JP2008161584A - Absorbent articles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an absorbent article with high liquid holding capability despite their thin and soft structure. <P>SOLUTION: The absorbent article 10 is provided with an absorptive core 13 having fibrous layers including synthetic fibers of 20 μm or less. The fibers of these fibrous layers of the absorbent article located on the side opposite to the skin are made wider in their intervals than those located on the side opposite to underwear. It is preferable to adjust the fiber intervals by more enlarging the fibers of the fibrous layers located on the side opposite to the skin in their average diameter than those located on the side opposite to the underwear. It is also preferable that very fine fibers with average 7 μm or less in diameter produced by the water needle method by splitting the fibers that can longitudinally be split into plural ones are included on the side opposite to the underwear in fibrous layers. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to various absorbent articles including sanitary napkins and panty liners.

  Patent Document 1 discloses a sanitary napkin aimed at improving liquid retention and preventing the occurrence of menstrual blood leakage despite its thin form. This napkin has an absorption layer having a pulverized pulp layer and a polymer absorption layer. Further, an absorbent diffuser in which absorbent cotton is entangled with a fiber by a water needle method to form a sheet is positioned closer to the human body contact side than the polymer absorbent layer. According to Patent Document 1, menstrual blood is rapidly absorbed and the human body contact surface side is in a dry state by capillary absorption by cellulose fibers which are components of the absorbent cotton constituting the absorption diffuser.

  Cellulose fibers, which are components of absorbent cotton constituting the absorbent diffuser, are generally about 14 μm thick and have a crimp shape. Accordingly, when a sheet-like absorbent diffuser is manufactured from absorbent cotton by the water needle method, the fiber spacing is very tight in the absorbent diffuser, and fiber movement is less likely to occur due to external force or the like. However, there is an advantage that the liquid diffusibility and the sheet shape are easily maintained due to clogging between the fibers. However, since the sheet shape is maintained and the movement of individual fibers is suppressed, the followability to various movements of the body is not sufficient, and the deviation from the body and the deviation from the absorber are partly It may happen, and it was difficult to fit flexibly.

JP-A-61-176345

  The objective of this invention is providing the absorbent article which can eliminate the fault which the prior art mentioned above has.

  The present invention is an absorbent article having at least an absorbent core mainly composed of a fiber material, which is interposed between the top sheet and the back sheet, and the absorbent core is a fiber containing synthetic fibers having an average fiber diameter of 20 μm or less. A fiber gap of fibers existing on the skin facing surface side in the absorbent core is made wider than a fiber gap of fibers existing on the underwear facing surface side, and the fiber layer on the skin facing surface side is substantially An absorbent article having a structure that does not hold liquid is provided.

  Although the absorbent article of the present invention is thin and soft, it has a high liquid holding power. Therefore, the absorbent article of the present invention is particularly suitable as a thin type, for example, card type napkin, panty liner, thin and soft incontinence pad, incontinence liner and the like.

  The present invention will be described below based on preferred embodiments with reference to the drawings. First, a first embodiment of the present invention will be described. FIG. 1 schematically shows a cross-sectional view in the width direction of a sanitary napkin as an example of the absorbent article of the present invention. The napkin 10 shown in the figure includes a top sheet 11 positioned on the skin facing surface side, a back sheet 12 positioned on the underwear facing surface side, and an absorbent core 13 interposed between both sheets. The absorption core 13 has a vertically long rectangular shape in plan view. The top sheet 11 and the back sheet 12 respectively extend outward from the front and rear end edges and the left and right side edges of the absorbent core 13, and the extending portions are joined to each other.

As the top sheet 11 and the back sheet 12, materials similar to those conventionally used in the technical field can be used without particular limitation. As the surface sheet 11, for example, a liquid permeable material such as a nonwoven fabric or an apertured film can be used. In particular, the top sheet 11 is preferably made of a bulky material with high liquid acquisition performance, such as an air-through nonwoven fabric. Above all, staples formed by hydrophilic treatment of composite fibers made of PET / PE, PP / PE, etc. are stacked by the card method, and bonded with hot air at a temperature equal to or higher than the heat fusion temperature, and a basis weight of 14 to 40 g / m ^2. A degree of air-through nonwoven is particularly preferred. This is because flexibility due to the movement of the fibers is obtained, the bulkiness is high, the liquid acquisition property is high, and a dry touch feeling on the surface is easily obtained. Further, as the surface sheet 11, a sheet (so-called cotton spunlace nonwoven fabric, rayon spunlace nonwoven fabric) formed by depositing essentially hydrophilic fibers such as cotton or rayon and interlaced fibers by the water needle method may be used. good.

As the back sheet 12, a liquid-impermeable or water-repellent material, for example, a film made of a thermoplastic resin, or a laminate of a nonwoven fabric can be used. A spunbond-meltblown-spunbond (SMS) nonwoven fabric or a spunbond-meltblown-meltblown-spunbond (SMMS) nonwoven fabric can also be used. The back sheet 12 may have moisture permeability. Examples of the back sheet having moisture permeability include a porous film obtained by extruding a resin composition containing a thermoplastic resin and fine particles incompatible with the thermoplastic resin into a film shape and uniaxially or biaxially stretching, and the above-described SMS nonwoven fabric. It is done. The thickness of the backsheet is preferably from the viewpoint of the balance between the strength of the order of basis weight 15 to 60 g / m ² is not broken in use and costs in films, 20~45g / m ² is particularly preferred. In the case of using the SMS or SMMS, in addition to the same reason, in order to absorb the liquid, not to be passing stain underwear side pressure, 25~100g / m ² approximately, in particular 40 and 80 g / m ² It is preferable that it is a grade. When laminating a nonwoven fabric on a film and when using a moisture-permeable film, the preferable thickness (basis weight) of the film is in the above-described range. The basis weight of the nonwoven fabric to be laminated is preferably 10 to 30 g / m ² , and more preferably 12 to 20 g / m ² from the viewpoint of cost and softness maintenance.

  The napkin 10 of the present embodiment has one of the features in the absorbent core 13. The absorbent core 13 includes a fiber layer containing synthetic fibers having an average fiber diameter of 20 μm or less. Here, the main feature of this embodiment is that the majority of the fiber layer is composed of overwhelmingly thin fibers. For example, a part of the fibers forming the absorbent core 13 may include a thick fiber having a fiber diameter of about 20 μm, but most of the remaining are overwhelmingly thin fibers. When attention is paid to the thin fibers, the thickness of the fibers is preferably 0.1 to 5 μm, more preferably 0.2 to 2 μm. Specifically, as shown in FIG. 1, the absorbent core 13 is located on the skin facing surface side and made of a fiber material, and is adjacent to the upper layer 14 and located on the underwear facing surface side and made of a fiber material. Two layers of the lower layer 15 are composed of a single fiber sheet, and at least the lower layer 15 includes synthetic fibers having a thickness in the above range.

