Nonwoven fabric, its manufacturing method, laminated nonwoven fabric, and sanitary material

Description

[Technical field]

[0001] The present invention relates to a nonwoven fabric, a method for producing the same, a laminated nonwoven fabric, and a sanitary material. [Background technology]

[0002] Spunbond nonwoven fabrics made of polyolefin resins, particularly nonwoven fabrics made of polypropylene resins, are low cost and have excellent processability and flexibility, and are therefore widely used primarily for sanitary material applications.

[0003] In recent years, in order to reduce the amount of petroleum-derived polymers used in sanitary material applications, there has been a demand to reduce the basis weight of nonwoven fabrics made of polypropylene-based resins used in sanitary material applications. Furthermore, even with a reduced basis weight, there is a demand for the fabric to exhibit the same mechanical properties and flexibility as current products.

[0004] As a nonwoven fabric that combines mechanical properties and flexibility, for example, Patent Document 1 proposes a nonwoven fabric containing thermally adhesive fibers in which a fiber-forming resin containing an ethylene-propylene copolymer is exposed on at least a part of the fiber surface, the fiber-forming resin containing an ethylene-propylene copolymer has an ethylene content within a specific range, and the amount of eluted components at 40°C measured by temperature-rise elution fractionation, the proportion of ethylene components in the eluted components, and the weight-average molecular weight of the eluted components are above a certain level. This invention also describes that the nonwoven fabric has excellent low-temperature adhesiveness and is soft and less sticky to the touch.

[0005] Patent Document 2 proposes a nonwoven fabric made of fibers containing polypropylene that is confirmed to have an isotactic pentad fraction, syndiotactic pentad fraction, heterogeneous bonds, weight average molecular weight, and polydispersity (Mw / Mn) within specific ranges and to have no terminal double bonds. This invention also describes that the nonwoven fabric is excellent in flexibility and strength.

[0006] Patent Document 3 proposes a thermally adhesive composite fiber that has a core component of crystalline polypropylene and a sheath component of polyolefin with a lower melting point than that of the core component, and the ratio of the weight average molecular weight of the core component to the weight average molecular weight of the sheath component (core component Mw / sheath component Mw) is equal to or less than a certain level. This invention also describes that a nonwoven fabric made of this fiber has high puncture strength.

[0007] Patent Document 4 proposes a fiber assembly made of thermally adhesive fibers having a first component as a core component made of highly crystalline polypropylene with a wide molecular weight distribution and a small amount of low molecular weight components, and a second component as a sheath component made of a resin whose melting point is lower than that of the first component. This invention also describes that the thermal shrinkage of this fiber assembly during thermal bonding is extremely small, and it can be easily processed into a nonwoven fabric with good texture.

[0008] Patent Document 5 proposes a nonwoven fabric for use as a recessed part of a mechanical fastener, which is made of constituent fibers including heat-fusible composite fibers having a core / sheath structure in which the sheath component has a lower melting point, the melting points of the core component and the sheath component being within a specific range, and the heat-fusible composite fibers having a fusion point strength and a content of a certain level or higher. This invention also describes that the nonwoven fabric has excellent fusion point strength, peel strength, and fuzz resistance.

[0009] Patent Document 6 proposes a nonwoven fabric in which the crystallite size of the polyolefin fiber and the bending stiffness of the nonwoven fabric are within a certain range. It is also described that the nonwoven fabric has high processability while maintaining excellent flexibility.

[0010] Patent Document 7 proposes a spunbond nonwoven fabric containing a polypropylene resin having a crystallization temperature, molecular weight distribution (Mw / Mn), and melt flow rate within a specific range, and describes that this invention provides a spunbond nonwoven fabric having good water resistance and tensile strength. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2003-171825 A [Patent Document 2] International Publication No. 1998 / 23799 [Patent Document 3] JP 2007-107143 A [Patent Document 4] Japanese Patent Application Publication No. 5-9809 [Patent Document 5] JP 2002-233404 A [Patent Document 6] JP 2012-21260 A [Patent Document 7] JP 2018-168509 A Summary of the Invention [Problem to be solved by the invention]

[0012] The technology proposed in Patent Document 1 enables thermal bonding at low temperatures and produces a flexible nonwoven fabric, but the strength of the individual fibers is insufficient, and as a result, there is a problem in that it is not possible to produce a nonwoven fabric exhibiting sufficient mechanical properties.

[0013] The technology proposed in Patent Document 2 makes it possible to obtain a nonwoven fabric that takes advantage of the inherent light weight and flexibility of polypropylene fibers and has improved heat resistance, but there are still issues with the mechanical properties of the nonwoven fabric.

[0014] Although the technique proposed in Patent Document 3 makes it possible to obtain a nonwoven fabric having a certain level of puncture strength, there are still problems to be solved with respect to the mechanical properties of the nonwoven fabric.

[0015] Although the technique proposed in Patent Document 4 makes it possible to obtain a nonwoven fabric with good texture, there are still problems to be solved with respect to the mechanical properties of the nonwoven fabric.

[0016] In the technology proposed in Patent Document 5, the constituent fibers are sheath-core conjugate fibers, and thus a nonwoven fabric having excellent strength at the fusion point can be obtained. However, the strength of the fiber alone is insufficient, and as a result, there is a problem in that a nonwoven fabric exhibiting sufficient mechanical properties cannot be obtained.

[0017] The technology proposed in Patent Document 6 suppresses molecular movement by using a large crystallite size, thereby producing a processable nonwoven fabric while maintaining a certain degree of flexibility; however, there are still issues with the mechanical properties of the nonwoven fabric.

[0018] Although the technique proposed in Patent Document 7 can obtain a nonwoven fabric having a certain tensile strength, there are still problems with the mechanical properties of the nonwoven fabric.

[0019] Therefore, an object of the present invention is to provide a nonwoven fabric that combines excellent flexibility and mechanical properties, a method for producing the same, a laminated nonwoven fabric, and a sanitary material. [Means for solving the problem]

[0020] As a result of further investigations, the inventors have found that in order for a nonwoven fabric to exhibit excellent mechanical properties, it is important that the constituent fibers exhibit excellent mechanical properties and that the fibers are sufficiently bonded to each other at the fusion joints. However, it was found that simply using composite fibers as the fibers constituting the nonwoven fabric in order to achieve sufficient bonding would result in insufficient fiber strength and therefore would not allow the production of a nonwoven fabric with excellent mechanical properties. As a result of further intensive investigations, it was found that a nonwoven fabric having excellent mechanical properties can be obtained by using composite fibers having a propylene fraction and an isotactic pentad fraction of at least a certain level and a molecular orientation parameter O in the fiber axis direction at the center of the fiber. C and the molecular orientation parameter O in the fiber axis direction at the fiber surface. S Difference with (O C -O S ) is in a specific range, and further, the melting point of the nonwoven fabric is in a specific range, thereby resulting in a nonwoven fabric that has both excellent mechanical properties and flexibility, and has thus completed the present invention.

[0021] The present invention aims to solve the above problems, and provides the following inventions.

[0022] [1] A nonwoven fabric made of composite fibers mainly composed of polypropylene-based resin, The composite fiber is Propylene fraction is 98.5% or more and 100.0% or less, The isotactic pentad fraction is 90.0% or more and 100.0% or less, and Molecular orientation parameter O in the fiber axis direction at the center of the fiber C and the molecular orientation parameter O in the fiber axis direction at the fiber surface. S Difference with (O C -O S ) is 0.2 or more and 4.0 or less, The nonwoven fabric has a melting point of 130°C or higher and 155°C or lower.

[0023] [2] The nonwoven fabric described in [1] above, wherein the heat of crystalline fusion of the nonwoven fabric is 82 J / g or more and 120 J / g or less.

[0024] [3] Molecular orientation parameter O in the fiber axis direction at the center of the fiber C The nonwoven fabric according to [1] or [2] above, wherein the MnO2 content is 5.0 or more and 10.0 or less.

[0025] [4] The nonwoven fabric according to any one of [1] to [3] above, wherein the nonwoven fabric is a spunbonded nonwoven fabric.

[0026] [5] The nonwoven fabric has a fused portion and a non-fused portion, The fused portion has a crystallite size of a (040) plane in wide-angle X-ray diffraction of 10.0 nm or more and 13.5 nm or less; The nonwoven fabric according to any one of the above [1] to [4], wherein the non-fused portion has a crystallite size of (110) plane in wide-angle X-ray diffraction of 5.0 nm or more and 10.0 nm or less.

[0027] [6] a step of melt-extruding, through a composite spinneret, a polypropylene-based resin A polymerized by a metallocene catalyst and having a propylene fraction of 98.5% or more and 100.0% or less, and a polypropylene-based resin B polymerized by a metallocene catalyst and having a melt flow rate higher than that of the polypropylene-based resin A by 6 g / 10 min to 200 g / 10 min, and having a propylene fraction of 98.5% or more and 100.0% or less, and pulling and stretching the spun polypropylene-based resin A and the polypropylene-based resin B to form islands-in-sea type composite fibers in which island components are the polypropylene-based resin A and a sea component is the polypropylene-based resin B; depositing the islands-in-the-sea type composite fibers to form a fiber web composed of the islands-in-the-sea type composite fibers; The method for producing a nonwoven fabric according to any one of the above [1] to [5], further comprising a step of thermally bonding the fiber web.

[0028] [7] The method for producing a nonwoven fabric according to [6] above, wherein the polypropylene-based resin A has a melt flow rate of 10 g / 10 min or more and 90 g / 10 min or less.

[0029] [8] The method for producing a nonwoven fabric according to [6] or [7], wherein the polypropylene-based resin A and / or the polypropylene-based resin B has an isotactic pentad fraction of 90.0% or more and 100.0% or less.

[0030] [9] The method for producing a nonwoven fabric according to any one of [6] to [8] above, wherein the number of islands in the islands-in-sea type composite fibers is 1 or more and 10 or less.

[0031]

[10] The method for producing a nonwoven fabric according to any one of [6] to [9] above, wherein the polypropylene resin A has a polydispersity (Mw / Mn) of 1.5 or more and 3.5 or less in molecular weight measurement.

[0032]

[11] A sanitary material comprising the nonwoven fabric according to any one of [1] to [5] above.

[0033]

[12] A laminated nonwoven fabric comprising a layer of the nonwoven fabric according to any one of [1] to [5] above and a fiber layer different from the layer of the nonwoven fabric.

[0034]

[13] A sanitary material comprising the laminated nonwoven fabric described in

[12] above. Effect of the Invention

[0035] The present invention provides a nonwoven fabric that has both excellent flexibility and mechanical properties, a method for producing the same, a laminated nonwoven fabric, and a sanitary material. Due to its properties, the nonwoven fabric of the present invention can be suitably used for sanitary materials, particularly for backsheets of disposable diapers. [Brief description of the drawings]

[0036] [Figure 1] FIG. 1 is a diagram illustrating the measurement points for the crystallite size of the (040) plane in wide-angle X-ray diffraction of the fused portion of the nonwoven fabric of the present invention, and the crystallite size of the (110) plane in wide-angle X-ray diffraction of the non-fused portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] The nonwoven fabric of the present invention is a nonwoven fabric composed of conjugated fibers mainly composed of polypropylene-based resin, and the conjugated fibers have a propylene fraction of 98.5% or more and 100.0% or less, an isotactic pentad fraction of 90.0% or more and 100.0% or less, and a molecular orientation parameter O in the fiber axis direction at the center of the fiber. C and the molecular orientation parameter O in the fiber axis direction at the fiber surface. S Difference with (O C -O S ) is 0.2 or more and 4.0 or less, and the melting point of the nonwoven fabric is 130°C or more and 155°C or less.

[0038] The nonwoven fabric of the present invention 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, and various modifications are possible without departing from the gist of the present invention.

[0039] [Polypropylene resin] The nonwoven fabric of the present invention is made of composite fibers mainly composed of polypropylene-based resin. By using a polypropylene-based resin, a low-cost nonwoven fabric having excellent flexibility can be obtained.

[0040] The polypropylene resin used in the present invention may be a propylene homopolymer, a copolymer of propylene and ethylene, or a copolymer of propylene and various α-olefins, etc. Here, α-olefin refers to a hydrocarbon having a double bond at the α-position, such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-hexadecene, or 4-methyl-1-pentene.

[0041] The polypropylene resin used in the present invention preferably has a propylene fraction of 98.5% or more and 100.0% or less. The propylene fraction of the polypropylene resin is preferably 98.5% or more, more preferably 98.8% or more, and even more preferably 99.0% or more, so that the tensile strength of the composite fiber is high, resulting in a nonwoven fabric with excellent mechanical properties. The upper limit of the propylene fraction of the polypropylene resin that can be achieved in the present invention is 100.0%.

[0042] The propylene fraction (%) of the polypropylene resin referred to here is a value measured and calculated by the following procedure. (1) Weigh out the polypropylene resin used as the raw material for the composite fiber, add orthodichlorobenzene-D4 (orthodichlorobenzene in which the hydrogen has been replaced with deuterium) to a sample concentration of 8 mass / v%, and heat to 135°C. (2) The resulting solution is analyzed using a nuclear magnetic resonance apparatus (e.g., JEOL RESONANCE "ECZ-600"). 13 C-NMR measurement is performed, and the peak area due to propylene units and the peak areas due to ethylene units and α-olefin units are calculated from the NMR spectrum. (3) The sum of the peak areas due to propylene units, ethylene units, and α-olefin units, A AP Peak area A due to propylene units PP The ratio of (A PP / A AP ) as a percentage. (4) Measurements are made three times for each level, and the arithmetic average value is rounded off to one decimal place to calculate the propylene fraction (%) of the polypropylene resin.

