Coating method and coating apparatus

Abstract

To provide a technology which can prevent a hot melt adhesive from being applied to a designed non-application range.SOLUTION: In an application method, a hot melt adhesive is intermittently applied from a coating gun to an object to be coated (coated object) transported in a given direction. The coating gun has a discharge port which discharges the hot melt adhesive. The application method includes: a first step in which the discharge port is placed in contact with the coated object in an application state where the hot melt adhesive is applied to the coated object; and a second step in which hot air is blown onto the downstream side of the discharge port when the application state is switched to a non-application state where the hot melt adhesive is not applied to the coated object.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a coating method and a coating apparatus.

Background Art

[0002] In the manufacturing process of absorbent articles such as disposable diapers, urine pads, and sanitary products, a hot-melt adhesive is intermittently applied to a workpiece such as a sheet material conveyed in a certain direction (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The hot-melt adhesive is applied from a coating gun to the workpiece in a state where the solid raw material is heated and melted. The hot-melt adhesive is applied with the discharge port of the coating gun in contact with the workpiece. Since the hot-melt adhesive has a high viscosity even in a molten state, there is a risk that the hot-melt adhesive that cannot be completely placed on the sheet material will accumulate on the downstream side of the discharge port of the coating gun in the conveyance direction. When attempting to apply the hot-melt adhesive intermittently, if the hot-melt adhesive accumulates on the downstream side of the discharge port in the conveyance direction, a phenomenon called trailing will occur, where the coating gun drags the accumulated hot-melt adhesive, and as a result, the hot-melt adhesive will be applied even to the non-application range where it is not designed to be applied.

[0005] An object of the present invention is to provide a technique capable of preventing the hot-melt adhesive from being applied to the non-application range in design.

Means for Solving the Problems

[0006] In order to solve the above problems, in the present invention, when switching from the applied state of the hot melt adhesive to the non-applied state where the hot melt adhesive is not applied to the object to be coated, hot air is blown to the downstream side of the discharge port.

[0007] Specifically, the present invention is a coating method for intermittently coating a hot melt adhesive from a coating gun onto an object to be coated that is conveyed in a certain direction. The coating gun has a discharge port for discharging the hot melt adhesive. In the coating state where the hot melt adhesive is applied to the object to be coated, a first step of bringing the discharge port into contact with the object to be coated, and a second step of blowing hot air to the downstream side of the discharge port when switching from the coating state to a non-coating state where the hot melt adhesive is not applied to the object to be coated.

[0008] In the above coating method, the object to be coated is a sheet material for absorbent articles, and the hot melt adhesive may be blended with a material that changes color when in contact with excrement.

[0009] Also, the present invention can be grasped from the side of the coating device. For example, the present invention is a coating device for intermittently coating a hot melt adhesive from a coating gun onto an object to be coated that is conveyed in a certain direction, the coating gun having a discharge port for discharging the hot melt adhesive, the coating gun that brings the discharge port into contact with the object to be coated in the coating state where the hot melt adhesive is applied to the object to be coated, and hot air that blows hot air to the downstream side of the discharge port when switching from the coating state to a non-coating state where the hot melt adhesive is not applied to the object to be coated. It may be provided with a supply device.

Effects of the Invention

[0010] According to the present invention, it is possible to prevent the hot melt adhesive from being applied to the non-coated range in the design.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the configurations of the following embodiments are examples, and the present invention is not limited to the configurations of these embodiments.

[0013] <Outline of Coating Method> The coating method according to the present embodiment is a method of intermittently applying a hot melt adhesive from a coating gun to a workpiece to be coated that is conveyed in a certain direction. Examples of the workpiece to be coated include sheet materials used for absorbent articles such as disposable diapers, urine pads, and sanitary products. In a production line for manufacturing absorbent articles, a hot melt adhesive is applied to a sheet material for absorbent articles that is conveyed in a certain direction. The hot melt adhesive may be intermittently applied to the sheet material so as not to be applied to the designed non-coating range (hereinafter referred to as the "non-coating range") but to be applied to the designed coating range (hereinafter referred to as the "coating range"). The coating range and the non-coating range are continuous in the conveyance direction of the sheet material, and when the coating range of the sheet material passes under the coating gun, the hot melt adhesive is discharged from the coating gun, and when the non-coating range of the sheet material passes under the coating gun, the hot melt adhesive is not discharged from the coating gun. Thereby, the hot melt adhesive is intermittently applied to the sheet material conveyed in a certain direction.

