Spunbond nonwoven fabric

Abstract

To provide a spunbond nonwoven fabric that can impart a cool feel and retains superior cooling performance even after friction.SOLUTION: A spunbond nonwoven fabric includes fibers composed of polyolefin resin with an average single fiber diameter of 6.5 μm or more and 14.5 μm or less. The spunbond nonwoven fabric includes particles including at least one selected from the group consisting of sugar alcohols and saccharides. The particles have an average diameter of 5 μm or more and 10 μm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a spunbond nonwoven fabric.

Background Art

[0002] In recent years, nonwoven fabrics have been used in various applications. Examples of the applications of nonwoven fabrics include industrial materials, civil engineering materials, building materials, daily necessities, agricultural materials, sanitary materials, and medical materials.

[0003] Among them, applications for masks have attracted attention due to the worldwide spread of infectious diseases. Although masks made of nonwoven fabrics are excellent in preventing the scattering and inhalation of droplets due to conversation or coughing, there is a problem that the space inside the mask for the mask wearer tends to become stuffy, especially in summer.

[0004] Conventionally, in order to solve such problems, a proposal has been made for a mask imparted with a cooling sensation by using a nonwoven fabric provided with a heat absorbent for the mask (see, for example, Patent Document 1).

[0005] In addition, a post-processing agent for fiber products using xylitol as a heat absorbent has been proposed (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the method disclosed in Patent Document 1, although there is a description of a non-woven fabric to which a heat-absorbing agent is applied and a method for applying the heat-absorbing agent such as impregnation and kiss roll, there is no description regarding the specific application state and application conditions of the heat-absorbing agent. Therefore, there are unevenness in the shape and application state of the heat-absorbing agent, and due to the friction during actual use, there is a problem that the heat-absorbing agent falls off and the cooling performance is likely to disappear.

[0008] Also, in the method disclosed in Patent Document 2, although there is a description that the heat-absorbing agent is in particulate form and the base material to which the heat-absorbing agent is applied is generally fiber products, there is no description regarding the specific details of the base material and the application state of the particles on the base material. Therefore, there are problems that it is difficult to uniformly coat the particles and due to the friction during actual use, the heat-absorbing agent falls off and the cooling performance is likely to disappear.

[0009] Therefore, although the conventional non-woven fabric provided with a heat-absorbing agent can exhibit a cooling performance, it is difficult to maintain the cooling performance during actual use.

[0010] Therefore, an object of the present invention is, in view of the above problems, to provide a spunbond non-woven fabric that can impart a cooling sensation and has excellent cooling performance even after friction.

Means for Solving the Problems

[0011] The non-woven fabric of the present invention is a spunbond non-woven fabric composed of fibers having an average single fiber diameter of 6.5 μm or more and 14.5 μm or less made of a polyolefin resin, and contains particles including one or more selected from the group consisting of sugar alcohols and sugars, and the average diameter of the particles is 5 μm or more and 10 μm or less.

[0012] According to a preferred embodiment of the spunbond non-woven fabric of the present invention, the ratio of the number of particles having a diameter of 5 μm or more and 10 μm or less in the particles is 50% or more and 100% or less.

[0013] According to a preferred embodiment of the spunbond non-woven fabric of the present invention, the total content of sugar alcohols and sugars is 0.1% by mass or more and 2.0% by mass or less.

Effects of the Invention

[0014] According to the present invention, a spunbond nonwoven fabric that can impart a cooling sensation and maintain high cooling performance even after friction can be obtained.

Brief Description of the Drawings

[0015]

Figure 1

Embodiments for Carrying Out the Invention

[0016] The spunbond nonwoven fabric of the present invention is a spunbond nonwoven fabric composed of fibers made of a polyolefin resin, with an average single fiber diameter of 6.5 μm or more and 14.5 μm or less, and contains particles including one or more selected from the group consisting of sugar alcohols and saccharides, and the average diameter of the particles is 5 μm or more and 10 μm or less. By adopting such a configuration, particles as heat absorbents can be uniformly coated, and furthermore, since there is little dropout of particles due to friction during actual use, high cooling performance can be maintained even after friction. Hereinafter, the components will be described in detail, but the present invention is not limited to the scope described below as long as it does not exceed the gist thereof.

[0017] [Polyolefin resin] The spunbond nonwoven fabric of the present invention is composed of fibers made of a polyolefin resin. Here, the "polyolefin resin" in the present invention refers to a resin whose main repeating unit is an olefin unit. Similarly, "polyethylene resin" and "polypropylene resin" refer to resins whose main repeating units are an ethylene unit and a propylene unit, respectively. Here, the "main repeating unit" refers to the repeating unit that is most contained in the resin in terms of the number of moles.

[0018] Examples of polyolefin resins include polyethylene resins, polypropylene resins, polybutene resins, polymethylpentene resins, and the like. Examples of polyethylene resins include homopolymers of ethylene or copolymers of ethylene and various α-olefins. Examples of polypropylene resins include homopolymers of propylene or copolymers of propylene and various α-olefins. From the viewpoints of spinnability and strength characteristics, polypropylene resins are preferably used. From the viewpoint of more easily expressing a cooling sensation, polyethylene resins are preferably used.

