Method for splicing absorbent sheets

Abstract

This prevents the deterioration of the waste rate due to splicing of absorbent sheets. [Solution] The above problem is solved by positioning the connection end of the first sheet S1, which consists of at least one sheet 11, 12, 13, at a predetermined distance closer to the non-connection end than the connection end of the second sheet S2, which consists of sheets 11, 12, 13 other than the first sheet S1, thereby forming a first connection portion C1 consisting only of the second sheet S2 at the connection end 10p of one absorbent sheet 10, and positioning the connection end of the third sheet S3, whose lamination position corresponds to the second sheet S2, at a predetermined distance closer to the non-connection end than the connection end of the fourth sheet S4, whose lamination position corresponds to the first sheet S1, thereby forming a second connection portion C2 consisting only of the fourth sheet S4 at the connection end 20d of the other absorbent sheet 20, and joining the first connection portion C1 and the second connection portion C2 by welding with a gap in between, and not attaching adhesive tape 16 to at least one side of the front and back of both absorbent sheets 10 and 20.

Description

Technical Field

[0001] The present invention relates to a method for splicing an absorbent sheet.

Background Art

[0002] In absorbent articles such as disposable diapers and sanitary napkins, in order to mainly reduce the thickness, a plurality of sheets made of non-woven fabric or the like are laminated, and superabsorbent polymer particles (Super Absorbent Polymer: SAP) are arranged between adjacent sheets. It is known to use an absorbent sheet (also called a SAP sheet) (see, for example, Patent Documents 1 to 3).

[0003] When continuously manufacturing an absorbent article provided with such an absorbent sheet, the absorbent sheet that is continuous in a strip shape is supplied along its continuous direction, cut at a predetermined interval to form individual absorbent sheets, and this individual absorbent sheet is incorporated into each absorbent article. This is common.

[0004] In addition, when manufacturing an absorbent sheet, a plurality of raw material rolls around which a liquid-permeable sheet that is continuous in a strip shape is wound are prepared, the sheets are respectively fed out from each raw material roll, and superabsorbent polymer particles are placed on the lower sheet. After that, the upper sheet is laminated thereon, and adjacent sheets are joined. Since the winding length of the raw material roll is finite, when the manufacturing length of the absorbent sheet does not match the winding length of the raw material roll, the tip (leading end) of the absorbent sheet to be manufactured next is connected to the end (tail end) of the absorbent sheet manufactured first. This is generally called splicing. For example, splicing is required when the manufacturing length of the absorbent sheet exceeds the winding length of a new raw material roll or the remaining winding length of a raw material roll used halfway.

[0005] Conventionally, such splicing of the absorbent sheet has been performed by winding an adhesive tape so as to straddle the joint between the end of the absorbent sheet manufactured first and the tip of the absorbent sheet manufactured later in order to ensure the strength required in the subsequent manufacturing stage of the absorbent article.

[0006] However, if absorbent articles are continuously manufactured using absorbent sheets spliced ​​with this conventional method, as described above, not only will one of the sequentially manufactured products contain an absorbent sheet with a seam, but adhesive tape will remain on the surface of the absorbent sheet in that product, resulting in a deterioration of texture, appearance, and absorbent performance.

[0007] Therefore, conventionally, products in which adhesive tape was detected during manufacturing were considered defective and discarded from the production line, which was one of the factors contributing to a high waste rate. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2013-39804 [Patent Document 2] Japanese Patent Publication No. 2019-136152 [Patent Document 3] Japanese Patent Publication No. 2024-129233 [Overview of the project] [Problems that the invention aims to solve]

[0009] Therefore, the main objective of the present invention is to prevent the deterioration of the waste rate due to splicing of absorbent sheets. [Means for solving the problem]

[0010] The splicing method for absorbent sheets that solves the above problems is as follows. <First aspect> A method for splicing an absorbent sheet having a laminated structure in which multiple liquid-permeable sheets are laminated together and highly absorbent polymer particles are arranged between adjacent sheets, wherein the laminated structure is continuous in the MD direction or regularly repeating in a pair of absorbent sheets, with one end and the other end of the absorbent sheet in the MD direction designated as a connecting end and a non-connecting end, respectively, wherein the connecting end of one absorbent sheet is spliced ​​to the connecting end of the other absorbent sheet, Of the one absorbent sheet, the connection end of the first sheet, which consists of at least one sheet, is positioned at a predetermined distance closer to the non-connection end than the connection end of the second sheet, which consists of sheets other than the first sheet, thereby forming a first connection portion consisting only of the second sheet at the connection end of the one absorbent sheet. Of the other absorbent sheet, the connection end of the third sheet whose stacking position corresponds to the second sheet is positioned at the non-connection end by a predetermined distance from the connection end of the fourth sheet whose stacking position corresponds to the first sheet, thereby forming a second connection portion consisting only of the fourth sheet at the connection end of the other absorbent sheet. The connection ends of the first sheet and the second sheet of one of the absorbent sheets are abutted against the connection ends of the fourth sheet and the third sheet of the other absorbent sheet, respectively, and the first and second connection portions are joined together with a gap between them by adhesive or welding. Adhesive tape is not applied to at least one of the front and back surfaces of the pair of absorbent sheets. A splicing method for an absorbent sheet, characterized by the following features.

[0011] (Effects and Benefits) In this splicing method, a first connecting portion consisting only of the second sheet is formed at the connection end of one absorbent sheet, and a second connecting portion consisting only of the fourth sheet is formed at the connection end of the other absorbent sheet. Then, while maintaining the continuity of the laminated structure across both absorbent sheets, the first and second connecting portions are joined by adhesive or welding. As a result, splicing can be performed without using adhesive tape at the joint, or by using adhesive tape only on one side of the joint. Therefore, by embedding the absorbent sheet in an absorbent article so that the side without adhesive tape is the front side (skin side), even products containing absorbent sheets with joints can have a texture, appearance, and absorption performance on the front side that is comparable to products containing absorbent sheets without joints, thus eliminating the need for disposal. Thus, this splicing method can prevent the deterioration of the waste rate due to splicing of absorbent sheets.

