Manufacturing method of nonwoven fabric for absorbent article

Abstract

To provide a method for manufacturing a nonwoven fabric for absorbent article, which can form apertures so as to be larger than that in conventional one.SOLUTION: A method for manufacturing a nonwoven fabric for absorbent article includes: a step to hold and form an unfused fiber web between a support having intermittently disposed open holes and a push-in member having projections capable of engaging with the open holes; and a step to thermally fuse fibers of the formed unfused fiber web on the support by heated fluid. The support has apertures having outer peripheries continuing in a circumferential direction while surrounding the open holes.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a nonwoven fabric for absorbent articles. [Background technology]

[0002] Conventionally, techniques relating to methods for producing nonwoven fabrics with concave and convex shapes have been disclosed. For example, Patent Document 1 describes a method for producing a nonwoven fabric in which a heat-fusible web is shaped by a flexible support having an uneven shape and a pushing member, and then fusion-treated with a heated fluid. In this production method, a technique is described in which protrusions are intermittently arranged on the surface of the flexible support, and the heat-fusible web is shaped into an uneven shape by the protrusions and the pushing member that bites into the spaces between the protrusions. Patent Document 2 describes a method for producing a concave-convex nonwoven fabric in which an unfused web is engaged and shaped using a male support member and a female support member, and then the fibers are thermally fused together using hot air. The female support member has projections that are continuous in one direction when viewed from above. The male support member has a plurality of independent projections, such as rectangular columns or cylinders, arranged at intervals. The projections of the male support member have sharp tips that form openings in the nonwoven fabric. Patent Document 3 describes a technique for shaping a nonwoven fabric in which fibers have already been fused together by meshing a concave roller M with a convex roller N. It describes that in this shaping, the concave holes a of the concave roller M and the needle tips d of the convex roller N perforate the nonwoven fabric, and an open structure D is formed in the nonwoven fabric under conditions of roll heating. Patent Document 4 describes a method for producing a nonwoven fabric sheet, in which a spread web is placed on a pattern plate having a regular arrangement of convex parts with relatively high airflow resistance and concave parts with relatively low airflow resistance, and then a fluid is sprayed onto the web to heat and fuse the web. The spray of the fluid moves the fibers at the convex parts of the pattern plate, forming openings in the web. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-076782 [Patent Document 2] JP 2020-000467 A [Patent Document 3] Special Publication No. 2017-507254 [Patent Document 4] JP 2012-052253 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the manufacturing method described in Patent Document 2, while the unfused web is supported by the protrusions of the male member of the support, holes are opened in the opposite direction to the pushing direction of the pushing member. In addition, these holes are opened in the opposite direction to the direction in which hot air is blown onto the support. Therefore, the size of the holes depends on the tip shape of the male member of the support, and in order to make the holes larger, the diameter of the tip needs to be increased. However, there is a limit to the enlargement of the diameter of the tip of the male member of the support in relation to the good shaping of the uneven shape, and there is room for improvement in order to make the holes larger. In this respect, the manufacturing method in Patent Document 1 does not mention opening holes. The manufacturing method described in Patent Document 3 involves partially destroying the nonwoven fabric in which the fibers have already been fused together, and since openings are formed while destroying the fused portions of the fibers, it is difficult to make the openings larger. In the manufacturing method described in Patent Document 4, the fibers are split by injecting a fluid to open holes, so to make the holes larger, the fluid must be stronger. However, there is a limit to changing conditions such as the fluid injection speed in relation to good shaping of the uneven shape, and there is a limit to how large the holes can be made.

[0005] In view of the above, the present invention relates to a method for producing a nonwoven fabric for absorbent articles, which is capable of forming larger openings than in the past. [Means for solving the problem]

[0006] The present invention provides a method for manufacturing a nonwoven fabric for absorbent articles, which includes the steps of clamping and shaping an unfused fiber web using a support having intermittently arranged through holes and a pushing member having protrusions that can engage with the through holes, and heat-fusing the fibers of the shaped unfused fiber web on the support using a heated fluid, wherein the support has an outer periphery that is continuous in the circumferential direction while surrounding the through holes, and has an opening portion. Effect of the Invention

[0007] According to the method for producing a nonwoven fabric for absorbent articles of the present invention, it is possible to form openings larger than before. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing a preferred embodiment of an apparatus used in a method for producing a nonwoven fabric for absorbent articles according to the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing another preferred embodiment of an apparatus used in the method for producing a nonwoven fabric for absorbent articles of the present invention. [Diagram 3] 4 is a cross-sectional view showing an example of a state in which a protrusion of a pushing member and a through-hole of a support are engaged with each other via an unfused fiber web. FIG. [Figure 4] 1 is a schematic explanation of a method for confirming that the outer periphery of a support is continuous. [Diagram 5] 1A is a plan view showing an example of a through hole and an outer peripheral portion arranged on the outer peripheral surface of a support body, FIG. 1B is an enlarged cross-sectional view of the cross section along line BB in FIG. 1A, and FIG. 1C is an enlarged cross-sectional view of the cross section along line CC in FIG. [Figure 6] FIG. 2 is a cross-sectional view showing a schematic example of a configuration in which a through hole in an outer surface of a support has different diameters at its surface and bottom. [Figure 7] 1 is a plan view showing a preferred embodiment of an arrangement of through holes and an outer periphery on an outer surface of a support body. FIG. [Figure 8] 13 is a plan view showing another preferred embodiment of the arrangement of through holes and an outer periphery on the outer surface of the support body. FIG. [Figure 9] 13 is a plan view showing yet another preferred embodiment of the arrangement of the through holes and the outer periphery on the outer surface of the support body. FIG. [Figure 10] 13 is a plan view showing yet another preferred embodiment of the arrangement of the through holes and the outer periphery on the outer surface of the support body. FIG. [Figure 11] 13 is a plan view showing yet another preferred embodiment of the arrangement of the through holes and the outer periphery on the outer surface of the support body. FIG. [Figure 12] 10 is a plan view showing a configuration in which a ring-shaped supporting portion is disposed on the outer surface of the support body shown in FIG. 9. FIG. [Figure 13] FIG. 2 is a side view of a nonwoven fabric, which is a schematic diagram showing the criteria for determining the perforation method in the nonwoven fabric produced by the method for producing a nonwoven fabric for absorbent articles of the present invention. [Figure 14] 1 is a side view showing a schematic relationship between the outer periphery and through holes of a support used in the manufacturing method of a nonwoven fabric for absorbent articles of the present invention and the uneven structure of the nonwoven fabric to be manufactured. [Figure 15] FIG. 2 is a side view showing the locations for measuring the fiber mass ratio in the peripheral areas of the apertures and the fiber density of the walls in the nonwoven fabric produced by the method for producing a nonwoven fabric for absorbent articles of the present invention. [Figure 16] 1A and 1B are photographs of a nonwoven fabric sample obtained by carrying out the manufacturing method of Example 1, in which (A) shows the state as viewed from the front side (convex portion side) of the nonwoven fabric sample, (B) shows a partially enlarged view of the openings of (A), and (C) shows the state as viewed from the back side (opening portion side). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A preferred embodiment of the method for producing a nonwoven fabric for absorbent articles according to the present invention will be described below with reference to the drawings. In this specification, the nonwoven fabric for absorbent articles may simply be referred to as a nonwoven fabric. Also, the method for producing a nonwoven fabric for absorbent articles may simply be referred to as a method for producing a nonwoven fabric, or simply as a production method. In this specification, the conveying direction during the production of the nonwoven fabric is also referred to as the MD direction (Machine Direction), and the width direction perpendicular to the conveying direction is also referred to as the CD direction (Cross Direction).