[0019] The proportion of propylene units in the polypropylene resin is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. The upper limit of the proportion of propylene units is 100% by mass. By setting the proportion of propylene units within such a range, good spinnability can be maintained and the strength can be further improved.

[0020] The polyolefin resin preferably has a melt flow rate (hereinafter sometimes abbreviated as MFR) of 75 g / 10 min or more and 850 g / 10 min or less. By setting the MFR to 75 g / 10 min or more, more preferably 120 g / 10 min or more, and even more preferably 155 g / 10 min or more, the stress during stretching can be reduced, and even when stretched at a high spinning speed, stable spinning can be easily achieved. As a result, the fiber diameter of the spunbond nonwoven fabric can be made finer, and the area for applying particles as a heat-absorbing agent increases. Furthermore, by making the surface smoother, the particles as a heat-absorbing agent can be more uniformly applied to the surface, and the cooling sensation can be more strongly expressed. On the other hand, by setting the MFR to 850 g / 10 min or less, more preferably 600 g / 10 min or less, and even more preferably 400 g / 10 min or less, the molecular weight of the polyolefin resin increases and the strength per fiber increases, so that a nonwoven fabric with sufficient strength for use as a mask can be easily obtained.

[0021] In the present invention, the MFR of the polyolefin resin is the value measured by ASTM D1238 (Method A). According to this standard, for example, polypropylene is measured at a load of 2.16 kg and a temperature of 230°C, and polyethylene is measured at a load of 2.16 kg and a temperature of 190°C.

[0022] In the present invention, the polyolefin resin may be a resin composition of two or more polyolefin resins, or may be a resin composition containing a thermoplastic elastomer or the like. Naturally, two or more resins with different MFRs can be blended at an arbitrary ratio to adjust the MFR of the polyolefin resin. In this case, the MFR of the resin blended with the main polyolefin resin is preferably 10 g / 10 min or more and 1000 g / 10 min or less. The MFR is more preferably 20 g / 10 min or more, and even more preferably 30 g / 10 min or more. Also, the MFR is more preferably 800 g / 10 min or less, and even more preferably 600 g / 10 min or less. By setting the MFR within such a range, it is possible to prevent the occurrence of viscosity spots in the blended polyolefin resin, the non-uniformity of the fineness, and the deterioration of the spinnability.

[0023] In the present invention, the polyolefin resin may contain additives such as antioxidants, weathering agents, light stabilizers, antifogging agents, blocking agents, lubricants, nucleating agents, and pigments such as titanium oxide, or other polymers, as long as the effects of the present invention are not impaired.

[0024] Also, when spinning the fibers described later, in order to prevent the occurrence of partial viscosity spots, to make the fineness of the fibers uniform, and to further make the fiber diameter thinner as described later, the molecular weight of the resin used may be decreased to increase the MFR. As a method for increasing the MFR, for example, a method of heating and thermally decomposing the resin before use or a method of adding a peroxide and performing heat treatment can be considered.

[0025] In the present invention, the melting point of the polyolefin resin is preferably 80°C or higher and 200°C or lower. By setting the melting point to preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 120°C or higher, it becomes easier to obtain higher heat resistance. Further, by setting the melting point to preferably 200°C or lower, more preferably 180°C or lower, the filaments discharged from the die are easily cooled, fusion between fibers is suppressed, and stable spinning is facilitated.

[0026] [Fiber] In the present invention, it is important that the fiber made of the polyolefin resin has an average single fiber diameter of 6.5 μm or more and 14.5 μm or less. By setting the average single fiber diameter to preferably 6.5 μm or more, more preferably 7.5 μm or more, and even more preferably 8.0 μm or more, a decrease in spinnability can be prevented, and a nonwoven fabric having a stable average single fiber diameter can be formed. On the other hand, by setting the average single fiber diameter to preferably 12.0 μm or less, more preferably 11.0 μm or less, and even more preferably 10.5 μm or less, the coating area of the particles as the heat-absorbing agent increases, making it easier to feel a cooling sensation, and the surface is smoothed, enabling the particles as the heat-absorbing agent to be uniformly applied to the surface.

[0027] Note that the average single fiber diameter (μm) of the fiber is calculated by the following procedure. For measurement, for example, a scanning electron microscope "VHX-D500" manufactured by Keyence Corporation can be used. Hereinafter, unless otherwise specified, this apparatus can be used as the scanning electron microscope (SEM) shown in the description of the measurement method. (1) For the nonwoven fabric, randomly collect 10 small piece samples. (2) Take a surface photograph with a magnification of 500 to 1000 times using SEM, and measure the widths of 10 polyolefin fibers each from each sample, for a total of 100 fibers. (3) Calculate the average single fiber diameter (μm) from the average value of the 100 measured values.

[0028] [Spunbond nonwoven fabric] The spunbond nonwoven fabric of the present invention comprises particles containing at least one selected from the group consisting of sugar alcohols and saccharides. Here, in the present invention, the spunbond nonwoven fabric "containing particles" means a state in which particles are imparted to the surface of the fibers constituting the spunbond nonwoven fabric. FIG. 1 shows a scanning electron microscope (SEM) photograph of an example of the spunbond nonwoven fabric of the present invention. As shown in FIG. 1, in an example of the spunbond nonwoven fabric of the present invention, particles P containing either sugar alcohols or saccharides are imparted to the surface of the fibers constituting the spunbond nonwoven fabric. Note that the magnification of the SEM photograph in FIG. 1 is 1000 times.

