JP6898056B2 - Liquid-absorbent non-woven fabric sheet - Google Patents

Description

The present invention relates to a liquid absorbing non-woven fabric sheet.

Conventionally, a non-woven fabric sheet has been used as a liquid-absorbent sheet for absorbing a liquid. For example, Japanese Patent Application Laid-Open No. 2006-239127 (Patent Document 1) discloses a diffusion sheet for an absorber in which a fine fineness layer and a large fineness layer are laminated, and Japanese Patent Application Laid-Open No. 2015-10846 (Patent Document 1). 2) discloses a bulky non-woven fabric as a liquid-absorbent sheet.

Japanese Unexamined Patent Publication No. 2006-239127 Japanese Unexamined Patent Publication No. 2015-10846

In the above technology, since the non-woven fabric sheet has a two-layer structure or a bulky structure in order to improve the liquid absorption property, it is difficult to achieve both thinness and improvement of the liquid absorption property. It is the actual situation. Therefore, there is a demand for a liquid-absorbent non-woven fabric sheet that has both thinness and improved liquid-absorbing property.

An object of the present invention is to provide a liquid-absorbent nonwoven fabric sheet that has both thinness and improved liquid-absorbing property.

The present invention provides the following liquid-absorbent nonwoven fabric sheets.
[1] A liquid-absorbent non-woven fabric sheet containing hydrophilic fibers, which has a thickness of 0.25 mm or more and 0.75 mm or less, and is provided with a plurality of through holes penetrating in the thickness direction. When the ratio of the through holes in the cross section in the thickness direction is A (%) and the overall apparent density of the liquid-absorbent non-woven fabric sheet is B (g / cm ³ ), A is 20% or more and 70. % Or less, and A and B are liquid-absorbent non-woven fabric sheets satisfying the relational expression of 0.12 ≦ {B × 100 / (100-A)} ≦ 0.26.

[2] The average opening area of the through holes is 0.25 mm ² or more 5.00 mm ² or less, the liquid-absorbent nonwoven sheet according to [1].

[3] above B is less 0.05 g / cm ³ or more 0.15 g / cm ^3, the liquid-absorbent nonwoven sheet according to [1] or [2].

[4] The liquid-absorbent nonwoven fabric according to any one of [1] to [3], wherein the rate of increase of the value C calculated from {B × 100 / (100-A)} with respect to B is 25% or more. Sheet.

[5] The liquid-absorbent nonwoven fabric sheet according to any one of [1] to [4], wherein the fineness of the fibers constituting the liquid-absorbent nonwoven fabric sheet is 1.0 dtex or more and 3.5 dtex or less.

[6] The liquid-absorbent non-woven fabric sheet according to any one of [1] to [5], wherein the content ratio of hydrophilic fibers contained in the fibers constituting the liquid-absorbent non-woven fabric sheet is 50% by weight or more.

[7] The liquid-absorbent nonwoven fabric sheet according to any one of [1] to [6], wherein the hydrophilic fiber is a cellulosic fiber.

According to the present invention, it is possible to provide a liquid-absorbent nonwoven fabric sheet that has both thinness and improved liquid-absorbing property.

It is a schematic sectional drawing which shows an example of the liquid-absorbing nonwoven fabric sheet which concerns on this invention. It is a schematic plan view which shows an example of the liquid-absorbing nonwoven fabric sheet which concerns on this invention. It is an optical micrograph of one cross section of the liquid-absorbing nonwoven fabric sheet according to Example 1.

Hereinafter, the present invention will be described in detail with reference to embodiments. In this specification, the notation in the form of "X to Y" means the upper and lower limits of the range (that is, X or more and Y or less), and there is no description of the unit in X, and the unit is described only in Y. If so, the unit of X and the unit of Y are the same.

