Method for manufacturing an elastic sheet and an elastic sheet manufactured using the same.

Abstract

The present invention provides a method for manufacturing an elastic sheet that can reliably weld both the first nonwoven fabric sheet and the second nonwoven fabric sheet to an elastic member while preventing an increase in equipment costs, and an elastic sheet manufactured using this method. [Solution] Prepare a first nonwoven fabric sheet 2 and a second nonwoven fabric sheet 3, each with a set degree of crystallinity, such that the first nonwoven fabric sheet 2 has a first welding temperature range E1 which includes a first temperature T1 determined by the distance from the ultrasonic horn 11 to the first nonwoven fabric sheet 2 in a predetermined direction and the amount of heat from the ultrasonic horn 11, and is a temperature range in which the first nonwoven fabric sheet 2 can be welded to the elastic member 4, and the second nonwoven fabric sheet 3 has a second welding temperature range E2 which includes a second temperature T2 determined by the distance from the ultrasonic horn 11 to the second nonwoven fabric sheet 3 in the opposing direction and the amount of heat from the ultrasonic horn 11, and is a temperature range in which the second nonwoven fabric sheet 3 can be welded to the elastic member 4.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a stretchable sheet having a first sheet, a second sheet facing the first sheet, and an elastic member provided between the first sheet and the second sheet and joined to both sheets.

Background Art

[0002] Conventionally, for example, a method for manufacturing a stretchable sheet described in Patent Document 1 is known. The manufacturing method described in Patent Document 1 includes a step of introducing a first sheet onto the outer peripheral surface of an anvil roll, a step of introducing an elastic member onto the first sheet of the anvil roll, a step of introducing a second sheet onto the first sheet and the elastic member on the anvil roll, and a step of vibrating a horn with ultrasonic waves and sandwiching both sheets and the elastic member between the horn and the anvil roll to weld the first sheet and the second sheet to the elastic member.

[0003] When melting the first sheet and the second sheet by ultrasonic vibration of the horn in this way, the amount of heat supplied to the first sheet located away from the horn, which is the heat source, may be insufficient, and the welding of the first sheet to the elastic member may be insufficient. Therefore, in the manufacturing apparatus for a stretchable sheet of Patent Document 1, the first sheet on the anvil before the introduction of the second sheet is heated by a heating device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when a heating device is provided as described in Patent Document 1, there is a problem that the cost of the equipment for manufacturing the stretchable sheet increases.

[0006] On the other hand, in order to reliably melt the first and second sheets without using a heating device, it is conceivable to increase the amount of heat supplied to both sheets (energy from ultrasonic vibrations of a horn in Patent Document 1). However, in this case, an excessive amount of heat may be supplied to the second sheet, which is closer to the heat source, potentially causing defects in the second sheet. If defects occur in the second sheet, the welding of the second sheet to the elastic member will be insufficient.

[0007] The object of the present invention is to provide a method for manufacturing an elastic sheet that can reliably weld both the first nonwoven fabric sheet and the second nonwoven fabric sheet to an elastic member while preventing an increase in equipment costs, and to provide an elastic sheet manufactured using this method. [Means for solving the problem]

[0008] The inventors of the present invention discovered that lowering the degree of crystallinity of a nonwoven fabric sheet shifts the lower limit of the welding temperature range to a lower temperature side, and thus came up with the method of the present invention, which involves preparing a first nonwoven fabric sheet and a second nonwoven fabric sheet set to a degree of crystallinity that has a temperature range corresponding to the temperature of both nonwoven fabric sheets heated by a heat supply member.

[0009] Specifically, in order to solve the above problems, the first invention is a method for manufacturing an expandable sheet having a first nonwoven fabric sheet, a second nonwoven fabric sheet facing the first nonwoven fabric sheet, and an elastic member joined to the first nonwoven fabric sheet and the second nonwoven fabric sheet between the first nonwoven fabric sheet and the second nonwoven fabric sheet, wherein the first nonwoven fabric sheet and the second nonwoven fabric sheet are prepared, a heat supply member for supplying heat to the first nonwoven fabric sheet and the second nonwoven fabric sheet to melt the first nonwoven fabric sheet and the second nonwoven fabric sheet, a clamping member facing the heat supply member in a predetermined opposing direction and for sandwiching the first nonwoven fabric sheet, the second nonwoven fabric sheet and the elastic member between the heat supply member and the heat supply member, and the first nonwoven fabric sheet, the second nonwoven fabric sheet and the elastic member are arranged in order in the direction away from the heat supply member in the opposing direction. The present invention provides a method for manufacturing an elastic sheet, comprising: placing a material between the heat supply member and the clamping member; supplying heat to the first nonwoven fabric sheet and the second nonwoven fabric sheet placed between the heat supply member and the clamping member using the heat supply member; and preparing the first nonwoven fabric sheet and the second nonwoven fabric sheet, wherein the crystallinity of the first nonwoven fabric sheet is set such that the first nonwoven fabric sheet has a first welding temperature range which includes a first temperature determined by the distance from the heat supply member to the first nonwoven fabric sheet in the opposing direction and the amount of heat from the heat supply member, and is a temperature range in which the first nonwoven fabric sheet can be welded to the elastic member; and the second nonwoven fabric sheet has a second welding temperature range which includes a second temperature determined by the distance from the heat supply member to the second nonwoven fabric sheet in the opposing direction and the amount of heat from the heat supply member, and is a temperature range in which the second nonwoven fabric sheet can be welded to the elastic member.

