Degradable breathable composite membrane based on gradient microporous structure and preparation method and application thereof

Abstract

The application 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, wherein PLA, PBAT, ADR, CaCO3 and modified master batches are melt-blended in proportion, a three-layer casting film is prepared by using a three-layer casting film forming device, the three-layer casting film is formed by a stretching process to obtain a gradient breathable film; a PLA non-woven fabric is prepared by a melt-blown or spun-bond process; and the gradient breathable film and the PLA non-woven fabric are compounded to obtain the degradable breathable composite film based on the gradient microporous structure. The three-layer casting co-extrusion process is adopted in the application, and the gradient porosity breathable film and the hydrophilic / hydrophobic design are combined to effectively improve the comprehensive performance of the protective material, not only increase the moisture permeation amount of the material, but also improve the hydrostatic pressure, thereby enhancing the barrier property and comfort of the material. The barrier layer is composed of PLA, PBAT and CaCO3 and is stretched into a porous film material, the comfort layer is composed of a PLA spun-bond / melt-blown non-woven fabric material, and the full degradation of the protective material is realized.

Description

TECHNICAL FIELD

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

[0002] Traditional paper diapers, sanitary napkins and other hygiene products are mostly composed of polypropylene non-woven fabric and PE breathable film. However, these products have poor breathability, which can cause skin overheating and allergic reactions. PE breathable film relies on dense micropores to achieve waterproof and breathable properties, but uneven distribution of micropores can lead to local leakage or insufficient breathability, thereby affecting the performance of the product. In addition, existing medical protective materials mainly use PE, PP and PU non-woven fabric. Although these materials have certain protective properties, they have poor degradability. After sterilization, they are directly landfilled, causing long-term pollution in the soil, and incineration can cause air pollution, posing a great threat to the environment.

[0003] In recent years, researchers have begun to develop degradable protective materials. Patent No. CN114633535A discloses a degradable medical protective clothing material and its preparation method and application. The material is composed of an outer layer made of biodegradable film, an inner layer made of all-cotton spunlace fabric, and a water-soluble adhesive between the inner and outer layers. The biodegradable film is mainly composed of polyglycolic acid, polybutylene succinate and polybutylene succinate. By compounding in a specific ratio, the water vapor barrier property of the material can be improved. However, since the material still uses a film as the barrier layer, its breathability is poor, resulting in insufficient comfort of the protective material.

[0004] Therefore, it is necessary to design a degradable breathable composite film based on gradient microporous structure and its preparation method and application to solve the above problems. SUMMARY

[0005] In view of the technical problems in the background art, the present application provides a degradable breathable composite film based on 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 preparation method of a degradable breathable composite film based on gradient microporous structure, comprising the following steps:

[0007] S1. Melt blend PLA, PBAT, ADR, CaCO3 and modified masterbatch in a certain proportion, and prepare a three-layer casting film using a three-layer casting film equipment, wherein the weight ratio is as follows:

[0008] The outer layer comprises 15-50 parts of PLA, 50-85 parts of PBAT, 5 parts of ADR, 30-35 parts of CaCO3 and 2-10 parts of hydrophobic masterbatch;

[0009] The intermediate layer comprises 15-50 parts of PLA, 50-85 parts of PBAT, 5 parts of ADR, and 40-45 parts of CaCO3;

[0010] The inner layer comprises 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;

[0011] The three-layer cast film is shaped through a stretching process to obtain a gradient breathable film;

[0012] S2. Preparing a PLA non-woven fabric through a melt-blown or spun-bond process;

[0013] S3. Compounding the gradient breathable film with the PLA non-woven fabric to obtain a degradable breathable composite film based on a gradient microporous structure.

[0014] As a further improvement of the present application, in step S1, the mass ratio of the PLA to PBAT is 15:85-50:50; the melt index of the PLA is 2-15 g / 10 min, and the weight average molecular weight is 100-250 thousand; the melt index of the PBAT is 2-20 g / 10 min, and the weight average molecular weight is 3-250 thousand.

