Spunbonded nonwoven fabric and core-sheath composite fiber

Abstract

To provide a spun-bonded nonwoven fabric which is excellent in softness, skin touch, texture uniformity, strength tolerable for practical use, and productivity. The present invention is a spun-bonded nonwoven fabric formed of core-sheath composite fibers using a polyethylene-based resin as a main component, wherein the spun-bonded nonwoven fabric has fusion portions and non-fusion portions, and the ratio (Ofs / Ofc) of the orientation parameter Ofs of the sheath component of the core-sheath composite fibers of the non-fusion portions to the orientation parameter Ofc of the core component of the core-sheath composite fibers of the non-fusion portions is 0.10 to 0.90.

Description

Technical Field

[0001] This invention relates to polyethylene spunbond nonwoven fabric and core-sheath type composite fiber. Background Technology

[0002] Typically, nonwoven fabrics used in hygiene materials such as diapers and sanitary napkins require a smooth feel, softness, and high productivity. In particular, the top sheet of a diaper is the raw material that comes into direct contact with the skin, making it one of the most demanding applications.

[0003] Thus, as a means to improve skin feel and softness, research has been conducted on using polyethylene with a lower elastic modulus and coefficient of friction than polypropylene. For example, polyethylene spunbond nonwoven fabrics formed from resin compositions obtained by mixing linear low-density polyethylene with different densities have been proposed (see Patent Document 1).

[0004] In addition, a density of 0.930–0.965 g / cm³ was proposed. 3 Furthermore, a polyethylene spunbond nonwoven fabric is formed from polyethylene fibers with an average single fiber diameter of 8.0–16.5 μm and a complex viscosity of less than 90 Pa·sec at a temperature of 230°C and 6.23 rad / s (see Patent Document 2).

[0005] Indeed, these nonwoven fabrics have high softness due to the properties of polyethylene resin.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2008-274445

[0009] Patent Document 2: Japanese Patent Application Publication No. 2019-26954 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, for spunbond nonwoven fabrics formed from polyethylene resin, imparting sufficient strength has always been a major challenge. Even the methods disclosed in Patent Documents 1 and 2 have not been able to achieve strength suitable for practical use.

[0012] Therefore, the object of the present invention is to provide a spunbond nonwoven fabric that is soft, has a good skin feel, a uniform texture, sufficient strength to withstand practical use, and excellent productivity.

[0013] Another objective of the present invention is to provide composite fibers that are soft, have a superior skin feel, and possess excellent spinning stability and thermal bonding properties.

[0014] Methods for solving problems

[0015] The spunbond nonwoven fabric of the present invention is a spunbond nonwoven fabric formed from core-sheath type composite fibers with polyethylene resin as the main component. The aforementioned spunbond nonwoven fabric has a welded portion and a non-welded portion. The ratio of the orientation parameter Ofs of the sheath component of the core-sheath type composite fiber in the aforementioned non-welded portion to the orientation parameter Ofc of the core component of the core-sheath type composite fiber in the aforementioned non-welded portion, Ofs / Ofc, is 0.10 to 0.90.

[0016] According to a preferred embodiment of the spunbond nonwoven fabric of the present invention, the orientation parameter Obs of the sheath component of the core-sheath type composite fiber of the aforementioned welded portion is 1.2 to 3.0, and the orientation parameter Obc of the core component of the core-sheath type composite fiber of the aforementioned welded portion is 2.0 to 10.0.

[0017] According to a preferred embodiment of the spunbond nonwoven fabric of the present invention, the solid density of the aforementioned core-sheath type composite fiber is 0.935 g / cm³. 3 Above 0.970g / cm 3 the following.

[0018] In a preferred embodiment of the spunbond nonwoven fabric according to the present invention, the aforementioned Ofs is 2.0 or more and 8.0 or less.

[0019] According to a preferred embodiment of the spunbond nonwoven fabric of the present invention, the aforementioned spunbond nonwoven fabric has a single melting peak temperature in the range of 100°C to 150°C in differential scanning calorimetry.

[0020] According to a preferred embodiment of the spunbond nonwoven fabric of the present invention, the transverse tensile strength per unit area weight of the aforementioned spunbond nonwoven fabric is 0.20 (N / 25mm) / (g / m²). 2 )above.

[0021] According to a preferred embodiment of the spunbond nonwoven fabric of the present invention, the stress of the aforementioned spunbond nonwoven fabric at 5% elongation in the longitudinal direction per unit area weight is 0.20 (N / 25mm) / (g / m²). 2 )above.

[0022] Furthermore, the core-sheath type composite fiber of the present invention is a core-sheath type composite fiber with polyethylene resin as the main component, and the ratio of the orientation parameter Ofs of the sheath component of the aforementioned core-sheath type composite fiber to the orientation parameter Ofc of the core component of the aforementioned core-sheath type composite fiber, Ofs / Ofc, is 0.1 to 0.9.

[0023] According to a preferred embodiment of the core-sheath composite fiber of the present invention, the aforementioned core-sheath composite fiber has a solid density of 0.935 g / cm³. 3 Above 0.970g / cm3 the following.

[0024] In a preferred embodiment of the core-sheath type composite fiber according to the present invention, the aforementioned Ofs is 2 or more and 8 or less.

[0025] According to a preferred embodiment of the core-sheath type composite fiber of the present invention, the aforementioned core-sheath type composite fiber has a single melting peak temperature in the range of 100°C to 150°C in differential scanning calorimetry.

[0026] The effects of the invention

[0027] According to the present invention, a polyethylene spunbond nonwoven fabric with softness, excellent skin feel, uniform texture, sufficient strength for practical use, and excellent productivity can be obtained. Due to these properties, the spunbond nonwoven fabric of the present invention is particularly suitable for use as a hygiene material.

[0028] Furthermore, according to the present invention, core-sheath type composite fibers with excellent softness, skin feel, and both excellent spinning stability and thermal bonding properties can be obtained. Spunbond nonwoven fabrics made using the core-sheath type composite fibers of the present invention possess the aforementioned excellent properties. Detailed Implementation

[0029] The spunbond nonwoven fabric of the present invention is a spunbond nonwoven fabric formed from core-sheath type composite fibers with polyethylene resin as the main component. The aforementioned spunbond nonwoven fabric has a welded portion and a non-welded portion. The ratio of the orientation parameter Ofs of the sheath component of the core-sheath type composite fiber in the aforementioned non-welded portion to the orientation parameter Ofc of the core component of the core-sheath type composite fiber in the aforementioned non-welded portion, Ofs / Ofc, is 0.10 to 0.90.

[0030] In this way, it is possible to form polyethylene spunbond nonwoven fabrics that are soft, have a good skin feel, uniform texture, sufficient strength for practical use, and excellent productivity.

[0031] Furthermore, the core-sheath type composite fiber of the present invention is a core-sheath type composite fiber with polyethylene resin as the main component, and the ratio of the orientation parameter Ofs of the sheath component of the aforementioned non-fusion-bonded core-sheath type composite fiber to the orientation parameter Ofc of the core component of the aforementioned core-sheath type composite fiber, Ofs / Ofc, is 0.10 to 0.90.

[0032] In this way, core-sheath type composite fibers can be formed that are soft, have excellent skin feel, and possess excellent spinning stability and thermal bonding properties. Spunbond nonwoven fabrics made using the core-sheath type composite fibers of the present invention can form polyethylene spunbond nonwoven fabrics that are soft, have excellent skin feel, uniform texture, sufficient strength for practical use, and excellent productivity.

[0033] The following describes these constituent elements of the present invention in detail, but the present invention is not limited in any way by the scope of the following description, as long as it does not depart from its spirit.

[0034] Polyethylene-based resins

[0035] The core-sheath type composite fiber of the present invention and the core-sheath type composite fiber constituting the spunbond nonwoven fabric of the present invention (hereinafter, they are sometimes referred to together as "core-sheath type composite fiber of the present invention") use polyethylene resin as the main component. By using polyethylene resin as the main component, core-sheath type composite fibers with both excellent spinning stability and thermal bonding properties can be formed. In addition, spunbond nonwoven fabrics with excellent softness and skin feel can be formed.

[0036] Polyethylene-based resins refer to resins that have ethylene units as repeating units, such as homopolymers of ethylene or copolymers of ethylene with various α-olefins. Among these, homopolymers of ethylene are preferred to prevent a decrease in spinning stability and strength.

[0037] When using copolymers of ethylene and various α-olefins, hepten or octene are preferred as copolymer components, considering their excellent spinning stability; octene is more preferred. Furthermore, to prevent a decrease in spinning stability and strength, the copolymerization ratio is preferably 5 mol% or less, more preferably 3 mol% or less, and even more preferably 1 mol% or less.

[0038] Regarding the polyethylene-based resin used in this invention, the proportion of ethylene homopolymer is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. This maintains good spinnability and improves strength.

[0039] Examples of polyethylene resins used in this invention include medium-density polyethylene, high-density polyethylene (hereinafter sometimes simply referred to as HDPE), or linear low-density polyethylene (hereinafter sometimes simply referred to as LLDPE). From the perspective of excellent spinnability, LLDPE is preferred.

[0040] Furthermore, the polyethylene resin used in this invention can be a mixture of two or more types. Alternatively, a resin composition containing other polyolefin resins such as polypropylene, poly-4-methyl-1-pentene, thermoplastic elastomers, low-melting-point polyesters, and low-melting-point polyamides can also be used. In order to fully exhibit the characteristics of polyethylene, the proportion of other thermoplastic resins mixed in is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0041] To improve skin feel and softness, the polyethylene resin used in this invention preferably contains a fatty acid amide compound with 23 to 50 carbon atoms. By preferably having 23 or more carbon atoms, more preferably 30 or more, excessive exposure of the fatty acid amide compound on the fiber surface can be suppressed, resulting in excellent spinning properties and processing stability, and maintaining high productivity. On the other hand, by preferably having 50 or fewer carbon atoms, more preferably 42 or fewer, the fatty acid amide compound can easily move on the fiber surface, imparting smoothness and softness to the spunbond nonwoven fabric.