[0014] In addition, in the coating method according to the present embodiment, in the coating state where the hot melt adhesive is applied to the sheet material, the discharge port of the coating gun is brought into contact with the sheet material. Different from this, when the hot melt adhesive is applied without bringing the discharge port of the coating gun into contact with the sheet material, the hot melt adhesive is applied by spraying, and when the hot melt adhesive is intermittently applied, the hot melt adhesive cannot be applied cleanly at the end portion. Therefore, when it is necessary to intermittently apply the hot melt adhesive (such as when it is necessary to provide a non-adhesive region or when applying a hot melt adhesive containing a coloring substance for forming an indicator), it is preferable to bring the coating gun into contact with the sheet material as in the coating method according to the present embodiment.

[0015] Further, in the coating method according to the present embodiment, the hot melt adhesive is applied from the coating gun to the sheet material in a state where the solid raw material is heated to about 140°C to 160°C and melted. Since the hot melt adhesive has a high viscosity even in a melted state, there is a risk that the hot melt adhesive that cannot fit on the sheet material will accumulate on the downstream side in the conveyance direction of the discharge port of the coating gun.

[0016] FIG. 1 is a schematic diagram showing a coating method according to a comparative example. The upper part of FIG. 1 is a schematic diagram of the sheet material S, which is the object to be coated, viewed from above, and the lower part of FIG. 1 is a schematic diagram of the sheet material S viewed from the side. The sheet material S is conveyed in the direction indicated by arrow A1 in FIG. 1 by a roller R100 that rotates in the direction indicated by arrow A2 in FIG. 1. The coating gun G is supplied with the raw material of the hot melt adhesive H heated to about 140°C to 160°C from a supply device (not shown) by a pump, and the coating gun G can discharge the hot melt adhesive H from a discharge port N provided at the tip. Also , by switching the pump of the supply device between an operating state and a non-operating state, it is possible to switch between a discharge state in which the hot melt adhesive H is discharged from the discharge port N and a non-discharge state in which the hot melt adhesive H is not discharged from the discharge port N. Further, in the comparative example, a contact-type coating gun G that constantly contacts the discharge port N with the sheet material is employed.

[0017] In this comparative example, the range B shown in FIG. 1 is the designed application range of the hot melt adhesive H. When the rear end of the application range B passes through the discharge port N, the hot melt adhesive H is in a non-discharging state. However, there is a trailing phenomenon in which the coating gun G drags the hot melt adhesive H accumulated on the downstream side in the conveyance direction of the discharge port N, and the hot melt adhesive H is also applied to the non-application range. Thus, when the hot melt adhesive H is intermittently applied with the discharge port N of the coating gun G constantly in contact with the sheet material S, a trailing phenomenon occurs where the coating gun G drags the hot melt adhesive H, and the hot melt adhesive H is also applied to the non-application range. In the absorbent article, it is not preferable that adhesiveness is exhibited in the non-application range where non-adhesion is desired. Although it is conceivable to suppress the occurrence of trailing by lowering the viscosity of the hot melt adhesive H by raising the temperature of the hot melt adhesive H above 160°C, if the hot melt adhesive H is heated above 160°C, there is a risk that the performance will change, which is not preferable.

[0018] Therefore, in the coating method according to the present embodiment, when switching from the application state of the hot melt adhesive to the non-application state where the hot melt adhesive is not applied to the workpiece, hot air is blown onto the downstream side of the discharge port. Thereby, by temporarily reducing the viscosity of the hot melt adhesive accumulated on the downstream side in the conveyance direction of the discharge port, the accumulated hot melt adhesive can be separated from the coating gun, and it is possible to prevent the hot melt adhesive from being applied to the non-application range in design.

[0019] Figure 2 is a flowchart showing an overview of the coating method according to the present embodiment. In the coating method according to the present embodiment, first, in a state where a hot melt adhesive is applied to a sheet material, the discharge port is brought into contact with the sheet material (step S101, an example of the "first step" referred to in the present application). Next, when switching from the state of applying the hot melt adhesive to a non-application state where the hot melt adhesive is not applied to the workpiece, hot air is blown to the downstream side of the discharge port (step S102, an example of the "second step" referred to in the present application). The coating method according to the present embodiment executes step S101 and step S102, and by providing a period of non-application state of the hot melt adhesive after step S102, the hot melt adhesive can be intermittently applied to the sheet material conveyed in a certain direction.

[0020] Next, based on FIG. 3, the coating method according to the present embodiment will be described in more detail. As shown in FIG. 3, in the present embodiment, the coating gun G has a discharge port N for discharging the hot melt adhesive H. The coating gun G is supplied with a raw material of the hot melt adhesive heated to about 140°C to 160°C from a supply device (not shown) by a pump. Also, similar to the above-described comparative example, by switching the pump of the supply device between an operating state and a non-operating state, the discharge state and the non-discharge state of the hot melt adhesive can be switched. Further, in the present embodiment, a contact-type coating gun G that brings the discharge port N into contact with the sheet material S in the discharge state is employed. Also, the sheet material is conveyed in the direction indicated by the arrow A1 in FIG. 3.

