Absorbent article

Abstract

The purpose of the present disclosure is to provide an absorbent article having exceptional absorption speed, rewetting resistance, and thickness suppression properties when repeatedly absorbing liquid.　This absorbent article (1) comprises an absorbent core (9) that includes pulp fibers (17) and highly water-absorbent polymer particles (19), the absorbent article (1) being characterized in that: the absorbent core (9) is provided with a plurality of high-basis-weight high-density portions (31) that extend continuously in a direction following a longitudinal direction L, and a plurality of low-basis-weight low-density portions (25) that extend in the direction following the longitudinal direction L; the plurality of high-basis-weight high-density portions (31) and the plurality of low-basis-weight low-density portions (25) are disposed so as to alternate in a width direction W; and the highly water-absorbent polymer particles (19) have a water retention ratio of 43 g / g or higher when not pressurized, and have a water retention ratio of 25 g / g or lower when pressurized at 2 kPa.

Description

absorbent articles

[0001] The present disclosure relates to absorbent articles.

[0002] Studies have been made to improve the absorbency of absorbent articles. For example, Patent Document 1 discloses an absorbent body having pulp and a water-absorbent polymer, the absorbent body having recesses with a depth of 20% to 100% of the thickness of the absorbent body, in which the mass ratio of [mass of pulp] / [mass of water-absorbent polymer] in the absorbent body is 1 / 3 to 1 / 0.01, the water-absorbent polymer has a water absorption capacity of 30 g / g to 50 g / g, and the liquid absorption capacity under a pressure of 2 kPa is 20 g / g to 40 g / g.

[0003] Paragraph

[0010] of Patent Document 1 states, "The absorbent body and absorbent article of the present invention use a water-absorbent polymer that has excellent absorbency even under a load, thereby preventing the absorbent polymer from collapsing and ensuring that the grooves arranged in the absorbent body are not blocked. As a result, a high absorption capacity and a high absorption rate are achieved at the same time, and the absorption rate is unlikely to decrease even with repeated excretion, resulting in the excellent effect of demonstrating high absorption performance from the start of use until the end of use."

[0004] JP 2012-143534 A

[0005] The absorbent body disclosed in Patent Document 1 has a water absorption capacity within a predetermined range, but its liquid absorption capacity under a pressure of 2 kPa is high, at 20 g / g or more and 40 g / g or less, i.e., the absorbent polymer is resistant to crushing. Therefore, when the absorbent body repeatedly absorbs liquid, the absorbent polymer absorbs the liquid and expands, which tends to reduce the voids in the recesses and slow the absorption rate. Furthermore, in the absorbent body disclosed in Patent Document 1, the absorbent polymer is resistant to crushing, and since the portions of the absorbent body other than the recesses are not continuous in the longitudinal direction, the liquid absorbed in the portions other than the recesses is less likely to diffuse in the longitudinal direction, resulting in localized thickness of the absorbent body. Localized swelling of the absorbent body not only reduces the wearability of the absorbent article, but also causes the absorbent body to lose its shape, which in turn makes the absorbed liquid more likely to leak. Therefore, the present disclosure aims to provide an absorbent article that exhibits excellent absorption rate, rewet resistance, and thickness suppression when repeatedly absorbing liquid.

[0006] The present inventors have discovered an absorbent article comprising an absorbent core containing pulp fibers and superabsorbent polymer particles, and having a longitudinal direction, a width direction, and a thickness direction, wherein the absorbent core comprises a plurality of high basis weight, high density portions extending continuously along the longitudinal direction, and a plurality of low basis weight, low density portions extending along the longitudinal direction, wherein each of the plurality of high basis weight, high density portions and each of the plurality of low basis weight, low density portions are arranged alternately in the width direction, each of the plurality of high basis weight, high density portions has a higher basis weight and higher density than each of the plurality of low basis weight, low density portions, and the superabsorbent polymer particles have a water retention capacity of 43 g / g or more under no pressure and a water retention capacity of 25 g / g or less under a pressure of 2 kPa.

[0007] The absorbent article is excellent in absorption speed, rewet resistance, and thickness suppression when repeatedly absorbing liquid.

[0008] Fig. 1 is a diagram for explaining a disposable diaper 1 according to a first embodiment. Fig. 2 is a diagram for explaining a disposable diaper 1 according to the first embodiment. Fig. 3 is a diagram for explaining a disposable diaper 1 according to the first embodiment. Fig. 4 is a diagram for explaining a disposable diaper 1 according to the first embodiment. Fig. 5 is a diagram for explaining an example. Fig. 6 is a diagram for explaining an example. Fig. 7 is a diagram for explaining an example.

[0009] Specifically, the present disclosure relates to the following aspects: [Aspect 1] An absorbent article having a longitudinal, width, and thickness directions, and including an absorbent core containing pulp fibers and superabsorbent polymer particles, wherein the absorbent core has a plurality of high basis weight, high density portions extending continuously along the longitudinal direction and a plurality of low basis weight, low density portions extending along the longitudinal direction, wherein each of the plurality of high basis weight, high density portions and each of the plurality of low basis weight, low density portions are arranged alternately in the width direction, each of the plurality of high basis weight, high density portions has a higher basis weight and higher density than each of the plurality of low basis weight, low density portions, and the superabsorbent polymer particles have a water retention capacity of 43 g / g or more under no pressure and a water retention capacity of 25 g / g or less under a pressure of 2 kPa.

[0010] In the absorbent article, the absorbent core has a plurality of high basis weight, high density portions extending continuously along the longitudinal direction and a plurality of low basis weight, low density portions extending along the longitudinal direction, and each of the plurality of high basis weight, high density portions has a higher basis weight and higher density than each of the plurality of low basis weight, low density portions.

[0011] When the absorbent core absorbs a relatively small amount of liquid (e.g., bodily fluid, e.g., urine), for example, the first urine, the multiple low basis weight, low density portions can diffuse the liquid in the longitudinal direction through the multiple low basis weight, low density portions. The liquid diffused in the longitudinal direction then migrates to the multiple high basis weight, high density portions, which have a high basis weight and high density, and the multiple low basis weight, low density portions themselves can prepare for absorbing the next liquid. The superabsorbent polymer particles present in the multiple high basis weight, high density portions absorb the liquid that has migrated to the multiple high basis weight, high density portions. Furthermore, because the multiple high basis weight, high density portions extend continuously along the longitudinal direction, the liquid that has migrated to the multiple high basis weight, high density portions can be diffused in the longitudinal direction through the multiple high basis weight, high density portions.

[0012] When the absorbent core absorbs a large amount of liquid, for example, urine for the second or subsequent time, the multiple low basis weight, low density portions can diffuse the liquid in the longitudinal direction through the multiple low basis weight, low density portions, just as in the first liquid absorption. Furthermore, the liquid that has diffused in the longitudinal direction through the multiple low basis weight, low density portions moves to the multiple high basis weight, high density portions, which have a high basis weight and high density, so the multiple low basis weight, low density portions themselves can prepare for absorbing the next liquid.

[0013] The superabsorbent polymer particles present in the multiple high-basis-weight, high-density portions and having a predetermined water retention capacity under no pressure have a predetermined water retention capacity under a pressure of 2 kPa (hereinafter sometimes referred to simply as "under pressure"), and therefore, when absorbing a certain amount of liquid, their shape tends to deform moderately, specifically, they tend to collapse moderately. To reduce the water retention capacity under pressure, methods include (i) reducing the degree of crosslinking on the surface of the superabsorbent polymer particles and (ii) reducing the degree of crosslinking inside the superabsorbent polymer particles. However, selecting option (i) reduces liquid permeability and tends to inhibit the movement of liquid beyond the superabsorbent polymer particles, so in the present invention, option (ii) was selected. The pressure of 2 kPa is an example of the average pressure exerted by an infant on the absorbent core when wearing an absorbent article.

[0014] The superabsorbent polymer particles that have absorbed liquid and undergone a moderate deformation can function as a retaining wall in the multiple high-basis-weight, high-density portions to maintain the shape of the multiple high-basis-weight, high-density portions. As a result, the multiple low-basis-weight, low-density portions are less likely to be compressed by the multiple high-basis-weight, high-density portions, and even when the absorbent core has absorbed a certain amount of liquid, the liquid can be diffused in the longitudinal direction through the multiple low-basis-weight, low-density portions. Furthermore, since the multiple high-basis-weight, high-density portions extend continuously in the longitudinal direction and the superabsorbent polymer particles have a predetermined water retention capacity under pressure, the multiple high-basis-weight, high-density portions can diffuse liquid that has migrated to the multiple high-basis-weight, high-density portions in the longitudinal direction via the multiple high-basis-weight, high-density portions, allowing the liquid to be absorbed by the entire multiple high-basis-weight, high-density portions, preventing the absorbent core from becoming thicker after absorbing liquid.

[0015] Furthermore, since the plurality of low basis weight, low density portions are not voids (for example, slit portions) but contain pulp fibers, superabsorbent polymer particles, etc., once liquid reaches the absorbent core, it passes through the plurality of low basis weight, low density portions and is less likely to return to the skin-contacting surface of the absorbent article, such as the liquid-permeable sheet, and the absorbent article has excellent rewet resistance. As a result, the absorbent article has excellent absorption speed, rewet resistance, and thickness suppression when repeatedly absorbing liquid.

[0016] In addition, as disclosed in paragraph

[0014] of Patent Document 1, the absorbent body according to Patent Document 1 discloses that "the water-absorbent polymer 22, whose absorption amount of excretory liquid under pressure is set within the above range, has an appropriately strong cross-linking, so that the water-absorbent polymer 22 itself is unlikely to be crushed." However, when the amount of liquid absorbed under pressure is high, the water-absorbent polymer tends to expand while maintaining its shape, and the expanded water-absorbent polymer tends to reduce the voids in the recesses, making it difficult for the absorbent body to diffuse the liquid in the longitudinal direction through the recesses when it has absorbed a certain amount of liquid.

[0017] Furthermore, in the absorbent body disclosed in Patent Document 1, the portions other than the recesses (hereinafter referred to as "protrusions") are not continuous in the longitudinal direction, making it difficult for the liquid absorbed by the protrusions to be diffused in the longitudinal direction through the protrusions. As a result, when the absorbent body repeatedly absorbs liquid, the absorbent body is likely to become locally thick near the excretory opening contact area.

