Medical high-barrier easy-peel composite membrane and its preparation method

Abstract

This invention discloses a medical high-barrier easy-to-peel composite film and its preparation method, belonging to the field of composite film technology. This invention, by setting an alumina coating and a dense nano-SiO2 layer on the surface of a BOPP base film, achieves a composite barrier structure through "the BOPP base film providing mechanical support and interface adaptation, the alumina coating constructing gradient barrier and stress buffering, and the dense nano-SiO2 layer realizing pore sealing and functional enhancement." Furthermore, a synergistic protective system is formed through three-layer chemical bonding, ultimately achieving the core objectives of "high barrier (significantly reduced water vapor / oxygen permeability), high stability (sterilization resistance, crack resistance), and high compatibility (easy recycling from a single material)," perfectly meeting the stringent requirements of medical packaging for barrier performance, mechanical properties, and environmental attributes.

Description

Technical Field

[0001] This invention relates to the field of composite membrane technology, specifically to a medical high-barrier easy-to-peel composite membrane and its preparation method. Background Technology

[0002] In the field of medical device and pharmaceutical packaging, the barrier properties, safety, and environmental attributes of packaging materials directly affect the quality stability and clinical application safety of products throughout their shelf life. They must also meet the stringent sterilization requirements of the medical industry. Currently, among mainstream medical packaging materials, multi-material composite films (such as aluminum foil / plastic, paper / plastic / aluminum multilayer structures) can achieve high oxygen and water vapor barrier effects through the aluminum foil layer, but they suffer from three major pain points in practical applications:

[0003] First, recycling is difficult and environmentally unfriendly. Due to the significant differences in chemical properties of the materials in each layer of the multi-material composite structure (such as the incompatibility between plastic and metal aluminum foil or paper substrate), it is difficult to achieve effective separation and recycling through conventional processes after disposal. A large amount of packaging waste can only be disposed of by incineration or landfill, which not only wastes resources but also easily causes environmental pollution, which is contrary to the global "dual carbon" goals and the green transformation trend of the medical industry.

[0004] Secondly, there are shortcomings in user experience and safety. Traditional aluminum foil composite films have the defect of being "invisible," making it impossible to directly observe the appearance of the internal medical devices (such as whether there is deformation or contamination), which can only be confirmed after unsealing, increasing the risk of damage to the sterile environment. In addition, the heat-sealed edges of aluminum foil composite films usually require a large peeling force to open, which can easily lead to problems such as difficulty in peeling, irregular tearing, and even aluminum foil fragments falling off during clinical operations. This not only affects the efficiency of use but may also contaminate the sterile operating environment.

[0005] Third, the production cost and process complexity are high. The preparation of aluminum foil composite film requires multiple lamination processes (such as dry lamination and extrusion lamination), and the thinning of aluminum foil requires extremely high precision in production equipment. Problems such as uneven lamination tension and fluctuations in adhesive coating can easily lead to a decrease in yield. At the same time, the price of aluminum foil raw materials is greatly affected by fluctuations in the metal market, which further increases the overall cost of packaging materials and is not conducive to cost control of medical products.

[0006] To address these issues, the industry has attempted to develop medical barrier films made from single materials, such as pure polypropylene (PP) films and polyethylene (PE) films. However, the barrier properties of these single-material plastic films are inherently insufficient. For example, the oxygen permeability of a conventional BOPP (biaxially oriented polypropylene) film is typically as high as 500-800 cm⁻¹. 3 / (m 2 24h (0.1 MPa), water vapor transmission rate is approximately 10-15 g / m³2 24 hours is far from meeting the requirements of medical devices (especially high-value-added consumables and biological agents) for a "low-oxygen and low-humidity" storage environment.

[0007] Furthermore, medical packaging must withstand a moist heat sterilization process at 121°C for 15 minutes. Conventional single-layer plastic films or simply coated modified films are prone to problems such as coating peeling and excessive reduction in heat-sealing strength after high-temperature sterilization, leading to packaging seal failure. Therefore, developing a medical composite film that combines "high barrier properties (low oxygen / low water vapor permeability), high stability (sterilization resistance, crack resistance), high compatibility (easy to recycle from a single material), and easy to peel and use" has become a key direction for solving current industry pain points, possessing significant technological value and market potential. Summary of the Invention

[0008] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies and provide a medical high-barrier easy-to-peel composite membrane and its preparation method. This medical high-barrier easy-to-peel composite membrane has excellent barrier properties and can withstand high-temperature sterilization. Furthermore, it uses homogeneous materials, achieving single-material standardization of the membrane, facilitating waste recycling and reuse, and contributing to environmental protection.

