JP7638657B2 - Nonwoven - Google Patents

Description

The present invention relates to nonwoven fabrics.

Nonwoven fabrics are often used in absorbent articles such as diapers. Technologies have been developed to give nonwoven fabrics various functions.

For example, Patent Document 1 describes incorporating a resin-bonded nonwoven fabric impregnated or coated with an adhesive into an absorbent article in order to improve the thickness recovery of the absorbent article. Specifically, the resin-bonded nonwoven fabric is disposed as a component of the absorbent article that does not come into contact with the skin.

JP 2001-187088 A

Among conventional nonwoven fabrics, there are some that have been made thicker than their basis weight by providing unevenness in the thickness direction, i.e., have a thick apparent thickness between the front and back surfaces. Such nonwoven fabrics tend to be soft to the touch and have a fluffy texture.
However, nonwoven fabrics with a large apparent thickness may be crushed and reduced in thickness depending on the pressure of a person's weight or the like during use. Therefore, there is room for improvement in terms of ensuring a sufficient texture during use. In addition, when such nonwoven fabrics are used as a member on the skin side of an absorbent body in an absorbent article, the distance separating the absorbent body from the skin side is likely to be reduced. In particular, when the nonwoven fabric has an uneven shape, the spaces in the concaves of the unevenness may be crushed, and from the viewpoint of the absorbency of body fluids (e.g., loose stool), it is desirable to improve the thickness retention of the nonwoven fabric when a compressive force is applied.

In consideration of the above problems, the present invention relates to a nonwoven fabric that minimizes the reduction in thickness when a compressive force is applied.

The present invention provides a nonwoven fabric having fusion points between fibers, which has fibers attached with a polymer having a glass transition point of 10°C or higher, has an apparent thickness of 1.5 mm or more when a load of 0.05 kPa is applied from one side using a horizontal plate, and on at least one side, the contact area between the horizontal plate and the nonwoven fabric under a pressure of 3 kPa is 90% or less of the surface area of the nonwoven fabric.

The nonwoven fabric of the present invention reduces the thickness of the fabric when compressed. In addition, the spaces that give the fabric its apparent thickness are less likely to collapse, and the fabric has good absorbency for body fluids, for example.

1A and 1B are side views showing specific examples of the uneven shape of the nonwoven fabric of the present invention. 1 is a drawing-substitute photograph showing an enlarged view of a polymer membrane that is fixed so as to form a membrane in a minute space surrounded by fibers. FIG. 2 is a schematic diagram showing a part of an observation screen used in a method for measuring the longitudinal orientation degree of fibers, together with a square reference line. FIG. 2 is a partially sectional perspective view showing a schematic diagram of specific example 1 of the uneven shape of a nonwoven fabric. 1 is a photograph showing a plane view of one side of specific example 2 of a nonwoven fabric having a concave-convex shape. 6 is a partial cross-sectional view of the nonwoven fabric shown in FIG. 5 taken along the line CC. 6 is a partial cross-sectional view of the nonwoven fabric shown in FIG. 5 along line DD. 6 is a photograph showing a plan view of the opposite side of the nonwoven fabric shown in FIG. 5 . 9 is a partial cross-sectional view of the nonwoven fabric shown in FIG. 8 taken along line EE. 9 is a partial cross-sectional view of the nonwoven fabric shown in FIG. 8 taken along the line FF. FIG. 1 is an explanatory diagram showing a preferred embodiment of the method for producing a nonwoven fabric of the present invention, in which (A) shows a process of placing a fiber web on a male support material and pressing a female support material into the male support material from above the fiber web, (B) shows a process of pressing the female support material into the male support material to form a fiber web, (C) shows a process of removing the female support material and blowing hot air from above the shaped fiber web to fuse the fibers together, (D) shows the state of the shaped raw nonwoven fabric removed from the male support material, and (E) shows a process of spraying a polymer coating solution onto one side of the removed raw nonwoven fabric (the side onto which the hot air was blown).

Preferred embodiments of the nonwoven fabric of the present invention will now be described.
The nonwoven fabric of the present invention has fusion points between fibers (fusion points at fiber intersections). The fusion points are the parts where the fibers are bonded to each other at the contact points between the intersecting fibers by fusion of the thermoplastic resin component of the fibers themselves. More specifically, the fusion points are formed by, for example, melting the surface of the thermoplastic fiber by heat treatment during the manufacturing process of the nonwoven fabric, and fusing the fibers together. Examples of the nonwoven fabric of the present invention include thermal bonded nonwoven fabrics, and more specifically, air-through nonwoven fabrics (nonwoven fabrics in which the fusion points are formed by hot air treatment. Short fibers of 60 mm or less are mainly used) and spunbonded nonwoven fabrics (nonwoven fabrics in which a resin in a molten state is spun into a nonwoven fabric as it is, and the fusion points are formed by embossing. Long fibers of 100 mm or more are mainly used). When used in contact with the skin, such as in the case of materials for absorbent articles, air-through nonwoven fabrics are preferable, especially from the viewpoint of texture.

The nonwoven fabric of the present invention has one side and a second side on the opposite side opposite to the first side. The first side and the second side form the front and back sides of the nonwoven fabric of the present invention. The first side and the second side are the side furthest from the horizontal plane in the vertical direction relative to the horizontal plane when the nonwoven fabric is placed still on the horizontal plane, and the side closest to the horizontal plane. The first side and the second side may be referred to as the first side and the second side.
Which of the first side and the second side is to be the front side (usage side) is appropriately set depending on the purpose of the article. The front side is the side that receives a compressive force during use. When the nonwoven fabric of the present invention is used as a member such as a top sheet of an absorbent article, the front side is the skin side and the back side is the non-skin side. The skin side and non-skin side refer to the side facing the skin of the user and the side opposite to it. The skin side and non-skin side are defined as indicating a relative positional relationship even when they do not directly contact the skin of the user.

The nonwoven fabric of the present invention has an apparent thickness under a load of 0.05 kPa of 1.5 mm or more.
Here, the "apparent thickness" means the vertical distance between a horizontal plane and an imaginary plane (horizontal plate) that is in contact with the outermost part of the side of the nonwoven fabric opposite to the side that is in contact with the horizontal plane when the nonwoven fabric is placed on the horizontal plane (hereinafter, the vertical direction to the horizontal plane may be simply referred to as the "vertical direction"). For example, when the nonwoven fabric of the present invention has an uneven shape on both sides, the apparent thickness is the vertical distance between the position of the apex of the convexity on one side and the position of the apex of the convexity on the other side.
The "apparent thickness" means the thickness when a load of 0.05 kPa is applied from one side using a horizontal plate. Specifically, it can be measured by the following method. Here, the "load of 0.05 kPa" means a load that suppresses fuzzing on the surface of the nonwoven fabric, and is a light load (a light load that is not a compressive force that would crush the thickness of the nonwoven fabric) necessary to properly measure the apparent thickness of the nonwoven fabric. The load of 0.05 kPa is applied to the nonwoven fabric by placing a horizontal plate, for example, a circular plate with a diameter of 2.5 cm and a mass of 2.45 g, on one side of the nonwoven fabric.

