TWI448597B - Nonwoven and absorbent articles - Google Patents

Description

Non-woven fabric and surface sheet for absorbent articles

The present invention relates to a nonwoven fabric using a heat-fusible composite fiber.

A technique has been proposed in which, as a non-woven fabric in which fibers are arranged in parallel, long fibers which are arranged in a direction such as a fiber bundle, that is, filaments are used, and the joint portions of the filaments are intermittently formed, thereby not inhibiting the freedom of the filaments. The activity can reflect the inherent softness of the fiber in the non-woven fabric, and the nonwoven fabric can be made soft and elastic (refer to Patent Document 1). In addition, it has been proposed to obtain a composite nonwoven fabric in which a fiber bundle-like filament is fixed to a non-woven fabric as a base material to improve strength and has a concavo-convex structure (see Patent Document 2).

In these non-woven fabrics, the fibers arranged in one direction are partially fixed, whereby the degree of freedom of the fibers between the fixing portions is improved to maintain the softness.

As described above, in the non-woven fabric in which fibers are arranged in parallel so far, in order to form a nonwoven fabric, it is necessary to form a joint portion of a certain degree of bonding fibers. Moreover, since the fixing portion does not exist between the joint portions, it is difficult to ensure the strength of the nonwoven fabric or the operability at the time of manufacture. Further, since the structure of the back surface of the non-woven fabric is the same, it is necessary to join the different sheets in order to impart different functions, and a separate portion is formed between the joint portions.

It is also proposed that, unlike the non-woven fabrics, the size of the gap formed by the fibers and the fibers is controlled by the thickness of the fibers used, and the size of the gap is controlled in a progressive order from the one side to the opposite side. (Refer to Patent Document 3). However, in this nonwoven fabric, the surface characteristics of the nonwoven fabric vary depending on the thickness of the fiber, so that it is difficult to respond to softness, skin feel, and the like.

Further, a technique of forming a convex portion between the crimping portions by using fibers elongated by heat has been proposed (see Patent Document 4). In this technique, the crimping portion that becomes the concave portion occupies only a small dot-like region, so that the convex portion can be effectively formed by the elongation of the fiber, but the elongation direction of the fiber is not restricted, and the original fiber entanglement state can be maintained. And the formation of a fluffy structure.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. Hei 10-151152

Patent Document 2: Japanese Patent Laid-Open Publication No. 2002-65736

Patent Document 3: Japanese Patent Laid-Open No. Hei 5-247816

Patent Document 4: Japanese Patent No. 3989468

Accordingly, it is an object of the present invention to provide a non-woven fabric in which the front and back structures of the nonwoven fabric are different from each other, and the nonwoven fabric is excellent in both strength and flexibility.

The present invention solves the above problems by providing a nonwoven fabric comprising a heat-fusible composite fiber including a first resin component and a second resin component having a higher melting point than the first resin component, and the heat-fusible composite fibers are in contact with each other. And the non-woven fabric includes a first surface and a second surface having a portion where the heat-fusible composite fiber is fixed in a parallel state, and a portion of the first surface in which the fibers are fixed in a parallel state. The ratio (percentage) of the number to the number of the fiber fusion portions is 5 to 30%.

Hereinafter, the present invention will be described based on preferred embodiments and with reference to the drawings. Fig. 1 is a perspective view showing a first embodiment of the nonwoven fabric of the present invention.

The nonwoven fabric 10 of the first embodiment has a single layer structure. The nonwoven fabric 10 has a first surface 10a and a second surface 10b. The second surface 10b of the nonwoven fabric 10 is substantially flat, and the first surface 10a has a concave-convex shape including a plurality of convex portions 11 and concave portions 12. The concave portion 12 includes a crimping portion 15 formed by crimping the constituent fibers of the nonwoven fabric 10 by embossing. The convex portion 11 is located between the concave portions 12. The convex portion 11 is filled with the constituent fibers of the nonwoven fabric 10. Examples of the method of crimping the fibers include embossing with or without heat, ultrasonic embossing, and the like.

On the other hand, the fixation of the fibers and the fibers in the portion in contact with the fibers other than the crimping portion 15 is achieved by the welding component of the fiber described later, and is substantially non-woven by the welding.

The convex portion 11 and the concave portion 12 are alternately arranged in one direction of the non-woven fabric (the X direction in Fig. 1). Further, the directions are orthogonal to the one direction (the Y direction in FIG. 1). By arranging the convex portion 11 and the concave portion 12 in this manner, when the nonwoven fabric 10 is used as a surface sheet in the field of disposable sanitary articles such as disposable diapers or menstrual napkins, the contact area with the wearer's skin is reduced. Effectively prevent stuffiness or rashes.

The crimping portion 15 of the nonwoven fabric 10 of the present embodiment is a thermocompression bonded portion formed by hot press working, and is formed in a lattice shape as shown in Fig. 1 .

More specifically, the crimping portion 15 includes a plurality of first linear embossments 15a formed parallel to each other at a predetermined interval, and a plurality of second embossments 15b formed parallel to each other at a predetermined interval. The first embossing 15a and the second linear embossing 15b form an angle of about 15 to 90 degrees and intersect each other. The interval between the first linear embossments 15a and the interval between the second linear embossments 15b are preferably 2 to 20 mm, and more preferably about 3 to 10 mm. The linear embossing may be a continuous linear embossing as in the present embodiment, and may be a dotted line embossing having a distance between dots of 5 mm or less, preferably 2 mm or less. The nonwoven fabric 10 is formed with a divided region surrounded by the crimping portion 15, and the central portion of each of the divided regions is relatively raised to the convex portion 11 with respect to the crimping portion 15 and the recessed portion 12 surrounding the partitioned region. The area of each of the divisional regions 22 is preferably 0.25 to 5 cm ² , and more preferably 0.5 to 3 cm ² .

The constituent fiber of the nonwoven fabric 10 of the present embodiment includes a heat-fusible composite fiber including a first resin component and a second resin component having a higher melting point than the first resin component. Further, a fiber fusion portion formed by welding a portion where the heat-fusible composite fibers are in contact with each other is formed in a portion other than the crimping portion 15 (see FIGS. 4(a) and 4(b)).

The nonwoven fabric 10 of the present embodiment is in the form of a core-sheath structure fiber, and is contained in a mesh of a fiber including a heat-fusible component (first resin component) and a high melting point component (second resin component) having a higher melting point than the first resin component. When the fibers which are elongated by heat are disposed, and the portions where the fibers are in contact with each other are welded by the heat-fusible component to form the fiber-welded portion, the first surface 10a and the second surface 10b have a different structure. In other words, in the first surface 10a, a plurality of fibers are arranged in parallel and the parallel state is fixed by the fusion of the welded components. As a result, the distance between the fibers (hereinafter referred to as the distance between fibers) becomes Large, the second surface 10b is a structure in which welding in a parallel state is small, and most of them are limited to the fusion of the fiber intersections, or fibers which are arranged on the plane (wavy undulations), and the distance between the fibers is relatively small. On the other hand, since the first surface 10a and the second surface 10b do not have the first surface and the second surface, or the structure is present in a small amount, the interfiber distance is considered to be in the middle of the two.

Such a specific structure is presumed to be formed by the fact that some fibers which are elongated by heat are disposed in the step of forming a non-woven fabric from the web.

