Spunbonded nonwoven fabric and sanitary material comprising the same

Abstract

A spunbond nonwoven fabric in which one surface (A) is formed of fibers (Fa) containing a propylene-based resin and the other surface (B) is formed of fibers (Fb) containing a propylene-based resin, the spunbond nonwoven fabric having a crystalline melting heat of 30 J / g or more and 98 J / g or less in differential scanning calorimetry and satisfying the following formula (1). Db / Da ≥ 1.1 … (1) Here, Da is the average single fiber diameter (μm) of the fibers (Fa) and Db is the average single fiber diameter (μm) of the fibers (Fb). A spunbond nonwoven fabric having excellent softness in addition to water absorption and quick drying properties for maintaining comfort when worn, and a sanitary material using the same are provided.

Description

Technical Field

[0001] The present invention relates to a spunbond nonwoven fabric that, in addition to having excellent absorbency and quick-drying properties for maintaining comfort when worn, also has excellent softness, and a sanitary material comprising at least a portion of the spunbond nonwoven fabric. Background Technology

[0002] In recent years, various studies have been conducted on spunbond nonwoven fabrics used in disposable diapers, sanitary napkins, masks, and other hygiene materials to further improve wearing comfort. In particular, for surface components that come into direct contact with the skin, there is a requirement to balance absorbency (rapidly absorbing moisture) and quick-drying properties (allowing absorbed moisture to be transferred from the outermost layer to prevent excessive moisture and maintain a dry state), i.e., "absorbency and quick-drying properties." Furthermore, the degree of skin-touch comfort is also an important factor in determining the quality of nonwoven fabrics; nonwoven fabrics with high "softness" and a pleasant skin-touch feel are required.

[0003] As a means of imparting water absorption to nonwoven fabrics, it is effective to use nonwoven fabrics containing hydrophilic fibers or to perform hydrophilic treatments on nonwoven fabrics. However, since these techniques do not have the function of transferring the absorbed water from the outermost surface layer, there is a problem of poor quick-drying properties.

[0004] Against this background, for the purpose of imparting water-absorbing and quick-drying properties to nonwoven fabrics, a laminated nonwoven fabric has been proposed, which has a laminated structure of fiber layers containing long fibers. The laminated nonwoven fabric is composed of a hydrophobic layer containing hydrophobic fibers and a hydrophilic layer containing hydrophilic fibers with inter-fiber spacing or flatness within a specific range, and is formed by placing the hydrophobic layer on the surface of the nonwoven fabric (see Patent Document 1).

[0005] In addition, as a technology to impart softness to nonwoven fabrics, the following have been proposed: a spunbond nonwoven fabric comprising a composition of an propylene polymer having a specific melting point and an propylene polymer containing a specific fatty acid amide compound (see Patent Document 2); or a spunbond nonwoven fabric manufactured by blending an elastic system random copolymer into polypropylene and blending a masterbatch containing an amide compound (see Patent Document 3).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2018 / 167881

[0009] Patent Document 2: International Publication No. 2014 / 050955

[0010] Patent Document 3: Japanese Patent Application Publication No. 2011-58157 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] In the technology of Patent Document 1, a hydrophilic gradient is formed in the thickness direction of the nonwoven fabric, so that even a surface with a hydrophobic layer on the outermost layer exhibits a certain degree of water absorption. However, since the outermost surface of the nonwoven fabric is a hydrophobic layer, its performance is insufficient for absorbing large amounts of water such as urine. In addition, liquid residue is easily generated, resulting in insufficient quick-drying properties. Furthermore, poor softness is also a problem.

[0013] On the other hand, the technologies in Patent Documents 2 and 3 both relate to a spunbond nonwoven fabric using polypropylene modified through polymer blending or additives. However, the water absorption and quick-drying properties of the spunbond nonwoven fabric are insufficient.

[0014] Therefore, the object of the present invention is to provide a spunbond nonwoven fabric that has excellent softness in addition to its absorbency and quick-drying properties for maintaining comfort when worn, and a sanitary material comprising at least a portion of the spunbond nonwoven fabric.

[0015] Technical means to solve the problem

[0016] To achieve the aforementioned objective, the spunbond nonwoven fabric of the present invention has the following structure. That is,

[0017] A spunbond nonwoven fabric, wherein one surface (A) is composed of fibers (Fa) containing acrylic resin and the other surface (B) is composed of fibers (Fb) containing acrylic resin, wherein the spunbond nonwoven fabric has a heat of melting of crystallization of 30 J / g or more and 98 J / g or less in differential scanning calorimetry, and satisfies the following formula (1).

[0018] Db / Da≧1.1…(1)

[0019] Here, Da is the average single fiber diameter (μm) of the fiber (Fa), and Db is the average single fiber diameter (μm) of the fiber (Fb).

[0020] In addition, the sanitary material of the present invention is a sanitary material comprising, in at least a portion, the spunbond nonwoven fabric.

[0021] The spunbond nonwoven fabric of the present invention is preferably a acrylic resin in which at least a portion of the acrylic resin is copolymerized with ethylene units at a concentration of 2 mol% or more and 30 mol% or less.

[0022] The spunbond nonwoven fabric of the present invention is preferably an acrylic resin in which at least a portion thereof is an isotactic pentad fraction of 50% or more and 92% or less.

[0023] The spunbond nonwoven fabric of the present invention preferably contains at least a portion of the acrylic resin as an acrylic resin containing 0.5% by mass or more of a fatty acid amide compound.

[0024] The spunbond nonwoven fabric of the present invention preferably has a contact angle of 30° or less between the surface (A) and water and the surface (B) and water.

[0025] The spunbond nonwoven fabric of the present invention is preferably an irregularly shaped fiber in which at least a portion of the fibers (Fa) and / or fibers (Fb) have a plurality of convex portions in the fiber cross-section and the lobularity of the fiber cross-section is more than 5.0%.

[0026] The sanitary material of the present invention is preferably configured such that the surface (B) is disposed facing the wearer's skin.

[0027] The effects of the invention

[0028] The spunbond nonwoven fabric of the present invention can be used as part of hygiene materials such as diapers, sanitary napkins, gauze, bandages, masks, gloves, and adhesive bandages. Attached Figure Description

[0029] Figure 1 This is a conceptual diagram showing an example of a cross-section of the spunbond nonwoven fabric containing acrylic resin that constitutes the present invention.

[0030] Figure 2 This is an example of a cross-section of the spunbond nonwoven fabric containing acrylic resin that constitutes the present invention, and a conceptual diagram illustrating a method for measuring the lobed structure. Detailed Implementation

[0031] In the spunbond nonwoven fabric of the present invention, one surface (A) is composed of fibers (Fa) containing acrylic resin, and the other surface (B) is composed of fibers (Fb) containing acrylic resin, and the heat of melting of crystallization in the differential scanning calorimetry is more than 30 J / g and less than 98 J / g, and satisfies the following formula (1).

[0032] Db / Da≧1.1…(1)

[0033] Here, Da is the average single fiber diameter (μm) of the fiber (Fa), and Db is the average single fiber diameter (μm) of the fiber (Fb).

[0034] The following is a detailed description of its constituent elements. This invention is not limited to the scope of the following description unless it departs from its spirit. Furthermore, in this invention, "surface (A)" refers to the surface of the spunbond nonwoven fabric with the smaller average single fiber diameter of the fibers used in its construction, as measured by the method described later.