[0009] The technical solution of this invention is as follows:

[0010] On one hand, this invention provides a medical high-barrier easy-peel composite film, comprising a high-barrier BOPP layer and a heat-sealing layer from the outside to the inside; the high-barrier BOPP layer comprises, from the outside to the inside, a dense nano-SiO2 layer, an alumina coating, and a BOPP base film; the heat-sealing layer is a three-layer easy-peel heat-sealing material obtained by co-extrusion, comprising, from the outside to the inside, an inner layer, a middle layer, and a nano-adhesive transition layer; by weight, the nano-adhesive transition layer comprises 60-100 parts of polypropylene and 0.5-1.5 parts of PPA masterbatch. The middle layer consists of 5-10 parts maleic anhydride-grafted polypropylene and 0.5-1.5 parts nano-montmorillonite; the middle layer consists of 120-135 parts polypropylene, 1-2.5 parts PPA masterbatch, 6-8 parts aramid nanofiber, and 9-14 parts maleic anhydride-grafted polypropylene; the inner layer consists of 90-200 parts PP high-temperature easy-to-peel material, 1-6.5 parts anti-sticking masterbatch, and 0.5-3.5 parts PPA masterbatch; the mass ratio of the nano-adhesive transition layer, the middle layer, and the inner layer is (1-2):(1-3):(2-4).

[0011] This invention involves depositing an alumina coating and a dense nano-SiO2 layer on the surface of a BOPP base film. The three-layer structure is not simply stacked, but rather achieves a synergistic effect through a combination of gradient transition, pore sealing, and interfacial linkage. The overall barrier mechanism is as follows:

[0012] (1) "Double extension" of the permeation path: gas and water vapor molecules first need to break through the three-dimensional network structure of the nano-SiO2 dense layer (first path extension), and then enter the "maze channel" of the alumina coating (second path extension). Finally, the permeation path is significantly extended compared with the single alumina coating, and the permeation amount is significantly reduced.

[0013] (2) "Two-way complementarity" of structural stability: The gradient structure of the alumina coating alleviates the stress difference between the BOPP base film and the nano-SiO2 dense layer. The nano-SiO2 dense layer fixes the alumina particles through chemical bonding, preventing them from falling off or cracking during high-temperature sterilization and high-low temperature cycling. This ensures that the entire barrier structure retains a high performance after cooking at 121℃ for 15 minutes.

[0014] In this invention, the core function of maleic anhydride-grafted polypropylene in the nano-adhesive transition layer is as a highly efficient "interfacial compatibilizer" and "molecular bridge" to solve the interfacial bonding problem caused by the surface inertness of the polypropylene matrix and improve interlayer bonding strength. The core function of nano-montmorillonite in the nano-adhesive transition layer is as a highly efficient reinforcing material with a nanosheet structure, simultaneously improving the material's strength and toughness, and acting like an internal labyrinth to block gases and water vapor, significantly improving barrier properties, while also improving the material's heat resistance and flame retardant properties. The aramid nanofibers in the middle layer can significantly improve the film's puncture resistance, tensile strength, and dimensional stability with extremely low addition amounts; the maleic anhydride-grafted polypropylene in the middle layer, as a key compatibilizer, can greatly enhance the interfacial bonding strength between the aramid nanofibers and the matrix, thereby significantly improving the overall mechanical properties of the composite material.

[0015] Preferably, in the nano-adhesive transition layer, the polypropylene has a melt index of 1-2 g / 10 min and a density of 0.9-0.91 g / cm³. 3 In the middle layer, the melt index of polypropylene is 1-2 g / 10 min, and the density is 0.9-0.91 g / cm³. 3 .

[0016] Preferably, in the inner layer, the melt index of the PP high-temperature easy-to-peel material is 5-6.5 g / 10 min, and the density is 0.9-0.92 g / cm³. 3 The melt index of the anti-sticking masterbatch is 5-6.5 g / 10 min, and the density is 0.89-0.91 g / cm³. 3 .

[0017] Preferably, in the nano-adhesive transition layer, middle layer, and inner layer, the PPA masterbatch has a melt index of 2-2.5 g / 10 min and a density of 0.7-0.72 g / cm³. 3 .

[0018] Preferably, the thickness of the BOPP base film is 12-50 μm, the thickness of the alumina coating is 50-80 nm, the thickness of the nano-SiO2 dense layer is 10-20 nm, the thickness of the inner layer is 12-40 μm, the thickness of the middle layer is 18-30 μm, and the thickness of the nano-adhesive transition layer is 12-20 μm.

[0019] On the other hand, the present invention provides a method for preparing the above-mentioned medical high-barrier easy-to-peel composite film, comprising the following steps:

[0020] S1 Preparation of high-barrier BOPP layer: Alumina coating is vapor-deposited on the surface of BOPP base film, and then a coating liquid containing nano-SiO2 sol is coated on its surface to form a dense nano-SiO2 layer, thus obtaining a high-barrier BOPP layer.