[0018] [Aspect 2] The absorbent article according to aspect 1, wherein the highly absorbent polymer particles have a liquid permeation rate of 1.0 g / 60 seconds or more.

[0019] In the absorbent article, the superabsorbent polymer particles have a predetermined liquid permeation rate. Therefore, in the multiple low basis weight, low density portions, the superabsorbent polymer particles are less likely to inhibit the liquid present in the multiple low basis weight, low density portions from diffusing in the longitudinal direction through the multiple low basis weight, low density portions. Similarly, in the multiple high basis weight, high density portions, the superabsorbent polymer particles are less likely to inhibit the liquid present in the multiple high basis weight, high density portions from diffusing in the longitudinal direction through the multiple high basis weight, high density portions. As a result, the absorbent article has excellent thickness suppression properties when repeatedly absorbing liquid.

[0020] [Aspect 3] The absorbent article according to aspect 1 or 2, wherein the plurality of low basis weight, low density portions are not connected to each other in the width direction.

[0021] In the absorbent article, the plurality of low basis weight, low density portions spaced apart from one another in the width direction are not connected to one another. Therefore, the plurality of low basis weight, low density portions are unlikely to inhibit liquid present in the plurality of high basis weight, high density portions from diffusing in the longitudinal direction through the plurality of high basis weight, high density portions. As a result, the absorbent article has superior thickness suppression properties when repeatedly absorbing liquid.

[0022] [Aspect 4] The absorbent article according to any one of Aspects 1 to 3, wherein the plurality of high basis weight, high density portions are connected to one another in the width direction.

[0023] In the absorbent article, the multiple high-basis-weight, high-density portions that are spaced apart from each other in the width direction are connected to each other, so that the high-basis-weight, high-density portions are more likely to diffuse absorbed liquid in the planar direction of the absorbent core, and when liquid is repeatedly absorbed, the absorbent core, and ultimately the absorbent article, is more likely to have excellent thickness suppression properties.

[0024] [Aspect 5] The absorbent article according to any one of Aspects 1 to 4, wherein each of the plurality of low basis weight, low density portions is a groove portion recessed in the thickness direction, and each of the plurality of high basis weight, high density portions is a ridge portion protruding in the thickness direction.

[0025] In the absorbent article, each of the plurality of low basis weight, low density portions is a predetermined groove portion, and each of the plurality of high basis weight, high density portions is a predetermined ridge portion, so that liquid that reaches the absorbent core can be rapidly diffused in the longitudinal direction through the voids in the groove portion. As a result, in the absorbent article, the absorbent core diffuses the liquid in the longitudinal direction and easily absorbs it, and the absorbent article has excellent absorption speed, rewet resistance, and thickness suppression when repeatedly absorbing liquid.

[0026] [Aspect 6] The absorbent article according to aspect 5, wherein the absorbent core has a skin side and a non-skin side, and the groove portion is disposed so as to be recessed from the skin side to the non-skin side.

[0027] In the absorbent article, the grooves are recessed from the skin-side surface to the non-skin-side surface, i.e., the grooves have voids on the skin-side surface, so that liquid that reaches the absorbent core can be rapidly diffused in the longitudinal direction through the voids in the grooves arranged on the skin-side surface of the absorbent core. As a result, in the absorbent article, the absorbent core can diffuse and absorb liquid in the longitudinal direction, thereby suppressing changes in the thickness of the absorbent core and, ultimately, the absorbent article.

[0028] [Aspect 7] The absorbent article according to aspect 5, wherein the absorbent core has a skin side and a non-skin side, and the groove portion is disposed so as to be recessed from the non-skin side to the skin side.

[0029] In the absorbent article, the grooves are recessed from the non-skin side to the skin side, i.e., the grooves have voids on the non-skin side, so that liquid that reaches the absorbent core is temporarily stored in the voids of the grooves, which are located on the non-skin side of the absorbent core and far from the skin, and then can be diffused in the longitudinal direction through the voids of the grooves. As a result, the absorbent article has excellent rewet resistance.

[0030] [Aspect 8] The absorbent article according to any one of aspects 1 to 7, wherein each of the plurality of low basis weight, low density portions has a basis weight that is 20 to 80% of that of the plurality of high basis weight, high density portions.

[0031] In the absorbent article, each of the plurality of low basis weight, low density portions has a predetermined basis weight. Therefore, the plurality of low basis weight, low density portions can temporarily retain liquid that reaches the plurality of low basis weight, low density portions, and facilitates the longitudinal diffusion of the liquid through the plurality of low basis weight, low density portions. Furthermore, liquid absorbed by the absorbent core is less likely to return to the skin-contacting surface of the absorbent article, such as the liquid-permeable sheet, through the plurality of low basis weight, low density portions. As a result, the absorbent article exhibits excellent absorption speed, rewet resistance, and thickness suppression when repeatedly absorbing liquid.

[0032] [Aspect 9] The absorbent article according to any one of aspects 1 to 8, wherein each of the plurality of low basis weight, low density portions has a density that is 20 to 80% of the density of the plurality of high basis weight, high density portions.

[0033] In the absorbent article, each of the plurality of low basis weight, low density portions has a predetermined density. Therefore, the plurality of low basis weight, low density portions can temporarily retain liquid that reaches the plurality of low basis weight, low density portions, and facilitates the longitudinal diffusion of the liquid through the plurality of low basis weight, low density portions. Furthermore, liquid absorbed by the absorbent core is less likely to return to the skin-contacting surface of the absorbent article, such as the liquid-permeable sheet, through the plurality of low basis weight, low density portions. As a result, the absorbent article exhibits excellent absorption speed, rewetability, and thickness suppression when repeatedly absorbing liquid.

[0034] [Aspect 10] The absorbent article according to any one of aspects 1 to 9, wherein the absorbent core contains the superabsorbent polymer particles in an average proportion of 40% by mass or more.

[0035] In the absorbent article, since the absorbent core contains the superabsorbent polymer particles at a predetermined ratio, when the absorbent core absorbs a certain amount of liquid, the superabsorbent polymer particles are easily crushed and more easily function as a retaining wall that maintains the shape of the multiple high-basis-weight, high-density portions. As a result, the absorbent article has superior absorption speed and thickness suppression when repeatedly absorbing liquid.

[0036] [Embodiment 11] The absorbent article according to any one of embodiments 1 to 10, wherein the superabsorbent polymer particles have a water retention capacity of 45 g / g or more under no pressure.

[0037] In the absorbent article, since the superabsorbent polymer particles have a predetermined water retention capacity, the multiple high-basis-weight, high-density portions of the absorbent core are more likely to retain liquid, and when the absorbent core has absorbed a certain amount of liquid, the superabsorbent polymer particles are more likely to function as retaining walls that maintain the shape of the multiple high-basis-weight, high-density portions.As a result, the absorbent article has superior repeated absorbency.

[0038] [Aspect 12] The absorbent article according to any one of Aspects 1 to 11, wherein at least some of the plurality of low basis weight, low density portions further include a plurality of secondary low basis weight, low density portions extending from the low basis weight, low density portion along the width direction and having edges.

[0039] In the absorbent article, the absorbent core has a predetermined secondary low-basis-weight, low-density portion in at least some of the multiple low-basis-weight, low-density portions. Therefore, the absorbent core can easily diffuse liquid that has been diffused in the longitudinal direction through the secondary low-basis-weight, low-density portion in the width direction, i.e., to the multiple high-basis-weight, high-density portions, through the secondary low-basis-weight, low-density portion. Furthermore, since the secondary low-basis-weight, low-density portion has edges and is unlikely to impede the continuous extension of the multiple high-basis-weight, high-density portions along the longitudinal direction, the multiple high-basis-weight, high-density portions can diffuse liquid that has migrated to the multiple high-basis-weight, high-density portions in the longitudinal direction through the multiple high-basis-weight, high-density portions. As a result, the absorbent article exhibits excellent absorption speed and thickness suppression when repeatedly absorbing liquid.

[0040] The absorbent article according to the present disclosure will be described in detail below. [Definitions] "Direction along a predetermined direction" In this specification, "direction along a predetermined direction" means a direction that has an intersecting angle of less than 45° with the predetermined direction. The direction along the predetermined direction means a direction that has an intersecting angle of preferably 30° or less, more preferably 20° or less, and even more preferably 5° or less with the predetermined direction. Examples of the predetermined direction include the longitudinal direction, width direction, and thickness direction. In this specification, when simply referring to something extending in a predetermined direction or (length) in a predetermined direction, this refers to a direction that has an intersecting angle of 0° with the predetermined direction.

[0041] 1 to 4 are diagrams illustrating an absorbent article, specifically a disposable diaper 1, according to one embodiment of the present disclosure (hereinafter, may be referred to as the "first embodiment"). Specifically, Fig. 1 is a plan view of the disposable diaper 1. Fig. 2 is a plan view of the absorbent body 7 of the disposable diaper 1 (a plan view of the skin side surface 11 of the absorbent core 9). Fig. 3 is a plan view of the skin side surface 11 of the absorbent core 9 of the disposable diaper 1. Fig. 4 is an end view taken along the line IV-IV in Fig. 3.

[0042] The disposable diaper 1 has a longitudinal direction L including a front direction FD and a rear direction RD, a width direction W, and a thickness direction T, which are perpendicular to each other. The disposable diaper 1 also has a longitudinal centerline LC that passes through the center of the width direction W of the disposable diaper 1 and extends parallel to the longitudinal direction L of the disposable diaper 1, and a widthwise centerline WC that passes through the center of the longitudinal direction L of the disposable diaper 1 and extends parallel to the width direction W of the disposable diaper 1.

[0043] The disposable diaper 1 comprises a liquid-permeable sheet 3, a liquid-impermeable sheet 5, and an absorber 7 between the liquid-permeable sheet 3 and the liquid-impermeable sheet 5. As shown in Fig. 1, the disposable diaper 1 comprises a pair of leakage barrier walls 101 including elastic members 103, fixing portions 105 for fixing the leakage barrier walls 101 to the liquid-permeable sheet 3, elastic members 107, tape fasteners 109, etc., but these are well known in the art and therefore will not be described here.

[0044] The absorbent body 7 has the same longitudinal direction L, width direction W and thickness direction T as the disposable diaper 1, which are perpendicular to each other, and is composed of an absorbent core 9 having a skin side 11 on the liquid-permeable sheet 3 side and a non-skin side 13 on the liquid-impermeable sheet 5 side, and a core wrap 15 made of tissue that covers the skin side 11 and non-skin side 13 of the absorbent core 9.