  On the condition that the lower layer 15 contains fibers having a thickness in the above range, the absorbent core 13 has a fiber gap between fibers contained in the upper layer 14, which is a layer existing on the skin facing surface side, on the underwear facing surface side. It is wider than the fiber gap of the fibers contained in the lower layer 15 which is an existing layer. Since the relationship between the fiber gaps in the upper and lower layers 14 and 15 is as described above, the napkin 10 according to this embodiment has the following remarkable effects. First, because the lower layer 15 contains fibers in the above-mentioned thickness range, the fiber gap in the lower layer 15 is reduced, and the capillary force acts strongly. As a result, the lower layer 15 has a higher liquid holding power, and the liquid once absorbed is less likely to be released. That is, liquid return is less likely to occur. However, the lower layer 15 tends to decrease the liquid absorption rate as the liquid holding power increases. Therefore, the upper layer 14 having a large fiber gap and a high liquid-acquiring action is disposed on the lower layer 15 in order to compensate for the decrease in the liquid absorption rate in the lower layer 15. In addition, since the absorbent core 13 is composed of only a sheet of fiber material having a two-layer structure of the upper layer 14 and the lower layer 15, the absorbent core 13 can be made extremely thin and soft. As a result, the napkin 10 of the present embodiment has the characteristics that it is thin and soft, absorbs the liquid quickly, and has little reversal of the absorbed liquid.

  The features of the absorbent core 13 described above can be organized as follows. The absorbent core 13 is mainly composed of a fiber sheet, and includes an upper layer 14 and a lower layer 15 that are integrally formed. Further, the fiber gap of the upper layer 14 is wider than that of the lower layer 15. Furthermore, the fiber gap in the lower layer is particularly small, so that the liquid can be held firmly without liquid return or liquid movement.

  The lower layer 14 having a particularly small fiber gap has high liquid retention due to high capillary force, but cannot quickly absorb body fluid into the structure. Specifically, for example, in the case of a female menstrual blood treatment device, there is a possibility that about 2 cc of menstrual blood is excreted instantaneously. In the case of the lower layer alone, the fiber gap is too small, so it takes more than 10 minutes to take this liquid into the interior, and the liquid that cannot be absorbed during that time diffuses to the surface and completely supports the next liquid excretion. Can not. The upper layer 14 has a relatively wide fiber gap, and can quickly absorb the excretory fluid within 1 minute and hold it as it is. Further, since the lower layer 15 is integrally formed and the capillary force of the lower layer 15 is large, the liquid once held by the upper layer 14 gradually moves to the lower layer 15 and finally the liquid remaining in the upper layer 14 is It disappears and it becomes possible to deal with the next liquid excretion. As a result, the napkin 10 of the present embodiment has the characteristics that it is thin and soft, absorbs the liquid quickly, and has little reversal of the absorbed liquid.

  From the viewpoint of making the above-described characteristics more prominent, the fiber gap of the fibers existing in the lower layer 15 is preferably 0.1 to 100 μm, particularly preferably 3 to 75 μm. On the other hand, the fiber gap of the fibers present in the upper layer 14 is preferably 0.5 to 400 μm. In the particularly preferred embodiment, the fiber gap of the upper layer 14 is 8 to 120 μm when the entire absorbent core 13 is composed of a single spunlace nonwoven fabric. By setting the fiber gap in such a range, it is possible to achieve both a high liquid acquisition property including a viscous liquid and a quick liquid absorption rate.

  The preferred thickness of the absorbent core 13 and the preferred thickness of the upper and lower layers 14 and 15 can be adjusted as appropriate. Generally, the preferable thickness of the absorption core 13 is 1 to 4 mm, and more preferably 1.2 to 3.5 mm. A preferable thickness of the upper layer 14 is 0.4 to 3 mm, and more preferably 0.8 to 2 mm. The preferred thickness of the lower layer 15 is 0.2 to 3 mm, and more preferably 0.4 to 2 mm. The regions of the upper layer 14 and the lower layer 15 in the absorbent core 13 are determined by visually observing the fiber assembly state based on, for example, an electron microscope enlarged observation of the longitudinal section of the absorbent core 13. However, as will be described later, between the upper layer 14 and the lower layer 15, the fiber composition (and the fiber assembly state) between the layers changes continuously, and both may be inseparable. In this case, since the distribution of the thickness of the upper and lower layers 14 and 15 cannot be measured, only the thickness of the entire core 13 is measured.

Preferred basis weights of the absorbent core 13 is a 45~250g / m ^2, more preferably from 70~170g / m ^2. The preferred basis weight of the upper layer 14 is 18 to 150 g / m ² , more preferably 20 to 100 g / m ² . The preferable basic weight of the lower layer 15 is 40-150 g / m < ² >, More preferably, it is 50-130 g / m < ² >. As described above, the upper and lower layers 14 and 15 may be inseparable. In this case, when the preparation amount at the time of producing the absorbent core 13 is known, the amount should be discussed, and when the amount is unknown, the basis weight of the entire absorbent core 13 should be discussed.

  In order to adjust the fiber gap between the upper and lower layers 14 and 15, it is easy to adjust the average fiber diameter of the fibers contained in these layers. Specifically, the fiber gap can be adjusted by making the average fiber diameter of the fibers present in the upper layer 14 larger than the average fiber diameter of the fibers present in the lower layer 15. In this case, the average fiber diameter of the fibers present in the lower layer 15 is preferably 10 μm or less, more preferably 0.1 to 10 μm, and particularly preferably 0.2 to 5 μm. As described above, the lower layer 15 may include a plurality of types of fibers having different thicknesses. In this case, the fiber diameter of the thin fibers present in the lower layer 15 is 0.1 to 5 μm, particularly 0.2 to 5 μm. It is preferable from the viewpoint that the fiber gap can be easily set within the above-described range. A preferable average fiber diameter of the fibers present in the upper layer 14 is 0.2 to 80 μm, particularly 4 to 40 μm.

The average fiber diameter, the average fiber gap, and the fiber diameter of the thin fibers of the lower layer 15 are measured by the following method regardless of whether the type of the constituent fibers is one type or many types.
Using an electron microscope (manufactured by Hitachi, Ltd .; product number S-4300SE / N), an enlarged photograph of a cross section in the Z-axis direction (upper surface to lower surface direction of the napkin) at an arbitrary position of the upper layer and the lower layer is taken. Although the magnification is arbitrary, it is preferable in terms of measurement that 20 to 40 fiber cross-sections are photographed in one photograph. Using an image analysis device (manufactured by NEXTUS; trade name NEW QUEBE ver. 4.20), from the obtained photograph, “number of fibers on the screen”, “total area measured”, “area occupied by fibers” and “Area per piece” is measured. The measurement is repeated until the total number of fibers exceeds 50. In calculating the “fiber area per fiber”, from the viewpoint of calculating the true cross-sectional area of the fiber as much as possible, the fiber cutting angle that is considered to be less than 60 °, particularly less than 80 °, is excluded from the measurement. Further, the cutting position and the cutting angle are selected so that the excluded fiber is less than 30%.
Average fiber diameter: The average of the measurement results of “fiber area per one” (average of at least 50 fibers) is calculated as the area of the circle and the diameter of the assumed circle (equivalent diameter of the circle). And
Some of the thin fibers are derived from the split fibers as described later, and the cross-sectional shape is a narrow fan shape like a tangerine bunch, which can be of an unusual cross-section with extremely different long and short axis lengths. As described above, it can be equalized by converting to an equivalent circular phase diameter.
Average fiber gap: Assume that the arrangement of fibers is a close-packed model, and two interfiber spaces (two dimensions) are formed by two fibers. Therefore, the number of measured spaces is “the number of fibers on the screen” × 2, and the area per inter-fiber space is obtained from the following formula 1, and the diameter (equivalent to a circle) Find the diameter.
Fiber diameter of fine fibers: When calculating the average fiber diameter, the minimum value of the equivalent circular phase diameter is obtained, and this is used as the fiber diameter of the thin fibers. That is, it is the fiber diameter of the smallest fiber among the fibres (equal diameter of circular phase) measured 50 or more. At this time, be careful not to misread the noise by referring to the original image.

