Sanitary nonwoven fabric and manufacturing method thereof

Abstract

To provide a sanitary nonwoven fabric having good touch and capable of giving a cool feeling when being brought into contact with the skin, and a manufacturing method thereof.SOLUTION: A sanitary nonwoven fabric of the invention has a fiber assembly containing fibers including polyamide resin and has a fused point at which constituent fibers of the fiber assembly are fused. Volume filling rate is 3.5% or higher. It is suitable that the constituent fiber is a core-sheath conjugate fiber consisting of core of polyamide resin and sheath of high-density polyethylene resin. In the manufacturing method, the fiber assembly is obtained by applying air-through processing to a web of a composite fiber containing polyamide resin, and consolidation processing is applied to the fiber assembly while heating at a temperature not higher than a melting point of the resin constituting the fiber assembly.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sanitary nonwoven fabric and a method for producing the same. [Background technology]

[0002] Fibers and articles having a structure that can make a cooling sensation perceptible have been proposed. For example, Patent Document 1 discloses a comfort fabric intended for use in clothing to alleviate the feeling of heat in summer. This fabric contains at least one type of organic polymer fiber with a thermal conductivity of 5 W / mK or more in the fiber axis direction at 20°C to 30°C, a thermal conductivity of 0.08 W / mK or more in the thickness direction of the fabric at 20°C to 30°C, and a contact cooling sensation of 0.13 W / cm². 2 The same document also discloses that the above is true.

[0003] Patent Document 2 discloses an absorbent article in which a cooling agent is applied to side flaps that extend outward from both lateral sides of the absorbent body.

[0004] Patent Document 3 discloses a fiber and a fabric using the same, in which the sheath polymer is composed of a polyamide and the core polymer is a polyether ester amide copolymer, with inorganic particles containing 0.1 to 5% by weight throughout the fiber, for the purpose of exhibiting hygroscopicity and a cool-to-the-touch feel.

[0005] Furthermore, Patent Document 4 discloses a knitted fabric made by knitting yarn of a composite fiber in which the sheath layer is polyethylene and the core layer is nylon or polyester. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2010-236130 [Patent Document 2] Japanese Patent Publication No. 2016-120208 [Patent Document 3] Japanese Patent Publication No. 2016-204784 [Patent Document 4] Utility Model Registration No. 3226090 Gazette [Overview of the project] [Problems that the invention aims to solve]

[0007] Sanitary products such as sanitary napkins and panty liners, which absorb bodily fluids, and sanitary items such as eye masks and face masks, which cover the mouth and nose, are made up of multiple components, including nonwoven fabric. When such items come into contact with the skin before use or during wear, they may cause the wearer to perceive warmth and recall discomfort such as stuffiness during use. This can be particularly noticeable in hot environments. Therefore, it is desirable that the parts of sanitary products that come into contact with the skin have a pleasant texture and a structure that provides a cooling sensation.

[0008] However, the technologies described in Patent Documents 1, 2, and 4 are applicable to items other than sanitary products such as clothing, and their application to sanitary products has not been considered at all.

[0009] The technology described in Patent Document 3 uses a cooling agent, and therefore has a delayed effect in producing a cooling sensation. Furthermore, when it comes into contact with areas of thick skin, such as the palms of the hands, the cooling sensation is less likely to be felt.

[0010] Therefore, the present invention relates to a hygienic nonwoven fabric that has a good texture and can be perceived as cool when it comes into contact with the skin. [Means for solving the problem]

[0011] The present invention comprises a fiber assembly containing fibers including a polyamide resin, The aforementioned fiber aggregate has fusion points where its constituent fibers are fused together, This invention provides a sanitary nonwoven fabric having a volume filling ratio of 3.5% or more of fiber aggregates containing polyamide resin fibers.

[0012] Furthermore, the present invention provides a method for manufacturing a sanitary nonwoven fabric, comprising the step of performing an air-through treatment or spunbond treatment on a fiber web containing a polyamide resin. [Effects of the Invention]

[0013] According to the present invention, a hygienic nonwoven fabric is provided that has a good texture and can be perceived as cool when it comes into contact with the skin. [Modes for carrying out the invention]

[0014] The present invention will be described below based on its preferred embodiments. The sanitary nonwoven fabric of the present invention is suitably used as a component of sanitary products. Typical examples of sanitary products include sanitary items such as face masks and eye masks, and absorbent items that absorb bodily fluids such as urine and menstrual blood, such as disposable diapers and sanitary napkins, and absorbent items are preferred. Sanitary nonwoven fabric is placed on the skin-contact side of the sanitary product, which is the side that comes into contact with the wearer's skin when the product is worn, or on the parts that come into contact with the wearer's hands or other body parts when handling the sanitary product. Sanitary nonwoven fabrics are applicable to uses not limited to those described herein.

[0015] The sanitary nonwoven fabric of the present invention is a sheet-like material comprising fiber aggregates containing polyamide resin fibers (hereinafter also referred to as "polyamide fiber-containing aggregates"). The sanitary nonwoven fabric may be composed of fiber aggregates consisting of a single fiber layer, either by the polyamide resin-containing fibers alone or by blending them with other fibers. Alternatively, the sanitary nonwoven fabric may be composed of fiber aggregates consisting of multiple fiber layers, by laminating a layer of fiber aggregates containing polyamide resin fibers with a layer of other fiber aggregates other than the polyamide resin-containing fiber aggregate layer.

[0016] The constituent fibers of the sanitary nonwoven fabric of the present invention maintain their shape as a fiber sheet through fusion. Specifically, from the viewpoint of further improving texture and breathability, the constituent fibers of the sanitary nonwoven fabric have fusion points where these fibers are fused together. Fusion refers to a state in which multiple fibers are melted by applying heat alone or heat and pressure, resulting in an indistinct boundary between the fibers. To create a structure with fusion points, for example, it can be formed by blowing hot air onto the fiber web, as will be described later.

[0017] As described above, the fibers contained in the sanitary nonwoven fabric contain polyamide resin. Examples of the polyamide resin present in the constituent fibers of the sanitary nonwoven fabric of the present invention include (i) a fiber in which the constituent resin is solely polyamide resin, and (ii) a fiber containing a resin component made of polyamide resin and a second resin component different from the said resin component.

[0018] Generally, polyamide resins have been widely used in textile products because they have relatively low rigidity and good processability compared to other organic polymer materials. Fibers containing polyamide resins are hygroscopic and have relatively high thermal conductivity among organic polymer materials. Focusing on the above-mentioned properties of polyamide resins, the inventors have found that by incorporating polyamide resin into the constituent fibers of a nonwoven fabric, it is possible to exhibit the high thermal conductivity of the polyamide resin itself while also giving flexibility to the fibers. As a result, it is possible to create a nonwoven fabric that exhibits both a good texture and a sense of coolness.

[0019] Specific examples of (i) above include fibers made of only one type of polyamide resin as the constituent resin, and fibers made of multiple types of polyamide resins as the constituent resin. An example of the latter is a fiber in which the outer surface and the interior of the fiber are made of different types of polyamide resin. Specific examples of (ii) above include (a) fibers made of a resin mixed with a polyamide resin, (b) core-sheath composite fibers in which the core is made of a polyamide resin and the sheath covering the surface of the core is made of another resin, and (c) side-by-side composite fibers having a polyamide resin and another resin, in which the other resin is continuously present along the fiber length direction on at least a part of the fiber surface made of polyamide resin. In this case, it is preferable from the viewpoint of ease of forming fusion points that the other resin is a resin other than polyamide resin and has a lower melting point than the polyamide resin. The fibers used in this invention may be solid or hollow. From the viewpoint of enhancing thermal conductivity and making it easier for the wearer to perceive coolness, solid fibers are preferred.

[0020] In terms of the configuration of the constituent resin in the fiber, it is preferable that the fiber is a composite fiber containing a polyamide resin, more preferably that the fiber contains a polyamide resin inside, even more preferably that the fiber is a composite fiber containing polyethylene resin as another resin on at least the entire outer surface of the fiber, and even more preferably that the fiber has a core-sheath structure in which the core is made of polyamide resin and the sheath is made of polyethylene resin. Since polyethylene resin has higher thermal conductivity than polyamide resin, a structure with polyethylene resin on the fiber surface allows the highly thermally conductive polyethylene resin to come into direct contact with the wearer's skin, resulting in a strong cooling sensation. Furthermore, the desirable properties of polyamide resin, such as high thermal conductivity, low rigidity, and moisture absorption, can be expressed in the fiber, further improving the texture of the nonwoven fabric.

[0021] Furthermore, by using it in combination with resins having different melting points, it is possible to create nonwoven fabric without completely fusing the fibers together, improving processability during manufacturing and enhancing the texture of the resulting nonwoven fabric. In addition, crimp can be introduced into the composite fibers to further enhance the texture. Moreover, the nonwoven fabric becomes smooth to the touch, and even if the user perceives a cool sensation when touching the nonwoven fabric, they are less likely to feel an unpleasant wetness.

[0022] Examples of polyamide resins used in the present invention include nylon 6, nylon 66, and aromatic nylon. From the viewpoint of ease of fiber formation, it is preferable to use nylon 6 as the polyamide resin.

[0023] Examples of polyethylene resins used in the present 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 individually, in combination, or in any combination of other materials.

[0024] From the viewpoint of having high thermal conductivity and enabling the wearer to perceive a stronger cooling sensation, it is preferable to include HDPE as the polyethylene resin, and more preferable to use HDPE alone. In other words, it is more preferable to use HDPE alone as the polyethylene resin. In particular, by arranging HDPE on the fiber surface, it is advantageous in that the fusion points between fibers can be formed more easily in the manufacturing method described later.

[0025] More specifically, it is even more preferable to use a composite fiber having a core-sheath structure in which the core is made of polyamide resin and the sheath is made of HDPE. This prevents unpleasant dampness because even if the polyamide resin absorbs moisture from bodily fluids such as sweat, urine, menstrual blood, and breath, the polyamide resin does not come into direct contact with the wearer's skin. In addition, it is easier to fuse the fibers only at the intersections during manufacturing, which improves the tactile feel. As a result, the sanitary nonwoven fabric maintains a good texture, has a smooth and pleasant feel on its surface, and allows the wearer to perceive a comfortable coolness.

[0026] Furthermore, in a preferred embodiment of the present invention, by using a core-sheath composite fiber in which the sheath constituent resin has a lower melting point than the core constituent resin, problems such as excessive melting of the fiber constituent resin and inability to maintain the fiber shape, or the occurrence of holes in the resulting nonwoven fabric, become less likely when, for example, a sanitary nonwoven fabric is manufactured by the air-through method, and manufacturing stability is further improved. In addition, by subjecting the above-mentioned core-sheath composite fiber to the air-through method, it becomes easier to fuse only the intersections of the fibers, allowing for nonwoven fabric formation without completely fusing the fibers together, resulting in a nonwoven fabric with an even better texture. In addition, the nonwoven fabric becomes smooth to the touch, and even when a cool sensation is perceived when touching the nonwoven fabric, the user is less likely to feel an unpleasant wetness.

[0027] Examples of resins other than those mentioned above that can be used in the present invention include polyolefin resins other than polyethylene resins such as polypropylene (PP) and polybutene, polyester resins such as polyethylene terephthalate (PET), vinyl resins such as polyvinyl chloride and polystyrene, acrylic resins such as polyacrylic acid and polymethyl methacrylate, and various thermoplastic fibers such as fluororesins such as polyperfluoroethylene. These resins can be used individually or in combination of two or more, as needed.