[0015] As a further improvement of the present application, the particle size of the CaCO3 is 500-3000 mesh.

[0016] As a further improvement of the present application, the hydrophobic masterbatch is a PLA-based masterbatch modified with a fluoropolymer or a silane compound; and the hydrophilic masterbatch is a PLA-based masterbatch modified with polyethylene glycol.

[0017] As a further improvement of the present application, the pore size of the gradient breathable film is 5-50 μm, and the porosity is 60-85%.

[0018] As a further improvement of the present application, in step S2, the grammage of the PLA non-woven fabric is 10-50 gsm.

[0019] As a further improvement of the present application, in step S1, the temperature of the melt blending is 175-200 ℃, and the extrusion temperature is 175-200 ℃; the stretching process is unidirectional stretching with a stretching ratio of 1.5-4.5; or the stretching process is bidirectional stretching with a transverse stretching ratio of 1.5-3.0 and a longitudinal stretching ratio of 1.5-3.0.

[0020] As a further improvement of the present application, in step S3, the compounding method is hot-press compounding at a temperature of 120-150 ℃, a pressure of 0.2-0.8 MPa, and a hot-press compounding speed of 20-200 m / min.

[0021] In a second aspect, the application provides a degradable and breathable composite film based on a gradient microporous structure, which is prepared by the preparation method of the first aspect, and has a moisture permeation amount of >2450 g / (m 2 , a biodegradation rate of >95.55%, and a tensile strength of >85 N.

[0022] In a third aspect, the application provides an application of the degradable and breathable composite film based on a gradient microporous structure according to the second aspect, and the composite film is used in the field of medical and health materials.

[0023] The application has the following beneficial effects:

[0024] The application provides a degradable and breathable composite film based on a gradient microporous structure, a preparation method and an application thereof. PLA, PBAT, ADR, CaCO3 and modified masterbatch are melt-blended in a proportion, a three-layer casting film is prepared by using a three-layer casting film forming device, the three-layer casting film is formed by a stretching process to obtain a gradient breathable film, a PLA non-woven fabric is prepared by a melt-blown or spun-bond process, and the gradient breathable film and the PLA non-woven fabric are compounded to obtain the degradable and breathable composite film based on the gradient microporous structure. The three-layer casting co-extrusion process is adopted in the application, and the gradient porosity breathable film and the hydrophilic / hydrophobic design are combined to effectively improve the comprehensive performance of the protective material, increase the moisture permeation amount of the material, improve the hydrostatic pressure, and thus enhance the barrier property and comfort of the material. The barrier layer is a porous film material prepared by stretching PLA and PBAT composite calcium carbonate powder, and the comfort layer is a degradable PLA spun-bond / melt-blown non-woven fabric material, so that the protective material is fully degradable.

[0025] The application further improves the hydrostatic pressure of the protective material under the same porosity condition, and significantly enhances the protective performance of the protective material. The multi-layer co-extrusion technology is used to prepare the breathable film, the micropore density of each layer is gradient-distributed, and the self-adaptive breathability under dynamic humidity is achieved.

[0026] The above description is only a summary of the technical solutions of the application, and in order to more clearly understand the technical means of the application, the specific embodiments of the application can be implemented according to the content of the description, and in order to make the above and other purposes, characteristics and advantages of the application more obvious and easy to understand, the following specific embodiments of the application are described. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the application, the following will briefly introduce the drawings used in the application. Obviously, the drawings described below are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creating any creative labor.

[0028] Figure 1 A structural schematic diagram of the degradable and breathable composite film based on the gradient microporous structure provided in the embodiments of the present application is shown in FIG. 1.

[0029] Figure 2 A physical diagram of the gradient breathable film provided in Embodiment 1 of the present application is shown in FIG. 2.

[0030] Figure 3 A surface scanning electron microscope diagram of the gradient breathable film provided in Embodiment 1 of the present application is shown in FIG. 3.

