CN115427621B - Sanitary nonwoven fabric, sanitary article and absorbent article having the same, and method for producing sanitary nonwoven fabric - Google Patents

Abstract

The sanitary nonwoven fabric contains fibers containing polyethylene resin on at least a portion of its surface, and the volume filling rate is 3.5% or more. It is also preferred that the fibers have a major axis and a minor axis, and the ratio of the major axis length to the minor axis length is 1.5 or more and 10 or less. It is also preferred that the fibers are in contact with each other at multiple points in a cross-sectional view of the nonwoven fabric. In addition, the present invention also provides an absorbent article having the sanitary nonwoven fabric. Furthermore, the present invention also provides a method for manufacturing a sanitary nonwoven fabric, wherein a web of fibers containing polyethylene resin on at least a portion of its surface is subjected to hot air treatment and compaction treatment.

Description

Nonwoven fabric for hygiene, sanitary article and absorbent article each comprising the same, and method for producing nonwoven fabric for hygiene

Technical Field

The present invention relates to a nonwoven fabric for hygiene, a sanitary article and an absorbent article each comprising the same, and a method for producing the nonwoven fabric for hygiene.

Background

There have been proposed fiber sheets that can feel cool and articles provided with the fiber sheets. For example, patent document 1 discloses a comfort fabric for use in clothing for eliminating summer heat. It is described that the fabric contains at least one organic polymer fiber having a thermal conductivity of 5W/mK or more in the fiber axial direction at 20 ℃ to 30 ℃, and the thermal conductivity of 0.08W/mK or more in the thickness direction of the fabric at 20 ℃ to 30 ℃ and the contact temperature sensation of 0.13W/cm ² or more.

Patent document 2 discloses a sheet-like fiber bundle aggregate having excellent touch cooling characteristics and used for bedding or bedding. The aggregate is formed by laminating a plurality of sheets containing polymer polyethylene fibers with an average fiber length of 10-200 mm.

Further, the present inventors have proposed a sheet for an absorbent article which is less likely to cause discomfort even when in contact with the skin in a wet state (see patent document 3). The sheet comprises a hydrophobic fiber and a cellulose fiber, and has a contact cooling sensation q _max of 2.5kW/m ² or less in a state of a water content of 50 mass% on both sides of the sheet.

Prior art literature

Patent literature

Patent document 1 Japanese patent application laid-open No. 2010-236130

Patent document 2 Japanese patent application laid-open No. 2018-145577

Patent document 3 Japanese patent application laid-open No. 2019-42403

Disclosure of Invention

The present invention relates to a sanitary nonwoven fabric.

In one embodiment, the sanitary nonwoven fabric includes fibers having at least a part of a surface thereof including a polyethylene resin.

In one embodiment, the sanitary nonwoven fabric preferably has a volume filling rate of 3.5% or more.

The present invention also relates to an absorbent article comprising the sanitary nonwoven fabric.

The present invention also relates to a sanitary article comprising the above sanitary nonwoven fabric.

In one embodiment, the sanitary article includes a 2 nd member disposed adjacent to the sanitary nonwoven fabric.

In one embodiment, the compression set of the 2 nd member under a load of 9.8mN/cm ²(1gf/cm²) is 0.3mm or more.

The present invention also relates to a method for producing a nonwoven fabric for hygiene, which comprises subjecting a web of fibers having at least a part of the surface thereof comprising a polyethylene resin to a hot air treatment to obtain a fiber aggregate.

In one embodiment, the fiber aggregate is preferably subjected to a compacting treatment.

Other features of the invention will be apparent from the scope of the patent claims and from the description which follows.

Detailed Description

Sanitary articles such as sanitary napkins, panty liners and the like for absorbing liquid discharged from the body are constituted by combining a plurality of constituent members including nonwoven fabrics, and when such articles are brought into contact with the skin before use or during wearing, the wearer is given a sensation of temperature, and discomfort such as a sensation of stuffiness during use is perceived. This situation may become more pronounced especially in summer-heat environments. Therefore, it is desirable that the portion of the sanitary article such as an absorbent article that contacts the skin has a structure that can feel cool.

However, the techniques described in patent documents 1 and 2 are applied to articles other than sanitary articles such as clothing and bedding, and no study has been made on the application to sanitary articles.

The technique described in patent document 3 is not likely to cause discomfort even when the absorbent article is in contact with the skin in a wet state, but there is still room for improvement in terms of how to reduce discomfort before the absorbent article is used or before the absorbent article is worn and the liquid is absorbed.

Accordingly, the present invention relates to a sanitary nonwoven fabric which gives a comfortable feel in use by being cooled when in contact with skin, and a sanitary article and an absorbent article each comprising the same.

The present invention will be described below based on preferred embodiments of the present invention.

In the case where the upper limit value, the lower limit value, or both the upper limit value and the lower limit value are defined in the present specification, the values of the upper limit value and the lower limit value themselves are also included. It should be understood that the numerical values or the numerical ranges in which the upper limit value or the lower limit value or the range of the upper limit value or the lower limit value is described are all values or numerical ranges, unless otherwise specifically stated.

In the present specification, "a" or "an" and the like mean one or more than one.

It will be appreciated that various modifications and variations of the present invention can be made in light of the above disclosure and the following disclosure in the present specification. Accordingly, it should be understood that the present invention can be implemented in terms of embodiments not explicitly described in the present specification within the technical scope of the disclosure based on the scope of patent claims.

The disclosures of the above-mentioned patent documents and the following patent documents are incorporated in the present specification as part of the present specification.

The nonwoven fabric for sanitary use of the present invention is suitably used as a constituent member of sanitary products. Typical examples of the sanitary products include sanitary products such as masks and eye shields, and absorbent articles for absorbing body fluids such as urine and menstrual blood, and the like, and the absorbent articles are preferable.

The sanitary nonwoven fabric is disposed on the skin contact surface side which is the surface that contacts the skin of the wearer when the sanitary article is worn, or on the portion that contacts the hand of the user when the sanitary article is handled.

The nonwoven fabric for hygiene can be used without particular limitation to the uses described herein.

The sanitary nonwoven fabric of the present invention is a fiber sheet containing fibers at least a part of which includes a polyethylene resin on the surface, and preferably comprises only the fibers.

The constituent fibers of the sanitary nonwoven fabric are entangled with each other, fused, or crimped to maintain the form of the fiber sheet. Therefore, the sanitary nonwoven fabric of the present invention is configured to mainly include the form in which the boundary between the constituent fibers in contact with each other is clear.

The fibers contained in the nonwoven fabric for hygiene have a polyethylene resin on at least a part of the fiber surface. Examples of the manner in which the polyethylene resin of the fibers included in the nonwoven fabric for hygiene of the present invention is present include (i) a manner in which the polyethylene resin is included in both the outer surface and the inner portion of the fibers, that is, a manner in which the constituent resin of the fibers is only the polyethylene resin, and (ii) a manner in which the bicomponent composite fiber including a low-melting-point component including the polyethylene resin and a high-melting-point component having a higher melting point than the low-melting-point component and continuously existing in at least a part of the surface of the fibers in the longitudinal direction is included.

It is known that polyethylene resins are generally high in thermal conductivity among organic polymer materials. Therefore, the method (i) is preferably employed in view of exhibiting high thermal conductivity of the polyethylene resin itself and suppressing a decrease in thermal conductivity due to an interface between the polyethylene resin and a resin other than the polyethylene resin, so that the user can feel a cool feeling.

Specific examples of the above (i) include fibers containing a single type of polyethylene resin as a constituent resin or fibers containing only a plurality of polyethylene resins as constituent resins. Specific examples of the (ii) include (a) a core-sheath fiber, (b) a side-by-side fiber, etc., (a) a core-sheath fiber having a core of a resin other than a polyethylene resin as a high-melting point component and a sheath of a polyethylene resin as a low-melting point component formed so as to cover the surface of the core, (b) a side-by-side fiber having a polyethylene resin as a low-melting point component and a resin other than a polyethylene resin as a high-melting point component, and having a polyethylene resin as a low-melting point component continuously present on at least a part of the surface of the fiber along the length direction of the fiber. The fibers used in the present invention may be solid or hollow. From the viewpoint of improving the thermal conductivity and making the user feel cool easily, solid fibers are preferable.

In the manner of existence of the polyethylene resin in the fiber, the polyethylene resin is preferably provided in at least the entire outer surface of the fiber, and the entire fiber is preferably formed of the polyethylene resin. That is, it is preferable that the fiber has a core-sheath structure in which a polyethylene resin is used as a sheath, or a solid fiber containing only a polyethylene resin. With this structure, the polyethylene resin having high thermal conductivity is in direct contact with the skin of the user, and thus the user can feel a strong cool feeling.

In particular, the fibers present in the nonwoven fabric for hygiene are more preferably fibers containing only a polyethylene resin as their constituent resin. The use of only a polyethylene resin having high thermal conductivity makes it easy to construct the fiber having high thermal conductivity, and thus makes it possible to make the user feel a cool feeling more strongly.

Examples of the polyethylene resin used in the present invention include low density polyethylene resin (LDPE), medium density polyethylene resin (MDPE), high density polyethylene resin (HDPE), linear low density polyethylene resin (LLDPE), and ethylene-propylene copolymer. These may be used singly or in combination of plural kinds.

When an ethylene-propylene copolymer is used as the polyethylene resin, the proportion of ethylene units in the copolymer is preferably 95% by mass or more, more preferably 98% by mass or more, from the viewpoint of improving the thermal conductivity.

The ratio of propylene units in the copolymer is preferably 5% by mass or less, more preferably 2% by mass or less.

Examples of the fibers containing only polyethylene resin include fibers containing only HDPE (that is, fibers containing 100 mass% HDPE), and core-sheath fibers or side-by-side fibers using a plurality of the above-mentioned various polyethylenes.

Examples of the core-sheath fiber or the side-by-side fiber using only a polyethylene resin include a fiber in which HDPE having different melting points is used for the core and the sheath, a core-sheath fiber in which HDPE is used for the core and HDPE is used for the sheath, a core-sheath fiber in which HDPE is used for the core and LLDPE is used for the sheath, and a side-by-side fiber in which HDPE is continuously present in at least a part of the surface of the fiber in which LLDPE is used in the longitudinal direction.

In the fiber containing only the polyethylene resin, the type or combination of the polyethylene resins may be employed without being limited to the above.

Among these, from the viewpoint of having physical properties of high thermal conductivity and making it possible for the user to feel a cool feeling more strongly, the polyethylene resin preferably contains HDPE, and more preferably contains HDPE alone. That is, it is further preferable to use HDPE alone.

