CN115678108B - Pore-forming agent and application thereof, breathable film and preparation method thereof - Google Patents

Abstract

The invention discloses a pore-forming agent, which comprises the following components: the calcium chloride crystal hydrate and the porous powder, wherein the calcium chloride crystal hydrate is adsorbed in the holes of the porous powder. The invention also discloses a preparation method of the pore-foaming agent and application of the pore-foaming agent in a breathable film. The invention also discloses a breathable film, which comprises the following raw materials: the resin, the pore-forming agent or the pore-forming agent prepared by the preparation method of the pore-forming agent. The invention also discloses a preparation method of the breathable film, which comprises the following steps: granulating the resin and Kong Jimi, casting to prepare a film, stretching and shaping to obtain the antibacterial breathable film, wherein the stretching is performed while microwave heating is performed. The invention has small size requirement on the pore-forming agent, adopts a mode of stretching and microwave heating at the same time, so that calcium chloride crystal hydrate in the pore-forming agent is heated to lose crystal water, steam is formed, and the interface between porous powder and resin in the pore-forming agent is expanded and destroyed, thereby realizing uniform pore-forming, and the pore-forming effect is good and the efficiency is high.

Description

A porogen and its application, a breathable film and its preparation method

Technical Field

The invention relates to the technical field of porogens, and in particular to a porogen and application thereof, a breathable film and a preparation method thereof.

Background Art

At present, the porogen commonly used in breathable membranes is ultrafine calcium carbonate. The principle of its breathability and waterproofing is that ultrafine calcium carbonate is added to the resin, and the film is stretched after forming to produce micropores. When stretching, the interface between the resin and the ultrafine calcium carbonate particles is peeled off, and interconnected winding pores or channels are formed around the ultrafine calcium carbonate particles, giving the film the function of being breathable and moisture-permeable but liquid-impermeable, thereby connecting the environments on both sides of the film.

In the process of preparing breathable membranes, the particle size and distribution of calcium carbonate directly affect the processing fluidity, which in turn determines the production speed and process stability of the breathable membrane, and also has an important impact on the stretching porosity, pore structure, air permeability and mechanical properties of the breathable membrane: (1) If the particle size is too small, the dispersibility is poor and the oil absorption value is high, resulting in unstable membrane quality and increasing the work intensity when mixing with the resin; in addition, the small-particle calcium carbonate powder itself has a large specific surface area and surface energy (i.e., the reverse agglomeration force relative to the crushing force), which easily causes agglomeration to form large particles, resulting in a wide distribution of powder particle size, affecting the stability and use effect of the breathable membrane processing technology; (2) If the particle size is too large, the pores in the cast membrane will become larger, which will cause the pores in the cast membrane to become larger and water permeable, and in severe cases, the membrane may break; in addition, large particles will become stress concentration points in the polymer matrix, affecting the performance of the product and even making it impossible to process it downstream.

Traditional inorganic powder porogens, such as ultrafine calcium carbonate, must have a D50 particle size of 1.8-2.2μm, a D97 particle size of <6.5μm, a content of particles with a particle size of 1-5μm of more than 60%, a content of particles with a particle size of more than 10μm of <100ppm, a specific surface area of ^5-15m2 /g, and a density of >2.9g/ ^cm3 to achieve effective pore formation. The index parameters of porogens are difficult to process, resulting in high production costs.

Summary of the invention

Based on the technical problems existing in the background technology, the present invention proposes a porogen and its application, a breathable membrane and its preparation method. The present invention obtains the porogen by distributing calcium chloride crystalline hydrate in the pores of a porous powder, and adopts a stretching and microwave heating method to heat the calcium chloride crystalline hydrate in the porogen to lose crystal water, form water vapor, expand and destroy the interface between the porous powder and the resin in the porogen, and realize uniform pore formation. The present invention has small requirements on the size of the porogen, and has good pore formation effect and high efficiency.

The invention provides a porogen, which comprises calcium chloride crystal hydrate and porous powder, wherein the calcium chloride crystal hydrate is adsorbed in the pores of the porous powder.

Preferably, the calcium chloride crystalline hydrate is CaCl ₂ ·2H ₂ O.

Preferably, the D97 particle size of the porous powder is less than 10 μm.

The above D97 refers to the sieve aperture through which 97 wt% of particles can pass.

Preferably, the porous powder is an inorganic porous powder.

