WO2019123875A1

WO2019123875A1 - Plastic bag manufacturing method and plastic bag

Info

Publication number: WO2019123875A1
Application number: PCT/JP2018/041444
Authority: WO
Inventors: 戸谷　幹夫
Original assignee: トタニ技研工業株式会社
Priority date: 2017-12-19
Filing date: 2018-11-08
Publication date: 2019-06-27

Abstract

This plastic bag comprises a sealed area formed from sections of at least two sheets of film where the sheets are sealed together, the sealed area being formed along some or all of the edge of the plastic bag. The edge of the plastic bag includes the seal edge portion of the sealed area. A manufacturing method for manufacturing this plastic bag comprises a step for forming the sealed area by heat-sealing the films together, and a step for melt-cutting the heat-sealed films and forming some or all of the seal edge portion from the edge resulting from said melt-cutting.

Description

Method of manufacturing plastic bag and plastic bag

The present invention relates to a method of manufacturing a plastic bag. The invention also relates to a plastic bag.

The plastic bag comprises a sealing area formed along all or part of its edge to ensure its sealing.

A manufacturing method for manufacturing such a plastic bag is disclosed in Patent Documents 1 to 3 and the like. The manufacturing method, for example, superposes at least two films on each other. The manufacturing method then heat seals the film to form a sealed area. Then, the manufacturing method cuts the film into bag units by a cutter, thereby manufacturing a plastic bag. At this time, the film is cut along the sealing area, the cutting edge forming the edge of the sealing area of the plastic bag.

When the film is cut along the seal area with a sharp blade, such as a cutter, the seal area has a very sharp cutting edge. Thus, if the plastic bag is displaced relative to the hand holding it, the hand may be injured by the cutting edge of the sealing area. Thus, there is a risk of injury to the hand or the like due to the cutting edge of the sealing area.

JP, 2011-020719, A Japanese Patent Application Laid-Open No. 11-320708 Patent No. 3333085

The first aspect of the present invention provides a method of manufacturing a highly safe plastic bag. Furthermore, the second aspect of the present invention provides a highly safe plastic bag.

According to a first aspect of the present invention there is provided a method of manufacturing a plastic bag having a rim, wherein the plastic bag is formed along part or all of the rim and sealed together of at least two films. It comprises a partial sealing area. The edge of the plastic bag comprises the sealing edge of the sealing area. The manufacturing method comprises the steps of heat sealing the films together to form a sealed area, and fusing the film after heat sealing the film to form part or all of the sealing edge with the fused edges.

The production method may use a hot blade to melt the film.

The production method may use a laser to melt the film.

The sealing edge may comprise the sealing side edge of the plastic bag. In the manufacturing method, the film may be melted and the seal side edge may be formed by the melted edge.

The sealing edge may comprise the sealing corner edge of a plastic bag. In the manufacturing method, the film may be melted and the sealing corner edge may be formed by the melted edge.

The sealing area comprises a first seal formed along the opposing first side edge of the plastic bag and a second seal formed along one of the opposing second side edge of the plastic bag. May be included. In the manufacturing method, the film is melted down along the first seal portion using a hot blade or a laser, the first seal side edge portion of the first seal portion is formed by the melted edge, and the film is sealed using the cutter. The second seal side edge of the second seal may be formed by the cutting edge, and the second seal side edge may be heated and smoothed.

The sealing edge may comprise the sealing side edge of the plastic bag. The manufacturing method uses a gusset material and two sheets of shell material as a film, places a folded or bent gusset material between the shell materials, heat seals the shell material and gusset material to each other, and seals the seal area. After forming and heat sealing the body and gusset, the body and side gusset may be fused at the location of the sealing area and the seal side edge may be formed by the fused rim.

The manufacturing method may heat the seal side edge after the cutting of the body material and the gusset material.

According to a second aspect of the present invention there is provided a plastic bag having an edge, the plastic bag comprising a seal consisting of mutually sealed parts of at least two films. The seal portion includes a flat portion and a seal side edge continuous with the flat portion and forming a part of the edge of the plastic bag. The seal side edge has a rounded cross-sectional shape and has a thickness greater than that of the flat portion.

