WO2024247950A1 - Stretchable sheet manufacturing method and stretchable sheet manufactured by same - Google Patents

Abstract

The purpose of the present invention is to reliably weld both a first nonwoven fabric sheet and a second nonwoven fabric sheet to an elastic member while preventing increase in device cost.　A first nonwoven fabric sheet (2) and a second nonwoven fabric sheet (3) each having a set degree of crystallinity are prepared such that: the first nonwoven fabric sheet (2) has a first welding temperature range (E1), which is a temperature range including a first temperature (T1) determined by a heat quantity from an ultrasonic horn (11) and the distance in a prescribed direction from the ultrasonic horn (11) to the first nonwoven fabric (2) and enabling the first nonwoven fabric sheet (2) to be welded to an elastic member (4); and the second nonwoven fabric sheet (3) has a second welding temperature range (E2), which is a temperature range including a second temperature (T2) determined by the heat quantity from the ultrasonic horn (11) and the distance in the opposing direction from the ultrasonic horn (11) to the second nonwoven fabric sheet (3) and enabling the second nonwoven fabric sheet (3) to be welded to the elastic member (4).

Description

Manufacturing method of elastic sheet and elastic sheet manufactured using the same

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

A manufacturing method for a stretchable sheet, for example, as described in Patent Document 1, has been known for some time. The manufacturing method described in Patent Document 1 includes the steps of introducing a first sheet onto the outer peripheral surface of an anvil roll, introducing an elastic member onto the first sheet on the anvil roll, introducing a second sheet onto the first sheet and the elastic member on the anvil roll, and ultrasonically vibrating a horn 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.

When melting the first and second sheets using ultrasonic vibrations from the horn in this way, there is a risk that the amount of heat supplied to the first sheet, which is located away from the horn (heat source), will be insufficient, resulting in insufficient welding of the first sheet to the elastic member. Therefore, in the stretchable sheet manufacturing device of Patent Document 1, the first sheet on the anvil is heated by a heating device before the second sheet is introduced.

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

On the other hand, it is possible to increase the amount of heat (energy from ultrasonic vibrations of the horn in Patent Document 1) supplied to both sheets in order to reliably melt the first and second sheets without using a heating device. However, in this case, there is a risk that damage will occur in the second sheet due to excessive heat being supplied to the second sheet, which is closer to the heat source, and if damage occurs in the second sheet, the welding of the second sheet to the elastic member will be insufficient.

International Publication No. 2018/070150

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

The inventors of the present application discovered that by lowering the crystallinity of the nonwoven fabric sheet, the lower limit of the welding temperature range shifts to the lower temperature side, and came up with the method of the present invention in which a first nonwoven fabric sheet and a second nonwoven fabric sheet are prepared with a crystallinity set to have a temperature range that matches the temperature of both nonwoven fabric sheets heated by a heat supply member.

Specifically, in order to solve the above problem, the first invention is a manufacturing method for manufacturing a stretchable sheet having a first nonwoven fabric sheet, a second nonwoven fabric sheet facing the first nonwoven fabric sheet, and an elastic member bonded to the first nonwoven fabric sheet and the second nonwoven fabric sheet between the first nonwoven fabric sheet and the second nonwoven fabric sheet, comprising the steps of: preparing the first nonwoven fabric sheet and the second nonwoven fabric sheet; preparing a heat supply member for supplying heat to the first nonwoven fabric sheet and the second nonwoven fabric sheet for melting the first nonwoven fabric sheet and the second nonwoven fabric sheet; and preparing a sandwiching member that faces the heat supplying member in a predetermined opposing direction and sandwiches the first nonwoven fabric sheet, the second nonwoven fabric sheet, and the elastic member between the heat supplying member and the sandwiching member; and bonding the first nonwoven fabric sheet, the second nonwoven fabric sheet, and the elastic member to the first nonwoven fabric sheet, so that the second nonwoven fabric sheet, the elastic member, and the first nonwoven fabric sheet are aligned in order in the opposing direction away from the heat supplying member. A method for manufacturing a stretchable sheet is provided, comprising: disposing a material between the heat supplying member and the sandwiching member; supplying heat to the first nonwoven fabric sheet and the second nonwoven fabric sheet disposed between the heat supplying member and the sandwiching member using the heat supplying member; and preparing the first nonwoven fabric sheet and the second nonwoven fabric sheet, the crystallization degrees of the first nonwoven fabric sheet and the second nonwoven fabric sheet are set so that the first nonwoven fabric sheet has a first welding temperature range that includes a first temperature determined by the distance from the heat supplying member to the first nonwoven fabric sheet in the opposing direction and the amount of heat provided by the heat supplying 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 that includes a second temperature determined by the distance from the heat supplying member to the second nonwoven fabric sheet in the opposing direction and the amount of heat provided by the heat supplying member, and is a temperature range in which the second nonwoven fabric sheet can be welded to the elastic member.