In the nonwoven fabric 10 of the present embodiment, before the fibers are stretched by heat, the compressed concave portion (the crimping portion 15) is formed in the web used as the raw material by embossing, and the area ratio of the compressed concave portion is 3~. It is about 30%, but it is not related to a dot shape, a dotted line shape, or a continuous line shape, and an enclosed area of about 0.5 to 5 cm ² is formed by compressing the concave portion. The bottom surface of the compressed concave portion is formed close to the second surface 10b in the cross-sectional view of the mesh, and the transport support or the like is present on the second surface 10b side, and the ridge on the second surface 10b side is closer to the first surface 10a side. When the bulge is more suppressed, when the elongation is exhibited by heat, it is considered that the fiber is elongated only in the surrounding region, and is elongated in the three-dimensional direction of the first surface side or folded on the plane.

As for the shape in which the fibers in the first surface 10a are arranged in parallel, it is conceivable that the length of the fibers is elongated at any position in the thickness direction of the mesh in which the thermally extensible fibers are disposed, and the original crimping is also When it is released, the three-dimensional activity is maximized in the first surface 10a. In this state, the heat-fusible component exhibits weldability at the intersection of the fibers and the resin of the heat-fusible component concentrates. The fibers themselves are pulled, forming a parallel state from the point of intersection. On the other hand, in the portion which is the inner surface in the thickness direction from the first surface, although the fiber is elongated and the fibers are welded, but there are other fibers in the periphery, the fibers are not free to move and are limited to the fusion near the intersection.

The nonwoven fabric 10 has a portion where the heat-fusible composite fibers are fixed in a parallel state (a portion where the fibers are fixed in a parallel state) on the first surface 10a (see FIG. 4( a )).

Here, the "parts fixed in the parallel state" means that the intersection angle of the fibers is less than 30°, and the length L1 of the welded portion of the fibers is twice or more the thickness P1 of the welded portion. In such a fiber parallel state, a welded portion which is three times or more the fiber thickness can be formed as compared with a welded portion in which a fiber thickness is formed to be about 1 to 2 times the fiber thickness. Core-sheath construction fibers (core composition: polyester, sheath component: high-density polyethylene) having a fiber thickness of 3.3 dtex × 51 mm, observed in an parallel state using an electron microscope in a range of about 2 mm × 1.5 mm The detection frequency of the fixed portion is 5 or more in the present invention, and is more than 8 or more in the present invention, and the length of the fixed portion is fixed in parallel (ie, welded). It is also longer, 3 to 10 times the fiber thickness, preferably 5 to 10 times (the maximum length is 10 to 20 times the fiber thickness).

The ratio (percentage) of the number of the portions in which the fibers are fixed in the parallel state to the number of the fiber fusion portions in the first surface 10a of the nonwoven fabric 10 is 5 to 30%. When the ratio is 30% or less, the fiber and the fiber are less welded, and the degree of freedom of movement of the fiber is high, so that the nonwoven fabric is excellent in flexibility and skin feel. On the other hand, when the ratio is 5% or more, the gap between the fibers and the fibers (the distance between the fibers) becomes large as a whole, and therefore it is difficult to change the structure due to external pressure such as pressure, especially for absorbent articles. Among them, it is a structure which is easy to improve absorption such as liquid retention or liquid permeability. From this point of view, the above ratio (percentage) is preferably from 5 to 30%, more preferably from 10 to 20%.

Further, the number of the fiber-welded portions is in accordance with the total of the fiber-welded portions of the "parts where the fibers are fixed in parallel" and the fiber-welded portions that do not conform to the portion where the fibers are fixed in parallel. Further, Fig. 4(b) is a typical example of a fiber fusion portion that does not conform to the "part where the fibers are fixed in a parallel state".

In addition, since the number of the fusion points of the fibers is smaller than that of the second surface 10b of the first surface 10a of the nonwoven fabric 10, the number of the portions where the fibers are fixed in parallel (hereinafter also referred to as parallel fusion portions) To the same extent, the proportion of the parallel welded portions is also increased [see FIGS. 4(a), (b) and FIGS. 5(a), (b)]. From the viewpoint of the degree of influence on the structure of the non-woven fabric, it is considered that the ratio of the parallel welded portion is high to exert the function of controlling the overall structure, but from the viewpoint of application to the absorbent article, the entire welded portion is dispersedly disposed as a whole. Further, it is preferable that the structure in which the nonwoven fabric is entirely functional is preferably such that the ratio of the parallel welded portion and the number of the parallel welded portions are high.

The ratio (percentage) of the number of the portions of the first surface 10a of the nonwoven fabric 10 fixed in the parallel state to the number of the fiber fusion portions is preferably 5% larger than the ratio of the corresponding portion of the second surface 10b. More preferably, it is 10% or more. The ratio of the correspondence of the second surface 10b of the nonwoven fabric 10 is preferably 0 to 5%, and particularly preferably 2 to 4%. Further, the multiple (average length) of the parallel welded portions in the second surface is preferably 2 to 5 times in terms of the distance between the fibers capable of improving the absorbability. In addition, FIG. 5 is an electron micrograph showing a fiber fusion portion of the parallel weld portion and the other, and the parallel weld portion is represented by a rectangle having substantially the same length drawn thereon or in the vicinity thereof, and a fiber fusion portion other than the parallel weld portion. It is represented by drawing a small circle on it.

The first surface has a plurality of portions fixed in a parallel state, whereby the interval between the fibers is enlarged, and a loose space is easily formed. Thus, the obtained nonwoven fabric is excellent in flexibility or elasticity. The interval between the fibers tends to increase as the number of portions fixed in the parallel state (indicated by the average length of the parallel welded portions and the total length of the parallel welded portions) increases or the fixed length becomes longer. On the other hand, in the second surface, the total amount of the parallel state is less than the length of the first surface or the welding, and the interval between the fibers is smaller than that of the first surface, so that the intersection of the fibers is larger than that of the first surface. Thereby, in the second surface, it is easy to obtain a structure which is the strength of the nonwoven fabric. Further, it is easy to form a fiber having a structure folded in a plane, and thus it is not only more difficult to cause fixation in a parallel state, but also a structure in which a fiber is folded (a structure in which a fiber is bent) is easily formed between the intersecting portion and the intersecting portion, so that softness is less likely to be impaired. . In addition, the distance between the fibers of the first surface and the second surface is different as described above, and the first surface is placed on the skin contact surface side and the second surface is placed on the non-surface sheet as the surface sheet of the absorbent article. The skin is in contact with the side of the face, so that it is easy to form a capillary gradient that easily causes the liquid to move.

In the observation of the bonding state of the fibers in the first surface and the second surface, an image was taken using a scanning electron microscope to determine the degree to which the fibers and the fibers were fixed in a parallel state, and the image was taken at 2 mm × 1.5. The number and fixed distance are measured within the range of mm.

Fig. 5 is an enlarged photograph showing the first surface and the second surface of the nonwoven fabric according to the embodiment of the present invention and the first surface of the nonwoven fabric formed by the prior fibers. The parallel welded portion described above has 10 portions in the first surface of the non-woven fabric according to the embodiment of the present invention [Fig. 5 (a)], and has four portions in the second surface of the same non-woven fabric [Fig. 5 (b) ], in the non-woven fabric formed by the previous fibers, there are three parts [Fig. 5 (c)], when compared with the second area and the previous non-woven fabric, the parallel welded portion is on the first side when compared with the same area. More formed in the middle. If they are different areas, they can be converted to the same area for comparison.

