Breathable film as well as preparation method and application thereof

Abstract

The invention discloses a breathable film as well as a preparation method and application thereof, and belongs to the technical field of film materials. The breathable film with the three-layer structure comprises a hydrophobic layer, a blocking layer and a water absorption layer, and the blocking layer is located between the hydrophobic layer and the water absorption layer; the hydrophobic layer comprises the following raw materials in parts by weight: 45-50 parts of PE, 45-50 parts of calcium carbonate, 1-2 parts of a hydrophobic agent and 3-4 parts of a processing aid; the barrier layer comprises the following raw materials in parts by weight: 40-45 parts of PE, 45-50 parts of calcium carbonate, 3-5 parts of a barrier agent, 3-4 parts of a processing aid and 0.1-1 part of a compatilizer; the water-absorbing layer is prepared from the following raw materials in parts by weight: 45-50 parts of PE, 45-50 parts of calcium carbonate, 1-2 parts of water-absorbing resin and 3-4 parts of a processing aid; the thickness ratio of the hydrophobic layer to the barrier layer to the water absorption layer is (4.0-6.0): (1.5-2.5): (2.5-3.5). The three-layer structure ensures the air permeability, reduces straight channels generated by micropores, and further reduces permeation channels of water. Under the combined action of the three layers, good air permeability is ensured, and meanwhile, the anti-permeation performance of the air-permeable membrane is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of film materials, and more specifically, relates to a breathable film and a preparation method and application thereof. Background Art

[0002] The structure of general sanitary products (sanitary napkins, diapers, etc.) can be divided into three layers: the surface layer (in contact with the human body), the absorbent core (absorbing liquid) and the bottom film (blocking liquid). The absorbent core has a high absorption rate. In the ideal use case, the liquid will be absorbed and no reverse osmosis will occur. However, in the case of long-term use, large amount of liquid or external force compression, the liquid absorbed by the absorbent core may still be released. The role of the bottom film is to prevent the liquid from contaminating the clothing in this case. The bottom film in sanitary products generally uses a breathable film. Its main breathability mechanism is to utilize the incompatible properties of polymer PE and calcium carbonate. Through a unidirectional axial stretching process, phase separation occurs between the two materials and a microporous structure is formed, ultimately achieving the purpose of being breathable and impermeable. However, in actual use (such as the use of sanitary napkins), when in contact with water for a long time and under continuous pressure, water molecules will penetrate the breathable film through these micropores, causing the risk of leakage (menstrual blood or urine, etc.).

[0003] Chinese patent CN110079001A discloses a skin-friendly, ultra-thin, highly breathable, zero-leakage bottom film, which is composed of nano-scale heavy calcium carbonate (30-50wt%), metallocene polyethylene (10-15%) and low-density polyethylene. It is prepared by high-multiple multi-stage stretching technology to make the formed pore size more uniform and consistent, and improve the product's anti-leakage function. However, under the conditions of long-term use, large amount of liquid or external force extrusion, water molecules will still pass through these micropores to penetrate the breathable film, resulting in poor anti-leakage performance of the breathable film. Therefore, the anti-liquid leakage performance of the breathable film still needs to be improved. Chinese patent CN207071116U discloses a low-weight waterproof film structure and a disposable sanitary product. Arranging a polyurethane resin coating, a polyvinyl chloride resin coating or a polyacrylate coating on the surface of the PE film can improve the waterproof performance of the PE film, but seriously reduces the air permeability of the PE film, affecting the user's experience. Therefore, it is hoped to develop a breathable film with further improved anti-liquid leakage performance while maintaining good air permeability. Summary of the invention

[0004] In order to solve the problem of liquid leakage of breathable membranes in the prior art, the primary purpose of the present invention is to provide a breathable membrane.

[0005] Another object of the present invention is to provide a method for preparing a breathable membrane.

[0006] Another object of the present invention is to provide a use of a breathable film in the preparation of sanitary products.

[0007] Another object of the present invention is to provide a sanitary product.

[0008] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0009] The present invention provides a breathable membrane, which has a three-layer structure, including a hydrophobic layer, a barrier layer and a water absorbing layer, wherein the barrier layer is located between the hydrophobic layer and the water absorbing layer;

[0010] The hydrophobic layer comprises the following raw materials by weight: 45-50 parts of PE, 45-50 parts of calcium carbonate, 1-2 parts of hydrophobic agent, and 3-4 parts of processing aid;

[0011] The barrier layer comprises the following raw materials by weight: 40-45 parts of PE, 45-50 parts of calcium carbonate, 3-5 parts of barrier agent, 3-4 parts of processing aid, and 0.1-1 part of compatibilizer;

[0012] The water-absorbing layer comprises the following raw materials by weight: 45-50 parts of PE, 45-50 parts of calcium carbonate, 1-2 parts of water-absorbing resin, and 3-4 parts of processing aid;

[0013] The thickness ratio of the hydrophobic layer, the barrier layer and the water absorbing layer is 4.0-6.0:1.5-2.5:2.5-3.5.

