Method for manufacturing a heating element and method for manufacturing a warming appliance

Abstract

To provide a method for successfully laminating sheets together in the manufacturing process of a heating body.SOLUTION: The present invention relates to a manufacturing method for a heating body 10 in which a heating layer 13 is arranged between a first substrate sheet 11 and a second substrate sheet 12. The second base material sheet 12 is a resin film with a lower air permeability than the first base material sheet, as measured according to JIS P8117. An adhesive agent 18 is coated on a surface scheduled to face the first base material sheet 11 in the second base material sheet so as to include an area other than an area scheduled to face the heating layer. Then, the first substrate sheet 11 and the second substrate sheet 12 are superposed so that an existence surface of the heating layer 13 and a coating surface of the adhesive agent 18 face each other to form a laminate. Furthermore, a nonexistent area of the heating layer 13 in the laminate is pressed to adhere both base sheets 11, 12. The present invention also provides a manufacturing method for a warmer comprising the heating body.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a heating element and a method for manufacturing a warming device.

Background Art

[0002] Techniques for manufacturing a heating element in which a layer of a functional composition is formed on a base sheet and a warming device using the same are known. The applicant of the present application has proposed a technique for manufacturing a heating element by applying a heat-generating composition containing an oxidizable metal on a base sheet to form a heat-generating layer (see Patent Document 1).

[0003] Patent Document 2 proposes a technique for manufacturing a heating element in which, at the peripheral portion of the heat-generating element composition, the base material and the coating material are sealed by adhesion, bonding, or heat fusion over the entire circumference or partially.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] When a plurality of base sheets are used as constituent materials of a heating element, depending on the constituent materials of the base sheet and the heating layer, the interaction between the base sheet and the heating layer is less likely to occur. Therefore, during manufacturing, the base sheet may unintentionally meander or shift in position, making it difficult to perform the bonding of the base sheets at the intended position. This phenomenon was likely to occur frequently when a resin film was used as the base sheet. Regarding the solution to such problems, the techniques of Patent Documents 1 and 2 have not been studied. That is, there was room for improvement in the handleability when obtaining a high-quality heating element or when subjecting the obtained heating element to subsequent processes.

[0006] The present invention relates to a manufacturing method capable of successfully bonding sheets to each other in the manufacturing process of a heating element or a heating appliance including the same.

Means for Solving the Problems

[0007] The present invention relates to a manufacturing method of a heating element. Preferably, in the heating element, the heating layer is disposed between a first base sheet and a second base sheet. As the second base sheet, it is preferable to use a resin film having an air permeability measured according to JIS P8117 of 1000 seconds / 100 mL or more and 4000 seconds / 100 mL or less, and the air permeability is lower than that of the first base sheet. In the manufacturing method, it is preferable to apply an adhesive to a surface of the second base sheet that is expected to face the first base sheet so as to include a region other than the region expected to face the heating layer. In the manufacturing method, it is preferable to form a laminate by overlapping the second base sheet so that the heating layer disposed on one surface of the first base sheet faces the surface coated with the adhesive. Alternatively, in the manufacturing method, it is preferable to dispose the heating layer on the surface of the second base sheet coated with the adhesive, and form a laminate by overlapping the first base sheet on the heating layer. In the manufacturing method, it is preferable to press the non - existence region of the heat - generating layer in the laminate to bond the two base material sheets.

[0008] The present invention also relates to a method for manufacturing a warming device. The manufacturing method preferably includes a step of accommodating the heating element between two films. It is preferable that at least one of the films has an air permeability measured according to JIS P8117 that is lower than the air permeability of the second base material sheet.

Advantages of the Invention

[0009] According to the present invention, in the manufacturing process of the heating element, the sheets can be successfully bonded together.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described with reference to the drawings based on its preferred embodiments. An example of the heating element obtained through the manufacturing method of the present invention is shown in FIG. 1. The heating element 10 shown in the figure includes a first base material sheet 11, a second base material sheet 12 which is a resin film having a predetermined air permeability, and a heat - generating layer 13 disposed between these sheets.

[0012] The heat - generating layer 13 includes a heat - generating composition 14 containing an oxidizable metal, an electrolyte, and water. The heat - generating composition 14 is preferably a paste - like substance. When the oxidizable metal in the heat - generating composition 14 comes into contact with an oxidizing substance such as oxygen in the air, heat is generated along with the oxidation reaction. The heat - generating layer 13 may be composed only of the above - described heat - generating composition 14, or may further contain a water - absorbent polymer 15. When the water - absorbent polymer 15 is included, the polymer is mixed in the heat - generating composition 14 or arranged in a layer adjacent to the heat - generating composition 14. The water - absorbent polymer 15 is used to control the state of existence of water contributing to the oxidation reaction of the oxidizable metal. In the embodiment shown in the figure, the heat - generating body 10 has an adhesive portion 40 where both base material sheets 11 and 12 are adhered by an adhesive 18. Also, the heat - generating layer 13 according to this embodiment is composed of a layered heat - generating composition 14 and a layer of water - absorbent polymer 15 particles arranged adjacent thereto.

[0013] Further, instead of the paste - like heat - generating composition, the heat - generating body 10 can be a sheet - like heat - generating composition (not shown). The sheet - like heat - generating composition can be, for example, in a form that further contains a fiber material in addition to an oxidizable metal, an electrolyte, and water. The sheet - like heat - generating composition is typically a paper - making body that contains the above - described materials and is shaped into a predetermined shape.

[0014] The above - described heat - generating body 10 can be used as a component of a warming device. The warming device is used to be brought into contact with an object to be heated during its use and impart warmth to the object to be heated. Examples of the object to be heated include various parts such as a human skin, eyes, nose, mouth, and mucous membranes, and articles having a hard surface. The warming device is preferably formed such that when the heat - generating body generates heat, water vapor heated to a predetermined temperature is generated from the warming device itself along with the heat generation. Thereby, the warming device 1 can impart warmth to the object to be heated.

[0015] An example of the heating device obtained through the manufacturing method of the present invention is shown in Fig. 2. In the heating device 1 shown in the figure, the heating element 10 is accommodated between two films 5 and 6. The first film 5 is arranged to face the first base sheet 11. The second film 6 is arranged to face the second base sheet 12. Details of the materials used for the heating element and the heating device and their physical properties will be described later.

[0016] The manufacturing method of the present invention will be described together with the manufacturing apparatus suitably used for the method. Fig. 3 shows an example of a manufacturing apparatus for manufacturing the heating element 10 by forming a heating layer 13 containing a paste-like heating composition. The manufacturing apparatus 100 shown in the figure includes a heating layer forming section 110, an adhesive coating section 120, a pressing section 130, and a cutting section 140 in this order.

[0017] The heating layer forming section 110 includes a coating section 111 for coating a metal slurry containing a powder of a metal to be oxidized and a dispersion medium such as water, an electrolyte spraying section 112 for spraying an electrolyte, and a polymer spraying section 113 for spraying particles of a water-absorbing polymer in this order.

[0018] The coating section 111 is configured to be able to continuously or intermittently coat a metal slurry containing a powder of a metal to be oxidized on a part or the whole of one surface of a strip-shaped first base sheet 11 continuously conveyed in one direction. The coating section 111 is connected to a slurry preparation facility (not shown), and the metal slurry is supplied through the facility. Thereby, the metal slurry containing the powder of the metal to be oxidized can be continuously or intermittently coated along the conveyance direction MD of the first base sheet 11. The coating section 111 can employ a coating apparatus such as a die coater or a gravure roll.

