Spunbonded nonwoven fabric and laminated nonwoven fabric, method for producing the same, and sanitary material

Abstract

To provide a spunbond nonwoven fabric and a laminated nonwoven fabric which can achieve excellent bending flexibility for use as a nonwoven fabric for sanitary materials while not impairing mechanical strength, the spunbond nonwoven fabric of the present invention is a spunbond nonwoven fabric composed of crimped composite fibers containing a first component in which a propylene-based polymer is a main component and a second component in which a propylene-based copolymer having copolymerized an α-olefin is a main component, the second component being disposed at the innermost side of crimping in the cross section of the crimped composite fibers, and the orientation parameter (I2) of the second component being 5.0 or more. In addition, the laminated nonwoven fabric of the present invention is composed of the spunbond nonwoven fabric and at least one elastic layer.

Description

TECHNICAL FIELD

[0001] The present application relates to a spunbond nonwoven fabric which is excellent in bending flexibility and is particularly suitable for sanitary material use, and a laminated nonwoven fabric obtained by laminating at least one elastic layer on the spunbond nonwoven fabric. BACKGROUND

[0002] In recent years, in sanitary materials such as paper diapers and sanitary napkins, there has been an increasing demand for improved wearing comfort. In particular, in members that cover the waist and the large buttocks, it is desired to conform to the body shape having unevenness, and therefore it is required to improve the bending flexibility of the nonwoven fabric member used.

[0003] In the past, in such parts, a polypropylene spunbond nonwoven fabric formed of linear fibers has been widely used. However, the fibers constituting the polypropylene spunbond nonwoven fabric do not have stretchability, and therefore the fibers are taut between the heat-welded points when the sheet is bent, and thus the bending flexibility is insufficient.

[0004] In order to solve the problem, in Patent Literature 1, a nonwoven fabric containing crimped composite fibers of two kinds of propylene-based polymer components is proposed. In addition, in Patent Literature 2, a method of manufacturing a spunbond high-loft nonwoven web is proposed, which performs a specific pre-compaction treatment on a nonwoven web containing crimped multi-component fibers formed of a polypropylene homopolymer and a copolymer of polypropylene and polyethylene.

[0005] Further, in Patent Literature 3, a nonwoven fabric in which composite fibers having a fine crimp are developed by heat treatment are proposed, the composite fibers being formed of a phase structure of a plurality of resins having different heat shrinkage rates.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT LITERATURE

[0008] Patent Literature 1: Japanese Patent Application Laid-Open No. 2007-308868

[0009] Patent Literature 2: Japanese Patent Application Laid-Open No. 2018-024965

[0010] Patent Literature 3: Japanese Patent Application Laid-Open No. 2012-012758 SUMMARY

[0011] PROBLEMS TO BE SOLVED BY THE INVENTION

[0012] In the spunbond nonwoven fabric, in the case where a spring-like crimp structure is formed in the fibers, since the crimp structure of the fibers can be gently stretched and contracted when the sheet is bent, excellent bending flexibility can be obtained. Furthermore, the finer the crimp structure of the fibers within the nonwoven fabric, that is, the smaller the interval between the peaks (mountains) of the adjacent crimps, the more sufficient the elongation space of the fibers, and the greater the effect.

[0013] In the technology of Patent Literature 1, the fiber is rendered crimped by setting the difference in melting point of the two kinds of propylene-based polymer components and the composite component ratio within a prescribed range. Further, in the technology of Patent Literature 2, the fiber is rendered crimped by using a prescribed raw material and further by carrying out a specific pre-compaction treatment. However, in these technologies, the crimp structure of the fiber cannot be sufficiently refined, and as a result, excellent bending flexibility cannot be obtained.

[0014] On the other hand, the technology of Patent Literature 3 promotes the crimp rendering of the fiber by carrying out heat treatment on the nonwoven fabric, and thus a fine crimp can be obtained. However, in order to form a desired crimp form, heat treatment is indispensable, and thus unevenness in weight per unit area is easily formed on the surface of the nonwoven fabric during heat treatment, and the mechanical strength deteriorates. In particular, in the case of a thin (approximately 100 g / m 2 the strength reduction resulting from such unevenness in weight per unit area is more significantly exhibited, and thus is not preferable. Further, the technology of Patent Literature 3 is essentially a polyester-based nonwoven fabric, and thus adhesiveness with a polypropylene spunbond nonwoven fabric, which is widely used as a sanitary material, becomes a large problem.

[0015] Thus, the present application was made in view of the above circumstances, and aims to provide a spunbond nonwoven fabric and a laminated nonwoven fabric which can simultaneously achieve excellent bending flexibility for use as a nonwoven fabric for a sanitary material without impairing the mechanical strength.

[0016] Means for solving the problem

[0017] The inventors of the present application repeatedly conducted intensive research in order to achieve the above object, and as a result, obtained the following insight: in crimped composite fibers constituting a spunbond nonwoven fabric, by using a specific raw material and further controlling the molecular orientation thereof, a spunbond nonwoven fabric having excellent bending flexibility for use as a nonwoven fabric for a sanitary material without impairing the mechanical strength can be obtained.

[0018] The present application was completed based on the above insight, and according to the present application, the following inventions are provided.

[0019] The spunbond nonwoven fabric of the present application is a spunbond nonwoven fabric composed of crimped composite fibers, the crimped composite fibers comprising a first component in which a propylene-based polymer is a main component, and a second component in which a propylene-based copolymer having copolymerized an α-olefin is a main component, the second component being disposed at the innermost side of the crimp in the cross section of the crimped composite fibers, and the orientation parameter (I2) of the second component being 5.0 or greater.

[0020] According to a preferred embodiment of the spun-bonded nonwoven fabric according to the present application, the propylene-based polymer of the aforementioned first component is a propylene homopolymer, and the orientation parameter (I1) of the first component is 6.0 or less.

[0021] According to a preferred embodiment of the spun-bonded nonwoven fabric according to the present application, in the cross section of the aforementioned crimped composite fiber, the area ratio of the second component is 1 to 80%.

[0022] According to a preferred embodiment of the spun-bonded nonwoven fabric according to the present application, the number of crimps of the aforementioned crimped composite fiber observed on the surface of the nonwoven fabric is 50 crimps / 25 mm or more.

[0023] Further, the layered nonwoven fabric according to the present application is formed by laminating at least one elastic layer to a spun-bonded nonwoven fabric layer formed of the aforementioned spun-bonded nonwoven fabric.

[0024] According to a preferred embodiment of the layered nonwoven fabric according to the present application, the aforementioned elastic layer is a layer formed of an elastic nonwoven fabric.

[0025] The sanitary material according to the present application is formed of at least a part of the aforementioned spun-bonded nonwoven fabric or the aforementioned layered nonwoven fabric.

[0026] Further, the method for manufacturing a spun-bonded nonwoven fabric according to the present application preferably melts the aforementioned first component and the aforementioned second component having a melt viscosity that is 1.20 times or more higher than the melt viscosity of the aforementioned first component, respectively, and spins out a composite polymer flow from a composite spinneret, and then forms the aforementioned crimped composite fiber by presenting crimping in a manner that the second component is arranged at the innermost side of the crimping between an air traction unit and a collection belt, and collects the crimped composite fiber on the collection belt.

[0027] According to a preferred embodiment of the method for manufacturing a spun-bonded nonwoven fabric according to the present application, a composite polymer flow is spun out in which the mass of the aforementioned first component and the aforementioned second component is 20:80 to 99:1.

[0028] Further, the method for manufacturing a layered nonwoven fabric according to the present application preferably includes: a step of melting the aforementioned first component and the aforementioned second component having a melt viscosity that is 1.20 times or more higher than the melt viscosity of the aforementioned first component, respectively, and spinning out a composite polymer flow from a composite spinneret, and then forming the aforementioned crimped composite fiber by presenting crimping in a manner that the second component is arranged at the innermost side of the crimping between an air traction unit and a collection belt, and collecting the crimped composite fiber on the collection belt to form a spun-bonded nonwoven fabric layer; and a step of laminating at least one elastic layer.