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 specified direction from the heat supply member to both nonwoven fabric sheets.

Therefore, according to the present invention, both nonwoven fabric sheets can be reliably welded to the elastic member without the need for a separate structure for heating the first nonwoven fabric sheet.

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 costs.

FIG. 2 is a front view showing a schematic diagram of a manufacturing apparatus for manufacturing a stretch sheet. 1 is a graph showing the relationship between the temperature applied to a nonwoven sheet and the heat absorbed in the nonwoven sheet. FIG. 2 is a schematic diagram showing a fibrous state of an amorphous resin. FIG. 2 is a schematic diagram showing a fibrous state of a crystalline resin. FIG. 2 is a schematic diagram showing a state in which a part of the manufacturing apparatus of FIG. 1 is enlarged and inverted from side to side, for explaining a method for manufacturing a stretch sheet. FIG. 2 is a cross-sectional view showing a schematic stacked state of a nonwoven fabric sheet according to a comparative example. FIG. 2 is a cross-sectional view showing a schematic stacking state of an embodiment of a nonwoven fabric sheet. FIG. 2 is a cross-sectional view showing a schematic stacking state of an embodiment of a nonwoven fabric sheet. FIG. 2 is a cross-sectional view showing a schematic stacking state of an embodiment of a nonwoven fabric sheet. FIG. 2 is a cross-sectional view showing a schematic stacking state of an embodiment of a nonwoven fabric sheet.

The following describes an embodiment of the present invention with reference to the attached drawings. Note that the following embodiment is an example of the present invention and is not intended to limit the technical scope of the present invention.

FIG. 5 is a side view that shows a schematic diagram of a method for manufacturing the elastic sheet 1 according to the present invention.

Referring to FIG. 5, the stretchable sheet 1 has a first nonwoven fabric sheet 2, a second nonwoven fabric sheet 3 facing the first nonwoven fabric sheet 2, and an elastic member 4 bonded to the first nonwoven fabric sheet 2 and the second nonwoven fabric sheet 3 between the first nonwoven fabric sheet 2 and the second nonwoven fabric sheet 3. Hereinafter, when there is no need 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.

The stretchable sheet 1 is manufactured by sandwiching the two nonwoven fabric sheets 2, 3 and the elastic member 4 between a heat supply member (in this embodiment, an ultrasonic horn 11) and a clamping member (in this embodiment, an anvil 12), and then receiving heat from the heat supply member, welding the first nonwoven fabric sheet 2 and the second nonwoven fabric sheet 3 to the elastic member 4. Note that, for the sake of convenience, FIG. 5 shows the first nonwoven fabric sheet 2, the elastic member 4, and the second nonwoven fabric sheet 3 separated from each other between the ultrasonic horn 11 and the anvil 12, but in reality the two nonwoven fabric sheets 2, 3 and the elastic member 4 are in close contact with each other between the ultrasonic horn 11 and the anvil 12.

Below, a manufacturing apparatus 10 for manufacturing the stretchable sheet 1 will be described with reference to Figure 1. Figure 1 is a front view showing a schematic diagram of the manufacturing apparatus 10 for manufacturing the stretchable sheet 1.