[0014] The present invention prepares a three-layer breathable film, including a hydrophobic layer, a barrier layer and a water-absorbing layer. The three-layer structure can stagger the micropores between the layers, while ensuring the air permeability, reducing the straight channels generated by the micropores, thereby reducing the water penetration channels. The hydrophobic layer has a high hydrophobicity, which can reduce the wetting of the liquid on its surface, thereby reducing the penetration phenomenon caused by the capillary effect caused by wetting, and effectively preventing the liquid from penetrating the hydrophobic layer. The barrier layer is located between the hydrophobic layer and the water-absorbing layer. The barrier layer has an excellent water-isolating effect and can intercept the liquid to prevent the liquid from penetrating the barrier layer. The water-absorbing layer can absorb excess water, and the water-absorbing resin will have a certain volume expansion after absorbing water, thereby causing partial micropore blockage, thereby preventing the liquid from penetrating the water-absorbing layer to cause leakage.

[0015] Since the hydrophobic layer contacts the liquid first, it has the best anti-liquid penetration effect, and plays a major role in the anti-leakage performance of the breathable membrane. The thickness of the hydrophobic layer in the prepared breathable membrane is greater than the water-isolating layer and the water-absorbing layer, which can effectively prevent the liquid from passing through the hydrophobic layer. Even if a small part of the liquid passes through the hydrophobic layer, the barrier layer can effectively block the body fluid that passes through the hydrophobic layer. Since the barrier layer has a good anti-liquid penetration effect, but the thickness of the barrier layer is too thick, it will affect the air permeability of the breathable membrane. Therefore, controlling the thickness ratio of the barrier layer within this range can effectively improve the anti-liquid leakage performance of the breathable membrane while keeping the breathable membrane with good air permeability. Through the effective blocking of the first two layers to the liquid, only a very small part of the liquid may pass through the hydrophobic layer and the barrier layer. The water-absorbing layer, as the last protection mechanism, can absorb and intercept it, and further improve the anti-leakage performance of the breathable membrane. The present invention can control the thickness ratio of the hydrophobic layer, the barrier layer and the water-absorbing layer of the breathable membrane so that they can work together to significantly improve the anti-liquid leakage performance of the breathable membrane, while keeping the breathable membrane with good air permeability.

[0016] The present invention can effectively improve the hydrophobic performance of the hydrophobic layer by adding a certain amount of hydrophobic agent. Too much hydrophobic agent content will cause the hydrophobic agent to block the pores, because the pore diameter of the pores is about 1-2 μm and is easily blocked by foreign objects. Too little content will lead to poor hydrophobic effect and weaken the anti-liquid leakage performance of the breathable membrane.

[0017] The present invention adds a certain amount of barrier agent to the barrier layer to make it have excellent water-proof performance. Too much barrier agent content will lead to air isolation, affecting the air permeability of the product and prone to stratification and precipitation. Too little content will lead to insufficient water-proof effective ingredients, affecting the liquid barrier effect of the barrier layer.

[0018] The present invention adds a certain amount of water-absorbing resin to the water-absorbing interlayer to make it have excellent water-absorbing performance. Too much water-absorbing resin content will cause the breathable film to easily rupture and significantly reduce physical properties. Too little content will cause the water-absorbing layer to fail to absorb water and prevent liquid leakage.

[0019] Specifically, the hydrophobic agent is at least one of silicone polyether copolymer, polysiloxane or fluorine-containing silane.

[0020] The hydrophobic agent selected in the present invention can still maintain good hydrophobic performance after the breathable membrane is used for a long time, which is beneficial to improving the service life of the breathable membrane.

[0021] Preferably, the hydrophobic agent is selected from at least one of silicone polyether copolymer, polymethylsiloxane, tridecafluorooctyltrimethoxysilane, perfluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilane or perfluorodecyltriethoxysilane.

[0022] Specifically, the barrier agent is EVOH and / or PVA.