  An unused feather razor blade (FAS-10) was used to form a cross-section when measuring the fiber gap. In the case of a fiber sheet that is bulky and has a large fiber gap, there is a risk that the fiber will be compressed by the cutting operation. You may devise not to change.

  In order to make the average fiber diameters of the fibers contained in the upper and lower layers 14 and 15 within the above-described range, fibers having appropriate fiber diameters may be used as the fibers contained in these layers. For example, the absorbent core 13 made of a fiber sheet having upper and lower layers 14 and 15 having a desired average fiber diameter can be obtained by the method described below.

[Method (1)]
A manufacturing apparatus 20 shown in FIG. 2 is used. The apparatus 20 includes a first card machine 21, a second card machine 22, and a high-pressure jet water jetting device 23. A first web 14 ′ is fed out from the first card machine 21. The first web 14 'is formed by mixing fibers that can be divided into a plurality of fibers in the length direction (hereinafter referred to as divided fibers) and fibers other than the divided fibers. Or 1st web 14 'consists only of fibers other than a division | segmentation fiber. The first web 14 ′ should be the upper layer 14 in the absorbent core 13. On the other hand, the second card machine 22 feeds out a second web 15 ′ made of the same or different kind of split fibers as the split fibers contained in the first web 14 ′. The second web 15 ′ is to be the lower layer 15 in the absorbent core 13. The split fibers can be split into a plurality of fibers in the length direction by, for example, external force or chemical action.

  As shown in FIG. 2, with the second web 15 'superimposed on the first web 14', both webs are conveyed to the position of the high pressure jet water jetting device 23. The constituent fibers are entangled in the webs 14 ′ and 15 ′ by the high-pressure jet water stream injected from the injection device 23, and the fibers are entangled between the webs 14 ′ and 15 ′.

  Along with the entanglement of the fibers, the split fibers included in each of the webs 14 'and 15' are split into a plurality of fibers in the length direction by the action of an external force applied by the high-pressure jet water flow to generate ultrafine fibers. In this case, since the high-pressure jet water stream is jetted from the second web 15 ′ side, the split fibers included in the second web 15 ′ have a higher degree of split than the split fibers included in the first web 14 ′. growing.

  The long nonwoven fabric 13 ′ thus manufactured is obtained by integrating the upper layer 14 derived from the first web 14 ′ and the lower layer 15 derived from the second web 15 ′. Since the split fibers contained in the second web 15 ′ have a large degree of splitting due to the action of the high-pressure jet water flow, in the lower layer 15 derived from the web 15 ′, the ultrafine fibers generated by splitting the split fibers are not. There are many. As a result, the average fiber diameter of the fibers contained in the lower layer 15 is small. On the other hand, when the first web 14 'includes split fibers, the split fibers have a smaller degree of splitting than the split fibers included in the second web 15'. The number of ultrafine fibers contained in the derived upper layer 14 is less than that of the lower layer 15. In addition, since the first web 14 ′ includes fibers other than the split fibers, that is, fibers that are not split by the high-pressure jet water stream, the average fiber diameter of the fibers included in the upper layer 14 is larger than that of the lower layer 15. As a result, in the nonwoven fabric 13 ′ manufactured by the method shown in FIG. 2, the fiber gap is larger in the upper layer 14 than in the lower layer 15. The nonwoven core 13 'having such a structure is hydrophilized and then cut into a desired size, whereby the intended absorbent core 13 is obtained.

  Various hydrophilizations known to those skilled in the art can be suitably used for the hydrophilization treatment. In particular, as hydrophilic agents, various alkyl sulfonates represented by α-olefin sulfonates, acrylates, acrylate / acrylamide copolymers, ester amides, ester amide salts, and polymer hydrophilic agents (for example, Polyethylene glycol and derivatives thereof, water-soluble polyester resins, various water-soluble polyvinyl alcohols and derivatives thereof, various silicone derivatives, various sugar derivatives, and mixtures thereof, etc., on wet webs after high-speed jet water flow application A method of applying a predetermined amount of a hydrophilizing agent aqueous solution and drying, a method of performing a hydrophilic treatment on the nonwoven fabric 13 ′ after drying, and the like can be appropriately performed.

  As is clear from the above description, the absorbent core 13 manufactured by the method shown in FIG. 2 is composed of a lower layer 15 containing ultrafine fibers generated by dividing the split fibers by the water needle method, and fibers other than the split fibers. Or it is comprised from the upper layer 14 containing the ultrafine fiber which a fiber other than a split fiber and a split fiber produced by splitting by a water needle method. The fiber diameter of the ultrafine fiber is preferably 5 μm or less, particularly 0.2 to 2 μm, from the viewpoint of sufficiently increasing the capillary force in the lower layer 15.

  As the fibers other than the split fibers, it is preferable to use fibers having a fiber diameter of 10 to 90 μm, particularly 12 to 80 μm because the fiber gap of the upper layer 14 can be surely widened. On the other hand, as the split fibers, as described above, fibers that can be split into multiple pieces in the length direction by an external force or chemical action are used. The split fibers have a fiber diameter before splitting of 10 to 30 μm, particularly 12 to 24 μm, because they are excellent in mixing with non-split fibers and can be easily formed in a general fiber stacking process such as a card method. preferable. The number of divisions is usually 6 to 24, and finer fibers are formed as the number of divisions increases. In order to easily divide, it is important to select two types of resins that are not compatible with each other and that have different SP values as the thermoplastic resin constituting the fiber. For example, two types of resins selected from polyethylene, polypropylene, polybutene, nylon, polyethylene terephthalate, polylactic acid, polyvinyl alcohol, water-soluble polyvinyl alcohol, and derivatives thereof can be used. This two-phase blend is continuously extruded into a predetermined cross-sectional pattern and drawn to form fibers. In particular, as the split fibers, those having a structure in which ultrafine fiber-forming resins and water-soluble thermoplastic resins are alternately arranged in a sector shape in the cross-sectional direction of the fibers and these resins extend in the length direction of the fibers are used. Then, the split fibers are split by the high-pressure jet water stream, and the water-soluble thermoplastic resin dissolves to cover the surface of the nonwoven fabric 13 ′, and the nonwoven fabric 13 ′ is hydrophilized. At this time, warm water can be used in the jet water stream to remove water-soluble components. Alternatively, a method such as warm water treatment after forming the nonwoven fabric can be used.