Preferably, the porous powder includes at least one of zeolite, diatomaceous earth, wollastonite and sepiolite.

The present invention also provides a method for preparing the porogen, comprising the following steps: mixing a saturated calcium chloride aqueous solution with porous powder, ultrasonicating for 30-60 minutes, separating the solid from the liquid, and drying to obtain the porogen.

Preferably, the saturated calcium chloride aqueous solution contains a surfactant.

The use of surfactants can promote the uniform dispersion of calcium chloride and porous powders and promote the entry of calcium chloride into the pores of porous powders. The amount of saturated calcium chloride aqueous solution and porous powder is not specified, as long as the pores of the porous powders can adsorb calcium chloride crystalline hydrates.

Preferably, the surfactant includes at least one of sodium linear alkylbenzene sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, and ammonium fatty alcohol polyoxyethylene ether sulfate.

Preferably, the mass ratio of surfactant to water is 0.1-2:100.

Preferably, the temperature during ultrasound is 20-40°C.

Preferably, the drying is spray drying.

Preferably, the drying temperature is 230-250°C.

The invention also proposes the application of the porogen in a breathable membrane.

The present invention also provides a breathable membrane, the raw materials of which include: resin, the above-mentioned porogen or the porogen prepared by the above-mentioned preparation method of the porogen, wherein the resin is at least one of a non-polar resin and a low-polar resin.

Preferably, the non-polar resin includes at least one of polyethylene and polypropylene.

Preferably, the low-polarity resin is at least one of nylon, polylactic acid, and polycarbonate resin.

The low-polarity resin mentioned above refers to a resin having relatively low polarity.

The present invention also proposes a method for preparing the above-mentioned breathable film, comprising the following steps: mixing and granulating the resin and the porogen, casting the film, stretching, and shaping to obtain the antibacterial breathable film, wherein microwave heating is performed while stretching.

Preferably, the temperature of microwave heating is 260-270°C.

Preferably, the microwave heating time and the stretching time are the same.

Preferably, the temperatures of banburying granulation and casting film formation are lower than the drying temperature during the preparation of the porogen.

Preferably, the temperature during stretching is set between the high elastic temperature and the viscous flow temperature of the resin.

When the temperature is low, the deformation of the resin is very small; when the temperature rises to a certain range, the deformation of the resin increases significantly, and the deformation is relatively stable in a certain temperature range thereafter. This state is the high elastic state, and its corresponding temperature range is the high elastic state temperature; if the temperature continues to rise, the resin gradually becomes a viscous fluid. This state is the viscous flow state, and its corresponding temperature range is the viscous flow temperature.

Before use, the above-mentioned resins and porogens need to be dried to remove free water but not crystal water, so as to avoid the presence of free water in the polymer and porogen, which may lead to large pores during film preparation.

The content of porogen in the breathable film is not specified, and can be determined based on the air permeability requirements of the product.

The raw materials of the above-mentioned breathable film may also contain additives such as antioxidants, lubricants, plasticizers, etc. The amount of the additives is not specified and is determined according to specific requirements. The additives can be purchased from the market; the above-mentioned breathable film can be used in multiple fields such as medical care, personal care, construction, and agricultural and sideline product packaging, and can be used to manufacture sanitary protection products, breathable rainproof cloth, etc.

Beneficial effects:

The porogen of the present invention has calcium chloride crystal hydrate adsorbed in the pores of the porous powder. During the stretching and film forming, microwave heating is adopted to heat the calcium chloride crystal hydrate in the porogen to lose crystal water and form water vapor, while the non-polar resin does not heat up after microwave heating, and the low-polar resin heats up slowly after microwave heating;

In the process of preparing the breathable membrane, the interfacial force has an important influence on the stretching porosity, pore structure, air permeability and mechanical properties of the breathable membrane. The calcium chloride crystal hydrate inside the pores of the porous powder is dehydrated by heat, forming water vapor in the pores, which will expand and combine with stretching to destroy the interface between the porous powder and the resin in the porogen, thereby achieving interfacial debonding, thereby forming fine and uniform micropores. The pore-making effect of the present invention is uniform; by adjusting the time and temperature of microwave heating, the size of the debonding interface area can be controlled, and then the pore size of the breathable membrane can be adjusted;

