JP5433043B2 - Nonwoven manufacturing method - Google Patents

Description

  The present invention relates to a non-woven fabric having a ridge groove structure and an opening in a groove portion, and a method for producing the same. This nonwoven fabric is particularly suitably used as a surface sheet for absorbent articles.

  Conventionally, as a technique related to a nonwoven fabric having a grooved structure and an opening in a groove portion, for example, a nonwoven fabric that imparts an opening and a wavy structure to a nonwoven fabric by a heated pin and a receiving structure and a manufacturing method thereof are known (Patent Literature). 1). Also known is a non-woven fabric that bonds fibers with hot air after embossing the web into the shape of the concavo-convex structure with gas, and a method for producing the same (see Patent Document 2). Furthermore, a method has been proposed in which a high-pressure water stream is blown from a nozzle to form a groove structure or an opening (see Patent Document 3).

  Apart from these techniques, a technique has been proposed for improving the flexibility of the nonwoven fabric by forming intersections at the bonding point between the fibers, where the fusion is shallow and the bonding area of the resin is not increased. (See Patent Document 4)

JP-A-6-330443 JP-A-4-24261 JP 58-132155 A JP-A-5-285172

  Patent Document 1 discloses a non-woven fabric having a groove structure and an opening formed in a groove portion by a heated convex pin and multi-row concave portions and a manufacturing method thereof. The resulting non-woven fabric has a wave-like structure. For this reason, it was easy to be stretched in the width direction or to close the gap between the buttocks. In addition, the heel structure is easily crushed by an external force such as bending, and further, the crushing is difficult to recover. Regarding the opening, when the nonwoven fabric is caught on the tip of the convex pin, the end of the opening may be warped on the opposite surface. Thus, the nonwoven fabric described in the same document is difficult to stabilize its structure.

  Patent Document 2 discloses a non-woven fabric obtained by heating a web on a support (net), then injecting gas to impart an uneven structure to the web, and heating. Since the pressure applied to the web is different between the process and the heat application process, there is a return of the web between the shape application process and the heat application process, and it is difficult to provide a shaping structure. For the purpose of preventing this, if the air volume applied to the web in the heat application process is set to be the same as the air volume in the shape application process and no pressure difference is generated, heat is sufficiently transmitted to the constituent fibers of the web in the heat application process. As a result, there is a problem with the strength of the nonwoven fabric.

  In Patent Document 3, a non-woven fabric having a ridge groove structure and independent protrusions is obtained, but the fibers are clogged in the process of imparting the shape only by the water flow, the rigidity becomes high, or the surface sheet of the absorbent article The space structure is easy to hold the liquid.

  In Patent Document 4, since there are fewer bonded portions at the intersections, the fiber resin to be used is limited, and relatively mild heating conditions are required, making manufacturing control difficult. In addition, the strength of the nonwoven fabric tends to be low.

  The objective of this invention is providing the nonwoven fabric which can eliminate the fault which the prior art mentioned above has, the manufacturing method, and the surface sheet of an absorbent article.

  The present invention is a non-woven fabric having alternating ridges and groove portions extending in one direction and having openings in the groove portions, and the amount of fibers in the heel portion is substantially larger than that of the groove portions, A nonwoven fabric having different fiber densities at the top of the collar and the end of the opening is provided.

  The present invention relates to a surface sheet of an absorbent article, the surface sheet comprising a non-woven fabric containing 50% by weight or more of self-bonding fibers and heat-bonded to each other, and the fibers are fused. It is an object of the present invention to provide a top sheet of an absorbent article in which the distance between the centers of the fibers in the wearing portion is larger than the sum of the distances from the center of each fiber to the outer surface of the fibers.

The present invention is a method for producing a nonwoven fabric having alternately ridges and grooves extending in one direction, and having openings in the grooves,
Supplying the fiber assembly and guiding the fiber assembly on a fluid-permeable support for forming a wave-like structure in a direction orthogonal to the supply direction of the fiber assembly;
A step of spraying a fluid onto the fiber assembly located on the support to further separate the constituent fibers to form a ridge groove structure and an opening; and a fluid again to the fiber assembly located on the support. Is provided to provide a method for producing a nonwoven fabric, which has a step of forming the fiber assembly in which the groove structure and the openings are formed into a nonwoven fabric.

  The nonwoven fabric of the present invention is excellent in flexibility because the rigidity improvement due to excessive clogging between fibers is suppressed. Moreover, the nonwoven fabric of this invention does not have the crushing of a collar part, a fall, and obstruction | occlusion of an opening. Moreover, the manufacturing method of the nonwoven fabric of this invention is excellent in the formation of a groove structure and stability of a shape, and can obtain a high strength nonwoven fabric simply. Furthermore, the surface sheet of the present invention has a good feeling of use because the liquid retainability is suppressed.

It is a schematic diagram which expands and shows the principal part of one Embodiment of the nonwoven fabric of this invention. It is the II-II sectional view taken on the line in FIG. It is a figure (figure 2 equivalent figure) which shows the state of the other cross section of the nonwoven fabric of this invention. It is a schematic diagram which shows the fusion | melting state of the fiber in the nonwoven fabric of this invention. It is a schematic diagram which shows an example of the apparatus which manufactures the nonwoven fabric shown in FIG. It is a perspective view which shows the fluid-permeable support body in FIG. It is a schematic diagram which shows the manufacturing process of the nonwoven fabric using the apparatus shown in FIG.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The principal part enlarged view of one Embodiment of the nonwoven fabric of this invention is shown by FIG. 2 is a cross-sectional view taken along line II-II in FIG. The nonwoven fabric of this embodiment assumes the use as a surface sheet of an absorbent article mainly. Therefore, in the following description, the nonwoven fabric of this embodiment is also referred to as a “surface sheet”.