The liquid-absorbent non-woven fabric sheet 10 (hereinafter, simply referred to as “sheet 10”) shown in FIGS. 1 and 2 is a sheet made of a liquid-absorbent non-woven fabric. A non-woven fabric is one in which fibers are three-dimensionally entangled by a dry method or a wet method, and liquid absorption means a property (performance) having a function of absorbing a liquid and a function of retaining a liquid. To do.

The sheet 10 of the present embodiment satisfies the following (1) to (4).
(1) Contains hydrophilic fibers;
(2) It has a thickness d of 0.25 to 0.75 mm;
(3) A plurality of through holes 1 penetrating in the thickness direction are provided, and the ratio A (%) of the through holes 1 in the cross section in the thickness direction is 20 to 70%;
(4) The ratio A and the overall apparent density B (g / cm ³ ) of the sheet 10 satisfy the relational expression of 0.12 ≦ {B × 100 / (100-A)} ≦ 0.26.

Regarding (1) above, examples of hydrophilic fibers include natural fibers, regenerated fibers, and synthetic fibers. As the hydrophilic fiber, only one kind may be used alone, or two or more kinds may be used in combination.

Examples of hydrophilic natural fibers include natural cellulose fibers such as cotton, hemp, wool and pulp. Examples of the hydrophilic regenerated fiber include regenerated cellulose fibers such as rayon and cupra. Examples of the hydrophilic synthetic fiber include a synthetic fiber composed of a hydrophilic functional group such as a hydroxyl group, a carboxyl group and a sulfonic acid group, and / or a thermoplastic resin having a hydrophilic bond such as an amide bond. A suitable example is given.

Among the above, particularly preferable fibers are rayon among regenerated cellulose fibers and polyamide-based resin among synthetic fibers. Suitable specific examples of rayon are viscose rayon, cuprammonium rayon, acetate rayon, and triacetate rayon, with viscose rayon being preferred. Suitable specific examples of the polyamide resin include aliphatic polyamides such as polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 612, polyamide 92, polyamide 9C (polyamide composed of nonanediamine and cyclohexanedicarboxylic acid). The copolymer is a semi-aromatic polyamide synthesized from an aromatic dicarboxylic acid such as polyamide 9T (polyamide composed of nonanediamine and terephthalic acid) and an aliphatic diamine, and a copolymer thereof.

Regarding (2) above, the thickness d of the sheet 10 is obtained as follows. First, using a razor ("Feather razor S single-edged", manufactured by Feather Safety Razor Co., Ltd.) so as to be parallel to the thickness direction of the sheet 10 and perpendicular to the machine direction (MD) direction. Cut any 10 places on the sheet 10. Then, the thickness d is obtained by observing each cross section with a digital microscope, measuring the thickness of each cross section, and calculating the average value of these.

Regarding (3) above, the ratio A is obtained as follows. First, a sheet using a razor ("Feather razor S single-edged", manufactured by Feather Safety Razor Co., Ltd.) so as to be parallel to the thickness direction of the sheet 10 and perpendicular to the MD direction of the sheet 10. Cut 10 arbitrary 10 places. Then, each cross section is observed with a digital microscope. As a result, an image as shown in FIG. 3 is obtained. Note that FIG. 3 shows an optical micrograph of a cross section of the liquid-absorbent nonwoven fabric sheet of Example 1 described later.

Then, in the cross section appearing in the image, the region where the fibers are not densely present is regarded as the region 11 occupied by the through hole 1, and the region where the fibers are densely present is regarded as the region 12 other than the through hole. However, cross sections without through holes are excluded. In addition, in FIG. 3, the fibers of the region 12 which are densely present are also scattered in the region of the through hole 1, but these are the fibers which are present in a portion deeper than the fibers observed in the region other than the through hole ( That is, it is a fiber existing in a portion other than the cross section), and the difference between the two can be easily distinguished in the image.

