depending on the thermoplastic resin used in the SB nonwoven fabric, sometimes the MD tensile strength is excellent, and the SB nonwoven fabric is easy to stretch, and also has excellent softness and shape conformability. Therefore, SB nonwoven fabric is suitable for use in sanitary materials and industrial materials (e.g., agricultural covering materials requiring conformability to uneven shapes). The method for determining the elongation of the SB nonwoven fabric monofilament is the same as the method described in the examples.

[0089] The preferred monofilament strength of the hollow fibers is 19.0 mN / denier or higher, and the preferred monofilament elongation is 300% or higher. Therefore, SB nonwoven fabric exhibits excellent tensile strength (MD). Consequently, SB nonwoven fabric is suitable for use in hygiene materials and industrial materials (such as agricultural covering materials).

[0090] (1.1.1.1) Material

[0091] Hollow fibers can be composed of thermoplastic resin compositions.

[0092] (1.1.1.1.1) Thermoplastic resin

[0093] The thermoplastic resin composition comprises a thermoplastic resin. Examples of thermoplastic resins include polyolefin resins, polyester resins (e.g., polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate), polyamide resins (e.g., nylon-6, nylon-66, and poly(m-phenylene adipamide), polyvinyl chloride, polyimide, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester-carbon monoxide copolymer, polyacrylonitrile, polycarbonate, polystyrene, and ionomers. "(meth)acrylic acid" refers to acrylic acid or methacrylic acid.

[0094] Examples of polyolefin resins include polyethylene resins (such as linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE)) and polypropylene resins.

[0095] Examples of polypropylene-based resins include propylene homopolymers (i.e., homopolymers), propylene-α-olefin random copolymers (e.g., propylene-ethylene random copolymers), and propylene-α-olefin block copolymers. Examples of α-olefins other than propylene include ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-pentene. When copolymerizing α-olefins, the copolymerization amount is preferably 1 mol% to 10 mol%. "Polypropylene-based resin" refers to a polymer containing 50% by mass or more structural units derived from propylene.

[0096] These thermoplastic resins can be used alone or in combination of two or more.

[0097] Hollow fibers can be single-component fibers. In other embodiments, hollow fibers may further include one or more polymer layers as components to further improve strength, processability, and other properties. The structure of hollow fibers may have a two-layer structure (e.g., sheath-core configuration) or a multi-layer structure (e.g., side-by-side, segmented pie, and island-type).

[0098] Hollow fibers can contain polypropylene-based resins or be made entirely of polypropylene-based resins. Hollow fibers can be made of polypropylene-based resins or homopolymer polypropylene. Because the main component of the thermoplastic resin in hollow fibers is homopolymer polypropylene, SB nonwoven fabric can possess both molecular weight (MD) tensile strength and MD elongation. "Main component of thermoplastic resin" refers to thermoplastic resin components that account for 50% or more of the total thermoplastic resin content.

[0099] The following section explains the case where hollow fibers contain propylene polymers.

[0100] The melting point of the propylene polymer is preferably above 140°C, more preferably above 150°C, even more preferably above 155°C, and particularly preferably between 157°C and 165°C.

[0101] The melting point (Tm) can be determined using differential scanning calorimetry (DSC) as follows. Using a Perkin Elmer DSC Pyris1 or a SII NanoTechnology DSC 7020, under a nitrogen atmosphere (20 ml / min), the sample (approximately 5 mg) is heated from room temperature to 200°C at 10°C / min, held at this temperature for 5 minutes, then cooled to -50°C at 10°C / min, held at -50°C for 5 minutes, and then reheated to 200°C at 10°C / min. The melting point (Tm) is calculated from the peak of the crystallization melting peak observed during this second heating process. It should be noted that when multiple crystallization melting peaks are observed, the higher-temperature side peak is taken as the melting point (Tm).

[0102] The melt flow rate (MFR) of polypropylene resins is not particularly limited as long as melt spinning is possible; it can range from 1 g / 10 min to 1000 g / 10 min, from 5 g / 10 min to 500 g / 10 min, or even from 10 g / 10 min to 100 g / 10 min. The MFR of polypropylene resins is determined according to ASTM D-1238, under the following conditions: 230°C and a load of 2.16 kg.

[0103] The content of polypropylene resin relative to the total amount of the thermoplastic resin composition can be 80.0% to 100.0% by mass, 90.0% to 100.0% by mass, or 100.0% by mass.

[0104] The thermoplastic resin (e.g., polypropylene resin) used in the first method can be a biomass-derived raw material. Since biomass-derived raw materials are carbon-neutral, the environmental impact of manufacturing SB nonwoven fabrics using the hollow fibers disclosed herein can be further reduced.

[0105] The monomers used as raw materials for biomass-derived thermoplastic resins are obtained by pyrolysis of biomass naphtha and synthesis from biomass-derived ethylene. Biomass-derived thermoplastic resins can be obtained by polymerizing the biomass-derived monomers synthesized therefrom using the same method as when using conventionally known petroleum-derived thermoplastic resins.

[0106] A thermoplastic resin polymer synthesized from monomers derived from biomass is called a biomass-derived thermoplastic polymer. The content of biomass-derived thermoplastic polymer in the raw material monomers is greater than 0% by mass relative to the total amount of raw material monomers, but can be 100% by mass or less.

[0107] It should be noted that "biomass content" refers to the percentage of carbon derived from biomass, which can be calculated by measuring radioactive carbon (C14). Atmospheric carbon dioxide contains C14 in a certain proportion (approximately 105.5 pMC). Therefore, it is known that plants grown using atmospheric carbon dioxide (such as corn) also contain approximately 105.5 pMC of C14. Fossil fuels are known to contain almost no C14. Therefore, by measuring the proportion of C14 in all carbon atoms in a polymer, the percentage of biomass-derived carbon in the feedstock can be calculated.

[0108] The thermoplastic polymer used as a raw material in the first manner includes thermoplastic polymers obtained through recycling, and the so-called recycled polymer is a preferred method. "Recycled polymer" refers to a substance containing polymers obtained through material recycling of waste polymer products, chemical recycling, etc., and can be manufactured, for example, by the method described in DE 102019127827(A1). The recycled polymer may contain a mark that identifies it as obtained through recycling. By including recycled polymers in the thermoplastic resin used in SB nonwoven fabrics, the amount of virgin petrochemical raw materials used can be reduced, and the environmental impact of manufacturing SB nonwoven fabrics using hollow fibers can be further reduced.