(Method for measuring the apparent thickness of a nonwoven fabric under a load of 0.05 kPa)
The nonwoven fabric to be measured is cut to 10 cm x 10 cm to prepare a measurement sample. Using a laser thickness gauge (high-precision displacement sensor ZS-LD80 (product name) manufactured by Omron Corporation; all laser thickness gauges used in this specification are of this type), a load of 0.05 kPa is applied to one side of the measurement sample using a horizontal plate, and the thickness is measured in this state. Measurements are taken at three locations, and the average value is taken as the apparent thickness of the nonwoven fabric to be measured.
In addition, when the nonwoven fabric to be measured is incorporated into a product, the adhesive strength of the adhesive or the like is weakened by a cooling means such as a cold spray, and the nonwoven fabric is removed from the product and the above measurement is performed. This method of removing the nonwoven fabric is similarly applied to other measurements in this specification.
If it is not possible to take out a nonwoven fabric measuring 10 cm x 10 cm, take out a piece as large as possible.

The nonwoven fabric of the present invention has an apparent thickness of 1.5 mm or more under a load of 0.05 kPa, so that the thickness can be felt at the beginning of use. In addition, this apparent thickness clearly manifests the effect of fiber reinforcement by the adhesion of a polymer with a glass transition point of 10°C or higher, as described below, when a compressive force is applied to the nonwoven fabric. From this viewpoint, the apparent thickness is preferably 2 mm or more, and more preferably 3 mm or more. From the viewpoints of storage efficiency and ease of processing, the apparent thickness is preferably 12 mm or less, more preferably 10 mm or less, and even more preferably 9 mm or less.

In addition, the nonwoven fabric of the present invention has a contact area between the horizontal plate and the nonwoven fabric of 90% or less of the surface area of the nonwoven fabric on at least one of the front and back sides. This contact area can be measured by applying a pressure of 3 kPa using the following method. The "surface area of the nonwoven fabric" means the area of the outline of the nonwoven fabric obtained by observing the surface of the nonwoven fabric to be measured from above. Therefore, when there are irregularities, the area of the part along the undulations is ignored.
The contact area ratio of 90% or less means that at least the surface of the nonwoven fabric to be measured has an uneven shape, and crushing is suppressed under a pressure of 3 kPa as described below. Note that the pressure of 3 kPa is assumed to be the pressure applied to the back side of the diaper when the nonwoven fabric of the present invention is used as the top sheet of the diaper and a premature baby (0 years 1 month to 0 years 4 months) wearing the diaper is lying on his back. The uneven shape means a shape in which convex parts protruding in the thickness direction and concave parts recessed in the thickness direction are alternately arranged in the planar direction when the nonwoven fabric is viewed in the thickness direction. In the uneven shape, it is preferable that there is a wall surface in the thickness direction connecting the first surface and the second surface, which are the front and back surfaces of the nonwoven fabric.
The uneven shape is not limited to only one of the front and back surfaces of the nonwoven fabric, but is preferably present on both surfaces. It is preferable that the proportion of the contact area on both the first and second surfaces, which are the front and back surfaces of the nonwoven fabric, is 90% or less.
The ratio of the contact area is preferably 80% or less, more preferably 70% or less, from the viewpoint of improving the feel, and is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more, from the viewpoint of improving the bonding strength with other members.

(Method of measuring contact area)
(1) A measurement sample measuring 50 mm x 50 mm is cut out from the nonwoven fabric.
(2) Place the measurement sample with the measurement surface facing up.
(3) Using a high-precision shape measurement system KS-1100 (product name, manufactured by Keyence Corporation), the measurement surface is irradiated with laser light to measure the surface shape (the height and depth shape of the thickness undulating along the surface direction of the measurement surface) of the measurement surface in a no-load state (natural state without load) and an image is captured. At this time, the measurement range is 1 cm ² (measurement pitch: vertical 20 μm, horizontal 20 μm), and the movement speed is 10 cm/sec.
(4) Next, a transparent acrylic plate with a mass of 170 g is placed on the measurement surface of the measurement sample, and a weight with a mass of 600 g is further placed on the acrylic plate. In this state, a pressure of 3 kPa is applied, and the surface shape of the measurement surface is measured and an image is captured in the same manner as in (3) above.
(5) The images captured in (3) and (4) above are analyzed using a shape analysis application KS-Analyzer (product name, manufactured by Keyence Corporation). Specifically, the area where the thickness changes from the no-load state to the application of a pressure of 3 kPa (minimum measurable scale: 0.01 μm) is extracted and binarized to obtain a surface image of that area.
(6) The surface image of the part where the thickness has changed obtained in (3) above is imported and processed using image processing software NewQube (Ver. 4.22, product name, manufactured by Nexus Co., Ltd.), and its area is measured. This area corresponds to the area of the part that comes into contact with the skin when the nonwoven fabric of the measurement sample is pressurized with 3 kPa, i.e., the contact area.
(7) The measured area is divided by the area of the measurement sample (measurement points: 251,001 points (=501 x 501)) to calculate the "proportion of contact area" on the measurement surface of the nonwoven fabric to be measured.

The nonwoven fabric of the present invention has fibers to which a polymer having a glass transition temperature of 10° C. or higher (hereinafter, also referred to as an attachment polymer) is attached. The attachment polymer is attached in a fixed state to the fibers constituting the nonwoven fabric, increasing the strength of the fiber surface and increasing the adhesive strength between the fibers. The fibers to which such a polymer is attached may be on the exposed surface of the nonwoven fabric of the present invention or may be inside the nonwoven fabric.
As a result, when the nonwoven fabric of the present invention is used, the attachment polymer acts to maintain the positional relationship between the fibers, improving the shape and thickness retention of the nonwoven fabric. The fibers to which the attachment polymer that acts in this way are attached in the nonwoven fabric of the present invention increase the thickness retention (compression resistance) against the applied compressive force. As a result, even when a compressive force is applied, the thickness loss of the thick nonwoven fabric of the present invention is kept small. In other words, the nonwoven fabric of the present invention has a large apparent thickness between the front and back surfaces, and is capable of thickness deformation due to the application of a compressive force, while the loss of thickness when a compressive force is applied is kept small.
When such a nonwoven fabric of the present invention is used as a member on the skin side of the absorbent body in an absorbent article, the distance separating the absorbent body from the skin side is maintained even when a compressive force is applied, and a space for absorbing body fluids (e.g., loose stool, etc.) can be secured. For example, loose stool, etc. is temporarily stored in the space during absorption, reducing the diffusion area in the planar direction, preventing the loose stool from adhering to the skin, and the liquid component of the loose stool smoothly transfers to the absorbent body, improving liquid absorption. In particular, when the nonwoven fabric of the present invention has an uneven shape (for example, when both sides of the nonwoven fabric 10 in FIG. 1(A) and the nonwoven fabric 20 in FIG. 1(B) have an uneven shape, or when only one of the front and back sides has an uneven shape (not shown)), the space formed along the unevenness becomes clearer, and the above-mentioned effect becomes more prominent. Note that in FIGS. 1(A) and (B), the one surface side 1A located at the top is shown as the skin side, and the other surface side located at the bottom is shown as the non-skin side.
Conventionally, when the apparent thickness of a nonwoven fabric is increased, the thickness change is large and the collapse is large. Also, when the apparent thickness of a nonwoven fabric is thin, the change in thickness when a compressive force is applied is small to begin with, and it is difficult to fully exert the thickness retention effect of the above-mentioned attached polymer. In contrast, the nonwoven fabric of the present invention has the above-mentioned apparent thickness and has fibers to which the attached polymer is attached, so that it can retain a thickness when a compressive force that could not be obtained conventionally is applied.
Furthermore, since the nonwoven fabric of the present invention has an uneven shape and the apparent thickness, and has fibers to which the above-mentioned attachment polymer is attached, it is able to retain its thickness when a compressive force is applied, which was not possible with conventional flat nonwoven fabrics in which thickness was ensured simply by increasing the basis weight.

