Degradable breathable composite membrane based on gradient microporous structure as well as preparation method and application of degradable breathable composite membrane

Abstract

The invention provides a degradable breathable composite film based on a gradient microporous structure and a preparation method and application thereof, and belongs to the field of protective materials.The preparation method comprises the steps that PLA, PBAT, ADR, CaCO3 and modified master batches are subjected to melt blending in proportion, a three-layer casting film is prepared through three-layer casting film forming equipment, the three-layer casting film is formed through a stretching technology, and a gradient breathable film is obtained; a PLA non-woven fabric is prepared through a melt-blowing or spun-bonding technology; and compounding the gradient breathable film with a PLA non-woven fabric to obtain the degradable breathable composite film based on the gradient microporous structure. The three-layer casting co-extrusion process is adopted, the gradient porosity breathable film and the hydrophilic / hydrophobic design are combined, the comprehensive performance of the protective material is effectively improved, the moisture permeation amount of the material is increased, the hydrostatic pressure of the material is improved, and therefore the barrier property and comfort of the material are enhanced. The blocking layer is made of a porous membrane material formed by stretching PLA and PBAT composite CaCO3, the comfortable layer is made of a PLA spunbond / melt-blown non-woven fabric material, and full degradation of the protective material is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of protective materials, and in particular to a degradable breathable composite membrane based on a gradient microporous structure, and a preparation method and application thereof. Background Art

[0002] Traditional diapers, sanitary napkins, and other hygiene products are often made from a composite of polypropylene non-woven fabric and PE breathable film. This results in poor air permeability and can easily lead to skin heatiness and allergies. PE breathable film relies on dense micropores to achieve waterproofness and breathability, but uneven micropore distribution can easily lead to localized leakage or insufficient air permeability, thus compromising product performance. Furthermore, existing medical protective materials primarily utilize PE, PP, and PU non-woven fabrics. While these materials offer some protective properties, they are poorly biodegradable. Direct landfill disposal after disinfection can cause long-term soil contamination, while incineration can cause air pollution, posing a significant threat to the environment.

[0003] In recent years, researchers have begun to focus on developing biodegradable protective materials. Patent publication number CN114633535A discloses a biodegradable medical protective clothing material, its preparation method, and its application. The material consists of an outer layer made of a biodegradable film, an inner layer made of 100% cotton spunlace fabric, and a water-soluble adhesive positioned between the inner and outer layers. The biodegradable film is primarily composed of polyglycolic acid, polybutylene adipate / terephthalate, and polybutylene succinate. By compounding them in specific proportions, the material's water vapor barrier properties can be improved. However, because the material still uses a film as a barrier layer, its air permeability is poor, resulting in insufficient comfort for the protective material.

[0004] In view of this, it is necessary to design a degradable breathable composite membrane based on a gradient microporous structure and its preparation method and application to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background technology, the present application provides a degradable breathable composite membrane based on a gradient microporous structure and its preparation method and application, aiming to solve the technical problem of poor comfort of existing degradable protective materials.

[0006] In a first aspect, the present application provides a method for preparing a degradable breathable composite membrane based on a gradient microporous structure, comprising the following steps: S1. PLA, PBAT, ADR, CaCO3 and modified masterbatch were melt-blended in proportion, and a three-layer cast film was prepared using a three-layer cast film forming apparatus, wherein, in parts by weight: The outer layer includes: 15-50 parts PLA, 50-85 parts PBAT, 5 parts ADR, 30-35 parts CaCO3 and 2-10 parts hydrophobic masterbatch; The middle layer includes: 15-50 parts of PLA, 50-85 parts of PBAT, 5 parts of ADR and 40-45 parts of CaCO3; The inner layer includes: 15~50 parts of PLA, 50~85 parts of PBAT, 5 parts of ADR, 50~55 parts of CaCO3 and 2~10 parts of hydrophilic masterbatch; The three-layer cast film is formed by a stretching process to obtain a gradient breathable film; S2. PLA nonwoven fabric prepared by meltblowing or spunbonding process; S3. Compounding the gradient breathable membrane with the PLA non-woven fabric to obtain a degradable breathable composite membrane based on a gradient microporous structure.