[0109] (1.1.1.1.2) Additives

[0110] Thermoplastic resin compositions may contain additives. Examples of additives include, for instance, antioxidants, heat stabilizers, weather stabilizers, antistatic agents, softeners, slip agents, antifogging agents, lubricants, dyes, pigments, natural oils, synthetic oils, waxes, compatibilizers, and fatty acid amides.

[0111] (1.1.3) Method for manufacturing hollow fibers

[0112] In the first method for manufacturing hollow fibers, the hollow fibers are manufactured by spinning and layering. In the first method for manufacturing hollow fibers, the traction speed (hereinafter also referred to as "traction speed") of the hollow fibers when they are layered on a moving mesh curtain is 2000 m / min to 4000 m / min.

[0113] In the first method for manufacturing hollow fibers, by setting the traction speed to 2000 m / min to 4000 m / min, the hollow fibers of the first method can be stably formed. Therefore, it is easy to obtain hollow fibers with a hollowness ratio (Cv) of less than 10%. Furthermore, it is possible to obtain hollow fibers with a cross-sectional area (Cv) of 300%. 3 the following.

[0114] The first method for manufacturing hollow fibers may include known processes in addition to a traction speed of 2000 m / min to 4000 m / min.

[0115] The hollow fibers of the first method can be made into spunbond fiber webs (hereinafter also referred to as "SB webs"). SB webs are webs composed of multiple layers of hollow fibers. If the SB webs are subjected to the bonding method described above (e.g., embossing), SB nonwoven fabric is obtained. The manufacturing method of the hollow fibers of the first method can be the same as the manufacturing method of SB nonwoven fabric, except that the bonding method (e.g., embossing) is not performed. (See reference...) Figures 1-5 An example of a manufacturing method for SB nonwoven fabric will be explained.

[0116] (1.1.4) Hollow fiber manufacturing apparatus

[0117] The hollow fiber manufacturing apparatus of the first embodiment is a hollow fiber manufacturing apparatus for manufacturing hollow fibers of the first embodiment. The manufacturing apparatus includes a spinneret. The ratio (hereinafter also referred to as "slot length L") of the length of the slot of the spinneret to the 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" as described in Patent Document 2 (International Publication No. 2016 / 100057). The slot has a nozzle orifice for discharging the melt of a thermoplastic resin composition used as a raw material for hollow fibers. The slot length L represents the length of the nozzle orifice in the thickness direction of the spinneret. Regarding the slot width W and the slot length L, refer to... Figures 2-5 To be described later.

[0118] Patent Document 2 discloses a method for manufacturing hollow fibers using a manufacturing apparatus for hollow fibers. Specifically, in an embodiment of Patent Document 2, it is disclosed that an SB nonwoven fabric containing multiple hollow fibers is manufactured using a spinneret with a slot ratio (length / width) of 8. However, since the slot ratio (length / width) is 8, the hollowness Cv of the hollow fibers contained in this SB nonwoven fabric is 10% or more, and the tensile strength and elongation of these hollow fibers may be insufficient. That is, Patent Document 2 does not disclose or provide any technical concept regarding improving the tensile strength and elongation of hollow fibers by making the hollowness Cv of the hollow fibers less than 10%.

[0119] Previously, it was believed that a larger slot ratio (length / width) allowed for more uniform stretching of the single fibers exiting the spinning orifice, resulting in more stable spinning. The inventors of this disclosure have discovered that in the hollow fiber manufacturing apparatus of the first embodiment, by making the slot ratio (length / width) less than 8, even at high-speed production (e.g., traction speed: 2000 m / min to 4000 m / min), the hollowness ratio (Cv) of the obtained hollow fiber can be less than 10%. Furthermore, the cross-sectional area (Cv) of the obtained hollow fiber is 300%. 3 The reasoning is not yet clear, but by making the slot ratio (length / width) less than 8, it is possible to mitigate the deformation in the thickness direction of the hollow fiber from discharge to cooling and solidification. Therefore, it is believed that hollow fibers with a uniform cross-sectional shape can be manufactured in high-speed production (traction speed: 2000m / min~4000m / min).

[0120] The spinneret has multiple spinning orifices. These orifices spin the melt of the thermoplastic resin composition to form hollow fibers (hereinafter also referred to as "continuous fiber bundles"). Unlike spinnerets for multifilament spinning, in spinning stacks, a spinneret with multiple spinning orifices (e.g., 100 or more than 1000) arranged at equal intervals is used. In conventional spinning stacks, it is difficult to uniformly cool the hollow fibers extruded from the center of the spinneret and those extruded from the ends of the spinneret. As a result, uneven temperatures occur between the hollow fibers extruded from the center and the ends of the spinneret, tending to cause deviations in the hollowness ratio of the hollow fibers.

[0121] The spinning orifice of the spinneret extends through the spinneret. The spinning orifice has at least one slot. Molten thermoplastic resin composition, serving as the raw material for hollow fibers, flows within the slot. Hollow fibers are formed from the molten thermoplastic resin composition that has passed through the slot. The shape of the slot (hereinafter also referred to as "orifice shape") is not particularly limited, and examples include C-shaped, arc-shaped, circular, triangular, square, star-shaped (e.g., four-pointed, five-pointed, six-pointed, or seven-pointed stars or more), flat elliptical, T-shaped, M-shaped, S-shaped, Y-shaped, H-shaped, and dumbbell-shaped. From the viewpoint of reducing the hollowness ratio (Cv) of the hollow fibers, the orifice shape is preferably a single C-shape, more preferably a combination of multiple C-shapes, and even more preferably a combination of two to six C-shapes. An orifice shape consisting of six C-shapes is one of the preferred options.

[0122] When the slot is not linearly symmetrical, the slot width W can be calculated using the maximum width of the slot. This is because the thicker the wall of the hollow fiber that exits from the spinning hole, the longer it takes for the hollow fiber to cool and solidify, and the more difficult it is to make the cross-sectional shape of the hollow fiber uniform.

[0123] From the viewpoint of ensuring that the hollow fiber ratio (Cv) is less than 10%, the slot ratio (length / width) is preferably less than 8, more preferably less than 6, and even more preferably 5 or less. From the viewpoint of reducing the hollow fiber ratio, the slot ratio (length / width) is preferably 3.0 or more.

[0124] The slot width W can be, for example, 0.05mm to 0.2mm, and the slot length L can be, for example, 0.3mm to 1.2mm. The slot length L is appropriately selected based on the slot ratio (length / width) and the slot width W.

[0125] The hollow fiber manufacturing apparatus of the first method can be the same as known hollow fiber manufacturing apparatuses, except that the slot ratio (length / width) is less than 8. For an example of a hollow fiber manufacturing apparatus, see [reference needed]. Figures 1-5 Please provide an explanation.