FIG. 1 is a front view of a plastic bag according to an embodiment of the present invention. FIG. 2 is a side view showing a schematic configuration of the bag making machine. FIG. 3 is a view for explaining the manufacturing method according to the embodiment of the present invention. FIG. 4A is a view for explaining melting of a film using a heat blade, and FIG. 4B is a perspective view of the heat blade. FIG. 5 is a front view of a plastic bag according to one embodiment. 6A and 6B are cross-sectional views of the seal side edge formed using a hot blade. FIG. 6C is a cross-sectional view of a seal side edge according to the related art. FIG. 7 is a diagram for explaining melting of a film using a laser. FIG. 8A illustrates the observation of the cross section of the seal side edge formed using a laser, and FIG. 8B shows the image. FIG. 9 is a front view of a plastic bag according to another embodiment. FIG. 10 is a view for explaining the manufacturing method according to another embodiment. FIG. 11 is a diagram for explaining the formation of a seal corner edge using a laser. 12A to 12C are diagrams for explaining the formation of a seal corner edge using a punch blade. FIGS. 13A and 13B are views showing the tip of a thermal blade according to another embodiment. FIG. 14 is a view for explaining the manufacturing method according to still another embodiment. FIG. 15 is a view for explaining the manufacturing method according to still another embodiment. FIG. 16A is a front view showing a plastic bag according to still another embodiment, and FIG. 16B shows an exploded view of the bag. FIG. 17 is a view for explaining the manufacturing method according to still another embodiment. FIG. 18 is a view for explaining the melting and breaking of the first body material, the second body material, and the side gusset material using the heat blade. FIG. 19 is a view showing welding of edge portions of the seal portion. FIG. 20A shows an observation result of welding of the edge portions of the seal portion, and FIG. 20B shows an image of a cross section of the edge portion after being separated.

Hereinafter, with reference to the drawings, a plastic bag according to an embodiment of the present invention and a method of manufacturing the plastic bag will be described. In each embodiment, the same or similar configurations are denoted by the same reference numerals, and the description thereof is omitted as much as possible. The components shown in the drawings are not to scale, and merely indicate functions and operations.

First Embodiment
As shown in FIG. 1, the plastic bag 1 (hereinafter sometimes simply referred to as a bag) is made of a plastic film. The bag 1 includes films 11 and 12 (hereinafter, may be referred to as a first body 11 and a second body 12) facing each other. The

films

11 and 12 of the embodiment are plastic films of a laminated structure. The inner surfaces of the

films

11 and 12 are formed of a sealant such as polyethylene or polypropylene. The outer surfaces of the

films

11 and 12 are formed of a base material such as nylon or PET.

The bag 1 has an edge 100 across its periphery. The edge 100 of the bag 1 comprises four

side edges

140, 150, 160 of linear shape. The bag 1 comprises a sealing area 13 formed along part or all of its edge 100. The sealing area 13 consists of mutually sealed parts of at least two films.

In the embodiment, the sealing area 13 is formed along a portion of the edge 100. The seal region 13 is a seal portion 14 (hereinafter, may be referred to as a first seal portion 14) formed along the opposing side edge 140 (hereinafter, may be referred to as a first side edge 140). A seal portion 15 (hereinafter referred to as a second seal) formed along one of the remaining opposite side edges 150, 160 (hereinafter sometimes referred to as second side edges 150, 160). 2 may be referred to as “seal portion 15”. In the embodiment, each sealing

portion

14, 15 consists of mutually sealed parts of two sheets of

film

11, 12.

Thus, the edge 100 of the bag 1 of the embodiment comprises the sealing edge 130 of the sealing area 13 and the open side edge 160 (i.e. the non-seal side edge), the sealing edge 130 being the three seal

sides Including edges

140, 150; The opening side edge 160 is used when filling the bag 1 with contents.

Hereinafter, one embodiment of a manufacturing method for manufacturing the bag 1 of FIG. 1 will be described. As shown in FIG. 2, the bag making machine 2 includes a feeding device 3, a heat sealing device 4, and a cutting device 5. The continuous two sheets of films 11 and 12 (first and second body members) are intermittently transported by the feeding device 3, and are repeatedly transported and stopped at predetermined time intervals. As shown in FIGS. 2 and 3, the

films

11 and 12 are superimposed on each other by the feeding device 3. The transport direction Y of the

continuous films

11 and 12 is the longitudinal direction (continuous direction).