[0010] The method for producing a nonwoven fabric for absorbent articles of the present invention includes the following two steps (hereinafter also referred to as step (I) and step (II)). (I) A step of shaping an unfused fiber web by clamping it between a support having intermittently arranged through holes and a pushing member having protrusions that can mesh with the through holes. (II) A step of thermally fusing the fibers of the shaped unfused fiber web on the support by using a heated fluid. In addition, the support body has an outer circumferential portion that is continuous in the circumferential direction and surrounds the through hole.

[0011] In step (I), the unfused fiber web is shaped to have projections and recesses to increase its thickness, and in step (II), fused fiber portions are formed at the intersections of the fibers to form a nonwoven fabric. In step (I), the protrusion and the through hole can be engaged with each other, which means that the tip of the protrusion of the pushing member is inserted beyond the outer peripheral surface (curved surface when the support is cylindrical, flat surface when the support is belt-shaped) that is extrapolated from the outer peripheral surface that is continuous in the circumferential direction surrounding the through hole. When the outer peripheral surface of the support has an uneven shape with a height difference of 1 mm or less as described later (see FIG. 4), for example, the surface that extrapolates the inner diameter side surface of the sector plate 9 shown in FIG. 4 is taken as the outer peripheral surface. Regarding the meshing amount, when the support and the pushing member are rotating bodies, the distance between the outer peripheral surface that extrapolates the outer peripheral surface of the support and the tip of the protrusion of the pushing member at the point where the tip of the protrusion of the pushing member is pushed into the support by the maximum amount when the respective rotating bodies rotate while meshing with each other is taken as the meshing amount. At this time, in order to reduce wear and deformation of the support and the pushing member, it is preferable that the support and the pushing member do not directly contact each other. The heated fluid in step (II) may be any of various fluids capable of thermally fusing the fibers. For example, hot air or steam may be used. However, hot air is preferred from the viewpoint of making the fiber oil on the fiber surface less likely to flow.

[0012] "Unfused fiber web" means an assembly of unfused fibers that can be fused by heat (hot air, steam, heat embossing, ultrasonic embossing, etc.), and excludes nonwoven fabrics that have been mechanically entangled by hydroentanglement or needle punching before the fusion treatment process. More specifically, unfused webs do not have the strength of nonwoven fabrics, and those with a maximum tensile strength of 100cN / 50mm or less in the MD and CD directions are considered to be unfused webs. For example, card webs are included. The unfused fiber web and the nonwoven fabric produced thereby contain thermoplastic fibers as constituent fibers.

[0013] The thermoplastic fibers may be made of various materials that are commonly used in nonwoven fabrics. Examples of the fibers include polyolefin fibers such as polyethylene (hereinafter also referred to as PE) fibers and polypropylene (hereinafter also referred to as PP) fibers, and fibers made solely of thermoplastic resins such as polyethylene terephthalate (hereinafter also referred to as PET) and polyamide. It is also possible to use composite fibers of a core-sheath type or side-by-side type structure. In the present invention, it is preferable to use composite fibers. The composite fibers referred to here include core-sheath fibers in which a high melting point component is the core and a low melting point component is the sheath, and side-by-side fibers in which a high melting point component and a low melting point component are arranged in parallel. A preferred example of such a fiber is a fiber with a core-sheath structure in which the sheath component is polyethylene or low melting point polypropylene, and representative examples of the fiber with the core-sheath structure include fibers with PET (core) and PE (sheath), PP (core) and PE (sheath), and PP (core) and low melting point PP (sheath). More specifically, the above-mentioned constituent fibers preferably include polyolefin fibers such as polyethylene fibers and polypropylene fibers, polyethylene composite fibers, and polypropylene composite fibers. Here, the composite composition of the polyethylene composite fiber is preferably polyethylene terephthalate and polyethylene, and the composite composition of the polypropylene composite fiber is preferably polyethylene terephthalate and low melting point polypropylene, more specifically, PET (core) and PE (sheath), and PET (core) and low melting point PP (sheath). The melting points of the resins used are measured under atmospheric pressure (N 2 The melting point is measured in a gas atmosphere. In addition to the thermoplastic fibers, the nonwoven fabric may contain non-thermoplastic fibers. Examples of non-thermoplastic fibers include cotton, regenerated cellulose fibers (viscose (rayon), cupra, lyocell, etc.), and semi-synthetic fibers (acetate, triacetate). From the viewpoints of hydrophilicity retention and nonwoven fabric strength, the nonwoven fabric preferably contains 3% to 40% by weight of non-thermoplastic fibers.

[0014] The "thermally fused" state means that the unfused fiber web melts, and the constituent fibers of the web in the heat-fused portion no longer have the fiber form before the fusion process. The fiber form means that the ratio (former / latter) of the fiber length to the diameter (calculated as a perfect circle) calculated from the cross-sectional area of ​​the fiber is 300 times or more. For example, in the "thermally fused" state, at least a part of the outer surface of the constituent fibers of the web melts, and the boundary with the outer surface of the other fibers becomes indistinguishable, and the fiber form before the fusion process is no longer retained. When the constituent fibers such as composite fibers are made of two or more resins, even if a specific resin does not melt and maintains the fiber form, the other resins melt, and the boundary between the outer surfaces of the constituent fibers becomes indistinguishable, and the fiber form before the fusion process is no longer retained. These can be observed by observing the cross section of the fused fiber portion with a scanning electron microscope (SEM).

[0015] In the method for producing a nonwoven fabric of the present invention, the "support" has intermittently arranged through holes and a circumferentially continuous outer periphery surrounding the through holes, can engage with the pushing member, and temporarily holds the nonwoven fabric or the unfused fiber web on its outer periphery. Various materials can be used for the substrate (hereinafter referred to as the holding substrate) that holds the nonwoven fabric or the unfused fiber web on the outer periphery. Examples include resin, metal, carbon, and ceramic. Such a support has the above-mentioned configuration and function, and can be of various forms that rotate in an endless shape. For example, the support may be a drum type as shown by reference numeral 1 (1A) in FIG. 1, or a belt conveyor type as shown by reference numeral 1 (1B) in FIG. 2.

[0016] The drum-type support 1 (1A) shown in Fig. 1 has a support substrate 11 (11A) for the unfused fibrous web on its outer circumferential surface. The belt conveyor-type support 1 (1B) shown in Fig. 2 has a pair of rolls B1 spaced apart in the conveying direction (MD) and a belt B2 supported by the rolls B1 and rotating along the conveying direction (MD). The belt B2 serves as the support substrate 11 (11B) for the unfused fibrous web. These supporting substrates 11A and 11B have the aforementioned intermittently arranged through holes and an outer peripheral portion that is continuous in the circumferential direction and surrounds the through holes (not shown). Preferred embodiments of the supporting substrates 11A and 11B will be described later. The circumferential direction of the support 1A means the direction of rotation or reverse rotation of the roll on the outer circumferential surface. The circumferential direction of the support 1B means the direction of rotation or reverse rotation of the belt B2. These circumferential directions are aligned with the conveying direction (MD).

[0017] In the method for producing a nonwoven fabric of the present invention, the "pushing member" may have various forms having protrusions that can mesh with the through-holes of the support. For example, the pushing member may be a rotating body as shown by reference symbol 2 in Figures 1 and 2, and may have protrusions 21 on its outer circumferential surface. Various materials may be used for the pushing member, such as resin, metal, carbon, and ceramic. In addition, the "protrusion" of the pushing member can be of various shapes that can mesh with the through-holes of the support. As described later, from the viewpoint of favorably forming the openings in the nonwoven fabric, the protrusion is preferably one having a small radius of curvature or a spire shape with a sharp tip. As for the spire shape, from the viewpoint of wear resistance and ease of opening holes in the nonwoven fabric, the radius of curvature of the tip is preferably 0.05 mm or more and 1.5 mm or less, and more preferably 0.1 mm or more and 0.7 mm or less. From the viewpoint of strength, the overall shape of the protrusion is preferably a trapezoid with the base wider than the top. The cross-sectional shape of the protrusion when viewed in a plane can be a circle, an ellipse, a rectangle, a polygon, or the like.

