Sanitary nonwoven fabrics and their manufacturing methods

Abstract

The nonwoven fabric for hygiene purposes of the present invention comprises a fiber aggregate containing fibers, the fibers comprising polyamide resin, and the nonwoven fabric having fusion points formed by the fusion of the constituent fibers of the fiber aggregate. The volume filler content of the fiber aggregate is 3.5% or more. Preferably, the constituent fibers are core-sheath composite fibers with a polyamide resin core and a high-density polyethylene resin sheath. The manufacturing method involves hot-air treating a fiber web containing polyamide resin composite fibers to obtain a fiber aggregate, and simultaneously heating the fiber aggregate at a temperature below the melting point of the resin constituting the fiber aggregate while compacting the fiber aggregate.

Description

[Technical Field]

[0001] This invention relates to a sanitary nonwoven fabric and its manufacturing method. [Previous Technology]

[0002] Industry experts have proposed fibers and articles with a composition that can induce a cooling sensation. For example, Patent Document 1 discloses a comfortable fabric for use in clothing to eliminate the feeling of summer heat. According to the document, the fabric contains at least one organic polymer fiber with an axial thermal conductivity of 5 W / mK or higher at 20°C to 30°C, a thickness direction thermal conductivity of 0.08 W / mK or higher at 20°C to 30°C, and a contact cooling sensation of 0.13 W / cm² or higher.

[0003] Patent document 2 discloses an absorbent article made by coating a cooling agent on the lateral wings extending outward from the lateral sides of the self-absorbing body.

[0004] In Patent Document 3, in order to exhibit hygroscopicity and a cool feeling upon contact, a fiber and a fabric using the fiber are disclosed, wherein the sheath polymer of the fiber contains polyamide, the core polymer contains polyether ester amide copolymer, and the fiber as a whole contains 0.1 to 5% by weight of inorganic particles.

[0005] Furthermore, Patent Document 4 discloses a knitted fabric made of yarns of composite fibers with a polyethylene sheath and a nylon or polyester core. (Prior Art Documents, Patent Documents)

[0006] Patent Document 1: Japanese Patent Application Publication No. 2010-236130; Patent Document 2: Japanese Patent Application Publication No. 2016-120208; Patent Document 3: US2017 / 0342606A1; Patent Document 4: Utility Model Registration No. 3226090 [Summary of the Invention]

[0007] This invention relates to a sanitary nonwoven fabric having fiber aggregates comprising fibers containing polyamide resin. In one embodiment, the fiber aggregates preferably have fusion points formed by the fusion of their constituent fibers. In another embodiment, the volume filler content of the fiber aggregates containing polyamide resin is preferably 3.5% or more.

[0008] Furthermore, the present invention relates to a method for manufacturing a sanitary nonwoven fabric, which includes the steps of hot air treatment or spunbonding treatment of a fiber web containing polyamide resin fibers.

Implementation Method

[0009] Sanitary products such as menstrual pads or panty liners, which absorbent items used to absorb bodily fluids, or eye masks or face masks covering the mouth or nose, are composed of multiple non-woven fabric components. If these items come into contact with the skin before or while wearing, the wearer may experience a warm sensation, leading to discomfort such as stuffiness. This discomfort is particularly pronounced in hot weather. Therefore, it is desirable for sanitary products to have a textured surface and a cooling sensation in the areas that come into contact with the skin.

[0010] However, the technologies described in Patent Documents 1, 2 and 4 are applied to articles other than clothing and other hygiene products, and no research has been conducted on their application in hygiene products.

[0011] The technology described in Patent Document 3 uses a cooling agent, so it has a delayed effect in terms of the cooling sensation. Also, it is difficult to feel the cooling sensation when it comes into contact with areas with thicker skin, such as the palm of the hand.

[0012] Therefore, the present invention relates to a sanitary nonwoven fabric having a good texture and providing a cooling sensation upon contact with the skin.

[0013] Hereinafter, the present invention will be described based on preferred embodiments. The sanitary nonwoven fabric of the present invention is suitable for use as a constituent component of sanitary products. Typical examples of sanitary products are sanitary items such as face masks or goggles, or absorbent items such as disposable diapers or menstrual sanitary napkins that absorb bodily fluids such as urine or menstrual blood, preferably absorbent items. The sanitary nonwoven fabric is disposed on the side that contacts the wearer's skin when wearing the sanitary product, i.e., the skin-contact side, or on the part that comes into contact with the wearer's hands when handling the sanitary product. The sanitary nonwoven fabric may be used without being particularly limited to the uses described herein.

[0014] The sanitary nonwoven fabric of the present invention comprises a sheet containing a fiber aggregate (hereinafter also referred to as "an aggregate containing polyamide fibers"), which contains fibers comprising polyamide resin. The sanitary nonwoven fabric may be composed solely of fibers comprising polyamide resin, or may be blended with other fibers to form a fiber aggregate comprising a single fiber layer. Alternatively, the sanitary nonwoven fabric may be constructed by laminating a fiber aggregate layer comprising fibers comprising polyamide resin with other fiber aggregate layers other than the fiber aggregate layer comprising polyamide resin to form a fiber aggregate comprising a plurality of fiber layers.

[0015] The constituent fibers of the sanitary nonwoven fabric of the present invention maintain the shape of a fiber sheet by fusing them together. Specifically, from the viewpoint of further improving texture and breathability, the constituent fibers of the sanitary nonwoven fabric have fusion points formed by fusing the fibers together. Fusion refers to the state in which heat is applied to a plurality of fibers, or heat and pressure are applied to melt the fibers, thereby making the boundaries between the fibers indistinct. In order to form a structure having fusion points, for example, as described below, it can be formed by blowing hot air onto the fiber web.

[0016] The fibers contained in the sanitary nonwoven fabric as described above contain polyamide resin. Examples of the forms in which the polyamide resin constituting the fibers contained in the sanitary nonwoven fabric of the present invention exists include: (i) the form in which the fiber's constituting resin is only polyamide resin, and (ii) fibers containing a resin component containing polyamide resin and a second resin component different from that resin component.

[0017] Generally speaking, polyamide resin has relatively low rigidity and good processability among organic polymer materials, and is therefore often used in textile products. Fibers containing polyamide resin are hygroscopic, and also have relatively high thermal conductivity among organic polymer materials. Focusing on the above-mentioned characteristics of polyamide resin, the inventors discovered that by including polyamide resin in the constituent fibers of nonwoven fabrics, the high thermal conductivity inherent in polyamide resin itself can be utilized, and the fibers can exhibit softness. As a result, the nonwoven fabric can exhibit a good texture while providing a cool sensation.

[0018] As a specific example of (i) above, examples include: fibers containing only a single type of polyamine resin as the constituent resin, and fibers containing multiple types of polyamine resin as the constituent resin. As an example of the latter, fibers containing different types of polyamine resin on the outer surface and inside of the fiber can be cited. As a specific example of (ii) above, examples include: (a) fibers containing a resin formed by mixing polyamine resin with other resins; (b) core-sheath composite fibers with a polyamine resin core and a sheath covering the surface of the core containing other resins; and (c) parallel composite fibers having polyamine resin and other resins, where the other resins are continuously present along the fiber length direction on at least a portion of the surface of the fiber containing polyamine resin. In this case, from the viewpoint of easily forming a melting point, the other resins are resin components other than polyamine resin with a lower melting point than polyamine resin. The fibers used in this invention can be solid or hollow. From the perspective of improving thermal conductivity so that the wearer can easily feel a cool sensation, solid fibers are preferable.

[0019] As for the state in which the constituent resin in the fiber exists, it is preferably a composite fiber containing polyamide resin, more preferably a composite fiber containing polyamide resin inside the fiber, and even more preferably a composite fiber containing polyethylene resin as another resin on at least the entire outer surface of the fiber, and even more preferably a composite fiber having a core-sheath structure with a polyamide resin core and a polyethylene resin sheath. Since polyethylene resin has higher thermal conductivity than polyamide resin, by having polyethylene resin on the fiber surface, the higher thermal conductivity polyethylene resin will come into direct contact with the wearer's skin, thus allowing the wearer to strongly feel a cooling sensation. Furthermore, the fiber can exhibit the good properties of polyamide resin, such as high thermal conductivity, low rigidity, and moisture absorption, thereby further improving the texture of the nonwoven fabric.

[0020] Furthermore, by using resins with different melting points together, the fibers can be nonwoven without completely fusing together, thereby improving the processability during manufacturing and enhancing the texture of the resulting nonwoven fabric. Additionally, the composite fibers can exhibit shrinkage, further improving the texture. Moreover, the nonwoven fabric becomes drier to the touch, and even when a cool sensation is felt upon contact with the nonwoven fabric, it is less likely to cause an uncomfortable damp feeling for the user.

[0021] Examples of polyamide resins used in this invention include nylon 6, nylon 66, and aromatic nylon. From the viewpoint of easy fiber formation, nylon 6 is preferred as the polyamide resin.

[0022] Examples of polyethylene resins used in this invention include: low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), high-density polyethylene resin (HDPE), linear low-density polyethylene resin (LLDPE), and ethylene-propylene copolymers. These can be used alone or in combination or mixed.

[0023] From the viewpoint of having high thermal conductivity and being able to provide the wearer with a strong cooling sensation, it is preferable to include HDPE as the polyethylene resin, and even more preferable to use only HDPE. That is, it is preferable to use HDPE alone as the polyethylene resin. In particular, it is advantageous in that by configuring HDPE on the fiber surface, the fusion points between the fibers can be formed more easily in the following manufacturing method.

[0024] More specifically, it is preferable to have a composite fiber with a core of polyamide resin and a sheath of HDPE. In this way, even if the polyamide resin absorbs moisture from bodily fluids such as sweat, urine, menstrual blood, and breath, the polyamide resin will not directly contact the wearer's skin, thus preventing an uncomfortable feeling of dampness. Furthermore, since fusion can be promoted only at the fiber intersections during manufacturing, the tactile feel is improved. As a result, the sanitary nonwoven fabric maintains a good texture and has a dry, pleasant feel, allowing the wearer to experience a comfortable coolness.

[0025] Furthermore, as a preferred embodiment of the present invention, by utilizing a core-sheath composite fiber composed of a resin whose melting point is lower than that of the resin constituting the core, for example, when manufacturing sanitary nonwoven fabrics by hot air method, it is less likely that the resin constituting the fiber will fail to maintain its shape due to excessive melting, or that the obtained nonwoven fabric will have defects such as holes, thereby further improving manufacturing stability. In addition, by using the above-mentioned core-sheath composite fiber for hot air method, it is easy to fuse only the intersections of the fibers, and the fibers can be nonwoven together without completely fusing them, thereby obtaining a nonwoven fabric with better texture. Furthermore, the nonwoven fabric becomes drier to the touch, and even when a cool sensation is felt when in contact with the nonwoven fabric, it is less likely to cause the user to feel an uncomfortable dampness.

[0026] Examples of resins other than polyethylene resin that can be used in this invention include: polypropylene (PP), polybutene, and other polyolefin resins other than polyethylene resin; polyethylene terephthalate (PET) and other polyester resins; vinyl resins such as polyvinyl chloride or polystyrene; acrylic resins such as polyacrylic acid or polymethyl methacrylate; and various thermoplastic fibers such as perfluoroethylene. One of these resins may be used alone, or two or more may be used in combination, as needed.

[0027] Relative to the total mass of fibers contained in the sanitary nonwoven fabric of the present invention, the content of polyamide resin is preferably 25% by mass or more, more preferably 30% by mass or more, further preferably 40% by mass or more, more preferably 100% by mass or less, more preferably 90% by mass or less, and further preferably 80% by mass or less. When the constituent fibers include polyethylene resin, the content of polyethylene resin is preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 90% by mass or less, and more preferably 80% by mass or less, relative to the total mass of fibers contained in the sanitary nonwoven fabric. The content of each of the above resins is also preferably satisfied within the aggregate containing polyamide fibers.

[0028] When the constituent fibers contain polyethylene resin, from the viewpoint of simultaneously exhibiting a cooling sensation and excellent texture, the mass ratio (polyamide resin / polyethylene resin) of polyamide resin to polyethylene resin contained in the sanitary nonwoven fabric of the present invention is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more. From the viewpoint of nonwoven fabric processability, it is preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.3 or less. The above-mentioned mass ratio is also preferably satisfied within an aggregate containing polyamide fibers.