[0043] The propylene fraction of the polypropylene-based resin used in the present invention can be controlled, for example, by the composition of the raw material monomer. Specifically, the propylene fraction of the polypropylene-based resin can be increased by increasing the propylene ratio of the raw material monomer during polymerization of the polypropylene-based resin.

[0044] The polypropylene resin used in the present invention preferably has an isotactic pentad fraction of 90.0% or more and 100.0% or less. When the polypropylene resin has an isotactic pentad fraction of preferably 90.0% or more, more preferably 92.0% or more, and even more preferably 94.0% or more, the heat of crystal fusion is increased when the polypropylene resin is made into fibers, so that the tensile strength of the composite fiber is increased, resulting in a nonwoven fabric with excellent mechanical properties. The upper limit of the isotactic pentad fraction of the polypropylene resin that can be achieved in the present invention is 100.0%.

[0045] The isotactic pentad fraction (%) of the polypropylene resin referred to here is a value measured and calculated by the following procedure. (1) Weigh out the polypropylene resin used as the raw material for the composite fiber, add orthodichlorobenzene-D4 (orthodichlorobenzene in which the hydrogen has been replaced with deuterium) to a sample concentration of 8 mass / v%, and heat to 135°C. (2) The resulting solution is analyzed using a nuclear magnetic resonance apparatus (e.g., JEOL RESONANCE "ECZ-600"). 13 Perform C-NMR measurement. (3) Based on the method described in "Zambelli et al., Macromolecules, Vol. 8, p. 687 (1975)", the peaks in the methyl group-derived spectrum of the obtained NMR spectrum are assigned, and the sum of the intensities of all peaks derived from the methyl groups, S AP The peak intensity S due to mesopentad sequences MP The ratio (S MP / S AP ) as a percentage. (4) Measurements are made three times for each level, and the arithmetic average value is rounded off to one decimal place to calculate the isotactic pentad fraction (%) of the polypropylene resin.

[0046] The isotactic pentad fraction of the polypropylene resin used in the present invention can be controlled, for example, by a polymerization catalyst. In order to increase the isotactic pentad fraction of the polypropylene resin, a conventionally known Ziegler-Natta catalyst or a metallocene catalyst having a cyclopentadienyl skeleton is usually used as a polymerization catalyst, but since the polypropylene resin produced with a Ziegler-Natta catalyst has a high melting point (160°C to 170°C), it is preferable to use a metallocene catalyst having a cyclopentadienyl skeleton.

[0047] The polypropylene resin used in the present invention preferably has a melt flow rate (MFR) of 10 g / 10 min or more and 1000 g / 10 min or less. By having the MFR of the polypropylene resin preferably of 10 g / 10 min or more, more preferably of 15 g / 10 min or more, and even more preferably of 20 g / 10 min or more, the stability during spinning is improved, resulting in a nonwoven fabric with a uniform texture. In addition, by having the MFR of the polypropylene resin preferably of 1000 g / 10 min or less, more preferably of 500 g / 10 min or less, and even more preferably of 300 g / 10 min or less, the tensile strength of the composite fiber is increased and the bonded portion is less likely to break, resulting in a nonwoven fabric with excellent mechanical properties.

[0048] The MFR (g / 10 min) of polypropylene resins referred to here is a value measured and calculated according to the following procedure in accordance with ASTM D1238 (Method A). According to this standard, polypropylene resins are measured at a load of 2.16 kg and a temperature of 230°C. (1) Collect 20 g of polypropylene resin, which is the raw material for composite fibers. (2) The collected polypropylene resin is placed in a melt flow rate measuring device (such as "MELT INDEXER F-F01" manufactured by Toyo Seiki Seisakusho Co., Ltd.) heated to 230°C, and the measurement is performed under conditions of a load of 2.16 kg and a temperature of 230°C. (3) Five measurements are made for each level, and the arithmetic average value is rounded off to the first decimal place to calculate the MFR (g / 10 min) of the polypropylene resin.

[0049] The MFR of the polypropylene resin used in the present invention can be controlled by, for example, the molecular weight and polydispersity (Mw / Mn) of the polypropylene resin. Specifically, the MFR of the polypropylene resin can be reduced by increasing the molecular weight and decreasing the polydispersity (Mw / Mn) of the polypropylene resin.

[0050] The polypropylene resin used in the present invention preferably has a polydispersity (Mw / Mn) of 1.5 or more and 3.5 or less. By having the polydispersity (Mw / Mn) of the polypropylene resin preferably be 1.5 or more, more preferably be 1.8 or more, and even more preferably be 2.0 or more, the molecular orientation is not excessively high, resulting in a nonwoven fabric with excellent flexibility. In addition, by having the polydispersity (Mw / Mn) be preferably 3.5 or less, more preferably be 3.2 or less, and even more preferably be 3.0 or less, the molecular orientation parameter of the composite fiber obtained at the same spinning speed is high, resulting in high strength of the composite fiber, resulting in a nonwoven fabric with excellent mechanical properties.

[0051] The polydispersity (Mw / Mn) of the polypropylene resin referred to here is a value measured and calculated by the following procedure. (1) Collect 5 mg of polypropylene resin, which is the raw material for the composite fiber. (2) 5 mL of 1,2,4-trichlorobenzene is added to 5 mg of the collected polypropylene-based resin, and the mixture is heated at 165°C for 20 minutes to dissolve the polypropylene-based resin, thereby obtaining a polypropylene-based resin solution. (3) The obtained polypropylene resin solution is filtered using a PTFE filter (for example, "T010A (pore size: 0.45 μm)" manufactured by Advantec Toyo Co., Ltd.) to prepare a sample solution. (4) The prepared sample solution is placed in a high-temperature GPC apparatus (e.g., Polymer Laboratories' PL-220) and measurement is performed at a column temperature of 145°C. The weight-average molecular weight Mw, number-average molecular weight Mn, and polydispersity (Mw / Mn) are calculated by analyzing the GPC discharge curve. (5) Measurements are made three times for each level, and the arithmetic average value is rounded off to one decimal place to calculate the polydispersity (Mw / Mn) of the polypropylene resin.

[0052] The polydispersity (Mw / Mn) of the polypropylene resin used in the present invention can be controlled, for example, by a polymerization catalyst. Specifically, the polydispersity (Mw / Mn) of the polypropylene resin can be reduced by using a metallocene catalyst.

[0053] The polypropylene resin used in the present invention can be blended with other component resins within a range that does not impair the effects of the present invention. In other words, within a range that does not impair the effects of the present invention, the polypropylene resin according to the present invention may be a resin obtained by blending at least one resin selected from a homopolymer of propylene, a copolymer of propylene and ethylene, and a copolymer of propylene and the above-mentioned α-olefin with other component resins. Examples of other component resins include polyolefin resins such as polyethylene and poly-4-methyl-1-pentene having a melting point close to that of polypropylene (note that, as in the example of the above-mentioned "polypropylene resin", the molar fraction of the polyolefin unit in the repeating unit is 80 mol % or more and 100 mol % or less. Unless otherwise specified, those described as "···-based resin" are the same.), polyester resins having a melting point close to that of polypropylene, and polyamide resins having a melting point close to that of polypropylene are listed, and low-crystalline polyolefin resins are preferably used from the viewpoint of imparting flexibility. As the low crystalline polyolefin resin, for example, an ethylene-propylene copolymer, a low stereoregular polypropylene (polypropylene having an isotactic pentad fraction of 0.60 or less), etc. are preferably used. In this case, the upper limit of the mass ratio of the other component resin is preferably 20 mass% or less, more preferably 10 mass% or less, in order to fully express the characteristics of the polypropylene resin.

[0054] To the polypropylene-based resin used in the present invention, additives such as commonly used antioxidants, weather resistance stabilizers, light resistance stabilizers, heat resistance stabilizers, antistatic agents, antistatic assistants, spinning agents, antiblocking agents, lubricants including polyethylene wax, crystal nucleating agents, and pigments, or other polymers may be added as necessary in order to further enhance the effects of the present invention or to impart other properties, within a range that does not impair the effects of the present invention.

[0055] The polypropylene resin used in the present invention preferably contains 0.01% by mass or more of a fatty acid amide compound in order to improve slipperiness and flexibility. The content of the fatty acid amide compound is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, so that the fatty acid amide compound acts as a lubricant on the fiber surface, resulting in a nonwoven fabric with excellent touch. In addition, the upper limit of the content of the fatty acid amide compound in the present invention is not particularly limited, but is preferably 5.0% by mass or less from the viewpoint of cost and productivity.

[0056] [Composite fiber] The nonwoven fabric of the present invention has a composite fiber with a propylene fraction of 98.5% or more and 100.0% or less, an isotactic pentad fraction of 90.0% or more and 100.0% or less, and a molecular orientation parameter O C and the molecular orientation parameter O in the fiber axis direction at the fiber surface. S Difference with (O C -O S ) is 0.2 or more and 4.0 or less. By using such composite fibers, the fibers have high molecular orientation and excellent adhesive strength at the fused portions, resulting in a nonwoven fabric with excellent mechanical properties.

[0057] The composite fiber according to the present invention is a fiber in which two or more kinds of resins are composited. The composite form is not particularly limited as long as it does not impair the effects of the present invention. island The components may be islands in the sea composed of different resins, and it is also possible to use two or more blended resins for the sea component and / or the island component. In the present invention, a composite fiber generally called a sheath-core composite fiber is considered to be one embodiment of islands-in-sea composite fibers having one island component. In other words, this islands-in-sea composite fiber having one island component includes concentric sheath-core composite fibers and eccentric sheath-core composite fibers.

[0058] The composite fiber according to the present invention preferably has an island component number of 1 or more and 10 or less. By having the island component number of preferably 10 or less, more preferably 6 or less, and even more preferably 4 or less, the tensile strength of the composite fiber is increased, resulting in a nonwoven fabric with excellent mechanical properties. When the number of island components is 2 or more, at least one island is arranged at least in the central portion. Furthermore, by having the island component number of preferably 1 or more, the composite fiber is easily bent, resulting in a nonwoven fabric with excellent flexibility.

[0059] The composite fiber according to the present invention has a propylene fraction of 98.5% or more and 100.0% or less. By having a propylene fraction of 98.5% or more, preferably 98.8% or more, more preferably 99.0% or more, the tensile strength of the composite fiber is increased, resulting in a nonwoven fabric with excellent mechanical properties. The upper limit of the propylene fraction of the composite fiber that can be achieved in the present invention is 100.0%.

[0060] The propylene fraction (%) of the composite fiber referred to here is a value measured and calculated by the following procedure. (1) Weigh the non-bonded composite fibers collected from the nonwoven fabric, add orthodichlorobenzene-D4 (orthodichlorobenzene in which the hydrogen is replaced with deuterium) to a sample concentration of 8 mass / v%, and heat to 135°C. (2) The resulting solution is analyzed using a nuclear magnetic resonance apparatus (e.g., JEOL RESONANCE "ECZ-600"). 13 C-NMR measurement is performed, and the peak area due to propylene units and the peak areas due to ethylene units and α-olefin units are calculated from the NMR spectrum. (3) The sum of the peak areas due to propylene units, ethylene units, and α-olefin units, A AF Peak area A due to propylene units PF The ratio of (A PF / A AF ) as a percentage. (4) For each level, measurements are taken three times at different sampling locations of the composite fiber, and the arithmetic average value is rounded off to one decimal place to calculate the propylene fraction (%) of the composite fiber.

[0061] The propylene fraction of the composite fiber according to the present invention can be controlled by, for example, the propylene fraction of the polypropylene-based resin. Specifically, the propylene fraction of the composite fiber can be increased by increasing the propylene fraction of the polypropylene-based resin.

[0062] The composite fiber according to the present invention has an isotactic pentad fraction of 90.0% or more and 100.0% or less. By having an isotactic pentad fraction of 90.0% or more, preferably 92.0% or more, and more preferably 94.0% or more, the tensile strength of the composite fiber is increased, resulting in a nonwoven fabric with excellent mechanical properties. The upper limit of the isotactic pentad fraction of the composite fiber that can be achieved in the present invention is 100.0%.

[0063] The isotactic pentad fraction (%) of the composite fiber referred to here is a value measured and calculated by the following procedure. (1) Weigh the non-bonded composite fibers collected from the nonwoven fabric, add orthodichlorobenzene-D4 (orthodichlorobenzene in which the hydrogen is replaced with deuterium) to a sample concentration of 8 mass / v%, and heat to 135°C. (2) The resulting solution is analyzed using a nuclear magnetic resonance apparatus (e.g., JEOL RESONANCE "ECZ-600"). 13 Perform C-NMR measurement. (3) Based on the method described in "Zambelli et al., Macromolecules, Vol. 8, p. 687 (1975)", the peaks in the methyl group-derived spectrum of the obtained NMR spectrum are assigned, and the sum of the intensities of all peaks derived from the methyl groups, S AF The peak intensity S due to mesopentad sequences MF The ratio (S MF / S AF ) as a percentage. (4) For each level, measurements are taken three times at different sampling locations of the composite fiber, and the arithmetic average value is rounded off to one decimal place to calculate the isotactic pentad fraction (%) of the composite fiber.