[0019] The electrolyte spraying section 112 is for spraying an electrolyte onto the layer of the metal slurry formed by the coating section 111. The electrolyte to be sprayed may be solid or may be a liquid dissolved or dispersed in water or the like. The sprayed electrolyte dissolves or disperses in the metal slurry, and the layer of the metal slurry becomes a layer of an exothermic composition containing a metal to be oxidized, an electrolyte, and water. Further, the polymer spraying section 113 is for spraying particles of a water-absorbing polymer onto the layer of the exothermic composition (i.e., the layer of the metal slurry containing the electrolyte) to form a layer of the water-absorbing polymer. The electrolyte spraying section 112 and the polymer spraying section 113 can each independently use various feeder devices.

[0020] The adhesive coating section 120 can continuously or intermittently apply the adhesive 18 to part or all of one surface of the strip-shaped second base material sheet 12 continuously conveyed in one direction (the conveyance direction MD). This second base material sheet 12 is a sheet separate from the first base material sheet 11.

[0021] The pressing section 130 is a member that presses the long strip-shaped laminate 1S in which the first base material sheet 11 having the exothermic layer 13 formed on one surface and the second base material sheet 12 having the adhesive 18 applied on one surface are overlapped in the thickness direction at a predetermined position. As the pressing section 130, an embodiment including a pair of rolls 131 and 132 is illustrated in FIGS. 3 and 4. The pressing section 130 shown in the figure uses a roll as a rotating body to press a predetermined position of the laminate 1S in the thickness direction to bond the two base material sheets 11 and 12. The pair of rolls 131 and 132 are arranged to face each other with their axial directions coinciding with each other and in a state where the rotation direction and the conveyance direction MD coincide with each other. It is preferable that at least one of the pair of rolls 131 and 132 is rotatable by having a driving force transmitted thereto by a driving source. In this case, the other roll may be rotated along or may be rotatable by a driving source.

[0022] In the present embodiment, the first pressing roll 131 is a stepped roll including a plurality of large-diameter portions 136 provided at intervals in both side regions and the central region in the axial direction of the roll, and a small-diameter portion 137 located between the large-diameter portions 136 and having a diameter smaller than that of the large-diameter portions 136. The circumferential surfaces of both the large-diameter portion 136 and the small-diameter portion 137 are flat. Further, the second pressing roll 132 is a columnar anvil roll having a flat circumferential surface and having a constant diameter along the axial direction. Alternatively, the second pressing roll 132 may be a stepped roll having the same configuration as the first pressing roll. In this case, it is preferable that the first pressing roll and the second pressing roll are arranged such that the small-diameter portions and the large-diameter portions of the respective rolls face each other.

[0023] The cutting unit 140 is a member for cutting the long strip-shaped laminate 1S to which both base material sheets are adhered along the width direction CD, which is a direction intersecting the conveyance direction MD, preferably a direction perpendicular to the conveyance direction MD, to obtain the heating element 10 in the form of individual sheets.

[0024] An embodiment including a pair of rolls 141 and 142 is illustrated in FIG. 3 as the cutting unit 140. The cutting unit 140 shown in the figure includes a cutter roll 141 having a cutter blade on its circumferential surface and an anvil roll 142 arranged to face the cutter roll 141. The cutter blade 145 in the cutter roll 141 extends in the axial direction of the roll and is arranged singly or in plurality at intervals in the circumferential direction of the roll. The anvil roll 142 is a roll having a flat circumferential surface. Preferably, a driving force is transmitted by a driving source to at least one of the pair of rolls 141 and 142 so as to be rotatable. In this case, the other roll may be rotated along, or may be rotatable by a driving source. In any case, it is preferable that the rotational speeds of both rolls 141 and 142 are the same as each other.

[0025] From the perspective of facilitating the shaping of the heating element into a predetermined shape and increasing the surface area of the heating element to enhance the contact efficiency with oxygen and improve the heating characteristics, the manufacturing apparatus 100 may further include a slit forming unit 170 between the pressing unit 130 and the cutting unit 140.

[0026] The slit forming unit 170 shown in FIG. 3 includes a slit roll 171 having a slit blade on its circumferential surface and a second anvil roll 172 arranged opposite to the slit roll 171. The slit blade on the slit roll 171 extends in the circumferential direction of the roll and is arranged singly or in plurality at intervals in the axial direction of the roll. The second anvil roll 172 is a roll with a flat circumferential surface. It is preferable that at least one of these pair of rolls 171, 172 has a driving force transmitted by a driving source and is rotatable. In this case, the other roll may be rotated along or may be rotatable by a driving source. In any case, it is preferable that the rotational speeds of both rolls 171, 172 are the same as each other.

[0027] The slit forming unit 170 of the present embodiment includes a slit blade 17a arranged on the circumferential surface of the slit roll 171. The slit blade 17a in the present embodiment is arranged singly in the central region in the axial direction of the slit roll 171 and is configured to continuously cut the first base sheet 11 and the second base sheet 12 located in the non - existing region of the heating layer 13 in the central region in the sheet width direction CD in the thickness direction along the conveyance direction MD so that the two base sheets can be separated in the width direction CD. Alternatively, the slit blade 17a may not be arranged.

[0028] When further manufacturing the warming device 1 after manufacturing the heating element 10, it is preferable to further include a warming device forming unit (not shown). In the manufacturing apparatus 100 shown in FIG. 3, the warming device 1 is manufactured continuously following the manufacturing of the heating element 10, but it is not limited to this form, and the manufacturing of the heating element 10 and the manufacturing of the warming device 1 may be performed separately.

[0029] The heat generating element forming part is a part that houses the heating element 10 between the strip-shaped first film 5 and second film 6 that are continuously conveyed in one direction. As necessary, the heat generating element forming part may further include a joint part forming part for joining the first film 5 and the second film 6 in the heat generating element precursor 1A in which the heating element 10 is housed between the first film 5 and the second film 6. As the above-described joint member, for example, a configuration such as a heat roll used in a known joint method such as heat sealing can be adopted.

[0030] Hereinafter, a preferred manufacturing method of the heating element 10 will be described with reference to FIGS. 3 and 4. This manufacturing method includes a step of applying an adhesive 18 to a surface of the second base sheet 12 that is planned to face the first base sheet 11 so as to include a region other than the region planned to face the heating layer 13, a step of forming a laminate 1S in which the heating layer 13 is disposed between the two base sheets 11 and 12, and a step of pressing a region where the heating layer 13 does not exist in the laminate 1S to bond the two base sheets 11 and 12. These steps are roughly classified into three steps. In forming the laminate 1S, the second base sheet 12 may be superposed so that the heating layer 13 disposed on one surface of the first base sheet 11 faces the surface of the second base sheet 12 coated with the adhesive 18 to form the laminate 1S. Alternatively, in forming the laminate 1S, the heating layer 13 may be disposed on the surface of the second base sheet 12 coated with the adhesive 18, and the first base sheet 11 may be superposed on the heating layer 13 to form the laminate 1S.

[0031] First, as the heating layer forming step, a long strip-shaped raw material of the first base sheet 11 is drawn out from a first raw material roll (not shown) and conveyed in the conveying direction MD. Then, while conveying the raw material of the first base sheet 11 in the conveying direction MD, a metal slurry 13a containing a powder of a metal to be oxidized supplied from the coating unit 111 is applied to one surface of the first base sheet 11.