[0045] The absorbent core 9 contains pulp fibers 17 and superabsorbent polymer particles 19. The absorbent core 9 is partitioned into a first absorbent core portion 21 disposed forward (FD) of the widthwise centerline WC and a second absorbent core portion 23 disposed rearward (RD) of the widthwise centerline WC. The second absorbent core portion 23 has a relatively larger mass than the first absorbent core portion 21. The absorbent core 9 has a skin side surface 11 on the liquid-permeable sheet 3 side and a non-skin side surface 13 on the liquid-impermeable sheet 5 side.

[0046] The absorbent core 9 has two longitudinal grooves 25, specifically a right longitudinal groove 27 and a left longitudinal groove 29, which are arranged from the first absorbent core portion 21 to the second absorbent core portion 23 across the widthwise centerline WC and extend in the longitudinal direction L. The right longitudinal groove 27 and the left longitudinal groove 29 are arranged in order from right to left of the wearer. The right longitudinal groove 27 and the left longitudinal groove 29 are also arranged on the skin-side surface 11 of the absorbent core 9. That is, each of the right longitudinal groove 27 and the left longitudinal groove 29 is recessed from the skin-side surface 11 of the absorbent core 9 toward the non-skin-side surface 13, and has a gap (not indicated by a reference symbol) on the skin-side surface 11.

[0047] The absorbent core 9 has three vertical ribs 31 extending continuously in the longitudinal direction L, specifically, a right vertical rib 33, a central vertical rib 35, and a left vertical rib 37. The right vertical rib 33 is located to the right of the right vertical groove 27 and extends in the longitudinal direction L, the central vertical rib 35 is located between the right vertical groove 27 and the left vertical groove 29 and extends in the longitudinal direction L, and the left vertical rib 37 is located to the left of the left vertical groove 29 and extends in the longitudinal direction L. The right vertical rib 33, the central vertical rib 35, and the left vertical rib 37 each protrude in a direction from the non-skin side 13 toward the skin side 11 of the absorbent core 9.

[0048] The three vertical ribs 31 (right vertical rib 33, central vertical rib 35, and left vertical rib 37) extend in the longitudinal direction L and correspond to a plurality of high-basis-weight, high-density portions that have a relatively higher basis weight and density than the two vertical grooves 25 (right vertical groove 27 and left vertical groove 29). The two vertical grooves 25 (right vertical groove 27 and left vertical groove 29) extend in the longitudinal direction L and correspond to a plurality of low-basis-weight, low-density portions that have a lower basis weight and density than the three vertical ribs 31 (right vertical rib 33, central vertical rib 35, and left vertical rib 37).

[0049] The three vertical ribs 31 (right vertical rib 33, central vertical rib 35, and left vertical rib 37) and the two vertical grooves 25 (right vertical groove 27 and left vertical groove 29) are alternately arranged in the width direction W. The three vertical ribs 31 (right vertical rib 33, central vertical rib 35, and left vertical rib 37) have portions that are connected to each other in the width direction W (the connected portions are not shown). This makes it easier for the three vertical ribs 31 to spread absorbed liquid in the width direction W of the absorbent core 9. Furthermore, the two vertical grooves 25 (right vertical groove 27 and left vertical groove 29) are not connected to each other in the width direction W. This makes it less likely that the two vertical grooves 25 will hinder the liquid present in the three vertical ribs 31 from spreading through the three vertical ribs 31 in the longitudinal direction L.

[0050] Each of the three longitudinal ridges 31 and the two longitudinal grooves 25 contains superabsorbent polymer particles 19 that have a predetermined water retention capacity under no pressure and a predetermined water retention capacity under pressure. This allows the absorbent core 9 to diffuse the liquid in the longitudinal direction L through the two longitudinal grooves 25 when it absorbs a first liquid (e.g., body fluid). The liquid that diffuses in the longitudinal direction through the two longitudinal grooves 25 is then absorbed by the superabsorbent polymer particles 19 that exist in the three longitudinal ridges 31 and have a predetermined water retention capacity under no pressure, leaving the two longitudinal grooves 25 ready to absorb the next liquid.

[0051] When the absorbent core 9 absorbs liquid for the second or subsequent time, the two vertical grooves 25 diffuse the liquid in the longitudinal direction L, just as in the first liquid absorption, and the liquid diffused in the longitudinal direction L through the two vertical grooves 25 is absorbed by the highly absorbent polymer particles 19 present in the three vertical ridges 31, so that the two vertical grooves 25 themselves are ready to absorb the next liquid.

[0052] When the absorbent core 9 absorbs a certain amount of liquid, the highly absorbent polymer particles, which have a predetermined water retention capacity under pressure, collapse under pressure and can function as a retaining wall that maintains the shape of the three vertical ridges 31. As a result, the gaps between the two vertical grooves 25 are less likely to be compressed by the three vertical ridges 31, and even when the absorbent core has absorbed a certain amount of liquid, the liquid can be dispersed in the longitudinal direction through the two vertical grooves 25.

[0053] The absorbent core 9 also contains a predetermined proportion or more of the superabsorbent polymer particles 19. As a result, when the absorbent core 9 absorbs a certain amount of liquid, the superabsorbent polymer particles 19 are appropriately crushed under pressure, and are more likely to function as a retaining wall that maintains the shape of the three vertical ridges 31.

[0054] The superabsorbent polymer particles 19 have a predetermined liquid permeation rate. As a result, the superabsorbent polymer particles 19 that have absorbed liquid are less likely to inhibit the movement of new liquid in the planar direction beyond the superabsorbent polymer particles in the three longitudinal ridges 31 and two longitudinal grooves 25. As a result, the disposable diaper 1 is more likely to absorb liquid throughout the entire absorbent core 9, making it easier to suppress changes in the thickness of the absorbent core 9, and ultimately the thickness of the disposable diaper 1, when liquid is absorbed.

[0055] The right longitudinal groove 27 and the left longitudinal groove 29 each have a plurality of minor grooves (not numbered) extending in the width direction W. Each of the minor grooves has an edge, is recessed from the skin side 11 of the absorbent core 9 toward the non-skin side 13, and has a void (not numbered) in the skin side 11. Each of the minor grooves has a lower basis weight and density than the three longitudinal ridges 31, which correspond to the plurality of high basis weight, high density portions, and corresponds to a low basis weight, low density portion. This makes it easier for the absorbent core 9 to diffuse liquid that has been diffused in the longitudinal direction L through the two longitudinal grooves 25 in the width direction W, i.e., to the three vertical ridges 31, through the minor grooves.

[0056] The right vertical groove 27 is composed of a right vertical groove first narrow portion 27a arranged in the first absorbent core portion 21 and a right vertical groove second wide portion 27b arranged continuously from the first absorbent core portion 21 to the second absorbent core portion 23. The right vertical groove first narrow portion 27a and the right vertical groove second wide portion 27b have a connecting portion (not shown) that directly connects them, and the width W of the right vertical groove first narrow portion 27a in the width direction W is 27a and the width W of the second wide portion 27b of the right longitudinal groove in the width direction W. 27b The relationship between the width W and the thickness W is as follows: 27b >Width W 27a

[0057] The left vertical groove 29 is composed of a left vertical groove first narrow portion 29a arranged in the first absorbent core portion 21 and a left vertical groove second wide portion 29b arranged continuously from the first absorbent core portion 21 to the second absorbent core portion 23. The left vertical groove first narrow portion 29a and the left vertical groove second wide portion 29b have a connecting portion (not shown) that directly connects them, and the width W of the left vertical groove first narrow portion 29a in the width direction W is 29a and the width W of the second wide portion 29b of the left vertical groove in the width direction W. 29b The relationship between the width W and the thickness W is as follows: 29b >Width W 29a

[0058] Because the first narrow portion 25a of the right vertical groove and the second wide portion 25b of the right vertical groove have a connecting portion (not shown) that directly connects them, and because the first narrow portion 29a of the left vertical groove and the second wide portion 29b of the left vertical groove have a connecting portion (not shown) that directly connects them, the disposable diaper 1 is more likely to have an excellent absorption rate when repeatedly absorbing body fluids, and the absorbent core 9 is less likely to become thick.

[0059] The right vertical groove first narrow portion 27a and the right vertical groove second wide portion 27b have a width W 27b >Width W 27a By satisfying the relationship, the first narrow portion 29a of the left vertical groove and the second wide portion 29b of the left vertical groove have a width W 29b >Width W 29aBy satisfying the above relationship, the disposable diaper 1 is likely to have a superior absorption rate when repeatedly absorbing body fluids, and the absorbent core 9 is unlikely to become thick.

[0060] In the absorbent core 9, the first absorbent core portion 21 has a region (not shown) in which the right vertical groove first narrow portion 27a and the left vertical groove first narrow portion 29a are each disposed so as to be farther away from the longitudinal centerline LC the closer they are to the end on the front FD side of the absorbent core 9. This makes it easier for the first absorbent core portion 21 to diffuse body fluids outward in the width direction W of the first absorbent core portion 21, making it easier for the entire first absorbent core portion 21 to absorb body fluids.

[0061] The absorbent core 9 has, on the skin side 11, six vertical grooves 39 arranged only in the first absorbent core portion 21 and two vertical grooves 41 arranged only in the second absorbent core portion 23, but explanation of these will be omitted.

[0062] 4, the three vertical ridges 31 corresponding to the high basis weight, high density portion have a higher basis weight and density than the two vertical grooves 25 corresponding to the low basis weight, low density portion. This allows the two vertical grooves 25 to temporarily retain liquid that reaches them, and also makes it easier for the liquid to diffuse in the longitudinal direction L through the two vertical grooves 25.

[0063] The absorbent article according to the present disclosure is not particularly limited as long as it comprises an absorbent core containing pulp fibers and superabsorbent polymer particles, and examples thereof include disposable diapers, urine absorption pads, incontinence pads, incontinence liners, etc. The above-mentioned absorbent articles generally comprise a liquid-permeable top sheet having a skin-contacting surface, a liquid-impermeable back sheet, and an absorbent core disposed therebetween.

[0064] The absorbent article according to the present disclosure has a longitudinal direction, a width direction, and a thickness direction that are perpendicular to each other. In the present disclosure, the longitudinal direction, the width direction, and the thickness direction refer to the longitudinal direction, the width direction, and the thickness direction of the absorbent article, respectively, unless otherwise specified. Note that the absorbent core according to the present disclosure often has the same longitudinal direction and width direction as the longitudinal direction and width direction, respectively, of the absorbent article.