Examples of the resins other than the polyethylene resin used in the present invention include polyolefin resins other than polyethylene resins such as polypropylene (PP) and polybutylene, polyester resins such as polyethylene terephthalate (PET), polyamide resins, vinyl resins such as polyvinyl chloride and polystyrene, acrylic resins such as polyacrylic acid and polymethyl methacrylate, fluororesins such as polyperfluoroethylene, and nylon. These resins may be used singly or in combination of two or more.

The content of the polyethylene resin is preferably 70 mass% or more, more preferably 80 mass% or more, further preferably 90 mass% or more, further more preferably 100 mass% or less, and particularly preferably 100 mass% relative to the total mass of the resins contained in the nonwoven fabric for hygiene.

As another embodiment of the sanitary nonwoven fabric of the present invention, the sanitary nonwoven fabric preferably contains fibers having a thermal conductivity of a predetermined value or more on at least a part of the surface.

Specifically, the nonwoven fabric for hygiene preferably contains fibers having a thermal conductivity of preferably 0.11W/mK or more, more preferably 0.13W/mK or more, and still more preferably 0.15W/mK or more in a part of the surface.

In addition, in reality, the nonwoven fabric for hygiene contains fibers having a thermal conductivity of 0.4W/mK or less in a part of the surface.

The thermal conductivity can be measured, for example, by melting a sanitary nonwoven fabric into a film-like sample having a thickness of about 1 mm. The detailed measurement method will be described below.

By having such thermal conductivity, a user of the sanitary article including the nonwoven fabric for sanitary can feel cool more strongly.

The structure related to the thermal conductivity in this embodiment may be used instead of or in addition to the above embodiment.

In addition, the above-described embodiments and the descriptions concerning the respective configurations may be appropriately used in combination with aspects not described in the present embodiment.

The nonwoven fabric for hygiene having the above thermal conductivity can be obtained, for example, by being constituted to contain, as constituent fibers, fibers containing one or two or more of the polyethylene resins used in the above embodiments.

In this case, the thermal conductivity of at least a part of the surface constituting the fiber is preferably 0.11W/mK or more, more preferably 0.13W/mK or more, and still more preferably 0.15W/mK or more. When a fiber having such a thermal conductivity is used, the range of the thermal conductivity of the nonwoven fabric for hygiene is easily achieved, and thus it is preferable.

The thermal conductivity of the constituent fibers can be easily achieved by using fibers containing only polyethylene resin, for example.

The thermal conductivity can be measured, for example, by the following method. First, a nonwoven fabric or fibers to be measured are peeled off from a product by cold spraying or the like, or fiber sampling or the like is performed to separate the fibers. Then, the separated nonwoven fabric or fiber is introduced into a heating and pressurizing device such as a press machine, and is pressurized while being heated at a temperature equal to or higher than the melting point of the nonwoven fabric or fiber raw material, thereby producing a film-like sample having a thickness of about 1 mm. At this time, the pressurizing conditions were appropriately adjusted so that air was not left in the sample.

Then, using a steady-state thermal conductivity measuring device (KES-F6, manufactured by add technologies corporation), thermal conductivity was measured based on the amount of heat transfer from the 30 ℃ hotplate to the 20 ℃ hotplate via the sample. In this measurement, 10 sites were measured on one film-like sample, and the highest thermal conductivity value was defined as the thermal conductivity (W/mK) in the present invention.

The nonwoven fabric for hygiene of the present invention has a volume filling ratio of preferably 3.5% or more, more preferably 7.0% or more, still more preferably 10.0% or more, still more preferably 14.0% or more, and particularly preferably 20.0% or more, from the viewpoint of reducing the content of air having a low thermal conductivity so as to improve the thermal conductivity of the nonwoven fabric.

In the case of using the composition as a disposable sanitary material to be brought into contact with the skin of a user, the volume filling rate is preferably 60.0% or less, more preferably 50.0% or less, and even more preferably 30.0% or less, from the viewpoint of improving the texture.

By having the above volume filling ratio, the content of air having low thermal conductivity is reduced in the nonwoven fabric for hygiene, and therefore heat transfer properties can be improved, whereby a user can feel a cool feeling more strongly.

In addition, the texture of the fiber sheet and the sanitary article with the fiber sheet can be fully expressed.

The above-described structure can be obtained by, for example, subjecting the fiber sheet to an operation such as compression as in the following production method. In the case where the nonwoven fabric for hygiene has a density gradient, the volume filling ratio of the outermost layer in contact with the skin of the user may fall within the above range.

The above-described constitution relating to the volume filling ratio can be applied to each embodiment of a nonwoven fabric for hygiene comprising fibers at least a part of which includes a polyethylene resin on the surface, a nonwoven fabric for hygiene comprising fibers having a thermal conductivity of a predetermined value or more on the surface, and a nonwoven fabric for hygiene having a thermal conductivity of a predetermined value or more on the nonwoven fabric.

The volume filling rate in the present invention can be expressed as a percentage of the apparent volume relative to the actual volume. Specifically, a predetermined area of the nonwoven fabric for hygiene to be measured was taken as a measurement sample, and the mass (g) thereof was measured. The predetermined area for cutting out the measurement sample is preferably 10cm square, but if the measurement sample of this size cannot be cut out, the area of the sanitary nonwoven fabric to be measured, which is visually uniform in weight per unit area, is cut out so as to have the largest possible width and length. Then, the weight per unit area A (g/cm ²) of the measurement sample was calculated.

The measurement method for measuring the thickness B (cm) of the sample is as follows. First, only 12.59g (diameter 55 mm) of the plate was placed on a laser shift meter (LK-080, manufactured by Kien Kabushiki Kaisha Co., ltd., each of which is a laser shift meter in the present specification), and zero point adjustment was performed by setting the measured thickness to zero. Then, the plate was placed on the measurement sample, and the thickness in this state was measured by a laser displacement meter, and the thickness was set as the thickness B (cm) of the measurement sample. In the measurement of the thickness B, a load of 4.9mN/cm ² was applied to the measurement sample by mounting the plate.

The volume filling rate (%) was calculated from the following formula using the density C (g/cm ³) of the constituent components of the fiber.

Volume filling rate (%) =100× (a)/(b×c)

When a sanitary nonwoven fabric to be measured is placed in a sanitary product such as an absorbent article, a cold spray is blown onto the sanitary product to cure the hot melt adhesive, and then the sanitary nonwoven fabric to be measured is carefully peeled off. This method is also common to other assays in this specification.

Since the sanitary nonwoven fabric having the above-described structure uses the fiber having the polyethylene resin having high thermal conductivity among the synthetic resins on at least a part of the surface, when the fiber is in contact with the skin of the user, heat due to the body temperature of the user can be quickly transferred from the user to the sanitary nonwoven fabric or other fiber not in contact with the user.

Further, by setting the volume filling ratio of the nonwoven fabric for hygiene to be within a predetermined value, the nonwoven fabric for hygiene can exhibit a good texture of the fiber sheet, and the content of air having low thermal conductivity in the nonwoven fabric for hygiene can be reduced, so that heat generated from a user can be rapidly transferred to the nonwoven fabric side for hygiene.

As a result, when the skin of the user is in contact with the sanitary nonwoven fabric, the user can feel cool and feel comfortable using feeling due to the cool feeling.

According to the preferred embodiment of the present invention, the user can feel cool more strongly, and thus the feeling of use can be further improved.

In addition, by configuring the sanitary nonwoven fabric to include fibers, the contact area of the skin of the user with the sanitary nonwoven fabric can be increased, and the user can feel a cool feeling, and the softness due to the configuration of the nonwoven fabric can be exhibited.

The fibers constituting the nonwoven fabric for hygiene are preferably in contact with each other, and more preferably in contact with each other at multiple points. Thus, heat generated by contact with the skin of the user can be transmitted in multiple directions, and heat caused by the body temperature of the user can be efficiently transferred, and as a result, the user can feel cool more efficiently.

The "contact" in the present invention includes a manner in which fibers are in contact with each other in a state in which the boundary between the fibers is clear, and a manner in which portions in which the fibers are fused to each other so that the boundary between the fibers becomes unclear.

The "multipoint contact" in the present invention means that when any fiber F on a cut surface is observed by cutting a nonwoven fabric in a direction orthogonal to the extending direction of its constituent fibers, upper and lower fibers positioned in the thickness direction of the nonwoven fabric and in contact with the fiber F are in contact with the fiber F at 2 or more points.

The structure in which the fibers are in multipoint contact with each other can be obtained by using, for example, fibers having a cross-sectional shape that is not exactly circular, such as an elliptical shape or a multi-lobal shape, and subjecting the raw material nonwoven fabric to a densification treatment by compression or the like in the following production steps.

In the case where the fibers of the nonwoven fabric for hygiene are in contact with each other, the contact method is preferably constituted by fusion or pressure bonding. With this structure, the contact area between the fibers can be increased, and the heat transfer efficiency can be further improved. As a result, the user can be efficiently cooled.

Fusion refers to a method in which heat or heat and pressure are applied only to a plurality of fibers to melt the fibers, and the boundary between the fibers becomes unclear.

The crimping means that only pressure is applied to a plurality of fibers, and the fibers are allowed to contact each other in a state where the boundary between the fibers is clear, so that gaps formed between the fibers are allowed to exist. In crimping, the above-described manner of "multipoint contact" is also preferable.

The cross-sectional shape of the fibers constituting the nonwoven fabric for hygiene may be, for example, circular such as a perfect circle and an ellipse, or geometric such as a convex polygon such as a triangle, a quadrangle, a pentagon and a hexagon, or a regular polygon. In addition to these geometric shapes, the present invention may be a multi-lobed shape having a structure in which a plurality of concave portions and convex portions are formed along the outer periphery of the cross section.

The "cross-sectional shape" in the present invention means a shape of a fiber constituting a nonwoven fabric for hygiene, which is seen when a cross section orthogonal to the extending direction thereof is observed.

Among them, the cross-sectional shape of the fiber is preferably a non-perfect circle, and more preferably an ellipse, or a shape obtained by combining an ellipse and a multi-blade, and the like, having a major axis and a minor axis. By using such a shape, the volume filling ratio of the nonwoven fabric for hygiene can be easily increased, and the number of contact points and the contact area between fibers can be increased, so that the heat transfer efficiency can be further improved, and the user can feel cool more effectively.

When the cross-sectional shape of the fiber has a long axis and a short axis, the ratio of the long axis length to the short axis length (long axis length/short axis length) is preferably 1.5 or more, more preferably 2 or more, and still more preferably 3 or more.

The ratio is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less, from the viewpoint of improving the productivity by improving the spinning property at the time of fiber production.

In addition, the above ratio is preferably satisfied over the entire length of the fiber.

The length of each of the major axis and the minor axis of the cross-sectional shape of the fiber can be measured, for example, by the following method. First, a nonwoven fabric to be measured was cooled with liquid nitrogen, and then the nonwoven fabric was cut by a cutter in a direction perpendicular to the fiber length direction, to prepare a measurement sample. The cross section of the sample was measured using a Scanning Electron Microscope (SEM) with any magnification sufficient to identify the fiber cross section and to measure the dimensions of the fiber cross section.