[0126] (1.1.5) An example embodiment of the method for manufacturing SB nonwoven fabric

[0127] In this embodiment, the SB nonwoven fabric is obtained by using a spinneret for hollow fibers to spin-pile spunbond fiber web (hereinafter also referred to as "SB fiber web"), and then embossing the SB fiber web.

[0128] Hereinafter, with reference to the accompanying drawings, a detailed description of an example of the manufacturing method of the SB nonwoven fabric of the first embodiment will be provided. Figure 1This is a schematic diagram illustrating a closed-loop SB nonwoven fabric manufacturing apparatus according to a first embodiment. In this closed-loop SB nonwoven fabric manufacturing apparatus, multiple continuous fiber groups extruded from a spinneret (spinning orifice) for hollow fibers are cooled and stretched in a closed space. The closed-loop SB nonwoven fabric manufacturing apparatus is an example of a hollow fiber manufacturing apparatus. The hollow fibers disclosed herein are not limited to a closed-loop SB nonwoven fabric manufacturing apparatus; they can also be manufactured using an open-loop SB nonwoven fabric manufacturing apparatus or a general-purpose SB nonwoven fabric manufacturing apparatus.

[0129] The first embodiment of the method for manufacturing SB nonwoven fabric uses Figure 1 The closed-loop SB nonwoven fabric manufacturing apparatus 100 shown is used for this process. The SB nonwoven fabric manufacturing method includes a melting process, a spinning process, a cooling and stretching process, a trapping process, and an embossing process. These processes are performed sequentially. The melting, spinning, cooling and stretching, trapping, and embossing processes are an example of a hollow fiber manufacturing method.

[0130] (1.1.5.1) Manufacturing apparatus

[0131] like Figure 1 As shown, the closed-type SB nonwoven fabric manufacturing apparatus 100 includes a spinning section 10. The spinning section 10 includes an extruder 11, a spinneret 12, a cooling chamber 13, a spinning air supply section 14, a spinning air supply section 15, and a stretching section 16.

[0132] The extruder 11 melts the thermoplastic resin composition and extrudes the melt of the thermoplastic resin composition into the spinneret 12.

[0133] The spinneret 12 spins the molten thermoplastic resin composition into continuous fiber bundles 1. The spinneret 12 is for hollow fiber applications. Specifically, the spinneret 12 forms the molten thermoplastic resin composition into continuous fiber bundles. The spinneret 12 has a plurality of spinning orifices 120. For example... Figure 3 As shown, the spinning orifice 120 extends from the surface S12A of the spinneret 12 to the surface S12B of the spinneret 12 (i.e., it extends along the thickness direction D of the spinneret 12). In the spinneret 12, as... Figure 2 As shown, the spinning orifice 120 for producing one hollow fiber has four slots 121A. The molten thermoplastic resin composition, which is the raw material for the hollow fiber, flows through the slots 121A. The shape of the slots 121A is... Figure 2 The irregularly shaped hole is shown. The slot 121A has a slot width W (refer to...). Figure 2 ).like Figure 3 As shown, the spinneret 12 has a guide hole 1201 and a nozzle hole 1202 continuously connected to the guide hole 1201. The slot length L (refer to...) Figure 3The length of the nozzle orifice 1202 in the thickness direction D of the spinneret 12 is indicated. The slot ratio (length / width) is less than 8. "Slot ratio (length / width)" indicates the slot length L (refer to...). Figure 2 ) relative to the slot width W (refer to Figure 2 The ratio of ).

[0134] It should be noted that, in the first embodiment, the spinning hole 120 used to make one hollow fiber is... Figure 2 The slot 121A shown is not limited to this. In this disclosure, the spinning hole 120 for making a hollow fiber can be... Figure 4 The slot 121B shown can also be Figure 5 The slot 121C shown.

[0135] The cooling chamber 13 cools the continuous fiber assembly 1 spun from the spinning orifice of the spinneret 12. The spinning air supply unit 14 and the spinning air supply unit 15 supply spinning air A to the cooling chamber 13 and the stretching section 16.

[0136] In the stretching section 16, the continuous fiber assembly 1 is stretched using spinning air A. The stretching section 16 has a bottleneck section 16a and a tubular section 16b. The tubular section 16b is formed at the lower end (i.e., the side of the mesh curtain 21) of the bottleneck section 16a in the vertical direction (i.e., the direction of gravity). The bottleneck section 16a is bottleneck-shaped. The tubular section 16b is tubular. Figure 1 As shown, the hollow portion of the cylindrical section 16b expands downwards. The suction unit 22 captures the continuous fiber assembly 1 onto the mesh curtain 21.

[0137] In the production of multifilament yarn, the yarn (multifilament) leached from the spinning hole is stretched using a stretching machine containing one or more rollers. Specifically, if the fiber is made of a thermoplastic resin capable of melt spinning, it is stretched axially by the ratio of the circumferential speed of the first roller to the second roller, and then heat-set and wound to produce the yarn (multifilament). The temperature of the first roller is set above the glass transition temperature of the thermoplastic resin and below its melting point. The temperature of the second roller is set to a temperature equivalent to the crystallization temperature of the thermoplastic resin. This stretching process is performed in multiple stages to improve the draw ratio and the mechanical properties of the yarn. As another method for stretching multifilament yarn, winding is not performed; instead, a two-stage stretching process is conducted in a stretching bath at a temperature of 60°C to 120°C with a predetermined total draw ratio.

[0138] The suction unit 22 is located at the lower part of the collection surface of the mesh curtain 21.

[0139] (1.1.5.2) Melting process

[0140] In the melting process, the thermoplastic resin composition is melt-blended using an extruder 11, and the melt of the thermoplastic resin composition is extruded from the extruder 11.

[0141] The melting temperature (hereinafter also referred to as "extrusion temperature") of the thermoplastic resin composition is not particularly limited as long as it is above the softening temperature and melting temperature of the thermoplastic resin composition and below the thermal decomposition temperature of the thermoplastic resin composition, and can be appropriately set according to the physical properties of the thermoplastic resin composition. When the thermoplastic resin composition contains a polypropylene resin, the extrusion temperature is preferably 180°C to 260°C, more preferably 190°C to 250°C.

[0142] (1.1.5.3) Spinning process

[0143] In the spinning process, a molten thermoplastic resin composition is extruded from the spinning orifice of a spinneret 12 using a spinneret 12. This forms a continuous fiber assembly 1 consisting of multiple hollow fibers.

