Absorbent sheet

Abstract

The invention provides an absorbent sheet capable of preventing channel breakage. An absorbent sheet (10) is provided with: a base sheet (12); a plurality of absorbent layers (21-23) that contain a superabsorbent polymer resin and are provided at intervals on the main surface (12s) of the base sheet (12); and a cover sheet (14) that covers the main surface (12s) of the base sheet (12) and the absorption layers (21-23). The structure of the absorbent sheet (10) is such that when the superabsorbent polymer resin in the absorbent layers (21-23) swells, the base sheet (12) deforms more easily than the cover sheet (14).

Description

Technical Field

[0001] The present invention relates to an absorbent sheet, and more particularly to an absorbent sheet for absorbing liquids such as disposable diapers. Background Art

[0002] Absorbent sheets for absorbing liquids are used in diapers, incontinence pads, sanitary napkins, and the like.

[0003] For example, Figure 9 and Figure 10 The absorbent sheet 1 shown has a superabsorbent polymer resin provided on a base sheet. Figure 9 is a partial cross-sectional perspective view of the absorbent sheet 1, Figure 10 is a schematic cross-sectional view of an absorbent sheet. Figure 9 and Figure 10 As shown, a first hot-melt adhesive layer S1 is disposed on a first nonwoven fabric 2 in two sections, and an absorbent resin powder layer 3 composed of superabsorbent polymer resin powder is disposed on the left and right sides of the first hot-melt adhesive layer S1. Furthermore, a second hot-melt adhesive layer S2 is disposed substantially over the entire surface of the first nonwoven fabric 2. Furthermore, a second nonwoven fabric 4 is disposed on the second hot-melt adhesive layer S2, having substantially the same area and structure as the first nonwoven fabric 2 (see, for example, Patent Document 1).

[0004] Patent Document 1: JP 4795612 B2

[0005] The second nonwoven fabric 4 is recessed in the middle region 2b between the absorbent resin powder existing regions 2c, where the absorbent resin powder layer 3 is provided. This forms a channel. When the fluid flows along the channel, the area where the liquid is absorbed by the superabsorbent polymer resin becomes wider.

[0006] However, if the superabsorbent polymer resin swells to squeeze the channels and cause the flow paths to be narrowed or cut off, the liquid absorption performance may be deteriorated. Summary of the Invention

[0007] An object of the present invention is to provide an absorbent sheet capable of preventing channel rupture.

[0008] The present invention provides an absorbent sheet having the following structure:

[0009] The absorbent sheet is provided with: a base sheet; a plurality of absorbent layers which are spaced apart on a major surface of the base sheet and contain a superabsorbent polymer resin; and a cover sheet which covers the major surface of the base sheet and the absorbent layers; the absorbent sheet is configured so that when the superabsorbent polymer resin in the absorbent layers swells, the base sheet is more easily deformed than the cover sheet.

[0010] With this structure, channels are formed between adjacent absorbent layers. Since the cover sheet covering the absorbent layers is less susceptible to deformation than the base sheet, the spacing between adjacent absorbent layers does not readily change when the superabsorbent polymer resin in the absorbent layers swells. This prevents channel compression.

[0011] Preferably, the absorbent sheet is configured so that when the superabsorbent polymer resin in the absorbent layer swells, the base sheet is compressed and deformed in the thickness direction.

[0012] In this case, when the super absorbent polymer resin in the absorbent layer swells, the interval between adjacent absorbent layers does not change easily, thereby preventing channel squeezing.

[0013] Preferably, the base sheet has a lower resiliency than the cover sheet.

[0014] In this case, to prevent channel squeezing, the absorbent sheet is configured so that when the superabsorbent polymer resin in the absorbent layer swells, the base sheet is compressed and deformed in the thickness direction.

[0015] Preferably, the cover sheet is bonded to an area of ​​the major surface of the base sheet where substantially no superabsorbent polymer resin is present.