[0023] The present invention selects a barrier agent with high barrier performance, which can effectively prevent the liquid that penetrates the hydrophobic layer from passing through the barrier layer, further reducing the possibility of liquid leakage.

[0024] Preferably, the barrier agent is EVOH.

[0025] More preferably, the ethylene content in the EVOH is 30-45 wt %, which can effectively block moisture and has good processability.

[0026] Specifically, the compatibilizer is at least one of PE grafted maleic anhydride, titanate coupling agent, and silane coupling agent.

[0027] Preferably, the compatibilizer is PE grafted maleic anhydride.

[0028] The addition of compatibilizer can further improve the compatibility of PE and barrier agent and improve its processing performance.

[0029] Specifically, the water-absorbing resin is polyacrylamide and / or sodium polyacrylic acid (SAP).

[0030] The present invention selects a water-absorbent resin with high water absorption, which can effectively absorb the water leaked from the hydrophobic layer and the barrier layer, and further reduce the possibility of liquid leakage.

[0031] The calcium carbonate used in the present invention is heavy calcium carbonate that has been subjected to surface activation treatment.

[0032] Specifically, the particle size of the calcium carbonate is D 50 ≤2.5μm, D 90 ≤6.0μm.

[0033] Preferably, the PE is low-density polyethylene (LDPE).

[0034] More preferably, the PE is metallocene-catalyzed linear low-density polyethylene (M-LLDPE).

[0035] Specifically, the processing aid is a processing aid commonly used in the art for preparing breathable films, including but not limited to at least one of liquid paraffin, PE wax, and PPA.

[0036] A method for preparing the above-mentioned breathable membrane comprises the following steps:

[0037] S1. Granulation: PE, calcium carbonate and a processing aid are blended and extruded to obtain hydrophobic layer granules and water-absorbing layer granules, respectively; PE, calcium carbonate, a processing aid, a barrier agent and a compatibilizer are blended and extruded to obtain barrier layer granules;

[0038] S2. Film making: The hydrophobic layer granules, barrier layer granules, water-absorbing layer granules and water-absorbing resin blend obtained in step S1 are respectively fed into three different screws, and the three layers are co-extruded, cast and stretched after extrusion, and a hydrophobic agent is coated on the surface of the hydrophobic layer after film formation to obtain the breathable film.

[0039] It should be noted that, since water cooling is involved in the granulation process, the water-absorbing resin of the water-absorbing layer needs to be added in the film-forming step.

[0040] Specifically, the longitudinal stretching ratio in the step S2 is 1.7 to 2.2.

[0041] Specifically, the extrusion temperature in step S1 is 180-200°C.

[0042] Specifically, the extrusion temperature in step S2 is 220-240°C.

[0043] Specifically, a twin-screw extruder is used for extrusion in step S1.

[0044] Specifically, a three-layer co-extruder is used for extrusion in step S2, and a unidirectional stretching device is used for stretching.

[0045] Specifically, the coating in step S2 is spraying.

[0046] Preferably, the coating in step S2 is performed by off-line spraying.

[0047] In the present invention, a processing aid may also be added in step S2 to improve product quality and production efficiency.

[0048] The present invention also protects the use of the above-mentioned breathable film in the preparation of sanitary products.

[0049] A sanitary product comprises the above-mentioned breathable film, wherein the hydrophobic layer in the breathable film contacts with the absorbent core.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The present invention provides a breathable membrane with a three-layer structure, including a hydrophobic layer, a barrier layer and a water-absorbing layer, wherein the barrier layer is located between the hydrophobic layer and the water-absorbing layer; compared with a breathable membrane with a single-layer structure, the three-layer structure reduces the straight channels generated by micropores while ensuring the air permeability, thereby reducing the water penetration channel. The hydrophobic layer reduces the wetting of the liquid on its surface, thereby reducing the penetration phenomenon caused by the capillary effect caused by wetting, and effectively prevents the liquid from penetrating the hydrophobic layer. The barrier layer has an excellent water-isolating effect and can intercept the liquid to prevent the liquid from penetrating the barrier layer. The water-absorbing layer can absorb excess water. The three layers work together to significantly improve the anti-permeability performance of the breathable membrane while ensuring good air permeability. DETAILED DESCRIPTION

[0052] The content of the present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present embodiment are conventional reagents, methods and equipment in the art.

[0053] The sources of raw materials used in the following examples and comparative examples are as follows:

[0054] The M-LLDPE was purchased from ExxonMobil Corporation, model 3518PA.

[0055] The hydrophobic agent was purchased from Dow Chemical, model DOWSIL TM 14Additive.