[0018] In the embodiment shown in FIG. 1, the support 1A and the pushing member 2 are rotated in opposite directions along the conveying direction (MD direction) to clamp the unfused fiber web 50, and the aforementioned through holes and protrusions are engaged to form the unevenness (step (I)). The shaped unfused fiber web 50A is conveyed in the roll rotation direction while being held on the outer circumferential surface of the support 1, and the fibers are thermally fused by blowing a heated fluid W1 onto it (step (II)). This results in a nonwoven fabric 5. The nonwoven fabric 5 is separated from the support 1A and conveyed further downstream. From the viewpoint of performing the separation more smoothly, it is preferable to blow a cooling air W2 from inside the support 1A toward the nonwoven fabric 5. The embodiment shown in FIG. 2 differs from the embodiment shown in FIG. 1 in that the unfused fiber web 50 is shaped into an uneven shape (step (I)) on the rotating belt B2 (holding substrate 11B) of the support 1B and then heat-fused (step (II)), but the other points are the same.

[0019] In the method for producing a nonwoven fabric of the present invention, an opening is formed in the nonwoven fabric at a position where the protrusion of the pushing member and the through-hole of the support are engaged with the unfused fiber web. More specifically, the opening is formed in the unfused fiber web at a portion corresponding to the tip of the protrusion inserted in the through-hole and its periphery. This forms the opening in the same direction as the pushing direction of the protrusion at the engagement position and further in the same direction as the blowing direction of the heated fluid.

[0020] The openings may be formed by step (I) or by steps (I) and (II). In either case, the openings are formed in the same direction as the pushing direction of the protrusions of the pushing member and the same direction as the blowing direction of the heating fluid to the support. In order to provide the openings, the force for separating the fibers of the unfused fiber web must be higher than the force caused by the entanglement of the fibers. In this respect, the former is preferred because the mechanical deformation force is higher than the deformation force caused by the heated fluid. In the former, the openings are formed by the protrusions of the pushing member penetrating the unfused fiber web. In this case, it is preferred that the protrusions of the pushing member penetrate the through-holes of the support and engage with the through-holes. This makes it possible to more reliably form larger openings in the unfused fiber web. For example, as shown in FIG. 3, the protrusions 21 of the pushing member 2 engage with the through-holes 12 surrounded by the outer periphery 13 in the holding substrate 11 of the support 1, and the protrusions 21 penetrate (penetrate) the through-holes 12 to form the openings 52. The phrase "the projection of the pushing member penetrates the unfused fiber web" refers to a state in which the tip of the projection of the pushing member penetrates the unfused fiber web and does not touch the fibers. In the latter case, even if the protrusion of the pushing member does not penetrate the unfused fiber web in step (I) (even if the protrusion of the pushing member enters the through-hole of the support, the unfused fiber web is stretched and no openings are formed in the unfused fiber web), the pressure of pushing the protrusion of the pushing member into the through-hole of the support can make the web more likely to open holes. In this state, the heated fluid is sprayed in the next step (II), so that pressure is further applied in the same direction as the pushing direction of the protrusion of the pushing member. That is, in step (II), holes are formed in the unfused fiber web in the same direction as the blowing direction of the heated fluid to the support. This makes it possible to form holes in the unfused fiber web in the parts that are subjected to the two types of pressure. In this case, the size of the openings can be controlled by appropriately setting the range in which the pressure of the protrusion of the pushing member is applied to the unfused fiber web while taking into account the effect of the heated fluid.

[0021] In the method for producing a nonwoven fabric of the present invention, as described above, the support has an outer peripheral portion that is continuous in the circumferential direction while surrounding the through holes. Therefore, in step (I), the unfused fiber web is fixed to the outer peripheral portion around the four sides of the outer peripheral surface at the position where the protrusion of the pushing member and the through holes of the support are engaged. This allows the unfused fiber web to be locally and significantly deformed at the engagement position. This localized large deformation is effective for forming holes at the engagement position. As a result, larger openings than before can be formed in either step (I) alone or steps (I) and (II).

[0022] On the other hand, in a conventional method for manufacturing a nonwoven fabric as shown in Patent Document 2, both the pushing member and the support have a protruding shape, and the protruding top of the support is sharpened to open holes. If the protruding arrangement of the pushing member is intermittent and discontinuous, there will be a portion between the protruding top of the pushing member and the protruding top of the support where the unfused fiber web is not gripped by both the protruding tops, so localized high deformation (high shear) cannot be achieved and it will be difficult to open large holes. In addition, the opening direction is opposite to the pushing direction of the pushing member into the support and the blowing direction of the heated fluid onto the support, so the size of the opening is limited. In this case, the fibers around the protrusions of the support are pushed toward the bottom side of the support by the hot air, so it tends to be difficult to obtain a large opening area due to the compression resistance of the fibers. In addition, there is a limit to the opening by blowing the heated fluid alone. If the blowing speed of the heated fluid is increased, the fibers will be compressed by the pressure, making the unevenness small, and the fiber density of the web located on the non-opening part of the support may also increase. In contrast, in the manufacturing method of the nonwoven fabric for absorbent articles of the present invention, as described above, a large local deformation is imparted to the unfused fiber web, making it possible to form larger openings than conventional ones while maintaining the height difference of the unevenness created by the uneven shaping.

[0023] In the method for manufacturing a nonwoven fabric for absorbent articles of the present invention, the unfused fiber web is stably held at the outer periphery around the through holes, and the fiber web is stretched while the multiple fibers around the through holes migrate and spread toward the through holes due to the pushing pressure of the protrusions of the pushing member and the heated fluid. The density is made uniform. That is, the fibers are uniformed toward the through holes along the pushing direction of the protrusions and the blowing direction of the heated fluid. More specifically, in step (I), the unfused fiber web is stretched by the protrusions and shaped into a convex shape toward the inside of the support. As described above, a convex fiber layer having an opening is formed by step (I) or by going through steps (I) and (II). Regardless of the stage at which the opening is formed, the heated fluid in step (II) blows through the opening, and the convex fiber layer can be further stretched. At that time, even the fibers on the surface on the outer periphery of the support tend to migrate appropriately to the convex fiber layer in the through holes, and the fibers are easily evened out along the thickness direction. This allows the fiber density from the fiber layer on the outer periphery (top 51T described later) to the shaped convex fiber layer (wall 51W described later) to be appropriately suppressed. In particular, the increase in fiber density of the wall 51W, which is directly affected by the blowing of the heated fluid, is well suppressed. In addition, since the fibers are difficult to press down at the bottom of the through-holes of the support (the S1 side of the fibers S2 of the wall portion 51W described later), an increase in fiber density around the openings is suppressed. As a result, the fiber layer of the unfused fiber web around the through-holes and the outer periphery of the support can satisfactorily form a larger uneven thickness while an increase in fiber density is suppressed, and a sufficient basis weight can be achieved. From the viewpoint of improving the above-mentioned action, it is preferable to form the opening by engaging the protrusion with the through hole so that the protrusion penetrates the through hole in step (I) (see, for example, FIG. 3). This makes it possible to more clearly blow through the heated fluid in the next step (II), and to make the above-mentioned action by the heated fluid more effective. In contrast, in the prior art as shown in the above-mentioned Patent Document 2, when the heated fluid is sprayed at a higher speed, the fibers around the openings formed at the tips of the protrusions of the support are biased downward from the protrusions, and the fiber weight around the openings increases. The thickness of the unevenness also decreases. In addition, the fibers at the bottom of the support are pressed down more strongly, which may increase the fiber density in some places, making it difficult to obtain the above-mentioned effects of the present invention.