[0065] In the absorbent article according to the present disclosure, the absorbent core has a skin-side surface and a non-skin-side surface and may contain pulp fibers, superabsorbent polymer particles, etc. The absorbent core can be arranged as an absorbent body comprising the absorbent core and a core wrap covering the absorbent core from the skin-side surface and / or the non-skin-side surface. Examples of the core wrap include those known in the art, such as tissue and nonwoven fabrics (e.g., spunbond nonwoven fabrics, SMS nonwoven fabrics, spunlace nonwoven fabrics, etc.). The manufacturing method of the absorbent core is not particularly limited, and examples thereof include those that are integrally molded.

[0066] In the absorbent article according to the present disclosure, the absorbent core contains highly absorbent polymer particles, preferably at a density of 50 g / m 2 More preferably, 100 g / m 2 The absorbent core preferably contains highly absorbent polymer particles at an average basis weight of 400 g / m or more. 2 or less, and more preferably 100 to 350 g / m 2 The absorbent core comprises pulp fibres at an average basis weight of preferably 50 g / m 2 More preferably, 100 g / m 2 The absorbent core preferably contains pulp fibers at an average basis weight of 400 g / m or more. 2 or less, and more preferably 350 g / m 2 Includes the following average basis weights:

[0067] The absorbent core can contain pulp fibers and superabsorbent polymer particles in any average ratio. The absorbent core preferably contains the superabsorbent polymer particles in an average ratio of 20% by weight or more, more preferably 30% by weight or more, and even more preferably 40% by weight or more. The absorbent core also preferably contains the superabsorbent polymer particles in an average ratio of 80% by weight or less, more preferably 70% by weight or less, and even more preferably 60% by weight or less. This makes it easier for the superabsorbent polymer particles to collapse when the absorbent core absorbs a certain amount of liquid, and the multiple high-basis-weight, high-density portions can function as retaining walls.

[0068] In the present disclosure, the average basis weight of the absorbent core, the superabsorbent polymer particles, and the pulp fibers, as well as the average ratio of the superabsorbent polymer particles, are measured as follows: (1) The absorbent core is removed from the absorbent article by a method known in the art, and a sample A having a predetermined size (e.g., 5 cm x 5 cm) is cut out. After drying in an atmosphere of 100°C or higher, the mass of the sample A: m A (g) and the area of ​​sample A: S A (m 2 (2) Basis weight of sample A: bs A (g / m 2 ) into the following formula: A (g / m 2 ) = m A / S A It is calculated as follows.

[0069] (3) The same measurement was repeated 10 times, and the basis weight of the 10 samples A was measured: bs A (g / m 2 ) is the average basis weight of the absorbent core: BS A (g / m 2 (4) A sample B of a predetermined size (for example, 4 mm x 4 mm) is cut out from the absorbent core, dried in an atmosphere of 100°C or higher, and then the mass of the sample B: m B (5) The pulp fibers and the superabsorbent polymer particles contained in sample B are separated, and the mass of the pulp fibers: m pf (g) and m of the highly absorbent polymer particles sap (g) and are measured.

[0070] (6) Basis weight of pulp fiber in sample B: bs pf (g / m 2 ) into the following formula: pf (g / m 2 ) = B.S. A ×m pf / m B (7) The same measurement is repeated 10 times, and the basis weight of the 10 pulp fibers is calculated as follows: pf (g / m 2 ) is the average basis weight of the pulp fiber: BS pf (g / m 2(8) Basis weight of the highly absorbent polymer particles in sample B: bs sap (g / m 2 ) into the following formula: sap (g / m 2 ) = B.S. A ×m sap / m B (9) The same measurement is repeated 10 times, and the basis weight of the 10 highly water-absorbent polymer particles is calculated as follows: sap (g / m 2 ) is the basis weight of the highly absorbent polymer particles: BS sap (g / m 2 (10) The average ratio of the highly water-absorbent polymer particles: AR (mass%) is calculated by the following formula: AR (mass%) = 100 × BS sap / BS A It is calculated as follows.

[0071] The absorbent core has a plurality of high basis weight, high density portions extending continuously in the longitudinal direction and a plurality of low basis weight, low density portions extending in the longitudinal direction, the plurality of high basis weight, high density portions and the plurality of low basis weight, low density portions being alternately arranged in the width direction.

[0072] The multiple high basis weight, high density portions spaced apart from one another in the width direction may or may not be connected to one another in the width direction. It is preferable that the multiple high basis weight, high density portions spaced apart from one another in the width direction are connected to one another in the width direction. This makes it easier for the high basis weight, high density portions to diffuse absorbed liquid in the planar direction of the absorbent core, particularly in the width direction, and when liquid is repeatedly absorbed, the absorbent core, and ultimately the absorbent article, will have excellent thickness suppression properties. Note that the multiple high basis weight, high density portions spaced apart from one another in the width direction may be connected to one another, for example, at the longitudinal ends of the absorbent core, for example, at both ends.

[0073] The plurality of low basis weight, low density portions spaced apart from one another in the width direction may or may not be connected to one another in the width direction. It is preferable that the plurality of low basis weight, low density portions spaced apart from one another in the width direction are not connected to one another in the width direction. This makes it difficult for the plurality of high basis weight, high density portions to inhibit liquid present within the plurality of high basis weight, high density portions from diffusing in the longitudinal direction through the interiors of the plurality of high basis weight, high density portions. As a result, the absorbent article has superior thickness suppression properties when repeatedly absorbing liquid.

[0074] Each of the plurality of high-basis-weight, high-density portions is preferably arranged continuously in the longitudinal direction over a range of preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, and even more preferably 80% or more of the longitudinal length of the absorbent core. The plurality of high-basis-weight, high-density portions is also preferably arranged continuously in the longitudinal direction over a range of 100% or less of the longitudinal length of the absorbent core. This allows the plurality of high-basis-weight, high-density portions to easily diffuse liquid that has migrated into the plurality of high-basis-weight, high-density portions in the longitudinal direction through the plurality of high-basis-weight, high-density portions.

[0075] Each of the plurality of low basis weight, low density portions is preferably arranged continuously in the longitudinal direction over a range of preferably 30% or more, more preferably 40% or more, even more preferably 45% or more, and even more preferably 50% or more of the longitudinal length of the absorbent core. The plurality of high basis weight, high density portions is preferably arranged continuously in the longitudinal direction over a range of preferably 100% or less, more preferably 80% or less, and even more preferably 70% or less of the longitudinal length of the absorbent core. This allows the plurality of high basis weight, high density portions to easily diffuse liquid that has migrated into the plurality of high basis weight, high density portions in the width direction through the plurality of high basis weight, high density portions.

[0076] Each of the plurality of high basis weight, high density portions has a higher basis weight and a higher density than each of the plurality of low basis weight, low density portions. Each of the plurality of low basis weight, low density portions is not a void (e.g., a slit) but contains pulp fibers, superabsorbent polymer particles, etc., and has a density of 0 g / m 2 It has a basis weight of over 10 ...

[0077] Each of the plurality of low basis weight, low density portions preferably has a basis weight of at least 10%, more preferably at least 20%, and even more preferably at least 30% of the basis weight of the plurality of high basis weight, high density portions. Furthermore, each of the plurality of low basis weight, low density portions preferably has a basis weight of at most 90%, more preferably at most 80%, and even more preferably at most 70% of the basis weight of the plurality of high basis weight, high density portions. This allows the plurality of low basis weight, low density portions to temporarily retain liquid that reaches the plurality of low basis weight, low density portions and facilitates the longitudinal diffusion of liquid through the plurality of low basis weight, low density portions. Furthermore, liquid absorbed by the absorbent core is less likely to pass through the plurality of low basis weight, low density portions and return to the skin-contacting surface of the absorbent article, such as a liquid-permeable sheet.

[0078] In the present disclosure, the basis weights of the high basis weight, high density portion and the low basis weight, low density portion are measured as follows: (1) A rubber plate is placed on a stable table, and the absorbent article from which the elastic members have been removed is spread out on the rubber plate in a wrinkle-free state, and the four corners are fixed with weights. The high basis weight, high density portion is measured by measuring the area: S (m 2 The upper and lower sheet members (e.g., a liquid-permeable sheet, a liquid-impermeable sheet, a core wrap, etc.) are punched out together using a punch having a hole diameter of 15 mm (e.g., a punch having an inner diameter of 15 mm, a punch for a long hole of 18 mm x 3 mm, etc.) to obtain a sample.

[0079] (2) The sample is immersed in a sufficient amount of toluene in a glass beaker, and the sample is stirred occasionally, and components other than the absorbent core (e.g., the separated sheet member) are removed with tweezers. (3) After 30 minutes of immersion of the sample in toluene, the contents of the glass beaker are filtered through filter paper to remove the toluene and separate the contents of the absorbent core (e.g., pulp fibers and superabsorbent polymer particles). (4) The separated contents of the absorbent core are washed by repeating the process of immersing in toluene for 5 minutes and filtering three times.

[0080] (5) After absorbing excess toluene from the contents of the washed absorbent core with dry filter paper, the contents of the absorbent core are dried in an explosion-proof oven at 40°C for 1 hour while ventilating, and the mass of the dried contents of the absorbent core: m1 (g) is measured with a precision balance. (6) Basis weight of the sample: BW (g / m 2 ) is calculated by the following formula: BW (g / m 2 )=m1(g) / S(m 2 (7) The average of the basis weights of the 10 samples is taken as the basis weight of the high basis weight, high density portion. (8) The basis weight of the low basis weight, low density portion is measured in the same manner as the basis weight of the high basis weight, high density portion.

[0081] Each of the plurality of low basis weight low density portions is 0 g / m 3 Each of the plurality of low basis weight, low density portions has a density of preferably 20% or more, more preferably 30% or more, and even more preferably 40% or more of the density of the plurality of high basis weight, high density portions. Furthermore, each of the plurality of high basis weight, low density portions has a density of preferably 80% or less, more preferably 70% or less, and even more preferably 60% or less. This allows the plurality of low basis weight, low density portions to temporarily retain liquid that reaches the plurality of low basis weight, low density portions, and facilitates the longitudinal diffusion of liquid through the plurality of low basis weight, low density portions. Furthermore, liquid absorbed by the absorbent core is less likely to pass through the plurality of low basis weight, low density portions and return to the skin-contacting surface of the absorbent article, such as a liquid-permeable sheet.

