A retort-resistant anticorrosion aluminum-plastic composite packaging bag and a preparation method thereof

Abstract

The application provides a kind of boiling-resistant anticorrosion aluminium plastic composite packaging bag and its preparation method.The aluminium plastic composite packaging bag is sequentially stacked from outside to inside: polyester film layer, ink layer, first adhesive layer, aluminium foil layer, second adhesive layer, polyamide film layer, third adhesive layer and modified polyolefin heat-sealing inner layer;The ink layer is directly compounded on the inner surface of the polyester film layer, the aluminium foil layer is bonded with the ink layer through the first adhesive layer, the polyamide film layer is bonded with the aluminium foil layer through the second adhesive layer, and the modified polyolefin heat-sealing inner layer is bonded with the polyamide film layer through the third adhesive layer.The application provides excellent oxygen, water vapor and light barrier properties through the composite structure of the aluminium foil layer and the polyester film layer, the polyamide film layer and the modified polyolefin heat-sealing inner layer;The modified heat-sealing inner layer further blocks the migration of flavor substances such as spices, ensuring that the original flavor of the sauce does not lose and does not smell.

Description

Technical Field

[0001] This invention belongs to the field of packaging bag material technology, and in particular relates to a heat-resistant and corrosion-resistant aluminum-plastic composite packaging bag and its preparation method. Background Technology

[0002] Sauces (such as hot pot base, curry sauce, and meat seasoning) typically require high-temperature, high-pressure sterilization (e.g., boiling or steaming at 121°C for 30 minutes) to extend their shelf life. Aluminum-plastic composite packaging bags, due to their good mechanical strength, are widely used for packaging meat sauces, tomato sauces, hot pot bases, and high-oil, high-salt sauces. Currently, to ensure the commercial sterility of sauces and extend their shelf life, the industry generally uses a 121°C high-temperature, high-pressure water bath sterilization method (usually for 30 minutes).

[0003] To meet this sterilization process, commercially available aluminum-plastic packaging bags typically employ a composite structure of "polyester (PET) / aluminum foil (AL) / heat-sealable layer (CPP) or polyester (PET) / aluminum foil (AL) / polypropylene film (RCPP)". However, traditional sauce packaging bags have the following prominent problems in practical use:

[0004] 1) During the high-temperature cooking process at 121℃, the interlayer adhesives of conventional aluminum-plastic packaging bags are prone to hydrolysis and aging, resulting in a significant decrease in peel strength; the polypropylene (CPP) heat-sealing layer is prone to softening and shrinking at high temperatures, causing a decrease in heat-sealing strength or even cracking of the seal. After cooking at 121℃ for 30 minutes, the interlayer peel strength of many products decreased by more than 50%, and the heat-sealing strength decreased by more than 30%, which cannot meet the requirements for multiple or long-term sterilization.

[0005] 2) Conventional aluminum-plastic packaging bags have poor resistance to the corrosive effects of sauces. Sauces contain various corrosive media such as oils (≥30%), salt (3%~8%), organic acids (pH 3.5~5.5), and spice essential oils. The inner layer material (CPP) of existing packaging is prone to the following problems after prolonged contact with these media: oil penetration leading to decreased interlayer adhesion; acidic substances eroding the adhesive layer and aluminum foil, causing "white spots" or "delamination"; essential oil components in spices extracting from the inner layer additives, causing flavor adsorption or off-odor migration; and excessive solvent residues, posing a food safety hazard.

[0006] 3) Sauces often contain hard ingredients such as chili seeds, crushed Sichuan peppercorns, ginger and garlic granules, and bone fragments. These particles are highly susceptible to puncturing the inner layer of the packaging bag during packaging, sterilization (high temperature and pressure cause the contents to expand), and transportation, leading to pinhole leakage. Once damage occurs, not only will the contents leak out, but secondary contamination will also occur, significantly shortening the shelf life of the entire batch of products. Summary of the Invention

[0007] To address the shortcomings of the prior art, the present invention aims to provide an aluminum-plastic composite packaging bag and its preparation method that achieves excellent high-temperature cooking resistance, resistance to sauce media, puncture resistance, and ensures long-term storage safety and flavor stability through the synergistic design of a multi-layer gradient high-temperature resistant composite structure, a special retortable adhesive system, and a modified media-resistant heat-sealing layer.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A heat-resistant and corrosion-resistant aluminum-plastic composite packaging bag comprises, from the outside to the inside, the following layers stacked together: a polyester film layer, an ink layer, a first adhesive layer, an aluminum foil layer, a second adhesive layer, a polyamide film layer, a third adhesive layer, and a modified polyolefin heat-sealable inner layer; the ink layer is directly laminated on the inner surface of the polyester film layer, the aluminum foil layer is bonded to the ink layer via the first adhesive layer, the polyamide film layer is bonded to the aluminum foil layer via the second adhesive layer, and the modified polyolefin heat-sealable inner layer is bonded to the polyamide film layer via the third adhesive layer.

[0010] Further, the polyester film layer comprises polyethylene terephthalate resin, antioxidant, slip agent and / or anti-blocking agent, and catalyst residue neutralizer; based on 100 parts by weight of the total weight of the polyester film layer, the polyethylene terephthalate resin is 97-99 parts by weight, the antioxidant is 0.2-0.5 parts by weight, the slip agent and / or anti-blocking agent is 0.3-1.0 parts by weight, and the catalyst residue neutralizer is 0.01-0.1 parts by weight.

[0011] Furthermore, the thickness of the polyester film layer is 10-15 μm, the thickness of the ink layer is 1-5 μm, the thickness of the aluminum foil layer is 6-10 μm, the thickness of the polyamide film layer is 12-18 μm, the thickness of the modified polyolefin heat-sealing inner layer is 80-120 μm, and the thicknesses of the first adhesive layer, the second adhesive layer, and the third adhesive layer are each independently 1-5 μm.

[0012] Furthermore, the polyester film layer is a biaxially oriented polyethylene terephthalate film, and the polyamide film layer is a biaxially oriented polyamide film.

[0013] Furthermore, the first adhesive layer, the second adhesive layer, and the third adhesive layer are two-component reactive polyurethane adhesives resistant to high-temperature boiling at 121°C. The two-component reactive polyurethane adhesive includes a main agent and a curing agent, and the weight ratio of the main agent to the curing agent is 100:10~13. The main agent is a polyester polyurethane polyol, and the curing agent is an aromatic curing agent.

[0014] Furthermore, the aluminum foil layer is a soft aluminum foil, and by weight percentage, the aluminum foil layer is composed of the following components: Fe 0.9% to 1.0%, Si 0.05% to 0.10%, the total weight percentage of Fe and Si is not greater than 1.0%, and the balance is Al and unavoidable impurities, wherein the content of Al is ≥99.0%, the total amount of unavoidable impurities is not more than 0.1%, and the impurities are selected from one or more of Cu, Mn, and Zn.