Here, the "region in which fibers are densely present" and the "region in which fibers are not densely present" are distinguished as follows. That is, of the observed cross sections, the width of the entire thickness direction (“thickness d” in the vertical direction in FIG. 1) and the width of 100 μm in the CD direction perpendicular to the thickness direction (100 μm in the left-right direction in FIG. 1). In the region surrounded by (width), the region where the number of fibers judged to be located in the cross section is 15 or less is defined as the "region where the fibers are not densely present", and the other region is referred to as the "region where the fibers are densely present". To do.

Next, the total length (mm) of each of the regions 11 observed in the range of 20 mm in length of each cross section is calculated. Then, the total value is divided by 20 and multiplied by 100 [total length of each region 11 (mm) / 20 mm × 100] is calculated, and the observed total cross section (that is, 10 cross sections) is calculated. The average value of the numerical values in the above is calculated, and this is defined as the ratio A.

The ratio A thus obtained can be regarded as the area ratio (opening ratio) occupied by the open portion formed by the through hole 1 in the vertical × horizontal area of the liquid-absorbent nonwoven fabric sheet 10. This is because, according to the manufacturing method described later, the non-woven fabric sheet is an accumulation of cross sections perpendicular to the MD direction of the sheet 10. Therefore, the proportion of the through hole 1 in the cross section of the sheet 10 in the MD direction is the same as that of A.

Regarding (4) above, the apparent density B (g / cm ³ ) of the entire sheet 10 is obtained by calculating the basis weight (g / m ² ) and the thickness (mm) and dividing the basis weight by the thickness. That is, the apparent density B is the apparent density of the entire sheet 10 composed of the through hole 1 and the region other than the through hole 1, whereas the equation [{B × 100 / (100-A)} in the above relational expression is used. ] Can be regarded as the apparent density C of the region other than the through hole 1 in the sheet 10.

Conventionally, in a liquid-absorbent non-woven fabric sheet, a method of having a two-layer structure or a bulky structure has been adopted in order to improve the liquid-absorbing property. For this reason, it tends to be difficult for the conventional liquid-absorbent non-woven fabric sheet to achieve both thinness and high liquid-absorbing property. The present inventors considered that a breakthrough in achieving both thinness and liquid absorbency could not be achieved by the conventional method, and changed the viewpoint significantly from the conventional method.

That is, the present inventors have repeatedly studied focusing on the diffusion direction of the liquid in the non-woven fabric sheet, and have found a structure of the non-woven fabric sheet capable of quickly diffusing and adsorbing the liquid in the plane. Then, by repeating diligent studies based on this finding, the liquid-absorbent nonwoven fabric sheet satisfying the above (1) to (4) has a sufficient thinness, but the liquid is highly diffused into the plane. It has been found that it has a property and a liquid-retaining property, and thus has a high liquid-absorbing property, and has completed the liquid-absorbing non-woven fabric sheet of the present invention.

The detailed mechanism of the reason why the liquid-absorbent nonwoven fabric sheet 10 satisfying the above (1) to (4) can achieve both thinness and high liquid-absorbing property has not been clarified. The inventors infer as follows.

The liquid in contact with the surface of the sheet 10 is quickly collected in the through holes 1 provided with an appropriate aperture ratio [A (%)] (appropriate pitch). In the manufacturing method described later, the fiber group located near the edge of the opening formed by the through hole 1 has a higher density than that of the liquid-absorbent nonwoven fabric sheet 10. Therefore, the liquid absorbed in the through hole 1 is quickly sucked into the fiber net of the liquid-absorbent non-woven fabric sheet 10 and quickly diffused by the strong capillary phenomenon in the region where the fiber density is high.

Therefore, the sheet 10 can exhibit a diffusibility of 300 or more, and thus has an excellent function of absorbing a liquid. Further, the sheet 10 can exhibit a low liquid return rate of 45% or less, and thus has an excellent function of retaining the liquid. On the other hand, when the diffusivity is less than 300, the liquid return rate tends to be high. When the liquid return rate exceeds 45%, the discomfort of the user tends to be remarkable.

