High-temperature-resistant pure nylon oven bag and preparation method thereof
By designing a pure nylon multilayer co-extruded film, the problems of adhesive decomposition, material deformation, and recycling difficulties in oven bags at high temperatures are solved, achieving safe and reliable packaging bags at high temperatures, easy recycling, and high production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANHUI YINGPIKE NEW MATERIALS CO LTD
- Filing Date
- 2026-02-11
- Publication Date
- 2026-04-28
AI Technical Summary
Existing oven packaging bags suffer from problems such as adhesive decomposition producing odors at high temperatures, deformation and cracking of non-heat-resistant materials, and difficulty in recycling composite materials.
The bag is made of pure nylon multilayer co-extruded film, including a high-melting-point polyamide outer layer, a high-strength polyamide middle layer, and a high-temperature resistant polyamide copolymer inner layer. The bag is made by heat sealing, avoiding the use of adhesives, and maintaining high strength and stability at 220°C.
It maintains high strength and stability at 220℃, avoids the migration of harmful substances, is easy to recycle, and has high production efficiency and low cost.
Smart Images
Figure CN121928840A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of food packaging materials technology, and more specifically to a high-temperature resistant pure nylon oven bag and its preparation method. Background Technology
[0002] Existing oven packaging bags are mostly made of composite films of polyester (PET), polypropylene (PP), or polyamide (nylon, PA) and other materials. To meet the requirements of high temperature resistance (usually above 200℃) and barrier properties, common structures are PET / PA / CPP or PA / aluminum foil / CPP, etc. These structures have the following drawbacks: 1) Use of adhesive layers: Multi-layer composites require adhesives, such as polyurethane glue. Under long-term high-temperature environments above 220℃, the adhesives may decompose, producing odors or even harmful substances, posing food safety risks. 2) Containing non-heat-resistant layers: For example, cast polypropylene (CPP) typically has a long-term heat resistance temperature below 150℃. It is prone to softening and deformation at high temperatures, leading to bag breakage. 3) Use of inorganic coatings: Some existing technologies use coatings such as silica to improve heat resistance on the film surface, but these coatings have problems such as poor abrasion resistance, easy peeling, and high cost. 4) Difficulty in recycling composite materials: Composite structures of multiple different materials are difficult to separate and recycle, which is not in line with environmental protection trends.
[0003] Therefore, there is an urgent need to develop a high-strength pure nylon oven bag that requires no adhesive, contains no non-heat-resistant material layers, and can be used safely for a long time at 220°C. Summary of the Invention
[0004] The purpose of this invention is to provide a high-temperature resistant pure nylon oven bag and its preparation method, so as to solve the problems mentioned in the background art.
[0005] To achieve the above objectives, the present invention employs the following technical means: A high-temperature resistant pure nylon oven bag includes a bag body made of a pure nylon multilayer co-extruded film by heat sealing. The pure nylon multilayer co-extruded film includes a high-melting-point polyamide outer layer, a high-strength polyamide intermediate layer, and a high-temperature resistant polyamide copolymer inner layer stacked sequentially. The pure nylon multilayer co-extruded film does not contain an adhesive resin layer. The high-melting-point polyamide outer layer has a melting point of 250℃-265℃ and a melt index (275℃ / 5kg) of 5-15g / 10min. The high-strength polyamide intermediate layer has a relative viscosity of 3.5-4.2 (measured in 96% concentrated sulfuric acid). The high-temperature resistant polyamide copolymer inner layer has a melting point of not less than 220℃ and a heat-sealing initiation temperature between 180℃ and 200℃.
[0006] In some embodiments, the total thickness of the pure nylon multilayer co-extruded film is 40-100 micrometers, wherein the thickness of the intermediate layer accounts for 50%-70% of the total thickness; the high-melting-point polyamide outer layer is selected from one of PA6T / 66, PA9T, or PA10T or a copolymer thereof; the high-strength polyamide intermediate layer is PA6 or PA66; the high-temperature resistant polyamide copolymer outer layer is PA6 / 66 copolymer or PA6 / 12 copolymer; after being treated in an oven at 220°C for 60 minutes, the pure nylon multilayer co-extruded film exhibits a longitudinal and transverse heat shrinkage rate of less than 5% and a tensile strength retention rate of greater than 85%.