[0010] According to the first invention, a first nonwoven fabric sheet and a second nonwoven fabric sheet are prepared, each having a degree of crystallinity set to have a welding temperature range that includes the temperature of each nonwoven fabric sheet, although the temperatures of the first nonwoven fabric sheet and the second nonwoven fabric sheet differ depending on the distance in a predetermined direction from the heat supply member to both nonwoven fabric sheets.

[0011] Therefore, according to the present invention, both nonwoven fabric sheets can be reliably welded to the elastic member without providing a separate configuration for heating the first nonwoven fabric sheet.

[0012] The second invention is the first invention, wherein when preparing the first nonwoven fabric sheet and the second nonwoven fabric sheet, it is preferable to prepare the first nonwoven fabric sheet and the second nonwoven fabric sheet having the same degree of crystallinity for setting the same first welding temperature range and the same second welding temperature range, which include both the first temperature and the second temperature.

[0013] According to the second invention, nonwoven fabric sheets having a common degree of crystallinity can be used as the first nonwoven fabric sheet and the second nonwoven fabric sheet. Therefore, compared to the case in which first and second nonwoven fabric sheets with different degrees of crystallinity are used, costs can be reduced by reducing the number of types of nonwoven fabric sheets.

[0014] The third invention is the first invention, wherein when preparing the first nonwoven fabric sheet and the second nonwoven fabric sheet, it is preferable to prepare the first nonwoven fabric sheet having a lower degree of crystallinity than the second nonwoven fabric sheet.

[0015] According to the third invention, a first nonwoven fabric sheet is prepared that has a lower degree of crystallinity than the second nonwoven fabric sheet located closer to the heat supply member compared to the first nonwoven fabric sheet. Therefore, the first nonwoven fabric sheet can be melted at a lower temperature than the second nonwoven fabric sheet, thereby ensuring that both nonwoven fabric sheets are reliably welded to the elastic member.

[0016] The fourth invention is any one of the first to third inventions, wherein when preparing the first nonwoven fabric sheet and the second nonwoven fabric sheet, it is preferable to prepare the first nonwoven fabric sheet having a plurality of layers laminated in the opposing directions, and to prepare the first nonwoven fabric sheet such that at least one of the plurality of layers in the first nonwoven fabric sheet has the first welding temperature range, and the crystallinity of the layers other than the at least one of the plurality of layers is set to be higher than the crystallinity of the at least one.

[0017] Furthermore, the fifth invention is the first to fourth invention, and when preparing the first nonwoven fabric sheet and the second nonwoven fabric sheet, it is preferable to prepare the second nonwoven fabric sheet having a plurality of layers laminated in the opposing directions, and to prepare the second nonwoven fabric sheet such that at least one of the plurality of layers in the second nonwoven fabric sheet has the second welding temperature range, and the crystallinity of the layers other than the at least one of the plurality of layers is set to be higher than the crystallinity of the at least one.

[0018] The inventors of the present invention have found that when using a first nonwoven fabric sheet and a second nonwoven fabric sheet made up of multiple layers, the adhesion to an elastic member is improved by reducing the degree of crystallinity of at least one of the multiple layers. This is thought to be because at least one layer with a low degree of crystallinity melts at a relatively low temperature, while melting is suppressed in the other layers, thereby efficiently securing the molten material for welding and the base portion for welding (the portion that remains unmelted). Therefore, as in the fourth and fifth inventions, by setting the degree of crystallinity of at least one layer to have the above-mentioned first or second welding temperature range, and by making the degree of crystallinity of the other layers higher than that, it is possible to improve adhesion by increasing the melting properties of at least one layer, and to improve strength by decreasing the melting properties of the other layers.

[0019] Furthermore, a sixth invention provides a stretchable sheet manufactured using the manufacturing methods of the first to fifth inventions.

Advantages of the Invention

[0020] According to the present invention, both the first sheet and the second sheet can be reliably welded to the elastic member while preventing an increase in equipment cost.