In addition, more preferable aspects of the sheet 10 are listed below, whereby the sheet 10 can exhibit a diffusibility of 350 or more, 400 or more, and further 450 or more, and 43% or less, 40% or less, Furthermore, it is possible to show a liquid return rate of 38% or less.

Regarding the sheet 10 of the present embodiment, fibers other than hydrophilic fibers (for example, hydrophobic fibers) can be included as the fibers constituting the sheet 10, but the content of the hydrophilic fibers is high from the viewpoint of water absorption. preferable.

Specifically, the content ratio of the hydrophilic fibers contained in the fibers constituting the sheet 10 is preferably 50% by weight or more , more preferably 60% by weight or more, and more preferably 70% by weight or more. Is more preferable, and 80% by weight or more is particularly preferable. Examples of non-hydrophilic fibers include fibers made of polyolefin resins such as polyethylene and polypropylene, polyester resins, and polyurethane resins.

The average fineness of the fibers constituting the sheet 10 can be selected from, for example, the range of 1.0 to 3.5 dtex. When the average fineness is included in this range, the above-mentioned effects are more appropriately exhibited. The average fineness of the fibers is more preferably 1.5 to 3 dtex. This is because it is suitable for carrying out the manufacturing method described later.

Further, the average length of the fibers constituting the sheet 10 can be selected from the range of, for example, 30 to 50 mm. More preferably, the average length of the fibers is 35-45 mm. This is because it is suitable for carrying out the manufacturing method described later.

Further, regarding the thickness d of the sheet 10, if it is less than 0.25 mm, the morphological stability and handleability tend to decrease, and if it exceeds 0.75 mm, the flexibility tends to decrease. The thickness d of the sheet 10 is preferably 0.30 to 0.60 mm, more preferably 0.35 to 0.50 mm, and particularly preferably 0.38 to 0.43 mm.

Further, regarding the above ratio A, if it is less than 20%, the fiber density in the region other than the through hole 1 tends not to be sufficient and the liquid absorption property tends to decrease, and if it exceeds 70%, the morphological stability of the sheet 10 tends to decrease. Is reduced, and it becomes difficult to maintain the sheet-like shape. The ratio A is preferably 25 to 65%, more preferably 27 to 65%, still more preferably 28 to 62%.

Further, in the above-mentioned cross-sectional observation, it is preferable that 4 to 15 through holes 1 are observed within a length of 20 mm in the direction perpendicular to the MD direction. As a result, the arrangement balance of the through holes 1 becomes suitable, and the liquid absorption property of the sheet 10 can be further improved. Further, for the same reason, it is preferable that 4 to 15 through holes are observed even within a length of 20 mm in a direction parallel to the MD direction.

The average opening area of the through-hole 1 (mm ²⁾ is preferably a 0.25~5.00mm ^2. When the average opening area of the through hole is within this range, the above-mentioned effect can be more preferably exhibited. The average opening area is more preferably ^{0.80 to 3.00 mm 2.}

The average opening area can be obtained as follows. First, the surface of the sheet 10 (the surface shown in FIG. 2) is observed using a digital microscope. Then, on the surface where the image appears, the region where the fibers are not densely present is defined as the region of the through hole 1, and the product of the maximum length (mm) in the MD direction and the maximum length (mm) in the CD direction of the region is set as the region. The opening area of the through hole 1 is used. Then, the average value of the opening areas of the 10 through holes 1 is defined as the average opening area. The method for identifying the region where the fibers are not densely present is as described above.