[0007] In some embodiments, the inner layer of the high-temperature resistant polyamide copolymer has a thickness of 0.03-0.05 mm, and the inner layer of the high-temperature resistant polyamide copolymer is made of 45-55 parts of low-temperature adaptable pure nylon substrate, 4-6 parts of pure nylon toughening modifier, and 1-2 parts of pure nylon antioxidant.
[0008] In some embodiments, the high-strength polyamide interlayer has a thickness of 0.06-0.09 mm and is composed of 60-70 parts of high-temperature resistant pure nylon substrate, 8-12 parts of pure nylon high-temperature resistant reinforcing agent, and 5-7 parts of pure nylon compatibilizer.
[0009] In some embodiments, the high-melting-point polyamide outer layer has a thickness of 0.04-0.06 mm and is composed of 50-60 parts of oil-resistant pure nylon substrate, 3-5 parts of pure nylon oil-resistant modifier, and 2-4 parts of pure nylon wear-resistant agent.
[0010] In some embodiments, a method for preparing a high-temperature resistant pure nylon oven bag includes the following steps: S1. Raw material drying: The polyamide resin particles of the outer layer, middle layer and inner layer are vacuum dried at 100-120℃ for 6-8 hours to make their moisture content less than 500ppm; S2. Multi-layer co-extrusion casting: Multiple single-screw extruders are used to co-extrude and cast each layer of material, with an extrusion temperature gradient of 260℃-300℃; the extrusion temperature gradient from the feeding section to the die head is 260℃-290℃-300℃-295℃-290℃ (die head). S3. Biaxial stretching: The cast sheet is simultaneously biaxially stretched, with a stretching ratio of 2.5-3.5:1 in both the longitudinal and transverse directions; S4. Heat setting: The stretched film is heat-set at 210℃-230℃ under tension; S5. Cool and rewind to obtain a pure nylon multilayer co-extruded film; S6. Bag making: Cut the rolled film into sections and heat seal three or four sides under the conditions of heat sealing temperature of 200℃-220℃, pressure of 0.3-0.5MPa, and time of 1-2 seconds to obtain oven bags.
[0011] In some embodiments, in step S2, the die head gap of the casting process is 0.8-1.2 mm, and the casting roller temperature is 30-50°C.
[0012] In some embodiments, in step S3, the temperature of the biaxial stretching is controlled within a range of 15-25°C lower than the melting point of the polyamide resin used.
[0013] In step S4, the heat setting process takes 5-10 seconds.
[0014] In step S6, the heat sealing conditions are: pressure 0.3-0.5MPa, time 1-2 seconds.
[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a high-melting-point outer layer (≥250℃) and a high-temperature resistant copolymer inner layer (≥220℃), combined with a high-temperature heat setting process, to achieve excellent thermal stability at 220℃, low heat shrinkage, and high strength retention, far exceeding that of ordinary PA6 films. It also exhibits superior tensile, impact, and puncture resistance, preventing food from being punctured by bones at high temperatures. The entire film is made of 100% polyamide, without any adhesives, other plastics (such as PP, PET), or inorganic coatings, posing no risk of harmful substance migration at high temperatures, ensuring safety and reliability. Its single pure nylon material structure facilitates recycling and reuse, simplifies the manufacturing process by eliminating the need for lamination, coating, and curing steps, resulting in high production efficiency and lower costs. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the structure of a pure nylon multilayer co-extruded film according to some embodiments of this specification.
[0017] Figure 2 This is a schematic diagram of the structure of a pure nylon multilayer co-extruded film according to some embodiments of this specification.
[0018] Figure 3 The pure nylon multilayer co-extruded film shown in some embodiments of this specification is along... Figure 2 A schematic diagram of the partial structure viewed along line AA. Detailed Implementation
[0019] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. The following embodiments and drawings are only used to more clearly illustrate the technical solution of this application, and are therefore merely examples and should not be used to limit the scope of protection of this application. The drawings only schematically show the parts related to the technical solution of this application, and do not represent their actual structure as a product.
[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.
[0021] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).
[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.
[0023] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.
[0024] In the description of the embodiments of this application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.
[0025] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.