In addition, after the holes are made, the porous powder is located on the inner surface of the pores of the breathable membrane, and can absorb harmful substances in the gas, such as bacteria or nanoparticles, during the ventilation process, achieving the effect of antibacterial and gas purification;

In addition, traditional inorganic powder porogens have high requirements on size, and effective pore formation can only be achieved after reaching a specified size. The present invention relies on the expansion of water vapor in the pores of porous powders to form pores, and has low requirements on the size of the porogen and porous powder, and a simple process; and the surface porosity of the porous powder is high and nanometer-level, and each pore can participate in pore formation, so the pore-forming effect of the porogen of the present invention is good and efficient; and the preparation method of the porogen and breathable membrane of the present invention is simple and suitable for industrial production.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of the preparation process of the breathable membrane of the present invention.

FIG. 2 is a diagram showing the working mechanism of the breathable membrane of the present invention.

DETAILED DESCRIPTION

The technical solutions of the present invention are described in detail below through specific embodiments. However, it should be clearly stated that these embodiments are for illustration only and are not to be construed as limiting the scope of the present invention.

Example 1

A preparation method of a porogen comprises the following steps: mixing calcium chloride, deionized water and linear sodium alkylbenzene sulfonate to obtain a saturated calcium chloride aqueous solution, wherein the mass ratio of the linear sodium alkylbenzene sulfonate to water is 1:100; then mixing with D97 zeolite with a particle size of 8 μm, ultrasonicating at 30°C for 40 minutes, wherein CaCl ₂ ·6H ₂ O is adsorbed and distributed in the pores of the zeolite; then filtering by pressure, and spray drying at 240°C to obtain a porogen, wherein CaCl ₂ ·2H ₂ O is adsorbed and distributed in the pores of the zeolite.

A method for preparing a breathable membrane comprises the following steps:

22 parts of the above-mentioned porogen and 100 parts of linear low-density polyethylene resin (melting point 125°C) were heated to 110°C in an oven under nitrogen protection for drying, and then mixed with 0.6 parts of antioxidant, 1.2 parts of lubricant and 1.9 parts of plasticizer for banburying and granulation; then a cast film was prepared on a small casting unit, the extruder temperature was 200°C, the casting die temperature was 220°C, the casting roll temperature was 90°C, the distance between the die and the casting roll was 4cm, and an air knife with a 0.5mm opening was set between the die and the casting roll to provide air to cool the surface of the melt film, and the air knife air speed was 2m/s; wherein, the temperatures of banburying granulation and casting film making were both lower than 240°C;

The prepared cast film was cut into samples of 100mm×45mm, and stretched using an electric stretching instrument equipped with a microwave heating device, with a stretching temperature of 100°C, a stretching ratio of 2.6, and a stretching rate of 400mm/min; then heat-set for 30min to obtain a polyethylene breathable film; during the stretching stage, it was passed through a microwave heating device and microwave heating was performed while stretching, with a microwave temperature of 262°C and the microwave heating time being the same as the stretching time, to obtain a breathable film with an average pore size of 3.9μm and a porosity of 59.8%.

FIG1 is a flow chart of the preparation process of the breathable membrane of the present invention.

FIG. 2 is a diagram showing the working mechanism of the breathable membrane of the present invention.

A breathable membrane was prepared according to the method in Example 1, wherein the porogen in Example 1 was replaced with ultrafine calcium carbonate (the ultrafine calcium carbonate had a D50 particle size of 1.8-2.2 μm, a D97 particle size of <6.5 μm, a content of particles with a particle size of 1-5 μm of more than 60%, a content of particles with a particle size of more than 10 μm of <100 ppm, a specific surface area of 5-15 m ² /g, and a density of >2.9 g/cm ³ ); it was found that when the stretching rate was 400 mm/min, the pore size distribution of the breathable membrane was uneven and varied, and the stretching rate could not be too high; when the stretching rate was adjusted to 110 mm/min, the porosity of the obtained breathable membrane was 37.8%, which was 22% lower than the porosity of Example 1.

Example 2

A preparation method of a porogen comprises the following steps: mixing calcium chloride, deionized water and sodium sulfate of fatty alcohol polyoxyethylene ether to obtain a saturated calcium chloride aqueous solution, wherein the mass ratio of sodium sulfate of fatty alcohol polyoxyethylene ether to water is 0.1:100; then mixing with diatomaceous earth with a particle size of 7 μm of D97, ultrasonicating at 30°C for 60 minutes, at which time _CaCl2 · _6H2O is adsorbed and distributed in the pores of the diatomaceous earth; then filtering by pressure, and spray drying at 245°C to obtain a porogen, at which time _CaCl2 · _2H2O is adsorbed and distributed in the pores of the diatomaceous earth.