[0015] Furthermore, the polyamide film layer is a multilayer co-extruded biaxially oriented polyamide film.

[0016] Furthermore, the polyamide film layer has a three-layer co-extruded structure, including a surface layer, a core layer, and an inner layer;

[0017] Based on a total weight of 100 parts by weight, the surface layer is composed of the following components: 2.5 to 3.5 parts of anti-hydrolysis additive, 1.0 to 2.0 parts of magnesium oxide, 1.0 to 2.0 parts of opening agent and slip agent combined, and the balance being polyamide 6 resin;

[0018] Based on 100 parts by weight of the total weight of the core layer, the core layer is composed of the following components: 1.5 to 2.0 parts of anti-hydrolysis additive, and the balance being polyamide 6 resin;

[0019] Based on 100 parts by weight of the total weight of the inner layer, the inner layer is composed of the following components: 1.0 to 1.5 parts of anti-hydrolysis additive, 1.0 to 2.0 parts of opening agent and slip agent combined, and the balance being polyamide 6 resin.

[0020] Furthermore, based on 100 parts by weight of the modified polyolefin heat-sealing inner layer, the modified polyolefin heat-sealing inner layer comprises: 30-40 parts by weight of linear low-density polyethylene, 15-25 parts by weight of metallocene linear low-density polyethylene, 2-5 parts by weight of opening slip agent and anti-blocking agent combined, 0.1-0.5 parts by weight of antioxidant, and the balance being low-density polyethylene.

[0021] This invention also provides a method for preparing a retort-resistant and corrosion-resistant aluminum-plastic composite packaging bag, the method comprising the following steps:

[0022] Step 1) Substrate pretreatment: Corona treatment is performed on the polyester film layer, and passivation or degreasing treatment is performed on the aluminum foil layer to improve surface activity;

[0023] Step 2) Multilayer adhesive coating: Apply two-component reactive polyurethane adhesive to both sides of the aluminum foil layer, and apply two-component reactive polyurethane adhesive to the side of the polyamide film layer facing the heat-sealing inner layer, controlling the dry coating amount to be 3.0~6.0 g / m².

[0024] Step 3) Gradient lamination: Using a dry lamination process, the pretreated polyester film layer is laminated to one side of the aluminum foil layer, then the other side of the aluminum foil layer is laminated to the polyamide film layer, and finally the adhesive-coated side of the polyamide film layer is laminated to the modified polyolefin heat-sealing inner layer at a temperature of 50℃~80℃ and a pressure of 0.3~0.6 MPa.

[0025] Step 4) Segmented curing: A gradient heating curing process is adopted, first curing at 35℃~45℃ for 12~24 hours, and then curing at 55℃~65℃ for 48~72 hours to eliminate composite stress;

[0026] Step 5) Molding and Inspection: After slitting, bag making, and performance testing, the packaging bags are obtained.

[0027] This invention also discloses a method for preparing a retort-resistant and corrosion-resistant aluminum-plastic composite packaging bag.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The aluminum-plastic composite packaging bag of the present invention comprises, from the outside to the inside, layers of: a polyester film layer, an ink layer, a first adhesive layer, an aluminum foil layer, a second adhesive layer, a polyamide film layer, a third adhesive layer, and a modified polyolefin heat-sealing inner layer. The ink layer is directly laminated onto the inner surface of the polyester film layer. The aluminum foil layer is bonded to the ink layer via the first adhesive layer. The polyamide film layer is bonded to the aluminum foil layer via the second adhesive layer. The modified polyolefin heat-sealing inner layer is bonded to the polyamide film layer via the third adhesive layer. The composite structure of the aluminum foil layer, polyester film layer, polyamide film layer, and modified polyolefin heat-sealing inner layer provides excellent oxygen, water vapor, and light barrier properties. The modified heat-sealing inner layer further prevents the migration of flavor substances such as spices, ensuring that the original flavor of the sauce is not lost or mixed with other flavors. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the heat-resistant and corrosion-resistant aluminum-plastic composite packaging bag of the present invention.

[0031] In the figure, there are polyester film layer 1, ink layer 2, first adhesive layer 3, aluminum foil layer 4, second adhesive layer 5, polyamide film layer 6, third adhesive layer 7, and modified polyolefin heat-sealing inner layer 8. Detailed Implementation

[0032] To better illustrate the objectives, technical solutions, and advantages of this invention, the following embodiments are provided. Obviously, the following embodiments are only a part of the embodiments of this invention, and not all of them; it should be understood that the embodiments of this invention are only used to illustrate the technical effects of this invention, and not to limit the scope of protection of this invention.

[0033] like Figure 1As shown, this invention provides a heat-resistant and corrosion-resistant aluminum-plastic composite packaging bag. The aluminum-plastic composite packaging bag comprises, from the outside to the inside, the following layers stacked sequentially: a polyester film layer 1, an ink layer 2, a first adhesive layer 3, an aluminum foil layer 4, a second adhesive layer 5, a polyamide film layer 6, a third adhesive layer 7, and a modified polyolefin heat-sealing inner layer 8. The ink layer 2 is directly laminated onto the inner surface of the polyester film layer 1. The aluminum foil layer 4 is bonded to the ink layer 2 via the first adhesive layer 3. The polyamide film layer 6 is bonded to the aluminum foil layer 4 via the second adhesive layer 5. The modified polyolefin heat-sealing inner layer 8 is bonded to the polyamide film layer 6 via the third adhesive layer 7. This invention provides excellent oxygen, water vapor, and light barrier properties through the composite structure of the aluminum foil layer 4, the polyester film layer 1, the polyamide film layer 6, and the modified polyolefin heat-sealing inner layer 8. The modified heat-sealing inner layer further prevents the migration of flavor substances such as spices, ensuring that the original flavor of the sauce is not lost or mixed with other flavors. Employing a seven-layer gradient high-temperature resistant composite structure combined with a specialized retort-resistant adhesive system, the outer polyester film layer 1 provides a heat-resistant skeleton support, the middle aluminum foil layer 4 forms a dense barrier, and the inner polyamide film layer 6 enhances the interlayer bonding force, thereby improving the overall puncture resistance and tear resistance of the aluminum-plastic composite packaging bag. It ensures no puncture damage or leakage during sterilization and transportation, solving the problem of damage to packaging hard granules in sauces. This achieves a synergistic improvement in three major properties: high-temperature resistance, sauce medium resistance, and puncture resistance, addressing the technical challenge that traditional aluminum-plastic composite packaging bags cannot simultaneously adapt to complex sauce media, high-temperature retort sterilization, and hard particle protection.