[0021] S2 Preparation of heat-sealing layer: The heat-sealing layer is prepared by co-extrusion process of raw materials of nano-adhesive transition layer, middle layer and inner layer, and plasma surface treatment is performed on the heat-sealing layer after co-extrusion to optimize the interlayer bonding performance;

[0022] S3 Preparation of medical high-barrier easy-to-peel composite film: The high-barrier BOPP layer prepared in step S1 and the heat-sealing layer prepared in step S2 are combined with an adhesive and then cured to obtain a medical high-barrier easy-to-peel composite film.

[0023] Preferably, in step S1, when applying the coating liquid, nano-SiO2 sol, TEOS and hydrochloric acid are first mixed in a mass ratio of (90-100):(5-10):(0.05-0.3) and stirred at 30-40℃ for 2-3 hours to form a uniform and stable coating liquid; then the coating liquid is applied to the alumina coating using a micro-gravure coating method, with a coating roller cavity depth of 30-50μm and a coating speed of 80-100m / min.

[0024] In this invention, the high-barrier BOPP layer adopts a two-step method of "vapor deposition + sol-gel". First, an aluminum oxide coating is deposited on the surface of the BOPP base film, and then a dense layer of nano-SiO2 is coated by the sol-gel method. The three-dimensional network structure of SiO2 fills the tiny pores of the aluminum oxide coating, forming a dual protection of "physical barrier + chemical inertness".

[0025] Preferably, in step S1, after forming a dense nano-SiO2 layer, it is pre-dried at 80-90℃ for 5-8 minutes to remove the solvent; then cured at 120-140℃ for 15-20 minutes to form a three-dimensional network dense structure with the nano-SiO2 particles and TEOS hydrolysis products; finally, it is cooled and shaped: naturally cooled to room temperature to obtain a medical high-barrier easy-to-peel composite film to avoid cracking of the coating due to temperature difference.

[0026] Preferably, in step S2, during the co-extrusion process, the extrusion temperatures of the five heating zones of the nano-adhesive transition layer, according to the order of raw material passage, are 200-210℃, 210℃, and 210℃ respectively. The extrusion temperatures of the six heating zones in the middle layer are -220℃, 220-230℃, 205-210℃, and 201-211℃, respectively. The extrusion temperatures of the five heating zones in the inner layer are 193-203℃, 190-200℃, 210-220℃, 205-215℃, and 186-196℃, respectively. The heating temperatures of the four heating zones in the die head are 205-215℃, 215-225℃, 220-230℃, and 205-215℃, respectively. The plasma surface treatment power is 3-7kW, and the speed is 50-120m / min.

[0027] Preferably, in step S3, the adhesive is a two-component solvent-free polyurethane coating adhesive, and the application amount is 1.2-1.8 g / cm³. 2 The lamination speed is 100-150 m / min; during lamination, the temperature of the metering roller is 30-40℃, the temperature of the coating guide roller is 40-50℃, and the temperature of the lamination guide roller is 20-40℃; the curing temperature is 40-50℃, and the curing time is 24-48 hours; after curing, the resulting composite film is cooled before slitting and bag making. The temperature of the welding knife used for slitting is 150-200℃, and the bag making speed is 10-40 bags / min. The metering roller's function is to precisely control and transfer the amount of coating material, determining the coating thickness; the coating guide roller's function is to support, tension, and smoothly convey the substrate through the coating area; the lamination guide roller's function is to press the coated substrate with another layer of material to achieve a strong lamination.

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

[0029] This invention utilizes an alumina coating and a dense nano-SiO2 layer on the surface of a BOPP base film. The composite barrier structure achieves its core objectives of "high barrier (significantly reduced water vapor / oxygen permeability), high stability (sterilization resistance, crack resistance), and high compatibility (easy recycling from a single material)." This perfectly meets the stringent requirements of medical packaging for barrier performance, mechanical properties, and environmental attributes. Its mechanism of action is significantly innovative and superior to traditional single-coating methods. Furthermore, the medical high-barrier, easy-to-peel composite film of this invention features a wide heat-sealing window, stable heat-sealing strength, strong heat-sealing, and resistance to stringing. It can withstand high-temperature sterilization at 121°C for 15 minutes, and the heat-sealing strength remains stable after sterilization without significant change. Finally, the medical high-barrier easy-tear composite film of the present invention is a single-material packaging structure, which can replace the traditional multi-structure aluminum foil composite film in the packaging field, thereby achieving the environmental protection purpose of single-material packaging that is easy to recycle, can be replasticized and granulated, and can be reused. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention.

[0031] The sources of some of the raw materials in the following examples are as follows:

[0032] The polypropylene used in the nano-adhesive transition layer, H03M, has a melt index of 1-2 g / 10 min and a density of 0.9-0.91 g / cm³. 3 Lanzhou Petrochemical Branch of China National Petroleum Corporation;

[0033] The middle layer uses polypropylene RB707CF, with a melt index of 1-2 g / 10 min and a density of 0.9-0.91 g / cm³. 3 Borouge Trading (Shanghai) Co., Ltd.;

[0034] PPA masterbatch, WF-SF120PPA, melt index 2-2.5 g / 10 min, density 0.7-0.72 g / cm³ 3 Shenzhen Xingda New Materials Technology Co., Ltd.