[0056] Calcium carbonate was purchased from Yingge Ceramics (Wuhu) Co., Ltd., model FL-520.

[0057] Polyacrylamide was purchased from Guangdong Qikang Industrial Development Co., Ltd., with the model number of PAM.

[0058] EVOH was purchased from Kuraray Co., Ltd. and the model number was EVOH F101.

[0059] The processing aid was purchased from Jiangmen Zhuobiao New Material Technology Co., Ltd., model GN-3039.

[0060] Example 1

[0061] A breathable film has a three-layer structure, including a hydrophobic layer, a barrier layer and a water-absorbing layer, wherein the barrier layer is located between the hydrophobic layer and the water-absorbing layer; the thickness ratio of the hydrophobic layer, the barrier layer and the water-absorbing layer is 5:2:3. The raw materials of the hydrophobic layer include 47 parts of M-LLDPE, 50 parts of calcium carbonate, 3 parts of processing aids, and 1.5 parts of silicone hydrophobic agent in parts by weight; the raw materials of the barrier layer include 42 parts of M-LLDPE, 5 parts of EVOH, 0.5 parts of PE grafted maleic anhydride, 50 parts of calcium carbonate, and 3 parts of processing aids; the raw materials of the water-absorbing layer include 46 parts of M-LLDPE, 1 part of polyacrylamide, 50 parts of calcium carbonate, and 3 parts of processing aids. The preparation method of the breathable film includes the following steps:

[0062] S1. Granulation: M-LLDPE, calcium carbonate and processing aid are mixed according to the above raw material ratio, extruded, plasticized, pelletized and dried to obtain hydrophobic layer granules and water-absorbing layer granules; PE, calcium carbonate, processing aid, barrier agent and compatibilizer are mixed according to the above raw material ratio, extruded, plasticized, pelletized and dried to obtain barrier layer granules; the extrusion temperature is 190°C;

[0063] S2. Film making: the water-absorbing layer granules and water-absorbing resin obtained in step S1 are mixed according to the above raw material ratios, and then fed into three different screws together with the hydrophobic layer granules and the barrier layer granules, respectively. Then, they are co-extruded and cast at the die head through a distributor to form a film embryo. After cooling, they are stretched and shaped to form a film. The surface of the hydrophobic layer of the film is sprayed with an organosilicon hydrophobic agent offline to obtain the breathable film. The extrusion temperature is 230°C.

[0064] Example 2

[0065] The difference between Example 2 and Example 1 is that the thickness ratio of the hydrophobic layer, the barrier layer and the water absorbing layer is 6:1.5:2.5, and the rest is the same as Example 1.

[0066] Example 3

[0067] The difference between Example 3 and Example 1 is that the thickness ratio of the hydrophobic layer, the barrier layer and the water absorbing layer is 4:2.5:3.5, and the rest is the same as Example 1.

[0068] Example 4

[0069] The difference between Example 4 and Example 1 is that the raw materials for the hydrophobic layer include 45 parts of M-LLDPE, 47 parts of calcium carbonate, 4 parts of processing aids, and 1 part of silicone hydrophobic agent by weight, and the rest is the same as Example 1.

[0070] Example 5

[0071] The difference between Example 5 and Example 1 is that the raw materials for the hydrophobic layer include 50 parts of M-LLDPE, 45 parts of calcium carbonate, 3.5 parts of processing aids, and 2 parts of silicone hydrophobic agents by weight, and the rest is the same as Example 1.

[0072] Example 6

[0073] The difference between Example 6 and Example 1 is that the raw materials of the barrier layer include 40 parts of M-LLDPE, 3 parts of EVOH, 0.1 parts of PE-grafted maleic anhydride, 47 parts of calcium carbonate, and 3 parts of processing aid, and the rest are the same as Example 1.

[0074] Example 7

[0075] The difference between Example 7 and Example 1 is that the raw materials of the barrier layer include 45 parts of M-LLDPE, 4 parts of EVOH, 1 part of PE-grafted maleic anhydride, 45 parts of calcium carbonate, and 3 parts of processing aids, and the rest are the same as Example 1.

[0076] Example 8

[0077] The difference between Example 8 and Example 1 is that the raw materials of the water-absorbing layer include 45 parts of M-LLDPE, 1.5 parts of polyacrylamide, 47 parts of calcium carbonate, and 3 parts of processing aid, and the rest is the same as Example 1.