Then, every time the

films

11, 12 stop, they are heat sealed together by the heat sealing device 4 to form the sealing area 13. The heat sealing device 4 is usually constituted by a vertical sealing mechanism and a horizontal sealing mechanism. In the embodiment, the second seal portion 15 is formed by the vertical seal mechanism, and the first seal portion 14 is formed by the horizontal seal mechanism.

After heat sealing of the

films

11 and 12, every time the

films

11 and 12 are intermittently conveyed, the

films

11 and 12 are melted down by the cutting device 5, and a part or all of the sealing edge portion 130 is formed by the melted edges. In the embodiment, the first seal side edge 140 of the first seal portion 14 is formed by the melting edge. And the shape of the bag 1 of FIG. 1 is completed. The details are described below.

In the present embodiment, the

films

11 and 12 are fused by using a hot blade. As shown in FIGS. 4A and 4B, the cutting device 5 includes the heat blade 50 and the receiving member 51 for receiving the heat blade 50. The heat blade 50 is vertically moved relative to the receiving member 51 by a drive mechanism (not shown). The heat blade 50 is provided with the blade main body 500 which has the bowl-shaped front-end | tip part 501, and the sheathed heater 502 inserted in the hole of the blade main body 500, as FIG. 4B. The blade main body 500 is heated by the sheathed heater 502. The heated tips 501 abut the

films

11 and 12 so that the

films

11 and 12 are fused.

The receiving member 51 is a roller and has a Teflon (registered trademark) processed outer circumferential surface 510. The diameter of the roller is about 60 mm. The

films

11 and 12 are less likely to adhere to the receiving member 51 by the Teflon process. Further, each time the heat blade 50 melts and cuts the

films

11 and 12, the receiving member 51 is rotated at a predetermined angle, and the contact position with the heat blade 50 is changed. Therefore, the

films

11 and 12 are less likely to adhere to the receiving member 51. As described above, the receiving member 51 preferably has a configuration to suppress the adhesion of the

films

11 and 12. The receiving member 51 may be, for example, a conveyor which has been subjected to surface treatment such as Teflon processing, instead of the roller.

When the

films

11 and 12 stop, the first seal portion 14 faces the heat blade 50. Then, the heat blade 50 descends to the receiving member 51 while the

films

11 and 12 are stopped. Thereby, the

films

11 and 12 are melted down along the first seal portion 14 by the heating blade 50 during stopping, and the melted edge forms the first seal side edge that constitutes a part of the edge 100 of the bag 1 140 are formed.

For example, when cutting two

films

11 and 12 of PET / LLDPE (polyethylene terephthalate / linear low density polyethylene) having a thickness of 70 μm to 120 μm at the seal area 13, the temperature of the heat blade is 400 ° and the heat blade seal The contact time to the area (seal portion) may be about 300 msec.

Thereafter, the contents are filled into the bag 1 from the open side edge 160. As shown in FIG. 5, after filling, the

films

11 and 12 may be heat sealed along the opening side edge 160 to form the seal portion 16. Side edge 160 becomes a seal side edge. In addition to this, a spout 19 may be provided at the position of the seal portion 16.

The cross section of the first seal portion 14 is shown in FIGS. 6A and 6B. The first seal portion 14 includes a seal side edge portion 140 and a flat portion 141. The seal side edge 140 is continuous with the flat portion 141 and constitutes a part of the edge 100 of the bag 1 as described above. In the seal portion 14, the two

films

11, 12 are integrated with each other by melting the sealant. At the time of melting, the

films

11 and 12 of the seal portion 14 melt, and as a result, the cross section of the seal side edge portion 140 has a rounded shape. Then, the thickness of the seal side edge portion 140 is larger than the thickness of the flat portion 141 (which is substantially the thickness of the two films 11 and 12).

FIG. 6C shows a cross section of a seal 14 'according to the related art. The seal portion 14 'has a seal edge side 140' formed by the cutting edge resulting from physical cutting (e.g., shearing) with a knife or the like rather than by melting. In this case, the seal side edge 140 'has a sharp shape.