[0144] The shape of the spinning orifice of the spinneret 12 is not particularly limited, and the shape of the above-mentioned slot, slot width W, slot length L, etc. can be combined for use.

[0145] The single-hole discharge rate of the spinning orifice of the spinneret 12 is preferably 0.1 g / min to 3.0 g / min, more preferably 0.2 g / min to 1.0 g / min.

[0146] The temperature of the spinneret 12 is appropriately adjusted according to the physical properties of the thermoplastic resin composition. When the thermoplastic resin composition contains a polypropylene resin, the temperature of the spinneret 12 is preferably 180°C to 260°C, more preferably 190°C to 250°C.

[0147] (1.1.5.4) Cooling and stretching process

[0148] In the cooling and stretching process, the continuous fiber assembly 1 is cooled and stretched using spinning air A. Specifically, spinning air A is supplied from spinning air supply unit 14 and spinning air supply unit 15 into the cooling chamber 13 and the stretching section 16. As a result, the continuous fiber assembly 1 extruded from the spinning orifice of the spinneret 12 is cooled in the cooling chamber 13. Then, the cooled continuous fiber assembly 1 is introduced into the stretching section 16, which is located downstream of the cooling chamber 13. The continuous fiber assembly 1 introduced into the stretching section 16 is stretched by increasing the speed of the spinning air at the bottleneck section 16a. The continuous fiber assembly 1 that has passed through the bobbin section 16b is dispersed and captured onto the mesh curtain 21. The dispersed continuous fiber assembly 1 is efficiently captured onto the mesh curtain 21 by the suction unit 22. Thus, the SB fiber web 2 is formed.

[0149] The air velocity of the spinning air A supplied from the spinning air supply unit 14 and the spinning air supply unit 15 respectively indicates the flow rate of the cooling air (Nm).3 / minute) relative to the cross-sectional area of ​​the bottleneck portion 16a of the stretching portion 16 (m²) 2 The ratio of the spinning air A to the speed at the bottleneck 16a of the stretching section 16 is the same as the "traction speed" mentioned above.

[0150] The traction speed of the continuous fiber assembly 1 (i.e., multiple hollow fibers) when it is stacked on the moving mesh curtain 21 is 2000 m / min to 4000 m / min. "Traction speed" indicates the flow rate of the cooling air (Nm³). 3 / minute) Cross-sectional area (m²) of the edge of the mesh curtain 21 side relative to the tube portion 16b of the stretching portion 16. 2 The ratio of ) to ). That is, the traction speed represents the speed of the spinning air A at the edge of the mesh curtain 21 side of the bobbin portion 16b of the stretching section 16.

[0151] The temperature of the spinning air A supplied from the spinning air supply unit 14 and the spinning air supply unit 15 is not particularly limited as long as it is the curing temperature of the thermoplastic resin composition. The temperature of the spinning air A is preferably 5°C to 50°C, and more preferably 10°C to 40°C.

[0152] (1.1.5.5) Embossing process

[0153] In the embossing process, the SB fiber web 2 is embossed. As a result, the hollow fibers contained in the SB fiber web 2 are bonded together, and thus, the SB nonwoven fabric is obtained.

[0154] "Embossing" refers to the process of heat-pressing a portion of the multiple fibers contained in an SB nonwoven fabric between an embossing roller and a flat roller. The embossing roller has multiple protrusions arranged in a regular pattern on its surface. The embossing roller transfers the shape of the top surfaces of the multiple protrusions onto a portion of the multiple fibers contained in the SB nonwoven fabric. Thus, the embossing roller forms multiple embossed portions arranged in a regular pattern on the SB nonwoven fabric. The ratio of the area of ​​the multiple protrusions of the embossing roller to the surface area of ​​the embossing roller (hereinafter also referred to as "embossing area ratio") can be appropriately selected according to the application of the SB nonwoven fabric. The embossing area ratio of the embossing roller is the same as the embossing area ratio of the SB nonwoven fabric described above.

[0155] The surface temperature of the embossing roller (hereinafter also referred to as "embossing temperature") can be appropriately set according to the application. For example, in applications requiring softness, it is preferable to have a temperature between (resin melting point -20°C) and (resin melting point +20°C), more preferably between (resin melting point -15°C) and (resin melting point +10°C), and even more preferably between (resin melting point -15°C) and the resin melting point. If the embossing temperature is between (resin melting point -10°C) and the resin melting point, the multiple hollow fibers in the embossed section will be fully fused together.

[0156] Before performing the embossing process, the SB fiber web 2 can be pressed and secured using clamping rollers.

[0157] In the manufacturing method of SB nonwoven fabric according to the first embodiment, by adjusting the extrusion temperature of the extruder 11, the single-hole discharge rate of the spinning orifice of the spinneret 12, and the spinning air speed of the spinning air supply unit 14 and the spinning air supply unit 15, it is possible to manufacture SB nonwoven fabric containing hollow fibers with a hollow rate Cv of less than 10%.

[0158] Specifically, methods for adjusting the hollow fiber's hollowness ratio (Cv) to less than 10% include, for example, adjusting the single-hole discharge rate of the molten thermoplastic resin composition to an appropriate range; and reducing the spinning air velocity. The appropriate range for the single-hole discharge rate varies depending on the type, viscosity, and melting point of the resin used, but when using the acrylic resin used in the first method and employing the manufacturing method and apparatus of the first method, the single-hole discharge rate is preferably in the range of 0.2 g / min to 1.0 g / min. Furthermore, by reducing the spinning air velocity, uneven stretching and cooling of the hollow fiber caused by airflow turbulence can be suppressed, thereby reducing the hollowness ratio (Cv).

[0159] The cross-sectional area (Cv) of the hollow fiber is adjusted to 300%. 3 The following methods may be cited as examples: adjusting the single-hole discharge rate of the molten thermoplastic resin composition to an appropriate range; reducing the air velocity of the spinning air, etc.

[0160] As an example of adjusting the hollow fiber's average outer diameter to 10 μm to 30 μm and its average hollowness to 10% to 40%, one method is to adjust the extrusion temperature, single-hole discharge rate, and spinning air velocity to appropriate ranges. The appropriate ranges for extrusion temperature and single-hole discharge rate vary depending on the type, viscosity, and melting point of the resin used. When using the acrylic resin used in the first method, an extrusion temperature of 190°C to 250°C and a single-hole discharge rate of 0.2 g / min to 1.0 g / min are preferred.

[0161] (1.2) Sanitary materials

[0162] The first type of sanitary material includes the first type of SB nonwoven fabric.