[0029] As a state in which particles are imparted to the surface of the fibers constituting the spunbond nonwoven fabric, a state in which particles containing at least one selected from the group consisting of sugar alcohols and saccharides are imparted to the surface of the fibers, more specifically, a state in which the total content of sugar alcohols and saccharides is 0.1% by mass or more and 2% by mass or less in 100% by mass of the spunbond nonwoven fabric can be mentioned. By setting the total content of sugar alcohols and saccharides to preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and still more preferably 1.0% by mass or more, the amount of particles contained per unit area increases, and the cooling performance is improved. Further, by setting the total content of sugar alcohols and saccharides to preferably 2.0% by mass or less, more preferably 1.8% by mass or less, and still more preferably 1.5% by mass or less, the dropout of particles due to friction can be reduced more.

[0030] Examples of sugar alcohols include xylitol, erythritol, dextrose, sorbitol and the like. Examples of saccharides include trehalose, sucrose, lactose, maltose and the like. Among them, since the endothermic amount when dissolved in water is large, it is a preferred embodiment to use xylitol or erythritol, or both.

[0031] Furthermore, since the spunbond nonwoven fabric of the present invention has a cooling effect, it may contain L-menthol, DL-camphor, eucalyptus oil and the like.

[0032] That the spunbond nonwoven fabric of the present invention contains particles including at least one selected from the group consisting of sugar alcohols and saccharides can be determined, for example, by separating components extracted from the spunbond nonwoven fabric of the present invention with water by high performance liquid chromatography (hereinafter sometimes referred to as HPLC), and analyzing them by infrared spectroscopy, proton nuclear magnetic resonance ( 1 1H-NMR), etc.

[0033] The spunbond nonwoven fabric of the present invention preferably further contains a surfactant and silicone oil. By doing so, it is possible to more easily suppress the dropout of particles including at least one selected from the group consisting of sugar alcohols and saccharides during the friction in the actual use of the spunbond nonwoven fabric.

[0034] Here, in the present invention, that the spunbond nonwoven fabric "contains a surfactant" means a state in which a surfactant is applied to the surface of the fibers constituting the spunbond nonwoven fabric. Further, the "surfactant" referred to in the present invention refers to one or more selected from the group consisting of nonionic surfactants, anionic surfactants, and cationic surfactants.

[0035] The total amount of the surfactant contained in the spunbond nonwoven fabric is preferably 0.05% by mass or more and 1.30% by mass or less. By setting the total amount of the surfactant contained in the spunbond nonwoven fabric to preferably 0.05% by mass or more, more preferably 0.20% by mass or more, and still more preferably 0.30% by mass or more, it is possible to reduce the dropout of particles due to friction. Further, by setting the total amount of the surfactant contained in the spunbond nonwoven fabric to preferably 1.30% by mass or less, more preferably 1.00% by mass or less, and still more preferably 0.70% by mass or less, the heat absorption amount per particle increases, so that the cooling performance is likely to be improved.

[0036] Also, the amount of the anionic surfactant contained in the spunbond nonwoven fabric is preferably 0.03% by mass or more and 0.50% by mass or less. By setting the amount of the anionic surfactant contained in the spunbond nonwoven fabric to preferably 0.03% by mass or more, more preferably 0.10% by mass or more, and still more preferably 0.15% by mass or more, the dropping of particles due to friction can be further reduced. Further, by setting the amount of the anionic surfactant contained in the spunbond nonwoven fabric to preferably 0.50% by mass or less, more preferably 0.40% by mass or less, and still more preferably 0.30% by mass or less, the heat absorption amount per particle increases, so that the cooling performance is likely to be improved.

[0037] Examples of the nonionic surfactant include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene cetyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene isodecyl ether, polyoxyalkylene tridecyl ether, and polyoxyethylene hydrogenated castor oil. Examples of the anionic surfactant include sodium alkyl sulfate, sodium alkyl ether sulfate, alkyl sulfate ester salt, alkylbenzene sulfonate, sodium polyoxyethylene lauryl ether sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium dodecylbenzene sulfonate, sodium di-2-ethylhexyl sulfosuccinate, and sodium dialkyl sulfosuccinate. Examples of the cationic surfactant include stearamidopropyldimethylamine, behenamidopropyldimethylamine, PPG-1 / PEG-1 stearamine, cetrimonium chloride, stearyltrimonium chloride, dimethylstearylammonium chloride, trimethylstearylammonium chloride, behentrimonium chloride, behentrimonium methosulfate, distearyldimonium chloride, quaternium-18, and benzalkonium chloride.

[0038] Furthermore, in the present invention, the spunbond nonwoven fabric "containing silicone oil" means a state in which silicone oil is applied to the surface of the fibers constituting the spunbond nonwoven fabric.