[0028] The polyamide resin content relative to the total mass of fibers in the sanitary nonwoven fabric of the present invention is preferably 25% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, preferably 100% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less. When the constituent fibers contain polyethylene resin, the polyethylene resin content relative to the total mass of fibers in the sanitary nonwoven fabric is preferably 30% by mass or more, more preferably 40% by mass or more, preferably 90% by mass or less, and more preferably 80% by mass or less. It is also preferable that the content of each resin mentioned above be filled within the polyamide fiber-containing aggregate.

[0029] When polyethylene resin is included in the constituent fibers, the mass ratio of polyamide resin to polyethylene resin (polyamide resin / polyethylene resin) in the sanitary nonwoven fabric of the present invention is preferably 0.1 or higher, more preferably 0.2 or higher, and even more preferably 0.3 or higher, from the viewpoint of achieving both a cool feel and excellent texture, and preferably 2.0 or lower, more preferably 1.5 or lower, and even more preferably 1.3 or lower, from the viewpoint of nonwoven fabric processability. The aforementioned mass ratio is also preferably satisfied within the polyamide fiber-containing aggregate.

[0030] The type of resin constituting the fiber is determined by confirming the melting point of the resin using differential scanning calorimetry, and by identifying the resin type using one or more methods of infrared spectroscopy (IR) and nuclear magnetic resonance (NMR). In addition, a scanning electron microscope (SEM) is used to estimate the spinning method from the surface and cross-sectional shapes of the fiber and to identify the type of resin in the fiber. To determine the resin content, first, the mass and thickness of the nonwoven fabric to be measured under no load are measured. Then, the fiber structure is fixed using liquid nitrogen or the like, and a cross-section of the nonwoven fabric is created so that the fiber cross-section can be observed perpendicular to the longitudinal direction of the fibers. The volume ratio is then confirmed using a SEM or similar method. The resin content is calculated from the obtained volume ratio and the specific gravity of the resin. If the nonwoven fabric to be measured is incorporated into a sanitary product, the nonwoven fabric is removed from the sanitary product using a cold spray before being used for measurement.

[0031] From the viewpoint of reducing the content of air, which has low thermal conductivity, and improving the thermal conductivity of the nonwoven fabric, the volume filling rate in the polyamide fiber-containing aggregate is preferably 3.5% or more, more preferably 7.0% or more, even more preferably 10.0% or more, even more preferably 12.0% or more, and even more preferably 14.0% or more. Furthermore, when used as a disposable sanitary material that comes into contact with the wearer's skin, from the viewpoint of improving the texture, the volume filling rate of the polyamide fiber-containing aggregate is preferably 60.0% or less, more preferably 50.0% or less, even more preferably 45.0% or less, even more preferably 35.0% or less, and even more preferably 30.0% or less. Therefore, the volume filling rate in the polyamide fiber-containing aggregate is preferably 3.5% to 60.0%, more preferably 7.0% to 50.0%, even more preferably 10.0% to 45.0%, even more preferably 12.0% to 35.0%, and even more preferably 14.0% to 30.0%.

[0032] Because the polyamide fiber-containing aggregate has the aforementioned volume filling ratio, the amount of air with low thermal conductivity is reduced within the sanitary nonwoven fabric, thereby improving heat transfer, and consequently, allowing the wearer to perceive a stronger cooling sensation. In addition, the hygienic nonwoven fabric of the present invention and the texture of the hygienic product incorporating the nonwoven fabric can be fully expressed. The above-described structure can be obtained, for example, by compacting the fiber aggregate obtained in the manufacturing process of sanitary nonwoven fabric, as in the manufacturing method described later.

[0033] In this invention, the volume filling rate can be expressed as a percentage of the apparent volume to the actual volume. Specifically, a predetermined area of ​​the sanitary nonwoven fabric to be measured is cut off to form a measurement sample, and its mass (g) is measured. The predetermined area for cutting the measurement sample is preferably 10 cm square, but if it is not possible to cut a measurement sample of that size, a sample is cut off with the largest possible width and length within the area where the basis weight of the sanitary nonwoven fabric to be measured appears uniform to the naked eye. Then, the basis weight A (g / cm²) of the measurement sample is measured. 2 Calculate ). Furthermore, the method for measuring the thickness B (cm) of the measurement sample is as follows. First, only the 12.59g (55mm diameter) plate is placed on a laser displacement meter (LK-080, manufactured by Keyence Corporation; all laser displacement meters in this specification are this type), and the measured thickness is set to zero for zero-point adjustment. Then, the plate is placed on the measurement sample, and the thickness in this state is measured using the laser displacement meter, and this is taken as the thickness B (cm) of the measurement sample. In the measurement of thickness B, the displacement of 4.9 mN / cm was obtained by placing the plate. 2 The load is applied to the measurement sample.

[0034] And the specific gravity C (g / cm³) of the constituent components of the fiber 3 Using the following formula (I), the volume filling rate (%) is calculated. In the case of fibers containing two or more types of resin, such as composite fibers, the sum of the specific gravities based on the mass ratio of each component is used as the specific gravity C. For example, specific gravity C1 (g / cm³) 3 The constituent components of ) and specific gravity C2 (g / cm³) 3 If the fiber contains a two-component system where the constituent components of the fiber are in a mass ratio of 30:70, then the specific gravity C (g / cm³) 3 The specific gravity is calculated as "0.3 × specific gravity C1 + 0.7 × specific gravity C2". Volume filling efficiency (%) = 100 × (A) / (B × C) ... (I)

[0035] If the sanitary nonwoven fabric to be measured is incorporated into a sanitary product such as an absorbent article, a cold spray is applied to the sanitary product to solidify the hot melt adhesive, and then the sanitary nonwoven fabric to be measured is carefully peeled off. Similarly, if it is joined to other components such as the second fiber aggregate described later by fusion or other means, the structure is fixed using a cold spray or liquid nitrogen, and then the object to be measured is peeled off and measured. This method is common to other measurements in this specification.

[0036] The sanitary nonwoven fabric of the present invention has an average deviation (MMD) of the coefficient of friction measured by the following method, preferably 0.010 or less, more preferably 0.009 or less, and even more preferably 0.008 or less, with 0.004 or more being practical. This configuration results in a nonwoven fabric surface that is smooth to the touch, has a good feel against the skin, and provides a high level of usability. The friction coefficient described above is preferably satisfied when applied to a polyamide fiber-containing assembly.

[0037] The average deviation of the coefficient of friction (MMD) is measured using the KES-FB4-AUTO-A (product name) manufactured by Kato Tech Co., Ltd. First, take out a 20 cm × 20 cm test piece from the sanitary non-woven fabric to be measured. If a test piece of this size cannot be taken out, the size of the test piece may be appropriately changed. Then, on this test piece, identify the surface on which the fiber aggregate containing the polyamide resin is arranged by a method such as infrared spectroscopy (FT-IR). Next, attach the test piece to a smooth metal flat test bench. Press the contactor against the surface of the fiber aggregate of the test piece with a force of 49 cN, and move the test piece horizontally by 2 cm at a constant speed of 0.1 cm / sec. A uniaxial tension of 7.3 cN / cm is applied to the test piece. The contactor is formed by bending 20 piano wires with a diameter of 0.5 mm in a U shape with a width of 10 mm. The contactor presses the contact surface against the test piece with a force of 49 cN by a weight. Perform this measurement in both the one direction (MD direction) of the non-woven fabric and the direction orthogonal to this direction (CD direction) to obtain MMD MD and MMD CD Find them, calculate the average value from the following formula (II), and use this as the average deviation MMD of the friction coefficient. When test pieces of the sample can be taken out from only one of the MD direction or the CD direction, use only the value of one side as the average deviation MMD of the friction coefficient. Average deviation MMD of friction coefficient ={(MMD MD 2 +MMD CD 2 ) / 2} 1 / 2 ···(II)

[0038] From the viewpoint of improving the texture of the non-woven fabric of the present invention, the overall thickness of the non-woven fabric is preferably 0.05 mm or more, more preferably 0.08 mm or more. Also, from the viewpoint of reducing the air content in the non-woven fabric and increasing the thermal conductivity, the overall thickness of the non-woven fabric of the present invention is preferably 8 mm or less, more preferably 7.5 mm or less, and still more preferably 7 mm or less. The thickness of the above-described sanitary non-woven fabric is measured using a laser displacement meter or the like under a load of 4.9 mN / cm 2 (0.5 gf / cm 2 ). The thickness of the sanitary nonwoven fabric of the present invention has the above-described configuration, which increases the heat capacity of the sanitary nonwoven fabric and makes it possible to efficiently manufacture a sanitary nonwoven fabric that allows the wearer to efficiently perceive a cooling sensation. From a similar perspective, 4.9 mN / cm 2 (0.5 gf / cm 2 It is also preferable that the polyamide fiber-containing aggregate satisfies the aforementioned thickness range under load.

[0039] The hygienic nonwoven fabric of the present invention is a polyamide fiber-containing aggregate with a cool-to-the-touch feel. max However, preferably 0.06 W / m 2 More preferably, 0.08 W / m 2 More preferably 0.10 W / m 2 The above is preferable, and preferably 0.80 W / m 2 More preferably, 0.60 W / m 2 More preferably, 0.50 W / m 2 The following applies: Specifically, the contact cooling sensation in polyamide fiber-containing aggregates of sanitary nonwoven fabrics q max Preferably, it is 0.06 W / m 2 More than 0.80W / m 2 More preferably, 0.08 W / m 2 More than 0.60W / m 2 Further preferably, 0.10 W / m 2 More than 0.50W / m 2 The following applies:

[0040] Cool touch q max This can be measured, for example, by the following method. First, a test piece measuring 10 cm in length and 10 cm in width is cut from the sanitary nonwoven fabric to be measured, and the test piece is left for 24 hours in an environment with room temperature of 23°C and relative humidity of 50%. If it is not possible to cut a test piece to the above dimensions, a test piece should be cut to the largest possible dimensions that are as close as possible to the above dimensions. Next, under these conditions, the test specimen is placed on the measuring stand and secured to the stand using double-sided tape. The measuring stand is one that has been kept at 23°C using a constant temperature device that uses gas or liquid as a heat transfer medium. Next, the contact cooling sensation of the target object was measured according to the measuring device (Kato Tech Co., Ltd., KES-F7 Thermolab II) and its measurement manual. max The measurement is taken. Specifically, the heating plate that comes into contact with the object to be measured has an area of ​​9.0 cm². 2 Using a pure copper plate with a mass of 9.8 g, the initial temperature of the copper plate is set to 33°C (10°C higher than the surface temperature of the object to be measured), and the contact pressure of the copper plate against the object to be measured is set to 1 kPa. The copper plate is brought into contact with the test piece, and the value of the heat flow rate at the moment of contact is set to zero, and the maximum value of the heat flow rate is measured. This measurement is performed 5 times for the surface of the object to be measured, and the arithmetic mean of these multiple measurements is taken as the contact cooling sensation q of the object to be measured. max (W / m 2 )

[0041] Contact cooling is a numerical representation of the skin sensation of feeling cold when the skin touches an object. This contact cooling sensation varies depending on the amount of heat transferred from the skin to the object; the greater the heat transfer, the colder the object feels. (Contact cooling q) max This corresponds to the maximum amount of heat transfer from the skin to the object, and the contact cooling sensation q max The value of q is larger when an object feels cold to the touch and smaller when it feels warm. Therefore, the value of contact coldness q max By having the value within the aforementioned range, the sensation of coldness can be perceived more effectively.