[0035] High-temperature easy-to-unwrap PP, GZ-46PP, melt index 5-6.5g / 10min, density 0.9-0.92g / cm³ 3 Shandong Gaozhuo New Material Technology Co., Ltd.

[0036] Anti-sticking masterbatch, ABPP922CPP, melt index 5-6.5 g / 10 min, density 0.89-0.91 g / cm³ 3 Best Technology Co., Ltd., Shantou City;

[0037] Two-component solvent-free polyurethane coating adhesives, 7795A and 6204B, Henkel, Germany.

[0038] Example 1

[0039] The preparation method of the medical high-barrier easy-peel composite film in this embodiment includes the following steps:

[0040] S1 Preparation of High-Barrier BOPP Layer

[0041] (1) A 50 nm thick alumina coating was vapor-deposited on the surface of a 12 μm thick BOPP base film;

[0042] (2) Mix nano-SiO2 sol, TEOS and hydrochloric acid in a mass ratio of 100:9:0.1 and stir at 30°C for 2 hours to form a uniform and stable coating solution;

[0043] (3) The above coating liquid is applied to the surface of the alumina coating by micro-gravure coating method (coating roller cavity depth 30μm). The coating speed is 80m / min to ensure that the coating is uniform and free of drips, forming a 10nm thick dense nano SiO2 layer.

[0044] (5) Pre-dry at 80℃ for 5 min to remove solvent; then cure at 120℃ for 15 min to form a three-dimensional network dense structure with the nano-SiO2 sol and the hydrolysis products of TEOS; finally, cool naturally to room temperature to avoid cracking of the alumina coating and the nano-SiO2 dense layer due to temperature difference, and obtain a high-barrier BOPP layer.

[0045] S2 Preparation of heat-sealing layer

[0046] (1) The heat-sealing layer is a three-layer easy-to-peel heat-sealing material obtained by co-extrusion process, which includes an inner layer, a middle layer and a nano-adhesive transition layer arranged sequentially from the outside to the inside. The raw materials, dosage and quality of each layer are shown in Table 1. The specific preparation process is as follows: the raw materials are mixed evenly to ensure the stability and consistency of the product; the mixed raw materials are fed into an extruder for melt extrusion to form a film material. The extrusion temperature and die temperature of each layer are shown in Table 2; the film material is water-cooled to quickly stabilize the molding and prevent deformation or shrinkage. Then the film material is wound up to obtain the heat-sealing layer. The thicknesses of the nano-adhesive transition layer, the middle layer and the inner layer are 12μm, 18μm and 12μm, respectively.

[0047] Table 1. Raw materials, dosage, and mass ratio of each layer in the heat-sealing layer

[0048]

[0049] Table 2. Extrusion temperatures and die temperatures for the nano-adhesive transition layer, middle layer, and inner layer.

[0050]

[0051] (2) The heat-sealing layer is subjected to plasma surface treatment with a power of 3kW and a speed of 50m / min.

[0052] S3 prepares medical high-barrier easy-peel composite membranes

[0053] The high-barrier BOPP layer prepared in step S1 and the heat-sealing layer prepared in step S2 were laminated using a two-component solvent-free polyurethane coating adhesive (7795A, 6204B). The adhesive ratio was 100:75, and the application rate was 1.4 g / m². 2 The lamination speed was 120 m / min, the metering roller temperature was 35℃, the coating guide roller temperature was 45℃, and the lamination guide roller temperature was 30℃. After lamination, the film was cured at 48℃ for 36 hours. After curing, the resulting composite film was cooled for 24 hours before being slit and bagged to obtain a 70 μm thick medical high-barrier easy-open composite film. The welding knife temperature and bag-making speed during slitting and bag-making are shown in Table 3.

[0054] Table 3 Welding knife temperature and bag making speed

[0055]

[0056] Example 2

[0057] The preparation method of the medical high-barrier easy-peel composite film in this embodiment includes the following steps:

[0058] S1 Preparation of High-Barrier BOPP Layer

[0059] (1) An 80 nm thick alumina coating was vapor-deposited on the surface of a 50 μm thick BOPP base film;

[0060] (2) Mix nano-SiO2 sol, TEOS and hydrochloric acid in a mass ratio of 95:10:0.3 and stir at 35°C for 2 hours to form a uniform and stable coating solution;

[0061] (3) The above coating liquid is applied to the surface of the alumina coating by micro-gravure coating method (coating roller cavity depth 40μm). The coating speed is 90m / min to ensure that the coating is uniform and free of drips, forming a 15nm thick dense nano SiO2 layer.