[0078] Example 9

[0079] The difference between Example 9 and Example 1 is that the raw materials of the water absorbing layer include 50 parts of M-LLDPE, 2 parts of polyacrylamide, 45 parts of calcium carbonate, and 3 parts of processing aid, and the rest is the same as Example 1.

[0080] Comparative Example 1

[0081] 47 parts of M-LLDPE, 50 parts of calcium carbonate and 3 parts of processing aid are fed into an extruder for mixing, extrusion, plasticization, drawing, cooling, pelletizing and dehydration to obtain breathable film particles, wherein the extrusion temperature of granulation is 190°C, and the obtained breathable film particles are extruded and cast through a single-screw extruder to form a film embryo, which is stretched after cooling, and then cooled and shaped for the second time, and rolled to obtain a breathable film, wherein the extrusion temperature of the film is 230°C, and the breathable film is a single-layer structure.

[0082] Comparative Example 2

[0083] The difference between Comparative Example 2 and Example 1 is that the surface of the hydrophobic layer of the prepared breathable membrane is not sprayed with a hydrophobic agent, and the rest is the same as Example 1.

[0084] Comparative Example 3

[0085] The difference between Comparative Example 3 and Example 1 is that the prepared breathable film barrier layer does not contain a barrier agent and a compatibilizer, and the rest is the same as Example 1.

[0086] Comparative Example 4

[0087] The difference between Comparative Example 4 and Example 1 is that the water-absorbing layer of the prepared breathable membrane does not contain water-absorbing resin, and the rest is the same as Example 1.

[0088] Comparative Example 5

[0089] The difference between Comparative Example 5 and Example 1 is that the thickness ratio of the hydrophobic layer, the barrier layer and the water absorbing layer in the prepared breathable membrane water absorbing layer is 8:1:1, and the rest is the same as Example 1.

[0090] Comparative Example 6

[0091] The difference between Comparative Example 5 and Example 1 is that the thickness ratio of the hydrophobic layer, the barrier layer and the water absorbing layer in the prepared breathable membrane water absorbing layer is 3:5:2, and the rest is the same as Example 1.

[0092] Comparative Example 7

[0093] The difference between Comparative Example 7 and Example 1 is that no hydrophobic agent is sprayed on the surface of the hydrophobic layer, no barrier agent and compatibilizer are contained in the barrier layer, and no water-absorbing resin is contained in the water-absorbing layer, and the rest is the same as Example 1. The obtained breathable membrane has a three-layer structure.

[0094] Performance Testing

[0095] 1. The breathable membranes obtained in the above examples and comparative examples were subjected to leakage tests. The test method is as follows:

[0096] (1) Cut the test specimens into 270 mm in length × material width; cut the filter paper into 240 mm × 100 mm and 240 mm × 70 mm sizes for later use.

[0097] (2) Before the experiment, check the experimental platform to ensure that it is flat, clean and free of water stains. Take two pieces of 240mm×100mm filter paper and lay them flat on the experimental platform. Lay the cut bottom film on the filter paper with the non-use side facing up, and then place four pieces of 240mm×70mm filter paper on the bottom film (try to ensure that the upper filter paper is in the center of the lower filter paper).

[0098] (3) Inject 10 ml of colored saline into the center of the upper filter paper.

[0099] (4) After standing for 2 minutes, cover the upper filter paper with a 10 kg pressure block. After 60 minutes of static pressure, observe whether the lower filter paper has leakage. If there is color penetration, record the diameter of the color point on the lower filter paper.

[0100] 2. The air permeability of the breathable membranes obtained in the above examples and comparative examples was tested according to standard GB / T 1037 (positive cup method, 40° C. temperature, 60% humidity). The test results are shown in Table 1.

[0101] The above embodiments and comparative examples were subjected to performance tests, and the test results are shown in Table 1.

[0102] Color point diameter(mm) <![CDATA[Water vapor transmission rate (g / m 2 / 24hr)]]> Example 1 No leakage 2619 Example 2 No leakage 2893 Example 3 No leakage 2230 Example 4 No leakage 2677 Example 5 No leakage 2559 Example 6 No leakage 2811 Example 7 No leakage 2707 Example 8 No leakage 2230 Example 9 No leakage 2025 Comparative Example 1 25.0 3201 Comparative Example 2 22.0 2655 Comparative Example 3 18.0 3167 Comparative Example 4 2.0 2702 Comparative Example 5 1.0 3026 Comparative Example 6 8.0 1823 Comparative Example 7 24.0 3105

[0103] It can be seen from the data of the leakage performance test in Table 1 that the breathable membrane prepared in the embodiment of the present invention has no liquid leakage during the test, and its liquid leakage prevention performance is relatively high. The breathable membrane has a moisture permeability of 2230 g / m 2 / 24hr or more, significantly improving the hydrophobicity while still maintaining good breathability.