[0032] At this time, from the viewpoint of efficiently bonding the base sheets described later, it is preferable that the metal slurry 13a is applied onto the first base sheet 11 so as to have a non-coated area. That is, the metal slurry 13a is preferably applied to a partial area on one surface of the first base sheet 11. Also, from the viewpoints of efficiently bonding the base sheets while maintaining a uniform coating state of the metal slurry, and further enhancing productivity by effectively using the constituent materials of the heating element, the metal slurry 13a is continuously coated along the conveyance direction MD, and it is more preferable that the coated area and the non-coated area of the metal slurry are alternately formed along the width direction CD. From the same viewpoint, it is also more preferable that the non-coated area of the metal slurry is formed at least in both end regions in the width direction CD of the first base sheet 11.

[0033] In the embodiment shown in FIG. 3, the metal slurry is applied such that the non-coated areas of the metal slurry 13a are formed in both end regions and the central region in the width direction CD of the first base sheet 11, respectively. A plurality of non-coated areas of the metal slurry are formed so as to continuously extend along the conveyance direction MD. Similarly, a plurality of coated areas of the metal slurry are formed so as to continuously extend along the conveyance direction MD.

[0034] Next, while conveying the first base sheet 11 having the metal slurry applied to one surface in the conveyance direction MD, an electrolyte is sprayed from the electrolyte spraying section 112 onto the coated surface side of the metal slurry 13a to obtain a heat-generating composition 14. In addition to this, a water-absorbing polymer is sprayed from the polymer spraying section 113 onto the coated surface side of the metal slurry. Thereby, a heat-generating layer 13 in which a layer of the paste-like heat-generating composition 14 and a layer of the water-absorbing polymer 15 are laminated in this order is formed on one surface of the first base sheet 11. The existing area of the heat-generating layer 13 substantially coincides with the coated area of the metal slurry, and the non-existing area of the heat-generating layer 13 substantially coincides with the non-coated area of the metal slurry.

[0035] Separately from this, the adhesive application section 120 applies an adhesive 18 to one surface of the web of the second base material sheet 12 conveyed in the conveyance direction MD (adhesive application step). The surface of the second base material sheet 12 to which the adhesive 18 is to be applied is the surface that is to face the first base material sheet 11. At this time, the adhesive 18 is preferably applied onto the second base material sheet 12 so as to have a non-coated region. That is, the adhesive 18 is preferably applied to a partial region on one surface of the second base material sheet 12.

[0036] Specifically, the adhesive 18 applied to the second base material sheet 12 is more preferably applied so as to include regions other than the region that is to face the heat generating layer 13 in the second base material sheet 12, and it is even more preferable that the adhesive 18 is applied only to the regions other than the above-described region that is to face the heat generating layer 13. That is, the application of the adhesive 18 to the second base material sheet 12 is more preferably performed so as to include at least the region that is to face the non-existing region of the heat generating layer 13 in the first base material sheet 11, and it is even more preferable that the application is performed only on the region that is to face the non-existing region of the heat generating layer 13 in the first base material sheet 11.

[0037] By performing the application of the adhesive so as to include the above-described specific regions, the bonding of the base material sheets can be efficiently performed, and the adhesiveness thereof is also improved. In particular, by applying the adhesive only to the regions other than the region that is to face the heat generating layer 13, while efficiently bonding the base material sheets, it is possible to secure an oxygen flow path that contributes to improving the heat generating property of the heat generating layer over the entire surface of the heat generating layer without inhibiting the air permeability of the base material sheet due to the presence of the adhesive. Therefore, it is advantageous in that a heat generating body having excellent heat generating characteristics and a warming device including the same can be obtained with high productivity.

[0038] In the present embodiment, the adhesive 18 is applied in a plurality of continuous straight lines along the conveyance direction MD of the second base material sheet 12, and the coated regions and non-coated regions of the adhesive 18 are alternately formed along the width direction CD. Specifically, in this embodiment, the adhesive 18 is applied such that the applied regions of the adhesive 18 are formed at both end regions and the central region in the width direction CD of the second base material sheet 12. The applied regions of the adhesive 18 are each formed in a plurality of strips extending along the conveyance direction MD. Similarly, the non-applied regions of the adhesive 18 are each formed in a plurality of strips extending along the conveyance direction MD.

[0039] As long as the effects of the present invention are achieved, the coating methods of the metal slurry 13a and the adhesive 18 are not limited to the continuous linear shape described above, respectively and independently. As examples of the coating method, respectively and independently, in addition to the continuous straight line, discontinuous lines, curves such as spiral or omega shapes, or combinations thereof can be appropriately adopted. Also, the line width may be constant or different throughout the entire area, respectively and independently.

[0040] The temperature of the adhesive 18 applied to the second base material sheet 12, which is a resin film, is preferably lower than the melting point of the constituent resin of the second base material sheet. By using an adhesive adjusted to such a temperature, the base material sheets can be bonded with high adhesiveness, and the unintended melting of the second base material sheet 12 composed of the resin film can be prevented, maintaining various physical properties useful for expressing the characteristics of the heating element such as the air permeability originally possessed by the second base material sheet 12, and a heating element excellent in heating characteristics can be obtained with high productivity. This is particularly advantageous in that, compared with the case of using heat fusion such as thermal embossing, which is a method of bonding base material sheets, for example, the joining of the sheets can be performed in a state where the adverse effects on maintaining the predetermined air permeability of each base material sheet and the predetermined magnitude relationship of the air permeabilities of each base material sheet are effectively reduced, so that a heating element capable of expressing excellent heating characteristics as designed can be efficiently obtained.

[0041] In this specification, the melting point refers to the endothermic peak caused by the phase change of the resin or adhesive to be measured from solid to liquid before the resin or adhesive thermally decomposes when it is heated. Specifically, the melting point is the temperature at which a melting peak is observed by differential scanning calorimetry (DSC). When multiple peaks are observed, it means the temperature at which the endothermic peak is the largest. When the melting point cannot be clearly measured by the above method, the softening point is used instead of the melting point.

[0042] The temperature of the adhesive can be appropriately changed according to the material of the second base sheet. From the viewpoint of maintaining the air permeability of the second base sheet and being able to manufacture a heating element with high heat generation characteristics, it is preferably 20°C or higher, more preferably 80°C or higher, preferably 200°C or lower, more preferably 170°C or lower, and still more preferably 120°C or lower. As such an adhesive having such physical properties, hot melt adhesives containing compounds such as ethylene-vinyl acetate copolymer systems, polyolefin systems, amorphous polyalphaolefin systems, synthetic rubber-based polyamide systems, polyester systems, and polyurethane systems are preferably mentioned. As such an adhesive, for example, HM-Dispomelt ME716E (manufactured by Henkel Corporation) can be mentioned. The melting points of these hot melt adhesives are preferably lower than the melting point of the constituent resin of the second base sheet. Therefore, in this manufacturing method, it is preferable to apply an adhesive 18 at a temperature equal to or higher than the melting point of the adhesive and lower than the melting point of the constituent resin of the second base sheet 12 to the second base sheet 12.

[0043] Subsequently, a first base sheet 11 with a heating layer 13 disposed in a partial region on one surface and a second base sheet 12 coated with an adhesive 18 are overlapped to form a long strip-shaped laminate 1S with the heating layer 13 disposed between the two base sheets 11 and 12. The overlapping of the two base sheets 11 and 12 is performed such that the surface where the heating layer 13 exists on the first base sheet 11 faces the surface coated with the adhesive 18 on the second base sheet 12.