[0026] In this embodiment, a high-temperature resistant pure nylon oven bag includes a bag body made of a pure nylon multilayer co-extruded film by heat sealing. The pure nylon multilayer co-extruded film includes a high-melting-point polyamide outer layer 100, a high-strength polyamide intermediate layer 200, and a high-temperature resistant polyamide copolymer inner layer 300 stacked sequentially. The pure nylon multilayer co-extruded film does not contain an adhesive resin layer. The high-melting-point polyamide outer layer 100 has a melting point of 250℃-265℃ and a melt index (275℃ / 5kg) of 5-15g / 10min. The high-strength polyamide intermediate layer 200 has a relative viscosity of 3.5-4.2 (measured in 96% concentrated sulfuric acid). The high-temperature resistant polyamide copolymer inner layer 300 has a melting point of not less than 220℃ and a heat-sealing initiation temperature between 180℃ and 200℃.
[0027] In some embodiments, the total thickness of the pure nylon multilayer co-extruded film is 40-100 micrometers, wherein the thickness of the intermediate layer accounts for 50%-70% of the total thickness; the high-melting-point polyamide outer layer 100 is selected from one of PA6T / 66, PA9T, or PA10T or a copolymer thereof; the high-strength polyamide intermediate layer 200 is PA6 or PA66; the high-temperature resistant polyamide copolymer outer layer is PA6 / 66 copolymer or PA6 / 12 copolymer; after being treated in an oven at 220°C for 60 minutes, the pure nylon multilayer co-extruded film has a longitudinal and transverse heat shrinkage rate of less than 5% and a tensile strength retention rate of greater than 85%. In some embodiments, the total thickness of the pure nylon multilayer co-extruded film is 75 μm; the high-melting-point polyamide outer layer 100 is PA6T / 66 with a thickness of 10 μm; the high-strength polyamide intermediate layer 200 is PA6 with a thickness of 50 μm; and the high-temperature resistant polyamide copolymer outer layer is PA6 / 66 copolymer with a melting point of 225°C, a heat-sealing initiation temperature of 185°C, and a thickness of 15 μm. The three layers of particles are vacuum dried at 110°C for 7 hours, and then extruded through a three-layer co-extrusion casting machine with an extrusion temperature gradient of 265°C-285°C-300°C-295°C-290°C (die head), a die head gap of 1.0 mm, and a casting roller temperature of 40°C to prepare a thick sheet. Simultaneous biaxial stretching is performed at 155°C, with a longitudinal and transverse stretch ratio of 3.0:1. Heat setting is carried out at 220°C for 8 seconds; cooling and winding are performed; and bags are made under heat-sealing conditions of 210°C, 0.4 MPa pressure, and 1.5 seconds.
[0028] Performance testing and comparative analysis: The prepared oven bags were placed together with two comparative products in a 220℃ constant temperature forced-air oven for 60 minutes. The key performance comparison is shown in the table below: Table 1: Comparison Test of High Temperature Resistance and Key Indicators Test Project Test methods / standards Embodiments of the present invention Comparative Example 1 (PET / PA / CPP composite film) Comparative Example 2 (Single-layer PA6 film) Test Conclusion High temperature appearance Observe with the naked eye after 220℃ for 60 minutes. No obvious deformation, blistering, or melt-through. Severe deformation, inner layers melted and stuck together Softening, collapsing, localized rupture This invention has the best stability Heat shrinkage rate (%) GB / T 12027-2004 Vertical dimension: 3.2 mm; Horizontal dimension: 2.8 mm >15 (Vertical) 18.5 (Vertical) The dimensional stability of this invention is significantly better than that of the comparative example. Tensile strength retention rate (%) GB / T 1040.3-2006 Vertical: 89 Horizontal: 87 Unable to measure (layered melting) <40 This invention exhibits the highest retention rate of mechanical properties after high temperature. Puncture strength retention rate (%) GB / T 10004-2008 82 Untested (Destroyed) ≈30 The present invention maintains good puncture resistance. Food safety (sensory perception) Smell after high temperature No odor It has a distinct chemical odor. Slight plastic smell The pure nylon system of this invention is the safest. Material structure and environmental friendliness Component analysis Pure PA, no adhesive, single material PET / PA / CPP composite, containing adhesive Single PA6 material This invention has the simplest structure and is the most environmentally friendly. Conclusion: The pure nylon oven bag prepared by this invention exhibits stability, safety and reliability far exceeding those of traditional composite films and ordinary single-layer nylon films at a high temperature of 220℃.