  1 and 2 has a first surface 10a and a second surface 10b opposite to the first surface 10a. The 1st surface 10a is a surface which faces a wearer's skin side, when the surface sheet 10 is integrated in absorbent articles, such as a sanitary napkin and a disposable diaper. The 2nd surface 10b is a surface which faces the absorber side of an absorbent article. The topsheet 10 has a flange portion 20 and a groove portion 30 that respectively extend in one direction Y. The flange portions 20 and the groove portions 30 are alternately arranged over a direction X orthogonal to the extending direction Y thereof. The flange portion 20 is configured from a relatively thick portion of the topsheet 10, and the groove portion 30 is configured from a relatively thin portion of the topsheet 10. As a result, the substantial thickness of the flange portion 20 is larger than the thickness of the groove portion 30. Here, the substantial thickness means not the length (apparent thickness) from the back surface of the top sheet 10 to each uppermost part, but the length of the portion where the fibers of the top sheet 10 are present.

  As shown in FIG. 2, in the cross section in the direction orthogonal to the extending direction (the direction indicated by X in the drawing), the flange portion 20 has a smooth curve that is convex upward on the first surface 10 a side. It has a contour to draw. The second surface 10b side has a contour that draws a smooth and gentle curve convex downward. The first surface 10a side of the flange portion 20 is raised higher than the second surface 10b side, and this is periodically continuous. Thus, the first surface 10a side has a waveform shape along the X direction. Therefore, when the 1st surface 10a side of the surface sheet 10 touches a wearer's skin, the top part of the collar part 20 and the area | region of the vicinity will contact partly, and the stickiness by the stuffiness resulting from a full surface contact Feeling and irritation caused by rubbing are reduced. Moreover, it becomes difficult for the liquid excreted from the wearer to adhere to the wearer's skin.

  The shape of the collar portion 20 is not limited to the above-described shape. For example, as shown in FIG. 3A, the second surface 10b side has a contour that draws a smooth and gentle curve upward. Alternatively, as shown in FIG. 3B, the second surface 10b side may be flat. Such a difference in shape mainly depends on the manufacturing conditions of the topsheet 10.

  The collar portion 20 is filled with the constituent fibers of the topsheet 10. That is, there is no cavity in the collar portion 20. Similarly, a portion of the groove portion 30 where an opening 31 described later is not formed is filled with constituent fibers of the topsheet 10. However, as will be described later, the fiber amount of the flange portion 20 is different from the fiber amount of the groove portion 30.

  As shown in FIG. 2, the flange portion 20 has a top portion 21 on the first surface 10 a side in the cross section in the X direction, and the substantial thickness is the largest at this portion. Then, with respect to the X direction, the substantial thickness gradually decreases as the distance from the top portion 21 increases. Therefore, when the surface sheet 10 is seen along the X direction, the substantial thickness is periodically changed. Although not shown in the drawing, the collar portion 20 has substantially the same thickness at the top portion 21 at any position in the extending direction (a direction perpendicular to the paper surface in FIG. 2). In the topsheet 10 of the present embodiment, there is no clear boundary between the flange portion 20 and the groove portion 30, and in general, a portion having the smallest substantial thickness located between the two top portions 21 adjacent to each other in the X direction and A portion in the vicinity thereof becomes the groove 30. When the boundary between the flange portion 20 and the groove portion 30 is clearly defined, the position of the apparent thickness at the top portion 21 of the flange portion 20 is defined as the boundary portion between the flange portion 20 and the groove portion 30.

  The apparent thickness of the collar portion 20 is preferably 0.3 to 5 mm, more preferably 0.5 to 2.5 mm, from the viewpoint of improving the touch of the topsheet 10. The height difference D (see FIG. 2) between the flange portion 20 and the groove portion 30 is preferably 0.1 to 3 mm from the viewpoint of enhancing the cushioning property and air permeability of the topsheet 10 and controlling the diffusion of the liquid. 3-2 mm is more preferable. The thickness and height difference D of the flange part 20 and the groove part 30 are measured by using a microscope VH-8000 (manufactured by Keyence) and observing the cross section of the topsheet 10 at 50 to 200 times. The cross section is obtained by cutting the top sheet 10 using a feather razor (part number FAS-10, manufactured by Feather Safety Razor Co., Ltd.).

  The width of the heel portion 20 in the X direction of the topsheet 10 is preferably 1 to 10 mm, and more preferably 2 to 5 mm, from the viewpoint of touch and absorbency. From the same viewpoint, the width of the groove 30 in the X direction of the topsheet 10 is preferably 0.5 to 7 mm, and preferably 1 to 3 mm. In the present embodiment, the flange portion 20 and the groove portion 30 are formed with the same width. However, the present invention is not limited to this. For example, the width of the flange portion 20 in the central region in the X direction of the topsheet 10 is set to the flange portion in the side region. The width may be wider than 20. Or it can be set as a desired form, such as making the width | variety of the collar part 20 and the groove part 30 random.