For 10 fibers, the respective cross sections were observed independently, and based on the scanning electron microscope image of each fiber, 2 points on the periphery of the fiber cross section were connected, a line segment passing through the maximum diameter of the centroid of the fiber cross section was taken as the major axis, and the maximum width of the minor axis orthogonal to the major axis was taken as the minor axis (in the case of a special cross section having a plurality of irregularities on the outer periphery, the minimum width of the minor axis corresponding to the concave portion was not considered). The arithmetic average of these is set as the major axis length or the minor axis length in the present invention.

When the cross-sectional shape of the fiber is a special-shaped cross-sectional shape having a plurality of irregularities on the outer periphery such as a multilobal shape, an ellipse approximation process is performed on the periphery of the fiber cross-section based on a scanning electron microscope image of each fiber cross-section obtained for any 10 fibers using image processing software or the like. The arithmetic average value calculated based on the lengths of the major axis and the minor axis of the ellipse obtained through this processing is set as the major axis length or the minor axis length in the present invention.

The thickness of the nonwoven fabric for hygiene of the present invention is preferably 0.1mm or more, more preferably 0.2mm or more, and still more preferably 0.3mm or more, from the viewpoint of improving the texture of the nonwoven fabric.

The thickness of the nonwoven fabric for hygiene of the present invention is preferably 3mm or less, more preferably 1.5mm or less, and even more preferably 0.5mm or less, from the viewpoint of reducing the air content in the nonwoven fabric to improve the thermal conductivity.

The thickness of the nonwoven fabric for hygiene was measured under a load of 4.9mN/cm ²(0.5gf/cm²) using a laser displacement meter or the like.

By setting the thickness of the nonwoven fabric for hygiene to the above-described configuration, the heat capacity of the nonwoven fabric for hygiene can be increased, and the nonwoven fabric for hygiene which can efficiently feel cool to the user can be produced with high efficiency.

The sanitary nonwoven fabric of the present invention preferably has a basis weight of 15g/m ² or more, more preferably 20g/m ² or more, and still more preferably 25g/m ² or more.

The sanitary nonwoven fabric of the present invention preferably has a basis weight of 140g/m ² or less, more preferably 90g/m ² or less, and still more preferably 50g/m ² or less.

With the above configuration, the difference in feeling of coolness caused by the weight unevenness per unit area of the nonwoven fabric for hygiene can be reduced, and the fibers can be effectively fused and compacted, so that the nonwoven fabric for hygiene having a predetermined volume filling ratio can be produced with high productivity.

The contact cooling sensation q _max of the sanitary nonwoven fabric of the present invention is preferably 0.06W/m ² or more, more preferably 0.08W/m ² or more, still more preferably 0.10W/m ² or more, and preferably 0.80W/m ² or less, more preferably 0.60W/m ² or less, still more preferably 0.50W/m ² or less.

Specifically, the contact cooling sensation q _max of the nonwoven fabric for hygiene is preferably 0.06 to ², more preferably 0.80 to ², still more preferably 0.08 to ², and still more preferably 0.60 to ², and still more preferably 0.10 to ².

The contact cooling sensation q _max can be measured, for example, by the following method.

First, a test piece was cut out of a sanitary nonwoven fabric to be measured so as to have a length of 10cm×a width of 10cm, and the test piece was left to stand at room temperature at 23 ℃ under an environment having a relative humidity of 50% for 24 hours.

Then, in this environment, the test piece was placed on the measurement stand, and the test piece was fixed to the measurement stand using a double-sided tape. A constant temperature apparatus using a gas or a liquid as a heat medium was used as a measurement table.

Then, the cooling sensation q _max of the object to be measured was measured by a measuring apparatus (KES-F7 Thermo Lab II manufactured by kagaku corporation) in accordance with the measurement guideline of the apparatus.

Specifically, a pure copper plate having an area of 9.0cm ² and a mass of 9.8g was used as a hot plate in contact with the measurement object, the initial temperature of the copper plate was set to 33 ℃ (a temperature higher than the surface temperature of the measurement object by 10 ℃), the contact pressure of the copper plate with the measurement object was set to 1kPa, the copper plate was in contact with the test piece, the value of the heat flow at the moment of the contact was set to zero, and the maximum value of the heat flow was measured.

The measurement was performed 5 times on each surface to be measured, and the arithmetic average of the obtained plurality of measured values was set as the contact cooling sensation q _max(W/m² of the measured object.

The touch cooling sensation is a value obtained by digitizing a skin feel that is cool when the skin is in contact with an object. The cooling sensation varies depending on the amount of heat transfer from the skin to the object when the skin is in contact with the object, and the cooling sensation is felt when the amount of heat transfer is larger. The contact cooling sensation q _max corresponds to the maximum value of the heat transfer amount from the skin to the object, and as for the value of the contact cooling sensation q _max, the more cool the contact with the object is, the more warm the contact is, and the less the contact is. Therefore, by setting the value of the contact cooling sensation q _max within the above range, the cooling sensation can be more effectively perceived.

The sanitary nonwoven fabric of the present invention is a sheet-like article having 2 faces, and it is preferable that the proportion of constituent fibers present on the surface of the sanitary nonwoven fabric (hereinafter, this will be also referred to as "fiber surface presence ratio") is equal to or greater than a predetermined value. The surface of the sanitary nonwoven fabric is a region ranging from the outermost surface of the sanitary nonwoven fabric to 20 μm in the thickness direction. The outermost surface of the nonwoven fabric for hygiene is a surface orthogonal to the thickness direction of the nonwoven fabric for hygiene, which surface is formed by the outermost portion in the thickness direction in the image when the nonwoven fabric for hygiene is cut in the thickness direction and the cross section in the thickness direction is observed by a Scanning Electron Microscope (SEM).

Specifically, the fiber surface presence rate of the nonwoven fabric for hygiene is preferably 40% or more, more preferably 45% or more, further preferably 50% or more, and preferably 90% or less, more preferably 85% or less, further preferably 80% or less.

More specifically, the fiber surface presence ratio of the nonwoven fabric for hygiene is preferably 40% or more and 90% or less, more preferably 45% or more and 85% or less, and still more preferably 50% or more and 80% or less.

The fiber surface existing rate is a ratio obtained by focusing on the existence ratio of fibers and expressing the relationship between the constituent fibers and the voids between the fibers on the surface of the nonwoven fabric. Therefore, when the fiber surface existing rate is within the above range, the air content in the fiber can be reduced, and a higher cool feeling can be obtained.

The fiber surface presence rate can be measured as a ratio of the area basis by the following method, for example.

Specifically, 2 sites were randomly cut out from a nonwoven fabric for hygiene to be measured using a 4cm×4 cm-sized slice as a sample. One surface of the obtained sample was measured with a Scanning Electron Microscope (SEM) at a voltage of 15kV and a magnification of 50 times, and an SEM image was obtained. Then, the SEM image was binarized with a value of 121 to 255 using image processing software windof 2018 (manufactured by san francisco corporation), and the ratio of the area of the binarized bright (white) portion to the area of the entire image was measured and calculated using the area calculation function built in the software, and the area ratio was set as the fiber surface presence ratio of the present invention.

When the measurement is difficult by the above method, the area ratio of the bright color portion is measured by binarizing the threshold value to a value of 70 to 255.

The sanitary nonwoven fabric of the present invention is preferably such that the fibers constituting the nonwoven fabric are arranged so as to have a constant orientation.

With this structure, heat transfer is easily caused along the fiber length direction, and the user can feel cool easily.

More specifically, when the nonwoven fabric for hygiene of the present invention is left standing on a horizontal plane, the fiber length direction of the fibers of the nonwoven fabric is preferably substantially parallel to the horizontal plane.

In addition, it is preferable that the fiber extends in one direction when the sanitary nonwoven fabric is viewed from above. For example, when considering the 1 st direction and the 2 nd direction orthogonal to the 1 st direction of the nonwoven fabric for hygiene in a plan view of the nonwoven fabric for hygiene, it is further preferable that the extending direction of the fibers coincides with the 1 st direction or the 2 nd direction of the nonwoven fabric. When the fibers have intersections, it is desirable that the angle between the fibers having the intersections is 50% or more of the obtuse angle in a plan view of the nonwoven fabric for hygiene. By obtuse angle is meant an angle greater than 90 °.

Regarding the quantification of the angle formed by the fibers, the obtained image data can be measured and counted by image analysis software attached to the SEM or arbitrary image analysis software, for example, by photographing any 3 sites of the nonwoven fabric for hygiene with SEM at a magnification at which the intersection point of the fibers at about 10 sites can be confirmed in the field of view. In addition, in the case where the image analysis software is not provided, the obtained image data may be printed, and the angle between fibers may be checked by a protractor or like measuring instrument, and written into a data table or the like to perform statistics.

By having at least one of the above-described structures related to the orientation of the fibers, the heat transfer can be easily advanced in a certain direction, and the user can easily and effectively feel a cool feeling.

Such a structure can be obtained, for example, by producing a long sheet using short fibers of HDPE as a material, transporting the long sheet while applying tension to the long sheet in the transport direction, and fusing the fibers to each other by a hot air method, or transporting the HDPE fibers in one direction while spinning the fibers to a transport device such as a belt conveyor.

In the above description, for convenience of description, the case where the sanitary nonwoven fabric has a single fiber layer and the single fiber layer contains fibers at least a part of which includes a surface of which includes a polyethylene resin (whether including only a single fiber or being blended with other fibers) has been described as an example, but the present invention is not limited to this form. Specifically, the sanitary nonwoven fabric may have a plurality of fiber layers of 2 or more layers.

As one embodiment of the nonwoven fabric for hygiene, for example, at least a fiber layer (hereinafter, also referred to as a1 st fiber layer) containing 1 st fibers having at least a part of the surface containing a polyethylene resin, and a layer (hereinafter, also referred to as a2 nd fiber layer) containing fibers other than the 1 st fibers, which is disposed adjacent to the fiber layer, are provided. The term "adjacent" as used herein means that the fibrous layers are adjacent to each other without any intervening fibrous layers, but that an adhesive is allowed to intervene between the fibrous layers.

In this case, from the viewpoint of more effectively feeling cool, it is preferable that the 1 st fiber layer forms the outer surface of the nonwoven fabric for hygiene. In addition, from the same viewpoint, it is preferable that at least the 1 st fiber layer satisfies various preferable forms related to the above-mentioned nonwoven fabric for hygiene, and it is more preferable that the above-mentioned preferable forms are satisfied in the entire nonwoven fabric for hygiene.