Further, in the comparison of the non-woven fabrics in which the thickness of the fibers is different, the thickness of the fibers to be the basis is determined and converted into the thickness of the fibers to be used as the reference. (In the present embodiment, the fiber diameter is 25 μm, and in the comparative embodiment, it is 28 μm. Therefore, 25 μm is used as the reference diameter for calculation. Refer to Table 1)

Further, the parallel state in the first surface of the present embodiment has a maximum length of 341 μm, an average length of 160 μm, and a total length of 1598 μm. On the other hand, the maximum length of the parallel state in the second surface and the previous non-woven fabric is as low as 134 μm, and the average length and total length are also lower values. According to the above, even in the case where the prior art or the elongation of the fiber is suppressed, the parallel state formed does not exceed 100 μm, and it is difficult to form a shape exceeding 100 μm, and the maximum length has more than 150 μm, preferably A maximum value of more than 300 μm is considered to exhibit the effect of forming a parallel state, and thus it is considered to be preferable.

As described above, the difference in the arrangement of the fibers in the first surface and the second surface was observed, and this case was expressed as a difference in the distance between fibers. The measurement of the distance between the fibers can be measured in accordance with the "measurement of the fiber space diameter" described in Japanese Patent Laid-Open No. Hei 5-285171, but it is preferable to carry out the measurement according to the procedure described below.

In the image for measuring the interfiber distance, it is preferable to use a scanning electron microscope (for example, manufactured by JEOL) from the depth of focus or the ease of designation of the gap between the fibers and the fibers, and use it as an image analyzing device. NEXUS manufactures NEWQUBE (ver.4.20) (through a CCD (charge-coupled device) camera or scanner, or directly based on electronic data, etc.) to take in an image and display the size displayed in the electron microscope image (100 μm in Figures 6 and 7) is used for calibration to perform each measurement. Further, the first surface 10a is formed by photographing the surface 10a from the direction perpendicular to the surface 10a (preferably, the central portion of the convex portion 11 farthest from the compression concave portion), and the second surface 10b is perpendicular to the surface 10b. The direction is taken by an electron microscope to the face 10b (preferably a portion corresponding to the central portion of the convex portion 11 farthest from the compression concave portion).

6 and 7 which are captured images of the first surface of the surface sheet of the present invention are described as an example. In the first step, the welding intersection is marked, and in the second step, the intersection is serialized and used. The alignment of the fibers is linearized, and the thickness and shape of the linear lines are adjusted in the third step. In the fourth step, the image analysis software is used to calculate the binarization and the distance between the fibers. In addition, the Microsoft office power point 2003 provided by Microsoft Corporation is used for the marking and sorting of the intersections of the images and the arrangement of the fibers.

In the first step, as shown in Fig. 6(a), a portion where the fibers are welded to each other (fiber fusion portion, hereinafter also referred to as "welding junction") is indicated by a hollow circle. As for the welding system, the following is the criterion for judging that the thickness of the fiber becomes thick as shown in Fig. 4(b) at the intersection of the fibers, or the shape of the fiber is lost at the intersection (the state of the boundary line of the fiber or the fiber is not observed) Impatient deformation, etc.). In order to know the fiber change and the nonwoven structure, it is preferably in the range of 2 mm × 1.5 mm in the nonwoven fabric formed by the fiber having a thickness of about 20 μm. Further, when an image obtained by photographing the same field of view from the oblique direction is used, it is possible to confirm that the fiber intersection is welded, and it is also possible to use it in a complementary manner.

In the second step, the marked fusion joints are classified into A to D, and the fibers for measuring the distance between the fibers are selected in the manner shown in Figs. 6(b) to 7(c).

In the classification, the fusion point of the fiber at the uppermost portion is defined as the intersection point A, and the fiber at the upper side (the surface side of the first surface) is assumed to be the fiber A at the intersection point A. The assumed fiber A usually has a plurality of fusion intersections, so that the fusion intersection on the fiber A is marked as the uppermost fiber when more than 80% of the fusion intersection in the assumed fiber A is above the fusion intersection. Fiber A. The fiber A as the uppermost fiber and its intersection A on the measurement screen were selected in the same manner.

In the non-woven fabric having the fiber A, it is surely welded to the other fibers at the intersection A thereof, and the fiber which is not welded to the fiber A at the intersection A is set as the fiber B, and the fiber B other than the intersection A is welded. The intersection point is the intersection point B. The fibers other than the fibers A and B in the fiber having the fusion point B at the intersection B are referred to as the fiber C, and are selected in the same manner as the fiber E.

The fiber at the top is set as the first fiber 1A, and is 80% or more of the fusion bonding point in the image. Further, when the ratio of the fusion bonding point in the above step was less than 80%, the measurement sample did not have the fiber A and the fusion bonding point A, the fiber B became the first fiber, and the fiber E became the fourth fiber. Further, "80% or more of the fusion junction is located at the upper portion" means that when focusing on a certain fiber, 80% or more of the plurality of fusion intersections (welding points with other fibers) of the fiber in the longitudinal direction pass. Above the other fibers. Further, when an image obtained by photographing the same field of view from the oblique direction is used, it is possible to confirm that the fiber intersection is welded, and it is also possible to use it in a complementary manner.

The second fiber 1B has at least one weld intersection A. The third fiber 1C is a fiber having no fusion bonding point A and having at least one fusion bonding point B. The fourth fiber 1D does not have a fusion intersection A and a fusion intersection B, and has at least one fiber with the fusion intersection C of the third fiber 1C, and the fifth fiber 1E has no fusion intersection A, B, C and has a fusion intersection. D and E fibers. Even if the fiber extends over the fusion intersection D, it is not the fifth fiber when there is no fusion intersection E [see Fig. 7(c)]. The first to fifth fibers 1A to 1E (or the first to fourth fibers) are determined in this manner.

The labeling of the fibers and intersections was carried out as follows.

As for the fiber, the fiber is used to identify the fiber by using the dotted line of the fiber on the image of the electron microscope. As for the intersection, the unidentified person and the grade are distinguished by setting the interior of the hollow circle to the same color as the fiber, especially 1 The ratio of the intersection of the fibers 1A is more important. Therefore, when the intersection point is above and when it is below, the color of the outer side of the circle is changed to distinguish. As for the fiber and the intersection point identifiable, the dotted line is a solid line to identify different fibers.

In the measurement of the present embodiment, the first fiber and the intersection are set to red, the second fiber and the intersection are set to blue, the third fiber and intersection are set to pink, and the fourth fiber and intersection are set to green. The fifth fiber and the intersection point are set to black. However, in Fig. 6 and Fig. 7, the intersection of the first fibers is ○, the intersection of the upper fibers is ○, the intersection of the second fibers is □, and the third fibers are used. The intersection point is ◇, the intersection of the fourth fibers is Δ, and the intersection of the fifth fibers is ×. Moreover, in order to distinguish the fibers from the intersection, the thicker power point lines are displayed to the extent of the fiber thickness, (b) the first fiber (dashed line) and its intersection, and (c) the first fiber (solid line). The second fiber broken line, and (d) is the first fiber and the second fiber (solid line).

In the third step, the thickness of the line is deformed to correspond to the thickness of the fiber to obtain a mesh shape of the fiber. [Refer to Fig. 8 (a), (b)].

