Composite long-fiber nonwoven fabric, method for manufacturing same, and hygienic material

Abstract

The present invention relates to a long-fiber nonwoven fabric formed from composite fibers constituted by a thermoplastic resin A and a thermoplastic resin B, wherein the thermoplastic resin A is a polyolefin resin, the absolute value |ΔTm|(°C) of the difference between the melting point Tm,A(°C) of the thermoplastic resin A and the melting point Tm,B(°C) of the thermoplastic resin B is 20-200°C, and the composite fibers are side-by-side type composite fibers or eccentric core-sheath type composite fibers and satisfy formula 1.　(Formula 1): 10 ≤ r / φ ≤ 80　In the formula, r is the coil diameter (μm) of the composite fibers and φ is the average single fiber diameter (μm) of the composite fibers.　Provided is a long-fiber nonwoven fabric which is sufficiently friction-durable for use as a hygienic material nonwoven fabric to be used on the surface of a hygienic material in contact with skin, and which has excellent cushioning properties.

Description

Composite long-fiber nonwoven fabric, its manufacturing method, and sanitary material

[0001] The present invention relates to a long-fiber nonwoven fabric.

[0002] With the global spread of sanitary materials such as disposable diapers, sanitary napkins, and masks, demands for the performance and quality of the components used have been increasing in recent years. In particular, components that come into direct contact with the skin of the user, such as diaper top sheets, are required to have a certain degree of bulkiness while being resistant to compression in the thickness direction, i.e., cushioning properties, in order to improve comfort when worn.

[0003] Various studies have been conducted to apply long-fiber nonwoven fabrics with excellent strength and productivity to top sheets, etc. For example, Patent Document 1 proposes a spunbond nonwoven fabric having specific ranges for the thickness of the nonwoven fabric, the compression work measured in a compression test using the KES method, the thickness under a specific load, the basis weight, and bending flexibility. Patent Document 1 describes that a spunbond nonwoven fabric can be obtained that is bulky, has excellent flexibility, and has low bending rigidity.

[0004] Furthermore, Patent Document 2 proposes a composite long-fiber nonwoven fabric containing a polypropylene resin as a first component and a polyethylene resin as a second component, in which the bonded points of the fibers within the nonwoven fabric and the distance between the bonded points are controlled within specific ranges. Patent Document 2 describes that the composite long-fiber nonwoven fabric has both high strength and high bulkiness providing cushioning softness, and is suitable for use as a top sheet or back sheet in sanitary materials.

[0005] International Publication No. 2020 / 152890 Japanese Patent Application Laid-Open No. 2019-85661

[0006] In the technology proposed in Patent Document 1, when a nonwoven fiber web is bonded with an embossing roll in the manufacturing process, the Rockwell hardness and embossing aspect ratio of the embossing are adjusted to maintain the bulkiness of the nonwoven fabric. However, this technology tends to reduce the proportion of fibers oriented in the thickness direction, resulting in a nonwoven fabric that is weak against compression in the thickness direction and easily crushed. As a result, although the resulting long-fiber nonwoven fabric is bulky, it has issues with cushioning properties.

[0007] Furthermore, the technology proposed in Patent Document 2 also tends to have a low proportion of fibers oriented in the thickness direction, resulting in a nonwoven fabric that is weak against compression in the thickness direction and easily collapses, posing a problem in terms of cushioning properties.

[0008] In view of the above circumstances, an object of the present invention is to provide a long-fiber nonwoven fabric having bulk and cushioning properties suitable for use in sanitary materials, particularly for surfaces that come into contact with the skin.

[0009] As a result of extensive research aimed at achieving the above-mentioned object, the present inventors have found that crimping composite fibers, such as side-by-side composite fibers or eccentric sheath-core composite fibers, can impart a certain level of bulkiness and cushioning properties, but the effect is still insufficient. Therefore, as a result of further research, they have found that by setting the ratio of the coil diameter to the average single fiber diameter of the composite fiber within a specific range, unprecedented superior bulkiness and cushioning properties can be achieved. Furthermore, they have found that the fibers constituting this long-fiber nonwoven fabric have good adhesion to each other, resulting in sufficient durability against friction.

[0010] The present invention has been completed based on these findings, and provides the following inventions.

[0011] [1] A long-fiber nonwoven fabric composed of conjugated fibers made of thermoplastic resin A and thermoplastic resin B, wherein at least one of the thermoplastic resin A and the thermoplastic resin B is a polyolefin-based resin, and the melting point T ｍ、Ａ (°C) and the melting point T ｍ、Ｂ Absolute value of the difference between (℃) |ΔT ｍ| (°C) is 20°C or more and 200°C or less, the conjugate fibers are side-by-side conjugate fibers or eccentric core-sheath conjugate fibers, and the continuous fiber nonwoven fabric further satisfies the following formula 1:

[0012] 10≦r / φ≦80 (Equation 1) Here, r is the coil diameter (μm) of the composite fiber, and φ is the average single fiber diameter (μm) of the composite fiber.

[0013] [2] The continuous fiber nonwoven fabric according to [1], wherein the average single fiber diameter of the conjugated fibers is 7.5 μm or more and 30.0 μm or less.

[0014] [3] In the cross section of a single fiber of the conjugated fiber, the area occupied by the thermoplastic resin having a lower melting point, of the thermoplastic resin A and the thermoplastic resin B, is defined as A. Ｌ When the cross-sectional area of ​​the single fiber (A ｆ ) to A Ｌ The ratio (100 × A Ｌ / A ｆ ) is 40% or more and 90% or less.

[0015] [4] A sanitary material at least partly composed of the long-fiber nonwoven fabric according to any one of [1] to [3] above.

[0016] [5] A hygienic material in which the long-fiber nonwoven fabric according to any one of [1] to [3] is arranged in a portion that comes into contact with the skin.

[0017] [6] A hygienic material comprising a top sheet containing the long-fiber nonwoven fabric according to any one of [1] to [3].

[0018] [7] A process of melting a thermoplastic resin A and a thermoplastic resin B and supplying them to a composite spinneret, and spinning a composite polymer stream from the outlet holes of the composite spinneret; A process of cooling the composite polymer stream and then drawing it with an air drawing unit to obtain fibers; A process of collecting the fibers on a belt to form a web; and A process of subjecting the web to T Ｗand a step of blowing a gas heated to (°C) onto the nonwoven fabric to form composite fibers that satisfy the following formula 1, wherein at least one of the thermoplastic resin A and the thermoplastic resin B is a polyolefin resin, and the composite fibers are side-by-side composite fibers or eccentric sheath-core composite fibers, and further satisfy the following formulas 2 to 4.

[0019] 10≦r / φ≦80 ... (Formula 1) 20≦|ΔT ｍ |≦200...(Formula 2) η Ａ / η Ｂ ≦0.50 or 2.00≦η Ａ / η Ｂ ...(Formula 3) T ｍｉｎ -20≦T Ｗ ≦T ｍｉｎ +100 (Equation 4) where r is the coil diameter (μm) of the composite fiber, φ is the average single fiber diameter (μm) of the composite fiber, and |ΔT ｍ |: Melting point T of thermoplastic resin A ｍ、Ａ (°C) and the melting point T ｍ、Ｂ Absolute value of the difference (℃) with η Ａ : Melt viscosity of the thermoplastic resin A (Pa s), η Ｂ : Melt viscosity of the thermoplastic resin B (Pa s), T Ｗ : temperature of the hot air (°C), T ｍｉｎ : The melting point (°C) of the thermoplastic resin having the lower melting point out of the thermoplastic resin A and the thermoplastic resin B.

[0020] [8] In the step of forming the web, the bulk density of the web is 0.010 g / cm ３ 0.050g / cm or more ３ The method for producing a long-fiber nonwoven fabric according to [7] above, wherein:

[0021] [9] The method for producing a long-fiber nonwoven fabric according to [7] or [8], wherein in the step of spinning the composite polymer stream, the extrusion ratio of the thermoplastic resin component having a lower melting point, out of the thermoplastic resin A and the thermoplastic resin B, is set to 40% by mass or more and 90% by mass or less.

[0022] According to the present invention, it is possible to provide a long-fiber nonwoven fabric that not only exhibits excellent bulkiness and cushioning properties but also sufficient durability against friction. Because of these properties, the long-fiber nonwoven fabric of the present invention is suitable for use in hygienic materials, particularly in the surfaces that come into contact with the skin, such as top sheets.

[0023] FIG. 1 is a diagram illustrating a part of a method for measuring the coil diameter r (μm) of a composite fiber in a long-fiber nonwoven fabric according to one embodiment of the present invention.

[0024] The long-fiber nonwoven fabric of the present invention is composed of conjugated fibers made of thermoplastic resin A and thermoplastic resin B, the thermoplastic resin A being a polyolefin-based resin, and the melting point T ｍ、Ａ (°C) and the melting point T ｍ、Ｂ Absolute value of the difference between (℃) |ΔT ｍ | (°C) is 20°C or more and 200°C or less, the composite fiber is a side-by-side type composite fiber or an eccentric core-sheath type composite fiber, and further satisfies the following formula 1: 10≦r / φ≦80 (Formula 1), where r is the coil diameter (μm) of the composite fiber, and φ is the average single fiber diameter (μm) of the composite fiber.

[0025] The components will be described in detail below, but the present invention is not limited to the scope of the following description as long as it does not deviate from the gist of the present invention.

[0026] [Composite Fiber] The composite fiber in the long-fiber nonwoven fabric of the present invention is composed of a thermoplastic resin A and a thermoplastic resin B. At least one of the thermoplastic resins A and B is a polyolefin-based resin. In the present invention, a polyolefin-based resin refers to a resin in which the molar fraction of olefin units in the repeating units is 80 mol % or more and 100 mol % or less. Hereinafter, any thermoplastic resin expressed as "...-based resin" will have the same meaning. When at least one thermoplastic resin in the composite fiber is a polyolefin-based resin, the long-fiber nonwoven fabric has a smooth feel and is suitable for use as a sanitary material.

