Flexible package vertical round-bottom bag and preparation method thereof

Abstract

The invention discloses a flexible package vertical round-bottom bag, and relates to the field of packaging. The packaging bag comprises a bag body and a bag bottom, the bag body and the bag bottom are prepared from a composite film, the bag bottom is of a circular structure, the circumferential edge of the bag bottom is provided with a shaping folded edge which is bent downwards in advance, and the shaping folded edge is connected with the bottom of the bag body through an annular heat sealing line in a heat sealing mode; the composite film comprises an outer layer, a middle barrier layer and an inner heat sealing layer. The vertical round-bottom bag for the flexible package is simple and reliable in structure, the inner capacity can be remarkably increased, the barrier property is improved, and stable standing can be achieved.

Description

Technical Field

[0001] This invention relates to the field of packaging technology, and in particular to a flexible upright round-bottom bag and its preparation method. Background Technology

[0002] Existing flexible packaging bag types, such as three-side seal, stand-up pouches, and eight-side seal bags, typically form their bottoms by folding the bag's own material. This process has the following drawbacks: First, the folded structure limits the effective use of internal space, failing to maximize packaging volume; second, for composite materials containing brittle barrier layers such as aluminum foil, repeated bending can easily cause micro-cracks or even damage to the barrier layer, severely compromising the packaging's sealing and barrier properties, thus affecting the shelf life of the packaged food.

[0003] Therefore, there is an urgent need for a new type of flexible packaging bag that can significantly increase volume while perfectly protecting the integrity of the barrier layer. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the purpose of this invention is to provide a flexible packaging upright round bottom bag and its preparation method, which has a novel structure, large capacity, good barrier properties and can stand stably.

[0005] This invention provides the following technical solution: In a first aspect, the present invention provides a flexible packaging upright round-bottom bag, comprising a bag body and a bag bottom, characterized in that the bag body and the bag bottom are made of a composite film, the bag bottom has a circular structure, and the circumferential edge of the bag bottom has a pre-bent-down shaping fold, the shaping fold being heat-sealed to the bottom of the bag body by an annular heat-sealing line; the composite film comprises an outer layer, an intermediate barrier layer and an inner heat-sealing layer.

[0006] Preferably, the outer layer can be laser-etched, gold-flecked, or printed to optimize the product display effect.

[0007] Furthermore, the sidewalls of the bag body are provided with longitudinal heat-sealed edges.

[0008] Furthermore, the longitudinal heat-sealed edge is an overlapping seal or a butt seal structure.

[0009] Furthermore, the outer layer is selected from polyethylene terephthalate (PET), biaxially oriented polypropylene film (BOPP), polyamide (PA), paper, and uniaxially oriented polyethylene film (MDOPE). The outer layer prevents the bag from being scratched, worn, or punctured during transportation, stacking, and sales. It also resists minor corrosion from external moisture, grease, and other substances, protecting the printed patterns inside.

[0010] Furthermore, the intermediate barrier layer is selected from one of aluminum foil, aluminized film, alumina film, polyvinylidene chloride (K-coated film) and ethylene-vinyl alcohol copolymer (EVOH film).

[0011] Furthermore, the inner heat-sealing layer is selected from polyethylene (PE), polypropylene (PP), and ethylene-vinyl acetate copolymer (EVA).

[0012] Furthermore, the top of the bag body is provided with a zipper, a suction nozzle, or a transverse heat-sealed edge.

[0013] Furthermore, the outer layer has a thickness of 10~25μm; the intermediate barrier layer has a thickness of 7~12μm; and the inner heat-sealing layer has a thickness of 50~100μm.

[0014] Furthermore, the flexible packaging upright round-bottom bag of the present invention can be used in the field of food packaging.

[0015] Secondly, the present invention also provides a method for preparing the above-mentioned flexible packaging upright round bottom bag, which includes the following steps: S1. After die-cutting the composite film according to the preset specifications, a rectangular bag body material is obtained. The bag body material is folded in half and its longitudinal overlapping edges are heat-sealed to form a longitudinal heat-sealed edge, thus obtaining the bag body. S2. Die-cut the composite film into a circular bag bottom; support the bottom of the bag bottom with a lower shaping device and preheat the lower shaping device to 60℃~80℃. An upper annular shaping device is provided directly above the lower shaping device. Press down the upper annular shaping device to bend the outer edge of the bag bottom downward to form a shaping fold. S3. Place the bag body onto a sleeve, and move the shaped bag bottom and the lower shaping device to directly below the sleeve. Move the sleeve down so that the bottom of the bag body contacts the shaping fold. S4. Heat seal the contact area between the bottom of the bag body and the shaping fold at a temperature of 170℃~190℃ and a pressure of 2kgf±0.5kgf. After holding the pressure for 2±0.5 seconds, release the pressure to form a ring-shaped heat seal line, thus obtaining a flexible packaging upright round bottom bag.

