Spunbonded nonwoven fabric

Abstract

To provide a spunbond nonwoven fabric having excellent strength, softness, and skin touch feeling even with a low unit area weight, the spunbond nonwoven fabric of the present invention is a spunbond nonwoven fabric containing core-sheath type composite fibers in which a polypropylene-based resin is a main component, wherein the spunbond nonwoven fabric has a fusion portion and a non-fusion portion, and the ratio (Os / Oc) of the orientation parameter Os of the sheath component of the core-sheath type composite fibers of the non-fusion portion to the orientation parameter Oc of the core component of the core-sheath type composite fibers of the non-fusion portion is 0.10 to 0.90.

Description

Technical Field

[0001] This invention relates to spunbond nonwoven fabrics. Background Technology

[0002] Most hygiene products such as diapers and sanitary napkins are incinerated or landfilled after use due to hygiene concerns, resulting in significant environmental impact from resource consumption and waste accumulation. To address these issues, efforts are underway to make these products thinner and lighter.

[0003] Even spunbond nonwoven fabrics, which are the main material for diapers, have long been subject to measures to reduce weight per unit area. For example, as a nonwoven fabric that still exhibits excellent water resistance, softness, and high tensile strength even with low weight per unit area, a spunbond / meltblown laminated nonwoven fabric comprising a polypropylene spunbond nonwoven fabric with a fineness of 0.7 to 1.5 dtex and a polypropylene meltblown nonwoven fabric with a fiber diameter of 1 to 3 μm has been proposed, and has a modulus index of 5% within a specific range (see Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 4245970 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, the method disclosed in Patent Document 1 has limited effect on increasing strength, and it is difficult to achieve a practically usable strength at the level of low weight per unit area required in recent years.

[0009] Therefore, the object of the present invention is to provide a spunbond nonwoven fabric that has excellent strength, softness and skin feel even with low weight per unit area.

[0010] Methods for solving problems

[0011] The spunbond nonwoven fabric of the present invention has the following structure.

[0012] [1] Spunbond nonwoven fabric, which is a spunbond nonwoven fabric containing core-sheath type composite fibers with polypropylene resin as the main component, wherein the spunbond nonwoven fabric has a welded part and a non-welded part, and the ratio (Os / Oc) of the orientation parameter Os of the sheath component of the core-sheath type composite fiber in the non-welded part to the orientation parameter Oc of the core component of the core-sheath type composite fiber in the non-welded part is 0.10 to 0.90.

[0013] [2] According to the spunbond nonwoven fabric described in [1], wherein the orientation parameter Os of the sheath component of the core-sheath type composite fiber of the non-fusion portion is 1.0 or more and 8.0 or less.

[0014] [3] The spunbond nonwoven fabric according to [1] or [2], wherein the spunbond nonwoven fabric has a single melting peak temperature Tm (°C) in differential scanning calorimetry.

[0015] [4] The spunbond nonwoven fabric according to any one of [1] to [3], wherein the tensile strength-elongation product per unit area weight of the spunbond nonwoven fabric is 1.20 (N / 50mm) / (g / m²). 2 )above.

[0016] [5] The spunbond nonwoven fabric according to any one of [1] to [4], wherein the melt flow rate of the polypropylene resin of the sheath component is 10 g / 10 min to 200 g / 10 min greater than the melt flow rate of the polypropylene resin of the core component.

[0017] The effects of the invention

[0018] According to the present invention, a spunbond nonwoven fabric exhibiting excellent strength, softness, and skin-touch properties even with a low weight per unit area can be obtained. Due to these characteristics, the spunbond nonwoven fabric of the present invention is particularly suitable for use as a hygiene material. Detailed Implementation

[0019] The spunbond nonwoven fabric of the present invention is a spunbond nonwoven fabric comprising a core-sheath type composite fiber with polypropylene resin as the main component, wherein the spunbond nonwoven fabric has a welded portion and a non-welded portion, and the ratio (Os / Oc) of the orientation parameter Os of the sheath component of the core-sheath type composite fiber in the non-welded portion to the orientation parameter Oc of the core component of the core-sheath type composite fiber in the non-welded portion is 0.10 to 0.90.

[0020] This allows for the production of spunbond nonwoven fabrics that possess excellent strength, softness, and skin-touch properties even with low unit area weight.

[0021] The following describes in detail the constituent elements of the present invention, but the present invention is not limited by the scope of the following description unless it departs from its spirit.

[0022] [Polypropylene Resin]

[0023] The core-sheath type composite fiber constituting the spunbond nonwoven fabric of the present invention is made of polypropylene resin as the main component. Compared with other polyolefin resins such as polyethylene resin, polypropylene resin has superior spinnability and strength properties, and is therefore preferred. It should be noted that in the present invention, "polypropylene resin" refers to a resin in which the propylene unit accounts for 60 mol% to 100 mol% of the molar fraction in the repeating unit. The same applies to "polyethylene resin". In addition, examples of polypropylene resin used in the present invention include homopolymers of propylene or copolymers of propylene with various α-olefins. Here, "main component" refers to a component that accounts for 50% or more by mass relative to the core-sheath type composite fiber as a whole.

[0024] Regarding the polypropylene-based resin used in this invention, the proportion of propylene 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.

[0025] The material constituting the composite fiber used in this invention (hereinafter sometimes referred to as "thermoplastic resin") can be a mixture of two or more resins that together with a polypropylene resin contain other resins. As such a mixture, a resin composition containing other olefin resins such as polyethylene, poly-4-methyl-1-pentene, thermoplastic elastomers, etc., can also be used.

[0026] In the polypropylene resin used in this invention, in order to further improve the effect of this invention or to impart other properties, commonly used antioxidants, weather stabilizers, light stabilizers, heat stabilizers, antistatic agents, charging agents, antifogging agents, anti-blocking agents, lubricants containing polyethylene wax, crystallizing nucleating agents, and pigments, or other polymers, may be added as needed within the scope that does not impair the effect of this invention.

[0027] The melting point (Tmr) of the polypropylene resin used in this invention is preferably 120°C to 200°C. By preferably setting the melting point (Tmr) to 120°C or higher, more preferably 130°C or higher, and even more preferably 140°C or higher, practically usable heat resistance is easily obtained. Furthermore, by preferably setting the melting point to 200°C or lower, more preferably 180°C or lower, and even more preferably 170°C or lower, the yarn ejected from the spinneret is easily cooled, fiber bonding is suppressed, and stable spinning becomes easier even with fine fiber diameters. The melting point (Tmr) of the polypropylene resin referred to here is the maximum (highest temperature) melting peak temperature obtained by differential scanning calorimetry (DSC) of the polypropylene resin.

[0028] The melt flow rate (MFR) of the polypropylene resin, the core component of the spunbond nonwoven fabric comprising core-sheath type composite fibers of the present invention, is preferably 10 g / 10 min to 100 g / 10 min. By preferably setting the MFR of the polypropylene resin to 10 g / 10 min or more, more preferably 20 g / 10 min or more, and even more preferably 30 g / 10 min or more, stable spinning can be achieved even with fine fiber diameters, resulting in spunbond nonwoven fabrics with excellent skin feel and uniform texture. On the other hand, by preferably setting the MFR of the polypropylene resin, the core component, to 100 g / 10 min or less, more preferably 80 g / 10 min or less, and even more preferably 60 g / 10 min or less, the reduction in monofilament strength can be suppressed, resulting in spunbond nonwoven fabrics with excellent strength.

[0029] In the spunbond nonwoven fabric comprising core-sheath composite fibers of the present invention, the MFR of the polypropylene resin in the sheath component is preferably 10 g / 10 min to 200 g / 10 min greater than the MFR of the polypropylene resin in the core component. By preferably setting the MFR of the polypropylene resin in the sheath component to be 10 g / 10 min or more, more preferably 15 g / 10 min or more, and even more preferably 20 g / 10 min or more greater than the MFR of the polypropylene resin in the core component, spinning stress can be concentrated on the core component during spinning, promoting the orientation of the core component and inhibiting the orientation of the sheath component. On the other hand, if the MFR of the polypropylene resin in the sheath component is more than 200 g / 10 min greater than the MFR of the polypropylene resin in the core component, the monofilament strength of the core-sheath composite fiber decreases, and it is prone to excessive softening during heat welding, causing operational problems such as adhesion to the hot roller, which is therefore undesirable. The MFR of the polypropylene resin in the sheath component is more preferably not more than 150 g / 10 min greater than that of the polypropylene resin in the core component, and even more preferably not more than 100 g / 10 min greater than that of the polypropylene resin in the core component.