[0027] Specific examples of this polyolefin resin include olefin homopolymers such as polyethylene, polypropylene, polybutene, and polymethylpentene, copolymers of ethylene, propylene, and the like with α-olefins (copolymerized polyethylene, copolymerized polypropylene, etc.), and mixed resins (blend resins) thereof. Among these, polyethylene (homopolymer of ethylene) is preferred, as polyethylene improves the adhesion between fibers, improves cushioning properties, and results in a long-fiber nonwoven fabric with excellent mechanical properties.

[0028] Furthermore, this polyolefin resin may contain inorganic particles such as titanium oxide particles, lubricants, pigments, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, antibacterial agents, etc., depending on various purposes, within the scope of not interfering with the object of the present invention.

[0029] Next, both the thermoplastic resin A and the thermoplastic resin B may be the polyolefin resins. For example, when one thermoplastic resin is polyethylene and the other thermoplastic resin is polypropylene, a long-fiber nonwoven fabric with high dimensional stability is obtained. On the other hand, in this case, from the viewpoint of increasing the rigidity of the fiber and improving the cushioning properties, it is preferable that the polypropylene used has a high degree of crystallinity. For this reason, it is preferable that the polypropylene used is isotactic polypropylene or that a crystal nucleating agent is blended. Furthermore, from the viewpoint of increasing the rigidity of the fiber and improving the cushioning properties, it is preferable that the crystallinity of the polyethylene used is also high. For this reason, the density of the polyethylene used is 0.930 g / cm ３ It is preferable that the density is 0.940 g / cm or more. ３ More preferably, it is set to be equal to or greater than this.

[0030] The density referred to here is the value measured based on Method D (density gradient tube method) of JIS K 7112 "Method for measuring density and specific gravity of plastics and non-foamed plastics."

[0031] When a polyolefin resin is used for either thermoplastic resin A or thermoplastic resin B, and another thermoplastic resin is used for the other, examples of the other thermoplastic resin include polyester resins such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyester elastomer, and polylactic acid, polyacetal resins, or copolymers and mixed resins (blend resins) thereof. Among these, when at least the other thermoplastic resin of the composite fiber is polyethylene terephthalate or polybutylene terephthalate, a long-fiber nonwoven fabric with high tensile strength and dimensional stability is obtained. In particular, polyethylene terephthalate is preferably used from the viewpoint of high polymer rigidity and ease of achieving cushioning properties.

[0032] Naturally, the thermoplastic resin B may contain inorganic particles such as titanium oxide particles, lubricants, pigments, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, antibacterial agents, etc., depending on various purposes, within the scope of not impairing the object of the present invention.

[0033] In the long-fiber nonwoven fabric of the present invention, the melting point T ｍ、Ａ (°C) and the melting point T ｍ、Ｂ Absolute value of the difference between (℃) |ΔT ｍ | (hereinafter, sometimes referred to as "absolute value of melting point difference |ΔTm|") (°C) is 20°C or more and 200°C or less.

[0034] In the long-fiber nonwoven fabric of the present invention, the absolute value of the melting point difference |ΔT ｍ If |(°C) is 20°C or higher, the components with higher melting points maintain their fiber structure during thermal bonding processing, while the components with lower melting points melt or soften sufficiently to act as an adhesive, resulting in a long-fiber nonwoven fabric that has excellent cushioning properties while still having tensile strength and fluff resistance. By maintaining the fiber shape and structure of the components with higher melting points, cushioning properties can be increased, so the absolute value of the melting point difference |ΔT ｍ On the other hand, the absolute value of the melting point difference |ΔT ｍIf | is made too large, the stiffness of the fibers during thermal bonding becomes high, making it difficult for the fibers to move, resulting in weak bonding and a decrease in tensile strength. ｍ | must be 200°C or less, more preferably 150°C or less.

[0035] The absolute value of the melting point difference |ΔT ｍ | (°C) is a value measured and calculated by the following procedure. (1) Using scissors, a 3 mg test piece is taken from the long-fiber nonwoven fabric. (2) Using a differential scanning calorimeter (e.g., a TA Instruments "DSCQ2000"), the test piece is heated from 20°C to 300°C at a heating rate of 16°C / min under a nitrogen atmosphere to melt the test piece. A graph is then obtained, with temperature (°C) on the horizontal axis and endothermic heat (mW / mg) on ​​the vertical axis. (3) If multiple endothermic peaks appear on the graph, the peaks with the largest and second largest endothermic heats are identified, and the absolute value (°C) of the difference in temperature (°C) between the peaks of these two peaks is calculated. (4) Steps (1) to (3) are repeated 10 times, and the arithmetic mean (°C) of the absolute values ​​of the melting point differences obtained is rounded to one decimal place.

[0036] Next, the conjugate fiber according to the present invention is a side-by-side type conjugate fiber or an eccentric sheath-core type conjugate fiber. The eccentric sheath-core type conjugate fiber as referred to in the present invention is a conjugate fiber in which, when the cross section of a single fiber is observed, two types of resin portions can be observed, one resin completely covering the other resin, and in the cross section of the single fiber, the position of the center of gravity of the completely covering resin is different from the position of the center of gravity of the single fiber.

[0037] In these composite fibers, the centers of gravity of the two resins are located at different positions in the cross section of a single fiber, so that when tension is released in the spinning process, the fiber curves according to the difference in the elastic recovery of thermoplastic resin A and thermoplastic resin B, and this curve continues in the fiber axial direction, allowing crimps to be generated. Such crimps cause the fibers to repel each other, thereby improving the bulkiness of the nonwoven fabric.

[0038] In the continuous fiber nonwoven fabric of the present invention, the center of gravity of thermoplastic resin A and the center of gravity of thermoplastic resin B in the cross section of a single fiber can be largely separated, and the crimp form can be precisely controlled. Therefore, it is preferable to use side-by-side conjugated fibers.

[0039] On the other hand, when using eccentric sheath-core composite fibers, it is preferable to use the thermoplastic resin with the lower melting point of thermoplastic resin A or thermoplastic resin B as the sheath component, as this provides good adhesion and improves tensile strength. When eccentric sheath-core composite fibers are used in the continuous-fiber nonwoven fabric of the present invention, the crimp morphology of the fibers can be controlled by the difference in the center of gravity position in the cross section of the single fiber, so it is sufficient to control the center of gravity position so as to obtain the desired nonwoven fabric properties. In particular, when the center of gravity position is to be significantly expanded, it is preferable to use eccentric sheath-core composite fibers having a thin skin portion as disclosed in WO 2020 / 095861.

[0040] The cross-sectional shape of the conjugated fiber according to the present invention is not particularly limited as long as it does not impair the effects of the present invention, and may be a circular cross section, or an irregular cross section such as an elliptical cross section, or a polygonal cross section such as a triangle, a rectangle, or a hexagon (including those with rounded corners and those with different aspect ratios such as a rectangle), and the single fiber cross section may have a hollow portion or the like.

[0041] In the composite fiber according to the present invention, the area occupied by the thermoplastic resin having a lower melting point, either the thermoplastic resin A or the thermoplastic resin B, in the cross section of the composite fiber is defined as A. Ｌ (μm ２ ) when the cross-sectional area A of the composite fiber ｆ (μm ２ ) to A Ｌ The ratio (100 × A Ｌ / A ｆ ) is preferably 40% or more and 90% or less.

[0042] Cross-sectional area A of the composite fiber ｆ A against Ｌ The ratio (100 × A Ｌ / A ｆ(hereinafter, sometimes simply referred to as "area ratio of low-melting-point thermoplastic resin") is preferably 40% or more and 90% or less, more preferably 50% or more and 90% or less, and even more preferably 50% or more and 85% or less. By controlling the area ratio of the low-melting-point thermoplastic resin within this range, it is possible to obtain a long-fiber nonwoven fabric with excellent cushioning properties, since the crimp of the conjugated fiber can be precisely controlled while maintaining appropriate rigidity.

[0043] The area ratio of the low-melting-point thermoplastic resin referred to here is a value measured and calculated by the following method: (i) Cross-sectional area A of the composite fiber ｆ (μm ２ ) is measured by the following steps (i-1) to (i-5). (i-1) Randomly cut out 1 cm square test pieces from the long-fiber nonwoven fabric. (i-2) Cool the test pieces to -30°C, embed them in ice, and cut them into sections using a microtome (e.g., "AUTOCUT R" manufactured by Leica Microsystems Co., Ltd.) and place them on a glass slide. (i-3) Photograph the sections using a microscope (e.g., "VHX-X1" manufactured by Keyence Corporation) at a magnification that allows the cross sections of 10 or more single fibers to be observed. (i-4) Using the photographed fiber cross-section images, image analysis software (e.g., "WinROOF2015" manufactured by Mitani Shoji Co., Ltd.) is used to calculate the area formed by the cross-sectional contour of the single fiber in units of μm ２ (i-5) The area is measured for 20 single fibers randomly extracted from the same test piece, and the arithmetic mean value (μm ２ ) rounded to the first decimal place and used as the cross-sectional area A of the single fiber. ｆ (μm ２ ) (ii) Among the thermoplastic resins constituting the composite fiber, the thermoplastic resin with the lower melting point is identified by the following steps (ii-1) to (ii-5). Since two types of thermoplastic resin portions can be observed in the cross section of the composite fiber, each thermoplastic resin component can be identified by Raman spectroscopy as shown here. (ii-1) Cross-sectional area A of the composite fiber ｆ (μm ２(ii-2) The Raman spectra of the two thermoplastic resins constituting the cross section of the composite fiber are measured using micro-Raman spectroscopy, using 20 cross-sectional images of the single fiber taken to measure the cross section. For this measurement, a micro-Raman spectroscopy device such as the "Laser Raman Microscope RAMAN Touch" manufactured by Nanophoton Inc. can be used. In this case, the beam spot diameter of the measurement light is preferably sufficiently small compared to the single fiber diameter of the composite fiber, for example, 1 μm or more and 2 μm or less. (ii-3) The types of the two thermoplastic resins are identified by comparing the Raman spectrum thus obtained with known Raman spectra. (ii-3) If the melting points of the two thermoplastic resins identified in (ii-2) are known, they are compared to determine the thermoplastic resin with the lower melting point. If the melting point is not known, obtain a thermoplastic resin having the same structure, measure the melting point based on JIS K 7121:2012 "Method for measuring transition temperature of plastics," and compare the measurement results to determine the thermoplastic resin with the lower melting point. ｆ (μm ２ Using 20 cross-sectional images of the composite fiber taken to measure the area occupied by the thermoplastic resin with a lower melting point among the thermoplastic resins identified in step (2), the area formed by the cross-sectional contour of the single fiber was calculated using image analysis software (for example, "WinROOF2015" manufactured by Mitani Shoji Co., Ltd.) in units of μm ２ The arithmetic mean value (μm ２ ) rounded to the first decimal place and used as the area A occupied by the thermoplastic resin with the lower melting point. Ｌ (μm ２ (iv) Using the values ​​measured in (i) and (iii), 100 x A Ｌ / A ｆ The value obtained by rounding off to the first decimal place is the area ratio of the low melting point thermoplastic resin.