[0044] From the viewpoint of maintaining a good formation state of the heat-generating layer and performing the bonding of the two base material sheets 11 and 12 with high bondability without inhibiting the heat-generating reaction during use, the overlapping of the two base material sheets 11 and 12 is such that the non-existent region of the heat-generating layer 13 in the first base material sheet 11 faces the coated region of the adhesive 18 in the second base material sheet 12, and the existent region of the heat-generating layer 13 in the first base material sheet 11 faces the non-coated region of the adhesive 18 in the second base material sheet 12. In any case, the overlapping of the two base material sheets 11 and 12 may be performed simultaneously with the pressing step described later. Alternatively, the two base material sheets 11 and 12 may be overlapped and then sequentially subjected to the pressing step described later.

[0045] Then, the laminate 1S obtained by overlapping the two base material sheets 11 and 12 is introduced into the pressing portion 130, and the non-existent region of the heat-generating layer 13 in the laminate 1S is pressed in the sheet thickness direction to bond the two base material sheets to each other via the adhesive 18 (pressing step). As a result, a laminate 1S in which an adhesive portion 40, which is a portion where the two base material sheets 11 and 12 are bonded, is formed is obtained. The pressed laminate 1S obtained through this step has the same configuration as the long-strip-shaped heat-generator 10.

[0046] In the present embodiment, the laminate 1S is introduced between a first pressing roll 131 having a large-diameter portion 136 and a small-diameter portion 137 and a second pressing roll 132 having a smooth peripheral surface to bond the two base material sheets 11 and 12. At this time, as shown in FIG. 4, it is preferably introduced into the pressing portion 130 such that the large-diameter portion 136 of the first pressing roll 131 faces the non-existent region of the heat-generating layer 13 in the laminate 1S, and the non-existent region is pressed in the thickness direction Z. With such a configuration, strong bonding between the base material sheets can be achieved, and the formation state of the heat-generating layer 13 can be maintained, enabling a high-quality heat-generator to be obtained with high productivity. When the non - existence region of the heat - generating layer 13 is pressed, a laminate 1S in which both base material sheets 11 and 12 are adhered is formed. And the pressed region in the laminate 1S after the pressing process becomes the adhesion part 40. There is no heat - generating layer 13 between the two base material sheets 11 and 12 in the adhesion part 40.

[0047] The pressure applied to the non - existence region of the heat - generating layer 13 in the pressing process, expressed as line pressure, is preferably 5 N / m or more. Also, the pressure, expressed as line pressure, is preferably 50 N / m or less. By configuring to apply such pressure, even when a heat - generating layer having a thickness is arranged compared with the base material sheet, the first base material sheet and the second base material sheet can be effectively adhered by an adhesive at an appropriate position. Such pressure can be adjusted as appropriate by changing the interval between the pressing rolls 131 and 132.

[0048] From the viewpoint of obtaining a high - quality heating element with high productivity while maintaining the formation state of the heat - generating layer 13, as shown in FIG. 4, it is also preferable that the small - diameter part 137 of the first pressing roll 131 and the existence region of the heat - generating layer 13 in the laminate 1S face each other and are introduced into the pressing part 130. More preferably, the existence region of the heat - generating layer 13 is configured not to be pressed in the sheet thickness direction. That is, it is preferably configured that only the non - existence region of the heat - generating layer 13 is pressed. With such a configuration, even when a resin film in which the interaction due to the surface tension with the heat - generating composition is difficult to occur is used as the base material sheet, the base material sheets can be bonded together as designed at an appropriate position. Also, even when the heat - generating layer 13 has a relatively large thickness, by pressing only the non - existence region of the heat - generating layer 13, the base material sheets can be sufficiently pressed. Thus, it is difficult to generate structural changes or displacements of the heat - generating layer 13 due to pressing, and the bonding strength between the base material sheets can be increased.

[0049] In order to achieve the above-described pressing mode, for example, a first pressing roll 131 having the same length along the axial direction of the large-diameter portion 136 and the length along the width direction CD of the non-existent region of the heating layer 13 can be used, or the difference between the radius of the large-diameter portion 136 and the radius of the small-diameter portion 137 is made larger than the thickness of the existing region of the heating layer 13, and the base material sheet located in the existing region of the heating layer 13 is configured not to contact the circumferential surface of the small-diameter portion 137. It can be easily achieved by using the first pressing roll 131.

[0050] As described above, the laminate 1S obtained by passing through the pressing portion 130 becomes the long-strip-shaped heating element 10 in which the bonding portions 40 where the two base material sheets 11 and 12 are bonded are formed. From the viewpoint of improving the handleability when the heating element is subjected to subsequent processes, it is preferable to further perform a process (cutting process) of introducing the long-strip-shaped heating element 10 into the cutting portion 140 while conveying it in the conveying direction MD and cutting it along the width direction CD. By passing through this process, the heating element 10 can be formed into a single-sheet form.

[0051] In the present embodiment, while conveying the long-strip-shaped heating element 10 in which the bonding portion 40 is formed in the conveying direction MD, it is introduced between the cutter roll 141 and the anvil roll 142, and is cut along the width direction CD at a predetermined interval by the cutter blade of the cutter roll 141 to obtain the single-sheet heating elements 10 separated before and after in the conveying direction MD.

[0052] The cutting method in the cutting process is cutting by narrow pressure between the cutter blade and the anvil roll 142 in a state where tension is applied to the sheet, that is, a so-called score cut method or a slip cut method. By adopting this method, it is possible to accurately cut with less occurrence of warping or displacement of the heating layer and the base material sheet during cutting, so that a high-quality heating element with little dimensional variation can be produced. This is advantageous in that, compared with a method of applying a shearing force from above and below to cut, such as a shear cut method, the cutting can be performed according to the design dimensions while maintaining the configuration and form of the base material sheet and the heating layer as designed.

[0053] In the cutting using the cutter roll 141 and the anvil roll 142 in the cutting part 140, it is preferable that the rotational speed V1 of the cutter roll 141 and the anvil roll 142 is faster than the conveyance speed V2 of the long strip-shaped heating element 10 which is the laminate 1S after the pressing process. The long strip-shaped heating element 10 is composed of including the second base material sheet 12 which is a resin film. Generally, due to the flexibility of the resin film, it may not be possible to efficiently perform cutting at a desired position. By making the rotational speed of each roll faster than the conveyance speed of the long strip-shaped heating element 10, an appropriate tension can be applied to the long strip-shaped heating element 10 to be cut. Therefore, even when including a resin film, cutting at a desired position can be efficiently performed.

[0054] In particular, since the resin film is thinner and more likely to elastically deform compared to non-woven fabric, paper, cloth, etc., it is more likely to cause blade spillage or crushing on the cutter blade, which can greatly affect the cutting performance of the sheet. Also, when trying to cut the resin film with a cutter blade with blade spillage or crushing, it becomes difficult to cut at a desired position due to the elastic deformability of the film itself. By satisfying the above-described relationship of the rotational speed, the occurrence of elastic deformation of the film itself can be reduced, and the base material sheet can be successfully cut at a predetermined position.

[0055] The rotational speed V1 of both rolls 141 and 142, expressed as the peripheral speed, is preferably 5 m / min or more, more preferably 8 m / min or more. Also, the rotational speed V1 of both rolls 141 and 142, expressed as the peripheral speed, is preferably 60 m / min or less, more preferably 45 m / min or less, still more preferably 20 m / min or less. With such a rotational speed, stable cutting of the laminate 1S can be performed.