[0012] <Second aspect> In the aforementioned absorbent sheet, adjacent sheets in the thickness direction are bonded together via a hot melt adhesive. The superabsorbent polymer particles are bonded to the adjacent sheet via a hot melt adhesive. When forming the first connecting portion, the connecting end of the first sheet in the one absorbent sheet is peeled off from the second sheet, and the connecting end of the first sheet is cut off by the predetermined distance to form the first connecting portion. When forming the second connecting portion, the connecting end of the third sheet in the other absorbent sheet is peeled off from the fourth sheet, and the connecting end of the third sheet is cut off by the predetermined distance to form the second connecting portion. A splicing method for an absorbent sheet according to a first embodiment.

[0013] (Effects and Benefits) The sheets adjacent to each other in the thickness direction of the absorbent sheet may be joined by welding, but it is preferable to be adhered via a hot-melt adhesive because peeling of the sheet when forming the first connection portion and the second connection portion becomes easy. Further, when the superabsorbent polymer particles are adhered to adjacent sheets via a hot-melt adhesive, there is an advantage that the superabsorbent polymer particles are less likely to fall off when the sheet is peeled when forming the first connection portion and the second connection portion. Further, due to this advantage, the superabsorbent polymer particles remaining on the surface on the first sheet side of the second sheet of the first connection portion and the surface on the third sheet side of the fourth sheet of the second connection portion are respectively arranged between the first connection portion and the second connection portion by joining the first connection portion and the second connection portion, and absorption performance similar to other locations is maintained also in the laminated region of the first connection portion and the second connection portion.

[0014] <The third aspect> With the connecting ends of the first sheet and the connecting ends of the second sheet in the one absorbent sheet abutted against the connecting ends of the fourth sheet and the connecting ends of the third sheet in the other absorbent sheet respectively, an adhesive tape is attached so as to straddle the butting portion only on one of the front and back surfaces of this butting portion, Thereafter, the first connection portion and the second connection portion are joined by an adhesive or welding with a space therebetween. A method for splicing an absorbent sheet according to the first or second aspect.

[0015] (Function and effect) In order to supplement the strength of the joint between one absorbent sheet and the other absorbent sheet, an adhesive tape can be attached to either the front or back surface of the joint. In this case, when the first connection portion and the second connection portion are joined after attaching the adhesive tape as in this aspect, joining of the first connection portion and the second connection portion becomes easy.

Effect of the invention

[0016] According to the present invention, it becomes possible to prevent deterioration of the waste rate due to splicing of the absorbent sheet.

Brief Description of the Drawings

[0017] [Figure 1] It is a cross-sectional view showing the splicing process of the absorption sheet. [Figure 2] It is a cross-sectional view showing an example of the use of an adhesive tape. [Figure 3] It is a cross-sectional view showing the splicing process of another absorption sheet. [Figure 4] It is a cross-sectional view showing the splicing process of another absorption sheet. [Figure 5] It is a schematic diagram showing the manufacturing flow of the absorption sheet. [Figure 6] It is a perspective view showing the main part of the absorption sheet broken. [Figure 7] It is a plan view showing an example of the arrangement of the joint part. [Figure 8] It is a plan view showing the front side of the pad-type disposable diaper in the unfolded state. [Figure 9] It is a plan view showing the back side of the pad-type disposable diaper in the unfolded state. [Figure 10] It is a cross-sectional view taken along the line A-A of FIG. 8. [Figure 11] It is a cross-sectional view taken along the line B-B of FIG. 8. [Figure 12] It is a cross-sectional view taken along the line C-C of FIG. 8.

Modes for Carrying Out the Invention

[0018] <Example of the manufacturing method of the absorption sheet> Figure 5 shows an example of the manufacturing flow of the absorbent sheet 10. In this manufacturing flow, multiple raw material rolls 11R, 12R, and 13R are prepared, each containing a continuous strip of liquid-permeable sheets 11, 12, and 13 wound onto it. Sheets 11, 12, and 13 are unwound from each of the raw material rolls 11R, 12R, and 13R, respectively. Highly absorbent polymer particles P are placed on the lower sheets 12 and 13, and then the upper sheets 11 and 12 are laminated on top of them. By joining adjacent sheets 11, 12, and 13 in the thickness direction TD (see Figure 1; the direction perpendicular to the plane consisting of the MD direction and the CD direction), a continuous strip of absorbent sheet 10 is manufactured. Reference numeral 18 in Figure 5 indicates a device for dispensing highly absorbent polymer particles P.

[0019] Sheets 11, 12, and 13 can be stacked in any number of layers. As shown in Figures 1 and 3, there can be three layers, as shown in Figure 4, there can be two layers, or there can be four or more layers (though these are not shown).

[0020] Adjacent sheets 11, 12, and 13 in the thickness direction TD can be bonded together, for example, with a hot-melt adhesive HM. Reference numeral 19 in Figure 5 indicates a hot-melt adhesive HM application apparatus. As shown in Figure 5, after placing the hot-melt adhesive HM and superabsorbent polymer particles P on the lower sheets 11, 12, and 13, the upper sheets 11, 12, and 13 are laminated on top of them, and adjacent sheets 11, 12, and 13 in the thickness direction TD are joined via the hot-melt adhesive HM. This allows for the production of absorbent sheets 10 and 20 in which adjacent sheets 11, 12, and 13 in the thickness direction TD are bonded together via the hot-melt adhesive HM, resulting in all sheets 11, 12, and 13 being laminated and integrated, and superabsorbent polymer particles P being bonded to adjacent sheets 11, 12, and 13 via the hot-melt adhesive HM. The application method for the hot melt adhesive HM is not particularly limited, and slot application, bead application, spiral application, or pattern coating (transfer of the hot melt adhesive HM using a relief printing method) can be employed. The application pattern of the hot melt adhesive HM can be determined as appropriate, for example, a pattern in which the applied portion of the hot melt adhesive HM is continuous in a planar manner so that there are no uncoated areas, a pattern in which the applied portion of the hot melt adhesive HM is continuous in a mesh-like manner so that uncoated areas are scattered, or a striped pattern in which the applied portion of the hot melt adhesive HM along the MD direction, the uncoated portion along the MD direction and the CD direction are arranged alternately. As for the hot melt adhesive HM, there are types such as EVA-based, adhesive rubber-based (elastomer-based), polyolefin-based, and polyester / polyamide-based, but they can be used without particular limitation.

