Composite film and microwaveable packaging bag

Abstract

The utility model discloses a kind of composite film and microwave-heatable packaging bag, the composite film includes heat-sealing layer, the heat-sealing layer has the heat-sealing surface for forming heat-sealing edge, the heat-sealing surface is provided with release layer, the release layer is provided with a plurality of through holes, the partial area of the heat-sealing surface is exposed by the plurality of through holes.The utility model is provided with the release layer with through hole on the heat-sealing surface of heat-sealing layer, after heat-sealing, a kind of composite heat-sealing structure by " weak intensity heat-sealing area " and " high intensity heat-sealing area " synergistic effect is formed.The structure, weak intensity heat-sealing area is ruptured when internal pressure reaches preset value, forms stable pressure relief channel;On the other hand, high intensity heat-sealing area provides the overall sealing strength required for daily transportation and storage for packaging bag.

Description

Technical Field

[0001] This utility model relates to the field of food packaging technology, and in particular to a composite film and a microwave-heatable packaging bag. Background Technology

[0002] With the prevalence of fast-paced lifestyles, microwave-heated food has become increasingly popular due to its convenience. However, during microwave heating, the evaporation of moisture or chemical reactions inside the food packaging produces a large amount of gas, causing a rapid increase in pressure inside the bag. If this pressure cannot be effectively released, the packaging bag can easily burst (commonly known as "bag explosion"), not only contaminating the inside of the microwave oven and affecting the user experience, but also potentially posing safety hazards. Therefore, developing microwave packaging bags with reliable automatic pressure relief functions has become an important issue in the industry.

[0003] To address the aforementioned issues, existing technologies typically employ the method of creating weak points in the heat-sealed area of ​​the packaging bag. For example, some solutions involve setting a low-strength easy-open strip along the heat-sealed edge, or using special processes (such as non-composite or special coatings) in localized areas of the heat-sealed edge to reduce its bonding strength. This allows the weak point to be breached by gas when the pressure inside the bag reaches a certain threshold, forming an exhaust channel.

[0004] However, in these existing solutions, if the strength of the pressure relief zone is too low, although it facilitates venting, it may prematurely rupture due to external forces during transportation and storage, leading to seal failure and leakage of contents. Conversely, if the strength is not properly controlled, making pressure relief difficult, the risk of bag bursting still exists. More importantly, once the pressure relief zone is breached, ensuring that the main structure of the packaging bag maintains a certain degree of integrity during and after pressure relief to prevent large-scale spillage of contents is a common challenge faced by existing technologies.

[0005] Therefore, there is an urgent need for a new technical solution that can achieve stable and controllable automatic pressure relief during microwave heating while ensuring the daily sealing performance of the packaging bag, and effectively maintain the basic structural shape of the packaging bag during the pressure relief process, so as to improve user experience and product safety. Utility Model Content

[0006] The main purpose of this utility model is to provide a composite film and a microwaveable packaging bag to solve the above-mentioned technical problems.

[0007] The objective of this utility model can be achieved by adopting the following technical solution:

[0008] A composite film includes a heat-sealing layer having a heat-sealing surface for forming a heat-sealing edge, a release layer being disposed on the heat-sealing surface, and a plurality of through holes being disposed on the release layer, the plurality of through holes exposing a local area of ​​the heat-sealing surface.

[0009] When the surface to be heat-sealed is heat-sealed with another surface to form the heat-sealed edge, the area covered by the release layer forms a weak-strength heat-sealed area, and the local area exposed by the several through holes forms a high-strength heat-sealed area.

[0010] The composite film includes a PET layer and a heat-sealing layer distributed sequentially from the outside to the inside. The heat-sealing layer is a PET heat-sealing layer, and the release layer is disposed on the inner side of the PET heat-sealing layer.

[0011] The thickness of the PET heat-sealing layer is 20-100 μm.

[0012] An adhesive layer and an ink layer are also provided between the PET layer and the PET heat-sealing layer.

[0013] The plurality of through holes are arranged in an array on the release layer to form multiple spaced high-strength heat-sealing areas within the weak-strength heat-sealing area.

[0014] The release layer is disposed on a predetermined heat-sealing area on the surface to be heat-sealed, and the coverage of the release layer extends beyond the boundary of the predetermined heat-sealing area in at least one direction.

[0015] The release layer extends beyond the boundary of the predetermined heat-sealing area in two opposite directions.