[0029] The type of resin constituting the fiber is identified as follows: the melting point of the resin constituting the fiber is determined by differential scanning calorimetry, and the type of resin is identified by one or more of infrared spectroscopy (IR) and nuclear magnetic resonance (NMR). Furthermore, the spinning method is deduced based on the surface and cross-sectional shape of the fiber using a scanning electron microscope (SEM), thereby identifying the type of resin in the fiber. The resin content is calculated as follows: First, the mass and thickness of the nonwoven fabric under no-load conditions are measured. Then, the fiber structure is fixed using liquid nitrogen, etc., to create a cross-section of the nonwoven fabric that can be observed in a direction orthogonal to the fiber's length direction. The volume ratio is determined using SEM, etc., and the resin content is calculated based on the obtained volume ratio and the resin's specific gravity. When the nonwoven fabric is incorporated into sanitary products, it is peeled off from the sanitary products by cold spraying and then used for testing.

[0030] From the viewpoint of reducing the content of air with low thermal conductivity to improve the thermal conductivity of the nonwoven fabric, the volume filler content in the polyamide fiber aggregate is preferably 3.5% or more, more preferably 7.0% or more, further preferably 10.0% or more, further preferably 12.0% or more, and further preferably 14.0% or more. Furthermore, when used as a disposable sanitary material in contact with the wearer's skin, from the viewpoint of achieving a good texture, the volume filler content in the polyamide fiber aggregate is preferably 60.0% or less, more preferably 50.0% or less, further preferably 45.0% or less, further preferably 35.0% or less, and further preferably 30.0% or less. Therefore, the volume filling rate of the polyamide fiber-containing aggregate is preferably 3.5% to 60.0%, more preferably 7.0% to 50.0%, further preferably 10.0% to 45.0%, further preferably 12.0% to 35.0%, and further preferably 14.0% to 30.0%.

[0031] By giving the polyamide fiber aggregate the aforementioned volumetric filling rate, the amount of air with low thermal conductivity is reduced within the sanitary nonwoven fabric, thereby improving heat transfer and allowing the wearer to experience a more intense cooling sensation. Furthermore, the texture of the sanitary nonwoven fabric of the present invention and the sanitary products containing the nonwoven fabric are fully realized. The above-mentioned configuration can be obtained, for example, by compacting the fiber aggregate obtained during the manufacturing process of the sanitary nonwoven fabric using the manufacturing method described below.

[0032] The volume fill rate in this invention can be expressed as a percentage of apparent volume relative to actual volume. Specifically, a predetermined area of ​​the sanitary nonwoven fabric to be tested is cut as a test sample, and its mass (g) is measured. The predetermined area for cutting the test sample is preferably 10 cm square; however, if a test sample of this size cannot be cut, it is cut from a region of uniform basis weight under visual inspection of the sanitary nonwoven fabric to be tested, according to the width and length of the maximum possible area. Then, the basis weight A (g / cm²) of the test sample is calculated. Furthermore, the method for measuring the thickness B (cm) of the test sample is as follows. First, a plate weighing only 12.59 g (55 mm in diameter) is placed on a laser displacement meter (LK-080 manufactured by Keyence Corporation. All laser displacement meters mentioned in this specification are this laser displacement meter), and the measured thickness is set to zero for zero-point adjustment. Next, the plate was placed on the test sample, and the thickness under this condition was measured using a laser displacement meter. This thickness was set as the thickness B (cm) of the test sample. In the measurement of thickness B, a load of 4.9 mN / cm² was applied to the test sample by placing the plate.

[0033] Then, using the specific gravity C (g / cm³) of the fiber's constituent components, the volumetric filling rate (%) is calculated according to the following formula (I). In the case of composite fibers or other fibers containing two or more resins, the specific gravity C is used as the sum of the specific gravities based on the mass ratio of each constituent component. For example, in the case of a bicomponent fiber containing a constituent component with specific gravity C1 (g / cm³) and a constituent component with specific gravity C2 (g / cm³) in a mass ratio of 30:70, the specific gravity C (g / cm³) is calculated as "0.3 × specific gravity C1 + 0.7 × specific gravity C2". Volumetric filling rate (%) = 100 × (A) / (B × C) ... (I)

[0034] When a non-woven sanitary fabric containing the test object is placed in a sanitary product such as an absorbent article, a cold spray is blown onto the sanitary product to cure the hot melt adhesive, and then the non-woven sanitary fabric containing the test object is carefully peeled off. Similarly, when it is joined to other components such as the second fiber aggregate described below by means of fusion, the structure is fixed using cold spray or liquid nitrogen, the test object is peeled off, and the measurement is performed. This method is common to other measurements described in this specification.

[0035] The average deviation (MMD) of the coefficient of friction of the sanitary nonwoven fabric of the present invention, measured by the following method, is preferably 0.010 or less, more preferably 0.009 or less, and even more preferably 0.008 or less, and practically 0.004 or more. With this configuration, the nonwoven fabric surface has a dry feel and a good skin feel, resulting in a nonwoven fabric with a superior user experience. The aforementioned coefficient of friction is preferably satisfied when the object is an assembly containing polyamide fibers.

[0036] The mean deviation of the coefficient of friction (MMD) was measured using KES-FB4-AUTO-A (trade name) manufactured by Jiaduo Technology Co., Ltd. First, a 20 cm × 20 cm test piece was removed from the sanitary nonwoven fabric of the test object. If a test piece of this size could not be obtained, the size of the test piece could be appropriately changed. Then, the side of the test piece containing the polyamide resin fiber aggregate was identified using methods such as Fourier transform infrared spectroscopy (FT-IR). Next, the test piece was mounted on a smooth metal test table. The contact surface of the joint was pressed against the fiber aggregate surface of the test piece with a force of 49 cN, and the test piece was moved horizontally 2 cm at a fixed speed of 0.1 cm / sec. A uniaxial tension of 7.3 cN / cm was applied to the test piece. The joint was formed by arranging 20 piano wires with a diameter of 0.5 mm and bending them into a U-shape with a width of 10 mm. A plumb bob is used to press the contact surfaces of the joints onto the test piece with a force of 49 cN. The measurement is performed in one direction of the nonwoven fabric (MD direction) and in the direction perpendicular to it (CD direction). MMDMD and MMDCD are calculated, and the average value is obtained according to the following formula (II), which is taken as the average deviation of the coefficient of friction, MMD. When the test piece can only be taken from either the MD or CD direction, the value in only one direction is taken as the average deviation of the coefficient of friction, MMD. Average deviation of the coefficient of friction, MMD = {(MMDMD / 2 + MMDCD / 2) / 2}1 / 2...(II)

[0037] From the viewpoint of improving the texture of the nonwoven fabric for hygiene purposes of the present invention, the overall thickness of the nonwoven fabric is preferably 0.05 mm or more, and more preferably 0.08 mm or more. Furthermore, from the viewpoint of reducing the air content within the nonwoven fabric for hygiene purposes of the present invention, thereby improving thermal conductivity, the overall thickness of the nonwoven fabric for hygiene purposes of the present invention is preferably 8 mm or less, more preferably 7.5 mm or less, and even more preferably 7 mm or less. The thickness of the nonwoven fabric for hygiene purposes described above was measured using a laser displacement meter or the like under a load of 4.9 mN / cm² (0.5 gf / cm²). By making the thickness of the nonwoven fabric for hygiene purposes of the present invention as described above, the heat capacity of the nonwoven fabric for hygiene purposes can be increased, thereby efficiently manufacturing a nonwoven fabric for hygiene purposes that can efficiently provide a cooling sensation to the wearer. From the same point of view, it is also preferable that the polyamide fiber-containing aggregate meets the above-mentioned thickness range under a load of 4.9 mN / cm 2 (0.5 gf / cm 2).

[0038] The contact cooling sensation qmax of the polyamide fiber aggregate in the sanitary nonwoven fabric of the present invention is preferably 0.06 W / m² or more, more preferably 0.08 W / m² or more, further preferably 0.10 W / m² or more, more preferably 0.80 W / m² or less, more preferably 0.60 W / m² or less, and further preferably 0.50 W / m² or less. Specifically, the contact cooling sensation qmax of the polyamide fiber aggregate in the sanitary nonwoven fabric is preferably 0.06 W / m² or more and 0.80 W / m² or less, more preferably 0.08 W / m² or more and 0.60 W / m² or less, and further preferably 0.10 W / m² or more and 0.50 W / m² or less.

[0039] The contact cooling sensation qmax can be measured, for example, by the following method. First, a test piece is cut from the sanitary non-woven fabric of the test object with dimensions of 10 cm long × 10 cm wide, and the test piece is placed in an environment with a room temperature of 23°C and a relative humidity of 50% for 24 hours. Alternatively, if it is not possible to cut the test piece to the above dimensions, the test piece is cut to the largest possible size to have dimensions close to the above dimensions. Then, in this environment, the test piece is placed on a measuring table and fixed to the measuring table using double-sided tape. A thermostat using a gas or liquid as a heat transfer medium and set to 23°C is used as the measuring table. Then, the contact cooling sensation qmax of the test object is measured using a measuring device (KES-F7 Thermo Lab II manufactured by JAD Technology Co., Ltd.) and according to the device's measurement guidelines. Specifically, a pure copper plate with an area of ​​9.0 cm² and a mass of 9.8 g was used as the hot plate in contact with the test object. The initial temperature of the copper plate was set to 33°C (10°C higher than the surface temperature of the test object), and the contact pressure between the copper plate and the test object was set to 1 kPa. The copper plate was brought into contact with the test piece, and the heat flow value at the instant of contact was set to zero. The maximum value of the heat flow was measured. This measurement was performed 5 times for each test object surface, and the arithmetic mean of the obtained multiple measurements was taken as the contact cooling sensation qmax (W / m²) of the test object.

[0040] The so-called cooling sensation upon contact is obtained by quantifying the feeling of coolness experienced by the skin when in contact with an object. This cooling sensation varies depending on the amount of heat transfer from the skin to the object during contact; the greater the heat transfer, the cooler the sensation upon contact. The cooling sensation qmax corresponds to the maximum value of the heat transfer from the skin to the object. Regarding the value of the cooling sensation qmax, the greater the cooler the sensation upon contact with the object, the larger the value; the warmer the sensation upon contact, the smaller the value. Therefore, by keeping the value of the cooling sensation qmax within the above range, the cooling sensation can be perceived more effectively.

[0041] The sanitary nonwoven fabric of the present invention is preferably configured such that the fibers constituting the nonwoven fabric have a fixed orientation. By having this configuration, heat can be easily transferred along the fiber length direction, thereby making it easier for the wearer to feel a cooling sensation.

[0042] More specifically, the sanitary nonwoven fabric of the present invention is preferably such that, when the nonwoven fabric is placed on a horizontal plane, the fiber length direction of the nonwoven fabric is substantially parallel to the horizontal plane. Furthermore, it is also preferable that, simultaneously or alternatively, when viewed from above, the fiber extension direction of the sanitary nonwoven fabric is unidirectional. For example, when viewed from above, considering the first direction of the sanitary nonwoven fabric and the second direction orthogonal to the first direction, it is further preferable that the fiber extension direction is consistent with either the first or second direction of the nonwoven fabric. When the fibers intersect each other, it is ideal that, when viewed from above, at least 50% of the angles formed by the intersecting fibers are obtuse angles. An obtuse angle is defined as an angle greater than 90°.

[0043] Regarding the quantitative determination of the angles formed by the fibers, the magnification of the fiber intersection points can be confirmed within a field of view of approximately 10 locations. This is achieved by photographing any three locations of the sanitary nonwoven fabric using SEM, and measuring and statistically analyzing the obtained image data using image analysis software attached to the SEM or any other image analysis software. Alternatively, in the absence of image analysis software, the image data can be printed, confirmed using an angle measuring instrument such as a protractor, and entered into a data table for statistical analysis. By having at least one of the aforementioned structures related to fiber orientation, heat can be easily transferred in a fixed direction, thereby making it easier and more effective for the wearer to feel a cooling sensation. This configuration can be obtained, for example, by manufacturing a long sheet using short fibers containing polyamide resin as the material, conveying the long sheet in a conveying direction while applying tension to the long sheet, and fusing the fibers together by hot air method, or by spinning fibers containing polyamide resin into a conveying device such as a belt conveyor while conveying the fibers in a unidirectional direction.