[0042] Examples of fatty acid amide compounds with 23 to 50 carbon atoms used in this invention include saturated fatty acid monoamide compounds, saturated fatty acid diamide compounds, unsaturated fatty acid monoamide compounds, and unsaturated fatty acid diamide compounds.

[0043] More specifically, examples include tetracosanoamide, hexacosanoamide, octacosanoamide, eicosenoamide, docosapentaenoamide, docosahexaenoamide, ethylene dilaurate, methylene dilaurate, ethylene bis-stearamide, ethylene dihydroxystearamide, ethylene dibenzylhexylamide, hexamethylene distearamide, hexamethylene dibenzylhexylamide, hexamethylene hydroxystearamide, distearate adipamide, distearate sebacic acid amide, ethylene dioleamide, ethylene dierucamide, and hexamethylene dioleamide, etc., and multiple combinations of these can also be used.

[0044] In this invention, considering the ability to impart high slip properties, softness, and excellent spinnability, ethylene bis-stearamide, as a saturated fatty acid diamide compound, is particularly preferred among fatty acid amide compounds.

[0045] In this invention, the amount of the aforementioned fatty acid amide compound added relative to the aforementioned polyethylene resin is preferably 0.01% to 5% by mass. By making the amount of fatty acid amide compound added preferably 0.01% to 5% by mass, more preferably 0.1% to 3% by mass, and even more preferably 0.1% to 1% by mass, it is possible to impart appropriate smoothness and softness while maintaining spinnability.

[0046] The amount added herein refers to the mass fraction of fatty acid amide compounds in all polyethylene resins constituting the spunbond nonwoven fabric of the present invention. For example, when fatty acid amide compounds are added only to the sheath component constituting the core-sheath type composite fiber, the addition ratio relative to the total amount of the core-sheath component is also calculated.

[0047] As a method for determining the amount of fatty acid amide compound added relative to fibers containing polyethylene resin, one example is solvent extraction of the additive from the aforementioned fibers followed by quantitative analysis using liquid chromatography-mass spectrometry (LS / MS). In this case, the extraction solvent is appropriately selected depending on the type of fatty acid amide compound; for example, in the case of ethylene distearate amide, a chloroform-methanol mixture is used.

[0048] Without impairing the effects of the present invention, commonly used antioxidants, weather stabilizers, light stabilizers, heat stabilizers, antistatic agents, charge-carrying agents, antifogging agents, anti-blocking agents, lubricants containing polyethylene wax, crystallizing nucleating agents, pigments, or other polymers may be added to the polyethylene resin used in the present invention as needed.

[0049] The melting point (Tmr) of the polyethylene resin used in this invention is preferably 100°C to 150°C. By preferably setting Tmr to 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher, heat resistance suitable for practical use is easily obtained. Furthermore, by preferably setting Tmr to 150°C or lower, more preferably 140°C or lower, and even more preferably 135°C or lower, the yarn exiting the nozzle is easily cooled, fiber bonding is suppressed, and stable spinning is easily achieved even with fine fiber diameters. Here, melting point (Tmr) refers to the maximum melting peak temperature obtained by measuring the resin using differential scanning calorimetry (DSC).

[0050] The melt flow rate (hereinafter, sometimes simply referred to as MFR) of the polyethylene resin used in this invention is preferably 1 g / 10 min to 300 g / 10 min. By making the MFR of the polyethylene resin preferably 1 g / 10 min or more, more preferably 10 g / 10 min or more, and even more preferably 30 g / 10 min or more, even with fine fiber diameters, stable spinning is possible, resulting in spunbond nonwoven fabrics with excellent skin feel, uniform texture, and sufficient strength to withstand practical use. On the other hand, by making the MFR of the polyethylene resin preferably 300 g / 10 min or less, the reduction in monofilament strength can be suppressed, and problems such as excessive softening during thermal bonding and adhesion to hot rollers can be prevented.

[0051] Regarding the core-sheath type composite fiber of the present invention, the MFR of the polyethylene resin in the core component is preferably 1 g / 10 to 100 g / 10 min. By making the MFR of the polyethylene resin in the core component preferably 1 g / 10 min or more, more preferably 10 g / 10 min or more, and even more preferably 30 g / 10 min or more, it is possible to spin stably even with fine fiber diameters, thereby forming a spunbond nonwoven fabric with excellent skin feel, uniform texture, and sufficient strength to withstand practical use. On the other hand, by making the MFR of the polyethylene resin preferably 100 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 the reduction of the monofilament strength of the core-sheath type composite fiber, thereby forming a spunbond nonwoven fabric with sufficient strength to withstand practical use.

[0052] Regarding the core-sheath type composite fiber of the present invention, the molecular weight ratio (MFR) of the polyethylene resin in the sheath component is preferably 5 g / 10 min to 200 g / 10 min greater than that of the polyethylene resin in the core component. By making the MFR of the polyethylene resin in the sheath component preferably 5 g / 10 min or more, more preferably 10 g / 10 min or more, and even more preferably 20 g / 10 min or more greater than that of the polyethylene resin in the core component, the spinning stress can be concentrated on the core component during spinning, promoting the molecular orientation of the core component and inhibiting the molecular orientation of the sheath component. On the other hand, if the MFR of the polyethylene resin in the sheath component is more than 200 g / 10 min greater than that of the polyethylene resin in the core component, the monofilament strength of the core-sheath type composite fiber will decrease, and it is prone to excessive softening during thermal bonding, causing operational problems such as adhesion to the hot roller, which is not preferred.

[0053] The MFR of polyethylene resins is determined using ASTM D1238 (Method A). According to this standard, regular polyethylene is measured under a load of 2.16 kg and a temperature of 190°C. The polyethylene resins involved in this invention are also measured under the same load and temperature.

[0054] Of course, two or more resins with different MFRs can be blended in any proportion to adjust the MFR of the polyethylene resin used in this invention. In this case, the MFR of the resin blended with the polyethylene resin that is the main component, i.e., the polyethylene resin that accounts for the largest mass fraction in the polyethylene resin, is preferably 10 to 1000 g / 10 min, more preferably 20 to 800 g / 10 min, and even more preferably 30 to 600 g / 10 min. In this way, local viscosity inhomogeneity can be prevented in the blended polyethylene resin, and the single fiber diameter and single fiber fineness can be made uniform, or even fine fibers can be spun stably.

[0055] Furthermore, the polyethylene resin used in this invention preferably does not contain substances that decompose the polyethylene resin and reduce the MFR, such as peroxides, especially dialkyl peroxides and other free radical agents. This prevents localized viscosity inconsistencies caused by uneven decomposition and gelation, enabling uniform fiber fineness and stable spinning even for fine fibers. Additionally, it prevents the spinning properties from deteriorating due to bubbles generated by decomposition gases.

[0056] The polyethylene resin used in this invention preferably has a solid density of 0.935 g / cm³. 3 ~0.970g / cm 3 The preferred solid density of the polyethylene resin is 0.935 g / cm³. 3 The above, and more preferably, is 0.940 g / cm³ 3 The above, and more preferably, is 0.945 g / cm³. 3 The above measures prevent excessive softening during heat bonding, which could lead to problems such as adhesion to the hot roller. Furthermore, the preferred solid density of the polyethylene resin is 0.970 g / cm³. 3 The following, or more preferably, is 0.965 g / cm³. 3 The following, and more preferably, is 0.96 g / cm³. 3 The following can improve spinning properties, enabling stable spinning even with fine fibers.

[0057] [Core-Sheath Composite Fiber]

[0058] The core-sheath type composite fiber in this invention also includes island-type composite fibers. In the case of island-type composite fibers, when measuring and interpreting the characteristic values ​​of the polyethylene resin of the core component or sheath component of the composite fiber, the term "sheath component" is replaced with "sea component" and the term "core component" is replaced with "island component," and the measurement is performed accordingly.

[0059] Regarding the core-sheath type composite fiber of the present invention, the mass ratio of the sheath component is preferably 20% to 80% by mass. By making the mass ratio of the sheath component preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, the sheath components are firmly fused together during thermal bonding, thereby forming a spunbond nonwoven fabric with sufficient strength to withstand practical use. On the other hand, by making the mass ratio of the sheath component preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less, the proportion of highly oriented core component can be increased, thereby improving the monofilament strength of the core-sheath type composite fiber and forming a spunbond nonwoven fabric with sufficient strength to withstand practical use.

[0060] For the core-sheath type composite fiber of the present invention and the core-sheath type composite fiber of the non-fusion portion of the spunbond nonwoven fabric of the present invention, the ratio of the orientation parameter Ofs of the sheath component to the orientation parameter Ofc of the core component, Ofs / Ofc, is 0.10 to 0.90.

[0061] Here, the orientation parameter of the core-sheath composite fiber in this invention refers to the following index (without units): the larger the value, the more the molecular chains of the polyethylene resin constituting the core-sheath composite fiber are oriented in a specific direction; the smaller the value, the more randomly the molecular chains are oriented. It should be noted that when the orientation is completely random, the orientation parameter becomes 1.2.

[0062] By setting the Ofs / Ofc ratio to 0.10 or higher, preferably 0.15 or higher, and more preferably 0.20 or higher, it is possible to prevent excessive concentration of tensile stress in the inner fiber layer where the core component exists during spinning, thus preventing a decrease in spinning stability. On the other hand, by setting the Ofs / Ofc ratio to 0.90 or lower, preferably 0.70 or lower, and more preferably 0.50 or lower, it is possible to soften only the fiber surface layer during thermal bonding. In this way, the molecular orientation of the inner fiber layer can be retained, while the fibers are firmly thermally bonded to each other. Moreover, as for the spunbond nonwoven fabric of the present invention, it is possible to form a polyethylene spunbond nonwoven fabric with softness, excellent skin feel, uniform texture, sufficient strength to withstand actual use, and excellent productivity.

[0063] The orientation parameters Ofs of the sheath component and Ofc of the core component of the core-sheath composite fiber in this invention were determined using the following method.

[0064] (1) The core-sheath type composite fiber or spunbond nonwoven fabric sample was embedded in bisphenol epoxy resin.