Referring to FIG. 1, the manufacturing device 10 has an ultrasonic horn (heat supply member) 11 that supplies heat to the nonwoven fabric sheets 2, 3 to melt the nonwoven fabric sheets 2, 3, and an anvil (clamping member) 12 that faces the ultrasonic horn 11 in a predetermined opposing direction (left-right direction in FIG. 1) and clamps the nonwoven fabric sheets 2, 3 and the elastic member 4 between the ultrasonic horn 11 and the anvil.

5 is a schematic diagram showing a state in which a part of the manufacturing apparatus of FIG. 1 is enlarged and inverted from left to right to explain the manufacturing method of the elastic sheet. As shown in FIG. 5, the ultrasonic horn 11 has a vibration surface 11a facing the anvil 12. On the other hand, the anvil 12 has an anvil roll 12a that can rotate in a rotation direction D1 around a rotation axis J1 extending in an axial direction (direction perpendicular to the paper surface in FIG. 5) perpendicular to the facing direction, and a plurality of protrusions 12b protruding from the outer peripheral surface of the anvil roll 12a to the outside in the radial direction of the anvil roll 12a. The rotation axis J1 is arranged at the center position of the vibration surface 11a of the ultrasonic horn 11 so as to be perpendicular (extending in the axial direction) to a virtual line (line extending in the facing direction) perpendicular to the vibration surface 11a. In addition, the plurality of protrusions 12b are arranged at equal intervals around the rotation axis J1 and have an arc-shaped outer peripheral surface 12b1 centered on the rotation axis J1. The nonwoven fabric sheets 2, 3 and the elastic member 4 are sandwiched between the vibration surface 11a of the ultrasonic horn 11 and the multiple outer peripheral surfaces 12b1 of the anvil 12 in the opposing direction, and the nonwoven fabric sheets 2, 3 are intermittently welded to the elastic member 4. In this embodiment, the elastic member 4 is a thread-like elastic member and is arranged between the vibration surface 11a and the outer peripheral surface 12b1 so as to extend in the opposing direction and in a direction perpendicular to the axial direction (tangential direction of the outer peripheral surface 12b1). In the outer peripheral surface 12b1 of the protrusion 12b, multiple grooves 12b2 are intermittently formed in the axial direction, extending in the circumferential direction around the rotation axis J1 to receive a part of the thickness direction of the elastic member 4 (only one is shown in FIG. 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.

Referring again to FIG. 1, the manufacturing apparatus 10 further includes a guide member 13 for guiding the first nonwoven fabric sheet 2 to the outer peripheral surface of the anvil 12 (protruding portion 12b), an elastic member guide mechanism 14 for guiding the elastic member 4 to the anvil 12 so as to be 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 as to cover the first nonwoven fabric sheet 2 and the elastic member 4 on the outer peripheral 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.

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

The elastic member guide mechanism 14 determines 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 fabric sheet 2 based on position P1 on the outer peripheral surface of the anvil 12. Specifically, the elastic member guide mechanism 14 has transport members 14a, 14b, and 14c for transporting the multiple elastic members 4 from a holding roll (not shown) around which the elastic members 4 are wound to position P2, and a delivery member 14d for delivering the multiple elastic members 4 to the anvil 12. The transport members 14a, 14b, and 14c transport the multiple elastic members 4 to the delivery member 14d while applying tension to the multiple 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 delivery member 14d delivers the multiple elastic members 4 to the anvil 12 in a state where the multiple elastic members 4 transported by the transport members 14a, 14b, and 14c are positioned so that they are guided to the groove 12b2 (see FIG. 5) of the anvil 12. Specifically, the delivery member 14d has a tip 14d1 disposed adjacent to position P2 on the outer circumferential surface of the anvil 12. The tip 14d1 has multiple grooves (not shown) intermittently formed in the axial direction for inserting the elastic members 4. These grooves are disposed to face the groove 12b2 of the anvil 12. Each elastic member 4 is changed in direction by the tip 14d1 of the delivery member 14d while inserted into the groove and guided to position P2 (in the groove 12b2) of the anvil 12.