[0030] It should be noted that when measuring and interpreting the MFR of polypropylene resins for the core or sheath components of island-type composite fibers, the measurement should be performed by renaming the "sheath component" as the "sea component" and the "core component" as the "island component".

[0031] The MFR of the polypropylene resin involved in this invention is determined using the value specified in ASTM D1238 (Method A). According to this standard, the MFR of the polypropylene resin is determined at a load of 2.16 kg and a temperature of 230 °C.

[0032] Of course, the MFR of the polypropylene resin used in this invention can be adjusted by blending two or more resins with different MFRs in any proportion. In this case, the MFR of the resin blended relative to the main polypropylene resin (referring to the polypropylene resin that accounts for the largest mass percentage in the polypropylene resin) is preferably 10 g / 10 min to 1000 g / 10 min, more preferably 20 g / 10 min to 800 g / 10 min, and even more preferably 30 g / 10 min to 600 g / 10 min. This prevents partial viscosity inhomogeneity in the blended polypropylene resin, enabling uniformity of single fiber diameter and fineness, and allowing stable spinning even with fine fibers.

[0033] In order to improve the smoothness and softness of the spunbond nonwoven fabric of the present invention, it is preferable to contain a fatty acid amide compound with 23 to 50 carbon atoms in the whole or sheath component of the core-sheath type composite fiber with polypropylene resin as the main component.

[0034] By preferably setting the number of carbon atoms of the fatty acid amide compound mixed in the polypropylene resin to 23 or more, and more preferably 30 or more, excessive exposure of the fatty acid amide compound to the fiber surface can be suppressed, resulting in excellent spinning properties and processing stability, and maintaining high productivity. On the other hand, by preferably setting the number of carbon atoms of the fatty acid amide compound to 50 or less, and more preferably 42 or less, the fatty acid amide compound can easily move to the fiber surface, imparting smoothness and softness to the spunbond nonwoven fabric.

[0035] 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.

[0036] Specifically, examples of fatty acid amide compounds with 23 to 50 carbon atoms include tetracosanoamide, hexacosanoamide, octacosanoamide, ceramide, docosapentaenoic acid amide, nisenoic acid amide, ethylene dilauric acid amide, methylene dilauric acid amide, ethylene bis-stearamide, ethylene dihydroxystearamide, ethylene dibenzylhexylamide, hexamethylene bis-stearamide, hexamethylene dibenzylhexylamide, hexamethylene hydroxystearamide, distearate adipamide, distearate sebacic acid amide, ethylene dioleoamide, ethylene dierucamide, and hexamethylene dioleoamide, etc., and combinations of several of them can also be used.

[0037] In this invention, ethylene bis-stearamide, as a saturated fatty acid diamide compound, is particularly preferred among these fatty acid amide compounds. Ethylene bis-stearamide is melt-spun due to its excellent thermal stability. By using fibers containing polypropylene resins incorporating this ethylene bis-stearamide, spunbond nonwoven fabrics with excellent smoothness and softness can be obtained while maintaining high productivity.

[0038] In this invention, the amount of the fatty acid amide compound added is preferably 0.01% to 5.0% by mass. By setting the amount of the fatty acid amide compound added preferably to 0.01% to 5.0% by mass, more preferably to 0.1% to 3.0% by mass, and even more preferably to 0.1% to 1.0% by mass, it is possible to impart appropriate smoothness and softness while maintaining spinnability.

[0039] The amount added here refers to the mass percentage of the fatty acid amide compound added relative to the total amount of the thermoplastic resin, which is mainly composed of polypropylene resin constituting the spunbond nonwoven fabric of the present invention. For example, when the fatty acid amide compound is 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.

[0040] As a method for determining the amount of fatty acid amide compound added relative to fibers containing polypropylene resin, one example is solvent extraction of the additive from the fibers followed by quantitative analysis using liquid chromatography-mass spectrometry (LS / MS). In this case, the extraction solvent is appropriately selected based on the type of fatty acid amide compound; for example, in the case of ethylene distearate amide, a chloroform-methanol mixture could be used.

[0041] Core-sheath type composite fiber with polypropylene resin as the main component

[0042] As for the composite form of the core-sheath type composite fiber constituting the spunbond nonwoven fabric of the present invention, for example, concentric core-sheath type, eccentric core-sheath type, and island type composite forms can be adopted. Among these, considering the excellent spinnability and the ability to uniformly bond the fibers together through thermal bonding, the core-sheath type composite form, that is, the composite fiber is a core-sheath type composite fiber, is preferred, and the concentric core-sheath type composite form, that is, the composite fiber is a concentric core-sheath type core-sheath composite fiber, is even more preferred.

[0043] The core-sheath type composite fibers constituting the spunbond nonwoven fabric of the present invention preferably have an average single fiber fineness of 0.5 dtex to 3.0 dtex. By preferably setting the average single fiber fineness to 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 a decrease in spinnability and produce a spunbond nonwoven fabric with excellent production stability. On the other hand, by preferably setting the average single fiber fineness to 3.0 dtex or less, more preferably 2.0 dtex or less, and even more preferably 1.5 dtex or less, it is possible to produce a spunbond nonwoven fabric with excellent skin feel, uniform texture, and excellent strength. The average single fiber fineness can be controlled by the spinning temperature, the amount of material ejected from a single orifice, the spinning speed, etc., as described later.

[0044] The core-sheath type composite fibers constituting the spunbond nonwoven fabric of the present invention preferably have an average single fiber diameter of 8 μm to 20 μm. By preferably setting the average single fiber diameter to 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 produce a spunbond nonwoven fabric with excellent production stability. On the other hand, by preferably setting the average single fiber diameter to 20 μm or less, more preferably 17 μm or less, and even more preferably 14 μm or less, it is possible to produce a spunbond nonwoven fabric with excellent skin feel, uniform texture, and excellent strength. The average single fiber diameter can be controlled by the spinning temperature, the amount ejected from a single orifice, the spinning speed, etc., as described later.

[0045] In this invention, the average single fiber diameter (μm) of the core-sheath type composite fiber constituting the above-mentioned spunbond nonwoven fabric is a value calculated by the following steps.

[0046] (1) Ten small samples (100×100mm) were randomly collected from spunbond nonwoven fabric.

[0047] (2) Take surface photographs at 500–2000x magnification using a microscope or scanning electron microscope. Measure the width (diameter) of 10 core-sheath composite fibers at the non-fusion joint of each sample, for a total of 100 fibers. If the cross-section of the core-sheath composite fiber is irregular, measure the cross-sectional area and determine the diameter of a perfect circle with the same cross-sectional area.

[0048] (3) Take the average of the diameter values ​​of the 100 measured fibers and round the second decimal place to get the average single fiber diameter (μm).

[0049] The core-sheath type composite fiber constituting the spunbond nonwoven fabric of the present invention preferably has a sheath component mass ratio of 20% to 80% by mass. The sheath component mass ratio is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, thereby enabling the sheath components to be firmly fused together during heat welding, resulting in a spunbond nonwoven fabric with sufficient strength for practical use. On the other hand, by preferably having a sheath component ratio of 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 components can be increased, thereby improving the monofilament strength of the core-sheath type composite fiber and producing a spunbond nonwoven fabric with sufficient strength for practical use.

[0050] The cross-sectional shape of the core-sheath type composite fiber constituting the spunbond nonwoven fabric of the present invention can be a circular cross-section, a flat cross-section, or irregular cross-sections such as Y-shaped or C-shaped cross-sections. Among these, a circular cross-section is preferred because it eliminates the bending difficulties inherent in structures with flat or irregular cross-sections, allowing for the production of spunbond nonwoven fabrics with excellent flexibility. While a hollow cross-section can also be used, a solid cross-section is preferred for its excellent spinnability and stable spinning even with fine fiber diameters.