[0016] Furthermore, the manufacturing process of this invention makes edge folding and shaping possible. By combining the process parameters of the subsequent annular heat sealing within a specific temperature range, the core problem of turning round-bottom soft bags from concept to industrial production is solved, achieving efficient and precise automated production.

[0017] Preferably, in step S1, the heat sealing parameters are: temperature 150~180℃, heat sealing time 1~3 seconds, heat sealing pressure adjusted by a spring without a pressure display gauge, spring gap representing heat sealing pressure, and gap 1~1.5mm.

[0018] Furthermore, in step S2, the gap between the upper annular shaper and the lower shaper when they overlap is 1 to 1.5 mm.

[0019] Preferably, in step S2, the composite film is die-cut into a circular bag bottom using a circular die-cutting blade.

[0020] Preferably, the method for preparing the composite membrane includes the following steps: the outer layer and the middle barrier layer are laminated by dry lamination and then laminated with the inner heat-sealing layer. After lamination, the membrane is cured at 45°C for 60 hours to obtain the composite membrane.

[0021] Preferably, the outer layer, the intermediate barrier layer, and the inner heat-sealing layer are bonded together with an adhesive and dried at 60-80°C; the adhesive is a two-component polyurethane adhesive; the amount of adhesive applied is 2-5 g / m³. 2 .

[0022] Preferably, in step S4, a pair of annular heat-sealing blocks are used to heat-seal the contact area between the bottom of the bag body and the shaping fold.

[0023] The present invention has the following technical effects: The flexible packaging upright round-bottom bag of this invention has a simple and reliable structure. Its unique round-bottom design eliminates wasted corner space, significantly increasing the filling capacity and reducing the packaging cost per unit. Furthermore, the round-bottom structure offers better physical stability, allowing the bag to stand upright after being filled, thus enhancing shelf display. By using a composite film to prepare the bag body and bottom, the flexible packaging upright round-bottom bag possesses excellent barrier properties, effectively preventing contact between the contents and the external environment, thereby extending the shelf life of the contents. Simultaneously, the composite film also has good flexibility and strength, making it less prone to damage during transportation and storage, ensuring product integrity and safety. In addition, the manufacturing process of the flexible packaging upright round-bottom bag of this invention is simple and efficient, easily enabling large-scale industrial production and meeting market demands. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the structure of the flexible packaging upright round bottom bag provided in Embodiment 1 of the present invention.

[0026] Figure 2This is a cross-sectional structural diagram of the flexible packaging upright round-bottom bag provided in Embodiment 1 of the present invention.

[0027] Figure 3 This is a schematic diagram of the structure of the composite membrane 7 provided in Embodiment 1 of the present invention.

[0028] Figure 4 This is a schematic diagram of the longitudinal heat-sealed edge provided in Embodiment 1 of the present invention.

[0029] Figure 5 This is a cross-sectional schematic diagram of the bag bottom at the die-cutting station according to Embodiment 1 of the present invention.

[0030] Figure 6 This is a top view of the bag bottom structure at the die-cutting station according to Embodiment 1 of the present invention.

[0031] Figure 7 This is a cross-sectional schematic diagram of the bag bottom at the die-cutting-preheating and shaping station provided in Embodiment 1 of the present invention.

[0032] Figure 8 This is a cross-sectional schematic diagram of the bagging-heat sealing station provided in Embodiment 1 of the present invention.

[0033] Figure 9 This is a top view of the bagging-heat sealing station provided in Embodiment 1 of the present invention.

[0034] Figure 10 This is a cross-sectional schematic diagram of the heat sealing process provided in Embodiment 1 of the present invention.

[0035] Figure 11 for Figure 10 A magnified view of part A in the image.

[0036] Figure 12 for Figure 10 A top-down view.

[0037] Figure 13 This is a cross-sectional schematic diagram of the demolding and bag removal process provided in Embodiment 1 of the present invention.

[0038] Figure 14 This is a schematic diagram of the packaging of the flexible packaging upright round bottom bag provided in Embodiment 1 of the present invention.

[0039] Figure 15 This is a schematic diagram of the structure of the flexible packaging upright round bottom bag provided in Embodiment 4 of the present invention.