The second sheet guide mechanism 15 determines the conveying path of the second nonwoven fabric sheet 3 so that the second nonwoven fabric sheet 3 is guided to a position P3 downstream in the conveying direction of the first nonwoven fabric sheet 2, based on a position P2 on the outer peripheral surface of the anvil 12. In this embodiment, the position P2 is set to a position slightly upstream in the rotation direction of the anvil 12, centered on the rotation axis J1, based on the opposing position of the ultrasonic horn 11 and the anvil 12. Specifically, the second sheet guide mechanism 15 has conveying members 15a and 15b for conveying the second nonwoven fabric sheet 3 so that the second nonwoven fabric sheet 3 is guided to a position P3 on the outer peripheral surface of the anvil 12 from a raw roll (not shown) on which the second nonwoven fabric sheet 3 is wound. The conveying members 15a and 15b are rollers that can rotate around the rotation axis J1.

The pull-out 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 in the figure. Specifically, the pull-out member 16 is a roller that can rotate around an axis that extends parallel to the rotation axis J1.

Below, a manufacturing method for manufacturing the stretchable sheet 1 using the manufacturing device 10 is described. The manufacturing method for the stretchable sheet 1 includes a nonwoven fabric sheet preparation process, a member preparation process, an arrangement process, and a heat supply process.

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

In the component preparation process, an ultrasonic horn 11 is prepared, which supplies heat to both nonwoven fabric sheets 2, 3 to melt them, and an anvil 12 is prepared, which faces the ultrasonic horn 11 in the opposing direction and which sandwiches both nonwoven fabric sheets 2, 3 and the elastic member 4 between the ultrasonic horn 11 and the anvil 12.

In the arrangement process, the nonwoven fabric sheets 2, 3, and the elastic member 4 are arranged 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 arranged in this order in the direction away from the ultrasonic horn 11. Specifically, in the arrangement process, the anvil 12 is rotated in the rotation direction D1, and the first nonwoven fabric sheet 2 is transported to position P1 on the outer circumferential surface of the anvil 12 using the guide member 13. In addition, in the arrangement process, the elastic member 4 is transported to position P2 on the outer circumferential surface of the anvil 12 using the elastic member guide mechanism 14 while tension is applied to the elastic member 4. Furthermore, in the arrangement process, the second nonwoven fabric sheet 3 is transported to position P3 on the outer circumferential surface of the anvil 12 using the second sheet guide mechanism 15. As a result, the nonwoven fabric sheets 2, 3, and the elastic member 4 are arranged between the ultrasonic horn 11 and the anvil 12 in the above order.

In the heat supply process, ultrasonic vibrations are applied to the ultrasonic horn 11 from an ultrasonic generator (not shown) to supply heat to both nonwoven fabric sheets 2 and 3 arranged between the ultrasonic horn 11 and the anvil 12. This causes both nonwoven fabric sheets 2 and 3 to be welded to the elastic member 4, producing the stretchable sheet 1.

Here, in the nonwoven fabric preparation step, a first nonwoven fabric sheet 2 and a second nonwoven fabric sheet 3 are prepared that 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 FIG. 5, a first nonwoven fabric sheet 2 is prepared in which the crystallinity is set to have a first welding temperature range E1 that includes 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 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 in which the crystallinity is set to have a second welding temperature range E2 that includes 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 is a temperature range in which the second nonwoven fabric sheet 3 can be welded to the elastic member 4. As shown in FIG. 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 than the first nonwoven fabric sheet 2. Below, the structure of the resin will be described with reference to FIG. 3 and FIG. 4 to explain the degree of crystallinity.

Fig. 3 is a schematic diagram showing the fibrous state of an amorphous resin, and Fig. 4 is a schematic diagram showing the fibrous state of a crystalline resin. As shown in Figs. 3 and 4, a resin is composed of a plurality of string-like molecules extending in a certain direction intertwined with each other. Thermoplastic resins are broadly classified into amorphous resins that do not have a crystal structure (Fig. 3) and crystalline resins that have a crystal structure (Fig. 4). 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 Terephthalate) resin. The crystalline resin has a crystalline region C (region surrounded by a two-dot chain line) formed by regular alignment of a part of a plurality of molecules, and an amorphous region G other than the crystalline part of the plurality of molecules. The degree of crystallinity is defined by the following formula (1).
Crystallinity = C/(C+G)×100...(1)