[0034] In a specific implementation, the polyester film layer 1 comprises polyethylene terephthalate resin, antioxidant, slip agent and / or anti-blocking agent, and catalyst residue neutralizer; based on 100 parts by weight of the total weight of the polyester film layer 1, the polyethylene terephthalate resin is 97-99 parts by weight, the antioxidant is 0.2-0.5 parts by weight, the total weight of slip agent and / or anti-blocking agent is 0.3-1.0 parts by weight, and the catalyst residue neutralizer is 0.01-0.1 parts by weight. The intrinsic viscosity (IV) of the polyethylene terephthalate resin is 0.64~0.72 dL / g. The antioxidant is a mixture of hindered phenolic antioxidants and phosphite antioxidants, wherein the weight ratio of hindered phenolic antioxidants to phosphite antioxidants is (1~5):(1~5). The slip / anti-blocking agent is selected from at least one of silica, talc, and erucamide. The neutralizing agent is phosphoric acid. In this embodiment, the slip agent is preferably erucamide, and the anti-blocking agent is preferably silica with an average particle size of 2~4 μm.

[0035] The polyester film layer 1 has a thickness of 10-15 μm, the ink layer 2 has a thickness of 1-5 μm, the aluminum foil layer 4 has a thickness of 6-10 μm, the polyamide film layer 6 has a thickness of 12-18 μm, the modified polyolefin heat-sealing inner layer 8 has a thickness of 80-120 μm, and the first adhesive layer 3, the second adhesive layer 5, and the third adhesive layer 7 each have an independent thickness of 1-5 μm. The aluminum-plastic composite packaging bag adopts a thickness gradient design (thinner outer layer, thicker inner layer), which is beneficial to the balance between heat-sealing strength and overall flexibility.

[0036] The polyester film layer 1 of this invention is a biaxially oriented polyethylene terephthalate (BOPET) film, and the polyamide film layer 6 is a biaxially oriented polyamide film. The polyester film is biaxially oriented polyethylene terephthalate (BOPET), which can withstand temperatures up to 120°C or higher; the polyamide film is biaxially oriented polyamide (BOPA), whose amide groups in the molecular chain do not hydrolyze under cooking conditions, thus maintaining mechanical properties; the modified polyolefin heat-sealing inner layer 8 is a modified polyethylene layer (PE-C layer), which achieves its anti-corrosion function by adding anti-media masterbatch or using comonomers (such as acrylic acid and maleic anhydride grafting).

[0037] The first adhesive layer 3, the second adhesive layer 5, and the third adhesive layer 7 of this invention are two-component reactive polyurethane adhesives resistant to high-temperature retorting at 121°C. The two-component reactive polyurethane adhesive includes a main agent and a curing agent, with a weight ratio of main agent to curing agent of 100:10~13. The main agent is a polyester polyurethane polyol, and the curing agent is an aromatic curing agent. Using this specialized two-component reactive polyurethane adhesive, the cross-linked structure of the polyurethane adhesive remains intact after retorting at 121°C for 30 minutes, resulting in aluminum-plastic composite packaging bags that are free from delamination, wrinkling, and heat-sealing layer cracking, far superior to conventional retort pouches.

[0038] The aluminum foil layer 4 provided in this invention is a soft aluminum foil. By weight percentage, the aluminum foil layer 4 is composed of the following components: Fe 0.9% to 1.0%, Si 0.05% to 0.10%, the total weight percentage of Fe and Si is not greater than 1.0%, and the balance is Al and unavoidable impurities, wherein the content of Al is ≥99.0%, the total amount of unavoidable impurities is not more than 0.1%, and the impurities are selected from one or more of Cu, Mn, and Zn.

[0039] In practice, the polyamide film layer 6 is a multilayer co-extruded biaxially oriented polyamide film. Specifically, the polyamide film layer 6 has a three-layer co-extruded structure, comprising a surface layer, a core layer, and an inner layer.

[0040] The polyamide film layer has a three-layer co-extruded structure, including a surface layer, a core layer, and an inner layer;

[0041] Based on 100 parts by weight of the total weight of the surface layer, the surface layer is composed of the following components: 2.5 to 3.5 parts of anti-hydrolysis additive, 1.0 to 2.0 parts of magnesium oxide, 1.0 to 2.0 parts of opening agent and slip agent combined, and the balance is polyamide 6 resin;

[0042] Based on 100 parts by weight of the total weight of the core layer, the core layer is composed of the following components: 1.5 to 2.0 parts of anti-hydrolysis additive, and the balance being polyamide 6 resin;

[0043] Based on 100 parts by weight of the total weight of the inner layer, the inner layer is composed of the following components: 1.0 to 1.5 parts of anti-hydrolysis additive, 1.0 to 2.0 parts of opening agent and slip agent combined, and the balance being polyamide 6 resin.

[0044] The modified polyolefin heat-sealing inner layer of the present invention comprises 100 parts by weight of: 30-40 parts by weight of linear low-density polyethylene, 15-25 parts by weight of metallocene linear low-density polyethylene, 2-5 parts by weight of opening slip agent and anti-blocking agent combined, 0.1-0.5 parts by weight of antioxidant, and the balance being low-density polyethylene. The modified polyolefin heat-sealing inner layer 8 exhibits excellent heat-sealing strength, resistance to media penetration, and processing stability, with minimal attenuation of heat-sealing strength after high-temperature retorting. The modified polyolefin heat-sealing inner layer 8 of the present invention improves the dimensional stability of the heat-sealing layer at high temperatures through the synergistic crosslinking of metallocene linear low-density polyethylene and low-density polyethylene. After retorting at 121°C for 30 minutes, the packaging bag shows no delamination, no wrinkling, and no significant attenuation of heat-sealing strength, far superior to conventional retort pouches.

[0045] The aluminum-plastic composite packaging bag of the present invention adopts a dual protection design of modified polyolefin heat-sealing inner layer 8 and aluminum foil barrier protective layer. In the modified polyolefin heat-sealing inner layer 8, the dense molecular chain network formed by metallocene linear low-density polyethylene (mLLDPE) effectively hinders the penetration of oil molecules. Linear low-density polyethylene (LLDPE) provides excellent acid and alkali resistance. The aluminum foil layer 4 acts as an absolute barrier layer to cut off the inward penetration path of the medium.

[0046] The ink layer 2 of this invention comprises a binder, pigment, solvent, and additives. The additives are selected from one or more of dispersants, leveling agents, defoamers, adhesion promoters, waxes, plasticizers, matting agents, antistatic agents, stabilizers, and crosslinking agents. The crosslinking agent can undergo a crosslinking reaction with the binder under ink drying or heating conditions, significantly improving the heat resistance, water resistance, solvent resistance, and cooking resistance of the ink film, thus adapting it to a 121°C high-temperature cooking process. Other additives are used to improve pigment dispersion, leveling, defoaming, adhesion, surface smoothness, flexibility, antistatic properties, and other printability and performance characteristics.

[0047] The ink layer 2 of this invention is a high-temperature resistant retort ink, and its formula is as follows, based on 100 parts by weight of the total ink composition:

[0048] 35 parts of binder (polyurethane resin),

[0049] 12 parts of pigment (heat-resistant organic pigments, such as azo condensates or phthalocyanines).