[0040] Figure 16 This is a schematic diagram of the structure of the flexible packaging upright round bottom bag provided in Embodiment 5 of the present invention.

[0041] Figure 17 This is a schematic diagram of the longitudinal heat-sealed edge provided in Embodiment 6 of the present invention.

[0042] Figure Descriptions: 1-Bag body; 11-Vertical heat-sealed edge; 12-Transverse heat-sealed edge; 13-Plastic reciprocating zipper; 14-Sucking nozzle; 2-Bag bottom; 3-Annular heat-sealing line; 4-Die-cutting-preheating and shaping station; 41-Circular die-cutting knife; 411-Blade; 412-Knife plate; 42-Lower shaping device; Shaping base 421; Shaping preheating block 422; 43-Upper circular shaping device; 5-Sleeve; 6-Annular heat-sealing block; 7-Composite film; 71-Outer layer; 72-Intermediate barrier layer; 73-Inner heat-sealing layer. Detailed Implementation

[0043] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] It should be understood that, when used in this specification and the appended claims, the terms “comprising” and “including” indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0045] Example 1 Please see Figure 1 This embodiment provides a flexible packaging upright round bottom bag, including a bag body 1 and a bag bottom 2.

[0046] The bag body 1 is a cylindrical structure made of composite film 7, and its side wall has a longitudinal heat-sealed edge 11. The longitudinal heat-sealed edge 11 is an overlap seal structure, that is, one side edge of the bag body material overlaps on the other side and is heat-sealed.

[0047] The bottom of the bag 2 is a circular sheet structure, die-cut from the same composite film 7 as the bag body 1. The circumferential edge of the bottom of the bag 2 has a pre-folded downward shaping hem 21. Please refer to further details. Figure 2 The bottom of the bag body 1 and the shaping folded edge 21 are sealed together by a ring heat sealing line 3.

[0048] Please refer to further information. Figure 3 The composite membrane 7 comprises, from the outside to the inside: Outer layer 71: is a 12μm thick biaxially oriented polyester film (PET), the outer surface of which can be color printed; Intermediate barrier layer 72: is a 7μm thick aluminum foil (Al); Inner heat-sealing layer 73: is a 100μm thick polyethylene (PE) film.

[0049] The layers are bonded together using polyurethane adhesive.

[0050] This embodiment also provides a manufacturing process for the above-mentioned flexible packaging upright round bottom bag, which specifically includes the following steps: S1. Composite film preparation and bag body prefabrication: a) Dry lamination: A 12μm thick PET film and a 7μm thick aluminum foil are coated with adhesive and then laminated for the first time using a dry laminating machine. The adhesive used is a two-component polyurethane adhesive, with an application rate of 3g / m². 2 After drying in an oven at 70℃, a PET / Al composite semi-finished product is obtained.

[0051] b) Secondary lamination: After coating the above PET / Al semi-finished product with adhesive and a 100μm thick PE film, a second lamination is performed using a dry laminating machine, with an adhesive application rate of 2g / m². 2 It is dried in an oven at 70℃.

[0052] c) Curing: The composite film 7 after secondary lamination is sent into the curing chamber and cured at 45°C for 60 hours to allow the adhesive to fully cross-link and cure, thus obtaining the final three-layer composite film 7.

[0053] d) Bag Body Forming: The cured composite film 7 is cut into rolls with a width of 233mm. Using a center-sealing bag forming machine, the composite film 7 is folded in half to form a bag body material with an inner diameter of 70mm and a heat-sealed edge of 6mm. Specifically, its longitudinal overlapping edge is heat-sealed at a temperature of 170℃. The heat-sealing pressure is spring-adjusted without a pressure gauge. The spring gap represents the heat-sealing pressure. In this embodiment, the gap is 1mm, and the heat-sealing time is 2 seconds, forming the longitudinal heat-sealed edge 11 of the overlapping structure (see...). Figure 4 This process yields a continuous tubular film. It is then cross-cut at 150mm intervals to obtain individual tubular bag body semi-finished products.