Specifically, the nonwoven fabric for hygiene having a multilayer structure can be obtained, for example, by subjecting a nonwoven fabric for hygiene having a multilayer structure to a hot air treatment or a spunbonding treatment in a state in which a fiber web containing the 1 st fiber and a fiber web containing fibers other than the 1 st fiber, at least a part of the surfaces of which are laminated. In this case, the boundary between the fiber layers is not usually clear, but may include a clear boundary portion. In the case of this embodiment, the fiber layers are maintained in the form of a fiber sheet by at least one of intertwining, fusing and crimping, for example.

As another embodiment of the sanitary nonwoven fabric having a multilayer structure, there is a method in which a fiber web or a fiber sheet containing the 1 st fiber in which at least a part of the surface contains a polyethylene resin is bonded to a fiber web or a fiber sheet containing fibers other than the 1 st fiber by an adhesive, thereby maintaining the fiber sheet. In this case, the interface of the fiber layers is generally clear.

In any case, the fibers other than the 1 st fiber include one or more of pulp fibers, rayon fibers, hydrophilized fibers, and the like, in addition to the fibers including the above-described constituent resins such as PET resins and PP resins.

The weight per unit area of the 2 nd fiber layer is preferably 15g/m ² or more, more preferably 20g/m ² or more, still more preferably 25g/m ² or more, and further preferably 140g/m ² or less, more preferably 90g/m ² or less, still more preferably 70g/m ² or less.

The nonwoven fabric for hygiene may be used as it is, or may be used as a constituent member of a hygiene article to produce a hygiene article comprising the nonwoven fabric for hygiene.

In the case of incorporating the sanitary nonwoven fabric of the present invention into a sanitary article, it is preferable that the nonwoven fabric forms a surface facing the skin of the user.

In either case, it is typically disposable.

The sanitary article comprising the sanitary nonwoven fabric of the present invention is, for example, an absorbent article or the like. That is, the nonwoven fabric for hygiene can be used as a constituent member of an absorbent article or the like.

Typically, an absorbent article includes a front sheet and a back sheet, and an absorber disposed between the front sheet and the back sheet, and may be used in a state in which a sanitary nonwoven fabric is disposed in addition to the front sheet and the back sheet, or in a state in which a sanitary nonwoven fabric is disposed instead of the front sheet or the back sheet. Examples of the absorbent article include disposable diapers, urine-leakage pads, sanitary napkins, panty liners, and the like, but are not limited to these, and include articles for absorbing liquid discharged from a human body.

When the sanitary nonwoven fabric is used as a constituent member of an absorbent article or the like, the sanitary nonwoven fabric may be disposed at a portion that is in direct contact with the skin of a user when the sanitary article such as an absorbent article is used or when the sanitary article such as an absorbent article is taken out of a package or the like. That is, the sanitary nonwoven fabric is preferably disposed on the outer surface of a sanitary article such as an absorbent article.

The outer surface of the sanitary product such as an absorbent article is a surface (including the front surface and the back surface, and is the surface side in the thickness direction, not the inner surface) of the sanitary product such as an absorbent article that can be touched by a user by hand after the package is opened and the sanitary product such as an absorbent article is taken out.

That is, the sanitary nonwoven fabric constituting the sanitary article may be disposed on a surface facing the skin of the wearer wearing the sanitary article, may be disposed on a surface not facing the skin of the wearer wearing the sanitary article, or may constitute a package of the sanitary article.

Specifically, when a sanitary nonwoven fabric is used as an absorbent article, for example, a disposable diaper, which is one embodiment of a sanitary article, it can be used as a constituent member such as a front sheet, a side nonwoven fabric, a waist gather, a gather disposed in the vicinity of a napped portion, and an outer package.

In addition, when a sanitary nonwoven fabric is used as an absorbent article, such as a urine leakage pad or a menstrual napkin, which is one embodiment of a sanitary article, it can be used as a constituent member such as a front sheet, a side nonwoven fabric, a hip guard, or a bag for individual packaging.

In addition, when a sanitary nonwoven fabric is used as an absorbent article, such as a urine leakage pad or a menstrual napkin, which is one embodiment of a sanitary article, it can be used as a constituent member such as a front sheet or a fold disposed in the vicinity of a groin portion.

In particular, from the viewpoint of reducing discomfort such as stuffiness due to a cool feeling when using the sanitary product such as an absorbent article, the sanitary nonwoven is preferably arranged such that, when the sanitary product of the absorbent article is worn in an accurate position, the side of the surface facing the skin of the wearer of the sanitary product of the absorbent article (hereinafter, this surface is also referred to as "skin-facing surface") is constituted.

Further, the sanitary nonwoven fabric is preferably disposed at a portion where the sanitary product of the absorbent article directly contacts the skin of the wearer when the wearer wears the sanitary nonwoven fabric.

Examples of the constituent members of the absorbent article include a front sheet, a side nonwoven fabric, a waist gather, and a gather disposed in the vicinity of the groin portion.

The front sheet used in the absorbent article is a sheet constituting a skin-facing surface side, and the back sheet is a sheet constituting a surface (hereinafter, also referred to as "non-skin-facing surface") facing the skin of a wearer wearing the absorbent article. When the front sheet and the back sheet used for the absorbent article are made of materials other than the sanitary nonwoven fabric of the present invention, materials conventionally used for the absorbent article can be used without particular limitation. As the front sheet, various nonwoven fabrics, apertured films, and the like having liquid permeability can be used, for example. As the back sheet, a sheet having liquid-impermeable properties or water-repellent properties or liquid-permeable properties can be used. The former includes a resin film, a laminate of a resin film and a nonwoven fabric, and the like. The latter may use the same as the front sheet.

An absorbent body used in an absorbent article is provided with an absorbent core. The absorbent core is composed of, for example, a fiber stack of hydrophilic fibers such as cellulose represented by pulp, a mixed fiber stack of the hydrophilic fibers and a water-absorbent polymer, a water-absorbent polymer stack, and the like, and typically contains hydrophilic fibers and a water-absorbent polymer.

The absorbent core may also be covered by a core-covering sheet. The covering method of the core sheet may be, for example, covering at least the skin-facing surface with a liquid-permeable core sheet, or covering the entire surface including the skin-facing surface and the non-skin-facing surface with a core sheet. As the core sheet, for example, a sheet paper containing hydrophilic fibers, a nonwoven fabric having liquid permeability, or the like can be used.

The fiber diameter of the fibers used in the nonwoven fabric for hygiene is preferably 3 μm or more, more preferably 5 μm or more, from the viewpoint of avoiding twisting of the skin with the fibers and ensuring a satisfactory touch feeling for the user.

In addition, from the viewpoint of reducing the air content in the nonwoven fabric by reducing the fiber gaps in the nonwoven fabric and improving the thermal conductivity, the fiber diameter of the fibers used in the nonwoven fabric for hygiene is preferably 70 μm or less, more preferably 50 μm or less.

As for the fiber diameter of the fiber, the measurement sample was prepared and SEM observed in the same manner as the measurement method of each length of the major axis and the minor axis of the cross-sectional shape of the fiber, and the fiber diameter of 10 fibers was measured for each 1 sample, and the arithmetic average value thereof was set as the fiber diameter of the present invention. When the fibers are not perfectly circular, the lengths of the major axis and the minor axis of the fibers are measured by the above method, the arithmetic average of the length of the major axis and the length of the minor axis of one fiber is defined as the fiber diameter, and the arithmetic average of the diameters of 10 fibers is defined as the fiber diameter of the fiber of the present invention.

The sanitary nonwoven fabric of the present invention may further comprise a filler for improving the thermal conductivity as long as the effect of the present invention can be exerted. Examples of such fillers include at least one of titanium oxide, aluminum oxide, boron nitride, magnesium oxide, silicon dioxide, carbon black, and carbon nanotubes. The filler may be present in the fibers, between the fibers, or by exposing a part of the surface of the fibers and embedding the filler in the fibers.

In the case of using the sanitary nonwoven fabric of the present invention to form a sanitary article, the sanitary article may further include other members (hereinafter, this member is also referred to as "the 2 nd member") in addition to the sanitary nonwoven fabric (hereinafter, this member is also referred to as "the 1 st fiber aggregate" for convenience of explanation) having the fiber aggregate of polyethylene resin as at least a part of the surface thereof.

As an embodiment of the sanitary article provided with the 2 nd member, for example, at least one of an absorbent sheet containing an absorbent polymer and a fiber, an absorber containing an absorbent polymer and a fiber, and the like can be used as the 2 nd member. These are examples of fiber aggregates different from nonwoven fabrics for sanitary use. The sanitary products provided with these 2 nd members are preferably the above-mentioned absorbent articles.

That is, in the present embodiment, the sanitary nonwoven fabric as the 1 st fiber aggregate and the absorbent sheet and/or the absorbent body as the 2 nd member are disposed as constituent materials of the sanitary article. It is also preferable that the 1 st fiber aggregate and the 2 nd member are disposed adjacent to each other. The fiber assemblies in this embodiment may or may not be joined to each other.

As the absorbent sheet, for example, an absorbent sheet described in japanese patent application laid-open No. 8-246395 or the like can be used.

In the case where the sanitary article includes the 2 nd member or the sanitary nonwoven fabric includes the 2 nd fiber layer, it is preferable to use a member having a thickness that varies by a predetermined value or more as the 2 nd member or the 2 nd fiber layer.

Specifically, the compression deformation amount of the 2 nd member under a load of 9.8mN/cm ²(1gf/cm²) is preferably 0.3mm or more, more preferably 0.5mm or more. The compression deformation of the 2 nd member under the load is preferably 3mm or less. As described below, the compression set is expressed as a change in the thickness of the 2 nd member under no load minus the thickness of the 2 nd member under 9.8mN/cm ²(1gf/cm²) load.

The same amount of compression set is preferably also present in the 2 nd fiber layer constituting the sanitary nonwoven fabric. In the case where the sanitary product includes both the sanitary nonwoven fabric having a multilayer structure and the 2 nd member, it is preferable that both the 2 nd member and the 2 nd fiber layer satisfy the compression set.

With this structure, when the 1 st fiber aggregate including the fibers having at least a part of the surface including the polyethylene resin comes into contact with the wearer, the 1 st fiber aggregate is easily deformed following the deformation of the 2 nd member, and the contact area with the wearer can be increased, so that the wearer can feel cool efficiently.

As for the 2 nd fiber layer having the above-mentioned physical properties, for example, in the following production method, a fiber containing a PET resin, a PP resin, a PET/HDPE core-sheath composite fiber, or the like is used as a constituent fiber, and the resultant is subjected to a hot air treatment to obtain a fiber web, and the fiber web is used to obtain the 2 nd fiber layer.

In the case where the 2 nd member is an absorbent sheet or an absorber, for example, the weight per unit area of the fibers, the fiber sheet, and the water-absorbent polymer constituting the absorbent sheet or the absorber can be appropriately adjusted.