[0031] Legend: 11, outer layer of the gradient breathable film; 12, middle layer of the gradient breathable film; 13, inner layer of the gradient breathable film; 2, PLA non-woven fabric. DETAILED DESCRIPTION

[0032] The embodiments of the technical solutions of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion.

[0034] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0035] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can 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 all refer to the same embodiment, nor is it necessarily mutually exclusive or alternative to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0036] The existing medical and health materials have the following problems: polypropylene non-woven fabric is compounded with PE breathable film, which has poor breathability and easily causes skin heat and allergy; PE, PP and PU non-woven fabric has poor degradability, causing environmental pollution; the biodegradable film has poor breathability, resulting in insufficient comfort of the protective material.

[0037] In order to solve the technical problems that the air permeability and protection of existing medical and health materials are difficult to balance, and the materials are difficult to degrade and pollute the environment, the application provides a degradable and air-permeable composite film based on a gradient microporous structure, a preparation method and application thereof, wherein a three-layer gradient air-permeable film material is prepared and compounded with a degradable PLA non-woven fabric, which not only has complete biodegradability, but also improves the hydrostatic pressure of the protective material and increases the comfort of the protective material due to the special design of the gradient air permeability.

[0038] In a first aspect, the application provides a preparation method of a degradable and air-permeable composite film based on a gradient microporous structure, comprising the following steps:

[0039] S1. PLA (polylactic acid), PBAT (polybutylene adipate terephthalate), ADR (epoxy chain extender), CaCO3 and modified masterbatch are melt blended in proportion, and a three-layer casting film is prepared by using a three-layer casting film equipment, wherein, in terms of weight fraction:

[0040] The outer layer comprises 15-50 parts of PLA, 50-85 parts of PBAT, 5 parts of ADR, 30-35 parts of CaCO3 and 2-10 parts of hydrophobic masterbatch;

[0041] The middle layer comprises 15-50 parts of PLA, 50-85 parts of PBAT, 5 parts of ADR and 40-45 parts of CaCO3;

[0042] The inner layer comprises 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;

[0043] The three-layer casting film is formed by a stretching process to obtain a gradient air-permeable film;

[0044] S2. PLA non-woven fabric is prepared by melt blowing or spun-bonding process;

[0045] S3. The gradient air-permeable film is compounded with the PLA non-woven fabric to obtain a degradable and air-permeable composite film based on a gradient microporous structure.

[0046] In the technical scheme of the embodiment of the present application, the gradient microporous structure of the breathable film is realized through the differential design and stretching process of the three-layer cast film, the porosity and pore size distribution are optimized, and thus the air permeability and waterproof performance are improved; the degradable materials such as PLA and PBAT are used, so that the composite film has good biodegradability and reduces pollution to the environment; the hydrophobic master batch is added to the outer layer and the hydrophilic master batch is added to the inner layer, so that the comfort and moisture absorption and perspiration performance of the composite film are improved; the addition of CaCO3 improves the barrier performance of the film and prevents liquid leakage, and finally the obtained composite film is fully degradable and more environmentally friendly. The composite film material prepared in the present application has excellent air permeability, waterproofness, comfort and degradability, and can be applied to the fields of sanitary products and medical protective materials.

[0047] Further, 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 100-250 thousand; the melt index of PBAT is 2-20 g / 10 min, and the weight average molecular weight is 3-250 thousand.

[0048] In the technical scheme of the embodiment of the present application, the mass ratio of PLA to PBAT ensures the balance of the mechanical properties and processing performance of the material. PLA provides certain strength and stiffness, and PBAT provides flexibility and processing fluidity. The melt index of PLA at 190°C and 2.16 kg is 2-15 g / 10 min, and the melt fluidity is moderate, which is beneficial to processing and molding. The weight average molecular weight is in the range of 10-25 thousand, which ensures that the molecular weight distribution of PLA is moderate, and the mechanical strength of the material is ensured, and the processing performance is not affected due to the too high molecular weight. The melt index of PBAT at 190°C and 2.16 kg is 2-20 g / 10 min, indicating that the melt fluidity is good, which is beneficial to forming a uniform system in the blending and film forming process. The weight average molecular weight is in the range of 3-25 thousand, which ensures that the molecular weight distribution of PBAT is moderate and provides good flexibility and elasticity.