[0054] S2. Die-cut the bag bottom and preheat to set: Please see Figure 5-7Another roll of the same composite film 7 is conveyed to the die-cutting-preheating and shaping station 4 via the conveying system, so that the lower shaping device 42 supports the bottom of the composite and the preheating temperature is set to 70°C by the shaping and preheating block 422. A circular die-cutting blade 41 is used to press down under the drive system (not shown in the figure) to die-cut a circular bag bottom 2 with a diameter of 75mm. At the same time, the upper circular shaping device 43 on the inner side of the circular die-cutting blade 41 presses down with the circular die-cutting blade 41 and closes with the lower shaping device 42. The mold closing gap is 1.2mm. During this process, at the same time as the die-cutting is completed, the upper circular shaping device 43 bends the outer edge of the circular bag bottom 2 downward by 90° and shapes it under heat for 2 seconds to form a shaping fold 21. In this embodiment, the depth of the shaping fold 21 is 6mm.

[0055] S3, Bagging: The lower shaping device 42, carrying the bottom of the shaping bag 2, is transferred to the bagging-heat sealing station via a conveyor system (not shown in the figure). Please also refer to [further details omitted]. Figure 8 The cylindrical bag body 1 obtained in step S1 is fitted onto a sleeve 5 and moved down by a driving device so that the bottom opening of the bag body 1 is in full contact with the inner and outer surfaces of the shaping fold 21 on the bottom of the bag 2.

[0056] S4, Annular heat seal: Please refer to further information. Figure 8-12 Driven by the drive system, a pair of annular heat-sealing blocks 6 (their temperature controlled at 180°C by thermocouples) are brought together towards the center. The annular heat-sealing blocks 6 apply a pressure of 2 kgf to the contact area between the bottom of the bag body 1 and the shaping fold 21, and hold the pressure for 2 seconds, causing the inner PE layer to melt and bond, forming a complete and sealed annular heat-sealing line 3. Subsequently, the annular heat-sealing blocks 6 are released and reset.

[0057] S5. Demolding and bag removal: The outer sleeve 5 moves upward, removing the finished bag with the bottom heat-sealed part from the lower shaping device 42 (see...). Figure 13 The bags are then transported away by a conveyor belt, completing the entire bag-making process.

[0058] Specifically, the flexible packaging upright round-bottom bag prepared in this embodiment has an opening at the top for filling the contents, and a transverse heat-sealed edge 12 can be formed at the top of the bag body 1 after filling by a heat-sealing process (see...). Figure 14 This allows for the sealing of the flexible, upright, round-bottomed bag.

[0059] Example 2 A flexible, upright, round-bottomed bag, which differs from Example 1 in that: Materials: The outer layer 71 is a 10μm biaxially oriented polypropylene film; the barrier layer is a 10μm aluminized polyester film; and the inner layer is a 50μm polyethylene film.

[0060] Process: In step S1, the lamination process uses a solvent-free lamination method, with a curing temperature of 35℃ and a curing time of 96 hours. In step S2, the preheating and shaping temperature of the bag bottom is adjusted to 60℃. In step S4, the annular heat sealing temperature is adjusted to 170℃.

[0061] Example 3 A flexible, upright, round-bottomed bag, which differs from Example 1 in that: Materials: Outer layer 71 is 20μm PET; barrier layer is 7μm aluminum foil; inner heat-sealing layer is 100μm cast polypropylene film.

[0062] Process: In step S4, the parameters of the annular heat sealing step are adjusted as follows: heat sealing temperature 190℃, pressure 2.5kgf, and time 2.5 seconds.

[0063] Example 4 A flexible, upright, round-bottomed bag, which differs from Example 1 in that: Structure: Please refer to Figure 15 In this embodiment, the top of the bag body 1 is not heat-sealed laterally, but sealed by installing a plastic reciprocating zipper 13.

[0064] Process: In step S1, after the bag body is prepared, an additional zipper hot sealing process is added, using a special zipper welding machine to heat seal the zipper to the inside of the bag opening.

[0065] Example 5 A flexible, upright, round-bottomed bag, which differs from Example 1 in that: Structure: Please refer to Figure 16 In this embodiment, the top of the bag body is not heat-sealed horizontally, but instead has a suction nozzle 14 installed.

[0066] Process: In step S5, after demolding and bag removal, a dedicated nozzle installation machine is used to place the nozzle 14 at a predetermined position on the top of the bag body 1. The heat-sealing mold is pressed down at a temperature of 180°C and a pressure of 0.6 MPa for 3 seconds, so that the nozzle 14 is fused with the PE film of the inner top layer of the bag body 1, thereby firmly and sealingly installing the nozzle 14 on the bag body 1.

[0067] Example 6 A flexible, upright, round-bottomed bag, which differs from Example 1 in that: Structure: Please refer to Figure 17 In this embodiment, the longitudinal heat-sealed edge 11 of the bag body 1 is a double-sealed structure.

