TW202321037A - Nonwoven fabric for hygiene and method for producing same - Google Patents

Abstract

A nonwoven fabric for hygiene according to the present invention comprises a fiber assembly which contains fibers that contain a polyamide resin, while having fusion points where the constituent fibers of the fiber assembly are fused with each other. This nonwoven fabric for hygiene has a volume filling rate of 3.5% or more. It is preferable that the constituent fibers are sheath-core composite fibers wherein the core is formed of a polyamide resin, while the sheath is formed of a high-density polyethylene resin. In a production method according to the present invention, a web of composite fibers that contain a polyamide resin is subjected to an air-through treatment, thereby obtaining a fiber assembly, and the fiber assembly is consolidated by being heated at a temperature that is not more than the melting point of the resin that constitutes the fiber assembly.

Description

Hygienic nonwoven fabric and manufacturing method thereof

The invention relates to a sanitary non-woven fabric and a manufacturing method thereof.

The industry has proposed fibers and articles with a composition that can make people feel cool. For example, Patent Document 1 discloses a comfortable fabric used as clothing for relieving summer heat. According to the document, the fabric contains at least one organic polymer fiber whose thermal conductivity in the fiber axis at 20°C to 30°C is 5 W/mK or more, and the thermal conductivity in the thickness direction of the fabric at 20°C to 30°C The rate is 0.08 W/mK or more, and the contact temperature and coolness is 0.13 W/cm ² or more.

Patent Document 2 discloses an absorbent article in which a cooling agent is applied to side flaps extending outward from both lateral sides of an absorber.

In Patent Document 3, a fiber and a fabric using the fiber are disclosed in order to express hygroscopicity and cool feeling to the touch. The sheath polymer in the fiber includes polyamide, and the core polymer includes polyetheresteramide. An amine copolymer, and the whole fiber contains 0.1 to 5% by weight of inorganic particles.

In addition, Patent Document 4 discloses a knitted fabric made of composite fiber yarn in which the sheath layer is polyethylene and the core layer is nylon or polyester. prior art literature patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2010-236130 Patent Document 2: Japanese Patent Laid-Open No. 2016-120208 Patent Document 3: US2017/0342606A1 Patent Document 4: Utility Model Registration No. 3226090

The present invention relates to a hygienic nonwoven fabric having a fiber aggregate containing fibers containing polyamide resin. In one embodiment, the above-mentioned fiber aggregate preferably has fusion points where the constituent fibers are fused to each other. In one embodiment, it is preferable that the volume filling rate of the fiber aggregate containing the fibers containing polyamide resin is 3.5% or more.

In addition, the present invention relates to a method for producing sanitary non-woven fabrics, which includes the step of hot-air treatment or spun-bonding treatment of fiber webs containing polyamide resin fibers.

Absorbent articles such as menstrual tampons or panty liners to absorb liquids discharged from the body, or hygienic articles such as eye masks covering the eyes or masks covering the mouth or nose, etc., are composed of multiple constituent members including non-woven fabrics However, if this kind of article is in contact with the skin before use or when wearing it, the wearer may feel a sense of warmth, which may lead to discomfort such as stuffy feeling during use. Especially in a hot environment, this situation may become more significant. Therefore, it is desired that the part of the hygiene product that contacts the skin has a good texture and a cool feeling.

However, the technologies described in Patent Documents 1, 2, and 4 are applied to articles other than sanitary products such as clothes, and no research has been conducted on application to sanitary products.

The technology described in Patent Document 3 uses a cooling agent, so it has a delayed effect on the feeling of coolness, and it is difficult to feel the coolness when it is in contact with thicker parts of the skin such as palms.

Therefore, the present invention relates to a hygienic nonwoven fabric which has a good texture and can feel cool when it comes into contact with the skin.

Hereinafter, the present invention will be described based on preferred embodiments of the present invention. The hygienic nonwoven fabric of the present invention is suitably used as a constituent member of hygienic products. Typical examples of sanitary products are sanitary products such as face masks and eye masks, or absorbent products such as disposable diapers and menstrual pads that absorb body fluids such as urine or menstrual blood, and are preferably absorbent products. Nonwovens for hygiene use are placed on the skin-contacting side of the wearer when wearing sanitary products, or on the parts that come into contact with the wearer's hands when handling sanitary products. The hygienic nonwoven fabric can be used without being particularly limited to the uses described here.

The sanitary nonwoven fabric of the present invention is a sheet-like article comprising a fiber aggregate (hereinafter also referred to as "polyamide fiber-containing aggregate") containing fibers containing a polyamide resin. The sanitary nonwoven fabric may be composed of fibers containing polyamide resin alone, or may be blended with other fibers to form a fiber aggregate containing a single fiber layer. Alternatively, the sanitary nonwoven fabric may be formed by laminating a fiber aggregate layer containing fibers containing polyamide resin and a fiber aggregate layer other than the fiber aggregate layer containing polyamide resin to form fibers containing a plurality of fiber layers. Aggregates.

The constituent fibers of the sanitary nonwoven fabric of the present invention maintain the form of a fiber sheet by fusion. Specifically, from the viewpoint of further improving texture and air permeability, the constituent fibers of the sanitary nonwoven fabric have fusion points where the fibers are fused together. Fusion refers to a state in which only heat or heat and pressure are applied to a plurality of fibers to melt the fibers, thereby making the boundary between the fibers unclear. In order to have fusion points, for example, it can be formed by blowing hot air to the fiber web as described below.

The fiber contained in the sanitary nonwoven fabric contains polyamide resin as mentioned above. Examples of the presence of the polyamide resin constituting the fiber contained in the sanitary nonwoven fabric of the present invention include: (i) a state in which the constituent resin of the fiber is only a polyamide resin; The resin component of the amide resin and the fibers of the second resin component different from the resin component, etc.

Generally speaking, polyamide resin has relatively low rigidity among organic polymer materials and has good processability, so it is mostly used in cloth products. Fibers containing polyamide resins are hygroscopic and have relatively high thermal conductivity among organic polymer materials. The inventors of the present invention focused on the above-mentioned characteristics of polyamide resin, and found that by containing polyamide resin in the constituent fibers of the nonwoven fabric, the high thermal conductivity of the polyamide resin itself can be brought into play, and the flexibility of the fiber can be exerted. , as a result, the non-woven fabric can show a good texture and feel cool at the same time.

Specific examples of the above (i) include fibers comprising only a single type of polyamide resin as the resin, and fibers comprising plural types of polyamide resins as the resin. As the latter aspect, for example, a fiber including a different type of polyamide resin on the outer surface and inside of the fiber can be mentioned. Specific examples of the above (ii) include: (a) fibers made of resin mixed with polyamide resin and other resins; (b) a sheath whose core is polyamide resin and covers the surface of the core A core-sheath composite fiber containing another resin, (c) a side-by-side composite fiber having a polyamide resin and another resin in which the other resin is continuously present on at least a part of the surface of the fiber containing the polyamide resin along the fiber length direction, and the like. In this case, the other resin is a resin component other than the polyamide resin whose melting point is lower than that of the polyamide resin from the viewpoint of easy formation of a fusion point. The fibers used in the present invention can be solid or hollow. From the viewpoint of improving thermal conductivity and making it easier for the wearer to feel cool, solid fibers are preferred.

The presence of the constituent resin in the fiber is preferably a composite fiber containing a polyamide resin, more preferably a composite fiber containing a polyamide resin inside the fiber, and more preferably a composite fiber containing polyamide resin on at least the entire outer surface of the fiber. The polyethylene resin is a composite fiber of other resins, and more preferably a composite fiber having a core-sheath structure in which the core is a polyamide resin and the sheath includes a polyethylene resin. Since the thermal conductivity of polyethylene resin is higher than that of polyamide resin, by setting the surface of the fiber to have polyethylene resin, the polyethylene resin with higher thermal conductivity will directly contact the wearer's skin, so it can make the wearer more comfortable. The patient feels a strong cooling sensation. In addition, the fiber can exhibit good properties such as high thermal conductivity, low rigidity and hygroscopicity of polyamide resin, thereby further improving the texture of the non-woven fabric.

In addition, by using resins with different melting points together, the fibers can be non-woven without being completely fused together, thereby improving the processability in the manufacturing process and improving the texture of the obtained non-woven fabric. In addition, the conjugate fiber can be crimped to further improve the texture. In addition, the touch of the non-woven fabric becomes dry, and even when the non-woven fabric feels cool when in contact with the non-woven fabric, it is difficult for the user to feel an uncomfortable moist feeling.

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

As the polyethylene resin used in the present invention, for example, low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), high-density polyethylene resin (HDPE), and linear low-density polyethylene Resin (LLDPE), and ethylene-propylene copolymer, etc. These can be used alone or in mixture or combination of plural kinds.

It is preferable to include HDPE as the polyethylene resin, and it is more preferable to use only HDPE from the viewpoint of having high thermal conductivity and enabling the wearer to feel a strong cool feeling. That is, 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 fusion points between fibers can be more easily formed in the production method described below.

More specifically, it is more preferable to use a composite fiber having a core-sheath structure in which a polyamide resin is used as the core and HDPE is used as the sheath. In this way, even if the polyamide resin absorbs moisture from body fluids such as sweat, urine, menstrual blood, and exhaled breath, the polyamide resin will not directly contact the wearer's skin, thus preventing an uncomfortable wet feeling. In addition, since the fusion can be promoted only at the intersecting points of the fibers during manufacture, the tactile feeling is improved. As a result, the hygienic nonwoven fabric can maintain a good texture, and its surface has a dry and good touch feeling, which can make the wearer feel a comfortable cool feeling.

Also, as a preferred aspect of the present invention, by using a core-sheath composite fiber composed of a sheath whose constituent resin has a lower melting point than the core constituent resin, for example, when manufacturing a sanitary nonwoven fabric by the hot-air method, It is less likely that the fiber constituent resin cannot maintain the shape of the fiber due to excessive melting, or that the obtained non-woven fabric has holes and other defects, which will further improve the stability of manufacturing. In addition, by using the above-mentioned core-sheath composite fiber in the hot-air method, it is easy to fuse only the intersection points of the fibers, and the fibers can be non-woven without being completely fused, so that a non-woven fabric with a better texture can be obtained. In addition, the touch of the non-woven fabric becomes dry, and even when the non-woven fabric feels cool when in contact with the non-woven fabric, it is difficult for the user to feel an uncomfortable moist feeling.

As resins other than polyethylene resins that can be used in the present invention, for example, polyolefin resins other than polyethylene resins such as polypropylene (PP) and polybutene; polyethylene terephthalate (PET ) and other polyester resins; vinyl resins such as polyvinyl chloride and polystyrene; acrylic resins such as polyacrylic acid and polymethyl methacrylate; various thermoplastic fibers such as fluorine resins such as polyperfluoroethylene. These resins may be used individually by 1 type or in combination of 2 or more types as needed.

The content of the polyamide resin is preferably at least 25% by mass, more preferably at least 30% by mass, further preferably at least 40% by mass, more preferably at least 40% by mass, relative to the total mass of fibers contained in the sanitary nonwoven fabric of the present invention. It is 100 mass % or less, More preferably, it is 90 mass % or less, More preferably, it is 80 mass % or less. When the polyethylene resin is contained in the constituent fibers, the content of the polyethylene resin is preferably at least 30% by mass, more preferably at least 40% by mass, more preferably at least 40% by mass, based on the total mass of the fibers contained in the sanitary nonwoven 90% by mass or less, more preferably 80% by mass or less. The content of the above-mentioned resins is also preferably satisfied in the aggregate containing polyamide fibers.

When the polyethylene resin is included in the constituent fibers, the mass ratio of the polyamide resin to the polyethylene resin contained in the sanitary nonwoven fabric of the present invention (poly Amide resin/polyethylene resin) is preferably 0.1 or more, more preferably 0.2 or more, and more preferably 0.3 or more, from the viewpoint of weaving processability, preferably 2.0 or less, more preferably 1.5 or less, and more preferably 0.3 or more. Preferably below 1.3. The above mass ratio is also preferably satisfied in an aggregate containing polyamide fibers.