[0051] [Spunbond Nonwoven Fabric]

[0052] The spunbond nonwoven fabric of the present invention comprises a core-sheath type composite fiber with the aforementioned polypropylene resin as the main component. The spunbond nonwoven fabric has a welded portion and a non-welded portion. The ratio (Os / Oc) of the orientation parameter Os of the sheath component of the core-sheath type composite fiber in the non-welded portion to the orientation parameter Oc of the core component of the core-sheath type composite fiber in the non-welded portion is 0.10 to 0.90. Therefore, it is possible to produce a spunbond nonwoven fabric with excellent strength, softness, and skin-feel even with a low unit area weight.

[0053] First, the spunbond nonwoven fabric of the present invention has welded portions and non-welded portions. This allows for the production of spunbond nonwoven fabrics that maintain softness, a skin-like feel, and sufficient strength for practical use. The welded portion refers to the area where the core-sheath composite fibers are fused together, while the non-welded portion refers to the area where the core-sheath composite fibers are not fused together and maintain their cross-sectional shape.

[0054] Furthermore, the orientation ratio (Os / Oc) of the spunbond nonwoven fabric of the present invention is 0.10 to 0.90. The orientation ratio (Os / Oc) is preferably 0.10 or more, more preferably 0.15 or more, and even more preferably 0.20 or more, thereby preventing excessive concentration of tensile stress in the inner layer of the fiber during spinning and preventing a decrease in spinning stability. On the other hand, the orientation ratio (Os / Oc) is preferably 0.90 or less, more preferably 0.85 or less, and even more preferably 0.80 or less, thereby allowing only the surface layer of the fiber to soften during thermal bonding. Preferably, it is 0.70 or less, and particularly preferably 0.50 or less. Regarding the orientation parameters, in the Raman spectrum obtained by Raman spectrometry, for example in the case of polypropylene, it can be determined based on 810 cm⁻¹. -1 and 840cm -1 The intensity of the nearby Raman band is determined. In the case of polypropylene, the value is known to be 810 cm. -1 and 840cm -1 The nearby Raman bands exhibit strong anisotropy for polarized incident light. These are attributed to the coupling modes of CH2 bending vibration and CC stretching vibration, and the CH2 bending vibration mode, respectively. Among them, regarding 810 cm⁻¹... -1 The Raman bands of the vibrational modes have principal axes of Raman tensors parallel to the main chain direction of the molecule, while on the other hand, at 840 cm⁻¹... -1 The Raman bands are orthogonal. Therefore, the orientation of the molecular chains can be obtained based on the band intensity ratio of these Raman bands relative to the polarization direction.

[0055] Regarding the orientation parameter I as referred to in this invention, as I 810 / I 840 (I 810 810cm -1 Nearby Raman band intensity, I 840 840cm -1 The value of the Raman band intensity in the vicinity is obtained.

[0056] In this invention, by setting the orientation ratio as described above, it is possible to firmly thermally bond the fibers together while maintaining the molecular orientation of the inner layer of the fiber, thus enabling the production of spunbond nonwoven fabrics with practical strength. Furthermore, by reducing the orientation parameter Os of the sheath component of the core-sheath type composite fiber in the non-fusion-bonded portion, it is possible to produce spunbond nonwoven fabrics with excellent softness.

[0057] Here, for the orientation parameter of the core-sheath composite fiber in this invention, a larger value indicates that the molecular chains are more oriented in a specific direction, while a smaller value indicates that the molecular chains of the polypropylene resin constituting the core-sheath composite fiber are more randomly oriented (unitless). It should be noted that this orientation parameter is 1.0 when completely randomly oriented.

[0058] Furthermore, in this invention, the orientation parameter Os of the sheath component and the orientation parameter Oc of the core component of the non-fusion-bonded core-sheath composite fiber of the spunbond nonwoven fabric are determined by the following method. It should be noted that in this invention, island-type composite fibers are also included in core-sheath composite fibers. In the case of island-type composite fibers, similar to the case of core-sheath composite fibers described above, the orientation parameters Os and Oc are measured and interpreted by renaming "sheath component" as "sea component" and "core component" as "island component," etc.

[0059] (1) Collect core-sheath type composite fibers near the center of the non-welded part (at a distance approximately equal to the surrounding welded parts), and embed the fiber sheet sample in bisphenol epoxy resin.

[0060] (2) After the resin has cured, slices are cut using a slicer. The slice thickness is 2 μm. At this point, the slice is cut at an angle from the fiber axis to make the cut surface elliptical. Then, the section where the minor axis thickness of the ellipse shows a constant thickness is selected for measurement. It should be noted that by keeping the cutting angle within 4°, the slice can be considered parallel to the fiber axis within a 2 μm film thickness.

[0061] (3) Raman spectroscopy is performed on the fiber surface of the core-sheath composite fiber slice from the non-fusion part to the center, with polarized light incident on the fiber axis (parallel direction) and polarized light in the direction orthogonal to the fiber axis (perpendicular direction).

[0062] (4) At the respective positions of the core and sheath components of the core-sheath composite fiber in the non-fusion section, calculate 810cm for each direction in the parallel and perpendicular directions. -1 Nearby and 840cm -1 Nearby Raman band intensity I 810 and I 840 Calculate its strength ratio I 810 / I 840 .

[0063] (5) Calculate the orientation parameter based on the following formula (a). When dividing the core component into multiple regions, the orientation parameter is measured in all regions, and the highest value is used.

[0064] Orientation parameter = (I 810 / I 840 ) 平行 / (I 810 / I 840 ) 垂直 (a)

[0065] (6) Change the position of the core-sheath type composite fiber along the fiber axis and perform the same measurement at 3 locations, calculate the average value of the orientation parameters, and round the second decimal place.

[0066] It should be noted that when it is difficult to sample the core-sheath type composite fiber near the center of the non-welded part (the part that is approximately equidistant from the surrounding welded parts), the following steps can also be used for measurement.

[0067] (1) The spunbond nonwoven fabric sample was embedded in bisphenol epoxy resin.

[0068] (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 2 μm. Subsequent measurements are performed on portions where the cut angle is within 4° of the fiber axis.

[0069] (3) Raman spectroscopy is performed by taking polarized light incident from the fiber surface of the non-fusion-bonded core-sheath composite fiber slice towards the center along the fiber axis (parallel direction) and in the direction perpendicular to the fiber axis.

[0070] (4) The positions of the core and sheath components of the core-sheath composite fiber in the non-fusion section are calculated for the parallel and perpendicular directions, respectively, at 810cm. -1 Nearby and 840cm -1 Nearby Raman band intensity I 810 and I 840 Calculate its strength ratio I 810 / I 840 .

[0071] (5) Calculate the orientation parameter based on the following formula (a). When dividing the core component into multiple regions, the orientation parameter is measured in all regions, and the highest value is used.

[0072] Orientation parameter = (I 810 / I 840 ) 平行 / (I 810 / I 840 ) 垂直 (a)

[0073] (6) 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] The spunbond nonwoven fabric of the present invention preferably has an orientation parameter Os of 1.0 to 8.0 for the sheath component of the core-sheath composite fiber in the non-fusion-bonded portion. The orientation parameter Os of the sheath component of the core-sheath composite fiber in the non-fusion-bonded portion is preferably 1.0 or more, more preferably 1.5 or more, and even more preferably 2.0 or more, thereby preventing problems such as excessive softening of the fiber surface and adhesion to hot rollers during thermal bonding. On the other hand, the orientation parameter Os of the sheath component of the core-sheath composite fiber in the non-fusion-bonded portion is preferably 8.0 or less, more preferably 6.0 or less, and even more preferably 5.0 or less, thereby improving softness and making it easier for the fiber surface to soften during thermal bonding, enabling the fibers to be firmly thermally bonded together, thus producing a spunbond nonwoven fabric with excellent strength. The orientation parameter Os of the sheath component of the core-sheath composite fiber in the non-fusion-bonded portion can be controlled by the MFR of the polypropylene resin, melting point, additives, mass ratio of the sheath component of the core-sheath composite fiber, and / or the spinning temperature and spinning speed described later.