[0065] (2) After the resin has cured, sections are cut using a slicer. The section thickness is set to 2 μm. At this time, the section is cut at an angle from the fiber axis so that the cut surface is elliptical. Then, the section where the thickness of the minor axis of the ellipse shows a constant thickness is selected for measurement. It should be noted that by keeping the cutting angle within 4°, the section can be considered parallel to the fiber axis within a film thickness of 2 μm.

[0066] When the sample is spunbond nonwoven fabric,

[0067] (2) After the resin has cured, slices are cut using a slicing machine with the cut surface near the center of the non-welded portion of the spunbond nonwoven fabric (at a distance approximately equidistant from the surrounding welded portions). The slice thickness is set to 2 μm. The following measurements are performed on the portion of the composite fiber that is a non-welded portion and where the cut angle is within 4° of the fiber axis.

[0068] (3) From the surface of the core-sheath type composite fiber slice to the center, polarized light parallel to the fiber axis is incident and Raman spectroscopy is measured.

[0069] (4) Calculate the position of the core component and the sheath component at 1130 cm. -1 Nearby and 1060cm -1 Nearby Raman band intensity I 1130 and I 1060 The orientation parameter is calculated based on its intensity ratio using the following formula (d). When the core component is divided into multiple independent regions, the orientation parameter is measured in all regions, and the highest value is used.

[0070] Orientation parameter = I 1130 / I 1060 ···(d).

[0071] (5) Change the position along the axial direction of the core-sheath type composite fiber and perform the same measurement at 3 locations. Calculate the average value of the orientation parameters and round the second decimal place.

[0072] When the sample is spunbond nonwoven fabric,

[0073] (5) For different non-fusion joints of spunbond nonwoven fabric, the same measurement was performed at 3 locations, the average value of the orientation parameters was calculated, and the second decimal place was rounded up.

[0074] Regarding the core-sheath type composite fiber of the present invention and the core-sheath type composite fiber of the non-fusion portion of the spunbond nonwoven fabric of the present invention, the orientation parameter Ofs of the sheath component is preferably 2 to 8. By making Ofs preferably 2.0 or more, more preferably 2.5 or more, and even more preferably 3.0 or more, it is possible to prevent the fiber surface from softening excessively during heat bonding, thus avoiding operational problems such as adhesion to the hot roller. On the other hand, by making Ofs preferably 8.0 or less, more preferably 7.0 or less, and even more preferably 6.0 or less, the fiber surface is easily softened during heat bonding, enabling the fibers to be firmly heat-bonded to each other, thereby forming a spunbond nonwoven fabric with strength that can withstand actual use.

[0075] Ofs can be controlled by the aforementioned MFR of polyethylene resin, melting point, additives, mass ratio of sheath components in composite fibers, and / or spinning temperature and spinning speed as described later.

[0076] Regarding the core-sheath type composite fiber of the present invention and the core-sheath type composite fiber of the non-fusion portion of the spunbond nonwoven fabric of the present invention, the orientation parameter Ofc of the core component is preferably 6 to 18. By making Ofc preferably 6.0 or more, more preferably 7.0 or more, and even more preferably 8.0 or more, the strength of the inner layer of the fiber can be improved, and a spunbond nonwoven fabric with strength that can withstand actual use can be formed after thermal bonding. In addition, it is possible to prevent the fiber surface from softening excessively during thermal bonding, thus preventing problems such as adhesion to the hot roller. On the other hand, by making Ofc preferably 18.0 or less, more preferably 16.0 or less, and even more preferably 14.0 or less, the excessive concentration of tensile stress in the inner layer of the fiber during spinning can be suppressed, thereby improving spinning stability.

[0077] Ofc can be controlled by the aforementioned MFR of polyethylene resin, melting point, additives, mass ratio of core components of composite fibers, and / or spinning temperature and spinning speed as described later.

[0078] For the core-sheath type composite fiber of the present invention and the core-sheath type composite fiber of the non-fusion portion of the spunbond nonwoven fabric of the present invention, the softening temperature Tss (°C) of the surface layer and the softening temperature Tsc (°C) of the inner layer preferably satisfy the following formula (a).

[0079] (Tss+5)≤Tsc≤(Tss+30)···(a).

[0080] By setting Tsc (°C) preferably to (Tss+5)°C or higher, more preferably to (Tss+7)°C or higher, and even more preferably to (Tss+10)°C or higher, only the components forming the fiber surface layer can be softened during thermal bonding. Furthermore, this method allows for the retention of molecular orientation in the inner fiber layers while ensuring strong thermal bonding between the fibers, thus enabling the formation of a spunbond nonwoven fabric with strength sufficient for practical use. On the other hand, by setting Tsc (°C) preferably to (Tss+30)°C or lower, more preferably to (Tss+25)°C or lower, and even more preferably to (Tss+20)°C or lower, excessive softening of the fiber surface layer during thermal bonding can be prevented, thus avoiding operational problems such as adhesion to the hot roller.

[0081] Tss (°C) and Tsc (°C) were calculated using nanoscale thermomechanical analysis (nano-TMA) through the following steps. This nano-TMA method enables thermal analysis in the submicron region and utilizes a device with a temperature sensor equipped with a heater mounted on the probe (cantilever) of an atomic force microscope (AFM).

[0082] In the spunbond nonwoven fabric of the present invention, the Tss (°C) and Tsc (°C) of the aforementioned non-fusion-bonded portion are measured and calculated by collecting 20 core-sheath type composite fibers from the non-fusion-bonded portion of the spunbond nonwoven fabric according to the following steps.

[0083] (1) Fix the core-sheath type composite fiber to the sample stage, and fix the AFM probe with a temperature sensor equipped with a heater near the center of the fiber diameter direction.

[0084] (2) The probe is heated from 25°C to 150°C at a heating rate of 10°C / second, and the change in probe height (au) is measured.

[0085] (3) Determine the temperature (softening temperature (°C)) of the probe penetrating the sample based on the change in probe height, and set them as Ts1, Ts2, Ts3, etc. according to the order of observation starting from the low temperature.

[0086] (4) Perform the same measurement on 20 fibers. Round the average value of Ts1 to the second decimal place as Tss (°C). Also, round the average value of Ts2 to the second decimal place as Tsc (°C). It should be noted that, depending on the contact position of the AFM probe, Ts2 may not be observed in some core-sheath composite fibers. In this case, only the observed Ts2 is averaged to determine the softening temperature of the inner layer, Tsc (°C).

[0087] Tss and Tsc can be controlled by the aforementioned MFR of polyethylene resin, melting point, additives, mass ratio of sheath components constituting core-sheath type composite fibers, and / or spinning temperature and spinning speed as described later.

[0088] The core-sheath composite fiber of the present invention and the spunbond nonwoven fabric of the present invention preferably have a single melting peak temperature Tm in differential scanning calorimetry (DSC). It should be noted that in the present invention, "the core-sheath composite fiber has a single melting peak temperature Tm in differential scanning calorimetry" and "the spunbond nonwoven fabric has a single melting peak temperature Tm in differential scanning calorimetry" means that the melting endothermic peak described in (3) of the following measurement method is actually only observed as one peak. In this way, when the core-sheath composite fiber of the present invention is used as, for example, the fiber constituting the spunbond nonwoven fabric, the spunbond nonwoven fabric of the present invention does not have operational problems such as low melting point components melting and adhering to the hot roller during thermal bonding, and the fibers can be firmly thermally bonded to each other at a sufficient temperature, thus easily obtaining a spunbond nonwoven fabric with strength that can withstand actual use.

[0089] The melting peak temperature Tm of core-sheath composite fibers or spunbond nonwoven fabrics obtained by differential scanning calorimetry (DSC) is calculated using the following steps.

[0090] (1) Take a sample of 0.5 to 5 mg of core-sheath type composite fiber or spunbond nonwoven fiber sheet.

[0091] (2) Using differential scanning calorimetry (DSC), the temperature was increased from room temperature to 200℃ at a rate of 20℃ / min to obtain the DSC curve.

[0092] (3) Read the peak temperature of the melting endothermic peak from the DSC curve and take it as the melting peak temperature Tm (°C).

[0093] It should be noted that when the core-sheath type composite fiber of the present invention is used as the fiber constituting the spunbond nonwoven fabric of the present invention, it can be considered that the Tm of the core-sheath type composite fiber and the Tm of the spunbond nonwoven fabric show the same value.

[0094] Furthermore, the core-sheath type composite fiber of the present invention and the spunbond nonwoven fabric of the present invention preferably satisfy the following formulas (b) and (c).

[0095] 100≤Tm≤150···(b)

[0096] (Tm-40)≤Tss≤(Tm-10)···(c)

[0097] In this way, core-sheath type composite fibers and spunbond nonwovens with heat resistance and strength that can withstand practical use, as well as excellent spinning stability and operational stability, can be obtained.

[0098] First, regarding formula (b), the melting peak temperature Tm (°C) of the core-sheath type composite fiber based on differential scanning calorimetry (DSC) is preferably 100°C or higher and 150°C or lower. By preferably setting the melting peak temperature Tm (°C) to 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher, heat resistance suitable for practical use can be imparted. In addition, by preferably setting the melting peak temperature Tm (°C) to 150°C or lower, more preferably 140°C or lower, and even more preferably 135°C or lower, the yarn discharged from the nozzle is easily cooled, fiber bonding is suppressed, and stable spinning is easily achieved even with fine fiber diameters.

[0099] Next, regarding formula (c), the softening temperature Tss (°C) of the surface layer of the aforementioned core-sheath type composite fiber is preferably (Tm-40)°C or higher and (Tm-10)°C or lower. By making the aforementioned softening temperature Tss (°C) of the surface layer preferably (Tm-40)°C or higher, more preferably (Tm-35)°C or higher, and even more preferably (Tm-30)°C or higher, it is possible to prevent the fiber surface layer from becoming excessively softened during thermal bonding, thus avoiding operational problems such as adhesion to the hot roller. On the other hand, by making Tss (°C) preferably (Tm-10)°C or lower, more preferably (Tm-15)°C or lower, and even more preferably (Tm-20)°C or lower, it is possible to firmly thermally bond the fibers together during thermal bonding, thereby forming a spunbond nonwoven fabric with strength that can withstand actual use.