[0064] The isotactic pentad fraction of the composite fiber according to the present invention can be controlled by, for example, the isotactic pentad fraction of the polypropylene resin. Specifically, the isotactic pentad fraction of the composite fiber can be increased by increasing the isotactic pentad fraction of the polypropylene resin.

[0065] The composite fiber according to the present invention has a molecular orientation parameter O C and the molecular orientation parameter O in the fiber axis direction at the fiber surface. S Difference with (O C -O S ) is between 0.2 and 4.0. C -O S When the fiber surface is softened while maintaining the orientation in the center of the fiber during thermal bonding, the fibers bond to each other, and the bonded portion is less likely to break, resulting in a nonwoven fabric with excellent mechanical properties. C -O S By making the ratio 4.0 or less, and preferably 3.5 or less, the process stability during spinning is improved, and the molecular orientation at the center of the fiber does not become excessively high, resulting in a nonwoven fabric with uniform texture and excellent flexibility.

[0066] Here, the molecular orientation parameter O in the fiber axis direction at the center of the fiber is C , the molecular orientation parameter O in the fiber axis direction at the fiber surface S , the difference between them C -O S is a value measured and calculated according to the following procedure. (1) Collect composite fibers from the non-bonded areas of the nonwoven fabric. (2) The collected composite fibers are cut with a razor at a cutting angle of approximately 4° relative to the fiber axis direction to expose the fiber cross section, which is then set in a Raman spectroscopic measurement device (e.g., Horiba, Ltd.'s "RAMANOR T64000") and microscopic Raman measurement is performed by irradiating the fiber cross section with a laser perpendicular to the fiber axis. (3) Measurements are performed under conditions in which the polarization direction is parallel to the fiber axis direction, and polarized Raman spectra are obtained for the center of the fiber (if an island component is present at the midpoint of the composite fiber in the fiber diameter direction in the sea-island composite fiber, the midpoint; if no island is present at the midpoint of the composite fiber in the fiber diameter direction, the midpoint in the fiber diameter direction of the island component closest to the midpoint) and the fiber surface (0.5 μm inward from the side surface of the fiber in the fiber diameter direction). (4) 810 cm assigned to the coupling mode of CH2 bending vibration and CC stretching vibration -1 The Raman band intensity near I 810 The CH2 bending vibration mode is assigned to 840 cm -1 The Raman band intensity of I 840 Then, the molecular orientation parameter is calculated using the following formula: Molecular orientation parameter = I 810 / I 840 (5) For each level, measurements were taken three times at both the center and surface of the fiber, with the composite fiber sample taken from different locations. The arithmetic mean value of the molecular orientation parameter in the fiber axis direction at the center of the fiber was rounded off to the nearest tenth to obtain the molecular orientation parameter in the fiber axis direction at the center of the fiber, O C The molecular orientation parameter O in the fiber axis direction at the fiber surface is calculated by rounding off the arithmetic average value of the molecular orientation parameters in the fiber axis direction at the fiber surface to one decimal place. S It is calculated as follows. (6) Molecular orientation parameter O in the fiber axis direction at the center of the fiber C and the molecular orientation parameter O in the fiber axis direction at the fiber surface. S From the value of O C -O S Calculate.

[0067] In addition, the composite fiber according to the present invention C-O S For example, the O-strip property of the composite fiber can be controlled by the difference in polymer properties, particularly the MFR difference, between the island and sea components when the composite fiber is made into an islands-in-sea type composite fiber. Specifically, by using a polypropylene resin for the sea component having a higher MFR than the polypropylene resin for the island component, the O-strip property of the composite fiber can be controlled by the difference in polymer properties, particularly the MFR difference. C -O S can be made larger.

[0068] The composite fiber according to the present invention has a molecular orientation parameter O C The molecular orientation parameter O in the fiber axis direction at the center of the fiber is preferably 5.0 or more and 10.0 or less. C is preferably 5.0 or more, more preferably 5.3 or more, and further preferably 5.5 or more, the molecular orientation of the composite fibers is high and the tensile strength is high, resulting in a nonwoven fabric with excellent mechanical properties. C By making the molecular orientation at the center of the fiber not excessively high and the composite fiber soft, a nonwoven fabric having excellent flexibility can be obtained by making the molecular orientation at the center of the fiber not excessively high and the composite fiber soft, so that the nonwoven fabric has excellent flexibility.

[0069] The cross-sectional shape of the composite fiber according to the present invention may be a round cross-section, a flat cross-section, or an irregular cross-section such as a Y-shape or a C-shape. Of these, a round cross-section is preferable because it allows for a nonwoven fabric with excellent flexibility without the difficulty in bending that is inherent to structures such as a flat cross-section or an irregular cross-section.

[0070] The composite fiber according to the present invention preferably has an average single fiber diameter of 5.0 μm or more and 20.0 μm or less. By having an average single fiber diameter of preferably 5.0 μm or more, more preferably 8.0 μm or more, and even more preferably 10.0 μm or more, thread breakage during spinning can be suppressed, resulting in a nonwoven fabric with fewer defects. In addition, by having an average single fiber diameter of preferably 20.0 μm or less, more preferably 17.0 μm or less, the nonwoven fabric has excellent touch, uniform texture, and excellent mechanical properties.

[0071] The average single fiber diameter (μm) of the composite fiber referred to here is a value measured and calculated by the following procedure. (1) Take a 5 mm x 5 mm test piece from the nonwoven fabric. (2) On the surface of the nonwoven fabric, composite fibers that are located at a distance of 10% or more from a bonded joint relative to the distance between adjacent bonded joints are embedded in an embedding agent such as epoxy resin, and the fibers are cut using a razor in a direction perpendicular to the fiber axis to expose the fiber cross section. An image is then taken using a scanning electron microscope (e.g., Hitachi High-Technologies Corporation's "SU1510") at a magnification that allows observation of 10 or more fibers. (3) Using the captured image, the area A formed by the cross-sectional profile of the single fiber is calculated using image analysis software (for example, "WinROOF2015" manufactured by Mitani Shoji Co., Ltd.). F Measure the area of ​​10 pieces and calculate the area A F Calculate the diameter (μm) of a perfect circle that has the same area as the above. (4) For each level, ten measurements are taken by changing the sampling locations of the test pieces, and the arithmetic mean value of the 100 pieces in total is rounded off to one decimal place to calculate the average single fiber diameter (μm).

[0072] The average single fiber diameter of the composite fiber according to the present invention can be controlled, for example, by the spinning temperature, single-hole throughput, spinning speed, etc., which will be described later. Specifically, the average single fiber diameter of the composite fiber can be reduced by increasing the spinning temperature, decreasing the single-hole throughput, or increasing the spinning speed.

[0073] The tensile strength of the composite fiber according to the present invention is preferably 1.2 cN / dtex or more and 5.0 cN / dtex or less. When the lower limit of the tensile strength of the composite fiber is 1.2 cN / dtex or more, a nonwoven fabric having excellent mechanical properties is obtained. On the other hand, when the upper limit of the tensile strength of the composite fiber is 5.0 cN / dtex or less, a nonwoven fabric having excellent flexibility is obtained.

[0074] The tensile strength of the composite fiber in the present invention is determined in accordance with "8.7 Tensile strength and elongation (ISO method)" of JIS L1015:2010 and is measured by the following procedure. (1) The density of the composite fiber is measured by the following steps (1-1) to (1-3). (1-1) Water and ethanol are mixed in a room whose temperature is controlled at 15°C. The mass fraction of ethanol is set to 40% to 70%, and 31 levels of ethanol aqueous solutions with different concentrations at 1% intervals are prepared. (1-2) After ultrasonic cleaning to remove impurities, 93 test pieces of 5 mm x 5 mm are randomly cut out from the nonwoven fabric, excluding the ends in the width direction. (1-3) Immerse the cut test piece in an aqueous ethanol solution while taking care not to trap air bubbles, and leave it for more than 6 hours. (1-4) Among the ethanol aqueous solutions in which the test piece did not sink to the bottom, the mass fraction X of the ethanol aqueous solution with the lowest ethanol mass fraction is E The operation of obtaining (unitless) is carried out three times, and the density is calculated from the arithmetic average value of the mass fraction of the obtained ethanol aqueous solution using the following formula. Density of composite fiber (g / cm 3 )=-0.000005×X E 2 -0.0017×X E +1.0153 (2) Six composite fibers that constitute a nonwoven fabric and are present at a position 10% or more away from the fused portion relative to the distance between adjacent fused portions are randomly taken out. At this time, the composite fibers are taken out so that the fiber length of each composite fiber is 50 mm or more. If the fiber length of the composite fiber taken out is less than 50 mm, another composite fiber is taken out at random so that all six composite fibers are 50 mm or more. (3) The extracted composite fiber is cut in half to obtain 12 composite fibers. Of the 12 composite fibers obtained, 6 are used as samples for (4) and (5) below, and the remaining 6 are used as samples for (6) to (8). (4) The composite fibers are embedded in an embedding agent such as epoxy resin, and an image of the fiber cross section perpendicular to the fiber axis is taken using a microscope (e.g., a scanning electron microscope "SU1510" manufactured by Hitachi High-Technologies Corporation) at a magnification such that 10 or more composite fibers can be observed. (5) Composite fibers randomly extracted from each captured image are analyzed using image analysis software to measure the area of ​​the fiber cross section, and the single fiber diameter of the composite fiber calculated as a perfect circle (circle equivalent diameter, μm) is calculated. Together with the density calculated in (1), the net fineness (dtex) is calculated based on the following formula and rounded off to two decimal places. Net fineness (dtex) = π × (single fiber diameter of composite fiber (cm) / 2) 2 ×Density (g / cm 3 )×1000000(cm) (6) With a spatial distance of 20 mm, each composite fiber is loosely stretched over the dividing line, and both ends are attached to pieces of paper with adhesive. Each division constitutes one sample, and six pieces are prepared. (7) Attach the sample from (6) to the grips of a tensile testing machine (e.g., the RTC1210A manufactured by A&D Co., Ltd.), pull with a grip distance of 20 mm and a pulling speed of 20 mm / min, and measure the load (cN) when the sample breaks. (8) Calculate the tensile strength (cN / dtex) by dividing the load obtained in (7) by the net fineness (dtex) obtained in (5). Obtain the average tensile strength (cN / dtex) calculated for each sample, and round off to one decimal place.

[0075] In order to set the tensile strength of the conjugate fiber according to the present invention within the above range, for example, a polypropylene-based resin polymerized using a metallocene catalyst may be used.

[0076] [Nonwoven fabric] The nonwoven fabric of the present invention contains the above-mentioned composite fiber and has a melting point of 130° C. or more and 155° C. or less. By producing such a nonwoven fabric, the nonwoven fabric can have both excellent flexibility and mechanical properties.

[0077] The nonwoven fabric of the present invention may be a long fiber nonwoven fabric such as a spunbonded nonwoven fabric or a meltblown nonwoven fabric, or a short fiber nonwoven fabric such as a needle-punched nonwoven fabric or a paper-made nonwoven fabric. Among them, a spunbonded nonwoven fabric is preferable because it is easy to reduce the basis weight and it is easy to achieve both excellent flexibility and mechanical properties.

[0078] The nonwoven fabric of the present invention may be a single-layer nonwoven fabric, which will be described later, or may be a nonwoven fabric consisting of multiple layers of the same type of nonwoven fabric. However, when the nonwoven fabric of the present invention has a fiber layer of a different type from the layer of the nonwoven fabric of the present invention, for example, when the nonwoven fabric of the present invention is a spunbond nonwoven fabric, a layer of a meltblown nonwoven fabric, a layer of a papermaking nonwoven fabric, or a layer of a woven fabric or a knitted fabric, it is considered to be a laminated nonwoven fabric, which will be described later.

[0079] The nonwoven fabric of the present invention has a melting point of 130° C. or higher and 155° C. or lower. By having a melting point of 130° C. or higher, preferably 135° C. or higher, and more preferably 138° C. or higher, heat resistance sufficient for practical use is obtained and the dimensional stability of the nonwoven fabric is improved, resulting in a nonwoven fabric with excellent flexibility. In addition, by having a melting point of 155° C. or lower, preferably 150° C. or lower, adhesion during thermal bonding is facilitated, resulting in a nonwoven fabric with excellent mechanical properties.

[0080] The melting point (°C) of the nonwoven fabric referred to here is a value measured and calculated by the following procedure. (1) Take a 2.0 mg test piece from the nonwoven fabric and set it in a differential scanning calorimeter (for example, "DSC Q2000" manufactured by TA Instruments). (2) Differential scanning calorimetry (1st DSC) is performed under nitrogen at a heating rate of 16°C / min and a measurement temperature range of 50°C to 230°C, followed by rapid cooling at a heating rate of 100°C / min and then differential scanning calorimetry (2nd DSC) again under nitrogen at a heating rate of 16°C / min and a measurement temperature range of 50°C to 230°C. (3) In the DSC curve of the 2nd DSC, the peak top temperature (°C) of the largest endothermic peak is calculated. (4) For each level, measurements are taken three times by changing the sampling location of the test piece, and the arithmetic mean value is rounded off to the first decimal place to calculate the melting point (°C).