[0029] In some other embodiments of the present invention, a high-temperature resistant pure nylon oven bag includes a bag body made of a pure nylon multilayer co-extruded film by heat sealing, a pure nylon sealing zipper provided at the opening of the bag body, and a pure nylon vent valve provided on one side of the bag body. This embodiment provides an example of the material preparation used for the pure nylon multilayer co-extruded film. The high-temperature resistant polyamide copolymer inner layer 300 has a thickness of 0.03-0.05 mm and is composed of 45-55 parts of a low-temperature adaptable pure nylon substrate, 4-6 parts of a pure nylon toughening modifier, and 1-2 parts of a pure nylon antioxidant. The low-temperature adaptable pure nylon substrate is composed of PA610, PA1010, and modified PA6 (pure nylon itself modified) in a weight ratio of 3:3:2; the pure nylon toughening modifier is PA12 elastomer, and the pure nylon antioxidant is a nylon-based antioxidant. The high-temperature resistant polyamide copolymer inner layer 300 comes into direct contact with food and uses a low-temperature compatible pure nylon compound system. It has good high-temperature resistance, food compatibility, and breathability. It has no odor or release of harmful substances at a high temperature of 220℃, and allows a small amount of gas to pass through to avoid excessive pressure inside the bag causing rupture. It also has a certain degree of oil resistance to prevent oil from penetrating into the middle layer and affecting the high-temperature resistance. The proportions of each pure nylon component have been optimized to improve compatibility with the middle high-temperature resistant pure nylon core layer.
[0030] In some embodiments, the high-strength polyamide interlayer 200 has a thickness of 0.06-0.09 mm, and is composed of 60-70 parts of high-temperature resistant pure nylon substrate, 8-12 parts of pure nylon high-temperature resistant reinforcing agent, and 5-7 parts of pure nylon compatibilizer. The high-temperature resistant pure nylon substrate is a blend of PA46 and PA9T in a weight ratio of 4:3; the pure nylon high-temperature resistant reinforcing agent is a nylon-based reinforcing agent with a particle size of 120-160 mesh; and the pure nylon compatibilizer is a PA6 / PA46 grafted compatibilizer. The high-strength polyamide intermediate layer 200 is the core high-temperature resistant layer, which adopts a high-proportion high-temperature resistant pure nylon composite system. It mainly achieves long-term high-temperature resistance at 220℃, and can withstand continuous baking at 220℃ for 4 hours without deformation or damage. At the same time, it has excellent mechanical properties, which play a supporting and connecting role between the inner and outer layers, prevent the penetration of oil and soup, regulate the gas flow speed in the bag, and prevent food from spoiling due to lack of oxygen.
[0031] In some embodiments, the high-melting-point polyamide outer layer 100 has a thickness of 0.04-0.06 mm. The high-melting-point polyamide outer layer 100 is composed of 50-60 parts of oil-resistant pure nylon substrate, 3-5 parts of pure nylon oil-resistant modifier, and 2-4 parts of pure nylon abrasion-resistant agent. The oil-resistant pure nylon substrate is a blend of PA610, PA12, and PA1010 in a weight ratio of 4:2:4. The pure nylon oil-resistant modifier is a PA610 / PA12 grafted oil-resistant modifier, and the pure nylon abrasion-resistant agent is a nylon-based abrasion-resistant agent. The high-melting-point polyamide outer layer 100, using an oil-resistant pure nylon blend system, possesses excellent high-temperature resistance, abrasion resistance, tear resistance, and oil resistance. It protects the bag from external friction and impact damage, further enhancing the bag's oil resistance and sealing performance, preventing external impurities from entering the bag, and exhibits certain high-temperature stability, remaining unshrinked and undeformed at 220°C.
[0032] In some embodiments, the opening of the bag is provided with a pure nylon sealing zipper. The pure nylon sealing zipper is made of high-temperature resistant pure nylon material and can withstand 220°C high temperature simultaneously with the bag body without deformation or damage. It replaces the existing conventional sealing structure, provides better sealing effect, and can be resealed, making it convenient to add seasonings or check the baking status of food midway. The overall thickness of the bag body is 0.13-0.20mm, tensile strength ≥28MPa, elongation at break ≥260%, tear strength ≥11kN / m, shrinkage rate ≤1.8% at 220°C, oil resistance grade ≥4, excellent sealing performance, no leakage under 0.1MPa pressure, and can fully meet the requirements of 220°C high-temperature baking, air fryer baking, microwave heating and high-temperature sterilization of meat, baked goods, vegetables, etc. In some embodiments, a pure nylon breathable valve is provided on one side of the bag body. The pure nylon breathable valve is made of high-temperature resistant pure nylon material, which can withstand temperatures up to 220°C. It can automatically adjust the pressure inside the bag body to prevent the gas inside the bag from expanding and causing rupture during high-temperature baking. The surface of the bag body is printed with pure nylon-compatible high-temperature resistant ink markings, such as high-temperature resistance up to 220°C, odorless, non-migrating, etc., indicating the operating temperature range and precautions for user convenience.