[0024] In the method for producing a nonwoven fabric for absorbent articles of the present invention, the temperature and wind speed of the heated fluid in step (II) are preferably set under the following conditions. Temperature of the heating fluid: Where Tm (°C) is the melting point of the thermal adhesive resin of the thermoplastic fiber, it is preferable to perform the heating in the range of Tm (°C) to Tm+40°C. It is further preferable to perform the heating in the range of Tm (°C)+10°C to Tm+30°C. Wind speed of the heating fluid: preferably 0.5 m / s to 5 m / s, more preferably 2 m / s to 4 m / s.

[0025] In this way, according to the manufacturing method of the nonwoven fabric for absorbent articles of the present invention, it is possible to make the openings in the manufactured nonwoven fabric larger, and moreover, to increase the height difference of the unevenness, thereby making the overall thickness thicker than before. The "overall thickness" referred to here is also called the apparent thickness, and means the thickness between the front and back surfaces measured by sandwiching the nonwoven fabric between flat plates. As described above, the nonwoven fabric obtained by the manufacturing method of the present invention has a thick overall thickness, and when the nonwoven fabric is incorporated as a component of an absorbent article (e.g., a top sheet), it has larger openings and can have better liquid absorption performance (e.g., wet-back prevention function) and better texture. Furthermore, since the fiber density is prevented from increasing and the fibers are uniform, the fiber distance is longer in the fiber layer of the nonwoven fabric having an uneven shape, especially in the fibers in the wall portion around the openings, and an excessive increase in capillary force can be suppressed. This improves the above-mentioned wet-back prevention function.

[0026] The "periphery" of the support is the portion of the support base material on the outer surface side of the support excluding the through holes. The outer periphery is "continuous" means that the outer periphery is connected within a range of 1 mm inward in the thickness direction from its surface. In other words, it means that the outer periphery is smooth along the circumferential direction, or even if there is unevenness, the unevenness height difference H is suppressed to within 1 mm and connected. For example, when the support is a rotating body such as the drum-type support 1A shown in FIG. 1, it means that the outer periphery 13 is connected within a range of 1 mm inward in the thickness direction from the fan-shaped plate 9 to which the outer periphery 13 is extrapolated, as viewed along the rotation axis direction as shown in FIG. 4. The measurement is performed on the end surface of the fan-shaped plate 9 by placing the fan-shaped plate 9 on the outer periphery of the support along the flow direction of the support. The connected portion may be linear or curved. The fan-shaped plate 9 extrapolated from the outer periphery is made to correspond to an angular range of 30° from the center, with a concentric disk formed by connecting the outermost contour of the outer periphery 13 as the outer shape of the support 1A. The thickness of the fan-shaped plate 9 is 20 mm. If the circle of the support 1A is not a perfect circle, the value will differ depending on the position where the sector plate 9 is placed, so it is measured as follows. That is, when the inner diameter side surface of the sector plate 9 is placed against the outer periphery of the circular support 1A, the gap distance between the inner diameter of the sector plate 9 and the outer surface of the support 1A is set so that the gap distance is the smallest, and the value when the sector plate 9 is placed against the support 1A is measured.

[0027] The outer periphery being continuous "in the circumferential direction while surrounding the through hole" means that the outer periphery surrounds the four sides of the through hole while the "continuous state" defined above extends in the circumferential direction as a whole. Therefore, the "continuous" part of the outer periphery extends at least in the circumferential direction and may include a part extending in a direction intersecting the circumferential direction. The portion where such an outer periphery is "continuous in the circumferential direction while surrounding the through-hole" is preferably present around the entire circumference in the circumferential direction, and more preferably around the entire portion excluding the through-hole. For example, as shown in Figs. 5(A) to (C), in a plan view of the outer periphery surface (holding substrate 11) of the support 1, it is preferable that each through-hole 12 is an independent hole whose outer periphery is surrounded by an outer periphery 13, and the entire portion excluding the through-hole 12 is the outer periphery 13. In this example, the outer periphery 13 is in a state where it is continuous in the circumferential direction when the portion excluding the through-hole 12 is viewed from the side in the circumferential direction (along the MD direction).

[0028] In this manner, when the outer periphery is "continuous in the circumferential direction while surrounding the through hole", the supporting substrate on the outer periphery of the support body is considered to have no protrusions.

[0029] Since the outer peripheral portion is continuous in the circumferential direction while surrounding the through hole, the unfused fibrous web can be stably held when the projection and the through hole engage in step (I), which results in a large local deformation of the unfused fibrous web and allows for large hole openings.

[0030] The "through hole" of the support means an opening on the surface of a support substrate on the outer circumferential surface of the support that penetrates from the outside to the inside. More specifically, the "through hole" means a hole through which the protrusion of the pushing member can penetrate the outer circumferential surface of the support when the protrusion of the pushing member engages with the opening on the outer circumferential surface of the support (the surface that is the outermost layer of the outer circumferential portion). The "through hole" has a diameter on the outer peripheral surface side that allows the protrusion of the pushing member to be inserted in step (I), and at the bottom thereof is provided with a blow-through hole through which at least the heated fluid in step (II) can blow through the unfused fiber web. In this case, the bottom hole of the "through hole" may have a diameter smaller than the thickness of the protrusion of the pushing member. For example, as shown in FIG. 6, the through hole 12 of the support 1 may have a form in which a net 12B is located below a bottom hole 12A. In this case, the diameter of the bottom hole 12A may be smaller than the diameter of the opening on the surface. More preferably, the "through hole" has a diameter larger than the protrusion from the opening on the surface of the support to the hole at the bottom, so as to allow not only the heating fluid in step (II) but also the protrusion of the pushing member in step (I) to pass through. More preferably, the "through hole" is formed of an opening on the surface without a bottom, and the opening has a diameter larger than that of the protrusion. For example, a support base material 11 such as punched metal 11C, 11C' (Figs. 7 and 8), diagonal lattice expanded metal 11D (Fig. 9), lattice net 11E (made of metal or resin) (Fig. 10), or honeycomb perforated panel 11F (Fig. 11) is arranged on the outer circumferential surface of the support, and through holes 12 formed of openings on the surface of the support base material 11 penetrate to the inside of the support. The planar shape of the through hole 12 in the punched metal 11C is circular, and the planar shape of the through hole 12 in the punched metal 11C' is circular and cross. The planar shape of the through hole 12 in the diagonal lattice expanded metal 11D is rhombus (diamond). The planar shape of the through-holes 12 in the lattice-like net 11E is rectangular, while the planar shape of the through-holes 12 in the honeycomb-like perforated panel 11F is hexagonal.