[0049] Further, in some embodiments, the particle size of CaCO3 is 500-3000 mesh.

[0050] In the technical scheme of the embodiment of the present application, the particle size of CaCO3 is relatively small and uniform, which is helpful to realize more uniform dispersion in the polymer matrix, and thus the microstructure and performance of the composite material are improved.

[0051] Further, in some embodiments, the hydrophobic master batch is a fluoropolymer or silane modified PLA-based master batch; and the hydrophilic master batch is a polyethylene glycol modified PLA-based master batch.

[0052] In the technical scheme of the embodiments of the present application, the PLA-based hydrophobic master batch modified by fluoropolymers or silane compounds can endow the material surface with excellent hydrophobic and oleophobic properties, and reduce the adhesion and penetration of liquid on the material surface. Specifically, the hydrophobic master batch comprises the following components in parts by weight: PLA 55-65 parts, fluoropolymers or silane compounds 5-20 parts, dispersant 5-15 parts, compatibility agent 0.1-5 parts, and lubricant 0.1-2 parts. The fluoropolymers include one or more of polytetrafluoroethylene, polyvinylidene fluoride, and fluorinated ethylene propylene copolymer. The silane compounds include one or more of polydimethylsiloxane and its derivatives, octadecyltrimethoxysilane, and octyltriethoxysilane. The PLA-based hydrophilic master batch modified by polyethylene glycol can endow the material surface with good hydrophilicity and moisture absorption, and improve the comfort and air permeability of the material. Specifically, the hydrophilic master batch comprises the following components in parts by weight: PLA 55-65 parts, polyethylene glycol and its derivatives 15-30 parts, dispersant 5-15 parts, and compatibility agent 0.1-5 parts. By blending the two master batches with PLA / PBAT matrix material and fillers such as CaCO3, a breathable film material with controllable gradient porosity and surface properties can be prepared, thereby further improving the comprehensive performance of the material and meeting the needs of different application scenarios.

[0053] Further, in some embodiments, the gradient breathable film has a pore size of 5-50 μm and a porosity of 60-85%.

[0054] In the technical scheme of the embodiments of the present application, the appropriate pore size can achieve fine control of the air permeability and barrier property of the breathable film to meet the needs of different application scenarios. The appropriate porosity can achieve a balance between the air permeability, moisture permeability, and barrier property of the breathable film to obtain the best comprehensive performance.

[0055] Further, in some embodiments, in step S2, the PLA non-woven fabric has a grammage of 10-50 gsm.

[0056] In the technical scheme of the embodiments of the present application, the melt-blowing process has a melt temperature of 200-240℃ to prevent thermal degradation of PLA; an air flow pressure of 0.2-0.8 MPa to control the fiber diameter; and a receiving distance of 10-30 cm to affect the uniformity of fiber laying. The spun-bonding process has a spinning temperature of 210-250℃. The melt-blowing or spun-bonding temperature ensures that the PLA material is in a suitable molten state, which not only ensures the fluidity of the melt and is conducive to the formation of fibers, but also avoids degradation of the PLA material caused by excessively high temperature. The PLA non-woven fabric with appropriate grammage can balance the air permeability and mechanical strength of the material.

[0057] Further, in some embodiments, in step S1, the temperature of melt blending is 175-200℃, the temperature of extrusion is 175-200℃, 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.