  As an alternative method of manufacturing the absorbent core 13 using the apparatus 20 shown in FIG. 2, only the second web 15 ′ consisting only of the split fibers fed from the second card machine 22 is used without using the first card machine 21. And a method of spraying a high-pressure jet water stream on the web 15 '. In this method, the split fibers located on the side of the second web 15 ′ on which the high-pressure jet water flow is sprayed have a higher degree of splitting than the split fibers located on the side opposite to the surface. As a result, in the thickness direction of the second web 15 ′, a gradient is generated in the number of ultrafine fibers generated by the division. That is, the closer to the spraying surface side of the high-pressure jet water flow in the second web 15 ′, the greater the number of ultrafine fibers generated by the division. As a result, in the absorbent core 13 obtained by this method, the number of ultrafine fibers existing on one surface side is larger than the number of ultrafine fibers existing on the other surface side. In other words, the average fiber diameter of the fibers present on one surface side of the absorbent core 13 is smaller than the average fiber diameter of the fibers present on the other surface side. In this way, the fiber gap can be made different between the one surface side and the other surface side of the absorbent core 13. For the purpose of reliably forming the gradient of the number of ultrafine fibers generated by the division, the water needle method using a high-pressure jet water flow may be performed in a plurality of stages.

  As a method of increasing the average fiber diameter of the upper layer 14 and reducing the average fiber diameter of the lower layer 15, in addition to the above-described method of mixing the non-dividing thick fibers into the upper layer web, (a) the first web 14 ' The splitting degree of the split fibers contained in the lower web is reduced, for example, six splits are used for the first web 14 ′, and 24 split splits are used for the second web 15 ′, or (b) the thickness of the fibers before splitting is changed, For example, it is possible to appropriately combine methods such as increasing the thickness before splitting of the split fibers included in the first web 14 'and decreasing the thickness before splitting of the split fibers included in the second web 15'. It is.

  Thus, in the most preferred embodiment, the absorbent core 13 as a whole includes the split fibers, the upper and lower layers 14 and 15 both have a narrow average fiber gap, and have high liquid capillary retention. In particular, the liquid is quickly transferred to the lower layer 15 by the capillary gradient of the upper and lower layers 14 and 15, and because of the high capillary holding power of the lower layer 15, high liquid retention can be achieved without additional liquid storage means such as a superabsorbent polymer. Force is feasible. On the other hand, since the sheet constituting the absorbent core 13 is thin and the sheet is not bonded by thermal bonding or chemical bonding, the absorbent core 13 is characterized by being flexible and soft.

Moreover, according to this manufacturing method, the surface sheet 11 and the absorption core 13 can also be integrated. For example, when a cotton spunlace nonwoven fabric is used as the top sheet, a cotton fiber web is arranged on the outer surface of the first web 14 'in FIG. 2, and the cotton fiber web, the first web 14' and the first web 14 'are formed by a water needle method. By integrating the two webs 15 ', the top sheet and the absorbent core are integrated. According to this method, there is an advantage that means for fixing the top sheet and the absorbent core is not required. In addition, since the degree of division of the split fibers changes so as to continuously decrease from the non-skin contact surface side to the skin contact surface side (because the cotton fiber becomes a barrier and the water flow is weakened) There is also the advantage that the gradient is formed naturally. Furthermore, since the strength of the cotton spunlace nonwoven fabric is reinforced by the absorbent core located thereunder, there is also an advantage that a surface sheet having a high basis weight as conventionally used is not necessary. Due to these advantages, an absorbent article (cotton liner) that is thinner, softer, and less sticky on the surface can be obtained. In this case, the preferred basis weight of the cotton spunlace nonwoven fabric is 15 to 60 g / m ² , particularly preferably 20 to 35 g / m ² . The preferred basis weight of the absorbent core integrated with this surface sheet is 20 to 100 g / m ² , particularly preferably 30 to 80 g / m ² .

  In the sheet in which the surface sheet 11 and the absorbent core 13 are integrated as described above, when the surface sheet 11 and the absorbent core 13 are classified, when the cross section of the sheet is observed, a portion including only cotton fibers is surfaced. It is possible to regard the sheet 13, a layer in which cotton and split fibers are mixed, as the upper layer 14 of the absorbent core 13, and a portion having only the split fibers as the lower layer 15 of the absorbent core 13. Also in this case, the relationship between the upper layer 14 and the lower layer 15 of the absorbent core 13 described above is maintained.

  Next, another preferred embodiment of the absorbent core 13 will be described. In the present embodiment, the absorbent core 13 is composed of two upper and lower layers, and the fibers, fiber gaps, and fiber thicknesses of the lower layer 15 are the same as those in the preferred embodiment.

  In the present embodiment, as the upper layer 14, a thermal bond nonwoven fabric that is mainly composed of heat-bonded fibers and in which a network is formed by thermally bonding the heat-bonded fibers is used. In particular, an air-through nonwoven fabric in which thermal bonding is performed by hot air treatment is preferably used. The upper layer 14 thus obtained has a relatively wide fiber gap, is bulky, and is soft, and thus is suitable for use as a liquid acquisition layer for temporarily holding liquid. On the other hand, when the upper layer 14 is not integrally coupled with the lower layer 15, the liquid cannot quickly move to the lower layer 15, and there is a possibility that the liquid spreads and returns in the upper layer 14 portion. For this reason, a method of integrally forming the upper and lower layers is important. This method will be described below.

[Method (2)]
A manufacturing apparatus 30 shown in FIG. 3 is used. The apparatus 30 includes a feeding portion 31 for a first original fabric 15 ″, a feeding portion 32 for a second original fabric 14 ″, and an emboss joint 33. The first raw fabric 15 ″ fed from the feeding portion 31 is to be the lower layer 15 in the absorbent core 13. The second raw fabric 14 ″ fed from the feeding portion 32 is to be the upper layer 14 in the absorbent core 13. Is.

  In a state where the second original fabric 14 ″ is superimposed on the first original fabric 15 ″, both the original fabrics 14 ″ and 15 ″ are conveyed to the position of the embossed joint 33, where embossing is performed. By embossing, a nonwoven fabric 13 ″ in which both raw fabrics are joined and integrated is obtained. Thereafter, the nonwoven fabric 13 ″ is cut into a desired size, whereby the intended absorbent core 13 is obtained.