[0021] As a joining method for joining adjacent sheets 11, 12, and 13 in the thickness direction TD, a material welding method such as heat sealing or ultrasonic sealing can also be used. In this case, welding can be performed over the entire thickness direction TD after all sheets 11, 12, and 13 have been laminated and the superabsorbent polymer particles P have been placed. When joining adjacent sheets 11, 12, and 13 in the thickness direction TD by welding, point-like joints can be scattered at appropriate intervals throughout the joining area, and linear joints that are continuous in an appropriate direction such as the MD direction or CD direction can be provided at appropriate intervals throughout the joining area. The welding joints of adjacent sheets 11, 12, and 13 in the thickness direction TD can be appropriately selected from the same dimensions and arrangement as the joints 14 of the first connecting portion C1 and the second connecting portion C2 described later. Even when adjacent sheets 11, 12, and 13 in the thickness direction TD are joined by welding, superabsorbent polymer particles P can be bonded to adjacent sheets 11, 12, and 13 via a hot melt adhesive HM as needed.

[0022] The width of the bonding area (dimension in the CD direction) of adjacent sheets 11, 12, and 13 in the thickness direction TD can be determined as appropriate. For example, it can be the same as or greater than the width of the arrangement area of ​​the superabsorbent polymer particles P (dimension in the CD direction).

[0023] Each sheet 11, 12, and 13 constituting the absorbent sheets 10 and 20 can be made of nonwoven fabric, paper, or resin, as long as it is permeable to liquid. It can also be made of nonwoven fabric that does not have permeable holes that penetrate the thickness direction TD formed by die-cutting or pinning, or it can be made of nonwoven fabric that has such permeable holes. To prevent the high absorbent polymer particles from falling out, it is preferable that at least one of the uppermost sheet 11 and the bottommost sheet 13 is a nonwoven fabric having a meltblown layer. All sheets 11, 12, and 13 constituting the absorbent sheets 10 and 20 may be the same sheet, or some or all of the sheets may differ in terms of material, thickness, basis weight, etc.

[0024] The term "superabsorbent polymer particles P" includes not only "particles" but also "powder." Superabsorbent polymer particles P can be those used in this type of disposable diaper, for example, those in which the percentage of particles remaining on the sieve after sieving (shaking for 5 minutes) using a 500 μm standard sieve (JIS Z8801-1:2006) is 30% by weight or less, and of the particles that fall below the sieve after sieving (shaking for 5 minutes) using a 180 μm standard sieve (JIS Z8801-1:2006) the percentage of particles remaining on the sieve is 60% by weight or more.

[0025] The material for the superabsorbent polymer particles P is not particularly limited, but materials with a water absorption capacity of 40 g / g or more are preferred. Examples of superabsorbent polymer particles P include starch-based, cellulose-based, and synthetic polymer-based materials. These include starch-acrylic acid (salt) graft copolymers, saponified starch-acrylonitrile copolymers, crosslinked sodium carboxymethylcellulose, and acrylic acid (salt) polymers. While the commonly used powder or granular form is preferred for the superabsorbent polymer particles P, other forms can also be used.

[0026] As the superabsorbent polymer particles P, those with a water absorption rate of 70 seconds or less, and particularly 40 seconds or less, are preferably used. If the water absorption rate is too slow, the liquid supplied into the absorbent sheets 10, 20 is likely to flow back out of the absorbent sheets 10, 20, a phenomenon known as backflow.

[0027] Furthermore, as the superabsorbent polymer particles P, those with a gel strength of 1000 Pa or more are preferably used. This effectively suppresses stickiness after liquid absorption, even when using bulky absorbent sheets 10 and 20.

[0028] The basis weight of the superabsorbent polymer particles P can be appropriately determined according to the amount of absorption required for the application of the absorbent sheets 10 and 20. Therefore, it is not possible to say definitively, but it is generally between 100 and 300 g / m². 2 It can be done this way.

[0029] The superabsorbent polymer particles P can be arranged continuously or intermittently in the MD direction of the absorbent sheets 10 and 20, and can also be arranged continuously or intermittently in the CD direction of the absorbent sheets 10 and 20. The superabsorbent polymer particles P may be arranged on both edges (both side edges) in the CD direction of the absorbent sheets 10 and 20, but they do not need to be arranged there.

[0030] <Example of splicing> When manufacturing absorbent sheets, if the raw material rolls 11R, 12R, and 13R are used up before the target length of absorbent sheets is reached, the raw material rolls 11R, 12R, and 13R are replaced, and the manufacture of the next absorbent sheet 10 can be started. The leading end (connecting end) 10p of the next absorbent sheet 10 can then be spliced ​​to the trailing end (connecting end) 20d of the previously manufactured absorbent sheet 20. Splicing can be performed not only when the raw material rolls are used up in the absorbent sheet manufacturing line, but also when the absorbent sheets are used up in the absorbent article assembly line. In addition, multiple absorbent sheets (including those wound on rolls) that have been manufactured in advance can be spliced ​​as needed. As is clear from these explanations, of the two ends of the absorbent sheet in the MD direction, the end that is joined during splicing is the connecting end, and the opposite end is the non-connecting end.