[0016] A microwave-heatable packaging bag includes a bag body, wherein the bag body is provided with a heat-sealed edge formed by a first heat-sealing surface and a second heat-sealing surface, a release layer is provided inside the heat-sealed edge, and a plurality of through holes are provided on the release layer;

[0017] Within the heat-sealed edge, the release layer blocks the area where the first heat-sealed surface and the second heat-sealed surface directly contact each other, forming a weak-strength heat-sealed area that ruptures under a preset pressure to release the internal pressure of the bag; at the position corresponding to the through hole, the first heat-sealed surface and the second heat-sealed surface directly contact each other, forming a high-strength heat-sealed area that maintains the structural integrity of the heat-sealed edge after the weak-strength heat-sealed area ruptures.

[0018] The bag body has two opposing multi-layer structures. Each multi-layer structure includes a PET layer, an adhesive layer, an ink layer, and a PET heat-sealing layer distributed sequentially from the outside to the inside. The inner sides of the PET heat-sealing layers of the two multi-layer structures respectively form the first heat-sealing surface and the second heat-sealing surface.

[0019] The release layer has two opposite ends, and the two ends of the release layer extend out of the corresponding boundaries of the heat-sealed edge.

[0020] The bag body is a back-sealed bag, a three-side-sealed bag, or a stand-up pouch.

[0021] The beneficial technical effects of this utility model are as follows:

[0022] This invention creates a composite heat-sealing structure after heat sealing by incorporating a release layer with through holes on the heat-sealing surface of the heat-sealing layer. This structure consists of a "weak-strength heat-sealing area" and a "high-strength heat-sealing area" working synergistically. On one hand, the weak-strength heat-sealing area ruptures when the internal pressure reaches a preset value, forming a stable pressure relief channel. On the other hand, the high-strength heat-sealing area provides the overall sealing strength required for daily transportation and storage. Simultaneously, during pressure relief, these high-strength areas act as "crack arrest points," preventing the tearing propagation of the weak-strength areas and maintaining the basic structural integrity of the heat-sealed edge, thus preventing complete disintegration of the packaging bag and significant spillage of contents. Therefore, this invention enables the heat-sealed edge to simultaneously possess reliable sealing performance, controllable pressure relief function, and structural stability after pressure relief, improving product safety and ease of use. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic cross-sectional view of the composite membrane provided in an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of the composite film provided in this embodiment of the present invention as a roll film;

[0026] Figure 3 This is a schematic diagram of the release layer and through-holes in the composite film provided in an embodiment of the present invention;

[0027] Figure 4 A schematic diagram of the packaging bag provided for an embodiment of this utility model.

[0028] Explanation of reference numerals in the attached figures:

[0029] In the diagram: 1-PET layer, 2-adhesive layer, 3-ink layer, 4-PET heat-sealing layer, 5-release layer, 6-through hole, 7-heat-sealing edge, 71-transverse heat-sealing edge, 72-longitudinal heat-sealing edge, 8-pressure relief channel. Detailed Implementation

[0030] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0031] 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.

[0032] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0033] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0034] like Figures 1-3 As shown, the composite film provided in this embodiment is a flexible film material suitable for packaging, particularly for packaging requiring heat sealing. The composite film includes a heat-sealing layer with a surface to be heat-sealed for forming a heat-sealed edge 7. A release layer 5 is disposed on the surface to be heat-sealed, and the release layer 5 has a plurality of through holes 6, which expose local areas of the surface to be heat-sealed. When the surface to be heat-sealed is heat-sealed with another surface to form the heat-sealed edge 7, the area covered by the release layer 5 forms a weak-strength heat-sealed area, and the local areas exposed by the through holes 6 form a high-strength heat-sealed area.

[0035] In this embodiment, the heat-sealing layer has a surface to be heat-sealed, which will be heat-pressed against another heat-sealing surface during the bag-making or sealing process. This other heat-sealing surface can be another portion of the same composite film after folding, or it can be the heat-sealing surface of another independent composite film.

[0036] Crucially, a release layer 5 is provided on the surface to be heat-sealed. The release layer 5 is a coating that can prevent or weaken the melting and adhesion of the heat-sealing layer under heat-sealing conditions. For example, it can be made of silicone oil, fluoride or other materials with anti-stick properties, and is applied to a predetermined area of ​​the surface to be heat-sealed by means of, for example, gravure coating, spraying or other methods.