[0039] The amount of silicone oil contained is preferably 0.1% by mass or more and 2.0% by mass or less in the spunbond nonwoven fabric. By doing so, in the friction during actual use of the spunbond nonwoven fabric, the silicone oil reduces the frictional resistance and makes it easier to suppress the dropout of particles.

[0040] Examples of the silicone oil include amino-modified silicone oil, epoxy-modified silicone oil, carbonyl-modified silicone oil, carbinol-modified silicone oil, polyether-modified silicone oil, amino / alkoxy-modified silicone oil, epoxy / polyether-modified silicone oil, amino / polyether-modified silicone oil, dimethyl silicone oil, phenyl silicone oil, and the like.

[0041] Whether the spunbond nonwoven fabric of the present invention contains a surfactant is determined by the following method. That is, a methylene blue chloroform test is carried out with a sample solution collected from the spunbond nonwoven fabric. If the lower chloroform layer shows a blue color, it is determined to contain an anionic surfactant. If both layers show the same color development, it is a nonionic surfactant. If only the upper layer shows a blue color, it is determined to contain a cationic surfactant. The methylene blue chloroform test is measured according to the following procedure. (1) Dilute 0.03 g of methylene blue, 12 g of concentrated sulfuric acid, and 50 g of anhydrous sodium acetate with water to make 1 L. (2) Immerse the spunbond nonwoven fabric in water for 30 minutes. (Sample solution) (3) Put 5 mL of methylene blue solution and 5 mL of chloroform into a test tube, stopper it, shake it vigorously and let it stand for separation. Add a few drops of the sample solution to this, shake it vigorously up and down, then let it stand for separation, and observe the color change.

[0042] Whether the spunbond nonwoven fabric of the present invention contains silicone oil is determined by the following method. That is, the surface of a test piece collected from the spunbond nonwoven fabric is analyzed by an infrared spectroscopic analyzer, and in the obtained spectrum, at 1260 cm -1 and 797 cm -1 for Si-CH3 bonds, and at 1089 cm -1 and 1019 cm -1 when Si-O-Si and Si-O-C bonds are detected, it is determined that the spunbond nonwoven fabric contains silicone oil.

[0043] In the spunbond nonwoven fabric of the present invention, the average diameter of the particles is 5 μm or more and 10 μm or less. By making the average diameter of the particles preferably 5 μm or more, more preferably 6 μm or more, and even more preferably 7 μm or more, the heat absorption amount per particle increases, so the cooling performance of the spunbond nonwoven fabric is improved. On the other hand, by making the average diameter of the particles 10 μm or less, more preferably 9.5 μm or less, and even more preferably 9 μm or less, since there are no coarse particles, the dropout of particles from the fiber surface during friction is reduced. The diameter of the particles here refers to the longest line segment among any line segments passing through the center and having both endpoints on the circumference when the particles observed on the surface of the spunbond nonwoven fabric are not perfect circles. The average diameter of the particles is measured as follows. (1) For the nonwoven fabric, randomly collect 10 small piece samples. (2) Take a surface photograph with a magnification of 1000 - 1500 times by SEM, and measure the diameters of 10 particles each from each sample, for a total of 100 particles. (3) Calculate the average diameter (μm) of the particles from the average value of the 100 measured values.

[0044] Examples of the method for making the average diameter of the particles within the above range include, for example, the method of adjusting the total amount of the surfactant contained in the dispersion liquid in which the particles are dispersed.

[0045] In the spunbond nonwoven fabric of the present invention, the ratio of the number of particles having a diameter of 5 μm or more and 10 μm or less in the particles is preferably 50% or more and 100% or less. By setting the ratio of the number of particles having a diameter of 5 μm or more and 10 μm or less to preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more, the variation in particle diameter is reduced, so that the particles are less likely to fall off from the fiber surface, and excellent cooling performance is exhibited even after friction in actual use. The ratio of the particles referred to here is measured as follows. (1) For the nonwoven fabric, randomly collect 10 small piece samples. (2) Take a surface photograph of the nonwoven fabric with a magnification of 1000 to 1500 times by SEM, and measure the diameters of 10 particles each from each sample, for a total of 100 particles. (3) Calculate the ratio of the particles from the number of particles that satisfy 5 μm or more and 10 μm or less among the 100 measured values.

[0046] Examples of the method for setting the ratio of the number of particles having a diameter of 5 μm or more and 10 μm or less within the above range include a method of adjusting the amount of an anionic surfactant contained in the dispersion liquid in which the particles are dispersed.

[0047] [Method for manufacturing a spunbond nonwoven fabric] Next, a preferred embodiment of the method for manufacturing the spunbond nonwoven fabric of the present invention will be specifically described.

[0048] The method for manufacturing the spunbond nonwoven fabric of the present invention preferably includes a step of forming a nonwoven fiber web (step 1), a step of fusing the nonwoven fiber web using a thermal embossing roll composed of a combination of a roll with a smooth surface on one side and a roll with an engraved surface on the other side to obtain a sheet (step 2), and a step of applying a liquid containing at least one of sugar alcohols and saccharides to the surface of the sheet (step 3).