Further, the apparent density B (g / cm ³⁾ of the sheet 10 is preferably 0.05~0.15g / cm ^3. When the apparent density B is ^{less than 0.05 g / cm 3, the} aperture ratio required for exhibiting sufficient liquid absorption tends to be high, and it may be difficult to maintain the sheet shape. When the apparent density B ^{exceeds 0.15 g / cm 3} , the flexibility of the sheet 10 tends to decrease. Apparent density B is more preferably 0.08~0.13g / cm ^3, more preferably 0.09~0.12g / cm ^3, particularly preferably 0.10~0.11g / cm ^3.

Further, when the value calculated by the formula {B × 100 / (100-A)} in the relational formula (4) above, that is, the apparent density C of the region other than the through hole 1 is less than ^{0.12 g / cm 3.} , Sufficient liquid absorption is not exhibited, and if it ^{exceeds 0.26 g / cm 3} , the flexibility of the sheet 10 decreases. The apparent density C of the region other than the through hole 1 ^{is preferably 0.14 g / cm 3} or more, and more preferably 0.16 g / cm ³ or more.

The rate of increase D of the density C with respect to the density B is preferably 25% or more, more preferably 40% or more, and further preferably 45% or more. When this increase rate D is less than 25%, it tends to be difficult to exhibit sufficient liquid absorbency. The upper limit of the increase rate D is not particularly limited, but is 170% or less due to the structure of the non-woven fabric sheet.

The basis weight of the sheet 10 is preferably 30 to 80 g / m ^2, more preferably from 32~70g / m ^2, further preferably 35~60g / m ^2. When the basis weight is ^{less than 30 g / m 2} , it tends to be difficult to design the apparent density C other than the through hole 1 to the above-mentioned desired value, and when it ^{exceeds 80 g / m 2} , the thickness of the sheet 10 is increased as described above. It tends to be difficult to design in the desired range of.

The sheet 10 of this embodiment can be manufactured as follows. First, hydrophilic fibers are used (hydrophobicity may be added if desired) to create a web. As a method for producing the web, the card method can be preferably used. Further, as the web, there are a random web, a semi-random web, a parallel web and the like, and it is preferable to prepare the semi-random web from the viewpoint of flexibility and shape stability.

Next, the created web is entangled in three dimensions. As the entanglement method, it is preferable to use a spunlace method in which entanglement is performed by a water flow entanglement treatment. Specifically, a web is placed on the first porous support member, entanglement treatment (Table WJ; water jet) is performed from the exposed surface side, and then on the second porous support member. , The web is placed so that the back surface opposite to the front surface is exposed, and entanglement processing (back WJ) is performed from the exposed back surface side.

After the entanglement treatment, the non-woven fabric sheet is dried to obtain the sheet 10. In particular, by appropriately selecting the porous support member for the back WJ, the above-mentioned through hole 1 can be provided in the web, and thus the sheet 10 of the present embodiment can be produced.

The sheet 10 of the present embodiment described in detail above can be suitably used as various liquid absorbing materials for general consumers, general households, or industries. The liquid absorbing material is a material or product for absorbing water or a liquid containing water or a hydrophilic liquid for some purpose, and includes a material or a product that retains the absorbed liquid.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these examples. The method for measuring each physical property value in the following Examples and Comparative Examples is as follows.

[1] Metsuke of liquid-absorbent non-woven fabric sheet (g / m ² )
The basis weight of the liquid-absorbent non-woven fabric sheet was measured according to 6.1 of JIS L 1913 “General non-woven fabric test method”.

[2] Thickness of liquid-absorbent non-woven fabric sheet (mm)
The thickness was determined by the above method using a razor (“Feather razor S single-edged”, manufactured by Feather Safety Razor Co., Ltd.) according to 6.2 of JIS L 1913 “General non-woven fabric test method”.

[3] Percentage of through-holes in the cross section of the liquid-absorbent non-woven sheet in the thickness direction A (%); Opening ratio razor ("Feather razor S single-edged", Feather Safety Razor Co., Ltd.) and digital microscope ("" Using "VHX-900 DIGITAL MICROSCOPE", manufactured by KEYENCE Co., Ltd.), the ratio A was determined by the above method.