[0037] Furthermore, the release layer 5 is provided with a plurality of through holes 6. These through holes 6 are openings that penetrate the thickness of the release layer 5, and their function is to expose a local area of ​​the surface to be heat-sealed within the area covered by the release layer 5. In other words, in the area where the release layer 5 is provided, the surface to be heat-sealed is not completely covered, but rather exhibits an alternating state of "release material covered area" and "heat-sealing layer material exposed area (i.e., at the through holes 6)". The shape of the through holes 6 is not limited to circular, but can also be elliptical, square, strip-shaped, or any other arbitrary geometric shape.

[0038] With the above structure, when the composite film of this embodiment is used to make bags, and its heat-sealed surface is heat-pressed to another heat-sealed surface to form a heat-sealed edge 7, two heat-sealed areas with different physical properties will be generated within the heat-sealed edge 7:

[0039] Weak heat-sealing area: In the area covered by release layer 5, the presence of release agent effectively hinders the full fusion bonding between the two heat-sealing surfaces. Therefore, this area forms a weak heat-sealing area. Although this area has a certain degree of sealing to ensure the sealing requirements of the packaging under normal conditions, its bonding strength is relatively low. When subjected to specific external forces or internal pressures, such as the water vapor pressure generated during microwave heating reaching a preset threshold, it can be relatively easily stretched or ruptured.

[0040] High-strength heat-sealing areas: In localized areas exposed by several through-holes 6, the surface of the heat-sealing layer to be heat-sealed can directly contact, be heated, and completely melt and bond with another heat-sealing surface. Since there is no release agent to block this, high-strength heat-sealing areas are formed. These high-strength heat-sealing areas act like "rivets" or "welds" in a structure, with heat-sealing strength essentially consistent with the heat-sealing strength of the heat-sealing layer material itself, providing a robust connection.

[0041] In summary, this embodiment, by providing a release layer 5 with through holes 6 on the surface of the heat-sealing layer to be heat-sealed, constructs two heat-sealing regions of different strengths at the microscopic level during the same heat-sealing operation. This structure allows the composite film, when used as a packaging material, to ensure both conventional sealing performance and provide a predictable, structurally stable pressure relief or tear-resistant function, thereby solving the problem in the prior art where sealing reliability and controllable opening / pressure relief functions are difficult to balance.

[0042] In one embodiment, the composite film includes a PET layer 1 and a heat-sealing layer distributed sequentially from the outside to the inside, the heat-sealing layer being a PET heat-sealing layer 4, and the release layer 5 being disposed on the inner side of the PET heat-sealing layer 4.

[0043] In this embodiment, the composite film is an all-PET (polyethylene terephthalate) structure, and its layer structure includes a PET layer 1 and the heat-sealing layer distributed sequentially from the outside to the inside.

[0044] The PET layer 1 forms the outer layer of the composite film and can be a general-purpose biaxially oriented PET film with a thickness of 12 μm. The heat-sealing layer is the inner layer that realizes the heat-sealing function, and this heat-sealing layer is specifically a PET heat-sealing layer 4. For example, a PET heat-sealing film with a thickness of 30 μm can be selected.

[0045] By bonding the outer PET layer 1 with the inner PET heat-sealing layer 4, the main structural material of the entire composite film is PET, forming a single PET material system. Packaging made with this structure can be recycled and reused as a whole after disposal without the need for complex multi-material separation, offering significant environmental advantages.

[0046] The release layer 5 and its through-holes 6 are located on the inner side of the PET heat-sealing layer 4. Here, "inner side" refers to the side of the PET heat-sealing layer 4 facing the inside of the bag after it is finally made into a packaging bag, which is used to form the surface to be heat-sealed. The release layer 5 plays its role in blocking heat sealing on this side, and together with the area exposed by the through-holes 6, it forms a heat-sealing structure with composite strength.

[0047] In one embodiment, the thickness of the PET heat-sealing layer is 20-100 μm.

[0048] In a preferred embodiment of this example, the PET heat-sealing layer 4 simultaneously meets the specific requirements for heat-sealing strength and thickness. Specifically, a PET heat-sealing film with a thickness of 30 μm is selected, and its heat-sealing strength is tested to be no less than 6.0 N / 15 mm.

[0049] The use of this "high-strength and moderately thick" PET heat-sealing layer 4 can ensure sufficient mechanical support while possessing good flexibility. It also ensures that the high-strength heat-sealing area formed at the through hole 6, namely the "rivet point", is relatively firm. Even if the weak-strength area breaks due to increased internal pressure, these "rivet points" can still effectively maintain the overall structural integrity of the heat-sealed edge 7, preventing the packaging bag from completely bursting, thus reliably achieving the effect of "directional pressure relief without bursting".