[0044] The thermal conductivity of the polyamide fiber aggregate of the sanitary nonwoven fabric of the present invention is preferably 0.08 W / mK or higher, more preferably 0.10 W / mK or higher, and even more preferably 0.13 W / mK or higher. The above thermal conductivity can be measured, for example, by melting the sanitary nonwoven fabric to form a film-like sample with a thickness of about 1 mm. Detailed measurement methods will be described below. By possessing this thermal conductivity, the wearer of sanitary products containing the sanitary nonwoven fabric can experience a more intense cooling sensation.

[0045] In the above description, for ease of explanation, a sanitary nonwoven fabric having a single fiber layer (containing only a single fiber or a blend with other fibers) was described as an example. The single fiber layer contains fibers containing polyamide resin, but is not limited to this form. Hereinafter, another embodiment of the sanitary nonwoven fabric of the present invention will be described.

[0046] As another embodiment of the sanitary nonwoven fabric, for example, the following configuration can be cited: the sanitary nonwoven fabric has at least a fiber aggregate layer containing a first fiber comprising polyamide resin (hereinafter also referred to as the first fiber layer), and a fiber aggregate layer containing a second fiber comprising fibers other than the first fiber (hereinafter also referred to as the second fiber layer) disposed adjacent to the fiber layer. That is, this embodiment is a sanitary nonwoven fabric with a plurality of layers. Here, "adjacent" means that the fiber layers are adjacent to each other without being separated by other fiber layers, but an adhesive is allowed to exist between the fiber layers. In this case, from the viewpoint of effectively feeling a cooling sensation, it is preferable that the first fiber layer constitutes the outer surface of the sanitary nonwoven fabric. Furthermore, based on the same viewpoint, it is preferable that at least the first fiber layer satisfies various preferred forms related to the above-mentioned sanitary nonwoven fabric, and more preferably that the sanitary nonwoven fabric as a whole satisfies the above-mentioned preferred forms.

[0047] In detail, a multi-layered sanitary nonwoven fabric can be obtained, for example, by performing hot air processing or spunbonding processing on a fiber web containing a first fiber including polyamide resin and a second fiber web containing fibers other than the first fiber. In this case, the boundaries between the fiber layers are usually not clear, but may include portions with clear boundaries. In this embodiment, the fiber layers maintain the shape of the fiber sheet, for example, by at least one of intertwining, fusing, and pressing. As another embodiment of the multi-layered sanitary nonwoven fabric, the following example can be cited: the fiber web or fiber sheet containing a first fiber including polyamide resin is bonded to a fiber web or fiber sheet containing fibers other than the first fiber by an adhesive, thereby maintaining the shape of the fiber sheet. In this case, the boundaries between the fiber layers are usually clearer.

[0048] Regardless of the form, the fibers other than the first fiber include, in addition to the fibers that constitute the resins such as PET resin or PP resin, one or more of the following can be included: pulp fibers or rayon fibers, and fibers that have undergone hydrophilic treatment.

[0049] From the viewpoint of fully experiencing a cooling sensation, the basis weight of the first fiber layer is preferably 10 g / m² or more, more preferably 15 g / m² or more, and even more preferably 18 g / m² or more, and preferably 200 g / m² or less, more preferably 150 g / m² or less, and even more preferably 100 g / m² or less. The basis weight of the second fiber layer is preferably 10 g / m² or more, more preferably 15 g / m² or more, and even more preferably 20 g / m² or more, and even more preferably 140 g / m² or less, more preferably 90 g / m² or less, and even more preferably 70 g / m² or less.

[0050] When the sanitary nonwoven fabric has a multi-layer structure, the thermal conductivity of the fiber layer containing the first fiber comprising polyamide resin is preferably 0.11 W / mK or higher, more preferably 0.13 W / mK or higher, and even more preferably 0.15 W / mK or higher. Using fibers with this thermal conductivity is preferable in terms of achieving a range of thermal conductivity in the sanitary nonwoven fabric. Furthermore, the aforementioned thermal conductivity in the constituent fibers can be achieved, for example, by using a composite fiber comprising polyamide resin and polyethylene resin as the constituent fiber.

[0051] Thermal conductivity can be measured, for example, by the following method. First, the nonwoven fabric or fiber product to be measured is peeled off using a cold spray or similar method, or fiber sampling is performed, and the fibers are separated. Then, the separated nonwoven fabric or fiber is introduced into a heating and pressurizing device such as a press, and heated and pressurized at a temperature above the melting point of the nonwoven fabric or fiber raw material to form a film sample with a thickness of about 1 mm. At this time, the pressurization conditions are adjusted appropriately to avoid air remaining in the sample. Then, using a steady-state thermal conductivity measuring device (manufactured by Jiaduo Technology Co., Ltd., KES-F7 Thermo Lab II), the thermal conductivity is measured based on the amount of heat transfer from a 33°C hot plate to a 23°C hot plate. This measurement is performed on three parts of a film sample, and the highest thermal conductivity value is set as the thermal conductivity (W / mK) in this invention. When the object of measurement is a multi-layered sanitary nonwoven fabric, the fiber layer on the side with the highest value of the contact cooling sensation qmax is designated as the first fiber layer, and the thermal conductivity of the fiber layer is used for the above measurement.

[0052] When the sanitary nonwoven fabric of the present invention includes a second fiber layer, from the viewpoint of reducing the content of air with low thermal conductivity to improve the thermal conductivity of the nonwoven fabric, the volume fill rate in the first fiber layer of the sanitary nonwoven fabric is preferably 3.5% or more, more preferably 7.0% or more, more preferably 10.0% or more, more preferably 12.0% or more, and more preferably 14.0% or more. Furthermore, when used as a disposable sanitary material in contact with the wearer's skin, from the viewpoint of improving the texture, the volume fill rate in the first fiber layer of the sanitary nonwoven fabric is preferably 60.0% or less, more preferably 50.0% or less, more preferably 45.0% or less, more preferably 35.0% or less, and more preferably 30.0% or less. With this configuration, heat mobility can be improved, thereby allowing the wearer to experience a more intense cooling sensation. Furthermore, the texture of the nonwoven fabric for hygiene and the hygiene products containing the nonwoven fabric of the present invention can be fully demonstrated. The volume filling rate of the first fiber layer is determined by designating the fiber layer on the side with the highest value of the contact cooling sensation qmax as the first fiber layer, and then using this fiber layer for the volume filling rate measurement.

[0053] When the sanitary nonwoven fabric has the aforementioned second fiber layer, the second fiber layer preferably has a thickness variation of a specified value or more. Specifically, the compression deformation of the second fiber layer under a load of 9.8 mN / cm² (1 gf / cm²) is preferably 0.3 mm or more, more preferably 0.5 mm or more. Furthermore, the compression deformation of the second fiber layer under this load is preferably 3 mm or less. As described below, the compression deformation is expressed as the change obtained by subtracting the thickness of the second fiber layer under a load of 9.8 mN / cm² (1 gf / cm²) from the thickness of the second fiber layer under no-load conditions. Furthermore, the compression deformation can be calculated by the following method. By having this configuration, when the first fiber layer comes into contact with the wearer, the first fiber layer deforms easily following the deformation of the second fiber layer, thereby increasing the contact area with the wearer and effectively allowing the wearer to feel a cooling sensation. The method for measuring the thickness of the second fiber layer is as follows.

[0054] The sanitary nonwoven fabric having the above-described structure uses fibers containing polyamide resin, a synthetic resin. Therefore, when these fibers come into contact with the wearer's skin, heat generated by the wearer's body temperature can be rapidly transferred from the wearer to the sanitary nonwoven fabric or other fibers not in contact with the wearer. As a result, when the wearer's skin comes into contact with the sanitary nonwoven fabric, the wearer can feel a cooling sensation, which brings a comfortable user experience. Furthermore, the softness and moisture absorption properties of polyamide resin are well exhibited, which also contributes to improving the user experience. In addition, by having fusion points between the fibers in the sanitary nonwoven fabric, heat can be easily transferred to other fibers, and the good texture of the fiber sheet can be exhibited, thereby improving the user experience and comfort. Furthermore, by making the sanitary nonwoven fabric into a sheet material, the contact area between the wearer's skin and the sanitary nonwoven fabric can be increased, allowing the wearer to feel a cooling sensation and exhibiting the softness brought about by the composition of the nonwoven fabric.

[0055] The basis weight of the sanitary nonwoven fabric of the present invention is preferably 10 g / m² or more, more preferably 15 g / m² or more, and even more preferably 18 g / m² or more. Furthermore, the basis weight of the sanitary nonwoven fabric of the present invention is preferably 200 g / m² or less, more preferably 150 g / m² or less, and even more preferably 120 g / m² or less. By adopting the above configuration, the difference in the sensation of coolness caused by uneven basis weight of the sanitary nonwoven fabric can be reduced, and the fibers can be effectively fused or compacted, thereby enabling the production of sanitary nonwoven fabrics with a specified volume fill rate with higher productivity. When the sanitary nonwoven fabric of the present invention is inserted as a component of a sanitary product, the fiber sheet with the highest contact coolness qmax value is used as the sanitary nonwoven fabric, and its basis weight is measured.

[0056] The aforementioned sanitary nonwoven fabric can be used directly, or it can be used as a component of sanitary products to manufacture sanitary products incorporating the sanitary nonwoven fabric. Furthermore, when the sanitary nonwoven fabric of the present invention is incorporated into sanitary products, it is preferable that the nonwoven fabric or the first fiber layer side of the nonwoven fabric forms the surface facing the wearer's skin. In either case, they are generally disposable.

[0057] Examples of sanitary products incorporating nonwoven fabric for hygiene purposes according to the present invention include: disposable diapers, menstrual sanitary napkins, underarm absorbent pads, urine-absorbing pads, panty liners, and other absorbent articles; and face masks or goggles, etc., but sanitary products are not limited to these. For example, absorbent articles incorporating nonwoven fabric for hygiene purposes broadly include articles for absorbing liquids excreted from the human body.

[0058] Sanitary nonwoven fabric can be used as a component of absorbent articles. Absorbent articles generally have a front sheet and a back sheet, and have an absorbent body disposed between the front sheet and the back sheet. In addition, the front sheet or the back sheet can be used when the sanitary nonwoven fabric is disposed thereon.

[0059] When a sanitary nonwoven fabric is used as a component of absorbent articles, the sanitary nonwoven fabric may be applied to the part that comes into direct contact with the wearer's skin when using the absorbent article or when removing the absorbent article from its packaging. That is, the sanitary nonwoven fabric is preferably applied to the outer surface of the absorbent article. The outer surface of the absorbent article refers to the surface of the absorbent article that the wearer can touch by hand after opening the package and removing the absorbent article (including the front and back, but the surface side in the thickness direction, not the inner surface). That is, the outer surface of the sanitary article is preferably the side facing the skin or the side not facing the skin.

[0060] In detail, when a sanitary nonwoven fabric is used in an absorbent article, such as a disposable diaper, as one embodiment of a hygiene product, the sanitary nonwoven fabric can be used as a front sheet, side nonwoven fabric, waist pleats or pleats located near the groin, and outer casing as constituent components. In these cases, by using a sanitary nonwoven fabric at least in the outer casing, the wearer can touch the absorbent article or other hygiene product by hand when it is taken out, thus the good skin feel easily leads the wearer to associate the hygiene product with its superior quality.

[0061] Furthermore, when using sanitary nonwoven fabric in absorbent pads and menstrual sanitary napkins, which are embodiments of sanitary products, the sanitary nonwoven fabric can be used as a front sheet, side nonwoven fabric, diaper protector, or individual packaging bag, for example, as a component. Furthermore, when using sanitary nonwoven fabric in absorbent pads and menstrual sanitary napkins, which are embodiments of sanitary products, the sanitary nonwoven fabric can be used as a front sheet or as a pleat placed near the groin, for example, as a component.

[0062] From the viewpoint of feeling a cool sensation when using absorbent sanitary products and reducing discomfort such as stuffiness, it is preferable that the sanitary non-woven fabric be arranged in the following manner: when the absorbent sanitary product is worn in the correct position, it is arranged on the side facing the skin of the wearer of the absorbent sanitary product (hereinafter also referred to as the "skin-facing side").