[0007] As a further improvement of the present application, in step S1, the mass ratio of PLA to PBAT is 15:85~50:50; the melt index of PLA is 2~15 g / 10 min, and the weight average molecular weight is 100,000~250,000; the melt index of PBAT is 2~20 g / 10 min, and the weight average molecular weight is 30,000~250,000.

[0008] As a further improvement of the present application, the particle size of the CaCO3 is 500~3000 mesh.

[0009] As a further improvement of the present application, the hydrophobic masterbatch is a PLA-based masterbatch modified with a fluorine-containing polymer or a silane compound; and the hydrophilic masterbatch is a PLA-based masterbatch modified with polyethylene glycol.

[0010] As a further improvement of the present application, the gradient breathable membrane has a pore size of 5 to 50 μm and a porosity of 60 to 85%.

[0011] As a further improvement of the present application, in step S2, the gram weight of the PLA non-woven fabric is 10-50 gsm.

[0012] As a further improvement of the present application, in step S1, the melt blending temperature is 175~200°C, and the extrusion temperature is 175~200°C; the stretching process is unidirectional stretching, and the stretching ratio is 1.5~4.5; or the stretching process is bidirectional stretching, and the transverse stretching ratio is 1.5~3.0, and the longitudinal stretching ratio is 1.5~3.0.

[0013] As a further improvement of the present application, in step S3, the compounding method is hot pressing compounding, the temperature is 120~150°C, the pressure is 0.2~0.8MPa, and the hot pressing compounding speed is 20~200m / min.

[0014] In the second aspect, the present application provides a degradable breathable composite membrane based on a gradient microporous structure, which is prepared by the preparation method described in the first aspect, and the moisture permeability of the degradable breathable composite membrane based on the gradient microporous structure is ≥2450g / (m 2 ·d), biodegradation rate ≥95.55%, tensile strength ≥85N.

[0015] In a third aspect, the present application provides an application of a degradable breathable composite membrane based on a gradient microporous structure as described in the second aspect, wherein the composite membrane is used in the field of medical and health materials.

[0016] The beneficial effects of this application are: The present application provides a degradable breathable composite film based on a gradient microporous structure, and its preparation method and application. PLA, PBAT, ADR, CaCO3 and modified masterbatch are melt-blended in proportion, a three-layer cast film is prepared using a three-layer cast film forming equipment, and the three-layer cast film is formed by a stretching process to obtain a gradient breathable film; PLA non-woven fabric is prepared by a melt-blown or spunbond process; the gradient breathable film is composited with the PLA non-woven fabric to obtain a degradable breathable composite film based on a gradient microporous structure. The present application adopts a three-layer cast co-extrusion process, and combines a gradient porosity breathable film and a hydrophilic / hydrophobic design to effectively improve the comprehensive performance of the protective material, not only increasing the moisture permeability of the material, but also increasing its hydrostatic pressure, thereby enhancing the barrier properties and comfort of the material. The barrier layer uses PLA and PBAT composite calcium carbonate powder to stretch into a porous membrane material, and the comfort layer uses a degradable PLA spunbond / melt-blown non-woven fabric material, realizing the full degradation of the protective material.

[0017] This application uses a gradient breathable membrane design to further increase the hydrostatic pressure of the protective material under the same porosity conditions, significantly enhancing its protective performance. The breathable membrane is manufactured using multi-layer co-extrusion technology, with a gradient distribution of micropore density in each layer, achieving adaptive breathability under dynamic humidity conditions.

[0018] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0020] Figure 1A schematic structural diagram of a degradable breathable composite membrane based on a gradient microporous structure provided in an embodiment of the present application; Figure 2 A physical image of the gradient breathable membrane provided in Example 1 of the present application; Figure 3 This is a scanning electron microscope image of the surface of the gradient breathable membrane provided in Example 1 of the present application; Explanation of reference numerals: 11, outer layer of gradient breathable membrane; 12, middle layer of gradient breathable membrane; 13, inner layer of gradient breathable membrane; 2, PLA non-woven fabric. DETAILED DESCRIPTION

[0021] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0023] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0024] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0025] Existing medical and health materials have the following problems: the use of polypropylene non-woven fabrics and PE breathable film for compounding has poor air permeability, which can easily cause skin stuffiness and allergies; PE, PP, and PU non-woven fabrics are poorly degradable, causing environmental pollution; and biodegradable films have poor air permeability, resulting in insufficient comfort of protective materials.