[0033] The preparation of a high-temperature resistant pure nylon oven bag using the above-disclosed embodiments includes the following steps: Step 1: Raw material pretreatment: Mix the low-temperature adaptable pure nylon substrate, high-temperature resistant pure nylon substrate, and oil-resistant pure nylon substrate separately. Dry the low-temperature adaptable pure nylon substrate and the oil-resistant pure nylon substrate at 70-80℃ for 3-4 hours, and dry the high-temperature resistant pure nylon substrate at 80-90℃ for 4-5 hours, until the moisture content is reduced to ≤5%. Dry the remaining pure nylon raw materials at 60-70℃ for 2-3 hours. The high-temperature resistant reinforcing agent for pure nylon is dispersed for 10-15 minutes before use. Step 2: Preparation of pure nylon substrate granules for each layer: Take the pretreated raw materials according to the corresponding weight proportions, mix them evenly, and then feed them into a twin-screw nylon extruder for extrusion granulation. Cool and seal for later use; the extrusion temperature of the inner layer is 210-230℃ and the speed is 300-350r / min, the extrusion temperature of the middle layer is 230-250℃ and the speed is 350-400r / min, and the extrusion temperature of the outer layer is 220-240℃ and the speed is 300-350r / min. Step 3: Three-layer pure nylon synergistic composite film formation: Pour the pure nylon substrate particles of each layer into the corresponding hopper of the three-layer pure nylon composite extruder, adjust the extrusion thickness of each layer, control the extrusion speed to 0.5-0.9 m / min, and adopt a three-stage layering and shaping process, shaping at 180-190℃ for 10-15 minutes, 200-210℃ for 8-12 minutes, and 170-180℃ for 10-15 minutes in sequence to obtain a three-layer pure nylon composite substrate film with a moisture content ≤3%; Step 4: Bag preparation: Cut the composite substrate film into rectangular sheets, weld on pure nylon breathable valves, heat seal the two sides and bottom edge at 180-190℃ and 0.4-0.5MPa to form the bag body prototype, then weld on pure nylon sealing zippers, and after UV sterilization for 6-10 minutes, print, inspect, and package to obtain the finished product. Step 5: Post-processing: After crushing the pure nylon scraps generated during the preparation process, add them to the preparation of the outer pure nylon substrate particles at a ratio not exceeding 10% for recycling.
[0034] In some embodiments of the present invention, a method for preparing a high-temperature resistant pure nylon oven bag is also disclosed, comprising the following steps: S1. Raw material drying: The polyamide resin particles of the outer layer, middle layer and inner layer are vacuum dried at 100-120℃ for 6-8 hours to make their moisture content less than 500ppm; S2. Multi-layer co-extrusion casting: Multiple single-screw extruders are used to co-extrude and cast each layer of material, with an extrusion temperature gradient of 260℃-300℃; the extrusion temperature gradient from the feeding section to the die head is 260℃-290℃-300℃-295℃-290℃ (die head). S3. Biaxial stretching: The cast sheet is simultaneously biaxially stretched, with a stretching ratio of 2.5-3.5:1 in both the longitudinal and transverse directions; S4. Heat setting: The stretched film is heat-set at 210℃-230℃ under tension; S5. Cool and rewind to obtain a pure nylon multilayer co-extruded film; S6. Bag making: Cut the rolled film into sections and heat seal three or four sides under the conditions of heat sealing temperature of 200℃-220℃, pressure of 0.3-0.5MPa, and time of 1-2 seconds to obtain oven bags.
[0035] In some embodiments, in step S2, the die head gap of the casting process is 0.8-1.2 mm, and the casting roller temperature is 30-50°C.
[0036] In some embodiments, in step S3, the temperature of the biaxial stretching is controlled within a range of 15-25°C lower than the melting point of the polyamide resin used.
[0037] In step S4, the heat setting process takes 5-10 seconds.
[0038] In step S6, the heat sealing conditions are: pressure 0.3-0.5MPa, time 1-2 seconds.