[0100] Furthermore, for the core-sheath type composite fiber of the present invention, since the core-sheath type composite fiber melts after softening, the softening temperature Tsc (°C) of the inner layer is lower than the melting peak temperature Tm (°C) based on differential scanning calorimetry (DSC). Moreover, the softening temperature Tsc (°C) of the inner layer of the aforementioned core-sheath type composite fiber is preferably (Tm-20)°C or higher and (Tm-1)°C or lower. By preferably setting the softening temperature Tsc (°C) of the inner layer to (Tm-20)°C or higher, more preferably (Tm-15)°C or higher, and even more preferably (Tm-10)°C or higher, the strength of the inner layer of the fiber can be improved, and a spunbond nonwoven fabric with strength that can withstand practical use can be formed after thermal bonding. On the other hand, by preferably setting Tsc (°C) to (Tm-1)°C or lower, more preferably (Tm-3)°C or lower, and even more preferably (Tm-5)°C or lower, the fibers can be firmly thermally bonded to each other during thermal bonding, and a spunbond nonwoven fabric with strength that can withstand practical use can be formed.

[0101] As the composite form of the core-sheath type composite fiber in this invention, for example, concentric core-sheath type, eccentric core-sheath type, and island type composite forms can be used. Among these, considering the excellent spinning properties and the ability to uniformly bond the fibers together through thermal bonding, a core-sheath type composite form is preferred, and a concentric core-sheath type composite form is even more preferred.

[0102] As for the cross-sectional shape of the core-sheath type composite fiber in this invention, circular cross-sections, flat cross-sections, and irregular cross-sections such as Y-shaped and C-shaped cross-sections can be used. Among these, a circular cross-section is preferred from the perspective of avoiding the bending difficulties of structures such as flat cross-sections and irregular cross-sections, and being able to form a spunbond nonwoven fabric that utilizes the softness of polyethylene resin. In addition, a hollow cross-section can also be used as the cross-sectional shape, but a solid cross-section is preferred from the perspective of excellent spinning properties and stable spinning even for fine fiber diameters.

[0103] The average single fiber fineness of the core-sheath type composite fiber in this invention is preferably 0.5 dtex to 3.0 dtex. By making the average single fiber fineness preferably 0.5 dtex or more, more preferably 0.6 dtex or more, and even more preferably 0.7 dtex or more, it is possible to prevent the reduction of spinnability and form a spunbond nonwoven fabric with excellent production stability. On the other hand, by making the average single fiber fineness preferably 3.0 dtex or less, more preferably 2.4 dtex or less, and even more preferably 2.0 dtex or less, it is possible to form a spunbond nonwoven fabric with excellent skin feel, uniform texture, and sufficient strength to withstand actual use.

[0104] The average single fiber fineness can be controlled by spinning temperature, single-hole discharge rate, spinning speed, etc., as described later.

[0105] The average single fiber diameter of the core-sheath type composite fiber in this invention is preferably 8 to 20 μm. By making the average single fiber diameter preferably 8 μm or more, more preferably 9 μm or more, and even more preferably 10 μm or more, it is possible to prevent a decrease in spinnability and form a spunbond nonwoven fabric with excellent production stability. On the other hand, by making the average single fiber diameter preferably 20 μm or less, more preferably 18 μm or less, and even more preferably 16 μm or less, it is possible to form a spunbond nonwoven fabric with excellent skin feel, uniform texture, and sufficient strength to withstand actual use.

[0106] It should be noted that, in this invention, the average single fiber diameter (μm) of the aforementioned core-sheath type composite fiber is a value calculated through the following steps.

[0107] (1) For core-sheath composite fibers, surface photographs were taken at 500 to 2000x magnification using a microscope or scanning electron microscope, and the width (diameter) of a total of 100 different core-sheath composite fibers was measured. In the case of irregular cross-section of core-sheath composite fibers, the cross-sectional area was measured, and the diameter of a perfect circle with the same cross-sectional area was determined.

[0108] (2) The average of the 100 measured diameter values ​​is rounded to the second decimal place to obtain the average single fiber diameter (μm).

[0109] In addition, in this invention, the average single fiber diameter (μm) of the core-sheath type composite fiber constituting the aforementioned spunbond nonwoven fabric is a value calculated by the following steps.

[0110] (1) Ten small samples (100×100mm) were randomly collected from the spunbond nonwoven fabric.

[0111] (2) Take surface photographs at 500–2000x magnification using a microscope or scanning electron microscope, and measure the width (diameter) of 10 core-sheath composite fibers from each sample, for a total of 100 fibers in the non-fusion section. If the cross-section of the core-sheath composite fiber is irregular, measure the cross-sectional area and determine the diameter of a circle with the same cross-sectional area.

[0112] (3) The average of the 100 measured diameter values ​​is rounded to the second decimal place to obtain the average single fiber diameter (μm).

[0113] The average single fiber diameter can be controlled by spinning temperature, single-hole discharge rate, spinning speed, etc., as described later.

[0114] The core-sheath type composite fiber in this invention preferably has a solid density of 0.935 g / cm³. 3 ~0.970g / cm 3 The preferred solid density of the polyethylene resin is 0.935 g / cm³. 3 The above, and more preferably, is 0.940 g / cm³ 3 The above, and more preferably, is 0.945 g / cm³. 3 The above measures prevent excessive softening during heat bonding, which could lead to problems such as adhesion to the hot roller. Furthermore, the preferred solid density of the polyethylene resin is 0.970 g / cm³. 3 The following, or more preferably, is 0.965 g / cm³. 3 The following, and more preferably, is 0.960 g / cm³. 3 The following can improve spinning properties, enabling stable spinning even with fine fibers.

[0115] It should be noted that, in this invention, the solid density (g / cm³) of the aforementioned composite fiber... 3 The value is calculated using the following steps.

[0116] (1) The test piece of composite fiber was immersed in ethanol for cleaning and then dried in the atmosphere.

[0117] (2) For the test pieces of composite fibers, the density was determined by using a water-ethanol mixture system and the flotation method.

[0118] (3) Perform the same measurement 5 times using different test pieces, and record the density values ​​(g / cm³) obtained. 3 The average value is calculated, and the fourth decimal place is rounded off to obtain the solid density (g / cm³) of the composite fiber. 3 ).

[0119] In addition, the solid density (g / cm³) of the composite fibers constituting the aforementioned spunbond nonwoven fabric 3The value is calculated using the following steps.

[0120] (1) Five small pieces were randomly collected from spunbond nonwoven fabric.

[0121] (2) The small pieces are soaked in ethanol for cleaning and then dried in the atmosphere.

[0122] (3) For small pieces of spunbond nonwoven fabric, the density is determined by using a water-ethanol mixture system and the flotation method.

[0123] (4) Perform the same measurement on 5 small pieces, and record the density values ​​(g / cm³). 3 The average value is calculated, and the fourth decimal place is rounded off to obtain the solid density (g / cm³) of the composite fiber. 3 ).

[0124] [Spunbond Nonwoven Fabric]

[0125] The spunbond nonwoven fabric of the present invention is formed from core-sheath type composite fibers with polyethylene resin as the main component.

[0126] The spunbond nonwoven fabric of the present invention has welded portions and non-welded portions. By shaping it in this way, a spunbond nonwoven fabric that retains the softness and skin-touch feel derived from polyethylene resin and has sufficient strength to withstand practical use can be formed. The welded portions refer to the areas where the core-sheath composite fibers are fused together, while the non-welded portions refer to the areas where the core-sheath composite fibers are not fused together and maintain their cross-sectional shape.

[0127] Regarding the spunbond nonwoven fabric of the present invention, in the core-sheath type composite fiber of the aforementioned welded portion, the orientation parameter Obs of the sheath component is preferably 1.2 to 3.0. When Obs is preferably 1.2, the molecular chains are in a state of completely random orientation and will not be smaller than that value. On the other hand, by making the orientation parameter Obs of the sheath component preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less, the sheath components forming the fiber surface layer are firmly thermally bonded to each other, and a spunbond nonwoven fabric with strength that can withstand actual use can be formed.

[0128] The orientation parameter Obs of the sheath component in the core-sheath type composite fiber of the welded part can be controlled by appropriately adjusting the orientation parameter Ofs of the sheath component of the aforementioned core-sheath type composite fiber, and / or the thermal bonding conditions (temperature, line pressure, etc.) described later.

[0129] Regarding the spunbond nonwoven fabric of the present invention, in the core-sheath type composite fiber of the aforementioned welded portion, the orientation parameter Obc of the core component is preferably 2 to 10. By preferably having Obc of 2.0 or more, more preferably 2.5 or more, and even more preferably 3.0 or more, the strength of the core component can be improved, resulting in a spunbond nonwoven fabric with strength that can withstand actual use. In addition, it is possible to prevent excessive softening of the fiber surface during thermal bonding, thus avoiding operational problems such as adhesion to the hot roller. On the other hand, by preferably having Obc of 10.0 or less, more preferably 9.0 or less, and even more preferably 8.0 or less, excessive tensile stress concentration in the core component during spinning can be suppressed, thereby improving spinning stability.

[0130] The orientation parameter Obc of the core component in the core-sheath type composite fiber of the welded part can be controlled by appropriately adjusting the orientation parameter Ofc of the core component of the aforementioned core-sheath type composite fiber, and / or the thermal bonding conditions (temperature, line pressure, etc.) described later.

[0131] Obs and Obc are determined through the following steps.

[0132] (1) The spunbond nonwoven fabric sample was embedded in bisphenol epoxy resin.

[0133] (2) After the resin has cured, slices are cut using a slicing machine with the area near the center of the welded portion of the spunbond nonwoven fabric as the cutting surface. The slice thickness is set to 2 μm. The following measurements are performed on a section with a cutting angle within 4° of the fiber axis. It should be noted that when it is difficult to determine the direction of the fiber axis, the polarization orientation is rotated by 15 degrees at the same point each time, and polarized Raman spectra are obtained in each orientation. The orientation with the largest orientation parameter is taken as the fiber axis.