[0035] [Fibers containing acrylic resins]

[0036] In the spunbond nonwoven fabric of the present invention, one surface (A) is composed of fibers (Fa) containing acrylic resin, and the other surface (B) is composed of fibers (Fb) containing acrylic resin. That is, both one surface (A) and the other surface (B) are composed of fibers containing acrylic resin. In other words, the spunbond nonwoven fabric of the present invention is a laminated structure of a nonwoven layer composed of fibers (Fa) containing acrylic resin and a nonwoven layer composed of fibers (Fb) containing acrylic resin.

[0037] In this invention, "propylene resin" refers to a resin having propylene units as the main repeating units. By using such propylene resin, spunbond nonwoven fabrics with low cost and excellent softness can be produced.

[0038] In this invention, propylene-based resins may include, for example, homopolymers of propylene, copolymers of propylene and ethylene, copolymers of propylene and various α-olefins, and mixtures of these polymers. Here, α-olefins refer to hydrocarbons with the double bond at the α-position, such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-hexadecene, and 4-methyl-1-pentene. Among these, copolymers of propylene and ethylene are preferred for their excellent process stability during spinning and for the superior softness of the resulting fibers. Furthermore, the propylene-based resin may also contain inorganic substances such as titanium dioxide, silicon dioxide, barium oxide, and calcium carbonate; colorants such as carbon black, dyes or pigments; flame retardants; fluorescent whitening agents; antioxidants; or various additives such as ultraviolet absorbers.

[0039] In this invention, the acrylic resin is preferably a acrylic resin in which at least a portion is copolymerized with ethylene units at a rate of 2 mol% or more and 30 mol% or less. By setting the copolymerization rate of the ethylene units preferably to 2 mol% or more, more preferably 3 mol% or more, the process stability in the spinning process is improved, and a spunbond nonwoven fabric with excellent softness is obtained. In addition, by setting the copolymerization rate of the ethylene units preferably to 30 mol% or less, more preferably 25 mol% or less, and even more preferably 20 mol% or less, the stickiness of the spunbond nonwoven fabric can be suppressed, resulting in a spunbond nonwoven fabric with excellent tactile feel.

[0040] The copolymerization rate (mol%) of the ethylene units mentioned here is calculated as follows.

[0041] (1) Take 50 mg of fiber containing acrylic resin from the surface (A) or surface (B) of spunbond nonwoven fabric, add 1 mL of a mixed solution of o-dichlorobenzene and benzene-d6 (the form of which the hydrogen of benzene is replaced by deuterium) (in a volume ratio of o-dichlorobenzene: benzene-d6 = 9:1), and heat to 135°C.

[0042] (2) Perform treatment on the obtained solution. 13 C-NMR ( 13 C-Nuclear Magnetic Resonance, 13 The area of ​​the peak originating from the propylene unit and the area of ​​the peak originating from the ethylene unit were calculated based on the NMR spectrum (C-NMR).

[0043] (3) Calculate the molar ratio of ethylene units based on the peak area ratio of propylene units to ethylene units, and round it to the first decimal place.

[0044] In this invention, the acrylic resin is preferably an acrylic resin in which at least a portion thereof has a mesoopentad fraction of 50% or more and 92% or less. By setting the mesoopentad fraction to preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more, the stickiness of the spunbond nonwoven fabric can be suppressed, resulting in a spunbond nonwoven fabric with excellent tactile feel. In addition, by setting the mesoopentad fraction to preferably 92% or less, more preferably 90% or less, the process stability in the spinning process is improved, and a spunbond nonwoven fabric with excellent softness can be produced.

[0045] The percentage of meso pentatonic tuples mentioned here is the value obtained as follows.

[0046] (1) Take 50 mg of fibers containing acrylic resin from the surface (A) or surface (B) of spunbond nonwoven fabric, add 1 mL of a mixed solution of o-dichlorobenzene and benzene-d6 (in a volume ratio of o-dichlorobenzene:benzene-d6 = 9:1), and heat to 135°C.

[0047] (2) Perform treatment on the obtained solution. 13 C-NMR determination.

[0048] (3) Based on the method described in Zambelli et al., Macromolecules, Vol. 8, p. 687 (1975), for the obtained NMR spectrum originating from methyl, the peaks appearing above 21.70 ppm and below 21.90 ppm are taken as the peaks originating from the isotactic pentagonal chain, and the peak intensity originating from the isotactic pentagonal chain is calculated as a percentage relative to the sum of the total peak intensities originating from methyl, and the fraction of the racemic pentagonal chain is calculated and rounded to the first decimal place.

[0049] In this invention, the acrylic resin is preferably an acrylic resin containing at least 0.5% by mass or more of a fatty acid amide compound. By setting the content of the fatty acid amide compound to preferably 0.5% by mass or more, more preferably 0.7% by mass or more, and even more preferably 1.0% by mass or more, the fatty acid amide compound acts as a lubricant on the fiber surface, thus resulting in a spunbond nonwoven fabric with excellent tactile feel. Furthermore, there is no particular upper limit to the content of the fatty acid amide compound in this invention; from the viewpoint of cost or productivity, it is preferably 5.0% by mass or less.

[0050] In this invention, when the propylene resin contains the fatty acid amide compound, the fatty acid amide compound preferably has 15 or more and 50 or less carbon atoms. Examples of fatty acid amide compounds with 15 or more and 50 or less carbon atoms include: saturated fatty acid monoamide compounds, saturated fatty acid diamide compounds, unsaturated fatty acid monoamide compounds, and unsaturated fatty acid diamide compounds. Furthermore, the "carbon number" in this invention refers to the number of carbon atoms contained in the molecule. Specifically, examples include: palmitamide, palmitoleamide, stearamide, oleamide, transoleamide, shea butteramide, linoleic acid amide, linolenic acid amide, pinolenic acid amide, oleostearamide, octadecanoatetraenoic acid amide, octadecanoatepentanoic acid amide, arachidic acid amide, cod oleamide, eicosenoic acid amide, eicosadienoic acid amide, medeamide, eicostrienoic acid amide, arachidic acid amide, eicosadienoic acid amide, eicosadienoic acid amide, icosenoic acid amide, icosenoic acid amide, icosenoic acid amide, icosenoic acid amide, icosenoic acid amide, icosenoic acid amide, icosenoic acid amide, icosenoic acid amide, sine acid amide, icosenoic acid amide, adrenal acid amide, osbond acid amide, gibberellinamide, icosenoic acid amide, icosenoic acid amide, icosenoic acid amide, nisinic acid amide. Fatty acid amides, including ethyl didecanoic acid amide, ethyl dilauric acid amide, methylene dilauric acid amide, ethyl distearic acid amide, ethyl dioleoic acid amide, ethyl dihydroxystearic acid amide, ethyl didodecanoic acid amide, ethyl disinic acid amide, hexamethylene distearic acid amide, hexamethylene didodecanoic acid amide, hexamethylene hydroxystearic acid amide, distearate adipamide, distearate sebacic acid amide, and hexamethylene dioleoic acid amide, can be used in various combinations. By setting the carbon number of the fatty acid amide compound to preferably 15 or more, more preferably 23 or more, and even more preferably 30 or more, excessive precipitation of fatty acid amide compounds on the fiber surface can be suppressed, resulting in excellent spinning properties and processing stability, while maintaining high productivity. Furthermore, by setting the number of carbon atoms in the fatty acid amide compound to preferably 50 or less, more preferably 45 or less, and even more preferably 42 or less, the fatty acid amide compound is appropriately precipitated on the fiber surface, thus resulting in a spunbond nonwoven fabric with excellent tactile feel.