[0050] Dispersant (high molecular weight polyurethane dispersant) 0.8 parts,

[0051] Leveling agent (polyether-modified polysiloxane) 0.3 parts,

[0052] Defoamer (polysiloxane type) 0.2 parts,

[0053] Adhesion promoter (phosphate-modified acrylate) 1.0 part,

[0054] 0.5 parts of wax (polyethylene wax powder),

[0055] Crosslinking agent (aliphatic polyisocyanate) 1.2 parts,

[0056] The remainder is a mixed solvent (ethyl acetate, isopropanol, and n-propyl ester in a volume ratio of 6:3:1).

[0057] This invention also provides a method for preparing a retort-resistant and corrosion-resistant aluminum-plastic composite packaging bag, the method comprising the following steps:

[0058] Step 1) Substrate pretreatment: Corona treatment is performed on polyester film layer 1, and passivation or degreasing treatment is performed on aluminum foil layer 4 to improve surface activity;

[0059] Step 2) Multilayer adhesive coating: Two-component reactive polyurethane adhesive is coated on both sides of the aluminum foil layer 4, and two-component reactive polyurethane adhesive is coated on the side of the polyamide film layer 6 facing the heat-sealing inner layer, controlling the dry coating amount to be 3.0~6.0 g / m².

[0060] Step 3) Gradient lamination: Using a dry lamination process, the pretreated polyester film layer 1 is laminated to one side of the aluminum foil layer 4, and then the other side of the aluminum foil layer 4 is laminated to the polyamide film layer 6. Finally, the adhesive-coated side of the polyamide film layer 6 is laminated to the modified polyolefin heat-sealing inner layer 8 at a temperature of 50℃~80℃ and a pressure of 0.3~0.6 MPa.

[0061] Step 4) Segmented curing: A gradient heating curing process is adopted, first curing at 35℃~45℃ for 12~24 hours, and then curing at 55℃~65℃ for 48~72 hours to eliminate composite stress;

[0062] Step 5) Molding and Inspection: After slitting, bag making, and performance testing, the packaging bags are obtained.

[0063] The present invention will be further described in detail below through specific embodiments and comparative examples. The following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention.

[0064] I. Specifications of Main Raw Materials

[0065] In the following embodiments:

[0066] The polyethylene terephthalate (PET) resin is of film grade, with an intrinsic viscosity IV of 0.68 dL / g;

[0067] The aluminum foil is a soft aluminum foil;

[0068] Polyamide 6 (PA6) resin is film grade with a relative viscosity of 2.8;

[0069] The melt flow index of low-density polyethylene is 2.0 g / 10min (190℃ / 2.16kg), and its density is 0.924 g / cm³.

[0070] The melt index of linear low-density polyethylene is 2.0 g / 10min (190℃ / 2.16kg), and the density is 0.918 g / cm³.

[0071] The melt index of metallocene linear low-density polyethylene is 1.0 g / 10min (190℃ / 2.16kg), and the density is 0.918 g / cm³.

[0072] The main component of the two-component reactive polyurethane adhesive is polyester polyurethane polyol (75% solid content), and the curing agent is an aromatic curing agent (100% solid content). The weight ratio of the main component to the curing agent can be adjusted within the range of 100:10 to 100:13.

[0073] The antioxidants are hindered phenolic antioxidants and / or phosphite antioxidants;

[0074] Open-type smooth masterbatch uses low-density polyethylene as a carrier and the active ingredient is erucamide (effective content 5%).

[0075] The anti-blocking masterbatch uses low-density polyethylene as a carrier, and the active ingredient is silicon dioxide (effective content 10%).

[0076] The anti-hydrolysis agent is a polymeric carbodiimide;

[0077] The opening agent is silicon dioxide;

[0078] The slip agent is erucamide;

[0079] All other additives without specified specifications are commercially available products commonly used in this field.

[0080] II. Ink Layer 2 Formulation

[0081] The ink layer 2 used in the following examples is a high-temperature resistant retort ink. Based on a total weight of 100 parts by weight, its formulation is as follows:

[0082]

[0083] Ink preparation method: The binder, pigment, dispersant, leveling agent, defoamer, adhesion promoter, waxes, and a portion of the mixed solvent are mixed and dispersed evenly (high-speed dispersion to a fineness ≤15 μm). Then, a crosslinking agent and the remaining solvent are added to adjust the viscosity to the printability range (using a Zahn 3# cup, pore size approximately 3.8 mm, viscosity 15~25 seconds). After filtration, a high-temperature resistant retort ink composition is obtained. The ink's resistance to 121℃ high-temperature retort meets the requirements of this invention.

[0084] Example 1

[0085] This embodiment 1 provides a retort-resistant and corrosion-resistant aluminum-plastic composite packaging bag. The aluminum-plastic composite packaging bag comprises, from the outside to the inside, the following layers stacked sequentially: a polyester film layer 1, an ink layer 2, a first adhesive layer 3, an aluminum foil layer 4, a second adhesive layer 5, a polyamide film layer 6, a third adhesive layer 7, and a modified polyolefin heat-sealing inner layer 8. The specific structure and parameters of each layer are as follows:

[0086] Polyester film layer 1 (PET): Biaxially oriented PET film, 12 μm thick; Formulation (parts by weight): 98 parts PET resin, 0.2 parts hindered phenolic antioxidant, 0.2 parts phosphite antioxidant (total antioxidant 0.4 parts), 0.5 parts silica (slip / anti-blocking agent), 0.05 parts phosphoric acid;

[0087] Ink layer 2: 3 μm thick, prepared according to the "High-Temperature Resistant Cooking Ink Formulation" in this section;

[0088] First adhesive layer 3: thickness 3 μm, the weight ratio of adhesive main agent to curing agent is 100:12;

[0089] Aluminum foil layer 4: 7 μm thick, soft aluminum foil, by weight percentage: Fe 1.0%, Si 0.1%, Al 98.8%, the remainder being unavoidable impurities, the total amount of which does not exceed 0.1%, and the content of each of Cu, Mn, and Zn is ≤0.05%;

[0090] Second adhesive layer 5: Thickness 3 μm, the weight ratio of adhesive main agent to curing agent is 100:12;

[0091] Polyamide film layer 6 (PA): Three-layer co-extruded biaxially oriented BOPA film with a total thickness of 15 μm, wherein the thickness ratio of the surface layer, core layer, and inner layer is 1:2:1; Surface layer formulation (parts by weight): 93 parts PA6 resin, 3 parts anti-hydrolysis additive, 1.5 parts magnesium oxide, and 1.5 parts total of opening agent and slip agent; Core layer formulation: 98.5 parts PA6 resin, and 1.5 parts anti-hydrolysis additive; Inner layer formulation: 97 parts PA6 resin, 1.2 parts anti-hydrolysis additive, and 1.8 parts total of opening agent and slip agent;

[0092] Third adhesive layer 7: Thickness 3 μm, the weight ratio of adhesive main agent to curing agent is 100:12;

[0093] Modified polyolefin heat-sealing inner layer 8: Thickness 100 μm; Formulation (parts by weight): 40 parts low-density polyethylene, 35.8 parts linear low-density polyethylene, 20 parts metallocene linear low-density polyethylene, 3 parts opening slip masterbatch (based on masterbatch, of which the active ingredient is 0.15 parts by weight of erucamide), 1 part anti-blocking masterbatch (based on masterbatch, of which the active ingredient is 0.10 parts by weight of silica), and 0.2 parts hindered phenolic antioxidant.