From the viewpoint of further enhancing the above-mentioned effects, the attachment polymer preferably has a glass transition point of 25°C or higher, and more preferably 40°C or higher. From the viewpoint of availability, the attachment polymer preferably has a glass transition point of 200°C or lower, more preferably 150°C or lower, and even more preferably 100°C or lower.

(Method for measuring the glass transition temperature of the attached polymer)
(1) Remove the nonwoven fabric from the product and prepare a 0.3 g sample of the nonwoven fabric as a measurement sample. Next, place the nonwoven fabric sample in a beaker containing 100 mL of ethyl acetate and stir for 30 minutes, remove the nonwoven fabric sample and dry it. This washes away any components attached to the nonwoven fabric sample, such as skin care agents and hot melt adhesives. Repeat this process to prepare a total of 1.0 g or more of sample.
(2) The nonwoven fabric sample is placed horizontally and the horizontal cross section is cut and cut into pieces of about 0.1 mm in length. 1.0 g of this nonwoven fabric sample is placed in a beaker and hexafluoroisopropanol (hereinafter also referred to as HFIP) is added to separate it into HFIP insoluble and HFIP soluble parts. This dissolves the polyethylene terephthalate (hereinafter also referred to as PET) component of the fiber.
(3) The HFIP-insoluble fraction obtained in (2) is added to heated xylene at 130°C, thoroughly stirred, and filtered to separate the heated xylene-insoluble fraction and the heated xylene-soluble fraction. This dissolves the polypropylene (hereinafter also referred to as PP) and polyethylene (hereinafter also referred to as PE) components of the fibers, leaving the cellulosic fibers.
(4) The heated xylene insoluble matter obtained in (3) above is measured by Fourier transform infrared spectroscopy (hereinafter also referred to as FT-IR) to determine the monomer composition, and the glass transition point is calculated from the following Fox formula (S1) (Adhesive Handbook, 2nd Edition, p. 144, October 12, 1995, published by the Japan Adhesive Tape Industry Association). However, if a peak derived from cellulose is observed in FT-IR, that peak is not used in the calculation.

In the formula, Tg represents the glass transition point of the attached polymer, Tg _i represents the glass transition point of a polymer made from monomer i, and W _i represents the mass fraction of monomer i in the attached polymer.

The aforementioned "polymer having a glass transition point of 10° C. or more" has a binding property that does not flow off after being fixed. The attachment polymer is fixed to the surface of the fibers constituting the nonwoven fabric of the present invention. The attachment polymer is fixed to the surface of the fibers so as to form a membrane in the space surrounded by the fibers, which is formed by the intersection of the fibers, while being fixed to the surface of the fibers (for example, the membrane 61 of the attachment polymer formed in the space surrounded by the fibers 7 shown in FIG. 2). The surface of the fibers to which the attachment polymer is fixed includes the surface of the fusion point between the fibers. It is preferable that the attachment polymer present on the surface of the fusion point covers the outer surface of the portion where the fibers cross and overlap (the outer surface of the fused fibers).
In this way, the attachment polymer increases the strength of the fiber surface at the portion where the fibers are fixed. The attachment polymer also bonds the fibers together, imparting an adhesive strength to the nonwoven fabric of the present invention that is greater than or equal to the fusion point. In particular, as shown in Figure 2, the attachment polymer film 61 extends beyond the fusion point to increase the adhesive strength between the fibers. The attachment polymer and the fusion point can be visually distinguished using a tabletop scanning electron microscope (SEM).

The attachment polymer is a resin component different from the constituent fibers of the nonwoven fabric, and is fixed to the surface of the constituent fibers after the nonwoven fabric is made. It can be fixed to one side of the nonwoven fabric by, for example, spraying, coating, impregnation, etc. As a result, the attachment polymer is uniformly fixed over the entire one side of the nonwoven fabric of the present invention. In particular, when one side of the nonwoven fabric of the present invention has an uneven shape, spraying by spraying or impregnation is preferred from the viewpoint of fixing the attachment polymer along the uneven shape (particularly, from the viewpoint of fixing to the wall surface along the thickness direction).
When the adhesion polymer is fixed, the coating agent before the application of the adhesion polymer may be applied as a 100% solution, but it is preferable to dilute and apply it from the viewpoint of suitable control of the application amount. Examples of the dilution liquid include water and ethanol. From the viewpoint of workability, the diluted polymer coating liquid is preferably a liquid in which the content concentration of the polymer having a glass transition point of 10° C. or more is 3% by mass or more and 55% by mass or less, and more preferably a liquid in which the content concentration is 5% by mass or more and 10% by mass or less.
The coating agent before application of the adhesion polymer (hereinafter also referred to as the adhesion polymer coating agent) refers to the agent before reactions such as crosslinking occur after application. The adhesion polymer coating agent is mainly solid, but may be liquid. A 100% solution of the adhesion polymer coating agent and a diluted one are referred to as the adhesion polymer coating liquid (a solution before dilution may be referred to as the adhesion polymer solution).

As the attachment polymer, various polymers having the above-mentioned glass transition point can be used. For example, styrene-butadiene rubber (hereinafter also referred to as SBR), (meth)acrylic polymer, vinyl acetate polymer, polyurethane, styrene polymer, etc., which have the above-mentioned glass transition point can be mentioned. Here, "(meth)acrylic polymer" means both acrylic polymer and methacrylic polymer.
In the styrene-butadiene rubber, the ratio of styrene to the total mass of styrene and butadiene is preferably 60 mass % or more.
The (meth)acrylic polymer is preferably a polymer mainly composed of a component in which ^R2 in the following formula (I) is an alkyl group having 4 or less carbon atoms, and more preferably a polymer mainly composed of a methacrylic acid ester in the following formula (I) in which ^R1 is a methyl group and ^R2 is an alkyl group having 4 or less carbon atoms. Note that the term "main component" refers to the component with the greatest content.
In the vinyl acetate polymer, the vinyl acetate component preferably accounts for 60% by mass or more based on the total mass of all components.
In the polyurethane, it is preferable that ^R3 and ^R4 in the following formula (II) have an aromatic ring or a heterocyclic ring. The term "having an aromatic ring or a heterocyclic ring" means that ^R3 and ^R4 are both linking groups consisting of an aromatic ring or a heterocyclic ring, and linking groups consisting of an aromatic ring or a heterocyclic ring and another component. Examples of the aromatic ring or heterocyclic ring include benzene, thiophene, and pyridine.

In the formula (I), R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkyl group or a hydrogen atom.

In the above formula, ^R3 and ^R4 represent linking groups.

Furthermore, it is preferable that the adhesive polymer coating agent to be fixed to the nonwoven fabric undergoes a crosslinking reaction (including pseudo-crosslinking) after application to further increase the strength of the fiber surface and the adhesive strength between the fibers. More specifically, it is preferable that the coating agent before crosslinking contains a monomer having a reactive site (crosslinking site) such as a vinyl group, a methylol group, an amino group, a carboxyl group, a carbonyl group, or a sulfhydryl group.