[0050] In another embodiment, the PET heat-sealing layer 4 is selected primarily from the perspective of material flexibility and versatility. In this case, a PET heat-sealing film with a thickness of 25 μm and a heat-sealing strength of 5.0 N / 15 mm is chosen. In this embodiment, the main technical consideration is its suitable thickness. As long as its strength can ensure that the high-strength heat-sealed area does not fail after pressure relief, it can be used in this embodiment.

[0051] In another embodiment, for a specific application requiring high sealing strength, the primary consideration is the heat-sealing strength of the PET heat-sealing layer 4 itself. Using a PET heat-sealing film with a heat-sealing strength of 7.0 N / 15 mm allows for the formation of a robust, high-strength heat-sealing area. In this case, the thickness is 50 μm.

[0052] In another embodiment, the PET heat-sealing layer 4 may be 100 μm thick.

[0053] In summary, whether it is the preferred embodiment that simultaneously meets the strength and thickness requirements, or the embodiment that focuses on meeting either of the technical features, a safe and controllable pressure relief function can be achieved.

[0054] In this embodiment, the surface tension on both sides of the PET heat-sealing layer 4 is greater than 38 mN / m to ensure that the ink layer 3 and the release layer 5 can adhere firmly. The heat-sealing temperature range for the PET heat-sealing layer 4 is between 130-180°C.

[0055] In one embodiment, an adhesive layer 2 and an ink layer 3 are further provided between the PET layer 1 and the PET heat-sealing layer 4.

[0056] In this embodiment, in order to firmly bond the outer PET layer 1 and the inner PET heat-sealing layer 4 together and achieve the effect required for commercial packaging, an adhesive layer 2 and an ink layer 3 are also provided between the PET layer 1 and the PET heat-sealing layer 4.

[0057] First, on one surface of the PET heat-sealable film (i.e., the surface facing outwards), the desired patterns, text, and other information are printed using gravure printing or flexographic printing to form an ink layer 3. Then, using a dry lamination process, an adhesive layer 2 is used to bond the PET heat-sealable film with the printed ink layer 3 to the outer PET film. This adhesive layer 2 can be a polyurethane adhesive, which acts as a bonding agent to firmly bond the two PET substrate layers into a single unit, ensuring that the composite film does not delaminate during use.

[0058] Therefore, the final layered structure of this composite film, from the outside to the inside, consists of: an outer PET layer 1, an adhesive layer 2, an ink layer 3, and an inner PET heat-sealing layer 4. This structure, which includes the adhesive layer 2 and the ink layer 3, ensures the recyclability of the single PET material while also considering structural strength (achieved through the adhesive layer 2) and information transmission functionality (achieved through the ink layer 3). The release layer 5 remains on the inner surface of the innermost PET heat-sealing layer 4, and its function is unaffected by this composite structure.

[0059] In one embodiment, the plurality of through holes 6 are arranged in an array on the release layer 5 to form a plurality of spaced high-strength heat-sealing regions within the weak-strength heat-sealing region.

[0060] In this embodiment, this array-like arrangement allows the high-strength heat-sealing area to be distributed in a regular and controllable manner within the heat-sealing edge 7. Specifically, the array-like distribution can be an orthogonal array, where the through holes 6 are aligned in both the horizontal and vertical directions; or it can be an interlaced array, where the through holes 6 in each row are staggered relative to the through holes 6 in their adjacent rows, similar to a checkerboard layout.

[0061] With this design, after the composite film is heat-sealed, multiple spaced, independent high-strength heat-sealing areas can be formed within the large area of ​​weak-strength heat-sealing formed by the release layer 5. These high-strength heat-sealing areas, like rivets, uniformly reinforce the entire heat-sealed edge 7.

[0062] For a concrete example: within a pre-defined release layer 5 area, multiple rows and columns of circular through-holes 6 can be set. The diameter of the through-holes 6 can be 1-5mm, for example, 2mm. The lateral and longitudinal spacing between adjacent through-holes 6 can both be set to 1-5mm, for example, 3mm. This array-like distribution ensures that the density of high-strength "rivet points" is consistent in every part of the heat-sealed edge 7, thereby guaranteeing the uniformity of the mechanical properties of the entire heat-sealed edge 7. When the internal pressure of the packaging bag increases, the weak-strength areas will undergo controlled tearing to release the pressure, while these uniformly distributed high-strength areas can effectively prevent the disorderly propagation of cracks, maintain the basic structural integrity of the heat-sealed edge 7, and prevent the entire packaging bag from bursting.