  In the raw fabrics 14 ″ and 15 ″ used in this production method, the average fiber diameter of the constituent fibers of the original fabric 14 ″ is larger than the average fiber diameter of the constituent fibers of the original fabric 15 ″. As a result, in the nonwoven fabric 13 ″, the fiber gap is larger in the upper layer 14 than in the lower layer 15. As the raw fabric 14 ″, a nonwoven fabric having a large fiber gap and a large liquid-capturing action is preferably used. As such a nonwoven fabric, for example, an air-through nonwoven fabric can be used as described above. On the other hand, as the raw fabric 15 ″, a nonwoven fabric having a small fiber gap and a large liquid holding action is preferably used. As such a nonwoven fabric, for example, a spunlace nonwoven fabric including ultrafine fibers obtained by dividing divided fibers, A melt blown nonwoven fabric or a spunbond nonwoven fabric can be used.

  As can be seen from the above description, the absorbent core 13 manufactured by the method shown in FIG. The lower layer 15 made of a bonded nonwoven fabric is joined and integrated. In this production method, it is desirable to hydrophilize each layer by a predetermined hydrophilization means before joining and integrating the two layers of nonwoven fabric. Of course, it is possible to hydrophilize after joining and integrating.

  Further, as the most preferable implementation method of the method (2), in place of the raw fabric 15 ″, the second web 15 ′ including the split fibers shown in FIG. An example is a method in which the fibers are superposed on the opposite 14 ″ and the fibers are entangled integrally by the water needle method. The raw fabric 14 ″ is preferably an air-through nonwoven fabric for the following reason. Details of the preferred fibers constituting the web 15 ′ are in accordance with the method (1) described above. The split fibers having a structure in which the water-soluble thermoplastic resin is alternately arranged in a sector shape in the cross-sectional direction of the fiber and these resins extend in the length direction of the fiber have the following reasons (1) to (3 ) Is particularly preferable.

Reason (1)
Even when fiber entanglement is performed from both above and below by the water needle method, the momentum of the high-pressure jet water stream sprayed to the original fabric 14 ″ side, that is, the air-through nonwoven fabric side is suppressed by the air-through nonwoven fabric. Among the split fibers included in 15 ′, the split fibers located on the side close to the air-through nonwoven fabric have a low degree of splitting, whereas the web 15 ′ is directly hit by the high-pressure jet water stream, so that the web 15 The splitting of the split fibers contained in 'is promoted. As a result, a natural gradient is formed in the splitting degree of the split fibers.

Reason (2)
The air-through nonwoven fabric 14 ″ is exposed to a high-pressure jet water stream, and the hydrophilizing agent adhering to the constituent fibers of the nonwoven fabric may be washed away and the hydrophilicity may be lowered. Since the water-soluble thermoplastic resin eluted from the split fibers contained in 'adheres to the constituent fibers of the air-through nonwoven fabric and the constituent fibers become hydrophilic, no additional hydrophilic treatment is required.

Reason (3)
The bulky network derived from the air-through nonwoven fabric which is the raw fabric 14 ″ is formed in advance, and the air-through nonwoven fabric has high tensile strength and surface strength. Therefore, even if the web 15 ′ combined with the air-through nonwoven fabric is thin, the absorbent core 13 It is easy to ensure the overall thickness, strength and absorbency.

In the upper layer 14 of the absorbent core 13 manufactured by the method (2), the preferable fiber gap is 12 to 400 μm, particularly 50 to 300 μm, and the preferable average fiber diameter of the constituent fibers is 8 to 80 μm, particularly 10 to 72 μm. The preferred thickness is 0.4 to 3 mm, particularly 0.4 to ² mm, and the preferred basis weight is 18 to 100 g / m ² , particularly 20 to 80 g / m ² . It is most desirable that the lower layer 15 has a structure in which a part of the constituent fibers enter the upper layer 14 and the fiber gap continuously changes by fiber entanglement by the water needle method or the like. It is desirable to select such fibers in that a fiber aggregate state that can absorb liquid quickly and can be temporarily retained can be formed. The fiber gap, the average fiber diameter, the thickness, and the basis weight of the lower layer 15 are in accordance with the embodiment described above.

  It is also possible to form a fiber assembly structure similar to that of the absorbent core 13 described so far without using the water needle method. The method will be described below.

[Method (3)]
A manufacturing apparatus 40 shown in FIG. 4 is used. The apparatus 40 includes a feed portion 41 of the raw fabric 14A and a spinning nozzle 42 of a melt blow method. The raw fabric 14 </ b> A fed out from the feed-out portion 41 should be the upper layer 14 in the absorbent core 13.

  The original fabric 14 fed out from the feeding unit 41 is conveyed to the position of the spinning nozzle 42. From the spinning nozzle 42, ultrafine fibers 43 spun by the melt blow method are conveyed to hot air and blown out. The ultrafine fibers 43 fall and accumulate on the original fabric 14A in a molten or semi-molten state, and are joined to the constituent fibers of the original fabric 14A by fusion. As a result, a layer 15A of melt blown nonwoven fabric is formed on the original fabric 14A. The melt blown nonwoven fabric layer 15 </ b> A should be the lower layer 15 in the absorbent core 13. In this way, the nonwoven fabric 13A in which the melt blown nonwoven fabric layer 15 is fused and integrated on the original fabric 14A is obtained. Then, the target absorbent core 13 is obtained by cutting the nonwoven fabric 13A into a desired size.

  The average fiber diameter of the constituent fibers of the raw fabric 14A used in this production method is larger than the average fiber diameter of the ultrafine fibers 43 constituting the layer 15A of the melt blown nonwoven fabric. As a result, in the nonwoven fabric 13A, the fiber gap is larger in the upper layer 14 than in the lower layer 15. As the original fabric 14A, an air-through nonwoven fabric, which is a nonwoven fabric having a large fiber gap and a large liquid-capturing action, is preferably used as in the original fabric 14 ″ used in the method shown in FIG.

  As is apparent from the above description, the absorbent core 13 manufactured by the method shown in FIG. It is an integrated product. In this production method, in order to promote integration of the melt blown nonwoven fabric as the upper layer 14 and the lower layer 15, joint integration by emboss bonding may be used together with the method (2). In order to make the melt-blown nonwoven fabric layer 15A hydrophilic, it is preferable that the raw fabric 14A and the melt-blown nonwoven fabric layer 15A are integrated and then hydrophilicized. Preferred values of the fiber gap, fiber thickness, thickness and basis weight in the melt blown nonwoven layer 15A obtained by this production method are the same as those of the lower layer 15 in the absorbent core obtained by the method (1).

  Even if any of the above methods (1) to (3) is used for manufacturing the absorbent core 13, the total thickness of the napkin 10 including the absorbent core 13 is thin, which is the object of the invention. From the viewpoint of realizing thickness and softness, it is preferably 1 to 7 mm, particularly preferably 2 to 4 mm.

  Although the thickness of the absorbent core 13 is as described above, the absorbent core 13 is flexible because of its small thickness. When bulk softness is used as a measure of the flexibility of the absorbent core 13, the value is preferably 20 to 300 gf (0.2 to 2.94 N), more preferably 40 to 160 gf (0.39 to 1.57 N). It becomes. The overall value of the napkin 10 including the absorbent core 13 is preferably 50 to 500 gf (0.49 to 4.9 N), more preferably 70 to 280 gf (0.686 to 2.74 N).