[0056] The conveyance speed V2 of the long strip-shaped heating element 10 which is the laminate 1S after the pressing process is preferably 5 m / min or more, more preferably 8 m / min or more. Also, the conveyance speed V2 of the heating element 10 is preferably 60 m / min or less, more preferably 45 m / min or less, and still more preferably 20 m / min or less. By having such a conveyance speed, it is possible to achieve both the cutting and the conveyance of the laminate 1S stably.

[0057] In the case of including a cutting step, in the conveyance process until the long strip-shaped heating element 10, which is the laminate 1S having undergone the pressing step, is supplied to the cutting step, that is, while the long strip-shaped heating element 10 is being conveyed from the pressing portion 130 to the cutting portion 140, it is preferable that the total of the bending angles in the side view along the conveyance direction MD of the laminate 1S having undergone the pressing step is equal to or less than a predetermined value. Specifically, it is conveyed so that the total of the above-described bending angles is preferably 180 degrees or less, more preferably 110 degrees or less. Also, the total of the above-described bending angles is preferably 0 degrees or more. By having such bending angles, it is possible to reduce unintended stretching, shrinkage, and displacement of the base material sheet, and while maintaining a good bonding state between the base material sheets, efficiently perform cutting at a desired position. In order to make the total of the bending angles within the above-described range, for example, it can be appropriately adjusted by reducing the number of guide rolls arranged in the conveyance path from the pressing portion 130 to the cutting portion 140, or reducing the angle at which it is wound around the roll circumferential surface. The embodiment shown in FIG. 3 is an example in which it is conveyed in one direction without being wound around a roll and the total of the bending angles is 0 degrees, but it is not limited to this form.

[0058] In a general sheet conveyance process, the sheet is wound around the circumferential surface of a roll such as a guide roll, and tension is applied to the sheet to prevent the sheet from meandering and enable stable conveyance. However, when a resin film is used as the base sheet as in the present invention, if it is conveyed in a state of being wound around the circumferential surface of the roll, the path difference between the first base sheet and the second base sheet caused by winding around the roll affects the conveyance speed difference and the tension difference, and can also affect the bondability between the sheets. Therefore, by conveying so as to be within the range of the above-described preferable bending angle, the laminated body 1S after the pressing step can be supplied to the subsequent steps while maintaining a good bonding state between the base sheets.

[0059] As shown in FIG. 3, when a slit forming portion 170 is provided between the pressing portion 130 and the cutting portion 140, a long strip-shaped heating element 10 is introduced between the slit roll 171 and the second anvil roll 172 in the slit forming portion 170, and the heating element 10 is continuously cut along the conveyance direction MD and separated in the width direction CD to form a strip-shaped body having a smaller width than the long strip-shaped laminated body 1S formed after the pressing portion 130.

[0060] Through the above steps, a heating element 10 having the form shown in FIG. 1 can be obtained. This heating element 10 is a single-sheet heating element having predetermined dimensions.

[0061] When manufacturing the heating device 1, whether it is performed continuously with the manufacturing of the heating element 10 or separately from the manufacturing of the heating element 10, it is also preferable to further perform the step of manufacturing the heating device in the step after manufacturing the heating element 10. In the embodiment shown in FIG. 3, a single-sheet heating element 10 is introduced between and accommodated in the long strip-shaped first film 5 and the second film 6 that are continuously conveyed in the conveyance direction MD. Thereby, a long strip-shaped heating device precursor 1A is obtained.

[0062] The heating device precursor 1A is a laminate in which the first film 5, the heating element 10, and the second film 6 are laminated in this order. More specifically, it is a laminate in which a first film 5, a first base sheet 11, a heating layer 13, a second base sheet 12, and a second film 6 are laminated in this order, and each member is adjacent to each other. Then, if necessary, the first film 5 and the second film 6 are joined simultaneously with the formation of the heating element precursor 1A or after the heating element precursor 1A is formed. In the present embodiment, an aspect in which a joint portion 8 where the first film 5 and the second film 6 are joined is formed is illustrated in FIG. 3. The joint portion 8 is formed on the entire outer periphery of the heating element 10 in plan view and at a portion where the heating element 10 does not exist.

[0063] In the conveying process until the manufactured heating element 10 is subjected to the manufacturing process of the heating device, from the viewpoint of improving manufacturing efficiency, the interval between the individual heating elements 10 may be adjusted as necessary. In order to adjust the interval between the individual heating elements 10, for example, a pitch member for widening the interval before and after in the conveying direction MD and a widening member for widening the interval in the width direction CD can be appropriately combined. The pitch member and the widening member can each be independently used by appropriately combining conveying members such as a conveyor and a roll.

[0064] Through the above steps, the heating device 1 having the form shown in FIG. 2 can be obtained. This heating device 1 can be used as it is, or can further include a step of laminating or joining with other constituent members in a subsequent step. As described above, for example, by manufacturing a heating device using a resin film as the second base sheet 12 or using each film 5, 6, the obtained heating device can easily control the degree of air flow by each film, while facilitating the supply of oxygen in the air to the heating element 10 constituting the heating device 1, and making it easy to release water vapor and heat generated by the heating of the heating element 10 to the outside. As a result, the obtained heating device is advantageous in that it can give a comfortable temperature feeling to the user for a long time. Furthermore, even when the gas inside the heating device expands due to heat or water vapor is generated from the heating element 10, it is possible to easily release the expanded gas or water vapor through each film and suppress the swelling of the heating device. Therefore, the obtained heating device is advantageous in that it can reduce discomfort such as pressure on the skin during use even when used for a long time, and can suppress deterioration of the appearance of the heating device during use due to swelling.

[0065] When obtaining the above-described heating element 10 and heating device using the heating layer 13 including the sheet-like heat-generating composition, for example, in the heating layer forming step, instead of applying the metal slurry by the coating portion 111, a mixture including a metal to be oxidized, water, and a fiber material is wet-laid to form an intermediate molded body, and then an electrolyte is contained in the intermediate molded body to obtain a heat-generating composition that is a wet-laid body. This heat-generating composition may be in a long strip shape, or may be in the form of sheets pre-manufactured or cut to have a predetermined size. If necessary, a layer of a water-absorbing polymer may be further disposed on one surface of the heat-generating composition that is a wet-laid body. Thereby, the heating layer 13 including the sheet-like heat-generating composition is obtained. Thereafter, the above-described heating layer 13 is disposed on one surface of the first base sheet 11 with respect to the second base sheet 12 that has undergone the adhesive coating step, and the second base sheet 12 is superposed so that the heating layer 13 and the coating surface of the adhesive 18 of the second base sheet 12 face each other to form a laminate 1S. Alternatively, the above-described heating layer 13 may be disposed on the coating surface of the adhesive 18 of the second base sheet 12, and the first base sheet 11 may be superposed on the heating layer 13 to form a laminate 1S. Then, by subjecting the above-described laminate 1S to a pressing step, the target heating element 10 and heating device 1 can be obtained. Regarding points not particularly described otherwise, the descriptions regarding the above-described manufacturing method are appropriately applied.

[0066] From the viewpoint of the adhesion between the heating layer and the base sheet, in order to stably achieve high-quality continuous productivity of the heating element, as shown in FIGS. 3 and 4, it is preferable to manufacture the heating element 10 provided with the heating layer 13 including the paste-like heat-generating composition. From the same perspective, when applying a metal slurry to form the heat-generating layer 13 on the base sheet, as shown in FIG. 3, it is preferable to perform the operation such that the heat-generating layer 13 is disposed on the first base sheet 11. That is, the heat-generating layer forming step is preferably performed on the first base sheet 11. When the heat-generating layer is applied on the second base sheet, the air permeability of the heat-generating layer is likely to change, and it is difficult to obtain stable quality of the heating element 10.