The mesh pattern of the obtained fiber is taken in by the image analysis software and processed (step 4). The processing sequence is as follows: the fiber is selected by binarization, and then the spatial projection shape formed by the inverted fiber of the binary image is specified, and then the peripheral portion not surrounded by the fiber is removed, and then the measurement is surrounded by the fiber. Each area [see Fig. 8(c)]. In the area measurement, in order to remove the minute as the noise, 1 to 5 pixels (pixel) are removed in the measurement and the average area is measured. Based on the average area obtained, the diameter of the circle when the circle is considered as the circle is calculated, and the value is set as the interfiber distance.

The ratio (percentage) of the number of the portions of the first surface 10a or the second surface 10b of the nonwoven fabric 10 that are fixed in the parallel state to the number of the fiber fusion portions may be based on the preferred fiber spacing The fusion junction obtained by the measurement method is obtained.

The intersection point at which the intersection angle of the fibers in the intersection designated at the time of measuring the interfiber distance was less than 30° and the length of the welded portion exceeded twice the fiber thickness was measured as a parallel welded portion. In Fig. 9, the parallel welded portions at 10 places are shown in a rectangle [Fig. 9(a)], and the intersection point including the parallel welded portions is 67 [Fig. 9(b)].

The average interfiber distance of the first surface of the present invention is preferably 100 to 150 μm, and the average interfiber distance of the second surface is preferably 60 to 120 μm, and the average interfiber distance of the first surface is subtracted from the second surface. The difference between the average interfiber distances obtained by the average interfiber distance is 20 to 70 μm, especially 30 to 50 μm, which is preferable from the viewpoint of the strength and shape stability of the non-woven fabric. In the case of a non-woven fabric formed by the same hot air method, the difference between the average interfiber distances of the first surface and the second surface by the hot air method is less than 20 μm, and the average interfiber distance is also small. Since the distance between the fibers of the first surface is large, the number of spatial projection areas divided by the fibers is also small. From this aspect, it can be understood that the first surface has a looser structure than the second surface.

In the nonwoven fabric of the present invention, as shown in Fig. 3(b), the concave portion 12a formed on the first surface 10a side is deeper than the concave portion 12b formed on the second surface 10b side. As a method of forming the concave portion, a method of forming a welded portion of the fibers by a hot press method or an ultrasonic embossing method is preferable, and the concave portion is formed by the methods even if the nonwoven fabric containing the usual welded fiber is formed, and even if it is only When the concave portion is formed by the convex mold on the one side surface side, the concave portion having the depth of the concave portion having substantially the same depth is also formed. However, in the article of the present invention, since the welded state of the fibers in the first surface and the second surface is different, when the concave portion is formed by the convex mold from the first surface side, the concave portion on the first surface side is deeper than the first portion. 2 concave side of the side. This is considered to be such a structure that the first surface side is loose, the number of fusion points on the second surface side is large, and the second surface side is more uniform.

The height d1 from the top of the first surface to the surface of the concave portion and the height d2 from the top of the second surface to the surface of the concave portion are enlarged by measuring the cross-section of the non-woven fabric passing through the respective top portions (the maximum height portion) [refer to FIG. 3 (b)] The concave portion is measured. An electron microscope can also be used for the measurement, but from the viewpoint of the ease of observation, the VH-3000 microscope is used for amplification by KEYENCE, and the measurement is performed by the two-point measurement method after the calibration setting.

The depth d1 of the concave portion of the first surface is preferably 60 to 99% of the thickness T of the nonwoven fabric, and the depth d2 of the concave portion of the second surface is preferably 0 to 40% of the thickness T of the nonwoven fabric, and the depth d1 of the concave portion 12a of the first surface is 0.3 to 1.5 mm, and the depth d2 of the concave portion 12b of the second surface is 0 to 0.3 mm, which is preferable in terms of flexibility and elasticity, and is low in liquidity as a surface sheet of an absorbent article. It is preferred in terms of low diffusivity and further liquid migration.

As a raw material of the constituent fibers of the nonwoven fabric 10 of the present embodiment, a fiber having a length elongated by heating (hereinafter referred to as a thermally extensible fiber) is used. The heat-expandable fiber is a fiber which is formed by, for example, changing the crystal state of the resin by heating and elongating, and the crimping of the crimping process formed in the fiber is released to extend the length in appearance. The heat-expandable fiber which is preferably used in the nonwoven fabric 10 of the present embodiment is preferably a combination of elongation of the resin of the core component under the welding condition of the sheath component, and specifically, the sheath component is preferably high-density. Medium density, or linear polyethylene, in combination with polypropylene or polyester.

Hereinafter, a preferred manufacturing method of the nonwoven fabric 10 using the thermally extensible conjugate fiber will be described with reference to Fig. 2 .

First, the mesh 20 is formed using a specific mesh forming mechanism (not shown). The mesh 20 is formed of a thermally extensible composite fiber or formed of a thermally extensible composite fiber. As the method for forming the web, for example, the following known methods can be used: (a) a carding method for opening a short fiber using a carding machine; (b) a continuous continuous drawing by melt drawing by aspirator a method in which filaments are deposited on a wire (spunbonding method); and (c) a method of conveying short fibers by air flow and depositing them on a net (air spinning method), but the flexibility and elongation of the fibers exhibiting elongation In view of the ease of formation of the structure after the elongation, it is preferred to use the carding method of (a), and the length of the fiber to be used is preferably about 25 to 70 mm.

The mesh 20 is conveyed to the hot pressing device 21 where it is subjected to hot press processing. The hot pressing device 21 includes a pair of rollers 22, 23. The roller 22 is an engraved roll in which a plurality of convex portions are formed on the circumferential surface. The roller 23 is a receiving roller which has a substantially smooth surface and pressurizes the web 20 between the roller 22. Each of the rolls 22, 23 can be heated to a specific temperature.

More preferably, the hot press processing is performed at a temperature higher than a melting point of a fusion component of a low-melting component of the heat-expandable composite fiber in the mesh 20, and at a temperature at which the melting point of the high-melting component is not reached. In the hot press processing, the side of the non-woven fabric which is the first surface is the side of the roll 23 having the convex portion, and heat is not applied to the heat-expandable fiber, thereby performing heat at a temperature at which the elongation temperature of the heat-extensible fiber is not reached. Press processing. The heat-expandable composite fibers in the web 20 are crimped by the hot press processing. Thereby, the crimping portion 15 is formed in the mesh 20 in a specific pattern to form the heat-bonded web 24.

The thermocompression bonding portion (pressure bonding portion) of the present embodiment is formed as a vertical base point for forming the fibers in the parallel state, and each of the crimping portions is a circle, a triangle, a rectangle, or the like having an area of about 0.1 to 3.0 mm ² . The polygon, the combination of the shapes, or the crimping portions are continuous straight lines and curves having a width of about 0.1 to 3.0 mm, and are formed in a regular manner and surrounded by the hot crimping portion over the entire area of the heat-bonded web 24. The way the area is configured. However, it is necessary to form a region surrounded by the thermally extensible conjugate fiber having a certain degree of uncompressed state for forming a three-dimensional shape to form a parallel state of the fiber, and the embossing ratio is 1 to 20%, more preferably It is preferably from 2 to 10% in terms of the difference in the structure of the first surface and the second surface which can effectively form the nonwoven fabric. Here, the enclosed region refers to a portion in which the fibers are fixed such that the elongation of the elongated fibers is not dispersed in the planar direction, and it is preferable to form a continuous curve in the alignment direction of the fibers in such a manner as to mask the alignment direction of the fibers. straight line.