[0042] In the present invention, it is preferable that the fibers constituting the sanitary nonwoven fabric are arranged with a certain orientation. This configuration allows heat transfer to occur more easily along the length of the fibers, making it easier for the wearer to perceive a cooling sensation.

[0043] More specifically, in the sanitary nonwoven fabric of the present invention, it is preferable that when the nonwoven fabric is placed on a horizontal surface, the fiber length direction of the nonwoven fabric is generally parallel to the horizontal surface. In addition to the above, or alternatively, it is preferable that the direction of fiber extension is unidirectional when the sanitary nonwoven fabric is viewed in plan. For example, when considering a first direction of the sanitary nonwoven fabric and a second direction perpendicular to the first direction in a plan view, it is even more preferable that the direction of fiber extension coincides with either the first or second direction of the nonwoven fabric. When fibers intersect, it is desirable that at least 50% of the intersecting fibers in a plan view of the sanitary nonwoven fabric have an obtuse angle. An obtuse angle refers to an angle greater than 90°.

[0044] The angles between fibers can be quantitatively determined by taking images of three arbitrary locations on a sanitary nonwoven fabric using a scanning electron microscope (SEM) at a magnification that allows approximately 10 fiber intersections to be observed within the field of view. The obtained image data can then be measured and compiled using image analysis software included with the SEM or other available software. If image analysis software is not available, the image data can be printed, checked with an angle measuring instrument such as a protractor, and recorded on a data sheet for compilation. By having at least one of the above-described configurations related to the orientation of the fibers, heat transfer becomes easier to occur in a certain direction, making it easier for the wearer to perceive a cooling sensation more effectively. Such a configuration can be obtained, for example, by manufacturing a long sheet using short fibers containing polyamide resin as a material, conveying the long sheet while applying tension in the conveying direction and fusing the fibers together by an air-through method, or by conveying the fibers containing polyamide resin in one direction while spinning them out onto conveying equipment such as a belt conveyor.

[0045] The sanitary nonwoven fabric of the present invention has a thermal conductivity of 0.08 W / mK or higher, more preferably 0.10 W / mK or higher, and even more preferably 0.13 W / mK or higher for the polyamide fiber-containing aggregate. The above-mentioned thermal conductivity can be measured, for example, by melting the sanitary nonwoven fabric and forming a film-like sample with a thickness of about 1 mm. A detailed measurement method will be described later. Having such thermal conductivity allows wearers of sanitary products, including sanitary nonwoven fabrics, to perceive a stronger cooling sensation.

[0046] In the above description, for the sake of clarity, the sanitary nonwoven fabric was described using an example of a form having a single fiber layer containing polyamide resin fibers (regardless of whether it consists only of a single fiber or is a blend with other fibers), but it is not limited to this form. Another embodiment of the sanitary nonwoven fabric of the present invention is described below.

[0047] Another embodiment of the sanitary nonwoven fabric includes, for example, a layer of fiber aggregates containing first fibers containing polyamide resin (hereinafter also referred to as the "first fiber layer") and a layer of fiber aggregates containing second fibers other than the first fibers, arranged adjacent to the fiber layer (hereinafter also referred to as the "second fiber layer"). In other words, this embodiment is a multi-layered sanitary nonwoven fabric. Here, "adjacent" means that the fiber layers are adjacent to each other without other fiber layers in between, and the presence of adhesive between the fiber layers is permissible. In this case, from the viewpoint of effective perception of coolness, it is preferable that the first fiber layer constitutes the outer surface of the sanitary nonwoven fabric. Also from a similar viewpoint, it is preferable that at least the first fiber layer satisfies the various preferred forms of the sanitary nonwoven fabric described above, and it is more preferable that the entire sanitary nonwoven fabric satisfies the preferred forms described above.

[0048] In detail, a multi-layered sanitary nonwoven fabric can be obtained, for example, by laminating a fiber web containing first fibers containing polyamide resin and a second fiber web containing fibers other than the first fibers, and then applying an air-through process or a spunbond process. In this case, the boundaries between each fiber layer are generally indistinct, but parts with clear boundaries may be included. In this embodiment, each fiber layer maintains the shape of a fiber sheet by at least one of the following: entanglement, fusion, and compression. Another embodiment of a multi-layered sanitary nonwoven fabric involves bonding a fiber web or fiber sheet containing first fibers containing polyamide resin to a fiber web or fiber sheet containing fibers other than the first fibers using an adhesive, thereby maintaining the shape of the fiber sheet. In this case, the boundaries between each fiber layer are generally clear.

[0049] In any embodiment, the fibers other than the first fiber include, in addition to the fibers containing the aforementioned constituent resins such as PET resin and PP resin, one or more other fibers such as pulp fibers, rayon fibers, and other hydrophilized treated fibers.

[0050] The basis weight of the first fiber layer is preferably 10 g / m², from the viewpoint of ensuring a sufficient sense of coolness. 2 Above, a comfortable 15g / m 2 More preferably 18 g / m² 2 The above applies, and preferably 200 g / m². 2 More preferably, 150 g / m² 2 More preferably 100 g / m 2 The following applies: The basis weight of the second fiber layer is preferably 10 g / m². 2 Above, a comfortable 15g / m 2 More preferably 20 g / m² 2 The above, and more preferably 140 g / m² 2 More preferably 90g / m 2 More preferably 70 g / m 2 The following applies:

[0051] When the sanitary nonwoven fabric has a multilayer structure, the thermal conductivity of the fiber layer containing the first fiber containing 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 such thermal conductivity is preferable because it allows for achieving the desired 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 composite fibers containing polyamide resin and polyethylene resin as the constituent fibers.

[0052] Thermal conductivity can be measured, for example, by the following method. First, the nonwoven fabric or fiber to be measured is separated from the product by using a cold spray or the like, or by collecting the fibers. Next, the separated nonwoven fabric or fiber is introduced into a heating and pressing device such as a press, and heated and pressed at a temperature above the melting point of the nonwoven fabric or fiber raw material to form a film-like sample with a thickness of about 1 mm. At this time, the pressurizing conditions are adjusted appropriately so that no air remains in the sample. Then, using a steady-state thermal conductivity measuring device (Kato Tech Co., Ltd., KES-F7 Thermolab II), the thermal conductivity is measured based on the amount of heat transferred in a steady state from a 33°C hot plate to a 23°C hot plate via the sample. This measurement is performed at three locations for each film-like sample, and the highest thermal conductivity value among these is taken as the thermal conductivity (W / mK) in this invention. If the object being measured is a multi-layered sanitary nonwoven fabric, the above-mentioned contact cooling q max The fiber layer on the side with the highest value is designated as the first fiber layer, and the thermal conductivity of this fiber layer is subjected to the measurement described above.

[0053] When the sanitary nonwoven fabric of the present invention has a configuration that includes a second fiber layer, from the viewpoint of reducing the content of air, which has low thermal conductivity, and improving the thermal conductivity of the nonwoven fabric, the volume filling rate of the first fiber layer of the sanitary nonwoven fabric is preferably 3.5% or more, more preferably 7.0% or more, even more preferably 10.0% or more, even more preferably 12.0% or more, and even more preferably 14.0% or more. Furthermore, when used as a disposable sanitary material that comes into contact with the wearer's skin, from the viewpoint of improving the texture, the volume filling rate of the first fiber layer of the sanitary nonwoven fabric is preferably 60.0% or less, more preferably 50.0% or less, even more preferably 45.0% or less, even more preferably 35.0% or less, and even more preferably 30.0% or less. This configuration enhances heat transfer, which in turn allows the wearer to perceive a stronger cooling sensation. In addition, it allows the hygienic nonwoven fabric of the present invention and the hygienic product incorporating the nonwoven fabric to be fully expressed. The measurement of the volume filling rate in the first fiber layer is the same as the above-mentioned contact cooling q max The fiber layer on the side with the highest value is designated as the first fiber layer, and this fiber layer is subjected to the measurement of the volume filling rate described above.

[0054] When the sanitary nonwoven fabric includes the second fiber layer described above, it is preferable to use a second fiber layer whose thickness change is greater than or equal to a predetermined value. In detail, the second fiber layer is 9.8 mN / cm². 2 (1 gf / cm²) 2 The amount of compressive deformation under load is preferably 0.3 mm or more, more preferably 0.5 mm or more. Furthermore, the amount of compressive deformation of the second fiber layer under the same load is preferably 3 mm or less. The amount of compressive deformation is 9.8 mN / cm², as will be described later, based on the thickness of the second fiber layer under no load. 2 (1 gf / cm²) 2 This is expressed as the change obtained by subtracting the thickness of the second fiber layer under load. The amount of compression deformation can be calculated using the method described later. This configuration allows the first fiber layer to easily deform in accordance with the deformation of the second fiber layer when it comes into contact with the wearer, thereby increasing the contact area with the wearer and efficiently allowing the wearer to perceive a cooling sensation. The method for measuring the thickness of the second fiber layer will be described later.

[0055] The sanitary nonwoven fabric having the above composition uses fibers containing polyamide resin among synthetic resins. Therefore, when these fibers come into contact with the wearer's skin, heat generated from the wearer's body temperature can be quickly transferred from the wearer to the sanitary nonwoven fabric or to other fibers that are not in contact with the wearer. As a result, when the wearer's skin touches the sanitary nonwoven fabric, the wearer perceives a cooling sensation, providing a comfortable feeling of use due to the cooling effect. Furthermore, the flexibility and moisture absorption properties of the polyamide resin are well exhibited, contributing to an improved user experience in this respect as well. In addition, because the hygienic nonwoven fabric has fusion points between fibers, heat can be easily transferred to other fibers, and a good texture as a fiber sheet can be achieved, improving the feel and comfort of use. Furthermore, because the sanitary nonwoven fabric is composed in the form of a fibrous sheet, the contact area between the wearer's skin and the sanitary nonwoven fabric is increased, allowing the wearer to perceive a cooling sensation more strongly, while also exhibiting the flexibility inherent in the nonwoven fabric's structure.

[0056] The sanitary nonwoven fabric of the present invention preferably has a total basis weight of 10 g / m². 2 Above, a comfortable 15g / m 2 More preferably 18 g / m² 2 That's all. Furthermore, the sanitary nonwoven fabric of the present invention preferably has a total basis weight of 200 g / m². 2 More preferably, 150 g / m² 2 More preferably 120 g / m 2 The following applies: As a result of the above-described configuration, differences in perceived coolness caused by variations in basis weight of the sanitary nonwoven fabric can be reduced, and fusion and compaction of fibers can be effectively carried out, enabling the highly productive manufacture of sanitary nonwoven fabric with a predetermined volume filling rate. When the sanitary nonwoven fabric of the present invention is incorporated as a component of a sanitary product, the following contact cooling q max The fiber sheet with the highest value is designated as the sanitary nonwoven fabric, and its basis weight is measured.