[0044] The continuous fiber nonwoven fabric of the present invention satisfies the following formula 1 with respect to the composite fibers: 10≦r / φ≦80 (Formula 1), where r is the coil diameter (μm) of the composite fibers, and φ is the average single fiber diameter (μm) of the composite fibers.

[0045] With regard to the range of the ratio of the coil diameter of the composite fiber to the average single fiber diameter of the composite fiber (r / φ, hereinafter sometimes simply referred to as the "coil diameter ratio"), if the lower limit is 10 or more, preferably 20 or more, more preferably 30 or more, the fibers will have a sufficiently large crimp diameter, and the proportion of fibers in the long-fiber nonwoven fabric that are oriented in the thickness direction and have a certain length or more will be high, resulting in a long-fiber nonwoven fabric that is bulky and soft to the touch. On the other hand, with regard to the range of the coil diameter ratio, if the upper limit is 80 or less, preferably 70 or less, more preferably 50 or less, the fibers will have a fine crimp, and a long-fiber nonwoven fabric that generates an appropriate resilience when the nonwoven fabric is crushed and has excellent cushioning properties.

[0046] Here, the coil diameter r (μm) and average single fiber diameter φ (μm) of the composite fiber are values ​​measured and calculated by the following method. <Coil diameter r (μm) of composite fiber> (1) Randomly cut 5 cm square test pieces from a long-fiber nonwoven fabric. (2) Observe the surface of the cut-out long-fiber nonwoven fabric using a scanning electron microscope (SEM, for example, the "VHX-6000" manufactured by Keyence Corporation) to find fibers that exhibit crimping as shown in Figure 1 without applying a load to the fibers, and take an image at a magnification that allows five or more fibers to be observed. (3) In the fibers that exhibit crimping as shown in Figure 1, select two adjacent peaks and draw a line L passing through each vertex (1A and 1B in Figure 1). Determine the distance d (μm) between the line L and the vertex of the valley between the two adjacent peaks (1C in Figure 1). (4) The distance d (μm) is measured for 20 fibers randomly extracted from the long-fiber nonwoven fabric, and the arithmetic mean value (μm) is rounded to one decimal place. <Average Single Fiber Diameter φ (μm) of Composite Fiber> (1) A 1 cm square test piece is cut out from the long-fiber nonwoven fabric. (2) The test piece is cooled to -30°C, embedded in ice, and sliced ​​using a microtome (e.g., "AUTOCUT R" manufactured by Leica Microsystems Co., Ltd.) and placed on a glass slide. (3) The slice is photographed using a microscope (e.g., "VHX-X1" manufactured by Keyence Corporation) at a magnification that allows the cross sections of 10 or more single fibers to be observed. (4) Using the photographed fiber cross-sectional image, the area A formed by the cross-sectional contour of the single fiber is calculated using image analysis software (e.g., "WinROOF2015" manufactured by Mitani Corporation). ｆ (μm ２ ) is measured. (5) This area A ｆ (6) Measure the diameter D (μm) of 20 single fibers randomly extracted from the long-fiber nonwoven fabric, and round off the arithmetic mean value (μm) to one decimal place.

[0047] The average single fiber diameter of the conjugated fiber according to the present invention is preferably 7.5 μm or more and 30.0 μm. By setting the average single fiber diameter of the conjugated fiber to preferably 7.5 μm or more, more preferably 10.0 μm or more, and even more preferably 12.5 μm or more, the fibers are less likely to bend even when a load is applied, resulting in a long-fiber nonwoven fabric with excellent cushioning properties. On the other hand, by setting the average single fiber diameter of the conjugated fiber to preferably 30.0 μm or less, more preferably 25.0 μm or less, and even more preferably 20.0 μm or less, the long-fiber nonwoven fabric is excellent in cushioning properties and softness.

[0048] The conjugate fiber according to the present invention preferably has micro-fused portions at least at some of the contact points between the fibers.

[0049] The micro-fused portions referred to here are portions (non-macro-fused portions) other than the macro-fused portions described below, which are fused to adjacent fibers. The contact points between fibers include not only these micro-fused portions, but also portions where fibers are entangled with each other and portions where fibers are simply in contact with each other without being fused.

[0050] The conjugate fibers in the long-fiber nonwoven fabric of the present invention have micro-fused portions, which results in a long-fiber nonwoven fabric with excellent cushioning properties and sufficient strength.

[0051] When the conjugated fiber has the above-mentioned micro-fused portions, this can be confirmed by observing the conjugated fiber from the cross section of the spunbonded nonwoven fabric using a microscope (for example, "VW-9000" manufactured by Keyence Corporation) or a scanning electron microscope (for example, "VHX-D500" manufactured by Keyence Corporation). In this case, when the spunbonded nonwoven fabric has macro-fused portions described below, the micro-fused portions are confirmed in the non-macro-fused portions.

[0052] [Long-fiber nonwoven fabric] The long-fiber nonwoven fabric of the present invention is composed of the above-mentioned composite fiber. This composite fiber is a long fiber, and by using this long fiber in the nonwoven fabric, sufficient mechanical properties can be obtained even with a low basis weight, even in high-speed production using high-speed conveying. Furthermore, by using long fibers, when the long-fiber nonwoven fabric is compressed, the load is not propagated in the plane direction, and the compressive stress is not easily unevenly distributed, thereby providing higher cushioning properties.

[0053] In addition, the long fiber nonwoven fabric of the present invention has a basis weight of 10 g / m ２ 50g / m or more ２ The basis weight is preferably 10 g / m or less. ２ More preferably, 20 g / m ２ By satisfying the above conditions, the long-fiber nonwoven fabric has a mechanical strength sufficient for practical use. ２ or less, more preferably 40 g / m ２ By satisfying the following conditions, the long-fiber nonwoven fabric has an appropriate flexibility suitable for use as a nonwoven fabric for sanitary materials.

[0054] The basis weight here is a value measured based on "6.2 Mass per unit area" of JIS L 1913:2010 "General nonwoven fabric testing methods."

[0055] The long-fiber nonwoven fabric of the present invention has a bulk density of 0.010 g / cm ３ 0.050g / cm or more ３ By controlling the bulk density within this range, the long-fiber nonwoven fabric can be felt to have sufficient bulkiness when touched. On the other hand, the bulk density is preferably 0.030 g / cm or less. ３ or less, more preferably 0.025 g / cm ３ By satisfying the above condition, a long-fiber nonwoven fabric having excellent bulkiness and flexibility can be obtained.

[0056] The bulk density referred to here is the value obtained by dividing the basis weight (W) of a long-fiber nonwoven fabric by its thickness (H), and is measured using the following procedure. (A) The thickness (H) of a long-fiber nonwoven fabric is measured using the following steps (A-1) to (A-4). (A-1) A 25 mm x 40 mm test piece is randomly taken from the long-fiber nonwoven fabric at a location that is free of wrinkles and folds. (A-2) The test piece is placed on the measurement table of a 3D microscope (for example, the "VR-3050" manufactured by Keyence Corporation). (A-3) A plastic plate measuring 80 mm x 80 mm, 1 mm thick, and with a 20 mm x 20 mm hole in the center is placed on top of the test piece so that one half of the hole (10 mm x 20 mm) is occupied by the test piece, and the test piece is fixed so that it is horizontal to the measurement table. (A-4) The thickness of the test piece inside the hole in the plastic plate is measured at eight random points in units of μm. (A-5) The arithmetic mean of the measured values ​​is rounded to the first decimal place in units of μm, and this value is taken as the thickness (H) of the long-fiber nonwoven fabric. (B) The basis weight W (g / m) of the long-fiber nonwoven fabric measured by the above method is ２ ) by the thickness H (μm) of the long-fiber nonwoven fabric, and the value is rounded off to three decimal places.

[0057] The continuous fiber nonwoven fabric of the present invention may have macro-fused portions for the purpose of adjusting bulkiness, as long as the effects of the present invention are not impaired.

[0058] The term "macro-fused portion" as used herein refers to a portion where the fibers are fused together by being compressed in the cross-sectional direction of the long-fiber nonwoven fabric, where the cross-sectional shape of the fibers is deformed to an extent that it differs from the shape of the remaining portions, and further where the fibers melt to the point that the portion becomes a lump or film. Specifically, this refers to a portion where the fibers are thermally compressed by a hot embossing roll or where the fibers are thermally fused by ultrasonic vibration.

[0059] When sufficient heat is applied to a portion during thermal compression bonding or thermal fusion bonding so that the entire composite fiber in that portion is fused, the shape and area of ​​the compressed portion of the thermal embossing roll or the like used can be considered to be the same as the shape and area of ​​the macro-fused portion. For example, in the case of thermal compression bonding using a thermal embossing roll, when thermal bonding is performed using a pair of rolls having projections and recesses as described below, the shape and area of ​​the macro-fused portion are considered to be the same as the shape and area of ​​the portion where the projections of the upper roll and the projections of the lower roll overlap and contact the nonwoven fiber web. Furthermore, when thermal bonding is performed using a roll having projections and recesses and a flat roll as described below, the shape and area of ​​the macro-fused portion are considered to be the same as the shape and area of ​​the portion where the projections of the roll having projections and recesses contact the nonwoven fiber web.