[0068] Process: In step S1, when making the bag body, adjust to the sealing mode, heat seal temperature 180℃, spring gap is 1.5mm in this embodiment, and heat pressing time is 3s. In step S2, the preheating and shaping temperature of the bag bottom is adjusted to 80℃. The annular heat sealing pressure is adjusted to 1.5kgf, and the time is adjusted to 1.5 seconds.

[0069] The bags prepared in Example 1 were subjected to sealing tests, barrier properties, standing stability tests, and drop tests. The test methods and standards are as follows: For the airtightness test, the empty bag is tested according to the airtight back pressure test method, with a back pressure of -0.05MPa for 1 minute. The bag after being filled with 100~200ml of water is tested by static pressure at 200N for 1~5 minutes, and the leak is observed. Barrier properties were tested using an oxygen barrier meter and a moisture barrier meter, according to the national standards GB / T1037 Water vapor transmission rate test method and GB / T1038 Oxygen transmission rate test method. Stand-up test: Visually inspect the stand-up effect after filling with 100-200ml of water. Check for any tilting or instability. If there is no tilting or instability, then it is OK. The bag is dropped three times from a height of 0.5m. The damage is then observed. If there is no damage, it is considered OK.

[0070] The test results are shown in Table 1 below: Table 1 Performance test results of Example 1 As shown in Table 1, the flexible packaging upright round bottom bag of the present invention has good sealing and barrier properties, can stand stably, and is not easily damaged.

[0071] Furthermore, the capacity of the flexible packaging upright round-bottom bag of the present invention can be significantly increased.

[0072] Furthermore, the present invention also provides a preparation system for a flexible packaging upright round bottom bag suitable for the above embodiments, for implementing the preparation process described above.

[0073] Please see Figure 5-13 The system includes a frame (not shown in the figure) and a die-cutting-preheating and shaping station 4, a bagging-heat sealing station, a station conveying system, a drive system and a control system, all mounted on the frame.

[0074] The die-cutting-preheating and shaping station 4 includes a lower shaping unit 42, a circular die-cutting blade 41, and an upper circular shaping unit 43, all coaxially arranged. The circular die-cutting blade 41 and the upper circular shaping unit 43 are correspondingly positioned above the lower shaping unit 42. The circular die-cutting blade 41 includes a circular blade plate 412 and a circular blade 411 disposed at its bottom. The upper circular shaping unit 43 is fixedly installed at the bottom of the circular blade plate 412 and located inside the blade 411. The first drive device of the drive system is connected to the blade plate 412 and is used to drive the circular die-cutting blade 41 and the upper circular shaping unit 43 to move up and down synchronously. The lower shaping unit 42 includes a shaping base 421 and a shaping preheating block 422 disposed at the upper end of the shaping base. The shaping preheating block 422 can precisely control its working temperature within the range of 60℃ to 80℃.

[0075] The bagging-heat-sealing station includes a sleeve 5 and a pair of annular heat-sealing blocks 6. The sleeve 5 is driven by a second drive unit of the drive system, allowing for vertical lifting and lowering, and is used to receive and expand the cylindrical bag body 1. The pair of annular heat-sealing blocks 6 are located on opposite sides of the bagging-heat-sealing station. Each annular heat-sealing block 6 is connected to a third drive unit of the drive system, used to drive it to move in opposite directions or in the same horizontal direction. The annular heat-sealing blocks 6 integrate heating elements, allowing their operating temperature to be controlled within the range of 170℃ to 190℃.

[0076] The conveying system is used to transfer materials between the die-cutting-preheating and shaping station and the bagging-heat sealing station. Specifically, the lower shaping device 42 is mounted on the conveying system at this station. The conveying system can employ a rotary arm mechanism or a linear module mechanism, driven by the fourth drive device of the drive system, capable of accurately transferring the lower shaping device 42, which carries the shaped bag bottom 2, from the die-cutting-preheating and shaping station to the bagging-heat sealing station, and positioning it directly below the sleeve 5. Specifically, in an embodiment of the present invention, the conveying system employs a rotary arm mechanism for conveying.

[0077] Specifically, in the embodiments of the present invention, each driving device is a cylinder.

[0078] Specifically, all the drive devices, heating elements and sensors in the above system are coordinated and controlled by the control system to achieve automated continuous production.