[0049] (Step 1: Step of forming a nonwoven fiber web) The nonwoven fiber web can be formed, for example, by spinning a molten polyolefin resin as long fibers from a spinneret, cooling and stretching the fibers, and then collecting the fibers on a moving net. The stretching may be performed by sucking with compressed air using an ejector or the like.

[0050] The shapes of the spinneret and the ejector can be various shapes such as circular and rectangular. Among them, a combination of a rectangular die and a rectangular ejector is preferably used because the amount of compressed air used is relatively small, the energy cost is excellent, fusing and rubbing between yarns are less likely to occur, and the fibrillation of the yarns is easy.

[0051] The polyolefin resin is melted in an extruder, metered, and supplied to a spinneret, and spun as long fibers. When melting and spinning the polyolefin resin, the spinning temperature is 200 °C or higher, more preferably 210 °C or higher, and even more preferably 220 °C or higher, so that the melt viscosity can be reduced. Also, by setting it to 270 °C or lower, more preferably 260 °C or lower, and even more preferably 250 °C or lower, thermal decomposition of the polymer can be suppressed. By setting the spinning temperature within the above range, a stable molten state can be obtained, and excellent spinning stability can be obtained.

[0052] The spun long fiber yarns are cooled. Examples of this cooling method include a method of forcibly blowing cold air onto the yarns, a method of natural cooling at the ambient temperature around the yarns, and a method of adjusting the distance between the spinneret and the ejector. Alternatively, a method of combining these methods can be adopted. Also, the cooling conditions can be appropriately adjusted and adopted in consideration of the discharge amount per single hole of the spinneret, the spinning temperature, the ambient temperature, and the like.

[0053] Next, the cooled and solidified yarn may be drawn and stretched by compressed air ejected from an ejector. The spinning speed is preferably 3000 m / min or more and 6500 m / min or less. More preferably, it is 3500 m / min or more, and even more preferably 4000 m / min or more, so that high productivity can be achieved, the orientation crystallization of the fibers proceeds, and high-strength long fibers can be obtained. On the other hand, by being 6500 m / min or less, spinning can be performed without yarn breakage.

[0054] Subsequently, the obtained long fibers are collected on a moving net to obtain a non-woven fiber web.

[0055] It is also a preferred embodiment to temporarily bond the non-woven fiber web by bringing a hot flat roll into contact with one side thereof on the net. By doing so, it is possible to prevent the surface layer of the non-woven fiber web from curling or being blown away during conveyance on the net, which would deteriorate the appearance, and to improve the conveyance property from when the yarn is collected to when it is thermocompression bonded.

[0056] (Step 2: A step of fusing the non-woven fiber web using a thermal embossing roll composed of a combination of a roll with a smooth surface on one side and a roll with an engraved surface on the other side to obtain a sheet) The method of fusing the non-woven fiber web is not particularly limited. For example, a thermal embossing roll with engravings (concave and convex portions) on the upper and lower pair of roll surfaces, a thermal embossing roll composed of a combination of a roll with a flat (smooth) surface on one side and a roll with engravings (concave and convex portions) on the other side, and a thermal calendar roll composed of a combination of the upper and lower pair of flat (smooth) rolls. Methods of thermal fusion using various rolls, methods of thermal fusion by ultrasonic vibration of a horn, and methods of passing hot air through the non-woven fiber web to soften or melt the surface of the core-sheath composite fiber and thermally fuse the fiber intersections are examples.

[0057] Among them, it is preferable to use a thermal embossing roll in which a pair of upper and lower roll surfaces are each engraved (with uneven portions), or a combination of a roll with a flat (smooth) surface on one side and a roll with an engraved (uneven) surface on the other side. By doing so, it is possible to provide a fused portion that improves the strength of the spunbond nonwoven fabric with good productivity and a non-fused portion that improves the texture and feel.

[0058] As the surface material of the thermal embossing roll, in order to obtain a sufficient thermocompression bonding effect and prevent the engraving (uneven portions) of one embossing roll from being transferred to the surface of the other roll, it is a preferred embodiment to pair a metal roll with a metal roll.

[0059] The embossing adhesion area ratio by the thermal embossing roll is preferably 5% or more and 30% or less. By setting the adhesion area preferably to 5% or more, more preferably to 8% or more, and even more preferably to 10% or more, higher strength can be obtained as a spunbond nonwoven fabric. On the other hand, by setting the adhesion area preferably to 30% or less, more preferably to 25% or less, and even more preferably to 20% or less, appropriate flexibility suitable for use in mask applications can be obtained as a spunbond nonwoven fabric for sanitary materials. Even when ultrasonic adhesion is used, the adhesion area ratio is preferably in the same range.

[0060] The embossing adhesion area ratio referred to here means the ratio of the area of the fused portion to the total area of the spunbond nonwoven fabric. Specifically, when thermally bonding with a roll having unevenness and a flat roll, it means the ratio of the portion where the convex portion of the roll having unevenness contacts the spunbond nonwoven fabric (fused portion) to the entire spunbond nonwoven fabric.

[0061] As the shape of the bonding part by the thermal embossing roll, a circle, an ellipse, a square, a rectangle, a parallelogram, a rhombus, a regular hexagon, a regular octagon, etc. can be used. Further, it is preferable that the bonding parts are uniformly present at regular intervals in the longitudinal direction (conveying direction) and the width direction of the spunbond nonwoven fabric. By doing so, the variation in the strength of the spunbond nonwoven fabric can be reduced.