[0063] The absorbent material used in absorbent articles has an absorbent core. The absorbent core may include, for example, a fiber stack of hydrophilic fibers such as cellulose (e.g., pulp), a mixed fiber stack of the hydrophilic fibers and a water-absorbing polymer, a stack of water-absorbing polymers, or an absorbent sheet with a water-absorbing polymer held between two sheets. Typically, it includes hydrophilic fibers and a water-absorbing polymer. The absorbent core may also be covered by a coating material. As a coating material, for example, at least the skin-facing side may be covered by a liquid-permeable coating material, or the entire surface, including both the skin-facing and non-skin-facing sides, may be covered by the coating material. As a coating material, for example, a sheet of paper containing hydrophilic fibers or a non-woven fabric with liquid permeability may be used.

[0064] When the sanitary nonwoven fabric is used as a cover, it can be used alone, or it can be used as a laminate formed by layering other nonwoven fabrics with the sanitary nonwoven fabric. Furthermore, the sanitary nonwoven fabric can be provided with ear loops to maintain the coverage of the mouth, nose, and eyes. In this configuration, it is preferable that the sanitary nonwoven fabric is positioned on the skin-facing side, and even more preferably on the part that directly contacts the wearer's skin.

[0065] When a sanitary product is made using the sanitary nonwoven fabric of the present invention, the sanitary product may also have other components (hereinafter referred to as "the second component") in addition to being a sanitary nonwoven fabric containing a polyamide resin fiber aggregate (hereinafter, for ease of explanation, also referred to as "the first fiber aggregate").

[0066] As an embodiment of a sanitary product equipped with the second component, at least one of the following can be used as the second component: an absorbent sheet containing an absorbent polymer and fibers, an absorbent body containing an absorbent polymer and fibers, or a hydrophilic nonwoven fabric. These are examples of fiber aggregates different from sanitary nonwoven fabrics. As a sanitary product equipped with such a second component, the aforementioned absorbent articles are preferably exemplified. That is, in this embodiment, a sanitary nonwoven fabric as a first fiber aggregate and an absorbent sheet, absorbent body, and / or nonwoven fabric as a second component, different from sanitary nonwoven fabric, are disposed as the constituent materials of the sanitary product. The first fiber aggregate and the second component are also preferably disposed adjacent to each other. The fiber aggregates in this embodiment may or may not be joined together. As an absorbent sheet, for example, the absorbent sheet described in Japanese Patent Application Publication No. 8-246395 can be used.

[0067] When the sanitary product includes the aforementioned second component, or when the sanitary nonwoven fabric includes the aforementioned second fiber layer, the second component or the second fiber layer preferably has a thickness variation of a specified value or more. Specifically, the compression deformation of the second component under a load of 9.8 mN / cm² (1 gf / cm²) is preferably 0.3 mm or more, more preferably 0.5 mm or more. Furthermore, the compression deformation of the second component under this load is preferably 3 mm or less. As described below, the compression deformation is expressed as the change in thickness of the second component under no-load conditions minus the thickness of the second component under a load of 9.8 mN / cm² (1 gf / cm²). Preferably, the second fiber layer constituting the sanitary nonwoven fabric also has the same compression deformation. Furthermore, in the case of sanitary products having both a multi-layered nonwoven fabric and a second component, it is preferable that both the second component and the second fiber layer satisfy the aforementioned compression deformation amount. With this configuration, when the first fiber aggregate comes into contact with the wearer, the first fiber aggregate deforms in accordance with the deformation of the second component, thereby increasing the contact area with the wearer and effectively allowing the wearer to experience a cooling sensation.

[0068] Regarding the second fiber layer having the above-mentioned physical properties, for example, it can be obtained by using fibers containing PET resin or PP resin, or PET / HDPE core-sheath composite fibers, as constituent fibers in the manufacturing method described below, and by using a fiber web subjected to hot air treatment. Furthermore, when the second component is an absorbent sheet or absorbent body, it can be obtained, for example, by appropriately adjusting the basis weight of the fibers constituting the absorbent sheet or absorbent body, the fiber sheet, and the water-absorbing polymer.

[0069] The thickness of the second component or the second fiber layer can be measured, for example, by the following method. First, the cross-section of the object to be measured is observed visually or by SEM, and the fiber diameter, the distance between fibers, or the interface between components are observed. By performing the above operations, it is confirmed whether it is a sanitary nonwoven fabric with multiple fiber layers, or whether there is a sanitary nonwoven fabric and a second component other than the sanitary nonwoven fabric. When the object to be measured is a sanitary product, after fixing the structure by immersing the sanitary product in liquid nitrogen, the sanitary nonwoven fabric and the second component other than the sanitary nonwoven fabric are carefully peeled off from the sanitary product to separate them. Then, the separated component is used for the above-mentioned measurement of the contact cooling sensation qmax. The fiber sheet with the highest qmax value is designated as the sanitary nonwoven fabric, and the component adjacent to the sanitary nonwoven fabric is designated as the second component. Next, operations such as placing the plate on the separated second component were performed. Under a load of 4.9 mN / cm² (0.5 gf / cm²), the thickness under this condition was measured using a laser displacement meter, and this was set as the thickness of the second component. When the object of measurement is a multi-layered sanitary nonwoven fabric, the fiber layer on the side with the highest qmax value as detailed in the following embodiments was designated as the first fiber layer, and the fiber layer adjacent to the first fiber layer was designated as the second fiber layer. The second fiber layer was then used for the above measurement.

[0070] Furthermore, in the overall sanitary product, the compression deformation under a load of 9.8 mN / cm² (1 gf / cm²) is preferably 0.3 mm or more, more preferably 0.4 mm or more. Also, the overall compression deformation of the sanitary product under this load is preferably 15 mm or less, more preferably 10 mm or less. By adopting this configuration, the nonwoven fabric as a whole exhibits softness, improving usability, and the contact area between the polyamide resin-containing fiber aggregate and the wearer is increased, effectively allowing the wearer to experience a cooling sensation.

[0071] Regarding the aforementioned compression set, for example, in the case of a hot air method, it is achieved by: lowering the temperature or velocity of the hot air compared to the normally used conditions, or increasing the number of fibers or using fibers containing resins with melting points higher than the hot air temperature, thereby reducing the fusion properties between the fibers. It can also be achieved by employing, in addition to, the following configurations, or by replacing the above configurations: providing two or more fiber layers, with only one fiber layer having a higher compression set than the other fiber layers; or increasing the basis weight of one fiber layer compared to the other fiber layers; or blending fibers with higher melting points into one fiber layer.

[0072] The compression deformation can be measured, for example, using a KES-FB-3 compression testing machine manufactured by Jiaduo Technology Co., Ltd. A fixed-size slice is cut from the sanitary nonwoven fabric of the test object and used as a sample. The sample is mounted on the test bench of the testing machine and placed between steel plates with a circular plane of 2 cm². The compression speed is 0.02 mm / sec, and the maximum compression load is set to 9.8 mN / cm² (1 gf / cm²). When the thickness under no load is defined as thickness T0 (mm), and the thickness under a load of 9.8 mN / cm² (1 gf / cm²) is defined as thickness Tm (mm), the compression deformation (mm) can be calculated by subtracting thickness Tm from thickness T0, i.e., "T0 - Tm".

[0073] When the second component is an absorbent sheet, the overall basis weight of the second component is preferably 40 g / m² or more, more preferably 60 g / m² or more, and even more preferably 70 g / m² or more, and preferably 500 g / m² or less, more preferably 400 g / m² or less, and even more preferably 300 g / m² or less. When the second component is an absorbent sheet, the overall basis weight of the second component is preferably 30 g / m² or more, more preferably 40 g / m² or more, and even more preferably 50 g / m² or more, and even more preferably 600 g / m² or less, more preferably 550 g / m² or less, and even more preferably 500 g / m² or less.

[0074] The nonwoven fabric for hygiene purposes preferably has a bending stiffness value below a specified value. Specifically, the bending stiffness value of the nonwoven fabric for hygiene purposes is preferably 0.25 gf·cm² / cm or less, more preferably 0.2 gf·cm² / cm or less, further preferably 0.15 gf·cm² / cm or less, and even more preferably 0.1 gf·cm² / cm or less. By having this structure, it is easy to bend in response to external forces, thereby increasing the contact area with the wearer's skin and effectively allowing the wearer to feel a cooling sensation.

[0075] The bending stiffness value of sanitary nonwoven fabric can be measured according to the method described on pages 27-28 of "Standardization and Analysis of Texture Evaluation (2nd Edition)" (Author: Kawabata Sueo; Publisher: Japan Textile Machinery Society, Texture Measurement and Standardization Research Committee; Publication Date: July 10, 1966). Specifically, a sample is obtained by cutting a piece with dimensions of 20 cm in length and 10 cm in width. The sample is mounted in the clamps of a pure bending tester (trade name: KES-FB2) manufactured by Kado Technology Co., Ltd., with a clamp spacing of 10 mm. The mounting direction is set so that the length direction of the sanitary nonwoven fabric is the bending direction. Pure bending with a constant curvature is performed within the range of curvature K = -2.5 to +2.5 cm⁻¹. The deformation speed is set to 0.50 cm⁻¹ / sec. This operation yields the relationship between the bending moment M per unit area of ​​the specimen and the curvature K (MK curve). The slope of the MK curve, i.e., the bending stiffness B per unit length (gf·cm² / cm), is calculated from the result. B is determined based on the characteristics of the increase in the absolute value of K, specifically the slopes between K = 0.5 cm⁻¹ and K = 1.5 cm⁻¹, and between K = -0.5 cm⁻¹ and K = -1.5 cm⁻¹, denoted as Bf and Bb respectively. Their arithmetic mean (Bf + Bb) / 2 is taken as the bending stiffness value of this invention.

[0076] From the viewpoint of avoiding fiber entanglement with the skin and ensuring a good feel and usability for the wearer, the fiber diameter of the fibers used in sanitary nonwoven fabrics is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 12 μm or more. Furthermore, from the viewpoint of reducing the gaps between fibers in the nonwoven fabric, thereby reducing the air content in the nonwoven fabric and improving thermal conductivity, the fiber diameter of the fibers used in sanitary nonwoven fabrics is preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 27 μm or less. Regarding the fiber diameter, similar to the method for measuring the lengths of the major and minor axes of the fiber's cross-sectional shape, sample preparation and SEM observation are performed. The fiber diameter of 10 fibers in each sample is measured, and their arithmetic mean is taken as the fiber diameter of the present invention. When the fiber is not perfectly round, the lengths of the major and minor axes of the fiber are measured by the above method. The arithmetic mean of the lengths of the major and minor axes of a single fiber is taken as the fiber diameter, and the arithmetic mean of the diameters of 10 such fibers is taken as the fiber diameter of the fiber in this invention.

[0077] From the viewpoint of maintaining a good feel and usability for the wearer, when the fibers used in the sanitary nonwoven fabric are short fibers, the fiber diameter is preferably 30 mm or more, and more preferably 38 mm or more. Furthermore, from the viewpoint of improving thermal conductivity, when the fibers used in the sanitary nonwoven fabric are short fibers, the fiber diameter is preferably 40 mm or more, and more preferably 45 mm or more. Also, when the fibers used in the sanitary nonwoven fabric are short fibers, from the viewpoint of not impairing processability, the fiber diameter is preferably 70 mm or less, and more preferably 60 mm or less. The fiber length is set as follows: when the fiber is in a curled state, the fiber is left stationary without stretching to avoid bending as much as possible; the distance from end to end of 10 fibers is measured using a ruler; and the arithmetic mean of the obtained fiber lengths is taken as the fiber length of the fiber of the present invention.

[0078] As long as the effects of the present invention can be achieved, the sanitary nonwoven fabric of the present invention may further include fillers for improving thermal conductivity. Examples of such fillers include at least one of titanium oxide, aluminum oxide, boron nitride, magnesium oxide, silicon oxide, carbon black, zinc oxide, and carbon nanotubes. The filler may exist within the fibers, between the fibers, or partially exposed on the fiber surface and embedded within the fibers.

[0079] The above description relates to the sanitary nonwoven fabric of the present invention and sanitary products containing the sanitary nonwoven fabric. The preferred manufacturing method of the sanitary nonwoven fabric of the present invention will be described below. This manufacturing method includes a step of hot-air treating a fiber web containing polyamide resin fibers to obtain a fiber aggregate (hot-air step). Preferably, in addition to this, a step of compacting the obtained fiber aggregate is also performed (compacting step). Furthermore, it is even more preferable that the composite fiber used in this manufacturing method is the aforementioned core-sheath composite fiber.