[0134] (3) At the center of the core-sheath type composite fiber slice at the welded part, polarized light parallel to the fiber axis is incident to perform Raman spectroscopy line measurement.

[0135] (4) Calculate the 1130cm position of the sheath component and core component of the core-sheath composite fiber at the welded section. -1 Nearby and 1060cm -1 Nearby Raman band intensity I 1130 and I 1060 The orientation parameter is calculated based on its intensity ratio using the following formula (d). When the core component is divided into multiple independent regions, the orientation parameter is measured in all regions, and the highest value is used.

[0136] Orientation parameter = I 1130 / I 1060 ···(d).

[0137] (5) For different welded parts of spunbond nonwoven fabric, the same measurement was performed at 3 locations, the average value of the orientation parameters was calculated, and the second decimal place was rounded up.

[0138] Regarding the spunbond nonwoven fabric of the present invention, the surface roughness (SMD) of at least one side based on the KES method is preferably 1.0 to 3.0 μm. By making the surface roughness (SMD) based on the KES method preferably 1.0 μm or more, more preferably 1.3 μm or more, and even more preferably 1.6 μm or more, it is possible to prevent the spunbond nonwoven fabric from becoming excessively dense, which would result in a poor hand feel or impaired softness. On the other hand, by making the surface roughness (SMD) based on the KES method preferably 3.0 μm or less, more preferably 2.8 μm or less, and even more preferably 2.5 μm or less, it is possible to form a spunbond nonwoven fabric with a smooth surface, low roughness, and excellent skin feel.

[0139] Surface roughness (SMD) based on the KES method can be controlled by appropriately adjusting the average single fiber diameter of the aforementioned core-sheath type composite fiber, the texture of the spunbonded nonwoven fabric, and / or the thermal bonding conditions described later (shape of the bonded part, compression ratio, temperature, and linear pressure, etc.).

[0140] It should be noted that, in this invention, the surface roughness (SMD) based on the KES method is measured as follows.

[0141] (1) Three test pieces with a width of 200mm×200mm were collected from the spunbond nonwoven fabric at equal intervals along the width direction of the spunbond nonwoven fabric.

[0142] (2) Place the test piece on the test stage.

[0143] (3) Using a surface roughness measuring contact head with a 10gf load applied (raw material: A piano wire (contact length: 5mm) was used to scan the surface of the test piece to measure the average deviation of the surface's unevenness.

[0144] (4) The above measurements were performed on the longitudinal (long side direction of the nonwoven fabric) and transverse (width direction of the nonwoven fabric) of all test pieces. The average deviation of these 6 points was averaged and the second decimal place was rounded off to obtain the surface roughness SMD (μm).

[0145] The friction coefficient MIU of the spunbond nonwoven fabric of the present invention, based on the KES method, is preferably 0.01 to 0.30. By making the friction coefficient MIU preferably 0.30 or less, more preferably 0.20 or less, and even more preferably 0.15 or less, the slipperiness of the nonwoven fabric surface can be improved, resulting in a spunbond nonwoven fabric with excellent skin feel. On the other hand, by making the friction coefficient MIU preferably 0.01 or more, more preferably 0.03 or more, and even more preferably 0.05 or more, it is possible to prevent the yarns from slipping against each other and the texture uniformity from deteriorating when the warp-spun yarns are captured to the capture conveyor.

[0146] The friction coefficient MIU based on the KES method can be controlled by appropriately adjusting the additives in the aforementioned polyethylene resin, the average single fiber diameter of the core-sheath composite fiber, the texture of the spunbond nonwoven fabric, and / or the thermal bonding conditions described later (shape of the bonded part, compression ratio, temperature, and linear pressure, etc.).

[0147] It should be noted that in this invention, the friction coefficient MIU based on the KES method is determined as follows.

[0148] (1) Three test pieces with a width of 200mm×200mm were collected from the spunbond nonwoven fabric at equal intervals along the width direction of the spunbond nonwoven fabric.

[0149] (2) Place the test piece on the test stage.

[0150] (3) Using a contact friction head with an applied load of 50gf (raw material: Piano wire (20 strands side by side), contact area: 1cm² 2 The surface of the test piece was scanned to determine the coefficient of friction.

[0151] (4) The above measurements were performed on the longitudinal (long side of the nonwoven fabric) and transverse (width of the nonwoven fabric) directions of all test pieces. The average deviation of these 6 points was averaged and the fourth decimal place was rounded off to obtain the friction coefficient MIU.

[0152] The MFR of the spunbond nonwoven fabric of the present invention is preferably 1 g / 10 min to 300 g / 10 min. By making the MFR of the spunbond nonwoven fabric preferably 1 g / 10 min or more, more preferably 10 g / 10 min or more, and even more preferably 30 g / 10 min or more, it is possible to spin stably even with fine fiber diameters, thereby forming a spunbond nonwoven fabric with excellent skin feel, uniform texture, and sufficient strength to withstand actual use. On the other hand, by making the MFR of the polyethylene resin preferably 300 g / 10 min or less, it is possible to suppress the reduction of strength and prevent problems such as excessive softening during heat bonding that could cause adhesion to the hot rollers.

[0153] The MFR of the spunbond nonwoven fabric involved in this invention is measured using the value obtained by ASTM D1238 (Method A). According to this standard, the MFR of polyethylene is measured under a load of 2.16 kg and a temperature of 190 °C.

[0154] The preferred unit area weight of the spunbond nonwoven fabric of the present invention is 10 g / m². 2 ~100g / m 2 The optimal weight per unit area is 10 g / m². 2 The above, and more preferably, is 13g / m 2 The above, and more preferably, is 15g / m 2 The above methods enable the formation of spunbond nonwoven fabrics with sufficient strength for practical use. Furthermore, by preferably setting the weight per unit area to 100 g / m²... 2 The following, or more preferably, is 50g / m 2 The following, and more preferably, is 30g / m 2 The following describes how to form a spunbond nonwoven fabric with softness suitable for use as a sanitary material.

[0155] It should be noted that, in this invention, the unit area weight of the spunbond nonwoven fabric is the value measured in accordance with "6.2 Mass per unit area" of JIS L1913:2010 "General Nonwoven Fabrics Test Methods" and through the following steps.

[0156] (1) Collect 3 test pieces of 20cm×25cm for every 1m wide sample.

[0157] (2) Weigh each of them under standard conditions (g).

[0158] (3) per 1m 2 mass (g / m 2 ) represents its average value.

[0159] The thickness of the spunbond nonwoven fabric of the present invention is preferably 0.05 mm to 1.5 mm. By making the thickness preferably 0.05 to 1.5 mm, more preferably 0.08 to 1.0 mm, and even more preferably 0.10 to 0.8 mm, a spunbond nonwoven fabric with softness and moderate cushioning properties can be formed, which is suitable for use as a sanitary material and is particularly suitable for use in diapers.

[0160] It should be noted that in this invention, the thickness (mm) of the spunbond nonwoven fabric is measured in accordance with "5.1" of JIS L1906:2000 "General long fiber nonwoven fabric test method" and through the following steps.

[0161] (1) Using a pressure head with a diameter of 10 mm, with a load of 10 kPa, the thickness of 10 points in 1 m is measured at equal intervals of 0.01 mm along the width direction of the nonwoven fabric.

[0162] (2) Round the third decimal place of the average of the above 10 points.

[0163] Furthermore, the apparent density of the spunbond nonwoven fabric of the present invention is preferably 0.05 g / cm³. 3 ~0.30g / cm 3 The apparent density is preferably 0.30 g / cm³. 3 The following, or more preferably, is 0.25 g / cm³. 3 The following, and more preferably, is 0.20 g / cm³. 3 The following measures prevent the fibers from tightly packing together and compromising the softness of the spunbond nonwoven fabric. On the other hand, by setting the apparent density to preferably 0.05 g / cm³... 3 The above, and more preferably, is 0.08 g / cm³. 3 The above, and more preferably, is 0.10 g / cm³. 3 The above methods can suppress fuzzing and interlayer delamination, resulting in spunbond nonwoven fabrics with sufficient strength and operability for practical use.

[0164] Apparent density can be controlled by appropriately adjusting the average single fiber diameter of the core-sheath type composite fiber and / or the conditions of thermal bonding described later (shape of the bonded part, compression ratio, temperature, and linear pressure, etc.).

[0165] It should be noted that in this invention, apparent density (g / cm³) is... 3 The value is calculated based on the unit area weight and thickness before rounding, using the following formula, and rounded to the third decimal place.

[0166] Apparent density (g / cm³) 3 = [weight per unit area (g / m²)] 2 )] / [thickness (mm)]×10 -3 …(Mode).

[0167] The stiffness of the spunbond nonwoven fabric of the present invention is preferably 60 mm or less. By making the stiffness preferably 60 mm or less, more preferably 50 mm or less, and even more preferably 40 mm or less, a spunbond nonwoven fabric for use as a hygiene material can be obtained, which has excellent softness and is particularly suitable for use in diapers. In addition, if the stiffness is too low, the workability is poor, so the stiffness is preferably 10 mm or more.

[0168] Stiffness can be controlled by appropriately adjusting the MFR of the aforementioned polyethylene resin, additives, average single fiber diameter of the core-sheath composite fiber, unit area weight of the spunbond nonwoven fabric, the ratio of the orientation parameter Ofs of the sheath component of the core-sheath composite fiber in the non-fusion section to the orientation parameter Ofc of the core component of the core-sheath composite fiber in the non-fusion section (Os / Oc), and / or the thermal bonding conditions described later (shape of the bonded part, compression ratio, temperature, and linear pressure, etc.).