[0057] The sanitary nonwoven fabric described above may be used as is, or it may be used as a component of a sanitary product, resulting in a sanitary product that includes the sanitary nonwoven fabric. Furthermore, when incorporating the sanitary nonwoven fabric of the present invention into a sanitary product, it is preferable that the nonwoven fabric, or the first fiber layer side of the nonwoven fabric, constitutes the surface that faces the wearer's skin. In either case, they are typically disposable.

[0058] Examples of sanitary products comprising the sanitary nonwoven fabric of the present invention include absorbent articles such as disposable diapers, sanitary napkins, underarm sweat pads, urine pads, and panty liners, as well as sanitary articles such as face masks and eye masks, but the sanitary products are not limited to these. For example, absorbent articles comprising the sanitary nonwoven fabric broadly include articles used to absorb fluids discharged from the human body.

[0059] Sanitary nonwoven fabrics can be used as components of absorbent articles and the like. Absorbent articles typically comprise a surface sheet and a backing sheet, with an absorbent material placed between the surface and backing sheets. In addition, or as part of the surface sheet or backing sheet itself, a sanitary nonwoven fabric may be used.

[0060] When sanitary nonwoven fabric is used as a component of absorbent articles, etc., the sanitary nonwoven fabric can be placed in areas that come into direct contact with the wearer's skin when using the absorbent article or other sanitary product, or when handling the absorbent article or other sanitary product, such as when removing it from its packaging. In other words, it is preferable that the sanitary nonwoven fabric be placed on the outer surface of the absorbent article or other sanitary product. The outer surface of absorbent articles and other sanitary products refers to the surface of the absorbent article or other sanitary product that the wearer can touch with their hands after opening the package and taking out the product (this includes both the front and back sides, but refers to the surface side, not the inner surface in the thickness direction). In other words, the outer surface of the sanitary product is preferably the skin-facing side or the non-skin-facing side.

[0061] In detail, as an absorbent article which is one embodiment of a sanitary product, for example, when using sanitary nonwoven fabric in a disposable diaper, it can be used as a component such as a surface sheet, side nonwoven fabric, waist gathers and gathers placed near the groin area, and outer casing. Of these, by using sanitary nonwoven fabric for at least the outer casing, the wearer can touch it with their hands when taking out the absorbent article or other sanitary product, so it has a pleasant feel against the skin and makes it easier for the wearer to recall the excellent quality of the sanitary product.

[0062] Furthermore, when using nonwoven fabric for hygiene purposes in absorbent articles, such as urine leakage pads and sanitary napkins, which are embodiments of hygiene products, it can be used as a component such as a surface sheet, side nonwoven fabric, hip guard, or individual packaging bag. Furthermore, when using nonwoven sanitary fabric as an absorbent article, which is one embodiment of a sanitary product, such as a urine leakage pad or a sanitary napkin, it can be used as a component such as a surface sheet or gathers placed near the groin area.

[0063] When using sanitary products such as absorbent articles, it is preferable that the sanitary nonwoven fabric be positioned on the side that faces the wearer's skin (hereinafter also referred to as the "skin-facing side") when the absorbent article is worn in the correct position, in order to provide a cooling sensation and reduce discomfort caused by stuffiness, etc.

[0064] The absorbent material used in absorbent articles comprises an absorbent core. The absorbent core is typically composed of a stack of hydrophilic fibers such as cellulose, including pulp; a stack of hydrophilic fibers and a superabsorbent polymer; a deposit of a superabsorbent polymer; or an absorbent sheet in which a superabsorbent polymer is held between two sheets. The absorbent core may be covered with a core wrap sheet. The core wrap sheet may be covered in various ways, for example, with at least its skin-facing surface covered with a liquid-permeable core wrap sheet, or the entire surface, including both the skin-facing and non-skin-facing surfaces, covered with the core wrap sheet. Examples of the core wrap sheet include thin paper made of hydrophilic fibers or a liquid-permeable nonwoven fabric.

[0065] When using sanitary nonwoven fabric as a mask, for example, it can be used alone or as a laminate by laminating other nonwoven fabrics onto the sanitary nonwoven fabric. In addition, ear loops can be provided on the component containing the sanitary nonwoven fabric to maintain coverage of the mouth, nose, or eyes. Even in this configuration, the sanitary nonwoven fabric is preferably placed on the skin-facing side, and even more preferably in the area that comes into direct contact with the wearer's skin.

[0066] When a sanitary product is made using the sanitary nonwoven fabric of the present invention, the sanitary product may further comprise another component (hereinafter referred to as the "second component") in addition to the sanitary nonwoven fabric, which is an aggregate of fibers containing polyamide resin (hereinafter also referred to as the "first fiber aggregate" for convenience of explanation).

[0067] Examples of sanitary products equipped with a second component include, for example, an absorbent sheet containing a water-absorbent polymer and fibers, an absorbent body containing a water-absorbent polymer and fibers, a hydrophilic nonwoven fabric, and at least one of these as the second component. These are examples of fiber aggregates different from sanitary nonwoven fabrics. The absorbent articles described above are preferred as sanitary products equipped with these second components. In other words, in this embodiment, the sanitary product consists of a first fiber aggregate, which is a sanitary nonwoven fabric, and a second component, which is an absorbent sheet, absorbent, and / or nonwoven fabric, separate from the sanitary nonwoven fabric. It is also preferable that the first fiber aggregate and the second component are arranged adjacent to each other. In this embodiment, each fiber aggregate may or may not be joined to each other. As an absorbent sheet, for example, the absorbent sheet described in Japanese Patent Publication No. 8-246395 can be used.

[0068] When a sanitary product includes the second component described above, or when a sanitary nonwoven fabric includes the second fiber layer described above, it is preferable to use a second component or second fiber layer whose thickness change is greater than or equal to a predetermined value. In detail, the second component has a load of 9.8 mN / cm². 2 (1 gf / cm²) 2 The compressive deformation under load is preferably 0.3 mm or more, more preferably 0.5 mm or more. Furthermore, the compressive deformation of the second member under the same load is preferably 3 mm or less. The compressive deformation is calculated from the thickness of the second member under no load, as described later, to 9.8 mN / cm². 2 (1 gf / cm²) 2 This is expressed as the change obtained by subtracting the thickness of the second member under load. It is preferable that the second fiber layer constituting the sanitary nonwoven fabric also has a similar amount of compressive deformation. In addition, if the sanitary product comprises both a multi-layered sanitary nonwoven fabric and a second component, it is preferable that both the second component and the second fiber layer satisfy the above-mentioned amounts of compressive deformation. This configuration allows the first fiber assembly to easily deform in accordance with the deformation of the second member when it comes into contact with the wearer, thereby increasing the contact area with the wearer and efficiently allowing the wearer to perceive a cooling sensation.

[0069] The second fiber layer having the above-described physical properties can be obtained, for example, by using a fiber web that has been subjected to air-through treatment, using fibers made of PET resin or PP resin, or PET / HDPE core-sheath composite fibers, as constituent fibers in the manufacturing method described later. Furthermore, if the second component is an absorbent sheet or absorbent material, it can be obtained, for example, by appropriately adjusting the basis weight of the fibers, fiber sheets, and water-absorbing polymer that constitute the absorbent sheet or absorbent material.

[0070] The thickness of the second member 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 to confirm whether it is a sanitary nonwoven fabric having multiple fiber layers, or whether a second component other than the sanitary nonwoven fabric exists, by observing the fiber diameter, inter-fiber distance, or boundaries between components. If the object to be measured is a sanitary product, the structure of the sanitary product is fixed by immersion in liquid nitrogen or similar means, and then the sanitary nonwoven fabric and the second component other than the sanitary nonwoven fabric are carefully peeled off and separated from the sanitary product. Then, the separated components are subjected to the aforementioned contact cooling q max Subject to measurement of q max The fiber sheet with the highest value is designated as the sanitary nonwoven fabric, and the member adjacent to the sanitary nonwoven fabric is designated as the second member. Then, by placing a plate on the separated second member, etc., 4.9 mN / cm 2 (0.5 gf / cm 2 With the load applied, the thickness in that state is measured using a laser displacement meter, and this is taken as the thickness of the second member. If the object to be measured is a multi-layered sanitary nonwoven fabric, then q, which will be described in detail in the examples below, is... max The fiber layer on the side with the highest value is designated as the first fiber layer, and the fiber layer adjacent to the first fiber layer is designated as the second fiber layer. The second fiber layer is then subjected to the measurement described above.

[0071] Furthermore, for hygiene products as a whole, the average load was 9.8 mN / cm². 2 (1 gf / cm²) 2 The amount of compressive deformation under load is preferably 0.3 mm or more, more preferably 0.4 mm or more. Furthermore, the amount of compressive deformation of the entire sanitary product under the same load is preferably 15 mm or less, more preferably 10 mm or less. This configuration allows for flexibility throughout the nonwoven fabric, improving the feel of the fabric, and also increases the contact area of ​​the polyamide resin-containing fiber aggregate with the wearer, enabling the wearer to efficiently perceive a cooling sensation.

[0072] The aforementioned amount of compression deformation can be achieved, for example, in the air-through method, by lowering the temperature and velocity of the hot air compared to the conditions normally used, increasing the number of fibers, or using fibers containing resin with a melting point higher than the temperature of the hot air, thereby reducing the fusion properties between the fibers. In addition to this, or as an alternative, this can be achieved by adopting a configuration in which two or more fiber layers are provided, with one fiber layer having a higher compressive deformation rate than the other fiber layers, or by increasing the basis weight of one fiber layer compared to the other fiber layers, or by blending fibers with a high melting point into one fiber layer.

[0073] Compression deformation can be measured, for example, using a KES-FB-3 compression tester manufactured by Kato Tech Co., Ltd. A section of a certain size is used as a sample from the sanitary nonwoven fabric to be measured. The sample is mounted on the test stand of the tester, with an area of ​​2 cm². 2 Compression is performed between steel plates with a circular plane. The compression speed is 0.02 mm / sec, and the maximum compression load is 9.8 mN / cm. 2 (1 gf / cm²) 2 ) The thickness under no load is defined as thickness T0 (mm), and the load capacity is 9.8 mN / cm². 2 (1 gf / cm²) 2 When the thickness under load is denoted as thickness Tm (mm), the compressive deformation (mm) obtained by subtracting thickness Tm from thickness T0 can be calculated as "T0-Tm".

[0074] When the second component is an absorbent sheet, the total basis weight is preferably 40 g / m². 2 More than 60g / m 2 More preferably 70 g / m² 2 The above, and more preferably 500 g / m² 2 More preferably, 400 g / m² 2 More preferably, 300 g / m 2 The following applies: When the second component is an absorbent, the total basis weight is preferably 30 g / m². 2 Above all, a comfortable 40g / m 2 More preferably 50 g / m2 Above, and preferably 600 g / m 2 or less, more preferably 550 g / m 2 or less, still more preferably 500 g / m 2 or less.

[0075] The sanitary nonwoven fabric preferably has a bending rigidity value that is below a predetermined value. Specifically, the bending rigidity 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, still more preferably 0.15 gf·cm 2 / cm or less, even more preferably 0.1 gf·cm 2 / cm or less. With such a configuration, it becomes easy to bend following an external force, so that the contact area with the wearer's skin can be increased and the cool feeling can be efficiently perceived.