[0016] In this case, compared with the case where the cover sheet and the base sheet are not bonded, the intervals between adjacent absorbent layers are less likely to change when the superabsorbent polymer resin in the absorbent layer swells, thereby better preventing channel squeezing.

[0017] Preferably, the transverse stress experienced by the base sheet at 5% expansion is lower than the transverse stress experienced by the cover sheet at 5% expansion. "Transverse stress during expansion" herein refers to "contraction stress acting in a transverse direction perpendicular to the expansion direction and thickness direction during expansion" or "tension per unit length in a transverse direction perpendicular to the expansion direction and thickness direction during expansion."

[0018] In this case, the absorbent sheet may be configured so that when the superabsorbent polymer resin in the absorbent layer swells, the base sheet is more easily deformed than the cover sheet.

[0019] Preferably, the base sheet has a bulky structure with pores formed between the fibers.

[0020] In this case, considering that the base sheet is easily deformed, the absorbent sheet may be configured so that when the superabsorbent polymer resin in the absorbent layer swells, the base sheet is more easily deformed than the cover sheet.

[0021] Preferably, the bulk density of the lofted structure of the base sheet is less than the bulk density of the cover sheet.

[0022] In this case, the absorbent sheet may be configured so that the base sheet is more easily deformed than the cover sheet.

[0023] Preferably, the thickness of the cover sheet is equal to or smaller than the thickness of the substrate.

[0024] In this case, the entire absorbent sheet can be made thinner compared to the case where the thickness of the cover sheet is greater than the thickness of the base sheet.

[0025] The absorbent sheet of the present invention can prevent channel squeezing. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 a is a plan view of the absorbent sheet of Example 1 of the present invention; Figure 1 b is along Figure 1 a is a cross-sectional view along line BB; Figure 1 c is the cross-sectional view during expansion. Figure 2 a is a plan view of an absorbent sheet according to modification 1 of the present invention; Figure 2 b is along Figure 2 a is a cross-sectional view along line BB; Figure 2 c is the cross-sectional view during expansion. Figure 3 a is a plan view of an absorbent sheet according to modification 2 of the present invention; Figure 3 b is along Figure 3 a is a schematic cross-sectional view of line BB; Figure 3 c is the cross-sectional view during expansion. Figure 4 a is a plan view of an absorbent sheet according to modification 3 of the present invention; Figure 4 b is along Figure 4 a is a cross-sectional view along line BB; Figure 4 c is the cross-sectional view during expansion. Figure 5 a is a plan view of an absorbent sheet according to modification 4 of the present invention; Figure 5 b is along Figure 5 a is a cross-sectional view along line BB; Figure 5 c is the cross-sectional view during expansion. Figure 6 a is a plan view of an absorbent sheet according to modification 5 of the present invention; Figure 6 b is along Figure 6 a is a cross-sectional view along line BB; Figure 6 c is the cross-sectional view during expansion. Figure 7 a is a perspective view of an absorbent sheet on the opposite side of the substrate relative to one major surface of the substrate in Modification 6 of the present invention; Figure 7 b is a perspective view of the base sheet of the absorbent sheet; Figure 7c is a perspective view of the absorbent sheet on the opposite side of the substrate relative to the other major surface of the substrate. Figure 8 a is a perspective view of an absorbent sheet on the opposite side of the substrate relative to one major surface of the substrate according to Modification 7 of the present invention; Figure 8 b is a perspective view of the base sheet of the absorbent sheet; Figure 8 c is a perspective view of the absorbent sheet on the opposite side of the substrate relative to the other major surface of the substrate. Figure 9 It is a partial cross-sectional view of the absorbent sheet of conventional embodiment 1. Figure 10 The conventional embodiment 1 is along Figure 9 Schematic diagram of the cross section of line XX. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Example 1: Figure 1 a- Figure 1 As shown in FIG. c, the absorbent sheet 10 of the present invention will be described. Figure 1 a is a plan view of the absorbent sheet 10; Figure 1 b is along Figure 1 a is a cross-sectional view along line BB; Figure 1 c is the cross-sectional view during expansion.