[0051] In this invention, the fibers (Fa) and / or fibers (Fb) containing acrylic resins can be single-component fibers or composite fibers composed of two or more resins. When the acrylic resin-containing fibers are composite fibers, the composite form is not particularly limited as long as it does not impair the effects of this invention, and can be suitably selected from core-sheath type, island type, side-by-side type, eccentric core-sheath type, blended type, etc. Furthermore, when the acrylic resin fibers are made into composite fibers, from the viewpoint of process stability or softness in the manufacturing process, the resin used with the acrylic resin is preferably an olefin resin with ethylene or propylene units as the main repeating units. For example, when making core-sheath type composite fibers, the core component can be the acrylic resin and the sheath component can be the olefin resin; or when making island type composite fibers, the island component can be the olefin resin and the island component can be the acrylic resin, etc. The spunbond nonwoven fabric with excellent tactile feel is produced by using a core component made of propylene resin and a sheath component made of olefin resin with ethylene units as the main repeating units.

[0052] In this invention, the fibers (Fa) and / or fibers (Fb) containing acrylic resin preferably have at least a portion having multiple protrusions in their cross-section. By having multiple protrusions in the fiber cross-section, grooves are formed on the fiber sidewalls in a continuous direction along the fiber axis, and the groove portions become liquid passageways, thus resulting in a spunbond nonwoven fabric with excellent water absorption.

[0053] The phrase "having multiple convex portions in the fiber cross-section" as used herein refers to the cross-sectional shape described below, and its application is... Figure 1 Please provide an explanation.

[0054] Figure 1 An example of a fiber cross-section with multiple convex portions is shown. In this fiber cross-section, at least two points (S) on the outline (C1) passing through the cross-section can be drawn. 11 S 12 A straight line, and S 11 With S 12 The line segment between these two points does not pass through the profile (C1) (e.g., L). 11 The cross-sectional shape of ).

[0055] In this invention, as described above, the fibers (Fa) and / or fibers (Fb) containing acrylic resin preferably have at least a portion having multiple protrusions in the fiber cross-section, and the lobed structure of the fiber cross-section is 5.0% or more. By setting the lobed structure of the fiber cross-section preferably to 5.0% or more, more preferably 10.0% or more, the moisture diffusion efficiency in the planar direction of the spunbond nonwoven fabric becomes higher, thus resulting in a spunbond nonwoven fabric with excellent water absorption. Furthermore, there is no particular upper limit to the lobed structure, but in terms of suppressing the peeling of the protrusions caused by friction during manufacturing and obtaining a high-quality spunbond nonwoven fabric, it is preferably 60.0% or less.

[0056] The lobed structure of the fiber profile described herein is a value determined using the method described below. Figure 2 Please provide a detailed explanation.

[0057] Figure 2 An example of a cross-section of the spunbond nonwoven fabric comprising acrylic resin is shown.

[0058] First, a cross-sectional image of the fibers constituting the spunbond nonwoven fabric was taken using a scanning electron microscope at a magnification that allows observation of a single fiber. Using the captured fiber cross-sectional image, an outline traversing the cross-section was drawn within the same section. Figure 2 Two points on C2) Figure 2 S 21 S 22 A straight line, and S 21 With S 22 The line segment between these two points does not pass through the outline (C2) (e.g., Figure 2 L 21 Measurement point S 21 With point S 22 The distance between them is 'a'. Next, draw the line (L) with respect to the line. 21 Parallel and in the contour (C2) at point S 21 With point S 22 There is only one point of intersection between them (V) 21 ) lines (e.g., L) 22 Then, the straight line (L) is measured. 21 ) and the straight line (L) 22 The distance b between (a and b) is then calculated. The percentage of b relative to a (b / a × 100) is then determined. The above values ​​are measured on 20 randomly selected fibers constituting the same surface. A simple numerical average is calculated, rounded to two decimal places, and this value is taken as the lobed structure (%) described in this invention.

[0059] Furthermore, in the spunbond nonwoven fabric of the present invention, it is preferable that the contact angle between the acrylic resin-containing fiber (Fa) and water, and the contact angle between the acrylic resin-containing fiber (Fb) and water, are both less than 90°. The contact angle between the acrylic resin-containing fiber and water is an indicator different from the contact angle between the surface of the spunbond nonwoven fabric and water, as described later. If the contact angle is 90° or more, it is hydrophobic; if it is less than 90°, the acrylic resin-containing fiber is hydrophilic. Moreover, the contact angle between the acrylic resin-containing fiber and water of the present invention is determined, for example, by measuring the angle between the air interface of the droplet and the fiber when a very small amount (15 μL) of water droplet falls onto the fiber surface using an automatic contact angle meter equipped with an inkjet water droplet ejection unit.

[0060] Furthermore, in this invention, without departing from its spirit, the thermoplastic resin or fiber profiles used to construct the acrylic resin-containing fiber (Fa) on surface (A) and the acrylic resin-containing fiber (Fb) on surface (B) may be the same or different.

[0061] [Surface (A) and Surface (B)]

[0062] In the spunbond nonwoven fabric of the present invention, the surface (A) is composed of the fibers (Fa) containing acrylic resin.

[0063] The spunbond nonwoven fabric of the present invention preferably contains long fibers as in conventional methods, i.e., the fibers (Fa) are preferably long fibers. This is because by including long fibers, spunbond nonwoven fabrics that combine high productivity with excellent mechanical properties can be easily produced.

[0064] The average single fiber diameter (Da) of the acrylic resin-containing fibers (Fa) constituting the surface (A) of the present invention is preferably 1.0 μm or more and 25.0 μm or less. By setting the average single fiber diameter (Da) preferably to 1.0 μm or more, more preferably 3.0 μm or more, and even more preferably 5.0 μm or more, when used as a hygiene material, the fiber arrangement is not too dense, and when used as a diaper, moisture is easily transferred to the adjacent absorbent material. In addition, by setting the average single fiber diameter (Da) preferably to 25.0 μm or less, more preferably 20.0 μm or less, and even more preferably 16.0 μm or less, high capillary force is easily obtained, resulting in a spunbond nonwoven fabric with excellent absorbency.

[0065] The average single fiber diameter (Da) (μm) of the acrylic resin-containing fiber (Fa) mentioned herein is a value obtained as follows.

[0066] (1) Using a scanning electron microscope, an image of the cross section of the fiber constituting the surface (A) is taken at a magnification that allows one fiber to be observed.

[0067] (2) Using the captured images and image analysis software (e.g., "WinROOF2015" manufactured by Mitani Corporation), the area Af (μm) formed by the cross-sectional profile of the single fiber is measured. 2 ), calculate the diameter of the true circle with the same area as the area Af.

[0068] (3) Measure the above values ​​for 20 fibers that are randomly selected to form the same surface, calculate the average value of the simple number and calculate the average single fiber diameter (Da), and round it to the second decimal place.