[0062] (5) Pre-dry at 85℃ for 6 min to remove solvent; then cure at 130℃ for 18 min to form a three-dimensional network dense structure with the nano-SiO2 sol and the hydrolysis products of TEOS; finally, cool naturally to room temperature to avoid cracking of the alumina coating and the nano-SiO2 dense layer due to temperature difference, and obtain a high-barrier BOPP layer.

[0063] S2 Preparation of heat-sealing layer

[0064] (1) The heat-sealing layer is a three-layer easy-to-peel heat-sealing material obtained by co-extrusion process, comprising an inner layer, a middle layer, and a nano-adhesive transition layer arranged sequentially from the outside to the inside. The raw materials, dosages, and mass of each layer are shown in Table 1. The specific preparation process is the same as in Example 1, and the extrusion temperature and die temperature of each layer are shown in Table 4. The thicknesses of the nano-adhesive transition layer, the middle layer, and the inner layer are 18 μm, 24 μm, and 24 μm, respectively.

[0065] Table 4. Extrusion temperatures and die temperatures for the nano-adhesive transition layer, middle layer, and inner layer.

[0066]

[0067] (2) The heat-sealing layer is subjected to plasma surface treatment with a power of 6kW and a speed of 80m / min.

[0068] S3 prepares medical high-barrier easy-peel composite membranes

[0069] The high-barrier BOPP layer prepared in step S1 and the heat-sealing layer prepared in step S2 were laminated using a two-component solvent-free polyurethane coating adhesive (7795A, 6204B). The adhesive ratio was 100:75, and the application rate was 1.2 g / m². 2 The lamination speed was 100 m / min, the metering roller temperature was 30℃, the coating guide roller temperature was 40℃, and the lamination guide roller temperature was 20℃. After lamination, the film was cured at 40℃ for 48 hours. After curing, the resulting composite film was cooled for 24 hours before being slit and bagged to obtain a 70 μm thick medical high-barrier easy-open composite film. The welding knife temperature and bag-making speed during slitting and bag-making are shown in Table 5.

[0070] Table 5 Welding knife temperature and bag making speed

[0071]

[0072] Example 3

[0073] The preparation method of the medical high-barrier easy-peel composite film in this embodiment includes the following steps:

[0074] S1 Preparation of High-Barrier BOPP Layer

[0075] (1) A 60 nm thick alumina coating was vapor-deposited on the surface of a 35 μm thick BOPP base film;

[0076] (2) Mix nano-SiO2 sol, TEOS and hydrochloric acid in a mass ratio of 90:5:0.05 and stir at 40°C for 3 hours to form a uniform and stable coating solution;

[0077] (3) The above coating liquid is applied to the surface of the alumina coating by micro-gravure coating method (coating roller cavity depth 50μm). The coating speed is 100m / min to ensure that the coating is uniform and free of drips, forming a 20nm thick dense nano SiO2 layer.

[0078] (5) Pre-dry at 90℃ for 8 min to remove solvent; then cure at 140℃ for 20 min to form a three-dimensional network dense structure with the nano-SiO2 sol and the hydrolysis products of TEOS; finally, cool naturally to room temperature to avoid cracking of the alumina coating and the nano-SiO2 dense layer due to temperature difference, and obtain a high-barrier BOPP layer.

[0079] S2 Preparation of heat-sealing layer

[0080] (1) The heat-sealing layer is a three-layer easy-to-peel heat-sealing material obtained by co-extrusion process, comprising an inner layer, a middle layer, and a nano-adhesive transition layer arranged sequentially from the outside to the inside. The raw materials, dosages, and mass of each layer are shown in Table 1. The specific preparation process is the same as in Example 1, and the extrusion temperature and die temperature of each layer are shown in Table 6. The thicknesses of the nano-adhesive transition layer, the middle layer, and the inner layer are 20 μm, 30 μm, and 40 μm, respectively.

[0081] Table 6. Extrusion temperatures and die temperatures for the nano-adhesive transition layer, middle layer, and inner layer

[0082]

[0083] (2) The heat-sealing layer is subjected to plasma surface treatment with a power of 7kW and a speed of 120m / min.

[0084] S3 prepares medical high-barrier easy-peel composite membranes

[0085] The high-barrier BOPP layer prepared in step S1 and the heat-sealing layer prepared in step S2 were laminated using a two-component solvent-free polyurethane coating adhesive (7795A, 6204B). The adhesive ratio was 100:75, and the application rate was 1.8 g / m². 2The lamination speed was 150 m / min, the metering roller temperature was 40℃, the coating guide roller temperature was 50℃, and the lamination guide roller temperature was 40℃. After lamination, the film was cured at 50℃ for 24 hours. After curing, the resulting composite film was cooled for 24 hours before being slit and bagged to obtain a 70 μm thick medical high-barrier easy-open composite film. The welding knife temperature and bag-making speed during slitting and bag-making are shown in Table 7.