Brief Description of the Drawings

[0021] [Figure 1] It is a front view schematically showing a manufacturing apparatus for manufacturing a stretchable sheet. [Figure 2] It is a graph showing the relationship between the temperature applied to the non-woven fabric sheet and the heat absorbed in the non-woven fabric sheet. [Figure 3] It is a schematic diagram showing the fibrous state of an amorphous resin. [Figure 4] It is a schematic diagram showing the fibrous state of a crystalline resin. [Figure 5] It is a schematic diagram showing a state in which a part of the manufacturing apparatus of FIG. 1 is enlarged and reversed left and right to explain the manufacturing method of the stretchable sheet. [Figure 6] [[ID=​​​​​​​​​​​​​​​​​​​​

[0023] Figure 5 is a schematic side view showing the method for manufacturing the stretchable sheet 1 according to the present invention.

[0024] Referring to Figure 5, the stretchable sheet 1 comprises a first nonwoven fabric sheet 2, a second nonwoven fabric sheet 3 facing the first nonwoven fabric sheet 2, and an elastic member 4 joined to the first nonwoven fabric sheet 2 and the second nonwoven fabric sheet 3 between them. Hereinafter, when it is not necessary to distinguish between the first nonwoven fabric sheet 2 and the second nonwoven fabric sheet 3, they will be collectively referred to as nonwoven fabric sheets 2 and 3.

[0025] The stretchable sheet 1 is manufactured by sandwiching both nonwoven fabric sheets 2 and 3 and the elastic member 4 between a heat supply member (an ultrasonic horn 11 in this embodiment) and a clamping member (anvil 12 in this embodiment), and receiving heat from the heat supply member, thereby welding the first nonwoven fabric sheet 2 and the second nonwoven fabric sheet 3 to the elastic member 4. In Figure 5, for the sake of explanation, the first nonwoven fabric sheet 2, the elastic member 4, and the second nonwoven fabric sheet 3 are shown to be separated from each other between the ultrasonic horn 11 and the anvil 12, but in reality, both nonwoven fabric sheets 2 and 3 and the elastic member 4 are in close contact with each other between the ultrasonic horn 11 and the anvil 12.

[0026] The manufacturing apparatus 10 for producing the stretchable sheet 1 will be described below with reference to Figure 1. Figure 1 is a schematic front view showing the manufacturing apparatus 10 for producing the stretchable sheet 1.

[0027] Referring to Figure 1, the manufacturing apparatus 10 includes an ultrasonic horn (heat supply member) 11 that supplies heat to the nonwoven sheets 2 and 3 to melt them, and an anvil (clamping member) 12 that faces the ultrasonic horn 11 in a predetermined opposing direction (left-right direction in Figure 1) and clamps the nonwoven sheets 2 and 3 and the elastic member 4 between itself and the ultrasonic horn 11.

[0028] Figure 5 is a schematic diagram showing a magnified and horizontally inverted portion of the manufacturing apparatus in Figure 1 to illustrate the manufacturing method of the stretchable sheet. As shown in Figure 5, the ultrasonic horn 11 has a vibrating surface 11a facing the anvil 12. The anvil 12 has an anvil roll 12a that is rotatable in the rotational direction D1 about a rotation axis J1 that extends in an axial direction perpendicular to the opposing direction (a direction perpendicular to the plane of the paper in Figure 5), and a plurality of protrusions 12b that project radially outward from the outer circumferential surface of the anvil roll 12a. The rotation axis J1 is positioned at the center of the vibrating surface 11a of the ultrasonic horn 11 so as to be perpendicular to a virtual line (a line extending in the opposing direction) perpendicular to the vibrating surface 11a (so as to extend in the axial direction). The plurality of protrusions 12b are arranged at equal intervals about the rotation axis J1 and have an arc-shaped outer circumferential surface 12b1 about the rotation axis J1. The nonwoven fabric sheets 2 and 3 and the elastic member 4 are sequentially sandwiched in opposing directions between the vibrating surface 11a of the ultrasonic horn 11 and the multiple outer peripheral surfaces 12b1 of the anvil 12, thereby intermittently welding both nonwoven fabric sheets 2 and 3 to the elastic member 4. In this embodiment, the elastic member 4 is a thread-like elastic member and is positioned between the vibrating surface 11a and the outer peripheral surface 12b1 so as to extend in opposing directions and in directions perpendicular to the axial direction (tangential direction of the outer peripheral surface 12b1). Multiple grooves 12b2 extending in the circumferential direction around the rotation axis J1 are intermittently formed in the axial direction on the outer peripheral surface 12b1 of the protruding portion 12b to receive a portion of the elastic member 4 in the thickness direction (only one is shown in Figure 5). In this embodiment, multiple elastic members 4 are guided to the anvil 12, and one elastic member 4 is inserted into each groove 12b2 via the first nonwoven fabric sheet 2.

[0029] Referring again to Figure 1, the manufacturing apparatus 10 further includes a guide member 13 for guiding the first nonwoven fabric sheet 2 to the outer surface of the anvil 12 (projection 12b), an elastic member guide mechanism 14 for guiding the elastic member 4 to the anvil 12 so that it is placed on the first nonwoven fabric sheet 2 guided to the anvil 12, a second sheet guide mechanism 15 for guiding the second nonwoven fabric sheet 3 to the anvil 12 so that it covers the first nonwoven fabric sheet 2 and the elastic member 4 on the outer surface of the anvil 12, and a pull-out member 16 for pulling out the stretchable sheet 1 from between the ultrasonic horn 11 and the anvil 12.