A method for preparing a breathable membrane comprises the following steps:

31 parts of the above-mentioned porogen and 100 parts of polypropylene resin (melting point 195°C) were heated to 120°C in an oven under nitrogen protection for drying, and then mixed with 2 parts of antioxidant, 1.5 parts of lubricant and 1.5 parts of plasticizer for banburying and granulation; then a cast film was prepared on a small casting unit, the extruder temperature was 222°C, the casting die temperature was 236°C, the casting roll temperature was 160°C, the distance between the die and the casting roll was 4cm, and an air knife with a 0.5mm opening was set between the die and the casting roll to provide air to cool the surface of the melt film, and the air knife air speed was 2m/s; wherein, the temperatures of banburying granulation and casting film making were both lower than 245°C;

The prepared cast film was cut into samples of 100mm×45mm, and stretched using an electric stretching instrument equipped with a microwave heating device, with a stretching temperature of 170°C, a stretching ratio of 3.1, and a stretching rate of 300mm/min; then heat-set for 35 minutes to obtain a polypropylene breathable film; during the stretching stage, it was passed through a microwave heating device and microwave heating was performed while stretching, with a microwave temperature of 262°C and the microwave heating time being the same as the stretching time, to obtain a breathable film with an average pore size of 3.6μm and a porosity of 62.7%.

A breathable membrane was prepared according to the method of Example 2, wherein the porogen in Example 2 was replaced with ultrafine calcium carbonate (the ultrafine calcium carbonate had a D50 particle size of 1.8-2.2 μm, a D97 particle size of <6.5 μm, a content of particles with a particle size of 1-5 μm of more than 60%, a content of particles with a particle size of more than 10 μm of <100 ppm, a specific surface area of 5-15 m ² /g, and a density of >2.9 g/cm ³ ); when the stretching rate was adjusted to 110 mm/min, the porosity of the obtained breathable membrane was 34.7%, which was 28% lower than the porosity of Example 2.

Example 3

A preparation method of a porogen comprises the following steps: mixing calcium chloride, deionized water and fatty alcohol polyoxyethylene ether ammonium sulfate to obtain a saturated calcium chloride aqueous solution, wherein the mass ratio of the fatty alcohol polyoxyethylene ether ammonium sulfate to water is 0.1:100; then mixing with wollastonite with a D97 particle size of 8.5 μm, ultrasonicating at 30°C for 30 minutes, at which time _CaCl2 · _6H2O is adsorbed and distributed in the pores of the wollastonite; then filtering by pressure, and spray drying at 250°C to obtain the porogen, at which time _CaCl2 · _2H2O is adsorbed and distributed in the pores of the wollastonite.

A method for preparing a breathable membrane comprises the following steps:

16 parts of the above-mentioned porogen and 100 parts of polypropylene resin (melting point 195° C.) were heated to 110° C. in an oven under nitrogen protection for drying, and then mixed with 1.1 parts of antioxidant, 2.1 parts of lubricant and 1.1 parts of plasticizer for banburying and granulation; then a cast film was prepared on a small casting unit, the extruder temperature was 222° C., the casting die temperature was 236° C., the casting roll temperature was 160° C., the distance between the die and the casting roll was 4 cm, and an air knife with a 0.5 mm opening was set between the die and the casting roll to provide air to cool the surface of the melt film, and the air knife air speed was 2 m/s; wherein the temperatures of banburying and granulation and casting film making were both lower than 250° C.;

The prepared cast film was cut into samples of 100mm×45mm, and stretched using an electric stretching instrument equipped with a microwave heating device, with a stretching temperature of 175°C, a stretching ratio of 3.1, and a stretching rate of 300mm/min; then heat-set for 35min to obtain a polypropylene breathable film; during the stretching stage, it was passed through a microwave heating device and microwave heating was performed while stretching, with a microwave temperature of 265°C and the microwave heating time being the same as the stretching time, to obtain a breathable film with an average pore size of 4.3μm and a porosity of 57.8%.