[0058] In the technical solutions of the embodiments of the present application, the melt blending temperature ensures that the components such as PLA, PBAT, and CaCO3 can be fully melted and mixed to form a uniform melt. A proper temperature is beneficial for the interaction between the components, and a too low temperature may lead to uneven mixing, and a too high temperature may cause material degradation, affecting the performance of the final product. The extrusion temperature needs to be matched with the melt blending temperature to ensure that the melt maintains good fluidity and stability during the extrusion process. A suitable extrusion temperature is beneficial for the formation of the three-layer casting film, ensuring the uniformity of the materials in each layer and the consistency of the thickness. Controlling the extrusion temperature can avoid degradation or performance decline of the material during the extrusion process. Unidirectional stretching is usually performed in one direction, which can significantly improve the mechanical properties such as tensile strength and elongation at break of the material in that direction. By controlling the stretching ratio, the shape and size of the pores can be adjusted to optimize the air permeability and barrier properties of the air permeable film. Bidirectional stretching is performed in two perpendicular directions, which can make the material have good mechanical properties in both directions. The transverse and longitudinal stretching ratios can be independently adjusted to achieve fine control of the pore structure, thereby better balancing the air permeability, barrier property, and mechanical property.

[0059] Further, in some embodiments, in step S3, the compounding method is hot-press compounding, the temperature is 120-150℃, the pressure is 0.2-0.8MPa, and the hot-press compounding speed is 20-200m / min.

[0060] In the technical solutions of the embodiments of the present application, through the hot-press compounding process, the interlayer bonding force of the composite material can be significantly enhanced, and its overall performance can be optimized.

[0061] Please refer to Figure 1 , in a second aspect, the embodiments of the present application provide a degradable air-permeable composite film based on gradient microporous structure, which is prepared by the above preparation method. The composite film has a moisture permeation amount ≥2450g / (m 2 ·d), a biodegradation rate ≥95.55%, and a tensile strength ≥85N.

[0062] In the technical scheme of the embodiment of the present application, the degradable and breathable composite film based on the gradient microporous structure comprises a gradient breathable film outer layer 11, a gradient breathable film middle layer 12, a gradient breathable film inner layer 13 and a PLA non-woven fabric 2. The high moisture permeation amount ensures that the composite film can quickly discharge moisture while maintaining good breathability, thereby improving the comfort of the wearer. The high biodegradation rate meets the needs of sustainable development and reduces the environmental pollution problem of waste. The tensile strength ensures that the composite film has good mechanical properties in actual use, and is not easy to tear or break, thereby improving the durability and reliability of the product.

[0063] In a third aspect, the embodiment of the present application provides an application of a degradable and breathable composite film based on a gradient microporous structure. The composite film is used in the field of medical and health materials.

[0064] In the technical scheme 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.

[0065] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are used to explain the present application, and cannot be understood as limiting the present application. If the specific technology or condition is not specified in the embodiments, the technology or condition described in the literature in the art or according to the product manual is used. If the reagent or instrument is not specified by the manufacturer, it is a conventional product that can be obtained by purchase.

[0066] I. Preparation method

[0067] Embodiment 1

[0068] The embodiment provides a preparation method of a degradable and breathable composite film based on a gradient microporous structure, comprising the following steps:

[0069] S1. PLA, PBAT, ADR, CaCO3 and modified masterbatch are melt blended according to the proportion, the temperature of melt blending is 185°C, a three-layer casting film device is used to prepare a three-layer casting film, the three-layer casting film is formed by a stretching process, the horizontal and vertical stretching ratios are both 2.0, and a gradient breathable film is obtained, as shown in FIG. 1, it can be seen that the film surface has irregular pores, pits and loose network structures; Figures 2 to 3

[0070] S2. A PLA non-woven fabric is prepared by a spunbond process, the spunbond temperature is 220°C, and the obtained PLA spunbond non-woven fabric has a grammage of 20gsm;

[0071] ​S3. The gradient breathable film was hot-pressed with the PLA non-woven fabric, the temperature was 130℃, the pressure was 0.6MPa, and the hot-pressing speed was 100m / min, to obtain a degradable breathable composite film based on a gradient microporous structure. The components of the three-layer cast film are shown in Table 1 in weight parts:

[0072] Table 1 Components of three-layer cast film

[0073]

[0074] Examples 2-18 and Comparative Examples 1-5

[0075] Examples 2-18 and Comparative Examples 1-5 each provide a method for preparing a degradable breathable composite film based on a gradient microporous structure, and the only difference compared with Example 1 is that the components of the composite film and the PLA non-woven fabric grammage are different, wherein the components of the three-layer cast film are shown in Table 2 in weight parts.