[0069] In the spunbond nonwoven fabric of the present invention, the surface (B) is composed of the fibers (Fb) containing the acrylic resin.

[0070] The spunbond nonwoven fabric of the present invention preferably contains long fibers as in conventional methods, that is, the constituent fibers (Fb) of the surface (B) are preferably long fibers. This is because by including long fibers, spunbond nonwoven fabrics that combine high productivity with excellent mechanical properties can be easily produced.

[0071] The average single fiber diameter (Db) of the fibers (Fb) constituting the surface (B) of the present invention is preferably 3.0 μm or more and 30.0 μm or less. By setting the average single fiber diameter (Db) preferably to 3.0 μm or more, more preferably 5.0 μm or more, and even more preferably 10.0 μm or more, moisture is easily transferred to the surface (A), resulting in a spunbond nonwoven fabric with excellent quick-drying properties. Furthermore, by setting the average single fiber diameter (Db) preferably to 30.0 μm or less, more preferably 28.0 μm or less, and even more preferably 25.0 μm or less, a spunbond nonwoven fabric with excellent softness is obtained.

[0072] The average single fiber diameter (Db) (μm) of the acrylic resin-containing fiber (Fb) mentioned herein is a value obtained as follows.

[0073] (1) Using a scanning electron microscope, an image of the cross section of the fiber constituting the surface (B) is taken at a magnification that allows one fiber to be observed.

[0074] (2) Using the captured images and image analysis software (e.g., "WinROOF2015" manufactured by Mitani Corporation), the area Af (μm) formed by the cross-sectional profile of the single fiber is measured. 2 ), calculate the diameter of the true circle with the same area as the area Af.

[0075] (3) Measure the above values ​​for 20 fibers that are randomly selected to form the same surface, calculate the simple average value and the average single fiber diameter (Db), and round it to the second decimal place.

[0076] The spunbond nonwoven fabric of the present invention is a spunbond nonwoven fabric in which one surface (A) is composed of fibers (Fa) containing acrylic resin and the other surface (B) is composed of fibers (Fb) containing acrylic resin, and satisfies the following formula (1).

[0077] Db / Da≧1.1…(1)

[0078] Here, Da is the average single fiber diameter (μm) of the fiber (Fa), and Db is the average single fiber diameter (μm) of the fiber (Fb). Db / Da in equation (1) can be obtained by calculating the average single fiber diameter (Da) and the average single fiber diameter (Db) obtained by the method described above, and rounding them to two decimal places.

[0079] Typically, in nonwoven fabrics, the size of the gaps between the interwoven fibers varies depending on the average single fiber diameter of the fibers used in their construction. Therefore, when layers with different average single fiber diameters are formed, layers with different inter-fiber gap sizes are created. When moisture is present, the difference in capillary force allows moisture absorbed in the layer containing coarse fibers to transfer to the layer containing fine fibers. Furthermore, the inventors conducted extensive research and discovered that by setting the Db / Da ratio to a specific range, not only is there an improved absorbency effect due to the difference in capillary effect, but the surface (B) containing coarse fibers is also given quick-drying properties.

[0080] Therefore, by setting Db / Da to 1.1 or higher, preferably 1.2 or higher, and more preferably 1.3 or higher, the capillary effect is utilized, resulting in good water absorption and quick-drying properties of the surface (B). Furthermore, there is no particular upper limit to the average single fiber diameter ratio in this invention, but from the viewpoint of process stability or productivity, it is preferably 10.0 or lower.

[0081] [Spunbond Nonwoven Fabric]

[0082] In the spunbond nonwoven fabric of the present invention, the heat of melting for crystallization in the differential scanning calorimetry measurement is 30 J / g or more and 98 J / g or less. By setting the heat of melting for crystallization to 30 J / g or more, preferably 40 J / g or more, more preferably 50 J / g or more, and even more preferably 60 J / g or more, the stickiness of the spunbond nonwoven fabric can be suppressed, resulting in a spunbond nonwoven fabric with excellent tactile feel. Furthermore, by setting the heat of melting for crystallization to 98 J / g or less, preferably 95 J / g or less, more preferably 92 J / g or less, and even more preferably 90 J / g or less, a spunbond nonwoven fabric with excellent softness is obtained.

[0083] Methods for improving the softness or feel of nonwoven fabrics typically involve reducing the average single fiber diameter of the fibers constituting the nonwoven fabric, thereby decreasing the second moment of the fiber profile. However, in the spunbond nonwoven fabric of the present invention, since the ratio of the average single fiber diameter (Db) to the average single fiber diameter (Da), i.e., Db / Da, is 1.1 or more, the average single fiber diameter (Db) inevitably becomes larger, tending to reduce softness. Furthermore, when used as a hygiene material, since the surface (B) with a larger average single fiber diameter is positioned on the wearer's skin side, the feel is also poor.

[0084] To address the aforementioned issue, the inventors conducted repeated and diligent research, discovering that the softness or tactile feel of spunbond nonwovens depends on the heat of crystallization. That is, by reducing the heat of crystallization, the crystallinity of the spunbond nonwoven is reduced, resulting in a spunbond nonwoven with excellent softness even when the Db / Da ratio is above 1.1. On the other hand, if the heat of crystallization is reduced too much, although softness is improved, the proportion of amorphous material becomes excessively high, causing the spunbond nonwoven to become sticky and deteriorate in tactile feel. Therefore, in this invention, it is important to set the heat of crystallization within a specific range to balance softness and tactile feel.

[0085] Furthermore, the heat of fusion during crystallization of spunbond nonwoven fabric can be controlled by the copolymerization ratio or the fraction of meso-pentacomponents in the acrylic resin, as well as the content of various additives. For example, increasing the copolymerization ratio or decreasing the fraction of meso-pentacomponents tends to reduce the heat of fusion during crystallization.

[0086] The heat of fusion of crystallization (J / g) in the differential scanning calorimetry described herein is calculated as follows.

[0087] (1) Place about 2 mg of spunbond nonwoven fabric in a differential scanning calorimeter and perform differential scanning calorimetry under nitrogen atmosphere, with a heating rate of 16 °C / min and a measurement temperature range of 50 °C to 200 °C.

[0088] (2) Calculate the heat of melting and crystallization based on the area of ​​the endothermic peak in the obtained measurement results (differential scanning calorimetry (DSC) curve). Furthermore, if multiple endothermic peaks are observed, calculate the heat of melting and crystallization based on the sum of the areas of all the endothermic peaks.

[0089] (3) For one level, change the measurement location and perform three measurements to obtain the simple quantitative average value and calculate the heat of crystallization and melting, rounding to the first decimal place.

[0090] The spunbond nonwoven fabric of the present invention preferably has a contact angle of 30° or less between the surface (A) and water, and a contact angle of 30° or less between the surface (B) and water. By setting the contact angle with water preferably to be 30° or less, more preferably 20° or less, and even more preferably 10° or less, the spunbond nonwoven fabric is hydrophilic, and therefore the water in contact with the surface is easily absorbed by the spunbond nonwoven fabric, resulting in a spunbond nonwoven fabric with excellent water absorption. In addition, the lower limit of the contact angle with water in the present invention is 0°. The so-called contact angle with water of 0° means that in the measurement method described later, all the water is absorbed by the spunbond nonwoven fabric.