The state of the cross section of the heat-bonded web 24 is schematically shown in Fig. 3(a). A plurality of crimping portions 15 are formed in the nonwoven fabric 24 by hot press processing. The heat-expandable composite fiber is pressure-bonded to the pressure-bonding portion 15 by heat and pressure, or is melt-solidified and welded to the pressure-bonding portion 15, thereby forming a concave portion on the first surface and the second surface. On the other hand, in the portion other than the crimping portion 15, the thermally extensible conjugate fiber is in a free state in which no pressure bonding, welding, or the like occurs on the first surface. Further, in FIGS. 3(a) and 3(b), the first surface is the upper surface side, and the second surface is the lower surface side.

Returning again to Fig. 2, it is preferable to heat or raise the smoothing roller 23 in Fig. 2 so that the second surface of the heat-adhesive web 24 is less likely to exhibit a weakly stretched state. By making the second surface into a weakly stretched state, the mesh structure can be made dense on the second surface, and the surface structures of the first surface and the second surface can be changed. Here, the weakly elongated state means an elongation of 10 to 50% when the elongation is fully exhibited, and about 3 to 10% of the length of the elongated fibril, so that the stability of the manufacturing step and the ease of control of the nonwoven structure are improved. In view of this, it is preferable that the surface temperature of the smoothing roller 23 is equal to or lower than the melting point of the fiber fusion component, and preferably 20 ° C or lower. Specifically, if it is a polyethylene having a melting point of 120 to 140 ° C as a fusion component of the fiber, the surface temperature of the smoothing roller 23 is 60 to 100 ° C. Further, in the control of the weakly stretched state from the surface layer of the second surface to the first surface side, the contact time with the smoothing roller 23, that is, the state of being surrounded by the smoothing roller, may be controlled.

The heat-bonded web 24 obtained in the above manner is conveyed to the hot air blowing device 26. The hot viscous mesh 24 is subjected to hot air processing by the hot air blowing device 26. That is, the hot air blowing device 26 is configured such that the hot air 28 heated to a specific temperature penetrates the heat-bonded mesh. Further, in view of the improvement of the penetration of the hot air in the mesh and the suppression of the mesh on the mesh surface, it is preferable to use a suction device in combination with the mesh surface.

The hot air processing is performed at a temperature at which the thermally extensible composite fibers in the heat-bonded web 24 are elongated by heating. Further, hot-air processing is performed at a temperature at which the portions of the thermally extensible conjugate fibers which are in a free state in the portion other than the crimping portion 15 in the heat-bonded web 24 are thermally welded. Of course, it is necessary to perform hot air processing at a temperature at which the temperature is not the melting point of the high melting component of the heat-expandable composite fiber.

By this hot air processing, the heat-expandable composite fiber existing in the portion other than the crimping portion 15 is elongated and stretched and stretched. One of the thermally extensible fibers is fixed by the crimping portion 15, and thus the portion other than the crimping portion 15 is elongated. In the hot air processing, since the mesh is placed on the support 27 such as a metal mesh, it is presumed that the heat-adhesive mesh 24 is on the second surface side of the support 27 side, except for the weakly stretched state described above. In addition to the suppression of the structural change caused by the hot air blowing during the hot air processing, the suppression of the suction, the suppression of the mesh itself, and the like, even if the fiber is stretched and the crimp is released, the fiber is less likely to be linear but is easily formed. The crucible is placed on the plane so that the fibers are easily in contact with each other in an intersecting state. Since the lanthanum is caused by a weakly stretched state, if the degree of elongation is not very large, it does not become a strong force to disturb the mesh structure, and the second surface is easily kept flat. Further, the more the pressure-bonding portion is formed, the more the fiber is fixed, and thus the degree of enthalpy tends to become larger.

On the other hand, the first surface side of the heat-adhesive mesh body 24 on the opposite side to the support body 27 is not restrained as in the second surface side, and the fiber is observed to be elongated in the thickness direction and released into a linear shape. The fibers which are close to the fibers and which extend in the same direction are easily concentrated by the melting of the welded components. As a result, it is presumed that the fibers in the first surface and the fibers are more fixed in parallel than the second surface.

Therefore, the convex structure which is bulged in the thickness direction is formed in the first surface, and the fibers and the fibers are fixed in parallel. Therefore, the gap formed by the fibers and the fibers in the first surface is large, and the fibers are easily crossed on the plane. Further, the gap between the fibers and the fibers in the second surface, which has a large number of intersections, becomes small. Since the first surface faces the second surface, it is easy to impose some restrictions on the elongation and the release of the crimp. Therefore, the gap between the fibers and the fibers tends to be small. Further, by the formation of the crimping portion, it is more likely to cause the bulging in the thickness direction as shown in Fig. 3(b).

As described above, in the nonwoven fabric 10, the thermally extensible conjugate fiber which is the constituent fiber of the nonwoven fabric 10 is press-bonded to the crimping portion 15, and the portion other than the crimping portion 15 is specifically mainly the crimp portion 11 by crimping. In the hot air method, the intersection of the thermally extensible composite fibers is joined by heat fusion, and the portion where the fibers and the fibers are fixed in parallel in the first surface side is formed more than the second surface. As a result, the average value and the maximum value of the gap between the fiber and the fiber of the first surface are larger than those of the second surface, and the nonwoven fabric 10 can be used for various purposes. For example, as a sheet for cleaning, in addition to the high trapping property of the second surface and the first collecting ability of the first surface, the adhesion to the object can be improved by the elasticity of the three-dimensional structure or the flexibility of the non-woven fabric. Sex. In addition, the surface sheet for an absorbent article is excellent in absorbability, that is, when the first surface is the front side, the uneven shape causes a decrease in flexibility or contact area, and the first surface faces the second surface. The capillary gradient of the liquid provides good transferability and maintains good contact with the absorbent surface due to the smoothness of the second surface.

In the second surface of the non-woven fabric according to the embodiment of the present invention, the phenomenon that the fibers are folded on the plane due to the elongation of the fibers and the release of the crimp is observed, but the fibers in the vicinity of the crimping portion in the concave portion do not appear. This embarrassing phenomenon. The length of the sputum phenomenon is 30 to 130 μm and 1.2 to 5 times the fiber thickness. It is considered that the reason for forming this structure is that the one end of the fiber is fixed by the crimping portion, so that if the fiber is not detached from the fixed portion, the degree of freedom of the fiber can not be ensured, and the absorbent article is caused by the structure. In the use of the surface sheet, it is difficult to form a random gap between the fiber and the fiber, and it is a structure that faces (or separates) the pressure-bonding portion, and thus has a structure in which the liquid from the pressure-contact portion of the second surface is easily moved. In particular, when the crimping portion is directly in contact with the absorber, the liquid moving effect can be further improved.

From the viewpoint of forming more parallel welded portions in the first surface 10a than the second surface 10b, it is preferable that the hot air processing is to make it easier to form the portion pressed by the embossing on the first surface side. Performed in the state of the convex portion. The assumption that the convex portion is more easily formed is as follows: a roll having a soft peripheral surface such as a cotton roll is used as the roll 23, or the net 24 is transported from the hot press device to the hot air blowing device while sucking from the second surface 10b side. Or, after the embossing, the hot air treatment is performed while maintaining the suction state.