[0086] Table 7 Welding knife temperature and bag making speed

[0087]

[0088] Comparative Example 1

[0089] The difference from Example 1 is that steps S1 and S3 are omitted, and the heat-sealing layer prepared in step S2 is directly cut into bags.

[0090] Comparative Example 2

[0091] The difference from Example 1 is that in step S1, an alumina coating is not vapor-deposited on the surface of the BOPP base film.

[0092] Comparative Example 3

[0093] The difference from Example 1 is that in step S1, a dense layer of nano-SiO2 is not coated on the surface of the alumina coating.

[0094] Comparative Example 4

[0095] The difference from Example 1 is that, in step S2, maleic anhydride-grafted polypropylene and nano-montmorillonite are not added to the nano-adhesive transition layer.

[0096] Comparative Example 5

[0097] The difference from Example 1 is that in step S2, aramid nanofibers and maleic anhydride-grafted polypropylene are not added to the middle layer.

[0098] Comparative Example 6

[0099] The difference from Example 1 is that in step S2, the heat-sealing layer is not subjected to plasma surface treatment.

[0100] The composite films prepared in Examples 1-3 and Comparative Examples 1-6 were tested for peel strength, water vapor transmission rate, and oxygen transmission rate before and after being boiled at 121°C for 15 min. Peel strength was determined according to General Chapter 4004 of the 2025 edition of the Chinese Pharmacopoeia, Part IV, "Determination of Peel Strength of Plastics"; water vapor transmission rate was determined according to General Chapter 4010 of the 2025 edition of the Chinese Pharmacopoeia, Part IV, "Determination of Water Vapor Transmission Rate of Pharmaceutical Packaging Materials"; and oxygen transmission rate was determined according to General Chapter 4007 of the 2025 edition of the Chinese Pharmacopoeia, Part IV, "Determination of Gas Transmission Rate of Pharmaceutical Packaging Materials". The test results are shown in Tables 8-9.

[0101] Table 8. Test results of peel strength and barrier properties of the composite films in Examples 1-3 before and after cooking.

[0102]

[0103] Table 9. Test results of peel strength and barrier properties of composite films in Comparative Examples 1-6 before and after cooking.

[0104]

[0105] The heat-sealing strength of the composite films prepared in Examples 1-3 and Comparative Examples 1-6 was tested before and after being boiled at 121°C for 15 min. The heat-sealing strength was determined according to Chapter 4008, General Section IV, "Determination of Heat-Sealing Strength," of the 2025 edition of the Chinese Pharmacopoeia. The test results are shown in Tables 10-11.

[0106] Table 10. Test results of heat-sealing strength of composite films before and after cooking in Examples 1-3

[0107]

[0108] Table 11 Test results of heat-sealing strength of composite films before and after cooking in Comparative Examples 1-6

[0109]

[0110] As can be seen from the above data, the present invention can withstand 121℃ and 15min of steaming, and has excellent barrier properties before and after steaming. It has a wide heat-sealing window and stable heat-sealing strength in the range of 25-28N / 15mm.

[0111] Comparative Example 1 lacks the high-barrier BOPP layer composed of "BOPP base film + alumina coating + nano-SiO2 dense layer", retaining only the heat-sealing layer. The "maze channel" of the alumina coating and the "three-dimensional network structure" of the nano-SiO2 dense layer form a double penetration path extension. However, Comparative Example 1 completely lacks this barrier system, and the heat-sealing layer has extremely poor natural barrier properties, which cannot prevent gas and water vapor from penetrating, resulting in the loss of barrier function and the inability to measure peel strength.

[0112] Comparative Example 2, which did not have an alumina coating deposited on the BOPP base film, showed a significant decrease in peel strength and barrier performance. This is because only the dense nano-SiO2 layer was retained, and the lack of the "secondary penetration path extension" provided by the alumina coating allowed gases and water vapor to directly penetrate the interfacial gap between the BOPP base film and the SiO2 layer, greatly weakening the barrier effect. The gradient structure of the alumina coating can alleviate the stress difference between the BOPP base film and the dense nano-SiO2 layer; without it, the interfacial stress is mismatched, resulting in decreased interlayer adhesion and peel strength.

[0113] Comparative Example 3, lacking a dense nano-SiO2 layer on the alumina coating surface, exhibited reduced water resistance and barrier stability. This is because the core function of the dense nano-SiO2 layer is "pore sealing" and "structural fixation." Its absence exposes defects in the alumina coating: the alumina coating contains micropores, which the dense nano-SiO2 layer can fill through its three-dimensional network structure, forming a defect-free barrier surface; however, its absence allows gases and water vapor to rapidly permeate through the pores, reducing barrier performance; structural stability is also weakened: the dense nano-SiO2 layer fixes alumina particles through chemical bonding, preventing them from detaching or cracking during high-temperature cooking. Its absence makes the alumina coating prone to microcracks in humid and hot environments. Although the peel strength does not decrease significantly, the barrier stability (fluctuation before and after cooking) deteriorates.