The type of the constituent resin in the fiber is confirmed in the following manner: Confirm the melting point of the constituent resin of the fiber by differential scanning calorimetry, and use one or more of infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) to confirm the resin type. In addition, using a scanning electron microscope (SEM), the spinning method is estimated from the surface shape and cross-sectional shape of the fiber, thereby specifying the type of resin in the fiber. The content of the constituent resin is calculated as follows: First, the mass of the nonwoven fabric to be measured and the thickness under no load are measured. Thereafter, the fiber structure is fixed using liquid nitrogen, etc., and the cross section of the nonwoven fabric is made so that the fiber cross section can be observed in the direction perpendicular to the longitudinal direction of the fiber, and the volume ratio is confirmed using SEM, etc. The specific gravity, calculate the resin content. When the nonwoven fabric to be measured is incorporated into a sanitary product, it is used for measurement after peeling off the nonwoven fabric from the sanitary product by cold spraying.

From the perspective of reducing the content of air with low thermal conductivity to increase the thermal conductivity of the nonwoven fabric, the volume filling rate of the aggregate containing polyamide fibers is preferably 3.5% or more, more preferably 7.0% or more , more preferably 10.0% or more, still more preferably 12.0% or more, still more preferably 14.0% or more. Also, when used as a disposable hygienic material in contact with the wearer's skin, the volume filling rate of the aggregate containing polyamide fibers is preferably 60.0% or less from the viewpoint of making the texture good, More preferably, it is 50.0% or less, More preferably, it is 45.0% or less, More preferably, it is 35.0% or less, More preferably, it is 30.0% or less. Therefore, the volume filling rate of the aggregate containing polyamide fibers is preferably from 3.5% to 60.0%, more preferably from 7.0% to 50.0%, further preferably from 10.0% to 45.0%, and still more preferably from 12.0% to 35.0%, more preferably 14.0% to 30.0%.

By making the aggregate containing polyamide fibers have the above-mentioned volume filling rate, the content of air with low thermal conductivity is reduced in the sanitary non-woven fabric, so the transfer of heat can be improved, thereby making the wearer feel stronger. feel the coolness. In addition, the texture of the sanitary nonwoven fabric of the present invention and sanitary products incorporating the nonwoven fabric can be fully expressed. The above-mentioned configuration can be obtained, for example, by densifying fiber aggregates obtained in the manufacturing process of the sanitary nonwoven fabric as in the following manufacturing method.

The volume filling rate in the present invention can be represented by the percentage of the apparent volume relative to the actual volume. Specifically, a predetermined area is cut out from a sanitary nonwoven fabric to be measured as a measurement sample, and its mass (g) is measured. The specified area when cutting the measurement sample is preferably 10 cm square, but if the measurement sample of this size cannot be cut out, in the area of uniform basis weight under the visual inspection of the sanitary non-woven fabric as the measurement object, according to the maximum area formed Width and length are intercepted. Then, the basis weight A (g/cm ² ) of the measurement sample was calculated. Moreover, the measuring method of measuring the thickness B (cm) of a sample is as follows. First, only a 12.59 g (diameter: 55 mm) plate is mounted on a laser displacement meter (LK-080 manufactured by Keyence Co., Ltd. The laser displacement meter in this specification is the laser displacement meter), Set the measured thickness to zero to perform zero point adjustment. Next, the said board|plate was mounted on the measurement sample, the thickness in this state was measured using the laser displacement meter, and this thickness was made into the thickness B (cm) of the measurement sample. In the measurement of the thickness B, a load of 4.9 mN/cm ² was applied to the measurement sample by placing the plate.

Then, the volume filling rate (%) was calculated from the following formula (I) using the specific gravity C (g/cm ³ ) of the constituent components of the fiber. In the case of fiber containing two or more resins, such as a composite fiber, the sum of the specific gravity based on the mass ratio of each constituent component is used as specific gravity C. For example, in the case of a bicomponent fiber with a mass ratio of 30:70 between the constituents of specific gravity C1 (g/cm ³ ) and the constituents of specific gravity C2 (g/cm ³ ), specific gravity C (g/cm ³ ) Calculated by "0.3 x specific gravity C1 + 0.7 x specific gravity C2". Volume filling rate (%)＝100×(A)/(B×C)・・・(I)

When a hygienic nonwoven fabric to be measured is placed in sanitary articles such as absorbent articles, cold spray is blown on the hygienic article to solidify the hot-melt adhesive, and then the nonwoven sanitary fabric to be measured is carefully peeled off. Also, in the case of bonding to another member such as the second fiber aggregate described below by fusion or the like, after the structure is fixed by cold spraying or liquid nitrogen, the measurement object is peeled off and measured. This method is common to other assays in this specification.

The mean deviation (MMD) of the coefficient of friction of the sanitary nonwoven fabric of the present invention measured by the following method is preferably 0.010 or less, more preferably 0.009 or less, further preferably 0.008 or less, and realistically 0.004 or more. With such a configuration, the surface of the non-woven fabric has a dry touch, and the skin feels good, and it becomes a non-woven fabric with a high usability. The above-mentioned coefficient of friction is preferably satisfied when an aggregate containing polyamide fibers is used as an object.

The average deviation MMD of the coefficient of friction was measured using KES-FB4-AUTO-A (trade name) manufactured by Kado Technology Co., Ltd. First, a 20 cm x 20 cm test piece is taken out from the sanitary nonwoven fabric to be measured. When the test piece of this size cannot be taken out, the size of the test piece can also be changed appropriately. Then, the surface of the test piece on which the fiber aggregate containing polyamide resin is arranged is specified by methods such as infrared spectroscopy (FT-IR). Then, install the test piece on a smooth metal flat test stand. The contact surface of the contact point is pressed against the surface of the fiber aggregate of the test piece with a force of 49 cN, and the test piece is moved horizontally for 2 cm at a fixed speed of 0.1 cm/sec. A uniaxial tension of 7.3 cN/cm was applied to the test piece. The contact point is formed by arranging 20 piano wires with a diameter of 0.5 mm and bending them into a U shape with a width of 10 mm. Use a plumb weight to crimp the contact surface of the contact to the test piece with a force of 49 cN. The measurement is carried out in one direction (MD direction) of the nonwoven fabric and a direction (CD direction) perpendicular to the direction (CD direction), and MMD _MD and MMD _CD are obtained, and the average value is obtained according to the following formula (II), which is used as the coefficient of friction The mean deviation MMD. When the test piece of the sample can only be taken out in either direction of MD direction or CD direction, the value of only one direction is taken as the average deviation MMD of the friction coefficient. Average deviation of friction coefficient MMD＝{(MMD _MD ² ＋MMD _CD ² )/2} ^1/2・・・(II)

From the viewpoint of improving the texture of the sanitary nonwoven fabric of the present invention, the overall thickness of the nonwoven fabric is preferably at least 0.05 mm, more preferably at least 0.08 mm. Also, from the viewpoint of reducing the air content in the sanitary nonwoven fabric of the present invention and thereby improving thermal conductivity, the overall thickness of the sanitary nonwoven fabric of the present invention is preferably less than 8 mm, more preferably less than 7.5 mm, and more preferably less than 7.5 mm. Preferably less than 7 mm. The thickness of the above-mentioned sanitary nonwoven fabric is measured with a laser displacement meter under a load of 4.9 mN/cm ² (0.5 gf/cm ² ). By making the thickness of the sanitary nonwoven fabric of the present invention the above configuration, the heat capacity of the sanitary nonwoven fabric can be increased, thereby efficiently producing a sanitary nonwoven fabric that can efficiently make the wearer feel cool. From the same viewpoint, it is also preferable that the aggregate containing polyamide fibers satisfy the above-mentioned thickness range under a load of 4.9 mN/cm ² (0.5 gf/cm ² ).

The contact coolness q _max of the polyamide fiber-containing aggregate of the sanitary nonwoven fabric of the present invention is preferably at least 0.06 W/m ² , more preferably at least 0.08 W/m ² , and still more preferably at least 0.10 W/m ² , preferably less than 0.80 W/m ² , more preferably less than 0.60 W/m ² , and still more preferably less than 0.50 W/m ² . Specifically, the cooling sensation q _max in the polyamide fiber-containing aggregate of the sanitary nonwoven fabric is preferably from 0.06 W/m ² to 0.80 W/m ² , more preferably from 0.08 W/m ² to 0.60 W/m 2 m ² or less, more preferably 0.10 W/m ² or more and 0.50 W/m ² or less.

The contact cooling sensation q _max can be measured, for example, by the following method. First, a test piece was cut out from the sanitary non-woven fabric of the measurement object with a size of 10 cm long x 10 cm wide, and the test piece was left for 24 hours at a room temperature of 23°C and a relative humidity of 50%. Furthermore, when the test piece cannot be cut out in the above-mentioned size, the test piece is cut out in a size as large as possible so that it has a size close to the above-mentioned size. Next, in this environment, the test piece was placed on the measurement table, and the test piece was fixed on the measurement table using a double-sided tape. A thermostat using gas or liquid as a heat medium and set at 23° C. was used as a measuring platform. Then, by means of a measuring device (KES-F7 Thermo Lab II manufactured by Kaduo Technology Co., Ltd.) and according to the measuring guide of the device, the contact coolness q _max of the measuring object was measured. Specifically, a pure copper plate with an area of 9.0 cm ² and a mass of 9.8 g was used as a hot plate in contact with the measurement object, and the initial temperature of the copper plate was set to 33°C (a temperature 10°C higher than the surface temperature of the measurement object). The contact pressure between the copper plate and the measurement object is set to 1 kPa, the copper plate is brought into contact with the test piece, and the value of the above-mentioned heat flow at the instant of contact is set to zero, and the maximum value of the heat flow is measured. The measurement was carried out 5 times for each surface to be measured, and the arithmetic mean value of the multiple measured values obtained was defined as the cooling sensation q _max (W/m ² ) of the object to be measured.

The so-called cooling sensation on contact is obtained by digitizing the skin feeling of coolness when the skin is in contact with an object. The cool feeling upon contact varies with the amount of heat transfer from the skin to the object when the skin is in contact with the object. The greater the amount of heat transfer, the cooler the feeling upon contact. Contact coolness q _max corresponds to the maximum value of heat transfer from the skin to the object. As for the value of contact coolness q _max , the cooler you feel when you are in contact with an object, the greater the value, and the warmer you feel, the smaller the value . Therefore, by setting the value of the cool feeling upon contact q _max within the above-mentioned range, the cool feeling can be felt more effectively.

The sanitary nonwoven fabric of the present invention is preferably arranged so that the fibers constituting the nonwoven fabric have fixed orientation. With such a configuration, it is easy to transfer heat along the fiber length direction, and it is easy for the wearer to feel a cool feeling.

More specifically, in the sanitary nonwoven fabric of the present invention, it is preferable that when the nonwoven fabric is placed on a horizontal plane, the fiber length direction of the fibers of the nonwoven fabric is substantially parallel to the horizontal plane. Moreover, it is preferable that the extension direction of the fiber is unidirectional when the sanitary nonwoven fabric is viewed from above or in place of it. For example, in the top view of the sanitary nonwoven fabric, considering the first direction of the sanitary nonwoven fabric and the second direction perpendicular to the first direction, it is more preferable that the extending direction of the fibers coincides with the first direction or the second direction of the nonwoven fabric . In the case where the fibers have intersections, it is preferable that the angles formed by the fibers having the intersections are obtuse angles account for more than 50% of the sanitary nonwoven fabric in a plan view. The so-called obtuse angle refers to an angle greater than 90°.

Regarding the quantification of the angle formed by the fibers, the magnification of the intersection point of the fibers can be confirmed in the field of view of about 10 parts, and any 3 parts of the sanitary nonwoven fabric are photographed by the SEM, and the image analysis attached to the SEM is performed. Software or any image analysis software to measure and count the obtained image data. Also, when there is no image analysis software, the image data can be printed, confirmed by an angle measuring device such as a protractor, and written into the data table for statistics. By having at least one of the above-mentioned configurations related to the orientation of the fibers, heat can be easily transferred to a fixed direction, thereby making it easier for the wearer to feel a cool feeling more effectively. Such a configuration can be obtained, for example, by manufacturing a long sheet using short fibers containing polyamide resin as a material, and conveying the long sheet in the conveying direction while applying tension to the long sheet. The fibers are fused to each other by the hot air method, or the fibers containing the polyamide resin are spun out towards a conveying device such as a belt conveyor and conveyed in one direction while the fibers are spun.