As apparent from FIGS. 6A-6C, the seal edge 130 (in the embodiment, the seal side edge 140) formed by the fusion edge does not become sharp. Thus, even if the plastic bag 1 is displaced relative to the hand holding it, the sealing edge 130 does not cause any injury. The safety of the plastic bag 1 is very high.

In addition, when the thickness of the seal side edge part 140 is too large with respect to the thickness of the flat part 141, it is hard to handle the bag 1 in the process until it fills the contents. From the viewpoint of handling, the thickness of the seal side edge portion 140 is preferably larger than the thickness of the flat portion 141 and less than twice the thickness of the flat portion 141 (a <b <2a).

Second Embodiment
In the embodiment, the

films

11, 12 are fused by using a laser instead of the heat blade. As shown in FIG. 7, the cutting device 5 according to the embodiment includes an irradiation unit 52 for irradiating a laser, and a moving mechanism (not shown) for moving the irradiation unit 52 in a direction perpendicular to the transport direction Y.

When the

films

11 and 12 stop, the first seal portion 14 faces the irradiation unit 52. While the

films

11 and 12 are at rest, the irradiation unit 52 moves in a direction perpendicular to the transport direction Y while irradiating the sealing unit 14 with a laser. Thereby, the

films

11 and 12 are fused by the laser along the first seal portion 14, and the fused edge forms the first seal side edge 140.

In order to melt down the

films

11 and 12 using a laser, for example, a CO ₂ laser device is used as an irradiation unit, and oxygen is used as an assist gas. The gas pressure may be 0.05 MPa, the output may be 200 W, and the fusing speed may be 2500 mm / min.

As shown in FIG. 7, when a laser is used, the cross section of the seal side edge portion 140 is not a rounded shape unlike the melting cutting using the heat blade 50. However, since the seal side edge portion 140 is melted and cut by a laser, it does not become sharp as in the case of the heat blade 50.

The cross section of the seal portion 14 of the film 11, 12 (which is a laminated film including the substrate and the sealant) fused by using a laser was observed with a microscope. FIG. 8A illustrates the result and FIG. 8B shows the image. When the

films

11 and 12 are melted and cut along the seal portion 14, the seal side edge portion 140 is smoothed by the substrate being curved inward. Therefore, as in the first embodiment, the safety of the plastic bag 1 is high.

In the above embodiment, a moving mechanism for moving the irradiation unit 52 is used as a means for moving the irradiation position of the

films

11 and 12 of the laser. Instead of this, the irradiation position of the laser may be moved using a galvano mirror or the like without moving the irradiation unit 52 itself. The same applies to the following embodiments.

Third Embodiment
The embodiment produces the bag 1 of FIG. The bag 1 further comprises four corner edges 170 connecting the first side edge 140 and the

second side edge

150, 160. These corner edges 170 are referred to as seal corner edges because they are included in the seal area 130. In an embodiment, the sealing corner edge 170 has a rounded and bulging shape, in particular an R shape.

As in FIG. 10, as in the previous embodiment, the continuous two

films

11, 12 are stacked together by the feeder 3 and heat sealed together by the heat sealing device 4 to form the sealing area 13. Therefore, the first and

second seal portions

14 and 15 are formed.

The cutting device 5 of the embodiment further includes an irradiation unit 53 for irradiating a laser. After heat sealing, the

films

11 and 12 are melted down along the second seal portion 15 by the laser of the irradiation unit 53 during transportation, and the melted edge forms the second seal side edge 150. The cutting device 5 further includes a cutter 54. The

films

11 and 12 are slit by the cutter 54 along one side opposite to the sealing portion 15 during transportation, and the cutting edge forms the open side edge 160. Then, the

films

11, 12 are melted down along the first seal portion 14 by the laser of the heating blade 50 or the irradiation unit 52 as in the previous embodiment, and the melted edge forms the first seal side edge 140. Be done.

For example, a laser is used to form the seal corner edge 170. In the present embodiment, the cutting device 5 further includes another irradiation unit and a moving mechanism for moving the irradiation unit in the direction perpendicular to the transport direction Y. As shown in FIG. 11, while the

films

11 and 12 are being transported, the irradiation unit reciprocates from the position L in a direction perpendicular to the transport direction Y from the position L while irradiating the laser. Thereby, the

films

11 and 12 are melted and cut by the laser in the sealing area 13 along the shape of two continuous sealing corner edges 170. And the two sealing corner edges 170 are formed by the fusion cutting edge. The R shape of the seal corner edge 170 can be realized by appropriately adjusting the moving speed of the irradiation unit and the transport speed of the

films

11 and 12.