[0091] Furthermore, the contact angle with water can be controlled by the hydrophilicity of the acrylic resin used in the fibers constituting the spunbond nonwoven fabric or by applying a hydrophilic oil in a subsequent process. For example, the higher the hydrophilicity of the thermoplastic resin and the greater the amount of hydrophilic oil applied, the smaller the contact angle with water tends to be.

[0092] The contact angles (°) between the surface (A) and surface (B) of the spunbond nonwoven fabric and water, as described here, are values ​​obtained as follows.

[0093] (1) Place the spunbond nonwoven fabric in an indoor environment with a room temperature of 20°C and a relative humidity of 65% for more than 24 hours.

[0094] (2) The spunbond nonwoven fabric that has undergone the treatment is placed on the platform of the contact angle meter in the same room with the surface (A) as the measuring surface.

[0095] (3) Make a 2μL droplet containing ion-exchanged water at the tip of the needle and let it fall onto the spunbond nonwoven fabric.

[0096] (4) Calculate the contact angle between the droplet and the spunbond nonwoven fabric based on the image of the droplet 2 seconds after it lands.

[0097] (5) For one level, change the measurement position and perform 5 measurements, calculate the simple average value and calculate the contact angle between the surface (A) and the water, rounding to the first decimal place. Furthermore, if all the water is absorbed by the spunbond nonwoven fabric within 2 seconds, it is determined that the interface between the droplet and the air exists on the same surface as the surface of the spunbond nonwoven fabric, and the contact angle with the water is defined as 0°.

[0098] (6) The spunbond nonwoven fabric that has undergone the same treatment as (1) is placed with surface (B) as the measuring surface, and the operations (2) to (5) are repeated to calculate the contact angle between surface (B) and water.

[0099] The spunbond nonwoven fabric of the present invention is preferably the highest breaking strength σ among the breaking strengths measured by rotating the fabric in 22.5° increments within its plane, with any direction set to 0°. max Relative to the minimum fracture strength σ min The ratio (σ) max / σ min The breaking strength ratio (hereinafter sometimes simply referred to as the tensile strength ratio) is 1.2 or higher and 4.0 or lower. By setting the breaking strength ratio preferably to 1.2 or higher, and more preferably to 1.3 or higher, the fibers are oriented in any direction within the spunbond nonwoven fabric surface. Therefore, the absorbed moisture can be spread in the fiber orientation direction through capillary effect, resulting in higher absorbency and quick-drying properties. In addition, by setting the breaking strength ratio preferably to 4.0 or lower, and more preferably to 3.5 or lower, the angle of extremely low breaking strength is eliminated, thereby suppressing the breakage of the nonwoven fabric during process flow or product processing.

[0100] The breaking strength ratio of the spunbond nonwoven fabric mentioned here is based on the value obtained from "6.3 Tensile strength and elongation (International Organization for Standardization, ISO method)" of Japanese Industrial Standard (JIS) L 1913:2010 "General nonwoven fabrics test method" as follows.

[0101] (1) Set any direction of the spunbond nonwoven fabric to 0°, and cut out test pieces with a longitudinal length of 300mm and a transverse length of 25mm in the same direction as the longitudinal length. Collect 3 test pieces at different locations.

[0102] (2) Hold the test piece and place it on the tensile testing machine at 200mm intervals.

[0103] (3) A tensile test was conducted at a tensile speed of 100 m / min. The strength at break [N] of the three test pieces collected was calculated, and the arithmetic mean of the values ​​was set as the breaking strength σ.

[0104] (4) Relative to any direction set to 0°, the direction of rotating 22.5° clockwise within the surface of the spunbond nonwoven fabric is set as the axis. With the longitudinal direction consistent with the axis, test pieces of 300mm in length and 25mm in width are cut out. Three test pieces are collected from different locations. Then, the operations described in (2) to (3) are performed to calculate the breaking strength σ.

[0105] (5) Repeat the operation described in (4) until the spunbond nonwoven fabric rotates 180° in the plane, and calculate the breaking strength σ at each angle.

[0106] (6) Calculate the middle and highest fracture strength σ calculated by the above method. max Relative to the minimum fracture strength σ min The ratio (σ) max / σ min Let ), and let be the breaking strength ratio of spunbond nonwoven fabric.

[0107] Without impairing the effects of the present invention, the spunbond nonwoven fabric of the present invention may also include other nonwoven layers composed of fibers other than those containing acrylic resin that constitute surfaces (A) and (B). When including nonwoven layers composed of fibers other than those containing acrylic resin that constitute surfaces (A) and (B), it is preferable that the nonwoven layer is hydrophilic in terms of not impairing the overall water absorption of the spunbond nonwoven fabric. Examples of such nonwoven layers include, for example, spunbond or meltblown nonwoven fabrics containing acrylic resin fibers of different diameters, and spunbond or meltblown nonwoven fabrics containing fibers other than acrylic resin fibers.

[0108] The spunbond nonwoven fabric of the present invention preferably has a water absorption rate of 20 seconds or less when measured on the surface (B). By setting the water absorption rate preferably to 20 seconds or less, more preferably 15 seconds or less, and even more preferably 10 seconds or less, a nonwoven fabric with good performance in removing moisture adhering to the surface, i.e., excellent water absorption and quick-drying properties, is obtained.

[0109] The water absorption rate (in seconds) mentioned here is based on the value obtained from "7.1.1 Drop Method" of JIS L 1907:2010 "Test Method for Water Absorption of Fiber Products". One drop of water is added to the surface (B) of the spunbond nonwoven fabric, and the time until it is absorbed and the specular reflection on the surface disappears is measured. The simple quantitative average of the values ​​obtained from measuring the above time at 10 different locations is calculated, and the water absorption rate is calculated and rounded to one decimal place.

[0110] The preferred unit area weight of the spunbond nonwoven fabric of the present invention is 5 g / m². 2 Above and 200g / m 2The following is an example. The preferred weight per unit area is 5 g / m². 2 The above, and more preferably 8g / m 2 The above, and more preferably, is 10g / m 2 The above results in a spunbond nonwoven fabric with usable mechanical strength. Furthermore, the preferred weight per unit area is 200 g / m². 2 The following, or more preferably, is 150g / m 2 The following, and more preferably, is 100g / m 2 The following is a spunbond nonwoven fabric with moderate softness suitable for use as a sanitary material.

[0111] The weight per unit area (g / m²) mentioned here 2 The value is derived from "6.2 Mass per unit area" of JIS L 1913:2010 "General Test Methods for Nonwoven Fabrics". Three 20cm × 25cm test pieces are collected from every 1m of sample width, and their mass (g) under standard conditions is measured. The mass per unit area is then calculated based on the simple quantitative average of the measured values. 2 Calculate the mass of the object, determine the weight per unit area, and round it to the first decimal place.

[0112] The spunbond nonwoven fabric of the present invention is preferably an integral nonwoven layer comprising fibers (Fa) constituting surface (A) and a nonwoven layer comprising fibers (Fb) constituting surface (B). Integration here refers to the bonding of these nonwoven layers through intertwining of fibers, fixation using adhesives or similar components, and fusion of the thermoplastic resins constituting each layer.

[0113] Furthermore, to further improve water absorption, the spunbond nonwoven fabric of the present invention may also be endowed with a hydrophilic agent. Examples of hydrophilic agents include surfactants, among which nonionic surfactants are preferred.