[0163] The sanitary material of the first type, due to its aforementioned structure, exhibits excellent mechanical strength (e.g., MD tensile strength) and is not easily damaged. Furthermore, compared to solid fibers of the same diameter, hollow fibers allow for a reduction in the amount of thermoplastic resin composition used. Therefore, nonwoven fabrics using hollow fibers can reduce weight per unit area, thereby reducing environmental impact.

[0164] Examples of hygiene materials include absorbent items (such as disposable diapers, disposable shorts, sanitary products, absorbent pads, and pet pads), medical hygiene materials (such as bandages, medical gowns, medical curtains, sterile pads, medical gauze, towels, sheets, hand warmers, cell culture sheets, and wet wipes), and masks (such as industrial masks and sanitary masks).

[0165] The sanitary materials are not limited to these and may also include other sanitary materials. The sanitary materials may comprise a nonwoven laminate. The nonwoven laminate may comprise two or more layers of the first-type SB nonwoven fabric, or it may comprise the first-type SB nonwoven fabric and other layers besides the first-type nonwoven fabric.

[0166] (1.3) Industrial Materials

[0167] The industrial materials of the first type include the SB nonwoven fabric of the first type.

[0168] Due to its aforementioned structure, the industrial material of the first type exhibits excellent mechanical strength and is not easily damaged. When used as an agricultural covering material, the industrial material of the first type is less prone to damage than conventional multi-layer sheets. The industrial material of the first type is suitable for use on uneven ground surfaces (e.g., loose soil). The industrial material of the first type reduces the frequency of replacement due to damage.

[0169] When industrial materials are used for industrial applications, it is possible to reduce weight while maintaining the same mechanical strength as before. Lightweight industrial materials can also be expected to reduce transportation costs and energy consumption associated with transportation.

[0170] When the industrial material is a sound-absorbing material, the sound-absorbing material can be appropriately used on curved surfaces or surfaces with concave or convex shapes.

[0171] The industrial material of the first approach can be a single-layer structure composed solely of SB nonwoven fabric, or a laminated structure. It should be noted that SB nonwoven fabric is composed of long fibers, thus reducing fiber shedding during transport and use compared to nonwoven fabrics containing short fibers, which is also useful from the perspective of reducing environmental impact.

[0172] As industrial materials, examples include agricultural covering materials (such as sheets for open-field cultivation, sheets for tunnel cultivation, sheets for greenhouse cultivation, sheets for full-coverage, and sheets for seedbeds), clothing (such as linings and adhesive linings), construction (such as roofing materials and tufted carpet base materials), civil engineering (such as drainage materials and filtration materials), vehicles (such as automotive interiors, automotive parts, seat cushioning base materials, and sound-absorbing materials), hygiene (such as first aid supplies and cleaning supplies), interior decoration (such as carpets, furniture components, building accessories, wall coverings, and decorative items), bedding (such as bedding bags, pillowcases, and sheets), leather (such as base fabrics for artificial leather and synthetic leather), household materials (such as storage items, packaging materials, and bags), and industrial materials.

[0173] Examples of industrial materials include abrasive materials, oil-absorbing pads, pipes, papermaking felt, cushioning materials, drainage materials for concrete formwork, water-blocking materials, heat insulation materials, sound insulation materials, cushioning materials, vibration damping materials, marine materials (e.g., interior trim, components, seat cushioning substrates, and sound-absorbing materials), wiping materials (e.g., cleaning sheets and cosmetic sheets), electrical materials (e.g., electrical insulation materials for printed wiring boards, electromagnetic wave shielding materials, wire pressing and winding tapes, and battery separators), product substrates (e.g., fiber-reinforced plastic substrates, printing substrates, synthetic paper substrates, electrostatic recording substrates, tape substrates, heat transfer film substrates, and radiation shielding pad substrates), office automation equipment materials (e.g., floppy disk liners and floppy disk packaging materials), audiovisual equipment materials (e.g., speaker diaphragms and sound-absorbing panels), rollers (e.g., polishing rollers, squeezing rollers, and oiling rollers), equipment components (e.g., V-belts, conveyor belts, and synchronous belts), and musical instrument materials (e.g., piano key seats and hammer guides).

[0174] The industrial material of the first type can be a laminate consisting of a film, an adhesive layer, and an SB nonwoven fabric stacked sequentially.

[0175] The industrial material of the first type can be an SMS laminate or an SMMS laminate. An SMS laminate is formed by sequentially layering spunbond nonwoven fabric, meltblown nonwoven fabric, and spunbond nonwoven fabric. An SMMS laminate is formed by sequentially layering spunbond nonwoven fabric, meltblown nonwoven fabric, meltblown nonwoven fabric, and spunbond nonwoven fabric. The unit area weight of the SMS or SMMS laminate can be adjusted according to the application, and can be as low as 10 g / m². 2 ~1500g / m 2 .

[0176] The industrial material of the first embodiment can be a laminate of the SB nonwoven fabric and the membrane disclosed herein. Examples of membranes include those with both liquid impermeability and vapor permeability, or those with only vapor permeability. Membranes with both liquid impermeability and vapor permeability are breathable. Therefore, by combining the SB nonwoven fabric of the present disclosure, which has excellent breathability, with a membrane that has both liquid impermeability and vapor permeability, the industrial material of the first embodiment achieves excellent breathability. The vapor permeability of the membrane can be 500 g / m³. 2 / 24 hours ~ Approximately 20000g / m 2 / 24 hours. The breathable membrane can be a microporous membrane or a monolithic film.

[0177] Examples of membranes include those made from thermoplastic synthetic resins (e.g., polyethylene resins, polypropylene resins, polyurethane resins, and polyvinyl chloride resins), commonly used in agriculture and other fields. Membranes can be single-layered or multi-layered. They can be colored or uncolored.

[0178] The mulch film can be either a permeable membrane (i.e., a porous membrane) or a non-permeable membrane. When the membrane is porous, the agricultural mulch material allows for the moderate escape of moisture and heat from the covered surface. When the membrane is non-permeable, the agricultural mulch material functions as a waterproof layer, preventing rainwater from rapidly seeping into the soil. In fruit cultivation, covering the ground with such a non-permeable membrane can reduce water supply in the months leading up to harvest and increase fruit sugar content.

[0179] The adhesive layer is formed by an adhesive. There are no particular limitations on the adhesive; examples include olefin-based adhesives, vinyl-based adhesives, styrene-based adhesives, (meth)acrylic adhesives, polyester-based adhesives, urethane-based adhesives, and so on. The adhesive can also be a known adhesive. These adhesives can be used alone or in combination of two or more.