[0031] The planar shape of the through-hole 12 is not limited to the above and may be various shapes. Among them, the planar shape of the through-hole 12 is preferably a rhombus (diamond) shape, from the viewpoint of easily catching and leaving the fiber in the through-hole 12 by the meshing between the protrusion 21 and the through-hole 12 and better maintaining the shape formed by the meshing. In addition, the preferred range of the pitch of the through holes 12 in the MD direction of the support is 2 mm to 30 mm, more preferably 10 mm to 25 mm. The preferred range of the pitch of the through holes 12 in the CD direction is 2 mm to 15 mm, more preferably 5 mm to 13 mm. The larger the pitch, the larger the openings can be provided in the nonwoven fabric, and the fiber amount of the wall portion 51W around the openings can be increased, so that the thickness of the nonwoven fabric can be increased. Conversely, the smaller the pitch, the more the number of openings 52 per unit area increases, and the unevenness of the nonwoven fabric is less likely to be left on the skin when the nonwoven fabric is in contact with the skin for a long time due to pressure dispersion. Furthermore, the ratio of the MD pitch to the CD pitch (MD pitch / CD pitch) is preferably 1.5 times to 3 times in terms of appearance. The aperture ratio of the through holes of the support is calculated as the sum of the areas of the through holes in a plan view of the outer periphery of the support (the surface of the outer periphery 13 obtained by extrapolating the inner diameter side surface of the sector plate 9 is set as the outer periphery of the support, and the projected cross-sectional area of ​​the through holes at the outer periphery position is added) / area of ​​the outer periphery of the support (the total area of ​​the outer periphery of the surface on which the through holes are provided) × 100 (%). In order to increase the aperture ratio of the nonwoven fabric and the fiber amount (basis weight) of the wall of the aperture, the aperture ratio of the through holes is 50% or more, more preferably 70% or more. In addition, in order to increase the strength of the support, the aperture ratio of the through holes is 95% or less, more preferably 90% or less. In addition, when the same support has a region with through holes and a region without through holes (for example, when a region with through holes intermittently arranged in the MD direction and / or CD direction is arranged), the aperture ratio of the through holes is calculated for the region with the through holes.

[0032] From the same viewpoint, it is preferable that the portion (hole wall) 13W (FIGS. 5(B) and (C)) of the outer circumferential portion 13 facing the through-hole 12 is roughened. By roughening the portion 13W of the outer circumferential portion 13 facing the through-hole 12, the coefficient of friction is increased, causing the constituent fibers of the unfused fiber web to get caught, thereby more effectively suppressing lifting. From this viewpoint, the surface roughness Rz of the portion 13W of the outer circumferential portion 13 facing the through hole 12 is preferably equal to or greater than 0.1 μm, more preferably equal to or greater than 0.5 μm, and even more preferably equal to or greater than 1.0 μm. In addition, the surface roughness Rz of the portion 13W of the outer periphery 13 facing the through hole 12 is preferably 10.0 μm or less, more preferably 5.0 μm or less, and even more preferably 3.0 μm or less, from the viewpoint of preventing the shaped nonwoven fabric from getting caught when peeling it off from the support. The above surface roughness Rz is preferably in an area of ​​20% or more of the area of ​​portion 13W of outer periphery 13 facing through hole 12, more preferably in an area of ​​30% or more, and even more preferably in an area of ​​40% or more. The above surface roughness Rz can be formed by using various methods applied to this type of support 10, such as grinding, sandblasting, plating, spraying, etching, etc. Grinding is particularly preferred in that it provides durability and a preferred micro-irregular shape.

[0033] From the same viewpoint, it is preferable that the outer peripheral surface of the outer peripheral portion is roughened around the through holes of the support. The surface roughness Rz indicating this roughening is preferably in the same range as the above-mentioned surface roughness Rz.

[0034] (Method of measuring surface roughness) The surface roughness (maximum height) Rz of the support protrusion wall is measured in accordance with ISO4287-1997. The measurement conditions are λc 0.8 mm, λs 2.5 mm, section 5, GAUSS filter, curve R, speed 0.5 mm / s, measurement range 4.8 mm, stylus tip angle 90 degrees, tip radius 2 μm, and measurement force 4 mN. As the measuring instrument, for example, SJ210 (product name) manufactured by Mitutoyo Corporation can be used. The measurement is performed in the direction in which the web 30 at the protruding portion is peeled off. The roughness of the portion 13W facing the through hole 12 and the outer peripheral surface side surface of different outer peripheral portions 13 are measured at three points, and the average value is taken as the respective surface roughness Rz.

[0035] Furthermore, in the meshing in step (I), the outer periphery is preferably flat. The flat outer periphery facilitates welding with improved pitch accuracy at the joints of the supports. The joints are welded by butting or overlapping. In addition, the retention of the unfused fiber web at the outer periphery can be improved. The "flat" of the outer periphery referred to here refers to a location that is 0.3 mm wide or more and has a difference in unevenness in the thickness direction of 1 mm or less. The width of the flat portion is more preferably 0.3 mm or more and 1 mm or less.

[0036] In the case where the support substrate on the outer peripheral surface of the support is a metal net such as an expanded metal, it is preferable to provide a ring-shaped support part (for example, the member indicated by the reference numeral 14 in FIG. 12) on the inside of the metal net at a position not corresponding to the protrusion of the push-in member on the underside of the support substrate (inside the support). This makes it possible to prevent the metal net from being significantly deformed when the protrusion 21 of the push-in member and the through-hole 12 of the support mesh as shown in FIG. 12. The metal net and the ring-shaped support part 14 can be fixed by welding or the like.

[0037] In the method for producing a nonwoven fabric for absorbent articles of the present invention, since the support has the aforementioned through holes and outer periphery, the openings in the unfused fiber web and the nonwoven fabric can be made larger than in the past. In particular, when the through holes are not provided with a bottom but are formed as openings on the surface, and the openings have a diameter larger than that of the protrusions, openings can be more reliably formed in the unfused fiber web in step (I), and the size of the openings can be more suitably controlled. Furthermore, the pressing depth can be freely set as appropriate according to the basis weight of the unfused fiber web. Furthermore, when openings in a nonwoven fabric are formed through steps (I) and (II), the pressing depth of the protrusions of the pressing member can be freely controlled to appropriately set the range over which the pressure of the protrusions is applied to the unfused fiber web, and the size of the openings can be more suitably controlled.

[0038] From the viewpoint of more reliably forming an opening on the side of the through hole at the meshing position between the protrusion and the through hole, it is preferable that the ratio of the area of ​​the protrusion of the pushing member in a plan view (the protrusion cross-sectional area of ​​the pushing member at the outer peripheral surface position extrapolated from the outer periphery around the through hole of the support in the meshed state) to the area of ​​the through hole in a plan view of the outer periphery of the support (the projected cross-sectional area of ​​the through hole at the outer peripheral surface position, with the surface of the outer peripheral portion 13 extrapolated from the inner diameter side surface of the sector plate 9 as the outer peripheral surface position of the support) is within the following range. When the pushing member or the support is a rotating body, it means the protrusion cross-sectional area at the point where the amount of meshing is maximum when they rotate. When the shape of the protrusion of the pushing member is a trapezoid that widens toward the bottom, the above ratio can be increased as the amount of meshing increases. The area ratio (area of ​​the protrusions in plan view / area of ​​the through holes in plan view of the outer periphery) is preferably 5% or more and 80% or less. More preferably, it is 15% or more and 50% or less, and even more preferably, it is 20% or more and 40% or less. By making it equal to or more than the above value, the gap between the protrusions of the pushing member and the through holes of the support is reduced, so that the unfused fiber web can be highly deformed to form large openings. In addition, by making it equal to or less than the above value, the protrusions of the pushing member can be pulled out of the through holes of the support without interfering with the support, and the unfused fiber web is not squeezed, so that the fiber density of the wall portion is lowered and the distance between the fibers is longer. In addition, it is preferable that the protrusions of the pushing member have a sharp spire shape toward the tip.