[0114] [Sanitary Materials]

[0115] The sanitary material of the present invention is made by including the spunbond nonwoven fabric in at least a portion thereof. By doing so, a sanitary material with excellent absorbency, quick-drying properties, and wearing comfort can be obtained. Furthermore, the sanitary material described herein refers, for example, to items used primarily for medical, nursing, or other health-related purposes and are mainly disposable. Examples of the sanitary material of the present invention include diapers, sanitary napkins, gauze, bandages, masks, gloves, adhesive bandages, etc., and regarding their structural components, for example, in diapers, this includes the top piece, back piece, side pleats, etc.

[0116] Hygiene materials configured with the surface (B) facing the wearer's skin can immediately absorb moisture adhering to the skin side into the interior of the spunbond nonwoven fabric, reducing the wearer's discomfort, and are therefore preferred.

[0117] For example, when the sanitary material is a diaper and spunbond nonwoven fabric is used for the top piece of the diaper, when the surface (B) is positioned with the wearer's skin facing it, it can quickly absorb sweat or urine produced during wear and quickly transfer the liquid to the surface (A), so that the surface (B) does not have excessive moisture and remains dry.

[0118] When the sanitary material is a mask and spunbond nonwoven fabric is used as the inner layer of the mask, when the surface (B) is placed facing the wearer's skin, even if sweat or exhaled breath condenses and moisture adheres to the surface (B) placed on the skin side, it will be immediately absorbed by the interior of the spunbond nonwoven fabric, so that the surface (B) will not have excessive moisture and will remain dry.

[0119] [Manufacturing method of spunbond nonwoven fabric]

[0120] Next, a preferred embodiment of the spunbond nonwoven fabric of the present invention will be specifically described.

[0121] The manufacturing method for the surfaces (A) and (B) constituting the spunbond nonwoven fabric of the present invention is by using a spunbonding method. Furthermore, in the case where the nonwoven layer comprises fibers other than those constituting surfaces (A) and (B), the manufacturing method for said nonwoven layer can be selected from known manufacturing methods such as spunbonding, meltblowing, and short fiber carding.

[0122] The preferred form of manufacturing the spunbond nonwoven fabric of the present invention will be described below, but it is not limited thereto.

[0123] The so-called spunbond method refers to a method for manufacturing nonwoven fabrics that requires the following steps: melting thermoplastic resin as raw material, spinning it from a spinning die, cooling and solidifying it, drawing and extending the obtained filaments using an ejector, capturing them on a moving web, sheeting the fibers, and then thermally bonding them.

[0124] The raw materials used can be single-component. When using two or more different resins, they can be pre-mixed, dry-blended, or metered separately and fed into the extruder. For example, the following methods can be used: the propylene resins obtained by copolymerizing ethylene units and propylene homopolymers can be metered separately and fed into the extruder.

[0125] In spunbond spinning, the shape of the spinning die or ejector can be round or rectangular, among other shapes. From the viewpoint that the amount of compressed air used is relatively small and it is difficult to cause the filaments to fuse or break together, a combination of rectangular die and rectangular ejector is preferred.

[0126] In manufacturing the spunbond nonwoven fabric of the present invention, the spinning temperature is preferably set to a temperature 10°C or higher above the melting temperature of the thermoplastic resin used as a raw material, and to a temperature 120°C or lower than the melting temperature of the thermoplastic resin used as a raw material. That is, when using acrylic resin, a range of approximately 170°C or higher and 280°C or lower is preferred. By setting the spinning temperature within this range, a stable molten state can be achieved, resulting in excellent spinning stability.

[0127] The spun filaments are then cooled. Methods for cooling the spun filaments include, for example, forcibly blowing cold air onto the filaments, allowing natural cooling at the ambient temperature, and adjusting the distance between the spinning die and the ejector. Alternatively, a combination of these methods can be used. Furthermore, regarding cooling conditions, appropriate adjustments can be made considering the ejection volume from each individual orifice of the spinning die, the spinning temperature, and the ambient temperature.

[0128] Next, the cooled and cured filaments are drawn and extended by compressed air ejected from the injector.

[0129] In the spunbond nonwoven fabric of the present invention, it is important to control the average single fiber diameter of the acrylic resin fibers constituting surface (A) and surface (B).

[0130] The average single fiber diameter of fibers containing acrylic resins is determined by the ejection rate and traction speed of each ejection orifice at the spinning die, i.e., the spinning speed. Therefore, it is preferable to determine the ejection rate and spinning speed based on the desired average single fiber diameter.

[0131] The spinning speed is preferably 2,000 m / min or more, and more preferably 3,000 m / min or more. By setting the spinning speed to 2,000 m / min or more, high productivity is achieved, and in addition, fiber orientation crystallization is carried out, resulting in high-strength long fibers.

[0132] The long fiber filaments, thus stretched by traction, are captured on a moving web and sheeted, and then provided to a heat bonding process.

[0133] The spunbond nonwoven fabric of the present invention is a spunbond nonwoven fabric in which the surface (A) and the surface (B) contain acrylic resin fibers with different single fiber diameters, i.e., it is formed by laminating a nonwoven layer containing fibers constituting surface (A) and a nonwoven layer containing fibers constituting surface (B). As a method for laminating the nonwoven layer containing fibers constituting surface (A) and the nonwoven layer containing fibers constituting surface (B), for example, the following methods can be used: on a collecting net, a nonwoven layer containing fibers constituting surface (B) formed by spunbonding is continuously collected online onto a nonwoven layer containing fibers constituting surface (A) formed by spunbonding, and then laminated together; or a method in which nonwoven layers containing fibers constituting surface (A) and nonwoven layers containing fibers constituting surface (B) are obtained separately in advance, the two nonwoven layers are overlapped offline, and then laminated together. In terms of superior productivity, the preferred method is to continuously capture a nonwoven layer containing fibers forming the surface (B) using a spunbonding method onto a nonwoven layer containing fibers forming the surface (A) using a spunbonding method on a capturing net, and then integrate them by laminating them together.

[0134] As a method for integrally laminating the spunbond nonwoven fabric of the present invention by thermal bonding, the following methods can be used: thermal bonding using various rollers such as a pair of thermal embossing rollers with engravings (protrusions and depressions) on their upper and lower roller surfaces, a thermal embossing roller consisting of a roller with a flat (smooth) roller surface and another roller with engravings (protrusions and depressions) on its roller surface, and a thermal embossing roller consisting of a pair of flat (smooth) rollers; or ultrasonic bonding based on thermal pressing, such as thermal fusion bonding by ultrasonic vibration of an ultrasonic welding head (horn).

[0135] In the case of manufacturing the spunbond nonwoven fabric of the present invention by hot pressing, the mechanical strength of the spunbond nonwoven fabric is increased by fully bonding multiple nonwoven layers, which is therefore preferred.

[0136] As a method for thermally bonding the spunbond nonwoven fabric of the present invention, the so-called hot air penetration method, which is a method of blowing hot air, can also be cited.

[0137] When the spunbond nonwoven fabric of the present invention is manufactured using the hot air penetration method, it has a large volume and excellent hand feel, and is therefore preferred.