[0180] The first type of agricultural covering material has excellent monofilament strength and monofilament elongation of hollow fibers, and the SB nonwoven fabric containing these hollow fibers has excellent MD tensile strength and good light transmittance. Therefore, it can be used, for example, by laying it on the ground surface used for cultivating crops. In the case of the first type of agricultural covering material having the above-mentioned laminated structure, the first type of agricultural covering material is preferably laid with the SB nonwoven fabric as the ground surface side.

[0181] (2) Second method

[0182] The second method for manufacturing hollow fibers involves spinning and layering hollow fibers using a hollow fiber manufacturing apparatus. This apparatus includes a spinneret. The spinneret's slot ratio (length / width) is less than 8. The traction speed (hereinafter also referred to as "traction speed") of the hollow fibers when layered on a moving mesh screen is 2000 m / min to 4000 m / min.

[0183] The second method for manufacturing hollow fibers, due to its aforementioned structure, enables the formation of stable spinning yarns, thereby achieving a hollowness ratio (Cv) of less than 10% in the resulting hollow fibers. Furthermore, it allows for a cross-sectional area (Cv) of 300% for the hollow fibers. 3 the following.

[0184] The manufacturing method of the hollow fiber in the second method does not necessarily require manufacturing the hollow fiber of the first method. Except for the slot ratio (length / width) being less than 8 and the traction speed being 2000 m / min to 4000 m / min, it is the same as the manufacturing method of the hollow fiber in the first method. Therefore, the description of the second method references the description of the first method, omitting any descriptions in the second method that are redundant with the description of the first method.

[0185] (3) Variations

[0186] (3.1) SB nonwoven fabric

[0187] The modified SB nonwoven fabric (hereinafter also referred to as "SB nonwoven fabric") is as follows:

[0188] The product contains hollow fibers, wherein the coefficient of variation of the hollow fiber ratio (hereinafter also referred to as "Cv of hollow fiber ratio") is less than 10%, and the average outer diameter of the hollow fiber is 30 μm or more.

[0189] Because of the above-described structure, the modified SB nonwoven fabric, like the first type, possesses hollow fibers with excellent tensile strength and elongation. Therefore, the modified SB nonwoven fabric exhibits excellent MD tensile strength and MD elongation.

[0190] The modified SB nonwoven fabric is the same as the first type of SB nonwoven fabric, except that the average outer diameter of the hollow fibers must be 30 μm or more. Therefore, the description of the modified example refers to the description of the first type, and the description of the manufacturing method of the hollow fibers in the modified example that is repeated in the description of the manufacturing method of the hollow fibers in the first type is omitted.

[0191] The average outer diameter of the hollow fibers is 30 μm or more. Even with an average outer diameter of 30 μm or more, the hollow fiber Cv of the disclosed hollow fiber can be less than 10%. By achieving a hollow fiber Cv of less than 10%, the monofilament elongation is superior to that of a structure with an average outer diameter of less than 30 μm, even when the average outer diameter of the hollow fibers is 30 μm or more. Therefore, SB nonwoven fabrics containing hollow fibers of 30 μm or more are useful in industrial materials requiring high mechanical strength.

[0192] The method for determining the average outer diameter of the hollow fibers is the same as that described in the examples.

[0193] In the modified example, similar to the first embodiment, the value shown by the following formula (I) (hereinafter also referred to as "Cv of the cross-sectional area of ​​the hollow fiber") is preferably 300%. 3 The following is preferred to be 100%. 3 ~300% 3 Preferably 100% 3 ~250% 3 .

[0194] Equation (I): (The variation coefficient of the outer diameter of the hollow fiber mentioned above) 2 × The coefficient of variation of the hollow fiber ratio mentioned above

[0195] In the modified example, similar to the first embodiment, the average value of the hollow fiber hollowness is preferably 10% to 40%.

[0196] In a modified example, similar to the first embodiment, the hollow fiber preferably comprises a polypropylene resin.

[0197] In a modified example, it is preferable that the monofilament linear strength of the hollow fiber is 19.0 mN / denier or higher, and the monofilament elongation of the hollow fiber is 300% or higher. More preferably, the monofilament linear strength of the hollow fiber is 22.0 mN / denier or higher, and the monofilament elongation of the hollow fiber is 360% or higher.

[0198] In a modified example, it is preferred that the average outer diameter of the hollow fiber is 30 μm to 40 μm and the average hollowness of the hollow fiber is 10% to 40%.

[0199] The sanitary material of the modified example is a sanitary material comprising the SB nonwoven fabric of the modified example. The sanitary material of the modified example is the same as the sanitary material of the first embodiment, except that it comprises the SB nonwoven fabric of the modified example instead of the SB nonwoven fabric of the first embodiment.

[0200] The industrial material of the modified example is the industrial material that includes the SB nonwoven fabric of the modified example. The industrial material of the modified example is the same as the industrial material of the first embodiment, except that it includes the SB nonwoven fabric of the modified example instead of the SB nonwoven fabric of the first embodiment.

[0201] Because the fiber diameter is larger than that of the industrial material of the first type, it is useful in applications requiring higher mechanical strength and high air permeability. In addition, the larger the fiber diameter, the more air is enclosed within the hollow fiber, thus allowing for better thermal insulation.

[0202] The hollow fiber manufacturing apparatus of the modified example is a hollow fiber manufacturing apparatus for manufacturing the hollow fiber of the modified example. The manufacturing apparatus has a spinneret, and the ratio of the length of the slot of the spinneret to the width of the slot is less than 8.

[0203] The apparatus for manufacturing hollow fibers in the modified example is the same as that for manufacturing hollow fibers in the second example, except that it manufactures SB nonwoven fabric of the modified example instead of SB nonwoven fabric of the first example.

[0204] The hollow fiber manufacturing method of the modified example is to manufacture the hollow fiber of the modified example by spinning and layering. When the hollow fiber is layered on a moving mesh curtain, the traction speed of the hollow fiber is 2000 m / min to 4000 m / min.

[0205] The manufacturing method of the hollow fiber in the modified example is the same as that of the hollow fiber in the first example, except that the modified SB nonwoven fabric is used instead of the SB nonwoven fabric in the first example. It is preferred in the manufacturing method of the hollow fiber in the modified example that the spinneret slot ratio (length / width) must be less than 8 and the traction speed must be 2000 m / min to 4000 m / min.

[0206] Example

[0207] The present disclosure is described in more detail below based on embodiments, but the present disclosure is not limited to the embodiments described below. The materials, amounts, proportions, processing steps, etc. shown in the following embodiments can be appropriately changed without departing from the spirit of the present disclosure. In addition, unless otherwise stated, "parts" means "parts by weight".