The thermal conductivity of the polyamide fiber-containing aggregate of the sanitary nonwoven fabric of the present invention is preferably at least 0.08 W/mK, more preferably at least 0.10 W/mK, and still more preferably at least 0.13 W/mK. The above-mentioned thermal conductivity can be measured, for example, by melting a sanitary nonwoven fabric into a film-like sample with a thickness of about 1 mm. The detailed measurement method will be described below. By having such a thermal conductivity, the wearer of the sanitary product including the sanitary nonwoven fabric can experience a more intense cooling sensation.

In the above description, for the convenience of explanation, the sanitary nonwoven fabric has a single fiber layer (only a single fiber or blended with other fibers) is taken as an example. The above single fiber layer contains polyamide resin. fibers, but not limited to this form. Next, another embodiment of the sanitary nonwoven fabric of the present invention will be described.

As another embodiment of the sanitary nonwoven fabric, for example, the following aspect can be cited: the sanitary nonwoven fabric includes at least a fiber aggregate layer (hereinafter, also referred to as the first fiber layer) containing first fibers containing a polyamide resin, and A fiber aggregate layer (hereinafter, also referred to as a second fiber layer) containing second fibers including fibers other than the first fibers and disposed adjacent to the fiber layer. That is, this embodiment is a sanitary nonwoven fabric with a multi-layer structure. Here, the so-called adjoining refers to that the fiber layers are adjacent to each other without intervening other fiber layers, but the interposition of an adhesive between the fiber layers is allowed. In this case, it is preferable that the first fiber layer constitutes the outer surface of the hygienic nonwoven fabric from the viewpoint of effectively feeling the coolness. Also, from the same viewpoint, it is preferable that at least the first fiber layer satisfies various preferred forms related to the above-mentioned sanitary nonwoven fabric, and it is more preferable that the whole sanitary nonwoven fabric satisfies the above-mentioned preferred forms.

Specifically, a sanitary nonwoven fabric with a multi-layer structure 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. State, the implementation of hot air processing or spunbond processing. In this case, the boundaries between the fiber layers are usually not clear, but the clear boundaries may also be included. In the case of this form, each fiber layer maintains the form of a fiber sheet, for example by at least one of intertwining, fusing and crimping. As another embodiment of the sanitary nonwoven fabric with a multi-layer structure, the following aspect can be cited: a fiber web or a fiber sheet containing a first fiber containing polyamide resin and a fiber sheet containing other than the first fiber are bonded by an adhesive. The fiber web or fiber sheet of the fiber is bonded to make it bonded, thereby maintaining the shape of the fiber sheet. In this case, the boundaries between the various fiber layers are usually relatively clear.

In any case, the fibers other than the first fibers include pulp fibers, rayon fibers, and fibers that have been hydrophilized, in addition to fibers containing the above-mentioned constituent resins such as PET resin or PP resin. more than one.

From the standpoint of sufficiently feeling the cooling sensation, the basis weight of the first fiber layer is preferably at least 10 g/m ² , more preferably at least 15 g/m ² , still more preferably at least 18 g/m ² , and , preferably less than 200 g/m ² , more preferably less than 150 g/m ² , further preferably less than 100 g/m ² . The basis weight of the second fiber layer is preferably at least 10 g/m ² , more preferably at least 15 g/m ² , further preferably at least 20 g/m ² , and more preferably at least 140 g/m ² , More preferably, it is 90 g/m ² or less, and still more preferably 70 g/m ² or less.

When the hygienic nonwoven fabric has a multi-layer structure, the thermal conductivity of the fiber layer containing the first fibers comprising polyamide resin is preferably 0.11 W/mK or more, more preferably 0.13 W/mK or more, and furthermore Preferably, it is 0.15 W/mK or more. It is preferable to use the fiber which has such thermal conductivity from the point which can realize the range of the thermal conductivity in a sanitary nonwoven fabric. In addition, the above-mentioned thermal conductivity in the constituent fibers can be realized, for example, by using a composite fiber containing a polyamide resin and a polyethylene resin as the constituent fibers.

Thermal conductivity can be measured by the following method, for example. First, the nonwoven fabric or fiber to be measured is peeled off from the product by cold spraying or the like, or fiber sampling is performed to separate the fiber. Then, the separated non-woven fabric or fiber is introduced into heating and pressing equipment such as a pressing machine, and is heated and pressed at a temperature above the melting point of the non-woven fabric or fiber raw material to make it into a thickness of about 1 mm. film samples. At this time, adjust the pressurization conditions appropriately so that air does not remain in the sample. Then, using a steady-state thermal conductivity measurement device (manufactured by Kado Technology Co., Ltd., KES-F7 Thermo Lab II), based on the heat transfer in the state where the sample is transferred from a 33°C hot plate to a 23°C hot plate measure the thermal conductivity. In this measurement, three locations were measured on one film-shaped sample, and the value of the highest thermal conductivity among them was set as the thermal conductivity (W/mK) in the present invention. When the object to be measured is a nonwoven sanitary fabric with a multi-layer structure, the fiber layer on the surface side with the highest value of the cooling sensation q _max is set as the first fiber layer, and the thermal conductivity of the fiber layer is used for the above measurement .

When the hygienic nonwoven fabric of the present invention includes the second fiber layer, from the viewpoint of reducing the content of air with low thermal conductivity to improve the thermal conductivity of the nonwoven fabric, the first fiber layer of the hygienic nonwoven fabric The volume filling rate is preferably at least 3.5%, more preferably at least 7.0%, still more preferably at least 10.0%, further preferably at least 12.0%, even more preferably at least 14.0%. Also, when used as a disposable sanitary material that comes into contact with the wearer's skin, the volume filling rate of the first fiber layer of the sanitary nonwoven fabric is preferably 60.0% from the viewpoint of improving the texture. or less, more preferably 50.0% or less, still more preferably 45.0% or less, still more preferably 35.0% or less, still more preferably 30.0% or less. By having such a structure, heat transferability can be improved, and a wearer can feel a cooling sensation more strongly by this. In addition, the texture of the sanitary nonwoven fabric of the present invention and sanitary products incorporating the nonwoven fabric can be fully expressed. The measurement of the volume filling rate in the first fiber layer is to use the fiber layer on the surface side with the highest value of the cooling sensation q _max as the first fiber layer, and use this fiber layer for the above measurement of the volume filling rate.

When the hygienic nonwoven fabric has the above-mentioned second fiber layer, it is preferable to use a second fiber layer whose thickness variation is more than a predetermined value. Specifically, the amount of compression deformation of the second fiber layer under a load of 9.8 mN/cm ² (1 gf/cm ² ) is preferably 0.3 mm or more, more preferably 0.5 mm or more. In addition, the amount of compression deformation of the second fiber layer under the load is preferably 3 mm or less. As described below, the compressive deformation is expressed as the change obtained by subtracting the thickness of the second fiber layer under a load of 9.8 mN/cm ² (1 gf/cm ² ) from the thickness of the second fiber layer under no load. In addition, the compressive deformation amount can be calculated by the following method. With such a structure, when the first fiber layer is in contact with the wearer, the first fiber layer easily deforms following the deformation of the second fiber layer, thereby increasing the contact area with the wearer, and effectively making the wearer feel comfortable. To cool. The method of measuring the thickness of the second fiber layer is as follows.

The hygienic nonwoven fabric with the above composition uses fibers containing polyamide resin in synthetic resins, so when the fibers come into contact with the wearer's skin, the heat caused by the wearer's body temperature can be quickly transferred from the wearer to the hygienic nonwoven fabric. Non-woven fabrics or other fibers not in contact with the wearer. As a result, when the wearer's skin is in contact with the hygienic nonwoven fabric, the wearer can feel a cool feeling, and the cool feeling brings a comfortable feeling of use. In addition, the flexibility and hygroscopicity of polyamide resins can be well expressed, and in this respect, it also contributes to the improvement of usability. In addition, by providing fusion points between fibers in the sanitary nonwoven fabric, heat can be easily transferred to other fibers, and a good texture of the fiber sheet can be exhibited, thereby improving usability and comfort. Also, by making the hygienic non-woven fabric into the form of a fiber sheet, the contact area between the wearer's skin and the hygienic non-woven fabric can be increased, so that the wearer can feel a cool feeling, and can show the benefits brought by the non-woven fabric. softness.

The overall basis weight of the sanitary nonwoven fabric of the present invention is preferably at least 10 g/m ² , more preferably at least 15 g/m ² , and still more preferably at least 18 g/m ² . Also, the basis weight of the whole sanitary nonwoven fabric of the present invention is preferably not more than 200 g/m ² , more preferably not more than 150 g/m ² , and still more preferably not more than 120 g/m ² . By adopting the above-mentioned structure, the difference in the feeling of coolness caused by the uneven basis weight of the sanitary nonwoven fabric can be reduced, and the fusion or compaction of the fibers can be effectively performed, so that it can be manufactured with high productivity. Hygienic non-woven fabrics. When the hygienic nonwoven fabric of the present invention is used as a component of a sanitary product, the fiber sheet with the highest q _max value of the following cooling feeling upon contact is used as the hygienic nonwoven fabric, and its basis weight is measured.

The above-mentioned hygienic nonwoven fabric can be used as it is, or the hygienic nonwoven fabric can be used as a component of a hygienic article to produce a hygienic article including the hygienic nonwoven fabric. Also, when the sanitary nonwoven of the present invention is incorporated into sanitary products, it is preferable that the nonwoven or the first fiber layer side of the nonwoven constitute a surface facing the wearer's skin. In either case, they are generally disposable.

Hygienic products including sanitary nonwoven fabrics of the present invention include, for example, absorbent articles such as disposable diapers, menstrual sanitary napkins, sweat-absorbing underarm pads, urine-absorbing pads, and panty liners; Articles for use, but sanitary articles are not limited to these. For example, absorbent articles provided with hygienic nonwoven fabrics broadly include articles for absorbing liquid discharged from the human body.

Hygienic nonwoven fabrics can be used as constituent members of absorbent articles and the like. Absorbent articles generally have a front sheet and a back sheet, and have an absorber arranged between the front sheet and the back sheet. In addition, the front sheet or the back sheet can also be used in a state where a hygienic nonwoven is arranged. material.

In the case of using sanitary non-woven fabrics as constituent members of absorbent articles, the sanitary non-woven fabrics can be placed together with hygienic articles such as absorbent articles when using hygienic articles such as absorbent articles, or when taking hygienic articles such as absorbent articles out of packages, etc. The part where the wearer's skin directly contacts. That is, the nonwoven fabric for hygiene is preferably arranged on the outer surface of hygiene products such as absorbent articles. The so-called outer surface of sanitary articles such as absorbent articles refers to the surface of sanitary articles such as absorbent articles that can be touched by the wearer after opening the package and taking out the sanitary articles such as absorbent articles (including the front and back, but the thickness direction on the surface side rather than the interior side). That is, the outer surface of the hygiene article is preferably a surface facing the skin or a surface not facing the skin.

Specifically, when using a sanitary nonwoven fabric in an absorbent article as an embodiment of a sanitary product, such as a disposable diaper, the above-mentioned sanitary nonwoven fabric can be used, for example, as a front sheet, side nonwoven fabric, or waist gathers Or the pleats arranged near the groin, and the outer body and other components. Among them, at least the nonwoven fabric for hygiene is used in the outer body, and it can be touched by the wearer's hands when taking out hygienic articles such as absorbent articles, so it is easy to remind the wearer of hygiene by virtue of the good skin touch. Supplies of excellent quality.

In addition, in the case of using a sanitary nonwoven fabric for an absorbent article such as a urine leakage pad or a menstrual napkin as one embodiment of a sanitary product, the above-mentioned sanitary nonwoven fabric can be used, for example, as a front sheet, a side nonwoven fabric, a cover sheet, etc. Buttocks, or independent packaging bags and other components. In addition, when using a sanitary nonwoven fabric for a urine leakage pad and a menstrual napkin of an absorbent article which is an embodiment of a sanitary product, for example, the above sanitary nonwoven fabric can be used as a front sheet or arranged in the groin The nearby pleats and other components constitute components.