[0029] According to a preferred embodiment of the method for manufacturing a layered nonwoven fabric according to the present application, the aforementioned elastic layer is formed by a spun-bonding method.

[0030] According to a preferred embodiment of the method for manufacturing a layered nonwoven fabric according to the present application, the aforementioned elastic layer is formed by a melt-blowing method.

[0031] The effects of the invention

[0032] According to the present invention, it is possible to obtain a spunbond nonwoven fabric that simultaneously achieves sufficient strength and excellent flexibility for use as a nonwoven fabric for hygiene materials, and a laminated nonwoven fabric obtained by laminating at least one elastomer layer thereon. Attached Figure Description

[0033] [ Figure 1 ] Figure 1 This is a schematic side view of the crimped composite fiber as observed using a scanning electron microscope (SEM) or similar instrument. Figure 1 A is a schematic side view of side-by-side composite fibers. Figure 1 B is a schematic side view of an eccentric core-sheath type composite fiber.

[0034] [ Figure 2 ] Figure 2 This figure illustrates a method for measuring the curl diameter on a scanning electron microscope (SEM) image obtained by observing the surface of an example of the spunbond nonwoven fabric involved in this invention. Detailed Implementation

[0035] The spunbond nonwoven fabric of the present invention is a spunbond nonwoven fabric composed of crimped composite fibers. The crimped composite fibers comprise a first component mainly composed of an propylene polymer and a second component mainly composed of an propylene copolymer copolymerized with α-olefins. In the cross-section of the aforementioned crimped composite fibers, the aforementioned second component is disposed on the innermost side of the crimp, and the orientation parameter (I2) of the second component is 5.0 or higher. Hereinafter, its constituent elements will be described in detail, but the present invention is not limited to the scope of the following description without departing from its spirit.

[0036] [Propylene polymers]

[0037] First, the propylene-based polymer involved in the spun-bonded nonwoven fabric of the present application refers to a polymer in which propylene is the main structural unit component. As such propylene-based polymers, there are propylene homopolymers, or copolymers in which propylene is the main structural unit component, and one or two or more kinds of α-olefins such as ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, and the like. The "main structural unit component" referred to here generally means that the main chain structure of polypropylene is contained in 80% by mass or more of each polymer component constituting the crimped composite fiber. In addition, other propylene-based polymers, ethylene-based polymers can be contained in the above-mentioned propylene-based polymers. In addition, inorganic substances such as titanium oxide, silicon dioxide, barium oxide, carbon black, dyes, pigments, various additives such as flame retardants, optical brighteners, antioxidants, or ultraviolet absorbers, and the like can be contained in the above-mentioned propylene-based polymers.

[0038] In the spun-bonded nonwoven fabric of the present application, by being composed of crimped composite fibers in which a propylene-based polymer is the main component, the adhesion to other components can be improved when used as a sanitary material.

[0039] Note that the "main component" referred to in the present application generally means a component that accounts for 80% by mass or more of each polymer component constituting each component crimped composite fiber.

[0040] In the propylene-based polymer involved in the present application, it is preferable that at least a part thereof contains a fatty acid amide compound. By making the content of the fatty acid amide compound preferably 0.5% by mass or more, more preferably 0.7% by mass or more, and further preferably 1.0% by mass or more, the fatty acid amide compound functions as a lubricant on the surface of the fiber, and thus a spun-bonded nonwoven fabric with excellent tactile sensation can be formed. Note that the upper limit of the content of the fatty acid amide compound in the present application is not particularly limited, and from the viewpoint of cost and productivity, it is preferable to be 5.0% by mass or less.

[0041] The number of carbon atoms of the fatty acid amide compound is preferably 15 or more and 50 or less. As the fatty acid amide compound having 15 or more and 50 or less carbon atoms, there are, for example, saturated fatty acid monoamide compounds, saturated fatty acid diamide compounds, unsaturated fatty acid monoamide compounds, and unsaturated fatty acid diamide compounds. The number of carbon atoms herein refers to the number of carbon atoms contained in the molecule. Specific examples of the fatty acid amide compound include palmitamide, palmitoleamide, stearic acid amide, oleic acid amide, elaidic acid amide, vaccenic acid amide, linoleic acid amide, linolenic acid amide, pinolenic acid amide, eleostearic acid amide, stearidonic acid amide, arachidic acid amide, gadoleic acid amide, eicosenoic acid amide, docosenoic acid amide, parinaric acid amide, eicosatrienoic acid amide, eicosatetraenoic acid amide, eicosapentaenoic acid amide, heneicosatrienoic acid amide, behenic acid amide, erucic acid amide, docosadienoic acid amide, docosatetraenoic acid amide, docosapentaenoic acid amide, docosahexaenoic acid amide, lignoceric acid amide, nervonic acid amide, tetracosanoic acid amide, tetracosanoic acid amide, tetracosanoic acid amide, tetracosanoic acid amide, tetracosanoic acid amide, tetracosanoic acid amide, cerotic acid amide, montanic acid amide, melissic acid amide, ethylene bisdecanoic acid amide, ethylene bislauric acid amide, methylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bisoleic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, ethylene biserucic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene bis hydroxystearic acid amide, distearyl adipic acid amide, distearyl sebacic acid amide, and hexamethylene bisoleic acid amide. These compounds can be used in combination. By having the number of carbon atoms of the fatty acid amide compound preferably be 15 or more, more preferably 23 or more, and further preferably 30 or more, the fatty acid amide compound is less likely to be excessively precipitated on the surface of the fiber, and the spun yarn has excellent spinnability and processing stability, and high productivity can be maintained. By having the number of carbon atoms of the fatty acid amide compound preferably be 50 or less, more preferably 45 or less, and further preferably 42 or less, the fatty acid amide compound is moderately precipitated on the surface of the fiber, and a laminate nonwoven fabric having excellent tactile sensation is obtained. The number of carbon atoms of the fatty acid amide compound is preferably 15 to 50, more preferably 23 to 45, and further preferably 30 to 42.

[0042] [crimped composite fiber]

[0043] The crimped composite fiber according to the present application is a composite fiber having a certain degree of crimp. As such a crimped composite fiber, there are, for example, side-by-side type composite fibers and eccentric core-sheath type composite fibers.

[0044] These composite fibers, since the center of gravity points of the respective components are separated on the cross section of the single fiber, when released from tension in the spinning process, the fiber bends according to the difference in the elastic recovery amount of the respective components, and is continuous in the fiber axial direction, whereby crimping can be exhibited.

[0045] In the spun-bonded nonwoven fabric of the present application, from the viewpoint that the fiber can exhibit fine crimping and the bending softness can be improved, it is preferable to use a side-by-side composite fiber in which the distance between the center of gravity points of the crimping is set to be large.

[0046] The crimped composite fiber according to the present application contains a first component in which a propylene-based polymer is the main component, and a second component in which a propylene-based copolymer in which an α-olefin is copolymerized is the main component, and in the cross section of the crimped composite fiber, the aforementioned second component is disposed at the innermost side of the crimping.

[0047] The "innermost side of the crimping in the cross section of the crimped composite fiber" referred to herein means the following site, which is observed using Figure 1 The explanation will be given.

[0048] Figure 1 is a schematic side view of the crimped composite fiber as observed when the crimped composite fiber according to the present application is observed using a scanning electron microscope (SEM) or the like, Figure 1 A is a schematic side view of a side-by-side composite fiber, Figure 1 B is a schematic side view of an eccentric core-sheath composite fiber. The crimped composite fiber according to the present application is bent by crimping, and in addition, the interface (B1) between the component (S1) and the component (S2) can be observed inside the fiber. At this time, in the cross section of the crimped composite fiber, the component (S2) disposed at the innermost side of the crimping inside the bent shape is the component (second component) referred to herein as the "innermost side of the crimping in the cross section of the crimped composite fiber", and the component (S1) disposed at the outermost side of the crimping outside the bent shape is the component (first component) referred to herein as the "outermost side of the crimping in the cross section of the crimped composite fiber".