[4] Overall apparent density B (g / cm ³ ) of the liquid-absorbent non-woven fabric sheet
The apparent density B was obtained by dividing the basis weight obtained in the above [1] by the thickness obtained in the above [2].

[5] Apparent density C (g / cm ³ ) in the area other than the through hole
The value calculated from the formula B × 100 / (100-A) was defined as the apparent density C.

[6] Increase rate D (%) of density C with respect to density B
The value calculated from the formula (CB) / B × 100 was defined as the rate of increase D.

[7] Average opening area (mm ² )
Using a digital microscope (“VHX-900 DIGITAL MICROSCOPE”, manufactured by KEYENCE Co., Ltd.), the average opening area was determined by the above method.

[8] A diffusible liquid-absorbent non-woven fabric sheet was cut into a size of 10 cm × 10 cm to prepare a sheet, which was allowed to stand on a horizontal table. Next, 1 g of ink (“PILOT Ink RED (INK-350-R)”, manufactured by Pilot Corporation) was added to 100 g of ion-exchanged water to prepare colored water. Next, one drop (0.05 g) of colored water was dropped from 1 cm above (above) of the stationary sheet to the center of the sheet using a dropper. Five seconds after the dropping, the length at which the colored water diffused in the plane, that is, the diffusion length in the MD direction (mm) and the diffusion length in the CD direction (mm) were determined. Then, the product of the diffusion length (mm) in the MD direction and the diffusion length (mm) in the CD direction was taken as the diffusivity value. The higher the diffusivity value, the wider the liquid is diffused.

[9] Liquid return rate (%)
A sheet obtained by cutting a liquid-absorbent non-woven fabric sheet into 6 cm × 6 cm was prepared and allowed to stand on an acrylic plate (12.5 cm × 12.5 cm) that does not absorb water. Next, 50 mg (a) of ion-exchanged water was added dropwise to the center of the sheet from 1 cm above (above) the stationary sheet. 60 seconds after dropping, 5 sheets of weighed circular filter paper (diameter: 55 mm, TOYO FILTER PAPER2) are placed on the sheet, and a weight (diameter: 55 cm, weight: 300 g) is placed on the circular filter paper for 30 seconds. After that, the weight was removed. Then, the amount of ion-exchanged water (b) contained in the filter paper was measured, and the value calculated from the formula (b / a × 100) was taken as the liquid return rate (%).

[10] Sensory Evaluation A sheet obtained by cutting a liquid-absorbent non-woven fabric sheet into a size of 6 cm × 6 cm was prepared and allowed to stand on an acrylic plate (12.5 cm × 12.5 cm) that does not absorb water. Next, 50 mg of ion-exchanged water was added dropwise to the center of the sheet from 1 cm above (above) the stationary sheet. 100 seconds after the dropping, three subjects brought the back of their hands into contact with the sheet to perform sensory evaluation according to the following three criteria.
+++: No liquid return is felt.
++: Almost no liquid return is felt.
+: I feel the liquid return clearly.
[Example 1]
A semi-random web was prepared using 100% by weight of rayon fiber (“Hope”, manufactured by Omikenshi Co., Ltd.) having a fineness of 1.7 dtex using the card method.

Next, the produced semi-random web is placed on a punching drum support having a hole opening ratio of 25% and a hole diameter of 0.3 mm, and is continuously transferred in the longitudinal direction at a speed of 5 m / min, and at the same time, high pressure is applied from above. An entanglement process was performed by injecting a water stream. As a result, an entangled fiber web (nonwoven fabric) was produced. In this entanglement process, two nozzles having an orifice with a hole diameter of 0.10 mm provided at an interval of 0.6 mm along the width direction of the web are used (distance between adjacent nozzles is 20 cm), and the first row. The water pressure of the high-pressure water stream jetted from the nozzle was 3.0 MPa, and the water pressure of the high-pressure water stream jetted from the nozzles in the second row was 5.0 MPa (Table WJ).