[0026] In order to solve the technical problems that it is difficult to strike a balance between air permeability and protectiveness of existing medical and health materials and that the materials are difficult to degrade and cause environmental pollution, the present application provides a degradable breathable composite membrane based on a gradient microporous structure and its preparation method and application. Among them, by preparing a three-layer gradient breathable membrane material and compounding it with a degradable PLA non-woven fabric, it not only has complete biodegradability, but its special gradient permeability design also improves the hydrostatic pressure of the protective material and increases the comfort of the protective material.

[0027] In a first aspect, the present invention provides a method for preparing a degradable breathable composite membrane based on a gradient microporous structure, comprising the following steps: S1. PLA (polylactic acid), PBAT (polybutylene adipate / terephthalate), ADR (epoxy chain extender), CaCO3 and modified masterbatch were melt-blended in proportion, and a three-layer cast film was prepared using a three-layer cast film forming equipment, wherein, in parts by weight: The outer layer includes: 15-50 parts PLA, 50-85 parts PBAT, 5 parts ADR, 30-35 parts CaCO3 and 2-10 parts hydrophobic masterbatch; The middle layer includes: 15-50 parts of PLA, 50-85 parts of PBAT, 5 parts of ADR and 40-45 parts of CaCO3; The inner layer includes: 15~50 parts of PLA, 50~85 parts of PBAT, 5 parts of ADR, 50~55 parts of CaCO3 and 2~10 parts of hydrophilic masterbatch; The three-layer cast film is formed by a stretching process to obtain a gradient breathable film; S2. PLA nonwoven fabric prepared by meltblowing or spunbonding process; S3. Composite the gradient breathable membrane with PLA non-woven fabric to obtain a degradable breathable composite membrane based on a gradient microporous structure.

[0028] In the technical solution of the embodiment of the present application, the gradient microporous structure of the breathable membrane is achieved through the differentiated design and stretching process of the three-layer cast film, the porosity and pore size distribution are optimized, thereby improving the air permeability and waterproof performance; the use of degradable materials such as PLA and PBAT makes the composite membrane have good biodegradability, reducing pollution to the environment; the addition of hydrophobic masterbatch to the outer layer and hydrophilic masterbatch to the inner layer improves the comfort and moisture absorption and perspiration performance of the composite membrane; the addition of CaCO3 improves the barrier performance of the membrane and prevents liquid leakage. The final composite membrane is fully degradable and more environmentally friendly. This application prepares a composite membrane material with excellent air permeability, waterproofness, comfort and degradability, which can be used in fields such as sanitary products and medical protective materials.

[0029] Furthermore, in some embodiments, in step S1, the mass ratio of PLA to PBAT is 15:85-50:50; the melt index of PLA is 2-15 g / 10 min, and the weight average molecular weight is 100,000-250,000; the melt index of PBAT is 2-20 g / 10 min, and the weight average molecular weight is 30,000-250,000.

[0030] In the technical solution of the embodiment of the present application, the mass ratio of PLA to PBAT ensures a balance between the mechanical properties and processing properties of the material. PLA provides a certain strength and rigidity, while PBAT provides flexibility and processing fluidity. The melt index of PLA at 190°C and 2.16kg is 2~15g / 10min, and its melt fluidity is moderate, which is convenient for processing and molding. The weight-average molecular weight is in the range of 100,000 to 250,000, which ensures that the molecular weight distribution of PLA is moderate, which not only ensures the mechanical strength of the material, but also does not affect the processing performance due to excessively high molecular weight. The melt index of PBAT at 190°C and 2.16kg is 2~20g / 10min, indicating that its melt fluidity is good, which is conducive to forming a uniform system during the blending and film-forming process. The weight-average molecular weight is in the range of 30,000 to 250,000, which ensures that the molecular weight distribution of PBAT is moderate, providing good flexibility and elasticity.