[0049] In the eccentric core-sheath composite fiber, in the case where the core component is completely covered with the sheath component, as Figure 1 B, two interfaces (B1, B1') are sometimes observed inside the fiber of the eccentric core-sheath composite fiber, namely, the interface between the component (S1) and the component (S2) and the interface between the component (S1') and the component (S2). In this case, a thin component (S1') as the sheath component exists on the innermost surface of the crimping, but the component (S2) as the core component is more contracted than the components (S1, S1') as the sheath components, and thus S2 is bent to the inside, crimping is generated, and therefore the component (S2) as the core component is set to be the component (second component) at the innermost side of the crimping.

[0050] In the crimped composite fiber according to the present application, it is an important requirement that the second component, which is mainly composed of a propylene-based copolymer copolymerized with an α-olefin, is disposed at the innermost side of the crimp.

[0051] The propylene-based copolymer copolymerized with an α-olefin has a lower crystallinity than a propylene homopolymer, and thus can increase the amount of elastic recovery when the crimp is presented. Therefore, in the crimped composite fiber according to the present application, by disposing the second component at the innermost side of the crimp, the radius of curvature of the crimped form can be reduced, and thus the crimp can be controlled to be finer, and the bending flexibility of the spun-bonded nonwoven fabric can be improved.

[0052] As the α-olefin that can be suitably used in the present application, ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, and 4-methyl-1-hexene can be given. These can also be used in combination. The copolymerization ratio of these α-olefins can be preferably 0.5 mol% or more. By setting the copolymerization ratio to this range, the amount of elastic recovery can be increased. On the other hand, if the copolymerization ratio is increased, the amount of elastic recovery becomes large, which is preferable, but if it is excessively increased, the crystallinity is significantly reduced, and the spinning becomes unstable, and thus the copolymerization ratio is preferably 20.0 mol% or less. More preferably, it is 0.5 to 20.0 mol%.

[0053] In the cross section of the crimped composite fiber according to the present application, the state in which the second component is disposed at the innermost side of the crimp can be evaluated, for example, by a micro-Raman spectroscopy. The second component according to the present application is a propylene-based copolymer copolymerized with an α-olefin, and thus in the Raman spectrum of the second component, a peak that is not present in the Raman spectrum of a propylene homopolymer can be detected. By using this point, the disposition of the second component in the crimped composite fiber can be discriminated. For example, in the case of ethylene copolymerization, a Raman band specific to the ethylene unit can be observed at around 730 cm -1 -1. The following shows an example of the measurement method.

[0054] First, a crimped single fiber (crimped composite fiber) is cut out from the spun-bonded nonwoven fabric and placed on a glass slide in a manner that the bending of the fiber can be discriminated. The side surface of the fiber is observed at a magnification at which one single fiber can be observed, and the Raman spectrum of the polymer component disposed at the innermost side of the crimp is measured using a micro-Raman spectroscopy. At this time, the beam spot diameter of the measuring light is preferably sufficiently small with respect to the fiber diameter, and for example, it is preferably 1 to 2 μm. By comparing the Raman spectrum obtained in this manner with the Raman spectrum of a propylene homopolymer, the component at the inner side of the crimp is discriminated.

[0055] Furthermore, regarding the crimped composite fiber involved in this invention, the orientation parameter (I2) of the aforementioned second component is 5.0 or higher. In this way, the elastic recovery of the second component can be made more significant.

[0056] The orientation parameter of the second component referred to here is the parameter determined using micro Raman spectroscopy. In the case of propylene polymers, the known orientation parameter is 810 cm⁻¹. -1 and 840cm -1 The nearby Raman bands exhibit strong anisotropy for polarized incident light. Therefore, it is possible to determine the anisotropy based on 810 cm⁻¹. -1 and 840cm -1 The intensity of nearby Raman bands is used to evaluate molecular orientation.

[0057] The orientation parameters of the second component were determined using the methods described below.

[0058] (1) Collect crimped composite fibers from spunbond nonwoven fabric and place them on a glass slide in a manner that allows the bending of the fibers to be discerned.

[0059] (2) For the polymer component disposed on the innermost side of the crimp of the crimped composite fiber, the Raman spectrum is measured using incident light with a beam diameter that is sufficiently small relative to the fiber diameter and polarized parallel to the fiber axis.

[0060] (3) Regarding the obtained Raman spectrum, at 750 cm⁻¹ -1 ~900cm -1 Peak fitting was performed within the range to calculate 800 cm⁻¹. -1 ~815cm -1 The maximum intensity of the peak with the maximum point between them is taken as I2 (810) , calculate 840~855cm -1 The maximum intensity of the peak with the maximum point between them is taken as I2 (840) .

[0061] (4) Using the above values, calculate I2. (810) Compared to I2 (840) The ratio (I2) (810) / I2 (840) ).

[0062] (5) Perform the same steps as (1) to (4) on 10 different fibers, calculate the arithmetic mean of the results, and round to the second decimal place. This value is the orientation parameter (I2) of the second component.

[0063] The higher the value of the orientation parameter (I2) of the second component, the higher the molecular orientation of the second component. Therefore, the higher the I2, the higher the orientation of the second component located on the inside of the curl, which increases the elastic recovery and allows for the formation of finer curls, resulting in a spunbond nonwoven fabric with excellent bending flexibility. From this perspective, I2 is more preferably 5.2 or higher, and particularly preferably 5.5 or higher. Furthermore, there is no upper limit to the orientation parameter; however, as a limit for manufacturing with acrylic polymer fibers, it is at most around 8.0.

[0064] On the other hand, in the crimped composite fiber of the present invention, from the viewpoint of making the differences in the elastic recovery of each component significant, the first component is preferably a propylene homopolymer. Propylene homopolymers have high crystallinity, thus reducing the amount of elastic recovery during the spinning process while simultaneously increasing strength.

[0065] Furthermore, in the crimped composite fiber of the present invention, in order to amplify the difference in elastic recovery among the components, the orientation parameter of the first component is preferably 6.0 or less. If the orientation parameter of the first component is within this range, it indicates that the orientation of the first component is sufficiently low, and the elastic recovery can be limited to a small value. On the other hand, if the orientation parameter of the first component becomes significantly smaller, the fiber strength decreases, so it is more preferable to have a value of 4.0 or more.

[0066] The orientation parameter of the first component referred to herein is the parameter determined by the method described below.

[0067] (1) Collect crimped composite fibers from spunbond nonwoven fabric and place them on a glass slide in a manner that allows the bending of the fibers to be discerned.

[0068] (2) For the polymer component on the outermost side of the crimp of the crimped composite fiber, Raman spectra are measured using incident light with a beam diameter that is sufficiently small relative to the fiber diameter and polarized parallel to the fiber axis.

[0069] (3) Regarding the obtained Raman spectrum, at 750 cm⁻¹ -1 ~900cm -1 Peak fitting was performed within the range to calculate 800 cm⁻¹. -1 ~815cm -1 The maximum intensity of the peak with the maximum point between them is taken as I1 (810) , calculate 840~855cm -1 The maximum intensity of the peak with the maximum point between them is taken as I1 (840) .

[0070] (4) Using the above values, calculate I1 (810) Compared to I1 (840) The ratio (I1) (810) / I1 (840)).

[0071] (5) The same operation as in (1) to (4) is performed for different 10 fibers, and the arithmetic mean of the obtained results is calculated, and the second digit after the decimal point is rounded off. This value is the orientation parameter (I1) of the first component.

[0072] In the case of the crimped composite fiber according to the present application, the area ratio of the second component in the cross section of the crimped composite fiber is preferably 1% to 80%. If the area ratio of the second component is within this range, the center-of-gravity distance can be sufficiently ensured, and fine crimping can be formed. From the viewpoint of further expanding the center-of-gravity distance, the area ratio of the second component is more preferably 50% or less, and particularly preferably 40% or less. As a lower limit, it is more preferably 10% or more, and particularly preferably 20% or more.

[0073] The cross section of the fiber referred to herein means the section when the fiber is cut in a plane orthogonal to the fiber length direction of the single fiber.

[0074] The area ratio of the second component in the cross section referred to herein means the ratio obtained in the following manner.