[0082] It should be noted that when each of the plurality of low basis weight and low density portions is a gap (for example, a slit), that is, when the basis weight is 0 g / m 2and the density is 0 g / m 3 In this case, the liquid absorbed by the absorbent core tends to return to the skin contact surface of the absorbent article via the low basis weight, low density portion, and the rewet resistance tends to be poor.

[0083] In the present disclosure, the densities of the high basis weight, high density portion and the low basis weight, low density portion are measured as follows: (1) A cold spray is sprayed onto the absorbent article, and the liquid-permeable sheet, the liquid-impermeable sheet, and the core wrap are peeled off to obtain an absorbent core. (2) The thickness: T (m) of the high basis weight, high density portion is measured in a non-contact manner using a laser displacement meter (for example, a high-precision two-dimensional laser displacement meter LJ-G series (model: LJ-G030) manufactured by Keyence Corporation).

[0084] (3) Density of high-weight, high-density portion: D (g / m 3 ) is calculated by the following formula: D (g / m 3 ) = BW (g / m 2 ) / T(m) where BW (g / m 2 ) is the value calculated in the above "Basis weight of the high basis weight high density portion and the low basis weight low density portion." (4) The average basis weight of the 10 samples is taken as the density of the high basis weight high density portion. (5) The density of the low basis weight low density portion is measured in the same manner as the density of the high basis weight high density portion.

[0085] Each of the plurality of low basis weight, low density portions is preferably a groove portion recessed in the thickness direction. Also, each of the plurality of high basis weight, high density portions is preferably a ridge portion protruding in the thickness direction. This makes it easier for the absorbent article to have excellent absorption rate, rewet resistance, and thickness suppression when repeatedly absorbing liquid.

[0086] The grooves preferably have a width (length in the width direction) of 1.0 mm or more, more preferably 1.5 mm or more, and even more preferably 2.0 mm or more. The grooves preferably have a width (length in the width direction) of 8.0 mm or less, more preferably 7.0 mm or less, and even more preferably 6.0 mm or less. This makes it easier to diffuse liquid in the longitudinal direction through the multiple low basis weight, low density portions.

[0087] The grooves have a height (length in the thickness direction) of preferably 20 to 80%, more preferably 30 to 70%, and even more preferably 40 to 60% of the height of the ridges, which makes it easier to spread the liquid in the longitudinal direction through the multiple low basis weight, low density portions.

[0088] In the present disclosure, the width of a groove portion (including a narrow portion and a wide portion) is measured as follows: (1) After immersing an absorbent article in liquid nitrogen to freeze it, the absorbent article is cut using a razor or the like at multiple locations passing through the groove portion to obtain multiple cross-sectional samples. The multiple cross-sectional samples are formed in both the width and thickness directions. (2) The multiple cross-sectional samples are returned to room temperature, and cross-sectional images are obtained at 50x magnification using an electron microscope (e.g., Keyence VE7800). The width of the groove portion on the surface (skin-side or non-skin-side) is then determined from the multiple cross-sectional images. (3) The average value of the groove widths for 10 samples is adopted as the groove width. (4) Optional minor groove portions are also measured in the same manner, except that multiple cross-sectional samples (formed in the longitudinal and thickness directions) are obtained from the absorbent article at multiple locations passing through the minor groove portion.

[0089] In the present disclosure, the height of the groove portion can be measured according to the method for measuring the thickness T (m) of the high basis weight, high density portion in the above-mentioned method for measuring the "density of the high basis weight, high density portion and the low basis weight, low density portion."

[0090] The ridges and grooves are arranged on the skin-side surface of the absorbent core, and the ridges can protrude in the thickness direction from the non-skin side to the skin-side surface of the absorbent core, and the grooves can be recessed in the thickness direction from the skin-side surface to the non-skin side of the absorbent core, i.e., have voids on the skin-side surface, allowing liquid that reaches the absorbent core to be rapidly diffused in the longitudinal direction through the voids in the grooves arranged on the skin-side surface of the absorbent core.

[0091] The ridges and grooves are arranged on the non-skin side of the absorbent core, and the ridges can protrude in the thickness direction from the skin side to the non-skin side of the absorbent core, and the grooves can be recessed in the thickness direction from the non-skin side to the skin side of the absorbent core, i.e., the non-skin side can have voids. This allows liquid that reaches the absorbent core to be temporarily stored in the voids of the grooves, which are arranged on the non-skin side of the absorbent core and are positioned far from the skin, and then to be diffused in the longitudinal direction through the voids of the grooves.

[0092] The superabsorbent polymer particles have a water retention capacity of 43 g / g or more, preferably 44 g / g or more, more preferably 45 g / g or more, even more preferably 46 g / g or more, and even more preferably 47 g / g or more under no pressure. The superabsorbent polymer particles also have a water retention capacity of 55 g / g or less, and more preferably 50 g / g or less under no pressure. This allows the multiple high-basis-weight, high-density portions to function more easily as retaining walls that maintain the shape of the multiple high-basis-weight, high-density portions.

[0093] In this specification, the water retention capacity of superabsorbent polymer particles under no pressure is measured as follows: (1) A sample of superabsorbent polymer particles is left standing in a constant temperature and humidity chamber at a temperature of 20±5°C and a humidity of 65±5% RH for 24 hours. (2) In the constant temperature and humidity chamber, a sample having a mass of about 20 mg (m 11 (g) is accurately weighed, and about 3.0 mL (about 150 times the mass of the sample) of physiological saline (0.9% by mass aqueous sodium chloride solution) is added to the weighed sample and left to stand for 3 hours to swell the sample. (3) The sample is placed in a bag made of nylon mesh with 75 μm openings, and the bag containing the sample is dehydrated in a centrifuge at 150 G for 90 seconds.

[0094] (4) Take a sample out of the bag and measure its mass: m 12 (5) Water retention capacity of sample: W HR (g / g) is calculated using the following formula: HR (g / g) = (m 12 -m 11 ) / m 11(6) Repeat steps (1) to (5) three times with different samples, and calculate the water retention capacity: W HR The average of these values ​​is used as the water retention capacity under no pressure.

[0095] The superabsorbent polymer particles have a water retention capacity of 25 g / g or less, preferably 24 g / g or less, more preferably 23 g / g or less, even more preferably 22 g / g or less, and even more preferably 21 g / g or less under a pressure of 2 kPa. The superabsorbent polymer particles also have a water retention capacity of 18 g / g or more, more preferably 19 g / g or more, and even more preferably 20 g / g or more under a pressure of 2 kPa. This allows the multiple high-basis-weight, high-density portions to function more easily as retaining walls that maintain the shapes of the multiple high-basis-weight, high-density portions.

[0096] In this specification, the water retention capacity of superabsorbent polymer particles under a pressure of 2 kPa is measured as follows: (1) A sample of superabsorbent polymer particles is left to stand for 24 hours in a constant temperature and humidity chamber at a temperature of 20±5°C and a humidity of 65±5% RH. (2) In the constant temperature and humidity chamber, a column is prepared by fixing a 250-mesh wire netting to the bottom end of a vertically standing cylinder having an inner diameter of 25 mm, and the mass of the column is measured. 21 (3) Measure the mass of the sample (m) (approximately 0.35 g). 22 (g) is accurately weighed, and the weighed sample is placed in the column so that the thickness is uniform. A weight (mass: m) with an outer diameter slightly smaller than the inner diameter of the column is placed so that the pressure applied to the sample is 2.0 kPa. 23 (g)) is placed on top of the sample.

[0097] (4) 70 mL of saline (0.9% by mass sodium chloride aqueous solution) is poured into a 100 mL beaker. Next, the column containing the sample and a weight is immersed in the saline so that the wire mesh does not contact the bottom of the beaker, and left to stand for 1 hour. (5) After leaving it to stand for 1 hour, the column is removed from the beaker, and the water is drained for 15 minutes with the weight placed on the sample. The mass of the column including the sample and weight: m 24(6) Water retention capacity of the highly water-absorbent polymer particles: W HRP (g / g) is calculated using the following formula: HRP (g / g) = (m 24 -m 23 -m 21 ) / m 22 (7) Repeat steps (1) to (6) three times with different samples, and calculate the water retention capacity: W HRR The average of these values ​​is used as the water retention capacity under pressure.

[0098] The superabsorbent polymer particles preferably have a liquid permeation rate of 1.0 g / 60 sec or more, more preferably 2.0 g / 60 sec or more, and even more preferably 2.5 g / 60 sec or more. The superabsorbent polymer particles also preferably have a liquid permeation rate of 12.0 g / 60 sec or less, more preferably 10.0 g / 60 sec or less, and even more preferably 8.0 g / 60 sec or less. This makes it difficult for the superabsorbent polymer particles to inhibit the longitudinal diffusion of liquid present in each of the low basis weight, low density portions, and also makes it difficult for the superabsorbent polymer particles to inhibit the longitudinal diffusion of liquid present in each of the high basis weight, high density portions.

[0099] In this specification, the liquid permeation rate is measured as follows. (1) A sample of superabsorbent polymer particles is left to stand for 24 hours in a constant temperature and humidity chamber at a temperature of 20±5°C and a humidity of 65±5% RH. (2) In the constant temperature and humidity chamber, a column is prepared by fixing a 250-mesh wire mesh to the bottom end of a vertically standing cylinder with an inner diameter of 25 mm. (3) The sample is placed on a sieve with 150 μm openings and sieved 30 times, and 0.2 g of the sample remaining on the sieve is placed in the column so as to have a uniform thickness.

[0100] (4) Pour 100 mL of saline (0.9% by mass sodium chloride aqueous solution) into a 100 mL beaker. Next, immerse the column containing the sample in saline so that the wire mesh does not contact the bottom of the beaker and let it stand for 30 minutes. (5) After leaving it standing for 30 minutes, remove the column from the saline and place it on a wire mesh placed on a petri dish. A 200 g weight with an outer diameter slightly smaller than the inner diameter of the column is placed on top of the sample, and let it stand for 3 minutes.

[0101] (6) After leaving it for 3 minutes, the column together with the wire mesh is moved onto a new petri dish and left to stand for 30 seconds. The mass of the saline solution accumulated on the new petri dish is: m 31 (g) was measured and converted to a value (m 31 (7) Repeat steps (1) to (6) three times for different samples, and use the average of the liquid passing speeds S for the three samples as the liquid passing speed.