[0114] In Comparative Example 4, the absence of maleic anhydride-grafted polypropylene and nano-montmorillonite in the nano-adhesive transition layer resulted in severely insufficient interlayer bonding and a significant decrease in peel strength. This is because polypropylene has a highly inert surface, and maleic anhydride-grafted polypropylene can act as a "molecular bridge" connecting the high-barrier BOPP layer and the heat-sealing layer, enhancing interlayer bonding. Without these elements, the interlayer interface bonding is weak, leading to a significant decrease in peel strength. The nanosheet structure of nano-montmorillonite can form an internal "maze," helping to block gases and water vapor while improving material toughness. Without these elements, the auxiliary barrier effect disappears, and the permeability of water vapor and oxygen increases slightly.

[0115] In Comparative Example 5, the absence of aramid nanofibers and maleic anhydride-grafted polypropylene in the middle layer resulted in a significant decrease in heat-sealing strength after high-temperature cooking. This is because aramid nanofibers can significantly improve the puncture resistance, tensile strength, and dimensional stability of the film. Their absence leads to insufficient strength in the middle layer structure, making it prone to deformation after high-temperature cooking and causing a substantial decrease in heat-sealing strength. Furthermore, the poor compatibility between aramid nanofibers and the polypropylene matrix in the middle layer, coupled with the fact that maleic anhydride-grafted polypropylene can enhance the interfacial bonding, results in uneven dispersion of aramid nanofibers in the matrix, preventing the formation of an effective reinforcing network. This leads to stress concentration between layers after cooking, resulting in a decrease in both heat-sealing strength and peel strength.

[0116] Plasma treatment can introduce polar groups, enhance the surface activity of the heat-sealing layer, and strengthen the adhesion with the adhesive. In Comparative Example 6, the heat-sealing layer was not subjected to plasma surface treatment, resulting in strong surface inertness, insufficient wetting and adhesion of the adhesive, and extremely poor interlayer adhesion. The interface bonding was not tight, with tiny gaps that allowed gas and water vapor to permeate through, slightly reducing the barrier performance. At the same time, the weak composite structure led to uneven stress transmission during heat sealing, significantly reducing the heat sealing strength and failing to meet the sealing requirements of medical packaging.

[0117] In summary, this invention constructs a multi-layered protective system of "physical barrier + chemical stability + structural adaptation" by setting an alumina coating and a dense nano-SiO2 layer on the surface of a BOPP base film. The complementary functions and interfacial synergy of the three layers fundamentally solve problems such as insufficient barrier properties of single coatings, easy cracking, and poor compatibility with substrates. This ultimately achieves highly efficient barrier against gases (oxygen) and water vapor, while ensuring the mechanical stability and environmental properties of the composite film. Furthermore, the medical high-barrier easy-open composite film prepared by this invention has advantages such as a wide heat-sealing window, stable heat-sealing strength, strong heat-sealing, and resistance to stringing. In addition, it can withstand high-temperature sterilization at 121℃ for 15 minutes, and the heat-sealing strength remains stable after high-temperature sterilization without significant change. Finally, the medical high-barrier easy-open composite film prepared by this invention is a single-material packaging structure, which can replace traditional multi-structured aluminum foil composite films in the packaging field, thereby achieving the environmentally friendly goal of easy recycling, replasticization and granulation, and reuse of single-material packaging materials.

Claims

1. A medical high-barrier easy-to-peel composite film, characterized in that, from outside to inside, the film comprises a high-barrier BOPP layer and a heat-sealing layer; the high-barrier BOPP layer comprises, from outside to inside, a nano-SiO2 dense layer, an aluminum oxide coating and a BOPP base film; the aluminum oxide coating is vapor-deposited on the surface of the BOPP base film, and the nano-SiO2 dense layer is formed by coating a coating liquid containing nano-SiO2 sol on the surface of the aluminum oxide coating; the heat-sealing layer is a three-layer easy-to-peel heat-sealing material obtained by a co-extrusion process, and comprises, from outside to inside, an inner layer, a middle layer and a nano-adhesion transition layer; in terms of mass fraction, the nano-adhesion transition layer comprises 60-100 parts of polypropylene, 0.5-1.5 parts of PPA master batch, 5-10 parts of maleic anhydride grafted polypropylene and 0.5-1.5 parts of nano-montmorillonite; the middle layer comprises 120-135 parts of polypropylene, 1-2.5 parts of PPA master batch, 6-8 parts of aramid nanofiber and 9-14 parts of maleic anhydride grafted polypropylene; and the inner layer comprises 90-200 parts of PP high-temperature easy-to-peel material, 1-6.5 parts of anti-adhesion master batch and 0.5-3.5 parts of PPA master batch; the mass ratio of the nano-adhesion transition layer, the middle layer and the inner layer is (1-2):(1-3):(2-4).