[0060] In the long-fiber nonwoven fabric of the present invention, it is preferable to set the area ratio of the macro-fused portions to 1% or more and 30% or less, since this allows for good bulkiness.

[0061] The long-fiber nonwoven fabric of the present invention has a compression work capacity of 10.0 mN cm / cm ２ 20.0 mN cm / cm or more ２ The compression work is preferably 10.0 mN cm / cm or less. ２ or more, more preferably 12.0 mN cm / cm ２ By setting the compression load at or above 20.0 mN cm / cm, the resistance when crushed increases, resulting in a long-fiber nonwoven fabric with appropriate cushioning properties and resilience. ２ or less, more preferably 19.0 mN cm / cm ２ When the thickness is equal to or less than 100 μm, the long-fiber nonwoven fabric has a soft feel.

[0062] The compression work load referred to here is measured and calculated according to the following procedure: (i) Ten 5 cm x 5 cm test pieces are randomly obtained from the long-fiber nonwoven fabric. (ii) The test pieces are placed on the metal sample stage of a compression tester (for example, the "KES-G5" manufactured by Kato Tech Co., Ltd.). (iii) The pressure area is 2 cm. ２ Between steel plates with circular flat surfaces, the compression speed is 0.020 mm / s and the compression load is 5.0 mN / cm２ The test piece was compressed until the compressive stress (mN / cm ２ (iv) The x-axis represents the thickness (mm) of the test piece, and the y-axis represents the compressive stress (mN / cm ２ (v) A graph (compression characteristic curve) is drawn showing the results when the compression load is 5.0 mN / cm. ２ Thickness of time (T ０ ) and a compressive load of 500 mN / cm ２ Thickness of time (T Ｍ (vi) The compression characteristic curves depicted in (iv) to (v), x-axis (y=0), x=T ０ , x=T Ｍ The area of ​​the region surrounded by S (mN mm / cm ２ ) was measured using the compression tester and divided by 10 to obtain a value in mN cm / cm. ２ (vii) Repeat steps (ii) to (vi) for all test pieces, and calculate the arithmetic mean value of the area S (mN cm / cm ２ ) and round to two decimal places.

[0063] The compression work load varies depending on the fiber morphology and the rigidity of the fibers themselves in the long-fiber nonwoven fabric and can be controlled, for example, by the coil diameter ratio. Therefore, it is advisable to adjust the coil diameter ratio according to the desired compression work load.

[0064] The fuzz grade of the long-fiber nonwoven fabric of the present invention, measured by the following procedure, is preferably 3.0 or higher, more preferably 3.5 or higher. When the fuzz grade of the long-fiber nonwoven fabric is in this range, it indicates that the fabric has sufficient durability against friction when used as a sanitary material.

[0065] The fluff grade of the long-fiber nonwoven fabric of the present invention is a value measured and calculated by the following method: (i) Five test pieces of 25 mm x 300 mm are randomly taken from the long-fiber nonwoven fabric. (ii) A test piece is placed in a Japan Society for the Promotion of Science type fastness tester (for example, the "RT-200" dyed fabric rubbing fastness tester manufactured by Daiei Scientific Instruments Co., Ltd.), and a frictional load of 200 g is applied to the frictional element. A cloth adhesive tape having a dynamic friction coefficient of 0.055 to 0.060 (for example, "Rinrei Cross - for heavy packaging No. 317" manufactured by Rinrei Tape Co., Ltd.) is attached to the frictional element side, and the test piece is operated 50 times. Here, the dynamic friction coefficient of the cloth adhesive tape is measured and calculated according to the procedures shown in (ii-1) to (ii-5) below. (ii-1) The cloth adhesive tape is cut into a piece having a width of 3 cm and a length of 27 cm, and attached to the measurement table of a friction tester (for example, "KES-SE" manufactured by Kato Tech Co., Ltd.). (ii-2) A 1 cm x 1 cm friction probe wrapped with 1 mm piano wire is placed on the adhesive cloth tape, and a load of 50 g, including the friction probe, is applied from above. (ii-3) The friction probe is moved at a speed of 1.0 mm / sec and a stroke length of 20 mm to measure the friction coefficient in dimensionless units, and a graph is plotted with the stroke length on the horizontal axis and the friction coefficient on the vertical axis. (ii-4) The average friction coefficient between 5.0 mm and 15.0 mm on the graph plotted in (ii-3) is calculated. (ii-5) The friction coefficients are measured at three different locations on the adhesive cloth tape using the procedures in (ii-1) to (ii-4), and the average is rounded to the nearest tenth. (iii) After measurement, the sample is visually inspected and the fuzziness is graded according to the following criteria: Grade 1.0: The test specimen is broken and the fibers are torn off. Grade 2.0: The fibers have been peeled off so much that the test piece has become thinner. Grade 2.5: Large, clearly visible pills have formed, and fibers have begun to lift in multiple places. Grade 3.0: Clear pills have begun to form, or multiple small pills are visible. Grade 3.5: The test piece is fuzzy to the extent that a small pill has begun to form in one place. Grade 4.0: No pilling. (iv) Turn the test piece over, and grade the fuzziness of the back side using the steps (ii) to (iii).(v) For all test pieces, determine the grades for the front and back using the procedures (ii) to (iv), and calculate the average value for a total of 10 grade data points for the front and back of each sample, and round off to two decimal places.

[0066] The fluff grade of the long fiber nonwoven fabric can be increased to grade 3.0 or higher by adjusting the coil diameter of the crimped composite fiber and by strengthening the adhesion between the fibers.

[0067] The long-fiber nonwoven fabric of the present invention may be laminated with other sheet members. In this case, it is preferable that at least the surface layer is made of the long-fiber nonwoven fabric, since the fabric has a good feel and cushioning properties due to its bulkiness.

[0068] Examples of the other sheet members include nonwoven fabric members such as spunbond nonwoven fabric and meltblown nonwoven fabric, and film members such as microporous films and stretchable films.

[0069] [Hygienic Material] Because the hygienic material of the present invention has the above-mentioned properties, it is at least partially composed of the above-mentioned long-fiber nonwoven fabric. It is also preferred that the long-fiber nonwoven fabric is disposed in a portion that comes into contact with the skin, or that the long-fiber nonwoven fabric is included in a top sheet. This provides excellent cushioning and softness, and is therefore very comfortable to wear.

[0070] The hygienic materials of the present invention specifically refer to mainly disposable articles used for health-related purposes such as medical care and nursing care, and examples thereof include disposable diapers, sanitary napkins, gauze, bandages, masks, gloves, and adhesive bandages, as well as their constituent parts, such as top sheets, back sheets, and side gathers of disposable diapers.

[0071] [Method for producing a continuous-fiber nonwoven fabric] Next, a preferred embodiment of the method for producing a continuous-fiber nonwoven fabric according to the present invention will be specifically described. The method for producing a continuous-fiber nonwoven fabric according to the present invention is preferably as follows: a step of melting thermoplastic resin A and thermoplastic resin B, respectively, and feeding them to a composite spinneret, and spinning a composite polymer stream from the discharge holes of the composite spinneret; a step of cooling the composite polymer stream and then drawing it with an air drawing unit to obtain fibers; a step of collecting the fibers on a belt to form a web; and a step of subjecting the web to T. Ｗ (°C) to form conjugate fibers that satisfy the following formula 1: and a method for producing a continuous-fiber nonwoven fabric, wherein at least one of the thermoplastic resin A and the thermoplastic resin B is a polyolefin-based resin, and the conjugate fibers are side-by-side conjugate fibers or eccentric core-sheath conjugate fibers, and further satisfy the following formulas 2 to 4: 10≦r / φ≦80 (Formula 1) 20≦|ΔT ｍ |≦200...(Formula 2) η Ａ / η Ｂ ≦0.50 or 2.00≦η Ａ / η Ｂ ...(Formula 3) T ｍｉｎ -20≦T Ｗ ≦T ｍｉｎ +100 (Equation 4) where r is the coil diameter (μm) of the composite fiber, φ is the average single fiber diameter (μm) of the composite fiber, and |ΔT ｍ |: Melting point T of thermoplastic resin A ｍ、Ａ (°C) and the melting point T ｍ、Ｂ Absolute value of the difference (℃) with η Ａ : Melt viscosity of the thermoplastic resin A (Pa s), η Ｂ : Melt viscosity of the thermoplastic resin B (Pa s), T Ｗ : temperature of the hot air (°C), T ｍｉｎ : The melting point (°C) of the thermoplastic resin having the lower melting point out of the thermoplastic resin A and the thermoplastic resin B.

[0072] These are described in detail below.

[0073] (a) Step of spinning a composite polymer stream In this step, thermoplastic resin A and thermoplastic resin B are each melted and supplied to a composite spinneret, and a composite polymer stream is spun from the discharge holes of the composite spinneret. Thermoplastic resin A and thermoplastic resin B here are those described above, and at least one of them is a polyolefin resin.

[0074] In this step, the following formulas 2 and 3 are satisfied: 20≦|ΔT ｍ |≦200...(Formula 2) η Ａ / η Ｂ ≦0.50 or 2.00≦η Ａ / η Ｂ ... (Equation 3) Here, each symbol is as defined above.

[0075] η Ａ / η Ｂ The melt viscosity ratio (hereinafter sometimes referred to as the melt viscosity ratio) is 0.50 or less or 2.00 or more. This allows for precise control of the coil diameter of the composite fiber, which makes it difficult for the web to be compressed in the heated gas blowing step described below, and as a result, a long-fiber nonwoven fabric with excellent cushioning properties can be easily obtained. The melt viscosity ratio is preferably 0.40 or less or 2.50 or more, and more preferably 0.33 or less or 3.00 or more. On the other hand, from the viewpoint of keeping the difference in flow speed between the two thermoplastic resins in the spinneret within a certain range and preventing the polymer flow from bending significantly after discharge, thereby enabling the long-fiber nonwoven fabric of the present invention to be stably obtained without yarn breakage, the melt viscosity ratio is preferably 10.00 or less or 0.10 or more, and more preferably 6.00 or less or 0.17 or more.