[0080] First, a fiber web comprising fibers of polyamide resin is formed. The fiber web can be formed, for example, by carding using a known carding machine.

[0081] Next, the fiber web is subjected to hot air treatment by blowing hot air to obtain an aggregate of fibers containing polyamide resin. This step is a step of non-woven the fiber web, and the fiber aggregate produced in this way is usually called hot air nonwoven fabric.

[0082] Generally, when hot-air processing is performed on fiber webs containing polyethylene resin, the use of core-sheath composite fibers is beneficial to improving the texture and strength of the obtained hot-air nonwoven fabric. However, there is still room for improvement in terms of improving thermal conductivity so that the wearer feels cool. The inventors have conducted in-depth research on these improvements and found that by controlling the temperature and wind speed of the hot air in the hot-air process, hot-air nonwoven fabrics with good texture and strength can be manufactured efficiently.

[0083] The hot air blown onto the fiber web during the hot air step is preferably within a specific range in terms of temperature and air velocity. Specifically, from the viewpoint of maintaining the fiber shape without causing it to become thinner, thereby resulting in a good texture for the obtained sanitary nonwoven fabric, the temperature of the hot air blown onto the fiber web is preferably below the melting point Mp (°C) of the resin contained on the surface of the fibers constituting the fiber web, more preferably below Mp + 10°C, and even more preferably below Mp + 9°C, and further preferably below Mp + 8°C. Furthermore, to ensure that the fibers constituting the fiber web are appropriately fused together so that the sanitary nonwoven fabric exhibits durable strength, the temperature of the hot air blown onto the fiber web is preferably above Mp - 4°C, more preferably above Mp - 2°C, and even more preferably above the melting point Mp. When core-sheath composite fibers are used in this manufacturing method, it is easier to form a fusion point and further improve the texture of the nonwoven fabric, thereby making it easier for people to feel a cool sensation. It is preferable to use fibers in which the melting point of the resin constituting the core of the core-sheath composite fiber is higher than the melting point of the resin constituting the sheath.

[0084] The hot air step can be performed, for example, by blowing hot air into the fiber web on the mesh conveyor belt using a hot air furnace. In this case, the temperature of the hot air is set to the temperature at the centroid of the hot air outlet in a top view and directly above the mesh conveyor belt. This temperature can be measured, for example, using a thermocouple.

[0085] For example, when using a core-sheath composite fiber composed of HDPE (melting point Mp: 130°C) sheath and nylon 6 (melting point: 225°C) polyamide resin core as the fiber web, the temperature of the hot air is preferably 126°C or higher, more preferably 128°C or higher, and even more preferably 130°C or higher. Furthermore, under the above conditions, the temperature of the hot air is preferably 140°C or lower, more preferably 139°C or lower, and even more preferably 138°C or lower.

[0086] When using fibers containing polyamide resin as the fibers constituting the fiber web, for example, nylon 6 (melting point Mp: 225°C), the temperature of the hot air is preferably set to 221°C or higher, more preferably 223°C or higher, and even more preferably 225°C or higher. Furthermore, under the above conditions, the temperature of the hot air is preferably set to 235°C or lower, more preferably 234°C or lower, and even more preferably 233°C or lower. Furthermore, when using nylon 66 (melting point Mp: 265°C) as the fiber containing polyamide resin, the temperature of the hot air is preferably set to 261°C or higher, more preferably 263°C, and even more preferably 265°C or higher. Furthermore, under the above conditions, the temperature of the hot air is preferably set to 275°C or lower, more preferably 274°C or lower, and even more preferably 273°C or lower.

[0087] The melting point Mp of the resin constituting the fiber surface can be determined using a differential scanning calorimeter (DSC7000x manufactured by Hitachi High-Tech Science Co., Ltd.). First, using a fiber sample (1 mg) cut into small pieces, thermal analysis of the sample is performed at a heating rate of 10°C / min to determine the melting peak temperature of each resin. The melting point is defined as the melting peak temperature at the first heating. If a definite melting point cannot be determined by this method, the resin is defined as "a resin without a melting point". In the case of a resin without a melting point, the softening point is set as the melting point Mp.

[0088] Furthermore, in the hot air step, from the viewpoint of ensuring that the hot air passes sufficiently through the thickness direction of the fiber web to facilitate fiber fusion, the wind speed of the hot air blown onto the fiber web is preferably 0.6 m / s or more, and more preferably 1.0 m / s or more. Also, based on the same viewpoint, the wind speed of the hot air blown onto the fiber web is preferably 2.0 m / s or less, and more preferably 1.4 m / s or less. By performing the hot air step under the aforementioned temperature and wind speed conditions, the polyethylene resin present on the surface of the fibers constituting the fiber web can be melted or softened, thereby randomly forming fusion points where the fibers fuse together. Therefore, the manufactured sanitary nonwoven fabric exhibits the softness and good texture of hot-air nonwoven fabric, and also exhibits durable strength.

[0089] The conveying speed of the fiber web in the hot air step is preferably 3 m / min or more, more preferably 10 m / min or more, more preferably 200 m / min or less, and more preferably 160 m / min or less within the above temperature and wind speed range.

[0090] Since the fiber aggregate obtained through the above steps has been nonwoven, it can also be directly used as the sanitary nonwoven fabric of the present invention. The sanitary nonwoven fabric is a hot-air nonwoven fabric.

[0091] From the viewpoint of easily obtaining a sanitary nonwoven fabric with a specified volume fill rate, it is preferable to further perform a compaction treatment (compaction step) on the fiber aggregate obtained through the above steps. The compaction treatment in this step can be performed by a method that can compress the fiber aggregate by applying pressure in its thickness direction.

[0092] As a compaction process, it can be performed, for example, by placing the fiber aggregate between two metal plates and applying pressure (hereinafter, this method is also referred to as "pressing method" or "pressure treatment"), or by introducing the fiber aggregate between a pair of rollers with a smooth circumferential surface and applying pressure (hereinafter, this method is also referred to as "calendering method" or "calendering treatment"). The compaction process can be performed only once, or it can be performed multiple times by the same or different methods as needed. Furthermore, the temperature in the compaction process can be room temperature, a heated state, or a combination thereof. From the viewpoint of improving manufacturing efficiency, the calendering method is preferred. From the viewpoint of efficiently performing compaction in a heated state without temperature unevenness, it is more preferable to use a pair of rollers with a circumferential surface including metal for the calendering process.

[0093] The compaction process is preferably performed under pressure while heated. Specifically, from the viewpoint of easily obtaining a sanitary nonwoven fabric with a high volumetric filling rate by sufficiently compacting the fiber aggregates, when using the pressing method, the pressure conditions during the compaction process, expressed as surface pressure, are preferably 5 MPa or more, and more preferably 7 MPa or more. Furthermore, from the viewpoint of preventing the fiber aggregates from becoming thin films, maintaining a clear fiber shape with distinct boundaries between the constituent fibers, and obtaining a sanitary nonwoven fabric with good texture, when using the pressing method, the pressure conditions during the compaction process, expressed as surface pressure, are preferably set to 72 MPa or less, and more preferably 32 MPa or less.

[0094] Furthermore, from the viewpoint of easily obtaining a sanitary nonwoven fabric with a high volumetric filling rate by sufficiently compacting the fiber aggregates, the pressure conditions during calendering, expressed in terms of linear pressure, are preferably 78.4 N / cm (8 kgf / cm) or more, and more preferably 127.4 N / cm (13 kgf / cm) or more. Furthermore, from the viewpoint of preventing the fiber aggregates from becoming thin films, maintaining the fiber shape with clear boundaries between the constituent fibers, and obtaining a sanitary nonwoven fabric with good texture, the pressure conditions during calendering, expressed in terms of linear pressure, are preferably 686 N / cm (70 kgf / cm) or less, more preferably 490 N / cm (50 kgf / cm) or less, and even more preferably 294 N / cm (30 kgf / cm) or less.

[0095] Furthermore, from the viewpoint of easily obtaining a sanitary nonwoven fabric with a high volumetric filling rate by sufficiently compacting the fiber aggregates, regardless of whether the pressing method or the calendering method is used, the heating temperature in the compaction process is preferably set to a range of 80°C or higher from the melting point Mp, more preferably to a range of 70°C or higher from the melting point Mp, and even more preferably to a range of 60°C or higher from the melting point Mp. Also, from the viewpoint of easily obtaining a sanitary nonwoven fabric with a high volumetric filling rate by sufficiently compacting the fiber aggregates, regardless of whether the pressing method or the calendering method is used, the heating temperature in the compaction process is preferably set to below the melting point Mp, more preferably to a range of 20°C or lower from the melting point Mp. When heating is performed in the compaction process, if it is a pressing method, it is sufficient to heat the metal plate to the above temperature range; if it is a calendering method, it is sufficient to heat the circumferential surface of the roller to the above temperature range.

[0096] The pressing time during the compaction process can be appropriately set, as long as it is within the conditions that maintain the fiber shape of the fibers constituting the fiber aggregate and allows compaction to proceed. For example, when using the pressing method, the pressing time under the aforementioned pressure and temperature conditions is preferably set to 5 seconds or more, and more preferably 10 seconds or more, in each compaction process. Furthermore, when using the pressing method, the pressing time under the aforementioned pressure and temperature conditions is preferably set to 25 seconds or less, and more preferably 20 seconds or less, in each compaction process.

[0097] For example, when using the calendering method, the pressurization time under the aforementioned pressure and temperature conditions in each compaction process is preferably set to 0.01 seconds or more, more preferably 0.04 seconds or more. Furthermore, when using the calendering method, the pressurization time under the aforementioned pressure and temperature conditions in each compaction process is preferably set to 0.10 seconds or less, and more preferably 0.08 seconds or less.

[0098] By performing compaction treatment under the above conditions, the fiber aggregate can be compressed in the thickness direction, thereby obtaining a sanitary nonwoven fabric with a specified volume filler ratio and thickness. In particular, within the above-mentioned pressure and temperature range, the resin constituting the fibers is in a state where it is not easily melted, which improves the morphological and dimensional stability brought about by heat treatment. Therefore, a sanitary nonwoven fabric that maintains the fiber shape and the specified volume filler ratio after manufacturing can be obtained. Furthermore, when using fibers with a perfectly circular cross-sectional shape, compaction treatment can flatten the cross-sectional shape of the fibers, thus also having the advantage of improving the volume filler ratio. The sanitary nonwoven fabric obtained by the above method is a hot-air nonwoven fabric even after compaction treatment.

[0099] In the case of manufacturing a multi-layered sanitary nonwoven fabric, for example, a second fiber web containing a thermoplastic resin, formed by carding, is laminated onto a fiber web containing a polyamide resin to form a laminated fiber web. Then, the laminated fabric is subjected to hot air treatment, thereby obtaining a hot-air nonwoven fabric as a multi-layered fiber aggregate. The boundaries between the fiber layers of this nonwoven fabric are not clear. In this case, regarding the temperature of the blown hot air, it is preferable to determine the temperature of the hot air by setting the melting point of the resin with the lowest melting point as the aforementioned melting point Mp.

[0100] Furthermore, in the above-described case, the hot air blowing step in the hot air treatment is preferably to arrange the fiber web in a laminated body so that the fiber web other than the fiber web containing polyamide resin can be blown. By adopting this method, the fibers in the fiber web containing polyamide resin are thermally fused together by the pressure of the hot air to form a first fiber aggregate with a high volume filler ratio, while the second fiber web side maintains its fluffiness, thereby obtaining a sanitary nonwoven fabric with excellent compression deformability. As such a method, for example, the hot air treatment can be performed by placing the side of the laminate containing the fiber web containing polyamide resin on the lower side of the hot air device, such as the web side.

[0101] As another form of manufacturing sanitary nonwoven fabric with multiple layers, fiber sheets can be obtained by hot air treatment of a fiber web containing polyamide resin and a second fiber web containing thermoplastic resin, and then the fiber sheets can be joined together by adhesive or various embossing processes, and by methods such as fusion, bonding or pressing.