In the embodiment, in addition to the first seal side edge 140, the second seal side edge 150 and the seal corner edge 170 are also formed by the melting edge. Thus, the entire seal edge 130 is formed by the molten edge. Therefore, the bag 1 manufactured in this embodiment is very safe.

Fourth Embodiment
The cutting device 5 of the embodiment includes a moving mechanism that moves the irradiation unit 53 in the transport direction Y and the direction perpendicular thereto.

As shown in FIG. 11, when the

films

11 and 12 are transported in the transport direction Y by one bag after heat sealing, the irradiation unit 53 irradiates the laser by the moving mechanism from the standby position O in the transport direction Y Move to position L. Thereby, the

films

11 and 12 are fused by the laser along the seal portion 15, and the fused edges form the seal side edge 150. Then, while the

films

11, 12 are at rest, the irradiation unit 53 follows the shape of two consecutive sealing corner edges 170 from position L through position M to position N while irradiating the laser, Move by the moving mechanism. Thereby, in the sealing area 13, the

films

11, 12 are melted down by means of a laser, and the melted edges form two sealing corner edges 170. Then, the irradiation unit 53 moves to the standby position O and stands by.

Fifth Embodiment
Embodiments use punches to form the sealing corner edge 170. The cutting device 5 of this embodiment further includes a punching blade 55 and a receiving blade (not shown) that receives the punching blade 55, as shown in FIG. 12A. The tip portion 550 of the punch blade 55 has a shape in which four corner edges 170 are combined, and the receiving blade has a hole shaped to face the tip portion 550. The punch blade 55 is moved up and down relative to the receiving blade by a drive mechanism (not shown), and cuts (shears) the

films

11 and 12 in cooperation with the receiving blade.

After heat sealing, the

films

11, 12 are sheared by the punch blade 55 during stopping, and the sheared edges form the sealing angular edge 170.

As shown in FIG. 12B, after the formation of the seal angular edge portion 170, when the

films

11, 12 are shifted out of their proper positions and fused, the protrusions 170a are formed. Therefore, as shown in FIG. 12C, it is preferable to irradiate the laser at the connection point of the two seal corner edges 170 after forming the seal corner edge 170 to make the contour of the connection point a curved shape. As a result, even if the

films

11 and 12 are shifted and melted off, the generation of the protrusions 170 a is prevented.

The sealing corner edge 170 is sharpened because it is formed by the shearing edge. Therefore, it is preferable that the sealing corner edge 170 be heated and smoothed by a heating device (not shown) such as, for example, a heater or a hot air device. Here, "smoothing" refers to removing a sharp shape of a symmetrical object to make it a smooth shape. That is, it is preferable to melt and smooth the sealing corner edge 170 by heat. This prevents injury to the hand at the sealing corner edge 170 formed by the shearing edge.

The conditions for smoothing vary depending on the material of the

laminate films

11 and 12 and the sealant. The tip of the cutting edge resulting from cutting (in particular, shearing) the

films

11 and 12 consists of the substrate of the

films

11 and 12. Therefore, the cutting edge can be smoothed by heating at a temperature above the melting point of the substrate. For example, when the substrate is PET, heating at 260 ° C. or higher of the melting point of PET is required for smoothing. Also, if the substrate is nylon, heating above 215 ° C. of the melting point of nylon is required for smoothing.

Sixth Embodiment
In the embodiment, while the

films

11 and 12 are stopped, a locus of the shape of the seal corner edge 170 (the locus of the same shape as the tip 550 of the punch blade 55) continues the irradiation position of the laser to the

films

11 and 12. The film is moved, and the

films

11 and 12 are cut by a laser. Then, the fused edges form a plurality (up to four) of sealing corner edges 170.