[0094] Preparation method:

[0095] Step 1) Print ink layer 2 on the inner surface of the PET film, and after drying, perform corona treatment on the printed surface (surface tension ≥ 42 dyn / cm); degrease the aluminum foil;

[0096] Step 2) Coat both sides of the aluminum foil with a two-component polyurethane adhesive, and coat the PA film on the side facing the heat-sealing inner layer with the adhesive. The dry coating amount is 4.5 g / m².

[0097] Step 3) Using a dry lamination process, first laminate the PET ink side with one side of the aluminum foil (lamination roller temperature 60℃, pressure 0.4 MPa), then laminate the other side of the aluminum foil with the PA layer, and finally laminate the PA adhesive side with the modified polyolefin heat-sealing inner layer 8 at 70℃ and 0.5 MPa.

[0098] Step 4) Segmented curing: First, cure at 40℃ for 18 hours, then cure at 60℃ for 60 hours. First, cure at low temperature to allow the adhesive to initially crosslink and slowly release the solvent, and then cure at high temperature to achieve deep crosslinking, so as to avoid the rapid curing at high temperature leading to a surge in solvent residue.

[0099] Step 5) Cut, bag, and test to obtain packaging bag sample S1.

[0100] Example 2

[0101] The difference between Example 2 and Example 1 lies in the adjustment of the thickness of each layer and some formula parameters, as detailed below:

[0102] Polyester film layer 1 (PET): 15 μm thick; the formulation contains 97.5 parts PET resin, 0.15 parts hindered phenolic antioxidant, 0.15 parts phosphite antioxidant (total antioxidant 0.3 parts), 0.8 parts talc (slip / anti-blocking agent), and 0.08 parts phosphoric acid.

[0103] Ink layer 2: 2 μm thick, prepared according to the "High-Temperature Resistant Cooking Ink Formulation" in this section;

[0104] First adhesive layer 3: thickness 2 μm, the weight ratio of adhesive main agent to curing agent is 100:11;

[0105] Aluminum foil layer 4: 9 μm thick, by weight percentage: Fe 0.95%, Si 0.08%, Al 98.9%, the remainder being unavoidable impurities (total content ≤0.1%).

[0106] Second adhesive layer 5: 2 μm thick, with a weight ratio of adhesive base to curing agent of 100:11;

[0107] Polyamide film layer 6 (PA): Three-layer co-extruded biaxially oriented BOPA film, 18 μm thick, with a thickness ratio of 1:1.5:1 for the three layers; 1.8 parts magnesium oxide in the surface layer formulation; 1.8 parts hydrolysis-resistant additive in the core layer formulation;

[0108] Third adhesive layer 7: 2 μm thick, with a weight ratio of adhesive base to curing agent of 100:11;

[0109] Modified polyolefin heat-sealing inner layer 8: thickness 110 μm; the formulation contains 35 parts low-density polyethylene, 38 parts linear low-density polyethylene, 22 parts metallocene linear low-density polyethylene, 2.5 parts open-slip masterbatch (based on masterbatch, of which the effective ingredient is 0.125 parts by weight of erucamide), 1.5 parts anti-blocking masterbatch (based on masterbatch, of which the effective ingredient is 0.15 parts by weight of silica), and 0.3 parts hindered phenolic antioxidant.

[0110] The preparation method is the same as in Example 1, and sample S2 is obtained.

[0111] Example 3

[0112] The difference between Example 3 and Example 1 is as follows: the PA film is not a three-layer co-extruded structure, but a common biaxially oriented PA6 single-layer film (15 μm thick). This common biaxially oriented PA6 single-layer film is a commercially available common BOPA film, without the addition of anti-hydrolysis additives and magnesium oxide; the ratio of adhesive main agent to curing agent is 100:13, and the dry coating amount is 5.5 g / m²; the thickness of each adhesive layer is 4 μm; the segmented curing conditions are adjusted to 45℃ / 12h and 65℃ / 48h. Ink layer 2 is prepared according to the "High-Temperature Resistant Retorting Ink Formulation" in this section. The remaining parameters are the same as in Example 1, resulting in sample S3.

[0113] VI. Comparative Example 1 (Conventional PET / Al / PA / CPP structure)

[0114] This comparative example provides an aluminum-plastic composite packaging bag with a simulated commercially available conventional structure as a control sample. Its structure from the outside to the inside is as follows: PET film layer (12μm) / ink layer / first adhesive layer / aluminum foil layer (7μm) / second adhesive layer / PA film layer (15μm) / third adhesive layer / ordinary cast polypropylene (CPP) heat-sealing layer (70μm).

[0115] The specific parameters for each layer are as follows:

[0116] PET film layer: 12μm thick, without added antioxidants and slip agents (substrate blank control).

[0117] Ink layer: 3μm thick, with the same formulation and preparation method as in Example 1.

[0118] Aluminum foil layer: 7μm thick, composition same as in Example 1.

[0119] PA film layer: Ordinary biaxially oriented PA6 single-layer film, 15μm thick, without added anti-hydrolysis additives and magnesium oxide.

[0120] Ordinary cast polypropylene (CPP) heat-sealing layer: thickness 70μm, formulation (parts by weight): 100 parts homopolymer polypropylene resin (melt index 7.0 g / 10min, 230℃ / 2.16kg); 0.2 parts hindered phenolic antioxidant (Irganox 1010); 0.3 parts slip agent (erucamide); 0.5 parts antiblocking agent (SiO2). Film is formed by casting method, without adding any metallocene polyethylene or linear low-density polyethylene components.

[0121] Adhesive system: The three-layer adhesive (first, second, and third layers) all use commercially available general-purpose retort-grade two-component polyurethane adhesive. The main component is a polyether-type polyol (75% solids content, hydroxyl value 56 ± 2 mg KOH / g, solvent: ethyl acetate); the curing agent is an aliphatic isocyanate (100% solids content, NCO content 12.0 ± 0.5%, based on trimer HDI). The weight ratio of main component to curing agent is 100:8 (NCO / OH molar ratio is approximately 0.85, lower than the crosslinking density of the example). The dry coating weight is 4.5 g / m².