[0169] The transverse tensile strength per unit area weight of the spunbond nonwoven fabric of the present invention is preferably 0.20 (N / 25mm) / (g / m²). 2 More preferably, it is 0.20 (N / 25mm) / (g / m³). 2 )~2.00(N / 25mm) / (g / m 2 The optimal tensile strength per unit area weight is 0.20 (N / 25mm) / (g / m²). 2 ) or more, preferably 0.25 (N / 25mm) / (g / m 2 ) or higher, and more preferably 0.30 (N / 25mm) / (g / m 2 This allows for the formation of spunbond nonwoven fabrics with strength sufficient for practical use. Furthermore, the transverse tensile strength per unit area weight is preferably 2.00 (N / 25mm) / (g / m²). 2 The following measures can prevent a decrease in the softness or damage to the hand feel of spunbond nonwoven fabric. It should be noted that the tensile strength of spunbond nonwoven fabric has both longitudinal and transverse properties. Generally, the transverse tensile strength is less than the longitudinal tensile strength. Therefore, the transverse tensile strength per unit area weight should be maintained at 0.2–2.00 (N / 25mm) / (g / m²). 2 This allows for the formation of spunbond nonwoven fabrics that also possess strength suitable for practical use in the longitudinal direction.

[0170] The transverse tensile strength per unit area weight can be controlled by appropriately adjusting the aforementioned MFR of the polyethylene resin, additives, average single fiber diameter of the core-sheath composite fiber, the ratio of the orientation parameter Ofs of the sheath component of the non-fusion-bonded core-sheath composite fiber to the orientation parameter Ofc of the core component of the non-fusion-bonded core-sheath composite fiber (Os / Oc), and / or the spinning speed described later, the thermal bonding conditions (shape of the bonded part, compression ratio, temperature, and linear pressure, etc.).

[0171] It should be noted that, in this invention, the transverse tensile strength per unit area weight of the spunbond nonwoven fabric is measured according to JIS L1913:2010 "General Nonwoven Fabrics Test Methods" "6.3 Tensile Strength and Elongation (ISO Method)" through the following steps.

[0172] (1) Take three test pieces of 25 mm × 200 mm per 1 m width of the non-woven fabric in such a way that the long single side (in Japanese: 長片側) becomes the lateral direction (width direction of the non-woven fabric) of the non-woven fabric.

[0173] (2) Set the test pieces on a tensile testing machine at a clamping interval of 100 mm.

[0174] (3) Conduct a tensile test at a tensile speed of 100 mm / minute and measure the maximum strength.

[0175] (4) Calculate the average value of the maximum strength measured in each test piece, calculate the tensile strength per unit area weight based on the following formula, and round off the third decimal place.

[0176] Tensile strength in the lateral direction per unit area weight ((N / 25 mm) / (g / m 2 )) = [Average value of maximum strength (N / 25 mm)] / Unit area weight (g / m 2 ) … (Formula).

[0177] The stress at 5% elongation in the longitudinal direction of the spunbond non-woven fabric of the present invention is preferably 0.20 (N / 25 mm) / (g / m 2 ) or more, more preferably 0.20 (N / 25 mm) / (g / m 2 ) to 2.00 (N / 25 mm) / (g / m 2 ). By making the stress at 5% elongation in the longitudinal direction per unit area weight preferably 0.2 (N / 25 mm) / (g / m 2 ) or more, more preferably 0.25 (N / 25 mm) / (g / m 2 ) or more, and further preferably 0.30 (N / 25 mm) / (g / m 2 ) or more, it is possible to suppress elongation caused by the tension during the production of the spunbond non-woven fabric and during processing for use as a sanitary material, and it is possible to stably produce at a high yield rate. In addition, by making the stress at 5% elongation in the longitudinal direction per unit area weight preferably 2.00 (N / 25 mm) / (g / m 2 ) or less, it is possible to prevent the softness of the spunbond non-woven fabric from decreasing or the hand feeling from being damaged.

[0178] The stress at 5% longitudinal elongation per unit area weight can be controlled by appropriately adjusting the aforementioned MFR of the polyethylene resin, additives, average single fiber diameter of the core-sheath composite fiber, the ratio of the orientation parameter Ofs of the sheath component of the non-fusion-bonded core-sheath composite fiber to the orientation parameter Ofc of the core component of the non-fusion-bonded core-sheath composite fiber (Os / Oc), and / or, the spinning speed described later, and the conditions of thermal bonding (shape of the bonded part, compression ratio, temperature, and linear pressure, etc.).

[0179] It should be noted that, in this invention, the stress at 5% longitudinal elongation per unit area weight of spunbond nonwoven fabric is the value measured in accordance with JIS L1913:2010 "General Nonwoven Fabrics Test Methods" "6.3 Tensile Strength and Elongation (ISO Method)" through the following steps.

[0180] (1) Take three 25mm×200mm test pieces for every 1m width of the nonwoven fabric, with the long side of the nonwoven fabric as the longitudinal direction (long side direction of the nonwoven fabric).

[0181] (2) Place the test piece on the tensile testing machine with a clamping interval of 100 mm.

[0182] (3) Perform a tensile test at a tensile speed of 100 mm / min and determine the stress at 5% elongation (stress at 5% elongation).

[0183] (4) Calculate the average value of the stress at 5% elongation measured in each test piece, and calculate the longitudinal stress at 5% elongation per unit area weight based on the following formula, rounding the third decimal place.

[0184] Stress per unit area weight at 5% longitudinal elongation ((N / 25mm) / (g / m)) 2 = [Average stress at 5% elongation (N / 25mm)] / Weight per unit area (g / m²) 2 )…(Mode).

[0185] [Manufacturing method of spunbond nonwoven fabric]

[0186] Next, a preferred embodiment of the method for manufacturing the spunbond nonwoven fabric of the present invention will be specifically described.

[0187] The spunbond nonwoven fabric of the present invention is a long-fiber nonwoven fabric manufactured using the spunbonding method. In addition to its excellent productivity and mechanical strength, the spunbonding method can also suppress fuzzing and fiber shedding, which are prone to occur in short-fiber nonwoven fabrics. Furthermore, the method of multi-layering the captured spunbond nonwoven fiber web or the heat-pressed spunbond nonwoven fabric is also preferred due to its improved productivity and uniform texture.

[0188] In the spunbond process, molten thermoplastic resin is first spun out as long fibers from a spinneret. These fibers are then drawn and stretched using compressed air via an ejector, and collected onto a moving web to obtain a nonwoven fiber web. The resulting nonwoven fiber web is then subjected to thermal bonding treatment to obtain spunbond nonwoven fabric.

[0189] There are no particular restrictions on the shape of the spinneret or ejector; for example, various shapes such as round and rectangular can be used. However, considering the lower consumption of compressed air, better energy cost, less likelihood of yarn welding and friction, and less likelihood of yarn breakage, a combination of rectangular nozzle and rectangular ejector is preferred.

[0190] In this invention, polyethylene resin is melted in an extruder, weighed, and then fed to a spinneret to be spun into long fibers. The spinning temperature during the melting and spinning of the polyethylene resin is preferably 180°C to 250°C, more preferably 190°C to 240°C, and even more preferably 200°C to 230°C. By maintaining the spinning temperature within the above range, a stable molten state can be formed, resulting in excellent spinning stability.

[0191] The spun long fiber yarn is then cooled. Methods for cooling the spun yarn include, for example, forcibly blowing cold air onto the yarn, allowing it to cool naturally at the ambient temperature, and adjusting the distance between the spinneret and the ejector. Alternatively, a combination of these methods can be used. Furthermore, the cooling conditions can be appropriately adjusted considering factors such as the discharge rate per orifice of the spinneret, the spinning temperature, and the ambient temperature.

[0192] Next, the cooled and solidified yarn is pulled and stretched by compressed air ejected from the ejector.

[0193] The spinning speed is preferably 3000 m / min to 6000 m / min, more preferably 3500 m / min to 5500 m / min, and even more preferably 4000 m / min to 5000 m / min. By setting the spinning speed to 3000 m / min to 6000 m / min, high productivity is achieved, and the orientation and crystallization of the fibers progress, resulting in high-strength long fibers. As mentioned above, the core-sheath type composite fiber of the present invention, with polyethylene resin as the main component, exhibits excellent spinning stability and can be stably produced even at fast spinning speeds.

[0194] Next, the obtained long fibers are captured onto a moving web to obtain a nonwoven fiber web.

[0195] In this invention, for the aforementioned nonwoven fiber web, it is also a preferred method to temporarily bond it by having one side of the web abut against a hot flattening roller. In this way, during the handling process on the web, the surface of the nonwoven fiber web can be prevented from rolling up or being blown away, which would lead to a deterioration in quality, and the handling performance from yarn capture to hot pressing can be improved.

[0196] Next, by fusing the obtained nonwoven fiber web to form a welded section, the desired spunbond nonwoven fabric can be obtained.

[0197] There are no particular limitations on the methods for welding nonwoven fiber webs. For example, methods such as using hot embossing rollers with engraved (convex and concave) surfaces on a pair of rollers, hot embossing rollers composed of a roller with one flat (smooth) surface and another roller with engraved (convex and concave) surfaces, and hot calendering rollers composed of a pair of flat (smooth) rollers can be used for thermal bonding. Methods such as using ultrasonic vibration of a welding head to achieve thermal bonding, and using hot air to penetrate the nonwoven fiber web to soften or melt the surface of the core-sheath type composite fibers, thereby thermally bonding the fiber intersections together, can also be used.

[0198] Preferably, a hot embossing roller with engravings (recessed or raised portions) on the surfaces of a pair of rollers is used, or a hot embossing roller consisting of a roller with a flat (smooth) surface and a roller with engravings (recessed or raised portions) on the surface of another roller is used. In this way, it is possible to efficiently set up welded portions that improve the strength of spunbond nonwoven fabrics and non-welded portions that improve the hand feel and skin feel.

[0199] As the surface material of the hot embossing roller, it is preferable to use metal rollers in pairs in order to obtain a sufficient hot pressing effect and to prevent the engraving (recessed and raised parts) of one embossing roller from being transferred to the surface of another roller.

[0200] The embossing bonding area ratio based on such a hot embossing roller is preferably 5% to 30%. By making the bonding area preferably 5% or more, more preferably 8% or more, and even more preferably 10% or more, a strength suitable for practical use can be obtained as the spunbond nonwoven fabric. On the other hand, by making the bonding area preferably 30% or less, more preferably 25% or less, and even more preferably 20% or less, a moderate softness can be obtained as a spunbond nonwoven fabric for hygiene materials, which is particularly suitable for use in diapers. When ultrasonic bonding is used, the bonding area ratio is also preferably within the same range.