  The substantial thickness of the collar portion 20 is preferably 60 to 100%, particularly 70 to 100% of the apparent thickness. It is preferable that the substantial thickness itself of the collar portion 20 is 0.2 to 4 mm, particularly 0.3 to 3 mm, at the largest portion (top portion 21). When the collar portion 20 has such a thickness, the collar portion 20 is unlikely to fall down, the cushioning property of the topsheet 10 is improved, and the liquid absorbability (liquid passage property) is further improved. Further, when the substantial thickness of the collar portion 20 is thinner than the apparent thickness, specifically 90% or less, the absorbent article is deformed into a curved shape when the absorbent article having the topsheet 10 is used. However, it is prevented that the clearance gap produced between the surface sheet 10 and an absorber becomes large. Moreover, the surface sheet 10 fits a wearer's skin flexibly. In addition, the substantial thickness of the groove part 30 is 0.1-1 mm.

The brim portion 20 and the groove portion 30 have different substantial basis weights. In other words, the amount of fiber is different between the flange 20 and the groove 30. Specifically, the amount of fibers is substantially larger in the flange portion 20 than in the groove portion 30. By forming the flange portion 20 and the groove portion 30 in this manner, the flange portion 20 can be deformed flexibly while being hardly crushed. When the fiber weight of the collar part 20 and the groove part 30 is expressed by basis weight, the basis weight of the collar part 20 is preferably 30 to 150 g / m ² , particularly preferably 40 to 100 g / m ² . On the other hand, the basis weight of the groove part 30 (excluding the opening 31) is preferably 10 to 70 g / m ² , particularly preferably 15 to 50 g / m ² . The basis weight as a whole of the top sheet 10 (including the opening 31) is preferably 20 to 80 g / m ² , particularly preferably 30 to 80 g / m ² from the viewpoints of flexibility and nonwoven fabric strength. The basis weight of the collar part 20 is determined from the weight and area of the collar part 20 from which the groove part 30 is removed. When the width of the opening 31 and the width of the groove 30 are approximately the same, the boundary between the flange 20 and the groove 30 is determined by the position when a plurality of end portions in the width direction of the opening 31 are viewed in series. When the width of the groove portion 30 is wider than the width of the opening 31, the inflection point is set as a reference point (priority) based on the cross-sectional shape of the topsheet 10 to be measured, as in the case of apparent thickness measurement. The reference position is the tilt position of °. The top sheet 10 is cut along a straight line connecting the two upper and lower reference points to obtain the flange 20 and its weight is measured. The weight of the groove part 30 is obtained by obtaining a difference between the weight of the top sheet 10 before cutting and the weight of the flange part 20 and further subtracting the area corresponding to the opening 31. Since calculation of the basic weight of the groove part 30 requires the area of the groove part 30 including the opening 31 and the area of the opening 31, it is measured using an image analysis device or the like described later.

Further, the flange 20 has a fiber density at the apex 21 that is different from the fiber density of the groove 30, particularly the fiber density at the end of the opening 31. In detail, compared with the top part 21 of the collar part 20, the groove part 30, especially the edge part of the opening hole 31, is made high in fiber density. As a result, the liquid from the wearer is easily guided from the top portion 21 of the flange portion 20 to the end portion of the opening 31 of the groove portion 30. The fiber density at the apex 21 of the flange 20 is preferably 0.01 to 0.1 g / cm ³ , and the fiber density at the end of the opening 31 is 0.05 to 0.5 g / cm ^3. preferable. The fiber density of each part is measured by the following method. First, the density of the collar 20 is calculated from the apparent thickness and basis weight. Next, the cut surface of the surface sheet 10 is magnified and observed using an electron microscope (150 to 500 times), and the area of the portion including the 10 cross-sections of the fiber (the area where the outer surface of the outermost fiber is connected by a straight line) Measurement is performed at the ends of the flange portion 20 and the opening 31 using an image analysis device described later. Using these measured values and the value of the fiber density of the collar portion 20 calculated previously, the fiber density of the end portion of the opening 31 is calculated by proportional calculation. The fiber density is higher as the area occupied by the area including 10 cross sections of the fiber is lower.

  As shown in FIG. 1, a large number of apertures 31 are formed in the groove 30. The apertures 31 are regularly formed at regular intervals along the direction in which the groove 30 extends. Therefore, the top sheet 10 is formed in a state in which a plurality of aperture rows made of a large number of apertures 31 arranged at regular intervals along the Y direction are formed in multiple rows over the X direction of the top sheet 10. It has become. The pitch of the arrangement of the apertures 31 in all aperture rows is the same. In two adjacent rows of apertures, the apertures 31 are located at the same position in the X direction of the topsheet 10. The opening 31 is arranged so that there is always a portion where the opening 31 is not formed when the entire sheet is viewed along the X direction of the sheet 10. Further, when viewed from the top sheet 10 as a whole, the apertures 31 are distributed and arranged so as to form a multi-row row in the X direction of the sheet 10 and a multi-row row also in the Y direction. By arranging the apertures 31 in this way, the apertures 31 can be efficiently formed by dividing the fibers as compared with the case where the apertures 31 are arranged in a staggered pattern, for example. Can do.

  The opening 31 is formed by separating the constituent fibers of the topsheet 10. In the vicinity of the end of the opening 31, a film-like structure resulting from the thermal deformation of the fiber is not formed. Due to this, the vicinity of the end portion of the opening 31 has low rigidity, and is excellent in flexibility and shape restoration property against deformation. Further, since the liquid passes through the structure, the liquid does not collect near the end of the opening 31. In addition, when it sees as the whole surface sheet, as for the constituent fiber, the fibers are basically entangled or the fibers are fused. Thereby, the form of the nonwoven fabric is maintained.