Fig. 10 is a view showing that the fibers in the 蜿蜒 state of the fibers involved in the fusion splicing points introduced from Figs. 5 to 8 are shown coarsely (a) the arrangement of the fibers of the second surface and (b) the angle of the second surface. Figure. The diameter of the circle is 100 μm (four times the thickness of the fiber). When the center of the circle is placed at the top of the 蜿蜒 part, the angle from the intersection of the top connecting circle and the fiber is set as the angle formed by the bending of the fiber. , the angle represents a portion below 100°. The fiber of the second surface has an angle formed by bending of the fiber at five or more points in the measurement range, but a plurality of portions are not formed in the nonwoven fabric of the first surface of Fig. 10 (c) and the normal fiber of (d).

Further, in the pressure-bonding portion of the prior nonwoven fabric, a plurality of random gaps are formed by concentrating the fibers. However, in the first surface of the nonwoven fabric of the present invention, the fibers are erected from the pressure-bonding portion, and the structure in which the fibers are separated in the thickness direction is easily used. In the same manner as the second surface, it is difficult to form a random gap between the fibers and the fibers, and it is difficult to maintain a liquid structure.

The parallel fusion of the fibers of the first surface is not only a large number but also longer than the fiber thickness. The previous non-woven fabric also partially has a fixed portion in a parallel state. However, since the fibers after the fiberization are three-dimensionally randomly arranged or the fibers are crimped, it is almost impossible to form adjacent fibers in parallel with each other at a long distance.

As described above, the nonwoven fabric 10 is composed of a heat-extensible composite fiber or a heat-extensible composite fiber. In the case where the non-woven fabric 10 is composed of a thermally extensible fiber, the other fibers contained in the nonwoven fabric 10 include fibers of a thermoplastic resin having a melting point having a higher thermal elongation temperature than the heat-expandable composite fiber. . The other fibers are preferably contained in the nonwoven fabric 10 in an amount of 5 to 50% by weight, more preferably 20 to 30% by weight. On the other hand, the thermally extensible conjugate fiber is preferably contained in the nonwoven fabric 10 in an amount of 50 to 95% by weight, particularly preferably 70 to 95% by weight, so that the difference in the structure of the first surface and the second surface can be easily realized. Preferably, the nonwoven fabric 10 is preferably formed of a thermally extensible composite fiber from the viewpoint of more easily forming the structure of the first surface.

The details of the heat-expandable composite fiber, which is a core-sheath structure type composite fiber, is preferably a cross-sectional structure in which the core structure and the center of gravity of the sheath structure are substantially the same. The heat-expandable composite fiber used in the present embodiment is a fiber which is unwound as the fiber is stretched as it is stretched. Therefore, it is preferable that the fiber which is a nonwoven fabric for obtaining the above structure is a core structure and a sheath structure. The eccentric fiber or the side-by-side type fiber in which the center of gravity deviates is likely to exhibit curling due to the fiber itself when the nonwoven fabric is formed by hot air.

The elongation of the heat-expandable composite fiber at a temperature 10 ° C higher than the melting point or softening point of the first resin component is 0.5 to 20%, particularly 3 to 10%, preferably from the viewpoint of obtaining the nonwoven fabric 10 having a remarkable uneven shape. .

In order to obtain the thermally extensible conjugate fiber having the thermal elongation, the conjugate fiber may be subjected to heat treatment or crimping treatment without stretching treatment after spinning the heat-expandable conjugate fiber as follows. Further, the reason for measuring the thermal elongation at the above temperature is that when the nonwoven fabric is thermally welded to the intersection of the fibers, it is usually at least the melting point or softening point of the second resin component and is about 10 ° C higher than the temperatures. Manufactured within the range of temperature.

The thermal elongation was measured by the following method. Using a thermomechanical analyzer TMA-50 (manufactured by Shimadzu Corporation), fibers arranged in parallel were mounted at a distance of 10 mm between the chucks, and were heated at a temperature increase rate of 10 ° C/min under a fixed load of 0.025 mN/tex. . The change in elongation of the fiber at this time was measured, and the elongation at a temperature higher than the melting point or softening point of the second resin component by 10 ° C was read and the elongation was defined as the thermal elongation.

The conditions for the heat treatment after the spinning can be selected according to the types of the first and second resin components constituting the conjugate fiber of the present invention. For example, when the composite fiber of the present invention is a core-sheath type and the core component is polypropylene and the sheath component is high-density polyethylene, the heating temperature is 50 to 120 ° C, especially 70 to 100 ° C, and the heating time is good. It is preferably 10 to 500 seconds, especially 20 to 200 seconds. Examples of the heating method include blowing hot air, irradiating infrared rays, and the like.

As the crimping process after spinning, it is relatively simple to perform mechanical crimping in a two-dimensional shape and a three-dimensional shape. In the case where the three-dimensionally apparent crimping observed in the core-sheath type composite fiber or the side-by-side type composite fiber of the eccentric type is used in the present invention, the blending amount is preferably 20% or less. Mechanical crimping is sometimes accompanied by heat. In this case, the heat treatment and the crimping treatment are simultaneously performed.

At the time of the crimping treatment, the fibers may be slightly stretched, but the stretching is not included in the elongation treatment of the present invention. The extension treatment referred to in the present invention refers to an extension operation in which the stretching ratio of the undrawn yarn is usually about 2 to 6 times.

The heat-expandable conjugate fiber is preferably a core-sheath type of the same core type described above. In this case, the first resin component constitutes a core and the second resin component constitutes a sheath, so that the thermal elongation of the heat-expandable composite fiber can be improved. It is better in terms of rate. The type of the first resin component and the second resin component is not particularly limited as long as it is a resin having the ability to form fibers. In particular, the difference in melting point between the two resin components or the difference between the melting point of the first resin component and the softening point of the second resin component is 10 ° C or higher, particularly 20 ° C or higher, so that the nonwoven fabric can be easily produced by heat welding. It is better in terms of aspects. In the case where the heat-expandable composite fiber is a core-sheath type, a resin having a core component having a melting point higher than a melting point or a softening point of the sheath component is used. The preferred combination of the first resin component and the second resin component is a high-density polyethylene (HDPE) and a low second resin component when the first resin component is polypropylene (PP). Density polyethylene (LDPE), linear low density polyethylene (LLDPE), ethylene propylene copolymer, polystyrene, and the like. In the case where a polyester resin such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT) is used as the first resin component, the second component is excluded as described above. Examples of the second resin component include polypropylene (PP), copolymerized polyester, and the like. Further, the first resin component may be a copolymer or a mixture of two or more kinds of a polyamidamide-based polymer or the above-mentioned first resin component, and the second resin component may be a second resin component as described above. Two or more kinds of copolymers or mixtures, and the like. These can be combined as appropriate. Among these combinations, polypropylene (PP) / high density polyethylene (HDPE) is preferably used. This is because the difference in melting point between the two resin components is in the range of 20 to 40 ° C, so that the nonwoven fabric can be easily produced. Further, since the specific gravity of the fiber is low, a non-woven fabric which is lightweight and excellent in cost and can be incinerated with low heat can be obtained.