[0201] The adhesive area referred to here is the proportion of the adhesive portion to the entire spunbond nonwoven fabric. Specifically, in the case of thermal bonding using a pair of rollers with concave and convex surfaces, it refers to the proportion of the portion (adhesive portion) where the convex parts of the upper and lower rollers overlap and abut against the nonwoven fiber web to the entire spunbond nonwoven fabric. Furthermore, in the case of thermal bonding using rollers with concave and convex surfaces and a flat roller, it refers to the proportion of the portion (adhesive portion) where the convex parts of the rollers abut against the nonwoven fiber web to the entire spunbond nonwoven fabric. Additionally, in the case of ultrasonic bonding, it refers to the proportion of the portion (adhesive portion) that is thermally fused through ultrasonic processing to the entire spunbond nonwoven fabric. When sufficient heat is applied to the adhesive portion during thermal bonding, causing the core-sheath composite fibers of the adhesive portion to fuse together, the areas of the adhesive portion and the fused portion can be considered equal.

[0202] The shape of the bonded portion obtained by hot embossing rollers and ultrasonic bonding is not particularly limited; for example, circular, elliptical, square, rectangular, parallelogram, rhombus, regular hexagon, and regular octagon can be used. Furthermore, the bonded portions are preferably evenly spaced along both the long side direction (transport direction) and the width direction of the spunbond nonwoven fabric. This reduces the strength deviation of the spunbond nonwoven fabric.

[0203] The surface temperature of the hot embossing roller during heat bonding is preferably 30°C lower to 10°C higher than the melting point Tm (°C) of the thermoplastic resin used, i.e., Tm-30°C or higher and Tm+10°C or lower. By setting the surface temperature of the hot roller to Tm-30°C or higher, more preferably Tm-20°C or higher, and even more preferably Tm-10°C or higher, a strong heat bond can be achieved, resulting in a spunbond nonwoven fabric with strength that can withstand actual use. Furthermore, by setting the surface temperature of the hot embossing roller preferably to Tm+10°C or lower, more preferably Tm+5°C or lower, and even more preferably Tm or lower, excessive heat bonding is suppressed, resulting in a spunbond nonwoven fabric suitable for use as a hygiene material, with moderate softness, particularly suitable for use in diapers.

[0204] The linear pressure of the heat-embossing roller during heat bonding is preferably 50 N / cm to 500 N / cm. By setting the linear pressure of the roller to preferably 50 N / cm or more, more preferably 100 N / cm or more, and even more preferably 150 N / cm or more, a strong heat bond can be achieved, resulting in a spunbond nonwoven fabric with strength that can withstand actual use. On the other hand, by setting the linear pressure of the heat-embossing roller to preferably 500 N / cm or less, more preferably 400 N / cm or less, and even more preferably 300 N / cm or less, a spunbond nonwoven fabric with appropriate softness, particularly suitable for use in diapers, can be obtained as a hygiene material.

[0205] Furthermore, in this invention, for the purpose of adjusting the thickness of the spunbond nonwoven fabric, hot bonding can be performed using a hot calendering roller composed of a pair of upper and lower flat rollers before and / or after hot bonding using the aforementioned hot embossing roller. The so-called pair of upper and lower flat rollers are metal rollers or elastic rollers with smooth surfaces, allowing metal rollers to be used in pairs or metal rollers to be used in pairs with elastic rollers.

[0206] Furthermore, the so-called elastic roller at this time is a roller made of a material that is more elastic than a metal roller. Examples of elastic rollers include paper rollers such as those made of paper, cotton, and aramid paper, or resin rollers made of urethane resins, epoxy resins, silicone resins, polyester resins, hard rubber, and mixtures thereof.

[0207] The spunbond nonwoven fabric of this invention has excellent softness, skin feel, uniform texture, sufficient strength to withstand practical use, and excellent productivity, thus it can be widely used in sanitary materials, medical materials, household materials, and industrial materials. In particular, in sanitary materials, it can be suitable as a base fabric for disposable diapers, menstrual products, and wet wipes, and in medical materials, it can be suitable as a base fabric for protective clothing, surgical gowns, etc.

[0208] Example

[0209] Next, based on embodiments, the spunbond nonwoven fabric of the present invention will be specifically described. However, the present invention is not limited to these embodiments. It should be noted that, unless otherwise specified, the determination of various physical properties is based on the methods described above.

[0210] [Determination Method]

[0211] (1) Melt flow rate (MFR) of resin (g / 10 min)

[0212] The MFR of the resin was determined under the conditions of a load of 2.16 kg and a temperature of 190 °C.

[0213] (2) Average single fiber diameter (μm) of the core-sheath type composite fibers constituting spunbond nonwoven fabric

[0214] The measurements were performed using the aforementioned method with an electron microscope, "VHX-D500," manufactured by KEYENCE Co., Ltd.

[0215] (3) Solid density (g / cm³) of the composite fibers constituting spunbond nonwoven fabric 3 )

[0216] The solid density of the composite fiber was determined using the method described above.

[0217] (4) Spinning speed (m / min)

[0218] Based on the average single fiber diameter and the solid density of the resin used, the mass per 10,000 m length is taken as the average single fiber fineness (dtex), and rounded to the second decimal place. Based on the average single fiber fineness and the resin discharge rate (hereinafter referred to as single-orifice discharge rate) (g / min) set under various conditions from a single spinneret orifice, the spinning speed is calculated using the following formula.

[0219] Spinning speed (m / min) = (10000 × [single hole discharge (g / min)]) / [average single fiber fineness (dtex)]... (formula).

[0220] (5) Softening temperature (°C) of core-sheath composite fibers and softening temperature (°C) of core-sheath composite fibers in the non-fusion-bonded part of spunbond nonwoven fabrics.

[0221] The measuring apparatus used was the Analysis Instruments Nano-TA2, the AFM apparatus was the PACIFIC NANOTECHNOLOGY Nano-R, and the probe was the Analysis Instruments PNI-AN2-300. The measurements were performed using the methods described above. The measurement conditions are as follows.

[0222] • Measurement method: nano-TMA (nano-thermomechanical analysis)

[0223] • Measurement temperature: 25~150℃

[0224] • Heating rate: 10℃ / second (600℃ / minute)

[0225] • Measurement environment: In the atmosphere.

[0226] (6) Orientation parameters of core-sheath composite fibers, orientation parameters of core-sheath composite fibers in the non-fusion-bonded portion of spunbond nonwoven fabric, and orientation parameters of core-sheath composite fibers in the fusion-bonded portion of spunbond nonwoven fabric.

[0227] The measurement was performed using a triple Raman spectrometer "T-64000" manufactured by Atago Bussan Co., Ltd., using the method described above. The measurement conditions are as follows.

[0228] • Measurement mode: Micro Raman (polarized light measurement)

[0229] • Objective lens: ×100

[0230] • Beam diameter: 1μm

[0231] • Light source: Ar + Laser / 514.5nm

[0232] Laser power: 100mW

[0233] • Diffraction grating: Single 1800gr / mm

[0234] • Cross-shaped slit: 100μm

[0235] • Detector: CCD / Jobin Yvon 1024×256.

[0236] (7) Melting peak temperature Tm (°C) of spunbond nonwoven fabric

[0237] The measuring apparatus used was a Perkin-Elmer DSC8500, and the determination was performed using the method described above. The measurement conditions were as follows.

[0238] • Atmosphere inside the apparatus: Nitrogen (20 mL / min)

[0239] • Temperature and heat correction: High-purity indium (Tm = 156.61℃, ΔHm = 28.70 J / g)

[0240] Temperature range: 20℃~200℃

[0241] • Heating rate: 20℃ / minute

[0242] • Sample size: Approximately 0.5–4 mg

[0243] • Sample container: Aluminum standard container.

[0244] (8) Longitudinal stiffness of spunbond nonwoven fabric (mm)

[0245] The stiffness of spunbond nonwoven fabrics was determined according to the method described in "6.7.4 Gurley Method" of "6.7 Stiffness (JIS Method and ISO Method)" of JIS L1913:2010 "General Test Methods for Nonwoven Fabrics," specifically in the longitudinal (long side) direction. It should be noted that for any spunbond nonwoven fabric, the stiffness in the longitudinal (long side) direction is greater than the stiffness in the transverse (width) direction. A longitudinal stiffness of 50 mm or less is considered acceptable.

[0246] (9) Tensile strength per unit area weight and stress at 5% elongation per unit area weight of spunbond nonwoven fabric (N / 25mm / (g / m)) 2 ))

[0247] The measuring apparatus used was an A&D Corporation "RTG-1250", and the measurement was performed using the aforementioned method. The transverse tensile strength per unit area weight was calculated as 0.2 (N / 25mm) / (g / m²). 2The above is considered acceptable. The stress at which 5% transverse elongation occurs per unit area weight is 0.2 (N / 25mm) / (g / m²). 2 The above is considered qualified.

[0248] [Example 1]

[0249] The melt flow rate (MFR) was 30 g / 10 min, the melting point was 128 °C, and the solid density was 0.955 g / cm³. 3 A polyethylene-based resin composed of homopolymers of linear low-density polyethylene (LLDPE) was used as the core component, with an MFR of 60 g / 10 min, a melting point of 127 °C, and a solid density of 0.940 g / cm³. 3 Polyethylene-based resins composed of LLDPE homopolymers are used as sheath components. They are melted in an extruder and spun from a spinneret with a diameter of 0.40 mm and a depth of 8 mm. The spinning temperature is 220 °C and the single-hole discharge rate is 0.50 g / min. The resulting sheath components are 40% by mass of concentric core-sheath type composite fibers.