[0039] With the increasing popularity of air fryers and high-temperature ovens, the demand for heat-resistant cooking bags is growing. Existing heat-resistant oven bags suffer from the following main problems: water vapor generated by food inside cannot escape at high temperatures, causing the bag to swell violently and risk bursting; steam surrounding the food also affects its crispness. While a few holes are pre-drilled in the bag for venting, these holes open at the beginning of cooking, leading to excessive heat loss and food drying out. Furthermore, the venting volume cannot be dynamically adjusted according to internal pressure, resulting in limited functionality.
[0040] Therefore, in some embodiments disclosed in this invention, a plurality of dynamic air-guiding microstructures 400 are provided on the inner surface of the bag body; the dynamic air-guiding microstructure 400 includes an elastic micro-dome 410 formed by a thin film body and protruding into the bag space, and a functional weak area 411 with reduced thickness located at the top of the micro-dome; at room temperature or low temperature, the functional weak area 411 is in a closed state, keeping the bag sealed; when the temperature and vapor pressure inside the bag rise to a set threshold, the functional weak area 411 softens under heat and expands or ruptures outward elastically under the action of internal vapor pressure, forming a micron-sized air-guiding hole or air-guiding gap that allows vapor to pass through but restricts liquid leakage; as the internal pressure decreases, the elastic micro-dome 410 can generate a certain rebound, thereby adjusting the size of the air-guiding channel or achieving secondary sealing.
[0041] In some embodiments, the dynamic air-guiding microstructures 400 are distributed in an array on the inner surface, with a distribution density of 10-100 per cm².
[0042] In some embodiments, the thickness of the functionally weak region 411 is 20%-50% of the thickness of the film body. In some embodiments, the functionally weak region 411 is formed through a thickness differentiation process during laser pre-etching, local pressing, or co-extrusion. In some embodiments, the heat distortion temperature of the functionally weak region 411 is 10-40°C lower than that of the film body.
[0043] In some embodiments, the present invention also discloses a method for preparing the high-temperature resistant pure nylon oven bag with dynamic air-guiding function, comprising the following steps: S1. Raw material drying: The polyamide resin particles of the outer layer, middle layer and inner layer are vacuum dried at 100-120℃ for 6-8 hours to make their moisture content less than 500ppm; S2. Multi-layer co-extrusion casting: Multiple single-screw extruders are used to co-extrude and cast each layer of material, with an extrusion temperature gradient of 260℃-300℃; the extrusion temperature gradient from the feeding section to the die head is 260℃-290℃-300℃-295℃-290℃ (die head). S3. Biaxial stretching: The cast sheet is simultaneously biaxially stretched, with a stretching ratio of 2.5-3.5:1 in both the longitudinal and transverse directions; S4: Dynamic air-conducting microstructure 400 forming: On one surface of the biaxially oriented film, a heated embossing roller with micro-convex molds is used to perform localized hot embossing at a temperature of 140-170°C, which is below the melting point of the film but above its glass transition temperature, in combination with specific pressure and contact time. S5: High-temperature heat setting: The embossed film is heat-set at a high temperature of 210-230℃ for 5-15 seconds in a tenter frame, and then cooled and wound up. S6. Bag making: Cut the rolled film into sections and heat seal three or four sides under the conditions of heat sealing temperature of 200℃-220℃, pressure of 0.3-0.5MPa, and time of 1-2 seconds to obtain oven bags.
[0044] In step S4 above, the temperature of the localized hot embossing is 140-170℃. The micro-convex mold of the embossing roller locally presses down and thins the film, forming the functionally weak area 411. At the same time, the film material around the micro-convex mold is squeezed and cooled to solidify into an outwardly convex elastic micro-dome 410 structure. By controlling the temperature and pressure of the embossing roller and the geometry of the micro-convex mold, such as hemispherical or conical, the thickness of the functionally weak area 411 and the elasticity of the micro-dome can be precisely controlled. In step S5 above, the temperature of the high-temperature heat setting is 210-230℃.
[0045] The microstructure activates only when the internal temperature and pressure reach a threshold, such as when food produces a large amount of steam, enabling on-demand venting. This effectively prevents the bag from over-inflating or even bursting, while also minimizing heat and moisture loss during the initial stages of cooking, optimizing the cooking result for a crispy exterior and tender interior. The venting function is achieved through a physical structure, eliminating the need for complex electronic components or external valves. The flexible micro-dome 410 design provides pressure buffering and a degree of self-adjustment, ensuring high reliability. Integrating the microstructure molding process with the biaxial stretching process chain, achieved through localized hot stamping, results in high production efficiency, controllable costs, and facilitates large-scale deployment.