2. The medical high-barrier easy-to-peel composite film according to claim 1, characterized in that, The nano-adhesion transition layer has a polypropylene melt index of 1-2 g / 10 min and a density of 0.9-0.91 g / cm 3 The middle layer has a polypropylene melt index of 1-2 g / 10 min and a density of 0.9-0.91 g / cm 3 .

3. The medical high-barrier easy-open complex film according to claim 1, wherein The melt index of the PP high-temperature easy-to-peel material in the inner layer is 5-6.5 g / 10 min, and the density is 0.9-0.92 g / cm 3 ; the melt index of the anti-adhesion masterbatch is 5-6.5 g / 10 min, and the density is 0.89-0.91 g / cm 3 .

4. The medical high-barrier easy-open complex film according to claim 1, wherein The melt index of the PPA masterbatch in the nanobonding transition layer, middle layer and inner layer is 2-2.5 g / 10 min, and the density is 0.7-0.72 g / cm 3 .

5. The medical high-barrier easy-open complex film according to claim 1, wherein The thickness of the BOPP base film is 12-50 μm, the thickness of the aluminum oxide coating is 50-80 nm, the thickness of the nano-SiO2 dense layer is 10-20 nm, the thickness of the inner layer is 12-40 μm, the thickness of the middle layer is 18-30 μm, and the thickness of the nano-adhesion transition layer is 12-20 μm.

6. Process for the production of a medical high barrier easy-to-peel composite film according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: S1.Preparing the high-barrier BOPP layer: vapor-depositing the aluminum oxide coating on the surface of the BOPP base film, and then coating the coating liquid containing nano-SiO2 sol on the surface of the aluminum oxide coating to form the nano-SiO2 dense layer, thereby preparing the high-barrier BOPP layer; S2.Preparing the heat-sealing layer: preparing the heat-sealing layer by co-extruding the raw materials of the nano-adhesion transition layer, the middle layer and the inner layer, and then performing plasma surface treatment on the heat-sealing layer after co-extrusion; S3.Preparing the medical high-barrier easy-to-peel composite film: compounding the high-barrier BOPP layer prepared in step S1 and the heat-sealing layer prepared in step S2 by using an adhesive, and then aging the composite film to obtain the medical high-barrier easy-to-peel composite film.

7. The method of producing a medical high-barrier easy-to-peel composite film according to claim 6, characterized by, In step S1, when coating the coating liquid, first, mix the nano-SiO2 sol, TEOS and hydrochloric acid in a mass ratio of (90-100):(5-10):(0.05-0.3), stir at 30-40 ℃ for 2-3 h to form a uniform and stable coating liquid; and then coat the coating liquid on the aluminum oxide coating by using a micro-gravure coating method, the depth of the coating roll net cavity is 30-50 μm, and the coating speed is 80-100 m / min.

8. The method of producing a medical high-barrier easy-to-peel composite film according to claim 6, characterized by, In step S1, after forming the nano-SiO2 dense layer, pre-dry at 80-90 ℃ for 5-8 min, then solidify at 120-140 ℃ for 15-20 min, and finally naturally cool to room temperature to obtain the medical high-barrier easy-to-peel composite film.

9. The method of producing a medical high-barrier easy-to-peel composite film according to claim 6, characterized by, In step S2, in the co-extrusion process, the extrusion temperature of the five heating zones of the nanometer bonding transition layer is 200-210℃, 210-220℃, 220-230℃, 205-210℃, 201-211℃ in turn, the extrusion temperature of the six heating zones of the middle layer is 205-215℃, 210-220℃, 215-225℃, 208-218℃, 202-212℃, 200-210℃ in turn, the extrusion temperature of the five heating zones of the inner layer is 193-203℃, 190-200℃, 210-220℃, 205-215℃, 186-196℃ in turn; the heating temperature of the four heating zones of the die head is 205-215℃, 215-225℃, 220-230℃, 205-215℃ in turn; the power of the plasma surface treatment is 3-7kW, and the speed is 50-120m / min.

10. The method of producing a medical high-barrier easy-to-peel composite film according to claim 6, characterized by, In step S3, the adhesive is two-component solvent-free polyurethane laminating adhesive, the adhesive amount is 1.2-1.8 g / cm 2 , the laminating speed is 100-150 m / min; during the laminating, the temperature of the metering roller is 30-40℃, the temperature of the coating guide roller is 40-50℃, and the temperature of the laminating guide roller is 20-40℃; the curing temperature is 40-50℃, and the curing time is 24-48 h; after the curing is completed, the obtained laminated film is cooled and then cut to make bags; during the cutting, the temperature of the cutting knife is 150-200℃, and the bag making speed is 10-40 bags / min.

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