[0122] Preparation method:

[0123] The conventional dry lamination process is adopted, which involves two steps (first laminating PET / Al, then laminating PA / CPP), with the lamination roller temperature at 60℃ and the pressure at 0.4 MPa.

[0124] The curing process adopts a conventional one-step method: 50℃ × 48 hours (heating to the target temperature in one go, without a low-temperature pre-curing stage).

[0125] Subsequent cutting and bag making were performed in the same manner as in Example 1, resulting in comparative sample D1.

[0126] Comparative Example 2 (insufficient heat seal layer thickness and no segmented curing process)

[0127] Comparative Example 2 uses the exact same seven-layer structure, all interlayer formulations, and adhesive grades as Example 1 (including the PET layer formulation, ink layer, aluminum foil, PA three-layer co-extrusion formulation, and the proportions of each polymer and additive in the modified polyolefin heat-sealing inner layer formulation). However, the following two key process / structural parameters are individually degraded to verify the synergistic necessity of the thickened heat-sealing layer and segmented curing in this invention:

[0128] Structural parameter differences: The thickness of the modified polyolefin heat-sealing inner layer was reduced from 100 μm in Example 1 to 50 μm (this is the conventional thickness of the heat-sealing layer of ordinary packaging bags). Its formulation by weight is exactly the same as that in Example 1 (i.e., 40 parts of low-density polyethylene, 35.8 parts of linear low-density polyethylene, 20 parts of metallocene linear low-density polyethylene, 3 parts of opening slip masterbatch, 1 part of anti-blocking masterbatch, and 0.2 parts of hindered phenolic antioxidant).

[0129] Adhesive differences: Completely identical to Example 1, using a two-component reactive polyurethane adhesive (main component is polyester polyurethane polyol, solid content 75%; curing agent is aromatic curing agent, solid content 100%, NCO content 15.0 ± 0.5%), with a main component to curing agent weight ratio of 100:12. The dry coating weight of the three-layer adhesive is 4.5 g / m².

[0130] Differences in the composite process: The conventional two-step composite process is adopted (first composite PET / Al, then composite PA / heat-sealing layer), with a composite temperature of 60℃ and a pressure of 0.4MPa (the 70℃ / 0.5MPa high-temperature and high-pressure composite process in the third step of Example 1 is omitted).

[0131] Differences in curing process: The conventional one-step curing process is adopted, 50℃ × 48 hours (without segmentation, without low-temperature pre-curing stage).

[0132] The thickness of the remaining layers and the slitting and bag making steps in the preparation process were the same as in Example 1, resulting in comparative sample D2.

[0133] To ensure a clear technical comparison between the process formulation design logic of the two comparative examples and the performance test results in Table 1, the following points are specifically noted:

[0134] Comparative Example 1 (D1) uses a low-crosslinking polyether adhesive (NCO / OH molar ratio of approximately 0.85) and a conventional one-step curing process, combined with a common homopolymer polypropylene (CPP) heat-sealing layer, to simulate and represent the existing technology level of commercially available low-end retort pouches.

[0135] Comparative Example 2 (D2) uses the high-performance polyester adhesive and modified polyolefin heat-sealing layer formulation described in this invention, but only degrades two key parameters: reducing the heat-sealing layer thickness from 100 μm in this invention to a conventional thickness of 50 μm, and replacing the segmented curing process with a conventional one-step curing process. The purpose of this setting is to verify, without eliminating interference from adhesive and material formulations, the irreplaceable role of the claimed technical features of "thickened heat-sealing layer" and "segmented curing" in synergistically improving interlayer peel strength and heat-sealing strength. The performance differences compared to the examples (see Table 1) will visually demonstrate the necessity of these two features in achieving the technical effects of this invention.

[0136] III. Performance Testing and Comparison

[0137] The following performance tests were performed on the packaging bag samples of Examples 1-3 and Comparative Examples 1-2:

[0138] (a) Testing methods

[0139] 1. High-temperature cooking resistance test

[0140] Each sample was prepared into a three-side-seal bag (200mm × 150mm), filled with water (80% fill), and boiled in a high-temperature reverse-pressure cooker at 121℃ for 30 minutes. After boiling, the samples were removed and tested.

[0141] Appearance evaluation: Visually inspect for delamination, wrinkles, bubbles, and white spots;

[0142] Interlayer peel strength: Refer to GB / T 8808-1988 "Test method for peel strength of flexible composite plastic materials", perform T-shaped peeling at a speed of 300 mm / min on a universal tensile testing machine, test the peel force of PET / Al layer (N / 15 mm), and calculate the peel force retention rate after cooking (after cooking / before cooking × 100%).

[0143] Test the T-shaped peel force of the PET / Al layer of the samples before and after cooking. For samples that can be peeled off in a quantitative manner before cooking, calculate the peel force retention rate after cooking (after cooking / before cooking × 100%). For samples where the substrate (PET or aluminum foil) breaks due to excessive adhesive strength before cooking and the interfacial peel value cannot be measured (such as in the embodiments of this invention), the absolute value of the peel force after cooking (N / 15mm) is used as the main evaluation index of cooking resistance, and the state before cooking is recorded as "substrate broken, unable to be quantitatively measured".

[0144] Heat seal strength: Refer to QB / T 2358-1998 "Test method for heat seal strength of plastic film packaging bags", cut a 15mm wide sample at the heat seal area, test the heat seal strength (N / 15mm), and calculate the strength retention rate.

[0145] 2. Sauce-resistant performance test

[0146] A simulated sauce medium was prepared (30% lard, 5% salt, 2% glacial acetic acid, 0.5% garlic oil, with the remainder being water), filled into packaging bags, and steamed at 121℃ for 30 minutes, then stored in a 60℃ constant temperature incubator for 30 days. Testing:

[0147] Appearance: Inspect the inner layer for swelling, discoloration, or delamination;

[0148] Total migration: Referring to GB 31604.8-2021 "National Food Safety Standard for Determination of Total Migration of Food Contact Materials and Articles", 95% ethanol (60℃ / 10 days) was used as the fat simulant to determine the total migration (mg / dm²).

[0149] Residual solvent in the bag: Refer to Clause 6.6.8 of GB / T 10004-2008 "Packaging Plastic Composite Films and Bags - Dry Lamination and Extrusion Lamination" and determine the total residual solvent (mg / m²) by gas chromatography.

[0150] 3. Puncture resistance test

[0151] Referring to Appendix A of GB / T 10004-2008 "Dry Lamination and Extrusion Lamination of Plastic Composite Films and Bags for Packaging", the maximum puncture force (N) was recorded by puncturing the packaging bag film (100 mm in diameter) at a speed of 50 mm / min on a puncture strength testing machine. Separately, samples soaked in simulated sauce medium (cooked at 121℃ for 30 min + stored at 60℃ for 30 days) were tested for leakage after puncture using the dye penetration method (filling the sample bag with red dye, applying a pressure of 0.02 MPa and observing whether dye seeps out).