[0102] Examples of the superabsorbent polymer particles include superabsorbent polymer particles such as polyacrylate-based, polysulfonate-based, maleic anhydride-based, polyacrylamide-based, polyvinyl alcohol-based, polyethylene oxide-based, polyaspartate-based, polyglutamate-based, polyalginate-based, starch-based, and cellulose-based particles; and starch-based or cellulose-based superabsorbent polymer particles such as starch-acrylic acid (salt) graft copolymer, saponified starch-acrylonitrile copolymer, and crosslinked product of sodium carboxymethyl cellulose.

[0103] The superabsorbent polymer particles satisfying the above-mentioned water retention capacity under no pressure, water retention capacity under pressure, and desired liquid permeability can be formed by adjusting the degree of crosslinking inside the superabsorbent polymer particles. For example, the superabsorbent polymer particles according to the present disclosure can be formed by reducing the degree of crosslinking inside commercially available superabsorbent polymer particles. Examples of the commercially available superabsorbent polymer particles include AQUALIC CA from Nippon Shokubai Co., Ltd. and AQUAKEEP from Sumitomo Seika Chemicals Co., Ltd.

[0104] The pulp fibers may be any known pulp fiber in the art, and include, without limitation, wood pulp fibers and non-wood pulp fibers. Examples of the wood pulp fibers include softwood pulp fibers and hardwood pulp fibers. Examples of the non-wood pulp fibers include straw pulp fibers, bagasse pulp fibers, reed pulp fibers, kenaf pulp fibers, mulberry pulp fibers, bamboo pulp fibers, hemp pulp fibers, and cotton pulp fibers (e.g., cotton linter fibers).

[0105] The absorbent core according to the present disclosure may further include other materials known in the art, such as fibers other than pulp fibers, such as natural fibers, synthetic fibers, and semi-synthetic fibers. Examples of natural fibers include regenerated cellulose fibers. Examples of regenerated cellulose fibers include rayon fibers, such as viscose rayon, polynosic, and modal obtained from viscose; cuprammonium rayon fibers (also known as "cupra") obtained from a cuprammonium salt solution of cellulose; and lyocell and tencel, which are obtained by an organic solvent spinning method using an organic solvent, which is a mixed solution of organic compounds and water, without first undergoing cellulose derivatization. Examples of semi-synthetic fibers include semi-synthetic cellulose fibers, such as acetate fibers, such as triacetate and diacetate fibers.

[0106] At least some of the plurality of low-basis-weight, low-density portions may further comprise a plurality of secondary low-basis-weight, low-density portions. Each of the plurality of secondary low-basis-weight, low-density portions extends from the low-basis-weight, low-density portion along the width direction and has an edge, i.e., is not connected to other low-basis-weight, low-density portions. This makes it easier for the absorbent core to diffuse liquid that has been diffused longitudinally through the low-basis-weight, low-density portions in the width direction, i.e., to the plurality of high-basis-weight, high-density portions. The width (length in the longitudinal direction of the absorbent article) of each of the plurality of secondary low-basis-weight, low-density portions is preferably narrower than the width (length in the width direction of the absorbent article) of the low-basis-weight, low-density portion that comprises the secondary low-basis-weight, low-density portion. This is to diffuse bodily fluid in the longitudinal direction.

[0107] The absorbent article according to the present disclosure may have a widthwise centerline passing through the center of the absorbent article in the longitudinal direction and extending in the width direction of the absorbent article. The absorbent article according to the present disclosure may also have a lengthwise centerline passing through the center of the absorbent article in the width direction and extending in the longitudinal direction of the absorbent article.

[0108] In the present disclosure, the widthwise centerline and the longitudinal centerline refer to the widthwise centerline and the longitudinal centerline of the absorbent article, respectively. In particular, it should be noted that the widthwise centerline defining the first and second absorbent core portions of the absorbent core, which will be described later, is the widthwise centerline of the absorbent article.

[0109] The absorbent core according to the present disclosure can be divided into a first absorbent core portion forward of the widthwise centerline and a second absorbent core portion rearward of the widthwise centerline. In the absorbent core, the first absorbent core portion and the second absorbent core portion can be divided into the second absorbent core portion having a relatively small mass and the first absorbent core portion having a relatively large mass (i.e., the first absorbent core portion having a larger mass than the second absorbent core portion). This makes it less likely that the absorbent article will cause discomfort in the buttocks of the wearer when repeatedly absorbing body fluids.

[0110] In this case, the first absorbent core portion has a mass greater than that of the second absorbent core portion by preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 15% by mass or more. The first absorbent core portion has a mass greater than that of the second absorbent core portion by preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. This makes it less likely that the absorbent article will cause discomfort in the buttocks of the wearer when repeatedly absorbing body fluids.

[0111] In the absorbent core, the first absorbent core portion and the second absorbent core portion can be partitioned into a first absorbent core portion having a relatively small mass and a second absorbent core portion having a relatively large mass (i.e., a second absorbent core portion having a larger mass than the first absorbent core portion), thereby making it less likely that the absorbent article will cause discomfort in the groin area of ​​the wearer when repeatedly absorbing body fluids.

[0112] In this case, the second absorbent core portion preferably has a mass greater than that of the first absorbent core portion by at least 1% by weight, more preferably at least 5% by weight, and even more preferably at least 15% by weight. The second absorbent core portion preferably has a mass greater than that of the first absorbent core portion by at most 60% by weight, more preferably at most 50% by weight, and even more preferably at most 45% by weight. This allows the wide portions of the longitudinal grooves (described below) to more easily spread the body fluid (e.g., urine) toward the second absorbent core portion, which has a relatively large mass, and the narrow portions of the longitudinal grooves to more difficultly spread the body fluid toward the first absorbent core portion, which has a relatively small mass.

[0113] In this specification, the mass of the first absorbent core portion and the mass of the second absorbent core portion can be compared by removing the absorbent core from the absorbent article by methods known in the art and directly measuring the mass of the first absorbent core portion and the mass of the second absorbent core portion.

[0114] In the absorbent core according to the present disclosure, each of the plurality of low basis weight, low density portions may be disposed continuously from the first absorbent core portion to the second absorbent core portion across the widthwise centerline. The plurality of low basis weight, low density portions may be disposed symmetrically with respect to the longitudinal centerline.

[0115] When each of the plurality of low basis weight, low density portions is a groove recessed in the thickness direction, the groove may have a relatively narrow portion disposed in the first absorbent core portion and a relatively wide portion (i.e., a wide portion wider than the narrow portion) disposed in the second absorbent core portion, thereby providing the absorbent article with excellent absorption rate and thickness suppression properties when the absorbent article repeatedly absorbs body fluids.

[0116] The wide portion preferably has a width of 4.0 mm or more, more preferably 4.5 mm or more, and even more preferably 5.0 mm or more, and preferably has a width of 8.0 mm or less, more preferably 7.5 mm or less, and even more preferably 7.0 mm or less.

[0117] The narrow portion has a width smaller than that of the wide portion, and is preferably 2.0 mm or more, more preferably 2.5 mm or more, and even more preferably 3.0 mm or more. The narrow portion has a width smaller than that of the wide portion, and is preferably 6.0 mm or less, more preferably 5.5 mm or less, and even more preferably 5.0 mm or less.

[0118] The wide portion has a width greater than that of the narrow portion, preferably 1.0 mm or more, more preferably 1.3 mm or more, and even more preferably 1.5 mm or more. The wide portion also has a width greater than that of the narrow portion, preferably 3.0 mm or less, more preferably 2.7 mm or less, and even more preferably 2.5 mm or less. This allows the absorbent article to have excellent absorption rate and thickness suppression when repeatedly absorbing body fluids.

[0119] The narrow portion and the wide portion may have the same depth (depth in the thickness direction of the absorbent article), which makes it easier to achieve the effects of the present invention. Furthermore, the narrow portion of the vertical groove and the wide portion of the vertical groove may have a depth greater than the depth of the narrow portion, which makes it easier to achieve the effects of the wide portion and the narrow portion.

[0120] The absorbent article has an excretory-portion-contacting area that contacts the wearer's excretory portion, and the absorbent core has an excretory-portion-contacting-area-equivalent area that corresponds to the excretory-portion-contacting area, and the excretory-portion-contacting-area-equivalent area completely overlaps the excretory-portion-contacting area in the thickness direction of the absorbent article.

[0121] In the groove, the narrow and wide portions do not need to be directly connected as long as they are connected via a region corresponding to the excretory opening contact area. This is because the effects of the present disclosure can be achieved as long as the narrow and wide portions are connected via the region corresponding to the excretory opening contact area, since bodily fluid excreted from the wearer's excretory opening reaches the region corresponding to the excretory opening contact area of ​​the absorbent core from the region corresponding to the excretory opening contact area of ​​the absorbent article.

[0122] In the absorbent core according to the present disclosure, the groove preferably has a connecting portion that directly connects the narrow portion and the wide portion, thereby providing the absorbent article with a high absorption rate and preventing the absorbent core from becoming thick when repeatedly absorbing body fluids.

[0123] In the absorbent core according to the present disclosure, when the narrow portion and the wide portion have the connecting point, the connecting point is preferably located at the third portion of the first absorbent core, the widthwise centerline, or the first portion of the second absorbent core, thereby providing excellent absorption rate and thickness suppression when the absorbent article repeatedly absorbs body fluids.

[0124] In addition, when the above-mentioned groove portion further comprises a subsidiary groove portion, and the width of the groove portion changes in front of and behind the subsidiary groove portion (i.e., there is a narrow portion in front of the groove portion and a wide portion behind the groove portion), the narrow portion and the wide portion are deemed to start at the longitudinal center of the subsidiary groove portion.

[0125] The absorbent core according to the present disclosure may have a region in the second absorbent core portion in which the wide portions of the grooves are positioned so as to be farther from the longitudinal centerline as they approach the ends of the absorbent core, thereby facilitating the second absorbent core portion to diffuse body fluids outward in the width direction of the second absorbent core portion, and facilitating the absorption of body fluids by the entire second absorbent core portion.

[0126] The absorbent core according to the present disclosure may have a region in the first absorbent core portion where the narrow portions of the grooves are positioned so as to be farther from the longitudinal centerline as they approach the ends of the absorbent core, thereby facilitating the first absorbent core portion to diffuse body fluids outward in the width direction of the first absorbent core portion, and facilitating the absorption of body fluids by the entire first absorbent core portion.