[0250] After the spun yarn is cooled and solidified, it is drawn and stretched using compressed air in an ejector and collected onto a moving web to form a spunbond nonwoven fiber web containing polyethylene-based long fibers. Regarding the characteristics of the core-sheath composite fibers constituting the formed nonwoven fiber web, the average single fiber diameter is 11.6 μm and the solid density is 0.949 g / cm³. 3 Based on this, the calculated spinning speed is 5000 m / min. Regarding spinning performance, no yarn breakage was observed during one hour of spinning, which is considered good.

[0251] Next, using a pair of upper and lower hot embossing rollers (comprising an upper and lower roller), the formed nonwoven fiber web is thermally bonded under conditions of 300 N / cm linear pressure and 126°C thermal bonding temperature, resulting in a unit area weight of 30 g / m². 2 spunbond nonwoven fabric.

[0252] Upper roller: A metal embossing roller with a water droplet pattern engraving and an adhesion area of ​​11%.

[0253] Lower roller: Metal flat roller

[0254] The resulting spunbond nonwoven fabric has a uniform texture and excellent skin feel. The evaluation results are shown in Table 1.

[0255] [Example 2]

[0256] The sheath component ratio was set to 50% by mass, and the compressed air flow rate of the ejector was reduced. Otherwise, the spunbond nonwoven fabric was obtained using the same method as in Example 1. Regarding the characteristics of the fibers constituting the formed spunbond nonwoven web, the average single fiber diameter was 13.7 μm, and the solid density was 0.948 g / cm³. 3 Based on this, the calculated spinning speed is 3600 m / min. Regarding spinning performance, no yarn breakage was observed during one hour of spinning, indicating good spinning properties. The resulting spunbond nonwoven fabric has a uniform texture and excellent skin feel. The evaluation results are shown in Table 1.

[0257] [Example 3]

[0258] The sheath component ratio was set to 30% by mass, and the flow rate of compressed air in the ejector was reduced. Otherwise, the spunbond nonwoven fabric was obtained using the same method as in Example 1. Regarding the characteristics of the fibers constituting the formed spunbond nonwoven web, the average single fiber diameter was 15.5 μm, and the solid density was 0.951 g / cm³. 3 Based on this, the calculated spinning speed is 2800 m / min. Regarding spinning performance, no yarn breakage was observed during one hour of spinning, indicating good spinning properties. The resulting spunbond nonwoven fabric has a uniform texture and excellent skin feel. The evaluation results are shown in Table 1.

[0259] [Example 4]

[0260] The MFR is 30 g / 10 min, the melting point is 128 °C, and the solid density is 0.955 g / cm³. 3 A polyethylene-based resin composed of LLDPE homopolymer was used as the core component, with an MFR of 50 g / 10 min, a melting point of 128 °C, and a solid density of 0.950 g / cm³. 3 A polyethylene-based resin composed of LLDPE homopolymer was used as the sheath component. Otherwise, a spunbond nonwoven fabric was obtained using the same method as in Example 2. Regarding the characteristics of the fibers constituting the formed spunbond nonwoven web, the average single fiber diameter was 13.7 μm and the solid density was 0.953 g / cm³. 3 Based on this, the calculated spinning speed is 3600 m / min. Regarding spinning properties, several yarn breaks occurred during one hour of spinning. The resulting spunbond nonwoven fabric was evaluated, and the results are shown in Table 1.

[0261] [Example 5]

[0262] By changing the spinneret to form an eccentric core-sheath type composite fiber, spunbond nonwoven fabric was obtained using the same method as in Example 2. Regarding the characteristics of the fibers constituting the formed spunbond nonwoven web, the average single fiber diameter was 13.7 μm and the solid density was 0.948 g / cm³. 3Based on this, the calculated spinning speed is 3600 m / min. Regarding spinning performance, no yarn breakage was observed during one hour of spinning, indicating good spinning properties. The resulting spunbond nonwoven fabric has a uniform texture and excellent skin feel. The evaluation results are shown in Table 1.

[0263] [Comparative Example 1]

[0264] Using only MFR of 30g / 10min, melting point of 128℃, and solid density of 0.955g / cm³. 3 A polyethylene-based resin composed of LLDPE homopolymer was spun as a single component, and spunbond nonwoven fabric was obtained using the same method as in Example 2. Regarding the characteristics of the fibers constituting the formed spunbond nonwoven web, the average single fiber diameter was 13.9 μm and the solid density was 0.955 g / cm³. 3 Based on this, the calculated spinning speed is 3500 m / min. Regarding spinning performance, frequent yarn breakage occurred during one hour of spinning, indicating poor spinning characteristics. The resulting spunbond nonwoven fabric was evaluated, and the results are shown in Table 1.

[0265] [Comparative Example 2]

[0266] Using only MFR of 60g / 10min, melting point of 127℃, and solid density of 0.940g / cm³. 3 A polyethylene-based resin composed of LLDPE homopolymer was spun as a single component, and a heat-bonding temperature of 120°C was used. Otherwise, a spunbond nonwoven fabric was obtained using the same method as in Example 2. Regarding the characteristics of the fibers constituting the formed spunbond nonwoven web, the average single fiber diameter was 13.7 μm and the solid density was 0.940 g / cm³. 3 The calculated spinning speed is 3600 m / min. Regarding spinning performance, no yarn breakage was observed during one hour of spinning, indicating good spinning properties. It should be noted that if the heat bonding temperature is set to 126℃, sheet breakage occurs due to adhesion to the heat embossing roller, making production impossible. The obtained spunbond nonwoven fabric was evaluated, and the results are shown in Table 1.

[0267] [Comparative Example 3]

[0268] Referring to the method disclosed in Patent Document 2 (Japanese Patent Application Publication No. 2019-26954), only an MFR of 100 g / 10 minutes, a melting point of 115 °C, and a solid density of 0.933 g / cm³ were used. 3 A polyethylene-based resin composed of LLDPE homopolymer was spun as a single component, and spunbond nonwoven fabric was obtained using the same method as in Example 2. Regarding the characteristics of the fibers constituting the formed spunbond nonwoven web, the average single fiber diameter was 15.2 μm and the solid density was 0.933 g / cm³. 3The calculated spinning speed is 3500 m / min, which is equivalent to Example 1 in Patent Document 2. Regarding spinnability, no yarn breakage was observed during 1 hour of spinning, indicating good performance. The obtained spunbond nonwoven fabric was evaluated, and the results are shown in Table 1.

[0269] [Comparative Example 4]

[0270] The MFR is 30 g / 10 min, the melting point is 128 °C, and the solid density is 0.955 g / cm³. 3 A polyethylene-based resin composed of LLDPE homopolymer was used as the core component, with an MFR of 40 g / 10 min, a melting point of 128 °C, and a solid density of 0.950 g / cm³. 3 A polyethylene-based resin composed of LLDPE homopolymer was used as the sheath component. Otherwise, a spunbond nonwoven fabric was obtained using the same method as in Example 2. Regarding the characteristics of the fibers constituting the formed spunbond nonwoven web, the average single fiber diameter was 13.7 μm and the solid density was 0.953 g / cm³. 3 Based on this, the calculated spinning speed is 3600 m / min. Regarding spinning performance, frequent yarn breakage occurred during one hour of spinning, indicating poor results. The obtained spunbond nonwoven fabric was evaluated, and the results are shown in Table 1.

[0271] [Table 1]

[0272]

[0273] For the spunbond nonwoven fabrics of Examples 1 to 5, which are formed from core-sheath type composite fibers with polyethylene resin as the main component and whose Ofs to Ofc ratio of Ofs / Ofc in the non-fusion section is 0.10 to 0.90, they have excellent softness, skin feel, uniform texture, sufficient strength to withstand actual use, and excellent productivity.

[0274] On the other hand, for the spunbond nonwoven fabrics shown in Comparative Examples 1 to 4, the tensile strength in the transverse direction per unit area weight and the stress at 5% elongation in the longitudinal direction per unit area weight are low, resulting in poor strength.

Claims

1. A spunbond nonwoven fabric, which is formed from core-sheath type composite fibers with polyethylene resin as the main component, the spunbond nonwoven fabric having a welded portion and a non-welded portion, wherein the ratio of the orientation parameter Ofs of the sheath component of the core-sheath type composite fiber in the non-welded portion to the orientation parameter Ofc of the core component of the core-sheath type composite fiber in the non-welded portion, Ofs / Ofc, is 0.10 to 0.90, and the spunbond nonwoven fabric has a single melting peak temperature Tm in the range of 100°C to 150°C in differential scanning calorimetry.

2. The spunbond nonwoven fabric as described in claim 1, wherein, The orientation parameter Obs of the sheath component of the core-sheath type composite fiber in the welded part is 1.2 to 3.0, and the orientation parameter Obc of the core component of the core-sheath type composite fiber in the welded part is 2.0 to 10.

0.

3. The spunbond nonwoven fabric as described in claim 1 or 2, wherein, The solid density of the core-sheath composite fiber is 0.935 g / cm³. 3 Above 0.970g / cm 3 the following.

4. The spunbond nonwoven fabric as described in claim 1 or 2, wherein, The Ofs value is above 2.0 and below 8.

0.

5. The spunbond nonwoven fabric as described in claim 1 or 2, wherein, The transverse tensile strength per unit area weight of the spunbond nonwoven fabric is 0.20 (N / 25mm) / (g / m²). 2 )above.

6. The spunbond nonwoven fabric as described in claim 1 or 2, wherein, The stress of the spunbond nonwoven fabric at 5% longitudinal elongation per unit area weight is 0.20 (N / 25mm) / (g / m²). 2 )above.

7. A core-sheath composite fiber, which is a core-sheath composite fiber with polyethylene resin as the main component, wherein the ratio of the orientation parameter Ofs of the sheath component to the orientation parameter Ofc of the core component of the core-sheath composite fiber is Ofs / Ofc, which is 0.10 to 0.90, and wherein the core-sheath composite fiber has a single melting peak temperature Tm in the range of 100°C to 150°C in differential scanning calorimetry.

8. The core-sheath type composite fiber as described in claim 7, wherein, The solid density of the polyethylene resin is 0.935 g / cm³. 3 Above 0.970g / cm 3 the following.

9. The core-sheath type composite fiber as described in claim 7 or 8, wherein, The Ofs value is above 2.0 and below 8.0.

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