On the other hand, cotton-like pulp, paper, superabsorbent polymers, and composites thereof have been suitably used as the absorbent core of absorbent articles. Pulp is an essentially hydrophilic short fiber made of cellulose fibers. Pulp is characterized by high capillary retention and high liquid retention when fibers are closely packed together. On the other hand, when the fibers are gathered densely, there is a drawback in that hydrogen bonding occurs and the fibers are brought into close contact and hardened. For example, a cotton-like pulp having a basis weight of 300~750g / m ^2, the superabsorbent polymer having a basis weight of 20 to 200 g / m ² were mixed layered, made wrapped in basis weight 20 g / m ² about absorbing paper Although the absorbent core has the softness of cotton-like pulp, the thickness of the absorbent core is as thick as 10 mm or more, and is inferior in fit and wearing feeling. Moreover, the fiber gap is wide as it is, and the wet-back prevention property and the centrifugal retention amount described later are inferior. Therefore, the absorbent core can be strongly compressed with an embossing roll to be formed into a compressed pulp layer having a thickness of about 4 mm. However, such an absorbent core becomes extremely hard as a result of increased fiber-to-fiber bonding. . Similarly, an absorbent core having a structure in which a superabsorbent polymer is sandwiched between two sheets of absorbent paper can also be produced. Due to the fixing of the polymer, it has a hard texture.

  Bulk softness is measured by the following method. Using Tensilon (Orientec Co., Ltd., model: RTC-1210A), the absorbent core 13 is cut 150 mm in the longitudinal direction and 30 mm in the width direction to obtain a rectangular piece. A cylinder with a height of 30 mm is made from this rectangular piece. The upper and lower ends are stapled to make a cylindrical sample for measurement. The cylindrical sample is compressed in the height direction at a compression speed of 10 mm / min. Measure the maximum load at that time, and use that value as the bulk softness value. The bulk softness of the napkin 10 is measured by sampling a specimen having a length of 150 mm and a width of 45 mm from the center of the napkin, making a cylinder with the topsheet side outside, and setting the end point as the first maximum point. Except for the above, the procedure is the same as the method for measuring the bulk softness of the absorbent core 13.

  The absorbent core 13 includes fibers having a small average fiber diameter in the lower layer 15 and has a narrow fiber gap, and therefore, the liquid retainability by capillary force is high. Conventionally, in order to improve liquid retention, it has been common to arrange a considerable amount of superabsorbent polymer in the absorbent core. In the present embodiment, it is preferable to use a superabsorbent polymer in combination, but it is extremely preferable from the following viewpoint that the essential liquid retention of the absorbent core itself is high. 1stly, according to the absorption core 13 of this embodiment, since the device which fixes particulate matters, such as a superabsorbent polymer, without dropping is unnecessary, a soft absorption core can be produced. Secondly, the performance of the superabsorbent polymer may change extremely depending on the properties of the target liquid. However, since the absorbent core 13 of the present embodiment has a stable absorption capacity, the wetback is stable even if it is thin. The amount can be maintained. Thirdly, as described above, according to the present embodiment, the thin and soft absorbent core 13 can be easily obtained, so that secondary processing that can be freely cut and folded is possible.

  As described above, the liquid retainability of the absorbent core 13 is high. When the liquid retainability of the absorbent core 13 is expressed by a centrifugal retention amount, the value is preferably 7 to 50 g / g, and more preferably. Is 10 to 35 g / g. Moreover, the centrifugal retention amount of the whole napkin is preferably 3 to 40 g / g, more preferably 5 to 25 g / g. The napkin 10 including the absorbent core 13 has a wetback amount of preferably 1 g or less, more preferably 0.5 g or less. The amount of centrifugal retention and the amount of wetback are measured by the following methods.

[Measurement method of centrifugal retention]
The entire absorbent core 13 is taken out and weighed in advance. This value is the initial weight. The absorbent core 13 is immersed in physiological saline and left for 1 minute. The absorption core is expanded and fixed in a Kokusan Co., Ltd. Centrifuge H-130C basket, centrifuged at 2000 rpm for 10 minutes, and its weight is measured. Using the obtained numerical value, the centrifugal retention amount is obtained from the following formula.
Centrifugal retention amount (g / g) = [sample weight after centrifugation−initial weight] / initial weight In the absorbent core 13, there are coexisting components such as particulate matter such as a superabsorbent polymer and short fibers that may fall off. In some cases, a bag made of non-woven fabric or nylon mesh may be prepared, and the absorbent core 13 may be expanded and placed in the bag. When the core 13 is large, the central portion of the absorbent core 13 may be cut off as appropriate, and the measurement may be performed in the same manner using 1 g, for example. When measuring the amount of the napkin 10 held by centrifugation, centrifuge the centrifuge so that about 5 g is cut from the center of the napkin to make a test piece, and the top sheet side of the napkin 10 faces the outside (basket opening surface) side. The measurement is the same as the measurement of the centrifugal holding amount of the absorbent core 13 except for the installation point.

[Method of measuring wetback]
Acrylic injection plate with a hole with a diameter of 10 mmφ (with a cylinder with an inner diameter of 22 mmφ and a height of 40 mm in the injection portion), an acrylic plate, Prepare 2 filter papers (1 set of 10 sheets of 80 × 190 mm), weight and equine defibrinated blood. Adjust the weight of the injection plate in advance so that a load of 5 g / cm ² is applied to the entire surface of the napkin (or the area where the load is applied to the injection plate), and acrylic so that a load of 50 g / cm ² is applied. The weight of the plate is adjusted in advance. Spread the napkin upward, and gently place the liquid injection plate on top of it and load to 5 g / cm ² . Weigh 3 g of equine defibrinated blood into a 10 ml beaker and pour it into the cylindrical part of the injection plate at once. At this time, the time from the start of pouring to the time when the blood in the plate cylinder is completely taken into the napkin is measured and defined as the absorption time. After 5 minutes from the start of injection, the injection plate was removed, and No. Two 10 filter papers are placed on the surface of the napkin, and an acrylic plate and a weight are gently placed thereon, and a load of 50 g / cm ² is applied for 1 minute. Remove the plate after 1 minute, take out 10 sheets of filter paper, and measure the weight. The increase in weight is defined as a wetback. The average value of the three points is taken as the measured value. When the liquid could not be absorbed even after 3 minutes had passed after the injection, the measurement was terminated with an absorption time of “3 minutes or longer” and a wetback “impossible to measure”.

  Next, another embodiment of the present invention will be described with reference to FIGS. Regarding the points that are not particularly described with respect to these embodiments, the description regarding the first embodiment described in detail above is appropriately applied. 5 to 10, the same members as those in FIGS. 1 to 4 are denoted by the same reference numerals.