[0127] The absorbent core may have any external shape commonly used in the art, such as a rectangular shape or an hourglass shape with a pair of waisted portions. When the absorbent core has an hourglass shape with a pair of waisted portions, the pair of waisted portions are preferably located in the first absorbent core portion. This allows the absorbent article to have a high absorption rate when repeatedly absorbing body fluids, and also prevents the absorbent core, particularly the pair of waisted portions, from becoming thick.

[0128] The absorbent article according to the present disclosure, particularly the absorbent core, can be manufactured by appropriately utilizing the disclosure of, for example, JP 2019-118722 A. For example, the basis weights of the multiple high basis weight, high density portions and the multiple low basis weight, low density portions, and the basis weight difference therebetween, can be adjusted by adjusting the depth of the mold member 207 shown in Figures 15 and 16 of JP 2019-118722 A. Furthermore, the densities of the multiple high basis weight, high density portions and the multiple low basis weight, low density portions, and the density difference therebetween can be adjusted by adjusting the press pressure of a press device 211 equipped with a pair of press rolls 211a, 211b shown in Figure 15 of JP 2019-118722 A.

[0129] The present disclosure will be described below with reference to examples, but the present disclosure is not limited to these examples. [Production Example 1] The absorbent core shown in Fig. 3 and the absorbent article shown in Fig. 1 were produced with reference to Patent Document 1, and absorbent core No. 1 containing superabsorbent polymer particles No. 1 and disposable diaper No. 1 equipped with absorbent core No. 1 were produced.

[0130] Absorbent core No. 1 had a size of 320 mm x 120 mm (longitudinal x transverse), and had the average basis weight of the absorbent core, the average basis weight of the superabsorbent polymer particles, and the average basis weight of the pulp fibers as shown in Table 1. 27a =W 29a = 4.0 mm, and W 27b =W 29b In absorbent core No. 1, the ridge portion corresponding to the high basis weight and high density portion had a thickness of 453 g / m 2 and a basis weight of 0.184 g / cm 3 The groove portion corresponding to the low basis weight low density portion has a density of 210 g / m 2 and a basis weight of 0.122 g / cm 3 The density was .gtoreq.1.

[0131] The superabsorbent polymer particles No. 1 were AQUAKEEP Sample 1 manufactured by Sumitomo Seika Chemicals Co., Ltd., and had a water retention capacity under no pressure of 47.9 (g / g), a water retention capacity under pressure of 20.1 g / g, and a liquid permeability rate of 2.6 g / 60 seconds. The pulp fibers were softwood pulp fibers. The results of absorbent core No. 1 are summarized in Table 1. The shape of the absorbent core shown in Figure 3 is referred to as the FB (fishbone) type.

[0132] Comparative Production Example 1 Absorbent core No. 2 containing superabsorbent polymer particles No. 1, as shown in Figure 5, and disposable diaper No. 2 equipped with absorbent core No. 2 were manufactured. In plan view, absorbent core No. 2 had a size of 320 mm x 120 mm (longitudinal x transverse), and two slit sections (175 mm x 7 mm) were arranged parallel to the longitudinal direction L with an interval of 18 mm. Absorbent core No. 2 had the average basis weight of the absorbent core, the average basis weight of the superabsorbent polymer particles, and the average basis weight of the pulp fibers as shown in Table 1. In absorbent core No. 2, the slit sections had a thickness of 0 g / m 2 and 0 g / cm 3 and had a density of .

[0133] In absorbent core No. 2, the pulp fibers were the same softwood pulp fibers as in absorbent core No. 1. The results for absorbent core No. 2 are summarized in Table 1. The shape of the absorbent core shown in Figure 5 is referred to as a slit type.

[0134] Comparative Production Example 2 Absorbent core No. 3 containing superabsorbent polymer particles No. 1 and disposable diaper No. 3 equipped with absorbent core No. 3 were produced, as shown in Figure 6. In plan view, absorbent core No. 3 had a size of 320 mm x 120 mm (longitudinal direction x width direction), and three absorbent core portions (from the left, (i) 320 mm x 42 mm, (ii) 320 mm x 20 mm, (iii) 320 mm x 42 mm) were arranged with a predetermined space between them.

[0135] Absorbent core No. 3 had the average basis weight of the absorbent core, the average basis weight of the superabsorbent polymer particles, and the average basis weight of the pulp fibers as shown in Table 1. In absorbent core No. 3, the space between the absorbent core portions was 0 g / m 2 and 0 g / cm 3 The absorbent core No. 3 had a density of 1000 sq. ft. The pulp fibers in absorbent core No. 3 were the same softwood pulp fibers as in absorbent core No. 1. The values ​​obtained for absorbent core No. 3 are summarized in Table 1. The shape of the absorbent core shown in Figure 6 is referred to as a split type.

[0136] Comparative Production Example 3 Absorbent core No. 4 containing superabsorbent polymer particles No. 1, as shown in Figure 7, and disposable diaper No. 4 equipped with absorbent core No. 4 were produced. Absorbent core No. 4 measured 320 mm x 120 mm (longitudinal x transverse) and had the average basis weight of the absorbent core, the average basis weight of the superabsorbent polymer particles, and the average basis weight of the pulp fibers as shown in Table 1. In absorbent core No. 4, the pulp fiber was the same softwood pulp fiber as in absorbent core No. 1. The results for absorbent core No. 4 are summarized in Table 1. The shape of the absorbent core shown in Figure 7 is referred to as a flat type.

[0137] [Production Example 2 and Comparative Production Examples 4 to 6] Absorbent cores Nos. 5 to 8 and disposable diapers Nos. 5 to 8 containing superabsorbent polymer particles No. 2 were produced in the same manner as Production Example 1 and Comparative Production Examples 1 to 3, except that superabsorbent polymer particles No. 1 were replaced with superabsorbent polymer particles No. 2 (AQUALIC, Sample 1, manufactured by Nippon Shokubai Co., Ltd.).

[0138] Superabsorbent polymer particles No. 2 had a water retention capacity under no pressure of 44.9 (g / g), a water retention capacity under pressure of 24.8 g / g, and a liquid permeability of 7.1 g / 60 seconds. The values ​​obtained for absorbent cores Nos. 5 to 8 are summarized in Table 1. In absorbent core No. 5, the ridge portion corresponding to the high basis weight, high density portion had a weight of 454 g / m 2 and a basis weight of 0.186 g / cm 3 The groove portion corresponding to the low basis weight low density portion has a density of 211 g / m 2 and a basis weight of 0.123 g / cm 3 The density was .gtoreq.1.

[0139] Comparative Production Examples 7 to 10 Absorbent cores Nos. 9 to 12 and disposable diapers Nos. 9 to 12 containing water-absorbent polymer particles No. 3 were produced in the same manner as in Production Example 1 and Comparative Production Examples 1 to 3, except that superabsorbent polymer particles No. 1 were changed to superabsorbent polymer particles No. 3 (AQUAKEEP, Sample 2, manufactured by Sumitomo Seika Chemicals Co., Ltd.).

[0140] Superabsorbent polymer particles No. 3 had a water retention capacity under no pressure of 39.4 (g / g), a water retention capacity under pressure of 24.6 g / g, and a liquid permeability rate of 2.9 g / 60 seconds. The values ​​obtained for absorbent cores Nos. 9 to 12 are summarized in Table 1. In absorbent core No. 9, the ridge portion corresponding to the high basis weight, high density portion had a weight of 450 g / m 2 and a basis weight of 0.178 g / cm 3 The groove portion corresponding to the low basis weight low density portion has a density of 209 g / m 2 and a basis weight of 0.118 g / cm 3 The density was .gtoreq.1.

[0141] Comparative Production Examples 11 and 12 Absorbent cores No. 13 and 14 containing absorbent polymer particles No. 4 and disposable diapers No. 13 and 14 were produced in the same manner as in Production Example 1 and Comparative Production Example 3, except that superabsorbent polymer particles No. 1 were replaced with superabsorbent polymer particles No. 4 (AQUAKEEP, Sample 3, manufactured by Sumitomo Seika Chemicals Co., Ltd.). Superabsorbent polymer particles No. 4 had a water retention capacity of 36.3 (g / g) under no pressure, a water retention capacity of 28.0 g / g under pressure, and a liquid permeability of 22.7 g / 60 seconds. The results of absorbent cores No. 13 and 14 are summarized in Table 1.

[0142] Comparative Production Examples 13 and 14 Absorbent cores No. 15 and 16 containing superabsorbent polymer particles No. 5 and disposable diapers No. 15 and 16 were produced in the same manner as in Production Example 1 and Comparative Production Example 3, except that superabsorbent polymer particles No. 1 were replaced with superabsorbent polymer particles No. 5 (Sunwet, Sample 1, manufactured by SDP Global Corporation). Superabsorbent polymer particles No. 5 had a water retention capacity of 37.5 (g / g) under no pressure, a water retention capacity of 23.9 g / g under pressure, and a liquid permeability of 10.3 g / 60 seconds. The results of absorbent cores No. 15 and 16 are summarized in Table 1.

[0143] [Production Example 3 and Comparative Production Examples 15 to 17] Absorbent cores Nos. 17 to 20 containing superabsorbent polymer particles No. 1 and disposable diapers Nos. 17 to 20 equipped with absorbent cores Nos. 17 to 20 were produced in the same manner as Production Example 1 and Comparative Production Examples 1 to 3, except that the basis weight of the superabsorbent polymer particles, the basis weight of the pulp fibers, and the average basis weight were changed as shown in Table 2. The obtained values ​​of absorbent cores Nos. 17 to 20 are summarized in Table 2. In absorbent core No. 17, the ridge portion corresponding to the high basis weight, high density portion had a density of 420 g / m 2 and a basis weight of 0.186 g / cm 3 The groove portion corresponding to the low basis weight low density portion has a density of 195 g / m 2 and a basis weight of 0.124 g / cm 3 The density was .gtoreq.1.

[0144] [Production Example 4 and Comparative Production Examples 18 to 20] Absorbent cores Nos. 21 to 24 containing water-absorbent polymer particles No. 2 and disposable diapers Nos. 21 to 24 were produced in the same manner as Production Example 2 and Comparative Production Examples 4 to 6, except that the basis weight of the superabsorbent polymer particles, the basis weight of the pulp fibers, and the average basis weight were changed as shown in Table 2. The values ​​obtained for absorbent cores Nos. 21 to 24 are summarized in Table 2. In absorbent core No. 21, the ridge portion corresponding to the high basis weight, high density portion had a density of 421 g / m 2 and a basis weight of 0.199 g / cm 3 The groove portion corresponding to the low basis weight low density portion has a density of 195 g / m 2 and a basis weight of 0.132 g / cm 3 The density was .gtoreq.1.