[0102] The sanitary nonwoven fabric of the present invention can also be manufactured by a spunbond method instead of the above-described manufacturing method. That is, it can also include a step of spunbonding polyamide resin to obtain fiber aggregates (spunbonding step). The sanitary nonwoven fabric manufactured in this manner is a spunbond nonwoven fabric.

[0103] In detail, the raw material resin for the fiber is extruded in a molten state from a spinning head having multiple fine pores, and the extruded resin is extended by rollers to form long fibers. These long fibers are then stacked on a mesh conveyor belt to obtain a fiber web containing polyamide resin fibers. Subsequently, the fiber web is guided between embossing rollers having multiple protrusions on its peripheral surface, and compacted (hot-pressed) by heating and pressing to obtain the sanitary nonwoven fabric of the present invention. That is, this method simultaneously performs the formation of fusion points between the fibers, the nonwoven fabricization of the fiber web, and the compaction treatment.

[0104] The temperature in the embossing roller is preferably set to a range of 40°C or higher from the melting point Mp, more preferably to a range of 35°C or higher from the melting point Mp, and even more preferably to a range of -30°C or higher from the melting point. From the viewpoint of fully fusing the embossed portion, the pressure applied using the embossing roller is preferably set to 0.3 MPa or higher, more preferably to 0.5 MPa or higher, and even more preferably to 1.0 MPa or higher. Furthermore, from the viewpoint of preventing holes caused by excessive pressure, the above-mentioned pressure conditions are preferably set to 40 MPa or lower, more preferably to 35 MPa or lower, and even more preferably to 30 MPa or lower.

[0105] In the case of manufacturing a multi-layered sanitary nonwoven fabric, for example, a second fiber web containing thermoplastic resin formed by carding is laminated onto a fiber web containing polyamide resin to form a laminated fiber web. Then, the laminated body is compacted (hot-pressed) by heating and pressurizing under the above conditions.

[0106] The sanitary nonwoven fabric of the present invention can be obtained through the above steps. Preferably, this sanitary nonwoven fabric is inserted as a constituent component of absorbent articles or other sanitary products in subsequent steps. When the sanitary nonwoven fabric is used as a constituent material of absorbent articles or other sanitary products, any step in manufacturing the sanitary product includes one or more of the following steps: using the sanitary nonwoven fabric manufactured by the above method as one of the constituent materials, and cutting the sanitary nonwoven fabric; and performing various operations such as laminating or bonding the sanitary nonwoven fabric with other constituent materials (e.g., absorbent bodies or sheets) constituting the sanitary product; thus, the target absorbent article or other sanitary product can be manufactured.

[0107] The present invention has been described above based on preferred embodiments, but the present invention is not limited to the above embodiments.

[0108] Regarding the above-described embodiments of the present invention, the following sanitary nonwoven fabric and its manufacturing method are further disclosed. <1> A sanitary nonwoven fabric comprising a fiber aggregate containing fibers, the fibers comprising polyamide resin, the fiber aggregate having a fusion point formed by the fusion of its constituent fibers, and the volume filler content of the fiber aggregate containing the polyamide resin being 3.5% or more.

[0109] <2> The sanitary nonwoven fabric described in <1> above, wherein the volume fill rate of the fiber aggregate containing the fiber containing polyamide resin is preferably 7.0% or more, more preferably 10.0% or more, further preferably 12.0% or more, further preferably 14.0% or more, the volume fill rate is preferably 60.0% or less, more preferably 50.0% or less, further preferably 45.0% or less, further preferably 35.0% or less, further preferably 30.0% or less, the volume fill rate is preferably 7.0% or more and 60.0% or less, more preferably 7.0% or more and 50.0% or less, further preferably 10.0% or more and 45.0% or less, further preferably 12.0% or more and 35.0% or less, further preferably 14.0% or more and 30.0% or less.

[0110] <3> The sanitary nonwoven fabric described in <1> or <2> above, wherein the fiber is a composite fiber containing polyamide resin. <4> The sanitary nonwoven fabric described in <3> above, wherein the composite fiber is a composite fiber in which polyamide resin is contained within the fiber. <5> The sanitary nonwoven fabric described in <3> or <4> above, wherein the composite fiber is a composite fiber in which polyethylene resin is contained on the entire outer surface of the fiber.

[0111] <6> The sanitary nonwoven fabric described in any one of <1> to <5> above, wherein the fiber core is a polyamide resin and the sheath comprises a core-sheath composite fiber of high-density polyethylene resin. <7> The sanitary nonwoven fabric described in any one of <1> to <6> above, wherein the content of polyamide resin relative to the total mass of fibers contained in the sanitary nonwoven fabric is preferably 25% by mass or more, more preferably 30% by mass or more, further preferably 40% by mass or more, preferably 100% by mass or less, more preferably 90% by mass or less, further preferably 80% by mass or less. <8> The sanitary nonwoven fabric described in any one of <1> to <7> above, wherein the polyamide resin is one or more of nylon 6, nylon 66, and aromatic nylon. <9> As described in any of <1> to <8> above, the nonwoven fabric for hygiene uses further comprises polyethylene resin, and the content of polyethylene resin is preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 90% by mass or less, and more preferably 80% by mass or less, relative to the total mass of the fibers contained in the nonwoven fabric for hygiene uses.

[0112] <10> The sanitary nonwoven fabric described in any of the above <1> to <9>, wherein the sanitary nonwoven fabric further comprises polyethylene resin, and the mass ratio of polyamide resin to polyethylene resin (polyamide resin / polyethylene resin) of the sanitary nonwoven fabric is preferably 0.1 or more, more preferably 0.2 or more, more preferably 0.3 or more, more preferably 2.0 or less, more preferably 1.5 or less, and more preferably 1.3 or less.

[0113] <11> The sanitary nonwoven fabric described in any one of <1> to <10> above further comprises polyethylene resin, wherein the polyethylene resin is one or more of low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), high-density polyethylene resin (HDPE), linear low-density polyethylene resin (LLDPE), and ethylene-propylene copolymer, preferably high-density polyethylene resin (HDPE). <12> The sanitary nonwoven fabric described in any one of <1> to <11> above has a mean deviation (MMD) of the coefficient of friction of 0.010 or less. <13> The sanitary nonwoven fabric described in any one of <1> to <12> above preferably has a mean deviation (MMD) of the coefficient of friction of 0.009 or less, more preferably 0.008 or less, and more preferably 0.004 or more.

[0114] <14> The sanitary nonwoven fabric described in any of the above-mentioned <1> to <13>, wherein the overall thickness of the sanitary nonwoven fabric under a load of 4.9 mN / cm 2 (0.5 gf / cm 2) is preferably 0.05 mm or more, more preferably 0.08 mm or more, more preferably 8 mm or less, more preferably 7.5 mm or less, and even more preferably 7 mm or less. <15> The sanitary nonwoven fabric described in any of the above-mentioned <1> to <14>, wherein the overall basis weight of the sanitary nonwoven fabric is preferably 10 g / m 2 or more, more preferably 15 g / m 2 or more, even more preferably 18 g / m 2 or more, more preferably 200 g / m 2 or less, more preferably 150 g / m 2 or less, and even more preferably 120 g / m 2 or less. <16> The sanitary nonwoven fabric described in any one of <1> to <15> above, wherein the contact cooling sensation qmax of the fiber aggregate of the sanitary nonwoven fabric is preferably 0.06 W / m² or more, more preferably 0.08 W / m² or more, further preferably 0.10 W / m² or more, preferably 0.80 W / m² or less, more preferably 0.60 W / m² or less, and further preferably 0.50 W / m² or less. <17> The sanitary nonwoven fabric described in any one of <1> to <16> above, wherein the thermal conductivity of the fiber aggregate of the sanitary nonwoven fabric is preferably 0.08 W / mK or more, more preferably 0.10 W / mK or more, and further preferably 0.13 W / mK or more.

[0115] <18> The sanitary nonwoven fabric described in any of the above-mentioned <1> to <17>, wherein the bending stiffness value of the sanitary nonwoven fabric is preferably 0.25 gf・cm 2 / cm or less, more preferably 0.2 gf・cm 2 / cm or less, further preferably 0.15 gf・cm 2 / cm or less, and further preferably 0.1 gf・cm 2 / cm or less. <19> The sanitary nonwoven fabric described in any of the above-mentioned <1> to <18>, wherein the fiber diameter of the above-mentioned fiber is preferably 1 μm or more, more preferably 5 μm or more, further preferably 12 μm or more, preferably 40 μm or less, more preferably 30 μm or less, and further preferably 27 μm or less. <20> The sanitary nonwoven fabric described in any of <1> to <19> above, wherein the fiber length of the aforementioned fibers is preferably 30 mm or more, more preferably 38 mm or more, more preferably 70 mm or less, and more preferably 60 mm or less. <21> The sanitary nonwoven fabric described in any of <1> to <20> above, wherein the sanitary nonwoven fabric further comprises a filler. <22> The sanitary nonwoven fabric described in <21> above, wherein the filler is one or more of titanium oxide, aluminum oxide, boron nitride, magnesium oxide, silicon oxide, carbon black, zinc oxide, and carbon nanotubes.

[0116] <23> The sanitary nonwoven fabric described in any one of <1> to <22> above has a first fiber layer comprising the aforementioned fiber aggregate, and a second fiber layer comprising a second fiber aggregate disposed adjacent to the first fiber layer, wherein the compression deformation of the second fiber aggregate under a load of 9.8 mN / cm² is 0.3 mm or more. <24> The sanitary nonwoven fabric described in <23> above, wherein the aforementioned first fiber layer is disposed on the outer surface. <25> The sanitary nonwoven fabric described in <23> or <24> above, wherein the basis weight of the first fiber layer is preferably 10 g / m² or more, more preferably 15 g / m² or more, and even more preferably 18 g / m² or more, and preferably 200 g / m² or less, more preferably 150 g / m² or less, and even more preferably 100 g / m² or less. <26> In the sanitary nonwoven fabric described in any of <23> to <25> above, the basis weight of the second fiber layer is preferably 10 g / m² or more, more preferably 15 g / m² or more, further preferably 20 g / m² or more, preferably 140 g / m² or less, more preferably 90 g / m² or less, further preferably 70 g / m² or less. <27> In the sanitary nonwoven fabric described in any of <23> to <26> above, the compression deformation of the second fiber layer under a load of 9.8 mN / cm² (1 gf / cm²) is preferably 0.3 mm or more, more preferably 0.5 mm or more, and more preferably 3 mm or less.

[0117] <28> A sanitary product comprising a sanitary nonwoven fabric as described in any one of <1> to <27> above, and a second member disposed adjacent to the nonwoven fabric, wherein the second member has a compression deformation of 0.3 mm or more under a load of 9.8 mN / cm². <29> In the sanitary product described in <28> above, the compression deformation of the second member under a load of 9.8 mN / cm² (1 gf / cm²) is preferably 0.5 mm or more, and preferably 3 mm or less. <30> In the sanitary product described in <28> or <29> above, the overall compression deformation of the sanitary product is 0.3 mm or more under a load of 9.8 mN / cm². <31> As described in any of <28> to <30> above, the sanitary product as a whole has a compression deformation of more than 0.4 mm under a load of 9.8 mN / cm 2 (1gf / cm 2), more preferably less than 15 mm, and even more preferably less than 10 mm.

[0118] <32> The sanitary product described in any one of <28> to <31> above, wherein the second component is an absorbent or an absorbent sheet. <33> The sanitary product described in any one of <28> to <32> above, wherein the second component is an absorbent sheet, and the basis weight of the absorbent sheet as a whole is preferably 40 g / m² or more, more preferably 60 g / m² or more, further preferably 70 g / m² or more, preferably 500 g / m² or less, more preferably 400 g / m² or less, further preferably 300 g / m² or less.

[0119] <34> The sanitary article described in any one of <28> to <32> above, wherein the second component is an absorbent, and the basis weight of the absorbent as a whole is preferably 30 g / m² or more, more preferably 40 g / m² or more, further preferably 50 g / m² or more, preferably 600 g / m² or less, more preferably 550 g / m² or less, and further preferably 500 g / m² or less. <35> An absorbent article comprising a sanitary nonwoven fabric described in any one of <1> to <27> above. <36> The absorbent article described in <35> above, wherein the sanitary nonwoven fabric is disposed on the outer surface of the absorbent article.