The thickness of the 2 nd member or the 2 nd fiber layer can be measured, for example, by the following method.

First, the cross section of the object to be measured is visually observed by SEM, and the fiber diameter, the distance between fibers, the boundary between members, or the like is observed to confirm whether the nonwoven fabric for sanitary having a plurality of fiber layers is a nonwoven fabric for sanitary or whether the nonwoven fabric for sanitary or the 2 nd member other than the nonwoven fabric for sanitary is present.

When the measurement object is a sanitary article, the structure is fixed by performing an operation such as immersing the sanitary article in liquid nitrogen, and then the sanitary nonwoven fabric and the 2 nd member other than the sanitary nonwoven fabric are carefully peeled from the sanitary article to be measured, and these are separated. The separated member was used for measurement of the contact cooling sensation q _max described in detail in examples below, the fiber sheet having the highest value of q _max was defined as a nonwoven fabric for hygiene, and the member adjacent to the nonwoven fabric for hygiene was defined as the 2 nd member.

Then, an operation such as placement of the plate was performed, and in a state where a load of 9.8mN/cm ²(1gf/cm²) was applied to the separated 2 nd member, the thickness in this state was measured using a laser displacement meter, and this was set as the thickness of the 2 nd member.

When the object to be measured is a nonwoven fabric for hygiene having a multilayer structure, the fiber layer on the surface side where the value of q _max measured by the above method is highest is the 1 st fiber layer, the fiber layer adjacent to the 1 st fiber layer is the 2 nd fiber layer, and the 2 nd fiber layer is used for the above measurement.

In the entire sanitary article, the compression set under a load of 9.8mN/cm ²(1gf/cm²) is preferably 0.3mm or more, more preferably 0.4mm or more. The compression set of the entire sanitary article under such a load is preferably 15mm or less, more preferably 10mm or less.

With this structure, the nonwoven fabric as a whole exhibits softness and thus gives an improved feel in use, and the contact area between the 1 st fiber aggregate including the fibers having at least a part of the surfaces thereof including the polyethylene resin and the wearer can be increased, so that the wearer can feel cool efficiently.

For example, in the case of the hot air method, the compression set can be easily achieved by making the temperature or wind speed of hot air lower than the conditions usually employed, or by increasing the number of fibers or using fibers containing a resin having a melting point higher than the temperature of hot air, thereby reducing the fusion properties of the fibers.

In addition to the above-described constitution, it is possible to easily realize a constitution in which 2 or more fiber layers are provided, only 1 fiber layer is provided with a layer having a higher compression set than the other fiber layers, or 1 fiber layer has a higher weight per unit area than the other fiber layers, or a fiber having a higher melting point is blended with 1 fiber layer, instead of the above-described constitution.

The compression set can be measured, for example, using a KES-FB-3 compression tester manufactured by Kagaku Kogyo Co. A slice of a predetermined size was taken from the sanitary nonwoven fabric to be measured, and this was used as a sample. The sample was mounted on a test stand of a tester and placed between steel plates having a circular plane with an area of 2cm ² for compression. The compression speed was 0.02mm/sec, and the compression maximum load was 9.8mN/cm ²(1gf/cm²). When the thickness under no-load conditions is defined as a thickness T0 (mm) and the thickness under a load of 9.8mN/cm ²(1gf/cm² is defined as a thickness Tm (mm), the compression set (mm) can be calculated as "T0-Tm" obtained by subtracting the thickness Tm from the thickness T0.

When the 2 nd member is an absorbent sheet, the total weight per unit area is preferably 40g/m ² or more, more preferably 60g/m ² or more, still more preferably 70g/m ² or more, and further preferably 500g/m ² or less, more preferably 400g/m ² or less, still more preferably 300g/m ² or less.

When the 2 nd member is an absorbent, the total weight per unit area is preferably 30g/m ² or more, more preferably 40g/m ² or more, still more preferably 50g/m ² or more, still more preferably 600g/m ² or less, still more preferably 550g/m ² or less, still more preferably 500g/m ² or less.

The above description is about the sanitary nonwoven fabric of the present invention and the sanitary article (including absorbent article) provided with the sanitary nonwoven fabric, and a preferred method for producing the sanitary nonwoven fabric of the present invention will be described below. The production method includes a step (hot air step) of subjecting a web of fibers, at least a part of the surface of which includes a polyethylene resin, to hot air treatment to obtain a fiber assembly.

In addition to this, a step of subjecting the obtained fiber aggregate to densification (densification step) is preferably employed.

It is also preferable that the thermal conductivity of the fiber used in the present production method is within the above-described range.

First, a web of fibers, at least a portion of which includes polyethylene resin, is formed. The web may be formed, for example, by carding using a known carding machine.

Then, a hot air treatment of blowing hot air to the web was performed to obtain an aggregate of fibers having at least a part of the surface containing a polyethylene resin. The present step is a step of nonwoven the web of fibers, and the fiber aggregate produced in this manner is generally called a hot air nonwoven fabric.

In general, when a web containing a polyethylene resin is subjected to hot air processing, core-sheath fibers in which a polyethylene resin is used as a sheath and a high-melting resin other than the polyethylene resin is used as a core are mainly used from the viewpoint of production efficiency, and it is extremely difficult to nonwoven fibers containing only the polyethylene resin by the hot air processing. In addition, the use of the core-sheath fiber is advantageous in improving the texture and strength of the obtained hot air nonwoven fabric, but there is room for improvement in improving the thermal conductivity so as to give the user a cool feeling.

As a result of diligent studies on these improvements, the inventors have found that by controlling the temperature and the wind speed of hot air in the hot air process, a hot air nonwoven fabric having a good texture and strength can be efficiently produced even when fibers containing only a polyethylene resin are used.

The temperature and the wind speed of the hot air blown to the web in the hot air process are preferably within a specific range. Specifically, from the viewpoint of improving the texture of the obtained nonwoven fabric for hygiene, the temperature of the hot air blown to the web may be preferably in the range of the melting point m+4 ℃ or less, more preferably in the range of the melting point m+3 ℃ or less, and still more preferably in the range of the melting point m+2 ℃ or less, in terms of the relationship with the melting point M (°c) of the resin contained on the fiber surface constituting the web.

In addition, from the viewpoint of appropriately fusing fibers constituting the web to each other so that the nonwoven fabric for hygiene exhibits a durable strength, the temperature of the hot air blown to the web may be preferably in the range of the melting point M-4 ℃ or higher, more preferably in the range of the melting point M-2 ℃ or higher, and still more preferably in the range of the melting point M or higher.

The temperature of the hot air is the temperature of the hot air at the air outlet. The temperature can be measured, for example, by attaching a thermocouple to the air outlet or to a position near the air outlet.

For example, when fibers containing HDPE (melting point M:130 ℃) on the surface thereof are used as the fibers constituting the web, the temperature of the hot air may be preferably 126 ℃ or higher, more preferably 128 ℃ or higher, and still more preferably 130 ℃ or higher.

The temperature of the hot air under the above conditions may be preferably 134 ℃ or less, more preferably 133 ℃ or less, and still more preferably 132 ℃ or less.

The melting point M of the resin constituting the fiber surface can be measured by using a differential scanning calorimeter (DSC 7000X 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 temperature rise rate of 10 ℃. The melting point is defined as the melting peak temperature at the first temperature rise. In the case where a clear melting point cannot be measured by this method, the resin is defined as "a resin having no melting point". In the case of a resin having no melting point, the softening point is set to the melting point M.

In the hot air step, the wind speed of the hot air blown to the web is preferably 0.6 m/sec or more, more preferably 1 m/sec or more, from the viewpoint of allowing the hot air to pass through sufficiently in the thickness direction of the web and easily fusing the fibers to each other.

From the same viewpoint, the wind speed of the hot air blown onto the web is preferably 2 m/sec or less, and more preferably 1.4 m/sec or less.

By performing the hot air process under the conditions of the above temperature and air velocity, the polyethylene resin present on the surface of the fibers constituting the fiber web is melted or softened, and the sites where the fibers are fused to each other are randomly formed, so that the produced nonwoven fabric for hygiene exhibits softness and good texture due to the hot air nonwoven fabric, and exhibits durable strength.

The transport speed of the web in the hot air step is preferably 3m/min or more, more preferably 10m/min or more, and is preferably 200m/min or less, more preferably 160m/min or less, in the above-described temperature and wind speed range.

The fiber aggregate obtained through the above steps is already nonwoven, and thus can be used as it is as a sanitary nonwoven fabric of the present invention. The sanitary non-woven fabric is hot air non-woven fabric.

From the viewpoint of easy availability of a sanitary nonwoven fabric having a predetermined bulk filling ratio, it is preferable to further carry out a densification treatment (densification step) on the fiber aggregate obtained through the above steps. The densification treatment in this step may be performed by a method in which the fiber aggregate is pressurized and compressed in the thickness direction.

The densification treatment may be performed, for example, by a method in which the fiber aggregate is placed between two metal plates and pressurized (hereinafter, this method is also referred to as a "pressing method"), or a method in which the fiber aggregate is introduced between a pair of rolls and pressurized (hereinafter, this method is also referred to as a "calendering method").

The densification may be performed only once, or may be performed a plurality of times by the same or different methods as needed. The temperature in the compacting treatment may be room temperature, a heated state, or a combination of these.

The conditions of the densification process are preferably pressurized in a heated state. In detail, from the viewpoint of sufficiently densifying the fiber aggregate to easily obtain a nonwoven fabric for hygiene having a high volume filling ratio, in the case of using the pressing method, the pressurizing condition in the densification treatment is expressed as a surface pressure, preferably 5MPa or more, and more preferably 10MPa or more.

In addition, from the viewpoint of keeping the fiber shape in which the boundaries between the constituent fibers are clear and making the texture of the obtained nonwoven fabric for hygiene good without forming the fiber aggregate into a film, in the case of using the pressing method, the pressing condition in the pressing treatment is expressed in terms of the surface pressure, and may be preferably 72MPa or less, and more preferably 32MPa or less.

In addition, from the viewpoint of sufficiently densifying the fiber aggregate to easily obtain a nonwoven fabric for hygiene having a high volume filling ratio, the pressurizing condition in the case of using a calendaring method is preferably 78.4N/cm (8 kgf/cm) or more, more preferably 127.4N/cm (13 kgf/cm) or more, as indicated by line pressure.

In addition, from the viewpoint of keeping the fiber shape in which the boundary between the constituent fibers is clear without forming the fiber aggregate into a film and making the texture of the obtained nonwoven fabric for hygiene good, the pressing condition at the time of calendering is preferably 686N/cm (70 kgf/cm) or less, more preferably 294N/cm (30 kgf/cm) or less, as indicated by line pressure.