[0067] Also, when laminating a base sheet on the heat-generating layer containing the paste-like heat-generating composition, for example, as in the reference example described later, a sheet material having water absorbency such as paper is often used as the base sheet. One of the reasons for this is that surface tension is likely to occur between the sheet material and the moisture contained in the heat-generating layer, making it easy to align the sheet materials with each other and facilitating bonding at a predetermined position. However, there is room for improvement in further enhancing the heat-generating characteristics associated with the control of air permeability for the heating element and the warming device obtained by using a water-absorbent sheet material. As in the above-described preferred manufacturing method, by using a paste-like heat-generating composition and using a resin film as the base sheet, it is possible to satisfactorily bond resin films, which has been difficult in the prior art. In addition, for the obtained heating element and warming device, the degree of air flow can be appropriately controlled by each film to achieve long-term heat generation, and a comfortable warm feeling can be given to the user for a long time. Furthermore, the obtained warming device can suppress its swelling, thereby reducing discomfort such as pressure on the skin during use caused by the swelling and deterioration of the appearance.

[0068] The details of the components of the heating element 10 and the warming device 1 will be described below. As the sheet material that can be used for the heating element 10 and the warming device 1, for example, fiber sheets such as non-woven fabrics, woven fabrics, and paper, resin films regardless of the presence or absence of through-holes, resin foam sheets, or combinations thereof are used. Examples of the nonwoven fabric include air-through nonwoven fabric, spunbond nonwoven fabric, needle-punched nonwoven fabric, meltblown nonwoven fabric, thermal-bonded nonwoven fabric, chemical-bonded nonwoven fabric, spunlace nonwoven fabric, and nonwoven fabric manufactured by the card method or the airlaid method. As the paper, airlaid nonwoven fabric or a wet-laid sheet can be used. In this case, the paper may contain a binder compound or the like for physically or chemically bonding the fibers together. These can be used alone or in combination of two or more.

[0069] Examples of the resin film include a film containing a thermoplastic resin, and a porous film obtained by uniaxially or biaxially stretching a sheet-like resin mixture containing a thermoplastic resin and a filler such as calcium carbonate. In addition, a laminate of the above-described various films and a fiber sheet such as nonwoven fabric or paper is also included in the resin film in this specification. As the porous film, for example, those described in International Publication No. 2007 / 046342, or commercially available products such as calcium carbonate-containing polyethylene film (trade name: TSF-EU, manufactured by Kojin Film & Chemicals Co., Ltd.) can be used.

[0070] Examples of the above-described thermoplastic resin include polyolefin resin, polyester resin, polyamide resin, vinyl resin, acrylic resin, and fluororesin. Examples of the polyolefin resin include polyethylene (PE), polypropylene, ethylene-α-olefin copolymer, and ethylene-propylene copolymer. Examples of the polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate, and polylactic acid-based resin. Examples of the polylactic acid-based resin include polylactic acid and lactic acid-hydroxycarboxylic acid copolymer. Examples of the vinyl resin include polyvinyl chloride, polyvinylidene chloride, and polystyrene. Examples of acrylic resins include polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, etc. Examples of fluororesins include polyperfluoroethylene, etc. These resins can be used alone or in combination of two or more.

[0071] When using the fiber sheet as a constituent material, as the constituent fibers, one or more of natural fibers, synthetic fibers, and regenerated fibers can be used. Examples of natural fibers include plant fibers such as cotton, kapok, wood pulp, non-wood pulp, and hemp. Examples of synthetic fibers include fibers containing the above-mentioned thermoplastic resins. Examples of regenerated fibers include cupra, rayon, etc. These fibers can be used alone or in combination of a plurality.

[0072] The second base material sheet 12 constituting the heating element 10 has higher air permeability than the first base material sheet 11. The air permeability in this specification means the degree of gas passage and can be quantified as the air permeability (seconds / 100 mL) measured according to JIS P8117. The air permeability (seconds / 100 mL) measured according to JIS P8117 means that the larger the value, the more time it takes for a gas of a predetermined volume to pass through. Therefore, the lower the value of the air permeability, the higher the degree of gas passage, that is, the higher the air permeability. On the contrary, the higher the value of the air permeability, the lower the air permeability. In the following description, unless otherwise specified, the air permeability measured according to JIS P8117 is also simply referred to as "air permeability".

[0073] From the viewpoint of preventing bleeding and leakage in the sheet thickness direction of the heating layer, the higher the air permeability of the first base material sheet 11, the more preferable. That is, the first base material sheet 11 preferably has low air permeability. From the same perspective, specifically, the air permeability of the first base sheet 11 is preferably 8000 seconds / 100 mL or more, more preferably 20000 seconds / 100 mL or more, and still more preferably non-ventilated. "Non-ventilated" means that the air permeability measured according to JIS P8117 is 80000 seconds / 100 mL or more. As the first base sheet 11 having the above-mentioned air permeability, for example, a resin film having no through holes, or a laminate of a fiber sheet such as a non-woven fabric or paper and a resin film is preferably mentioned.

[0074] From the perspective of appropriately controlling the air flow to the heating element and enhancing the sustainability of heat generation due to the oxidation reaction, the air permeability of the second base sheet 12 is preferably 1000 seconds / 100 mL or more, more preferably 1200 seconds / 100 mL or more, and still more preferably 1500 seconds / 100 mL or more. From the same perspective, the air permeability of the second base sheet 12 is preferably 4000 seconds / 100 mL or less, more preferably 3500 seconds / 100 mL or less, and still more preferably 3000 seconds / 100 mL or less. The air permeability of the second base sheet 12 is conditioned to be lower than that of the first base sheet 11. As the second base sheet 12 having the above-mentioned air permeability, for example, a resin film having a plurality of through holes such as a porous film is preferably mentioned.

[0075] When a resin film is used for the second base sheet 12, the melting point of the constituent resin is preferably 80°C or more, more preferably 95°C or more, preferably 180°C or less, and more preferably 140°C or less. The second base sheet 12 having the above-mentioned melting point can be configured to contain a polyolefin resin such as polyethylene as its constituent resin, for example.

[0076] At least one of the first film 5 and the second film 6 constituting the heating device 1 preferably has a lower air permeability than the second base material sheet 12, and it is more preferable that the film disposed opposite to the second base material sheet 12 has a lower air permeability than the second base material sheet 12. In the present embodiment, it is more preferable that the second film 6, which is the film disposed opposite to the second base material sheet 12, has a lower air permeability than the second base material sheet 12. Also, in the heating device 1, it is more preferable that the film disposed opposite to the first base material sheet 11 has a higher air permeability than the second base material sheet 12. In the present embodiment, it is more preferable that the first film 5, which is the film disposed opposite to the first base material sheet 11, has a higher air permeability than the second base material sheet 12.

[0077] From the viewpoint of preventing bleeding and leakage of the heating layer in the sheet thickness direction, the air permeability of the first film 5 is preferably 8000 seconds / 100 mL or more, more preferably 10000 seconds / 100 mL or more, and still more preferably a non-ventilated sheet. Examples of the first film 5 having the above-described air permeability preferably include a resin film having no through holes, or a laminate of a fiber sheet such as a non-woven fabric or paper and a resin film.