From the point of view of feeling cool when using hygienic products such as absorbent articles and reducing discomfort caused by stuffy heat, etc., the sanitary non-woven fabric is preferably arranged in the following way: after wearing the hygienic products of absorbent articles at the correct position In some cases, it is placed on the side facing the skin of the wearer wearing the hygienic absorbent article (hereinafter, also referred to as "the skin-facing surface").

The absorber used for the absorbent article has an absorbent core. The absorbent core includes, for example, fiber accumulations of hydrophilic fibers such as cellulose typified by pulp, mixed fiber accumulations of the hydrophilic fibers and water-absorbent polymers, accumulations of water-absorbent polymers, and interlayers between two sheets. The absorbent sheet and the like holding the water-absorbent polymer typically contain hydrophilic fibers and a water-absorbent polymer. The absorbent core may also be covered by a corewrap. As the covering form of the core-wrapping material, for example, at least the skin-facing surface may be covered with a liquid-permeable core-wrapping material, or the entire surface including the skin-facing surface and the non-skin-facing surface may be covered with a covering. Chip sheet covered. As the core wrapping material, for example, a thin paper containing hydrophilic fibers, a liquid-permeable nonwoven fabric, or the like can be used.

In the case of using the sanitary non-woven fabric as a cover, for example, the sanitary non-woven fabric can be used alone, or it can be used as a laminate in which other non-woven fabrics and sanitary non-woven fabrics are laminated. In addition, the member including the sanitary nonwoven fabric can be provided with ear loops, and the member including the sanitary nonwoven fabric can be configured in such a manner that the mouth, nose, and eyes can be kept covered. In the case of this form, it is also preferable that the hygienic nonwoven fabric is arranged on the surface facing the skin, and more preferably, it is arranged on the part directly in contact with the wearer's skin.

When the hygienic nonwoven fabric of the present invention is used to make a hygienic article, the hygienic article may also be a hygienic nonwoven fabric which is an aggregate of fibers containing polyamide resin (hereinafter, for convenience of description, also referred to as "first nonwoven fabric"). In addition to the "fiber aggregate"), another member is further provided (hereinafter, this member is also referred to as a "second member").

As an embodiment of the hygienic article in which the second member is arranged, for example, at least one of an absorbent sheet containing an absorbent polymer and fibers, an absorber containing an absorbent polymer and fibers, a hydrophilic nonwoven fabric, etc. can be used. 2nd member. These are examples of fiber aggregates different from sanitary nonwoven fabrics. As a hygienic article provided with such a 2nd member, Preferably, the above-mentioned absorbent article is mentioned. That is, in this embodiment, the nonwoven fabric for hygiene as the first fiber aggregate, and the absorbent sheet, absorber, and/or nonwoven fabric as the second member different from the nonwoven fabric for hygiene are arranged as the constituent materials of the hygiene product. . It is also preferable that the first fiber aggregate and the second member are arranged adjacent to each other. The respective fiber aggregates in this embodiment may or may not be joined to each other. As an absorbent sheet, the absorbent sheet described in Unexamined-Japanese-Patent No. 8-246395, etc. can be used, for example.

When the hygienic article has the above-mentioned second member, or when the hygienic nonwoven fabric includes the above-mentioned second fiber layer, it is preferable to use the second member or the second fiber layer whose thickness change is more than a predetermined value. Specifically, the amount of compression deformation of the second member under a load of 9.8 mN/cm ² (1 gf/cm ² ) is preferably at least 0.3 mm, more preferably at least 0.5 mm. Also, the amount of compression deformation of the second member under the load is preferably 3 mm or less. As described below, the amount of compressive deformation is represented by the amount of change obtained by subtracting the thickness of the second member under a load of 9.8 mN/cm ² (1 gf/cm ² ) from the thickness of the second member under no load. It is preferable to have the same amount of compression deformation also in the second fiber layer constituting the sanitary nonwoven fabric. Moreover, when a hygienic article has both the sanitary nonwoven fabric of a multilayer structure, and a 2nd member, it is preferable that both a 2nd member and a 2nd fiber layer satisfy|fill the said amount of compression deformation, respectively. With such a configuration, when the first fiber aggregate comes into contact with the wearer, the first fiber aggregate deforms following the deformation of the second member, thereby increasing the contact area with the wearer and effectively making the wearer feel comfortable. To cool.

For the second fiber layer having the above-mentioned physical properties, for example, in the following manufacturing method, fibers containing PET resin or PP resin, or PET/HDPE core-sheath composite fibers, etc., can be used as constituent fibers, and a fiber web subjected to hot air treatment can be used And get. Moreover, when a 2nd member is an absorbent sheet or an absorbent body, it can obtain it, for example by suitably adjusting the basis weight of the fiber which comprises an absorbent sheet or an absorbent body, a fiber sheet, and a water-absorbent polymer.

The thickness of the second member or the second fiber layer can be measured by the following method, for example. First, observe the cross-section of the object to be measured visually or by SEM, and observe the fiber diameter, the distance between fibers, or the boundary between members, etc., and confirm that it is a hygienic nonwoven fabric with a plurality of fiber layers by performing the above operations, etc. There are also sanitary nonwoven fabrics and second members other than sanitary nonwoven fabrics. When the object of measurement is a hygienic product, after fixing the structure by immersing the hygienic product in liquid nitrogen, etc., carefully peel off the sanitary non-woven fabric and the second member other than the sanitary non-woven fabric from the hygienic product of the measurement object And make it equal to separate. Then, the separated member is used for the measurement of the above-mentioned cooling sensation q _max , the fiber sheet with the highest value of q _max is set as the sanitary nonwoven fabric, and the member adjacent to the sanitary nonwoven fabric is set as the second member . Next, perform operations such as mounting the plate on the separated second member, and measure the thickness in this state using a laser displacement meter under a state where a load of 4.9 mN/cm ² (0.5 gf/cm ² ) is applied, and Let this be the thickness of the second member. When the object of measurement is a sanitary nonwoven fabric with a multi-layer structure, the fiber layer on the surface side with the highest q _max value described in detail in the following examples is set as the first fiber layer, and the first fiber layer is the same as the first fiber layer. The adjacent fiber layer was set as the second fiber layer, and the second fiber layer was used for the above-mentioned measurement.

In addition, the amount of compression deformation under a load of 9.8 mN/cm ² (1 gf/cm ² ) is preferably at least 0.3 mm, more preferably at least 0.4 mm, in the entire sanitary article. In addition, the amount of compression deformation of the entire sanitary article under the load is preferably 15 mm or less, more preferably 10 mm or less. By adopting such a structure, the softness of the non-woven fabric as a whole can be enhanced to improve the usability, and the contact area between the fiber aggregate including the polyamide resin and the wearer can be increased, so that the wearer can feel a cool feeling efficiently.

Regarding the amount of compression deformation mentioned above, for example, if it is the hot air method, it can be realized by making the temperature or wind speed of the hot air lower than the conditions usually used, or increasing the number of fibers or using fibers containing a resin whose melting point is higher than the temperature of the hot air. , thereby reducing the fusion of fibers with each other. It can be realized by adopting the following structure in addition to the above-mentioned structure, or adopting the following structure instead of the above-mentioned structure, that is, providing two or more fiber layers, and only providing a layer with a higher compressive deformation amount than the other fiber layers in one fiber layer ; or increase the basis weight of one fiber layer compared to other fiber layers; or blend fibers with higher melting points in one fiber layer.

The amount of compression deformation can be measured, for example, using a KES-FB-3 compression tester manufactured by Kado Technology Co., Ltd. A slice of a fixed size is cut out from the sanitary nonwoven fabric to be measured, and used as a sample. The sample is installed on the test bench of the testing machine, and placed between steel plates with a circular plane with an area of 2 cm ² for compression. The compression speed was 0.02 mm/sec, and the maximum compression load was set at 9.8 mN/cm ² (1 gf/cm ² ). When the thickness without load is defined as thickness T0 (mm), and the thickness under a load of 9.8 mN/cm ² (1 gf/cm ² ) is defined as thickness Tm (mm), the amount of compressive deformation (mm) can be expressed as thickness T0 Calculated by subtracting "T0-Tm" from the thickness Tm.

When the second member is an absorbent sheet, the basis weight of the entire second member is preferably at least 40 g/m ² , more preferably at least 60 g/m ² , further preferably at least 70 g/m ² , and, preferably 500 g/m ² or less, more preferably 400 g/m ² or less, further preferably 300 g/m ² or less. When the second member is an absorbent sheet, the basis weight of the entire second member is preferably at least 30 g/m ² , more preferably at least 40 g/m ² , further preferably at least 50 g/m ² , and preferably less than 600 g/m ² , more preferably less than 550 g/m ² , and still more preferably less than 500 g/m ² .

It is preferable that the nonwoven fabric for sanitary use has a bending rigidity value of a predetermined value or less. Specifically, the bending stiffness of the sanitary nonwoven fabric is preferably at most 0.25 gf·cm ² /cm, more preferably at most 0.2 gf·cm ² /cm, still more preferably at most 0.15 gf·cm ² /cm, and even more preferably at most 0.2 gf·cm 2 /cm. Preferably, it is 0.1 gf·cm ² /cm or less. With such a configuration, it is easy to bend following an external force, so that the area in contact with the wearer's skin can be increased, thereby efficiently making the wearer feel cool.

The flexural stiffness of sanitary nonwovens can be based on "Standardization and Analysis of Texture Evaluation (Second Edition)" (Author: Toshio Kawabata; Publisher: Textile Measurement and Standardization Research Committee, Japan Textile Machinery Society; Release Date: Showa The method described on pages 27 to 28 of 10 July 55) was measured by the following method. Specifically, a sample was obtained by cutting to a size of 20 cm in the longitudinal direction×10 cm in the width direction. The sample was mounted on the chucks of a pure bending tester (trade name: KES-FB2) manufactured by Kado Technology Co., Ltd. so that the distance between the chucks became 10 mm. The installation direction is set so that the longitudinal direction of the sanitary nonwoven fabric becomes the bending direction. Perform pure bending with constant velocity curvature within the range of curvature K=-2.5～+2.5 cm ^-1 . The deformation speed was set at 0.50 cm ^-1 /sec. Through this operation, the relationship between the bending moment M and the curvature K per unit area of the sample (MK curve) was obtained. Calculate the slope of the MK curve from the result, that is, the bending stiffness B per unit length (gf·cm 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 ^-1 determined according to the characteristics of the increase process of the absolute value of K The slopes are denoted as Bf and Bb respectively. The arithmetic mean value (Bf+Bb)/2 is used as the bending stiffness value of the present invention.

From the viewpoint of avoiding fiber entanglement and ensuring a good touch and use feeling for the wearer, the fiber diameter of the fibers used in sanitary nonwoven fabrics is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 12 μm or more. Also, from the perspective of reducing the fiber gap in the nonwoven fabric, thereby reducing the air content in the nonwoven fabric and improving thermal conductivity, the fiber diameter of the fiber used in the sanitary nonwoven fabric is preferably 40 μm or less, more preferably 30 μm or less , and more preferably 27 μm or less. Regarding the fiber diameter of the fiber, in the same manner as the method of measuring the lengths of the major axis and the minor axis of the cross-sectional shape of the fiber, the preparation of the measurement sample and SEM observation were carried out, and the fiber diameter of 10 fibers was measured for each sample. Let the arithmetic mean thereof be the fiber diameter of the present invention. When the fiber is not a true circle, the lengths of the major axis and the minor axis of the fiber are measured by the above method, and the arithmetic mean of the major axis length and the minor axis length of a fiber is set as the fiber diameter, and 10 The arithmetic mean of the diameters of the fibers is set as the fiber diameter of the fibers in the present invention.