[0062] In a preferred embodiment, the surface temperature of the thermal embossing roll during fusion bonding is preferably -50°C or higher and -15°C or lower with respect to the melting point of the polyolefin resin used. By setting the surface temperature of the thermal embossing roll to preferably -50°C or higher, more preferably -45°C or higher, with respect to the melting point of the polyolefin resin, a spunbond nonwoven fabric with appropriately fused and higher strength can be obtained. Also, by setting the surface temperature of the thermal embossing roll to preferably -15°C or lower, more preferably -20°C or lower, with respect to the melting point of the polyolefin resin, excessive fusion can be suppressed, and appropriate flexibility and processability suitable for use in mask applications, in particular, can be obtained as a spunbond nonwoven fabric.

[0063] The linear pressure of the thermal embossing roll during fusion bonding is preferably 50 N / cm or higher and 500 N / cm or lower. By setting the linear pressure of the thermal embossing roll to preferably 50 N / cm or higher, more preferably 100 N / cm or higher, and even more preferably 150 N / cm or higher, a spunbond nonwoven fabric with appropriately fused and higher strength can be obtained. On the other hand, by setting the linear pressure of the thermal embossing roll to preferably 500 N / cm or lower, more preferably 400 N / cm or lower, and even more preferably 300 N / cm or lower, appropriate flexibility and processability suitable for use in mask applications, in particular, can be obtained as a spunbond nonwoven fabric.

[0064] In addition, in the present invention, for the purpose of adjusting the thickness of the spunbond nonwoven fabric, before and / or after the fusion by the above-mentioned thermal embossing roll, thermocompression bonding can also be performed by a thermal calendar roll composed of a pair of upper and lower flat rolls. The pair of upper and lower flat rolls refers to metal rolls or elastic rolls without unevenness on the surface of the rolls, and they can be used in pairs of metal rolls or in pairs of a metal roll and an elastic roll.

[0065] Here, the elastic roll is a roll made of a material having elasticity as compared with a metal roll. Examples of the elastic roll include so-called paper rolls such as paper, cotton, and aramid paper, resin rolls made of urethane-based resins, epoxy-based resins, silicone-based resins, polyester-based resins, hard rubber, and mixtures thereof.

[0066] (Step 3: A step of applying a dispersion solution containing particles containing at least one of sugar alcohols and sugars to the surface of the sheet) In this step, by applying a dispersion liquid containing particles containing at least one of sugar alcohols and sugars with a controlled particle diameter to the surface of the above-mentioned sheet, a spunbond nonwoven fabric having intended cooling performance can be obtained.

[0067] It is preferable that the total amount of the surfactant contained in the dispersion liquid containing the particles is 1% by mass or more and 26% by mass or less. Preferably, the total amount of the surfactant is 1% by mass or more, more preferably 4% by mass or more, and even more preferably 6% by mass or more, so that the particle diameter of the particles containing at least one of sugar alcohols and sugars can be made smaller due to the surfactant effect. On the other hand, preferably, the total amount of the surfactant is 26% by mass or less, more preferably 20% by mass or less, and even more preferably 14% by mass or less, so that the stickiness caused by the surfactant when the solution is applied to the spunbond nonwoven fabric can be suppressed.

[0068] Moreover, it is preferable that the amount of the anionic surfactant contained in the dispersion containing the particles is 0.5% by mass or more and 10.0% by mass or less. By setting the amount of the anionic surfactant preferably at 0.5% by mass or more, more preferably at 1.0% by mass or more, and even more preferably at 3.0% by mass or more, the dispersibility of the particles is improved, and a dispersion with more uniform particle sizes can be obtained. On the other hand, by setting the amount of the anionic surfactant preferably at 10.0% by mass or less, more preferably at 8.0% by mass or less, and even more preferably at 6.0% by mass or less, stickiness caused by the anionic surfactant when the solution is applied to the spunbond nonwoven fabric can be suppressed.

[0069] Further, the dispersion containing the particles preferably contains silicone oil in an amount of 1% by mass or more and 30% by mass or less. By setting the silicone oil preferably at 1% by mass or more, more preferably at 10% by mass or more, and even more preferably at 15% by mass or more, when the dispersion diluted with water is coated on the spunbond nonwoven fabric, the frictional force between the particles and the spunbond nonwoven fabric is reduced, and the dropping of the particles can be further suppressed. On the other hand, by setting the silicone oil preferably at 30% by mass or less, more preferably at 25% by mass or less, and even more preferably at 20% by mass or less, stickiness caused by the silicone oil when the dispersion is applied to the spunbond nonwoven fabric can be suppressed.

[0070] As the conditions for coating particles containing at least any one of sugar alcohols and saccharides, it is preferable to coat the spunbond nonwoven fabric with a dilution with water such that the total concentration of sugar alcohols and saccharides in the dispersion containing the particles is 0.2% by mass or more and 4.0% by mass or less.