[0029] like Figure 1 a- Figure 1 As shown in Figure c, the absorbent sheet 10 includes: a base sheet 12; a plurality of absorbent layers 21-23, which are spaced apart on the main surface 12s of the base sheet 12; and contain a superabsorbent polymer resin; a covering sheet 14, which covers the main surface 12s of the base sheet 12 and the absorbent layers 21-23; and a core wrapping sheet 18, which wraps the base sheet 12 and the covering sheet 14.

[0030] The substrate 12 is rectangular; and in the length direction ( Figure 1 Extending in the vertical direction in a).

[0031] The absorbent layers 21 to 23 are formed of a powdered or granular superabsorbent polymer resin; the resin is arranged in a predetermined area of ​​a main surface 12s of the substrate 12 and has a predetermined thickness; the absorbent layers 21 to 23 are arranged at intervals in the width direction intersecting with the length direction of the substrate 12; and extend parallel to each other in the length direction; the absorbent layers 21 to 23 are arranged so that gaps are left between the absorbent layers and the edges 12p and 12q and the edges 12m and 12n of the substrate 12.

[0032] The covering sheet 14 is formed of a liquid-permeable sheet material, and its portion covering the absorbent layers 21 to 23 is higher than the portion covering the surrounding areas of the absorbent layers 21 to 23. As a result, groove-like channels 26 and 27 extending in the length direction are formed between the adjacent absorbent layers 21 and 22 and the absorbent layers 22 and 23.

[0033] The core wrap sheet 18 covers the other major surface 12t and side surfaces 12u and 12v of the base sheet 12 and overlaps the cover sheet 14, exposing the channels 26 and 27, thereby wrapping the base sheet 12 and the cover sheet 14 in a C-shaped structure. The core wrap sheet 18 can be bonded to the base sheet 12 and / or the cover sheet 14 by an adhesive such as hot melt, ultrasonic bonding, hot melt bonding, etc.

[0034] The absorbent sheet 10 may be structured so that the base sheet 12 is more easily deformed than the cover sheet 14 when the superabsorbent polymer resin in the absorbent layers 21-23 swells.

[0035] For example, Figure 1 As shown in FIG. 3 c, the absorbent sheet 10 is structured so that when the superabsorbent polymer resin in the absorbent layers 21 to 23 of the absorbent sheet 10 absorbs liquid and swells, the base sheet 12 is compressed and deformed in the thickness direction.

[0036] Specifically, base sheet 12 is a nonwoven fabric sheet having a bulky structure, wherein voids are formed between fibers along one major surface 12s; cover sheet 14 is a nonwoven fabric sheet without a bulky structure; and the bulk density of base sheet 12 is lower than that of cover sheet 14. In this case, when the superabsorbent polymer resin in absorbent layers 21-23 swells, base sheet 12 deforms more easily in the longitudinal direction than cover sheet 14; and the intervals between adjacent absorbent layers 21 and 22, and between adjacent absorbent layers 22 and 23, do not easily change, thereby preventing the channels from being squeezed.

[0037] Since the structure of the base sheet 12 has lower resilience than that of the cover sheet 14, when the superabsorbent polymer resin in the absorbent layers 21 to 23 swells, the base sheet 12 is more easily deformed in the thickness direction than the cover sheet 14; and the intervals between adjacent absorbent layers 21 and 22 and between adjacent absorbent layers 22 and 23 are not easily changed, thereby preventing the channels from being squeezed.

[0038] The transverse stress experienced by the base sheet 12 at 5% expansion is lower than the transverse stress experienced by the cover sheet 14 at 5% expansion.

[0039] The thickness of the cover sheet 14 is equal to or smaller than the thickness of the base sheet 12 .

[0040] The basis weight of the cover sheet 14 is equal to or less than the basis weight of the base sheet 12 .