A breathable membrane was prepared according to the method of Example 3, wherein the porogen in Example 3 was replaced with ultrafine calcium carbonate (the ultrafine calcium carbonate had a D50 particle size of 1.8-2.2 μm, a D97 particle size of <6.5 μm, a content of particles with a particle size of 1-5 μm of more than 60%, a content of particles with a particle size of more than 10 μm of <100 ppm, a specific surface area of 5-15 m ² /g, and a density of >2.9 g/cm ³ ); when the stretching rate was adjusted to 110 mm/min, the porosity of the obtained breathable membrane was 39.8%, which was 18% lower than the porosity of Example 3.

Example 4

A method for preparing a porogen is the same as that in Example 3.

A method for preparing a breathable membrane comprises the following steps:

20 parts of the above-mentioned porogen and 100 parts of nylon resin (melting point 177°C) were heated to 110°C in an oven under nitrogen protection for drying, and then mixed with 2 parts of antioxidant, 1 part of lubricant and 2.5 parts of plasticizer for banburying and granulation; then a cast film was prepared on a small casting unit, the extruder temperature was 180°C, the casting die temperature was 190°C, the casting roll temperature was 100°C, the distance between the die and the casting roll was 4cm, an air knife with a 0.5mm opening was set between the die and the casting roll to provide air to cool the surface of the melt film, and the air knife air speed was 2m/s; wherein, the temperatures of banburying granulation and casting film making were both lower than 250°C;

The prepared cast film was cut into samples of 100mm×45mm, and stretched using an electric stretching instrument equipped with a microwave heating device, with a stretching temperature of 175°C, a stretching ratio of 2.5, and a stretching rate of 300mm/min; then heat-set for 35min to obtain a nylon breathable film; during the stretching stage, it was passed through a microwave heating device and microwave heating was performed while stretching, with a microwave temperature of 265°C and the microwave heating time being the same as the stretching time, to obtain a breathable film with an average pore size of 4.5μm and a porosity of 55%.

A breathable membrane was prepared according to the method of Example 4, wherein the porogen in Example 4 was replaced with ultrafine calcium carbonate (the ultrafine calcium carbonate had a D50 particle size of 1.8-2.2 μm, a D97 particle size of <6.5 μm, a content of particles with a particle size of 1-5 μm of more than 60%, a content of particles with a particle size of more than 10 μm of <100 ppm, a specific surface area of 5-15 m ² /g, and a density of >2.9 g/cm ³ ); when the stretching rate was adjusted to 110 mm/min, the porosity of the obtained breathable membrane was 35%, which was 20% lower than the porosity of Example 4.

Microwave heating is performed while stretching. The non-polar resin is not heated, and the weak polar resin heats up slowly after microwave heating. Only the inorganic porous powder in the porogen is heated. At this time, the CaCl ₂ ·2H ₂ O in the inorganic porous powder is dehydrated by heat, and the water vapor expands along the surface of the porous powder, causing the porous powder and the resin interface to debond, forming a microporous structure. The porous powder is at the debonded interface, which can adsorb pathogens or nanoparticles in the penetrating gas, thereby achieving the effect of antibacterial and gas purification.

By adjusting the extruder temperature, casting die temperature, casting roll temperature, the distance between the die and the casting roll, stretching, microwave and other process parameters, the pore size distribution of the breathable membrane can be made more uniform.

When the porogen of the present invention is used to prepare a breathable film, the stretching rate can be ≤500 mm/min, and the maximum can be 500 mm/min; the stretching rate is much higher than the stretching rate when ultrafine calcium carbonate is used as a porogen. When ultrafine calcium carbonate is used as a porogen, the maximum stretching rate is 110 mm/min. If the speed is higher than this, the pores will be uneven. The porogen of the present invention has an excellent pore-forming effect and can prepare a breathable film with smaller pores.

Comparative Example 1

A breathable membrane was prepared according to the method in Example 1, wherein the porogen in Example 1 was replaced by CaCl ₂ ·2H ₂ O (the particle size of CaCl ₂ ·2H ₂ O was the same as that of the ultrafine calcium carbonate in Example 1), the stretching rate was 110 mm/min, and the other conditions were the same as in Example 1. The average pore size of the obtained breathable membrane was 12 μm, and the porosity was 30%.