[0021] The coating apparatus used in the coating method according to the present embodiment includes a coating gun G and a hot air supply device M. The hot air supply device M blows hot air to the downstream side of the discharge port N when switching from the state of applying the hot melt adhesive H to the non-application state. The temperature of the hot air is set lower than the melting point of the sheet material S so as not to melt the sheet material S, and higher than the softening point of the hot melt adhesive H so as to melt the hot melt adhesive H. Also, the hot air is blown so as to hit the mass of the hot melt adhesive. Thereby, by heating the hot melt adhesive H accumulated on the downstream side in the conveyance direction of the discharge port N, the viscosity of this hot melt adhesive is temporarily Lower it so that the hot melt adhesive H can be detached from the application gun, and prevent the hot melt adhesive H from being applied to the non-application range in the design.

[0022] Also, in the present embodiment, hot air may be blown on the downstream side of the discharge port N in the application state where the hot melt adhesive H is applied to the sheet material S. Thereby, it is possible to prevent the hot melt adhesive from accumulating on the downstream side of the discharge port N, and it is possible to prevent the trailing phenomenon in which the application gun drags the hot melt adhesive in the non-application state of the hot melt adhesive H. Thereby, the coating method according to the present embodiment can prevent the hot melt adhesive from being applied to the non-application range where the hot melt adhesive is not designed to be applied.

[0023] Also, in the present embodiment, the hot melt adhesive H may be blended with a material for an indicator that changes color when it comes into contact with excrement. In the absorbent article, the portion where the material for the indicator is applied functions as an indicator that shows the presence or absence of excrement such as urination to the outside. The indicator is provided, for example, by applying a hot melt adhesive containing a material for the indicator to the skin surface side of the back sheet. Note that, as the material for the indicator, a moisture detection material, a pH reaction material, or the like is used. According to the coating method according to the present embodiment, the hot melt adhesive H containing this material can be applied to the arrangement area of the indicator, and the hot melt adhesive H can be prevented from being applied to the non-arrangement area of the indicator, so that the indicator can be arranged within the designed range. Thereby, since the indicator can be arranged within the range as designed for the absorbent article, it is possible to prevent the indicator from becoming an obstacle to the design of the absorbent article.

[0024] <Other Embodiments> As described above, the embodiments of the present invention have been described, but the various embodiments described above can be combined as much as possible.

Explanation of Reference Numerals

[0025] A1, A2 ··· Arrow C1, C3, C4 ··· Circumferential part C2 ··· Flat part G ··· Coating gun H ··· Hot melt adhesive M1 ··· Lifting device M2 ··· Suction device N ··· Nozzle R1, R2, R3, R4, R100 ··· Roller S ··· Sheet material

Claims

1. A coating method for intermittently applying a hot melt adhesive from a coating gun to a workpiece to be coated that is conveyed in a certain direction, wherein the coating gun has a discharge port for discharging the hot melt adhesive, in a coating state where the hot melt adhesive is applied to the workpiece to be coated, a first step of bringing the discharge port into contact with the workpiece to be coated without blowing hot air to the downstream side of the discharge port; a second step of blowing hot air to the downstream side of the discharge port when switching from the coating state to a non - coating state where the hot melt adhesive is not applied to the workpiece to be coated, thereby reducing the viscosity of the hot melt adhesive accumulated on the downstream side of the discharge port and separating the hot melt adhesive from the coating gun; A coating method comprising the above.

2. The workpiece to be coated is a sheet material for absorbent articles, and the hot melt adhesive is blended with a material that changes color when coming into contact with excrement. The coating method according to Claim 1.

3. A coating apparatus for intermittently applying a hot melt adhesive from a coating gun to a workpiece to be coated that is conveyed in a certain direction, the coating gun having a discharge port for discharging the hot melt adhesive, the coating gun bringing the discharge port into contact with the workpiece to be coated in a coating state where the hot melt adhesive is applied to the workpiece to be coated; a hot air supply device that, without blowing hot air to the downstream side of the discharge port in the coating state and blowing hot air to the downstream side of the discharge port when switching from the coating state to a non - coating state where the hot melt adhesive is not applied to the workpiece to be coated, reduces the viscosity of the hot melt adhesive accumulated on the downstream side of the discharge port and separates the hot melt adhesive from the coating gun; A coating apparatus comprising the above.

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