[0075] The crimped single fiber (crimped composite fiber) is cut out from the spunbond nonwoven fabric (in the case of a laminated nonwoven fabric, the spunbond nonwoven fabric layer), and a section is prepared using a microtome in a manner that enables observation of the cross section of the single fiber, and is placed on a glass slide. Then, the fiber section is observed using a microscope built into a Raman spectrometer equipped with a 100x objective lens, and micro-Raman spectroscopy is performed for the two components constituting the fiber section. By comparing the obtained Raman spectrum with the Raman spectrum of the propylene-based copolymer constituting the second component measured in advance, the component having the same spectrum is identified as the second component.

[0076] Then, an image is captured at a magnification that enables observation of the section of one single fiber using a transmission electron microscope for the section used in the above measurement. From the captured SEM image, the cross-sectional area (Af) of the fiber and the area (A2) of the second component are measured using image analysis software (for example, "WinROOF 2015" manufactured by Sambashi Corporation), and the area ratio of the second component is calculated using Equation 1.

[0077] (2) Area ratio of second component) = 100 x A2 / Af Equation (1)

[0078] The same operation as this is performed for different 20 crimped composite fibers, and the value obtained by rounding off the first digit after the decimal point of the arithmetic mean of the obtained results is the area ratio of the second component in the cross section referred to in the present application.

[0079] In the crimped composite fiber according to the present application, by achieving the above-mentioned such requirements, a fine crimp that has not been available so far can be formed. Also, the bending softness of a spunbond nonwoven fabric composed of the fiber is extremely excellent. In the crimped composite fiber according to the present application, the number of crimps is preferably 50 or more per 25 mm.

[0080] The number of crimps referred to herein is a number obtained in the following manner.

[0081] With respect to the surface of the spunbond nonwoven fabric, an image is captured at a magnification at which 10 or more crimped composite fibers can be observed using a scanning electron microscope (SEM). Using the captured image, the apparent length of the crimped composite fibers in the measurement range is measured. The total number of peaks and valleys of the crimped composite fibers present in the apparent length is counted, and the total number is divided by 2. The total number is converted to a number per 25 mm. The same operation as the above is performed with respect to different 20 fibers, and the arithmetic mean of the obtained results is calculated, and the value obtained by rounding off the first digit after the decimal point is the number of crimps referred to herein.

[0082] The larger the value of the number of crimps, the higher the elongation of the crimped composite fiber, and when a spunbond nonwoven fabric is produced, the tightness of the fibers between the heat fixation points can be suppressed, and thus the bending softness can be made excellent. From such a viewpoint, the number of crimps is more preferably 80 or more per 25 mm, and 100 or more per 25 mm can be cited as a particularly preferable range. Also, since the number of crimps differs depending on the fiber diameter of the crimped composite fiber, the upper limit of the number of crimps is not particularly limited, and for example, 1000 or less per 25 mm is preferable, and 750 or less per 25 mm is more preferable.

[0083] Further, in the crimped composite fiber according to the present application, the crimp diameter is preferably 400 μm or less. The crimp diameter referred to herein can be obtained in the following manner, using Figure 2 An explanation will be given.

[0084] Figure 2 is a diagram explaining a method of measuring the crimp diameter on a scanning electron microscope (SEM) image obtained by observing the surface of an example of the spunbond nonwoven fabric according to the present application. As with the measurement of the number of crimps described above, an image of the surface of the spunbond nonwoven fabric is captured. Using the captured SEM image, with respect to the crimped composite fibers in the measurement range, a tangent line (L) that is tangent to the peaks (P1) of two adjacent crimps and the peak (P2) of a crimp is drawn. The perpendicular distance (D) from the valley (V) between P1 and P2 to the tangent line (L) is measured as an integer value with the unit of μm. The same operation as the above is performed with respect to different 20 fibers, and the arithmetic mean of the obtained results is calculated, and the value obtained by rounding off the first digit after the decimal point is the crimp diameter referred to herein.

[0085] By controlling the crimped diameter to be small, the thickness of the spunbond nonwoven fabric can be made thin, and good softness can be obtained. From this viewpoint, the crimped diameter is more preferably 300 μm or less.

[0086] In the crimped composite fiber according to the present application, the fiber diameter is not particularly limited, and the thinner the fiber diameter, the smaller the radius of curvature of the crimp, and the finer the crimp, and thus the fiber diameter is preferably 25.0 μm or less. On the other hand, if the fiber diameter is too small, there is a concern that the strength will decrease, and thus the fiber diameter is more preferably 5.0 μm or more.

[0087] [Spunbond Nonwoven Fabric]

[0088] The spunbond nonwoven fabric according to the present application is composed of the aforementioned characteristic crimped composite fiber, and thus has extremely good bending softness.

[0089] Therefore, the spunbond nonwoven fabric according to the present application preferably has a stiffness of 0.50 mN-cm or less. By making the stiffness within this range, good bending softness suitable for sanitary material use can be obtained.

[0090] Note that the stiffness in the present application is measured based on "6.7.3 41.5° Cantilever Method" of JIS L1913:2010 "General Nonwoven Fabric Test Methods".

[0091] In addition, in the case of use for sanitary material use, the tensile strength per unit area weight of the spunbond nonwoven fabric according to the present application is preferably 0.40 (N / 5 cm) / (g / m 2 ) or more. If the nonwoven fabric strength is within this range, a product that can withstand processability during manufacture of paper diapers and the like and that can be used as an article can be obtained.

[0092] Note that the strength in the present application is a value obtained by dividing the average of the tensile strengths (strength at the time of sample breakage) of two orthogonal directions by the unit area weight, by performing a tensile test in which the clamping interval is at least 5 cm, in accordance with "6.3.1 Standard Time" of "6.3 Tensile Strength and Elongation (ISO Method)" of JIS L1913:2010 "General Nonwoven Fabric Test Methods".

[0093] The unit area weight of the spunbond nonwoven fabric according to the present application is preferably 10 g / m 2 or more and 150 g / m 2 or less. By making the unit area weight 10 g / m 2 or more, it is easy to make the spunbond nonwoven fabric have a thickness suitable for sanitary material use, and a spunbond nonwoven fabric having a mechanical strength that can be used in practice can be obtained. On the other hand, by making it 150 g / m 2The following, more preferably 120 g / m 2 The following, further preferably 100 g / m 2 The following, a spun-bonded nonwoven fabric that can form a nonwoven fabric with excellent air permeability.

[0094] Note that the unit area weight (g / m 2 ) of the spun-bonded nonwoven fabric in the present application is measured based on "6.2 Mass per unit area" of JIS L1913:2010 "General Nonwoven Fabric Test Methods".

[0095] The thickness of the spun-bonded nonwoven fabric of the present application is preferably 2.00 mm or less. By controlling the thickness within this range, good bending flexibility can be obtained. From this viewpoint, the thickness is more preferably 1.50 mm or less. On the other hand, since the thickness is reduced and the fiber density increases, the bending flexibility is impaired, and thus the thickness is preferably 0.01 mm or more.

[0096] Note that the thickness of the spun-bonded nonwoven fabric in the present application is not particularly limited, and for example, refers to the thickness under no load measured by a shape measuring machine (for example, "VR3050" manufactured by KEYENCE Co., Ltd.).

[0097] [Method for manufacturing spun-bonded nonwoven fabric]

[0098] Next, a preferred method for manufacturing the spun-bonded nonwoven fabric of the present application will be described in detail.

[0099] The method for manufacturing the spun-bonded nonwoven fabric of the present application is preferably a method in which the aforementioned first component and the aforementioned second component having a melt viscosity that is 1.20 times or more higher than the melt viscosity of the aforementioned first component are melted, a composite polymer flow is discharged from a composite spinneret to perform spinning, and then the aforementioned crimped composite fibers are formed by presenting crimping with the second component disposed at the innermost side of the crimping from an air drafting unit to a collection belt, and the crimped composite fibers are collected on the collection belt.