From the standpoint of keeping the wearer's touch and usability well, when the fibers used in the hygienic nonwoven fabric are short fibers, the fiber diameter is preferably 30 mm or more, more preferably 38 mm or more. Also, from the viewpoint of improving thermal conductivity, when the fibers used in the sanitary nonwoven fabric are short fibers, the fiber diameter is preferably 40 mm or more, more preferably 45 mm or more. Also, when the fibers used in the sanitary nonwoven fabric are short fibers, the fiber diameter is preferably 70 mm or less, more preferably 60 mm or less, from the viewpoint of not impairing processability. The fiber length of the fiber is set as follows: When the fiber is in a crimped state, let the fiber stand in this state without stretching it, so as to avoid fiber bending as much as possible, and use a ruler to measure the length of 10 fibers. As for the distance from the end point to the end point, the arithmetic mean of the fiber lengths thus obtained is taken as the fiber length of the fiber of the present invention.

As long as the effects of the present invention can be exhibited, the nonwoven sanitary fabric of the present invention may further contain fillers for improving thermal conductivity. Such a filler may, for example, be at least one of titanium oxide, aluminum oxide, boron nitride, magnesium oxide, silicon oxide, carbon black, zinc oxide, and carbon nanotubes. The filler may exist within the fibers, may exist between the fibers, or may be partially exposed on the surface of the fibers and embedded in the fibers.

The above is the explanation about the sanitary nonwoven fabric of the present invention and the sanitary article including the sanitary nonwoven fabric, and a preferable manufacturing method of the sanitary nonwoven fabric of the present invention will be described below. This manufacturing method has the step (hot air step) of obtaining fiber aggregates by hot-air treatment of a fiber web containing polyamide resin fibers. It is preferable to employ a step of densifying the obtained fiber aggregate (compacting step) in addition to this. Furthermore, it is more preferable that the conjugate fiber used in this production method is the above-mentioned core-sheath conjugate fiber.

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

Then, a hot air treatment of blowing hot air to the fiber web was performed to obtain an aggregate of fibers made of a polyamide resin. This step is the step of making the fiber web non-woven, and the fiber aggregates made in this way are usually called air-through non-woven fabrics.

Generally speaking, in the case of hot-air processing of fiber webs containing polyethylene resin, the use of core-sheath composite fibers is beneficial to improve the texture and strength of the obtained air-through non-woven fabric, but it is important to improve thermal conductivity so that the wearer can feel cool. There is still room for improvement. The inventors of the present invention have conducted diligent research on these improvements, and found that: by controlling the temperature and wind speed of the hot air in the hot air step, air through nonwoven fabrics with good texture and strength can be manufactured efficiently.

It is preferable that the temperature and wind speed of the hot air blown to the fiber web in the hot air step are within a specific range. Specifically, the temperature of the hot air blown to the fiber web is related to the temperature of the fiber surface that constitutes the fiber web from the viewpoint of maintaining the shape of the fiber without making the fiber thin and thus making the texture of the obtained sanitary nonwoven fabric good. In terms of the relationship between the melting point Mp (°C) of the resin, it is preferably in the range of melting point Mp+10°C or lower, more preferably in the range of melting point Mp+9°C or lower, and more preferably in the range of melting point Mp+8°C or lower. Also, in order to make the fibers constituting the fiber web moderately fused with each other so that the sanitary non-woven fabric exhibits durable strength, the temperature of the hot air blown to the fiber web is preferably in the range above the melting point Mp-4°C, more preferably at The melting point Mp is in the range of -2°C or higher, and more preferably, it can be in the range of the melting point Mp or higher. In the case of using the core-sheath composite fiber in this production method, fusion points are easily formed, and the texture of the nonwoven fabric can be further improved, so that it is easy to feel cool, and it is preferable to use a core-sheath composite fiber. The fiber of which the melting point of the constituent resin of the core is higher than the melting point of the constituent resin of the sheath.

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

For example, when a core-sheath composite fiber composed of nylon 6 (melting point: 225°C) whose sheath is HDPE (melting point Mp: 130°C) and polyamide resin as the core is used as the fiber constituting the fiber web is used, The temperature of the hot air is preferably 126°C or higher, more preferably 128°C or higher, and more preferably 130°C or higher. Moreover, the temperature of the hot air under the above conditions is preferably set to be 140°C or lower, more preferably 139°C or lower, and still more preferably 138°C or lower.

In the case of using fibers containing polyamide resin as fibers constituting the fiber web, for example, if it is nylon 6 (melting point Mp: 225°C), the temperature of the hot air is preferably set to 221°C or higher, more preferably set to 223°C or higher, more preferably 225°C or higher. Moreover, the temperature of the hot air under the above conditions is preferably set to be 235°C or lower, more preferably 234°C or lower, and still more preferably 233°C or lower. Also, when nylon 66 (melting point Mp: 265°C) is used as the fiber containing polyamide resin, the temperature of the hot air is preferably set at 261°C or higher, more preferably at 263°C, and more preferably at 263°C. It is above 265°C. Moreover, the temperature of the hot air under the above conditions is preferably set to be 275°C or lower, more preferably 274°C or lower, and still more preferably 273°C or lower.

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

Also, in the hot air step, in terms of allowing the hot air to pass sufficiently in the thickness direction of the fiber web so that the fibers are easily fused to each other, the wind speed of the hot air blown to the fiber web is preferably 0.6 m/sec or more, more preferably 1.0 m/s or more. Also, from the same viewpoint, the wind speed of the hot air blown onto the fiber web is preferably 2.0 m/sec or less, more preferably 1.4 m/sec or less. By carrying out the hot air step under the conditions of the above temperature and wind speed, the polyethylene resin present on the surface of the fibers constituting the fiber web can be melted or softened, thereby randomly forming fusion points where the fibers are fused with each other, so the sanitary nonwoven fabric produced It shows the softness and good texture brought by air-through non-woven fabric, and shows durable strength.

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

Since the fiber aggregate obtained through the above steps has been non-woven, it can also be directly used as the sanitary non-woven fabric of the present invention. The hygienic nonwoven fabric is air-through nonwoven fabric.

From the viewpoint of easily obtaining a hygienic nonwoven fabric having a predetermined volume filling rate, it is preferable to further perform compaction treatment on the fiber aggregate obtained through the above steps (compaction step). The densification treatment in this step can adopt a method capable of pressing and compressing the fiber aggregate in its thickness direction.

As the compaction treatment, for example, a method of placing a fiber aggregate between two metal flat plates to pressurize (hereinafter, this method is also referred to as "press method" or "pressurization treatment"), or by A method in which fiber aggregates are introduced between a pair of rolls with smooth peripheral surfaces and pressed (hereinafter, this method is also referred to as "calendering" or "calendering"). The compaction treatment may be performed only once, or may be performed multiple times by the same or different methods as required. In addition, the temperature in the densification treatment may be room temperature, may be in a heated state, or may be a combination thereof. From the viewpoint of improving manufacturing efficiency, it is preferable to use the calendering method, and from the viewpoint of compacting in a heated state efficiently without temperature unevenness, it is more preferable to use a method containing metal, etc. on the peripheral surface. A pair of rolls are used for calendering.

The conditions for the compaction treatment are preferably pressurized under heating. Specifically, from the viewpoint of sufficiently compacting the fiber aggregates to easily obtain a hygienic nonwoven fabric with a high volume filling rate, in the case of using the pressing method, the pressure conditions in the densification process are surface pressure. indicates that it is preferably at least 5 MPa, and more preferably at least 7 MPa. In addition, from the viewpoint of preventing the fiber aggregate from being thinned, keeping the fiber shape with a clear boundary between the constituent fibers, and improving the texture of the obtained sanitary nonwoven fabric, when the pressing method is used, the densification treatment The pressurization conditions are represented by the surface pressure, and it is preferably set at 72 MPa or less, and more preferably set at 32 MPa or less.

Also, from the point of view of fully compacting the fiber aggregates and easily obtaining a sanitary nonwoven fabric with a high volume filling rate, the pressure conditions when using the calendering method are expressed in terms of linear pressure, preferably 78.4 N/cm ( 8 kgf/cm), more preferably 127.4 N/cm (13 kgf/cm). In addition, from the viewpoint of avoiding the thinning of the fiber aggregates, keeping the fiber shape with a clear boundary between the constituent fibers, and making the obtained sanitary nonwoven fabric have a good texture, the pressure conditions when using the calendering method are based on the linear pressure. It means that it is preferably not more than 686 N/cm (70 kgf/cm), more preferably not more than 490 N/cm (50 kgf/cm), and still more preferably not more than 294 N/cm (30 kgf/cm).

Also, from the viewpoint of sufficiently compacting the fiber aggregates to easily obtain a hygienic nonwoven fabric with a high volume filling rate, the heating temperature in the compacting treatment is the same regardless of which of the pressing method and the calendering method are used. Preferably, it can be set in the range of melting point Mp-80°C or higher, more preferably, it can be set in the range of melting point Mp-70°C or higher, and still more preferably, it can be set in the range of melting point Mp-60°C or higher. Also, from the viewpoint of sufficiently compacting the fiber aggregates to easily obtain a hygienic nonwoven fabric with a high volume filling rate, the heating temperature in the compacting treatment is the same regardless of which of the pressing method and the calendering method are used. Preferably, it can be set as below melting point Mp, More preferably, it can set it as the range of melting point Mp - 20 degreeC or less. In the case of heating during the compaction process, it is sufficient to heat the flat metal plate to the above temperature range for the pressing method, or to heat the peripheral surface of the roll to the above temperature range for the calendering method.

The pressing time in the compaction treatment can be appropriately set as long as it is a condition under which the fiber shape of the fibers constituting the fiber aggregate can be maintained and the compaction can be performed. For example, when the pressing method is used, the pressing time under the above-mentioned pressure and temperature conditions is preferably 5 seconds or more, and more preferably 10 seconds or more in each compaction treatment. In addition, when the pressing method is used, the pressing time under the above-mentioned pressure and temperature conditions is preferably set to 25 seconds or less, and more preferably 20 seconds or less in each compaction process.

For example, in the case of using the calendering method, the pressing time under the above-mentioned pressure and temperature conditions can be preferably set to 0.01 second or longer, more preferably 0.04 second or longer in each compaction process. Also, when the calendering method is used, the pressing time under the above-mentioned pressure and temperature conditions is preferably set to 0.10 seconds or less, and more preferably 0.08 seconds or less in each compaction process.

By carrying out the densification treatment under the above conditions, the fiber aggregate can be compressed in the thickness direction, thereby obtaining a sanitary nonwoven fabric having a predetermined volume filling rate and thickness. In particular, within the above-mentioned pressure and temperature ranges, the resin constituting the fiber is in a state where the resin is not easily melted, and the shape stability and dimensional stability brought about by heat treatment can be improved, so it is possible to obtain a fiber shape and maintain the specified fiber shape after manufacture. Hygienic nonwovens with volume filling rate. In addition, when using fibers with a true circular cross-section, the cross-sectional shape of the fibers can be flattened by the compaction process, which also has the advantage of increasing the volume filling rate. The hygienic nonwoven fabric obtained by the above method is air-through nonwoven fabric even after compaction treatment.

In the case of producing a multi-layered hygienic nonwoven fabric, for example, a fiber web containing a polyamide resin is laminated with a second fiber web formed by a carding method to form a fiber web laminate . Next, air-through treatment is performed on this laminate to obtain an air-through nonwoven fabric which is a fiber aggregate having a multi-layer structure. The boundaries between the various fiber layers of the non-woven fabric are not clear. At this time, as for the temperature of the hot air to be blown, it is preferable to determine the temperature of the hot air by setting the melting point of the resin with the lowest melting point as the above-mentioned melting point Mp.

In addition, in the above case, the step of blowing hot air in the hot air treatment is preferably to arrange the laminated body of the fiber web so that the fiber web other than the fiber web containing polyamide resin can be blown. By adopting this method, using the pressure of hot air, the fibers in the polyamide resin fiber web are thermally fused together to form a first fiber aggregate with a high volume filling rate, and the second fiber web side maintains bulkiness Thereby, a hygienic nonwoven fabric having a structure excellent in compression deformability can be obtained. As such a method, for example, the side where the fiber web containing polyamide resin is arranged in the laminate is arranged on the lower side such as the mesh side of the hot air device, and the hot air treatment may be performed.

As another form of producing a sanitary non-woven fabric with a multi-layer structure, the fiber web containing polyamide resin and the second fiber web containing thermoplastic resin can be subjected to hot air treatment to obtain fiber sheets respectively, and the fiber sheets can be obtained by using an adhesive or Various embossing processes are obtained by joining these fiber sheets by means of fusion, bonding or crimping.