[0041] In one embodiment, the transverse stress at 5% expansion is set to decrease in the order of core wrap sheet 18, cover sheet 14, and base sheet 12. In this case, when the superabsorbent polymer resin in absorbent layers 21-23 swells and compresses base sheet 12, cover sheet 14, and core wrap sheet 18, base sheet 12 is most susceptible to deformation, while core wrap sheet 18 is least susceptible to deformation. Consequently, deformation of base sheet 12 in the planar direction is limited by core wrap sheet 18, making it easier for base sheet 12 to deform in the thickness direction. Furthermore, the intervals between adjacent absorbent layers 21 and 22, and between adjacent absorbent layers 22 and 23, are less likely to change, thereby preventing channels 26 and 27 from being compressed.

[0042] In another embodiment, the transverse stress experienced by core wrap sheet 12 at 5% expansion is lower than the transverse stress experienced by core wrap sheet 18 at 5% expansion. In this case, when the superabsorbent polymer resin in absorbent layers 21-23 swells and compresses base sheet 12, cover sheet 14, and core wrap sheet 18, core wrap sheet 14 deforms more easily than base sheet 12. Consequently, base sheet 12 easily deforms in the planar direction, and the spacing between adjacent absorbent layers 21-23 increases. Consequently, channels 26 and 27 are prevented from being compressed.

[0043] The thickness of the core package sheet 18 is smaller than the thickness of the base sheet 12 .

[0044] The basis weight of the core wrap sheet 18 is less than the basis weight of the base sheet 12 .

[0045] The basis weight of the core sheet 18 is not less than 20g / m 2 And not more than 70g / m 2 .

[0046] For example, air-permeable nonwoven fabric is used for base sheet 12; spunlace nonwoven fabric is used for cover sheet 14; (SMS) nonwoven fabric is used for core wrap sheet. SMS nonwoven fabric here refers to three-layer nonwoven fabric, in which meltblown nonwoven fabric is sandwiched between spunbond nonwoven fabrics.

[0047] While it is possible to employ a configuration where the cover sheet 14 and the base sheet 12 are not bonded, it is preferable that the cover sheet 14 and the base sheet 12 are bonded. Specifically, the cover sheet 14 is bonded to the area surrounding the absorbent layers 21 to 23 (the area where the superabsorbent polymer resin is substantially absent) on one major surface 12s of the base sheet 12 using an adhesive such as heat fusion, ultrasonic bonding, or hot melt bonding. Compared to a case where the cover sheet 14 and the base sheet 12 are not bonded, when the cover sheet 14 and the base sheet 12 are bonded, the spacing between adjacent absorbent layers 21 and 22, and adjacent absorbent layers 22 and 23, is less likely to change, thereby better preventing the channels 26 and 27 from being squeezed. The cover sheet 14 can be bonded to the base sheet 12 by heat fusion bonding the entire area of ​​one major surface 12s of the base sheet 12 from above the absorbent layers 21 to 23.

[0048] like Figure 2 a- Figure 2 c to Figure 8 a- Figure 8 c, Modifications 1 to 7 of the present invention will be described. Components similar to those in Embodiment 1 will be denoted by the same reference numerals as in Embodiment 1, and differences from Embodiment 1 will be mainly described.

[0049] Modification 1: The following structure can be adopted, in which the core wrapping sheet 18 that wraps the base sheet 12 and the cover sheet 14 is removed from the absorbent sheet 10 of Example 1 of the present invention, similar to Figure 2 a- Figure 2 c shows the absorbent sheet 10a in Modification 1.

[0050] For example, Figure 2 As shown in FIG. 3 c, the structure of the absorbent sheet 10a is such that when the superabsorbent polymer resin in the absorbent layers 21 to 23 swells, the base sheet 12 is compressed and deformed in the thickness direction, thereby preventing the channels 26 and 27 from being squeezed.

[0051] Modification 2: The following structure may be adopted to form channels 26 and 27 and channels 36 and 37 on both surfaces of the substrate 12, similar to Figure 3 a-3c shows an absorbent sheet 10b in Modification 2.