[0071] As a method for applying the dispersion containing the particles to the sheet, there are a roll coating method, a gravure method, a flexo method, a spray coating method, etc., in which the solution is wound up by a metal roll rotating in a chemical liquid tank filled with a dispersion diluted with water, and the spunbond nonwoven fabric is brought into contact with the upper part of the metal roll to transfer the dispersion to the surface of the spunbond nonwoven fabric. Among them, it is preferable to use the roll coating method because of its excellent productivity, the ability to uniformly apply the dispersion, and the ease of adjusting the application amount of the dispersion.

[0072] After applying the dispersion, it is preferable to dry the solvent contained in the dispersion. As this drying method, a method of drying with hot air and infrared rays, a method of drying by contacting a heat source, etc. may be used.

[0073] The spunbond nonwoven fabric of the present invention can be suitably used for sanitary materials such as disposable diapers and masks.

Examples

[0074] Based on the examples, the spunbond nonwoven fabric of the present invention will be specifically described, but the present invention is not limited to these examples. In the measurement of each physical property, those without special description were measured based on the above method.

[0075] (1) Basis weight of the spunbond nonwoven fabric (g / m 2 ) The basis weight of the spunbond nonwoven fabric was measured according to the following procedures A to C in accordance with "6.2 Mass per unit area" of JIS L1913:2010 "General Test Methods for Nonwoven Fabrics". A. Three test pieces of 20 cm × 25 cm were taken per 1 m width of the sample. B. The mass (g) of each in the standard state was measured. C. The average value was expressed as the mass per 1 m 2 per (g / m 2 ).

[0076] (2) Average single fiber diameter (μm) of the spunbond nonwoven fabric Measured by the above method using "VHX-D500" manufactured by KEYENCE CORPORATION as a scanning electron microscope.

[0077] (3) Total content (mass%) of sugar alcohols and saccharides in the spunbond nonwoven fabric The total content of sugar alcohols and saccharides in the spunbond nonwoven fabric was measured by the following procedures A to E.

[0078] Whether the spunbond nonwoven fabric of the present invention contains either sugar alcohols or saccharides was determined by separating the components extracted from the spunbond nonwoven fabric of the present invention with water by HPLC (high performance liquid chromatograph "Chromaster (registered trademark)" manufactured by Hitachi High-Technologies Corporation) and analyzing by infrared spectroscopy or 1 1H-NMR, etc. A. A test piece of 20 cm × 25 cm was taken from the spunbond nonwoven fabric. B. The test piece whose mass was measured was immersed in 200 mL of water and stirred for 30 minutes. C. The components extracted with water were separated by HPLC, and the mass (g) of sugar alcohols and saccharides after isolation under standard conditions was measured. D. The test piece was dried, and the mass (g) of the spunbond nonwoven fabric under standard conditions was measured. E. The total content (mass%) of sugar alcohols and saccharides in the spunbond nonwoven fabric was calculated by the following formula.

[0079] [Number]

[0080] In the formula, X represents the total content (mass%) of sugar alcohols and saccharides. A represents the mass (g) of sugar alcohols and saccharides after isolation. W represents the mass (g) of the spunbond nonwoven fabric under standard conditions after drying.

[0081] (4) Average diameter (μm) of the particles on the spunbond nonwoven fabric As a scanning electron microscope, “VHX-D500” manufactured by KEYENCE CORPORATION was used, and the measurement was carried out by the above method.

[0082] (5) Ratio (%) of particles of 5 μm or more and 10 μm or less on the spunbond nonwoven fabric As a scanning electron microscope, “VHX-D500” manufactured by KEYENCE CORPORATION was used, and the measurement was carried out by the above method.

[0083] (6) Cooling sensation performance (°C) of the spunbond nonwoven fabric The cooling sensation performance of the spunbond nonwoven fabric was measured by the following procedures A to C. A. A nonwoven fabric folded in half was used as a test piece, and a temperature sensor was installed at the center inside the folded part. B. 0.2 mL of water (containing 0.2 mass% penetrant) was dropped onto the center of the test piece (on the sensor) in an atmosphere of 33°C, and the temperature of the wet part was measured for 10 minutes. C. In comparison with the uncoated spunbond nonwoven fabric of the heat absorbent, the cooling sensation performance was evaluated by the maximum temperature difference, and it was determined that there was a “cooling sensation” when the maximum temperature difference was 0.6°C or more.

[0084] (7) Friction treatment of the spunbond nonwoven fabric assuming actual use For the friction treatment of the spunbond nonwoven fabric assuming actual use, the spunbond nonwoven fabric to be a test piece was installed on a Kagaku-Shinkou type friction testing machine (“No. 428” manufactured by Yasuda Seiki Seisakusho Co., Ltd.) without load, and the friction treatment was carried out by operating 50 times using a linen cross-packaging No. 314 cloth adhesive tape on the friction element side. [Method for preparing the dispersion solution] [Dispersion A] 20.0 g of xylitol, 10.0 g of polyoxyethylene cetyl ether (CAS registration number: 9004-95-9), and 1.2 g of sodium dodecylbenzenesulfonate (CAS registration number: 25155-30-0) were stirred and mixed at room temperature and atmospheric pressure. To the resulting mixture, 20.0 g of water at 70 °C (hereinafter sometimes referred to as "Water I") was added at room temperature and atmospheric pressure. Then, at the same temperature and pressure, while stirring the mixture, 20.0 g of amino-modified silicone oil (amino equivalent: about 1500, viscosity (25 °C): 800 mm 2 / s, weight average molecular weight: about 10,000) was added dropwise. Next, while stirring the mixture at room temperature and atmospheric pressure, 28.8 g of water at 70 °C (hereinafter sometimes referred to as "Water II") was added to obtain Dispersion A.