[0081] The melting point of the nonwoven fabric of the present invention can be controlled by, for example, a polymerization catalyst or the propylene fraction of the composite fiber. Specifically, the melting point of the nonwoven fabric can be lowered by using a metallocene catalyst as a polymerization catalyst or by lowering the propylene fraction of the composite fiber.

[0082] The nonwoven fabric of the present invention preferably has a heat of crystalline fusion of 82 J / g or more and 120 J / g or less. By having a heat of crystalline fusion of 82 J / g or more, preferably 85 J / g or more, more preferably 88 J / g or more, the degree of crystallization of the nonwoven fabric can be appropriately increased, resulting in a nonwoven fabric with excellent mechanical properties. In addition, by having a heat of crystalline fusion of 120 J / g or less, more preferably 110 J / g or less, the degree of crystallization of the nonwoven fabric does not become excessively high, resulting in a nonwoven fabric with excellent flexibility.

[0083] The heat of crystalline fusion (J / g) of the nonwoven fabric referred to here is a value measured and calculated by the following procedure. (1) Take a 2.0 mg test piece from the nonwoven fabric and set it in a differential scanning calorimeter (for example, "Q2000" manufactured by TA Instruments). (2) Differential scanning calorimetry (1st DSC) is performed under nitrogen at a heating rate of 16°C / min and a measurement temperature range of 50°C to 230°C, followed by rapid cooling at a heating rate of 100°C / min and then differential scanning calorimetry (2nd DSC) again under nitrogen at a heating rate of 16°C / min and a measurement temperature range of 50°C to 230°C. (3) In the DSC curve of the 2nd DSC, calculate the endothermic heat (J / g) of the largest endothermic peak. (4) For each level, measurements are taken three times by changing the sampling location of the test piece, and the arithmetic mean value is rounded off to the first decimal place to calculate the heat of crystal fusion (J / g).

[0084] The heat of crystalline fusion of the nonwoven fabric of the present invention can be controlled, for example, by the propylene fraction of the composite fiber. Specifically, the heat of crystalline fusion of the nonwoven fabric can be increased by increasing the propylene fraction of the composite fiber.

[0085] The nonwoven fabric of the present invention has a fused portion and a nonfused portion. In the present invention, the fused portion refers to a portion where the composite fibers are melted to such an extent that the cross-sectional shape of the composite fibers is deformed to a degree different from the shape of the other portions by being pressed in the cross-sectional direction of the nonwoven fabric, and further, the composite fibers are fused to each other to such an extent that the composite fibers become lumpy or film-like. Specifically, in the case of thermal bonding using a roll having projections and recesses (embossing roll) and a flat roll, the fused portion refers to the portion where the projections of the embossing roll contact the nonwoven fabric. On the other hand, the nonfused portion refers to the portion other than the fused portion.

[0086] In the nonwoven fabric of the present invention, the crystallite size of the (040) plane in the fused portion is preferably 10.0 nm or more and 13.5 nm or less in wide-angle X-ray diffraction, and the crystallite size of the (110) plane in the nonfused portion is preferably 5.0 nm or more and 10.0 nm or less in wide-angle X-ray diffraction. By simultaneously satisfying these two requirements, the nonwoven fabric has excellent mechanical properties due to high fiber strength and high adhesive strength in the fused portion.

[0087] As described above, the nonwoven fabric of the present invention preferably has a crystallite size of the (040) plane of the fused portion in wide-angle X-ray diffraction of 10.0 nm or more and 13.5 nm or less. The lower limit of the crystallite size of the (040) plane of the fused portion is preferably 10.0 nm or more, more preferably 11.0 nm or more, so that the crystallite size is sufficiently large, resulting in a nonwoven fabric with better mechanical properties. On the other hand, the upper limit of the crystallite size of the (040) plane of the fused portion is preferably 13.5 nm or less, more preferably 13.0 nm or less, resulting in a nonwoven fabric with better flexibility.

[0088] Next, the nonwoven fabric of the present invention has a crystallite size of the (110) plane in the non-fused portion in wide-angle X-ray diffraction of 5.0 nm or more and 10.0 nm or less. The lower limit of the crystallite size of the (110) plane of the non-fused portion is 5.0 nm or more, preferably 6.0 nm or more, and more preferably 8.0 nm or more, so that the crystallite size is sufficiently large, resulting in a nonwoven fabric with better mechanical properties. On the other hand, the upper limit of the crystallite size of the (110) plane of the non-fused portion is 10.0 nm or less, preferably 9.5 nm or less, so that the crystallite size is uniform, resulting in a nonwoven fabric with excellent mechanical properties. That is, the crystallite size of the (110) plane of the non-fused portion is 5.0 nm or more and 10.0 nm or less, so that the crystallite size is sufficient and uniform, resulting in a nonwoven fabric with excellent mechanical properties.

[0089] In the present invention, the crystallite sizes of the (040) plane of the fused portion of the nonwoven fabric and the (110) plane of the nonwoven fabric can be controlled by the catalyst and melt flow rate used when polymerizing the polypropylene resin. The higher the melt flow rate, the smaller the crystallite sizes of the (040) plane of the fused portion of the nonwoven fabric and the (110) plane of the nonwoven fabric.

[0090] In the present invention, the crystallite size of the (040) plane in wide-angle X-ray diffraction of the fused portion and the crystallite size of the (110) plane in wide-angle X-ray diffraction of the non-fused portion refer to values ​​measured and calculated by the following methods. (1) A 5 cm x 5 cm test piece is taken at random from a portion of the nonwoven fabric excluding 10 cm from the widthwise end, which has both fused and non-fused portions. The portions to be used for measuring the fused and non-fused portions are determined according to (1-1) and (1-2) below. (1-1) For the measurement of the fused portion of the nonwoven fabric, a fused portion that is present near the center of the test piece and is at a distance (13) of 50% or less of the radius of the inscribed circle from the center of the inscribed circle (12) of the fused portion (11) of the test piece (1) as shown in FIG. 1 is used. (1-2) To measure the unfused portions of the nonwoven fabric, a portion of the unfused portion near the center of the test piece that is at least 10% away from the fused portion relative to the distance between adjacent fused portions is used. (2) To measure the unfused portion, group the 20 fibers present in the location determined in (1-2) together so that their fiber axes are in the same direction. (3) For the sample at the location determined in (1-1) (the fused portion sample) and the sample collected in (2) (the non-fused portion sample), wide-angle X-ray diffraction measurement is performed using an X-ray diffractometer (e.g., Bruker AXS's "D8 DISCOVER μHR Hybrid"). Here, the fused portion sample is irradiated with X-rays from the thickness direction of the nonwoven fabric, and the non-fused portion sample is irradiated with X-rays from the fiber diameter direction. (4) An X-ray diffraction profile is obtained by measuring a sample from the fused portion and averaging the entire circumference of the peak corresponding to the (040) plane, and by measuring a sample from the non-fused portion and averaging a sector in the equatorial direction of the peak corresponding to the (110) plane. (5) The crystallite size of each peak is expressed as the half-width β e (°) using the following formula (Scherrer's formula). Crystallite size L (nm) = 0.9λ / ((β e 2 -β0 2 ) 0.5 ×cosθ) In the formula, λ represents the wavelength of the incident X-ray, β0 represents the correction value of the half-width, and θ represents the Bragg angle (°) of the peak top.

[0091] In order to bring the crystallite size of the (040) plane in wide-angle X-ray diffraction of the fused portion and the crystallite size of the (110) plane in wide-angle X-ray diffraction of the non-fused portion into the above-mentioned ranges, for example, a polypropylene-based resin using a metallocene catalyst as a polymerization catalyst can be used.

[0092] The melt flow rate of the nonwoven fabric of the present invention is preferably 20 g / 10 min or more and 100 g / 10 min or less. By setting the melt flow rate of the nonwoven fabric in this range, it becomes easy to control the crystallite size of the (040) plane of the fused portion of the nonwoven fabric and the (110) plane of the nonwoven fabric in the above range. The melt flow rate of the nonwoven fabric has a lower limit of preferably 20 g / 10 min or more, more preferably 30 g / 10 min or more, so that the nonwoven fabric has excellent flexibility. In addition, the melt flow rate of the nonwoven fabric has an upper limit of preferably 100 g / 10 min or less, more preferably 60 g / 10 min or less, so that the nonwoven fabric has sufficient strength for practical use.

[0093] The melt flow rate of the nonwoven fabric in the present invention refers to the arithmetic mean value of values ​​obtained by taking five 5 g test pieces from the nonwoven fabric excluding 10 cm from each end in the width direction, and measuring the taken test pieces under conditions of a load of 2160 g and a temperature of 230° C., in accordance with ASTM D1238 (Method A). For example, a melt indexer "F-F01" manufactured by Toyo Seiki Seisakusho Co., Ltd. can be used for the measurement.

[0094] The melt flow rate of the nonwoven fabric can be controlled by the weight average molecular weight of the polypropylene resin. The higher the weight average molecular weight of the polypropylene resin, the smaller the melt flow rate.

[0095] The nonwoven fabric of the present invention has a basis weight of 5 g / m 2 More than 100g / m 2 The weight per unit area is preferably 5 g / m or less. 2 More preferably, 7 g / m 2 By satisfying the above requirements, the nonwoven fabric has a uniform texture and excellent mechanical properties. 2 Less than 50 g / m 2 The nonwoven fabric having excellent flexibility can be obtained by satisfying the following conditions.

[0096] The basis weight of the nonwoven fabric (g / m 2) is a value measured and calculated according to the following procedure in accordance with "6.2 Mass per unit area (ISO method)" of JIS L1913:2010 "General nonwoven fabric testing methods." (1) Take a test piece measuring 20cm x 25cm from the nonwoven fabric. However, if a test piece measuring 20cm x 25cm cannot be taken, the total area of ​​the test pieces shall be 500cm. 2 Take multiple test pieces from the nonwoven fabric so that the test pieces meet the following criteria: (2) Measure the mass (g) of the sampled test piece under standard conditions and measure its area (1 m2). 2 Mass per unit (g / m 2 ) to (3) For each level, the test piece was taken from different locations and measurements were taken three times. The arithmetic mean value was rounded off to the nearest tenth and expressed as the basis weight (g / m 2 ) is calculated as follows.

[0097] The basis weight of the nonwoven fabric of the present invention can be controlled, for example, by the single hole discharge rate and conveying speed during spinning, which will be described later. Specifically, the basis weight of the nonwoven fabric can be reduced by decreasing the single hole discharge rate and increasing the conveying speed.

[0098] The nonwoven fabric of the present invention has a tensile strength per unit area of ​​1.40 (N / 25 mm) / (g / m 2 ) or more 3.00(N / 25mm) / (g / m 2 The tensile strength per unit area is preferably 1.40 (N / 25 mm) / (g / m 2 ) or more, more preferably 1.50 (N / 25mm) / (g / m 2 ) or more, more preferably 1.55 (N / 25mm) / (g / m 2 ) or more, the nonwoven fabric has excellent mechanical properties. In addition, the tensile strength per unit area is preferably 3.00 (N / 25 mm) / (g / m 2 ) or less, more preferably 2.80 (N / 25mm) / (g / m 2 ) or less, the nonwoven fabric has excellent flexibility.

[0099] The tensile strength per unit area of ​​nonwoven fabric referred to here is (N / 25mm) / (g / m 2 )) is a value measured and calculated according to the following procedure in accordance with "6.3 Tensile strength and elongation (ISO method)" of JIS L1913:2010 "General nonwoven fabric test methods." (1) Take test pieces measuring 25 mm x 40 mm from the nonwoven fabric in both the longitudinal (lengthwise) and transverse (widthwise) directions of the nonwoven fabric. (2) The long side direction (40 mm) of the collected test piece is set as the tensile direction, and the test piece is set in a tensile testing machine (for example, the RTC-1210A manufactured by A & D Co., Ltd.) with a gripping distance of 20 mm. (3) A tensile test is carried out at a tensile speed of 20 mm / min, and the maximum point load (N / 25 mm) is measured. (4) For each level, the test pieces were taken in different locations and measurements were taken five times in both the longitudinal and transverse directions. The arithmetic mean of the 10 measurements was rounded off to the third decimal place to obtain the average maximum load (N / 25mm). The tensile strength per unit area ((N / 25mm) / (g / m 2 ) is calculated. Tensile strength per unit area ((N / 25mm) / (g / m 2 )) = Maximum point load (N / 25mm) / Weight (g / m 2 ).

[0100] The tensile strength per unit area of ​​the nonwoven fabric of the present invention can be determined by, for example, the propylene fraction and isotactic pentad fraction of the polypropylene resin, the MFR, and the molecular orientation parameter difference (O C -O S ) and the molecular orientation parameter O in the fiber axis direction at the center of the fiber C It can be controlled by the melting point and heat of crystal fusion of the nonwoven fabric, and / or the spinning speed and heat bonding conditions (bonding rate, temperature, linear pressure, etc.) during spinning, which will be described later. Specifically, the propylene fraction and isotactic pentad fraction of the polypropylene resin are increased, the MFR is lowered, and the molecular orientation parameter difference (O C -O S ) and the molecular orientation parameter O in the fiber axis direction at the center of the fiber CThe tensile strength per unit area of ​​the nonwoven fabric can be increased by increasing the fiber diameter, increasing the melting point or heat of crystalline fusion of the nonwoven fabric, increasing the spinning speed during spinning, and increasing the bonding rate, temperature, and line pressure during thermal bonding.