[0031] Characteristically, during these splicing operations, as shown in Figure 1, the connection end of the first sheet S1, which consists of at least one sheet 11, of one absorbent sheet 10 is positioned a predetermined distance closer to the non-connected end than the connection end of the second sheet S2, which consists of sheets 12 and 13 other than the first sheet S1, thereby forming a first connection portion C1 consisting only of the second sheet S2 at the connection end of one absorbent sheet 10. Similarly, the connection end of the third sheet S3, whose stacking position corresponds to the second sheet S2, of the other absorbent sheet 20 is positioned a predetermined distance closer to the non-connected end than the connection end of the fourth sheet S4, whose stacking position corresponds to the first sheet S1, thereby forming a second connection portion C2 consisting only of the fourth sheet S4 at the connection end of the other absorbent sheet 20. In other words, the first connection portion C1 can be formed by making the connection end of the second sheet S2 protrude a predetermined distance from the connection end of the first sheet S1, and the second connection portion C2 can be formed by making the connection end of the fourth sheet S4 protrude a predetermined distance from the connection end of the third sheet S3.

[0032] In the example shown in Figure 1, when splicing absorbent sheets 10 and 20 having three layers of sheets 11, 12, and 13, the top layer sheet 11 of one absorbent sheet 10 becomes the first sheet S1, the middle layer sheet 12 and the bottom layer sheet 13 of the other absorbent sheet 10 become the second sheet S2, the middle layer sheet 12 and the bottom layer sheet 13 of the other absorbent sheet 20 become the third sheet S3, and the top layer sheet 11 becomes the fourth sheet S4. However, the number of layers of the first sheet S1, second sheet S2, third sheet S3, and fourth sheet S4 can be appropriately changed considering the number of sheets 11, 12, and 13 included in absorbent sheets 10 and 20, as well as workability.

[0033] Therefore, although not shown in the diagram, the bottom sheet 13 of one absorbent sheet 10 can be designated as the first sheet S1, the top sheet 11 and middle sheet 12 of one absorbent sheet 10 can be designated as the second sheet S2, the top sheet 11 and middle sheet 12 of the other absorbent sheet 20 can be designated as the third sheet S3, and the bottom sheet 13 can be designated as the fourth sheet S4. In other words, the front and back can be reversed from the example shown in Figure 1.

[0034] Furthermore, as shown in Figure 3, for example, when splicing absorbent sheets 10 and 20 having three layers of sheets 11, 12, and 13, the middle layer sheet 12 of one absorbent sheet 10 can be designated as the first sheet S1, the top layer sheet 11 and bottom layer sheet 13 of one absorbent sheet 10 can be designated as the second sheet S2, the top layer sheet 11 and bottom layer sheet 13 of the other absorbent sheet 20 can be designated as the third sheet S3, and the middle layer sheet 12 can be designated as the fourth sheet S4. In this example, the middle layer sheet 12 of the second connection portion is sandwiched between the top layer sheet 11 and bottom layer sheet 13 of the first connection portion C1, which increases the strength compared to the example shown in Figure 1, but the connection work becomes somewhat more complicated. Compared to the example shown in Figure 5, if the connection end 10p of one absorbent sheet 10 and the connection end 20d of the other absorbent sheet 20 are peeled off in the thickness direction TD, and the length of one of them is shortened to form the first connection portion C1 and the second connection portion C2, as in the example shown in Figure 1, the connection work can be simplified because only the first connection portion C1 and the second connection portion C2 need to be overlapped. This difference in connection work occurs when there are three or more layers of sheets 11, 12, and 13 (i.e., when there are multiple sheets 12 in the middle layer). When splicing absorbent sheets 10 and 20 that have two layers of sheets 11, 12, and 13, as in the example shown in Figure 4, there is no difference like when there are three or more layers of sheets 11, 12, and 13, and it has the same advantages as the example shown in Figure 1. Note that the example shown in Figure 4 is basically the same as the example shown in Figure 1 except for the number of sheets, so the same reference numerals are used and the explanation is omitted.

[0035] The first connecting portion C1 and the second connecting portion C2 can be formed, for example, by shifting the starting positions of the sheets 11, 12, and 13 supplied from each raw material roll 11R, 12R, and 13R in the MD direction during the manufacturing of the absorbent sheets 10 and 20. Alternatively, in one absorbent sheet 10 after manufacturing, the connecting end of the first sheet S1 can be peeled from the second sheet S2 and the connecting end of the first sheet S1 can be cut off by a predetermined distance to form the first connecting portion C1, and in the other absorbent sheet 20 after manufacturing, the connecting end of the third sheet S3 can be peeled from the fourth sheet S4 and the connecting end of the third sheet S3 can be cut off by a predetermined distance to form the second connecting portion C2.

[0036] In the latter case, if sheets 11, 12, and 13 adjacent to each other in the thickness direction TD of the absorbent sheets 10 and 20 are bonded together via a hot-melt adhesive HM, and the superabsorbent polymer particles P are also bonded to the adjacent sheets 11, 12, and 13 via the hot-melt adhesive HM, then when forming the first connection portion C1 and the second connection portion C2, the sheets 11, 12, and 13 can be easily peeled off by melting the hot-melt adhesive HM with a heat gun or the like. Furthermore, if the superabsorbent polymer particles P are bonded to the adjacent sheets 11, 12, and 13 via the hot-melt adhesive HM, there is also the advantage that the superabsorbent polymer particles P are less likely to spill out when the sheets 11, 12, and 13 are peeled off to form the first connection portion C1 and the second connection portion C2.

[0037] Once the first connecting portion C1 and the second connecting portion C2 are formed, the connecting ends of the first sheet S1 and the second sheet S2 of one absorbent sheet 10 are abutted against the connecting ends of the fourth sheet S4 and the third sheet S3 of the other absorbent sheet 20, respectively. The first connecting portion C1 and the second connecting portion C2 are then joined together at intervals using adhesive or welding at a number of joints 14, completing the splicing without applying adhesive tape to at least one of the front or back surfaces. If it is predetermined whether the front or back of the manufactured absorbent sheets 10 and 20 will be the front or back of the absorbent article, then the adhesive tape 16 should not be applied to the surface of the absorbent sheets 10 and 20 that will be the front side of the absorbent article.