[0046] Following steps S1-S4 above, a biaxially oriented film with a thickness of approximately 25 μm is prepared. A steel heated embossing roller with a hemispherical micro-convex mold array on its surface is used. The hemispheres have a diameter of 100 μm and a height of 30 μm. The embossing roller temperature is set to 155 °C, and continuous embossing is performed on the inner surface of the film. After embossing, the film forms an array of micro-domes, with a thickness of approximately 8 μm in the thinnest area at the top and a film body thickness of 25 μm. The film is then heat-set at 225 °C for 8 seconds, followed by slitting and heat-sealing to produce 20 cm * 30 cm flat-bottomed stand-up pouches.
[0047] Performance testing: 1. Dynamic air conduction test: 100ml of water was injected into the bag and sealed, then placed in an air fryer preheated to 200℃. Observation revealed that the bag slightly inflated during the initial cooking stage, but no air was released. After approximately 3 minutes, as the internal steam pressure increased, multiple microstructures on the bag surface opened, generating a fine mist that was sprayed out. The bag's inflation level remained at a low to medium level, without any severe bulging. After cooking, the bag returned to its flat state.
[0048] 2. Temperature resistance and strength test: The bag was placed in a 220℃ oven for 30 minutes without shrinkage or melting, and the heat-sealed edges remained intact. The initial heat distortion temperature (TMA method) of the film reached 235℃.
[0049] 3. Comparative experiment: Compared with commercially available sealed composite oven bags of the same size, under the same cooking conditions, the commercially available bags inflate like balloons within 5 minutes, posing a risk of bursting, while the product of this invention always maintains a controllable shape.
[0050] Conclusion: This invention, through innovative design of a dynamic air-guiding microstructure 400 in product structure and innovative adoption of local hot embossing technology integrated with biaxial stretching process, successfully prepared a pure nylon high-temperature oven bag that can intelligently respond to internal temperature and pressure, automatically adjust exhaust, effectively prevent bulging, and is environmentally friendly.
[0051] The specific embodiments disclosed in this invention fall within the scope of protection of the claims of this invention, and are specific subordinate implementations of the characteristic parts of this invention. The protection content of the specific embodiments is merely an explanation of the scope of protection of the claims of this invention, and the scope of protection of this invention is not limited to the protection content of the specific embodiments. The protection content of the specific embodiments should not be construed as a limitation on the scope of protection of the claims of this invention. All product structural connection relationships falling within the scope of protection of this invention are also within the scope of protection of this invention. Conventional technical improvements to the structure of product components without departing from the essence of protection of this invention, such as the improvements to the structure of some parts of the product as described in the specific embodiments of this invention, will also fall within the essence of protection of this invention.
Claims
1. A high-temperature resistant pure nylon oven bag, characterized in that: The bag body is made of pure nylon multilayer co-extruded film through heat sealing. The pure nylon multilayer co-extruded film includes a high-melting-point polyamide outer layer, a high-strength polyamide intermediate layer, and a high-temperature resistant polyamide copolymer inner layer stacked sequentially. The pure nylon multilayer co-extruded film does not contain an adhesive resin layer. The high-melting-point polyamide outer layer has a melting point of 250℃-265℃, the high-strength polyamide intermediate layer has a relative viscosity of 3.5-4.2, and the high-temperature resistant polyamide copolymer inner layer has a melting point of not less than 220℃.
2. The high-temperature resistant pure nylon oven bag according to claim 1, characterized in that: The high-melting-point polyamide outer layer is selected from one of PA6T / 66, PA9T or PA10T or a copolymer thereof; The high-strength polyamide intermediate layer is PA6 or PA66; the high-temperature resistant polyamide copolymer outer layer is PA6 / 66 copolymer or PA6 / 12 copolymer.