[0101] The nonwoven fabric of the present invention preferably has a bending resistance of 10 mm or more and 50 mm or less. By having a bending resistance of preferably 10 mm or more, more preferably 20 mm or more, the nonwoven fabric exhibits appropriate rigidity and has excellent handleability. In addition, by having a bending resistance of preferably 50 mm or less, more preferably 45 mm or less, the nonwoven fabric has excellent flexibility.

[0102] The bending resistance (mm) of the nonwoven fabric referred to here is the value obtained by measuring three times in each of the longitudinal direction (length direction of the nonwoven fabric) and transverse direction (width direction of the nonwoven fabric) of the nonwoven fabric in accordance with "6.7 Bending resistance (JIS method and ISO method)" "6.7.3 41.5° cantilever method" of JIS L1913:2010 "Testing methods for general nonwoven fabrics", and then rounding off the arithmetic mean value (mm) of all the values ​​in the longitudinal and transverse directions to the nearest tenth place.

[0103] The bending resistance of the nonwoven fabric of the present invention can be determined, for example, by the cross-sectional shape of the composite fiber and the molecular orientation parameter O in the fiber axis direction at the center of the fiber. C The nonwoven fabric can be controlled by the heat of crystal fusion and the basis weight, and / or the thermal bonding conditions (bonding rate, temperature, linear pressure, etc.) described later. Specifically, the molecular orientation parameter O in the fiber axis direction at the center of the fiber when the cross section of the composite fiber is a round cross section can be controlled by the C The bending resistance of the nonwoven fabric can be reduced by decreasing the heat of crystal fusion of the nonwoven fabric, decreasing the basis weight, and decreasing the bonding rate, temperature, and line pressure during thermal bonding.

[0104] [Nonwoven fabric manufacturing method] Next, the method for producing the nonwoven fabric of the present invention will be described. The method for producing the nonwoven fabric of the present invention preferably includes the steps of: a step of melt-extruding, through a composite spinneret, a polypropylene-based resin A which has a propylene fraction of 98.5% or more and 100.0% or less and which has been polymerized by a metallocene catalyst, and a polypropylene-based resin B which has a melt flow rate higher than that of the polypropylene-based resin A by 6 g / 10 min to 200 g / 10 min and which has a propylene fraction of 98.5% or more and 100.0% or less and which has been polymerized by a metallocene catalyst, and pulling and stretching the spun polypropylene-based resin A and the polypropylene-based resin B to form islands-in-sea type composite fibers in which island components are the polypropylene-based resin A and a sea component is the polypropylene-based resin B; depositing the islands-in-the-sea type composite fibers to form a fiber web composed of the islands-in-the-sea type composite fibers; and a step of thermally bonding the fiber web. By using such a production method, a nonwoven fabric having both excellent flexibility and mechanical properties can be stably obtained. Each step of the above-mentioned preferred embodiment will be described in more detail below.

[0105] (a) Forming islands-in-the-sea composite fibers First, in this process, A polypropylene resin A polymerized by a metallocene catalyst and having a propylene fraction of 98.5% or more and 100.0% or less; A polypropylene resin B having a melt flow rate of 6 g / 10 min or more and 200 g / 10 min or less higher than that of the polypropylene resin A, polymerized by a metallocene catalyst, and having a propylene fraction of 98.5% or more and 100.0% or less; The mixture is melt-extruded through a composite spinneret. In this manner, a nonwoven fabric having excellent mechanical properties can be obtained.

[0106] (a-1) Polypropylene resin A In the method for producing a nonwoven fabric of the present invention, the polypropylene resin A to be arranged in the island component is preferably a polypropylene resin made by using a metallocene catalyst as a polymerization catalyst. By using a metallocene catalyst as the polypropylene resin A, the process stability during spinning is improved and the molecular orientation parameter O of the island component having the polypropylene resin A arranged therein is reduced compared to the polypropylene resin obtained by using a Ziegler-Natta catalyst. C Since it is possible to increase the viscosity and decrease the melting point, it is possible to obtain a nonwoven fabric having a highly uniform texture and excellent mechanical properties and flexibility.

[0107] Specific examples of the metallocene catalyst include ethylene bisindenyl zirconium dichloride, ethylene bis(tetrahydroindenyl)zirconium dichloride, dimethylsilylene bis(dimethylcyclopentadienyl)zirconium dichloride, dimethylsilylene bis(trimethylcyclopentadienyl)zirconium dichloride, dimethylsilylene bis(indenyl)zirconium dichloride, dimethylsilylene bis(2-methylindenyl)zirconium dichloride, dimethylsilylene bis(2-methyl-4-isopropylindenyl)zirconium dichloride, isopropylidene(cyclopentadienyl)(9-fluorenyl)zirconium dichloride, cyclohexylidene(cyclopentadienyl)(9-fluorenyl)zirconium dichloride, and the like. nyl) zirconium dichloride, diphenylmethylene (cyclopentadienyl) (9-fluorenyl) zirconium dichloride, methylphenylmethylene (cyclopentadienyl) (9-fluorenyl) zirconium dichloride, isopropylidene (cyclopentadienyl) (2,7-di-t-butyl-9-fluorenyl) zirconium dichloride, cyclohexylidene (cyclopentadienyl) (2,7-di-t-butyl-9-fluorenyl) zirconium dichloride, diphenylmethylene (cyclopentadienyl) (2,7-di-t-butyl-9-fluorenyl) zirconium dichloride, methylphenylmethylene (cyclopentadienyl) (2,7-di-t-butyl-9-fluorenyl) zirconium dichloride, and the like can be mentioned. Among these, in the present invention, it is preferable to use a metallocene catalyst having a cyclopentadienyl skeleton, since this makes it possible to increase the isotactic pentad fraction of the polypropylene-based resin.

[0108] In addition to aluminoxane, examples of the co-catalyst that can be used include dimethylanilinium tetrakis(pentafluorophenyl)borate, and also triphenylcarbenium tetrakis(pentafluorophenyl)borate, triphenylcarbenium tetrakis(pentafluorophenyl)aluminate, magnesium chloride, alumina, and tris(pentafluorophenyl)boron.

[0109] In the method for producing a nonwoven fabric of the present invention, the polypropylene resin A to be used in the island components preferably has a propylene fraction of 98.5% or more and 100.0% or less. By making the propylene fraction of the polypropylene resin A preferably 98.5% or more, more preferably 98.8% or more, and even more preferably 99.0% or more, the process stability during spinning is improved and the heat of crystal fusion of the obtained nonwoven fabric is increased, so that a nonwoven fabric having high uniformity of texture and excellent mechanical properties can be obtained. The upper limit of the propylene fraction of the polypropylene resin A that can be achieved in the present invention is 100.0%.

[0110] In the method for producing a nonwoven fabric of the present invention, the polypropylene resin A in the island component preferably has an isotactic pentad fraction of 90.0% or more and 100.0% or less. When the isotactic pentad fraction of the polypropylene resin A is preferably 90.0% or more, more preferably 92.0% or more, and even more preferably 94.0% or more, the heat of crystal fusion of the resulting nonwoven fabric is increased, so that a nonwoven fabric having excellent mechanical properties can be obtained. The upper limit of the isotactic pentad fraction of the polypropylene resin A that can be achieved in the present invention is 100.0%.

[0111] In the method for producing a nonwoven fabric of the present invention, the polypropylene resin A to be used in the island components preferably has a polydispersity (Mw / Mn) of 1.5 or more and 3.5 or less. When the polydispersity (Mw / Mn) of the polypropylene resin A is preferably 1.5 or more, more preferably 1.8 or more, and even more preferably 2.0 or more, the spinning stress of the island components is not excessively high, thereby suppressing yarn breakage and producing a nonwoven fabric with fewer defects. In addition, when the polydispersity (Mw / Mn) is preferably 3.5 or less, more preferably 3.2 or less, and even more preferably 3.0 or less, the molecular orientation parameter of the island components of the islands-in-sea type composite fiber obtained at the same spinning speed is high, so that the strength of the composite fiber is high and a nonwoven fabric with excellent mechanical properties is obtained.

[0112] In the method for producing a nonwoven fabric of the present invention, the polypropylene resin A preferably has a melt flow rate of 10 g / 10 min or more and 90 g / 10 min or less. By setting the lower limit of the melt flow rate range to preferably 10 g / 10 min or more, more preferably 25 g / 10 min or more, it is possible to stably spin even a fine fiber diameter, and to obtain a nonwoven fabric that is excellent in texture and has a uniform texture. On the other hand, by setting the upper limit of the melt flow rate range to preferably 90 g / 10 min or less, more preferably 80 g / 10 min or less, and even more preferably 60 g / 10 min or less, it is possible to suppress a decrease in the single yarn strength of the islands-in-the-sea type composite fiber, and to provide a nonwoven fabric with excellent mechanical properties.

[0113] The melt flow rate of the polypropylene resin in the present invention refers to a value measured in accordance with ASTM D1238 (Method A) under conditions of a load of 2160 g and a temperature of 230° C., similar to the method for measuring the melt flow rate of a nonwoven fabric. For example, a melt indexer "F-F01" manufactured by Toyo Seiki Seisakusho Co., Ltd. can be used for the measurement.

[0114] The melt flow rate of the polypropylene resin can be controlled by the weight average molecular weight of the polypropylene resin. The higher the weight average molecular weight of the polypropylene resin, the smaller the melt flow rate.

[0115] (a-2) Polypropylene resin B In the method for producing a nonwoven fabric of the present invention, the polypropylene resin B disposed in the sea component is preferably a polypropylene resin produced using a metallocene catalyst as a polymerization catalyst. By using a metallocene catalyst as the polypropylene resin B, the process stability during spinning is improved and the melting point can be lowered compared to polypropylene resins obtained using a Ziegler-Natta catalyst, so that a nonwoven fabric having high uniformity of texture and excellent flexibility can be obtained.

[0116] In the method for producing a nonwoven fabric of the present invention, the polypropylene resin B to be used in the sea component preferably has a propylene fraction of 98.5% or more and 100.0% or less. By making the propylene fraction of the polypropylene resin B preferably 98.5% or more, more preferably 98.8% or more, and even more preferably 99.0% or more, the process stability during spinning is improved and the heat of crystal fusion of the obtained nonwoven fabric is increased, so that a nonwoven fabric having high uniformity of texture and excellent mechanical properties can be obtained. The upper limit of the propylene fraction of the polypropylene resin B that can be achieved in the present invention is 100.0%.

[0117] In the method for producing a nonwoven fabric of the present invention, the polypropylene resin B to be contained in the sea component preferably has an isotactic pentad fraction of 90.0% or more and 100.0% or less. By making the isotactic pentad fraction of the polypropylene resin B preferably 90.0% or more, more preferably 92.0% or more, and even more preferably 94.0% or more, the heat of crystal fusion of the obtained nonwoven fabric is increased, so that a nonwoven fabric having excellent mechanical properties can be obtained. In addition, the upper limit of the isotactic pentad fraction of the polypropylene resin B that can be achieved in the present invention is 100.0%.

[0118] In the method for producing the nonwoven fabric of the present invention, the melt flow rate MFR B and the melt flow rate MFR of the above polypropylene resin A A Melt flow rate difference (MFR B -MFR A ) is preferably 6 g / 10 min or more and 200 g / 10 min or less. B -MFR A ) is preferably 6 g / 10 min or more, more preferably 10 g / 10 min or more, and further preferably 15 g / 10 min or more, so that spinning stress is concentrated on the island component having the polypropylene-based resin A, and the molecular orientation parameter difference (O C -O S ) is large, it is possible to obtain a nonwoven fabric with excellent mechanical properties.B -MFR A ) is preferably 200 g / 10 min or less, more preferably 150 g / 10 min or less, and further preferably 100 g / 10 min or less, so that the spinning stress is not excessively concentrated on the island components having the polypropylene-based resin A, and the process stability during spinning is improved, so that a nonwoven fabric with a uniform texture can be obtained.

[0119] In the method for producing a nonwoven fabric of the present invention, it is preferable that polypropylene resin B has a melt flow rate of 30 g / 10 min or more and 290 g / 10 min or less while satisfying the above relationship. By setting the lower limit of the melt flow rate range to preferably 30 g / 10 min or more, more preferably 45 g / 10 min or more, it is possible to stably spin even a fine fiber diameter, and to obtain a nonwoven fabric that is excellent in texture and has a uniform texture. On the other hand, by setting the upper limit of the melt flow rate range to preferably 290 g / 10 min or less, more preferably 280 g / 10 min or less, and even more preferably 250 g / 10 min or less, it is possible to suppress a decrease in the single yarn strength of the islands-in-the-sea type composite fiber, and to provide a nonwoven fabric with excellent mechanical properties.