[0120] <37> A method for manufacturing a sanitary nonwoven fabric, which is the method for manufacturing a sanitary nonwoven fabric as described in any one of <1> to <27> above, comprising the following steps: hot air treatment or spunbonding treatment of a fiber web containing polyamide resin fibers. <38> The manufacturing method described in <37> above includes the step of hot air treatment of a fiber web containing polyamide resin fibers. In the above step, when the melting point of the resin constituting the fiber is set as melting point Mp, the temperature of the hot air blown onto the fiber web is preferably set to melting point Mp + 10°C or lower, more preferably to melting point Mp + 9°C or lower, further preferably to melting point Mp + 8°C or lower, more preferably to melting point Mp - 4°C or higher, more preferably to melting point Mp - 2°C or higher, and further preferably to a temperature above melting point Mp. <39> The manufacturing method described in <37> or <38> above includes a step of hot air treatment of a fiber web containing polyamide resin fibers. In the above step, the air velocity of the hot air blown onto the fiber web is preferably 0.6 m / s or more, more preferably 1.0 m / s or more, more preferably 2.0 m / s or less, and more preferably 1.4 m / s or less. <40> The manufacturing method described in any one of <37> to <39> above includes a step of hot air treatment of a fiber web containing polyamide resin fibers. In the above step, the conveying speed of the fiber web is preferably 3 m / min or more, more preferably 10 m / min or more, more preferably 200 m / min or less, and more preferably 160 m / min or less.

[0121] <41> The manufacturing method described in any one of <37> to <40> above further includes a step of compacting the fiber aggregate obtained by the above-mentioned hot air treatment or spunbonding treatment, wherein the compaction treatment is performed while heating at a temperature below the melting point of the resin constituting the fiber. <42> The manufacturing method described in <41> above, wherein the compaction treatment is performed by placing the fiber aggregate between two metal plates and applying pressure, or by introducing the fiber aggregate between a pair of rollers and applying pressure. <43> The manufacturing method described in <41> or <42> above, wherein the compaction treatment is performed by the above-mentioned pressure treatment, wherein the pressure conditions in the pressure treatment are preferably 5 MPa or more, more preferably 7 MPa or more, more preferably 72 MPa or less, and more preferably 32 MPa or less.

[0122] <44> The manufacturing method described in <41> or <42> above, wherein the above-mentioned compaction treatment is performed by the above-mentioned calendering treatment, and the pressure conditions in the above-mentioned calendering treatment are preferably 78.4 N / cm (8 kgf / cm) or more, more preferably 127.4 N / cm (13 kgf / cm) or more, more preferably 686 N / cm (70 kgf / cm) or less, more preferably 490 N / cm (50 kgf / cm) or less, and even more preferably 294 N / cm (30 kgf / cm) or less. <45> In the manufacturing method described in any of <41> to <44> above, when the melting point of the resin constituting the fiber is set as melting point Mp, the heating temperature in the compaction treatment is preferably above melting point Mp - 80°C, more preferably above melting point Mp - 70°C, further preferably above melting point Mp - 60°C, more preferably below melting point Mp, and even more preferably below melting point Mp - 20°C. [Example]

[0123] Hereinafter, the present invention will be described in more detail by way of examples. However, the scope of the present invention is not limited to these examples. Columns indicated by "-" in the table mean that they do not contain or have not been measured.

[0124] [Examples 1-3] A core-sheath composite fiber was used, with nylon 6 as the polyamide resin as the core and HDPE as the sheath. The resin mass ratio, fiber diameter, and fiber length are shown in Table 1 below. First, the fiber web of the above composite fiber, which was adjusted to the basis weight shown in Table 1 below, was subjected to hot air treatment to obtain a nonwoven fiber aggregate. The hot air treatment conditions are as described in Table 1 below. Then, the fiber aggregate was compacted under the heating and pressure conditions shown in Table 1 below by pressing a pair of flat metal plates to obtain the target sanitary nonwoven fabric. These nonwoven fabrics are all single-layer structures.

[0125] [Example 4] Except that the air velocity during hot air treatment was set to 1.2 m / s and compaction treatment was performed by calendering, the procedure was carried out in the same manner as in Example 1 to obtain a single-layer sanitary nonwoven fabric with the desired structure. The pressure conditions for calendering were set to 483 N / cm (49.3 kgf / cm), and a pair of smoothing rollers with smooth surfaces were used.

[0126] [Example 5] A core-sheath composite fiber with nylon 6 as polyamide resin as core and HDPE as sheath was used, and the mass ratio of the resin was changed as shown in Table 1 below. Otherwise, the same procedure as in Example 1 was performed to obtain the target sanitary nonwoven fabric.

[0127] [Example 6] A fiber web consisting only of nylon 6 fibers, which is a polyamide resin, was formed by spunbonding. The fiber web was then fused and compacted using an embossing roller to obtain a sanitary nonwoven fabric containing spunbond nonwoven material. The conditions for the spunbonding process are shown in Table 1 below. The nonwoven fabric has a single-layer structure. Furthermore, the fiber length obtained by spunbonding is substantially infinite; the fiber length was not measured in this example.

[0128] [Example 7] A fiber web containing only nylon 66 fibers as polyamide resin was formed by spunbonding. Under the same conditions as in Example 6, the fiber web was fused and compacted using an embossing roller to obtain a sanitary nonwoven fabric containing spunbond nonwoven fabric.

[0129] [Example 8] In this example, a sanitary nonwoven fabric with a multi-layer structure was manufactured. Specifically, under the same conditions as in Example 1, a fiber web containing a core-sheath composite fiber with nylon 6 as a polyamide resin as the core and HDPE as the sheath was subjected to hot air treatment, and then, under the same conditions as in Example 1, was subjected to compaction treatment to obtain a single-layer nonwoven fabric (basis weight: 90 g / m2). In addition, a second fiber web containing a core-sheath composite fiber with PET as the core and PE as the sheath was prepared, and under the same conditions as in Example 1, was subjected to hot air treatment and compaction treatment to obtain a single-layer nonwoven fabric (basis weight: 20 g / m2). Finally, the nonwoven fabrics were laminated by hot melt adhesive to bond them together to obtain the desired multi-layer structure sanitary nonwoven fabric (basis weight: 110 g / m2).

[0130] [Example 9] A core-sheath composite fiber with nylon 6 as polyamide resin as the core and HDPE as the sheath and a core-sheath composite fiber with PET as the core and PE as the sheath were mixed at a mass ratio of 1:1. Under the same conditions as in Example 1, hot air treatment and compaction treatment were performed to obtain the target nonwoven fabric. The nonwoven fabric is a single-layer structure without the second fiber aggregate.

[0131] [Comparative Example 1] Except for using a core-sheath composite fiber with a core of PET and a sheath of HDPE without using polyamide resin, the same procedure as in Example 1 was performed to obtain the target sanitary nonwoven fabric.

[0132] [Comparative Example 2] Except for using a core-sheath composite fiber with a core of PP and a sheath of HDPE without using polyamide resin, the same procedure as in Example 1 was performed to obtain the target sanitary nonwoven fabric.

[0133] [Determination of the thickness of sanitary nonwoven fabric] The thickness of the sanitary nonwoven fabric in the Example and Comparative Examples was determined. The thickness was measured at 5 or more locations using a laser displacement meter under a load of 4.9 mN / cm² (0.5 gf / cm²) applied to the sanitary nonwoven fabric being measured, and the arithmetic mean of these measurements was taken as the thickness (mm). The results are shown in Table 1.

[0134] [Determination of volume fill rate] The volume fill rate (%) of the sanitary nonwoven fabrics of the Examples and Comparative Examples was calculated by the above method. The results are shown in Table 1.

[0135] [Determination of Compression Deformation under 9.8 mN / cm² Load] The compression deformation (mm) of the sanitary nonwoven fabrics of the Examples and Comparative Examples under a 9.8 mN / cm² load was calculated using the method described above. The results are shown in Table 1.

[0136] [Determination of MMD] The MMD of the sanitary nonwoven fabrics of the Examples and Comparative Examples was calculated using the method described above. The results are shown in Table 1.

[0137] [Thermal Conductivity of Nonwoven Fabrics] The thermal conductivity and cooling sensation upon contact of the sanitary nonwoven fabrics of the Examples and Comparative Examples were determined by the following method. (1. Sample Preparation) The sanitary nonwoven fabrics to be tested were cut into small pieces. A laminate of approximately 10 g, formed by stacking multiple pieces, was placed between two stainless steel plates and positioned in the center of the plates. The laminate was heated for 1 minute without pressure to obtain a molten material. The heating temperature was set to the melting point M + 20°C as measured by the differential scanning calorimeter described above. In the case of nonwoven fabrics containing multiple resin materials, the melting point of the resin with the highest melting point was used as the reference for heating. Specifically, heating was performed at 245°C. Next, while maintaining the above heating temperature, a gauge pressure of 200 kgf (total mass including the top plate: 21848 kg; when calculating pressure by surface pressure, since the area of ​​the melt changes with the melting of the resin, the surface pressure should be calculated based on the area of ​​the final obtained circular resin plate. For example, if the diameter of the circular resin plate is 15 cm, the surface pressure is 12 MPa) is applied and maintained for 1 minute. Then, while maintaining the pressure, it is water-cooled to 20°C to obtain a circular resin plate with a diameter of approximately 15 to 20 cm (the diameter of the obtained circular resin plate may vary depending on the melt viscosity of the resin). Next, the obtained circular resin plate is cut radially from the center. If the maximum diameter is 5 cm or more, it is further cut into pieces of 5 cm or less. Next, to eliminate the influence of resin alignment by randomly directing the extension direction of the imaginary line segment with the maximum diameter, the cut resin plate was stacked in the center of the stainless steel plate. Two 1 mm thick gap-filling sheets were then placed parallel to each other 10 cm from the center of the stainless steel plate, and the stainless steel plate was stacked on top of them. Subsequently, heating under no-pressure conditions and heating and cooling under pressure conditions were performed using the same procedures as described above. If air bubbles were introduced, the same steps were repeated. The purpose of the two heating and melting processes was to temporarily melt the sample, eliminating the influence of resin crystallization and other changes that occur during fiber spinning, thus fixing the thermal process. This yielded a thin film.

[0138] (2. Measurement of Thermal Conductivity) The thermal conductivity was measured using a measuring device (KES-F7 Thermo Lab II manufactured by Jiaduo Technology Co., Ltd.) and by the following method. First, a 10 cm long × 10 cm wide section was cut from the prepared film and placed in an environment of 23°C room temperature and 50% relative humidity for 24 hours. Then, the thermal conductivity of the test object was measured using the aforementioned measuring device and in accordance with the device's measurement guidelines. Specifically, the temperature of the heat source (BT-BOX, which is an integrated structure of a 5 cm long × 5 cm wide and 1 mm thick aluminum plate and heater) was set to 33°C (10°C higher than the surface temperature of the test object). To prevent the film from warping and reducing the contact area, a load of 1 kg was applied to every 0.25 m² of the film to bring the heat source into contact with the film. On the display panel of the measuring instrument, the point at which the heat flow from the heat source to the object being measured becomes constant is set as the start point of the measurement. The average heat flow is measured over 60 seconds from that point. Based on the measurement conditions and the measured heat flow, the following formula (III) is used for calculation. The thickness D of the film is the arithmetic mean of the thickness obtained by measuring at least three locations under no-load conditions using a laser displacement meter. The above measurement is performed three times for each object being measured, and the maximum value of these measurements is set as the thermal conductivity (W / mK) of the sample. The results are shown in Table 1.