[0038] The joining of the first connecting portion C1 and the second connecting portion C2 is preferably performed by welding, from the viewpoint of ensuring strength while suppressing the joining area. In this case, as shown in Figure 7, point-shaped joining portions 14 can be scattered at appropriate intervals throughout the joining area, and linear joining portions that are continuous in an appropriate direction such as the MD direction or CD direction can be provided at appropriate intervals throughout the joining area.

[0039] The planar shape of the point-shaped joint 14 can be determined as appropriate. The joint 14 can be an elongated hole shape as shown in Figure 7(b), or it can be any shape such as a perfect circle as shown in Figure 7(e), an ellipse as shown in Figures 7(a) and (d), a curved shape (arc shape) as shown in Figure 7(f), a triangle, a rectangle, a rhombus or other polygon, a star shape, a cloud shape, etc. As shown in Figure 7(c), joints 14 of different shapes may be mixed together. The dimensions of each joint 14 can be determined as appropriate. For example, the dimension 14L in the MD direction of the joint 14 (dimension of the longest part) can be 0.5 to 13 mm, and the dimension 14W in the CD direction of the joint 14 (dimension of the longest part) can be 0.5 to 13 mm. If the shape of the joint 14 is elongated in one direction, such as a long hole, ellipse, rectangle, rhombus, or arc (a shape in which the total length in one direction is longer than the total length in the direction perpendicular to it), then for example, the lengthwise dimension (the dimension of the longest part) can be 1.5 to 50 times the lengthwise dimension (the dimension of the longest part). Furthermore, if the shape of the joint 14 is elongated in one direction, the lengthwise direction of the joint 14 can be the MD direction, the CD direction, or an oblique direction inclined to these directions.

[0040] The planar arrangement of the joints 14 can be determined as appropriate. For example, a row of joints 14 spaced apart in the MD direction perpendicular to the CD direction can be arranged with spacing in the CD direction. An example of such an arrangement is shown in Figures 7(a), 7(c), and 7(d), where the arrangement of joints 14 is a matrix in which rows of joints 14 linearly arranged at predetermined intervals in the MD direction are repeated at predetermined intervals in the CD direction. In this case, as shown in Figure 7(a), the arrangement can be such that the spacing 14x of the joints 14 in the CD direction is shorter than the spacing 14y of the joints 14 in the MD direction, as shown in Figure 7(c), the spacing 14x of the joints 14 in the CD direction and the spacing 14y of the joints 14 in the MD direction are approximately equal, or as shown in Figure 7(d), the arrangement can be such that the spacing 14x of the joints 14 in the CD direction is longer than the spacing 14y of the joints 14 in the MD direction. Furthermore, as shown in Figures 7(b), (e), and (f), the rows of joints 14, which are linearly arranged at predetermined intervals in the MD direction, can also be arranged with gaps in the CD direction and with their positions offset in the MD direction. The example shown in Figure 7(b) is a so-called staggered (hexagonal lattice) arrangement in which the joints 14 are staggered in adjacent rows of joints 14. Also, as shown in Figure 7(f), the orientation of the joints 14 may be opposite in adjacent rows of joints 14.

[0041] The spacing 14y in the MD direction and the spacing 14x in the CD direction of the joint 14 may be constant or vary. The spacing 14y in the MD direction and the spacing 14x in the CD direction of the joint 14 can be determined as appropriate. For example, the spacing 14y in the MD direction of the joint 14 can be 1 to 50 mm, and the spacing 14x in the CD direction of the joint 14 can be 1 to 50 mm.

[0042] In this splicing method, a first connecting portion C1 consisting only of the second sheet S2 is formed at the connecting end of one absorbent sheet 10, and a second connecting portion C2 consisting only of the fourth sheet S4 is formed at the connecting end of the other absorbent sheet 20. Then, while maintaining the continuity of the laminated structure across both absorbent sheets 10 and 20, the first connecting portion C1 and the second connecting portion C2 are joined by adhesive or welding. As a result, splicing can be performed by not using adhesive tape 16 at the joint 15, or by using adhesive tape 16 only on one side of the joint 15. Therefore, by embedding the absorbent sheets 10 and 20 in an absorbent article so that the side without adhesive tape 16 is the front side (skin side), even if the product contains absorbent sheets 10 and 20 with a joint 15, the feel, appearance, and absorption performance on the front side will be comparable to that of a product containing absorbent sheets without a joint 15, thus eliminating the need for disposal. Therefore, this splicing method makes it possible to prevent the deterioration of the waste rate due to splicing of the absorbent sheets 10 and 20.

[0043] Furthermore, when adjacent sheets 11, 12, and 13 in the thickness direction TD are bonded together via a hot-melt adhesive HM, and superabsorbent polymer particles P are bonded to adjacent sheets 11, 12, and 13 via the hot-melt adhesive HM, as shown in Figures 1, 3, and 4, after the formation of the first connection portion C1 and the second connection portion C2, superabsorbent polymer particles P remain on the surface of the second sheet S2 of the first connection portion C1 that faces the first sheet S1, and on the surface of the fourth sheet S4 of the second connection portion C2 that faces the third sheet S3. These superabsorbent polymer particles P are then positioned between the first connection portion C1 and the second connection portion C2 due to the bonding of the two, and the same absorption performance is maintained in the laminated region of the first connection portion C1 and the second connection portion C2 as in other areas.

[0044] As shown in Figure 2, to reinforce the strength of the joint 15 between one absorbent sheet 10 and the other absorbent sheet 20, adhesive tape 16 can be applied to either the front or back surface of the joint 15. That is, with the connection ends of the first sheet S1 and the second sheet S2 of one absorbent sheet 10 butted against the connection ends of the fourth sheet S4 and the third sheet S3 of the other absorbent sheet 20, adhesive tape 16 is applied to only one of the front or back surfaces of this butt joint, so as to straddle the butt joint. It is preferable to use adhesive tape 16 of the same color as other components (e.g., white) or a light color so that it is not noticeable. The adhesive tape 16 can also be applied after joining the first connection part C1 and the second connection part C2, but it is preferable to join the first connection part C1 and the second connection part C2 after applying the adhesive tape 16, as this makes joining the first connection part C1 and the second connection part C2 easier.