[0031] Furthermore, in some embodiments, the particle size of CaCO3 is 500-3000 mesh.

[0032] In the technical solution of the embodiment of the present application, the particle size of CaCO3 is relatively small and uniform, which helps to achieve more uniform dispersion in the polymer matrix, thereby improving the microstructure and performance of the composite material.

[0033] Furthermore, in some embodiments, the hydrophobic masterbatch is a PLA-based masterbatch modified with a fluoropolymer or a silane; and the hydrophilic masterbatch is a PLA-based masterbatch modified with a polyethylene glycol.

[0034] In the technical solution of the embodiment of the present application, the PLA-based hydrophobic masterbatch modified with a fluoropolymer or a silane compound can impart excellent hydrophobic and oleophobic properties to the surface of the material, reducing the adhesion and penetration of liquids on the surface of the material; specifically, the hydrophobic masterbatch comprises the following components in parts by weight: 55-65 parts of PLA, 5-20 parts of a fluoropolymer or a silane compound, 5-15 parts of a dispersant, 0.1-5 parts of a compatibilizer, and 0.1-2 parts of a lubricant; the fluoropolymer comprises one or more of polytetrafluoroethylene, polyvinylidene fluoride, and fluoroethylene-propylene copolymer; the silane compound comprises one or more of polydimethylsiloxane and its derivatives, octadecyltrimethoxysilane, and octyltriethoxysilane. Polyethylene glycol-modified PLA-based hydrophilic masterbatch imparts excellent hydrophilicity and hygroscopicity to the material surface, improving the material's comfort and breathability. Specifically, the hydrophilic masterbatch comprises the following components by weight: 55-65 parts PLA, 15-30 parts polyethylene glycol and its derivatives, 5-15 parts dispersant, and 0.1-5 parts compatibilizer. By blending these two masterbatches with a PLA / PBAT matrix and fillers such as CaCO₃, breathable membrane materials with gradient porosity and controllable surface properties can be prepared, further enhancing the material's overall performance to meet the needs of diverse application scenarios.

[0035] Furthermore, in some embodiments, the gradient breathable membrane has a pore size of 5 to 50 μm and a porosity of 60 to 85%.

[0036] In the technical solutions of the embodiments of the present application, the appropriate pore size can achieve fine-tuning of the breathable membrane's air permeability and barrier properties to meet the needs of different application scenarios. The appropriate porosity can achieve a balance between the breathable membrane's air permeability, moisture permeability, and barrier properties to achieve optimal overall performance.

[0037] Furthermore, in some embodiments, in step S2, the gram weight of the PLA non-woven fabric is 10-50 gsm.

[0038] In the technical solutions of the embodiments of this application, the meltblowing process is characterized by a melt temperature of 200-240°C to prevent thermal degradation of PLA, an airflow pressure of 0.2-0.8 MPa to control fiber diameter, and a receiving distance of 10-30 cm to influence fiber laydown uniformity. The spunbond process is characterized by a spinning temperature of 210-250°C and a stretching airflow velocity of 3000-6000 m / min. The meltblowing or spunbond temperature ensures that the PLA material is in an optimal molten state, which not only ensures melt fluidity and facilitates fiber formation, but also prevents degradation of the PLA material caused by excessive temperatures. A PLA nonwoven fabric with an appropriate weight balances the material's air permeability and mechanical strength.

[0039] Furthermore, in some embodiments, in step S1, the melt blending temperature is 175~200°C, the extrusion temperature is 175~200°C, the stretching process is unidirectional stretching, and the stretching ratio is 1.5~4.5; or the stretching process is bidirectional stretching, the transverse stretching ratio is 1.5~3.0, and the longitudinal stretching ratio is 1.5~3.0.