[0030] The guide member 13 defines the transport path for the first nonwoven fabric sheet 2 so that the first nonwoven fabric sheet 2 is guided from the raw material roll (not shown) around which the first nonwoven fabric sheet 2 is wound to position P1 on the outer surface of the anvil 12. Specifically, the guide member 13 is a roller that can rotate about an axis extending parallel to the rotation axis J1.

[0031] The elastic member guide mechanism 14 defines the transport path of the elastic member 4 so that the elastic member 4 is guided to position P2 downstream in the transport direction of the first nonwoven sheet 2, with position P1 as the reference point on the outer circumferential surface of the anvil 12. Specifically, the elastic member guide mechanism 14 includes transport members 14a, 14b, and 14c for transporting multiple elastic members 4 from a holding roll (not shown) around which the elastic member 4 is wound to position P2, and a transfer member 14d for transferring the multiple elastic members 4 to the anvil 12. The transport members 14a, 14b, and 14c transport the multiple elastic members 4 to the transfer member 14d while tension is applied to the elastic members 4. Specifically, the transport members 14a, 14b, and 14c are rollers that can rotate about an axis parallel to the rotation axis J1. The transfer member 14d transfers the multiple elastic members 4, which have been transported by the transport members 14a, 14b, and 14c, to the anvil 12 in a position such that each elastic member 4 is guided into the groove 12b2 (see Figure 5) of the anvil 12. Specifically, the transfer member 14d has a tip portion 14d1 positioned adjacent to position P2 on the outer circumferential surface of the anvil 12. Multiple grooves (not shown) for inserting the elastic members 4 are intermittently formed in the axial direction on the tip portion 14d1. These grooves are positioned opposite the groove 12b2 of the anvil 12. Each elastic member 4, while inserted into a groove, is redirected by the tip portion 14d1 of the transfer member 14d and guided to position P2 (inside the groove 12b2) of the anvil 12.

[0032] The second sheet guiding mechanism 15 defines the transport path of the second nonwoven fabric sheet 3 so that the second nonwoven fabric sheet 3 is guided to position P3 downstream in the transport direction of the first nonwoven fabric sheet 2, with reference to position P2 on the outer circumferential surface of the anvil 12. In this embodiment, position P2 is set to a position slightly upstream in the rotation direction of the anvil 12 with respect to the rotation axis J1, with reference to the opposing position of the ultrasonic horn 11 and the anvil 12. Specifically, the second sheet guiding mechanism 15 has transport members 15a and 15b for transporting the second nonwoven fabric sheet 3 so that the second nonwoven fabric sheet 3 is guided from the raw material roll (not shown) on which the second nonwoven fabric sheet 3 is wound to position P3 on the outer circumferential surface of the anvil 12. The transport members 15a and 15b are rollers that can rotate about the rotation axis J1.

[0033] The extraction member 16 defines a path for transporting the stretchable sheet 1 from the opposing position between the ultrasonic horn 11 and the anvil 12 to a downstream device (not shown). Specifically, the extraction member 16 is a roller that can rotate about an axis extending parallel to the rotation axis J1.

[0034] The following describes a manufacturing method for producing the stretchable sheet 1 using the manufacturing apparatus 10. The manufacturing method for the stretchable sheet 1 includes a nonwoven fabric sheet preparation step, a component preparation step, an arrangement step, and a heat supply step.

[0035] In the nonwoven fabric sheet preparation process, the first nonwoven fabric sheet 2 and the second nonwoven fabric sheet 3 are prepared. The nonwoven fabric sheet preparation process will be described in detail later.

[0036] In the component preparation process, an ultrasonic horn 11 is prepared to supply heat to both nonwoven fabric sheets 2 and 3 in order to melt them, and an anvil 12 is prepared to face the ultrasonic horn 11 in the opposing direction and to sandwich both nonwoven fabric sheets 2 and 3 and the elastic member 4 between the ultrasonic horn 11 and the anvil 12.

[0037] In the placement process, the two nonwoven fabric sheets 2, 3, and the elastic member 4 are placed between the ultrasonic horn 11 and the anvil 12 so that the second nonwoven fabric sheet 3, the elastic member 4, and the first nonwoven fabric sheet 2 are aligned in that order, facing away from the ultrasonic horn 11. Specifically, in the placement process, the anvil 12 is rotated in the rotational direction D1, and the first nonwoven fabric sheet 2 is transported to position P1 on the outer surface of the anvil 12 using the guide member 13. In addition, in the placement process, the elastic member 4 is transported to position P2 on the outer surface of the anvil 12 while tension is applied to the elastic member 4 using the elastic member guide mechanism 14. Furthermore, in the placement process, the second nonwoven fabric sheet 3 is transported to position P3 on the outer surface of the anvil 12 using the second sheet guide mechanism 15. As a result, the two nonwoven fabric sheets 2, 3, and the elastic member 4 are placed between the ultrasonic horn 11 and the anvil 12 in the order described above.