The hygienic nonwoven fabric of the present invention can also be produced by a method based on the spunbond method instead of the above-mentioned production method. That is, a step of obtaining a fiber aggregate by spunbonding the polyamide resin (spunbonding step) may also be provided. The hygienic nonwoven fabric manufactured in this way is a spunbonded nonwoven fabric.

Specifically, the raw material resin of the fiber is extruded in a molten state from a spinneret having a plurality of fine holes, and the extruded resin is stretched by rollers to form long fibers, and the long fibers are gathered Lamination was carried out on a mesh conveyor belt to obtain a fiber web comprising fibers of polyamide resin. Thereafter, the fiber web is introduced between embossing rolls having a plurality of protrusions on the peripheral surface, and compacted (thermocompression bonding) by heating and pressing to obtain the sanitary nonwoven fabric of the present invention. That is, in this method, the formation of the fusion points between constituent fibers, the non-woven fabric of the fiber web, and the compaction process are performed simultaneously.

The temperature in the embossing roll is preferably in the range of melting point Mp - 40°C or higher, more preferably in the range of melting point Mp - 35°C or higher, and still more preferably in the range of melting point - 30°C or higher. From the viewpoint of sufficiently fusing the embossed part, the pressure condition by the embossing roll is preferably 0.3 MPa or more, more preferably 0.5 MPa or more, and still more preferably 1.0 MPa or more. scope. Also, from the viewpoint of preventing voids caused by excessive pressurization, the above-mentioned pressurization conditions are preferably 40 MPa or less, more preferably 35 MPa or less, and still more preferably 30 MPa The following range.

In the case of producing a multi-layered hygienic nonwoven fabric, for example, a fiber web containing a polyamide resin is laminated with a second fiber web formed by a carding method to form a fiber web laminate . Next, this laminated body may be compacted (thermocompression bonding) by heating and pressurizing under the above-mentioned conditions.

Through the above steps, the hygienic nonwoven fabric of the present invention can be obtained. The sanitary nonwoven fabric is preferably incorporated as a constituent member of sanitary products such as absorbent articles in a subsequent step. In the case of using sanitary nonwoven fabrics as constituent materials of hygienic articles such as absorbent articles, any step of manufacturing hygienic articles includes at least one of the following steps: using hygienic nonwoven fabrics manufactured by the above method as constituent materials One of the materials, and cutting the sanitary non-woven fabric; and performing various operations such as laminating or bonding the sanitary non-woven fabric and other constituent materials (such as absorbent bodies or sheets, etc.) constituting sanitary products; in this way, the target absorbent article can be manufactured And other hygiene products.

As mentioned above, although this invention was demonstrated based on the preferable embodiment of this invention, this invention is not limited to the said embodiment.

Regarding the above-mentioned embodiment of the present invention, the following sanitary nonwoven fabric and its manufacturing method are further disclosed. <1> A nonwoven fabric for hygiene, which has a fiber aggregate containing fibers, the fibers comprising polyamide resin, The above-mentioned fiber aggregate has a fusion point where its constituent fibers are fused to each other, and The volume filling rate of the fiber aggregate containing the fibers containing polyamide resin is 3.5% or more.

<2> The sanitary nonwoven fabric as described in <1> above, wherein the volume filling ratio of the fiber aggregates containing fibers containing a polyamide resin is preferably at least 7.0%, more preferably at least 10.0%, and still more preferably at least 12.0%. above, and more preferably above 14.0%, The above volume filling rate is preferably 60.0% or less, more preferably 50.0% or less, still more preferably 45.0% or less, still more preferably 35.0% or less, still more preferably 30.0% or less, The above volume filling rate is preferably from 7.0% to 60.0%, more preferably from 7.0% to 50.0%, still more preferably from 10.0% to 45.0%, still more preferably from 12.0% to 35.0%, still more preferably Above 14.0% and below 30.0%.

<3> The sanitary nonwoven fabric according to <1> or <2> above, wherein the fiber is a composite fiber containing a polyamide resin. <4> The sanitary nonwoven fabric as described in <3> above, wherein the composite fiber is a composite fiber containing a polyamide resin inside the fiber. <5> The sanitary nonwoven fabric as described in <3> or <4> above, wherein the composite fiber is a composite fiber that is formed over the entire outer surface of the fiber and further contains a polyethylene resin.

<6> The sanitary nonwoven fabric according to any one of <1> to <5> above, wherein the fiber-based core is a core-sheath composite fiber made of a polyamide resin and a sheath made of a high-density polyethylene resin. <7> The sanitary nonwoven fabric described in any one of <1> to <6> above, wherein the polyamide resin content is preferably 25% by mass or more based on the total mass of fibers contained in the sanitary nonwoven fabric, More preferably, it is 30 mass % or more, More preferably, it is 40 mass % or more, More preferably, it is 100 mass % or less, More preferably, it is 90 mass % or less, More preferably, it is 80 mass % or less. <8> The sanitary nonwoven fabric described in any one of <1> to <7> above, wherein the polyamide resin is one or two or more of nylon 6, nylon 66, and aromatic nylon. <9> The sanitary nonwoven fabric according to any one of <1> to <8> above, wherein the fibers further contain polyethylene resin, and The content of the polyethylene resin is preferably at least 30% by mass, more preferably at least 40% by mass, preferably at most 90% by mass, more preferably at most 80% by mass, based on the total mass of fibers contained in the nonwoven sanitary fabric. the following.

<10> The sanitary nonwoven fabric according to any one of <1> to <9> above, wherein the sanitary nonwoven fabric further contains a polyethylene resin, and The mass ratio (polyamide resin/polyethylene resin) of the polyamide resin contained in the sanitary nonwoven fabric to the polyethylene resin is preferably 0.1 or more, more preferably 0.2 or more, further preferably 0.3 or more, more preferably It is 2.0 or less, more preferably 1.5 or less, still more preferably 1.3 or less.

<11> The sanitary nonwoven fabric described in any one of <1> to <10> above, wherein the sanitary nonwoven fabric further contains a polyethylene resin, The above-mentioned polyethylene resins are 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 one or more of the two High density polyethylene resin (HDPE) is preferred. <12> The sanitary nonwoven fabric according to any one of <1> to <11> above, wherein the mean deviation (MMD) of the coefficient of friction is 0.010 or less. <13> In the sanitary nonwoven fabric described in any one of <1> to <12> above, the mean deviation (MMD) of the coefficient of friction is preferably 0.009 or less, more preferably 0.008 or less, more preferably 0.004 or more.

<14> The sanitary nonwoven fabric described in any one of the above <1> to <13>, wherein the overall thickness of the sanitary nonwoven fabric under a load of 4.9 mN/cm ² (0.5 gf/cm ² ) is preferably 0.05 mm or more, more preferably 0.08 mm or more, preferably 8 mm or less, more preferably 7.5 mm or less, further preferably 7 mm or less. <15> The sanitary nonwoven fabric described in any one of the above <1> to <14>, wherein the basis weight of the entire sanitary nonwoven fabric is preferably 10 g/m ² or more, more preferably 15 g/m ² Above, more preferably 18 g/m ² or more, preferably 200 g/m ² or less, more preferably 150 g/m ² or less, still more preferably 120 g/m ² or less. <16> The sanitary nonwoven fabric described in any one of the above <1> to <15>, wherein the contact coolness q _max in the fiber aggregate of the sanitary nonwoven fabric is preferably 0.06 W/m ² or more, more preferably Preferably at least 0.08 W/m ² , more preferably at least 0.10 W/m ² , more preferably at most 0.80 W/m ² , more preferably at most 0.60 W/m ² , still more preferably at most 0.50 W/m ² . <17> The sanitary nonwoven fabric according to any one of the above <1> to <16>, wherein the thermal conductivity in the fiber aggregate of the sanitary nonwoven fabric is preferably at least 0.08 W/mK, more preferably 0.10 W/mK or more, and more preferably 0.13 W/mK or more.

<18> The sanitary nonwoven fabric described in any one of <1> to <17> above, wherein the bending stiffness of the sanitary nonwoven fabric is preferably at most 0.25 gf·cm ² /cm, more preferably 0.2 gf· cm ² /cm or less, more preferably 0.15 gf·cm ² /cm or less, still more preferably 0.1 gf·cm ² /cm or less. <19> The sanitary nonwoven fabric according to any one of <1> to <18> above, wherein the fiber diameter of the above-mentioned fibers is preferably at least 1 μm, more preferably at least 5 μm, further preferably at least 12 μm , preferably less than 40 μm, more preferably less than 30 μm, further preferably less than 27 μm. <20> The sanitary nonwoven fabric according to any one of <1> to <19> above, wherein the fiber length of the fibers is preferably at least 30 mm, more preferably at least 38 mm, more preferably at most 70 mm, More preferably, it is less than 60 mm. <21> The sanitary nonwoven fabric according to any one of the above <1> to <20>, wherein the sanitary nonwoven fabric further contains a filler. <22> The sanitary nonwoven fabric as described in <21> above, wherein the above-mentioned filler is one of titanium oxide, aluminum oxide, boron nitride, magnesium oxide, silicon oxide, carbon black, zinc oxide, and carbon nanotubes or Two or more.

<23> The hygienic nonwoven fabric according to any one of <1> to <22> above, which has a first fiber layer comprising the above-mentioned fiber aggregate, and a second fiber layer disposed adjacent to the first fiber layer. 2. The second fiber layer of the fiber aggregate, and the compression deformation of the second fiber aggregate under a load of 9.8 mN/cm ² is 0.3 mm or more. <24> The sanitary nonwoven fabric according to the above <23>, wherein the first fiber layer is disposed on the outer surface. <25> The sanitary nonwoven fabric as described in <23> or <24> above, wherein the basis weight of the first fiber layer is preferably at least 10 g/m ² , more preferably at least 15 g/m ² , and still more preferably 18 g/m ² or more, and preferably 200 g/m ² or less, more preferably 150 g/m ² or less, still more preferably 100 g/m ² or less. <26> The sanitary nonwoven fabric described in any one of <23> to <25> above, wherein the basis weight of the second fiber layer is preferably 10 g/m 2 or ^more , more preferably 15 g/m ² or more , and more preferably 20 g/m ² or more, preferably 140 g/m ² or less, more preferably 90 g/m ² or less, and still more preferably 70 g/m ² or less. <27> The sanitary nonwoven fabric according to any one of <23> to <26> above, wherein the compression deformation of the second fiber layer under a load of 9.8 mN/cm ² (1 gf/cm ² ) is preferably 0.3 mm or more, more preferably 0.5 mm or more, preferably 3 mm or less.

<28> A hygienic product comprising the sanitary nonwoven fabric described in any one of the above <1> to <27>, and a second member adjacent to the nonwoven fabric, wherein the second member is 9.8 mN The compressive deformation under load/cm ² is more than 0.3 mm. <29> The sanitary article as described in <28> above, wherein the amount of compression deformation of the second member under a load of 9.8 mN/cm ² (1gf/cm ² ) is preferably 0.5 mm or more, preferably 3 mm or less . <30> The sanitary article as described in <28> or <29> above, wherein the compression deformation of the entire sanitary article under a load of 9.8 mN/cm ² is 0.3 mm or more. <31> The sanitary article as described in any one of <28> to <30> above, wherein the compressive deformation of the entire sanitary article under a load of 9.8 mN/cm ² (1gf/cm ² ) is preferably 0.4 mm Above, preferably below 15 mm, more preferably below 10 mm.

<32> The sanitary article according to any one of <28> to <31> above, wherein the second member is an absorber or an absorbent sheet. <33> The sanitary article according to any one of <28> to <32> above, wherein the second member is an absorbent sheet, and the basis weight of the entire absorbent sheet is preferably 40 g/m ² above, more preferably above 60 g/m ² , more preferably above 70 g/m ² , preferably below 500 g/m ² , more preferably below 400 g/m ² , further preferably below 300 g/m 2 ^m2 or less.