[0145] Comparative Production Examples 21 to 24 Absorbent cores Nos. 25 to 28 containing water-absorbent polymer particles No. 3 and disposable diapers Nos. 25 to 28 were produced in the same manner as in Comparative Production Examples 7 to 10, except that the basis weight of the superabsorbent polymer particles, the basis weight of the pulp fibers, and the average basis weight were changed as shown in Table 2. The values ​​obtained for absorbent cores Nos. 25 to 28 are summarized in Table 2. In absorbent core No. 25, the ridge portion corresponding to the high basis weight, high density portion had a weight of 421 g / m 2 and a basis weight of 0.188 g / cm 3 The groove portion corresponding to the low basis weight low density portion has a density of 195 g / m 2 and a basis weight of 0.125 g / cm 3 The density was .gtoreq.1.

[0146] Comparative Production Examples 25 and 26 Absorbent cores No. 29 and 30 containing water-absorbent polymer particles No. 4 and disposable diapers No. 29 and 30 were produced in the same manner as in Comparative Production Examples 11 and 12, except that the basis weight of the superabsorbent polymer particles, the basis weight of the pulp fibers, and the average basis weight were changed as shown in Table 2. The obtained values ​​of absorbent cores No. 29 and 30 are summarized in Table 2.

[0147] Comparative Production Examples 27 and 28 Absorbent cores No. 31 and 32 containing water-absorbent polymer particles No. 5 and disposable diapers No. 31 and 32 were produced in the same manner as in Comparative Production Examples 13 and 14, except that the basis weight of the superabsorbent polymer particles, the basis weight of the pulp fibers, and the average basis weight were changed as shown in Table 2. The obtained values ​​of absorbent cores No. 31 and 32 are summarized in Table 2.

[0148] In absorbent cores No. 1 to No. 32, the average basis weight of the absorbent core, the average basis weight of the superabsorbent polymer particles, and the average basis weight of the pulp fibers differ depending on the absorbent core. However, these values ​​are due to the fact that the average basis weight of the FB-type absorbent core is the value in the region including the ridges and grooves, while the average basis weight of the slit-type and segmented-type absorbent cores is the value in the region that does not include the slits and predetermined spaces. Absorbent cores No. 1 to No. 32 have, as the entire absorbent core, approximately the same total amount of superabsorbent polymer particles, total amount of pulp fibers, and total amount of absorbent core, and are adjusted to have approximately the same absorption capacity.

[0149] [Examples 1 to 4 and Comparative Examples 1 to 28] The following absorbency test was conducted on each of disposable diapers No. 1 to No. 32, and the repeated absorption capacity index was calculated. The results are shown in Tables 1 and 2. In Tables 1 and 2, the superabsorbent polymer particles are abbreviated as "SAP."

[0150] [Absorbency Test] (1) Mark 1 is placed at the intersection of the longitudinal centerline and the widthwise centerline of the disposable diaper in an unfolded state, and mark 2 is placed 70 mm away from mark 1 on the ventral side. The thickness: T0 (mm) of the disposable diaper at mark 1 is measured using a Peacock dial gauge manufactured by Ozaki Seisakusho Co., Ltd. (2) The disposable diaper is set in a U-shaped fixture that is approximately U-shaped in side view. The disposable diaper is set in the U-shaped fixture so that mark 1 on the disposable diaper is aligned with the center of the U-shaped fixture (the lowest position).

[0151] <First cycle> (3) 80 mL of artificial urine (first injection) is injected from the burette at the position of mark 2 on the disposable diaper at a rate of 80 mL / 10 seconds. (4) The time from the start of the first injection of artificial urine until the artificial urine on the liquid-permeable sheet is completely absorbed is recorded as the absorption time (seconds, 80 mL).

[0152] <Second Cycle> (5) Ten minutes after the start of the first artificial urine injection, 80 mL of artificial urine (second injection) is injected from the burette at the position of mark 2 on the disposable diaper at a rate of 80 mL / 10 seconds. (6) The time from the start of the second injection of artificial urine until the artificial urine on the liquid-permeable sheet disappears is recorded as the absorption time (seconds, 160 mL). (7) Four minutes after the start of the second injection of artificial urine, the thickness T1 (mm) at mark 1 of disposable diaper No. 1 is measured using a Peacock dial gauge manufactured by Ozaki Seisakusho Co., Ltd. (8) The change in thickness ΔT (mm, 160 mL) of the disposable diaper is calculated using the following formula: ΔT (mm, 160 mL) = T1 - T0.

[0153] <Third Cycle> (9) 10 minutes after the start of the second injection of artificial urine, 80 mL of artificial urine (third time) is injected from the burette at a rate of 80 mL / 10 seconds into the disposable diaper at the position marked 2. (10) The time from the start of the third injection of artificial urine until the artificial urine on the liquid-permeable sheet is completely removed is recorded as the absorption time: AT (seconds, 240 mL).

[0154] (11) Four minutes after the start of the third injection of artificial urine, the disposable diaper is removed from the U-shaped device and left to stand in a spread state on a horizontal surface. Five minutes after the start of the third injection of artificial urine, the mass: m 41 Approximately 75 g of 100 mm x 100 mm filter paper with the mass (g) measured is placed on the liquid-permeable sheet of a disposable diaper, with the artificial urine injection point at the center. Furthermore, a 3.5 kg weight measuring 100 mm x 100 mm x 50 mm (height) is placed on top of it. (12) Eight minutes after the start of the third injection of artificial urine, the weight is removed and the mass of the filter paper: m 42 (g) was measured, and the rewet: R (g, 240 mL) was calculated using the following formula: R (g, 240 mL) = m 42 -m 41 It is calculated as follows.

[0155] (13) The repeated absorption capacity index (RAI) is calculated by the following formula: RAI = ΔT (mm, 160 mL) × AT (sec, 240 mL) × R (g, 240 mL). The repeated absorption capacity index (RAI) is calculated by multiplying the averages of ΔT (mm, 160 mL), AT (sec, 240 mL), and R (g, 240 mL) for three different disposable diapers. The artificial urine was prepared by dissolving 200 g of urea, 80 g of sodium chloride, 8 g of magnesium sulfate, 3 g of calcium chloride, and approximately 1 g of blue No. 1 dye in 10 L of ion-exchanged water.

[0156]

[0157]

[0158] Disposable diapers No. 1 to No. 32 that had undergone the water absorbency test were cooled with liquid nitrogen, cut along the center line in the width direction, and their cross sections were observed. It was found that the grooves in disposable diapers Nos. 1, 5, and 9 tended to retain their original shapes compared to the grooves in disposable diapers Nos. 13 and 15. Similarly, the grooves in disposable diapers Nos. 17, 21, and 25 tended to retain their original shapes compared to the grooves in disposable diapers Nos. 29 and 31. Similarly, the grooves in disposable diapers Nos. 1, 5, 9, 17, 21, and 25 tended to retain their original shapes compared to the slits and spaces in disposable diapers containing the same superabsorbent polymer particles and having slit-type and segmented absorbent cores.

[0159] REFERENCE SIGNS LIST 1 disposable diaper 3 liquid-permeable sheet 5 liquid-impermeable sheet 7 absorbent body 9 absorbent core 11 skin-facing side 13 non-skin-facing side 15 core wrap 17 pulp fibers 19 superabsorbent polymer particles 21 first absorbent core portion 23 second absorbent core portion 25 longitudinal groove portion 27 right longitudinal groove portion 29 left longitudinal groove portion 31 longitudinal rib portion 33 right longitudinal rib portion 35 central longitudinal rib portion 37 left longitudinal rib portion

Claims

1. An absorbent article comprising an absorbent core containing pulp fibers and superabsorbent polymer particles, and having longitudinal, widthwise, and thicknesswise directions, The absorption core comprises a plurality of high basis weight, high density portions extending continuously in the longitudinal direction and a plurality of low basis weight, low density portions extending in the longitudinal direction. Each of the aforementioned multiple high basis weight, high density portions and each of the aforementioned multiple low basis weight, low density portions are arranged alternately in the width direction. Each of the aforementioned multiple high basis weight, high density portions has a higher basis weight and higher density than each of the aforementioned multiple low basis weight, low density portions. The superabsorbent polymer particles have a water retention ratio of 43 g / g or more under no pressure and a water retention ratio of 25 g / g or less under pressure of 2 kPa. An absorbent article characterized by the following features.

2. The absorbent article according to claim 1, wherein the superabsorbent polymer particles have a liquid flow rate of 1.0 g / 60 seconds or more.

3. The absorbent article according to claim 1, wherein the plurality of low basis weight, low density portions are not connected to each other in the width direction.

4. The absorbent article according to claim 1, wherein the plurality of high basis weight, high density portions are connected to one another in the width direction.

5. The absorbent article according to claim 1, wherein each of the plurality of low basis weight, low density portions is a groove that is recessed in the thickness direction, and each of the plurality of high basis weight, high density portions is a ridge that protrudes in the thickness direction.

6. The absorbent article according to claim 5, wherein the absorbent core has a skin-side and a non-skin-side, and the groove is arranged to recess from the skin-side to the non-skin-side.

7. The absorbent article according to claim 5, wherein the absorbent core has a skin-side and a non-skin-side, and the groove is arranged to recess from the non-skin-side to the skin-side.

8. The absorbent article according to claim 1, wherein each of the plurality of low basis weight, low density portions has a basis weight of 20 to 80% of the plurality of high basis weight, high density portions.

9. The absorbent article according to claim 1, wherein each of the plurality of low basis weight, low density portions has a density of 20 to 80% of the plurality of high basis weight, high density portions.

10. The absorbent article according to claim 1, wherein the absorbent core contains the superabsorbent polymer particles in an average ratio of 40% by mass or more.

11. The absorbent article according to claim 1, wherein the superabsorbent polymer particles have a water retention ratio of 45 g / g or more under non-pressurized conditions.

12. The absorbent article according to claim 1, wherein at least a portion of the plurality of low basis weight, low density portions further comprises a plurality of sub-low basis weight, low density portions that extend from the low basis weight, low density portions along the width direction and have edges.