[0152] 4. Kneading resistance test

[0153] Referring to ASTM F392-23 "Standard Test Method for Flex Durability of Flexible Barrier Materials" (Gelbo method), the uncooked sample was subjected to reciprocating twisting and rubbing (440° twisting and horizontal compression) for 1000 cycles. The number of pinholes was checked using the dye penetration method (in pinholes / m²).

[0154] 5. Barrier performance test: Water vapor transmission rate shall be tested in accordance with GB / T 1037-2021 (cup method) or GB / T 26253-2010 (infrared method); Oxygen transmission rate shall be tested in accordance with GB / T 1038-2022 (differential pressure method) or GB / T 19789-2021 (coulometric method).

[0155] (II) Test Results

[0156] Table 1 compares the performance of each embodiment with that of the comparative example.

[0157]

[0158] Table 1

[0159] Note: The total migration data in Table 1 are test results under 95% ethanol simulant conditions and are only used for relative performance comparison between the embodiments and comparative examples of this invention;

[0160] During the T-type peel test before cooking, the PET / Al interface in Examples 1-3 exhibited extremely high cross-linking density due to the cured adhesive. During peeling, the PET film or aluminum foil substrate fractured before the adhesive layer (fracture force approximately 25.0 N / 15mm), making it impossible to obtain a quantitative value for interfacial peeling. Therefore, it was qualitatively characterized as "substrate fracture." After cooking at 121℃ for 30min, the aluminum foil underwent slight softening due to high-temperature annealing, and the PET molecular chains relaxed under humid heat conditions, causing a slight decrease in the critical value for substrate fracture. This allowed for the measurement of effective interfacial peeling values ​​(as shown in the table above). The absolute value of the peeling force after cooking remained significantly higher than the national standard limit (≥2.0 N / 15mm), and the appearance remained intact, indicating that the adhesive layer itself maintained extremely high adhesive strength both before and after cooking.

[0161] (III) Results Analysis

[0162] As shown in Table 1:

[0163] 1) Regarding high-temperature cooking resistance: The "peel force of the PET / Al layer after cooking" data in Examples 1-3 are the measured absolute values ​​(N / 15mm) after cooking at 121℃ for 30min. Before cooking, due to the extremely high chemical bond strength between the first adhesive layer of this invention and the PET / Al interface, cohesive fracture of the PET film or aluminum foil substrate occurred during the T-shaped peeling process (the substrate broke before the adhesive layer), making it impossible to obtain a quantitative value for interface peeling. Therefore, in the routine performance test in Table 2, "substrate fracture" was used for qualitative characterization. After high-temperature cooking, the aluminum foil substrate underwent slight softening due to the annealing effect, and its tensile strength decreased slightly, allowing the adhesive layer interface to be quantitatively peeled off. The measured data are shown in the table above. The absolute value of the peel force after cooking (≥22.0 N / 15mm) far exceeds the national standard GB / T 10004-2008 requirement of peel force ≥2.0 N / 15mm, which fully demonstrates that the interlayer cooking resistance of the present invention is extremely excellent. Although the absolute value of the peel force of Comparative Example 2 is acceptable, its heat seal strength retention rate is only 63.5%, and the inner layer turns white after being soaked in the medium, indicating that its overall sealing integrity and medium resistance performance are far inferior to those of the example, and cannot meet the long-term safety requirements of sauce packaging.

[0164] 2) Regarding resistance to sauce media: The total migration amount in Examples 1-3 was ≤3.3 mg / dm², far below the national standard limit (10 mg / dm²), and the appearance remained intact after soaking in the medium; while the total migration amount in Comparative Example 1 reached 18.6 mg / dm² (exceeding the standard), and the inner layer swelled and delaminated; the total migration amount in Comparative Example 2 was 9.8 mg / dm² (close to the limit), and the inner layer turned white. This indicates that the modified polyolefin heat-sealing layer of the present invention (containing a compound of metallocene linear low-density polyethylene and linear low-density polyethylene) has excellent resistance to permeation and extraction by oils, acids, and spices.

[0165] 3) Puncture resistance: The puncture resistance of Examples 1-3 is ≥81.5 N, the leakage rate after puncture is 0, and the number of pinholes for resistance to rubbing is ≤12 / m²; Comparative Example 1 has only 48.2 N and a leakage rate of 30%; Comparative Example 2 has 52.4 N and a leakage rate of 20%. This invention significantly improves the overall puncture resistance and resistance to rubbing through a comprehensive design that includes a thickened heat-sealing layer (100~110 μm), PA three-layer co-extrusion reinforcement, and modification of the toughness of soft aluminum foil.

[0166] 4) Comprehensive comparison: Example 1 is the optimal implementation scheme. Example 3 (PA layer is not three-layer co-extrusion) has a slight decrease in tumble resistance, but it is still significantly better than the comparative example. Comparative example 1 (conventional CPP structure) has the worst performance in all aspects. Comparative example 2 (insufficient heat seal layer thickness and no segmented curing process) has significantly worse performance in all aspects than the example, which confirms the necessity and synergistic effect of thickening the heat seal layer (80~120 μm) and the segmented curing process.

[0167] IV. Routine Quality Performance Testing

[0168] To further verify the comprehensive performance of the aluminum-plastic composite packaging bag of the present invention, the packaging bag sample (S1) obtained in Example 1 was subjected to a full-item quality inspection according to relevant national standards, and the results are shown in Table 2. All mechanical property data in Table 2 are test results of the sample before cooking.

[0169] Table 2 shows the aluminum-plastic composite packaging bag samples from Example 1 of the present invention. Subsequently, 5 rolls were randomly selected for various tests, and the quality performance test results are as follows:

[0170]

[0171] Table 2

[0172] Note 1: The peel force data after cooking in Table 1 are the measured values ​​of the samples after cooking. Before cooking, due to the extremely high bonding strength between the first adhesive layer of this invention and the PET / Al interface, film breakage occurred during T-shaped peeling (the PET or Al substrate broke before the adhesive layer), making it impossible to obtain a quantitative value of the peel interface. Therefore, it was qualitatively characterized by 'substrate breakage'. After cooking, the aluminum foil softened slightly, allowing for the measurement of effective peel force data. The retention rate was conservatively calculated using the maximum range of the instrument when the substrate broke before cooking as the denominator.

[0173] Note²: The indicators in Table 2 are reference values ​​set with reference to relevant national standards (including but not limited to GB / T 10004-2008, GB 4806.7-2023, etc.) and common practices in the packaging industry, and are only used to illustrate the performance level of the product of this invention.