[0078] From the viewpoint of enhancing the air flow to the heating element and efficiently generating heat due to the oxidation reaction, the air permeability of the second film 6 is preferably 0 seconds / 100 mL or more. From the same viewpoint, the air permeability of the second film 6 is preferably 100 seconds / 100 mL or less, more preferably 50 seconds / 100 mL or less, and still more preferably 10 seconds / 100 mL or less. Examples of the second film 6 having the above-described air permeability preferably include a laminate of a resin film having a plurality of through holes such as a porous film and a non-woven fabric.

[0079] The basis weight of the first base material sheet 11 is preferably 20 g / m 2 or more, and more preferably 30 g / m 2 or more, and still more preferably 70 g / m 2It is preferably the following, 65 g / m 2 More preferably, it is the following. The basis weight of the second base sheet 12 is preferably 20 g / m 2 or more, preferably 30 g / m 2 or more, more preferably 70 g / m 2 or less, preferably 65 g / m 2 More preferably, it is the following. The basis weight of the first film 5 is preferably 20 g / m 2 or more, preferably 40 g / m 2 or more, more preferably 150 g / m 2 or less, preferably 80 g / m 2 More preferably, it is the following. The basis weight of the second film 6 is preferably 20 g / m 2 or more, preferably 40 g / m 2 or more, more preferably 150 g / m 2 or less, preferably 130 g / m 2 More preferably, it is the following.

[0080] The heat generating layer 13 is composed of a composition containing a metal to be oxidized, an electrolyte, and water. Examples of the metal to be oxidized include metal particles such as iron, aluminum, zinc, manganese, magnesium, and calcium. From the viewpoints of handleability, safety, and manufacturing cost, the metal to be oxidized is preferably reduced iron powder or atomized iron powder.

[0081] Examples of the electrolyte include salts of alkali metals or alkaline earth metals and phosphoric acid or sulfuric acid, or one or more of chlorides or hydroxides of alkali metals or alkaline earth metals. Among these, from the viewpoints of excellent chemical stability and production cost, it is preferable to use one or more of potassium phosphate, potassium hydroxide, sodium chloride, and potassium chloride as the electrolyte. The electrolyte used in the production of the heating element may be used in a solid form such as a powder, or may be used in a liquid state dissolved in a liquid medium such as water.

[0082] From the viewpoint of enhancing the oxygen retention and supply property and playing the role of a catalyst for promoting the oxidation reaction of the oxidizable metal to enhance the heat generation characteristics, it is preferable that the heat generating layer 13 further contains carbon material powder. When manufacturing a heating element by containing a carbon material, it is also preferable from the viewpoint of improving productivity that the carbon material is blended in the metal slurry 13a. Examples of the carbon material include activated carbons such as coconut shell charcoal, charcoal powder, calendar blue charcoal, peat and lignite, carbon black, acetylene black, and powders such as graphite, and activated carbon powder is preferable.

[0083] Examples of the water-absorbing polymer 15 constituting the heat generating layer 13 include starch, crosslinked carboxymethylated cellulose, polymers or copolymers of acrylic acid or alkali metal salts of acrylic acid, etc., and one or more of polyacrylic acid and its salts and polyacrylate graft polymers. As the polyacrylate salt, a sodium salt can be used. In addition, examples of the shape of the water-absorbing resin include particles in the form of spherical, massive, grape-like, fibrous, or combinations thereof, and powders preferably composed of aggregates of these particles.

[0084] When the heat generating layer 13 is in the form of a sheet-like heat generating composition, as the fiber material, natural and synthetic fiber materials and regenerated fiber materials can be used without particular limitation. Examples of the natural fiber material include plant fibers such as cotton, caboc, wood pulp, non-wood pulp, peanut protein fiber, corn protein fiber, soybean protein fiber, mannan fiber, rubber fiber, hemp, Manila hemp, sisal hemp, New Zealand hemp, ramie, coconut, bamboo, rush, wheat straw; animal fibers such as wool, goat hair, mohair, cashmere, alpaca, angora, camel, vicuña, silk, feathers, down, feather, algin fiber, chitin fiber, casein fiber; and mineral fibers such as asbestos. These fiber materials can be used alone or in combination of a plurality.

[0085] Examples of the synthetic fiber material include synthetic resin fibers containing thermoplastic resins such as polyolefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; poly(meth)acrylic resins such as polymethyl methacrylate; polyvinyl resins such as polyvinyl chloride, polyvinylidene chloride, and polystyrene; polyamide resins such as nylon 6 and nylon 66; aramid resins; polyurethane resins; and copolymers of these resins; etc., semi-synthetic resin fibers containing semi-synthetic resins such as acetate, metal fibers, carbon fibers, glass fibers, and the like. Examples of the regenerated fiber material include regenerated fibers such as cupra and rayon. These fiber materials can be used alone or in combination of two or more. Among these, from the viewpoint of improving the heat generation characteristics while achieving both the uniform dispersibility of the metal to be oxidized and the oxygen permeability by ensuring voids, the fiber material preferably contains wood pulp or cotton.

[0086] The basis weight of the heat generating composition 14 is preferably 625 g / m 2 or more, more preferably 830 g / m 2 or more, and most preferably 2080 g / m 2 or less, more preferably 1450 g / m 2 or less. The basis weight of the water-absorbing polymer 15 is preferably 50 g / m 2 or more, more preferably 55 g / m 2 or more, and most preferably 70 g / m 2 or less, more preferably 65 g / m 2 or less.

[0087] As described above, the present invention has been described based on its preferred embodiments, but the present invention is not limited to the above embodiments.

Examples

[0088] Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. The "air permeability" shown below indicates the value measured in accordance with JIS P8117. In the following table, the columns indicated by "-" indicate unmeasured, not applicable, or not evaluated (including not evaluable).

[0089] [Example 1] Using the manufacturing apparatus shown in FIGS. 3 and 4, the heating element 10 and the warmer 1 were manufactured by the following method. As the first base material sheet 11, a thin paper laminated with PE (basis weight: 32 g / m 2 ) was used, and the formation of the paste-like heat-generating composition and the spraying of the water-absorbing polymer were sequentially performed to form the heat-generating layer 13 on the first base material sheet 11. The heat-generating layer 13 was formed in a plurality of continuous linear strips along the conveyance direction MD so as to have a non-existent region thereof.

[0090] Separately from this, as the second base material sheet 12, a porous resin film containing PE and calcium carbonate (Cousin TSF-EU 4000 second type, manufactured by Kojin Film & Chemicals Co., Ltd., basis weight: 40 g / m 2 ) was used, and an adhesive was applied in a plurality of continuous linear strips on one surface of the second base material sheet 12. The application temperature of the adhesive was 100°C, and the application was performed at a temperature lower than the melting point (105°C) of PE, which is the constituent resin of the second base material sheet. The adhesive was applied only to the regions other than the region of the second base material sheet 12 that is expected to face the heat-generating layer 13.

[0091] Next, the above-described first base material sheet 11 and second base material sheet 12 were overlapped to form a laminate, and the laminate was introduced into the pressing portion 130, and a pressing step of pressing the non-existent region of the heat-generating layer 13 was performed. As a result, a long strip-shaped heating element 10 in the form of a laminate 1S in which the first base material sheet 11 and the second base material sheet 12 are adhered was obtained. This heating element 10 has the form shown in FIG. 1. The overlapping of the first base material sheet 11 and the second base material sheet 12 was performed such that the existing region of the heat-generating layer 13 and the non-existent region of the adhesive 18 face each other, and the non-existent region of the heat-generating layer 13 and the existing region of the adhesive 18 face each other.