Figure 2 shows the results of measurements by differential scanning calorimetry. Specifically, Figure 2 shows the heat that a nonwoven fabric sheet can absorb at a certain temperature, that is, the extent to which the nonwoven fabric sheet melts at a certain temperature. The waveforms W1 of both nonwoven fabric sheets 2 and 3 are shown by two-dot chain lines in Figure 2. A certain amount of material needs to be melted 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 of 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 a state in which a certain amount of heat is absorbed, based on the heat flow value H0 in a state in which no heat is absorbed. On the other hand, the upper limit Max1 in the welding temperature ranges E1 and E2, which is the temperature above the lower limit defined in this way and 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 heat flow value begins to substantially stop fluctuating in the waveform in Figure 2).

Furthermore, in Figure 2, a waveform W2 of a nonwoven fabric sheet made of the same material as both nonwoven fabric sheets 2, 3 and having a higher degree of crystallinity than both nonwoven fabric sheets 2, 3 is shown by a solid line. As is clear from the waveforms W1 and W2 in Figure 2, lowering the degree of crystallinity of the nonwoven fabric sheet reduces the lower limit temperature in the welding temperature range. Specifically, the lower limit temperature Min1 of the welding temperature ranges E1, E2 of waveform W1 is lower than the lower limit temperature Min2 of the welding temperature range E3 of waveform W2. On the other hand, the upper limit of the welding temperature range E3 of waveform W2 is substantially the same as the upper limit Max1 of the welding temperature ranges E1, E2 of waveform W1.

In this embodiment, in the nonwoven fabric preparation process, nonwoven fabric sheets 2 and 3 are prepared that are mainly composed of polypropylene and have a crystallinity characteristic of the waveform W1. In other words, in this embodiment, the crystallinity of the nonwoven fabric sheets 2 and 3 is the same. As shown in FIG. 5, the welding temperature ranges E1 and E2 in the waveform W1 include a first temperature T1 determined by the distance in a specified direction from the ultrasonic horn 11 to the first nonwoven fabric sheet 2 and the amount of heat from the ultrasonic horn 11. In addition, the welding temperature ranges E1 and E2 include a second temperature T2 determined by the distance in a specified 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 waveform W2 is prepared as the first nonwoven fabric sheet 2, the welding temperature range E3 of the waveform W2 does not include the first temperature T1, so the first nonwoven fabric sheet 2 cannot be sufficiently melted and the elastic member 4 cannot be reliably welded.

In addition, in the nonwoven fabric preparation process in this embodiment, as shown in FIG. 7, nonwoven fabric sheets 2 and 3 having multiple layers stacked in the opposing direction in which the ultrasonic horn 11 and the anvil 12 face each other are prepared. Specifically, the nonwoven fabric sheets 2 and 3 have three layers manufactured by the spunbond method. Note that S in the figure 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 FIG. 2 also has three layers manufactured by the spunbond method as shown in FIG. 6. In FIGS. 6 and 7, H and L respectively indicate the degree of crystallinity, and L means that the crystallinity is lower 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 premise of these, is substantially proportional to the conveying speed of the nonwoven fabric sheet 2. For example, when the conveying speed of the nonwoven fabric sheet 2 is 350 m/min, the amount of heat generated by the ultrasonic horn 11 is 765 W. In addition, the distance in a specified direction from the ultrasonic horn 11 to the second nonwoven fabric sheet 3 is 0 mm (close contact state), and the distance in a specified direction from the ultrasonic horn 11 to the first nonwoven fabric sheet 2 (thickness of the second nonwoven fabric sheet 3 + width of the elastic member 4) is 1 mm or less.

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

Therefore, both nonwoven fabric sheets 2 and 3 can be reliably welded to the elastic member 4 without the need for a separate structure for heating the first nonwoven fabric sheet 2.

Furthermore, according to the above embodiment, since both nonwoven fabric sheets 2 and 3 having the same crystallinity are prepared, it is possible to use nonwoven fabric sheets having a common crystallinity as the first nonwoven fabric sheet 2 and the second nonwoven fabric sheet 3. Therefore, compared to the case where the first nonwoven fabric sheet 2 and the second nonwoven fabric sheet 3 having different crystallinity are used, it is possible to reduce costs by reducing the number of types of nonwoven fabric sheets.