[0076] The melt viscosity ratio referred to here is measured and calculated as follows: (i) 10 g of each of the thermoplastic resins A and B is sampled, heated to the spinning temperature using a rheometer (for example, "Rheosol-G3000" manufactured by UBM Co., Ltd.), and measured at a shear rate of 0.3 s －１ The viscosity (Pa s) when a shear force of 1000 MPa was applied was measured, and this was determined as the melt viscosity η Ａ(Pa s) and the melt viscosity η of thermoplastic resin B Ｂ (Pa・s). (ii) η Ａ (Pa s) to η Ｂ Divide by (Pa·s) and round to three decimal places.

[0077] In addition, at least one of the thermoplastic resins A and B to be extruded is a polyolefin resin. The use of a polyolefin resin increases the elastic recovery after fiberization, allowing for precise control of the coil diameter of the composite fiber. As a result, a long-fiber nonwoven fabric can be obtained that combines a soft, voluminous feel with excellent cushioning properties.

[0078] Among these, polyolefin resins having a glass transition temperature of 30°C or lower are more preferable. Furthermore, polyethylene, polypropylene, or copolymers thereof are particularly preferable because they enable stable spinning. The glass transition temperature of the thermoplastic resin referred to here is a value measured based on JIS K 7121:2012 "Method for measuring transition temperature of plastics."

[0079] The melting point T ｍ、Ａ (°C) and the melting point T ｍ、Ｂ Absolute value of the difference between (℃) |ΔT ｍ By setting the melting point difference | (°C) (hereinafter sometimes referred to as melting point difference) to 20°C or higher, preferably 30°C, the web is less likely to be compressed in the heated gas blowing step described below, and a long-fiber nonwoven fabric with excellent bulkiness can be obtained. On the other hand, by setting the melting point difference to 200°C or lower, preferably 150°C, the thermoplastic resin with the lower melting point can be discharged without thermal decomposition in the composite spinneret, and a long-fiber nonwoven fabric can be stably obtained. Furthermore, in the heated gas blowing step described below, the composite fibers can be appropriately softened, allowing for good adhesion. As a result, a long-fiber nonwoven fabric with excellent bulkiness can be obtained.

[0080] Said T ｍ、Ａ , T ｍ、Ｂis a value measured for the thermoplastic resin A and the thermoplastic resin B under a nitrogen atmosphere based on JIS K 7121:2012 "Method for measuring transition temperature of plastics."

[0081] The thermoplastic resin A and the thermoplastic resin B may both be polyolefin resins. For example, when one thermoplastic resin is polyethylene and the other thermoplastic resin is polypropylene, the difference in elastic recovery can be increased, and the coil diameter of the composite fiber can be easily and precisely controlled. In this case, from the viewpoint of increasing the crystallinity and significantly increasing the difference in elastic recovery, the density of the polyethylene used is preferably 0.930 g / cm. ３ It is preferable that the density is 0.940 g / cm or more. ３ On the other hand, from the viewpoint of the stability of spinning, the polypropylene used is preferably isotactic polypropylene.

[0082] Furthermore, it is preferable that the melt viscosity of the polyethylene is higher than that of the polypropylene, since this allows for easy and precise control of the coil diameter of the composite fiber.

[0083] When one of the thermoplastic resins A and B is a polyolefin-based resin and the other is another thermoplastic resin, examples of the other thermoplastic resin include polyester-based resins such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyester elastomers, and polylactic acid, polyacetal-based resins, and copolymers and mixed resins (blend resins) thereof. Among these, when at least the other thermoplastic resin of the composite fiber is polyethylene terephthalate or polybutylene terephthalate, the difference in elastic recovery with the polyolefin-based resin can be increased, making it easy to precisely control the coil diameter of the composite fiber. Among these, polyethylene terephthalate is preferably used because the polymer itself has high rigidity and can make the web less likely to be compressed in the heated gas blowing process described below.

[0084] Furthermore, when a polyolefin-based resin is used for either the thermoplastic resin A or the thermoplastic resin B, and another thermoplastic resin is used for the other, it is preferable to make the melt viscosity of the polyolefin-based resin higher than the melt viscosity of the other thermoplastic resin, since this makes it possible to easily and precisely control the coil diameter of the composite fiber.

[0085] The melt viscosity of the polyolefin resin is preferably 20 Pa s or more, more preferably 50 Pa s or more. By setting the melt viscosity of the polyolefin resin in this range, the elastic recovery of the polyolefin resin in the composite fiber can be more significantly increased, and the coil diameter of the composite fiber can be precisely controlled. On the other hand, in order to maintain an appropriate tension during the composite fiber formation process and improve spinnability, the melt viscosity of the polyolefin resin is preferably 700 Pa s or less, more preferably 600 Pa s or less.

[0086] In this step, the extrusion ratio of the thermoplastic resin with the lower melting point, between thermoplastic resin A and thermoplastic resin B, is preferably 40% by mass or more and 90% by mass or less. It is more preferably 50% by mass or more and 90% by mass or less. The thermoplastic resin with the lower melting point melts and bonds in the step of blowing heated gas, which will be described later, so it is preferable to control the ratio within this range from the viewpoint of obtaining sufficient adhesive strength and maintaining the rigidity of the fibers when melted in the bonding step. Furthermore, the coil diameter of the crimp in the composite fiber can be made finer, resulting in excellent bulkiness and cushioning properties.

[0087] The conjugate spinneret used in this step preferably has a mechanism capable of forming side-by-side conjugate fibers or eccentric core-sheath conjugate fibers.

[0088] Here, the conjugate spinneret equipped with a mechanism capable of forming eccentric sheath-core conjugate fibers is preferably a spinneret capable of spinning eccentric sheath-core conjugate fibers having a thin skin portion as disclosed in WO 2020 / 095861. The shape of the nozzle holes of the spinneret may be freely selected as long as it does not impair the effects of the present invention, but from the viewpoint of spinning stability, round holes are preferred.

[0089] In the method for producing a continuous-fiber nonwoven fabric of the present invention, it is preferable to change the discharge amount per discharge hole of the spinneret as desired according to the desired average single fiber diameter, taking into consideration the spinning speed.

[0090] (b) Fiber Obtaining Step In this step, the composite polymer stream is cooled and then pulled by an air pulling unit to obtain a fiber. In this way, the coil diameter of the fiber can be precisely controlled. In particular, by using the air pulling unit, the difference in elastic recovery between thermoplastic resin A and thermoplastic resin B can be increased during the cooling process of the composite polymer stream, allowing the coil diameter of the obtained fiber to be precisely controlled. Note that the air pulling unit referred to here is a device that flows compressed gas in at least one direction and accelerates and pulls the polymer stream with the air flow.

[0091] In this step, the speed at which the composite polymer flow is pulled (spinning speed) is preferably 2,000 m / min or more and 5,000 m / min or less, more preferably 2,500 m / min or more and 5,000 m / min or less. By setting the spinning speed within this range, the difference in elastic recovery and the average single fiber diameter can be easily controlled, and the fiber coil diameter ratio can be appropriately controlled.

[0092] (c) Web Forming Step In this step, the fibers are collected on a belt to form a web.

[0093] In the method for producing a long-fiber nonwoven fabric of the present invention, the fibers produced as described above are mixed with a nonwoven fabric having a bulk density of 0.010 g / cm ３ 0.050g / cm or more ３ It is preferable that the density is 0.010 g / cm or less. More preferably, it is 0.010 g / cm ３ 0.035g / cm or more ３ Particularly preferably, 0.010 g / cm ３ 0.030g / cm or more ３ The following is the result.

[0094] The bulk density referred to here is a value measured by taking a sample of the web collected on the belt from the process before thermal bonding and measuring the bulk density in the same manner as in the measurement of the bulk density of the long-fiber nonwoven fabric described above.

[0095] In the method for producing a long-fiber nonwoven fabric of the present invention, by setting the bulk density within this range, the gas permeability can be improved and uniform thermal bonding can be achieved in the heated gas blowing step described below, which results in both bulkiness and cushioning properties, and a pleasant feel when the surface is stroked with a hand.

[0096] In this process, after the web is formed, the web may be subjected to a crimping process to control the coil diameter ratio, which will be described later. The crimping process referred to here is a process in which the web collected on the belt is heated or stretched to change the shape of the fibers that make up the web, and is a separate process from the process of blowing heated gas, which will be described later. Among these, heat processing is preferred, as it can uniformly change the fibers within the web.

[0097] (d) A step of blowing heated gas onto the web. Ｗ In this process, the gas heated to a temperature T Ｗ (°C) satisfies the following formula 4 described above. ｍｉｎ -20≦T Ｗ ≦T ｍｉｎ +100 ... (Equation 4) T here ｍｉｎ The melting point of the thermoplastic resin A measured as described above is the lower melting point of the thermoplastic resin B. The temperature of the heated gas is the temperature at a point 0.50 cm above the upper surface of the web on the belt.

[0098] In this step, T Ｗ By satisfying formula 4, it is possible to adequately melt only the thermoplastic resin with the lower melting point, out of thermoplastic resin A and thermoplastic resin B, while maintaining the rigidity of the composite fibers, thereby adequately bonding the composite fibers together. As a result, it is possible to obtain a long-fiber nonwoven fabric that has both bulkiness and cushioning properties and is also excellent in softness when stroked.

[0099] The temperature range of the heated gas preferably satisfies the following formula 4-1, and more preferably satisfies formula 4-2: Tｍｉｎ -20≦T Ｗ ≦T ｍｉｎ +75...(Formula 4-1) T ｍｉｎ -20≦T Ｗ ≦T ｍｉｎ +100...(Formula 4-2).

[0100] The gas used in this step may be any gas, but air is preferred from the viewpoints of cost and safety. Also, heated steam may be used from the viewpoint of increasing the thermal conductivity of the composite fiber.