The opening 31 can take various shapes in a plan view of the topsheet 10. For example, a shape such as a circle, an oval, an ellipse, a triangle, a quadrangle, a hexagon, or a combination thereof can be given. What is necessary is just to determine the shape and magnitude | size of the opening 31 suitably according to the specific use of the surface sheet 10. FIG. For example, when used for a top sheet of an absorbent article, the size of the opening 31 is about 0.5 to ⁵ mm ² in terms of the projected area of the top sheet 10 in plan view. From the viewpoint of maintaining the strength and strength of the top sheet 10. The size of the opening 31 is measured using an image analysis system. Specifically, a light source [Sunlight SL-230K2; manufactured by LPL Co., Ltd.], stand [copy stand CS-5; manufactured by LPL Co., Ltd.], lens [24 mm / F2.8D Nikkor lens], CCD camera [(HV-37; manufactured by Hitachi Electronics Co., Ltd.) connection with lens by F mount] and video board [Spectra 3200; manufactured by Canopus Co., Ltd.] take in. The captured image is binarized by the image analysis software NEW QUABE (ver. 4.20) manufactured by NEXTUS. The average value of the individual areas obtained from the binarized image is taken as the size of the aperture.

  The opening 31 may have an end projecting toward the second surface 10b of the topsheet 10 to form a liquid introduction pipe including the projecting portion. As described above, since the end portion of the opening 31 has low rigidity, the cushioning property of the topsheet 10 is further enhanced by forming the protruding portion. Moreover, since the contact between the topsheet 10 and the absorber can be maintained regardless of the structure of the absorber located on the lower side of the topsheet 10 by forming the protruding portion, the liquid excreted from the wearer is It is efficiently transmitted from the top sheet 10 to the absorber.

  As described above, the fibers constituting the topsheet 10 are entangled with each other or are fused with each other. When the fibers are fused, it is preferable that the fibers are separated and bonded by a bridging structure B formed by solidification of a resin stretched by melting, as shown in FIG. . By being in such a combined state, the flexibility of the topsheet 10 is further improved. What is necessary is just to manufacture the surface sheet 10 according to the method mentioned later, for example, in order to implement | achieve the combined state of a bridge structure.

  In the surface sheet 10 having the connection state of the bridging structure described above, the fibers are thermally fused, and the distance between the centers of the fibers in the fused portion of the bridging structure between the fibers is determined from the center of each fiber to the fiber. It has a part which is larger than the value which added the distance to the outer surface. In this case, it is preferable to include 50% by weight or more of the self-bonding fiber as the constituent fiber from the viewpoint of realizing a reliable connected state of the bridge structure. The surface sheet 10 having such a characteristic structure is a very novel one that the present inventors have found for the first time. This state can be measured from observation with an electron microscope or the like. It is desirable to measure the distance from the center of the fiber to the outer surface from the fibers that are joined, but even when multiple types of fibers are blended, the average fiber diameter from about 10 to about 20 fibers. You may ask.

  In the enlarged observation with the electron microscope of the surface sheet 10, the bridging structure is present at 5 to 20% when randomly measuring the intersection of about 50 to 100, and the flexibility and cushioning properties and the strength of the surface sheet 10 It is preferable from the viewpoint.

  As the fibers constituting the top sheet 10, fibers conventionally used in the technical field such as natural fibers, semi-natural fibers, and synthetic fibers can be used without particular limitation. From the viewpoint of imparting flexibility to the topsheet 10 without causing clogging between fibers, it is preferable to use synthetic fibers. The blending amount of the synthetic fiber is preferably 50% by weight or more, more preferably 70% by weight or more of the entire surface sheet. Of course, you may comprise the surface sheet 10 from 100% of synthetic fiber. When the topsheet 10 is made of 100% synthetic fiber, the grooving structure is not easily crushed even under the condition where the body pressure of the wearer is applied, so that the air permeability along the groove 30 is good.

  Examples of the synthetic fiber used include core-sheath fibers and side-by-side fibers that are self-bonding fibers. In addition, single fibers and composite fibers such as polyethylene, polypropylene, and polyester can be used. From the viewpoint of improving the flexibility by forming a groove structure and an opening shape, and by forming a bridging bond shape, it is possible to use a core-sheath fiber having polyethylene as a sheath component or a side-by-side fiber having a polyethylene portion. preferable. The (average) fineness of the fiber is preferably in the range of 1 to 6 dtex.

  It is preferable to use crimped fibers as the synthetic fibers because the cushioning property of the topsheet 10 is further improved. As the crimped fibers, any of two-dimensionally crimped fibers and coiled three-dimensionally crimped fibers can be used. In particular, it is preferable that the surface sheet 10 includes fibers that are three-dimensionally crimped in a coil shape by application of heat. Such a fiber can be included in the topsheet 10 by using latent crimped fibers as a raw material. The latent crimped fiber is composed of, for example, an eccentric core-sheath type composite fiber or a side-by-side type composite fiber containing two types of thermoplastic resins having different shrinkage rates as components. Examples thereof include those described in JP-A-9-296325 and Japanese Patent No. 2759331.

  Even if a fiber that elongates by application of heat is used as the synthetic fiber, the cushioning property of the topsheet 10 is further enhanced, which is preferable. This is because clogging between fibers due to heat applied during the manufacture of the topsheet 10 is prevented. As such a fiber, for example, WO2007 / 66599 according to the previous application of the present applicant can be mentioned.