[0075] The spunbond nonwoven fabric of the present invention preferably has an orientation parameter Oc of 4.0 or more for the core component of the core-sheath type composite fiber in the non-fusion-bonded portion, more preferably 5.0 or more, and even more preferably 6.0 or more. Preferably, it is between 8.0 and 20.0. The orientation parameter Oc of the core component of the core-sheath type composite fiber in the non-fusion-bonded portion is generally 4.0 or more, preferably 5.0 or more, more preferably 6.0 or more, even more preferably 8.0 or more, particularly preferably 9.0 or more, and most preferably 10.0 or more. This improves the strength of the inner layer of the fiber, resulting in a spunbond nonwoven fabric with usable strength after thermal bonding. Furthermore, it prevents problems such as excessive softening of the fiber surface and adhesion to hot rollers during thermal bonding. On the other hand, the orientation parameter Oc of the core component of the core-sheath type composite fiber in the non-fusion-bonded portion is preferably 20.0 or less, more preferably 19.0 or less, and even more preferably 18.0 or less. This improves softness and suppresses excessive tensile stress concentration in the inner layer of the fiber during spinning, thus improving spinning stability. The orientation parameter Oc of the core component of the non-fusion-bonded core-sheath composite fiber can be controlled by the MFR, melting point, additives, mass ratio of the sheath component of the core-sheath composite fiber, and / or the spinning temperature and spinning speed described later.

[0076] Furthermore, the spunbond nonwoven fabric of the present invention preferably has a single melting peak temperature Tm (°C) in differential scanning calorimetry (DSC). It should be noted that, in the present invention, "the spunbond nonwoven fabric has a single melting peak temperature Tm (°C) in differential scanning calorimetry" means that the melting endothermic peak described in (3) of the following measurement method is substantially only observed as one peak. Therefore, problems such as low-melting-point components melting and adhering to the hot roller during thermal bonding are avoided, and the fibers can be firmly thermally bonded to each other at a sufficient temperature, thus easily obtaining a spunbond nonwoven fabric with practical strength.

[0077] Here, the melting peak temperature Tm (°C) of the spunbond nonwoven fabric obtained by differential scanning calorimetry (DSC) is the value calculated through the following steps.

[0078] (1) Collect 0.5 to 5 mg of spunbond nonwoven fabric fiber sheets as a sample.

[0079] (2) The differential scanning calorimetry (DSC) method was used to obtain the DSC curve by heating from room temperature to 200℃ at a heating rate of 20℃ / min.

[0080] (3) Read the peak temperature of the melting endothermic peak from the DSC curve and use it as the melting peak temperature Tm (°C) of the spunbond nonwoven fabric.

[0081] The spunbond nonwoven fabric of the present invention preferably has a surface roughness (SMD) of 1 μm to 3 μm on at least one side based on the KES method. The KES-based SMD is preferably 1.0 μm or more, more preferably 1.3 μm or more, and even more preferably 1.6 μm or more, thereby preventing the spunbond nonwoven fabric from becoming excessively dense, resulting in a deterioration in hand feel and loss of softness. On the other hand, the KES-based SMD is preferably 3.0 μm or less, more preferably 2.8 μm or less, and even more preferably 2.5 μm or less, thereby enabling the production of a spunbond nonwoven fabric with a smooth surface, low roughness, and excellent skin feel. The KES-based SMD can be controlled by appropriately adjusting the average single fiber diameter of the core-sheath type composite fibers, the texture of the spunbond nonwoven fabric, and / or the conditions of the thermal bonding described later (shape of the bonded portion, compression ratio, temperature, and linear pressure, etc.).

[0082] It should be noted that, in this invention, the surface roughness SMD based on the KES method is measured using the following values.

[0083] (1) Three test pieces with a width of 200mm × 200mm were collected at equal intervals along the width direction of the spunbond nonwoven fabric.

[0084] (2) Place the test piece on the test specimen stage.

[0085] (3) The surface of the test piece was scanned with a surface roughness measuring probe (material: φ0.5mm piano wire, contact length: 5mm) with a load of 10gf (0.098N) to measure the average deviation of the surface unevenness.

[0086] (4) The above measurements were performed on the longitudinal (length 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).

[0087] It should be noted that the longitudinal direction (length direction) of spunbond nonwoven fabric refers to the direction in which the spunbond nonwoven fabric is wound onto the winding device during the manufacturing process; it is also called the mechanical direction. The transverse direction relative to the longitudinal direction refers to the width direction of the spunbond nonwoven fabric.

[0088] The friction coefficient MIU of the spunbond nonwoven fabric based on the KES method of the present invention is preferably 0.01 to 0.30. A friction coefficient MIU of 0.30 or less, more preferably 0.20 or less, and even more preferably 0.15 or less, can improve the slipperiness of the nonwoven fabric surface, resulting in a spunbond nonwoven fabric with excellent skin feel. On the other hand, a friction coefficient MIU of 0.01 or more, more preferably 0.03 or more, and even more preferably 0.05 or more, can prevent the yarns from sliding against each other and deteriorating the texture uniformity when the spun yarns are collected in the collection conveyor. The friction coefficient MIU based on the KES method can be controlled by appropriately adjusting the additives in the polypropylene resin, the average single fiber diameter of the core-sheath composite fiber, the texture of the spunbond nonwoven fabric, and / or the conditions of thermal bonding described later (shape of the bonded portion, compression ratio, temperature, and linear pressure, etc.).

[0089] It should be noted that, in this invention, the friction coefficient MIU based on the KES method is measured using the following values.

[0090] (1) Three test pieces with a width of 200mm × 200mm were collected at equal intervals along the width direction of the spunbond nonwoven fabric.

[0091] (2) Place the test piece on the test specimen stage.

[0092] (3) Using a contact friction head with an applied load of 50gf (0.49N) (material: φ0.5mm piano wire (20 strands in parallel), contact area: 1cm²) 2 The surface of the test piece was scanned to determine the coefficient of friction.

[0093] (4) The above measurements were performed on the longitudinal (length 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 fourth decimal place was rounded off to obtain the friction coefficient MIU.

[0094] The MFR of the spunbond nonwoven fabric of the present invention is preferably from 10 g / 10 min to 300 g / 10 min. The MFR of the spunbond nonwoven fabric is preferably 10 g / 10 min or more, more preferably 15 g / 10 min or more, and even more preferably 20 g / 10 min or more. This allows for stable spinning even with fine fiber diameters, enabling the production of spunbond nonwoven fabrics with excellent skin feel, uniform texture, and excellent strength. On the other hand, the MFR of the spunbond nonwoven fabric is preferably 300 g / 10 min or less, more preferably 200 g / 10 min or less, and even more preferably 100 g / 10 min or less. This suppresses the reduction in strength and prevents operational problems such as excessive softening and adhesion to hot rollers during thermal bonding.

[0095] The MFR of the spunbond nonwoven fabric involved in this invention is determined using the value specified in ASTM D1238 (Method A). According to this standard, the MFR of the polypropylene resin is determined at a load of 2.16 kg and a temperature of 230 °C.

[0096] The preferred unit area weight of the spunbond nonwoven fabric of the present invention is 10 g / m². 2 ~100g / m 2 The preferred weight per unit area is 10 g / m². 2 The above, and more preferably 13g / m 2 The above, and more preferably, is 15g / m 2 Therefore, a spunbond nonwoven fabric with sufficient strength for practical use can be produced. On the other hand, the preferred weight per unit area is 100 g / m². 2 The following, or more preferably, is 50g / m 2 The following, and more preferably, is 30g / m 2 Therefore, it is possible to produce spunbond nonwoven fabric with softness suitable for use as a sanitary material.

[0097] It should be noted that, in this invention, the weight per unit area of ​​the spunbond nonwoven fabric is determined by measuring the value according to "6.2 Mass per unit area" of JIS L1913:2010 "General Nonwoven Fabrics Test Methods" through the following steps.

[0098] (1) Collect 3 test pieces of 20cm×25cm for each 1m width of the sample.

[0099] (2) Weigh each of them under standard conditions (g).