[0040] In the technical solutions of the embodiments of the present application, the melt blending temperature ensures that components such as PLA, PBAT, and CaCO3 are fully melt-mixed to form a uniform melt. An appropriate temperature facilitates the interaction between the components. Too low a temperature may lead to uneven mixing, while too high a temperature may cause material degradation, affecting the performance of the final product. The extrusion temperature needs to match the melt blending temperature to ensure that the melt maintains good fluidity and stability during the extrusion process. A suitable extrusion temperature facilitates the formation of a three-layer cast film, ensuring uniformity and thickness consistency of each layer. Controlling the extrusion temperature can prevent material degradation or performance degradation during the extrusion process. Uniaxial stretching, typically performed in one direction, can significantly improve the material's mechanical properties in that direction, such as tensile strength and elongation at break. By controlling the stretch ratio, the shape and size of the pores can be adjusted, thereby optimizing the permeability and barrier properties of the breathable film. Biaxial stretching, performed simultaneously in two perpendicular directions, can achieve good mechanical properties in both directions. The transverse and longitudinal stretch ratios can be adjusted independently to achieve precise control of the pore structure, thereby better balancing permeability, barrier properties, and mechanical properties.

[0041] Furthermore, in some embodiments, in step S3, the compounding method is hot pressing compounding, the temperature is 120-150° C., the pressure is 0.2-0.8 MPa, and the hot pressing compounding speed is 20-200 m / min.

[0042] In the technical solution of the embodiment of the present application, the interlayer bonding force of the composite material can be significantly enhanced and its overall performance can be optimized through the hot pressing composite process.

[0043] Please refer to Figure 1 In the second aspect, the present invention provides a degradable breathable composite membrane based on a gradient microporous structure, which is prepared by the above-mentioned preparation method, and the moisture permeability of the composite membrane is ≥2450g / (m 2 ·d), biodegradation rate ≥95.55%, tensile strength ≥85N.

[0044] In the technical solution of the embodiments of the present application, a degradable breathable composite membrane based on a gradient microporous structure comprises a gradient breathable membrane outer layer 11, a gradient breathable membrane middle layer 12, a gradient breathable membrane inner layer 13, and a PLA nonwoven fabric 2. The high moisture permeability ensures that the composite membrane can quickly expel moisture while maintaining good breathability, thereby improving wearer comfort. The high biodegradability meets the needs of sustainable development and reduces environmental pollution caused by waste. The tensile strength ensures that the composite membrane has good mechanical properties during actual use and is not easily torn or damaged, thereby improving the durability and reliability of the product.

[0045] In a third aspect, an embodiment of the present application provides an application of a degradable breathable composite membrane based on a gradient microporous structure, which is used in the field of medical and health materials.

[0046] In the technical solution of the embodiment of the present application, the application of the composite film in the field of medical and health materials includes medical protective clothing, surgical pads / towels, wound dressings, and sanitary products.

[0047] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0048] 1. Preparation method Example 1 This embodiment provides a method for preparing a degradable breathable composite membrane based on a gradient microporous structure, comprising the following steps: S1. PLA, PBAT, ADR, CaCO3 and modified masterbatch were melt blended in proportion at a melt blending temperature of 185°C. A three-layer cast film was prepared using a three-layer cast film forming device. The three-layer cast film was formed by a stretching process with a transverse and longitudinal stretch ratio of 2.0 to obtain a gradient breathable film. Figures 2 to 3 As shown, it can be seen that the membrane surface has irregular pores, pits and loose network structure; S2. PLA nonwoven fabric was prepared by spunbonding process at a spunbonding temperature of 220°C. The obtained PLA spunbond nonwoven fabric had a gram weight of 20 gsm. S3. The gradient breathable membrane was hot-pressed with the PLA non-woven fabric at a temperature of 130°C, a pressure of 0.6 MPa, and a hot-pressing lamination speed of 100 m / min to obtain a degradable breathable composite membrane based on a gradient microporous structure. The components of the three-layer cast membrane, in parts by weight, are shown in Table 1: Table 1 Three-layer cast film components Examples 2-18 and Comparative Examples 1-5 Examples 2-18 and Comparative Examples 1-5 respectively provide a method for preparing a degradable breathable composite membrane based on a gradient microporous structure. Compared with Example 1, the only difference is that the components of the composite membrane and the gram weight of the PLA non-woven fabric are different. Among them, the components of the three-layer cast membrane are calculated in parts by weight, as shown in Table 2.