  When any of the above-described crimped fibers and heat-extensible fibers is used, it is preferable that those fibers are mixed in the top sheet 10 in a total amount of 30 to 70% by weight.

  The constituent fiber of the top sheet 10 is not particularly limited in the fiber length, and any of staple fibers and continuous filaments can be used. When two or more kinds of fibers are used, the fiber lengths of these fibers may be the same or different. When two or more kinds of fibers having different fiber lengths are used in combination, it is preferable that these fibers are unevenly distributed in the topsheet 10. Specifically, it is preferable that the first surface 10 a side of the flange portion 20 has many fibers having a longer fiber length than the end portion of the opening 31. Thereby, it is possible to obtain a smooth feel by suppressing the ease of fluff removal and fluffiness of short fibers on the surface of the topsheet 10. Further, the clarity of the groove structure and the opening 31 can be improved. Further, the liquid can be easily guided to the opening 31. For example, when two types of fibers having different fiber lengths are used, the fiber length of the longer fiber is preferably 40 to 80 mm, and the fiber length of the shorter fiber is preferably 2 to 15 mm. In order to unevenly distribute fibers having different fiber lengths as described above, for example, the surface sheet 10 is manufactured using a web having a multilayer structure including a layer containing long fibers and a layer containing short fibers, What is necessary is just to manufacture the surface sheet 10 combining the web containing and the nonwoven fabric containing a short fiber.

  When two or more kinds of fibers having different fiber lengths are used in combination, it is preferable that the topsheet 10 has a portion in which a long fiber and a short fiber are entangled. Thereby, the advantageous effect that the strength improvement resulting from an entangled part and the movement of the liquid from the collar part 20 as a surface sheet can be made easy is produced. The portion where the long fiber and the short fiber are entangled with each other is preferably the peripheral portion of the groove 30 or the opening 31 in the topsheet 10. In order to form such a partially entangled portion, for example, the surface sheet 10 is manufactured using a web having a multilayer structure including a layer containing long fibers and a layer containing short fibers, or a web containing long fibers. What is necessary is just to manufacture the surface sheet 10 combining the nonwoven fabric containing a short fiber.

  The top sheet 10 is preferably made hydrophilic. Examples of the hydrophilization method include a method of treating a hydrophobic non-woven fabric with a hydrophilizing agent. Moreover, the method of manufacturing a nonwoven fabric from the fiber which knead | mixed the hydrophilizing agent is mentioned. Further, there is a method of using a fiber having hydrophilicity inherently, for example, a natural or semi-natural fiber. Hydrophilicity can also be achieved by applying a surfactant after the production of the nonwoven fabric.

  Regarding the hydrophilicity of the topsheet 10, it is preferable that the hydrophilicity on the first surface 10 a side in the top portion 21 of the flange portion 20 is weakly hydrophilic to hydrophobic. On the other hand, it is preferable that the surface on the first surface 10a side in the vicinity of the end portion of the opening 31 has at least a hydrophilic property of weak hydrophilicity or more. And about these both, it is preferable that the direction near the edge part of the opening 31 has higher hydrophilicity than the top part 21 of the collar part 20. FIG. By providing such a difference in the degree of hydrophilicity, the drawability of the liquid from the first surface 10a side to the second surface 10b side is promoted, and the liquid residue hardly occurs on the first surface 10a side. The dry feeling on the first surface 10a side is enhanced. In order to provide such a difference in the degree of hydrophilicity, for example, among the surfactants that make the fiber surface hydrophilic, those having high solubility in water are used, and high temperature (40 to 80 ° C.) and high humidity ( What is necessary is just to process the surface sheet 10 on the conditions of about 80% RH. Alternatively, the surface sheet 10 may be treated with a plurality of surfactants having different solubility, or a bleed-out surfactant may be added to the resin constituting the fiber. The degree of hydrophilicity in each part of the topsheet 10 is evaluated by a droplet method (measurement of five or more points) using test solutions having different known surface tensions. In the present specification, hydrophilic means a contact angle of 50 degrees or less, weak hydrophilic means a contact angle larger than 50 degrees and 80 degrees or less, and hydrophobic means a contact angle ranging from 90 degrees to 100 degrees. I mean. The contact angle can be measured by a method described in “Measurement of initial contact angle” in JP-A-2005-324010.

  Although the topsheet 10 shown in FIGS. 1 and 2 has a single-layer structure, the topsheet 10 may be a multilayer structure having two or more layers instead. When the topsheet 10 has a two-layer structure including, for example, an upper layer including the first surface 10a and a lower layer including the second surface 10b, it is preferable to increase the capillary gradient of the lower layer as compared to the upper layer. Thereby, the drawability of the liquid from the first surface 10a side to the second surface 10b side is promoted. As a method of increasing the capillary gradient, for example, a method of reducing the fiber diameter of the lower layer fibers than the upper layer can be mentioned. In this case, it is preferable that the upper fiber is 2 to 8 dtex and the lower fiber is 0.1 to 6 dtex. Also, the capillary gradient can be increased by increasing the hydrophilicity of the lower layer than the upper layer. Or you may employ | adopt both these means.

  When the topsheet 10 has a two-layer structure, the layers are integrated at the end of the opening 31, and there is no film-like structure due to thermal deformation of the fiber near the end of the opening. preferable. As a result, the rigidity in the vicinity of the end portion of the opening 31 is lowered, and the flexibility against deformation and the shape restoring property are improved.