[0063] In addition, the staggered array distribution helps to more effectively prevent external dust or foreign objects from entering the bag through any possible pressure relief channels 8, thus improving the product's protective properties.

[0064] In one embodiment, the release layer 5 is disposed on a predetermined heat-sealing area on the surface to be heat-sealed, and the coverage of the release layer 5 extends beyond the boundary of the predetermined heat-sealing area in at least one direction.

[0065] In this embodiment, the predetermined heat-sealing area, for example on the roll film used for bag making, is the strip-shaped area where the top or bottom transverse sealing edge of the packaging bag will be formed in the future.

[0066] The release layer 5 extends beyond the boundary of the predetermined heat-sealing area in at least one direction. This is equivalent to providing a "tolerance zone" or "safe zone" for the coating of the release layer 5.

[0067] To illustrate, consider a packaging bag with a 10mm wide transverse heat-sealed edge 71 as an example. This 10mm wide strip is the "pre-determined heat-sealed area." When applying the release layer 5, its coverage area in the direction perpendicular to the extension of the heat-sealed edge 7 (i.e., the longitudinal direction of the roll film) can be designed to be 14mm, with its center line aligned with the center line of the predetermined heat-sealed area. This allows the actual coverage area of ​​the release layer 5 to extend outwards by more than 2mm at both the upper and lower boundaries of the predetermined heat-sealed area.

[0068] During high-speed, continuous bag-making processes, slight misalignment of the heat-sealing cutter's position relative to the predetermined heat-sealing area of ​​the roll film can occur due to mechanical tolerances or minor film vibrations. If the release layer 5 completely overlaps with the predetermined heat-sealing area, any slight misalignment could cause part of the heat-sealing cutter to press into an area without the release layer 5, resulting in an unexpectedly high-strength heat seal and compromising the original weak-strength pressure relief design. By extending the release layer 5 beyond the boundary, even with minor alignment deviations, an effective release layer 5 is always present within the entire area pressed by the heat-sealing cutter. This ensures the reliable implementation of the weak-strength to high-strength heat-sealing zone, improving production stability and the consistency of the final product's quality. The extension width can be adjusted within the range of 2-8 mm depending on actual needs.

[0069] In one embodiment, the release layer 5 extends beyond the boundary of the predetermined heat-sealing area in two opposite directions.

[0070] In this embodiment, a specific application scenario is used for illustration: On the roll film used to prepare packaging bags, a transverse heat-sealing edge 71 area is reserved for forming the bag opening or bottom; this area is called the "predetermined heat-sealing area". Assume that the width of this predetermined heat-sealing area (i.e., the dimension along the longitudinal direction of the roll film) is designed to be 10 mm.

[0071] The release layer 5 coated on the predetermined heat-sealing area will have a width greater than 10 mm. Specifically, in the direction perpendicular to the heat-sealing edge 7 (i.e., the longitudinal direction of the roll film), both the upper and lower edges of the release layer 5 extend beyond the boundary of the 10 mm wide predetermined heat-sealing area.

[0072] The design, extending beyond the roll in both opposite directions, provides sufficient buffering for bidirectional alignment deviations (i.e., upward or downward offset of the film roll) during the bag-making process. Regardless of slight upward or downward drift of the heat-sealing cutter relative to the film roll, the entire 10mm wide heat-sealing area is always covered by the release layer 5 (and its through-holes). This minimizes the creation of unexpected, continuous high-strength heat-sealed areas on the heat-sealed edge 7 due to misalignment, thus greatly ensuring the stability and reliability of the final product's pressure relief function and significantly improving the yield rate during production.

[0073] like Figure 4 As shown, corresponding to the above-mentioned composite film, this utility model embodiment also provides a microwave-heatable packaging bag. During microwave heating, the packaging bag can safely and controllably release the internal gas pressure, thereby avoiding the risk of the packaging bag bursting due to excessive pressure. The packaging bag includes a bag body, on which a heat-sealed edge 7 formed by a first heat-sealing surface and a second heat-sealing surface is provided. A release layer 5 is provided within the heat-sealed edge 7, and the release layer 5 has a plurality of through holes 6. Within the heat-sealed edge 7, the release layer 5 blocks the area where the first heat-sealing surface and the second heat-sealing surface directly contact each other, forming a weak-strength heat-sealed area that bursts under a preset pressure to release the internal pressure of the bag body. At the positions corresponding to the through holes 6, the first heat-sealing surface and the second heat-sealing surface directly contact each other, forming a high-strength heat-sealed area that maintains the structural integrity of the heat-sealed edge 7 after the weak-strength heat-sealed area bursts.