[0076] The bending rigidity value of the sanitary nonwoven fabric can be measured by the following method in accordance with the method described on pages 27 to 28 of "Standardization and Analysis of Texture Evaluation (2nd Edition)" (Author: Toshio Kawabata, Publisher: The Japan Society for Fiber Science and Technology, Texture Measurement and Standardization Research Committee, Publication Date: July 10, 1980). Specifically, a sample is obtained by cutting out a size of 20 cm in the length direction and 10 cm in the width direction. The sample is attached to the chuck of a pure bending tester (Product Name: KES-FB2) manufactured by Kato Tech Co., Ltd. so that the distance between the chucks is 10 mm. The attachment direction is such that the longitudinal direction of the sanitary nonwoven fabric becomes the bending direction. Pure bending with a constant velocity curvature is performed within the range of curvature K = -2.5 to +2.5 cm -1 . The deformation speed is 0.50 cm -1 / sec. By this operation, the relationship (M-K curve) between the bending moment M per unit area of the sample and the curvature K is obtained. From the result, the bending rigidity B (gf·cm of per unit length, which is the slope of the M-K curve, is calculated 2 / cm). B is the slope between K = 0.5 cm -1 and K = 1.5 cm -1 , and the slope between K = -0.5 cm -1 and K = -1.5 cm -1The slope between these two points is measured from the characteristics of the increasing process of the absolute value of K, and these are denoted as Bf and Bb, respectively. The arithmetic mean (Bf + Bb) / 2 is taken as the bending stiffness value of the present invention.

[0077] The fiber diameter of the fibers used in sanitary nonwoven fabrics is preferably 1 μm or larger, more preferably 5 μm or larger, and even more preferably 12 μm or larger, from the viewpoint of preventing the constituent fibers from clinging to the skin and maintaining a good tactile and comfortable feel for the wearer. Furthermore, from the viewpoint of reducing the interfiber gaps in the nonwoven fabric and decreasing the air content in the nonwoven fabric to improve thermal conductivity, the gaps are preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 27 μm or less. The fiber diameter of a fiber is determined by preparing a sample and performing SEM observation, similar to the method for measuring the lengths of the major and minor axes in the cross-sectional shape of the fiber. The fiber diameters of 10 fibers per sample are measured, and the arithmetic mean of these measurements is taken as the fiber diameter of the present invention. If the fiber is not perfectly circular, the lengths of the major and minor axes of the fiber are measured using the method described above. The arithmetic mean of the major and minor axis lengths of a single fiber is taken as the fiber diameter, and the arithmetic mean of 10 such fiber diameters is taken as the fiber diameter of the fiber in the present invention.

[0078] The fiber length of the fibers used in sanitary nonwoven fabrics is preferably 30 mm or more, more preferably 38 mm or more, when they are short fibers, from the viewpoint of maintaining a good feel and usability for the wearer. Furthermore, from the viewpoint of improving thermal conductivity, when they are short fibers, the fiber length is preferably 40 mm or more, more preferably 45 mm or more. Furthermore, when they are short fibers, from the viewpoint of not impairing processability, the fiber length is preferably 70 mm or less, more preferably 60 mm or less. If the fiber is in a crimped state, the fiber length is determined by measuring the distance from one end point to the other of 10 fibers using a ruler while the fiber is left undisturbed to minimize bending, and the arithmetic mean of these lengths is taken as the fiber length of the fiber in this invention.

[0079] To the extent that the effects of the present invention are achieved, the sanitary nonwoven fabric of the present invention may further contain a filler for increasing thermal conductivity. Examples of such fillers include at least one of titanium oxide, alumina, boron nitride, magnesium oxide, silica, carbon black, zinc oxide, and carbon nanotubes. The filler may be present within the fibers, between the fibers, or partially exposed on the fiber surface and embedded within the fibers.

[0080] The above has been a description of the sanitary nonwoven fabric and sanitary products comprising the sanitary nonwoven fabric of the present invention. A preferred method for manufacturing the sanitary nonwoven fabric of the present invention will be described below. This manufacturing method includes a step (air-through step) in which an air-through treatment is performed on a fiber web containing polyamide resin to obtain a fiber aggregate. In addition, it is preferable to employ a step of consolidating the obtained fiber aggregate (consolidation step). Furthermore, it is even more preferable that the composite fiber used in this manufacturing method is the core-sheath composite fiber described above.

[0081] First, a fiber web containing polyamide resin is formed. The fiber web can be formed, for example, by a carding method using a known carding machine.

[0082] Next, an air-through treatment is performed on the fiber web by blowing hot air onto it to obtain a fiber aggregate containing polyamide resin fibers. This process is a process of turning the fiber web into a nonwoven fabric, and the fiber aggregate produced in this way is generally called an air-through nonwoven fabric.

[0083] Generally, when processing polyamide resin fiber webs with an air-through design, using composite fibers such as core-sheath composite fibers is advantageous in terms of improving the texture and strength of the resulting air-through nonwoven fabric. However, there was room for improvement in terms of the cooling sensation perceived by the wearer due to improved thermal conductivity. The inventors diligently investigated these areas for improvement and discovered that by controlling the temperature and airflow velocity of the hot air in the air-through process, it is possible to efficiently manufacture air-through nonwoven fabrics with good texture and strength.

[0084] In the air-through process, it is preferable that the temperature and air velocity of the hot air blown onto the fiber web be within a specific range. More specifically, the temperature of the hot air blown onto the fiber web can be preferably in the range of melting point Mp (°C) or less, more preferably melting point Mp + 9°C or less, and even more preferably melting point Mp + 8°C or less, in relation to the melting point Mp (°C) of the resin constituting the fiber surface constituting the fiber web, from the viewpoint of maintaining the shape of the fibers without causing the fibers to form a film and improving the texture of the resulting sanitary nonwoven fabric. Furthermore, from the viewpoint of appropriately fusing the fibers constituting the fiber web together to give the sanitary nonwoven fabric sufficient strength for use, the temperature of the hot air blown onto the fiber web can preferably be in the range of melting point Mp - 4°C or higher, more preferably melting point Mp - 2°C or higher, and even more preferably above the melting point Mp. In this manufacturing method, when using core-sheath composite fibers, it is preferable to use fibers in which the melting point of the core's constituent resin is higher than that of the sheath's constituent resin, as this combines the ease of forming fusion points, further improvement of the texture of the resulting nonwoven fabric, and ease of conveying a cooling sensation.

[0085] The air-through process can be carried out, for example, by blowing hot air onto the fiber web on the net conveyor using an air-through furnace. In this case, the temperature of the hot air is defined as the temperature at the centroid of the hot air outlet in a plan view and directly above the net conveyor. This temperature can be measured, for example, using a thermocouple.

[0086] When using a core-sheath composite fiber as the fiber constituting the fiber web, for example, in which the sheath constituting the fiber surface is made of HDPE (melting point Mp: 130°C) and the core is made of nylon 6 (melting point: 225°C), which is a polyamide resin, the temperature of the hot air can preferably be 126°C or higher, more preferably 128°C or higher, and even more preferably 130°C or higher. Furthermore, the temperature of the hot air under the above conditions can preferably be 140°C or lower, more preferably 139°C or lower, and even more preferably 138°C or lower.

[0087] When polyamide resin fibers are used as the fibers constituting the fiber web, for example, if nylon 6 (melting point Mp: 225°C) is used, the temperature of the hot air can preferably be 221°C or higher, more preferably 223°C or higher, and even more preferably 225°C or higher. Furthermore, the temperature of the hot air under the above conditions can preferably be 235°C or lower, more preferably 234°C or lower, and even more preferably 233°C or lower. Furthermore, when nylon 66 (melting point Mp: 265°C) is used as the fiber made of polyamide resin, the temperature of the hot air can preferably be 261°C or higher, more preferably 263°C, and even more preferably 265°C or higher. Also, under the above conditions, the temperature of the hot air can preferably be 275°C or lower, more preferably 274°C or lower, and even more preferably 273°C or lower.

[0088] The melting point Mp of the resin constituting the fiber surface can be measured using a differential scanning calorimetry meter (DSC7000x, Hitachi High-Tech Science Corporation). First, a finely cut fiber sample (1 mg) is subjected to thermal analysis at a heating rate of 10°C / min to measure the melting peak temperature of each resin. The melting point is defined as the melting peak temperature during the first heating. If the melting point cannot be clearly measured 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 taken as the melting point Mp.

[0089] Furthermore, in the air-through process, the wind speed of the hot air blown onto the fiber web is preferably 0.6 m / sec or more, and more preferably 1.0 m / sec or more, from the viewpoint of allowing the hot air to pass sufficiently in the thickness direction of the fiber web and facilitating the formation of fusion between fibers. From a similar 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 air-through process under the temperature and wind speed conditions described above, the resin present on the surface of the fibers constituting the fiber web is melted or softened, allowing for the random formation of fusion points where the fibers fuse together. As a result, the manufactured sanitary nonwoven fabric exhibits flexibility and a good texture characteristic of air-through nonwoven fabrics, while also possessing sufficient strength for use.

[0090] The conveying speed of the fiber web in the air-through process is preferably 3 m / min or more, more preferably 10 m / min or more, preferably 200 m / min or less, and more preferably 160 m / min or less, within the above-mentioned temperature and wind speed range.

[0091] The fiber aggregate obtained through the above process is nonwoven, and can therefore be used as is as the sanitary nonwoven fabric of the present invention. This sanitary nonwoven fabric is an air-through nonwoven fabric.

[0092] From the viewpoint of easily obtaining a sanitary nonwoven fabric having a predetermined volume filling rate, it is preferable to further perform a densification treatment on the fiber aggregate obtained through the above-described process (densification step). In this step, a method can be employed in which the fiber aggregate can be compressed by applying pressure in the thickness direction.

[0093] The compaction process can be carried out by, for example, placing a fiber aggregate between two metal plates and applying pressure (hereinafter, this method is also called the "pressing method" or "pressing treatment"), or by introducing a fiber aggregate between a pair of rolls with smooth circumferential surfaces and applying pressure (hereinafter, this method is also called the "calendering method" or "calendering treatment"). The compaction process may be performed only once, or multiple times using the same or different methods as necessary. The temperature during the compaction process may be room temperature, heated, or a combination of these. From the viewpoint of increasing manufacturing efficiency, it is preferable to employ the calendering method, and from the viewpoint of efficiently performing compaction in a heated state without temperature unevenness, it is even more preferable to use a pair of rolls whose circumferential surfaces are made of metal or the like in the calendering method.

[0094] The conditions for the densification process are preferably those involving heating and pressurization. More specifically, the pressurization conditions in the densification process, when using the pressing method, are preferably 5 MPa or higher, and more preferably 7 MPa or higher, expressed as surface pressure, from the viewpoint of sufficiently densifying the fiber aggregate and making it easier to obtain a sanitary nonwoven fabric with a high volume filling rate. Furthermore, from the viewpoint of maintaining a fiber shape in which the boundaries between constituent fibers are clearly defined without forming a film from the fiber aggregate, and while ensuring a good texture for the resulting sanitary nonwoven fabric, the pressurization conditions in the densification process, when using the pressing method, can be expressed as surface pressure and preferably set to 72 MPa or less, more preferably 32 MPa or less.