[0045] The absorbent sheets 10 and 20 can be packaged with a packaging sheet 34 after splicing. As the packaging sheet 34, liquid permeable materials such as tissue paper, especially crepe paper, nonwoven fabric, poly-laminated nonwoven fabric, or sheets with small holes can be used. However, it is desirable that the sheet does not allow the highly absorbent polymer particles P to escape. When using nonwoven fabric instead of crepe paper, a hydrophilic nonwoven fabric having a dense layer is preferred. As such a nonwoven fabric, laminated nonwoven fabric (including SMS nonwoven fabric, SSMMS nonwoven fabric, etc.) is particularly preferred, in which one or more meltblown layers and one or more protective layers such as spunbond layers are laminated, and the material can be polypropylene, polyethylene / polypropylene composite material, etc.

[0046] The basis weight and thickness of the packaging sheet 34 can be determined as appropriate. For example, if the packaging sheet 34 is a laminated nonwoven fabric, the basis weight of the packaging sheet 34 is 8 to 17 g / m². 2 It is preferable that the packaging sheet 34 has a thickness of 0.05 to 0.8 mm.

[0047] The packaging structure of the packaging sheet 34 can be determined as appropriate, but from the viewpoint of ease of manufacturing and preventing leakage of highly absorbent polymer particles P from the front and rear edges, it can be wrapped around the front and back surfaces and both sides of the absorbent sheets 10 and 20 in a cylindrical shape, as shown in Figure 6(a). In addition, in order to make the thickness of the absorbent element consisting of the absorbent sheets 10 and 20 and the packaging sheet 34 thinner, the packaging sheet 34 can also be wrapped around only one side of one surface of the absorbent sheet 10 or 20 (if it is predetermined whether the front or back of the manufactured absorbent sheet 10 or 20 will be the front or back side of the absorbent article, then the surface that will be located on the front side of the absorbent article), as shown in Figure 6(b), so as to cover only the area from one side of the absorbent sheet 10 or 20 through one side edge, the other surface and the other side edge, to the other side of the first surface.

[0048] The packaging sheet 34 can be bonded to the absorbent sheets 10 and 20 via hot melt adhesive HM over almost the entire surface facing the absorbent sheets 10 and 20, as shown in the example in Figure 6(a), or it can be bonded to only a portion of the absorbent sheets 10 and 20, as shown in the example in Figure 6(b).

[0049] The example shown in Figure 5 involves winding the manufactured absorbent sheets 10 and 20 onto a roll to produce an absorbent sheet roll. However, the absorbent sheets can also be supplied directly to the assembly line without being wound onto a roll. As can be seen from this, the pair of absorbent sheets 10 and 20 used in splicing may both have portions wound onto a roll, or one or both may not be wound onto a roll.

[0050] <Examples of absorbent materials> The absorbent sheets 10, 20 manufactured as described above, or those packaged in the packaging sheet 34, can be cut to an appropriate length and incorporated into absorbent articles as absorbent components. Figures 8 to 12 show examples of application to pad-type disposable diapers. This pad-type disposable diaper 100 has a crotch area M including the center of the anterior-posterior direction LD, a front portion F extending forward from the crotch area M, and a rear portion B extending backward from the crotch area M. The crotch area M refers to the range of the anterior-posterior direction LD that has a constriction formed in the middle of the anterior-posterior direction LD in the absorbent sheet 10, 20 or the product's outer shape, which is narrower than both the front and rear sides (a well-known hourglass shape). If neither the absorbent sheet 10, 20 nor the product's outer shape has a constriction, the crotch area M refers to the portion located in the center of the anterior-posterior direction LD, where the dimension of the anterior-posterior direction LD is 20-40% of the total length of the product.

[0051] This pad-type disposable diaper 100 has absorbent sheets 10 and 20 built in, extending across the front portion F, the crotch portion M, and the back portion B. The front side of the absorbent sheets 10 and 20 is covered with a liquid-permeable top sheet 32, and the back side of the absorbent sheets 10 and 20 is covered with a liquid-impermeable sheet 31. The absorbent sheets 10 and 20 may have a seam 15 formed by the aforementioned splicing. In this way, even in products that have absorbent sheets 10 and 20 with a seam 15 built in, if the side of the absorbent sheet 10 and 20 without adhesive tape 16 is the front side (skin side), the feel, appearance, and absorbency on the front side are comparable to products that have absorbent sheets 10 and 20 without a seam 15, and the product does not need to be discarded.

[0052] As mentioned above, the absorbent sheets 10 and 20 can be packaged with the packaging sheet 34 as needed.

[0053] As the liquid-impermeable sheet 31, in addition to polyethylene film, a sheet that is permeable to moisture without impairing water resistance can also be used to prevent stuffiness. In the illustrated example, the liquid-impermeable sheet 31 extends beyond the periphery of the absorbent sheets 10 and 20, but it does not have to extend beyond the periphery of the absorbent sheets 10 and 20. Preferably, the outer surface (back surface) of the liquid-impermeable sheet 31 is covered with an outer sheet 35 made of nonwoven fabric.

[0054] As the top sheet 32, any known material such as a permeable permeable perforated or non-perforated nonwoven fabric or a perforated resin sheet can be appropriately selected and used. In the illustrated example, the absorbent sheets 10 and 20 partially protrude from the side edges of the top sheet 32, but the width of the top sheet 32 ​​can be widened so that the side edges of the absorbent sheets 10 and 20 do not protrude. As the top sheet 32, perforated or non-perforated nonwoven fabric or a perforated plastic sheet can be used.

[0055] The front and rear ends of the pad-type disposable diaper 100 are end flaps EF that extend beyond the front and rear ends of the absorbent sheets 10 and 20, respectively, and where the absorbent sheets 10 and 20 are absent. The material constituting the end flaps EF is not particularly limited, but in the illustrated example, it is the portion of the liquid-impermeable sheet 31, outer sheet 35, and top sheet 32 ​​that extends on both the front and rear sides of the absorbent sheets 10 and 20.