[0138] For the spunbond nonwoven fabric thus obtained, it is preferable to apply a hydrophilic agent before winding. Methods for applying a hydrophilic agent to the spunbond nonwoven fabric include coating or impregnation coating using a matching roller or spraying. In terms of ease of uniformity and control of adhesion amount, coating using a matching roller is preferred for applying a hydrophilic agent to the spunbond nonwoven fabric.

[0139] Example

[0140] The present invention will now be described in detail based on embodiments. However, the present invention is not limited to these embodiments. Furthermore, in the determination of various physical properties, unless otherwise specified, the determinations are performed based on the described method.

[0141] (1) Weight per unit area

[0142] Perform the measurements as described above.

[0143] (2) Average single fiber diameter (Da, Db) and Db / Da

[0144] Regarding surfaces (A) and (B), fiber samples were randomly collected from the nonwoven fabric surface, and images of the cross-section of the fibers were taken at a magnification that allowed observation of a single fiber using a Hitachi High Technologies S-5500 scanning electron microscope. Subsequently, measurements were performed using the WinROOF2015 image analysis software manufactured by Mitani Corporation, as described above.

[0145] (3) Heat of crystallization

[0146] The measurements were performed using a differential scanning calorimeter "DSC Q2000" manufactured by TA Instruments, as described.

[0147] (4) Lobe-like structure

[0148] The measurements were performed using a scanning electron microscope “S-5500” manufactured by Hitachi High Tech Co., Ltd., as described above.

[0149] (5) Copolymerization rate of ethylene units

[0150] Using products manufactured by Bruker 13 C-NMR “DRX-500” was measured under the following conditions as described.

[0151] • Observation kernel: 13 C core

[0152] • Observation frequency: 125.8MHz

[0153] • Pulse width: 5.0 μs (45° pulse)

[0154] • Pulse wait time: 5.0 seconds

[0155] • Total number of times: 25,000 or more

[0156] • Measurement temperature: 135℃

[0157] • Measurement method: with reverse gating 1 H decoupled single 13 C-pulse (single) 13 C pulse withinverse gated 1 H decoupling).

[0158] (6) Fractions of the meso-race quintuple

[0159] Using products manufactured by Bruker 13 C-NMR “DRX-500” was measured under the following conditions as described.

[0160] • Observation kernel: 13 C core

[0161] • Observation frequency: 125.8MHz

[0162] • Pulse width: 5.0 μs (45° pulse)

[0163] • Pulse wait time: 5.0 seconds

[0164] • Total number of times: 25,000 or more

[0165] • Measurement temperature: 135℃

[0166] • Measurement method: with reverse gating 1 H decoupled single 13 C-pulse (single) 13 C pulse withinverse gated 1 H decoupling)

[0167] (7) Contact angles of water between the surfaces (A) and (B) of spunbond nonwoven fabric.

[0168] The measurements were performed using a contact angle meter “DMo-501” manufactured by Kyowa Interface Science Co., Ltd., as described.

[0169] (8) Fracture strength ratio (σ) max / σ min )

[0170] Using a tensile testing machine "Tensilon UCT100" manufactured by Orientec Corporation, based on "6.3 Tensile strength and elongation (ISO method)" of JIS L 1913:2010 "General nonwoven fabrics test methods", the tensile strength ratio was determined by the following method and the breaking strength ratio was calculated.

[0171] (8.1) Set any direction of the laminated nonwoven fabric to 0°, and cut out test pieces with a length of 300mm and a width of 25mm in the same direction as the longitudinal direction. Collect 3 test pieces at different locations.

[0172] (8.2) Hold the test piece and place it on the tensile testing machine at 200mm intervals.

[0173] (8.3) A tensile test was conducted at a tensile speed of 100 m / min. The strength at fracture [N] of the three test pieces collected was determined and the arithmetic mean of the strength was set as the fracture strength σ.

[0174] (8.4) Relative to any direction set at 0°, the direction of clockwise rotation by 22.5° within the surface of the laminated nonwoven fabric is set as the axis. Test pieces with a length of 300mm and a width of 25mm are cut out, with the longitudinal direction aligned with the axis. Three test pieces are collected from different locations. Then, the operations described in (8.2) to (8.3) are performed to calculate the breaking strength σ.

[0175] (8.5) Repeat the operation described in (8.4) until the rotation angle of the stacked nonwoven fabric in the plane reaches 180°, and calculate the breaking strength σ at each angle.

[0176] (8.6) Calculate the intermediate and highest fracture strengths σ calculated by the above method. max Relative to the minimum fracture strength σ min The ratio (σ) max / σ min Let ), and let be the breaking strength ratio of the laminated nonwoven fabric.

[0177] (9) Water absorption rate

[0178] For the surface (B) of spunbond nonwoven fabric, the water absorption rate was determined based on the "7.1.1 Drop Method" of JIS L 1907:2010 "Test Method for Water Absorption of Fiber Products". One drop of water was added to the laminated nonwoven fabric, and the time until the water was absorbed and the specular reflection on the surface disappeared was measured. The simple quantitative average of the values ​​obtained from measuring the above time at 10 different locations was calculated, and the unit was set to seconds, rounded to one decimal place. This value was then taken as the water absorption rate. Furthermore, if the test was conducted for 60 seconds, and the specular reflection on the surface (B) of the spunbond nonwoven fabric still hadn't disappeared after 60 seconds, it was always designated as "60 seconds or more (>60)".

[0179] (10) Water absorption and quick drying properties

[0180] The surface (B) of the spunbond nonwoven fabric was placed on top and one drop of water was added. The surface texture was assessed by touch after one minute by healthy, ordinary adults (15 men and 15 women, totaling 30 people), and evaluated according to the following three stages. For each nonwoven fabric, the average score of the evaluation results was calculated and set as the water absorption and quick-drying property (grade) of the spunbond nonwoven fabric.

[0181] 5: The surface is dry and you can't feel any moisture.

[0182] 3: The surface has no moisture, but it is damp.

[0183] 1: The surface is damp.

[0184] (11) Softness

[0185] Healthy, average adults (15 men and 15 women, totaling 30) touched spunbond nonwoven fabrics by hand, and the surface texture was evaluated according to the following three stages. For each spunbond nonwoven fabric, the average score of the evaluation results was calculated and set as the softness (grade) of the nonwoven fabric.

[0186] 5: It feels very soft (the surface feels smooth to the touch, and the nonwoven fabric is soft when bent).

[0187] 3: It feels a bit soft

[0188] 1: Not soft (feels like a snag when you touch the surface, and feels stiff when you bend the nonwoven fabric).

[0189] [Example 1]

[0190] (The fiber sheet that makes up surface (A))

[0191] A propylene resin with a copolymerization rate of 3 mol% ethylene units and a meso-pentamericate fraction of 95% was melted using an extruder and spun out through a rectangular die with a circular orifice diameter of 0.4 mmΦ at a single-orifice extrusion rate of 0.3 g / min. The spinning temperature was set to 230°C. After the spun filaments were cooled and solidified with cold air, they were drawn, stretched, and collected onto a moving web using compressed air at a pressure of 0.08 MPa in a rectangular ejector at a spinning speed of 3700 m / min to obtain fiber sheets. The average single fiber diameter Da of the propylene resin fibers constituting the obtained surface (A) was 10.6 μm.