[0095] Furthermore, when employing the calendering method, the pressurization conditions, expressed as linear pressure, are preferably 78.4 N / cm (8 kgf / cm) or higher, and more preferably 127.4 N / cm (13 kgf / cm) or higher, from the viewpoint of sufficiently compacting the fiber aggregate and making it easier to obtain a sanitary nonwoven fabric with a high volume filling rate. Furthermore, from the viewpoint of maintaining a fiber shape in which the boundaries between constituent fibers are clearly defined without forming a film from the fiber aggregate, and while ensuring a good texture for the resulting sanitary nonwoven fabric, the pressurization conditions when employing the calendering method 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, expressed as linear pressure.

[0096] Furthermore, the heating temperature in the compaction process can be preferably in the range of melting point Mp-80°C or higher, more preferably Mp-70°C or higher, and even more preferably Mp-60°C or higher, in both the pressing method and the calendering method, from the viewpoint of sufficiently compacting the fiber aggregate and making it easier to obtain a sanitary nonwoven fabric with a high volume filling rate. From the viewpoint of maintaining a fiber shape in which the boundaries between constituent fibers are clearly defined without forming a film from the fiber aggregate, and while ensuring a good texture for the resulting sanitary nonwoven fabric, the melting point can preferably be below Mp, and more preferably below Mp-20°C, in both the pressing method and the calendering method. When heating is required during the compaction process, if using the press method, the metal plate should be heated to the temperature range mentioned above, and if using the calendering method, the circumferential surface of the roll should be heated to the temperature range mentioned above.

[0097] The pressurization time during the densification process can be set as appropriate, provided that the fiber shape of the fibers constituting the fiber aggregate is maintained and densification is possible. For example, when using the pressing method, the pressurizing time under the above-mentioned pressure and temperature conditions can be preferably 5 seconds or more, more preferably 10 seconds or more, per compaction treatment. Furthermore, when using the pressing method, the pressurization time under the above-mentioned pressure and temperature conditions can preferably be 25 seconds or less, more preferably 20 seconds or less, per compaction treatment.

[0098] For example, when using the calendering method, the pressurization time under the above-mentioned pressure and temperature conditions can be preferably 0.01 seconds or more, more preferably 0.04 seconds or more, per compaction treatment. Furthermore, when using the calendering method, the pressurization time under the above-mentioned pressure and temperature conditions can be preferably 0.10 seconds or less, more preferably 0.08 seconds or less, per compaction treatment.

[0099] By performing a compaction treatment under the above conditions, the fiber aggregate can be compressed in the thickness direction to obtain a sanitary nonwoven fabric having a predetermined volume filling ratio and thickness. In particular, within the pressure and heating temperature range described above, melting of the constituent resin of the fibers is unlikely, while the morphological and dimensional stability due to heat treatment can be enhanced. As a result, a sanitary nonwoven fabric can be obtained that maintains its fiber shape and a predetermined volume filling rate even after manufacturing. Furthermore, when using fibers with a perfectly circular cross-section, the densification process can flatten the cross-section of the fibers, which has the advantage of increasing the volume filling rate. The sanitary nonwoven fabric obtained by the method described above remains an air-permeable nonwoven fabric even after undergoing compaction treatment.

[0100] When manufacturing a multilayered nonwoven fabric for sanitary purposes, for example, a second fiber web containing a thermoplastic resin formed by the carding method is laminated onto a fiber web containing a polyamide resin to form a fiber web laminate. Then, by applying an air-through treatment to this laminate, an air-through nonwoven fabric, which is a multilayered fiber assembly, can be obtained. In this nonwoven fabric, the boundaries between each fiber layer are indistinct. In this case, it is preferable to determine the temperature of the hot air to be blown using the melting point Mp of the resin with the lowest melting point as described above.

[0101] Furthermore, in the above-described case, it is preferable to arrange the fiber web laminate so that the hot air blowing step in the air-through treatment is blown onto fiber webs other than the fiber web containing polyamide resin. By employing such a method, the pressure of the hot air causes the fibers in the fiber web containing polyamide resin to heat-fuse together, forming a first fiber aggregate with a high volume-filling rate, while the second fiber web side maintains its bulkiness and has a structure with excellent compressive deformability, making it possible to obtain a sanitary nonwoven fabric. One such method involves, for example, positioning the side of the laminate containing the polyamide resin fiber web towards the bottom side of the air-through device, such as the net side, and then performing the air-through treatment.

[0102] Another method for manufacturing a multi-layered sanitary nonwoven fabric involves obtaining fiber sheets by air-through treatment of a fiber web containing polyamide resin and a second fiber web containing thermoplastic resin, and then joining these fiber sheets together using adhesives or various embossing methods such as fusion, bonding, or compression.

[0103] The sanitary nonwoven fabric of the present invention can also be manufactured by a method based on the spunbond method instead of the manufacturing method described above. That is, the method may include a step (spunbond step) in which a polyamide resin is subjected to spunbond treatment to obtain a fiber aggregate. The sanitary nonwoven fabric manufactured in this way is a spunbond nonwoven fabric.

[0104] In detail, the raw material resin for the fibers is extruded in a molten state from a spinneret having numerous pores, and the extruded resin is stretched into long fibers using a roll or the like. These long fibers are then accumulated on a net conveyor to obtain a fiber web containing polyamide resin. Subsequently, the fiber web is introduced between embossing rolls having multiple protrusions on their circumferential surface, and compaction (thermocompression bonding) is performed by heating and pressurizing to obtain the sanitary nonwoven fabric of the present invention. In other words, this method simultaneously performs the formation of fusion points between constituent fibers, the nonwoven fabricization of the fiber web, and the compaction treatment.

[0105] The temperature in the embossing roll can preferably be in the range of melting point Mp - 40°C or higher, more preferably melting point Mp - 35°C or higher, and even more preferably melting point - 30°C or higher. The pressurizing conditions applied by the embossing roll can preferably be in the range of 0.3 MPa or higher, more preferably 0.5 MPa or higher, and even more preferably 1.0 MPa or higher, from the viewpoint of sufficiently fusing the embossed portion. Furthermore, from the viewpoint of preventing perforation due to excessive pressure, the aforementioned pressurizing conditions can preferably be in the range of 40 MPa or less, more preferably 35 MPa or less, and even more preferably 30 MPa or less.

[0106] When manufacturing a multi-layered nonwoven fabric for sanitary purposes, for example, a second fiber web containing a thermoplastic resin formed by the carding method is laminated onto a fiber web containing a polyamide resin to form a fiber web laminate. Then, the laminate is subjected to densification (thermocompression bonding) by heating and pressurizing under the conditions described above.

[0107] Through the above steps, the sanitary nonwoven fabric of the present invention can be obtained. Preferably, this sanitary nonwoven fabric is incorporated as a component of a sanitary product such as an absorbent article in a subsequent step. When using sanitary nonwoven fabric as a component material for sanitary products such as absorbent articles, the sanitary product can be manufactured by including one or more steps in the manufacturing process of the sanitary product, such as cutting the sanitary nonwoven fabric or laminating or joining the sanitary nonwoven fabric with other components of the sanitary product (e.g., absorbents or sheets), as one of the component materials.

[0108] Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to the above embodiments.

[0109] With regard to the embodiments of the present invention described above, the following sanitary nonwoven fabrics and methods for manufacturing the same are further disclosed. <1> A fiber aggregate containing fibers including polyamide resin, The aforementioned fiber aggregate has fusion points where its constituent fibers are fused together, A sanitary nonwoven fabric having a volume filling ratio of 3.5% or more of fiber aggregates containing polyamide resin fibers.

[0110] <2> The volume filling rate of the fiber aggregate containing the polyamide resin is preferably 7.0% or more, more preferably 10.0% or more, even more preferably 12.0% or more, and even more preferably 14.0% or more. The volume filling rate is preferably 60.0% or less, more preferably 50.0% or less, even more preferably 45.0% or less, even more preferably 35.0% or less, and even more preferably 30.0% or less. The volume filling rate is preferably 7.0% to 60.0%, more preferably 7.0% to 50.0%, even more preferably 10.0% to 45.0%, even more preferably 12.0% to 35.0%, and even more preferably 14.0% to 30.0%. <1> The sanitary nonwoven fabric described above.

[0111] <3> The fiber is a composite fiber containing a polyamide resin. <1> or <2> The sanitary nonwoven fabric described above. <4> The composite fiber is a composite fiber containing a polyamide resin inside the fiber. <3> The sanitary nonwoven fabric described above. <5> The composite fiber is a composite fiber that further contains polyethylene resin throughout the entire outer surface of the fiber. <3> or <4> The sanitary nonwoven fabric described above.

[0112] <6> The fiber is a core-sheath composite fiber in which the core is made of polyamide resin and the sheath is made of high-density polyethylene resin. <1> ~ <5> A sanitary nonwoven fabric as described in any one of the following. <7> The polyamide resin content 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, even more preferably 40% by mass or more, preferably 100% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less. <1> ~ <6> A sanitary nonwoven fabric as described in any one of the following. <8> The polyamide resin is one or more of nylon 6, nylon 66, and aromatic nylon. <1> ~ <7> A sanitary nonwoven fabric as described in any one of the following. <9> The aforementioned fiber further contains polyethylene resin, The polyethylene resin content relative to the total mass of fibers contained in the sanitary nonwoven fabric is preferably 30% by mass or more, more preferably 40% by mass or more, preferably 90% by mass or less, and more preferably 80% by mass or less. <1> ~ <8> A sanitary nonwoven fabric as described in any one of the following.

[0113] <10> The aforementioned sanitary nonwoven fabric further contains polyethylene resin, The mass ratio of polyamide resin to polyethylene resin contained in the aforementioned sanitary nonwoven fabric (polyamide resin / polyethylene resin) is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.3 or more, preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.3 or less. <1> ~ <9> A sanitary nonwoven fabric as described in any one of the following.

[0114] <11> The aforementioned sanitary nonwoven fabric further contains polyethylene resin, The polyethylene resin is one or more of the following: 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, the above is made of high-density polyethylene resin (HDPE). <1> ~ <10> A sanitary nonwoven fabric as described in any one of the following. <12> The mean deviation (MMD) of the coefficient of friction is 0.010 or less. <1> ~ <11> A sanitary nonwoven fabric as described in any one of the following. <13> The mean deviation of the coefficient of friction (MMD) is preferably 0.009 or less, more preferably 0.008 or less, and preferably 0.004 or more. <1> ~ <12> A sanitary nonwoven fabric as described in any one of the following.

[0115] <14> 4.9 mN / cm 2 (0.5 gf / cm 2The overall thickness of the sanitary nonwoven fabric under load is preferably 0.05 mm or more, more preferably 0.08 mm or more, preferably 8 mm or less, more preferably 7.5 mm or less, and even more preferably 7 mm or less. <1> ~ <13> A sanitary nonwoven fabric as described in any one of the following. <15> The total basis weight of the aforementioned sanitary nonwoven fabric is preferably 10 g / m². 2 Above, a comfortable 15g / m 2 More preferably 18 g / m² 2 The above is preferable, preferably 200 g / m² 2 More preferably, 150 g / m² 2 More preferably 120 g / m 2 The following is the aforementioned <1> ~ <14> A sanitary nonwoven fabric as described in any one of the following. <16> The contact cooling sensation q in the fiber aggregate of the sanitary nonwoven fabric max However, preferably 0.06 W / m 2 More preferably, 0.08 W / m 2 More preferably 0.10 W / m 2 The above is preferable, and preferably 0.80 W / m 2 More preferably, 0.60 W / m 2 More preferably, 0.50 W / m 2 The following is the aforementioned <1> ~ <15> A sanitary nonwoven fabric as described in any one of the following. <17> The thermal conductivity of the fiber aggregate of the sanitary nonwoven fabric 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. <1> ~ <16> A sanitary nonwoven fabric as described in any one of the following.