Comparative Example 2

A breathable membrane was prepared according to the method in Example 1, wherein the porogen in Example 1 was replaced by zeolite (the particle size of the zeolite was the same as the particle size of the ultrafine calcium carbonate in Example 1), the stretching rate was 110 mm/min, and the other conditions were the same as in Example 1. The average pore size of the obtained breathable membrane was 15 μm, and the porosity was 26%.

The breathable membranes prepared in Examples 1-4 were tested, and the results are shown in Table 1.

The porosity was determined according to the ASTM D-2873 liquid absorption method. The bacterial filtration efficiency and non-oily particle filtration efficiency were determined using an air permeability tester. The penetration of synthetic blood through the breathable membrane under a certain pressure was detected using a synthetic blood tester.

Table 1 Test results

Test items Example 1 Example 2 Example 3 Example 4 Bacterial filtration efficiency % 81 79.1 78 77.7 Non-oily particle filtration efficiency % 90.1 88.1 72.4 72.0 Synthetic blood penetration mmHg 121 141 159 162 Respiratory resistance mmH ₂ O/cm ² 6.8 8.8 6.8 6.8 Average pore size of breathable membrane μm 3.9 3.6 4.3 4.5 Porosity % 59.8 62.7 57.8 55

It can be seen from Table 1 that the present invention has good antibacterial properties, air permeability and filterability.

The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims (18)

1. A breathable membrane, characterized in that its raw materials include: resin and porogen, wherein the resin is at least one of a non-polar resin and a low-polar resin; The porogen comprises: calcium chloride crystal hydrate and porous powder, wherein the calcium chloride crystal hydrate is adsorbed in the pores of the porous powder; the calcium chloride crystal hydrate is CaCl ₂ ·2H ₂ O; The preparation method of the breathable film comprises the following steps: mixing and granulating the resin and the porogen, casting the film, stretching, and shaping to obtain the antibacterial breathable film, wherein microwave heating is performed while stretching. 2. The breathable membrane according to claim 1, characterized in that the D97 particle size of the porous powder is less than 10 μm. 3 . The breathable membrane according to claim 1 , wherein the porous powder is an inorganic porous powder. 4 . The breathable membrane according to claim 1 , wherein the porous powder comprises at least one of zeolite, diatomaceous earth, wollastonite and sepiolite. 5. The breathable membrane according to claim 1, characterized in that the preparation method of the porogen comprises the following steps: mixing a saturated calcium chloride aqueous solution with the porous powder, ultrasonicating for 30-60 minutes, separating the solid from the liquid, and drying to obtain the porogen. 6. The breathable membrane according to claim 5, characterized in that the saturated calcium chloride aqueous solution contains a surfactant. 7. The breathable membrane according to claim 6, characterized in that the surfactant comprises at least one of linear alkylbenzene sulfonate sodium, fatty alcohol polyoxyethylene ether sodium sulfate, and fatty alcohol polyoxyethylene ether ammonium sulfate. 8. The breathable membrane according to claim 6, characterized in that the mass ratio of surfactant to water is 0.1-2:100. 9. The breathable membrane according to claim 5, characterized in that the temperature during ultrasound is 20-40°C. 10. The breathable membrane according to claim 5, characterized in that the drying is spray drying. 11. The breathable membrane according to claim 5, characterized in that the drying temperature is 230-250°C. 12 . The breathable membrane according to claim 1 , wherein the non-polar resin comprises at least one of polyethylene and polypropylene. 13. The breathable membrane according to claim 1, characterized in that the low-polarity resin is at least one of nylon, polylactic acid, and polycarbonate resin. 14. A method for preparing a breathable membrane according to any one of claims 1 to 13, characterized in that it comprises the following steps: mixing and granulating the resin and the porogen, casting the membrane, stretching, and shaping to obtain the antibacterial breathable membrane, wherein microwave heating is performed while stretching. 15. The method for preparing the antibacterial breathable membrane according to claim 14, characterized in that the temperature of microwave heating is 260-270°C. 16 . The method for preparing the antibacterial breathable membrane according to claim 14 , wherein the microwave heating time is the same as the stretching time. 17 . The method for preparing an antibacterial breathable membrane according to claim 14 , wherein the temperatures of banburying granulation and casting film making are lower than the drying temperature during the preparation of the porogen. 18. The method for preparing an antibacterial breathable membrane according to claim 14, characterized in that the temperature during stretching is set between the high elastic state temperature and the viscous flow state temperature of the resin.