In addition, from the viewpoint of sufficiently densifying the fiber aggregate to easily obtain a nonwoven fabric for hygiene having a high volume filling ratio, in both the pressing method and the calendering method, the heating temperature in the densification treatment is preferably 70 ℃ or higher, more preferably 80 ℃ or higher.

In the case of both the pressing method and the calendering method, the heating temperature in the compacting treatment may be preferably 120 ℃ or less, and more preferably 110 ℃ or less, from the viewpoint of keeping the fiber shape in which the boundaries between the constituent fibers are clear without forming the fiber aggregate into a film and improving the texture of the obtained nonwoven fabric for hygiene.

In the case of heating in the compacting treatment, the metal flat plate may be heated to the above temperature range in the pressing method, and the peripheral surface of the roll may be heated to the above temperature range in the calendaring method.

The pressing time in the densification treatment may be appropriately set as long as the conditions are such that the fiber shape of the fibers constituting the fiber aggregate can be maintained and densification can be performed.

For example, in the case of using the pressing method, the pressing time under the above pressure and temperature conditions may be preferably 5 seconds or more, and more preferably 10 seconds or more in each press-densification treatment.

In the case of using the pressing method, the pressing time under the above pressure and temperature conditions may be preferably 25 seconds or less, and more preferably 20 seconds or less in each press-densification treatment.

For example, in the case of using the calendaring method, the pressing time under the above pressure and temperature conditions may be preferably 0.01 seconds or more, and more preferably 0.04 seconds or more in each densification treatment.

In the case of using the calendaring method, the pressing time under the pressure and temperature conditions may be preferably 0.1 seconds or less, and more preferably 0.08 seconds or less in each densification treatment.

By performing the densification treatment under the above conditions, the fiber aggregate can be compressed in the thickness direction, and thus a nonwoven fabric for hygiene having a predetermined bulk filling ratio can be easily obtained.

In particular, in the above pressure and temperature ranges, the constituent resin of the fibers is not easily melted, and the form stability and dimensional stability due to the heat treatment can be improved, so that a nonwoven fabric for hygiene which maintains a predetermined volume filling ratio even after production can be obtained.

In addition, when a fiber having a perfectly circular cross-sectional shape is used, the cross-sectional shape of the fiber can be flattened by the densification treatment, and thus there is an advantage that the volume filling rate can be improved.

The sanitary nonwoven fabric obtained by the above method is a hot air nonwoven fabric even when subjected to a densification treatment.

The nonwoven fabric for hygiene of the present invention may be produced by a method based on a spunbond method instead of the above-described production method. The hygiene nonwoven produced in this way is a spunbond nonwoven.

Specifically, a raw material resin of fibers is extruded in a molten state from a spinneret having a plurality of fine holes, and the extruded resin is stretched by a roll or the like to form long fibers, and the long fibers are accumulated on a mesh conveyor belt to obtain a web of fibers having at least a part of the surface including a polyethylene resin. Thereafter, the web was introduced between embossing rolls, and densification (thermocompression bonding) was performed by heating and pressing, thereby obtaining the nonwoven fabric for hygiene of the present invention. That is, the method is to simultaneously perform the nonwoven fabric formation and densification treatment of the web. The temperature and the pressurizing conditions of the embossing roller may be set in the same ranges as those of the above-described densification treatment.

In the case of producing a nonwoven fabric having a multilayer structure, for example, a nonwoven fabric having a laminate of a2 nd web including a thermoplastic resin formed by a carding process is laminated on a web at least a part of which includes a polyethylene resin on the surface, and a web laminate is produced. Then, the laminate is subjected to a hot air treatment, whereby a hot air nonwoven fabric which is a fiber aggregate of a multilayer structure can be obtained. In this case, regarding the temperature of the blown hot air, it is preferable to determine the temperature of the hot air by setting the melting point of the resin having the lowest melting point as the melting point M.

As another method for producing a nonwoven fabric for hygiene having a multilayer structure, a method is available in which a fiber web containing a polyethylene resin and a fiber web containing a thermoplastic resin at least in part of the surface are subjected to a hot air treatment to obtain fiber sheets, respectively, and then the fiber sheets are bonded via an adhesive.

The fiber aggregate obtained through the above steps can be directly used as the sanitary nonwoven fabric of the present invention. In addition, the densification step may be performed under the above-described conditions.

Instead, the target nonwoven fabric can also be produced by a method based on a spunbond process. As a production method, for example, the 2 nd web may be laminated on a web at least a part of which includes a polyethylene resin, and in this state, densification (thermocompression bonding) may be performed by heating and pressing. The hygiene nonwoven produced in this way is a spunbond nonwoven.

Through the above steps, the sanitary nonwoven fabric of the present invention can be obtained. The sanitary nonwoven fabric is preferably incorporated as a constituent member of a sanitary article such as an absorbent article in a subsequent step.

In the case where the nonwoven fabric for hygiene is used as a constituent material of a sanitary article such as an absorbent article, any one of the steps of producing a sanitary article such as a target absorbent article may include at least one of the steps of using the nonwoven fabric for hygiene produced by the above method as one of the constituent materials and cutting the nonwoven fabric for hygiene, and the step of performing various operations such as laminating or bonding the nonwoven fabric for hygiene with other constituent materials (for example, an absorber, a sheet, and the like) constituting the sanitary article.

In the case of manufacturing the sanitary article including the 2 nd member, for example, after separately manufacturing the sanitary nonwoven fabric, the sanitary nonwoven fabric as the 1 st fiber aggregate may be laminated or joined to the absorbent body or the absorbent sheet as the 2 nd member in an adjacent state at any stage of the manufacturing process of the sanitary article. In this case, the sanitary nonwoven fabric may be disposed so as to form a surface facing the skin of the wearer when the sanitary article is worn, or may be disposed on a surface side not facing the skin of the wearer when the sanitary article is worn.

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

The embodiments of the present invention described above also disclose the following nonwoven fabric for hygiene, an absorbent article provided with the same, and a method for producing the nonwoven fabric for hygiene.

<1>

A nonwoven fabric for hygiene, comprising fibers having at least a part of the surface thereof comprising a polyethylene resin, and

The volume filling rate is 3.5% or more, more preferably 7% or more, still more preferably 10% or more, and still more preferably 14% or more.

<2>

A nonwoven fabric for hygiene, which comprises fibers having a thermal conductivity of 0.11W/mK or more, more preferably 0.13W/mK or more, still more preferably 0.15W/mK or more, on at least a part of the surface thereof, and

The volume filling ratio is 3.5% or more, more preferably 7% or more, and still more preferably 14% or more.

<3>

The nonwoven fabric for hygiene according to item <1> or <2>, wherein the volume filling ratio is 60% or less, preferably 50% or less, more preferably 30% or less.

<4>

The nonwoven fabric for hygiene according to any one of the above items <1> to <3>, wherein the fibers are (i) bicomponent composite fibers each comprising a polyethylene resin on the outer surface and the inner portion of the fibers, or (ii) low-melting-point components comprising a polyethylene resin and high-melting-point components each comprising a high-melting-point low-melting-point component, and the low-melting-point components are continuously present on at least a part of the surfaces of the fibers in the longitudinal direction.

<5>

The nonwoven fabric for hygiene according to any one of the above items <1> to <4>, wherein the content of the polyethylene resin is 70 mass% or more and 100 mass% or less, preferably 80 mass% or more, more preferably 90 mass% or more, and even more preferably 100 mass% relative to the total mass of the resin contained in the nonwoven fabric for hygiene.

<6>

The nonwoven fabric for hygiene according to any one of the above items <1> to <5>, wherein the resin constituting the fibers is only a polyethylene resin.

<7>

The nonwoven fabric for hygiene according to any one of the above items <1> to <6>, wherein the fibers have a cross-sectional shape having a major axis and a minor axis, and

The ratio of the major axis length to the minor axis length (major axis length/minor axis length) is 1.5 to 10.

<8>

The nonwoven fabric for hygiene according to any one of the above items <1> to <7>, wherein the fibers are in multi-point contact with each other in a cross-sectional view.

<9>

The nonwoven fabric for hygiene according to any one of <1> to <8>, which has a thickness of 0.1mm or more and 3mm or less under a load of 4.9mN/cm ².

<10>

The nonwoven fabric for hygiene according to any one of <1> to <9>, wherein the nonwoven fabric has a thickness of 0.3mm or more and 0.5mm or less under a load of 4.9mN/cm ².

<11>

The nonwoven fabric for hygiene according to any one of the above items <1> to <10>, wherein the weight per unit area is 15g/m ² or more and 140g/m ² or less.

<12>

The nonwoven fabric for hygiene according to any one of the above items <1> to <11>, wherein the weight per unit area is 25g/m ² or more and 50g/m ² or less.

<13>

The nonwoven fabric for hygiene according to any one of the above items <1> to <12>, wherein the polyethylene resin comprises a high-density polyethylene resin, preferably only a high-density polyethylene resin.

<14>

The nonwoven fabric for hygiene according to any one of the above items <1> to <13>, wherein the fibers have a fiber diameter of 3 μm or more, preferably 5 μm or more.

<15>

The nonwoven fabric for hygiene according to any one of the above items <1> to <14>, wherein the fibers have a fiber diameter of 70 μm or less, preferably 50 μm or less.

<16>

The nonwoven fabric for hygiene according to any one of the above items <1> to <15>, which is a hot air nonwoven fabric.

<17>

A sanitary article comprising the nonwoven fabric for sanitary use according to any one of the above items <1> to <16 >.

<18>

The sanitary article according to item <17>, wherein the sanitary nonwoven fabric forms a surface of the sanitary article facing the skin of the user.

<19>

The sanitary article according to the above <17> or <18>, which is an absorbent article.

<20>

The sanitary article according to any one of <17> to <19>, wherein the sanitary nonwoven fabric is disposed on an outer surface of the sanitary article.

<21>

The nonwoven fabric for hygiene or sanitary article according to any one of <1> to <20>, which is disposable.

<22>

A method for producing a nonwoven fabric for hygiene, comprising subjecting a web of fibers having at least a part of the surface thereof comprising a polyethylene resin to a hot air treatment to obtain a fiber aggregate,

The fiber aggregate is subjected to densification treatment.

<23>

The method for producing a nonwoven fabric for hygiene according to item <22>, wherein the densification treatment is performed under a surface pressure of 5MPa or more, preferably 10MPa or more, or under a line pressure of 78.4N/cm (8 kgf/cm) or more, preferably 127.4N/cm (13 kgf/cm) or more, and

At a temperature of 70 ℃ to 120 ℃.

<24>

The method for producing a nonwoven fabric for hygiene according to item <22> or <23>, wherein the densification treatment is performed at a surface pressure of 30MPa or less, preferably 20MPa or less, or at a line pressure of 686N/cm (70 kgf/cm) or less, preferably 294N/cm (30 kgf/cm) or less.