[0208] [1] Determination method

[0209] [1.1] Collection of fiber samples for testing

[0210] Fiber samples were collected as follows for determining the outer diameter, hollowness, monofilament strength, and monofilament elongation of hollow fibers. Using tweezers, 100 monofilaments, each 100 mm in length, were randomly selected from the SB nonwoven fabric without stretching. These monofilaments were then cut at their midpoints with a blade in a direction orthogonal to the fiber axis of the hollow fiber, creating two groups of 100 monofilaments each, each 50 mm in length. One group was used for determining the outer diameter, monofilament strength, and monofilament elongation. The remaining group was used for determining the hollowness.

[0211] [1.2] Average outer diameter [μm], Cv value of outer diameter [%]

[0212] Using an optical microscope (Nikon ECLIPSE E-400), the outer diameter of each single fiber along its axial direction was measured at 10 arbitrary points. This operation was performed on 100 single fibers. The average value of the 1000 outer diameter measurements was taken as the "average outer diameter" of the single fiber. The value obtained by multiplying the standard deviation of the 1000 outer diameter measurements by 100 and dividing by the average outer diameter was taken as the "Cv value" of the single fiber.

[0213] [1.3] Average hollowness (%), Cv value of outer diameter (%)

[0214] The single fiber of the test object was embedded in epoxy resin, and then the fiber was cut at 10 arbitrary points along the fiber axis using a dicing machine to obtain 10 sample pieces. These were observed using an optical microscope (Nikon ECLIPSE E-400), and the hollowness of the fiber cross-section at any 10 points along the fiber axis was measured. This operation was performed on all 10 sample pieces. The average value of the hollowness measurements at 100 points was taken as the "average hollowness" of the single fiber. The value obtained by multiplying the standard deviation of the hollowness measurements at 100 points by 100 and dividing by the average hollowness was taken as the "Cv value" of the single fiber.

[0215] [1.4] Fineness (denier)

[0216] The fineness of a single fiber is determined using the average of the measured outer diameter and the average of the measured hollowness, according to the following formula (A). In formula (A), "0.91" represents the density of polypropylene (g / cm³). 3 In Comparative Example 7 (solid fiber), the average hollow ratio was set to 0 for calculation.

[0217] Formula (A): Fineness = 3.14 × (average outer diameter ÷ 2 ÷ 10000) 2 ×(100 - average hollow rate) ÷ 100 × 0.91 × 900000

[0218] [1.5] Monofilament strength (N / denier), monofilament elongation (%)

[0219] According to JIS L 1095 (Method 9.5.1), a tensile test was performed on the monofilament used in the outer diameter determination to determine the tensile load and elongation. A tensile testing machine (Instron 5564 model, manufactured by Instron Japan Company Limited) was used for the tensile test. The test conditions were a clamping distance of 20 mm and a tensile speed of 20 mm / min. The measured value of the tensile load was taken as "monofilament strength". The measured value of the elongation was taken as "monofilament elongation". Using the measured value of monofilament strength, the monofilament strength was evaluated according to the following criteria. Using the measured value of monofilament elongation, the monofilament elongation was evaluated according to the following criteria. The permissible evaluation of monofilament strength is "A1". The permissible evaluation of monofilament elongation is "A2".

[0220] [1.5.1] Evaluation Criteria for Monofilament Strength

[0221] "A1": Monofilament strength ≥ 19.0 mN / denier

[0222] "B1": Monofilament strength <19.0 mN / denier

[0223] [1.5.2] Evaluation Criteria for Monofilament Elongation

[0224] "A2": Monofilament elongation ≥ 300%

[0225] "B2": Monofilament elongation <300%

[0226] [1.6] Weight per unit area (g / m²) 2 ]

[0227] Ten 100mm (mechanical direction (MD)) × 100mm (width direction (CD)) test pieces were collected from SB nonwoven fabric. The test pieces were collected from the center of the width direction (CD). Then, the mass (g) of each test piece was measured using an electronic balance (manufactured by Kensei Kogyo Co., Ltd.) at 20°C and 50% RH. The average mass of the test pieces was converted to a per-m³ mass. 2 The mass [g] is rounded to the nearest decimal place. The resulting value is taken as the "weight per unit area" of the nonwoven fabric.

[0228] [1.7] MD tensile strength (N / 25mm) and MD elongation (%)

[0229] The tensile strength (MD) and elongation (MD) of SB nonwoven fabric were determined according to JIS L 1906, 6.12.1 [Method A] (transferred to JIS L 1913:2010, corresponding to ISO 9073-3:1989). Ten 200 mm (mechanical direction (MD)) × 25 mm (width direction (CD)) test pieces were collected from the SB nonwoven fabric. The test pieces were collected at any 10 locations along the width direction (CD) of the SB nonwoven fabric. Using a tensile testing machine, the fabric was stretched along the mechanical direction (MD) with a clamping distance of 100 mm and a machine head speed of 100 mm / min. The maximum tensile strength (N / 25 mm) and the elongation (%) at this point were determined. The average of the measured maximum tensile strength values ​​at the 10 points was taken as the "MD tensile strength". The average of the measured maximum elongation values ​​at the 10 points was taken as the "MD elongation". The MD tensile strength was evaluated using the measured MD tensile strength values ​​according to the following criteria. The MD elongation was evaluated using the measured values ​​of MD elongation according to the following criteria.

[0230] [1.7.1] Evaluation Criteria for MD Tensile Strength

[0231] "A3": MD tensile strength ≥ 20.0 N / 25 mm

[0232] "B3": MD tensile strength < 20.0 N / 25 mm

[0233] [1.7.2] Evaluation Criteria for MD Elongation

[0234] "A4": MD elongation ≥ 60%

[0235] "B4": MD elongation <60%

[0236] [1.8] Air permeability (cm) 3 / cm 2 ·sec]

[0237] Ten 100mm (mechanical direction (MD)) × 100mm (width direction (CD)) test pieces were collected from SB nonwoven fabric. Using a Fraser-type testing machine, the air permeability was measured at a pressure difference of 125 Pa according to JIS L 1096. The average value of the air permeability measurements at the ten points was taken as the "air permeability". The air permeability was evaluated using the measured values ​​according to the following criteria.

[0238] [1.8.1] Evaluation criteria for air permeability

[0239] "A5": Breathability ≥ 500cm 3 / cm 2 ·sec

[0240] "B5": Breathability <500cm3 / cm 2 ·sec

[0241] [1.9] Light transmittance [%]

[0242] The light transmittance at 10 random points on the SB nonwoven fabric was measured using Nomura Corporation's "FMT-MIII" formability tester. The average of the measured light transmittance values ​​at the 10 points was taken as the "light transmittance". The light transmittance was evaluated according to the following criteria using the measured values.