  Next, the preferable manufacturing method of the surface sheet 10 shown in FIG. 1 is demonstrated. The topsheet 10 is manufactured by the fluid entanglement method using the apparatus shown in FIG. In the manufacturing method using this apparatus, (a) a fiber assembly is supplied, and the fiber assembly is formed on a fluid-permeable support for forming a wavy structure in a direction orthogonal to the supply direction of the fiber assembly. (B) a step of spraying a fluid to the fiber assembly located on the support to further separate the constituent fibers to form a groove structure and an opening; and (c) continuously on the support. There is a step of spraying a fluid again on the fiber assembly positioned to make the fiber assembly in which the groove structure and the opening are formed into a nonwoven fabric.

  The apparatus 40 shown in FIG. 5 includes a fluid permeable support 50, a first injection nozzle 51, and a second injection nozzle 52. As shown in FIG. 6, the fluid permeable support 50 is in a roll shape, and its peripheral surface is made of a fluid permeable material such as a mesh. On the peripheral surface of the support 50, convex portions and concave portions extending along the rotation direction of the roll are alternately formed in the axial direction of the roll. Thereby, a wave-like structure can be formed in the fiber assembly 53 which is a raw material of the topsheet 10 in a direction orthogonal to the supply direction. Projections 54 formed intermittently along the rotation direction of the roll are located on the tops of the protrusions. The protrusions 54 are arranged at regular intervals along the rotation direction of the roll. And when it sees in the axial direction of a roll, the projection part 54 is arrange | positioned so that it may be located on a straight line.

  The 1st injection nozzle 51 and the 2nd injection nozzle 52 are arrange | positioned so that the surrounding surface of the support body 50 may be opposed. Each of the nozzles 51 and 52 has a structure capable of ejecting fluid over the entire width of the support 50. In the nozzles 51 and 52, the first injection nozzle 51 is located on the upstream side and the second injection nozzle 52 is located on the downstream side in the supply direction of the fiber assembly 53 that is the raw material of the topsheet 10.

  In the step (a), the fiber assembly 53 is supplied to the fluid permeable support 50 rotating in the direction of the arrow in FIG. 5 and conveyed while being held by the peripheral surface of the support 50. Is done. Next, in step (b), the fluid ejected from the first ejection nozzle is sprayed onto the fiber assembly 53 on the peripheral surface of the support 50. With the pressure by this fluid spraying, the fiber assembly 53 is made of the constituent fibers at the position of the convex portion 55 formed on the peripheral surface of the support 50 as shown in FIGS. 7 (a) and 7 (b). Dividing occurs. By this division, the constituent fibers move into the concave portions 56 located between the convex portions 55. That is, fiber distribution occurs.

  Further, in the case where the protrusion 54 is formed on the top of the protrusion 55, as shown in FIG. 7C, the separation of the constituent fibers is further promoted, and the fiber assembly located on the protrusion 55 A hole is formed at 54. This hole becomes the opening 31 in the topsheet 10.

  As the fiber assembly, there can be used those in which fibers such as card web are not bonded or entangled, or the degree thereof is low, or those in which fibers such as nonwoven fabric are bonded or entangled. In particular, as a non-woven fabric, a non-woven fabric containing fibers having a fiber length of 30 mm or less and having no binder component itself, specifically, a dry type in which fibers between pulp fibers are fixed by a binder (adhesive component). It is preferable to use a pulp sheet.

  As the fluid used in this step, a liquid such as water and a gas such as air can be used. The type of fluid is selected according to the fiber assembly guided on the support 50. For example, when using a fiber assembly that is not bonded or entangled like a card web, it is preferable to use an air flow or a water vapor flow (steam jet). In the case of using a fiber assembly having bonds at fiber intersections, such as an air-through nonwoven fabric, it is preferable to use a water stream or a steam stream (steam jet). In the latter case, the grooving structure and the opening can be formed by the movement of the fiber while partly peeling the bond at the fiber intersection and keeping the degree of fiber entanglement low. In addition, it is possible to prevent clogging between the fibers. As described above, this step mainly forms the groove structure and the opening by the movement of the fiber, and the degree of the entanglement of the fiber is kept low.

  The above-mentioned water flow means a complete liquid flow such as water. A water vapor stream (steam jet) refers to a fluid stream of water that is not in a liquid state. When a liquid water flow or a water vapor flow (steam jet) is used, the fiber entanglement progresses as the fiber is located in the vicinity of the protrusion 55, and the fiber density of the portion tends to increase. In particular, when a nonwoven fabric is used as the fiber assembly (that is, re-nonwoven fabric), since the fiber 55 is hardly entangled with the convex portion 55, the cushion feeling inherent to the nonwoven fabric is maintained. On the other hand, the fibers located in the vicinity of the concave portion 56 and the protruding portion 55 are entangled, and the capillary gradient (density gradient) is relatively large with respect to the fibers located in the convex portion 55.

  When the groove structure and the opening are formed by spraying the fluid from the first injection nozzle 51 which is the step (b), then fiber entanglement is performed by spraying the fluid from the second injection nozzle 52 which is the step (c). And the fiber assembly is made into a nonwoven fabric (when a nonwoven fabric is used as the fiber assembly, it is made into a non-woven fabric). As the fluid used in this case, it is preferable to use a liquid water stream or a water vapor stream. By using these fluids, fiber entanglement can be performed efficiently. The above-mentioned re-non-woven fabric refers to the re-melting of the fiber from which the cut or fused portion of the fiber was peeled off in the previous step of forming the groove structure and the opening when the non-woven fabric was used as the fiber assembly. It means that the form as a nonwoven fabric is maintained by wearing or entanglement again.