[0100] The spun-bonding method is generally a method for manufacturing a nonwoven fabric in which a thermoplastic resin as a raw material is melted, spinning is performed from a spinneret, and then a sliver obtained by performing cooling and solidification is drafted and stretched using an air drafting unit such as an air jet, and is webbed into a nonwoven fabric web, and a process of heat bonding is required. In the case of the spun-bonded nonwoven fabric of the present application, by adopting the spun-bonding method, molecular orientation is promoted by air drafting, and the fibers are firmly fixed to each other by heat bonding, and thus sufficient strength for use as a sanitary material can be obtained.

[0101] As the suitable composite spinneret used in the production method of the spun-bonded nonwoven fabric of the present application, it is preferable to have a mechanism capable of forming a side-by-side composite cross-section or an eccentric core-sheath composite cross-section. Further, the shape of the discharge hole of the nozzle is freely selected as long as it does not impair the effects of the present application, and from the viewpoint of spinning stability, a round hole is preferable.

[0102] In the production method of the spun-bonded nonwoven fabric of the present application, it is preferable to melt and discharge the aforementioned first component and the aforementioned second component having a melt viscosity 1.20 times or more higher than that of the aforementioned first component as a composite polymer stream from the aforementioned composite spinneret.

[0103] The melt viscosity referred to in the present application means the melt viscosity at a shear rate of 31.4 s -1 at the spinning temperature, and is measured using the method described below.

[0104] (1) A rotational rheometer (for example, "Rheosol-G3000" manufactured by UBM Co.) is used, and the temperature is raised to a temperature corresponding to the spinning temperature.

[0105] (2) The polymer is sandwiched between parallel plates, and after melting, the gap between the plates is set to 0.5 mm.

[0106] (3) The strain is applied at a rate of 31.4 rad / s -1 .

[0107] (4) Under the above conditions, the melt viscosity is measured in units of Pa-s.

[0108] The spun-bonding method is a production method in which the discharged polymer stream is cooled while being deformed at high speed, and therefore the molecular orientation of the produced fiber changes in correspondence with the melt viscosity at high shear. In particular, in the production of composite fibers, when there is a difference in the melt viscosity at high shear between the components, a high stress is applied to the component having a high viscosity, and therefore the molecular orientation can be improved. In the present application, it is found that this phenomenon can be evaluated by comparing the melt viscosity at a shear rate of 31.4 s -1 .

[0109] In the production method of the spun-bonded nonwoven fabric of the present application, it is preferable to set the ratio of the melt viscosity of the aforementioned second component to the aforementioned first component to 1.20 times or more, and more preferably to 1.30 times or more. By setting the ratio of the melt viscosities to this range, the second component can be highly molecularly oriented (in the manner desired for the spun-bonded nonwoven fabric of the present application), and finer crimping can be formed. The greater the ratio of the melt viscosities, the finer the crimping becomes, and therefore it is preferable, but when it becomes excessively large, the deformation behavior of the components greatly differs, and this becomes a cause of yarn breakage, and therefore it is more preferable to be 3.00 times or less. ​

[0110] In addition, in the method of manufacturing the spunbond nonwoven fabric according to the present application, in order to improve the orientation of the second component and improve the stability of the jet, it is preferable that the jet be a composite polymer flow in which the mass ratio of the first component to the second component is 20:80 to 99:1. In addition, from the viewpoint of being able to stably jet while the jet speed of each component is equivalent, it is more preferable that the mass ratio of the first component to the second component be 50:50 to 90:10, and particularly preferable that the mass ratio be 40:60 to 80:20.

[0111] In addition, when the melting temperature of one of the first component and the second component having a higher melting temperature is set to Tm, the spinning temperature in the present application is preferably (Tm + 10°C) or higher and (Tm + 100°C) or lower. By setting the spinning temperature within the above range, a stable molten state can be formed, and excellent spinning stability can be obtained.

[0112] The spun yarn is then cooled, and as a method of cooling the spun yarn, for example, a method in which cold air is forcibly blown on the yarn, a method in which natural cooling is performed at the atmospheric temperature around the yarn, a method in which the distance between the spinneret and the air drafting unit is adjusted, or the like can be mentioned, or a method in which these methods are combined can be employed. In addition, the cooling conditions can be appropriately adjusted taking into consideration the jet amount of each single hole of the spinneret, the spinning temperature, the atmospheric temperature, and the like, and then employed.

[0113] Next, the cooled and solidified yarn is drawn and stretched by compressed air jetted from the air drafting unit. The spinning speed is preferably 2000 m / minute or higher, and more preferably 3000 m / minute or higher. By setting the spinning speed to 2000 m / minute or higher, a high productivity is obtained, and in addition, the oriented crystallization of the fiber progresses, and a fiber having a higher strength can be obtained.

[0114] The yarn stretched by the air drafting is subjected to a process of being sheeted by being caught to a moving catching belt, and then subjected to a process of being heat-bonded.

[0115] At this time, in the method of manufacturing the spunbond nonwoven fabric according to the present application, it is preferable that the second component be curled so as to be disposed at the innermost side of the curling between the air drafting unit and the catching belt, and the curled composite fiber described above be formed. Between the air drafting unit and the catching belt, the distance between the fibers is sufficiently large with respect to the curling size, and thus the curling can be exhibited without interference between the fibers, and thus it is advantageous in forming a fine curl. In addition, by completing the curling exhibition before sheeting, the amount of deformation of the sheet can be reduced, and a decrease in strength due to unevenness in the weight per unit area can be prevented.

[0116] In the production method of the spun-bonded nonwoven fabric of the present application, as a method of integrating the sheet captured by the aforementioned capturing belt, a method of bonding the sheet by heating and pressing using a pair of rolls each of which has a surface provided with engravings (protrusions and depressions), a pair of rolls in which one roll has a flat (smooth) surface and the other roll has a surface provided with engravings (protrusions and depressions), and the like can be used. A method of melting the sheet by ultrasonic vibration of a horn, and the like can also be used.

[0117] In particular, in the case where the sheet is integrated by heating and pressing using the aforementioned rolls, the nonwoven fabric layer is sufficiently bonded, and thus the mechanical strength of the spun-bonded nonwoven fabric is increased, and thus this is preferred.

[0118] On the other hand, as a method of integrating the aforementioned sheet, a method of melting the sheet by blowing heated air, nitrogen, or the like, that is, a so-called hot air method can also be used.

[0119] In the case where the spun-bonded nonwoven fabric of the present application is produced using the hot air method, the bulkiness and the hand feeling are excellent, and thus this is preferred.

[0120] [Layered Nonwoven Fabric]

[0121] The layered nonwoven fabric of the present application is preferably formed of a spun-bonded nonwoven fabric layer formed of the aforementioned spun-bonded nonwoven fabric and at least one elastic layer. By using the aforementioned spun-bonded nonwoven fabric as the spun-bonded nonwoven fabric layer and laminating at least one elastic layer thereon, excellent bending flexibility can be achieved in combination with the low rigidity specific to an elastic body.

[0122] First, the elastic body involved in the layered nonwoven fabric of the present application refers to a high molecular compound having a hard segment and a soft segment at normal temperature. As its characteristics, deformation by a weak force can be cited, and in the present application, as an index indicating the same, the bending elastic modulus is preferably 500 MPa or less. Note that the bending elastic modulus in the present application is determined based on JIS K7171:2016 "Plastics - Determination of flexural properties", and the softness of the raw material itself is evaluated. In the layered nonwoven fabric of the present application, by laminating an elastic layer using such an elastic body, high bending flexibility can be obtained.

[0123] In addition, from the viewpoint of productivity, the elastomer is preferably a thermoplastic resin. By making the elastomer a thermoplastic resin, the fiber cross section, the surface morphology is easily controlled. Note that the thermoplastic resin constituting the elastomer layer exhibits a thermoplastic property when heated to above the melting point, and on the other hand, is a polymer that can be deformed by a weak force at ordinary temperature. Specifically, a urethane-based elastomer, a polypropylene-based elastomer, a polyethylene-based elastomer, a polyester-based elastomer, a polystyrene-based elastomer, a polybutadiene-based elastomer, or the like.