[0101] In this step, the heated gas is preferably blown at a velocity Va (m / sec) in the range of 1.0 m / sec to 13.0 m / sec. Here, the term "blowing velocity Va (m / sec)" as used herein refers to the velocity of the gas blown vertically downward from the belt at a point 0.50 cm above the web surface.

[0102] In this step, by controlling the velocity of the heated gas within this range, thermal bonding can be achieved without excessively compressing the web in the thickness direction, thereby improving the bulkiness of the long-fiber nonwoven fabric.

[0103] Furthermore, in this process, it is preferable to blow the heated gas onto the web as described above while simultaneously sucking the gas downward from the belt. By simultaneously blowing and sucking in this process, the heated gas is diffused within the web without crushing it, enabling uniform bonding in the thickness direction. As a result, it is possible to achieve both bulkiness and cushioning properties while maintaining good softness when touching the surface.

[0104] The air velocity Vq (m / sec) during suction is preferably 1.0 m / sec or more, and more preferably 1.0 m / sec or more and 12.0 m / sec or less, from the viewpoint of not compressing the web more than necessary and maintaining bulkiness.

[0105] The suction air speed in this invention means the speed of the air blowing vertically downward from the belt directly above the belt, and is the value measured at a position 0.50 cm above the belt surface without blowing gas from above the belt.

[0106] In this step, when suction is performed simultaneously with blowing of heated gas, the bulkiness and cushioning properties can be controlled by balancing the wind speed Va (m / s) of the blown heated gas and the wind speed Vq (m / s) of the suction. The difference between Va and Vq (Va-Vq) is preferably 0.0 m / s or more, and more preferably 0.0 m / s or more and 3.0 m / s or less. By controlling Va-Vq within the above preferred range, the web is not excessively compressed, and the heated gas can be uniformly heat-treated without stagnating within the web, thereby improving the bulkiness and cushioning properties of the long-fiber nonwoven fabric.

[0107] Furthermore, before or after this step, nipping may be performed between a pair of opposing rolls to control the bulk density. The rolls used here may be flat rolls or uneven rolls, or a combination of these. Of these, it is preferable to use an uneven roll on one side and a flat roll on the other side. With this configuration, a long-fiber nonwoven fabric with excellent bulkiness can be obtained.

[0108] Furthermore, the pair of rolls may be heated. In this case, the nipped portion between the rolls becomes the macro-fused portion. When one roll is a roll having projections and recesses and the other roll is a flat roll, it is preferable that the area ratio of the projections of the roll having projections and recesses be 1% or more and 30% or less so that the area ratio of the macro-fused portion is appropriate.

[0109] This process makes it possible to form a composite fiber that satisfies the following formula 1: 10≦r / φ≦80 (formula 1).

[0110] By setting the coil diameter ratio of the composite fiber within this range, a long-fiber nonwoven fabric having excellent bulkiness and cushioning properties can be obtained.

[0111] In order to control the coil diameter ratio of the composite fiber within the above range, it is preferable to appropriately control the types of thermoplastic resin A and thermoplastic resin B, the melt viscosity ratio, the extrusion ratio of the thermoplastic resin with a lower melting point, the cross section of the single fiber, the pulling conditions, and the conditions for blowing the heated gas, as described above.

[0112] (e) Other Finishing Steps In the method for producing the long-fiber nonwoven fabric of the present invention, it is also preferable to carry out various finishing steps, as in the case of general long-fiber nonwoven fabrics. Of course, in the present invention, the long-fiber nonwoven fabric obtained by these finishing steps is also considered to be the long-fiber nonwoven fabric of the present invention.

[0113] For example, when the long-fiber nonwoven fabric of the present invention is used as a top sheet of a diaper, it may be subjected to a hydrophilization treatment, which may be appropriately selected from known methods such as a spray method, a nip-dip method, or a kiss-roll method.

[0114] The present invention will be described in detail below based on examples, but the present invention is not limited to the following examples. In the long-fiber nonwoven fabric, the machine direction in production was defined as the MD direction, and the direction perpendicular to the MD direction was defined as the CD direction.

[0115] [Measurement Methods] The property values ​​in the examples were determined by the following methods. Unless otherwise specified, the values ​​were measured according to the above methods.

[0116] (1) Melting point T of thermoplastic resin A ｍ、Ａ (°C), melting point T of thermoplastic resin B ｍ、Ｂ (°C), melting point T of thermoplastic resin A ｍ、Ａ (°C) and the melting point T of thermoplastic resin B ｍ、Ｂ Absolute value of the difference between (℃) |ΔT ｍ | (°C) Measurements were performed using a differential scanning calorimeter "DSCQ2000" manufactured by TA Instruments in accordance with the above-mentioned method, and calculations were performed. In Tables 1 to 3, the melting point T ｍ、Ａ (°C) and the melting point T of thermoplastic resin B ｍ、Ｂ Absolute value of the difference between (℃) |ΔT ｍ | (℃), the absolute value of the melting point difference | ΔT ｍ | (℃)".

[0117] (2) Melt viscosity η of thermoplastic resin A Ａ (Pa s), melt viscosity η of thermoplastic resin B Ｂ (Pa s), and the ratio η Ａ / η Ｂ (No unit) Measurements were made and calculated according to the above-mentioned method using a rheometer "Rheosol-G3000" manufactured by UBM Co., Ltd. In Tables 1 to 3, the ratio η Ａ / η Ｂ (unitless) for "melt viscosity ratio η Ａ / η Ｂ It is abbreviated as (-).

[0118] (3) Bulk density of the web (g / cm ３ ), bulk density of long fiber nonwoven fabric (g / cm ３ ) Measurements and calculations were carried out using a 3D microscope "VR-3050" manufactured by Keyence Corporation according to the above-mentioned method. The bulkiness of the long-fiber nonwoven fabric was evaluated based on the measurement results into three levels from A (excellent bulkiness) to C (poor bulkiness) as follows: A: Bulk density is 0.010 g / cm ３ 0.030g / cm or more ３ B: Bulk density is 0.030 g / cm or less ３ Greater than 0.050 g / cm ３ C: Bulk density is 0.010 g / cm or less ３ or less than 0.050 g / cm ３ Greater than.

[0119] (4) Coil diameter r (μm) of composite fiber, average single fiber diameter φ (μm) of composite fiber, and ratio r / φ (unitless) thereof. Measurements were performed and calculated according to the above-described methods using a scanning electron microscope "VHX-6000" manufactured by Keyence Corporation, a microtome "AUTOCUT R" manufactured by Leica Microsystems Co., Ltd., a microscope "VHX-X1" manufactured by Keyence Corporation, and image analysis software "WinROOF2015" manufactured by Mitani Corporation.

[0120] (5) Area ratio of low melting point thermoplastic resin 100 x A Ｌ / Aｆ (%) Measurements and calculations were carried out according to the above-described methods using an "AUTOCUT R" microtome manufactured by Leica Microsystems, a "VHX-X1" microscope manufactured by Keyence Corporation, "WinROOF2015" image analysis software manufactured by Mitani Shoji Co., Ltd., and a "Laser Raman Microscope RAMAN touch" manufactured by Nanophoton Inc. as the microscopic Raman spectrometer.

[0121] (6) Basis weight of long fiber nonwoven fabric (g / m ２ ) Measured and calculated according to the method described above.

[0122] (7) Compression work (mN cm / cm ２ The compression tester used was a "KES-G5" manufactured by Kato Tech Co., Ltd., and measurements and calculations were carried out according to the above-mentioned method.

[0123] (8) Cushioning (Grade) Cushioning was evaluated and calculated according to the following method. (i) 10 cm x 10 cm test pieces were randomly taken from the long-fiber nonwoven fabric. (ii) Ten healthy, general adult subjects pressed the test pieces with their fingers in a manner that compressed them in the thickness direction, and evaluated each long-fiber nonwoven fabric on a 5-point scale according to the following criteria. The average score of the evaluation results for each nonwoven fabric was then used to represent the cushioning of that nonwoven fabric. 5: Easily crushed with fingers, with a slight rebound force felt when pressed. 3: Crushed with fingers, but no or a strong rebound force felt when pressed. 1: When crushed with fingers, there was no rebound at all and the crushed shape remained, or it was so hard that it could not be crushed with fingers at all.

[0124] (9) Fluff grade (grade) Using a Japan Society for the Promotion of Science type fastness tester, a dyed material rubbing fastness tester "RT-200" manufactured by Daiei Scientific Instruments Mfg. Co., Ltd., as a cloth adhesive tape, "Rinrei Cross - for heavy packaging No. 317" manufactured by Rinrei Tape Co., Ltd., as a friction feel tester, and "KES-SE" manufactured by Kato Tech Co., Ltd. as a friction feel tester, the fluff grade was measured and calculated according to the above-mentioned method.

[0125] (10) Area ratio of macro-fused portion 100 x S ２ / S １The area ratio of the macro-fused portions (%) was measured and calculated according to the following method. (i) Five samples (100 x 100 mm) were randomly taken from the long-fiber nonwoven fabric. (ii) For each sample, the area of ​​the repeating unit of the arrangement of the macro-fused portions (S １ ) and the area of ​​the macro-fused portion contained in the repeating unit (S ２ ) was measured at five points, and S ２ S １ (iii) The area ratios (%) of the 25 locations were averaged and rounded to the nearest whole number.