[0092] Subsequently, while conveying the long strip-shaped heating element 10 so that the total bending angle becomes the value shown in Table 1 below, a cutting step was performed in which the long strip-shaped heating element 10 was introduced into the cutting portion 140 and cut in the direction along the width direction CD to obtain a single-sheet heating element 10. The rotational speeds V1 of both rolls 141 and 142 in the cutting portion 140 and the conveying speed V2 of the long strip-shaped heating element 10 were set to be the same so as to be the values shown in Table 1 below. Hereinafter, the cutting method in which the speeds V1 and V2 are the same is also referred to as "score cut".

[0093] Then, the single-sheet heating element 10 that had been subjected to pitch adjustment and width expansion was introduced between the first film 5 and the second film 6, and the first film 5 and the second film 6 were joined together. As a result, a warming device 1 in which the heating element 10 was housed between two films was obtained. This warming device 1 has the form shown in FIG. 2. As the first film 5, paper (basis weight: 71 g / m 2 ) made of pulp fibers laminated with PE was used. As the second film 6, a film (basis weight: 120 g / m 2 ) in which a porous resin film containing PE and calcium carbonate and a nonwoven fabric of PET fibers were integrated was used.

[0094] [Example 2] In the cutting step, a warming device 1 was obtained in the same manner as in Example 1, except that, as shown in Table 1 below, the rotational speed V1 of both rolls 141 and 142 was changed to be higher than the conveying speed V2 of the long strip-shaped heating element 10. Hereinafter, the cutting method in which the speeds V1 and V2 are different is also referred to as "slip cut".

[0095] [Comparative Example 1] The long strip-shaped heating element 10 was conveyed so that the total bending angle became the value shown in Table 1 below, and the cutting step was performed with the rotational speeds V1 of both rolls 141 and 142 and the conveying speed V2 of the long strip-shaped heating element 10 being the same, respectively, in the same manner as in Example 2. As a result, the base sheets could not be bonded together, and the heating element and the warming device could not be manufactured. Therefore, Comparative Example 1 could not be evaluated thereafter (evaluation not possible).

[0096] 〔Reference Examples 1 and 2〕 This reference example was manufactured using the same components as in the prior art, and kraft paper (basis weight: 50 g / m 2 ) was used as the second base sheet 12. In Reference Example 1, the porous resin film containing PE and calcium carbonate used as the second base sheet in Example 2 was used as the second film 6. In Reference Example 2, the same sheets as in Comparative Example 1 were used, except that the above-mentioned kraft paper was used as the second base sheet 12. Except for these changes, the heating element 10 and the warming device 1 were obtained in the same manner as in Comparative Example 1.

[0097] 〔Evaluation of Bonding of Base Sheets〕 Regarding the heating elements of the examples, comparative examples, and reference examples, the bonding state between the first base sheet and the second base sheet was visually evaluated according to the following criteria. The results are shown in Table 1 below. <Evaluation Criteria> A: No peeling was observed, and the bonding of the base sheets was excellent. D: Bonding could not be performed, or peeling was observed, and the bonding of the base sheets was poor.

[0098] 〔Evaluation of Cutability〕 The variation in the position of the individual heating elements 10 obtained through the cutting process was evaluated as the standard deviation σ of the dimensions. The smaller the standard deviation σ, the less variation in the position of the heating element 10, which means that it can be manufactured with high productivity in a state where the position is controlled with uniform positional accuracy. When the cutability is poor, the position of the heating element 10 becomes unstable due to the influence of the heating elements 10 of the individual sheets located before and after in the conveying direction, so the standard deviation σ tends to increase. The results are shown in Table 1 below.

[0099]

Table 1

[0100] As shown in Table 1, it can be seen that the manufacturing method of the example can perform good lamination between base sheets even when a resin film is used as the base sheet, and a heating element can be obtained with high productivity as compared with the manufacturing method of the comparative example. In particular, Rotate faster than the conveyance speed of the heating element the example in which the cutting process is performed using a roll 2 is 1 also found to efficiently obtain a heating element with high dimensional accuracy as compared with the example

[0101] Note that since paper is used for the second base sheet in the reference example, appropriate retention of the sheet position can be exhibited due to the interaction with water contained in the heating layer. As a result, it is presumed that good lamination between the base sheets can be performed. On the other hand, when a resin film is used for the second base sheet as in Comparative Example 1, interaction with water contained in the heating layer hardly occurs, and the resin film cannot be held at a predetermined position. As a result, displacement or detachment of the base sheet easily occurs, and consequently, the heating layer and the adhesive adhere to the manufacturing apparatus, easily causing contamination of the manufacturing environment.

[0102] In addition to this, the heating device obtained by the method of Example 1 is excellent in heat generation sustainability and water vapor generation amount as compared with that of Reference Example 1, and the swelling of the heating device is reduced. This is an advantage of using a resin film for the second base sheet. Therefore, according to the present invention, it is also advantageous in that both improvement in heat retention and reduction of excessive swelling can be achieved, and a heating element and a heating device having an excellent feeling of use can be manufactured.

Explanation of Signs

[0103] 1 Heating device 5 First film 6 Second film 10 Heating element 11 First base sheet 12 Second base sheet 13 Heating layer 18 Adhesive 100 Manufacturing apparatus 130 Pressing part 140 Cutting part

Claims

1. A method for manufacturing a heating element in which a heat generating layer is disposed between a first base sheet and a second base sheet, as the second base sheet, a resin film having an air permeability measured according to JIS P8117 of 1000 seconds / 100 mL or more and 4000 seconds / 100 mL or less, and the air permeability being lower than that of the first base sheet is used, an adhesive is applied to a surface of the second base sheet that is expected to face the first base sheet so as to include an area other than the area expected to face the heat generating layer, and then, the second base sheet is overlapped with the first base sheet such that the heat generating layer disposed on one surface of the first base sheet faces the adhesive-coated surface to form a laminate, or, the heat generating layer is disposed on the adhesive-coated surface of the second base sheet, and the first base sheet is overlapped on the heat generating layer to form a laminate, and then, the area where the heat generating layer does not exist in the laminate is pressed to bond the two base sheets, while conveying the laminate in which the two base sheets are bonded in one direction, it is introduced between a cutter roll having a cutter blade extending in the axial direction on its peripheral surface and an anvil roll having a smooth peripheral surface, and the laminate is cut in a direction intersecting the conveying direction, the rotational speeds of the two rolls are made faster than the conveying speed of the laminate, In the conveying process until the laminate in which the two base sheets are bonded is cut in a direction intersecting the conveying direction, it is conveyed so that the total bending angle in a side view along the conveying direction of the laminate is 110 degrees or less. A method for manufacturing a heating element.

2. The manufacturing method according to claim 1, wherein the adhesive is applied at a temperature lower than the melting point of the constituent resin of the second base sheet.

3. The manufacturing method according to claim 1 or 2, wherein the adhesive is applied only to an area of the surface of the second base sheet that is expected to face the first base sheet and is other than the area expected to face the heat generating layer in the second base sheet.

4. A method for manufacturing a warming device, comprising a step of housing the heating element obtained by the manufacturing method according to any one of claims 1 to 3 between two films, wherein at least one of the films has an air permeability measured according to JIS P8117 that is lower than the air permeability of the second base sheet.

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