(Method for confirming the presence of polymer attached to nonwoven fabric)
(1a) The above-mentioned process (1) in (Method for measuring the glass transition temperature of the deposited polymer) is carried out.
(1b) The nonwoven fabric sample is dyed using an identification reagent (fiber identification reagent Bouken Stain II, manufactured by Bouken Quality Evaluation Organization, a general incorporated foundation) that dyes the attached polymer fixed to the fiber surface a color different from the fiber to distinguish between the two.
(1c) With one surface of the nonwoven fabric sample placed on a horizontal surface with one side facing up, an observation image of the exposed surface is captured at 150x magnification using a digital microscope VHX-900 (product name, manufactured by Keyence Corporation; all digital microscopes in this specification refer to this type). The captured image is used as the observation image. The observation image size is 1600 x 1200 pixels.
(1d) The observed image is subjected to a ternary value process, and the fiber regions not covered with the attached polymer, the attached polymer regions, and other regions (such as voids between fibers) are identified by the ternary values of color to confirm the presence of the attached polymer. If the presence of the attached polymer is not observed on the first surface side, the same measurement as above is performed on the second surface side, which is the opposite surface, to confirm the presence of the attached polymer.

The dyeing process (1b) will now be described.
(1b-1) Shake the container of Bouken Stain II well to mix thoroughly.
(1b-2) Place 5 mL of the mixed Bouken Stain II in a beaker of approximately 200 mL size, add tap water, and make the dye solution to a total volume of 100 mL.
(1b-3) The dye solution is heated, and when the temperature is about 90°C before boiling, the nonwoven fabric sample is added and boiled at 95°C for 2 minutes.
(1b-4) The nonwoven fabric sample is taken out, thoroughly washed with water, and then dried.
(1b-5) The color is compared with the identification color and judged. For example, the attached polymer containing acrylic resin or styrene-butadiene rubber is dyed red and the fiber remains white. However, the color of the dyed attached polymer varies depending on the attached polymer component.

A specific example of the calculation process of (1d) above is shown below. In this example, the fiber identification reagent Bouken Stain II is used to dye the attached polymer region containing acrylic resin or styrene-butadiene rubber red, the fiber region remains white, and other regions other than the attached polymer region and the fiber region (such as voids between fibers) are black.
(1d-1) The observed image is subjected to a three-value process (white, red, black). This is performed by image processing on a computer, and the red area and white area in the RGB color model are calculated.
(1d-2) Convert from the RGB color model to the HSV color model. In the HSV color model, red is defined as H: 0° to 60° and 270° to 360°, S: 30% to 100%, and V: 40% to 100%. White is defined as H: 0° to 360°, S: 0% to 20%, and V: 40% to 100%. Black is defined as any range other than the above.
(1d-3) In this way, the red area (deposited polymer) and the white area (fiber) are calculated in the HSV color model, and the process of (1d) above is carried out.

The nonwoven fabric of the present invention has an uneven shape, and preferably has a wall surface in the thickness direction connecting the first and second surfaces, which are the front and back surfaces of the nonwoven fabric, and the attached polymer is present on the wall surface. For example, in the uneven nonwoven fabric 10 shown in FIG. 1(A), it is preferable that the attached polymer is present on the slightly inclined wall surface 14 connecting the top 12A of the pyramidal convex portion 12 on the first surface side 1A and the top 13A of the pyramidal convex portion 13 on the second surface side 1B. Also, in the uneven nonwoven fabric 20 shown in FIG. 1(B), it is preferable that the attached polymer is present on the vertical wall surface 24 connecting the flat top 22A of the columnar convex portion 22 on the first surface side 1A and the flat top 23A of the columnar convex portion 23 on the second surface side 1B. In addition, it is not limited to the case where both sides have an uneven shape as shown in Figures 1 (A) and (B), but one of the front and back sides may have an uneven shape and the other side may have a flat shape. In this case, it is preferable that a wall surface in the thickness direction exists at the part connecting the top of the convex part on one side and the flat part on the other side (not shown), and the attached polymer is present on this wall surface.

The above-mentioned wall surface has more fibers aligned in the thickness direction than the fibers on the front and back sides of the nonwoven fabric, and the fibers have a high vertical orientation, so it has a structure that supports the nonwoven fabric in the thickness direction. The presence of the attached polymer on such a wall surface increases the strength of the vertically oriented fiber surface and the shape retention of the wall surface including this, further improving the thickness retention (compression resistance) of the nonwoven fabric against compressive forces. This effect is difficult to obtain with conventional flat nonwoven fabrics in which thickness is ensured by simply increasing the basis weight of the fiber layers oriented in the planar direction.

From the viewpoint of further improving the thickness retention of the nonwoven fabric of the present invention, the adhesion area ratio of the adhesion polymer to the wall surface is preferably 20% or more, more preferably 30% or more, and even more preferably 40% or more.
From the viewpoint of improving the feel of the nonwoven fabric, the adhesion area ratio of the adhesion polymer to the wall surface is preferably 60% or less, more preferably 55% or less, and even more preferably 50% or less.

(Method of measuring the adhesion area ratio of the adhesion polymer on the wall surface)
Based on the above-mentioned (method for confirming the presence of attached polymer in nonwoven fabric), the wall surface is cut out, and fiber areas not covered with attached polymer, attached polymer areas, and other areas (such as voids between fibers) are identified from the captured image of the wall surface.
Specifically, three points of the wall surface of the nonwoven fabric stained with Bouken Stain II are photographed at 150x magnification using a digital microscope. The image size is 1600x1200 pixels.
The observed image is then subjected to a ternary value process and converted from RGB to an HSV color model (under the same conditions as above), and the number of pixels determined to be red in the observed image is regarded as the polymer adhesion area (unit: px) on the wall surface.
From the obtained value, the adhesion area ratio of the adhered polymer is calculated based on the following formula (S2).
Polymer adhesion area ratio (%) on the wall surface = polymer adhesion area (px) on the wall surface ÷ total number of pixels in the image (1600px × 1200px) × 100 (S2)
The average value of the three photographed images of the wall surface is taken as the polymer adhesion area ratio on the wall surface of the nonwoven fabric being measured.

The longitudinal orientation of the fibers on the wall surface is indicated by the longitudinal orientation degree of the fibers. The "longitudinal orientation degree" is a value measured by the following (Method for measuring longitudinal orientation degree of fibers), and indicates the degree to which the orientation of fibers having a thickness direction component is uniform.
The "fibers having a thickness direction component" refers to fibers that have a vertical component as a vector relative to the horizontal plane when the nonwoven fabric of the present invention is placed on a horizontal plane with one of the front and back surfaces facing up.

From the viewpoint of improving the thickness retention of the nonwoven fabric when pressed, the degree of longitudinal orientation is preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more.
From the viewpoint of increasing the strength of the nonwoven fabric, the degree of longitudinal orientation is preferably 85% or less, more preferably 80% or less, and even more preferably 75% or less.

The wall surface having the above-mentioned degree of longitudinal orientation may extend along any direction in the plane of the nonwoven fabric. It is preferable that the wall surface extending along at least one direction has the above-mentioned degree of longitudinal orientation in the thickness direction. For example, it is preferable that the nonwoven fabric has an MD (machine flow direction during manufacturing; Machine Direction) and a CD (direction perpendicular to the MD; Cross Direction), and that the wall surface extending along at least either the MD or the CD has the above-mentioned degree of longitudinal orientation in the thickness direction, and it is more preferable that the wall surface extending along both the MD and the CD has the above-mentioned degree of orientation in the thickness direction.