  In the absorbent core 13 of the second embodiment shown in FIG. 5, functional particles 16 are added to the lower layer 15. By using various functional particles 16, an additional function can be imparted to the absorbent core 13. For example, by using superabsorbent polymer particles as the functional particles 16, the liquid holding force of the absorbent core 13 can be further enhanced. In addition, the amount of liquid retained can be increased. By using particles having a deodorizing action or a deodorizing action, such as activated carbon, zeolite, or silica, as the functional particles 16, it is possible to impart a deodorizing function or a deodorizing function to the absorbent core.

  The absorption core 13 of this embodiment can be manufactured using the manufacturing apparatus shown in FIG. The apparatus shown in the figure includes a first card machine 21, a second card machine 22, and a functional particle hopper 24. From the first card machine 21 and the second card machine 22, a web W of split fibers of the same type or different types is fed out. Functional particles 16 are dispersed from the hopper 24 between the two webs W. That is, the functional particles 16 are sandwiched between the two webs W. Under this condition, a high-pressure jet water stream is jetted onto the web W from a high-pressure jet water stream injection device (not shown). The high-pressure jet water flow is first injected toward the upper web W, and then injected toward the lower web W. Subsequently, a high-pressure jet water stream is jetted in the order of the upper and lower webs W. By this operation, the split fibers are split to produce ultrafine fibers and the spunlace nonwoven fabric 15 ″ is formed. The splitting of the split fibers is promoted by the polishing effect by the functional particles. Thereafter, the production shown in FIG. The same operation as that performed using the apparatus is performed.

  In the third embodiment shown in FIG. 7, a mixed fiber layer 17 of pulp and superabsorbent polymer is disposed below the fiber sheet having the upper layer 14 and the lower layer 15, and the absorbent core 13 is configured. Yes. By using the mixed fiber layer 17 of pulp and superabsorbent polymer, the liquid holding amount of the napkin 10 can be further increased. As a modification of the present embodiment, there is a form in which a mixed fiber layer 17 of pulp and superabsorbent polymer is disposed on the upper side of the fiber sheet having the upper layer 14 and the lower layer 15.

  In the fourth embodiment shown in FIG. 8, the absorbent core 13 includes a middle-high portion 18 extending in the longitudinal direction formed by folding a fiber sheet having an upper layer 14 and a lower layer 15 into a substantially Ω shape in the width direction. Have. The longitudinal direction of the mid-high portion 18 coincides with the longitudinal direction of the napkin 10. By forming the middle-high part 18, it becomes possible to make the napkin 10 contact | abut to a wearer's excretion site | part more reliably, and a liquid leak can be prevented.

  In the fifth embodiment shown in FIG. 9, the absorbent core 13 has an absorbent paper 19A such as tissue paper disposed below the fiber sheet having the upper layer 14 and the lower layer 15, and the fiber sheet and the absorbent paper 19A. Between the two layers, a superabsorbent polymer spray layer 19B is formed. According to the absorbent core 13 of the present embodiment, it is possible to further increase the liquid absorption capacity while maintaining the thin thickness.

  In the napkin 10 according to the sixth embodiment shown in FIG. 10, the top sheet 11 is formed integrally with the fiber sheet on the upper layer 16 of the absorbent core 13 made of the fiber sheet having the upper layer 14 and the lower layer 15. For the integration, it is preferable to use fiber entanglement using a high-pressure jet water stream. As the surface sheet 11 in this embodiment, it is preferable to use a cellulose fiber such as cotton or rayon as a constituent fiber.

  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, in each of the embodiments described above, the fiber sheet forming a part of the absorbent core 13 has a two-layer structure of the upper and lower layers 14 and 15. However, the fiber sheet may have a structure of three or more layers. In that case, a hydrophilic fiber layer such as pulp, rayon, or cotton may be integrally included between the upper and lower layers 14 and 15.

  A mixed fiber layer 17 of pulp and superabsorbent polymer shown in FIG. 7 may be disposed below the fiber sheet having a medium and high structure shown in FIG.

Further, a liquid permeable layer may be added between the top sheet 11 and the absorbent core 13. This layer supplements a part of the liquid temporary holding function of the upper layer 14 of the absorbent core 13. An air-through nonwoven fabric made of heat-sealing fibers having a basis weight of about 16 to 45 g / m ² is particularly preferably used for the transmission layer.

  Further, in the manufacture of the absorbent core 13 using the apparatus 30 shown in FIG. 3, after the particles of the superabsorbent polymer or silica gel are spread on the first raw fabric 15 ″, the second raw fabric 14 ″ is overlapped, The embossed joint 33 may be joined and integrated. The absorbent core 13 thus obtained has a structure in which superabsorbent polymer and silica gel particles are disposed between the upper layer 14 and the lower layer 15.

  The absorbent article of the present invention is particularly effective when applied to thin articles such as sanitary napkins and panty liners, but the same applies to other absorbent articles such as disposable diapers and urine pads. Applicable to. In particular, when the present invention is applied to a panty liner, it is preferable to use the above-described cotton spunlace nonwoven fabric or rayon spunlace nonwoven fabric as the surface sheet. For example, a cotton spunlace nonwoven fabric is used as a surface sheet, and a fiber sheet containing split fibers is used as the absorbent core 13 and the fiber gap of the fiber sheet is adjusted by a predetermined method. However, since the capillary force is large, no liquid remains on the surface of the cotton spunlace nonwoven fabric and stickiness is reduced.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” means “% by weight”.

[Example 1]
In accordance with the method shown in FIG. 2, an absorbent core 13 made of one fiber sheet was manufactured. As the first web 14 'in FIG. 2, 60% of a split fiber composite fiber shown below and 40% of PET fiber having a fineness of 4.6 dtex and a fiber length of 52 mm were premixed and carded, and a basis weight of 50 g / An m ² web was used. For the second web 15 ′ in FIG. 2, a card web having a basis weight of 50 g / m ² made of 100% of the above-described splittable conjugate fiber was used.

  The splittable composite fiber used in common for both webs is made of PP / PE. The fineness before division is 3.3 dtex. This composite fiber is obtained by melting and kneading each resin, introducing it into the same spinning nozzle in a predetermined pattern, spinning and stretching. The cross-section of the composite fiber is a shape in which fan-shaped resin regions are gathered to form a circle. The sector shape is 8 pieces of each resin, and 16 pieces can be divided into 16 pieces. The fiber length of the fiber is 52 mm.

Both webs were stacked with the above basis weight and then overlapped, and the fibers were entangled by the water needle method using the jet nozzle 23. Although not shown in the figure, fiber entanglement by the same jet nozzle is repeated downstream, and eventually water entanglement is made three times, twice on the second web 15 'side and once on the first web 14' side. A spunlace nonwoven fabric was obtained. 0.75% nonionic surfactant (alkyl glycoside of Kao Corporation) was attached to this nonwoven fabric to make it hydrophilic. Thus, an absorbent core 13 having a basis weight of 100 g / m ² was obtained.

In the obtained absorbent core 13, the top sheet 11 was arranged on the first web side, and the back sheet 12 made of polyethylene film was arranged on the second web side to obtain a napkin 10. As the surface sheet 11, an air-through nonwoven fabric having a basis weight of 25 g / m ² subjected to a hydrophilic treatment was used. The constituent fiber of this nonwoven fabric was a PET / PE core-sheath composite fiber having a fineness of 2.2 dtex.