[0100] (3) Take its average value per 1m 2 mass (g / m 2 )express.

[0101] The thickness of the spunbond nonwoven fabric of the present invention is preferably 0.05 mm to 1.5 mm. A thickness of 0.05 mm to 1.5 mm is preferred, more preferably 0.08 mm to 1.0 mm, and even more preferably 0.10 mm to 0.8 mm, thereby providing softness and moderate cushioning, enabling the fabrication of spunbond nonwoven fabrics for hygiene materials, particularly suitable for use in diapers.

[0102] It should be noted that in this invention, the thickness of the spunbond nonwoven fabric is determined according to "5.1" of JIS L1906:2000 "General long fiber nonwoven fabric test method", through the following steps.

[0103] (1) Using a pressure head with a diameter of 10 mm, the thickness of 10 points within 1 m is measured at equal intervals of 0.01 mm in the width direction of the nonwoven fabric with a load of 10 kPa.

[0104] (2) Round the third decimal place of the average value of the above 10 places.

[0105] 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 Therefore, it is possible to prevent the dense stacking of fibers from compromising the softness of the spunbond nonwoven fabric. On the other hand, the apparent density is 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, producing spunbond nonwoven fabrics with sufficient strength and workability for practical use. Apparent density can be controlled by appropriately adjusting the average single fiber diameter of the core-sheath composite fibers and / or the thermal bonding conditions described later (shape of the bonded portion, compression ratio, temperature, and linear pressure, etc.).

[0106] It should be noted that, in this invention, apparent density (g / cm³) is... 3 Based on the unit area weight and thickness before rounding, the following formula is used to calculate the weight and thickness, rounding the third decimal place.

[0107] Apparent density (g / cm³)3 = [weight per unit area (g / m²)] 2 )] / [thickness (mm)]×10 -3 .

[0108] The stiffness of the spunbond nonwoven fabric of the present invention is preferably 65 mm or less. A stiffness of 65 mm or less is more preferably 60 mm or less, and even more preferably 55 mm or less, thereby obtaining a spunbond nonwoven fabric suitable for use as a hygiene material, and particularly suitable for use in diapers, exhibiting excellent softness. Furthermore, if the stiffness is extremely low, the workability is poor; therefore, a stiffness of 10 mm or more is preferred. The stiffness can be controlled by appropriately adjusting the MFR of the polypropylene resin, additives, the average single fiber diameter of the core-sheath composite fiber, the unit area weight of the spunbond nonwoven fabric, the ratio (Os / Oc) of the orientation parameter Os of the sheath component of the core-sheath composite fiber in the non-fusion portion to the orientation parameter Oc of the core component of the core-sheath composite fiber in the non-fusion portion, and / or the thermal bonding conditions described later (shape of the bonded portion, compression ratio, temperature, and linear pressure, etc.).

[0109] The product of tensile strength and elongation per unit area weight of the spunbond nonwoven fabric of the present invention is preferably 1.20 (N / 50mm) / (g / m²). 2 More preferably, it is 1.20 (N / 50mm) / (g / m³). 2 )~10.0(N / 50mm) / (g / m 2 The product of tensile strength and elongation per unit area weight is preferably 1.20 (N / 50mm) / (g / m²). 2 ) or more, preferably 1.3 (N / 50mm) / (g / m 2 ) or higher, and more preferably 1.4 (N / 50mm) / (g / m 2 The above can produce spunbond nonwoven fabrics that are soft, have a good skin feel and hand feel, and possess excellent strength even with low unit area weight. On the other hand, the tensile strength-elongation product per unit area weight is preferably 10.0 (N / 50mm) / (g / m²). 2 The following measures can prevent a decrease in the softness and damage to the hand feel of spunbond nonwoven fabric. The tensile strength-elongation product per unit area weight can be controlled by appropriately adjusting the MFR of the polypropylene resin, additives, the average single fiber diameter of the core-sheath composite fiber, the ratio (Os / Oc) of the orientation parameter Os of the sheath component of the core-sheath composite fiber in the non-fusion-bonded part of the spunbond nonwoven fabric to the orientation parameter Oc of the core component of the core-sheath composite fiber in the non-fusion-bonded part, and / or the spinning speed and thermal bonding conditions (shape of the bonded part, compression ratio, temperature, and linear pressure, etc.) described later.

[0110] It should be noted that, in this invention, the tensile strength and elongation product per unit area weight of spunbond nonwoven fabric is the value determined by the following steps according to "6.3 Tensile strength and elongation (ISO method)" of JIS L1913:2010 "General nonwoven fabric test methods".

[0111] (1) Take the long side as the longitudinal (length direction of the nonwoven fabric) and transverse (width direction of the nonwoven fabric) directions of the nonwoven fabric, and collect 3 test pieces of 50mm×300mm for every 1m width of the nonwoven fabric.

[0112] (2) Place the test piece on the tensile testing machine with a clamping interval of 200 mm.

[0113] (3) Perform a tensile test at a tensile speed of 100 mm / min and determine the maximum strength and elongation at the maximum strength. Here, the elongation is not converted to a percentage (%).

[0114] (4) Calculate the average value of the maximum strength and elongation at the maximum strength for each test piece, and calculate the tensile strength-elongation product per unit area weight based on the following formula, rounding the third decimal place.

[0115] Tensile strength-elongation product per unit area weight (N / 50mm) / (g / m²) 2 = [Average value of maximum strength (N / 50mm)] × [Average value of elongation at maximum strength (-)] / Weight per unit area (g / m²) 2 ).

[0116] The tensile strength of the spunbond nonwoven fabric per unit area weight in the transverse direction (width direction of the nonwoven fabric) is preferably 0.40 (N / 25mm) / (g / m²). 2 More preferably, it is 0.40 (N / 25mm) / (g / m³). 2 )~2.00(N / 25mm) / (g / m 2 The tensile strength per unit area weight is preferably 0.40 (N / 25mm) / (g / m²). 2 ) or more, preferably 0.60 (N / 25mm) / (g / m 2 ) or higher, and more preferably 0.80 (N / 25mm) / (g / m 2 A spunbond nonwoven fabric with usable strength can be produced. Furthermore, the transverse tensile strength per unit area weight is preferably 2.00 (N / 25mm) / (g / m²). 2The following parameters can prevent a decrease in the softness and damage to the hand feel of spunbond nonwoven fabric. It should be noted that the tensile strength of spunbond nonwoven fabric has both longitudinal (length direction) and transverse (width direction) properties. Generally, the transverse tensile strength is lower than the longitudinal tensile strength. Therefore, by ensuring that the transverse tensile strength per unit area weight is 0.4–2.00 (N / 25mm) / (g / m²), [further measures can be taken]. 2 This allows for the production of spunbond nonwoven fabrics with usable strength in the longitudinal direction as well. The transverse tensile strength per unit area weight can be controlled by appropriately adjusting the MFR of the aforementioned polypropylene resin, additives, the average single fiber diameter of the core-sheath composite fiber, the ratio (Os / Oc) of the orientation parameter Os of the sheath component of the core-sheath composite fiber in the non-fusion-bonded portion of the spunbond nonwoven fabric to the orientation parameter Oc of the core component of the core-sheath composite fiber in the non-fusion-bonded portion, and / or the spinning speed and thermal bonding conditions (shape of the bonded portion, compression ratio, temperature, and linear pressure, etc.) described later.

[0117] It should be noted that, in this invention, the transverse tensile strength per unit area weight of the spunbond nonwoven fabric is determined according to JIS L1913:2010 "General Nonwoven Fabrics Test Methods" "6.3 Tensile Strength and Elongation (ISO Method)" through the following steps.

[0118] (1) Take 3 test pieces of 25mm×200mm for every 1m width of nonwoven fabric with the long side as the transverse direction (width direction of nonwoven fabric).

[0119] (2) Place the test piece on the tensile testing machine with a clamping interval of 100 mm.

[0120] (3) Perform a tensile test at a tensile speed of 100 mm / min and determine the maximum strength.

[0121] (4) Calculate the average value of the maximum strength measured for each test piece, and calculate the tensile strength per unit area weight based on the following formula, rounding the third decimal place.