[0052] As in Example 1, the absorbent sheet 10b is constructed so that the absorbent layers 21 to 23 are provided on one main surface 12s of the substrate 12; the one main surface 12s of the substrate 12 and the absorbent layers 21 to 23 are covered by the covering sheet 14; and groove-shaped channels 26 and 27 are formed between adjacent absorbent layers 21 and 22 and between adjacent absorbent layers 22 and 23.

[0053] Unlike Example 1, the absorbent sheet 10b further includes: a plurality of absorbent layers 31 to 33, which are spaced apart and disposed on the other major surface 12t of the substrate 12 and contain a superabsorbent polymer resin; and a cover sheet 16, which covers the other major surface 12t of the substrate 12 and the absorbent layers 31 to 33. The absorbent layers 31 to 33 and the cover sheet 16 on the other major surface 12t side of the substrate 12 are formed of similar materials and have structures similar to those of the absorbent layers 21 to 23 and the cover sheet 14 on the one major surface 12s of the substrate 12. Grooved channels 36 and 37 are formed between adjacent absorbent layers 32 and 32, and between adjacent absorbent layers 32 and 33.

[0054] For example, Figure 3As shown in FIG. 3 , the absorbent sheet 10 b is structured so that when the superabsorbent polymer resin in the absorbent layers 21 to 23 and 31 to 33 swells, the base sheet 12 is compressed and deformed in the thickness direction, thereby preventing the channels 26 and 27 and the channels 36 and 37 from being squeezed.

[0055] Variation 3: Figure 4 a- Figure 4 As shown in c, in the absorbent sheet 10c in Modification 3, the cover sheet 16 in Modification 2 can be changed to a core wrap sheet 19.

[0056] Core wrap sheet 19 covers the other major surface 12t of base sheet 12 and absorbent layers 31 to 33, as does cover sheet 16 in Modification 2; covers side surfaces 12u and 12v of base sheet 12, as does core wrap sheet 18 in Modification 1; and overlaps cover sheet 14, exposing channels 26 and 27, thereby wrapping base sheet 12 and cover sheet 14 in a C-shape. Core wrap sheet 19 can be bonded to base sheet 12 and / or cover sheet 14 by an adhesive such as heat fusion, ultrasonic bonding, hot melt bonding, or the like.

[0057] For example, Figure 4 As shown in FIG. 3 , the absorbent sheet 10 c is structured so that when the superabsorbent polymer resin in the absorbent layers 21 to 23 and the absorbent layers 31 to 33 swells, the base sheet 12 is compressed and deformed in the thickness direction, thereby preventing the channels 26 and 27 and the channels 36 and 37 from being squeezed.

[0058] Variation 4: Figure 5 a- Figure 5 As shown in FIG. 3 , in the absorbent sheet 10 d in Modification 4, one channel 28 may be provided on one major surface 12 s side of the base sheet 12 , and one channel 38 may be provided on the other major surface 12 t side of the base sheet 12 .

[0059] In the absorbent sheet 10d, two absorbent layers 24 and 25 are provided on one major surface 12s of the substrate 12, and a channel 28 is formed between the absorbent layers 24 and 25. In addition, two absorbent layers 34 and 35 are provided on the other major surface 12t of the substrate 12, and a channel 38 is formed between the absorbent layers 34 and 35.

[0060] For example, Figure 5 As shown in FIG. 3 , the absorbent sheet 10 d is structured so that when the superabsorbent polymer resin in the absorbent layers 24 and 25 and the absorbent layers 34 and 35 swells, the base sheet 12 is compressed and deformed in the thickness direction, thereby preventing the channels 28 and 38 from being squeezed.

[0061] Variation 5: Figure 6 a- Figure 6As shown in FIG. 3 , in the absorbent sheet 10 e of Modification 5, the cover sheet 16 of Modification 4 can be changed to a core wrap sheet 19 as in Modification 3.

[0062] For example, Figure 6 As shown in FIG. 3 , the absorbent sheet 10e is structured so that when the superabsorbent polymer resin in the absorbent layers 24 and 25 and the absorbent layers 34 and 35 swells, the base sheet 12 is compressed and deformed in the thickness direction, thereby preventing the channels 28 and 38 from being squeezed.