[0116] <18> The bending stiffness value of the aforementioned sanitary nonwoven fabric is preferably 0.25 gf·cm. 2 Less than or equal to / cm, more preferably 0.2gf·cm 2 Less than or equal to / cm, more preferably 0.15gf·cm 2 Less than or equal to / cm, more preferably 0.1gf·cm 2The above is less than or equal to / cm <1> ~ <17> A sanitary nonwoven fabric as described in any one of the following. <19> The fiber diameter of the aforementioned fiber is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 12 μm or more, preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 27 μm or less. <1> ~ <18> A sanitary nonwoven fabric as described in any one of the following. <20> The fiber length of the fiber is preferably 30 mm or more, more preferably 38 mm or more, preferably 70 mm or less, more preferably 60 mm or less. <1> ~ <19> A sanitary nonwoven fabric as described in any one of the following. <21> The sanitary nonwoven fabric further comprises a filler, <1> ~ <20> A sanitary nonwoven fabric as described in any one of the following. <22> The filler is one or more of the following: titanium oxide, alumina, boron nitride, magnesium oxide, silica, carbon black, zinc oxide, and carbon nanotubes. <21> The sanitary nonwoven fabric described above.

[0117] <23> The material comprises a first fiber layer made of the aforementioned fiber aggregate and a second fiber layer made of a second fiber aggregate arranged adjacent to the first fiber layer. The second fiber aggregate has a density of 9.8 mN / cm². 2 The compressive deformation under load is 0.3 mm or more, <1> ~ <22> A sanitary nonwoven fabric as described in any one of the following. <24> The first fiber layer is arranged on the outer surface, <23> The sanitary nonwoven fabric described above. <25> The basis weight of the first fiber layer is preferably 10 g / m². 2 Above, a comfortable 15g / m 2 More preferably 18 g / m² 2 The above applies, and preferably 200 g / m². 2 More preferably, 150 g / m² 2 More preferably 100 g / m 2The following is the aforementioned <23> or <24> The sanitary nonwoven fabric described above. <26> The basis weight of the second fiber layer is preferably 10 g / m². 2 Above, a comfortable 15g / m 2 More preferably 20 g / m² 2 The above is preferable, preferably 140 g / m² 2 More preferably 90g / m 2 More preferably 70 g / m 2 The following is the aforementioned <23> ~ <25> A sanitary nonwoven fabric as described in any one of the following. <27> 9.8 mN / cm² of the second fiber layer 2 (1 gf / cm²) 2 The amount of compressive deformation under load is preferably 0.3 mm or more, more preferably 0.5 mm or more, and preferably 3 mm or less. <23> ~ <26> A sanitary nonwoven fabric as described in any one of the following.

[0118] <28> The aforementioned <1> ~ <27> The system comprises a sanitary nonwoven fabric as described in any one of the above, and a second member disposed adjacent to the nonwoven fabric, The second member has a load capacity of 9.8 mN / cm². 2 Sanitary products with a compressive deformation of 0.3 mm or more under load. <29> 9.8 mN / cm² for the second component 2 (1 gf / cm²) 2 The amount of compressive deformation under load is preferably 0.5 mm or more, and preferably 3 mm or less. <28> The hygiene products listed. <30> The total sanitary product load is 9.8 mN / cm². 2 The compressive deformation under load is 0.3 mm or more, <28> or <29> The hygiene products listed. <31> The total sanitary product load is 9.8 mN / cm². 2 (1 gf / cm²) 2 The amount of compressive deformation under load is preferably 0.4 mm or more, preferably 15 mm or less, and more preferably 10 mm or less. <28> ~ <30> A hygiene product listed in any one of the following.

[0119] <32> The second member is an absorbent or an absorbent sheet, <28> ~ <31> A hygiene product listed in any one of the following. <33> The second component is an absorbent sheet. The total basis weight of the absorbent sheet is preferably 40 g / m². 2 More than 60g / m 2 More preferably 70 g / m² 2 The above is preferable, preferably 500 g / m² 2 More preferably, 400 g / m² 2 More preferably, 300 g / m 2 The following is the aforementioned <28> ~ <32> A hygiene product listed in any one of the following.

[0120] <34> The second component is an absorbent, The total basis weight of the absorbent material is preferably 30 g / m². 2 Above all, a comfortable 40g / m 2 More preferably 50 g / m 2 The above is preferable, preferably 600 g / m² 2 More specifically, 550g / m 2 More preferably, 500 g / m 2 The following is the aforementioned <28> ~ <32> A hygiene product listed in any one of the following. <35> The aforementioned <1> ~ <27> An absorbent article comprising a sanitary nonwoven fabric as described in any one of the following. <36> The sanitary nonwoven fabric is arranged on the outer surface of the absorbent article, <35> Absorbent articles as described above.

[0121] <37> The aforementioned <1> ~ <27> A method for producing a sanitary nonwoven fabric as described in any one of the following: A method for producing a sanitary nonwoven fabric, comprising a step of performing an air-through treatment or spunbond treatment on a fiber web containing polyamide resin. <38> The process includes an air-through treatment of a fiber web containing polyamide resin. In the above process, the temperature of the hot air blown onto the fiber web is preferably below the melting point Mp, more preferably below the melting point Mp + 10°C, more preferably below the melting point Mp + 9°C, even more preferably below the melting point Mp + 8°C, preferably above the melting point Mp - 4°C, more preferably above the melting point Mp, and even more preferably above the melting point Mp. <37> The manufacturing method described above. <39> The process includes an air-through treatment of a fiber web containing polyamide resin. In the above process, the wind speed 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, preferably 2.0 m / s or less, and more preferably 1.4 m / s or less. <37> or <38> The manufacturing method described above. <40> The process includes an air-through treatment of a fiber web containing polyamide resin. The conveying speed of the fiber web in the above process is preferably 3 m / min or more, more preferably 10 m / min or more, preferably 200 m / min or less, more preferably 160 m / min or less. <37> ~ <39> A manufacturing method described in any one of the following.

[0122] <41> The process further includes a step of consolidating the fiber aggregate obtained by the air-through treatment or the spunbond treatment, The densification process is carried out while heating at a temperature below the melting point of the constituent resin of the fiber. <37> ~ <40> A manufacturing method described in any one of the following. <42> As the densification process, a press process is performed in which the fiber assembly is placed between two metal plates and pressurized, or a calender process is performed in which the fiber assembly is introduced between a pair of rolls and pressurized. <41> The manufacturing method described above. <43> As the aforementioned compaction treatment, the aforementioned pressing treatment is performed. The pressurizing conditions in the aforementioned pressing process are preferably 5 MPa or higher, more preferably 7 MPa or higher, preferably 72 MPa or lower, and more preferably 32 MPa or lower. <41> or <42> The manufacturing method described above.

[0123] <44> As the aforementioned compaction treatment, the calendering treatment is performed. The pressurization conditions in the calendering process are preferably 78.4 N / cm (8 kgf / cm) or higher, more preferably 127.4 N / cm (13 kgf / cm) or higher, preferably 686 N / cm (70 kgf / cm) or lower, more preferably 490 N / cm (50 kgf / cm) or lower, and even more preferably 294 N / cm (30 kgf / cm) or lower. <41> or <42> The manufacturing method described above. <45> The heating temperature in the densification process is preferably Mp-80°C or higher, more preferably Mp-70°C or higher, even more preferably Mp-60°C or higher, preferably Mp or lower, and more preferably Mp-20°C or lower, when the melting point of the constituent resin of the fiber is defined as melting point Mp. <41> ~ <44> A manufacturing method described in any one of the following. [Examples]

[0124] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to these examples. In the table, a "-" indicates that the substance is not contained or not measured.

[0125] [Examples 1-3] A core-sheath composite fiber was used, with nylon 6 as the polyamide resin core and HDPE as the sheath. The mass ratio of the resins, fiber diameter, and fiber length are shown in Table 1 below. First, the composite fiber web, adjusted to the basis weight shown in Table 1 below, was subjected to an air-through treatment to obtain a nonwoven fiber assembly. The conditions for the air-through treatment were as shown in Table 1 below. Next, the fiber assembly was compacted using a pressing method with a pair of flat metal plates under the heating and pressurizing conditions shown in Table 1 below to obtain the desired sanitary nonwoven fabric. All of these nonwoven fabrics had a single-layer structure.

[0126] [Example 4] Except for setting the airflow velocity during the air-through treatment to 1.2 m / sec and performing the compaction treatment by calendering, the same procedure as in Example 1 was used to obtain the desired single-layer sanitary nonwoven fabric. The pressure conditions for the calendering method were 483 N / cm (49.3 kgf / cm), and a pair of flat rolls with smooth surfaces were used.

[0127] [Example 5] A core-sheath composite fiber was used, with nylon 6 as the polyamide resin core and HDPE as the sheath. The target sanitary nonwoven fabric was obtained in the same manner as in Example 1, except that the mass ratio of the resins was changed as shown in Table 1 below.

[0128] [Example 6] A spunbond nonwoven fabric was obtained by forming a fiber web consisting solely of nylon 6 as the polyamide resin using the spunbond method, and then subjecting the web to fusion and compaction treatment using an embossing roll. The conditions for the spunbond method were as shown in Table 1 below. This nonwoven fabric had a single-layer structure. Furthermore, the length of the fibers obtained by the spunbond method is virtually infinite, and therefore the fiber length was not measured in this example.

[0129] [Example 7] A fiber web consisting solely of nylon 66 as a polyamide resin was formed by the spunbond method, and the web was subjected to fusion and compaction treatment using an embossing roll under the same conditions as in Example 6 to obtain a sanitary nonwoven fabric made of spunbond nonwoven fabric.

[0130] [Example 8] This embodiment produced a multi-layered sanitary nonwoven fabric. In detail, a fiber web consisting of a core-sheath composite fiber with nylon 6 as a polyamide resin as the core and HDPE as the sheath was subjected to air-through treatment under the same conditions as in Example 1, and then compacted under the same conditions as in Example 1 to form a single layer nonwoven fabric (basis weight: 90 g / m²). 2 ) was obtained. Separately, a second fiber web was prepared, consisting of a core-sheath composite fiber in which the core is PET and the sheath is PE. This web was subjected to air-through treatment and compaction treatment under the same conditions as in Example 1, resulting in a single-layer nonwoven fabric (basis weight: 20 g / m²). 2 ) was obtained. Finally, each nonwoven fabric is laminated and joined together using hot melt adhesive to create the desired multi-layered sanitary nonwoven fabric (basis weight: 110 g / m²). 2 ) was obtained.

[0131] [Example 9] A core-sheath composite fiber with nylon 6 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 in a mass ratio of 1:1. Air-through treatment and compaction treatment were performed under the same conditions as in Example 1 to obtain the target nonwoven fabric. This nonwoven fabric had a single-layer structure without a second fiber aggregate.

[0132] [Comparative Example 1] A nonwoven fabric for hygiene purposes was obtained in the same manner as in Example 1, except that a core-sheath composite fiber was used, in which the core was made of PET and the sheath of HDPE, instead of using polyamide resin.