[0122] Transverse tensile strength per unit area weight ((N / 25mm) / (g / m)) 2 = [Average maximum strength (N / 25mm)] / Weight per unit area (g / m²) 2 ).

[0123] The preferred stress of the spunbond nonwoven fabric of the present invention at 5% longitudinal elongation per unit area weight is 0.40 (N / 25mm) / (g / m²). 2 More preferably, it is 0.40 (N / 25mm) / (g / m³). 2 )~2.00(N / 25mm) / (g / m 2The stress is preferably 0.40 (N / 25mm) / (g / m²) when the longitudinal elongation is 5% per unit area weight. 2 ) or more, preferably 0.50 (N / 25mm) / (g / m 2 ) or higher, and more preferably 0.60 (N / 25mm) / (g / m 2 The above-mentioned properties can suppress elongation caused by tension during the production of spunbond nonwoven fabric and processing for use as a sanitary material, resulting in stable production with a high yield. Furthermore, the stress at which 5% longitudinal elongation occurs per unit area weight is preferably 2.00 (N / 25mm) / (g / m²). 2 The following measures can prevent a decrease in the softness and damage to the hand feel of spunbond nonwoven fabric. The stress at 5% longitudinal elongation per unit area weight can be controlled by appropriately adjusting the MFR of the polypropylene resin, additives, the average single fiber diameter of the core-sheath composite fiber, the ratio (Os / Oc) of the orientation parameter Os of the sheath component of the core-sheath composite fiber in the non-fusion-bonded part of the spunbond nonwoven fabric to the orientation parameter Oc of the core component of the core-sheath composite fiber in the non-fusion-bonded part, and / or the spinning speed and thermal bonding conditions (shape of the bonded part, compression ratio, temperature, and linear pressure, etc.) described later.

[0124] It should be noted that, in this invention, the stress at 5% longitudinal elongation per unit area weight of spunbond nonwoven fabric is determined by the following steps according to JIS L1913:2010 "General Nonwoven Fabrics Test Methods" "6.3 Tensile Strength and Elongation (ISO Method)".

[0125] (1) Take three 25mm×200mm test pieces of nonwoven fabric for every 1m width, with the long side as the longitudinal direction of the nonwoven fabric (the length direction of the nonwoven fabric).

[0126] (2) Place the test piece on the tensile testing machine with a clamping interval of 100 mm.

[0127] (3) Perform a tensile test at a tensile speed of 100 mm / min and determine the stress at 5% elongation (stress at 5% elongation).

[0128] (4) Calculate the average value of the stress at 5% elongation for 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.

[0129] 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 ).

[0130] [Manufacturing method of spunbond nonwoven fabric]

[0131] The preferred embodiments of the method for manufacturing the spunbond nonwoven fabric of the present invention will now be described in detail.

[0132] The spunbond nonwoven fabric of the present invention is a long-fiber nonwoven fabric manufactured by the spunbonding method. In addition to its excellent productivity and mechanical strength, the spunbonding method can also suppress fuzzing and fiber shedding that are easily caused by short-fiber nonwoven fabrics. Furthermore, by stacking the captured spunbond nonwoven fiber web or the heat-pressed spunbond nonwoven fabric (both labeled S) in multiple layers of SS, SSS, and SSSS, productivity and texture uniformity are improved, making this a preferred embodiment.

[0133] 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 finally collected onto a moving web to obtain a nonwoven fiber web. Subsequently, the obtained nonwoven fiber web is subjected to a thermal bonding treatment to obtain spunbond nonwoven fabric.

[0134] There are no particular restrictions on the shape of the spinning spinneret or jet injector; various shapes such as round and rectangular can be used. However, since the amount of compressed air used is relatively small, the energy cost is excellent, it is less likely to cause yarn welding and friction, and the yarn is easier to open, the combination of rectangular spinneret and rectangular jet injector is preferred.

[0135] In this invention, thermoplastic resin is melted and metered in an extruder and fed to a spinning spinneret for manufacturing core-sheath type composite fibers, where it is spun into long fibers. The spinning temperature during the melting and spinning of the thermoplastic resin is preferably 180°C to 250°C, more preferably 200°C to 240°C, and even more preferably 220°C to 230°C. By setting the spinning temperature within the above range, a stable molten state can be formed, resulting in excellent spinning stability.

[0136] Next, the spun long fiber yarn is cooled. Methods for cooling the spun yarn include, for example, forcibly blowing cold air onto the yarn, naturally cooling it using the ambient temperature, and adjusting the distance between the spinning 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 ejection rate per orifice of the spinning spinneret, the spinning temperature, and the ambient temperature.

[0137] Next, compressed air ejected from the ejector is used to pull and stretch the cooled and solidified yarn.

[0138] 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, higher productivity is achieved, and the orientation and crystallization of the fibers are advanced, resulting in high-strength long fibers. As described above, the core-sheath type composite fiber of the present invention, with polypropylene resin as the main component, exhibits excellent spinning stability, and stable production can be carried out even at high spinning speeds.

[0139] Next, the obtained long fibers are captured onto a moving web to obtain a nonwoven fiber web.

[0140] In this invention, the nonwoven fiber web is temporarily bonded by abutting a hot flattening roller from one side of the web, which is also a preferred embodiment. This prevents the surface layer of the nonwoven fiber web from rolling up or being blown away during transport on the web, thus preventing deterioration of its texture and improving transportability from yarn collection to hot pressing.

[0141] Next, the obtained nonwoven fiber web is welded to form a welded section, thus obtaining the desired spunbond nonwoven fabric.

[0142] There are no particular limitations on the methods for welding nonwoven fiber webs. For example, methods for welding include using a hot embossing roller with engravings (concave and convex portions) on the surfaces of a pair of rollers, a hot embossing roller composed of a roller with a flat (smooth) surface and another roller with engravings (concave and convex portions) on its surface, and a hot calendering roller composed of a pair of flat (smooth) rollers. Methods for welding using ultrasonic vibration of a welding head include: hot air penetrating the nonwoven fiber web to soften or melt the surface of the core-sheath type composite fiber, thereby welding the fiber intersections together.

[0143] Preferably, a pair of hot embossing rollers with engravings (recessed or raised sections) on their respective roller surfaces are used, or a hot embossing roller composed of one roller with a flat (smooth) surface and another roller with engravings (recessed or raised sections) on its surface is used. This results in good productivity and allows for the setting of welded sections that improve the strength of spunbond nonwoven fabrics and non-welded sections that improve the hand feel and skin feel.

[0144] In order to obtain a sufficient hot pressing effect and prevent the engraving (recessed or recessed portion) of one embossing roller from being transferred to the surface of another roller, the preferred embodiment is to pair metal rollers together as the surface material of the hot embossing roller.

[0145] The embossing bonding area ratio using such a hot embossing roller is preferably 5% to 30%. By preferably having a bonding area ratio of 5% or more, more preferably 8% or more, and even more preferably 10% or more, a strength suitable for use as a spunbond nonwoven fabric can be obtained. On the other hand, by preferably having a bonding area ratio of 30% or less, more preferably 25% or less, and even more preferably 20% or less, a moderate softness suitable for use as a hygiene material, and particularly suitable for use in diapers, can be obtained. Even when ultrasonic bonding is used, the bonding area ratio is preferably within the same range.

[0146] The term "bonded area" here refers to the proportion of the bonded portion within the overall 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 (bonded portion) where the convex parts of the upper and lower rollers overlap and abut against the nonwoven fiber web within the overall spunbond nonwoven fabric. Similarly, in the case of thermal bonding using a roller with concave and convex surfaces and a flat roller, it refers to the proportion of the portion (bonded portion) where the convex parts of the rollers abut against the nonwoven fiber web within the overall spunbond nonwoven fabric. Furthermore, in the case of ultrasonic bonding, it refers to the proportion of the portion (bonded portion) that is thermally fused together through ultrasonic processing within the overall spunbond nonwoven fabric. When sufficient heat is applied to the bonded portion during thermal bonding, resulting in the complete fusion of the core-sheath type composite fibers, the areas of the bonded portion and the fused portion can be considered equal.