[0174] As shown in Table 2, the aluminum-plastic composite packaging bag of Example 1 of this invention meets or exceeds the relevant index requirements in terms of specifications and dimensions, mechanical strength (tensile strength, elongation at break, peel force, heat seal strength), barrier performance (water vapor transmission rate, oxygen transmission rate), food safety performance (solvent residue, hygiene performance), and packaging reliability (pressure resistance / drop resistance). Specifically, the PET / Al layer peel force was too high to peel off, further verifying the significant improvement effect of the two-component reactive polyurethane adhesive and gradient composite process on the interlayer bonding strength. The total solvent residue was only 0.4 mg / m², far below the national standard limit (≤5.0 mg / m²), proving that the segmented curing process can effectively eliminate residual organic solvents during the composite process, ensuring food contact safety. Both the water vapor transmission rate (0.39 g / (m²·24h)) and oxygen transmission rate (0.24 cc / (m²·24h)) were far below the index limits, indicating that the barrier system formed by the aluminum foil layer 4 and the functional layers has excellent moisture-proof and anti-oxidation properties.

[0175] The embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A retort-resistant and corrosion-resistant aluminum-plastic composite packaging bag, characterized in that, The aluminum-plastic composite packaging bag comprises, from the outside to the inside, the following layers: a polyester film layer, an ink layer, a first adhesive layer, an aluminum foil layer, a second adhesive layer, a polyamide film layer, a third adhesive layer, and a modified polyolefin heat-sealing inner layer. The ink layer is directly laminated onto the inner surface of the polyester film layer. The aluminum foil layer is bonded to the ink layer via the first adhesive layer. The polyamide film layer is bonded to the aluminum foil layer via the second adhesive layer. The modified polyolefin heat-sealing inner layer is bonded to the polyamide film layer via the third adhesive layer.

2. The retort-resistant and corrosion-resistant aluminum-plastic composite packaging bag according to claim 1, characterized in that, The polyester film layer comprises polyethylene terephthalate resin, antioxidant, slip agent and / or anti-blocking agent, and catalyst residue neutralizer; based on 100 parts by weight of the total weight of the polyester film layer, the polyethylene terephthalate resin comprises 97-99 parts by weight, the antioxidant comprises 0.2-0.5 parts by weight, the slip agent and / or anti-blocking agent comprises 0.3-1.0 parts by weight, and the catalyst residue neutralizer comprises 0.01-0.1 parts by weight.

3. The retort-resistant and corrosion-resistant aluminum-plastic composite packaging bag according to claim 2, characterized in that, The thickness of the polyester film layer is 10-15 μm, the thickness of the ink layer is 1-5 μm, the thickness of the aluminum foil layer is 6-10 μm, the thickness of the polyamide film layer is 12-18 μm, the thickness of the modified polyolefin heat-sealing inner layer is 80-120 μm, and the thickness of the first adhesive layer, the second adhesive layer, and the third adhesive layer is each independently 1-5 μm.

4. The retort-resistant and corrosion-resistant aluminum-plastic composite packaging bag according to claim 3, characterized in that, The polyester film layer is a biaxially oriented polyethylene terephthalate film, and the polyamide film layer is a biaxially oriented polyamide film.

5. The retort-resistant and corrosion-resistant aluminum-plastic composite packaging bag according to claim 3, characterized in that, The first adhesive layer, the second adhesive layer, and the third adhesive layer are two-component reactive polyurethane adhesives that can withstand high-temperature boiling at 121°C. The two-component reactive polyurethane adhesive includes a main agent and a curing agent, and the weight ratio of the main agent to the curing agent is 100:10~13. The main agent is a polyester polyurethane polyol, and the curing agent is an aromatic curing agent.

6. The retort-resistant and corrosion-resistant aluminum-plastic composite packaging bag according to claim 3, characterized in that, The aluminum foil layer is a soft aluminum foil, and by weight percentage, the aluminum foil layer is composed of the following components: Fe 0.9% to 1.0%, Si 0.05% to 0.10%, the total weight percentage of Fe and Si is not greater than 1.0%, and the balance is Al and unavoidable impurities, wherein the content of Al is ≥99.0%, the total amount of unavoidable impurities is not more than 0.1%, and the impurities are selected from one or more of Cu, Mn, and Zn.

7. The retort-resistant and corrosion-resistant aluminum-plastic composite packaging bag according to claim 1, characterized in that, The polyamide film layer is a multilayer co-extruded biaxially oriented polyamide film.

8. The retort-resistant and corrosion-resistant aluminum-plastic composite packaging bag according to claim 3, characterized in that, The polyamide film layer has a three-layer co-extruded structure, including a surface layer, a core layer, and an inner layer; Based on a total weight of 100 parts by weight, the surface layer is composed of the following components: 2.5 to 3.5 parts of anti-hydrolysis additive, 1.0 to 2.0 parts of magnesium oxide, 1.0 to 2.0 parts of opening agent and slip agent combined, and the balance being polyamide 6 resin; Based on 100 parts by weight of the total weight of the core layer, the core layer is composed of the following components: 1.5 to 2.0 parts of anti-hydrolysis additive, and the balance being polyamide 6 resin; Based on 100 parts by weight of the total weight of the inner layer, the inner layer is composed of the following components: 1.0 to 1.5 parts of anti-hydrolysis additive, 1.0 to 2.0 parts of opening agent and slip agent combined, and the balance being polyamide 6 resin.

9. The retort-resistant and corrosion-resistant aluminum-plastic composite packaging bag according to claim 1, characterized in that, Based on a total weight of 100 parts by weight of the modified polyolefin heat-sealing inner layer, the modified polyolefin heat-sealing inner layer comprises: 30-40 parts by weight of linear low-density polyethylene, 15-25 parts by weight of metallocene linear low-density polyethylene, 2-5 parts by weight of opening slip agent and anti-blocking agent combined, 0.1-0.5 parts by weight of antioxidant, and the balance being low-density polyethylene.

10. A method for preparing a retort-resistant and corrosion-resistant aluminum-plastic composite packaging bag, characterized in that, The preparation method includes the following steps: Step 1) Substrate pretreatment: Corona treatment is performed on the polyester film layer, and passivation or degreasing treatment is performed on the aluminum foil layer to improve surface activity; Step 2) Multilayer adhesive coating: Apply two-component reactive polyurethane adhesive to both sides of the aluminum foil layer, and apply two-component reactive polyurethane adhesive to the side of the polyamide film layer facing the heat-sealing inner layer, controlling the dry coating amount to be 3.0~6.0 g / m². Step 3) Gradient lamination: Using a dry lamination process, the pretreated polyester film layer is laminated to one side of the aluminum foil layer, then the other side of the aluminum foil layer is laminated to the polyamide film layer, and finally the adhesive-coated side of the polyamide film layer is laminated to the modified polyolefin heat-sealing inner layer at a temperature of 50℃~80℃ and a pressure of 0.3~0.6 MPa. Step 4) Segmented curing: A gradient heating curing process is adopted, first curing at 35℃~45℃ for 12~24 hours, and then curing at 55℃~65℃ for 48~72 hours to eliminate composite stress; Step 5) Molding and Inspection: After slitting, bag making, and performance testing, the packaging bags are obtained.

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