Next, from the surface opposite to the surface on which the front WJ was applied, the fiber diameter was 0.90 mm, 10 meshes / inch, and the plain weave was placed on a flat net support and continuously transferred, and a high-pressure water stream was injected. Then, the entanglement treatment was performed to transfer the unevenness of the net to the surface of the non-woven fabric. This entanglement treatment uses three nozzles in which orifices having a hole diameter of 0.10 mm are provided at intervals of 0.6 mm along the width direction of the web, all under the condition of a high-pressure water flow pressure of 4.0 MPa. I did it (back WJ).

Then, the non-woven fabric after the back WJ treatment was dried at 135 ° C. using a cylinder-dryer. As a result, the non-woven fabric sheet of Example 1 was produced.

[Example 2]
The non-woven fabric sheet of Example 2 was produced by the same method as in Example 1 except that a fiber diameter of 0.65 mm, 25 meshes / inch, and a plain weave were used as the net used for the back WJ.

[Example 3]
The non-woven fabric sheet of Example 3 was produced by the same method as in Example 1 except that a fiber diameter of 1.20 mm, 12 meshes / inch, and a plain weave were used as the net used for the back WJ.

[Example 4]
The non-woven fabric sheet of Example 4 was produced by the same method as in Example 1 except that a fiber diameter of 0.90 mm, 8 meshes / inch, and a plain weave were used as the net used for the back WJ.

[Example 5]
The non-woven fabric sheet of Example 5 was produced by the same method as in Example 1 except that a fiber diameter of 0.90 mm, 12 meshes / inch, and a plain weave were used as the net used for the back WJ.

[Comparative Example 1]
As the net used for the back WJ, a fiber diameter of 0.20 mm, 76 meshes / inch, and a plain weave were used, and the comparison was made by the same method as in Example 1 except that the water pressure of the high-pressure water flow of the back WJ was 6.0 MPa. The non-woven fabric sheet of Example 1 was prepared.

[Comparative Example 2]
The non-woven fabric sheet of Comparative Example 2 was produced by the same method as in Example 1 except that a fiber diameter of 0.90 mm, 5 meshes / inch, and a plain weave were used as the net used for the back WJ.

[Comparative Example 3]
A non-woven fabric sheet of Comparative Example 3 was produced by the same method as in Example 1 except that a fiber diameter of 0.90 mm, 13 meshes / inch, and a plain weave were used as the net used for the back WJ.

[Comparative Example 4]
As the net used for the back WJ, a fiber diameter of 0.90 mm, 10 meshes / inch, and a plain weave were used, and the comparison was made by the same method as in Example 1 except that the water pressure of the high-pressure water flow of the back WJ was 6.0 MPa. The non-woven fabric sheet of Example 4 was prepared.

[Comparative Example 5]
As the net used for the back WJ, a fiber diameter of 0.90 mm, 10 meshes / inch, and a plain weave were used, and the comparison was made by the same method as in Example 1 except that the water pressure of the high-pressure water flow of the back WJ was set to 2.0 MPa. The non-woven fabric sheet of Example 5 was prepared.

The above [1] to [12] were measured for each of the non-woven fabric sheets of Examples and Comparative Examples. The results are shown in Table 1. However, it was difficult to maintain the shape of the non-woven fabric sheet of Comparative Example 3, and various tests such as diffusivity could not be performed.

As is clear from Table 1, the non-woven fabric sheets of Examples 1 to 5 have both thinness and improved liquid absorption as compared with the non-woven fabric sheets of Comparative Examples 1 to 5.

The embodiments and examples disclosed this time should be considered as exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the embodiments and examples described above, and is intended to include meaning equivalent to the scope of claims and all modifications within the scope.

1 through hole, 10 liquid-absorbent non-woven fabric sheet, 11, 12 areas.