Seventh Embodiment
The heat blade 50 of the cutting device 5 of the embodiment has a tip 501 shown in FIG. 13A or 13B. The tip portion 501 includes a straight portion 501a and corner portions 501b positioned at both ends of the straight portion 501a. The corner portion 501 b has the shape of a continuous corner edge 170. The heat blade 50 of FIG. 13A is used when forming the straight-shaped seal corner edge 170, and the heat blade 50 of FIG. 13B is used when forming the R-shaped seal corner edge 170.

During stoppage, the

films

11, 12 are fused along the sealing portion 14 by the straight portion 501a, and the fused edges form the seal side edge 140. At the same time, the

films

11, 12 are fused by the corner portion 501b, and the fused edges form the seal corner edge 170. Thus, the seal side edge 140 and the seal corner edge 170 are simultaneously formed by the hot blade 50.

Eighth Embodiment
In the embodiment, two bags 1 are formed each time the

continuous films

11 and 12 are fused and cut in the direction perpendicular to the transport direction Y.

As shown in FIG. 14, the

continuous films

11 and 12 are superimposed on each other, conveyed intermittently, and heat-sealed to form a sealed area 13. The first seal portion 14 extends in a direction perpendicular to the transport direction Y, and the second seal portion 15 extends in the transport direction Y.

The

films

11, 12 are sheared by the punch 55 (FIG. 12A) during stopping to form the sealing corner edge 170. The

films

11 and 12 are melted and cut along the second seal portion 15 by the laser of the irradiation unit 53 during transportation, and the second seal side edge 150 is formed. In addition, the

films

11 and 12 are slit along the both sides by the cutter 54 to form the opening side edge 160. The

films

11, 12 are fused along the first seal portion 14 by the laser or the heat blade 50 (FIG. 4) of the irradiation unit 52 (FIG. 7) to form the first seal side edge portion 140. Thereafter, the seal corner portion 170 is heated at a temperature equal to or higher than the melting point of the material of the

films

11, 12, melted and smoothed.

[Ninth embodiment]
In the embodiment, three bags 1 are formed each time the

continuous films

11 and 12 are fused and cut in the direction perpendicular to the transport direction Y. As in the other embodiments, as shown in FIG. 15, the

films

11, 12 are heat sealed to one another to form the sealing area 13. The first seal portion 14 extends in the transport direction Y, and the second seal portion 15 extends in a direction perpendicular to the transport direction Y. The first seal portion 14 is spaced from each other by one bag, and the second seal portion 15 is spaced from each other by two bags.

The sealing corner edge 170 is formed by shearing the

film

11, 12 with the punch blade 55. The first seal side edge portion 140 is formed by melting and cutting along the second seal portion 14 of the

films

11 and 12 using the laser of the irradiation unit 53.

The second seal side edge 150 is formed by cutting along the second seal portion 15 of the

film

11, 12 using a cutter. The opening side edge 160 is formed by cutting in a direction perpendicular to the transport direction Y of the

films

11 and 12 using a cutter. The cutting position is a position between the second seal portions 15. Therefore, the second seal side edge and the

opening side edge

150, 160 are alternately formed.

Thereafter, the seal corner edge 170 and the second seal side edge 160 are heated and smoothed.

The seal corner edge 170 and the second seal side edge 150 are not formed by the melting edge. However, since they are smoothed, they do not injure their hands.

Instead of the above, the cutting device 5 may be configured to switch between the heating blade 50 / irradiation unit 52 and the cutter every time the

films

11 and 12 are intermittently transported. When the cutting device 5 alternately forms the second seal side edge 150 and the opening side edge 160, the second seal side edge 150 is melted and cut by cutting the

films

11, 12 using the heat blade 50 / irradiation unit 52. And the open side edge 160 may be formed by cutting the

films

11, 12 with a cutter.

Tenth Embodiment
The embodiment produces the bag 1 of FIG. 16A. The bag 1 of FIG. 16A has, in addition to the first and

second body members

11 and 12 as a film, at least one gusset 18 for expanding the bag. In the embodiment, a pair of side gusset members are used as the gusset members 18. The gusset material 18 is also a film having a laminated structure, like the

body members

11 and 12. The inner surface (surface facing the body) of the gusset material 18 is formed of a sealant. The outer surface of the gusset material 18 is formed of a base material.