[Example 2]
Using the apparatus 30 shown in FIG. 3, an absorbent core 13 made of one fiber sheet was manufactured. An air-through nonwoven fabric having a basis weight of 40 g / m ² was used as the first raw fabric 15 ″. The constituent fiber of this nonwoven fabric was a PET / PE core-sheath type composite fiber having a fineness of 2.2 dtex. As 14 ″, a melt blown nonwoven fabric (basis weight 40 g / m ² ) of ethylene / 1-octene copolymer resin (density 0.93 g / cm ³ ) was used. The melt blown nonwoven fabric and the air-through nonwoven fabric were hydrophilized in the same manner as in Example 1. An air-through nonwoven fabric was layered on the meltblown nonwoven fabric, embossed, and integrated to obtain an absorbent core 13. Except for these, a sanitary napkin 10 was obtained in the same manner as in Example 1 (the air-through nonwoven fabric side was the surface sheet side).

[Comparative Example 1]
The 16 divided fibers used in Example 1 were piled up and entangled by the water needle method twice each on the front and back sides. Subsequently, hydrophilicization and drying were performed in the same manner as in Example 1 to obtain a spunlace nonwoven fabric having a basis weight of 20 g / m ² . This nonwoven fabric was in the same fiber split state on both sides. Separately from this nonwoven fabric, a superabsorbent polymer (AQUALIC (trade name, manufactured by Nippon Shokubai Co., Ltd.)) is sprayed on an absorbent paper having a basis weight of 18 g / m ^{2 at} a basis weight of 30 g / m ² , and a small amount of water is sprayed. Thereafter, the same absorbent paper was stacked and dried to obtain a polymer sheet. Further, separately from these, the pulverized pulp was piled up at a basis weight of 100 g / m ² to obtain a pulp layer. And the said polymer sheet, the said spunlace nonwoven fabric, and the said pulp layer were piled up in this order, and the absorption core was obtained. Except these, it carried out similarly to Example 1, and obtained the napkin of the comparative example (a pulp layer is a surface sheet side).

[Comparative Example 2]
A spunlace nonwoven fabric having a basis weight of 100 g / m ² was obtained using the same fiber and method as in Comparative Example 1. A napkin of Comparative Example 2 was obtained in the same manner as Comparative Example 1 except that the obtained non-woven fabric was used as an absorbent core.

[Evaluation]
(1) Absorption core About the napkin obtained by the Example and the comparative example, the average fiber diameter and fiber space | gap of the constituent fiber of the upper and lower layers of the absorption core were measured. Furthermore, the bulk softness, centrifugal holding capacity and thickness of the absorbent core were measured. These results are shown in Table 1.

(2) Napkin The thickness, absorption time, wetback amount, absorption amount, and wearing feeling of the napkins obtained in Examples and Comparative Examples were measured. These results are shown in Table 2.

In the measurement of the amount of absorption, the maximum amount of absorption by which horse defibrinated blood leaked was measured using a movable female waist model described in JP-A-2-239863. Specifically, after attaching a test sample to the movable model and putting on shorts, 2 g of equine defibrinated blood was injected with a dropping tube pump every 3 minutes while the model was walking at 100 steps / minute. The amount of equine defibrinated blood absorbed before the side sag was measured. The result is an average value of N = 3.
The feeling of wearing was evaluated by a wearing test. Twelve women were allowed to wear each sample and put it on freely to select the number closest to their feelings for the next evaluation item. The average value was defined as the wearing feeling. The closer the average value is to 1, the better the feeling of wearing.
A feeling of wearing; Good, Somewhat good. 3. I can't say either. Slightly bad 5. bad

  As is clear from the results shown in Table 1, it can be seen that the napkin of the example has a small bulk softness value of the absorbent core and is flexible. It can also be seen that the centrifugal holding capacity is high despite the thin thickness of the absorbent core. Further, as apparent from the results shown in Table 2, it can be seen that the napkin of the example has a high absorption amount and a small wetback amount despite being thin. Further, it can be seen that the feeling of wearing is good due to being thin and flexible. On the other hand, since the napkin of Comparative Example 1 is thick and difficult to bend, the bulk softness value is large and the wearing feeling is inferior. In addition, since the liquid is not completely absorbed and fixed, the wetback amount is large and the absorption amount is not high. Further, the napkin of Comparative Example 2 is composed of a thin spunlace absorbent body equivalent to the napkin of Example 1, has a small bulk softness value, and is flexible so that the feeling of wearing is good, but the liquid is put inside the absorbent body. It cannot absorb and is extremely poor in absorbability.

It is width direction sectional drawing which shows one Embodiment of the absorbent article of this invention. It is a schematic diagram which shows the apparatus for manufacturing the absorption core in the absorbent article shown in FIG. It is a schematic diagram which shows another apparatus for manufacturing the absorption core in the absorbent article shown in FIG. It is a schematic diagram which shows another apparatus for manufacturing the absorption core in the absorbent article shown in FIG. It is sectional drawing which shows the structure of the absorption core in other embodiment of the absorbent article of this invention. It is a schematic diagram which shows the apparatus for manufacturing the absorption core shown in FIG. It is sectional drawing which shows the structure of the absorption core in other embodiment of the absorbent article of this invention. It is sectional drawing which shows the structure of the absorption core in other embodiment of the absorbent article of this invention. It is sectional drawing which shows the structure of the absorption core in other embodiment of the absorbent article of this invention. It is sectional drawing which shows the structure of other embodiment of the absorbent article of this invention.

Explanation of symbols

10 Napkin 11 Top sheet 12 Back sheet 13 Absorption core 14 Upper layer 15 Lower layer

Claims (4)

  An absorbent article having at least an absorbent core mainly composed of a fiber material, interposed between the top sheet, the back sheet, and both, the absorbent core having a fiber layer containing synthetic fibers having an average fiber diameter of 20 μm or less The fiber gap of the fibers existing on the skin facing surface side of the absorbent core is made wider than the fiber gap of the fibers existing on the underwear facing surface side, and the fiber layer on the skin facing surface side substantially holds the liquid. Absorbent article that has a structure that does not.   The absorptivity of Claim 1 which adjusted the said fiber gap | interval by making the average fiber diameter of the fiber which exists in the skin opposing surface side in the said fiber layer larger than the average fiber diameter of the fiber which exists in the underwear opposing surface side. Goods.   When the fiber layer entangles the fibers by the water needle method, the average fiber gap of the fibers existing on the skin facing surface side in the fiber layer becomes larger than the average fiber gap of the fibers existing on the underwear facing surface side. The absorbent article according to claim 1 or 2, wherein the absorbent article is formed as described above.   The absorption according to claim 3, wherein at least the underwear facing surface side of the fiber layer includes fibers having a fiber diameter of 5 µm or less generated by dividing a fiber that can be divided into a plurality of pieces in a length direction by the water needle method. Sex goods.

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