[0085] [Dispersions B - F] Dispersions B - F were obtained in the same manner as Dispersion A, except that the amounts of polyoxyethylene cetyl ether, sodium dodecylbenzenesulfonate, Water I, and Water II were changed as shown in Table 1.

[0086]

Table 1

[0087] [Example 1] A polypropylene resin composed of a homopolymer with an MFR of 200 g / 10 min and a melting point of 163 °C was melted in an extruder and spun from a rectangular die with a pore diameter of φ0.30 mm and a pore depth of 2 mm under the conditions of a spinning temperature of 235 °C and a single-hole discharge rate of 0.25 g / min. After the spun filaments were cooled and solidified, they were drawn and stretched by compressed air with an ejector pressure of 0.65 MPa in a rectangular ejector and collected on a moving net to obtain a fiber web.

[0088] Next, the obtained fiber web was thermally bonded using a pair of upper and lower thermal embossing rolls composed of a metal embossing roll with a water droplet pattern engraved on the adhesive surface area ratio of 16% on the lower roll and a metal flat roll on the upper roll under the conditions of a linear pressure of 400 N / cm and a thermal bonding temperature of 135 °C to obtain a basis weight of 30 g / m2 A spunbond nonwoven fabric was obtained. The average single fiber diameter of the fibers constituting the spunbond nonwoven fabric was 11.9 μm.

[0089] On one side of the obtained spunbond nonwoven fabric, using a metal roll rotating at a speed of 15% of the web conveyance speed in a tank filled with a liquid obtained by diluting dispersion liquid A with 400 g of water at 25°C, dispersion liquid A was adhered, and the volatile components were removed by passing it through a dryer set at 120°C for 1 second, obtaining a spunbond nonwoven fabric. The evaluation results are shown in Table 2.

[0090] [Example 2] In Example 1, a spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that the single-hole discharge amount was changed to 0.45 g / min and the ejector pressure was changed to 0.30 MPa. The evaluation results are shown in Table 2.

[0091] [Example 3] In Example 1, a spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that the liquid obtained by diluting dispersion liquid A with 400 g of water at 25°C was changed to a liquid obtained by diluting dispersion liquid A with 9900 g of water at 25°C. The evaluation results are shown in Table 2.

[0092] [Example 4] In Example 1, a spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that dispersion liquid A was changed to dispersion liquid C. The evaluation results are shown in Table 2.

[0093] [Example 5] In Example 1, a spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that the liquid obtained by diluting dispersion liquid A with 400 g of water at 25°C was changed to a liquid obtained by diluting dispersion liquid D with 390 g of water at 25°C. The evaluation results are shown in Table 2.

[0094] [Comparative Example 1] In Example 1, a spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that the single-hole discharge amount was changed to 0.50 g / min and the ejector pressure was changed to 0.25 MPa. The evaluation results are shown in Table 2.

[0095] [Comparative Example 2] In Example 1, a spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that dispersion liquid A was changed to dispersion liquid B. The evaluation results are shown in Table 2.

[0096] [Comparative Example 3] In Example 1, a spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that the liquid obtained by diluting dispersion liquid A with 400 g of water at 25°C was changed to the liquid obtained by diluting dispersion liquid E with 380 g of water at 25°C. The evaluation results are shown in Table 2.

[0097] [Comparative Example 4] In Example 1, a spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that dispersion liquid A was changed to dispersion liquid F. The evaluation results are shown in Table 2.

[0098]

Table 2

[0099] As shown in Table 2, the spunbond nonwoven fabrics of Examples 1 to 5 were spunbond nonwoven fabrics capable of imparting a cooling sensation and having excellent cooling performance even after friction. On the other hand, the spunbond nonwoven fabrics of Comparative Examples 1 to 4 were spunbond nonwoven fabrics that did not impart sufficient cooling sensation or had a significantly reduced cooling sensation after friction.

Explanation of Symbols

[0100] Particles containing either P sugar alcohols or saccharides

Claims

1. A spunbond nonwoven fabric composed of fibers with an average single fiber diameter of 6.5 μm or more and 14.5 μm or less made of a polyolefin resin, containing particles including one or more selected from the group consisting of sugar alcohols and saccharides, and having an average diameter of the particles of 5 μm or more and 10 μm or less.

2. The spunbond nonwoven fabric according to claim 1, wherein the proportion of the number of particles having a diameter of 5 μm or more and 10 μm or less in the particles is 50% or more and 100% or less.

3. The spunbond nonwoven fabric according to claim 1 or 2, wherein the total content of sugar alcohols and saccharides is 0.1% by mass or more and 2.0% by mass or less.

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