[0038] In the heat supply process, ultrasonic vibrations are applied to the ultrasonic horn 11 from an ultrasonic generator (not shown), thereby supplying heat to the two nonwoven fabric sheets 2 and 3 positioned between the ultrasonic horn 11 and the anvil 12. As a result, the two nonwoven fabric sheets 2 and 3 and the elastic member 4 are welded together, and the stretchable sheet 1 is manufactured.

[0039] In the nonwoven fabric preparation step, a first nonwoven fabric sheet 2 and a second nonwoven fabric sheet 3 are prepared, which have properties that allow them to be reliably welded to the elastic member 4 by the heat supply step. Specifically, in the nonwoven fabric preparation step, as shown in Figure 5, a first nonwoven fabric sheet 2 is prepared, whose crystallinity is set to include a first temperature T1 determined by the distance in a predetermined direction from the ultrasonic horn 11 to the first nonwoven fabric sheet 2 and the amount of heat from the ultrasonic horn 11, and a first welding temperature range E1 which is a temperature range in which the first nonwoven fabric sheet 2 can be welded to the elastic member 4. Furthermore, in the nonwoven fabric preparation step, a second nonwoven fabric sheet 3 is prepared, whose crystallinity is set to include a second temperature T2 determined by the distance in a predetermined direction from the ultrasonic horn 11 to the second nonwoven fabric sheet 3 and the amount of heat from the ultrasonic horn 11, and a second welding temperature range E2 which is a temperature range in which the second nonwoven fabric sheet 3 can be welded to the elastic member 4. As shown in Figure 5, the first temperature T1 of the first nonwoven fabric sheet 2 is lower than the second temperature T2 of the second nonwoven fabric sheet 3, which is located closer to the ultrasonic horn 11, compared to the first nonwoven fabric sheet 2. The resin structure will now be described in order to explain the degree of crystallinity, with reference to Figures 3 and 4.

[0040] Figure 3 is a schematic diagram showing the fibrous state of amorphous resin, and Figure 4 is a schematic diagram showing the fibrous state of crystalline resin. As shown in Figures 3 and 4, resins are composed of multiple string-like molecules intertwined in a certain direction. Thermoplastic resins are broadly classified into amorphous resins (Figure 3), which do not have a crystalline structure, and crystalline resins (Figure 4), which do have a crystalline structure. Examples of amorphous resins include polystyrene (PS), polyvinyl chloride (PVC), AS (Acrylonitrile Styrene) resin, ABS (Acrylonitrile Butadiene Styrene) resin, and acrylic resin. On the other hand, examples of crystalline resins include polyethylene (PE), polypropylene (PP), nylon (polyamide synthetic resin), PET (Polyethylene terephthalate) resin, and PBT (Poly Butylene Terephtalate) resin. Crystalline resins have crystalline regions C (regions enclosed by dashed lines) formed by the regular alignment of parts of multiple molecules, and amorphous regions G other than the crystalline parts of multiple molecules. The degree of crystallinity is defined by the following formula (1).

[0041] Crystallinity=C / (C+G)×100...(1) Figure 2 shows the measurement results obtained by differential scanning calorimetry. Specifically, Figure 2 shows the heat that a nonwoven fabric sheet can absorb at a certain temperature, that is, to what extent the nonwoven fabric sheet melts at a certain temperature. The waveforms W1 of both nonwoven fabric sheets 2 and 3 are shown by dashed lines in Figure 2. A certain amount of material needs to melt in the nonwoven fabric sheets 2 and 3 in order to weld them to the elastic member 4. Therefore, in Figure 2, the lower limit Min1 in the welding temperature ranges E1 and E2 of the nonwoven fabric sheets 2 and 3 is defined as the temperature corresponding to the heat flow value H1 in the state where a predetermined amount of heat has been absorbed, based on the heat flow value H0 in the state where no heat has been absorbed. On the other hand, the upper limit Max1 in the welding temperature ranges E1 and E2, which is the temperature that exceeds the lower temperature limit defined in this way and is the temperature at which the nonwoven fabric sheets 2 and 3 are damaged, is defined as the temperature at which no more heat can be absorbed (the temperature at which the substantial fluctuation of the heat flow value begins to disappear in the waveform in Figure 2).