In the above embodiment, both nonwoven fabric sheets 2 and 3 have the same degree of crystallinity, but the degree of crystallinity of the first nonwoven fabric sheet 2 can be made lower than the degree of crystallinity of the second nonwoven fabric sheet 3.

Specifically, as shown in FIG. 5, a first nonwoven fabric sheet 2 having a crystallinity characteristic of waveform W1 may be adopted, and a second nonwoven fabric sheet 3 having a crystallinity characteristic of waveform W2 may be adopted. 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, and the elastic member 4 can be reliably welded to both nonwoven fabric sheets 2 and 3.

In this way, a first nonwoven fabric sheet 2 is prepared that has a lower 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, and this allows both nonwoven fabric sheets 2, 3 to be reliably welded to the elastic member 4.

In the above embodiment, the nonwoven fabric sheets 2 and 3 each having three layers are illustrated, but the number of layers of the nonwoven fabric sheets 2 and 3 may be one or four or more.

In addition, it has been confirmed that when the nonwoven fabric sheets 2 and 3 have multiple layers, the lower limit of the welding temperature range can be lowered by lowering the crystallinity of at least one of the multiple layers. This is thought to be because at least one layer with a low crystallinity melts at a relatively low temperature, and the melting of the other layers is suppressed, 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 fabric sheet 2 in which at least one of the multiple layers in the first nonwoven fabric sheet 2 has the first welding temperature range E1, and the crystallinity of the layers other than the at least one of the multiple layers is set to be higher than the crystallinity of the at least one layer. Here, the first welding temperature range E1 includes the first temperature T1. Furthermore, in the nonwoven fabric preparation step, a second nonwoven fabric sheet can be prepared in which at least one of the multiple layers in the second nonwoven fabric sheet 3 has a second welding temperature range E2, and the crystallinity of the layers other than the at least one of the multiple layers is set to be higher than the crystallinity of the at least one layer. Here, the second welding temperature range E2 includes the second temperature T2. Also, as described above, the welding temperature range E3 can be adopted as the second welding temperature range in the second nonwoven fabric sheet 3.

The degree of crystallinity of at least one layer may be set as described above for either the first nonwoven fabric sheet 2 or the second nonwoven fabric sheet 3, or the degree of crystallinity of at least one layer may be set as described above for both nonwoven fabric sheets 2, 3. However, since the second nonwoven fabric sheet 3 is adjacent to the ultrasonic horn 11, it is relatively easy to control the amount of heat supplied to the second nonwoven fabric sheet 3, whereas the first nonwoven fabric sheet 2 is located at a greater distance from the ultrasonic horn 11 than the second nonwoven fabric sheet 3, so it is difficult to control the amount of heat supplied to the first nonwoven fabric sheet 2. From this perspective, it is preferable that the degree of crystallinity is adjusted in the first nonwoven fabric sheet 2.

Examples of the setting of the degree of crystallinity of at least one layer as described above are shown in Figures 8 to 10. Note that Figures 8 to 10 show examples in which the degree of crystallinity is adjusted as described above for both nonwoven fabric sheets 2 and 3.

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

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

In the example shown in FIG. 10, the nonwoven fabric sheet has five layers, two of which (layers manufactured by the meltblown method) have a low crystallinity, and the remaining three layers (layers manufactured by the spunbond method) have a higher crystallinity than the two layers. Assuming that the amount of heat from the ultrasonic horn 11 and the distance from the ultrasonic horn 11 to both nonwoven fabric sheets 2 and 3 are the same as in the above embodiment, a crystallinity of over 40% can be used for H and a crystallinity of 5% can be used for L.

As shown in Figures 9 and 10, in the nonwoven fabric sheet, it is preferable that at least one layer with a low crystallinity is sandwiched in a predetermined direction by layers other than the at least one layer. In a nonwoven fabric sheet configured in this manner, the molten material of the at least one layer that melts preferentially impregnates the layers on both sides of that layer and also contributes to welding of the elastic member 4. Therefore, the molten portion of the nonwoven fabric sheet can be fused with the underlying portion to more firmly weld the elastic member 4.