[0120] (a-3) Melt extrusion from a composite spinneret In the method for producing the nonwoven fabric of the present invention, the method for obtaining islands-in-sea type composite fibers can be a melt spinning method using an extruder such as a pressure melter type, single-screw or twin-screw extruder type. Polypropylene resin A and polypropylene resin B, which are melted and extruded separately, pass through piping, are metered by a metering device such as a gear pump, pass through a filter to remove foreign matter, and are then each introduced to a spinneret. At this time, the temperature from the resin piping to the spinneret (spinning temperature) is preferably 180°C or higher and 280°C or lower. By setting the spinning temperature within the above range, a stable molten state can be achieved, and excellent spinning stability can be obtained.

[0121] It is preferable that the polypropylene-based resin A and the polypropylene-based resin B respectively introduced into the spinneret join together at the top of the spinneret to form a cross section of an islands-in-sea type composite fiber in which the polypropylene-based resin A is arranged as island components and the polypropylene-based resin B is arranged as a sea component.

[0122] The spinneret used for extrusion preferably has a nozzle hole diameter D of 0.1 mm or more and 0.6 mm or less, and furthermore, L / D, defined as the quotient obtained by dividing the land length L of the nozzle hole (the length of the straight tube portion having the same diameter as the nozzle hole diameter) by the hole diameter D, is preferably 1 or more and 10 or less.

[0123] In the present invention, the mass ratio of polypropylene resin A as the island component and polypropylene resin B as the sea component is preferably 10% by mass or more and 70% by mass or less, with respect to the total mass ratio of polypropylene resin B. By setting the mass ratio of polypropylene resin B to preferably 10% by mass or more, more preferably 20% by mass or more, a nonwoven fabric having excellent mechanical properties can be obtained because of excellent thermal adhesiveness. On the other hand, by setting the mass ratio of polypropylene resin B to preferably 70% by mass or less, more preferably 50% by mass or less, the islands-in-sea type composite fiber has excellent single yarn strength, and therefore a nonwoven fabric having excellent mechanical properties can be obtained.

[0124] In the present invention, the number of islands in the islands-in-sea type composite fiber is preferably 1 or more and 10 or less. When the lower limit of the number of islands is preferably 1 or more, a nonwoven fabric having excellent single yarn strength of the composite fiber can be obtained. On the other hand, when the upper limit of the number of islands is preferably 10 or less, a nonwoven fabric having excellent thermal adhesiveness can be obtained.

[0125] (a-4) Pulling and stretching of polypropylene resin It is preferable that the polypropylene-based resin A and the polypropylene-based resin B extruded (spun) from the spinneret holes are pulled and stretched to form islands-in-sea type composite fibers in which the island component is the polypropylene-based resin A and the sea component is the polypropylene-based resin B.

[0126] The islands-in-sea type composite fiber spun from the spinneret is then cooled. Examples of a method for cooling the islands-in-sea type composite fiber include a method of forcibly blowing cold air onto the yarn, a method of naturally cooling the yarn at the ambient temperature around the yarn, and the like, or a combination of these methods can be used.

[0127] The mixture is cooled and solidified by blowing cooling wind (air). The temperature of the cooling wind can be determined in consideration of the cooling efficiency and the cooling wind speed, but it is preferably 30°C or less. By setting the upper limit of the cooling wind temperature to preferably 30°C or less, more preferably 20°C or less, and even more preferably 15°C or less, the cooling efficiency of the islands-in-sea type composite fiber can be increased and the spinnability can be improved. In addition, the lower limit of the cooling wind temperature is preferably 0°C or more from the viewpoint of the cooling cost of the air and from the viewpoint of preventing adhesion of moisture to the fiber due to cooling.

[0128] The cooling air is preferably blown in a direction substantially perpendicular to the islands-in-sea type composite fiber discharged from the spinneret (when the fiber runs vertically, the direction refers to a direction parallel to the ground). In this case, the speed of the cooling air is preferably 10 m / min or more from the viewpoints of cooling efficiency and uniformity of fineness, and is preferably 100 m / min or less from the viewpoint of spinning stability.

[0129] In addition, it is preferable to start cooling at a distance of 0 mm or more and 300 mm or less downstream from the nozzle hole of the spinneret. By setting the lower limit of the distance from the spinneret to the start of cooling to preferably 0 mm or more, more preferably 5 mm, it is possible to stabilize extrusion without causing a decrease in the spinneret surface temperature. In addition, by setting the upper limit of the distance from the spinneret to the start of cooling to preferably 300 mm or less, more preferably 100 mm or less, it is possible to stabilize the thinning behavior of the islands-in-sea type composite fiber and improve spinnability.

[0130] Next, the cooled and solidified filaments are drawn. When the spunbond method is used, the cooled and solidified filaments are not wound up, but are drawn by compressed air ejected from an ejector installed below the spinneret. The islands-in-sea type composite fibers entering the ejector are accelerated by the accelerating air flow, and the spinning speed, which is the running speed of the islands-in-sea type composite fibers, reaches a speed close to the air flow speed.

[0131] The accelerating air flow can be achieved by sealing the area where the cooling air is blown and gradually reducing the cross-sectional area of ​​the sealed area toward the downstream of the spinning line to accelerate the air flow rate. However, in order to obtain high cooling efficiency and air flow rate, it is preferable to not seal the area where the cooling air is blown and to use an ejector.

[0132] In the spunbonding method, various shapes of spinneret and ejector can be used, such as round and rectangular shapes. Among them, it is preferable to use a combination of a rectangular spinneret and a rectangular ejector, from the viewpoints that the amount of compressed air used is relatively small and fusion and abrasion between the yarns are unlikely to occur.

[0133] In this case, the distance from the spinneret to the ejector inlet is preferably 400 mm or more and 3000 mm or less. By making the distance from the spinneret to the ejector inlet 400 mm or more, the islands-in-the-sea type composite fiber enters the ejector after being cooled and solidified, and excellent spinning stability can be obtained. In addition, by making the distance from the spinneret to the ejector inlet 3000 mm or less, the spinning stress does not become too high, so that thread breakage can be suppressed and a nonwoven fabric with few defects can be obtained.

[0134] The spinning speed is preferably 2.0 km / min or more and 6.0 km / min or less. By setting the spinning speed to preferably 2.0 km / min or more, more preferably 2.3 km / min or more, the molecular orientation parameter O reported to the fiber axis at the center of the fiber can be reduced. CSince the average fiber diameter is increased and the average single fiber diameter is decreased, a nonwoven fabric having excellent mechanical properties and flexibility can be obtained. In addition, by setting the spinning speed to preferably 6.0 km / min or less, it is possible to suppress yarn breakage during spinning and to increase spinning stability.

[0135] The spinning speed referred to here is a value measured and calculated by the following procedure. (1) The average single fiber diameter W (μm) of islands-in-the-sea type composite fiber, and the density ρ (g / cm 3 ) shall be the value measured by the above procedure. (2) The polypropylene resin discharged from the die is collected for 1 minute and weighed, and the value obtained is regarded as the discharge rate (g / min). This operation is carried out three times, and the arithmetic average value is divided by the number of die holes, and the value is adopted as the single hole discharge rate Q (g / min). (3) Calculate the spinning speed using the following formula, rounding off to one decimal place. Spinning speed (km / min) = Q × 1000 / ((W / 2) 2 ×π×ρ) (In the formula, Q represents the single hole output rate (g / min), W represents the average single fiber diameter (μm), and ρ represents the density (g / cm 3 ).

[0136] (b) forming a fibrous web The islands-in-sea type composite fibers obtained in the above steps are piled up to form a fiber web composed of the islands-in-sea type composite fibers. Specifically, the islands-in-sea type composite fibers are opened by passing through a fiber-opening part where the surrounding air flow speed is reduced, and then landed on a net conveyer where air is sucked from the back side, and collected as a fiber web.

[0137] The collected fiber web is preferably transported at a transport speed of 5 m / min to 1200 m / min. In another preferred embodiment, the collected fiber web is temporarily bonded by contacting one side of the web with a hot flat roll on a net. This prevents the surface layer of the fiber web from turning over or being blown away while being transported on the net, which may cause the formation to deteriorate, and improves transportability from the collection of the yarns to the thermal bonding.

[0138] In the method for producing the nonwoven fabric of the present invention, the method for forming the fiber web can be selected from known production methods such as the meltblowing method and the short fiber carding method in addition to the spunbonding method described above, but it is preferable to use the spunbonding method because of its excellent productivity. The spunbonding method is excellent in productivity and mechanical strength, and can suppress fluffing and fiber dropout that are likely to occur in short fiber nonwoven fabrics. Furthermore, by laminating multiple layers of the collected spunbonded nonwoven fiber web or heat-bonded spunbonded nonwoven fabric (both are written as S) with SS, SSS, and SSSS, the productivity and uniformity of the texture are improved.

[0139] (c) A step of thermally bonding the fiber web In this step, the fiber web obtained in (b) is thermally bonded. The thermal bonding method is not particularly limited, but examples thereof include a method of thermally fusing the nonwoven fiber web with various rolls, such as a thermal embossing roll having engraved (uneven) portions on the surface of a pair of upper and lower rolls, a thermal embossing roll consisting of a combination of a roll with one flat (smooth) surface and a roll with engraved (uneven) portions on the surface of the other roll, and a thermal calendar roll consisting of a combination of a pair of upper and lower flat (smooth) rolls, a method of thermally fusing the nonwoven fiber web with ultrasonic vibration of a horn, and a method of softening or melting the surface of the islands-in-the-sea type composite fiber by passing hot air through the nonwoven fiber web, thereby thermally fusing the fiber intersections. Among these, it is preferable to use a thermal embossing roll having engraved (uneven) portions on the surface of a pair of upper and lower rolls, or a thermal embossing roll consisting of a combination of a roll with flat (smooth) surface and a roll with engraved (uneven) portions on the surface of the other roll. This not only increases productivity, but also provides a bonded portion that improves the strength of the nonwoven fabric and a non-bonded portion that improves the texture and feel.

[0140] The adhesion rate during thermal bonding is preferably 5% or more and 30% or less. By setting the adhesion rate to preferably 5% or more, more preferably 10% or more, a nonwoven fabric with excellent mechanical properties can be obtained. In addition, by setting the adhesion rate to preferably 30% or less, more preferably 20% or less, a nonwoven fabric with excellent flexibility can be obtained.

[0141] The adhesion rate here refers to the area ratio of the adhesive part to the entire nonwoven fabric. Specifically, in the case of thermal bonding using a pair of uneven rolls, it refers to the area ratio of the part (adhesive part) where the convex parts of the upper roll and the convex parts of the lower roll overlap and contact the nonwoven fiber web to the entire nonwoven fabric. In addition, in the case of thermal bonding using an uneven roll and a flat roll, it refers to the area ratio of the part (adhesive part) where the convex parts of the uneven roll contact the nonwoven fiber web to the entire nonwoven fabric. In addition, in the case of ultrasonic bonding, it refers to the area ratio of the part (adhesive part) thermally bonded by ultrasonic processing to the entire nonwoven fabric.

[0142] The shape of the bonded portion by the hot embossing roll or ultrasonic bonding is not particularly limited, but for example, a circle, an ellipse, a square, a rectangle, a parallelogram, a rhombus, a regular hexagon, and a regular octagon can be used. In addition, it is preferable that the bonded portions are uniformly present at regular intervals in the longitudinal direction (transport direction) and the width direction of the nonwoven fabric. In this way, the variation in strength of the nonwoven fabric can be reduced.

[0143] In addition, the surface temperature of the hot embossing roll during thermal bonding is preferably 100° C. or more and 150° C. or less. By setting the surface temperature of the hot embossing roll to preferably 100° C. or more, more preferably 110° C. or more, it is possible to obtain a nonwoven fabric having excellent mechanical properties because moderate thermal bonding can be achieved. In addition, by setting the surface temperature of the hot embossing roll to preferably 150° C. or less, more preferably 145° C. or less, it is possible to suppress excessive thermal bonding, and therefore it is possible to obtain a nonwoven fabric having excellent flexibility.

[0144] The line pressure of the hot embossing roll during thermal bonding is preferably 50N / cm or more and 500N / cm or less. By setting the line pressure of the hot embossing roll to preferably 50N / cm or more, more preferably 100N / cm or more, and even more preferably 150N / cm or more, sufficient thermal bonding can be achieved, so that a nonwoven fabric with excellent mechanical properties can be obtained. In addition, by setting the line pressure of the hot embossing roll to preferably 500N / cm or less, more preferably 400N / cm or less, and even more preferably 300N / cm or less, excessive thermal bonding can be suppressed, so that a nonwoven fabric with excellent flexibility can be obtained.

[0145] In order to adjust the thickness of the nonwoven fabric, after the thermal bonding by the above-mentioned hot embossing roll, the nonwoven fabric may be further subjected to hot compression bonding by a hot calendar roll consisting of a pair of upper and lower flat rolls. The pair of upper and lower flat rolls refers to a metal roll or an elastic roll having a smooth surface, and a pair of a metal roll and a metal roll or a pair of a metal roll and an elastic roll may be used.

[0146] Here, the elastic roll refers to a roll made of a material having elasticity compared to a metal roll. Examples of the elastic roll include so-called paper rolls made of paper, cotton, aramid paper, etc., and resin rolls made of urethane resin, epoxy resin, silicon resin, polyester resin, hard rubber, and mixtures of these.