(Method of measuring the degree of longitudinal orientation of fibers)
(1) A nonwoven fabric sample is frozen with liquid nitrogen and placed on a horizontal surface, and then a thickness cross section (cross section in the vertical direction) of a portion of the nonwoven fabric sample that is 50% of the thickness in the vertical direction relative to the horizontal surface (the thickness center portion) is cut with a razor blade to prepare a thickness cross section.
(2) The thickness cross section is observed at 35x magnification using a SEM, and an observed image is taken.
(3) A reference line L forming a square of 0.5 mm x 0.5 mm (dimensions within the observed image) is added to the observed image. Here, the reference line L is composed of an upper side L1 and a lower side L2 that are aligned in a direction along the horizontal plane, and a left side L3 and a right side L4 that are aligned in the vertical direction.
(4) Count the total number of fibers passing through the reference lines formed by each side of the square. The total number of fibers passing through the reference lines L of the top and bottom sides L1 and L2 of the square is the "top and bottom fiber number," and the total number of fibers passing through the reference lines L of the left and right sides L3 and L4 of the square is the "left and right fiber number."
(5) The degree of longitudinal orientation Q of the fibers of a nonwoven fabric is calculated as (number of upper and lower fibers)/(number of upper and lower fibers + number of left and right fibers)×100.
Three observation images of each of these points are prepared and measured for the same nonwoven fabric sample, and the average is used as the measurement data.
3 shows an observation screen with square reference lines L. In the drawing, black dots 71 indicate positions where the fiber 7 passes through the reference lines L (L1 to L4).

The "thickness center" means a portion between a horizontal plane and an imaginary plane in the "apparent thickness" of the nonwoven fabric defined above, the portion being 50% of the distance in the vertical direction to the horizontal plane.
The apparent thickness of the nonwoven fabric here is measured based on the above-mentioned (method of measuring the apparent thickness of a nonwoven fabric under a load of 0.05 kPa).

The nonwoven fabric of the present invention is suppressed to a small reduction in thickness when a compressive force is applied. From the viewpoint of ensuring a sufficient thickness during use, the apparent thickness of the nonwoven fabric of the present invention when compressed at 3 kPa is preferably 1.5 mm or more, more preferably 1.8 mm or more, and even more preferably 2.0 mm or more.
As a result, the nonwoven fabric of the present invention has a thickness that can be felt even when it is pressed and used, and has a comfortable texture. Furthermore, when the nonwoven fabric of the present invention is used as a member on the skin side of the absorbent body in an absorbent article, the distance and space between the absorbent body and the skin surface can be more effectively secured during use. For example, even if a baby excretes loose stools while sleeping, the diffusion area of the loose stools in the planar direction is reduced, the adhesion of the loose stools to the skin is suppressed, and absorbency is improved.
Moreover, the apparent thickness of the nonwoven fabric of the present invention when pressed at 3 kPa is preferably 5 mm or less, more preferably 4 mm or less, and even more preferably 3 mm or less, from the viewpoint of improving liquid absorbency.

The apparent thickness at a pressure of 3 kPa can be measured by changing the load in the above-mentioned (method for measuring the apparent thickness of a nonwoven fabric under a load of 0.05 kPa) to 3 kPa and leaving the material to stand for 1 minute with the load (compressive force) applied.

In the nonwoven fabric of the present invention, the content of the aforementioned attachment polymer is preferably 100 g/ ^m2 or less, more preferably 80 g/ ^m2 or less, and even more preferably 50 g/m2 or less per unit area of the nonwoven fabric from the viewpoint of improving the texture of the nonwoven fabric. The content of the aforementioned attachment polymer is preferably 15 g/ ^{m2 or} more, more preferably 20 g/m2 or ^more , and even more preferably 25 g/m2 or ^more per unit area of the nonwoven fabric from the viewpoint of improving the thickness retention of the nonwoven fabric when pressed.

In addition, in the nonwoven fabric of the present invention, from the viewpoint of having a thickness both before and after pressing as described above and a soft and flexible feel, the basis weight is preferably 100 g/ ^m2 or less, more preferably 80 g/ ^m2 or less, and even more preferably 60 g/ ^m2 or less.
The lower limit of the basis weight is not particularly limited, but from the viewpoint of improving the texture of the nonwoven fabric, it is preferably 10 g/m2 or ^more , more preferably 15 g/ ^m2 or more, and even more preferably 20 g/m2 or ^more .

When the nonwoven fabric of the present invention 1 has an uneven shape, various uneven shapes can be used. In addition, various materials that are usually used as materials that come into contact with the skin can be used.
For example, there are various types of uneven shapes of nonwoven fabrics, such as those with solid convexities, those with hollow convexities, those with a single fiber layer structure, those with a double fiber layer structure, those with convexities arranged in a scattered manner in a planar direction, those with convexities and concaves arranged in a ridge-like pattern, etc. In addition, the uneven shape is not limited to being on one side, and may be on both sides.
Among these, preferred is a nonwoven fabric having a single layer structure in which the convex portions of the concave-convex shape are hollow and the concave-convex shape is present on both sides of the nonwoven fabric, for example, the following nonwoven fabric 80 (specific example 1) and nonwoven fabric 90 (specific example 2).
These are explained below.

The nonwoven fabric 80 (Specific Example 1) has a single layer structure containing thermoplastic fibers, and has the uneven shape shown below.
That is, the sheet has outer fiber layers 81, 82 on the first side 1A and the second side 1B, and a plurality of connecting portions 83 disposed between the outer fiber layer 1 on the first side 1A and the outer fiber layer 2 on the second side 1B. The outer fiber layer 81 on the first side 1A and the outer fiber layer 82 on the second side 1B are partially fused to the connecting portions 83.
In addition, the outer fiber layer 82 and the connecting portion 83 on the second surface 1B side have the attachment polymer present on the fiber surfaces, and the attachment polymer is attached so as to cover the fiber entanglement points.
The outer fiber layers 81, 82 and the connecting portion 83 form an uneven shape in the thickness direction of the nonwoven fabric 80, which includes hollow convex portions, concave portions, and wall surfaces connecting the convex portions and the concave portions. The uneven shape is formed on both the first surface 1A side and the second surface 1B side. Specifically, on the first surface 1A side, the convex portions 81 formed by the outer fiber layer 81 and the concave portions 88 between the outer fiber layers 81 have an uneven shape. On the second surface 1B side, the convex portions 82 formed by the outer fiber layer 82 and the concave portions 89 between the outer fiber layers 82 have an uneven shape. The convex portions 81 formed by the outer fiber layer 81 and the convex portions 82 formed by the outer fiber layer 82 are both hollow. The connecting portion 83 forms a wall surface 83 connecting the convex portions 81 and the concave portions 88 (the convex portions 82 and the concave portions 89).
The nonwoven fabric 80 may have various configurations described in paragraphs [0010] to [0048] of JP 2019-44319 A. For example, the uneven shape of the nonwoven fabric 80 may be a shape in which the convex portions 81 formed by the outer surface fiber layer 81 and the concave portions 88 between them are arranged in a ridge-like shape on the first surface 1A side. Similarly, the convex portions 82 formed by the outer surface fiber layer 82 and the concave portions 89 between them may be arranged in a ridge-like shape on the second surface 1B side. In addition, the outer surface fiber layers 81 and 82 may have fibers oriented in the planar direction. The wall surface 83 formed by the connecting portion 83 may have fibers oriented vertically. The outer surface fiber layer 1 that becomes the convex portion on the first surface 1A side may have two types (a first outer surface fiber layer 81A and a second outer surface fiber layer 81B) having lengths extending along different directions that intersect in a plan view of the nonwoven fabric. The multiple connecting parts 83 may be arranged along different directions that intersect in a plan view of the nonwoven fabric, and may have two types (first connecting parts 83A and second connecting parts 83B) with different wall surface orientations of the connecting parts 83. In this case, the first connecting parts 83A and the second connecting parts 83B may have wall surface orientations that are different from each other, or the fibers may be oriented vertically.
This nonwoven fabric 80 typically has the shape shown in FIG.
Such an uneven shape of nonwoven fabric 80 can be produced by the method described in paragraphs [0049] to [0057] of JP 2019-44319 A.