[0056] Furthermore, both sides of the pad-type disposable diaper 100 are side flaps SF that extend laterally beyond the side edges of the absorbent core, and do not contain absorbent sheets 10 and 20. The material constituting the side flaps SF is not particularly limited, but in the illustrated example, it consists of the liquid-impermeable sheet 31, outer sheet 35, top sheet 32, and gather sheet 62, which extend on both sides of the absorbent sheets 10 and 20 in the width direction WD. The bonding of these materials can be performed by material welding, such as heat sealing or ultrasonic sealing, in addition to the hot melt adhesive shown as a dot pattern in the figure.

[0057] To block urine and loose stool moving laterally on the top sheet 32 ​​and prevent leakage, the disposable diaper surface is provided with rise-up gathers 60 that extend from the sides of the top sheet 32 ​​towards the skin, extending along the entire front-to-back direction.

[0058] The illustrated example of the rising gather 60 has a base portion 65 fixed to the region including the side flap SF, a protruding portion 66 extending from the base portion 65, a collapsed portion 67 at both front-rear ends of the protruding portion fixed in a collapsed state, an unfixed rising portion 68 located between the front-rear collapsed portions of the protruding portion 66, and a gathering elastic member 63 fixed to at least the tip of the rising portion 68 in an extended state in the front-rear direction. The rising gather 60 is formed by a gathered sheet 62 that is folded back at the tip, with the gathering elastic member 63 sandwiched between the layers of the gathered sheet 62.

[0059] In the illustrated example, the base portion 65 of the rising gather 60 is provided only on the side flap SF and is joined to the side of the liquid-impermeable sheet 31 and the side of the outer sheet 35, but it may also extend from the side flap SF to the side of the area overlapping with the absorbent sheets 10 and 20.

[0060] The protruding portion 66 of the rise-up gather 60 has a folded portion at both ends in the front-to-back direction LD, but the portion in between is an unfixed rise-up portion 68, which stands up due to the contraction force of the gather elastic member 63. When the diaper is put on, the diaper is fitted to the body in a boat shape, and the contraction force of the gather elastic member 63 acts on it, causing the rise-up gather 60 to stand up and elastically adhere to the legs. As a result, so-called side leakage from around the legs is prevented.

[0061] As the gathered sheet 62, any known material such as a water-repellent nonwoven fabric can be used without any particular limitations. As the gathered elastic member 63, any known rubber formed in the form of a thread, string, strip, etc., can be used without any particular limitations.

[0062] Of course, the absorbent sheets 10, 20 manufactured as described above, or the absorbent elements packaged in the packaging sheet 34, can also be applied to other types of absorbent articles such as pant-type disposable diapers, tape-type disposable diapers, and sanitary napkins. In other words, the absorbent sheets 10, 20 described above can be used in all types of absorbent articles that have an absorbent element between a liquid-permeable top sheet and a liquid-permeable or liquid-impermeable back sheet.

[0063] <Explanation of terms used in the specification> The following terms in this specification shall have the meanings set forth below, unless otherwise specified in this specification.

[0064] "Nonwoven fabric" refers to any known nonwoven fabric, which can be appropriately selected depending on the application. The constituent fibers of the nonwoven fabric can be selected without particular limitation, including, for example, polyolefin-based fibers such as polyethylene or polypropylene, polyester-based fibers, polyamide-based fibers, etc. (including single-component fibers as well as composite fibers such as core-sheath fibers), regenerated fibers such as rayon and cupro, and natural fibers such as cotton, and these can also be used in mixtures. To increase the flexibility of the nonwoven fabric, it is preferable to use crimped fibers as constituent fibers. Furthermore, the constituent fibers of the nonwoven fabric may be hydrophilic fibers (including fibers made hydrophilic by a hydrophilizing agent), hydrophobic fibers, or water-repellent fibers (including fibers made water-repellent by a water-repellent agent). Furthermore, nonwoven fabrics are generally classified according to the length of the fibers, the sheet formation method, the fiber bonding method, and the lamination structure into short fiber nonwoven fabrics, long fiber nonwoven fabrics, spunbond nonwoven fabrics, meltblown nonwoven fabrics, spunlace nonwoven fabrics, thermal bond (air-through) nonwoven fabrics, needle punch nonwoven fabrics, point bond nonwoven fabrics, and laminated nonwoven fabrics (including SMS nonwoven fabrics and SMMS nonwoven fabrics, etc., which have a meltblown layer sandwiched between spunbond layers), and any of these nonwoven fabrics can be used.

[0065] • "MD direction (machine direction or line flow direction)" and "CD direction (transverse direction perpendicular to the MD direction)" refer to the "MD direction" and "CD direction" of the manufacturing equipment. Therefore, the MD direction is the direction of fiber orientation of the nonwoven fabric. Fiber orientation is the direction along which the fibers of the nonwoven fabric run, and can be determined, for example, by a measurement method conforming to the fiber orientation test method by zero-distance tensile strength of the TAPPI standard method T481, or by a simple measurement method that determines the fiber orientation direction from the ratio of tensile strength in the front-to-back direction and the width direction. In most absorbent products, the front-to-back direction is the MD direction and the width direction is the CD direction.

[0066] "Front-to-back direction" refers to the direction indicated by the symbol LD in the diagram (vertical direction), and "width direction" refers to the direction indicated by WD in the diagram (left-to-right direction). The front-to-back direction and the width direction are orthogonal to each other.

[0067] "Front side" refers to the side of a pull-up type disposable diaper that is closer to the wearer's skin, while "back side" refers to the side of a pull-up type disposable diaper that is further away from the wearer's skin.

[0068] "Surface" refers to the side of the material that is closer to the wearer's skin when wearing the pull-up type disposable diaper, while "back" refers to the side that is further away from the wearer's skin when wearing the pull-up type disposable diaper.