[0126] [Resins Used] The resins used in the Examples and Comparative Examples are as follows: PE1: melting point 127°C, solid density 0.955 g / cm ３ , a melt viscosity at 280 ° C of 196 Pa s, and a melt index (hereinafter, MI) of 26 g / 10 min (measured in accordance with JIS-K7210 at a temperature of 190 ° C and a load of 2.16 kg. The same applies hereinafter unless otherwise specified). PE2: a melting point of 127 ° C, a solid density of 0.955 g / cm ３ PE3: Polyethylene with a melting point of 127°C and a solid density of 0.955 g / cm3, and a melt viscosity of 390 Pa s at 280°C and an MI of 10 g / 10 min. ３ PE4: melting point 127°C, solid density 0.955 g / cm ３, a melt viscosity of 120 Pa·s at 230°C, and an MI of 50 g / 10 min. PET1: Polyethylene terephthalate with a melting point of 260°C and a melt viscosity of 65 Pa·s at 280°C. PET2: Polyethylene terephthalate with a melting point of 260°C and a melt viscosity of 93 Pa·s at 280°C. PET3: Polyethylene terephthalate with a melting point of 260°C and a melt viscosity of 250 Pa·s at 280°C. PET4: Polyethylene terephthalate with a melting point of 260°C and a melt viscosity of 108 Pa·s at 280°C. iPP1: a propylene homopolymer having a melting point of 160°C, a melt viscosity of 365 Pa·s at 230°C, a melt viscosity of 150 Pa·s at 280°C, and a melt mass-flow rate (MFR) of 25 g / 10 min (measured in accordance with ASTM D1238 at a temperature of 230°C and a load of 2.16 kg; the same applies hereinafter unless otherwise specified). iPP2: a propylene homopolymer having a melting point of 160°C, a melt viscosity of 290 Pa·s at 230°C, and an MFR of 30 g / 10 min. iPP3: a propylene homopolymer having a melting point of 160°C, a melt viscosity of 1500 Pa·s at 230°C, and an MFR of 3 g / 10 min. iPP4: a propylene homopolymer having a melting point of 162°C, a melt viscosity of 190 Pa·s at 230°C, and an MFR of 60 g / 10 min. iPP5: Propylene homopolymer with a melting point of 162°C, a melt viscosity of 202 Pa·s at 230°C, and an MFR of 55 g / 10 min. Copolymer PP1: Propylene-ethylene random copolymer with a melting point of 145°C, a melt viscosity of 290 Pa·s at 230°C, and an MFR of 45 g / 10 min. Copolymer PP2: Propylene-ethylene random copolymer with 15% by mass of ethylene copolymerized therein, a melting point of 59°C, a melt viscosity of 202 Pa·s at 280°C, and an MFR of 35 g / 10 min. Copolymer PP3: Propylene-ethylene random copolymer with a melting point of 142°C, a melt viscosity of 190 Pa·s at 230°C, and an MFR of 60 g / 10 min. PBT1: Polybutylene terephthalate with a melting point of 220°C, a melt viscosity of 201 Pa·s at 280°C.

[0127] Example 1 (a) Step of spinning a composite polymer stream PE1 was used as thermoplastic resin A, and PET1 was used as thermoplastic resin B. These were melted in separate extruders, and the spinning temperature was set to 280°C. A rectangular spinneret capable of obtaining a side-by-side composite cross section was used as the composite spinneret, and a composite polymer stream was spun from the composite spinneret at a throughput rate per hole of 0.75 g / min and a throughput mass ratio of thermoplastic resin A:thermoplastic resin B = 50:50.

[0128] (b) Step of Obtaining Fibers After cooling the composite polymer stream, it was drawn using a rectangular ejector as an air drawing unit to obtain fibers, at a spinning speed of 3070 m / min.

[0129] (c) Forming a Web The resulting fibers are then collected on a moving collection belt to form a web having a bulk density of 0.015 g / cm. ３ A web of the above formula was formed, in which the fibers in the web had crimps.

[0130] (d) Step of blowing heated gas The web thus obtained was thermally bonded by blowing air heated to 200°C from above the web toward the vertically downward side of the belt at a wind speed of 3.6 m / s while sucking the air vertically downward of the collecting belt at a wind speed of 2.2 m / s, thereby forming a web with a basis weight of 35.0 g / m. ２ A long-fiber nonwoven fabric of 100g was obtained. The obtained long-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 1.

[0131] [Example 2] (a) In the step of spinning a composite polymer stream, the composite spinneret was changed to a rectangular spinneret that could obtain an eccentric core-sheath composite cross section, and thermoplastic resin A (PE1) was used as the sheath component and thermoplastic resin B (PET1) as the core component. (c) In the step of forming a web, a bulk density of 0.020 g / cm ３ A long-fiber nonwoven fabric was obtained in the same manner as in Example 1, except that a web of 1000 μm was obtained. The obtained long-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 1.

[0132] [Example 3] (a) In the step of spinning a composite polymer stream, the output per hole was set to 2.20 g / min, (b) In the step of obtaining fibers, the spinning speed was set to 2600 m / min, and (c) In the step of forming a web, the bulk density was set to 0.040 g / cm. ３ A long-fiber nonwoven fabric was obtained in the same manner as in Example 1, except that a web of 1000 μm was obtained. The obtained long-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 1.

[0133] [Example 4] (a) In the step of spinning a composite polymer stream, the output per hole was set to 0.15 g / min, (b) In the step of obtaining fibers, the spinning speed was set to 3050 m / min, and (c) In the step of forming a web, the bulk density was set to 0.023 g / cm ３ A long-fiber nonwoven fabric was obtained in the same manner as in Example 1, except that a web of 1000 μm was obtained. The obtained long-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 1.

[0134] [Example 5] (a) In the step of spinning a composite polymer stream, a composite polymer stream was spun at a discharge mass ratio of thermoplastic resin A:thermoplastic resin B = 30:70, and (c) in the step of forming a web, a bulk density of 0.034 g / cm ３ A long-fiber nonwoven fabric was obtained in the same manner as in Example 1, except that a web of 1000 μm was obtained. The obtained long-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 2.

[0135] [Example 6] (a) In the step of spinning a composite polymer stream, PET2 was used as thermoplastic resin B, and (c) in the step of forming a web, a bulk density of 0.038 g / cm ３ A long-fiber nonwoven fabric was obtained in the same manner as in Example 1, except that a web of 1000 μm was obtained. The obtained long-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 2.

[0136] [Example 7] (a) In the step of spinning a composite polymer stream, PE2 was used as thermoplastic resin A, and (c) in the step of forming a web, a bulk density of 0.014 g / cm ３A long-fiber nonwoven fabric was obtained in the same manner as in Example 1, except that a web of 1000 μm was obtained. The obtained long-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 2.

[0137] [Example 8] (a) In the step of spinning a composite polymer stream, PE3 was used as thermoplastic resin A and PET3 was used as thermoplastic resin B, and (c) in the step of forming a web, a bulk density of 0.032 g / cm ３ A long-fiber nonwoven fabric was obtained in the same manner as in Example 1, except that a web of 1000 μm was obtained. The obtained long-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 2.

[0138] [Example 9] (a) In the step of spinning a composite polymer stream, PE4 was used as thermoplastic resin A, iPP1 was used as thermoplastic resin B, and the spinning temperature was set to 230°C; (b) In the step of obtaining fibers, the spinning speed was set to 3800 m / min; and (c) In the step of forming a web, a bulk density of 0.019 g / cm ３ A long-fiber nonwoven fabric was obtained in the same manner as in Example 1, except that in (d) the heated gas blowing step, the temperature of the heated air was set to 150°C. The obtained long-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 3.

[0139] [Example 10] (a) In the step of spinning a composite polymer stream, iPP2 was used as thermoplastic resin B, and (c) in the step of forming a web, a bulk density of 0.036 g / cm ３ A long-fiber nonwoven fabric was obtained in the same manner as in Example 9, except that a web of 0.025 g / cm2 was obtained. The obtained long-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 3. [Example 11] (a) In the step of spinning a composite polymer stream, iPP1 was used as thermoplastic resin A, (b) In the step of obtaining fibers, the spinning speed was set to 2955 m / min, and (c) In the step of forming a web, a web of 0.025 g / cm2 was used as thermoplastic resin A. ３A long-fiber nonwoven fabric was obtained in the same manner as in Example 1, except that a web of the above formula was obtained. The obtained long-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 3.

[0140] [Example 12] (c) In the step of forming a web, a bulk density of 0.015 g / cm ３ After obtaining the web, the obtained web was passed through a flat roll and an embossing roll (pattern specification: diamond pattern, bonded area ratio 11%) set at a temperature of 80°C, and the web was partially bonded at a linear pressure of 50 N / cm, except that a long-fiber nonwoven fabric was obtained in the same manner as in Example 1. The obtained long-fiber nonwoven fabric had both micro-fused portions and macro-fused portions. The results are shown in Table 3.

[0141]

[0142]

[0143]

[0144] [Comparative Example 1] (a) In the step of spinning a composite polymer stream, PBT1 was used as thermoplastic resin A, (b) in the step of obtaining fibers, the spinning speed was set to 2700 m / min, and further, in the step of forming a web, a bulk density of 0.025 g / cm ３ A long-fiber nonwoven fabric was obtained in the same manner as in Example 1, except that in (d) the heated gas blowing step, the temperature of the heated air was set to 240°C. The obtained long-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 4.

[0145] [Comparative Example 2] (a) In the step of spinning a composite polymer stream, the composite spinneret was changed to a rectangular spinneret that could produce concentric sheath-core composite fibers, and (c) in the step of forming a web, a bulk density of 0.077 g / cm ３ A continuous-fiber nonwoven fabric was obtained in the same manner as in Example 2, except that a web of 1000 kJ / cm2 was obtained. In this case, the fibers in the web were not crimped. The obtained continuous-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 4.

[0146] [Comparative Example 3] (a) In the step of spinning a composite polymer stream, iPP5 was used as thermoplastic resin B, the discharge mass ratio of thermoplastic resin A:thermoplastic resin B was set to 33:67, and the spinning temperature was set to 230°C. (b) In the step of obtaining fibers, the spinning speed was set to 2777 m / min. Furthermore, (c) In the step of forming a web, a bulk density of 0.065 cg / m was set to 0.065 cg / m. ３ A long-fiber nonwoven fabric was obtained in the same manner as in Example 2, except that in (d) the step of blowing heated gas, the temperature of the heated air was 140°C, the velocity of the heated gas was 1.0 m / s, and the velocity of the sucked gas was 0.0 m / s. The obtained long-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 4.