The nonwoven fabric 90 (Specific Example 2) has a single layer structure containing thermoplastic fibers, and has the uneven shape shown below.
That is, on the first surface 1A side, a plurality of vertical ridges 911 protruding toward the first surface 1A side in the thickness direction of the nonwoven fabric are arranged extending in one direction on the first surface 1A side in a plan view. The vertical ridges 911 are arranged side by side at a distance in another direction on the first surface 1A side in a plan view different from the one direction on the first surface 1A side. In addition, horizontal ridges 921 extending in the other direction on the first surface 1A side are arranged connecting the vertical ridges 911. The vertical ridges 911 and the horizontal ridges 921 each form a hollow convex portion. The nonwoven fabric 90 has an uneven shape in its thickness direction, which includes convex portions, concave portions, and wall surfaces 911W connecting the convex portions and the concave portions, due to the vertical ridges 911 and the horizontal ridges 921 and the concave portions 922 between them. On the first surface 1A side, the convex portions formed by the vertical ridge portions 911 and the horizontal ridge portions 921 have lengths extending along different directions that intersect in a plan view of the nonwoven fabric 90. In this case, the uneven shape on the first surface side of the nonwoven fabric 90 may be a shape in which the convex portions formed by the vertical ridge portions 911 and the horizontal ridge portions 921 and the concave portions therebetween are arranged in a ridge-groove shape.
In addition, on the second surface 1B side, a plurality of hollow convex ridges 931 are arranged, which extend in one direction on the second surface 1B side in plan view and are arranged in another direction on the second surface 1B side different from the one direction on the second surface 1B side. In addition, a concave ridge 936 sandwiched between the plurality of convex ridges 931 extends in one direction on the second surface 1B side. The uneven shape on the second surface 1B side of the nonwoven fabric 90 has a shape in which the convex ridges 931 and the concave ridges 936 are arranged in a ridge-like shape. The convex ridges 931 are formed by a plurality of convex portions 934 connected in a ridge-like shape, and narrow and wide portions are alternately connected and arranged in a plan view. Between the convex portions 934 connected in a ridge-like shape, there is a slightly low depression 935. The nonwoven fabric 90 has an uneven shape in its thickness direction, which includes protrusions, recesses, and wall surfaces 931W connecting the protrusions and recesses, formed by the protrusions 931 and the recesses 936.
In addition, the adhesion polymer is present on the fiber surfaces of the ridges 931, the grooves 936 and the wall surfaces 931W, and the adhesion polymer is adhered so as to cover the fiber entanglement points.
The nonwoven fabric 90 may employ various configurations described in paragraphs [0012] to [0058] of JP 2019-44320 A. For example, the orientation direction of the fibers constituting the vertical ridge portion 911 and the fibers constituting the horizontal ridge portion 921 may be different. The height of the vertical ridge portion 911 and the height of the horizontal ridge portion 921 may be different, and the horizontal ridge portion 921 may be curved in the thickness direction of the nonwoven fabric 90 or may have an equal height. In addition, each of the two lines constituting the widthwise outline of the convex strip portion 931 when viewed in plan from the second surface 1B side may be a curve having multiple arcs. Fuzz may be arranged on the side of the convex strip portion 931.
The nonwoven fabric 90 typically has the shape shown in FIGS.
Such an uneven shape of nonwoven fabric 90 can be produced by the method described in paragraphs [0059] to [0065] of JP2019-44320A.

The method for producing the nonwoven fabric of the present invention preferably includes a step of spraying the nonwoven fabric after forming the uneven shape as described above as a raw material nonwoven fabric with an adhesion polymer coating solution by a spray or the like, and drying the raw material nonwoven fabric. This can avoid adhesion (sticking) between the nonwoven fabric and a mold for forming unevenness used when producing a nonwoven fabric from a fiber web. In addition, the spraying method is preferable because it allows suitable control of the amount of adhesion polymer applied to the nonwoven fabric.
In the above-mentioned manufacturing method, the deposition polymer coating solution is preferably sprayed from the side of the raw nonwoven fabric where the wall surface is exposed, which is preferable because the deposition polymer is more easily and reliably fixed to the wall surface of the uneven shape of the nonwoven fabric of the present invention.

For example, the method for producing a nonwoven fabric of the present invention is preferably carried out through the steps shown in FIG.
In Fig. 11 (A) and (B), a fiber web 110 containing thermoplastic fibers is placed on a support male member 120, and a support female member 130 is pressed into the support male member 120 from above the fiber web 110. At this time, the protrusion 121 of the support male member 120 is inserted into the support recess 132 of the support female member 130. Also, the protrusion 131 of the support female member 130 is inserted into the support recess 122 of the support male member 120. This causes the fibers to be oriented in the thickness direction and the planar direction. Next, as shown in Fig. 11 (C), the support female member 130 is removed, and hot air W is blown from above the shaped fiber web to fuse the fibers together. This forms a raw material nonwoven fabric 140.
Thereafter, as shown in Figures 11 (D) and (E), the raw nonwoven fabric 140 is removed from the support male material 120, and the adhesion polymer coating solution 66 is sprayed with a spray or the like to fix the adhesion polymer 6, thereby obtaining the nonwoven fabric of the present invention. At this time, the surface side to which the adhesion polymer coating solution 66 is sprayed on the raw nonwoven fabric is preferably the surface side on which the wall surface in the thickness direction connecting the front and back surfaces is exposed by the shaping. This allows the adhesion polymer to be reliably attached to the wall surface. In addition, the surface side on which the wall surface is exposed is preferably the surface side 1B on which hot air is blown in Figure 11 (D). This allows the surface on which the fibers have been relatively fused by the hot air to be the adhesion surface of the adhesion polymer, and the surface side can be the back side (non-skin side in an absorbent article) during use.

The drying temperature is preferably 60°C or higher, more preferably 100°C or higher, and even more preferably 110°C or higher. This is preferable because it facilitates the crosslinking reaction of the adhesion polymer coating agent in the sprayed adhesion polymer coating solution, and it facilitates the improvement of the strength of the fiber surface and the adhesive strength at the fusion point, and thus the compression resistance of the nonwoven fabric. From the viewpoint of improving the texture of the nonwoven fabric, the drying temperature is preferably 130°C or lower, more preferably 125°C or lower, and even more preferably 120°C or lower. Furthermore, from the viewpoint of improving the crosslinking reaction of the polymer, the drying time is preferably 1 minute or longer, more preferably 3 minutes or longer, and even more preferably 5 minutes or longer.