A pair of gusset members 18 extend along the opposing first side edge 130 of the bag 1 and are folded in half between the first and

second body members

11 and 12. Therefore, as shown in FIG. 16B, the gusset material 18 includes a first side 181 facing the first body 11 and a second side 182 facing the second body 12.

As shown in FIGS. 16A and 16B, the first seal portion 14 includes a first seal portion 14a formed of mutually sealed portions of the first body member 11 and the first side portion 181, a second body member 12 and a second member. It includes a second sealing portion 14b which is a sealed portion with the side portion 182, and a third sealing portion 14c which is a sealing portion of the first body 11 and the second body 12 with each other. Accordingly, the seal side edge portion 140 includes the first edge portion 140a of the first seal portion 14a, the second edge portion 140b of the second seal portion 14b, and the third edge portion 140c of the third seal portion 14c.

Hereinafter, an example of the manufacturing method which manufactures the bag 1 of FIG. 16 is demonstrated. As shown in FIG. 17, a double side gusset material is used as the gusset material 18. The gusset material 18 is folded in two on both sides of the longitudinal center line. The gusset material 18 is supplied in a direction perpendicular to the conveyance direction Y by a supply device (not shown) every time intermittent conveyance.

The first and

second body members

11 and 12 are intermittently transported by the feeding device 3 (FIG. 2) and superimposed on each other. At this time, the folded gusset material 18 is disposed between the first and

second body members

11 and 12 in a direction perpendicular to the transport direction Y. Since this is the same as Patent Document 3, the details thereof are omitted.

The first and

second body members

11 and 12 and the gusset member 18 are heat-sealed by the heat sealing device 4 to form the sealing area 13 during stoppage. Specifically, the

films

11 and 12 are heat-sealed to each other along one side thereof to form the second seal portion 15. Furthermore, the first and

second body members

11 and 12 and the gusset member 18 are heat-sealed with each other in the direction perpendicular to the transport direction Y at the longitudinal center line of the gusset member 18 to form the first seal The part 14 is formed. Thus, the first to third seal portions 14a-14c are formed. The opposing surfaces of the first side portion 181 and the second side portion 182 are not welded to each other because they are substrates.

Next, as shown in FIG. 18, the first and

second body members

11 and 12 and the gusset member 18 are melted and cut along the first seal portion 14 by the heat blade 50 of the cutting device 5 and the seal side edge 140 Is formed by the melting edge. Thus, the first to third seal portions 14a-14c are formed by the melting edge. The first and

second body members

11 and 12 and the gusset member 18 may be melted and cut by the laser of the irradiation unit 52 instead of the heating blade 50.

As shown in FIG. 18, the first to third edge portions 140a to 140c are not sharpened because they are formed by the melting edge. Therefore, there is no risk of injury to the hand by the first to third edge portions 140a-140c.

As shown in FIG. 19, when the

films

11, 12, 18 are fused and cut using the heat blade 50 or a laser, the first edge portion 140a and the second edge portion 140b may be welded to each other. This phenomenon may occur depending on the conditions of the heat blade (such as its temperature) and the laser (such as its output).

This was observed with a microscope. As the

films

11 and 12, laminated films including a substrate and a sealant were used, and melting was performed using a laser. FIG. 20A illustrates the results. As shown in FIG. 20A, the edges of the base of the

films

11, 12, 18 are smoothly curved inward. The melted sealant passes over the base of the film (side gusset material) 18 to connect the edge portion 140a and the edge portion 140b. The welding of the

edge portions

140 a and 140 b is not preferable because it interferes with the function of the gusset material 18.

In order to eliminate this, the embodiment comprises the step of heating the seal side edge 140 (and thus the first and

second edge portions

140a, 140b). The folded side gusset material 18 is under restoration stress in the direction to unfold it. Therefore, the first and

second edge portions

140a and 140b welded to each other are separated from each other by the stress when they are heated and melted. Thus, by melting the

films

11, 12, 18, even if the

edge portions

140a, 140b are welded to one another, they can be separated from one another by heating the

edge portions

140a, 140b.

FIG. 20B shows an image of a cross section of one of the

edge portions

140a, 140b after separation. As shown in FIG. 20B, since the edges of both outer substrates are smoothed by heating, the separated

edges

140a and 140b will not be sharp and will not be damaged.