[0133] [Comparative Example 2] A nonwoven fabric for hygiene purposes was obtained in the same manner as in Example 1, except that a core-sheath composite fiber was used, with the core being PP and the sheath being HDPE, instead of using polyamide resin.

[0134] [Measuring the thickness of sanitary nonwoven fabric] The thickness of the sanitary nonwoven fabrics in the examples and comparative examples was measured. The thickness was measured using a 4.9 mN / cm² solution on the sanitary nonwoven fabric being measured.2 (0.5 gf / cm 2 With the load of ) applied, measurements were taken at five or more locations using a laser displacement meter, and the arithmetic mean of these measurements was taken as the thickness (mm). The results are shown in Table 1.

[0135] [Measurement of volume filling efficiency] The volume filling rate (%) of the sanitary nonwoven fabrics in the examples and comparative examples was calculated using the method described above. The results are shown in Table 1.

[0136] [9.8 mN / cm 2 Measurement of compressive deformation under load. For the sanitary nonwoven fabrics of the examples and comparative examples, 9.8 mN / cm was obtained using the method described above. 2 The amount of compressive deformation (mm) under load was calculated. The results are shown in Table 1.

[0137] [MMD measurement] The MMD was calculated for the sanitary nonwoven fabrics of the examples and comparative examples using the method described above. The results are shown in Table 1.

[0138] [Thermal conductivity of nonwoven fabrics] The thermal conductivity and contact cooling sensation of the sanitary nonwoven fabrics in the examples and comparative examples were measured using the following method. (1. Create a sample) The sanitary nonwoven fabric to be measured was cut into small pieces, and multiple pieces were stacked to form a laminate weighing approximately 10g each. This laminate was held in the center of two stainless steel plates and heated for 1 minute under no-pressure conditions to obtain a fused material. The heating temperature was set to the melting point Mp + 20°C measured by the differential scanning calorimetry meter described above. In the case of nonwoven fabrics containing multiple resin materials, the heating temperature was set based on the melting point of the resin with the highest melting point. Specifically, it was heated to 245°C. Next, the resulting fused material was subjected to a gauge pressure of 200 kgf (total mass including top plate: 21848 kg; when calculating the pressure as surface pressure, the surface pressure is calculated based on the area of ​​the final circular resin plate, as the area of ​​the fused material changes as the resin melts. For example, if the circular resin plate has a diameter of 15 cm, the surface pressure is 12 MPa) while maintaining the aforementioned heating temperature, and held for 1 minute. Then, while maintaining the pressurized state, it was cooled with water to 20°C to obtain a circular resin plate with a diameter of approximately 15-20 cm (the diameter of the resulting circular resin plate may vary depending on the melt viscosity of the resin). Next, the obtained circular resin plate was cut radially through its center, and if the maximum span length was 5 cm or more, it was cut again so that it was 5 cm or less. Then, to eliminate the influence of resin orientation, the cut resin plate was placed on top of the stainless steel plate so that the direction of extension of the imaginary line segment at the maximum span length was random. Two 1 mm thick shims were then placed parallel to each other 10 cm from the center of the stainless steel plate, and the stainless steel plate was placed on top of them. After that, heating under no pressure and heating and cooling under pressure were performed using the same procedure as described above. If air bubbles formed, the same procedure was repeated. The purpose of heating and melting twice is to melt the sample once to eliminate the influence of resin crystallization and other changes that occur during the fiber spinning process, and to make the thermal history constant. A film was obtained as a result.

[0139] (2. Measurement of thermal conductivity) The thermal conductivity was measured using a measuring device (Kato Tech Co., Ltd., KES-F7 Thermolab II) in the following manner. First, the prepared film was cut to dimensions of 10 cm in length and 10 cm in width, and left for 24 hours in an environment with a room temperature of 23°C and a relative humidity of 50%. Next, the thermal conductivity of the object to be measured was measured according to the aforementioned measuring device and its measurement manual. Specifically, the temperature of the heat source for measurement (BT-BOX, which is an integrated unit of an aluminum plate measuring 5 cm in length and 5 cm in width with a thickness of 1 mm and a heater, etc.) was set to 33°C (10°C higher than the surface temperature of the object to be measured), and to prevent the film from curling and reducing the contact area, the film was covered with a 0.25 m² area.2 The heat source was brought into contact with the object so that a load of 1 kg per unit was applied. The measurement start time was defined as the point when the heat flow rate from the heat source to the object became constant on the measuring instrument's display panel, and the average heat flow rate for 60 seconds from that point was measured. The following formula (III) was used to calculate the thermal conductivity of the film based on the measurement conditions and the measured heat flow rate. The film thickness D was taken as the arithmetic mean of the thickness measured at three or more locations under no load using a laser displacement meter. The above measurement was performed three times for each object, and the maximum value of these measurements was taken as the thermal conductivity (W / mK) of the sample. The results are shown in Table 1.

[0140] k=100×(W×D) / (A×ΔT) ···(III) (k: thermal conductivity [W / mK], W: heat flow rate [W / m 2 ], D: Film thickness [cm], A: Aluminum plate area (25cm²) 2 ), ΔT: Temperature difference between the heat source and the film (10°C)

[0141] [Measurement of contact cooling sensation] The contact cooling sensation was measured using a measuring device (Kato Tech Co., Ltd., KES-F7 ThermoLab II) in the following manner. First, the sanitary nonwoven fabric to be measured was cut to dimensions of 23 cm in length and 14 cm in width, and left for 24 hours in an environment with a room temperature of 23°C and a relative humidity of 50%. Next, in accordance with the aforementioned measuring device and its measurement manual, the sanitary nonwoven fabric to be measured was heated to 23°C using a constant temperature device that uses gas or liquid as a heat transfer medium, in order to specify the temperature difference with the heat source. Next, in accordance with the above-mentioned measuring device and its measurement manual, the contact cooling sensation q of the object to be measured is measured. max The following measurements were taken. Specifically, a heating plate with an area of ​​9.0 cm² was used as the heating element to be in contact with the object being measured. 2 Using a measuring terminal made of pure copper (T-Box) with a mass of 9.8g, the initial temperature of the copper plate was set to 33°C (10°C higher than the surface temperature of the object being measured), and the contact pressure of the copper plate with the object being measured was set to 98mN / cm². 2 (10gf / cm 2The copper plate was brought into contact with the test piece, and the value of the heat flow at the moment of contact was set to zero, and the maximum value of the heat flow was measured. This measurement was performed five times for each surface to be measured, and the arithmetic mean of these multiple measurements was used to determine the contact cooling sensation q of the measured object. max (W / m 2 ) Cool touch q max A higher value indicates a greater and faster heat transfer, making it easier for the wearer to perceive a cooling sensation. The results are shown in Table 1 below.

[0142] [Evaluation of texture] The nonwoven fabrics of the examples and comparative examples were evaluated for texture using the following method. The items for the texture evaluation test were flexibility, smoothness, and feel. First, 20 expert panelists were asked to touch the surface of the nonwoven fabric and score each item according to the evaluation criteria below, and the average score for each item was calculated. Then, the overall average score was calculated from 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: Fairly good. 3 points: Average. 2 points: Slightly bad. 1 point: Bad.

[0143] [Evaluation of cooling sensation] The nonwoven fabrics of the examples and comparative examples were evaluated for their cooling sensation using the following method. First, 20 expert panelists were asked to touch the surface of the nonwoven fabric and rate the cooling sensation they felt according to the following criteria. The arithmetic mean of these ratings was used as the evaluation of the cooling sensation. The results are shown in Table 1. 5 points: Excellent cooling effect. (The cooling sensation is as strong as that of a contact-cooling fabric with a q-max of 0.20 or higher.) 4 points: Provides good cooling sensation. 3 points: You can perceive the sensation of cold. 2 points: It doesn't feel very cool. 1. No cooling sensation is felt at all. (Similar to air-through nonwoven fabrics with a q-max of 0.06 or less, no cooling sensation is felt.)

[0144] As shown in Table 1, the sanitary nonwoven fabrics of each example have a better texture compared to the comparative example, while also having high thermal conductivity and volume filling efficiency, and a cool-to-the-touch feel. max The temperature is also high, indicating that the feeling of coldness is perceived more strongly. Therefore, the hygienic nonwoven fabric of the present invention has a good texture and can provide a comfortable feeling of coolness when it comes into contact with the skin.

[0145] [Table 1]

Claims

1. A fibrous assembly comprising a composite fiber containing a polyamide resin and a polyethylene resin, The fibrous assembly has fusion points where the constituent fibers are fused together, A sanitary nonwoven fabric, wherein the volume filling rate of the fibrous assembly containing the composite fiber containing the polyamide resin and the polyethylene resin is 3.5% or more.

2. The sanitary nonwoven fabric according to Claim 1, wherein the volume filling rate of the fibrous assembly containing the composite fiber containing the polyamide resin and the polyethylene resin is 12.0% or more.

3. The sanitary nonwoven fabric according to Claim 1 or 2, wherein the polyamide resin is one or more of nylon 6, nylon 66, and aromatic nylon.

4. The sanitary nonwoven fabric according to Claim 1 or 2, wherein the mass ratio of the polyamide resin to the polyethylene resin (polyamide resin / polyethylene resin) contained in the sanitary nonwoven fabric is 0.1 or more and 2.0 or less.

5. The sanitary nonwoven fabric according to Claim 1 or 2, 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 according to Claim 1 or 2, wherein the composite fiber is a core - sheath composite fiber having a core of polyamide resin and a sheath of high density polyethylene resin (HDPE).

7. The sanitary nonwoven fabric according to Claim 1 or 2, wherein the fiber diameter of the composite fiber is 1 μm or more and 40 μm or less.

8. The sanitary nonwoven fabric according to Claim 1 or 2, wherein the fiber length of the composite fiber is 30 mm or more and 70 mm or less.

9. The sanitary nonwoven fabric according to Claim 1 or 2, further comprising a filler.

10. The filler is one or more of titanium oxide, alumina, boron nitride, magnesium oxide, silica, carbon black, zinc oxide, and carbon nanotubes. The sanitary nonwoven fabric according to Claim 9.

11. It has a first fiber layer composed of the fiber assembly and a second fiber layer composed of a second fiber assembly arranged adjacent to the first fiber layer. The second fiber assembly has a compression deformation amount of 0.3 mm or more under a load of 9.8 mN / cm. The sanitary nonwoven fabric according to Claim 1 or 2. ２

12. The sanitary nonwoven fabric according to Claim 1 or 2, and a second member arranged adjacent to the nonwoven fabric. The second member has a compression deformation amount of 0.3 mm or more under a load of 9.8 mN / cm. A sanitary product. ２

13. The second member is an absorber. The sanitary product according to Claim 12.

14. An absorbent article comprising the sanitary nonwoven fabric according to Claim 1 or 2.

15. A method for manufacturing the sanitary nonwoven fabric according to Claim 1 or 2, The method for manufacturing a sanitary nonwoven fabric having a step of subjecting a web of composite fibers containing a polyamide resin and a polyethylene resin to an air-through treatment or a spunbond treatment.

16. The method further has a step of performing a densification treatment on the fiber assembly obtained by the air-through treatment or the spunbond treatment. The manufacturing method according to Claim 15, wherein the densification treatment is performed while heating at a temperature below the melting point of the constituent resin of the composite fiber.

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