[0069] The "gel strength" is measured as follows: 49.0 g of artificial urine (a mixture of urea: 2 wt%, sodium chloride: 0.8 wt%, calcium chloride dihydrate: 0.03 wt%, magnesium sulfate heptahydrate: 0.08 wt%, and deionized water: 97.09 wt%) is mixed with 1.0 g of superabsorbent polymer and stirred with a stirrer. The resulting gel is left in a constant temperature and humidity chamber at 40°C × 60% RH for 3 hours, then returned to room temperature, and the gel strength is measured using a card meter (I.techno Engineering: Curdmeter-MAX ME-500).

[0070] "Weight" is measured as follows: After pre-drying the sample or test piece, leave it in a test room or apparatus under standard conditions (temperature 23±1°C, relative humidity 50±2%) to reach a constant weight. Pre-drying means bringing the sample or test piece to a constant weight in an environment of 100°C. Note that pre-drying is not necessary for fibers with an official moisture content of 0.0%. Using a sample-taking template (100mm x 100mm), cut out a sample measuring 100mm x 100mm from the test piece that has reached a constant weight. Measure the weight of the sample, multiply it by 100 to calculate the weight per square meter, and this is the weight.

[0071] The "thickness" of thick materials such as absorbent sheets and absorbent elements 50 is measured using a thickness measuring instrument (Peacock, dial thickness gauge, model H (measurement range 0-10 mm, measurement area diameter 10 mm circular terminal, measuring force approximately 1.7 N, pressure approximately 21.7 KPa)) manufactured by Ozaki Seisakusho Co., Ltd., with the sample and the thickness measuring instrument held horizontally.

[0072] The "thickness" of thin sheets such as nonwoven fabrics is measured using an automatic thickness measuring instrument (KES-G5 handy compression measurement program) with a load of 0.098 N / cm². 2 , and pressure area: 2cm 2 Automatic measurement is performed under these conditions.

[0073] • Water absorption is measured according to JIS K7223-1996 "Test method for water absorption of superabsorbent polymers".

[0074] The water absorption rate shall be the "time to the endpoint" when 2 g of superabsorbent polymer and 50 g of physiological saline solution are used in the JIS K7224-1996 "Test method for water absorption rate of superabsorbent polymers".

[0075] "Deployed state" refers to the state in which the material has been stretched to its elastic limit (in other words, the state in which it has been unfolded flat without any contraction (including contraction due to elastic members, etc.) or slack).

[0076] Unless otherwise specified, the dimensions of each part refer to the dimensions in the unfolded state, not the natural length state.

[0077] Unless otherwise specified, the tests and measurements shall be conducted in a test room or apparatus under standard conditions (temperature 23±1°C, relative humidity 50±2%). [Industrial applicability]

[0078] This invention can be used for splicing absorbent sheets in all types of absorbent articles, such as disposable diapers, sanitary napkins, and pet sheets, regardless of the intended use of the absorbent sheet. [Explanation of Symbols]

[0079] 10, 20… Absorbent sheet, 10… One absorbent sheet, 11, 12, 13… Sheet, 11R, 12R, 13R… Raw material roll, 20… Other absorbent sheet, 31… Liquid impermeable sheet, 32… Top sheet, C1… First connection part, C2… Second connection part, P… Super absorbent polymer particles, S1… First sheet, S2… Second sheet, S3… Third sheet, S4… Fourth sheet, TD… Thickness direction, LD… Front-to-back direction, WD… Width direction, 11… Topmost sheet, 13… Bottommost sheet, 12… Middle sheet, 15… Seam, 16… Adhesive tape, 34… Packaging sheet, 100… Pad-type disposable diaper, EF… End flap, 35… Outer sheet, SF… Side flap.

Claims

1. A method for splicing an absorbent sheet having a laminated structure in which multiple liquid-permeable sheets are laminated together and highly absorbent polymer particles are arranged between adjacent sheets, wherein the laminated structure is continuous in the MD direction or regularly repeating in a pair of absorbent sheets, with one end and the other end of the absorbent sheet in the MD direction designated as a connecting end and a non-connecting end, respectively, wherein the connecting end of one absorbent sheet is spliced ​​to the connecting end of the other absorbent sheet, Of the one absorbent sheet, the connection end of the first sheet, which consists of at least one sheet, is positioned a predetermined distance closer to the non-connection end than the connection end of the second sheet, which consists of sheets other than the first sheet, thereby forming a first connection portion consisting only of the second sheet at the connection end of the one absorbent sheet. Of the other absorbent sheets, the connection end of the third sheet whose stacking position corresponds to the second sheet is positioned at the non-connection end by a predetermined distance from the connection end of the fourth sheet whose stacking position corresponds to the first sheet, thereby forming a second connection portion consisting only of the fourth sheet at the connection end of the other absorbent sheet. The connection ends of the first sheet and the second sheet of one of the absorbent sheets are butted against the connection ends of the fourth sheet and the third sheet of the other absorbent sheet, respectively, and the first and second connection portions are joined together with a gap between them by adhesive or welding. Adhesive tape is not applied to at least one of the front and back surfaces of the pair of absorbent sheets. A splicing method for an absorbent sheet, characterized by the following features.

2. In the aforementioned absorbent sheet, adjacent sheets in the thickness direction are bonded together via a hot melt adhesive. The superabsorbent polymer particles are bonded to the adjacent sheet via a hot melt adhesive. When forming the first connecting portion, the connecting end of the first sheet in the one absorbent sheet is peeled off from the second sheet, and the connecting end of the first sheet is cut off by the predetermined distance to form the first connecting portion. When forming the second connecting portion, the connecting end of the third sheet in the other absorbent sheet is peeled off from the fourth sheet, and the connecting end of the third sheet is cut off by the predetermined distance to form the second connecting portion. A splicing method for an absorbent sheet according to claim 1.

3. With the connection ends of the first sheet and the second sheet of one of the absorbent sheets abutted against the connection ends of the fourth sheet and the third sheet of the other absorbent sheet, respectively, adhesive tape is applied to only one side of the abutted portion, so as to straddle the abutted portion. Subsequently, the first connecting portion and the second connecting portion are joined together with an interval between them by adhesive or welding. A splicing method for an absorbent sheet according to claim 1 or 2.

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