[0243] [1.9.1] Evaluation criteria for air permeability

[0244] "A6": Light transmittance ≤ 93.4%

[0245] "B6": Light transmittance >93.4%

[0246] [2] Examples and Comparative Examples

[0247] [2.1] Example 1

[0248] Prepare the following ingredients.

[0249] hPP: Homopolymer polypropylene (melting point 163℃, MFR (temperature 230℃, load 2.16kg) 60g / 10min)

[0250] use Figure 1 and Figure 2 The closed-type SB nonwoven fabric manufacturing apparatus 100 shown below produces SB nonwoven fabric.

[0251] The raw material hPP is melted using an extruder 11 with a diameter of 75 mm. The molten hPP is introduced into a die with a spinneret 12. The spinneret 12 is for hollow fibers. The slot ratio (length / width) of the slots 121A of the spinneret 12 is the value listed in Table 1. The number of slots in the orifice shape 121A of the spinning orifice 120 is 6. The extrusion temperature of the extruder 11 is set to 200°C. The amount of molten hPP introduced into the die is adjusted so that the resin discharge rate (single orifice discharge rate) at each point of the spinneret 12 is 0.8 g / min. The hollow fibers discharged from the spinneret 12 are cooled and stretched with spinning air A to obtain single fibers. The temperature of the spinning air A is 20°C. The air velocity for traction speed is the value listed in Table 1.

[0252] The single fibers spun as described above are deposited on the mesh curtain 21 to obtain a fiber web. The fiber web is then embossed using an embossing roller (embossing area ratio: 18%, embossing temperature: 135℃) to produce SB nonwoven fabric. The unit area weight of the SB nonwoven fabric is 20 g / m². 2In Example 1, the single fibers constituting the SB nonwoven fabric are hollow fibers.

[0253] [2.2] Examples 2 to 7 and Comparative Examples 1 to 6

[0254] Except for changing the extrusion temperature, single-hole discharge rate, and spinning air velocity as shown in Tables 1 and 2, the same procedure as in Example 1 was followed to obtain SB nonwoven fabric.

[0255] [2.3] Examples 8 and 9

[0256] Except for changing hPP to rPP as described below, and changing the extrusion temperature, single-hole discharge rate and spinning air velocity as shown in Table 1, the same procedure as in Example 1 was followed to obtain SB nonwoven fabric.

[0257] rPP: a random copolymer of propylene and ethylene (melting point 138℃, MFR (temperature 230℃, load 2.16kg) 60g / 10min)

[0258] [2.4] Comparative Example 7

[0259] Except for changing the extrusion temperature, single-hole discharge rate and spinning air velocity as shown in Table 2, and changing the spinneret 12 for hollow fibers to a spinneret for solid fibers, the same procedure as in Example 1 was followed to obtain SB nonwoven fabric.

[0260] [3] Results

[0261] [Table 1]

[0262]

[0263] [Table 2]

[0264]

[0265] The SB nonwoven fabrics of Comparative Examples 1 to 6 contain only a plurality of hollow fibers. The hollowness Cv of the hollow fibers in Comparative Examples 1 to 6 exceeds 10%. Therefore, in Comparative Examples 1 to 6, the monofilament strength is evaluated as "B1" and the monofilament elongation is evaluated as "B2".

[0266] The SB nonwoven fabric of Comparative Example 7 does not contain hollow fibers. Therefore, in Comparative Example 7, the monofilament strength is evaluated as "B1" and the monofilament elongation is evaluated as "B2".

[0267] These results show that the SB nonwoven fabrics of Comparative Examples 1 to 7 are not "SB nonwoven fabrics with hollow fibers having excellent tensile strength and elongation".

[0268] The SB nonwoven fabrics of Examples 1 to 9 contain only a plurality of hollow fibers. The hollowness Cv of the hollow fibers in Examples 1 to 9 is less than 10%. Therefore, the monofilament strength of Examples 1 to 9 is evaluated as "A1", and the monofilament elongation of the SB nonwoven fabrics of Examples 1 to 7 is evaluated as "A2".

[0269] These results show that the SB nonwoven fabrics of Examples 1 to 9 are "SB nonwoven fabrics with hollow fibers that have excellent tensile strength and elongation".

[0270] The entire disclosure of Japanese Patent Application 2023-167879, filed on September 28, 2023, is incorporated herein by reference.

[0271] All documents, patent applications and technical standards described in this specification are incorporated herein by reference to the same extent as the specific documents, patent applications and technical standards described separately are incorporated herein by reference.

Claims

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

2. The spunbond nonwoven fabric according to claim 1, wherein, The value of the following formula (I) is 300% 3 In the following, Formula (I): (coefficient of variation of the outer diameter of the hollow fiber) 2 × coefficient of variation of the hollow rate of the hollow fiber.

3. The spunbond nonwoven fabric according to claim 1, wherein, The average outer diameter of the hollow fiber is less than 30 μm.

4. The spunbond nonwoven fabric according to claim 1, wherein, The average hollowness of the hollow fiber is 10% to 40%.

5. The spunbond nonwoven fabric according to claim 1, wherein, The hollow fiber contains polypropylene resin.

6. The spunbond nonwoven fabric according to claim 1, wherein, The hollow fiber has a monofilament linear strength of 19.0 mN / denier or higher, and a monofilament elongation of 300% or higher.

7. The spunbond nonwoven fabric according to claim 1, wherein, The average outer diameter of the hollow fiber is greater than 10 μm and less than 30 μm, and the average hollowness of the hollow fiber is 10% to 40%.

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

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

10. A hollow fiber manufacturing apparatus for manufacturing hollow fibers according to any one of claims 1 to 7, the manufacturing apparatus having a spinneret, wherein the length of the slot of the spinneret is less than 8 relative to the width of the slot.

11. A method for manufacturing hollow fibers, wherein the hollow fibers according to any one of claims 1 to 7 are manufactured by spinning and layering, wherein... The traction speed of the hollow fibers when they are stacked on the moving mesh curtain is 2000m / min to 4000m / min.

12. A method for manufacturing hollow fibers, wherein hollow fibers are manufactured by spinning and stacking using a hollow fiber manufacturing apparatus, the manufacturing apparatus having a spinneret, wherein the length of the slot of the spinneret is less than 8 relative to the width of the slot, and the traction speed of the hollow fibers when stacked on a moving mesh curtain is 2000 m / min to 4000 m / min.

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