Using a differential scanning type thermal analyzer DSC-50 (manufactured by Shimadzu Corporation), a finely divided fiber sample (sample mass: 2 mg) was subjected to thermal analysis at a temperature increase rate of 10 ° C/min, and the melting peak temperature of each resin was measured. The melting point of the first resin component and the second resin component is defined by the melting peak temperature. When the melting point of the second resin component cannot be clearly measured by the method, the temperature at which the molecules of the second resin component start to flow, and the temperature at which the second resin component is welded to the strength of the weld point of the measurable fiber is set to Softening Point.

The ratio (weight ratio) of the first resin component to the second resin component in the conjugate fiber of the present invention is preferably 10:90 to 90:10, particularly preferably 30:70 to 70:30. If it is in this range, the mechanical properties of the fiber become sufficient, and it becomes a durable fiber. Further, the amount of the welded component becomes sufficient, so that the fibers are welded to each other to become sufficient.

The thickness of the heat-expandable composite fiber can be selected according to the specific use of the composite fiber. The general range is 1.0 to 10 dtex, especially 1.7 to 8.0 dtex, which is preferable in terms of spinning properties or cost of the fiber, card passability, productivity, cost, and the like. The thickness of the conjugate fiber used as the surface sheet of the absorbent article is preferably 0.1 dtex or more from the viewpoint of the formability of the fusion bonding point, and particularly preferably 0.5 dtex or more, from the viewpoint of the water absorbing mechanism using the capillary gradient. Below 10 dtex, especially below 8 dtex is preferred.

Next, a second embodiment of the present invention will be described. In the second embodiment, it is a form in which a region completely surrounded by the thermocompression bonding portion formed in the nonwoven fabric is formed, and the hot air temperature is lowered during the production, the hot air treatment time is extended, and the hot air handling property of the suction device is improved from the mesh surface side. Other than the above, it is the same as that of the first embodiment.

Fig. 11 (a) and (b) show electron micrographs (photographs in which a plurality of photographs are combined) of the first surface and the second surface of the obtained non-woven fabric. As a result of the same measurement method as in Fig. 5, the number of parallel states in the first plane is eight, the maximum length is 485 μm, and the average length is 200 μm, which is in any parallel state. The length of more than 94 μm was obtained, and the shape of the crucible in the second side was also confirmed.

As a configuration for promoting the characteristic structure of the first surface and the second surface, a two-dimensional crimping fusion fiber layer having no thermal extensibility is disposed between the first surface and the second surface, so that the first aspect can be easily expressed. The starting point of one surface is formed to suppress the structure of the second surface. Further, the heat-extensible composite fiber which is three-dimensionally crimped and observed in the core-sheath type composite fiber or the side-by-side type composite fiber of the eccentric type is used as the surface sheet of the absorbent article. In the case of the liquid, it is excellent in the permeability of the liquid, particularly the passability and retention of the highly viscous material. Further, the three-dimensionally-obtrusive fiber in the prior non-woven fabric has the advantage of a fluffy structure, but there is a difficulty in the ease of raising or the strength of the non-woven fabric, and the first surface is set to the skin side, and the full surface can be fully utilized. As a property of the surface sheet, a structure which does not impair the above advantages can be formed.

The non-woven fabric of the present embodiment can be applied to various fields in which the uneven shape, bulkiness, and high strength are utilized. For example, it can be preferably used for a surface sheet of a disposable diaper or a disposable sanitary article such as a sanitary napkin, a second sheet (a sheet disposed between the surface sheet and the absorbent body), and a back sheet. Materials, leak-proof sheets, or dry wipe sheets for humans, sheets for skin care, and rags for other things.

When used for the above purposes, the nonwoven fabric of the present invention has a basis weight of 15 to 60 g/m ² , particularly preferably 20 to 40 g/m ² . Further, the thickness is preferably 1 to 5 mm, particularly preferably 2 to 4 mm. However, the appropriate thickness will vary depending on the application, and thus it will be appropriately adjusted according to the purpose.

The nonwoven fabric of the present invention can be preferably used as a surface sheet of an absorbent article.

Absorbent articles are mainly used to absorb excretion of body fluids such as urine or menstrual blood. The absorbent article contains, for example, disposable diapers, menstrual sanitary napkins, incontinence pads, and the like, but is not limited thereto, and can widely include articles for absorbing body fluids discharged from the human body.

The absorbent article is typically an absorbent body comprising a topsheet, a backsheet, and a liquid retaining property disposed between the two sheets. The absorbent article usually has a skin contact surface that comes into contact with the wearer's skin when worn, and a non-skin contact surface that faces the opposite side (usually a garment side such as shorts), and the surface sheet is placed on the skin contact surface side, and the back sheet is disposed. On the non-skin contact side.

In the case where the nonwoven fabric of the present invention is used as a surface sheet, the first surface side is used toward the skin side of the wearer, and it is preferable from the viewpoint of improving the dry feeling, flexibility, and the like by reducing the amount of liquid storage.

As the absorber and the back sheet, materials generally used in the art can be used without particular limitation. For example, as the absorber, a fiber aggregate including a fiber material such as pulp fibers or a sheet in which a sheet is covered with a thin paper or a non-woven fabric can be used. As the back sheet, a film of a thermoplastic resin or a liquid-impermeable or water-repellent sheet such as a laminate of the film and the nonwoven fabric can be used. The back sheet may also have water vapor permeability. The absorbent article can also have various components corresponding to the particular use of the absorbent article. This component is well known to those skilled in the art. For example, when the absorbent article is applied to a disposable diaper or a menstrual sanitary napkin, one or two or more pairs of three-dimensional protection may be disposed on the left and right sides of the surface sheet.

The present invention has been described above based on the preferred embodiments, but the present invention is not limited to the above embodiments. For example, in the above embodiment, the crimping portion 15 is formed by hot pressing using embossing with heat. Alternatively, the crimping may be performed without embossing or ultrasonic embossing. unit. Alternatively, the crimping portion may be formed by an adhesive.

Example (Example 1)

A core-sheath type composite fiber having a sheath of polyethylene (PE) and a core of polypropylene (PP) (having a fiber thickness of 4 dtex before elongation) was used to form a network by a carding method. The mesh is subjected to hot press processing to form a lattice-shaped crimping portion 15 in which the first linear embossing 15a and the second linear embossing 15b intersect at an angle of 65 degrees. The line width of each of the first and second linear embossments 15a and 15b is 0.5 mm, and the interval between the first linear embossments 15a and the second linear embossments 15b is set to 6 mm. The area surrounded by the crimping portion 15 has an area of 0.735 cm ² .

The nonwoven fabric of Example 1 was obtained by subjecting the obtained hot-pressed web to a hot air treatment by a hot air blowing device. In the hot air treatment, the treatment temperature (=temperature in the hot air treatment device) was 138 ° C, and the treatment time was 11 seconds. Further, the suction is not intentionally performed on the opposite side (the mesh side) from the side where the hot air is blown.

(Example 2)

The treatment temperature of the hot air treatment was 135 ° C, the treatment time was 24 seconds, and the hot air treatment was performed while sucking from the side opposite to the side where the hot air was blown (the mesh side), and the same as in the first embodiment except the above. The nonwoven fabric of Example 2 was obtained.

(Comparative Example 1)

A core-sheath type composite fiber having a sheath of polyethylene (PE) and a core of polypropylene (PP) (non-thermal elongation, a fiber thickness of 3.3 dtex) is used, and a mesh is formed by a carding method. The nonwoven fabric of Comparative Example 1 was obtained in the same manner as in Example 1.