[0039] Regardless of the form of the support, it is preferable that the inside of the support (for example, the inside of a drum or the inside of a belt conveyor) has a cavity to a certain depth at least in the portion corresponding to the through-hole 12. Furthermore, from the viewpoint of making the action of blowing the heated fluid more effective, it is preferable to have an air suction section further inside the hollow part of the support. This suppresses turbulence of the flow of the heated fluid through the through-hole. As a result, the heated fluid can be applied as perpendicularly as possible to the unevenly shaped unfused fiber web, and the holes can be opened more suitably. In addition, at that time, the multiple fibers of the unfused fiber web can be spread and leveled toward the through-holes of the support, and the uneven thickness can be made larger.

[0040] From the same viewpoint as above, in step (I), it is preferable to blow air W3 toward the support through the protrusions from inside the pushing member (e.g., Fig. 1 and Fig. 2). More specifically, it is preferable to provide a plurality of holes between the protrusions of the pushing member, and to blow air W3 toward the unfused fiber web through the holes of the pushing member. This makes it possible to prevent the unfused fiber web from wrapping around the pushing member in step (I). Also, it becomes easier to hold the unfused fiber web in a state in which an opening is formed in the through hole of the support. Furthermore, it is possible to further spread and level the plurality of fibers toward the through hole of the support, and to make the uneven thickness even thicker than before.

[0041] It is preferable that the temperature and the wind speed of the wind W3 from the inside of the pushing member are set under the following conditions. Temperature: 10℃ or higher and 120℃ or lower Wind speed: 0.1m / s or more and 1m / s or less

[0042] In the nonwoven fabric produced by the method for producing a nonwoven fabric for absorbent articles of the present invention, the fact that "open holes are formed" can be confirmed by the following method. That is, the open holes of the nonwoven fabric are faced downward, a black mount is placed under the nonwoven fabric, and the nonwoven fabric is observed from the surface side with a microscope at a magnification of 20 to 100 times and the focus is appropriately changed. Next, a 1 mm square area is partitioned where the black mount is projected between the fibers of the nonwoven fabric, and the number of projected fibers within the area is determined to be 20 fibers / mm. 2 A portion where the number of fibers is equal to or less than 1 mm (preferably 0) is regarded as an opening. The projected number of fibers is calculated as the number of fibers crossing the four sides of a 1 mm square divided by 2.

[0043] The "open area" indicating the size of the open pores is defined as the area where the number of fibers is 20 / mm2 when observed by projection from the surface side of the nonwoven fabric (the non-open pore side). 2 The outline of the boundary of the following places is drawn, and the area enclosed by the outline is the area of ​​the opening. The average area of ​​the opening is calculated by cutting the nonwoven fabric into a 10 cm square, and dividing the total area of ​​all the openings observed by the number of openings. The open area ratio is calculated by dividing the area of ​​all the open holes observed in the nonwoven fabric placed on the above-mentioned black mount by the area of ​​the nonwoven fabric. The aperture area is set to 0.5 mm to allow high-viscosity liquids such as loose stool to pass through without remaining on the surface, and to prevent skin from touching other components underneath through the aperture. 2 More than 300mm 2 It is preferable that the thickness is less than 5 mm. 2 More than 100mm 2 It is preferable that: In addition, the open area ratio is preferably 1% or more and 40% or less, and more preferably 5% or more and 25% or less, from the viewpoints of shortening the permeation time of high-viscosity liquids such as loose stool and of suppressing width shrinkage due to necking-in during transport of the nonwoven fabric.

[0044] The "opening direction" is the direction in which fibers S2 of wall portions 51W around hole portions 52 are located in the thickness direction with respect to fibers S1 of non-opening portions (tops 51T of convex portions 51) as a reference when observing the sheet-like nonwoven fabric 5 from the cross-sectional direction, as shown by symbol F1 in Fig. 13. Fibers S2 of wall portions 51W around hole portions 52 may be formed in a cylindrical shape, such as a funnel shape or a trumpet shape, from hole portions 52. When holes are opened in both directions, the respective directions are used.

[0045] As described above, in the nonwoven fabric 5 produced by the nonwoven fabric production method of the present invention, as shown in Fig. 14, the fiber layer held on the outer periphery 13 of the support 1 to the fiber layer stretched into the through-holes 12 form the convex portions 51. Furthermore, at the end of the stretched portion at the position of the through-holes 12 of the support 1, a bottom portion 53 having an opening 52 is formed. As described above, the opening 52 is formed along the opening direction F1, which is the pushing direction of the projections 21 and the blowing direction of the heated fluid W1 in the production method of the present invention. The nonwoven fabric 5 thus obtained has an uneven structure including a plurality of protrusions 51 and bottoms 53 provided between adjacent protrusions 51. Each of the plurality of protrusions 51 includes a top 51T and a wall 51W supporting the top 51T. The bottom 53 has an opening 52 penetrating in the thickness direction. The top 51T is a portion that was held by the outer periphery 13 of the support 1, and the wall 51W is a portion that is stretched by the projections 21 and the heated fluid W1 at the position of the through-hole 12 of the support 1.

[0046] In the nonwoven fabric 5, the above-mentioned manufacturing method of the nonwoven fabric for absorbent articles of the present invention allows the openings 52 to be larger than in the past. Specifically, the opening area can be increased to 7 mm 2 (corresponding to a diameter of 3 mm) or more. This allows the nonwoven fabric 5 to have improved anti-wetback function as described above, while at the same time improving permeability to high-viscosity body fluids such as loose stool.

[0047] In the nonwoven fabric 5, the fibers of the top portion 51T and the wall portion 51W are leveled and the fiber density is appropriately suppressed by the above-mentioned manufacturing method of the nonwoven fabric for absorbent articles of the present invention. In particular, the fiber density of the wall portion 51W that is directly leveled along the blowing direction of the heated fluid can be made lower than the fiber density of the top portion 51T. Therefore, in the nonwoven fabric 5, it is preferable that the wall portion fiber density is lower than the top portion fiber density. Specifically, the ratio of the fiber density of the wall portion 51W to the fiber density of the top portion 51T (wall portion fiber density / top portion fiber density×100) can be preferably 30% to 90%, more preferably 40% to 80%, and even more preferably 45% to 70%. This can be achieved in the above-mentioned manufacturing method by controlling the engagement between the protrusions 21 of the pushing member and the through holes 12 of the support, and the extension of the web by concentrating the airflow of the heated fluid into the through holes 12 of the support. As a result, the fiber density is reduced, so that the inter-fiber distance in the wall portion 51W is relatively longer, the capillary force is reduced, and the wetback prevention function is further improved. The fiber density of the top portion 51T is preferably 0.02 g / cm 3 More than 0.05g / cm 3 or less, more preferably 0.03 g / cm 3 More than 0.045g / cm 3 This can be achieved by controlling the elongation of the web through the engagement of the protrusions of the pushing member with the through holes 12 of the support and the concentration of the heated fluid flow at the through holes 12 of the support in the above-mentioned manufacturing method. In this regard, in the prior art shaping by engagement and heated fluid as shown in Patent Document 2, for example, the unfused fiber web is consolidated by the fibers at the top 51T being pushed by the pushing member (for example, 0.052 g / cm 3 ) it is difficult to reduce the fiber density at the apex 51T as described above. The fiber density of the wall portion 51W is preferably 0.01 g / cm 3 More than 0.04g / cm 3 or less, more preferably 0.01 g / cm 3 More than 0.03g / cm 3 The following can be done: In this way, nonwoven fabric 5 has larger openings 52 than conventional fabrics, yet can have a thicker overall thickness than conventional fabrics, and the fiber density of tops 51T as well as walls 51W is reduced, thereby further improving the anti-wetback function.