As described above, by setting the crystallinity of at least one layer to fall within the first or second welding temperature range E1, E2, and by making the crystallinity of the other layers higher, it is possible to increase the meltability of at least one layer and improve adhesion, and to decrease the meltability of the other layers and improve strength.

The present invention is not limited to the above embodiment, and may also be modified in the following ways:

In the above embodiment, multiple types of crystallization settings are described, but it is also possible to combine several of these crystallization settings.

Although an ultrasonic horn 11 has been exemplified as a heat supply member, the heat supply member is not limited to an ultrasonic horn 11. For example, a heater that generates heat by itself can also be used as the heat supply member.

In the above embodiment, polypropylene is used as the crystalline resin, but other crystalline resins can also be used.

The specific embodiments described above mainly include inventions with the following configurations:

The inventors of the present application discovered that by lowering the crystallinity of the nonwoven fabric sheet, the lower limit of the welding temperature range shifts to the lower temperature side, and came up with the method of the present invention in which a first nonwoven fabric sheet and a second nonwoven fabric sheet are prepared with a crystallinity set to have a temperature range that matches the temperature of both nonwoven fabric sheets heated by a heat supply member.

Specifically, in order to solve the above problem, the first invention is a manufacturing method for manufacturing a stretchable sheet having a first nonwoven fabric sheet, a second nonwoven fabric sheet facing the first nonwoven fabric sheet, and an elastic member bonded to the first nonwoven fabric sheet and the second nonwoven fabric sheet between the first nonwoven fabric sheet and the second nonwoven fabric sheet, comprising the steps of: preparing the first nonwoven fabric sheet and the second nonwoven fabric sheet; preparing a heat supply member for supplying heat to the first nonwoven fabric sheet and the second nonwoven fabric sheet for melting the first nonwoven fabric sheet and the second nonwoven fabric sheet; and preparing a sandwiching member that faces the heat supplying member in a predetermined opposing direction and sandwiches the first nonwoven fabric sheet, the second nonwoven fabric sheet, and the elastic member between the heat supplying member and the sandwiching member; and bonding the first nonwoven fabric sheet, the second nonwoven fabric sheet, and the elastic member to the first nonwoven fabric sheet, so that the second nonwoven fabric sheet, the elastic member, and the first nonwoven fabric sheet are aligned in order in the opposing direction away from the heat supplying member. A method for manufacturing a stretchable sheet is provided, comprising: disposing a material between the heat supplying member and the sandwiching member; supplying heat to the first nonwoven fabric sheet and the second nonwoven fabric sheet disposed between the heat supplying member and the sandwiching member using the heat supplying member; and preparing the first nonwoven fabric sheet and the second nonwoven fabric sheet, the crystallization degrees of the first nonwoven fabric sheet and the second nonwoven fabric sheet are set so that the first nonwoven fabric sheet has a first welding temperature range that includes a first temperature determined by the distance from the heat supplying member to the first nonwoven fabric sheet in the opposing direction and the amount of heat provided by the heat supplying 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 that includes a second temperature determined by the distance from the heat supplying member to the second nonwoven fabric sheet in the opposing direction and the amount of heat provided by the heat supplying member, and is a temperature range in which the second nonwoven fabric sheet can be welded to the elastic member.

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 specified direction from the heat supply member to both nonwoven fabric sheets.

Therefore, according to the present invention, both nonwoven fabric sheets can be reliably welded to the elastic member without the need for a separate structure for heating the first nonwoven fabric sheet.

The second invention is the first invention, and 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 crystallinity to set the same first welding temperature range and the same second welding temperature range that include both the first temperature and the second temperature.

According to the second invention, nonwoven fabric sheets having a common crystallinity can be used as the first nonwoven fabric sheet and the second nonwoven fabric sheet. Therefore, compared to using a first nonwoven fabric sheet and a second nonwoven fabric sheet having different crystallinity, it is possible to reduce costs by reducing the number of types of nonwoven fabric sheets.

The third invention is the first invention, and 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 crystallinity lower than the crystallinity of the second nonwoven fabric sheet.