The spray mass of the adhesion polymer coating agent is preferably 10 g/ ^m2 or more, more preferably 20 g/ ^m2 or more, per unit area of the raw nonwoven fabric from the viewpoint of improving the thickness retention of the nonwoven fabric when pressed. Also, the spray mass of the adhesion polymer coating agent is preferably 300 g/ ^m2 or less, more preferably 250 g/ ^m2 or less, per unit area of the raw nonwoven fabric from the viewpoint of improving production efficiency and preventing contamination of the production line.
In addition, within the above range, the spray mass of the adhesion polymer coating agent can be appropriately set depending on the application of the nonwoven fabric. When the nonwoven fabric of the present invention is used for sanitary products (absorbent articles, wiping sheets, masks, etc.), the spray mass of the adhesion polymer coating agent is preferably 10 g/m ² or more and 30 g/m ² or less per unit area of the raw nonwoven fabric, more preferably 15 g/m ² or more and 25 g/m ² or less, from the viewpoint of improving the texture of the nonwoven fabric. When the nonwoven fabric of the present invention is used for industrial purposes such as filters, the spray mass of the adhesion polymer coating agent is preferably 100 g/m ² or more and 300 g/m ² or less per unit area of the raw nonwoven fabric, more preferably 150 g/m ² or more and 250 g/m ² or less, from the viewpoint of improving the thickness retention of the nonwoven fabric when pressed.

Next, the thermoplastic fibers constituting the nonwoven fabric of the present invention will be described.
The thermoplastic fibers may be any fibers that are commonly used as materials for nonwoven fabrics without any particular limitations. For example, they may be fibers made of a single resin component or composite fibers made of multiple resin components. Composite fibers may have, for example, a core-sheath structure or a side-by-side structure.
When using composite fibers containing a low melting point component and a high melting point component as the thermoplastic fiber (for example, composite fibers having a core-sheath structure in which the sheath is a low melting point component and the core is a high melting point component), the temperature of the hot air blown onto the fiber web in the manufacturing process is preferably equal to or higher than the melting point of the low melting point component and lower than the melting point of the high melting point component. More preferably, the temperature is equal to or higher than the melting point of the low melting point component and lower than the melting point of the high melting point component by 10°C or more, and even more preferably, the temperature is higher than the melting point of the low melting point component by 5°C or more and lower than the melting point of the high melting point component by 20°C or more. In addition, from the viewpoint of elasticity, the more the core of the core-sheath structure composite fiber is, the higher the elasticity is. Therefore, it is preferable that the core component is larger in terms of cross-sectional area ratio. Specific examples of composite fibers having a core-sheath structure in which the sheath is a low melting point component and the core is a high melting point component include composite fibers having a core-sheath structure in which the sheath is a polyethylene resin (hereinafter also referred to as PE) and the core is a polyethylene terephthalate resin (hereinafter also referred to as PET).
Furthermore, in composite fibers with a core-sheath structure, when the resin component of the sheath has a lower glass transition point than the resin component of the core (hereinafter referred to as low glass transition point resin) (for example, the resin component of the core is PET and the resin component of the sheath is PE), the thickness recovery of the nonwoven fabric can be further improved by reducing the mass ratio of the low glass transition point resin component.

Such a nonwoven fabric of the present invention can be used for various purposes.
For example, the nonwoven fabric of the present invention can be used in absorbent articles such as diapers, sanitary napkins, panty liners, and urine pads. Absorbent articles typically have a liquid-permeable top sheet, a back sheet, and an absorbent sandwiched between them. The nonwoven fabric of the present invention can be particularly suitably used as a top sheet. Furthermore, the nonwoven fabric can also be used as a sheet in the gather part, an exterior sheet, or a sheet in the wing part of an absorbent article.
The nonwoven fabric of the present invention can also be used as a component of an eye mask or a mask.

The present invention will be explained in more detail below based on examples, but the present invention should not be construed as being limited thereto. In the examples, "parts" and "%" are all based on mass unless otherwise specified. In Table 1 below, "-" means that the item does not have a corresponding value, etc.

Example 1
(1) Preparation of raw material nonwoven fabric First, a fiber web was prepared using thermoplastic fibers of a core-sheath type (polyethylene terephthalate (PET) (core): polyethylene (PE) (sheath) = 5:5 (mass ratio)) with a fineness of 1.8 dtex. The fiber web was subjected to uneven shaping using the same male support material and female support material as in Example 1 described in JP-A-2019-44320 (FIGS. 13(A) to (C) of the same document). At that time, the female support material was pushed in 8 mm.
Next, the female support was removed, and the shaped fiber web held on the male support was transported at a transport speed of 10 m/min, while a hot air blowing treatment (air-through treatment) was performed twice from above the fiber web. The first blowing treatment was performed under conditions of a temperature of 160° C., a wind speed of 68 m/sec, and a blowing time of 5 seconds. The second blowing treatment was performed under conditions of a temperature of 160° C., a wind speed of 6.0 m/sec, and a blowing time of 5 seconds.
As a result, a raw material nonwoven fabric having a constituent fiber fineness of 1.8 dtex and a basis weight of 40±4 g/ ^m2 and having the uneven shape shown in Figures 5 to 10 was produced. The size of the raw material nonwoven fabric was 100 mm x 100 mm.
(2) Preparation of the adhesion polymer coating solution An adhesion polymer coating solution was prepared by mixing 10% by mass of an adhesion polymer solution with a solid content of about 50% and 90% by mass of deionized water. The adhesion polymer solution used had a glass transition point of 60°C for the solid content (adhesion polymer coating agent) (Polysol AT-860 (trade name) manufactured by Showa Denko K.K., components: acrylic resin 49.8% by mass, water 50.2% by mass). The adhesion polymer solution had a pH of 4.6 and a viscosity of 69 mPa·s.
(3) Spraying of Adhesion Polymer Coating Solution Next, the adhesion polymer coating solution was evenly applied by spraying to the second surface 1B (hot air blowing surface) of the raw nonwoven fabric on which the convex streak portion 931 and the concave streak portion 936 were arranged as shown in Figures 8 to 10. Next, it was dried for 5 minutes at 120°C in an electric dryer.
This produced nonwoven fabric sample A1 of Example 1 having the apparent thickness and contact area shown in Table 1. The apparent thickness and contact area were measured based on the above-mentioned (Method for measuring the apparent thickness of a nonwoven fabric under a load of 0.05 kPa) and (Method for measuring the contact area).
The applied amount of the solid content of the deposition polymer solution was 22.1 g/ ^m2 , which was measured by the change in the mass of the nonwoven fabric before and after the deposition polymer was applied.

Example 2
A nonwoven fabric sample A2 of Example 2 was prepared in the same manner as in Example 1, except that an attachment polymer solution having a glass transition point of 10° C. (Aron NW-7060 (product name) manufactured by Toa Gosei Co., Ltd.; components: 49.9% by mass of acrylic acid-based polymer, 49.6% by mass of water, 0.5% by mass of methanol) was used as the attachment polymer solution, and a coating method was used in which the raw nonwoven fabric was impregnated with the attachment polymer coating solution. The attachment polymer solution had a pH of 5.3 and a viscosity of 58 mPa·s.
The solids coating weight of the deposition polymer solution was 16.9 g/ ^m2 .

Example 3
A nonwoven fabric sample A3 of Example 3 was prepared in the same manner as in Example 1, except that an attachment polymer solution having a glass transition point of 15° C. (Sumikaflex 752 (product name) manufactured by Sumika Chemtex Corporation; components: ethylene-vinyl acetate copolymer (concentration about 50%), water (concentration about 50%), emulsifier (undisclosed)) was used as the attachment polymer solution, and a coating method was used in which the raw nonwoven fabric was impregnated with the attachment polymer coating solution. The attachment polymer solution had a pH of 5.4 and a viscosity of 1020 mPa s.
The solids coating weight of the deposition polymer solution was 22.1 g/ ^m2 .