[0124] Such a thermoplastic resin can be one kind, or can include a plurality of thermoplastic resins. In the laminated nonwoven fabric of the present application, it can be appropriately selected and used from among the above, taking into consideration the adhesiveness to the spunbond nonwoven fabric layer, the fibers constituting the same.

[0125] In the laminated nonwoven fabric of the present application, the elastomer layer refers to a layer formed of the aforementioned elastomer, and the morphology can be a film shape, a cloth shape such as a woven fabric, a knitted fabric, a nonwoven fabric, a composite material in which the elastomer resin is impregnated in the cloth, a laminated body thereof, or the like. Among these, the nonwoven fabric morphology is preferred. The nonwoven fabric layer in which the fibers are folded can greatly reduce the cross-sectional second moment of inertia compared to a film. Therefore, by laminating the elastomer layer in which the morphology is a nonwoven fabric layer, the bending softness of the laminated nonwoven fabric can be made even better.

[0126] As the morphology of such a nonwoven fabric, it can be selected from known nonwoven fabrics such as a spunbond nonwoven fabric, a meltblown nonwoven fabric, a staple fiber nonwoven fabric, and the like, and from the viewpoint of productivity, a spunbond nonwoven fabric, a meltblown nonwoven fabric is preferred.

[0127] The laminated nonwoven fabric of the present application is, as described above, a laminated body of a spunbond nonwoven fabric layer and at least one elastomer layer. That is, as the laminated structure, if the spunbond nonwoven fabric layer is represented as (S) and the elastomer layer is represented as (E), for example, when it is two layers, it is (S) / (E), when it is three layers, it is (S) / (E) / (S), and the like, and when it is four layers, it is (S) / (E) / (E) / (S), and the like, and (S) / (E) / (S) / (E) / (S), and the like. Among these, more preferably, it is a structure in which the spunbond nonwoven fabric layer is laminated on both surfaces of the elastomer layer, that is, a structure such as (S) / (E) / (S), (S) / (E) / (S) / (E) / (S). The laminated structure is selected according to the purpose of use, and the like.

[0128] The laminated nonwoven fabric of the present application is preferably integrated with these spunbond nonwoven fabric layers and elastomer layers. The integration referred to here means that the layers are joined by the interweaving of the fibers, the fixation based on the components such as an adhesive, the fusion of the thermoplastic resins constituting each layer, and the like.

[0129] [Method for producing laminated nonwoven fabric]

[0130] The manufacturing method of the layered nonwoven fabric of the present application includes: a step of forming a spunbond nonwoven fabric layer by respectively melting and discharging a first component and a second component having a melt viscosity higher than that of the first component by 1.20 times or more from a composite spinneret to perform spinning, and then forming crimped composite fibers by crimping the fibers between an air traction unit and a collection belt so that the second component is disposed at the innermost side of the crimp, and collecting the crimped composite fibers on the collection belt; and a step of laminating at least one elastomer layer. Note that the step of forming the spunbond nonwoven fabric layer is the same as the manufacturing method of the spunbond nonwoven fabric described above.

[0131] Further, specifically, the step of laminating at least one elastomer layer can employ, for example, a method of continuously collecting an elastomer layer on the spunbond nonwoven fabric layer formed on the collection belt in an in-line manner using a general method including known methods, thereby laminating, and integrating by heating and pressurization; a method of laminating the separately obtained spunbond nonwoven fabric layer and elastomer layer in an off-line manner, and integrating by heating and pressurization or the like; and the like. Among them, from the aspect of excellent productivity, a method of continuously collecting an elastomer layer on the spunbond nonwoven fabric layer formed on the collection belt in an in-line manner, thereby laminating, and integrating by heating and pressurization is preferred. Note that as the method of integration, a method of interlacing fibers with each other by needle punching or the like, a method of bonding using an adhesive or the like can also be given.

[0132] As one of the preferred modes in the manufacturing method of the layered nonwoven fabric of the present application, a method of forming the above-mentioned elastomer layer by a spunbond method can be given. By employing the spunbond method, a layered nonwoven fabric having high strength can be obtained, and thus is preferred.

[0133] In addition, as another preferred mode in the manufacturing method of the layered nonwoven fabric of the present application, a method of forming the above-mentioned elastomer layer by a meltblown method can be given. The reason for this is that by employing the meltblown method, a sheet can be stably formed compared to the spunbond method. In addition, the fiber diameter can be reduced compared to the spunbond method, and thus has the advantage of being able to improve the bending flexibility.

[0134] Note that the manufacturing method of the layered nonwoven fabric of the present application is only required to laminate the above-mentioned spunbond nonwoven fabric layer and at least one elastomer layer, and as for the number of layers, combination, an arbitrary configuration can be employed according to the purpose.

[0135] [Hygienic materials]

[0136] At least a part of the sanitary material of the present application is composed of the aforementioned spunbond nonwoven fabric, or the aforementioned laminated nonwoven fabric, and excellent bending flexibility can be obtained. Note that the sanitary material of the present application is an article used for health-related purposes such as medical care, and is mainly disposable, and examples include paper diapers, sanitary napkins, gauze, bandages, masks, gloves, and hemostatic patches, and also include constituent components thereof, such as topsheets, back sheets, and side gathers of paper diapers.

[0137] Examples

[0138] Next, the present application will be specifically described based on examples. However, the present application is not limited to these examples. Note that in the measurement of each property, items not specifically described were measured based on the aforementioned methods.

[0139] [Measurement method]

[0140] (1) Identification of the innermost component of the curl

[0141] The measurement device used was a Raman spectrometer "inVia" manufactured by RENISHAW. The measurement conditions were as follows.

[0142] Beam spot diameter: 1 μm

[0143] Light source: 532 nm

[0144] Laser power: 10 mW

[0145] Diffraction lattice: Single 1800 gr / mm, 3000 (-1) gr / mm

[0146] Slit: 65 μm

[0147] A curled single fiber (curled composite fiber) was cut out from the spunbond nonwoven fabric (in the case of a laminated nonwoven fabric, the spunbond nonwoven fabric layer) and placed on a glass slide in a manner that enabled discrimination of the bend of the fiber. Then, the fiber was observed from the side with a microscope built into the Raman spectrometer equipped with a 100x objective lens in a manner that enabled observation of one single fiber. Micro-Raman spectroscopy was performed on the component disposed on the inner side of the bend as observed from the side of the fiber. The component disposed on the innermost side of the curl was identified by comparison of the obtained Raman spectrum with the Raman spectrum of the propylene homopolymer measured in advance.

[0148] (2) Area ratio of the second component

[0149] From the spunbond nonwoven fabric (in the case of a laminated nonwoven fabric, the spunbond nonwoven fabric layer), a curled single fiber (curled conjugated fiber) was cut out, and a section was made using a microtome in a manner that enables observation of the cross section of the single fiber, and was placed on a glass slide. Then, the fiber cross section was observed using a microscope built into a Raman spectrometer equipped with a 100x objective lens. Micro-Raman spectroscopy was performed with respect to the two components that constitute the fiber cross section. By comparing the Raman spectrum obtained with the Raman spectrum of the propylene-based copolymer measured in advance, the component having the same spectrum was identified as the second component.

[0150] Then, with respect to the section used in the above measurement, an image was captured using a transmission electron microscope at a magnification that enables observation of the cross section of one single fiber. From the SEM image captured, using image analysis software (Sambuco Corporation, "WinROOF 2015"), the cross-sectional area of the fiber (Af) and the area of the second component (A2) were measured, and the area ratio of the second component was calculated using Equation 1.

[0151] (Area ratio of the second component) = 100 x A2 / Af Equation (1)

[0152] The same operation was performed with respect to 20 different curled conjugated fibers, the arithmetic mean of the results obtained was calculated, and the value obtained by rounding off the first digit after the decimal point was taken as the area ratio of the second component in the cross section.

[0153] (3) Orientation parameter

[0154] The measuring device was a Raman spectrometer "inVia" manufactured by RENISHAW. The measurement was performed under the following conditions.