[0063] Variant 6: Figure 7 a is a perspective view of a cover sheet 14 and absorbent layers 21 to 23 provided on one main surface side of a base sheet 12 of an absorbent sheet of Modification 6; Figure 7 b is a plan view of the substrate 12; Figure 7 c is a perspective view of the cover sheet 16 and the absorption layers 31 to 33 provided on the other major surface side of the substrate 12 .

[0064] like Figure 7 a- Figure 7 As shown in FIG. 3 c , the absorption layers 21 to 23 and the absorption layers 31 to 33 may be arranged so as not to have any gaps between them and the edges 12 p and 12 q of the substrate 12 .

[0065] Variant 7: Figure 8 a is a perspective view of a cover sheet 14 and absorbent layers 41 to 45 provided on one principal surface side of a base sheet 12 of an absorbent sheet of Modification 7; Figure 8 b is a plan view of the substrate 12; Figure 8 c is a perspective view of the cover sheet 16 and the absorption layers 51 to 55 provided on the other major surface side of the substrate 12 .

[0066] like Figure 8 a- Figure 8 As shown in FIG. 3 , a plurality of absorbent layers 41 to 45 and 51 to 55 having different sizes and configurations may be provided on the major surface of the substrate 12. Furthermore, the plurality of absorbent layers 41 to 45 and 51 to 55 may be spaced apart in the length direction of the substrate 12 to form channels extending in a width direction intersecting the length direction.

[0067] The absorbent sheet can be constructed by appropriately selecting and combining the structures disclosed in Example 1 and Modifications 1 to 7. For example, a structure can be adopted in which the absorbent layer is provided only on one main surface 12s and the other main surface 12t of the base sheet 12 of the absorbent sheets 10b to 10e of Modifications 2 to 5, as in the variation of Modification 7.

[0068] In summary, the absorbent sheet of the present invention can prevent channel squeezing.

[0069] The present invention is not limited to the above-described embodiment, and various modifications can be made in practice.

[0070] For example, the shapes of the substrate and the absorbent layer are not limited to rectangles. Reference numerals

[0071] 10 and 10a-10e absorbent sheets 12 substrate 12S and 12t main surface 14 and 16 cover sheets 21 to 25 Absorption layer 31 to 35 Absorption layer 41 to 45 Absorption layer 51-55 Absorption layer

Claims

1. An absorbent sheet, characterized in that: It includes: substrate; a plurality of absorbent layers disposed at intervals on the major surface of the substrate and comprising a superabsorbent polymer resin; and a cover sheet covering the major surface of the substrate and the absorbent layer; Wherein, when the superabsorbent polymer resin in the absorbent layer swells, the base sheet is more easily deformed than the cover sheet.

2. The absorbent sheet according to claim 1, characterized in that: When the super absorbent polymer resin in the absorbent layer swells, the base sheet is compressed and deformed in the thickness direction.

3. The absorbent sheet according to claim 1 or 2, characterized in that: The base sheet has a lower resilience than the cover sheet.

4. The absorbent sheet according to any one of claims 1 to 3, characterized in that: The cover sheet is bonded to areas of the major surface of the substrate where the superabsorbent polymer resin is substantially absent.

5. The absorbent sheet according to any one of claims 1 to 4, characterized in that: The transverse stress to which the base sheet is subjected when it expands by 5% is lower than the transverse stress to which the cover sheet is subjected when it expands by 5%.

6. The absorbent sheet according to any one of claims 1 to 5, characterized in that: The base sheet has a bulky structure with pores formed between fibers.

7. The absorbent sheet according to claim 6, characterized in that: The bulk density of the lofted structure of the base sheet is less than the bulk density of the cover sheet.

8. The absorbent sheet according to any one of claims 1 to 7, characterized in that: The thickness of the cover sheet is equal to the thickness of the base sheet; or is smaller than the thickness of the base sheet.

Images