[0074] In this embodiment, the packaging bag includes a bag body, which is made of one or more composite films through a heat-sealing process to form an internal space that can hold items such as pre-cooked dishes, instant rice, etc.

[0075] The bag body is provided with heat-sealed edges 7, such as a top transverse heat-sealed edge 71, a bottom transverse heat-sealed edge 71, and / or a side longitudinal heat-sealed edge 72. These heat-sealed edges 7 are formed by hot-pressing and fusing the first heat-sealing surface and the second heat-sealing surface of the bag body. For example, in a three-side seal bag made by folding a single roll of film in half and sealing both sides, the first heat-sealing surface and the second heat-sealing surface are two opposing inner surfaces of the same film material.

[0076] A release layer 5 is provided inside the heat-sealed edge 7, that is, between the first and second heat-sealed surfaces. The release layer 5 is provided with a plurality of through holes 6.

[0077] This structure creates two functionally different regions inside the heat-sealed edge 7, and its working principle is as follows:

[0078] Weak heat-sealed area: Within the heat-sealed edge 7, the release layer 5 prevents direct contact between the first and second heat-sealed surfaces. Due to the release agent, the fusion strength between these two surfaces is weak at this location. This area is designed so that when the packaging bag is heated in a microwave oven, the steam and other gases produced by the food inside will gradually increase the internal pressure. When the pressure reaches a preset value, this weak heat-sealed area will preferentially rupture or be expanded, forming one or more pressure relief channels 8, thereby releasing the pressure inside the bag. The preset value here is the critical pressure that the steam and other gases inside the packaging bag can reach, just enough to expand the weak heat-sealed area.

[0079] High-strength heat-sealing area: At the location corresponding to the through-hole 6, due to the absence of a release layer 5, the first heat-sealing surface and the second heat-sealing surface can directly contact and fully fuse during the heat-sealing process, forming a strong connection. The function of this area is to maintain the connection even after the weak-strength heat-sealing area ruptures due to increased internal pressure, acting like a rivet to maintain the structural integrity of the heat-sealed edge 7. This ensures that the packaging bag only releases pressure at a predetermined location, preventing serious problems such as complete tearing of the entire seal, leakage of contents, or disintegration of the packaging bag.

[0080] Through the synergistic effect of the low-strength and high-strength heat-sealed areas, the packaging bag in this embodiment achieves a "smart" pressure relief mechanism. Under normal storage and transportation conditions, the entire heat-sealed edge 7 provides sufficient sealing; while under specific microwave heating conditions, it can automatically and safely open the pressure relief channel 8, greatly improving the safety and convenience for consumers.

[0081] In one embodiment, the bag body has two opposing multi-layer structures, each multi-layer structure including a PET layer 1, an adhesive layer 2, an ink layer 3 and a PET heat-sealing layer 4 distributed sequentially from the outside to the inside, and the inner sides of the PET heat-sealing layers 4 of the two multi-layer structures respectively form the first heat-sealing surface and the second heat-sealing surface.

[0082] In this embodiment, the two multilayer structures can be either a structure formed by folding a single composite film material in half, or a structure formed by heat-sealing the periphery of two independent composite film materials. In both cases, there are two opposing multilayer structures that constitute the main wall surface of the bag.

[0083] Each of the multilayer structures has the same hierarchical structure, specifically including a PET layer 1, an adhesive layer 2, an ink layer 3, and a PET heat-sealing layer 4 distributed sequentially from the outside to the inside.

[0084] PET layer 1: As the outermost layer of the bag, it provides mechanical support, abrasion resistance, and a good substrate for printing appearance. For example, a PET film with a thickness of 12μm can be used.

[0085] Adhesive layer 2: Used to reliably bond the outer PET layer 1 to the inner PET heat-sealing layer 4 (whose outer surface is printed with ink), ensuring the integrity of the bag structure and its resistance to boiling. Composite adhesives such as polyurethane can be used.