[0076] Table 2 Comparison of experimental parameters

[0077]

[0078]

[0079] II. Test methods

[0080] 1. Biodegradation rate: The biodegradation rate after 90 days was determined according to the "Evaluation of the Biodegradability of Textile Nonwovens - Determination of Carbon Dioxide Evolution" GB / T 33616-2017;

[0081] 2. Hydrostatic pressure: The hydrostatic pressure was tested using a water resistance tester according to the method of GB / T 4744-1997;

[0082] 3. Moisture permeation amount: The test method and requirements for moisture permeation amount in the technical requirements for medical disposable protective clothing GB 19082-2009 were used for testing;

[0083] 4. Tensile strength: The tensile strength of the material was determined using an electronic strength tester according to GB / T 3923.1-1997.

[0084] III. Analysis of test results of each example and comparative example

[0085] The test results are shown in Table 3.

[0086] Table 3 Test results

[0087]

[0088]

[0089] As can be seen from Examples 1 to 5, the higher the proportion of PBAT in the PLA and PBAT composite film, the lower the biodegradation rate of the protective material, which is mainly due to the fact that the molecular chain of PLA is a linear structure composed of multiple lactic acid monomers connected by ester bonds, has a relatively regular molecular weight, good flexibility and processing performance, and is more likely to interact with water, carbon dioxide, microorganisms and the like to cause degradation; while the molecular chain of PBAT is a linear structure composed of random arrangement of butylene adipate monomers and butylene terephthalate monomers, contains benzene ring structure in the molecular chain, and the density of ester groups is significantly lower than that of polylactic acid, and the biodegradability is also reduced. In Comparative Example 1, the proportion of PLA is too small, resulting in a decrease in the mechanical strength of the material.

[0090] As can be seen from Examples 14 to 18, the higher the grammage of the PLA non-woven fabric, the greater the tensile strength of the protective material, which is mainly due to the fact that the strength of the PLA spun-bond 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, and the more the number of fibers, the greater the strength of the non-woven fabric.

[0091] As can be seen from Examples 3, 6 and 7, the higher the calcium carbonate content, the greater the moisture permeability of the protective material, and the better the comfort. This is mainly due to the fact that with the increase of calcium carbonate content, the porosity of the three-layer co-extrusion cast film is greater after bidirectional stretching, and the moisture permeability of the protective material is greater. In Comparative Example 4, insufficient calcium carbonate content can reduce the formation of micropores, reduce the porosity and connectivity of the film, and thus significantly reduce the moisture permeability; in Comparative Example 5, excessive addition of calcium carbonate can cause the micropores to be too large or unevenly distributed, which can destroy the uniformity of the film and reduce its waterproof performance. At the same time, excessive calcium carbonate can affect the mechanical properties of the film, causing the microporous structure to be unstable during stretching, and affecting the stability of the material.