[0139] k=100×(W×D) / (A×ΔT)・・・(III) (k: thermal conductivity [W / mK], W: heat flow [W / m 2], D: film thickness [cm], A: aluminum plate area (25cm 2), ΔT: temperature difference between heat source and film (10℃))

[0140] [Determination of Cooling Sensation Upon Contact] The cooling sensation upon contact was determined using a testing device (KES-F7 Thermo Lab II manufactured by Jiaduo Technology Co., Ltd.) and conducted as follows: First, a piece measuring 23cm in length and 14cm in width was cut from the sanitary nonwoven fabric of the test object and placed in an environment with a room temperature of 23°C and a relative humidity of 50% for 24 hours. Next, using the aforementioned testing device and following its testing guidelines, a thermostatic device employing a gas or liquid as the heat medium was used to place the test piece at 23°C to measure the temperature difference between the heat source and the sanitary nonwoven fabric of the test object. Then, using the aforementioned testing device and following its testing guidelines, the cooling sensation upon contact, qmax, was measured. Specifically, a pure copper (T-Box) measuring terminal with an area of ​​9.0 cm² and a mass of 9.8 g was used as the hot plate in contact with the test object. The initial temperature of the copper plate was set to 33°C (10°C higher than the surface temperature of the test object), and the contact pressure between the copper plate and the test object was set to 98 mN / cm² (10 gf / cm²). The copper plate was brought into contact with the test piece, and the heat flux at the moment of contact was set to zero. The maximum value of this heat flux was measured. This measurement was performed five times for each test object surface, and the arithmetic mean of these multiple measurements was taken as the contact cooling sensation qmax (W / m²). A larger contact cooling sensation qmax indicates a greater amount of heat transfer, and a faster heat transfer, making it easier for the wearer to feel a cooling sensation. The results are shown in Table 1 below.

[0141] [Texture Evaluation] The texture of the nonwoven fabrics of the Examples and Comparative Examples was evaluated using the following methods. The texture evaluation test included softness, smoothness, and skin feel. First, 20 professional sensory inspectors touched the surface of the nonwoven fabric and scored each item according to the following evaluation criteria, calculating the average score for each item. Then, the overall average score was calculated based on the average scores for each item, and this average score was used as the texture evaluation. The results are shown in Table 1. 5 points: Good. 4 points: Slightly better. 3 points: Average. 2 points: Slightly worse. 1 point: Poor.

[0142] [Cooling Sensation Evaluation] The cooling sensation of the nonwoven fabrics of the Examples and Comparative Examples was evaluated using the following method. First, 20 professional sensory inspectors touched the surface of the nonwoven fabric and scored the cooling sensation upon contact with the nonwoven fabric according to the following criteria. The arithmetic mean of the scores was used as the evaluation of the cooling sensation. The results are shown in Table 1. 5 points: Excellent cooling sensation. (The cooling sensation is as strong as that of contact cooling fabrics with a q-max of 0.20 or higher.) 4 points: Good cooling sensation. 3 points: Cooling sensation is perceptible. 2 points: Slight cooling sensation is perceptible. 1 point: No cooling sensation is perceptible at all. (The cooling sensation is not perceptible, similar to that of hot-air nonwoven fabrics with a q-max of 0.06 or lower.)

[0143] As shown in Table 1, compared with the comparative example, the non-woven sanitary fabrics of each embodiment have a better texture, higher thermal conductivity and volumetric filler ratio, and a higher contact cooling sensation (qmax), allowing for a stronger cooling sensation. Therefore, the non-woven sanitary fabric of the present invention has a better texture and provides a cooling sensation when in contact with the skin, giving a comfortable user experience.

[0144] [Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Comparative Example 1 Comparative Example 2 First fiber aggregate Fiber 1 Fiber Core-sheath composite fiber Core-sheath composite fiber Core-sheath composite fiber Core-sheath composite fiber Core-sheath composite fiber Single fiber Single fiber Core-sheath composite fiber Core-sheath composite fiber Core-sheath composite fiber Core-sheath composite fiber Core resin Types of resins Nylon 6 Nylon 6 Nylon 6 Nylon 6 Nylon 6 Nylon 6 Nylon 66 Nylon 6 Nylon 6 PET PP Quality ratio [quality%] 50 50 50 50 30 100 100 50 50 50 50 Sheath resin Types of resins HDPE HDPE HDPE HDPE HDPE - - HDPE HDPE HDPE HDPE Quality ratio [quality%] 50 50 50 50 70 - - 50 50 50 50 Fiber diameter [μm] 17 17 17 17 17 17 17 17 17 17 18 Fiber length [mm] 51 51 51 51 51 - - 51 51 51 51 Fiber 2 Fiber - - - - - - - - Core sheath Composite Fiber - - Core resin Types of resins - - - - - - - - PET - - Quality ratio [quality%] - - - - - - - - 50 - - Sheath resin Types of resins - - - - - - - - HDPE - - Quality ratio [quality%] - - - - - - - - 50 - - Fiber diameter [μm] - - - - - - - - 17 - - Fiber length [mm] - - - - - - - - 51 - - 2nd Fiber aggregates Fiber - - - - - - - Core-sheath composite fiber - - - Core resin type - - - - - - - PET / PE - - - Quality ratio [quality%] - - - - - - - 50 - - - Sheath resin Types of resins - - - - - - - HDPE - - - Quality ratio [quality%] - - - - - - - 50 - - - Fiber diameter [μm] - - - - - - - 17 - - - Fiber length [mm] - - - - - - - 51 - - - Nonwoven fabric conditions Manufacturing method hot air hot air hot air hot air hot air spunbond spunbond hot air hot air hot air hot air Temperature [°C] 134 134 134 134 134 - - 134 134 134 134 Wind speed [m / s] 1.7 1.2 1.2 1.2 1.2 - - 1.7 1.7 1.7 1.7 Web transfer speed [m / minute] 10 10 10 10 10 10 10 10 10 10 10 Compacting conditions Manufacturing method pressurization pressurization pressurization calendering pressurization Embossing Embossing pressurization pressurization none none Temperature [°C] 80 80 80 80 80 250 250 80 80 - - Pressure [MPa] 10 10 10 Linear voltage 483 N / cm 10 5 5 10 10 - - Pressurization time [seconds] 15 15 15 0.08 15 0.05 0.05 15 15 - - Physical properties of the first fiber aggregate Basis weight [g / m 2 ] 90 40 20 90 90 90 90 90 90 90 57.6 Volumetric fill rate [%] 16.0 15.0 19.0 12.7 16.0 5.8 5.8 16.0 29.0 1.3 2.8 Thickness [mm] 0.6 0.3 0.1 0.7 0.6 1.5 1.5 0.6 0.3 5.9 2.2 9.8 mN / cm 2 Compressive deformation under load [mm] 0.6 0.6 0.5 0.6 1.1 0.7 0.7 0.6 0.9 0.7 0.6 Second fiber aggregate physical properties Basis weight [g / m 2 ] - - - - - - - 20 - - - Thickness [mm] - - - - - - - 2.0 - - - 9.8 mN / cm 2 Compressive deformation under load [mm] - - - - - - - 0.5 - - - Properties of sanitary non-woven fabrics The fusion point of the fibers that make up nonwoven fabric have have have have have have have have have have have MMD[-] 0.008 0.008 0.008 0.008 0.008 0.008 0.008 0.008 0.005 0.006 0.008 9.8 mN / cm 2 Compressive deformation under load [mm] 0.6 0.6 0.5 0.6 1.1 0.7 0.7 0.4 0.9 0.7 0.6 Overall basis weight [g / m 2 ] 90 40 20 90 90 90 90 110 90 90 57.6 Overall thickness [mm] 0.6 0.3 0.1 0.7 0.6 1.5 1.5 2.6 0.3 5.9 2.2 Volumetric fill rate [%] 16 15 19 13 16 5.8 5.8 16 29 1.3 2.8 Evaluate Texture assessment [points] 5 5 4 5 4 4 4 5 4 3 3 Cooling sensation assessment [points] 4.5 4 4 4.5 4 4 4 5 3 1 1 Thermal conductivity of the first fiber aggregate [W / mK] 0.18 0.18 0.18 0.18 0.18 0.16 0.16 0.18 0.18 0.14 0.17 q-max[W / m 2 ] 0.15 0.14 0.14 0.15 0.15 0.15 0.15 0.15 0.16 0.06 0.06 [Industrial Applicability]

[0145] According to the present invention, a sanitary nonwoven fabric with good texture and capable of providing a cooling sensation upon contact with the skin is provided.

Claims

1. A sanitary nonwoven fabric comprising a fiber aggregate containing composite fibers, the composite fibers comprising polyamide resin and polyethylene resin, the fiber aggregate having a fusion point formed by the fusion of its constituent fibers, and the volume filler content of the fiber aggregate containing the composite fibers comprising the polyamide resin and polyethylene resin being 3.5% to 60%.

2. The sanitary nonwoven fabric of claim 1, wherein the volume fill rate of the fiber aggregate containing the composite fibers comprising polyamide resin and the aforementioned polyethylene resin is 12.0% or more.

3. As in claim 1, the sanitary nonwoven fabric wherein the polyamide resin is one or more of nylon 6, nylon 66, and aromatic nylon.

4. The sanitary nonwoven fabric of claim 1, wherein the mass ratio of polyamide resin to polyethylene resin (polyamide resin / polyethylene resin) contained in the sanitary nonwoven fabric is 0.1 to 2.

0.

5. The sanitary nonwoven fabric of claim 1, wherein the polyethylene resin is one or more of low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), high-density polyethylene resin (HDPE), linear low-density polyethylene resin (LLDPE), and ethylene-propylene copolymer.

6. The sanitary nonwoven fabric of claim 5, wherein the composite fiber is a core-sheath composite fiber in which the core is polyamide resin and the sheath comprises high-density polyethylene resin (HDPE).

7. The average deviation (MMD) of the coefficient of friction of the sanitary nonwoven fabric as requested in item 1 is less than 0.

010.

8. The sanitary nonwoven fabric of claim 1, wherein the thermal conductivity of the fiber aggregate of the sanitary nonwoven fabric is 0.08 W / mK or higher.

9. The sanitary nonwoven fabric of claim 1, wherein the bending stiffness of the sanitary nonwoven fabric is 0.25 gf・cm2 / cm or less.

10. The sanitary nonwoven fabric of claim 1, wherein the diameter of the composite fibers is more than 1 μm and less than 40 μm.

11. The sanitary nonwoven fabric of claim 1, wherein the fiber length of the composite fiber is more than 30 mm and less than 70 mm.

12. The sanitary nonwoven fabric of claim 1, wherein the sanitary nonwoven fabric further includes filler.

13. The sanitary nonwoven fabric of claim 12, wherein the filler is one or more of titanium oxide, aluminum oxide, boron nitride, magnesium oxide, silicon oxide, carbon black, zinc oxide, and carbon nanotubes.

14. The sanitary nonwoven fabric of claim 1, having a first fiber layer comprising the aforementioned fiber aggregate, and a second fiber layer comprising a second fiber aggregate disposed adjacent to the first fiber layer, wherein the second fiber aggregate has a compression deformation of 0.3 mm or more under a load of 9.8 mN / cm2.

15. The sanitary nonwoven fabric of claim 14, wherein the first fiber layer is disposed on the outer surface.

16. A sanitary product comprising a sanitary nonwoven fabric as claimed in claim 1, and a second member disposed adjacent to the nonwoven fabric, wherein the second member has a compression deformation of 0.3 mm or more under a load of 9.8 mN / cm2.

17. The sanitary products of claim 16 have a compression deformation of 0.3 mm or more under a load of 9.8 mN / cm2.

18. The sanitary product as claimed in claim 16, wherein the second component mentioned above is an absorbent.

19. An absorbent article comprising a sanitary nonwoven fabric as claimed in claim 1.

20. The absorbent article of claim 19, wherein the aforementioned sanitary nonwoven fabric is disposed on the outer surface of the absorbent article.

21. A method for manufacturing a sanitary nonwoven fabric, which is the method for manufacturing a sanitary nonwoven fabric as claimed in claim 1, comprising the steps of hot air treatment or spunbonding treatment of a fiber web comprising composite fibers of polyamide resin and polyethylene resin.

22. The manufacturing method of claim 21 further includes a step of compacting the fiber aggregate obtained by the above-mentioned hot air treatment or spunbonding treatment, wherein the compaction treatment is performed while heating at a temperature below the melting point of the resin constituting the composite fiber.

23. The manufacturing method of claim 22, wherein the above-mentioned compaction process is performed by placing the fiber aggregate between two metal plates and applying pressure, or by introducing the fiber aggregate between a pair of rollers and applying pressure.

24. The manufacturing method of claim 22, wherein the above-mentioned compaction process is performed by the above-mentioned pressurization process, and the pressurization conditions in the above-mentioned pressurization process are set to 5 MPa or more and 72 MPa or less.

25. The manufacturing method of claim 22, wherein the above-mentioned compaction process is performed by the above-mentioned calendering process, and the pressure conditions in the above-mentioned calendering process are 78.4 N / cm (8 kgf / cm) or more and 686 N / cm (70 kgf / cm) or less.