<25>

The method for producing a nonwoven fabric for hygiene according to any one of the above items <22> to <24>, wherein the densification treatment is performed at a temperature of 80 ℃ to 110 ℃.

<26>

The method for producing a nonwoven fabric for hygiene according to any one of <22> to <25>, wherein the hot air treatment is performed by blowing hot air having a temperature of at least-4 ℃ and at most +4 ℃ of the melting point of the resin constituting the fiber surface onto the web at a wind speed of at least 0.6 m/sec and at most 2 m/sec.

<27>

The method for producing a nonwoven fabric for hygiene according to any one of the above items <22> to <26>, wherein the heat treatment is more preferably performed by blowing a heat blast having a temperature of from-2 ℃ to +2 ℃ of the melting point of the resin constituting the fiber surface to the web.

<28>

The method for producing a nonwoven fabric for hygiene according to any one of <22> to <27>, wherein the surface of the fiber comprises a high-density polyethylene resin,

The high-density polyethylene resin has a melting point of 130 DEG C

The heat treatment is performed by blowing heat having a temperature of 126 ℃ or higher, preferably 128 ℃ or higher, and more preferably 130 ℃ or higher onto the web.

<29>

The method for producing a nonwoven fabric for hygiene according to any one of <22> to <28>, wherein the surface of the fiber comprises a high-density polyethylene resin,

The high-density polyethylene resin has a melting point of 130 DEG C

The heat treatment is performed by blowing heat having a temperature of 134 ℃ or less, preferably 133 ℃ or less, more preferably 132 ℃ or less onto the web.

<30>

The method for producing a nonwoven fabric for hygiene according to any one of <22> to <29>, wherein the heat treatment is performed by blowing the heat at a wind speed of 1 m/sec to 1.4 m/sec.

<31>

A method for producing a sanitary article, comprising at least one of the steps of using the sanitary nonwoven fabric produced by the method for producing a sanitary nonwoven fabric according to any one of the above <22> to <30> as one of constituent materials and cutting the sanitary nonwoven fabric, and laminating or bonding the sanitary nonwoven fabric with another constituent material constituting the sanitary article.

<32>

The nonwoven fabric for hygiene according to any one of <1> to <16>, wherein the contact cooling sensation q _max is 0.06W/m ² or more.

<33>

The nonwoven fabric for hygiene according to any one of <1> to <16> and <32>, wherein the proportion of constituent fibers on the surface of the nonwoven fabric for hygiene is 40% or more by area.

<34>

The nonwoven fabric for hygiene according to any one of <1> to <16>, <32> and <33>, wherein the volume filling ratio is 10.0% or more.

<35>

A sanitary article comprising the sanitary nonwoven fabric according to any one of <1> to <16>, and <32> to <34>, and a2 nd member disposed adjacent to the nonwoven fabric, wherein the sanitary nonwoven fabric is a nonwoven fabric for sanitary use

The compression set of the 2 nd member under a load of 9.8mN/cm ²(1gf/cm²) is 0.3mm or more.

<36>

The sanitary article according to <35> above, wherein the 2 nd member is a fiber aggregate different from the sanitary nonwoven fabric.

<37>

The sanitary article according to <36> above, wherein the 2 nd member is an absorber.

<38>

A method for producing a nonwoven fabric for hygiene according to any one of the above <1> to <16>, and <32> to <34>, wherein the nonwoven fabric for hygiene is produced by the method

Subjecting a web of fibers having at least a part of the surface thereof comprising a polyethylene resin to a hot air treatment to obtain a fiber aggregate, and then,

The fiber aggregate is subjected to densification treatment.

Examples

Hereinafter, the present invention will be described in more detail with reference to examples. The scope of the invention is not limited to this embodiment.

Examples 1 to 5

A fiber comprising a single resin HDPE and having a flat and multilobal cross-sectional shape having a long axis and a short axis (hereinafter, this shape is also referred to as "flat profile" as shown in the table) is used. The ratio of the major axis length, the minor axis length, and the major axis length to the minor axis length in the fiber cross section (this ratio is also referred to as "major axis/minor axis ratio" in the table) is shown in table 1 below.

First, a web of the fibers whose weight per unit area was adjusted as shown in table 1 below was subjected to a hot air treatment to obtain a nonwoven fabric-like fiber aggregate. The conditions of the hot air treatment are shown in table 1 below. Then, the fiber aggregate was densified by a compression method under the heating and pressurizing conditions shown in table 1 below, to obtain a nonwoven fabric for target hygiene. The obtained nonwoven fabrics are all single layers.

Examples 6 to 8

A nonwoven fabric for target hygiene was obtained in the same manner as in examples 1 to 5, except that the weight per unit area was adjusted as shown in table 1 below, and densification was performed by a calendaring method under the heating and pressurizing conditions shown in table 1 below. The obtained nonwoven fabrics are all single layers.

Example 9

A core-sheath fiber (hereinafter, also referred to as PET/HDPE fiber) in which the core is PET, the sheath (fiber surface) is HDPE, and the cross-sectional shape is a perfect circle is used. The polyethylene resin content of the fiber was 50 mass%. The web containing the fibers was subjected to a hot air treatment and a densification treatment under the same conditions as in example 1 to obtain a nonwoven fabric for target hygiene. The nonwoven fabric obtained was a single layer.

Example 10

Fibers comprising a single resin HDPE and having a right circular cross-sectional shape are used. A web of the above fibers whose weight per unit area was adjusted as shown in table 1 below was produced by the spunbond method, and the web was subjected to densification treatment by an embossing roll to obtain a nonwoven fabric for hygiene composed of the spunbond nonwoven fabric. The conditions of the spunbond process are shown in table 1 below. The nonwoven fabric obtained was a single layer.

Example 11

A nonwoven fabric for hygiene was obtained in the same manner as in example 1, except that the densification treatment was not performed.

Examples 12 to 14

A core-sheath fiber (hereinafter, also referred to as PP/HDPE fiber) having a PP core, HDPE sheath (fiber surface) and a right circular cross-sectional shape is used. The polyethylene resin content of the fiber was 50 mass%. A web of the fibers whose basis weights were adjusted as shown in table 1 below was formed, and the web was subjected to a hot air treatment and a densification treatment under the same conditions as in example 1 to obtain a nonwoven fabric for target hygiene. The obtained nonwoven fabrics are all single layers.

Comparative example 1

A web of the same core-sheath fiber as in example 9 was formed, and the web was subjected to a hot air treatment under the conditions shown in table 1 below to obtain a nonwoven fabric for hygiene. In this comparative example, the densification treatment was not performed.

Comparative example 2

A web of the same core-sheath fiber as in example 12 was formed, and the web was subjected to a hot air treatment under the conditions shown in table 1 below to obtain a nonwoven fabric for hygiene. In this comparative example, the densification treatment was not performed.

Comparative example 3

A web of the same core-sheath fiber as in example 12 was formed, and was subjected to a hot air treatment under the conditions shown in table 1 below, and thereafter, a densification treatment was performed by a calendering method under the conditions shown in table 1 below without heating, to obtain a nonwoven fabric for target hygiene.

[ Measurement of thickness of nonwoven fabric for sanitary purposes ]

The thickness of the sanitary nonwoven fabrics of examples and comparative examples was measured. In the measurement of the thickness, 5 or more portions of the nonwoven fabric for hygiene to be measured were measured with a laser displacement meter under a load of 4.9mN/cm ², and the arithmetic average of the obtained measured values was set as the thickness (mm). The results are shown in Table 1.

[ Measurement of thermal conductivity of nonwoven Fabric ]

The thermal conductivity of the nonwoven fabrics for hygiene of examples and comparative examples was measured as follows.

(1. Sample preparation)

The nonwoven fabric for sanitary use, which was the object of measurement, was cut into small pieces, and a laminate of about 10g, which was formed by stacking a plurality of pieces, was held between 2 pieces of SUS plates and was placed in the center of the SUS plates, and heated under no pressure for 1 minute to obtain a fused product. The heating temperature is the melting point m+20 ℃ measured by the differential scanning calorimeter, and in the case of a nonwoven fabric comprising a plurality of resin materials, heating is performed based on the melting point of the resin having the highest melting point. Specifically, the nonwoven fabric containing the pure HDPE fibers was heated at 50 ℃, the nonwoven fabric containing the PP/HDPE fibers was heated at 180 ℃, and the nonwoven fabric containing the PET/HDPE fibers was heated at 300 ℃.

Then, while maintaining the above heating temperature, a gauge pressure of 200kgf (total mass: 21848kg including top plate; in the case of calculating the pressure by face pressure, since the area of the alloy varies with melting of the resin, the face pressure is calculated based on the area of the finally obtained round resin plate, for example, in the case of a round resin plate having a diameter of 15cm, the face pressure is 12 MPa) is applied to the obtained alloy, and after maintaining the pressure for 1 minute, the pressure is maintained in a pressurized state and cooled to 20 ℃ to obtain a round resin plate having a diameter of about 15 to 20cm (there is a possibility that the diameter of the obtained round resin plate varies depending on the melt viscosity of the resin).

Then, the obtained circular resin plate is cut in a radial line passing through the center, and if the maximum diameter length is 5cm or more, the circular resin plate is further cut into 5cm or less. Then, after the cut resin plates were overlapped in the center of the SUS plate so that the extending direction of the virtual line segment of the maximum diameter length was random and the influence of the resin orientation was eliminated, 2 shims of 1mm in thickness were arranged in parallel at a position 10cm from the center of the SUS plate, and the SUS plate was overlapped thereon. Thereafter, heating under no-pressure conditions, and heating and cooling under pressure conditions were performed by the same operations as described above. If a bubble is introduced, the same operation is repeated. The purpose of the 2-time heating and melting is to make the thermal history constant in order to temporarily melt the sample and to eliminate the influence of crystallization of the resin which changes during the fiber spinning process. Thus, a film was obtained.

(2. Measurement of thermal conductivity)

The thermal conductivity was measured by the following method using a measuring apparatus (KES-F7 Thermo Lab II manufactured by Kagaku Co., ltd.).

First, a round shape of 17cm in diameter was cut out from the film to be produced, and left to stand at room temperature of 23℃under a relative humidity of 50% for 24 hours. Then, the thermal conductivity of the measurement object is measured by the above-mentioned measuring apparatus in accordance with the measurement guideline of the apparatus. Specifically, the temperature of the heat source body for measurement (BT-BOX, formed by integrating an aluminum plate having a thickness of 1mm and a heater in a longitudinal direction of 5cm×a lateral direction of 5 cm) was set to 33 ℃. In a display panel of the measuring instrument, a point at which the heat flow rate from the heat source body to the measuring object becomes constant is set as a measurement start point, and the average heat flow rate within 60 seconds from the point is measured. Based on the measurement conditions and the heat flow rate obtained by the measurement, the calculation was performed based on the following formula (I). The film thickness D is an arithmetic average of thicknesses obtained by measuring 3 or more points under no load by a laser shifter. The above measurement was performed 3 times for each measurement object, and the maximum value among the obtained measurement values was set as the thermal conductivity (W/mK) of the sample. The results are shown in Table 1.