3. The high-temperature resistant pure nylon oven bag according to claim 1, characterized in that: The inner layer of the high-temperature resistant polyamide copolymer has a thickness of 0.03-0.05 mm. The inner layer of the high-temperature resistant polyamide copolymer is made of 45-55 parts of low-temperature adaptable pure nylon substrate, 4-6 parts of pure nylon toughening modifier, and 1-2 parts of pure nylon antioxidant. The low-temperature adaptable pure nylon substrate is made of PA610, PA1010, and modified PA6 of pure nylon itself in a weight ratio of 3:3:
2. The pure nylon toughening modifier is PA12 elastomer, and the pure nylon antioxidant is a nylon-based antioxidant.
4. The high-temperature resistant pure nylon oven bag according to claim 1, characterized in that: The high-strength polyamide interlayer has a thickness of 0.06-0.09 mm. It is composed of 60-70 parts of high-temperature resistant pure nylon substrate, 8-12 parts of high-temperature resistant pure nylon reinforcing agent, and 5-7 parts of pure nylon compatibilizer. The high-temperature resistant pure nylon substrate is a blend of PA46 and PA9T in a weight ratio of 4:
3. The high-temperature resistant pure nylon reinforcing agent is a nylon-based reinforcing agent with a particle size of 120-160 mesh. The pure nylon compatibilizer is a PA6 / PA46 grafted compatibilizer.
5. The high-temperature resistant pure nylon oven bag according to claim 1, characterized in that: The high-melting-point polyamide outer layer has a thickness of 0.04-0.06 mm. The high-melting-point polyamide outer layer is composed of 50-60 parts of oil-resistant pure nylon substrate, 3-5 parts of pure nylon oil-resistant modifier, and 2-4 parts of pure nylon wear-resistant agent. The oil-resistant pure nylon substrate is composed of PA610, PA12, and PA1010 in a weight ratio of 4:2:
4. The pure nylon oil-resistant modifier is a PA610 / PA12 grafted oil-resistant modifier, and the pure nylon wear-resistant agent is a nylon-based wear-resistant agent.
6. The high-temperature resistant pure nylon oven bag according to claim 1, characterized in that: It also includes a dynamic air-guiding microstructure disposed on the inner surface of the bag body; the dynamic air-guiding microstructure includes an elastic micro-dome formed by the film body and protruding into the bag space, and a thinned functional weak area located at the top of the micro-dome; the functional weak area is configured such that: at room temperature or low temperature, the functional weak area is in a closed state to keep the bag sealed; when the temperature and vapor pressure inside the bag rise to a set threshold, the functional weak area softens under heat and elastically expands or ruptures outward under the action of internal vapor pressure, forming a micron-sized air-guiding hole or air-guiding gap that allows vapor to pass through but restricts liquid leakage.
7. The high-temperature resistant pure nylon oven bag according to claim 6, characterized in that: The dynamic air-guiding microstructures are distributed in an array on the inner surface, with a distribution density of 10-100 per cm².
8. A high-temperature resistant pure nylon oven bag according to claim 6, characterized in that: The thickness of the functionally weak area is 20%-50% of the thickness of the film body, and the heat distortion temperature of the functionally weak area is 10-40℃ lower than that of the film body.
9. A method for preparing a high-temperature resistant pure nylon oven bag as described in any one of claims 1-8, characterized in that: Includes the following steps: S1. Raw material drying: Dry the outer, middle and inner layers of polyamide resin particles separately until the moisture content is less than 500 ppm; S2. Multi-layer co-extrusion casting: Multiple single-screw extruders are used to co-extrude and cast each layer of material, with an extrusion temperature gradient of 260℃-300℃; the die gap of the casting process is 0.8-1.2mm, and the casting roller temperature is 30-50℃; S3. Biaxial stretching: The cast sheet is simultaneously biaxially stretched, with a stretching ratio of 2.5-3.5:1 in both the longitudinal and transverse directions; the biaxial stretching temperature is controlled within a range of 15-25°C lower than the melting point of the polyamide resin used. S4. Heat setting: The stretched film is heat-set at 210℃-230℃ under tension; the heat setting time is 5-10 seconds. S5. Cool and rewind to obtain a pure nylon multilayer co-extruded film; S6. Bag making: The film is heat-sealed at 200℃-220℃, wherein the heat-sealing conditions are: pressure 0.3-0.5MPa, time 1-2 seconds.
10. The method for preparing a high-temperature resistant pure nylon oven bag according to claim 9, characterized in that: It also includes a dynamic air-guiding microstructure forming step located between the biaxial stretching and thermoforming steps. The dynamic air-guiding microstructure forming step includes using a heated embossing roller with micro-convex molds on one surface of the biaxially stretched film, at a temperature of 140-170°C, which is below the melting point of the film but above its glass transition temperature, in combination with specific pressure and contact time, to perform localized hot embossing.