<34> The sanitary article as described in any one of <28> to <32> above, wherein the second member is an absorber, and the basis weight of the absorber as a whole is preferably 30 g/m ² or more, more preferably It is 40 g/m ² or more, more preferably 50 g/m ² or more, preferably 600 g/m ² or less, more preferably 550 g/m ² or less, still more preferably 500 g/m ² or less. <35> An absorbent article comprising the hygienic nonwoven fabric as described in any one of <1> to <27> above. <36> The absorbent article as described in the above <35>, wherein the sanitary nonwoven fabric is disposed on the outer surface of the absorbent article.

<37> A method of manufacturing a sanitary nonwoven fabric, which is a method of manufacturing a sanitary nonwoven fabric as described in any one of <1> to <27> above, It comprises the following steps: performing hot air treatment or spun-bonding treatment on the fiber web containing polyamide resin fibers. <38> The production method described in <37> above, which includes the step of hot-air-treating the fiber web comprising polyamide resin fibers, In the above steps, when the melting point of the resin constituting the fiber is set as the melting point Mp, the temperature of the hot air blown to the fiber web is preferably set to be below the melting point Mp+10°C, more preferably set to be below the melting point Mp+9°C, and more preferably set to It is melting point Mp + 8°C or lower, preferably melting point Mp - 4°C or higher, more preferably melting point Mp - 2°C or higher, and still more preferably melting point Mp or higher. <39> The production method described in <37> or <38> above, which includes the step of hot-air-treating the fiber web comprising polyamide resin fibers, In the above steps, the wind speed of the hot air blown to the fiber web is preferably set at 0.6 m/s or more, more preferably at least 1.0 m/s, preferably below 2.0 m/s, more preferably at 1.4 m/s seconds or less. <40> The production method described in any one of <37> to <39> above, which includes the step of subjecting a fiber web comprising polyamide resin fibers to hot air treatment, The conveying speed of the fiber web in the above step is preferably at least 3 m/min, more preferably at least 10 m/min, preferably at most 200 m/min, more preferably at most 160 m/min.

<41> The production method described in any one of the above <37> to <40>, which further includes the step of compacting the fiber aggregates obtained by the above-mentioned hot air treatment or the above-mentioned spun-bonding treatment, The above-mentioned densification treatment is carried out while heating at a temperature not higher than the melting point of the resin constituting the above-mentioned fibers. <42> The production method described in the above <41>, wherein as the compaction treatment, the above-mentioned fiber aggregate is placed between two metal flat plates and pressurized, or the fiber aggregate is introduced between a pair of rollers. The above-mentioned fiber aggregates are calendered under pressure. <43> The production method described in the above <41> or <42>, wherein the above-mentioned pressure treatment is performed as the above-mentioned compaction treatment, The pressurization conditions in the above pressurization treatment are preferably at least 5 MPa, more preferably at least 7 MPa, more preferably at most 72 MPa, more preferably at most 32 MPa.

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

Hereinafter, the present invention will be described in more detail by means of examples. However, the scope of the present invention is not limited by the examples. The column indicated by "-" in the table means not contained or not measured.

[Embodiments 1 to 3] A core-sheath composite fiber having nylon 6 as a polyamide resin as a core and HDPE as a sheath was used. The mass ratio of resin, fiber diameter and fiber length are shown in Table 1 below. First, the fiber web of the above-mentioned conjugate fiber adjusted so as to have the basis weight shown in Table 1 below was subjected to hot air treatment to obtain a non-woven fiber aggregate. The conditions of the hot air treatment are as described in Table 1 below. Next, the fiber aggregate was densified under the conditions of heating and pressure shown in Table 1 below by pressing a metal plate with a flat surface to obtain the target sanitary nonwoven fabric. These non-woven fabrics are all of single-layer structure.

[Example 4] Except that the wind speed during the hot air treatment was set to 1.2 m/sec, and the compaction treatment was performed by the calendering method, it was carried out in the same manner as in Example 1, and a sanitary nonwoven fabric with a single-layer structure as the target was obtained. The pressurization condition by the calendering method is set to 483 N/cm (49.3 kgf/cm), and a pair of smooth rolls with smooth surfaces are used.

[Example 5] Using a core-sheath composite fiber using nylon 6 as a polyamide resin as a core and HDPE as a sheath, and changing the mass ratio of the resin as shown in Table 1 below, the target was obtained in the same manner as in Example 1. Hygienic nonwovens.

[Example 6] A fiber web containing only nylon 6 fibers as a polyamide resin is formed by a spunbond method, and the fiber web is fused and compacted by an embossing roller, thereby obtaining a sanitary nonwoven fabric including a spunbonded nonwoven fabric. The conditions of the spunbond method are shown in Table 1 below. The nonwoven fabric is of a single-layer construction. Furthermore, the length of the fiber obtained by the spunbond method is substantially infinite, and the fiber length was not measured in this example.

[Example 7] A fiber web comprising only nylon 66 fibers as a polyamide resin was formed by a spunbond method, and under the same conditions as in Example 6, the fiber web was fused and compacted using an embossing roller, thereby A hygienic nonwoven comprising a spunbond nonwoven is obtained.

[Example 8] In this example, a sanitary nonwoven fabric having a multi-layer structure was produced. Specifically, under the same conditions as in Example 1, hot air treatment was carried out on the fiber web comprising the core-sheath composite fiber having nylon 6 as the polyamide resin as the core and HDPE as the sheath, and then, in the same manner as in Example 1. 1 Under the same conditions, perform compaction treatment to obtain a single-layer non-woven fabric (basis weight: 90 g/m ² ). In addition, prepare the second fiber web comprising the core-sheath composite fiber whose core is PET and the sheath is PE, and under the same conditions as in Example 1, carry out hot air treatment and compaction treatment to obtain a single-layer non-woven fabric (basis weight: 20 g/m ² ). Finally, the respective nonwoven fabrics were laminated with a hot-melt adhesive and bonded together to obtain a target sanitary nonwoven fabric with a multi-layer structure (basis weight: 110 g/m ² ).

[Example 9] Mix the core-sheath composite fiber with nylon 6 as polyamide resin as the core and HDPE as the sheath with the core-sheath composite fiber with PET as the core and PE as the sheath at a mass ratio of 1:1, in the same manner as in Example 1. Under the conditions, hot air treatment and compaction treatment are carried out to obtain the target non-woven fabric. This nonwoven fabric has a single-layer structure without a second fiber aggregate.

[Comparative example 1] Except having used the core sheath composite fiber which made PET the core and HDPE the sheath without using a polyamide resin, it carried out similarly to Example 1, and obtained the target sanitary nonwoven fabric.

[Comparative example 2] Except having used the core-sheath composite fiber which used PP as a core and HDPE as a sheath without using a polyamide resin, it carried out similarly to Example 1, and obtained the target sanitary nonwoven fabric.

[Measurement of thickness of sanitary nonwoven fabric] The thickness of the sanitary nonwoven fabric of Examples and Comparative Examples was measured. The measurement of the thickness is carried out at more than 5 locations using a laser displacement meter under the condition that a load of 4.9 mN/cm ² (0.5 gf/cm ² ) is applied to the sanitary non-woven fabric to be measured, and the arithmetic mean value is set as is the thickness (mm). The results are shown in Table 1.

[Determination of volume filling rate] The volume filling rate (%) of the sanitary nonwoven fabric of the Example and the comparative example was calculated by the said method. The results are shown in Table 1.

[Measurement of Compression Deformation Under Load of 9.8 mN/cm ² ] The compressive deformation (mm) of the sanitary nonwoven fabrics of Examples and Comparative Examples under a load of 9.8 mN/cm ² was calculated by the above method. The results are shown in Table 1.

[Measurement of MMD] The MMD of the sanitary nonwoven fabrics of Examples and Comparative Examples was calculated by the above method. The results are shown in Table 1.

[Thermal conductivity of non-woven fabrics] The thermal conductivity and cool touch of the sanitary nonwoven fabrics of Examples and Comparative Examples were measured by the following methods. (1. Sample making) Cut the hygienic non-woven fabric as the measurement object into small pieces, hold the laminated body of about 10 g by lamination of multiple pieces between two stainless steel plates and place it in the center of the stainless steel plate, and heat it for 1 minute without pressure. A fusion is obtained. The heating temperature is set to the melting point M + 20°C measured by the above-mentioned differential scanning calorimeter. In the case of a nonwoven fabric containing multiple resin materials, the heating is performed based on the melting point of the resin with the highest melting point. Specifically, heating was performed at 245°C. Then, while maintaining the above heating temperature, apply a gauge pressure of 200 kgf to the obtained fusion (total mass including the top plate: 21848 kg; when calculating the pressure by surface pressure, since the area of the fusion will vary It changes with the melting of the resin, so the surface pressure should be calculated based on the area of the finally obtained circular resin plate. For example, when the diameter of the circular resin plate is 15 cm, the surface pressure is 12 MPa) and After keeping it for 1 minute, water-cool it to 20°C while maintaining the pressurized state, and obtain a circular resin plate with a diameter of about 15-20 cm (depending on the melt viscosity of the resin, the diameter of the obtained circular resin plate may vary. Variety). Next, the obtained circular resin plate was cut radially through the center, and if the maximum diameter was 5 cm or more, it was further cut into 5 cm or less. Next, in such a way that the extension direction of the imaginary line segment with the maximum diameter length is randomized and the effect of resin alignment is eliminated, after the cut resin plate is stacked in the center of the stainless steel plate, two spacers with a thickness of 1 mm are arranged in parallel At a position 10 cm away from the center of the stainless steel plate, and overlap the stainless steel plate on it. Thereafter, heating under non-pressurized conditions, and heating and cooling under pressurized conditions were performed by the same operation as above. When there are air bubbles entering, repeat the same action. The purpose of the secondary heating and melting is to temporarily melt the sample, eliminate the influence of crystallization of the resin that changes during the fiber spinning process, and fix the heat history. Thereby, a thin film was obtained.

(2. Measurement of thermal conductivity) The measurement of thermal conductivity was carried out by the following method using a measuring device (KES-F7 Thermo Lab II manufactured by Kado Technology Co., Ltd.). First, a size of 10 cm in length and 10 cm in width was cut out from the prepared film, and placed in an environment with room temperature of 23°C and relative humidity of 50% for 24 hours. Then, the thermal conductivity of the measurement object is measured by the above-mentioned measurement device and according to the measurement guide of the device. Specifically, the temperature of the heat source body for measurement (BT-BOX, which is made of an aluminum plate with a height of 5 cm x 5 cm and a thickness of 1 mm and a heater) is set at 33°C (compared to the surface of the measurement object The temperature is 10°C higher than the temperature), in order to prevent the warping of the film from reducing the contact area, the heat source body is brought into contact with the film by applying a load of 1 kg per 0.25 m ² area of the film. On the display panel of the measuring device, set the time point when the heat flow from the heat source body to the measurement object becomes constant as the measurement start point, and measure the average heat flow within 60 seconds from this point. Calculate based on the following formula (III) according to the measurement conditions and the heat flow rate obtained from the measurement. The thickness D of the film is the arithmetic mean value of the thickness measured by the laser displacement meter at more than 3 locations under the condition of no load. The above-mentioned measurement was performed three times for each measurement object, and the maximum value of these measurement values was defined as the thermal conductivity (W/mK) of the sample. The results are shown in Table 1.

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

[Measurement of cooling sensation to contact] The measurement of cooling sensation to contact was carried out by the following method using a measuring device (KES-F7 Thermo Lab II manufactured by Kado Technology Co., Ltd.). First, cut out a size of 23 cm x 14 cm from the sanitary nonwoven fabric to be measured, and place it in an environment with a room temperature of 23° C. and a relative humidity of 50% for 24 hours. Then, with the above-mentioned measuring device and in accordance with the measuring guide of the device, using a constant temperature device using gas or liquid as a heat medium, the test piece is placed at 23°C, and the sanitary non-woven fabric of the measuring object is measured to define the heat source and The temperature difference. Then, with the above-mentioned measuring device and according to the measuring guide of the device, measure the contact coolness q _max of the measuring object. Specifically, a measurement terminal made of pure copper (T-Box) with an area of 9.0 cm ² and a mass of 9.8 g was used as a hot plate in contact with the measurement object, and the initial temperature of the copper plate was set at 33°C (higher than the surface temperature of the measurement object temperature of 10°C), set the contact pressure between the copper plate and the measurement object to 98 mN/cm ² (10 gf/cm ² ), make the copper plate contact the test piece, and set the above-mentioned heat flow value at the instant of contact to zero , to determine the maximum value of the heat flow. The measurement was carried out 5 times for each surface to be measured, and the arithmetic mean value of these multiple measured values was defined as the cooling sensation q _max (W/m ² ) of the object to be measured. The larger the value of the cooling sensation q _max , the greater the amount of heat transfer, and the faster the heat transfer, the easier it is for the wearer to feel the cooling sensation. The results are shown in Table 1 below.