[0147] (d) Other post-processing steps The nonwoven fabric of the present invention can be post-processed to the extent that the effect of the present invention is not impaired. Of course, in the present invention, the nonwoven fabric obtained by carrying out this post-processing step is also considered to be the nonwoven fabric of the present invention. Examples of post-processing include physical processing such as drilling and rubbing, and chemical processing such as hydrophilization and charging.

[0148] [Laminated nonwoven fabric] The nonwoven fabric of the present invention can be used as it is, but it is also preferable to form a laminated nonwoven fabric having a layer of the nonwoven fabric and a fiber layer or film layer of a different type from the layer of the nonwoven fabric.

[0149] Here, in the present invention, the "fiber layer of a type different from the nonwoven fabric layer" refers to, for example, when the nonwoven fabric is a spunbond nonwoven fabric, a meltblown nonwoven fabric layer formed by a meltblowing method, a staple fiber nonwoven fabric layer formed by a papermaking method, or a woven or knitted layer made of long fibers or spun yarn.

[0150] The laminated nonwoven fabric according to the present invention has a lamination structure in which at least one layer of the nonwoven fabric of the present invention is laminated. By laminating at least one layer of the nonwoven fabric, the nonwoven fabric acts as a reinforcing material, resulting in a laminated nonwoven fabric with excellent mechanical properties.

[0151] Furthermore, the method for producing the laminated nonwoven fabric according to the present invention is not particularly limited, but examples thereof include a method in which the nonwoven fabric of the present invention is overlaid on a fiber layer or film layer of a different type from that of the nonwoven fabric without bonding, and a method in which a part or the whole of the interlayers are integrated by an adhesive or thermal bonding process.

[0152] Of course, the laminated nonwoven fabric of the present invention can be post-processed in the same manner as the nonwoven fabric described above, so long as the effects of the present invention are not impaired. In the present invention, the laminated nonwoven fabric obtained by carrying out this post-processing step is also considered to be the laminated nonwoven fabric of the present invention.

[0153] The resin constituting the structure other than the nonwoven fabric of the present invention is not particularly limited, but it is preferably composed of a polypropylene-based resin because of ease of adhesion.

[0154] [Hygiene materials] The sanitary material of the present invention is made of the nonwoven fabric or the laminated nonwoven fabric, and more specifically, at least partly comprises the nonwoven fabric or the laminated nonwoven fabric. The nonwoven fabric or the laminated nonwoven fabric has excellent flexibility and texture, is uniform, and has sufficient strength for practical use, so that a sanitary material with excellent comfort when worn can be obtained. The sanitary material referred to here is, for example, a disposable item used for health-related purposes such as medical care and nursing. Examples of the sanitary material of the present invention include paper diapers, sanitary napkins, gauze, bandages, masks, gloves, bandages, etc., and in the case of paper diapers, the components thereof, for example, the top sheet, back sheet, side gathers, etc., are also included. In particular, it is preferably used for the back sheet of paper diapers, which requires high strength and flexibility. EXAMPLES

[0155] Next, the nonwoven fabric of the present invention will be described more specifically based on examples, although the present invention is not limited to these examples.

[0156] [Measurement and evaluation method] The respective property values ​​in the examples were determined by the following methods. Unless otherwise specified, the measurements were carried out according to the above-mentioned methods.

[0157] A. Propylene fraction, isotactic pentad fraction The nuclear magnetic resonance apparatus used was a JEOL RESONANCE "ECZ-600," and measurements were performed under the following conditions as described above. Measurement method: single 13 C pulse with inverse gated 1 H decoupling Observation core: 13 C Observation frequency: 150.9MHz Chemical shift reference: orthodichlorobenzene-d4 (133.0 ppm) ·Measurement temperature: 135℃.

[0158] B. Melt Flow Rate (MFR A , M.F.R. B、 MFR B -MFR A ) The melt flow rate was measured as described above using a "MELT INDEXER F-F01" manufactured by Toyo Seiki Seisakusho Co., Ltd. as a melt flow rate measuring device.

[0159] C. Weight average molecular weight (Mw), polydispersity (Mw / Mn) The high-temperature GPC apparatus used was a Polymer Laboratories PL-220, and measurements were performed under the following conditions as described above. Standard samples: Monodisperse polystyrene manufactured by Tosoh Corporation, dibenzyl manufactured by Tokyo Chemical Industry Co., Ltd. ·Injection volume: 0.200mL ·Flow rate: 1.0mL / min Guard column: Showa Denko Co., Ltd. Shodex HT-G Column: Showa Denko Co., Ltd. Shodex HT-806M (2 columns) · Detector: Differential Refractive Index Detector RI.

[0160] D. Average Single Fiber Diameter and Spinning Speed The measurements were carried out as described above using a scanning electron microscope "SU1510" manufactured by Hitachi High-Technologies Corporation and image analysis software "WinROOF2015" manufactured by Mitani Shoji Co., Ltd. The spinning speed (km / min) was calculated from the obtained average single fiber diameter, the density measured by the above-mentioned method, and the single-hole output volume according to the above-mentioned formula.

[0161] E. Molecular orientation parameter (O C , O S , O C -O S ) The Raman spectrometer used was a "RAMANOR T64000" manufactured by Horiba, Ltd., and measurements were performed under the following conditions as described above. Measurement mode: Raman microscopy Beam diameter: 1μm ·Light source: Ar + Laser / 514.4nm Laser power: 100mW Diffraction grating: Single 1800gr / mm Slit: 100μm Detector: CCD(1024×256).

[0162] F. Tensile strength of composite fibers The tensile strength (cN / dtex) of the composite fiber was measured and calculated using the tensile tester "RTC1210A" manufactured by A&D Co., Ltd., as described above.

[0163] G. Melting point, heat of crystal fusion The differential scanning calorimeter used was a TA Instruments "DSC Q2000," and measurements were carried out as described above.

[0164] H. Crystallite size of the (040) plane of the fused portion of the nonwoven fabric and the (110) plane of the nonwoven fabric The crystallite sizes (nm) of the (040) plane of the fused portion of the nonwoven fabric and the (110) plane of the nonwoven fabric's nonfused portion were measured and calculated using a wide-angle X-ray diffraction measurement device, Bruker AXS's "D8 DISCOVER μHR Hybrid," according to the method described above.

[0165] I. Metsuke The measurements were carried out as described above in accordance with "6.2 Mass per unit area" of JIS L1913:2010 "General nonwoven fabric testing methods."

[0166] J. Tensile strength per unit area The tensile tester used was the "RTC-1210A" manufactured by A&D Co., Ltd., and measurements were carried out as described above in accordance with "6.3 Tensile strength and elongation (ISO method)" of JIS L1913:2010 "General nonwoven fabric test methods."

[0167] K. Bending resistance The measurement was carried out as described above in accordance with "6.7.3 41.5° cantilever method" in "6.7 Bending resistance (JIS method and ISO method)" of JIS L1913:2010 "General nonwoven fabric test methods."

[0168] [Polypropylene resin] The polypropylene resins used in the examples of the present invention are as follows.

[0169] [Polypropylene resin A1] It is a propylene homopolymer obtained using a metallocene catalyst (denoted as "M" in Tables 1 to 4). This polypropylene resin A1 has a propylene fraction of 100.0%, an MFR of 30 g / 10 min, an isotactic pentad fraction of 94.0%, and a polydispersity (Mw / Mn) of 2.4.

[0170] [Polypropylene resin A2] This is a propylene homopolymer obtained using a metallocene catalyst. The propylene fraction of this polypropylene resin A2 is 100.0%, the MFR is 36 g / 10 min, the isotactic pentad fraction is 91.0%, and the polydispersity (Mw / Mn) is 2.9.

[0171] [Polypropylene resin A3] It is a propylene homopolymer obtained using a Ziegler-Natta catalyst (referred to as "ZN" in Tables 1 to 4). The propylene fraction of this polypropylene resin A3 is 100.0%, the MFR is 35g / 10min, the isotactic pentad fraction is 95.0%, and the polydispersity (Mw / Mn) is 3.7.

[0172] [Polypropylene resin A4] This is a propylene homopolymer obtained using a metallocene catalyst. The propylene fraction of this polypropylene resin A4 is 100.0%, the MFR is 36g / 10min, the isotactic pentad fraction is 93.0%, and the polydispersity (Mw / Mn) is 2.6.

[0173] [Polypropylene resin A5] This is a propylene homopolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this polypropylene resin A5 is 100.0%, the MFR is 36g / 10min, the isotactic pentad fraction is 95.0%, and the polydispersity (Mw / Mn) is 3.4.

[0174] [Polypropylene resin A6] This is a propylene homopolymer obtained using a metallocene catalyst. The propylene fraction of this polypropylene resin A6 is 100.0%, the MFR is 150g / 10min, the isotactic pentad fraction is 94.0%, and the polydispersity (Mw / Mn) is 2.1.

[0175] [Polypropylene resin A7] This is a propylene homopolymer obtained using a metallocene catalyst. 7The propylene fraction is 100.0%, the MFR is 9 g / 10 min, the isotactic pentad fraction is 94.0%, and the polydispersity (Mw / Mn) is 2.8.

[0176] [Polypropylene resin B1] This is a propylene homopolymer obtained using a metallocene catalyst. The propylene fraction of this polypropylene resin B1 is 100.0%, the MFR is 60 g / 10 min, the isotactic pentad fraction is 94.0%, and the polydispersity (Mw / Mn) is 2.0.

[0177] [Polypropylene resin B2] It is an ethylene-propylene copolymer obtained using a metallocene catalyst. The propylene fraction of this polypropylene resin B2 is 98.5%, the MFR is 60g / 10min, the isotactic pentad fraction is 94.0%, and the polydispersity (Mw / Mn) is 2.6.

[0178] [Polypropylene resin B3] It is an ethylene-propylene copolymer obtained using a metallocene catalyst. The propylene fraction of this polypropylene resin B3 is 90.0%, the MFR is 60g / 10min, the isotactic pentad fraction is 94.0%, and the polydispersity (Mw / Mn) is 2.0.

[0179] [Polypropylene resin B4] This is a propylene homopolymer obtained using a metallocene catalyst. The propylene fraction of this polypropylene resin B4 is 100.0%, the MFR is 50g / 10min, the isotactic pentad fraction is 60.0%, and the polydispersity (Mw / Mn) is 2.0.

[0180] [Polypropylene resin B5] This is a propylene homopolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this polypropylene resin B5 is 100.0%, the MFR is 60g / 10min, the isotactic pentad fraction is 94.0%, and the polydispersity (Mw / Mn) is 3.5.

[0181] [Polypropylene resin B6] This is a propylene homopolymer obtained using a metallocene catalyst. The propylene fraction of this polypropylene resin B6 is 100.0%, the MFR is 230 g / 10 min, the isotactic pentad fraction is 94.0%, and the polydispersity (Mw / Mn) is 2.1.

[0182] [Polypropylene resin B7] It is an ethylene-propylene copolymer obtained using a metallocene catalyst. The propylene fraction of this polypropylene resin B7 is 93.0%, the MFR is 50g / 10min, the isotactic pentad fraction is 45.0%, and the polydispersity (Mw / Mn) is 2.1.

[0183] [Polypropylene resin B8] This is a propylene homopolymer obtained using a Ziegler-Natta catalyst. The propylene fraction of this polypropylene resin B8 is 100.0%, the MFR is 60g / 10min, the isotactic pentad fraction is 95.0%, and the polydispersity (Mw / Mn) is 4.0.

[0184] [Polypropylene resin B9] This is a propylene homopolymer obtained using a metallocene catalyst. The propylene fraction of this polypropylene resin B9 is 100.0%, the MFR is 30g / 10min, the isotactic pentad fraction is 94.0%, and the polydispersity (Mw / Mn) is 2.4.

[0185] [Example 1] (a) forming a fiber The following polypropylene-based resins were used. Polypropylene resin A: Polypropylene resin A1 Polypropylene resin B: Polypropylene resin B1 Then, the polypropylene-based resin A and the polypropylene-based resin B were melt-extruded by a single-screw extruder, and while being metered by a gear pump, they were fed to a spinneret so that the polypropylene-based resin A was the island component and the polypropylene-based resin B was the sea component. At this time, the mass ratio of the polypropylene-based resin A to the polypropylene-based resin B was polypropylene-based resin A:polypropylene-based resin B=70:30. The temperature of the spinneret was set to 230°C, and the polypropylene-based resin was extruded from a nozzle hole having a hole diameter D of 0.3 mm and a hole depth L of 0.6 mm under the condition of a single-hole discharge rate of 0.40 g / min. The introduction hole located directly above the nozzle hole was a straight hole, and the connection portion between the introduction hole and the nozzle hole was tapered. The island component of the polypropylene-based resin A1 (the number of islands when the composite fiber was formed) was 1.

[0186] The extruded fibrous resin was cooled and solidified by blowing cooling air at a temperature of 10°C and a speed of 60 m / min from the outside, and then pulled by an air flow using a rectangular ejector to obtain fibers. In this case, cooling was started 20 mm downstream from the nozzle hole of the composite spinneret, and the distance from the spinneret to the ejector inlet was 550 mm.