As reference examples, the thickness D and the thermal conductivity of the film produced by the above method using only PET and the film produced by the above method using only PP were measured, respectively. The results are shown in Table 2 together with the results of examples and comparative examples.

k=100×(W×D)/(A×ΔT)...(I)

(K: thermal conductivity [ W/mK ], W: heat flow [ W/m ² ], D: film thickness [ cm ], A: aluminum plate area (25 cm ²), deltaT: temperature difference (10 ℃ C.) between the heat source body and the film)

[ Measurement of volume filling Rate ]

The volume filling ratio (%) of the sanitary nonwoven fabrics of examples and comparative examples was calculated by the above method. The results are shown in Table 1.

[ Measurement of touch Cool feeling q _max ]

The heat stored in the hot plate is immediately transferred to the measuring object on the low temperature side after the contact, and the maximum value of the heat flow rate is the contact cooling sensation q _max.

The measurement of the cooling sensation of contact q _max was performed by the following method using a measuring apparatus (KES-F7 Thermo Lab II manufactured by Kagaku Co., ltd.).

First, a test piece was cut out of a nonwoven fabric for hygiene to be measured in a length of 10cm by a width of 10cm, and the test piece was left to stand at room temperature of 23 ℃ in an environment having a relative humidity of 50% for 24 hours.

Then, in this environment, the test piece was placed on the measurement stand, and the test piece was fixed to the measurement stand using a double-sided tape. A constant temperature apparatus using a gas or a liquid as a heat medium is used as a measurement table.

Then, the contact cooling sensation q _max of the measurement object was measured by the above-mentioned measuring apparatus in accordance with the measurement guideline of the apparatus. Specifically, a pure copper plate having an area of 9.0cm ² and a mass of 9.8g was used as a hot plate in contact with the measurement object, the initial temperature of the copper plate was set to 33 ℃ (a temperature higher than the surface temperature of the measurement object by 10 ℃), the contact pressure between the copper plate and the measurement object was set to 1kPa, the copper plate was in contact with the test piece, the value of the heat flow at the moment of contact was set to zero, and the maximum value of the heat flow was measured. This measurement was performed 5 times for each measurement target surface, and the arithmetic average of the obtained plurality of measurement values was set as the contact cooling sensation q _max(W/m² of the measurement target surface).

The larger the value of the contact cooling sensation q _max, the faster the heat transfer, and the more easily the user can feel the cooling sensation. The results are shown in table 1 below.

TABLE 1

TABLE 2

As shown in tables 1 and 2, it is understood that the nonwoven fabrics for hygiene of each example had higher thermal conductivity and volume filling ratio than those of the comparative examples, and also had higher contact cooling sensation q _max.

In particular, as is clear from examples 1 to 8, the effect is remarkable by using the flat profiled fiber.

Therefore, the sanitary nonwoven fabric of the present invention can feel cool when contacting with the skin of a user, thereby providing a comfortable feeling of use.

Examples 15 and 16

The hot air nonwoven fabric containing the single resin HDPE used in example 2 was set as the 1 st fiber layer, and the single layer hot air nonwoven fabric containing PET/HDPE fibers whose basis weight was adjusted as shown in table 3 below was set as the 2 nd fiber layer. These fiber layers were laminated and bonded by an adhesive to obtain a nonwoven fabric for hygiene comprising a fiber sheet having a plurality of fiber layers (2 layers). The 1 st fiber layer in this example had the same structure as that of the sanitary nonwoven fabric in example 2.

Examples 17 to 21

The hot air nonwoven fabric containing the single resin HDPE used in example 4 was set as the 1 st fiber layer, and the single layer hot air nonwoven fabric containing PET/HDPE fibers whose basis weight was adjusted as shown in table 3 below was set as the 2 nd fiber layer. These fiber layers were laminated and bonded by an adhesive to obtain a nonwoven fabric for hygiene comprising a fiber sheet having a plurality of fiber layers (2 layers). The structure of the 1 st fiber layer in this example was the same as that of the sanitary nonwoven fabric in example 4.

Example 22

The hot air nonwoven fabric containing the single resin HDPE used in example 10 was set as the 1 st fiber layer, and the single layer hot air nonwoven fabric containing PET/HDPE fibers whose basis weight was adjusted as shown in table 3 below was set as the 2 nd fiber layer. These fiber layers were laminated and bonded by an adhesive to obtain a nonwoven fabric for hygiene comprising a fiber sheet having a plurality of fiber layers (2 layers). The 1 st fiber layer in this example had the same structure as that of the sanitary nonwoven fabric in example 10.

[ Measurement of volume filling Rate ]

The volume filling rate (%) of the nonwoven fabric for hygiene of the example was calculated in the same manner as described above. The results are shown in table 3 below. In table 3, the results of the sanitary nonwoven fabrics of examples 2, 4 and 10 are disclosed again.

[ Measurement of touch Cool feeling q _max ]

The contact cooling sensation q _max of the nonwoven fabric for hygiene of the example was measured in the same manner as described above. For examples 15 to 22, the measurement was performed with respect to the surface on the side where the 1 st fiber layer was disposed. The results are shown in Table 3.

[ Functional evaluation of Cool feeling ]

The cooling sensation felt when the surfaces were contacted was evaluated by 20 professional functional inspectors in contact with the 1 st fiber layer side surfaces of the sanitary nonwoven fabrics of examples 2, 4, and 10 and the sanitary nonwoven fabrics of examples 15 to 22, respectively, as follows. The nonwoven fabrics for sanitary use used for evaluation were placed in an environment of 23 ℃ and brought into a state of isothermal with the ambient temperature. The higher the arithmetic average value of the evaluation score, the more effective the feeling of cooling of the nonwoven fabric for hygiene was. The results are shown in table 3 below.

5 Minutes, the fiber sheet having q _max of 0.15 or more strongly felt cool feeling, and the cool feeling was very excellent.

4 Minutes, the cool feeling can be well felt.

3 Minutes, the cool feeling can be felt.

2 Minutes, almost no cool feeling is felt.

1 Min, the cool feeling is completely not felt to the same extent as that of the hot air non-woven fabric with q _max smaller than 0.06.

TABLE 3

As shown in table 3, the sanitary nonwoven fabrics of the respective examples were high in both the volume filling ratio and the contact cooling sensation q _max, and were excellent in cooling sensation.

The fiber surface presence (%) of the nonwoven fabrics for hygiene of example 9 and comparative example 1 was calculated by the above method.

As a result, the fiber surface existing rate of example 9 was 58%, and the fiber surface existing rate of comparative example 1 was 36%. Therefore, the fiber surface existing rate in example 9 is higher than that in comparative example 1, and the contact property of the fiber with respect to the contact object can be further improved. As a result, the user can feel excellent cool feeling.

Industrial applicability

The present invention provides a sanitary nonwoven fabric which gives a comfortable feeling of use by feeling cool when in contact with skin, and a sanitary article and an absorbent article each comprising the same.

Claims (16)

1. An absorbent article comprising a sanitary nonwoven fabric,

The sanitary nonwoven fabric comprises fibers having at least a part of the surface comprising a polyethylene resin and having a thermal conductivity of 0.11W/mK or more,

The volume filling rate of the non-woven fabric for sanitation is more than 14.0 percent,

The fiber diameter of the fiber used in the sanitary nonwoven fabric is 5 μm or more and 50 μm or less,

The thickness of the sanitary nonwoven fabric under a load of 4.9 mN/cm ² is 0.2 to mm and 0.5 to mm,

The weight per unit area of the nonwoven fabric for hygiene is 25 g/m ² or more and 90 g/m ² or less,

The contact cool feeling q _max of the non-woven fabric for sanitation is more than 0.22W/m ²,

The non-woven fabric for sanitation is hot air non-woven fabric,

The sanitary nonwoven fabric is used as a front sheet, a side nonwoven fabric, a waist gather, a gather disposed in the vicinity of a groin portion, or a constituent member of an outer package.

2. The absorbent article of claim 1, wherein the cross-sectional shape of the fibers has a major axis and a minor axis, an

The ratio of the major axis length to the minor axis length is 1.5 to 10.

3. The absorbent article of claim 1 or 2, wherein the fibers are in multipoint contact with each other in cross-sectional view.

4. The absorbent article according to claim 1 or 2, wherein the proportion of constituent fibers on the surface of the sanitary nonwoven fabric is 40% or more by area.

5. The absorbent article according to claim 1 or 2, wherein the fibers are fibers each comprising a polyethylene resin on the outer surface and the inside of the fibers, or

The fiber is a composite fiber containing a low-melting-point component including a polyethylene resin and a high-melting-point component having a higher melting point than the low-melting-point component, and the low-melting-point component is continuously present on at least a part of the surface of the fiber in the longitudinal direction.

6. The absorbent article according to claim 1 or 2, wherein the fibers comprise polyethylene resin, and

The content of the polyethylene resin is 70 mass% or more and 100 mass% or less with respect to the total mass of the fiber.

7. The absorbent article according to claim 1 or 2, wherein the fibers comprise only polyethylene resin.

8. The absorbent article of claim 1 or 2, wherein the fibers comprise a high density polyethylene resin.

9. The absorbent article according to claim 1 or 2, wherein the fibers comprise only high density polyethylene resin.

10. The absorbent article according to claim 1 or 2, further comprising a2 nd member disposed adjacent to the nonwoven fabric, and

The compression deformation of the 2 nd component under the load of 9.8 mN/cm ² is more than 0.3 mm.

11. The absorbent article according to claim 10, wherein the 2 nd member is a fiber aggregate different from the sanitary nonwoven fabric.

12. The absorbent article of claim 10, wherein the 2 nd member is an absorbent body.

13. The absorbent article according to claim 1 or 2, wherein the sanitary nonwoven is disposed on an outer surface.

14. A method for producing the absorbent article according to any one of claims 1 to 13, comprising the steps of:

subjecting a web of fibers having at least a part of the surface thereof comprising a polyethylene resin to a hot air treatment to obtain a fiber aggregate, and then,

The nonwoven fabric for hygiene is produced by subjecting the fiber aggregate to densification treatment.

15. The production method according to claim 14, wherein the densification treatment is performed at a surface pressure of 5 MPa or more or a line pressure of 78.4N/cm or more and at a temperature of 70 ℃ or more and 120 ℃ or less.

16. The production method according to claim 14 or 15, wherein the heat-air treatment is performed by blowing hot air having a temperature of not less than-4 ℃ and not more than +4 ℃ of the melting point of the resin constituting the fiber surface to the web at a wind speed of not less than 0.6 m/sec and not more than 2 m/sec.