[0049] Table 2 Experimental parameter comparison 2. Test Method 1. Biodegradation rate: The biodegradation rate of the material after 90 days is determined according to the "Evaluation of the Biodegradability of Nonwoven Fabrics - Determination of Carbon Dioxide Emission Method" GB / T33616-2017; 2. Hydrostatic pressure: Use a water resistance tester to perform hydrostatic pressure test according to GB / T4744-1997 method; 3. Moisture permeability: Use the test method and requirements for moisture permeability in GB19082-2009 Technical Requirements for Medical Disposable Protective Clothing; 4. Tensile strength: Use an electronic strength meter to measure the tensile strength of the material according to GB / T3923.1-1997.

[0050] 3. Analysis of test results of various embodiments and comparative examples The test results are shown in Table 3.

[0051] Table 3 Test results As can be seen from Examples 1 to 5, the biodegradation rate of the protective material decreases as the PBAT content in the PLA / PBAT composite film increases. This is primarily due to the fact that PLA's molecular chain is composed of linear polylactic acid monomers connected by ester bonds, resulting in a relatively regular molecular weight, good flexibility and processing properties, and relatively easy reaction with water, carbon dioxide, microorganisms, and other factors, leading to degradation. PBAT, on the other hand, is a linear structure composed of randomly arranged butylene adipate and butylene terephthalate monomers. The molecular chain contains benzene rings, and the density of ester groups is significantly lower than that of polylactic acid, resulting in a decrease in biodegradability. In Comparative Example 1, the low proportion of PLA resulted in a decrease in the material's mechanical strength.

[0052] It can be seen from Examples 14 to 18 that as the grammage of the PLA non-woven fabric increases, the tensile strength of the protective material also increases. This is mainly because the strength of the PLA spunbond non-woven fabric is closely related to the grammage of the non-woven fabric. The higher the grammage, the more fiber entanglement points of the non-woven fabric, the more fibers there are, and the greater the strength of the non-woven fabric.

[0053] As can be seen from Examples 3, 6, and 7, as the calcium carbonate content increases, the moisture permeability of the protective material gradually increases, and the comfort also improves. This is mainly because as the calcium carbonate content increases, the porosity of the three-layer co-extruded cast film increases after biaxial stretching, and the moisture permeability of the protective material increases. In Comparative Example 4, insufficient calcium carbonate content reduces the formation of micropores, reduces the porosity and connectivity of the membrane, and thus significantly reduces the moisture permeability; in Comparative Example 5, excessive addition of calcium carbonate causes the micropores to be too large or unevenly distributed, destroying the uniformity of the membrane and reducing its waterproof performance. At the same time, excessive calcium carbonate may affect the mechanical properties of the membrane, resulting in unstable microporous structure during stretching and affecting the stability of the material.

[0054] As can be seen from Examples 8, 9, and 10, as the content of hydrophilic and hydrophobic masterbatches increases, the barrier properties of the protective material improve, and the hydrostatic pressure also increases. This is primarily due to the hydrophobic treatment of the outer layer of the multilayer cast film, forming a water-repellent protective layer on its surface that can withstand deeper water penetration. Compared to Example 8, Example 10 incorporates greater amounts of both hydrophobic and hydrophilic masterbatches, resulting in a more pronounced difference in the hydrophilic and hydrophobic properties of the composite film. Because the present application material is a heterogeneous film material, the difference between the front and back surfaces is significant. In the hydrostatic pressure test, when the test surface is the hydrophobic layer, the hydrostatic pressure of Example 10, which contains 10% hydrophobic masterbatch, is higher than that of Example 8, which contains 2% hydrophobic masterbatch. Similarly, in the moisture permeability test, when moisture diffuses from the hydrophobic layer to the hydrophilic layer, the moisture diffusion rate in contact with the hydrophobic layer is much lower than that of the hydrophilic layer, resulting in a lower moisture permeability of Example 10 than that of Example 8. Furthermore, Examples 11, 12, 13, and 14 show that hydrophilic treatment of the inner layer of the membrane material increases the moisture permeability of the protective material, while hydrophobic treatment of the outer layer of the membrane material increases the hydrostatic pressure of the protective material. In Comparative Example 2, the absence of a hydrophobic component resulted in a decrease in hydrostatic pressure; in Comparative Example 3, the absence of a hydrophilic component resulted in a decrease in moisture permeability.