[0104] It can be seen from the comparison between Comparative Example 1 and Example 1 that the single-layer PE breathable membrane prepared in Comparative Example 1 has higher air permeability, but its leakage is more serious and the anti-leakage effect is poor.

[0105] Comparison of Comparative Examples 2 to 4 with Example 1 shows that there is no hydrophobic layer, barrier layer or water absorbing layer in the breathable membrane, and the obtained breathable membranes all have liquid leakage to varying degrees, and their anti-leakage performance is poor.

[0106] It can be seen from the comparison between Comparative Example 5 and Example 1 that the thickness of the hydrophobic layer in the breathable membrane is too large, and the thickness of the barrier layer and the water-absorbing layer are too small, which will result in that the liquid penetrating the hydrophobic layer cannot be completely blocked or absorbed, resulting in liquid leakage in the breathable membrane.

[0107] It can be seen from Comparative Example 6 and Example 1 that the thickness of the hydrophobic layer in the breathable membrane is relatively small, while the thickness of the barrier layer is relatively large, which will result in the hydrophobic layer being unable to effectively block the penetration of liquid, resulting in a high degree of liquid leakage in the breathable membrane. Moreover, due to the excessive thickness of the barrier layer, its air permeability is relatively poor.

[0108] It can be seen from Comparative Example 7 and Example 1 that the three-layer breathable membrane prepared in Comparative Example 7 has poor anti-leakage performance.

[0109] The above embodiments are preferred experimental methods of the present invention, but the implementation methods of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A breathable membrane, characterized in that: The breathable membrane has a three-layer structure, including a hydrophobic layer, a barrier layer and a water absorbing layer, wherein the barrier layer is located between the hydrophobic layer and the water absorbing layer; The hydrophobic layer comprises the following raw materials by weight: 45-50 parts of PE, 45-50 parts of calcium carbonate, 1-2 parts of hydrophobic agent, and 3-4 parts of processing aid; The barrier layer comprises the following raw materials by weight: 40-45 parts of PE, 45-50 parts of calcium carbonate, 3-5 parts of barrier agent, 3-4 parts of processing aid, and 0.1-1 part of compatibilizer; The water-absorbing layer comprises the following raw materials by weight: 45-50 parts of PE, 45-50 parts of calcium carbonate, 1-2 parts of water-absorbing resin, and 3-4 parts of processing aid; The thickness ratio of the hydrophobic layer, the barrier layer and the water absorbing layer is 4-6:1.5-2.5:2.5-3.

5.

2. The breathable membrane according to claim 1, characterized in that: The hydrophobic agent is at least one of an organosilicon polyether copolymer, polysiloxane or a fluorine-containing silane.

3. The breathable membrane according to claim 1, characterized in that: The barrier agent is EVOH and / or PVA.

4. The breathable membrane according to claim 1, characterized in that: The compatibilizer is at least one of PE grafted maleic anhydride, titanate coupling agent and silane coupling agent.

5. The breathable membrane according to claim 1, characterized in that: The water-absorbing resin is polyacrylamide and / or polyacrylic acid sodium salt.

6. The breathable membrane according to claim 1, characterized in that: The particle size of the calcium carbonate is D 50 ≤2.5μm, D 90 ≤6.0μm.

7. A method for preparing a breathable membrane according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Granulation: PE, calcium carbonate and a processing aid are blended and extruded to obtain hydrophobic layer granules and water-absorbing layer granules, respectively; PE, calcium carbonate, a processing aid, a barrier agent and a compatibilizer are blended and extruded to obtain barrier layer granules; S2. Film making: The hydrophobic layer granules, barrier layer granules, water-absorbing layer granules and water-absorbing resin blend obtained in step S1 are respectively fed into three different screws for three-layer co-extrusion. After extrusion, the three layers are cast and stretched. After film formation, a hydrophobic agent is applied on the surface of the hydrophobic layer to obtain the breathable film.

8. The preparation method according to claim 7, characterized in that: The longitudinal stretching ratio in the stretching in step S2 is 1.7 to 2.

2.

9. Use of the breathable film according to any one of claims 1 to 6 in the preparation of sanitary products.

10. A sanitary product, characterized in that: The invention comprises the breathable membrane according to any one of claims 1 to 6.