[0192] (Fiber sheet constituting surface (B))

[0193] A propylene resin with a copolymerization rate of 3 mol% ethylene units and a meso-pentamericate fraction of 95% was melted using an extruder and spun out through a rectangular die with a 0.4 mm Φ orifice at a single-hole extrusion rate of 0.9 g / min. The spinning temperature was set to 230°C. After the spun filaments were cooled and solidified, they were drawn and stretched in a rectangular ejector using compressed air at a pressure of 0.10 MPa at a spinning speed of 3700 m / min, and captured on a moving net onto the fiber sheet constituting surface (A), thus obtaining the fiber sheet. The average single fiber diameter Db of the propylene resin fibers constituting the obtained surface (B) is 18.4 μm.

[0194] (Spunbond nonwoven fabric)

[0195] The upper roller uses a metal embossing roller with orthogonal grid patterns formed by straight lines of circular protrusions, known as a quilting pattern. The lower roller uses a metal flat roller with a pair of heating mechanisms. The resulting fiber sheet is then heat-fused at a linear pressure of 300 N / cm and a heat-fusion temperature of 125°C, yielding a unit area weight of 40 g / m². 2 The spunbond nonwoven fabric. Subsequently, a nonionic surfactant as a hydrophilizing agent is coated onto the nonwoven fabric using a matching roller at an active ingredient content of 0.5 wt% relative to the weight of the spunbond nonwoven fabric.

[0196] The evaluation results of the obtained spunbond nonwoven fabrics are shown in Table 1.

[0197] [Table 1]

[0198] [Table 1]

[0199]

[0200] [Example 2]

[0201] In surfaces (A) and (B), a propylene-based resin with a copolymerization rate of 5 mol% of ethylene units and a meso-pentameric fraction of 95% was used. Otherwise, spunbond nonwoven fabrics were obtained using the same method as in Example 1. The evaluation results of the obtained spunbond nonwoven fabrics are shown in Table 1.

[0202] [Example 3]

[0203] In surfaces (A) and (B), a propylene-based resin with a copolymerization rate of 0 mol% of ethylene units and a meso-pentamericate fraction of 88% was used. Otherwise, spunbond nonwoven fabrics were obtained using the same method as in Example 1. The evaluation results of the obtained spunbond nonwoven fabrics are shown in Table 1.

[0204] [Example 4]

[0205] In surfaces (A) and (B), a propylene-based resin with a copolymerization rate of 3 mol% ethylene units and a meso-pentamericate fraction of 88% was used. Otherwise, spunbond nonwoven fabrics were obtained using the same method as in Example 1. The evaluation results of the obtained spunbond nonwoven fabrics are shown in Table 1.

[0206] [Comparative Example 1]

[0207] In surfaces (A) and (B), a propylene-based resin with a copolymerization rate of 0 mol% of ethylene units and a meso-pentamericate fraction of 95% was used. Otherwise, spunbond nonwoven fabrics were obtained using the same method as in Example 1. The evaluation results of the obtained spunbond nonwoven fabrics are shown in Table 1.

[0208] [Example 5]

[0209] In surfaces (A) and (B), 1.2 wt% of ethylene bis-stearamide as a fatty acid amide compound was added to the acrylic resin. Otherwise, spunbond nonwoven fabric was obtained using the same method as in Example 1. The evaluation results of the obtained spunbond nonwoven fabric are shown in Table 2.

[0210] [Table 2]

[0211] [Table 2]

[0212]

[0213] [Example 6]

[0214] In surface (A), a rectangular die with a Y-shaped hole was used when manufacturing the fiber sheet, and the cross-section of the fiber was set as a triangular section. Otherwise, the spunbond nonwoven fabric was obtained using the same method as in Example 1. The evaluation results of the obtained spunbond nonwoven fabric are shown in Table 2.

[0215] [Comparative Example 2]

[0216] In surface (B), the single-hole ejection rate was set to 0.3 g / min, and compressed air with a pressure of 0.08 MPa was used for traction and stretching at a spinning speed of 3700 m / min. Otherwise, spunbond nonwoven fabric was obtained using the same method as in Example 1. The evaluation results of the obtained spunbond nonwoven fabric are shown in Table 2.

[0217] [Example 7]

[0218] In the spunbond nonwoven fabric, a nonionic surfactant as a hydrophilizing agent was applied to the nonwoven fabric using a matching roller at an active ingredient content of 0.1 wt% relative to the weight of the spunbond nonwoven fabric. Otherwise, the spunbond nonwoven fabric was obtained using the same method as in Example 1. The evaluation results of the obtained spunbond nonwoven fabrics are shown in Table 2.

[0219] It was found that the spunbond nonwoven fabrics obtained in Examples 1 to 7 have excellent water absorption, quick-drying properties and softness in their surface (B) due to their large Db / Da ratio and moderately small heat of melting during crystallization.

[0220] On the other hand, it was found that the spunbond nonwoven fabric obtained in Comparative Example 1 had poor softness due to the large heat of crystallization and melting, and the spunbond nonwoven fabric obtained in Comparative Example 2 had poor water absorption and quick-drying properties because the Db / Da ratio was small.

[0221] Explanation of symbols

[0222] C1: Profile of the section

[0223] L 11 : Two points (S) on the profile (C1) that cross the fiber section. 11 S 12 (a straight line)

[0224] S 11 S 12 Points on the profile (C1) of the fiber cross-section.

[0225] C2: Profile of the section

[0226] L 21 : Two points (S) on the profile (C2) that cross the fiber section. 21 S 22 (a straight line)

[0227] L 22 : with line (L) 21 Parallel and in the contour (C2) at point S 21 With point S 22There is only one point of intersection between them (V) 21 ) line

[0228] S 21 S 22 V 21 Points on the profile (C2) of the fiber cross-section.

[0229] a: Point S 21 S 22 Distance between

[0230] b: Line (L) 21 ) and the straight line (L) 22 Distance between )

Claims

1. A sanitary material comprising at least a portion of a spunbond nonwoven fabric, wherein one surface (A) is composed of fibers Fa containing an acrylic resin, and another surface (B) is composed of fibers Fb containing an acrylic resin, wherein the spunbond nonwoven fabric has a heat of fusion of 30 J / g or more and 98 J / g or less in differential scanning calorimetry, and satisfies the following formula (1), wherein the other surface (B) is disposed facing the wearer's skin. Db / Da ≧ 1.1 …(1) Here, Da is the average single fiber diameter (μm) of the fiber Fa, and Db is the average single fiber diameter (μm) of the fiber Fb.

2. The sanitary material according to claim 1, wherein at least a portion of the acrylic resin is an acrylic resin copolymerized by copolymerizing ethylene units at a concentration of 2 mol% or more and 30 mol% or less.

3. The sanitary material according to claim 1 or 2, wherein at least a portion of the acrylic resin is an acrylic resin having a meso-pentamericate fraction of 50% or more and 92% or less.

4. The sanitary material according to claim 1 or 2, wherein at least a portion of the acrylic resin is an acrylic resin containing more than 0.5% by mass of a fatty acid amide compound.

5. The sanitary material according to claim 1 or 2, wherein the contact angle between the surface (A) and water and the contact angle between the other surface (B) and water are both less than 30°.

6. The sanitary material according to claim 1 or 2, wherein at least a portion of the fibers Fa and / or Fb are irregularly shaped fibers having a plurality of protrusions in the fiber cross-section and wherein the lobed structure of the fiber cross-section is more than 5.0%.

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