[0042] Furthermore, Figure 2 shows a solid line representing the waveform W2 of a nonwoven fabric sheet made of the same material as both nonwoven fabric sheets 2 and 3, but with a higher degree of crystallinity than both nonwoven fabric sheets 2 and 3. As is clear from the waveforms W1 and W2 in Figure 2, reducing the degree of crystallinity of the nonwoven fabric sheet reduces the lower limit of the welding temperature range. Specifically, the lower limit Min1 of the welding temperature range E1 and E2 for waveform W1 is lower than the lower limit Min2 of the welding temperature range E3 for waveform W2. On the other hand, the upper limit of the welding temperature range E3 for waveform W2 is substantially the same as the upper limit Max1 of the welding temperature range E1 and E2 for waveform W1.

[0043] In this embodiment, in the nonwoven fabric preparation step, nonwoven fabric sheets 2 and 3 are prepared, which are mainly composed of polypropylene and have a degree of crystallinity that has the characteristics of a waveform W1. In other words, in this embodiment, the degree of crystallinity of nonwoven fabric sheets 2 and 3 is the same. As shown in Figure 5, the welding temperature ranges E1 and E2 in the waveform W1 include a first temperature T1 determined by the distance in a predetermined direction from the ultrasonic horn 11 to the first nonwoven fabric sheet 2 and the amount of heat from the ultrasonic horn 11. The welding temperature ranges E1 and E2 also include a second temperature T2 determined by the distance in a predetermined direction from the ultrasonic horn 11 to the second nonwoven fabric sheet 3 and the amount of heat from the ultrasonic horn 11. Therefore, both nonwoven fabric sheets 2 and 3 can be sufficiently melted, and the elastic member 4 can be reliably welded. On the other hand, for example, if a nonwoven fabric sheet having a corrugated shape W2 is prepared as the first nonwoven fabric sheet 2, the welding temperature range E3 of the corrugated shape W2 does not include the first temperature T1. Therefore, the first nonwoven fabric sheet 2 cannot be sufficiently melted, and the elastic member 4 cannot be reliably welded.

[0044] Furthermore, in the nonwoven fabric preparation process in this embodiment, as shown in Figure 7, nonwoven fabric sheets 2 and 3 are prepared, each having multiple layers laminated in a direction opposite to the ultrasonic horn 11 and the anvil 12. Specifically, the nonwoven fabric sheets 2 and 3 have three layers manufactured by the spunbond method. In the figures, S indicates that it was manufactured by the spunbond method. On the other hand, the nonwoven fabric sheet having the characteristics shown by the waveform W2 in Figure 2 also has three layers manufactured by the spunbond method, as shown in Figure 6. In Figures 6 and 7, H and L indicate the degree of crystallinity, respectively, where L means a lower degree of crystallinity than H. In this embodiment, a crystallinity of 40% is adopted as H, and a crystallinity of 34% is adopted as L. The amount of heat generated by the ultrasonic horn 11, which is the basis for these assumptions, is substantially proportional to the transport speed of the nonwoven fabric sheet 2. For example, if the transport speed of the nonwoven fabric sheet 2 is 350 m / min, the amount of heat generated by the ultrasonic horn 11 is 765 W. Furthermore, the distance from the ultrasonic horn 11 to the second nonwoven fabric sheet 3 in a predetermined direction is 0 mm (in a tight-fitting state), and the distance from the ultrasonic horn 11 to the first nonwoven fabric sheet 2 in a predetermined direction (thickness of the second nonwoven fabric sheet 3 + thickness of the elastic member 4) is 1 mm or less.

[0045] As described above, although the temperatures of the two nonwoven fabric sheets 2 and 3 differ depending on the distance in a predetermined direction from the ultrasonic horn 11 to the two nonwoven fabric sheets 2 and 3, a first nonwoven fabric sheet 2 and a second nonwoven fabric sheet 3 are prepared, each having a degree of crystallinity set to have a welding temperature range E1 and E2 that includes the temperatures T1 and T2 of each nonwoven fabric sheet 2 and 3.

[0046] Therefore, both nonwoven fabric sheets 2 and 3 can be reliably welded to the elastic member 4 without requiring a separate configuration for heating the first nonwoven fabric sheet 2.

[0047] Furthermore, according to the above embodiment, since both nonwoven fabric sheets 2 and 3 having the same degree of crystallinity are prepared, nonwoven fabric sheets having a common degree of crystallinity can be used as the first nonwoven fabric sheet 2 and the second nonwoven fabric sheet 3. Therefore, compared to the case in which the first nonwoven fabric sheet 2 and the second nonwoven fabric sheet 3 have different degrees of crystallinity, it is possible to reduce costs by reducing the number of types of nonwoven fabric sheets.

[0048] In the above embodiment, the two nonwoven fabric sheets 2 and 3 are made of materials with the same degree of crystallinity. However, the degree of crystallinity of the first nonwoven fabric sheet 2 can be made lower than that of the second nonwoven fabric sheet 3.