[0048] (Method of measuring fiber density of top portion 51T and wall portion 51W) The top 51T is punched out at 50 points with a circular screw punch having a diameter of 2 mm when viewed from above. The mass of the entire punched samples is divided by 50 from the 50 samples punched out with a microscope to obtain the average mass. The punched diameter of the samples punched out with a microscope is measured to obtain the average area. The nonwoven fabric is also cut along a line connecting the center point of the top 51T and the center point of the opening 52 (in various directions such as MD direction, CD direction, and diagonal direction in the plane direction), and the cross section is observed with a microscope (at 20 to 100 times magnification), and the thickness of 10 points of the top 51T is measured, and the average value is the thickness of the top 51T. The center point of the top 51T and the center point of the opening 52 are the center of gravity positions of each shape when viewed from above. If the fibers are fuzzed from the nonwoven fabric, the non-fuzzed parts are measured. The average mass is divided by the average area and average thickness to calculate the fiber density. The punching position of top portion 51T is set to the midpoint position between openings 52. When the area of ​​top portion 51T has a diameter of 2 mm or less, the diameter of the punch is appropriately changed. The same process is carried out for wall portion 51W. The punching position of wall portion 51W is at a height position in the hole direction 1 mm or more from the hole direction surface of the non-hole portion, and the upper end position of the punching circle is at a height position L0 of 1 mm in the thickness direction (FIG. 15(A)). The non-opening portion means the apex 51T, or an intermediate height portion (also called a saddle portion) when there is an intermediate height other than the apex 51T and the open hole 52. The punching direction in the wall portion 51W is a direction perpendicular to the wall surface of the wall portion 51W. The punching location in the planar direction of the nonwoven fabric is a linear wall portion connecting the center point of the apex 51T and the center point of the open hole 52. The thickness of wall portion 51W is measured as an average over a range of 1 mm to 2 mm (range L0 to L2) from the surface in the hole direction of the non-hole portion surrounding hole portion 52. The thickness is measured in the same manner as the thickness measurement of top portion 51T, and the thickness is measured in the actual thickness direction of wall portion 51W (perpendicular to the wall surface of wall portion 51W). The opening direction surface of the non-perforated portion refers to the surface of the fiber layer of the non-perforated portion facing the opening portion 52. This surface refers to the surface of the top portion 51T or the intermediate height portion surrounding the opening portion 52. When the thickness of the non-perforated portion is constant, "1 mm from the opening direction surface of the non-perforated portion" refers to a position L1 that is 1 mm vertically downward from the plane L0 of the opening direction surface of the non-perforated portion toward the opening portion 52 side, as shown in FIG. 15(B). When the non-perforated portion is curved upward in the thickness direction, "1 mm from the opening direction surface of the non-perforated portion" refers to a position L1 that is 1 mm vertically downward from the opening direction surface L0 of the highest part of the non-perforated portion toward the opening portion 52 side, as shown in FIG. 15(C). In either case, the thickness of the wall portion 51W refers to the thickness up to a position L2 (2 mm from L0) that is 1 mm further vertically downward from the above position L1.

[0049] Furthermore, in the nonwoven fabric 5, the wall portion 51W is leveled and stretched by the manufacturing method of the nonwoven fabric for absorbent articles of the present invention described above, particularly by blowing the heated fluid through the through holes of the support in step (II) after step (I). That is, the wall portion 51W can be made to have a long distance from the top portion 51T to the opening portion 52 while suppressing an increase in fiber density. This causes the nonwoven fabric 5 to have a large overall thickness as described above, and the wetback prevention function is further improved. As an indication of this, the fiber mass ratio of the peripheral area of ​​the hole in the wall portion 51W obtained by the measurement method described below can be preferably 10% by mass or more and 80% by mass or less, and more preferably 20% by mass or more and 45% by mass or less. In this regard, conventional nonwoven fabrics, such as spunlace nonwoven fabrics, generally cannot be made thicker than 1 mm, so the fiber mass ratio of the peripheral area of ​​the hole is 0 (zero) mass%, and the above value is difficult to achieve.

[0050] (Method of measuring fiber mass ratio in peripheral area of ​​opening in wall portion 51W) In an area including 20 openings 52, the fibers around the openings are cut with scissors at a height L0 position in the opening direction 1 mm from the opening direction surface of the non-opening part (the surface height of the non-opening part is near the opening 52 to be cut) (Figures 15(A) to (C)). Next, the fiber mass ratio in the peripheral portion of the hole in the wall portion 51W is calculated by the following formula. Percentage of fiber mass around hole=100-(fiber mass of non-hole part where fiber of wall part 51W has been cut / fiber mass of nonwoven fabric before cutting)×100

[0051] In addition, by increasing the fiber mass ratio in the peripheral portion of the hole, the fiber amount (basis weight) is increased while suppressing the fiber density in the wall portion 51W, so that the fibers oriented in the thickness direction in the wall portion 51W increase, and the overall thickness of the nonwoven fabric 5 is less likely to be crushed. The total thickness of this nonwoven fabric 5 is 30 g / cm 2 From the viewpoint of reducing the amount of liquid wetted back under a seating pressure load, the thickness is preferably 0.8 mm or more, and more preferably 0.9 mm or more. The total thickness of the nonwoven fabric 5 is 30 g / cm 2 From the viewpoint of preventing the device from becoming bulky when carried under load, the thickness is preferably 2.5 mm or less, more preferably 2.2 mm or less, and even more preferably 2.0 mm or less. In addition, the above-mentioned "30 g / cm 2 The "load" corresponds to the pressure when the nonwoven fabric 5 is incorporated as a constituent member of an absorbent article and a plurality of absorbent articles are stored in a packaging bag, or the seating pressure load in the absorbent article. Similarly, the nonwoven fabric 5 has a g / cm 2 The overall thickness under load is preferably 5 mm or more, and more preferably 7 mm or more, from the viewpoint of increasing the permeation rate during liquid absorption. In addition, the nonwoven fabric 5 has a density of 0.5 g / cm 2 The overall thickness under load is preferably 15 mm or less, more preferably 10 mm or less, from the viewpoint of preventing an excessive increase in bending rigidity of the nonwoven fabric and improving the fit to the body. In addition, the above-mentioned "0.5 g / cm 2"Load" refers to the thickness under a low load where almost no load is applied, and refers to a load that is sufficient to suppress fuzzing on the surface of the nonwoven fabric, and is a light load (a light load that is not equivalent to a compressive force that would crush the thickness of the nonwoven fabric) necessary to properly measure the total thickness of the nonwoven fabric.

[0052] (Nonwoven fabric 5 30g / cm 2 Under load and 0.5g / cm 2 (Method of measuring total thickness under load) The nonwoven fabric to be measured is cut into a piece of 10 cm x 10 cm to prepare a measurement sample. Using a laser thickness gauge (Omron Corporation, high-precision displacement sensor ZS-LD80 (product name)), the measurement sample is measured with a thickness of 30 g / cm using a 10 cm x 10 cm flat plate with the non-opening portion (top 51T of convex portion 5) facing up. 2 The load is applied, and after 10 seconds, the thickness is measured in that state. Measure three points and take the average value to determine the total thickness (30 g / cm 2 load). Also, 0.5g / cm 2 The thickness of the nonwoven fabric under load was measured using the above method with a load of 30 g / cm 2 From 0.5 g / cm 2 (0.05kPa) instead.

[0053] The nonwoven fabric produced by the method for producing a nonwoven fabric for absorbent articles of the present invention can be used for various applications. For example, it can be used as a component of various absorbent articles. The various absorbent articles broadly include articles used to absorb liquids discharged from the body, such as diapers for adults and infants, sanitary napkins, panty liners, and urine pads. The absorbent article having the nonwoven fabric typically includes a top sheet, a back sheet, and a liquid-retentive absorbent interposed between the top sheet and the back sheet. In the absorbent article, the nonwoven fabric can be suitably used as the top sheet that contacts the skin of the wearer. When the nonwoven fabric is used in a portion of an absorbent article that comes into contact with the skin, it is preferable in terms of feel and absorption performance to use the upper surface so that it faces the skin when the perforations face downward. EXAMPLES

[0054] The present invention will be described in more detail below based on examples, but the present invention is not 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. "←" means that the value is the same as the value in the left column.