[0147] [Comparative Example 4] (a) In the step of spinning a composite polymer stream, copolymer PP1 was used as thermoplastic resin B, and (c) in the step of forming a web, a bulk density of 0.045 g / cm ３ A long-fiber nonwoven fabric was obtained in the same manner as in Example 9, except that a web of the above formula was obtained. The obtained long-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 4.

[0148] [Comparative Example 5] (a) In the step of spinning a composite polymer stream, copolymerized PP2 was used as thermoplastic resin A, (b) in the step of obtaining fibers, the spinning speed was set to 3150 m / min, and further, in the step of forming a web, a bulk density of 0.065 g / cm ３ A long-fiber nonwoven fabric was obtained in the same manner as in Example 9, except that in (d) the heated gas blowing step, the temperature of the heated air was set to 110°C. The obtained long-fiber nonwoven fabric had micro-fused portions but no macro-fused portions. The results are shown in Table 4.

[0149] Comparative Example 6 (a-1) Step of spinning a composite polymer stream Copolymer PP3 was used as thermoplastic resin A, and a mixture of copolymer PP3 and iPP3 in a weight ratio of 96:4 was used as thermoplastic resin B. These were melted in separate extruders, and a composite polymer stream was spun from the composite spinneret at a spinning temperature of 230°C using a rectangular spinneret capable of obtaining a side-by-side composite cross section at a throughput rate per hole of 0.75 g / min and a throughput mass ratio of thermoplastic resin A:thermoplastic resin B = 60:40.

[0150] (b-1) Step of Obtaining Fibers After cooling the composite polymer stream, it was pulled using a rectangular ejector as an air pulling unit to obtain fibers. At this time, the spinning speed was set to 3,420 m / min.

[0151] (c-1) Step of forming a web Subsequently, the obtained fibers are collected on a moving collection belt to form a web having a basis weight of 11.4 g / m ２ , bulk density 0.030 g / cm ３ A web of the formula was formed. This web was used as the lower-layer web. At this time, the fibers in the lower-layer web had crimps. (a-2) Step of spinning a composite polymer stream Copolymer PP3 was used as thermoplastic resin A, and iPP4 was used as thermoplastic resin B. These were melted in separate extruders, and the spinning temperature was set to 230°C. A rectangular spinneret capable of obtaining a side-by-side composite cross section was used as the composite spinneret, and a composite polymer stream was spun from the composite spinneret at a throughput rate per hole of 0.75 g / min and a throughput mass ratio of thermoplastic resin A:thermoplastic resin B = 80:20.

[0152] (b-2) Step of Obtaining Fibers After cooling the composite polymer stream, it was pulled using a rectangular ejector as an air pulling unit to obtain fibers, at a spinning speed of 3,420 m / min.

[0153] (c-2) Web Forming Step Subsequently, the obtained fibers were collected in-line on a lower web to prepare a laminated web. The upper web of the laminated web was designated as the upper web. The basis weight of the upper web was 5.6 g / m. ２ , bulk density is 0.028 g / cm ３In this case, the fibers in the upper web had crimps.

[0154] (d) Step of thermocompressing the web with an embossing roll The laminated web thus obtained was subjected to an embossing area ratio of 11% and an embossing aspect ratio of 4.1 mm / mm. ２ The embossing base material was heat-sealed using an embossing roll with a Rockwell hardness of 37 HRC at an embossing temperature of 140°C and an embossing line pressure of 784 N / cm, resulting in a total basis weight of 17 g / m. ２ A long-fiber nonwoven fabric having a diameter of 1 / 4" was obtained. The obtained long-fiber nonwoven fabric had macro-fused portions. The results are shown in Table 5.

[0155]

[0156]

[0157] As shown in Tables 1 to 3, the long-fiber nonwoven fabrics of Examples 1 to 12 had good bulkiness, excellent cushioning properties, and excellent fluffing grades. In particular, Examples 1 and 2 achieved both high levels of cushioning properties and fluffing resistance. In Examples 3 to 8, changes in bulkiness and cushioning properties were observed due to changes in the coil diameter ratio caused by changes in the average single fiber diameter of the constituting composite fibers, the area ratio of the low-melting point thermoplastic resin, and the coil diameter, but bulkiness and cushioning properties were well-balanced. In Examples 9 to 11, despite changes in the melting point difference between the thermoplastic resins used, bulkiness and cushioning properties were well-balanced. In particular, Example 9 achieved a high level of cushioning properties and fluffing resistance. In Example 12, changes in bulkiness and cushioning properties were observed due to the presence of macro-fused portions, but bulkiness and cushioning properties were well-balanced.

[0158] On the other hand, as shown in Tables 4 and 5, the long-fiber nonwoven fabrics of Comparative Examples 1 to 6 did not achieve both bulkiness and cushioning, and the fluff grade was also insufficient. In Comparative Example 1, the PBT with a low melting point was difficult to melt with heated air, resulting in poor adhesion. As a result, although the fabric had bulkiness, cushioning was not achieved and the fluff grade was significantly inferior. In Comparative Example 2, the composite fiber did not have crimps, resulting in insufficient bulkiness and cushioning. In Comparative Example 3, the coil diameter ratio of the composite fiber could not be controlled within an appropriate range, resulting in a low proportion of fibers oriented in the thickness direction. This resulted in a nonwoven fabric that was weak against compression in the thickness direction and easily collapsed, resulting in poor cushioning. In Comparative Example 4, the difference in melting points between the two thermoplastic resins used was small. When heated air was blown onto the web, the fibers in the web softened excessively, resulting in the web being crushed. As a result, the long-fiber nonwoven fabric had a high bulk density and was coarse and hard, resulting in poor bulkiness and cushioning. In Comparative Example 5, the difference in melting points between the two thermoplastic resins used was large, so the fibers in the web did not soften and were difficult to move during the heated air blowing process, resulting in poor adhesion and poor cushioning.In Comparative Example 6, the coil diameter ratio of the composite fibers could not be controlled within an appropriate range, resulting in a low proportion of fibers oriented in the thickness direction, which made the nonwoven fabric weak against compression in the thickness direction and prone to collapse, resulting in poor cushioning.

[0159] 1A, 1B: Apex of the crimped fiber peaks 1C: Apex of the valley between the crimped fiber peaks 1A and 1B L: A straight line passing through the crimped fiber peaks 1A and 1B d: The distance between the line L and the peak 1C

Claims

1. A long-fiber nonwoven fabric made of composite fibers consisting of thermoplastic resin A and thermoplastic resin B, wherein at least one of the thermoplastic resin A and the thermoplastic resin B is a polyolefin resin, and the melting point T ｍ、Ａ (°C) and the melting point T ｍ、Ｂ Absolute value of the difference between (℃) |ΔT ｍ A long-fiber nonwoven fabric, wherein |(°C) is 20°C or more and 200°C or less, the composite fibers are side-by-side composite fibers or eccentric core-sheath composite fibers, and the following formula 1 is satisfied: 10≦r / φ≦80 (Formula 1), where r is the coil diameter (μm) of the composite fibers, and φ is the average single fiber diameter (μm) of the composite fibers.

2. The continuous fiber nonwoven fabric according to claim 1, wherein the average single fiber diameter of the composite fibers is 7.5 μm or more and 30.0 μm or less.

3. In the cross section of a single fiber of the composite fiber, the area occupied by the thermoplastic resin with a lower melting point, of the thermoplastic resin A and the thermoplastic resin B, is defined as A. Ｌ When the cross-sectional area of ​​the single fiber (A ｆ ) to A Ｌ The ratio (100 × A Ｌ / A ｆ 3. The long-fiber nonwoven fabric according to claim 1, wherein the ratio of the total fiber density to the total fiber density is 40% or more and 90% or less.

4. A sanitary material at least partly composed of the long-fiber nonwoven fabric according to claim 1 or 2.

5. A hygienic material in which the long-fiber nonwoven fabric according to claim 1 or 2 is arranged in a portion that comes into contact with the skin.

6. A hygienic material comprising a top sheet containing the long-fiber nonwoven fabric according to claim 1 or 2.

7. A process of melting thermoplastic resin A and thermoplastic resin B and feeding them to a composite spinneret, and spinning a composite polymer stream from the outlet holes of the composite spinneret; a process of cooling the composite polymer stream and then drawing it with an air drawing unit to obtain fibers; a process of collecting the fibers on a belt to form a web; and a process of subjecting the web to T Ｗ (°C) to form composite fibers that satisfy the following formula 1, wherein at least one of the thermoplastic resin A and the thermoplastic resin B is a polyolefin resin, and the composite fibers are side-by-side composite fibers or eccentric core-sheath composite fibers, and further satisfy the following formulas 2 to 4: 10≦r / φ≦80 (Formula 1) 20≦|ΔT ｍ |≦200...(Formula 2) η Ａ / η Ｂ ≦0.50 or 2.00≦η Ａ / η Ｂ ...(Formula 3) T ｍｉｎ -20≦T Ｗ ≦T ｍｉｎ +100 (Equation 4) where r is the coil diameter (μm) of the composite fiber, φ is the average single fiber diameter (μm) of the composite fiber, and |ΔT ｍ |: Melting point T of thermoplastic resin A ｍ、Ａ (°C) and the melting point T ｍ、Ｂ Absolute value of the difference (℃) with η Ａ : Melt viscosity of the thermoplastic resin A (Pa s), η Ｂ : Melt viscosity of the thermoplastic resin B (Pa s), T Ｗ : temperature of the hot air (°C), T ｍｉｎ : The melting point (°C) of the thermoplastic resin having the lower melting point out of the thermoplastic resin A and the thermoplastic resin B.

8. In the step of forming the web, the bulk density of the web is 0.010 g / cm ３ 0.050g / cm or more ３ The method for producing a long-fiber nonwoven fabric according to claim 7, wherein:

9. A method for producing a long-fiber nonwoven fabric according to claim 7 or 8, wherein in the step of spinning the composite polymer flow, the extrusion ratio of the thermoplastic resin component with a lower melting point, of thermoplastic resin A and thermoplastic resin B, is 40% by mass or more and 90% by mass or less.

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