In the non-woven fabrics of Examples 1 and 2 and Comparative Example 1, the mesh side was set as the second surface, and the interfiber distance, the number of welded joints, and the parallel welded portion of the first surface and the second surface were measured (abbreviated as The number of "parallel parts" and the like are shown in Table 1.

(liquid storage assessment)

The non-woven fabric sheets of Examples 1, 2 and Comparative Example 2 were each cut into a size of 150 × 70 mm to obtain a surface sheet.

A sheet of 200 g/m ² was cut into a size of 150 × 70 mm in a state where 16 g/m ² of absorbent paper was placed on the lower side of the pulp, and the sheet was used as an absorbent body.

As an evaluation tool, an injection hole of Φ 10 mm is installed in the center of an acrylic plate of 200 × 100 mm and a thickness of 8 mm, and an inner diameter of 23 mm and a height of 50 mm for temporarily storing the liquid and passing the liquid through the injection hole. In the case of the cylinder (the inclined portion with an angle of 30 degrees between the injection hole and the injection hole), the horse's fiber blood obtained from the Japan BIOTEST Research Institute (the viscosity is about 7 cp, using TOKI SANGYO Co. LTD) Manufacture of VISCOMETER TVB-10M for measurement).

The evaluation surface was prepared by laminating the second surface (mesh surface) side of the surface sheet having the weight before the evaluation to the absorber side.

The evaluation instrument is stacked on the evaluation sample by means of the evaluation instrument and the weight-adjusting weighing device so as to be 3 g/cm ² , and 3 g of the evaluation liquid is injected into the cylindrical portion of the evaluation instrument using a beaker or the like, and allowed to stand. 1 minute. The weight of the surface sheet was measured after 1 minute of injection, and the difference from the weight before the evaluation was calculated. The average value of the three measurement results was defined as the liquid storage amount and shown in Table 1.

According to the results shown in Table 1, it is understood that the non-woven fabric of the present invention has a significantly reduced liquid storage amount as compared with the non-woven fabric of the comparative example.

Industrial availability

According to the present invention, the structure of the front and back surfaces of the non-woven fabric can be obtained to be different and integrated, thereby maintaining the non-woven fabric which is excellent in strength and softness as the nonwoven fabric.

10. . . Non-woven

10a. . . First side

10b. . . Second side

11. . . Convex

12. . . Concave

12a. . . Concave on the side of the first side 10a

12b. . . Concave on the side of the second side 10b

15. . . Crimp section

15a. . . First linear embossing

15b. . . Second linear embossing

20. . . Mesh

twenty one. . . Hot pressing device

22, 23. . . Roll

twenty four. . . Hot sticky mesh

26. . . Hot air blowing device

27. . . Support

28. . . Hot air

D1. . . Height from the top of the first face to the surface of the recess

D2. . . Height from the top of the second face to the surface of the recess

L1. . . Length of the welded portion of the fiber

P1. . . Thickness of the welded portion

X, Y. . . direction

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing a portion of a nonwoven fabric according to an embodiment of the present invention.

Fig. 2 is a schematic view showing a method of manufacturing the nonwoven fabric shown in Fig. 1.

3 is a schematic view showing a state of the non-woven fabric shown in FIG. 1 and a manufacturing process thereof, and FIG. 3(a) is a cross-sectional view showing a state before hot pressing and hot air treatment, and FIG. 3(b) is a cross-sectional view showing a non-woven fabric. .

Fig. 4(a) is an electron micrograph showing a portion where the fibers are fixed in a parallel state (parallel welded portion), and Fig. 4(b) is an electron micrograph showing a fiber welded portion other than the parallel welded portion.

5 is an electron micrograph showing a portion welded in a parallel state, FIG. 5(a) is a photograph of the first surface of the nonwoven fabric of the present invention, and FIG. 5(b) is a photograph of the second surface of the nonwoven fabric of the present invention. 5(c) is a photograph of the first side of the previous non-woven fabric.

Fig. 6 is an electron micrograph showing the first surface of the nonwoven fabric of the present invention, Fig. 6(a) is a view showing a fusion intersection where fibers are welded to each other, and Fig. 6(b) is a diagram of drawing a first fiber and its intersection. Figure 6(c) is a diagram of the second fiber and its intersection.

Fig. 7 is an electron micrograph of the first surface of the nonwoven fabric of the present invention, Fig. 7(a) is a view of the third fiber and its intersection, and Fig. 7(b) is a fourth fiber and its intersection. Fig. 7(c) is a diagram of the fifth fiber.

Fig. 8 is a view showing a method of measuring the distance between fibers, and Fig. 8(a) is a view showing a state in which the lines of the first to fifth fibers shown in Fig. 7(c) are adjusted to the fiber thickness, and Fig. 8 (Fig. 8) b) is a diagram of the fiber after the coarseness adjustment, and Fig. 8(c) is a diagram showing the area surrounded by the fibers.

Fig. 9(a) shows a parallel welding portion, and Fig. 9(b) shows a method of counting welding points.

Fig. 10 is a view showing a fiber passing through a fiber intersection of the sawtooth structure, Fig. 10 (a) is a photograph of the second face of the nonwoven fabric of the present invention, and Fig. 10 (b) is a photograph of the second face of the nonwoven fabric of the present invention. FIG. 10(c) is a view of the fiber taken from the photograph of the first side of the non-woven fabric of the present invention, and FIG. 10(d) is taken from the photograph of the first side of the previous non-woven fabric. Take the picture of the fiber. Furthermore, the sawtooth structure is indicated by a thick line.

Fig. 11 is an electron micrograph showing another embodiment of the present invention, wherein Fig. 11(a) is a photograph of the first surface of the nonwoven fabric, and Fig. 11(b) is a photograph of the second surface of the nonwoven fabric.

Length of the welded portion of the L1‧‧‧ fiber

Thickness of the welded portion of P1‧‧‧ fiber

Claims (6)

a non-woven fabric comprising a heat-fusible composite fiber comprising a first resin component and a second resin component having a higher melting point than the first resin component, wherein the heat-fusible composite fibers are in contact with each other to form a fiber fusion joint; The nonwoven fabric includes a first surface and a second surface having a portion where the heat-fusible composite fiber is fixed in a parallel state, and the number of portions of the first surface in which the fibers are fixed in a parallel state with respect to the number of the fiber fusion portions The ratio (percentage) is 5 to 30%; the ratio (percentage) of the first surface is larger than the second surface; the concave portion of the first surface of the non-woven fabric and the concave portion of the second surface are formed at the same plane position, the first surface The depth of the recess is deeper than the recess of the second surface. The non-woven fabric of claim 1, wherein the non-woven fabric has a basis weight of 20 to 100 g/m ² and the interfiber distance of the first surface is greater than the second surface. In the non-woven fabric of claim 1, the non-woven fabric has a concave portion on the first surface and/or the second surface, and a pressure-bonding portion in which the fibers are welded by embossing is formed in the concave portion. The non-woven fabric of claim 1, wherein the non-woven fabric is formed of a single layer. The non-woven fabric of claim 1, wherein the heat-fusible composite fiber is a composite fiber which is not subjected to elongation treatment after spinning. A surface sheet for an absorbent article, wherein the first side of the non-woven fabric of claim 1 is used for the skin contact surface side.