[0187] (b) forming a fibrous web The fibers obtained above were then spread by passing through a spreading section where the surrounding air flow rate was reduced, and then landed on a net conveyer where air was sucked from the back side to obtain a fiber web made of composite fibers. The collected fiber web was then transported at a speed of 8 m / min.

[0188] (c) a step of subjecting the obtained fiber web to adhesive processing The fiber web made of the composite fiber obtained as described above was thermally bonded at 125°C using a pair of upper and lower thermal embossing rolls consisting of an upper roll made of a metal embossing roll engraved with a polka dot pattern and having an adhesion area ratio of 11%, and a lower roll made of a metal flat roll, to obtain a nonwoven fabric. The evaluation results of the obtained nonwoven fabric are shown in Table 1.

[0189] [Examples 2 and 3] (a) In the step of forming fibers, the mass ratio of polypropylene-based resin A to polypropylene-based resin B was polypropylene-based resin A:polypropylene-based resin B = 70:30, but in Example 2 it was polypropylene-based resin A:polypropylene-based resin B = 80:20, and in Example 3 it was polypropylene-based resin A:polypropylene-based resin B = 50:50, but other than that, a nonwoven fabric was obtained in the same manner as in Example 1. The evaluation results of the obtained nonwoven fabric are shown in Table 1.

[0190] [Examples 4 and 5] (a) In the step of forming the fiber, the spinning speed was 2.5 km / min, whereas in Example 4 it was 4.4 km / min, and in Example 5 it was 3.8 km / min. Except for this, nonwoven fabrics were obtained in the same manner as in Example 1. The evaluation results of the obtained nonwoven fabrics are shown in Table 1.

[0191] [Comparative Example 1] (a) forming a fiber Regarding the polypropylene-based resin, the polypropylene-based resin A1 was melt-extruded by a single-screw extruder, and was supplied to a spinneret while being metered by a gear pump. At this time, the temperature of the spinneret was set to 230°C, and the polypropylene-based resin was extruded from a nozzle hole having a hole diameter D of 0.3 mm and a hole depth L of 0.6 mm under the condition of a single hole discharge rate of 0.40 g / min. The introduction hole located directly above the nozzle hole was a straight hole, and the connection part between the introduction hole and the nozzle hole was tapered.

[0192] The discharged fibrous resin was cooled and solidified by blowing cooling air at a temperature of 10°C and a speed of 60 m / min from the outside, and then pulled by an air flow using a rectangular ejector to obtain fibers. In this case, cooling was started 20 mm downstream from the nozzle hole of the composite spinneret, and the distance from the spinneret to the ejector inlet was 550 mm.

[0193] (b) forming a fibrous web The fibers obtained above were then spread by passing through a spreading section where the surrounding air flow rate was reduced, and then landed on a net conveyer where air was sucked from the back side to obtain a fiber web made of single component fibers. The collected fiber web was then transported at a speed of 8 m / min.

[0194] (c) a step of subjecting the obtained fiber web to adhesive processing The fiber web made of the monocomponent fibers obtained as above was thermally bonded at 125°C using a pair of upper and lower thermal embossing rolls consisting of an upper roll made of a metal embossing roll engraved with a polka dot pattern and having an adhesion area ratio of 11%, and a lower roll made of a metal flat roll, to obtain a nonwoven fabric. The evaluation results of the obtained nonwoven fabric are shown in Table 1.

[0195] [Table 1]

[0196] [Example 6, Comparative Example 2] (a) In the step of forming fibers, polypropylene-based resin B was polypropylene-based resin B1, but was changed to polypropylene-based resin B2 in Example 6 and polypropylene-based resin B3 in Comparative Example 2, and a nonwoven fabric was obtained in the same manner as in Example 1. The evaluation results of the obtained nonwoven fabric are shown in Table 2.

[0197] [Example 7] (a) In the step of forming fibers, a nonwoven fabric was obtained in the same manner as in Example 1, except that the polypropylene resin A was changed from the polypropylene resin A1 to the polypropylene resin A2. The evaluation results of the obtained nonwoven fabric are shown in Table 2.

[0198] [Comparative Example 3] (a) In the step of forming fibers, a nonwoven fabric was obtained in the same manner as in Example 1, except that the polypropylene resin B was changed from the polypropylene resin B1 to the polypropylene resin B4. The evaluation results of the obtained nonwoven fabric are shown in Table 2.

[0199] [Comparative Example 4] (a) In the step of forming fibers, the polypropylene resin A was changed from the polypropylene resin A1 to the polypropylene resin A3, and the polypropylene resin B was changed from the polypropylene resin B1 to the polypropylene resin B5, but the same method as in Example 1 was used to obtain a nonwoven fabric. The evaluation results of the obtained nonwoven fabric are shown in Table 2.

[0200] [Example 8] (a) In the step of forming fibers, a nonwoven fabric was obtained in the same manner as in Example 1, except that the polypropylene resin B was changed from the polypropylene resin B1 to the polypropylene resin B6. The evaluation results of the obtained nonwoven fabric are shown in Table 2.

[0201] [Table 2]

[0202] [Example 9] (a) In the step of forming fibers, the mass ratio of polypropylene-based resin A to polypropylene-based resin B was changed from 70:30 to 60:40, but a nonwoven fabric was obtained in the same manner as in Example 1. The evaluation results of the obtained nonwoven fabric are shown in Table 3.

[0203] [Example 10] A nonwoven fabric was obtained in the same manner as in Example 8, except that (a) in the step of forming fibers, the spinning speed was changed from 2.5 km / min to 3.0 km / min, and further, (c) in the step of adhesively processing the obtained fiber web, the temperature of the embossing roll was changed from 125° C. to 120° C. The evaluation results of the obtained nonwoven fabric are shown in Table 3.

[0204] [Example 11] A nonwoven fabric was obtained in the same manner as in Example 1, except that (a) in the step of forming fibers, polypropylene-based resin A4 was used instead of polypropylene-based resin A1, the spinning speed was changed from 2.5 km / min to 2.0 km / min, and (c) in the step of adhesively processing the obtained fiber web, the temperature of the embossing roll was changed from 125° C. to 135° C. The evaluation results of the obtained nonwoven fabric are shown in Table 3.

[0205] [Example 12] (a) In the step of forming fibers, the single-hole output rate was changed from 0.40 g / min to 0.80 g / min, and the spinning speed was changed from 3.0 km / min to 2.5 km / min, but other than that, a nonwoven fabric was obtained in the same manner as in Example 10. The evaluation results of the obtained nonwoven fabric are shown in Table 3.

[0206] [Comparative Example 5] A nonwoven fabric was obtained in the same manner as in Example 1, except that (a) in the step of forming fibers, polypropylene-based resin B7 was used instead of polypropylene-based resin B1, and (c) in the step of adhesively processing the obtained fiber web, the temperature of the embossing roll was changed from 125° C. to 110° C. The evaluation results of the obtained nonwoven fabric are shown in Table 3.

[0207] [Comparative Example 6] A nonwoven fabric was obtained in the same manner as in Example 1, except that (a) in the step of forming fibers, polypropylene-based resin A5 was used instead of polypropylene-based resin A1, the spinning speed was changed from 2.5 km / min to 2.1 km / min, and (c) in the step of adhesively processing the obtained fiber web, the temperature of the embossing roll was changed from 125° C. to 140° C. The evaluation results of the obtained nonwoven fabric are shown in Table 3.

[0208] [Table 3]

[0209] [Comparative Example 7] A nonwoven fabric was obtained in the same manner as in Comparative Example 1, except that (a) in the step of forming fibers, the spinning speed was changed from 2.5 km / min to 3.1 km / min, and further, (c) in the step of adhesively processing the obtained fiber web, the temperature of the embossing roll was changed from 125° C. to 135° C. The evaluation results of the obtained nonwoven fabric are shown in Table 4.

[0210] [Comparative Example 8] (a) In the step of forming fibers, polypropylene resin A6 was used instead of polypropylene resin A1, polypropylene resin B6 was used instead of polypropylene resin B1, and the spinning speed was changed from 2.5 km / min to 3.0 km / min, but other than these, a nonwoven fabric was obtained in the same manner as in Example 1. The evaluation results of the obtained nonwoven fabric are shown in Table 4.

[0211] [Comparative Example 9] (a) In the step of forming fibers, polypropylene resin A5 was used instead of polypropylene resin A1, polypropylene resin B8 was used instead of polypropylene resin B1, and the spinning speed was changed from 2.5 km / min to 2.0 km / min, but other than these, a nonwoven fabric was obtained in the same manner as in Example 1. The evaluation results of the obtained nonwoven fabric are shown in Table 4.

[0212] [Comparative Example 10] (a) In the step of forming fibers, an attempt was made to obtain a nonwoven fabric by the same method as in Example 1, except that polypropylene resin A7 was used instead of polypropylene resin A1, and polypropylene resin B9 was used instead of polypropylene resin B1. However, since the melt flow rate of the polypropylene resin used was low, it was not possible to obtain composite fibers and nonwoven fabric.

[0213] [Table 4]

[0214] The nonwoven fabrics of Examples 1 to 12 have a propylene fraction of 98.5% or more and 100.0% or less, an isotactic pentad fraction of 90.0% or more and 100.0% or less, and C -O S Since the nonwoven fabric was made of composite fibers with a modulus of 0.2 or more and 4.0 or less, and the melting point of the nonwoven fabric was 130°C or more and 155°C or less, it can be seen that the nonwoven fabric was excellent in flexibility and mechanical properties.

[0215] On the other hand, the nonwoven fabrics of Comparative Examples 1, 7, and 8 were O C -O S The nonwoven fabric of Comparative Example 2 and Comparative Example 5 had a low propylene fraction, and therefore both had poor tensile strength per unit area. The nonwoven fabric of Comparative Example 3 had a low isotactic pentad fraction, and the nonwoven fabrics of Comparative Examples 4, 6, and 9 had high melting points, and therefore also had poor tensile strength per unit area. Furthermore, a nonwoven fabric could not be obtained in Comparative Example 10. [Explanation of symbols]

[0216] 1: Test piece 11: Fusion part 12: Inscribed circle of fusion part 13: A point that is less than 50% of the radius of the inscribed circle from the center of the inscribed circle of the fused part

Claims

1. A nonwoven fabric made of composite fibers mainly composed of polypropylene-based resin, The composite fiber is The propylene fraction is 99.0% or more and 100.0% or less, the isotactic pentad fraction is 90.0% or more and 100.0% or less, and Molecular orientation parameter O in the fiber axis direction at the center of the fiber Ｃ and the molecular orientation parameter O in the fiber axis direction at the fiber surface. Ｓ Difference with (O Ｃ -O Ｓ ) is 0.8 or more and 3.5 or less, O C is 5.0 or more and 9.5 or less, The melting point of the nonwoven fabric is 138°C or higher and 155°C or lower.

2. The nonwoven fabric according to claim 1 , wherein the nonwoven fabric has a heat of crystalline fusion of 82 J / g or more and 120 J / g or less.

3. The nonwoven fabric according to claim 1 or 2, wherein the nonwoven fabric is a spunbond nonwoven fabric.

4. The nonwoven fabric has a fused portion and a non-fused portion, The fusion portion has a crystallite size of a (040) plane in wide-angle X-ray diffraction of 10.0 nm or more and 13.5 nm or less; 3. The nonwoven fabric according to claim 1, wherein the non-fused portion has a crystallite size of a (110) plane in wide-angle X-ray diffraction of 5.0 nm or more and 10.0 nm or less.

5. a step of melt-extruding, through a composite spinneret, a polypropylene-based resin A which has a propylene fraction of 99.0% or more and 100.0% or less and which has been polymerized by a metallocene catalyst, and a polypropylene-based resin B which has a melt flow rate higher than that of the polypropylene-based resin A by 6 g / 10 min to 200 g / 10 min and which has a propylene fraction of 99.0% or more and 100.0% or less and which has been polymerized by a metallocene catalyst, and pulling and stretching the spun polypropylene-based resin A and polypropylene-based resin B to form islands-in-sea type composite fibers in which island components are the polypropylene-based resin A and a sea component is the polypropylene-based resin B; depositing the islands-in-the-sea type composite fibers to form a fiber web composed of the islands-in-the-sea type composite fibers; The method for producing a nonwoven fabric according to claim 1 , further comprising the step of thermally bonding the fibrous web.

6. The method for producing a nonwoven fabric according to claim 5, wherein the polypropylene-based resin A has a melt flow rate of 10 g / 10 min or more and 90 g / 10 min or less.

7. The method for producing a nonwoven fabric according to claim 5 or 6, wherein the polypropylene-based resin A and / or the polypropylene-based resin B has an isotactic pentad fraction of 90.0% or more and 100.0% or less.

8. The method for producing a nonwoven fabric according to claim 5 or 6, wherein the number of islands in the islands-in-sea type composite fiber is 1 or more and 10 or less.

9. The method for producing a nonwoven fabric according to claim 5 or 6, wherein the polypropylene resin A has a polydispersity (Mw / Mn) in molecular weight measurement of 1.5 or more and 3.5 or less.

10. A sanitary material comprising the nonwoven fabric according to claim 1 or 2.

11. A laminated nonwoven fabric comprising a layer of the nonwoven fabric according to claim 1 or 2 and a fiber layer different from the layer of the nonwoven fabric.

12. A sanitary material comprising the laminated nonwoven fabric according to claim 11.

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