Example 4
A nonwoven fabric sample A4 of Example 4 was prepared in the same manner as in Example 1, except that an attachment polymer solution having a glass transition point of 40° C. (DICFINE AJ-1820 (product name) manufactured by DIC Corporation; components: 50-60% by mass of water, 44.5% by mass of acrylic resin, less than 1% ammonia (containing water), less than 1% others) was used and a coating method was used in which the raw nonwoven fabric was impregnated with the attachment polymer coating solution. The attachment polymer solution had a pH of 6.1 and a viscosity of 588 mPa s.
The solids coating weight of the polymer solution was 16.8 g/ ^m2 .

Example 5
A nonwoven fabric sample A5 of Example 5 was prepared in the same manner as in Example 1, except that a coating method in which the raw nonwoven fabric was impregnated with a polymer coating solution was used.
The solids coating weight of the deposition polymer solution was 20.1 g/ ^m2 .

(Example 6)
A nonwoven fabric sample A6 of Example 6 was prepared in the same manner as in Example 3, except that the coating solution was adjusted to contain 30% by mass of an attachment polymer solution having a solid content of about 50% and 70% by mass of deionized water.
The solids coating weight of the deposition polymer solution was 97.9 g/ ^m2 .

(Example 7)
A nonwoven fabric sample A6 of Example 6 was prepared in the same manner as in Example 3, except that a stock solution of the deposition polymer having a solid content of about 50% was used without diluting it.
The solids application weight of the deposition polymer solution was 331 g/ ^m2 .

(Comparative Example 1)
The raw material nonwoven fabric produced in Example 1 was used as nonwoven fabric sample C1 of Comparative Example 1. In other words, nonwoven fabric sample C1 had no attached polymer.

(Comparative Example 2)
A nonwoven fabric sample C2 of Comparative Example 2 was prepared in the same manner as in Example 1, except that an attachment polymer solution having a glass transition point of -40°C (Boncoat AB-886 (product name) manufactured by DIC Corporation; components: 50.8% by mass of acrylic resin, 45-55% by mass of water, less than 1% by mass of n-butyl acrylate, less than 1% by mass of isopropyl alcohol, and less than 1% by mass of others) was used and a coating method was used in which the raw nonwoven fabric was impregnated with the attachment polymer coating solution. The attachment polymer solution had a pH of 6.6 and a viscosity of 40 mPa·s.
The solids application weight of the deposition polymer solution was 20.0 g/ ^m2 .

The following measurements and tests were carried out for each of the above examples and comparative examples.
(1) Adhering area and adhering area ratio of polymer on wall surface These were measured and calculated based on the above-mentioned (Method for measuring the adhering area ratio of the polymer on the wall surface).
(2) Test for apparent thickness under a pressure of 3 kPa The load in the above-mentioned (method for measuring the apparent thickness of a nonwoven fabric under a load of 0.05 kPa) was changed to 3 kPa, and the sample was left to stand for 1 minute with the load (compressive force) applied, and then the measurement was carried out.
(3) Test for spreading area of soft stool The top sheet of "Merry's Tape S size" (product name) manufactured by Kao Corporation was peeled off with a cold spray, and the nonwoven fabric sample prepared in each Example and Comparative Example was placed as a top sheet. At that time, the surface of the nonwoven fabric sample that was to come into contact with the skin (the surface shown in FIG. 5) was placed facing up.
The diaper was spread out flat, and 10 g of simulated loose stool (viscosity 40 mPa·s) was poured into the diaper at a position 30 mm behind the longitudinal center at a flow rate of 6 g/s. The simulated loose stool was made by dispersing bentonite in ion-exchanged water, and the bentonite concentration was adjusted to a viscosity of 40 mPa·s.
A resin film was placed over the injection position, and a weight was placed on the resin film so as to apply a pressure of 3 kPa, followed by leaving the film to stand for 2 minutes.
After 2 minutes, the weight and resin film were removed, and the area on the surface sheet (each nonwoven fabric sample) where the simulated soft stool had spread was transferred to an OHP sheet, scanned and imported into Image-Pro Plus (product name, manufactured by Nippon Roper Co., Ltd.) to determine the area of stool spread on the surface sheet (each nonwoven fabric sample).

As shown in Table 1, the nonwoven fabric samples of each Example had the same apparent thickness as the nonwoven fabric samples of each Comparative Example, but had a greater thickness of 1.5 mm or more when pressurized with 3 kPa, and thus the reduction in thickness when a compressive force was applied was smaller than that of the nonwoven fabric samples of each Comparative Example.
Furthermore, when the diffusion area of simulated loose stool was tested for Example 1, which had a small reduction in thickness upon compression, and Comparative Example 1, which had a large reduction in thickness, the diffusion area was smaller in Example 1 than in Comparative Example 1. In other words, it was found that the small reduction in thickness in Example 1 was significant in suppressing the diffusion area of body fluids such as loose stool, and was significant in the liquid absorbency of the absorbent article and in preventing body fluids from adhering to the skin.

10, 20 Nonwoven fabric 12, 22 Convex portion 12A, 22A on one surface side Apex of convex portion on one surface side 13, 23 Convex portion 13A, 23A on the second surface side Apex of convex portion on the second surface side 14, 24 Wall surface 6 Deposition polymer 61 Deposition polymer film 66 Deposition polymer coating liquid 7 Fiber 71 Black dots L, L1 to L4 Reference line

Claims (9)

An air- through nonwoven fabric having fusion points between fibers,
The fiber has a polymer having a glass transition temperature of 10° C. or more attached thereto ,
The apparent thickness is 1.5 mm or more when a load of 0.05 kPa is applied from one side using a horizontal plate ,
On at least one side of the air-through nonwoven fabric, the ratio of the contact area between the horizontal plate and the air-through nonwoven fabric under a pressure of 3 kPa to the surface area of the air-through nonwoven fabric is 90% or less;
The polymer is fixed to the surface of the fusion points between the fibers .
Air-through nonwoven fabric. 2. The air- through nonwoven fabric according to claim 1, which has one surface and a second surface opposite to the first surface, and the proportion of the contact area on both the first surface and the second surface is 90% or less. The air-through nonwoven fabric according to claim 1 or 2, wherein the air-through nonwoven fabric has a wall surface in the thickness direction connecting one side and a second side of the air-through nonwoven fabric, and the degree of longitudinal orientation of the fibers in the wall surface is 50% or more and 85% or less. The air- through nonwoven fabric according to any one of claims 1 to 3, wherein the air-through nonwoven fabric has a wall surface in a thickness direction connecting one surface and a second surface of the air-through nonwoven fabric, and the adhesion area ratio of the polymer on the wall surface is 20% or more. The air-through nonwoven fabric according to any one of claims 1 to 4 , having an apparent thickness of 1.5 mm or more when pressurized at 3 kPa. The air- through nonwoven fabric according to any one of claims 1 to 5, which is for an absorbent article. An absorbent article comprising the air-through nonwoven fabric according to any one of claims 1 to 6. A method for producing the air- through nonwoven fabric according to any one of claims 1 to 6 , comprising the steps of spraying a polymer coating liquid containing a polymer having a glass transition point of 10°C or higher onto a raw material air-through nonwoven fabric , and drying the fabric. The method for producing an air-through nonwoven fabric according to claim 8, wherein the polymer coating liquid is a liquid containing 3% by mass or more and 55% by mass or less of a polymer having a glass transition point of 10° C. or more.

Images