  When the fluid sprayed to the fiber assembly 53 in the step (b) and the step (c) is concentrated on the convex portion 55 of the support body 50, the fluid pressure of the convex portion 55 is increased compared to the concave portion 56 of the support body 50. Therefore, it is preferable because the openability is improved. Moreover, it is preferable at the point which can make the fiber density of the edge part vicinity of a hole higher.

  When a steam flow is used as the fluid in the step (c), the steam flow from the second injection nozzle 52 is set to a relatively low temperature of 100 to 150 ° C. (a temperature lower than the fiber fusion temperature on the web). Thus, only fiber entanglement is performed. Since the water vapor stream has lower energy (injection pressure) than the liquid water stream (the dispersion of the fluid stream is large), it is preferable to use it when spraying the web rather than using a nonwoven fabric as the fiber assembly. This is because the movement of the fiber is easier in the web than in the non-woven fabric. However, even when a nonwoven fabric is used as the fiber assembly, the jet pressure that results in a weak fiber entangled state that does not recover the shape of the groove structure and the opening formed by the step (b) is caused by the steam flow. Can be given. Furthermore, in the case where the temperature of the water vapor flow is about 160 to 200 ° C., which is higher than the fiber fusion temperature on the web, even if the temperature is 20 ° C. or more higher than the fiber fusion temperature, the fibers in the fiber assembly The amount of heat applied is not so great that the resin constituting the fiber melts and flows strongly, and the flow of the resin does not always occur at the intersection of all fibers, so that the entire fiber assembly is not melted. It does not solidify. Therefore, even when the jet pressure of the water vapor flow is high and the fibers are in close proximity to each other, it is possible to perform fusion at the fiber intersection without causing fiber clogging.

  Since this fusion is performed by the water vapor flow blown from the second injection nozzle 52, a stronger pressure is applied to the fiber assembly in a short time compared to the air-through method, which is a known nonwoven fabric manufacturing technique. Therefore, the pressure is removed before the fusion at the fiber intersection is stabilized, that is, before the outflow of the fiber sheath component resin that spreads on the surface of each fiber and becomes a strong fusion point is fixed. As a result, the fibers are separated to form the bridging structure B as shown in FIG. 4 described above. Such a bridging structure is presumed to be caused by stretching the sheath component resin of one of the two fibers. This is because, although this fusion process is in a state of causing fiber fusion, the application of heat is completed in a relatively short time, so the resins constituting the fibers that cause fiber fusion fuse together to form a resin. This is because it is considered that there is an interface between the resins constituting each fiber that causes fiber fusion rather than a state in which the interface between them disappears. In addition, if elongation occurs near the interface between the resin, which is the fusion part that has caused fiber fusion, the interface is pulled, the fusion part is reduced, and the resins are separated at the interface. Because it is. For this reason, the bridging structure has a portion where the area of the joint portion is large but the resin is stretched and thinned. As a result, the obtained surface sheet 10 is improved in the degree of freedom of its constituent fibers, and the flexibility and cushioning properties are improved. On the other hand, since it is manufactured under a pressure stronger than that of the air-through method, it is easier to make a multi-intersection of more than two fibers. With such a structure, the strength of the topsheet 10 is improved.

  By forming the bridging structure and the multiple intersections together, the surface sheet 10 manufactured by the present manufacturing method has high strength and good flexibility and cushioning properties. In addition, since the fiber structure related to the multi-intersection is easy to arrange the fibers in the direction to suppress the thickness of the topsheet 10, the part due to the bridging structure is more easily exposed on the surface, thereby further enhancing the flexibility and cushioning properties. Become. The multi-intersection structure is likely to occur on a surface near the second injection nozzle 52 or a portion near the opening. The bridging structure is likely to occur on a surface far from the second injection nozzle 52 or a portion far from the support 50 related to the opening.

  When a liquid water stream is used in step (b) and / or step (c), the surfactant used for imparting hydrophilicity may flow down from the fiber surface, so that the surface activity into the fiber may occur. It is preferable to use a kneaded agent or a natural / semi-natural hydrophilic fiber. Or it is preferable to apply | coat surfactant in a post process. On the other hand, when the water vapor flow is used, there is an advantage that the surfactant on the surface of the fiber is less likely to flow down and the surfactant can be easily collected at a part where the fiber density is high. As a result, when the water vapor flow is used, the fiber density of the portions located in the concave portions 56 and the projections 54 of the support 50 in the fiber assembly 53 is increased, so that the hydrophilicity of these portions can be inevitably increased. As an application example of this effect, there is a technique in which two or more kinds of surfactants to be applied to the fiber surface or surfactants kneaded into the fiber are used, and the water resistance of the surfactant is made different. This method is advantageous because the hydrophilic gradient can be designed more easily.

  In order to further control the fiber density of the obtained surface sheet 10, it is also preferable to subject the nonwoven fabric after the step (c) to a hot air treatment step. The hot air treatment has an effect of promoting the formation of a nonwoven fabric (bonding the fibers of the fiber assembly) and / or eliminating clogging between the fibers. In other words, in the step (c), from the viewpoint of preventing clogging, the fluid spraying condition may be weakened, and the hot air treatment step may be applied to compensate for the lack of fiber entanglement or fiber fusion resulting therefrom. preferable. Moreover, it is preferable to attach to the hot air treatment process in order to recover the bulk of the nonwoven fabric clogged in the process (c) or to develop fiber deformation (crimping or stretching). In particular, when the steam flow is used in the step (c), the second spray nozzle 52 is used, so that the heat application step is completed in a shorter time than the air-through method. Therefore, from the viewpoint of stabilizing the heat-sealed state, it is desirable to perform a hot air treatment process at about 80 to 120 ° C. as a subsequent process of the process (c). Or it is preferable to perform the stabilization process which does not raise | generate a rapid temperature fall as a post process of the process of (c). The hot air treatment may be performed in one stage, or the hot air treatment for promoting the formation of a nonwoven fabric and the hot air treatment for restoring the bulk of the nonwoven fabric may be performed in a plurality of stages.