[0086] Ink layer 3: The graphic layer printed with product information is sandwiched between PET layer 1 and PET heat-sealing layer 4. It is protected by the outer PET layer and is not easy to fall off or wear.

[0087] PET heat-sealing layer 4: As the innermost layer of the bag, it comes into direct contact (or may come into contact) with the contents of the package and is the key layer for achieving the heat-sealing function. This layer uses a special PET heat-sealing film, such as a PET heat-sealing film with a thickness of 20-50μm (e.g., 30μm).

[0088] Importantly, the entire bag material system (except for inks and adhesives) is based on PET, forming a single-material packaging, which is very beneficial for subsequent recycling and reuse, and meets the environmental protection requirements of sustainable development.

[0089] In this packaging bag, the inner sides (i.e., the surfaces facing the inside of the bag) of the two opposing multi-layered PET heat-sealing layers 4 respectively form a first heat-sealing surface and a second heat-sealing surface. During bag making, it is these two inner surfaces of the PET heat-sealing layers 4 that come into contact with each other and are subjected to heat and pressure, thereby forming a heat-sealed edge 7 with a release layer 5 and through-holes 6. This design ensures that the heat-sealing function is performed by a uniform PET heat-sealing layer 4, guaranteeing the consistency of heat-sealing parameters and the reliability of the sealing quality.

[0090] In this embodiment, the packaging bag is referred to as "single-material packaging" because the main materials constituting the bag's structural framework—namely, the outer support layer and the inner heat-sealing layer—are both polyethylene terephthalate (PET). Although the structure contains trace amounts of ink and adhesives, under the technical standards of the recycling industry, due to their extremely low proportion, the overall product is still considered a pure PET material stream. The core advantage of this design lies in solving the pain point of difficult recycling of traditional composite packaging (such as PET / PE). Different types of plastics have vastly different melting points and physical properties; mixing them for recycling leads to low-quality recycled materials and limited applications. The all-PET structure of this embodiment eliminates the need for complex and expensive separation processes, allowing direct entry into a mature PET recycling system, thereby significantly improving the actual recycling rate of the packaging.

[0091] In one embodiment, the release layer 5 has two opposite ends, and the two ends of the release layer 5 extend out of the corresponding boundaries of the heat-sealing edge 7.

[0092] In this embodiment, the release layer 5 has two opposing ends. Taking a transverse heat-sealing edge 71 located at the top of the bag as an example, the strip-shaped release layer 5 has an upper edge and a lower edge, which are its "opposite ends". Similarly, the heat-sealing edge 7 itself also has an upper boundary and a lower boundary.

[0093] The release layer 5 extends from the corresponding boundaries of the heat-sealing edge 7 at both ends. This means that the width of the release layer 5 in the direction perpendicular to the extension of the heat-sealing edge 7 is greater than the width of the heat-sealing edge 7 itself.

[0094] To illustrate more specifically, suppose the packaging bag design requires a 10mm wide transverse heat-sealing edge 71. Here, "width" refers to the dimension of the heat-sealing edge 7 in the longitudinal direction of the bag. This 10mm wide strip area is the predetermined heat-sealing area. When applying the release layer 5, the width of the applied release layer 5 can be designed to be 14mm. When this 14mm wide release layer 5 is aligned with the center of the 10mm wide heat-sealing area, the upper edge of the release layer 5 will extend 2mm beyond the upper boundary of the heat-sealing edge 7, and its lower edge will also extend 2mm beyond the lower boundary of the heat-sealing edge 7. This achieves the goal of "the two ends of the release layer 5 extending beyond the corresponding boundaries of the heat-sealing edge 7."

[0095] The technical advantage of this design is that during high-speed, continuous bag-making processes, the position of the heat-sealing cutter (or heat-sealing roller) may experience a slight longitudinal offset (i.e., vertical fluctuation) relative to the predetermined position of the film. If the width of the release layer 5 is exactly the same as the width of the heat-sealing edge 7, any slight offset may cause part of the heat-sealing cutter to press into the area without the release layer 5, thereby forming an unintended, complete, strong heat seal at that location. This would disrupt the continuity and effectiveness of the weak-strength pressure relief area.

[0096] By extending the two ends of the release layer 5 beyond the boundary of the heat-sealing edge 7, a "safety margin" is provided for the heat-sealing operation. Even if the position of the heat-sealing blade fluctuates slightly, it ensures that its entire effective width falls within the coverage area of ​​the release layer 5. This guarantees that the heat-sealing edge 7 of each finished packaging bag can reliably form the preset strong-weak composite structure, thereby ensuring the stability of the controllable pressure relief function and significantly improving product quality consistency and yield.