[0055] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a degradable breathable composite membrane based on a gradient microporous structure, characterized in that: The following steps are involved: S1. PLA, PBAT, ADR, CaCO3 and modified masterbatch were melt-blended in proportion, and a three-layer cast film was prepared using a three-layer cast film forming apparatus, wherein, in parts by weight: The outer layer includes: 15-50 parts PLA, 50-85 parts PBAT, 5 parts ADR, 30-35 parts CaCO3 and 2-10 parts hydrophobic masterbatch; The middle layer includes: 15-50 parts of PLA, 50-85 parts of PBAT, 5 parts of ADR and 40-45 parts of CaCO3; The inner layer includes: 15~50 parts of PLA, 50~85 parts of PBAT, 5 parts of ADR, 50~55 parts of CaCO3 and 2~10 parts of hydrophilic masterbatch; The three-layer cast film is formed by a stretching process to obtain a gradient breathable film; S2. PLA nonwoven fabric prepared by meltblowing or spunbonding process; S3. Compounding the gradient breathable membrane with the PLA non-woven fabric to obtain a degradable breathable composite membrane based on a gradient microporous structure.

2. The method for preparing a degradable breathable composite membrane based on a gradient microporous structure according to claim 1, characterized in that: In step S1, the mass ratio of PLA to PBAT is 15:85-50:50; the melt index of PLA is 2-15 g / 10 min, and the weight average molecular weight is 100,000-250,000; the melt index of PBAT is 2-20 g / 10 min, and the weight average molecular weight is 30,000-250,000.

3. The method for preparing a degradable breathable composite membrane based on a gradient microporous structure according to claim 2, characterized in that: The particle size of the CaCO3 is 500-3000 mesh.

4. The method for preparing a degradable breathable composite membrane based on a gradient microporous structure according to claim 1, characterized in that: The hydrophobic masterbatch is a PLA-based masterbatch modified by a fluorine-containing polymer or a silane compound; the hydrophilic masterbatch is a PLA-based masterbatch modified by polyethylene glycol.

5. The method for preparing a degradable breathable composite membrane based on a gradient microporous structure according to claim 1, characterized in that: The gradient breathable membrane has a pore size of 5-50 μm and a porosity of 60-85%.

6. The method for preparing a degradable breathable composite membrane based on a gradient microporous structure according to claim 1, characterized in that: In step S2, the PLA non-woven fabric has a gram weight of 10-50 gsm.

7. The method for preparing a degradable breathable composite membrane based on a gradient microporous structure according to claim 1, characterized in that: In step S1, the melt blending temperature is 175-200°C, the extrusion temperature is 175-200°C; the stretching process is uniaxial stretching, and the stretching ratio is 1.5-4.5; Or the stretching process is biaxial stretching, with a transverse stretching ratio of 1.5 to 3.0 and a longitudinal stretching ratio of 1.5 to 3.

0.

8. The method for preparing a degradable breathable composite membrane based on a gradient microporous structure according to claim 1, characterized in that: In step S3, the compounding method is hot pressing compounding, the temperature is 120-150° C., the pressure is 0.2-0.8 MPa, and the hot pressing compounding speed is 20-200 m / min.

9. A degradable breathable composite membrane based on a gradient microporous structure, prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The moisture permeability of the degradable breathable composite membrane based on the gradient microporous structure is ≥2450g / (m 2 ·d), biodegradation rate ≥95.55%, tensile strength ≥85N.

10. An application of the degradable breathable composite membrane based on a gradient microporous structure according to claim 9, characterized in that: The degradable breathable composite membrane based on the gradient microporous structure is used in the field of medical and sanitary materials.

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