[Texture Evaluation] The textures of the nonwoven fabrics of Examples and Comparative Examples were evaluated by the following method. The items of the texture evaluation test are softness, smoothness and skin touch. First, ask 20 professional sensory inspectors to touch the surface of the non-woven fabric, score each item according to the following evaluation criteria, and calculate the average score of each item. Then, calculate the overall average score based on the average score of each item, and use this average score as an evaluation of texture. The results are shown in Table 1. 5 points: Good. 4 points: slightly better. 3 points: ordinary. 2 points: slightly worse. 1 point: Poor.

[Cool feeling evaluation] The cooling sensation of the nonwoven fabrics of Examples and Comparative Examples was evaluated by the following method. First, ask 20 professional sensory inspectors to touch the surface of the non-woven fabric, score the cool feeling when touching the non-woven fabric according to the following standards, and use the arithmetic mean as the evaluation of the cool feeling. The results are shown in Table 1. 5 points|pieces: The cool feeling is very excellent. (The cooling sensation can be felt as strongly as that of the contact cooling fabric whose q-max is 0.20 or more.) 4 points|pieces: Cool feeling is favorable. 3 points|pieces: A cooling sensation can be felt. 2 points|pieces: A slight cooling sensation is sensed. 1 point|piece: No cool feeling is sensed at all. (Same as air-through nonwoven fabric with q-max of 0.06 or less, no cool feeling can be felt.)

As shown in Table 1, it is judged that compared with the sanitary nonwoven fabric of the comparative example, the sanitary nonwoven fabric of each embodiment has a good texture, and the thermal conductivity and volume filling rate are high, and the cool feeling q _max is also high, which can It makes people feel the coolness more strongly. Therefore, the hygienic nonwoven fabric of the present invention has a good texture, and can make people feel a cool feeling when in contact with the skin, giving a comfortable feeling of use.

[Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Comparative example 1 Comparative example 2 1st fiber aggregate Fiber 1 Constituent fiber core sheath composite fiber core sheath composite fiber core sheath composite fiber core sheath composite fiber core sheath composite fiber single fiber single fiber core sheath composite fiber core sheath composite fiber core sheath composite fiber core sheath composite fiber core resin Resin type Nylon 6 Nylon 6 Nylon 6 Nylon 6 Nylon 6 Nylon 6 Nylon 66 Nylon 6 Nylon 6 PET PP Mass ratio [mass%] 50 50 50 50 30 100 100 50 50 50 50 sheath resin Resin type HDPE HDPE HDPE HDPE HDPE - - HDPE HDPE HDPE HDPE Mass ratio [mass%] 50 50 50 50 70 - - 50 50 50 50 Fiber diameter [μm] 17 17 17 17 17 17 17 17 17 17 18 Fiber length [mm] 51 51 51 51 51 - - 51 51 51 51 fiber 2 Constituent fiber - - - - - - - - core sheath composite fiber - - core resin Resin type - - - - - - - - PET - - Mass ratio [mass%] - - - - - - - - 50 - - sheath resin Resin type - - - - - - - - HDPE - - Mass ratio [mass%] - - - - - - - - 50 - - Fiber diameter [μm] - - - - - - - - 17 - - Fiber length [mm] - - - - - - - - 51 - - 2nd fiber aggregate Constituent fiber - - - - - - - core sheath composite fiber - - - core resin type - - - - - - - PET/PE - - - Mass ratio [mass%] - - - - - - - 50 - - - sheath resin Resin type - - - - - - - HDPE - - - Mass ratio [mass%] - - - - - - - 50 - - - Fiber diameter [μm] - - - - - - - 17 - - - Fiber length [mm] - - - - - - - 51 - - - Non-woven conditions manufacturing method hot air hot air hot air hot air hot air Spunbond Spunbond hot air hot air hot air hot air temperature [°C] 134 134 134 134 134 - - 134 134 134 134 Wind speed [m/s] 1.7 1.2 1.2 1.2 1.2 - - 1.7 1.7 1.7 1.7 Net conveying speed [m/min] 10 10 10 10 10 10 10 10 10 10 10 Compaction conditions Manufacturing method Pressurize Pressurize Pressurize calendering Pressurize Embossed Embossed Pressurize Pressurize none none temperature [°C] 80 80 80 80 80 250 250 80 80 - - pressure [MPa] 10 10 10 Line pressure 483 N/cm 10 5 5 10 10 - - Pressurization time [seconds] 15 15 15 0.08 15 0.05 0.05 15 15 - - Physical properties of the first fiber aggregate Basis weight [g/m ² ] 90 40 20 90 90 90 90 90 90 90 57.6 Volume filling rate[%] 16.0 15.0 19.0 12.7 16.0 5.8 5.8 16.0 29.0 1.3 2.8 Thickness [mm] 0.6 0.3 0.1 0.7 0.6 1.5 1.5 0.6 0.3 5.9 2.2 Compressive deformation under load of 9.8 mN/cm ² [mm] 0.6 0.6 0.5 0.6 1.1 0.7 0.7 0.6 0.9 0.7 0.6 Physical properties of the second fiber aggregate Basis weight [g/m ² ] - - - - - - - 20 - - - Thickness [mm] - - - - - - - 2.0 - - - Compressive deformation under load of 9.8 mN/cm ² [mm] - - - - - - - 0.5 - - - Hygienic Nonwovens The fusion point between the fibers of the non-woven fabric have have have have have have have have have have have MMD[-] 0.008 0.008 0.008 0.008 0.008 0.008 0.008 0.008 0.005 0.006 0.008 Compressive deformation under load of 9.8 mN/cm ² [mm] 0.6 0.6 0.5 0.6 1.1 0.7 0.7 0.4 0.9 0.7 0.6 Overall basis weight [g/m ² ] 90 40 20 90 90 90 90 110 90 90 57.6 Overall thickness [mm] 0.6 0.3 0.1 0.7 0.6 1.5 1.5 2.6 0.3 5.9 2.2 Volume filling rate[%] 16 15 19 13 16 5.8 5.8 16 29 1.3 2.8 Evaluate Texture evaluation [points] 5 5 4 5 4 4 4 5 4 3 3 Cooling evaluation [points] 4.5 4 4 4.5 4 4 4 5 3 1 1 Thermal conductivity of the first fiber aggregate [W/mK] 0.18 0.18 0.18 0.18 0.18 0.16 0.16 0.18 0.18 0.14 0.17 q-max[W/m ² ] 0.15 0.14 0.14 0.15 0.15 0.15 0.15 0.15 0.16 0.06 0.06 [Industrial availability]

According to the present invention, there is provided a hygienic nonwoven fabric which has a good texture and can feel a cool feeling when it comes into contact with the skin.

Claims (27)

A nonwoven fabric for hygiene, which has a fiber aggregate containing fibers, the fibers comprising polyamide resin, The above-mentioned fiber aggregate has a fusion point where its constituent fibers are fused to each other, and The volume filling rate of the fiber aggregate containing the fibers containing polyamide resin is 3.5% or more. The sanitary nonwoven fabric according to claim 1, wherein the volume filling rate of the fiber aggregates containing fibers containing polyamide resin is 12.0% or more. The sanitary nonwoven fabric as claimed in claim 1, wherein the above-mentioned fibers are composite fibers containing polyamide resin. The sanitary nonwoven fabric as claimed in claim 1, wherein the polyamide resin is one or more of nylon 6, nylon 66, and aromatic nylon. Such as the sanitary non-woven fabric of claim 1, wherein the above-mentioned sanitary non-woven fabric further comprises polyethylene resin, The mass ratio (polyamide resin/polyethylene resin) of the polyamide resin contained in the sanitary nonwoven fabric to the polyethylene resin is not less than 0.1 and not more than 2.0. Such as the sanitary non-woven fabric of claim 1, wherein the above-mentioned sanitary non-woven fabric further comprises polyethylene resin, The above-mentioned polyethylene resins are 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 one or more of them. The hygienic nonwoven fabric as claimed in claim 6, wherein the fiber core is a polyamide resin and the sheath comprises a core-sheath composite fiber of high-density polyethylene resin (HDPE). For example, the sanitary nonwoven fabric according to claim 1, the mean deviation (MMD) of the coefficient of friction is 0.010 or less. The hygienic nonwoven fabric according to claim 1, wherein the contact cool feeling q _max in the fiber aggregate of the hygienic nonwoven fabric is not less than 0.06 W/m ² and not more than 0.80 W/m ² . The hygienic nonwoven fabric according to claim 1, wherein the thermal conductivity in the fiber aggregate of the hygienic nonwoven fabric is 0.08 W/mK or more. The sanitary nonwoven fabric as claimed in claim 1, wherein the bending stiffness of the sanitary nonwoven fabric is 0.25 gf·cm ² /cm or less. The hygienic nonwoven fabric according to claim 1, wherein the fiber diameter of the above-mentioned fibers is not less than 1 μm and not more than 40 μm. The hygienic nonwoven fabric according to claim 1, wherein the fiber length of the above-mentioned fibers is not less than 30 mm and not more than 70 mm. The non-woven fabric for hygiene according to claim 1, wherein the non-woven fabric for hygiene further contains a filler. The sanitary non-woven fabric of claim 14, wherein the above-mentioned filler is one or more of titanium oxide, aluminum oxide, boron nitride, magnesium oxide, silicon oxide, carbon black, zinc oxide, and carbon nanotubes. The hygienic nonwoven fabric according to claim 1, which has a first fiber layer comprising the above-mentioned fiber aggregate, and a second fiber layer comprising a second fiber aggregate disposed adjacent to the first fiber layer, and the above-mentioned second fiber layer is The compressive deformation of the fiber aggregate under a load of 9.8 mN/cm ² is above 0.3 mm. The sanitary nonwoven fabric according to claim 16, wherein the first fiber layer is disposed on the outer surface. A hygienic product comprising the nonwoven fabric for hygiene according to claim 1, and a second member adjacent to the nonwoven fabric, wherein the compressive deformation of the second member under a load of 9.8 mN/cm ² is 0.3 mm or more. For example, the hygienic article according to claim 18 has a compressive deformation of 0.3 mm or more under a load of 9.8 mN/cm ² . The sanitary article according to claim 18, wherein the second member is an absorber. An absorbent article comprising the hygienic nonwoven fabric according to Claim 1. The absorbent article according to claim 21, wherein the sanitary nonwoven fabric is disposed on the outer surface of the absorbent article. A method of manufacturing a sanitary non-woven fabric, which is the manufacturing method of a sanitary non-woven fabric as claimed in claim 1, It includes the step of hot-air treatment or spun-bonding treatment of the fiber web containing polyamide resin fibers. The manufacturing method according to claim 23, which further includes the step of compacting the fiber aggregates obtained by the above-mentioned hot air treatment or the above-mentioned spun-bonding treatment, The above-mentioned densification treatment is carried out while heating at a temperature not higher than the melting point of the resin constituting the above-mentioned fibers. The production method according to claim 24, wherein as the above-mentioned compaction treatment, a pressurization treatment in which the above-mentioned fiber aggregate is placed between two metal flat plates and pressurized, or the above-mentioned fiber aggregate is introduced between a pair of rollers Body and pressurized calendering treatment. The manufacturing method according to claim 24, wherein the above-mentioned pressure treatment is performed as the above-mentioned compaction treatment, The pressurization conditions in the above-mentioned pressurization treatment are set at 5 MPa or more and 72 MPa or less. The manufacturing method according to claim 24, wherein the above-mentioned calendering treatment is performed as the above-mentioned densification treatment, The pressure conditions in the above-mentioned calendering process are not less than 78.4 N/cm (8 kgf/cm) and not more than 686 N/cm (70 kgf/cm).