[0049] Specifically, as shown in Figure 5, a first nonwoven fabric sheet 2 having a degree of crystallinity exhibiting the characteristics of waveform W1 can be used, and a second nonwoven fabric sheet 3 having a degree of crystallinity exhibiting the characteristics of waveform W2 can also be used. In this case, the first welding temperature range E1 of the first nonwoven fabric sheet 2 includes the first temperature T1, and the second welding temperature range of the second nonwoven fabric sheet 3 is the welding temperature range E3, which includes the second temperature T2. Therefore, both nonwoven fabric sheets 2 and 3 can be sufficiently melted by the heat from the ultrasonic horn 11, thereby ensuring that the elastic member 4 is reliably welded to both nonwoven fabric sheets 2 and 3.

[0050] In this way, a first nonwoven fabric sheet 2 is prepared that has a lower degree of crystallinity than the second nonwoven fabric sheet 3, which is located closer to the ultrasonic horn 11 than the first nonwoven fabric sheet 2. Therefore, the first nonwoven fabric sheet 2 can be melted at a lower temperature than the second nonwoven fabric sheet 3, thereby ensuring that both nonwoven fabric sheets 2 and 3 are reliably welded to the elastic member 4.

[0051] In the above embodiment, nonwoven fabric sheets 2 and 3 having three layers were exemplified, but the number of layers in the nonwoven fabric sheets 2 and 3 may be one or four or more.

[0052] Furthermore, it has been confirmed that when nonwoven sheets 2 and 3 have multiple layers, the lower limit of the welding temperature range can be lowered by reducing the degree of crystallinity of at least one of the multiple layers. This is thought to be because at least one layer with a low degree of crystallinity melts at a relatively low temperature, while melting is suppressed in the other layers, thereby efficiently securing the molten material for welding and the base portion for welding (the portion that remains unmelted). Therefore, in the nonwoven fabric preparation process, it is also possible to prepare a first nonwoven sheet 2 in which at least one of the multiple layers of the first nonwoven sheet 2 has a first welding temperature range E1, and the degree of crystallinity of the layers other than the aforementioned at least one layer is set to be higher than the degree of crystallinity of the at least one layer. Here, the first welding temperature range E1 includes a first temperature T1. Furthermore, in the nonwoven fabric preparation process, a second nonwoven fabric sheet can also be prepared in which at least one of the multiple layers of the second nonwoven fabric sheet 3 has a second welding temperature range E2, and the crystallinity of the layers other than at least one of the multiple layers is set to be higher than the crystallinity of at least one layer. Here, the second welding temperature range E2 includes the second temperature T2. Also, as described above, a welding temperature range E3 can be adopted as the second welding temperature range in the second nonwoven fabric sheet 3.

[0053] For either the first nonwoven sheet 2 or the second nonwoven sheet 3, the above-described degree of crystallinity may be set for at least one layer, or for both nonwoven sheets 2 and 3, the above-described degree of crystallinity may be set for at least one layer. However, since the second nonwoven sheet 3 is adjacent to the ultrasonic horn 11, controlling the amount of heat supplied to the second nonwoven sheet 3 is relatively easy, whereas the first nonwoven sheet 2 is further from the ultrasonic horn 11 than the second nonwoven sheet 3, making it difficult to control the amount of heat supplied to the first nonwoven sheet 2. From this viewpoint, it is preferable to adjust the degree of crystallinity in the first nonwoven sheet 2.

[0054] Examples of setting the degree of crystallinity of at least one layer as described above include those shown in Figures 8 to 10. Figures 8 to 10 illustrate the case where the above degree of crystallinity adjustment is performed on both nonwoven fabric sheets 2 and 3.

[0055] In the example shown in Figure 8, the nonwoven sheet has three layers (layers manufactured by the spunbond method), of which two layers have a low degree of crystallinity, and the remaining layer has a higher degree of crystallinity than the aforementioned two layers. Assuming that the amount of heat from the ultrasonic horn 11 and the distance from the ultrasonic horn 11 to both nonwoven sheets 2 and 3 are the same as in the above embodiment, a crystallinity of 40% for H and a crystallinity of 34% for L can be adopted.

[0056] In the example shown in Figure 9, the nonwoven sheet has four layers, one of which (a layer manufactured by the meltblown method [indicated by the symbol M]) has a low degree of crystallinity, while the remaining three layers (layers manufactured by the spunbond method) have a higher degree of crystallinity than the aforementioned one layer. Assuming that the amount of heat from the ultrasonic horn 11 and the distance from the ultrasonic horn 11 to both nonwoven sheets 2 and 3 are the same as in the above embodiment, a crystallinity of H exceeding 40% and a crystallinity of L of 10% can be adopted.

[0057] In the example shown in Figure 10, the nonwoven sheet has five layers, of which two layers (produced by the meltblown method) have a low degree of crystallinity, while the remaining three layers (produced by the spunbond method) have a higher degree of crystallinity than the aforementioned two layers. Assuming that the amount of heat from the ultrasonic horn 11 and the distance from the ultrasonic horn 11 to both nonwoven sheets 2 and 3 are the same as in the above embodiment, a crystallinity of H exceeding 40% and a crystallinity of L of 5% can be adopted.