[0092] As can be seen from Example 8, Example 9, and Example 10, as the content of hydrophilic and hydrophobic masterbatch increases, the barrier performance of the protective material improves, and the hydrostatic pressure also increases. This is mainly because after the outer layer material of the multilayer cast film is treated to be hydrophobic, a water-repellent protective layer is formed on the surface, which can withstand deeper water penetration. In Example 10, compared with Example 8, the addition amount of hydrophobic masterbatch and hydrophilic masterbatch is larger, and the difference between the hydrophilic and hydrophobic composite film is more obvious. Since the material of the application is a heterogeneous film material, the difference between the front and back surfaces is large. In the hydrostatic pressure test, when the test surface is the hydrophobic layer, the hydrostatic pressure of Example 10 with 10% hydrophobic masterbatch is higher than that of Example 8 with 2% hydrophobic masterbatch. Similarly, in the moisture permeation test, when the moisture diffuses from the hydrophobic layer to the hydrophilic layer, the diffusion speed of the moisture in contact with the hydrophobic layer is much smaller than that in the hydrophilic layer. Therefore, the moisture permeation of Example 10 is smaller than that of Example 8. In addition, as can be seen from Example 11, Example 12, Example 13, and Example 14, when the inner layer of the film material is treated to be hydrophilic, the moisture permeation of the protective material increases, and when the outer layer of the film material is treated to be hydrophobic, the hydrostatic pressure of the protective material increases. In Comparative Example 2, no hydrophobic component is added, resulting in a decrease in hydrostatic pressure. In Comparative Example 3, no hydrophilic component is added, resulting in a decrease in moisture permeation.

[0093] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications of the embodiments that can be thought of by those skilled in the art, and other ways constructed by combining part of the components of the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a degradable, gas permeable composite membrane based on gradient microporous structure, characterized in that, Comprising the following steps: S1. melt blending PLA, PBAT, ADR, CaCO3 and modified masterbatch according to the proportion, using three-layer casting film equipment to prepare three-layer casting film, wherein, in terms of weight fraction: The outer layer comprises: 15-50 parts of PLA, 50-85 parts of PBAT, 5 parts of ADR, 30-35 parts of CaCO3 and 2-10 parts of hydrophobic masterbatch; The middle layer comprises: 15-50 parts of PLA, 50-85 parts of PBAT, 5 parts of ADR and 40-45 parts of CaCO3; The inner layer comprises: 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 casting film is formed by a stretching process to obtain a gradient breathable film; Wherein, the mass ratio of PLA to PBAT is 15:85-50:50; the particle size of CaCO3 is 500-3000 mesh; the hydrophobic masterbatch is a fluoropolymer or silane compound modified PLA-based masterbatch; the hydrophilic masterbatch is a polyethylene glycol modified PLA-based masterbatch; S2. Prepare a PLA non-woven fabric by melt blowing or spun-bonding process; S3. Compound the gradient breathable film with the PLA non-woven fabric to obtain a degradable breathable composite film based on gradient microporous structure.

2. The method of claim 1, wherein the method further comprises: In step S1, the melt index of the PLA is 2-15 g / 10 min, and the weight average molecular weight is 100-250 thousand; the melt index of the PBAT is 2-20 g / 10 min, and the weight average molecular weight is 3-250 thousand.

3. The method of claim 1, wherein the method further comprises: The pore size of the gradient breathable film is 5-50 μm, and the porosity is 60-85%.

4. The method of claim 1, wherein the method further comprises: In step S2, the grammage of the PLA non-woven fabric is 10-50 gsm.

5. The method of claim 1, wherein the method further comprises: In step S1, the temperature of the melt blending is 175-200℃, and the extrusion temperature is 175-200℃; 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.

6. The method of claim 1, wherein the method further comprises: In step S3, the compounding method is hot pressing compounding, the temperature is 120-150℃, the pressure is 0.2-0.8 MPa, and the hot pressing compounding speed is 20-200 m / min.

7. A degradable, gas permeable composite membrane based on gradient microporous structure, prepared by the method of any one of claims 1-6, characterized in that, The degradable breathable composite film based on gradient microporous structure has a moisture permeation amount of ≥2450 g / (m 2 ·d), a biodegradation rate of ≥95.55%, and a tensile strength of ≥85 N.

8. Use of a degradable, gas permeable composite membrane based on gradient microporous structures according to claim 7, characterized in that, The degradable breathable composite film based on gradient microporous structure is used in the field of medical and health materials.

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