[0079] Furthermore, the present invention also provides a system for the preparation process of flexible packaging upright round bottom bags applicable to the above embodiments (see...). Figure 5-13The system includes a frame (not shown in the figure) and a die-cutting station 4, a bagging-heat-sealing station, a drive system (not shown in the figure), and a conveying system (not shown in the figure) mounted on the frame. The die-cutting station 4 includes a coaxially arranged annular die-cutting blade 41, a lower shaping device 42, and an upper annular shaping device 43. The annular die-cutting blade 41 and the upper annular shaping device 43 are respectively positioned above the lower annular shaping device 42 and can move up and down above the lower annular shaping device 42 via a drive device. The annular die-cutting blade 41 includes a blade 411 and a blade plate 412, with the blade 411 positioned at the bottom of the blade plate 412. The upper annular shaping device 43 is mounted on the blade plate 412 and located inside the blade 411. The drive device is connected to the blade plate 412 and drives it to move up and down, thereby causing the blade plate 412 to drive the blade 411 and the upper annular shaping device 43 to move up and down synchronously. The bagging-heat-sealing station drive system includes a sleeve 5 and a pair of annular heat-sealing blocks 6. A conveying system transports the lower annular shaper 42 to the bagging-heat-sealing station, positioning it directly below the sleeve 5. The drive system drives the sleeve 5 to reciprocate up and down above the lower annular shaper 42. The pair of annular heat-sealing blocks 6 are located on either side of the upper end of the lower annular shaper 42 and can be compressed inwards by the drive system, allowing the annular heat-sealing blocks 6 to contact the material to be heat-sealed and achieve heat sealing.

[0080] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A flexible, upright, round-bottomed bag, comprising a bag body and a bag bottom, characterized in that, The bag body and bag bottom are made of composite film. The bag bottom has a circular structure and a pre-bent-down shaping fold on the circumferential edge. The shaping fold is heat-sealed to the bottom of the bag body by an annular heat-sealing line. The composite film includes an outer layer, a middle barrier layer and an inner heat-sealing layer.

2. The flexible packaging upright round-bottom bag as described in claim 1, characterized in that, The side walls of the bag body are provided with longitudinal heat-sealed edges.

3. The flexible packaging upright round-bottom bag as described in claim 2, characterized in that, The longitudinal heat-sealed edge is an overlapping seal or a butt seal structure.

4. The flexible packaging upright round-bottom bag as described in claim 1, characterized in that, The outer layer is selected from one of polyethylene terephthalate, biaxially oriented polypropylene film, polyamide, paper, and uniaxially oriented polyethylene film.

5. The flexible packaging upright round-bottom bag as described in claim 1, characterized in that, The intermediate barrier layer is selected from one of aluminum foil, aluminized film, alumina film, polyvinylidene chloride and ethylene-vinyl alcohol copolymer.

6. The flexible packaging upright round-bottom bag as described in claim 1, characterized in that, The inner heat-sealing layer is selected from polyethylene, polypropylene, and ethylene-vinyl acetate copolymer.

7. The flexible packaging upright round-bottom bag as described in claim 1, characterized in that, The top of the bag is equipped with a zipper, a suction nozzle, or a horizontal heat-sealed edge.

8. The flexible packaging upright round-bottom bag as described in claim 1, characterized in that, The outer layer has a thickness of 10~25μm; the middle barrier layer has a thickness of 7~12μm; and the inner heat-sealing layer has a thickness of 50~100μm.

9. The method for preparing a flexible packaging upright round-bottom bag as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. After die-cutting the composite film according to the preset specifications, a rectangular bag body material is obtained. The bag body material is folded in half and its longitudinal overlapping edges are heat-sealed to obtain the bag body. S2. Die-cut the composite film into a circular bag bottom; support the bottom of the bag bottom with a lower shaping device and preheat the lower shaping device to 60℃~80℃. An upper annular shaping device is provided directly above the lower shaping device. Press down the upper annular shaping device to bend the outer edge of the circular bag bottom downward to form a shaping fold. S3. Place the bag body onto a sleeve, and move the shaped bag bottom and the lower shaping device to directly below the sleeve. Move the sleeve down so that the bottom of the bag body contacts the shaping fold. S4. Heat seal the contact area between the bottom of the bag body and the shaping fold at a temperature of 170℃~190℃ and a pressure of 2kgf±0.5kgf. After holding the pressure for 2±0.5 seconds, release the pressure to form a ring-shaped heat seal line, thus obtaining a flexible packaging upright round bottom bag.

10. The method for preparing the flexible packaging upright round-bottom bag as described in claim 9, characterized in that, In step S2, the gap between the upper annular shaper and the lower shaper when they overlap is 1 to 1.5 mm.

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