[0155] Measurement mode: Micro-Raman (polarization measurement)

[0156] Polarization direction: parallel direction with respect to the fiber axis

[0157] Beam spot diameter: 1 μm

[0158] Light source: 532 nm

[0159] Laser power: 10 mW

[0160] Diffraction lattice: Single 800 gr / mm, 3000 (-1) gr / mm

[0161] Slit: 65 μm

[0162] From the spunbond nonwoven fabric, crimped single fibers were cut out and placed on a glass slide in a manner that enabled discrimination of the curvature of the fibers. Then, for the crimped conjugate fibers, observation was performed from the fiber side using a 50x objective lens. For the polymer components disposed at the innermost and outermost sides of the curvature in observation from the fiber side, Raman spectroscopy was performed. Based on the obtained Raman spectra, the orientation parameter of each component was determined as described above.

[0163] (4) Number of crimps

[0164] For the surface of the spunbond nonwoven fabric, an image was captured at a magnification at which the peaks of the crimps of 10 to 50 of the crimped conjugate fibers formed could be observed using a scanning electron microscope (SEM, "VHX6000" manufactured by KEYENCE). Among these, in a case where the number of peaks of the crimps within a field of view of 10 mm x 10 mm could be confirmed to be less than 10, the number of crimps of the fibers was set to 0. The total number of peaks and valleys of the fibers per 25 mm was counted, and the value obtained by dividing the total number by 2 was used as the number of crimps per 25 mm. This was similarly determined for 20 different fibers, and the value obtained by rounding off the first digit after the decimal point of the arithmetic mean to the nearest integer was used as the number of crimps per 25 mm.

[0165] (5) Weight per unit area

[0166] The weight per unit area was determined based on "6.2 Mass per unit area" of JIS L1913:2010 "General Nonwoven Fabric Test Methods".

[0167] (6) Stiffness

[0168] The stiffness was determined based on "6.7.3 41.5° Cantilever Method" of JIS L1913:2010 "General Nonwoven Fabric Test Methods".

[0169] (7) Tensile strength per unit area

[0170] The tensile strength per unit area was determined using a tensile testing machine ("TENSILON UCT-100" manufactured by ORIENTEC) based on "6.3.1 Standard Time" of "6.3 Tensile Strength and Elongation (ISO Method)" of JIS L1913:2010 "General Nonwoven Fabric Test Methods". Based on the measured data, the average of the tensile strengths (strength at the time of sample breakage) in two orthogonal directions was divided by the weight per unit area, thereby calculating the tensile strength per unit area.

[0171] [Example 1]

[0172] As the first component, a shearing speed of 31.4 s -1Homopolymer polypropylene (hereinafter, including Table 1, sometimes abbreviated as "homogeneous PP") with a melt viscosity of 153 Pa·s was used as the second component, with a shear rate of 31.4 s. -1 Ethylene copolymer polypropylene (hereinafter, including Table 1, sometimes abbreviated as "coPP") with a melt viscosity of 270 Pa·s and copolymerized with 2.7 mol% ethylene was melted in a separate extruder and extruded from a rectangular nozzle with a side-by-side composite cross-section at a spinning temperature of 230°C at a per-hole ejection rate of 0.55 g / (min·hole) and an ejection mass ratio of component 1:component 2 = 50:50. After the spun yarn was cooled and solidified, it was pulled and stretched in a rectangular ejector using compressed air at a pressure of 0.10 MPa and collected onto a moving collection belt to obtain a nonwoven fiber web. At this point, the fibers in the nonwoven fiber web have fine crimps. For the nonwoven fiber web obtained in this way, the upper roller is a metal embossing roller with circular protrusions staggered at equal intervals in both the MD and CD directions. The lower roller is an embossing roller with a pair of upper and lower heating mechanisms, which is made of a flat metal roller. The web is integrated by heating and pressing at a linear pressure of 300 N / cm and a surface temperature of 125°C, resulting in a weight per unit area of ​​20 g / m². 2 The spunbond nonwoven fabric was obtained. For the obtained spunbond nonwoven fabric, the innermost component of the crimp, orientation parameters, crimp number, weight per unit area, stiffness, and tensile strength were evaluated. The results are shown in Table 1.

[0173] [Example 2]

[0174] As the first component, a shear rate of 31.4 s was used. -1 Homopolymer PP with a melt viscosity of 220 Pa·s was used, and the same procedure as in Example 1 was followed to obtain a spunbond nonwoven fabric. For the obtained spunbond nonwoven fabric, the innermost component of the crimp, orientation parameters, crimp number, weight per unit area, stiffness, and tensile strength were evaluated. The results are shown in Table 1.

[0175] [Example 3]

[0176] The spunbond nonwoven fabric was produced by spraying at a mass ratio of component 1:component 2 = 80:20, and otherwise operated in the same manner as in Example 1. The innermost component of the crimp, orientation parameters, crimp number, weight per unit area, stiffness, and tensile strength were evaluated for the obtained spunbond nonwoven fabric. The results are shown in Table 1.

[0177] [Example 4]

[0178] As the second component, a shear rate of 31.4 s was used. -1The spunbond nonwoven fabric was obtained by using an ethylene copolymer polypropylene with a melt viscosity of 280 Pa·s and copolymerized with 5.3 mol% ethylene, otherwise operated in the same manner as in Example 1. For the obtained spunbond nonwoven fabric, the innermost component of the crimp, orientation parameters, crimp number, weight per unit area, stiffness, and tensile strength were evaluated. The results are shown in Table 1.

[0179] [Example 5]

[0180] The spunbond nonwoven fabric was produced by spraying at a mass ratio of component 1:component 2 = 99:1, and otherwise operated in the same manner as in Example 1. The innermost component of the crimp, orientation parameters, crimp number, weight per unit area, stiffness, and tensile strength were evaluated for the obtained spunbond nonwoven fabric. The results are shown in Table 1.

[0181] [Comparative Example 1]

[0182] As the first component, a shear rate of 31.4 s was used. -1 The homopolymer PP with a melt viscosity of 280 Pa·s was used, and the same procedure as in Example 1 was followed to obtain a spunbond nonwoven fabric.

[0183] [Comparative Example 2]

[0184] As the second component, a shear rate of 31.4 s was used. -1 The homopolymer PP with a melt viscosity of 270 Pa·s was used, and the same procedure as in Example 1 was followed to obtain the spunbond nonwoven fabric.

[0185] [Table 1]

[0186] [Table 1]

[0187]

[0188] As shown in Table 1, the spunbond nonwoven fabrics of Examples 1-4 exhibit excellent flexibility and strength. In particular, Examples 1, 3, and 4 demonstrate extremely excellent flexibility. On the other hand, the nonwoven fabrics of Comparative Examples 1-2 show that the fibers on the surface of the spunbond nonwoven fabric are loose and have low flexibility.

[0189] [Example 6]

[0190] (Spunbond nonwoven fabric layer)

[0191] Using a shearing speed of 31.4s -1 Homopolymer polypropylene with a melt viscosity of 153 Pa·s was used as the second component, with a shear rate of 31.4 s⁻¹. -1Example 1 (Spun-bonded nonwoven fabric) An ethylene copolymerized polypropylene having a melt viscosity of 270 Pa-s and copolymerized with 2.7 mol% of ethylene was used. They were melted with separate extruders, and spun out from a rectangular nozzle with a discharge amount of 0.55 g / (min-hole) per single hole, a discharge mass ratio of component 1 : component 2 = 50 : 50 at a spinning temperature of 230°C to obtain a parallel composite cross-section. After cooling and solidifying the spun yarn, it was drawn and stretched in a rectangular jet using compressed air with a pressure of 0.10 MPa through the jet, and was caught on a moving catching belt to obtain a spun-bonded nonwoven fabric layer (expressed as "PP / coPP-SB" in Table 2) with a weight per unit area of 10 g / m 2 . At this time, the fibers in the spun-bonded nonwoven fabric layer had fine crimping.