[0058] Furthermore, as shown in Figures 9 and 10, it is preferable that in the nonwoven fabric sheet, at least one layer with a low degree of crystallinity is sandwiched in a predetermined direction by the other layers. In a nonwoven fabric sheet configured in this way, the at least one layer of molten material that melts preferentially impregnates the layers located on both sides of that layer, contributing to the welding of the elastic member 4. As a result, the molten portion of the nonwoven fabric sheet and the underlying portion are fused together, allowing for a stronger welding of the elastic member 4.

[0059] As described above, by setting the crystallinity of at least one layer to have a first or second welding temperature range E1, E2, and by making the crystallinity of the other layers higher, it is possible to improve adhesion by increasing the meltability of at least one layer, while improving strength by decreasing the meltability of the other layers.

[0060] Furthermore, the present invention is not limited to the embodiments described above, and for example, the following embodiments may also be adopted.

[0061] In the above embodiment, several types of crystallization settings were described, but it is also possible to combine some of these crystallization settings.

[0062] Although an ultrasonic horn 11 was given as an example of a heat supply member, the heat supply member is not limited to an ultrasonic horn 11. For example, a heater that generates heat itself can also be used as a heat supply member.

[0063] In the above embodiment, polypropylene is used as the crystalline resin, but other crystalline resins can also be used. [Explanation of symbols]

[0064] 1. Stretchable sheet 2. First nonwoven fabric sheet 3. Second nonwoven fabric sheet 4 Elastic members 11. Ultrasonic horn (an example of a heat supply component) 12 Anvil (an example of a clamping component) E1 First welding temperature range E2 2nd welding temperature range T1 1st temperature T2 2nd temperature

Claims

1. A method for manufacturing an elastic sheet comprising a first nonwoven sheet, a second nonwoven sheet facing the first nonwoven sheet, and an elastic member joined to the first nonwoven sheet and the second nonwoven sheet between the first and second nonwoven sheets, Prepare the first nonwoven fabric sheet and the second nonwoven fabric sheet, A heat supply member for supplying heat to the first nonwoven sheet and the second nonwoven sheet to melt them, and a clamping member which faces the heat supply member in a predetermined opposing direction and clamps the first nonwoven sheet, the second nonwoven sheet, and the elastic member between itself and the heat supply member, are prepared. The first nonwoven fabric sheet, the second nonwoven fabric sheet, and the elastic member are arranged between the heat supply member and the clamping member such that they are arranged in order in the direction away from the heat supply member in the opposing direction. The heat supply member is used to supply heat to the first nonwoven fabric sheet and the second nonwoven fabric sheet, which are placed between the heat supply member and the clamping member. A method for manufacturing an elastic sheet, comprising: preparing the first nonwoven sheet and the second nonwoven sheet, wherein the crystallinity of the first nonwoven sheet is set such that the first nonwoven sheet has a first welding temperature range which includes a first temperature determined by the distance in the opposing direction from the heat supply member to the first nonwoven sheet and the amount of heat from the heat supply member, and is a temperature range in which the first nonwoven sheet can be welded to the elastic member; and the crystallinity of the second nonwoven sheet has a second welding temperature range which includes a second temperature determined by the distance in the opposing direction from the heat supply member to the second nonwoven sheet and the amount of heat from the heat supply member, and is a temperature range in which the second nonwoven sheet can be welded to the elastic member.

2. The method for manufacturing an expandable sheet according to claim 1, wherein when preparing the first nonwoven sheet and the second nonwoven sheet, the first nonwoven sheet and the second nonwoven sheet are prepared having the same degree of crystallinity for setting the same first welding temperature range and the same second welding temperature range, which include both the first temperature and the second temperature.

3. The method for manufacturing an expandable sheet according to claim 1, wherein when preparing the first nonwoven sheet and the second nonwoven sheet, the first nonwoven sheet is prepared having a degree of crystallinity lower than that of the second nonwoven sheet.

4. A method for manufacturing an expandable sheet according to any one of claims 1 to 3, wherein when preparing the first nonwoven sheet and the second nonwoven sheet, the first nonwoven sheet is prepared having a plurality of layers laminated in the opposing directions, and the crystallinity of the first nonwoven sheet is set such that at least one of the plurality of layers has a first welding temperature range, and the crystallinity of the layers other than the at least one of the plurality of layers is higher than the crystallinity of the at least one.

5. A method for manufacturing an expandable sheet according to any one of claims 1 to 3, wherein when preparing the first nonwoven sheet and the second nonwoven sheet, the second nonwoven sheet is prepared having a plurality of layers laminated in the opposing directions, and the crystallinity of the second nonwoven sheet is set such that at least one of the plurality of layers has the second welding temperature range, and the crystallinity of the layers other than the at least one of the plurality of layers is higher than the crystallinity of the at least one.

6. An elastic sheet manufactured using the manufacturing method described in any one of claims 1 to 3.

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