  When only the web is used as the fiber assembly in this production method, it is preferable to use an air flow or a water vapor flow in the step (b) and use a water vapor flow in the step (c). This is because clogging between fibers can be prevented, a flexible structure can be formed by forming a nonwoven fabric by fusing the fiber intersections, and the fiber density at the periphery of the apertures 31 can be easily increased. Further, when an air flow is used in the step (b), it becomes easy to form a liquid introduction pipe in the opening 31, and parts other than the opening 31 are likely to have the shape of FIG. Improves. On the other hand, when the steam flow is used in the step (b), the scattering of the fibers is suppressed and the fluid pressure is easily made higher than the air flow, so that the fibers are easily separated, and the cross-sectional shape of FIG. 2 is obtained. It becomes easy to improve flexibility such as cushioning. Even if the water vapor flow is used in the step (b), it is possible to achieve both the liquid guide tube structure and the cross-sectional shape of FIG. 2 by adjusting the fluid pressure in the opening 31.

  In this production method, when a water stream is used in the steps (b) and (c), it is preferable to use a nonwoven fabric having a fusion point at the fiber intersection. The reason for this is that fiber clogging can be prevented by the movement of fibers (formation of a density-enhanced portion) by the separation portion at the fiber intersection and the remaining fusion point. In this case, in the step (b), the nonwoven fabric is adapted to the shape of the support by applying a water flow so as to be substantially uniform over the entire nonwoven fabric, and in the step (c), the grooves 30 including the openings 31 are It is preferable from the viewpoint of facilitating re-entanglement by facilitating peeling of the fusion point and making the water pressure in the step (c) higher than (b) by facilitating entanglement by blowing a stronger water flow than the part 20. Further, when a method of supplying a fiber assembly 53 by using a laminate of a web and a nonwoven fabric as a fiber assembly 53 or by laminating both webs and a nonwoven fabric while supplying the fiber assembly 53, (B) and ( Integration of the two can be promoted in step c). The nonwoven fabric produced in this way has a structure (integrated structure) that can easily guide the liquid from the top portion 21 of the collar portion 20 to the end portion of the opening 31. In this case, it is preferable to use a nonwoven fabric from the viewpoint of preventing fiber clogging in the web and the nonwoven fabric from which water is directly sprayed. Thus, when a water flow is used in the steps (b) and (c), it becomes easy to obtain a cross-sectional shape as shown in FIG.

  When a non-woven fabric is used as the fiber assembly 53 and the non-woven fabric is separately guided onto the support before the step (b), the flexibility and cushioning properties of the resulting non-woven fabric can be improved. In addition, when using a nonwoven fabric as the fiber assembly 53, if the fibers are strongly bonded or entangled in the nonwoven fabric, fiber movement in the step (b) may be difficult to occur, so before the step (b), It is also preferable to subject the non-woven fabric to a portion to be positioned in the concave portion 56 of the support 50.

  Thus, the target nonwoven fabric (surface sheet) is obtained. This top sheet is typically used together with a liquid-impermeable or water-repellent back sheet, and an absorbent article is formed by sandwiching a liquid-retaining absorbent between the two sheets. Examples of such absorbent articles include various products known in the art such as sanitary napkins and disposable diapers.

  As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment. For example, although the said embodiment is a thing at the time of applying the nonwoven fabric of this invention to the surface sheet of an absorbent article, of course, the nonwoven fabric of this invention can be used also for the other use. Examples of such applications include cleaning sheets.

10 Nonwoven fabric (surface sheet)
20 Groove 30 Groove 31 Opening

Claims (5)

It is a method for producing a nonwoven fabric having alternately ridges and grooves extending in one direction, and having openings in the grooves,
Supplying a fiber assembly free of fiber bonding and entanglement and guiding the fiber assembly on a fluid-permeable support for forming a wave-like structure in a direction perpendicular to the supply direction of the fiber assembly ,
A step of spraying a water vapor stream onto the fiber assembly located on the support to further separate the constituent fibers to form a groove structure and an opening; and subsequently , a flow to the fiber assembly located on the support. A method for producing a nonwoven fabric, comprising a step of spraying a body to make the fiber assembly in which the groove structure and the apertures are formed into a nonwoven fabric. The method for producing a nonwoven fabric according to claim 1, wherein, in the step of forming the fiber assembly into a nonwoven fabric, a water vapor stream is sprayed on the fiber assembly to form a bridging structure between the fibers of the fiber assembly. The method for producing a nonwoven fabric according to claim 1 or 2, further comprising a hot air treatment step after the step of forming the nonwoven fabric. The method for producing a nonwoven fabric according to claim 3, wherein the hot air treatment step is a step of bonding constituent fibers of the fiber assembly. The manufacturing method of the nonwoven fabric of Claim 4 which has a bulk recovery process by a hot air after the process of couple | bonding the constituent fibers of the said fiber assembly.

Images