[0192] (Elastomer layer)

[0193] An elastomer layer was formed using a polypropylene-based elastomer (expressed as "PP-based" in Table 2) having a melt viscosity of 423 Pa-s and a flexural elastic modulus of 13 MPa, copolymerized with 15 wt% of an ethylene component, by a spun-bonding method. That is, the polypropylene-based elastomer having a melt viscosity of 423 Pa-s was melted with an extruder, and was spun out from a rectangular nozzle at a spinning temperature of 230°C with a discharge amount of 0.20 g / (min-hole) per single hole. After cooling and solidifying the spun yarn, it was drawn and stretched in a rectangular jet using compressed air with a pressure of 0.10 MPa through the jet, and was caught on a moving catching belt to obtain an elastomer layer (spun-bonding method) with a weight per unit area of 30 g / m 2 .

[0194] (Laminated nonwoven fabric)

[0195] On the spun-bonded nonwoven fabric layer obtained above, the elastomer layer was caught using the above-described method, and further a spun-bonded nonwoven fabric layer identical to the aforementioned spun-bonded nonwoven fabric layer was caught thereon, and the integration of the laminated nonwoven fabric layers was performed using the same pressurization and heating conditions as in Example 1 to obtain a laminated nonwoven fabric of a 3-layer structure of a spun-bonded nonwoven fabric layer-elastomer layer (spun-bonding method)-spun-bonded nonwoven fabric layer (regarding the laminated structure, expressed as S / E S1 / S in Table 2). The weight per unit area, stiffness, and tensile strength of the obtained laminated nonwoven fabric were evaluated. The results are shown in Table 2.

[0196] [Example 7]

[0197] The same operations as in Example 6 were performed except that the elastomer layer was produced using a melt-blowing method as described below to obtain a 3-layer structure of a spun-bonded nonwoven fabric layer-elastomer layer (melt-blowing method)-spun-bonded nonwoven fabric layer (regarding the laminated structure, expressed as S / E M / S)Laminated nonwoven fabric. The weight per unit area, stiffness, and tensile strength of the resulting laminated nonwoven fabric were evaluated. The results are shown in Table 2.

[0198] (Elastomer layer)

[0199] Using an extruder, a polypropylene elastomer with a melt viscosity of 423 Pa·s and a flexural modulus of 13 MPa was melted and spun at a spinning temperature of 255°C with a pore size of [missing information]. After spinning under conditions of 0.25 mm diameter and a single-hole ejection rate of 0.12 g / (min·hole), air was injected at a temperature of 275℃ and a pressure of 0.15 MPa to obtain a unit area weight of 30 g / m². 2 The elastomer layer (melt-blown method).

[0200] [Example 8]

[0201] As the elastomer layer, the polypropylene-based elastomer used in Example 6, with a unit area weight of 30 g / m², was employed. 2 The membrane, except for the steps described in Example +, yields a laminated nonwoven fabric (the laminate composition is described as S / E in Table 2). F / S). For the obtained laminated nonwoven fabric, the weight per unit area, stiffness, and tensile strength were evaluated. The results are shown in Table 2.

[0202] [Example 9]

[0203] A polyethylene-based elastomer (described as PE-based in Table 2) with a melt viscosity of 252 Pa·s and a flexural modulus of 23 MPa was used in the elastomer layer. Otherwise, the process was the same as in Example 6 to obtain the laminated nonwoven fabric (described as S / E in Table 2 regarding the laminate composition). S2 / S). For the obtained laminated nonwoven fabric, the weight per unit area, stiffness, and tensile strength were evaluated. The results are shown in Table 2.

[0204] [Reference Example 1]

[0205] The elastomer layer was made into a typical spunbond nonwoven layer (not an elastomer layer) as shown below, and otherwise operated in the same manner as in Example 6 to obtain a laminated nonwoven fabric (the laminate configuration is described as S / S / S in Table 2). The weight per unit area, stiffness, and tensile strength of the resulting laminated nonwoven fabric were evaluated. The results are shown in Table 2.

[0206] (Spunbond nonwoven fabric layer)

[0207] An homopolypropylene which is not an elastomer having a melt viscosity of 290 Pa-s and a flexural modulus of 1550 MPa was melted by using an extruder, spun out from a rectangular nozzle at a spinning temperature of 230°C under conditions where the single-hole jet amount was 0.45 g / (min-hole), and cooled and solidified. Then, by using compressed air having a pressure of 0.10 MPa which passed through the nozzle to pull and stretch the spun yarn in the rectangular jet, the spun yarn was caught on a moving catching belt in the rectangular jet to obtain a spun-bonded nonwoven fabric layer having a weight per unit area of 30 g / m 2

[0208] [Table 2]

[0209] [Table 2]

[0210]

[0211] As shown in Table 2, it was found that the laminated nonwoven fabric of Examples 6 to 9 was excellent in both the bending flexibility and the strength. On the other hand, as to the nonwoven fabric of Reference Example 1, since the spun-bonded nonwoven fabric layer which was laminated between the spun-bonded nonwoven fabric layers was hard, the bending flexibility of the laminated nonwoven fabric was also low.

[0212] Explanation of Reference Numerals

[0213] S1 Component

[0214] S1' Component

[0215] S2 Component

[0216] B1 Interface

[0217] B1' Interface

[0218] P1, P2 Peak of crimp

[0219] L Tangent line to P1 and P2

[0220] V Valley between P1 and P2

[0221] D Perpendicular distance from valley V to tangent line L​

Claims

1. A spunbond nonwoven fabric which is a spunbond nonwoven fabric composed of crimped composite fibers, the crimped composite fibers comprising a first component of a propylene-based polymer as a main component, and a second component of a propylene-based copolymer copolymerized with an α-olefin as a main component, In a cross section of the crimped composite fibers, the second component is disposed at the innermost side of crimping, and an orientation parameter (I2) of the second component is 5.0 or more.

2. The spunbond nonwoven fabric according to claim 1, wherein, The propylene-based polymer of the first component is a propylene homopolymer, and an orientation parameter (I1) of the first component is 6.0 or less.

3. The spunbond nonwoven fabric according to claim 1 or 2, wherein In a cross section of the crimped composite fibers, an area ratio of the second component is 1% to 80%.

4. The spunbond nonwoven fabric according to any one of claims 1 to 3, wherein A number of crimps of the crimped composite fibers observed on a surface of the nonwoven fabric is 50 / 25 mm or more.

5. A laminated nonwoven fabric which is formed by laminating at least one elastomer layer to a spunbond nonwoven fabric layer of the spunbond nonwoven fabric described in any one of claims 1 to 4.

6. The layered nonwoven fabric according to claim 5, wherein The elastomer layer is a layer formed of an elastomer nonwoven fabric.

7. A sanitary material composed of at least a part of the spunbond nonwoven fabric described in any one of claims 1 to 4, or the laminated nonwoven fabric described in claim 5 or 6.

8. The method for producing a spun-bonded nonwoven fabric according to any one of claims 1 to 4, wherein The first component and the second component having a melt viscosity 1.20 times or more higher than that of the first component are respectively melted, a composite polymer stream is discharged from a composite spinneret to perform spinning, and the crimped composite fibers are formed by presenting crimping in a manner that the second component is disposed at the innermost side of crimping between an air drafting unit and a catching belt, and the crimped composite fibers are caught on the catching belt.

9. The method of producing a spunbond nonwoven fabric according to claim 8, wherein The composite polymer stream in which the mass of the first component and the second component is 20:80 to 99:1 is discharged.

10. A method for producing the laminated nonwoven fabric described in claim 5 or 6, comprising: The first component and the second component having a melt viscosity 1.20 times or more higher than that of the first component are respectively melted, a composite polymer stream is discharged from a composite spinneret to perform spinning, and the crimped composite fibers are formed by presenting crimping in a manner that the second component is disposed at the innermost side of crimping between an air drafting unit and a catching belt, and the crimped composite fibers are caught on the catching belt to form a spunbond nonwoven fabric layer; and A step of laminating at least one elastomer layer.

11. The method for manufacturing a layered nonwoven fabric according to claim 10, wherein The elastomer layer is formed by a spunbond method.

12. The method for manufacturing a laminated nonwoven fabric according to claim 10, wherein The elastomer layer is formed by a melt-blowing method.

Images