As an example, a plastic bag composed of a film in which the substrate is made of PET and the sealant is made of LDPE (low density polyethylene) was used. Then, while the plastic bag was passed by the side of the halogen light source at 60 mm / sec, the welded edge portions of the bag were heated at 270 ° C. by the halogen light source. Thereby, it was confirmed that these edge portions were separated from each other.

The melting point of the film depends on the base material and the material of the sealant. The optimum conditions of heating temperature and speed for separating the edge portions from one another vary depending on what film is used. When the melting point of the film is high, the heating temperature is raised or the conveying speed is decreased, while when the melting point of the film is low, the heating temperature is lowered or the conveying speed is increased. With such adjustments, the optimum conditions can be found.

The at least one gusset material 18 may include other gusset materials instead of or in addition to the pair of side gusset materials. Another gusset material is, for example, a bottom gusset material provided along the side edge 150 of the bag 1 or a top gusset material provided along the side edge 160 of the bag 1. And other gusset materials may also be heated after melting to separate the welds of their edge portions (welding edges) from each other.

Not only folded gusset material 18 but also bent gusset material may be used. It is because the said restoration stress arises also with the bent gusset material.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. Each of the

seal portions

14 and 15 may be a portion where three or more films are laminated and sealed to each other.

Other plastic bags, such as, for example, plastic bags having chucks for opening and closing the bags may be manufactured by the manufacturing method of the present invention.

1 plastic bag 100 plastic bag edge 11 film (first body material)
12 film (2nd body material)
13 seal area 130 seal edge 14 first seal portion 140 first seal side edge portion 141 flat portion 15 of first seal portion second seal portion 150 second seal side edge portion 160 opening side edge portion 170 seal corner edge portion 18 Film (side gusset material)
2 Bag-making machine 3 Feed mechanism 4 Seal device 5 Cutting device 50 Hot blade Y Conveying direction

Claims

A method of manufacturing a plastic bag having a rim, comprising:
The plastic bag comprises a sealing area formed along a part or all of the rim and consisting of mutually sealed parts of at least two films, the rim of the plastic bag being the sealing rim of the sealing area Including
The manufacturing method is
Heat sealing the films together to form the sealed area;
After heat sealing the film, melting the film to form a part or all of the sealing edge with the melting edge;
A manufacturing method characterized by
Melt off the film using a hot blade,
The manufacturing method according to claim 1, characterized in that:
Melting the film with a laser,
The manufacturing method according to claim 1, characterized in that:
The sealing edge comprises the sealing side edge of the plastic bag,
The manufacturing method is
Melt cutting the film to form the seal side edge by the melt cutting edge;
The manufacturing method according to claim 1, characterized in that:
The sealing edge comprises the sealing corner edge of the plastic bag,
The manufacturing method is
Melt cutting the film to form the sealing corner edge by the melting edge;
The manufacturing method according to claim 1, characterized in that:
The seal area is
A first seal formed along the opposing first side edges of the plastic bag;
A second seal formed along one of the opposing second side edges of the plastic bag;
The manufacturing method is
Cutting the film along the first seal using a hot blade or a laser, and forming a first seal side edge of the first seal by the melting edge;
The film is cut along a second seal using a cutter, and the second seal side edge of the second seal is formed by the cutting edge,
Heating and smoothing the second seal side edge;
The manufacturing method according to claim 1, characterized in that:
The sealing edge comprises the sealing side edge of the plastic bag,
The manufacturing method is
As the film, a gusset material and two body materials are used,
Placing the folded or bent gusset material between the body members,
The body and the gusset material are heat sealed together to form the sealing area;
After heat sealing the body material and the gusset material, the body material and the side gusset material are fusion cut at the position of the seal area, and the seal side edge is formed by the fusion cut edge.
The manufacturing method according to claim 1, characterized in that:
Heating the seal side edge after the cutting of the body material and the gusset material;
The manufacturing method according to claim 7, characterized in that.
A plastic bag with a rim,
A seal consisting of mutually sealed parts of at least two films;
The seal portion includes a flat portion, and a seal side edge continuous with the flat portion and forming a part of the edge of the plastic bag,
The seal side edge has a rounded cross-sectional shape and has a thickness greater than the thickness of the flat portion.
A plastic bag characterized by