[0097] In one embodiment, the bag body is a back-sealed bag, a three-side-sealed bag, or a stand-up pouch.

[0098] In this embodiment, taking a back-sealed bag as an example, this is a packaging bag made by rolling a single piece of packaging film into a tube, overlapping or finning its two longitudinal edges on the back (or middle) of the bag body, and then laterally heat-sealing the top and bottom. In this type of bag, the pressure relief structure (i.e., the release layer with through-holes 6) of this embodiment can be provided on the lateral heat-sealed edges 71 of the top and / or bottom.

[0099] In another specific embodiment, taking a three-side seal bag as an example, this is a flat bag made by folding a single piece of packaging film in half and then heat-sealing the other two sides, or by heat-sealing two separate pieces of packaging film on three sides. The contents are filled through a pre-reserved opening and then sealed. The pressure relief structure of this embodiment can be provided on any one or more of the heat-sealed edges 7, particularly the final top transverse seal edge.

[0100] In another specific embodiment, taking a stand-up pouch as an example, this is a packaging bag with an unfoldable folded edge structure at the bottom, allowing it to stand upright independently after being filled with contents. Its main structure consists of two film materials, with an independent bottom film added. The pressure relief structure in this embodiment can be applied to its top transverse heat-sealed edge 71.

[0101] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model 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 this utility model, and these modifications or substitutions should all be covered within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A composite membrane, characterized in that, Includes a heat-sealing layer, the heat-sealing layer having a heat-sealing surface for forming a heat-sealing edge, a release layer being disposed on the heat-sealing surface, the release layer having a plurality of through holes, the plurality of through holes exposing a local area of ​​the heat-sealing surface; When the surface to be heat-sealed is heat-sealed with another surface to form the heat-sealed edge, the area covered by the release layer forms a weak-strength heat-sealed area, and the local area exposed by the several through holes forms a high-strength heat-sealed area.

2. The composite membrane according to claim 1, characterized in that, The composite film includes a PET layer and a heat-sealing layer distributed sequentially from the outside to the inside. The heat-sealing layer is a PET heat-sealing layer, and the release layer is disposed on the inner side of the PET heat-sealing layer.

3. The composite membrane according to claim 2, characterized in that, The thickness of the PET heat-sealing layer is 20-100 μm.

4. The composite membrane according to claim 2, characterized in that, An adhesive layer and an ink layer are also provided between the PET layer and the PET heat-sealing layer.

5. The composite membrane according to claim 1, characterized in that, The plurality of through holes are arranged in an array on the release layer to form multiple spaced high-strength heat-sealing regions within the weak-strength heat-sealing region.

6. The composite membrane according to claim 1, characterized in that, The release layer is disposed on a predetermined heat-sealing area on the surface to be heat-sealed, and the coverage of the release layer extends beyond the boundary of the predetermined heat-sealing area in at least one direction.

7. The composite membrane according to claim 6, characterized in that, The release layer extends beyond the boundary of the predetermined heat-sealing area in two opposite directions.

8. A microwave-heatable packaging bag, characterized in that, Includes a bag body, on which a heat-sealing edge is formed by a first heat-sealing surface and a second heat-sealing surface, and a release layer is provided inside the heat-sealing edge, and a plurality of through holes are provided on the release layer; Within the heat-sealed edge, the release layer blocks the area where the first heat-sealed surface and the second heat-sealed surface directly contact each other, forming a weak-strength heat-sealed area that ruptures under a preset pressure to release the internal pressure of the bag; at the position corresponding to the through hole, the first heat-sealed surface and the second heat-sealed surface directly contact each other, forming a high-strength heat-sealed area that maintains the structural integrity of the heat-sealed edge after the weak-strength heat-sealed area ruptures.

9. The packaging bag according to claim 8, characterized in that, The bag body has two opposing multi-layer structures. Each multi-layer structure includes a PET layer, an adhesive layer, an ink layer, and a PET heat-sealing layer distributed sequentially from the outside to the inside. The inner sides of the PET heat-sealing layers of the two multi-layer structures respectively form the first heat-sealing surface and the second heat-sealing surface.

10. The packaging bag according to claim 9, characterized in that, The release layer has two opposite ends, and the two ends of the release layer extend out of the corresponding boundaries of the heat-sealed edge.

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