[0147] The shape of the bonding portion using hot embossing rollers and ultrasonic bonding is not particularly limited; for example, it can be circular, elliptical, square, rectangular, parallelogram, rhombus, regular hexagon, and regular octagon. Furthermore, the bonding portion is preferably present at a constant and uniform interval in both the length direction (transport direction) and width direction of the spunbond nonwoven fabric. This reduces the strength deviation of the spunbond nonwoven fabric.

[0148] A preferred embodiment is one where the surface temperature of the hot embossing roller during hot bonding is 30°C lower to 10°C higher (i.e., (Tms-30°C) to (Tms+10°C)) relative to the melting point (hereinafter sometimes referred to as Tms(°C)) of the thermoplastic resin constituting the sheath component. By preferably having the surface temperature of the hot roller at -30°C (i.e., (Tms-30°C), hereinafter the same) or higher, more preferably -20°C (Tms-20°C) or higher, and even more preferably -10°C (Tms-10°C) or higher, relative to the melting point of the aforementioned thermoplastic resin, a spunbond nonwoven fabric with usable strength can be obtained through strong hot bonding. In addition, by preferably setting the surface temperature of the hot embossing roller to +10°C (Tms+10°C) or less, more preferably +5°C (Tms+5°C) or less, and even more preferably +0°C (Tms+0°C) or less, relative to the melting point of the thermoplastic resin, excessive thermal bonding can be suppressed, resulting in a spunbond nonwoven fabric suitable for use as a hygiene material, and particularly suitable for use in diapers.

[0149] The linear pressure of the heat-embossing roller during heat bonding is preferably 50 N / cm to 500 N / cm. By preferably setting the roller's linear pressure to 50 N / cm or more, more preferably 100 N / cm or more, and even more preferably 150 N / cm or more, a spunbond nonwoven fabric with usable strength can be obtained through strong heat bonding. On the other hand, by preferably setting the linear pressure of the heat-embossing roller to 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 suitable for use as a hygiene material, and particularly suitable for use in diapers, can be obtained.

[0150] Furthermore, in this invention, for the purpose of adjusting the thickness of the spunbond nonwoven fabric, hot pressing can be performed using a hot calendering roller comprising a pair of upper and lower flat rollers before and / or after hot bonding using the aforementioned hot embossing roller. The term "pair of upper and lower flat rollers" refers to metal rollers or elastic rollers whose surfaces are not uneven. Metal rollers can be used in pairs, or metal rollers and elastic rollers can be used in pairs.

[0151] Furthermore, the so-called elastic roller mentioned here is a roller made of a material that is more elastic than a metal roller. Examples of elastic rollers include paper rollers made of paper, cotton, and aramid paper, as well as rollers made of resins such as urethane resins, epoxy resins, silicone resins, polyester resins, and hard rubber, and mixtures thereof.

[0152] The spunbond nonwoven fabric of this invention is widely used in hygiene materials, medical materials, household materials, and industrial materials due to its softness, excellent skin feel, uniform texture, sufficient strength for practical use, and excellent productivity. In particular, it is suitable as a base fabric for disposable diapers, sanitary products, and wet wipes in hygiene materials, and as a base fabric for protective clothing and surgical gowns in medical materials.

[0153] Example

[0154] The spunbond nonwoven fabric of the present invention will now be specifically described based on embodiments. However, the present invention is not limited to these embodiments. It should be noted that, in the determination of various physical properties, those not specifically described were determined based on the methods described above.

[0155] [Determination Method]

[0156] (1) Melt flow rate (MFR) of resin (g / 10 min):

[0157] The MFR of the resin was determined by the above method under the conditions of 2.16 kg load and 230 °C.

[0158] (2) Average single fiber diameter (μm) of the core-sheath type composite fibers constituting spunbond nonwoven fabric:

[0159] The measurements were performed using the "VHX-D500" electron microscope manufactured by KEYENCE Co., Ltd., using the method described above.

[0160] (3) Spinning speed (m / min):

[0161] Based on the above average single fiber diameter and resin solid density (0.91 g / cm³), 3 The mass per 10,000 m length is taken as the average single fiber fineness (dtex), and the result is calculated by rounding to the second decimal place. Based on the average single fiber fineness and the amount of resin ejected from the spinning spinneret under each condition (hereinafter referred to as the single-hole ejection rate) (g / min), the spinning speed is calculated to two significant figures based on the following formula.

[0162] Spinning speed (m / min) = (10000 × [single orifice ejection rate (g / min)]) / [average single fiber fineness (dtex)].

[0163] (4) Orientation parameters of core-sheath type composite fibers in the non-fusion-bonded part of spunbond nonwoven fabric:

[0164] 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 were as follows.

[0165] • Measurement mode: Micro Raman (polarization measurement)

[0166] • Objective lens: ×100

[0167] • Beam diameter: 1μm

[0168] • Light source: Ar + Laser / 514.5nm

[0169] Laser power: 60mW

[0170] • Diffraction grating: Single 1800gr / mm

[0171] • Cross-shaped slit: 100μm

[0172] • Detector: CCD / Jobin Yvon 1024×256.

[0173] (5) Melting peak temperature Tm (°C) of spunbond nonwoven fabric:

[0174] The measuring apparatus used was a Perkin-Elmer DSC8500, and the measurements were performed using the method described above. The measurement conditions were as follows.

[0175] • Atmosphere inside the apparatus: Nitrogen (20 mL / min)

[0176] • Temperature / heat correction: High-purity indium (Tm = 156.61℃, ΔHm = 28.70 J / g)

[0177] Temperature range: 20℃~200℃

[0178] • Heating rate: 20℃ / minute

[0179] • Sample size: Approximately 0.5–4 mg

[0180] • Sample container: Aluminum standard container.

[0181] It should be noted that when a single melting peak temperature Tm (°C) is observed for spunbond nonwoven fabric in the table, this value is recorded; when multiple melting peak temperatures Tm (°C) are observed, each value is recorded.

[0182] In addition, regarding the melting point of the polypropylene resin used in the examples, the polypropylene resin used was collected, and the melting peak temperature was measured in the same manner as the above-described method for measuring the melting peak temperature, as the largest (highest temperature) melting peak temperature obtained.

[0183] (6) Longitudinal stiffness (mm) of spunbond nonwoven fabric:

[0184] Regarding the stiffness of spunbond nonwoven fabrics, the method described in "6.7.4 Gurley Method" of "6.7.7 Stiffness (JIS Method and ISO Method)" of JIS L1913:2010 "General Test Methods for Nonwoven Fabrics" is used to determine the stiffness in the longitudinal direction (length direction). It should be noted that, regardless of the type of spunbond nonwoven fabric, the stiffness in the longitudinal direction (length direction) is greater than the stiffness in the transverse direction (width direction). The lower the longitudinal stiffness, the better the softness; a stiffness of 65mm or less is considered acceptable.

[0185] (7) Tensile strength per unit area weight of spunbond nonwoven fabric (N / 25mm / (g / m)) 2 )):

[0186] The measuring apparatus used was an A&D Corporation "RTG-1250", and the measurement was performed using the method described above. The higher the transverse tensile strength per unit area weight, the higher the longitudinal strength. (0.80 (N / 25mm) / (g / m)) 2 The above is considered qualified.

[0187] (8) Tensile strength and elongation product per unit area weight of spunbond nonwoven fabric (N / 50mm / (g / m²)) 2 )):

[0188] The measuring apparatus used was an A&D Corporation "RTG-1250", and the measurements were performed using the method described above. A larger tensile strength-elongation product per unit area weight indicates a softer spunbond nonwoven fabric and a superior balance between skin feel, hand feel, and strength. The product was 1.20 (N / 50mm) / (g / m²). 2 The above is considered qualified.