Claims (4)

A liquid-absorbent non-woven fabric sheet containing 50% by weight or more of hydrophilic fibers.
The liquid-absorbent nonwoven fabric sheet has a thickness of 0.25 mm or more and 0.75 mm or less, and is provided with a plurality of through holes penetrating in the thickness direction.
A sword (“Feather Sword S Single-edged”, Feather Safety Sword Co., Ltd.) is installed so that it is parallel to the thickness direction of the liquid-absorbent non-woven fabric sheet and perpendicular to the MD direction of the liquid-absorbent non-woven fabric sheet. Use to cut any 10 points of the liquid-absorbent non-woven fabric sheet, observe each cross section with a digital microscope, and out of the observed cross sections, the width of the entire thickness direction and 100 μm in the CD direction perpendicular to the thickness direction. In the region surrounded by the width of, the region where the number of fibers judged to be located in the cross section is 15 or less is defined as "the region where the fibers are not densely present", and the other region is defined as the "region where the fibers are densely present". The "region where the fibers are not densely present" is regarded as the region occupied by the through holes, the region where the fibers are densely present is regarded as the "region other than the through holes", and the length of each cross section is excluded, excluding the cross section where the through holes are not present. The total length (mm) of each of the observed regions in the range of 20 mm was calculated, the total value was divided by 20, and the value multiplied by 100 was calculated, and all 10 cross sections observed were observed. Let A (%) be the average value of the values in
When the overall apparent density of the liquid-absorbent non-woven fabric sheet is B (g / cm ³ ),
The A is 20% or more and 70% or less.
The A and the B satisfy the relational expression of 0.12 ≦ {B × 100 / (100-A)} ≦ 0.26.
The average opening area of the through hole state, and are 0.25 mm ² or more 5.00 mm ² or less,
The average opening area is determined by observing the surface of the liquid-absorbent non-woven fabric sheet with a digital microscope, and on the surface where the image appears, the "region in which fibers are not densely present" is defined as the through-hole region, and the MD of the region is defined as the region. It is the average value of the opening areas of 10 through holes when the product of the maximum length (mm) in the direction and the maximum length (mm) in the CD direction is taken as the opening area of the through holes.
The B is 0.05 g / cm ³ or more, and is
The value C calculated from {B × 100 / (100-A)} is 0.12 g / cm ³ or more.
The rate of increase D of the C with respect to the B is 25% or more.
The basis weight of the liquid-absorbent non-woven fabric sheet is 30 to 80 g / m ² .
The fineness of the fibers constituting the liquid-absorbent non-woven fabric sheet is 1.0 dtex or more and 3.5 dtex or less.
The liquid-absorbent non-woven fabric sheet is produced by three-dimensionally entwining a web containing 50% by weight or more of hydrophilic fibers and then drying it.
The entanglement is carried out using a spunlace method of entanglement by a water flow entanglement treatment, the web is placed on the first porous support member, and the entanglement treatment is performed from the exposed surface side, and then the entanglement treatment is performed. A web is placed on the second porous support member so that the back surface opposite to the front surface is exposed, and entanglement processing is performed from the exposed back surface side.
The second porous support is a liquid-absorbent non-woven fabric sheet having a fiber diameter of 0.65 to 1.20 mm, meshes of 8 to 25 fibers / inch, and a net support flat throughout the plain weave. Wherein B is, 0.05 g / cm ³ or more 0.15 g / cm ³ or less, the liquid-absorbent nonwoven fabric sheet according to claim 1. The liquid-absorbent non-woven fabric sheet according to claim 1 or 2 , wherein the content ratio of the hydrophilic fibers contained in the fibers constituting the liquid-absorbent non-woven fabric sheet is 80 % by weight or more. The liquid-absorbent nonwoven fabric sheet according to any one of claims 1 to 3 , wherein the hydrophilic fiber is a cellulosic fiber.

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