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

The fourth invention is any one of the first to third inventions, and 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 stacked in the opposing direction, 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 layer.

The fifth invention is any one of the first to fourth inventions, 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 stacked in the opposing direction, 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 crystallization degree of the layers other than the at least one of the plurality of layers is set to be higher than the crystallization degree of the at least one layer.

The inventors of the present application have found that when a first nonwoven fabric sheet and a second nonwoven fabric sheet are used in which multiple layers are laminated, the adhesion to the elastic member is improved by reducing the crystallinity of at least one of the multiple layers. This is believed to be because at least one layer with a low crystallinity melts at a relatively low temperature, and the melting of the other layers is suppressed, 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 crystallinity of at least one layer to have the first or second welding temperature range described above and setting the crystallinity of the other layers higher than that, it is possible to increase the meltability of at least one layer to improve adhesion, and reduce the meltability of the other layers to improve strength.

Furthermore, the sixth invention provides a stretchable sheet manufactured using the manufacturing method of the first to fifth inventions.

Claims (6)

A manufacturing method for manufacturing a stretchable sheet having a first nonwoven fabric sheet, a second nonwoven fabric sheet facing the first nonwoven fabric sheet, and an elastic member bonded to the first nonwoven fabric sheet and the second nonwoven fabric sheet between the first nonwoven fabric sheet and the second nonwoven fabric sheet, comprising:
providing the first nonwoven fabric sheet and the second nonwoven fabric sheet;
a heat supplying member for supplying heat to the first nonwoven fabric sheet and the second nonwoven fabric sheet for melting the first nonwoven fabric sheet and the second nonwoven fabric sheet, and a sandwiching member for sandwiching the first nonwoven fabric sheet, the second nonwoven fabric sheet, and the elastic member between the heat supplying member and the heat supplying member, the sandwiching member being opposed to the heat supplying member in a predetermined opposing direction;
the first nonwoven fabric sheet, the second nonwoven fabric sheet, and the elastic member are disposed between the heat supplying member and the sandwiching member such that the second nonwoven fabric sheet, the elastic member, and the first nonwoven fabric sheet are aligned in this order in the opposing direction toward a direction away from the heat supplying member;
supplying heat to the first nonwoven fabric sheet and the second nonwoven fabric sheet disposed between the heat supply member and the sandwiching member using the heat supply member;
A method for manufacturing an elastic sheet, comprising the steps of: preparing the first nonwoven fabric sheet and the second nonwoven fabric sheet, the first nonwoven fabric sheet and the second nonwoven fabric sheet each having a degree of crystallinity set so that the first nonwoven fabric sheet has a first welding temperature range that 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 provided by the heat supply member, and is a temperature range in which the first nonwoven fabric sheet can be welded to the elastic member; and preparing the second nonwoven fabric sheet has a second welding temperature range that 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 provided by the heat supply member, and is a temperature range in which the second nonwoven fabric sheet can be welded to the elastic member. The method for producing a stretchable sheet according to claim 1, wherein when preparing the first nonwoven fabric sheet and the second nonwoven fabric sheet, the first nonwoven fabric sheet and the second nonwoven fabric sheet are prepared to have the same crystallinity in order to set the same first welding temperature range and the same second welding temperature range that include both the first temperature and the second temperature. The method for producing a stretchable sheet according to claim 1, wherein when preparing the first nonwoven fabric sheet and the second nonwoven fabric sheet, the first nonwoven fabric sheet is prepared to have a crystallinity lower than that of the second nonwoven fabric sheet. The method for producing a stretchable sheet according to any one of claims 1 to 3, wherein when preparing the first nonwoven fabric sheet and the second nonwoven fabric sheet, the first nonwoven fabric sheet is prepared having a plurality of layers stacked in the opposing direction, and the first nonwoven fabric sheet is prepared 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 layer. The method for producing a stretchable sheet according to any one of claims 1 to 3, wherein when preparing the first nonwoven fabric sheet and the second nonwoven fabric sheet, the second nonwoven fabric sheet is prepared having a plurality of layers stacked in the opposing direction, and 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 layer. An elastic sheet manufactured using the manufacturing method described in any one of claims 1 to 3.

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