[0055] Example 1 First, as the constituent fibers of the unfused fiber web, thermoplastic concentric type composite short fibers with a fineness of 1.1 dtex and a core-sheath type (polyethylene terephthalate (PET) (core): polyethylene (PE) (sheath) = 5:5 (mass ratio)) were prepared, which were coated with a hydrophilic oil agent. Then, the carding machine is used to make the sheet with a basis weight of 30 g / m 2 The non-fused fiber web was formed, and a non-woven fabric having an opening and an uneven shape was produced as shown in FIG. 1 under the conditions shown in Table 1. Specifically, unevenness was formed by meshing the support 1 and the pushing member 2 shown in FIG. 1, and holes were opened in the pushing direction of the pushing member at the meshing positions of the protrusions of the pushing member and the through holes of the support. The meshing amount between the support and the pushing member was set to 15 mm. At this time, wind W3 (at 30°C) was blown from the inside of the pushing member 2 to improve the retention of the non-fused fiber web on the support 1. The opening direction coincides with the blowing direction of the heating fluid (hot air). Next, the heating fluid W1 (hot air) was blown onto the non-fused fiber web downstream on the support 1 to thermally fuse the fibers. The heating fluid (hot air) was blown onto the non-fused fiber web at a hot air temperature of 136°C, a wind speed of 3 m / s, and a blowing time of 6 s. In this way, a nonwoven fabric sample of Example 1 was produced (FIG. 16).

[0056] Example 2 A nonwoven fabric sample of Example 2 was produced by carrying out the same manufacturing method as in Example 1, except that the amount of meshing was changed to 7 mm.

[0057] Comparative Example 1 Using the support and pressing member shown in FIG. 8 of Patent Document 2, a nonwoven fabric sample of Comparative Example 1 having openings and an uneven shape was produced under the conditions shown in Table 1. The support used in Comparative Example 1 had 10 mm high protrusions with a spire at the tip with a tip radius of 0.5 mm arranged intermittently in the vertical and horizontal directions. The pushing member used was a parallel plate with continuous protrusions in the MD direction, and the protrusions were arranged intermittently in the CD direction with a pitch of 5 mm. In Comparative Example 1, openings were formed at the tips of the protrusions of the support. That is, the openings were in the pushing direction of the support (the opposite direction to the pushing direction of the pushing member) and the opposite direction to the blowing direction of the heated fluid.

[0058] Comparative Example 2 A nonwoven fabric was produced in the same manner as in Example 1, except that no pushing member was used and the wind speed of the heated fluid (hot air) was set to 5.6 m / s. This resulted in the production of a nonwoven fabric sample of Comparative Example 2. The produced nonwoven fabric sample of Comparative Example 2 did not have any open pores.

[0059] The nonwoven fabric samples of each of the Examples and Comparative Examples were subjected to the following measurements. (1) Average pore area and pore area ratio of nonwoven fabric Measurements were made based on the method using the black mount described above. (2) Fiber mass ratio around the opening in wall 51W The measurement was performed based on the above-mentioned (method of measuring the fiber mass ratio in the peripheral portion of the hole in the wall portion 51W). (3) Thickness of top portion 51T and wall portion 51W The fiber density of the top portion 51T and the wall portion 51W was measured based on the above-mentioned method for measuring the fiber density. (4) Weight of top portion 51T and wall portion 51W Based on the above-mentioned method for measuring the fiber density of the top portion 51T and the wall portion 51W, the average weight per unit area was calculated by dividing the average mass by the average area. (5) Fiber Density of Top 51T and Wall 51W The measurement was performed based on the above-mentioned (Method of Measuring Fiber Density of Top Part 51T and Wall Part 51W). Furthermore, based on the measured values, "(fiber density of wall portion 51W / fiber density of top portion 51T) x 100" was calculated. (6) Thickness of nonwoven fabric (0.5g / cm 2 Load, 30g / cm 2 load) The aforementioned (nonwoven fabric 5 30 g / cm 2 The measurement was based on the total thickness measurement method under load.

[0060] The results of the above measurements are shown in Table 1 below.

[0061] [Table 1]

[0062] As shown in Table 1, in the manufacturing method of Comparative Example 2, the same support as in Example 1 was used, and a heated fluid (hot air) was blown at a high wind speed about 1.8 times that of Example, but since shaping was performed using only the heated fluid (hot air), no holes were formed. In contrast, the nonwoven fabric samples obtained by carrying out the manufacturing methods of Examples 1 and 2 were able to form large open holes with the open hole area and open hole area ratio shown in Table 1. The nonwoven fabric sample obtained by carrying out the manufacturing method of Example 1 had an average open area of ​​about 40 times and an open area ratio of about 9 times larger than those of the nonwoven fabric sample obtained by carrying out the manufacturing method of Comparative Example 1, and thus was able to form larger open pores. Furthermore, the nonwoven fabric sample obtained by carrying out the manufacturing method of Example 1 had a smaller ratio of fiber density of the wall part to the top part, less than one-third, compared to the nonwoven fabric sample obtained by carrying out the manufacturing method of Comparative Example 1. In other words, it was found that the fiber distance of the wall part of Example 1 was longer than that of Comparative Example 1, and the wetback prevention function was enhanced. The nonwoven fabric sample obtained by carrying out the manufacturing method of Example 2 had an average open area of ​​about 4.7 times larger than that of the nonwoven fabric sample obtained by carrying out the manufacturing method of Comparative Example 1, and thus larger open pores could be formed. Also, the nonwoven fabric sample obtained by carrying out the manufacturing method of Example 2 had a smaller ratio of fiber density in the wall portion to the top portion, about one-third, than that of the nonwoven fabric sample obtained by carrying out the manufacturing method of Comparative Example 1. That is, it was found that the fiber distance in the wall portion of Example 2 was longer than that of Comparative Example 1, and the wetback prevention function was improved. [Explanation of symbols]

[0063] 1 Support 11 Retention base material 12 Through hole 13 External part 2 Push-in member 21 Protrusion

Claims

1. A step of clamping and shaping an unfused fiber web between a support having intermittently arranged through holes and a pushing member having protrusions that can mesh with the through holes; and heat-fusing the shaped unfused fiber web on the support by a heated fluid, The support body has an outer circumferential portion that is continuous in a circumferential direction while surrounding the through hole. A method for producing a nonwoven fabric for absorbent articles having apertures.

2. The method for producing a nonwoven fabric for absorbent articles according to claim 1, wherein holes are formed in the unfused fiber web in the same direction as the direction in which the heated fluid is sprayed onto the support.

3. The method for producing a nonwoven fabric for absorbent articles according to claim 1 or 2, wherein the outer periphery of the support is flat.

4. The method for manufacturing a nonwoven fabric for absorbent articles according to any one of claims 1 to 3, wherein the openings in the nonwoven fabric for absorbent articles are formed at positions where the protrusions of the pushing member and the through holes of the support are engaged with each other.

5. The method for manufacturing a nonwoven fabric for absorbent articles according to any one of claims 1 to 4, wherein in the shaping step, the protrusions of the pushing member are engaged with the through holes of the support so as to pass through the through holes.

6. The method for producing a nonwoven fabric for absorbent articles according to any one of claims 1 to 5, wherein the protrusion of the pushing member has a spire shape.

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