[0189] (Example 1)

[0190] Polypropylene resin containing a homopolymer with a melt flow rate (MFR) of 35 g / 10 min and a melting point of 163 °C was used as the core component, and polypropylene resin containing a homopolymer with an MFR of 60 g / 10 min and a melting point of 163 °C was used as the sheath component. These components were melted separately in an extruder and spun at a spinning temperature of 235 °C and a single-hole extrusion rate of 0.40 g / min from a spinning spinneret with an orifice diameter of 0.40 mm and an orifice depth of 0.8 mm to produce concentric core-sheath composite fibers with a sheath component ratio of 30% by mass. After the spun yarn was cooled and solidified, it was drawn and stretched using compressed air in an ejector and collected onto a moving web to form a spunbond nonwoven fiber web containing polypropylene long fibers. It should be noted that, regarding the characteristics of the core-sheath composite fibers constituting the formed nonwoven fiber web, the average single fiber diameter is 14.0 μm, and the corresponding spinning speed is 2900 m / min. Regarding spinnability, no filament breakage was observed during 1 hour of spinning, indicating good spinnability.

[0191] 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 the conditions of a linear pressure of 500 N / cm and a heat bonding temperature of 140℃, resulting in a unit area weight of 15 g / m² for both welded and non-welded sections. 2 spunbond nonwoven fabric.

[0192] (Upper Roller): A metal embossing roller engraved with water droplet patterns, with an adhesion area of ​​11%.

[0193] (Lower Roller): Metal Flat Roller

[0194] The resulting spunbond nonwoven fabric has a uniform texture and excellent skin feel. The evaluation results are shown in Table 1.

[0195] (Example 2)

[0196] Set the weight per unit area to 10g / m² 2 In addition, a spunbond nonwoven fabric with welded and non-welded portions 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 14.0 μm, and the corresponding spinning speed was 2900 m / min. Regarding spinnability, no fiber breakage was observed during 1 hour of spinning, indicating good spinnability. The obtained spunbond nonwoven fabric had a uniform texture and excellent skin feel. The evaluation results are shown in Table 1.

[0197] (Example 3)

[0198] Set the weight per unit area to 30g / m² 2 In addition, a spunbond nonwoven fabric with welded and non-welded portions 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 14.0 μm, and the corresponding spinning speed was 2900 m / min. Regarding spinnability, no fiber breakage was observed during 1 hour of spinning, indicating good spinnability. The resulting spunbond nonwoven fabric had a uniform texture and excellent skin feel. The evaluation results are shown in Table 1.

[0199] (Example 4)

[0200] The sheath component ratio was set to 50% by mass, and the thermal bonding temperature was set to 145°C. Otherwise, a spunbond nonwoven fabric with welded and non-welded portions 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 14.0 μm, and the corresponding spinning speed was 2900 m / min. Regarding spinnability, no fiber breakage was observed during 1 hour of spinning, indicating good spinnability. The resulting spunbond nonwoven fabric had a uniform texture and excellent skin feel. The evaluation results are shown in Table 1.

[0201] (Example 5)

[0202] The pressure of the compressed air in the ejector was adjusted, and otherwise, a spunbond nonwoven fabric with welded and non-welded sections 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 11.2 μm, and the corresponding spinning speed was 4400 m / min. Regarding spinnability, no fiber breakage was observed during 1 hour of spinning, indicating good spinnability. The obtained spunbond nonwoven fabric had a uniform texture and excellent skin feel. The evaluation results are shown in Table 1.

[0203] (Example 6)

[0204] Polypropylene resin containing a homopolymer with an MFR of 170 g / 10 min and a melting point of 161 °C was used as the sheath component. Otherwise, a spunbond nonwoven fabric with welded and non-welded sections 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 14.0 μm, and the corresponding spinning speed was 2900 m / min. Regarding spinnability, no fiber breakage was observed during 1 hour of spinning, indicating good spinnability. The resulting spunbond nonwoven fabric had a uniform texture and excellent skin feel. The evaluation results are shown in Table 1.

[0205] (Example 7)

[0206] Polypropylene resin containing a homopolymer with an MFR of 30 g / 10 min and a melting point of 148 °C was used as the sheath component. The thermal bonding temperature using a pair of hot embossing rollers was set to 130 °C. Otherwise, a spunbond nonwoven fabric with welded and non-welded portions 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 14.0 μm, and the corresponding spinning speed was 2900 m / min. Regarding spinnability, no fiber breakage was observed during 1 hour of spinning, indicating good spinnability. The resulting spunbond nonwoven fabric had a uniform texture and excellent skin feel. The evaluation results are shown in Table 1.

[0207] (Example 8)

[0208] Polypropylene resin containing a homopolymer with an MFR of 20 g / 10 min and a melting point of 163 °C was used as the core component. Otherwise, a spunbond nonwoven fabric with welded and non-welded sections 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 14.0 μm, and the corresponding spinning speed was 2900 m / min. Regarding spinnability, no fiber breakage was observed during 1 hour of spinning, indicating good spinnability. The resulting spunbond nonwoven fabric had a uniform texture and excellent skin feel. The evaluation results are shown in Table 1.

[0209] (Comparative Example 1)

[0210] Using only a single-component fiber made from a homopolymer of polypropylene resin with a melt flow rate (MFR) of 35 g / 10 min and a melting point of 163 °C, and with the heat-bonding temperature set at 150 °C, a spunbond nonwoven fabric with welded and non-welded portions was obtained using the same method as in Example 1. Regarding the characteristics of the fibers constituting the formed spunbond nonwoven fiber web, the average single fiber diameter was 14.0 μm, and the corresponding spinning speed was 2900 m / min. Regarding spinnability, two fiber breaks occurred during one hour of spinning. The evaluation results of the obtained spunbond nonwoven fabric are shown in Table 1. It should be noted that when the heat-bonding temperature was set to 155 °C, the sheet ends adhered to the hot rollers, resulting in poor handling.

[0211] (Comparative Example 2)

[0212] Polypropylene resin containing a homopolymer with an MFR of 45 g / 10 min and a melting point of 163 °C was used as the sheath component, and the thermal bonding temperature was set to 150 °C. Otherwise, a spunbond nonwoven fabric with welded and non-welded portions 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 14.0 μm, and the corresponding spinning speed was 2900 m / min. Regarding spinnability, no fiber breakage was observed during 1 hour of spinning, indicating good spinnability. The evaluation results of the obtained spunbond nonwoven fabric are shown in Table 1.

[0213] [Table 1]

[0214]

[0215] The spunbond nonwoven fabrics in Examples 1-8, which contain core-sheath composite fibers with polypropylene resin as the main component, have excellent strength, softness, and skin feel even with low unit area weight. The ratio of the orientation parameter Os of the sheath component of the non-fusion-bonded core-sheath composite fiber to the orientation parameter Oc of the core component of the non-fusion-bonded core-sheath composite fiber (Os / Oc) satisfies 0.10 to 0.90.

[0216] On the other hand, the spunbond nonwoven fabric containing only a single polypropylene resin in Comparative Example 1 and the spunbond nonwoven fabric with an Os / Oc greater than 0.90 in Comparative Example 2 are inferior in terms of strength and softness.

Claims

1. Spunbond nonwoven fabric, which is a spunbond nonwoven fabric containing core-sheath type composite fibers with polypropylene resin as the main component, wherein, The spunbond nonwoven fabric has a welded portion and a non-welded portion, wherein the ratio (Os / Oc) of the orientation parameter Os of the sheath component of the core-sheath composite fiber in the non-welded portion to the orientation parameter Oc of the core component of the core-sheath composite fiber in the non-welded portion is 0.10 to 0.

90.

2. The spunbond nonwoven fabric according to claim 1, wherein, The orientation parameter Os of the sheath component of the core-sheath type composite fiber in the non-fusion section is 1.0 or higher and 8.0 or lower.

3. The spunbond nonwoven fabric according to claim 1 or 2, wherein, The spunbond nonwoven fabric has a single melting peak temperature Tm in differential scanning calorimetry, and the unit of the melting peak temperature Tm is °C.

4. The spunbond nonwoven fabric according to claim 1 or 2, wherein, The tensile strength-elongation product per unit area weight of the spunbond nonwoven fabric is 1.20 (N / 50mm) / (g / m²). 2 )above.

5. The spunbond nonwoven fabric according to claim 1 or 2, wherein, The melt flow rate of polypropylene resin with sheath component is 10 g / 10 min to 200 g / 10 min greater than that of polypropylene resin with core component.

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