Breathable microporous polyolefin film and preparation method therefor
By surface treatment and process optimization of inorganic fillers, a polyolefin breathable microporous film with uniform overall structure, excellent air permeability and strength was prepared, which solved the problem of uneven dispersion of calcium carbonate particles and improved high air permeability and aging resistance.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SHANGHAI ZIHUA FILM TECH CO LTD
- Filing Date
- 2025-05-16
- Publication Date
- 2026-06-04
Smart Images
Figure PCTCN2025095411-FTAPPB-I100001 
Figure PCTCN2025095411-FTAPPB-I100002 
Figure PCTCN2025095411-FTAPPB-I100003
Abstract
Description
A polyolefin breathable microporous film and its preparation method Technical Field
[0001] This application relates to the field of organic polymer film technology, and more specifically, to a polyolefin breathable microporous film and its preparation method. Background Technology
[0002] Microporous breathable membranes are plastic films with countless interconnected micropores. These films have high tensile strength and good permeability to air and water vapor, but exhibit high hydrostatic resistance to liquid water permeation. In other words, these polyolefin breathable microporous membranes contain many openings or channels that allow passage from one surface to another. The size of the pores allows air and water vapor molecules to pass through the membrane, while providing good resistance to the permeation of liquid water molecules.
[0003] In current microporous breathable membrane production processes, calcium carbonate is the most common additive for creating pores. However, due to the surface properties of calcium carbonate particles, they are often difficult to disperse uniformly in the resin, resulting in a disordered overall structure of the microporous breathable membrane. Summary of the Invention
[0004] To improve the uniformity of the overall structure of the microporous breathable membrane, this application provides a polyolefin breathable microporous film and its preparation method.
[0005] In a first aspect, this application provides a polyolefin breathable microporous film, which adopts the following technical solution:
[0006] A breathable microporous polyolefin film is made by filling a polyolefin substrate with modified inorganic fillers and then forming the film through casting extrusion, stretching, and heat setting processes.
[0007] The weight ratio of the polyolefin substrate to the modified inorganic filler is 9:11 to 1:1;
[0008] The method for preparing the modified inorganic filler includes: stirring and mixing titanium dioxide, vinyl silane and water at 100-120°C for 2-5 hours, filtering, and drying to obtain the modified inorganic filler.
[0009] By employing the above technical solution, vinyl silane is used to surface-treat the inorganic filler. The resulting modified inorganic filler contains vinyl groups on its surface, exhibiting good dispersibility in the polyolefin substrate. It can be uniformly distributed within the polyolefin substrate and form a stable structure. Therefore, the excellent dispersibility of the modified inorganic filler helps to form uniform and fine pores in the polyolefin breathable microporous film, thereby improving the air permeability and water permeability of the polyolefin breathable microporous film.
[0010] Preferably, the modified inorganic filler is composed of titanium dioxide and calcium carbonate mixed in a weight ratio of 13:7 to 1:1.
[0011] Preferably, in the modified inorganic filler, the particle size of the inorganic filler is 2-5 μm, and the particle size distribution is greater than or equal to 85%.
[0012] Titanium dioxide is a stable, non-toxic ultraviolet light absorber. Due to its stability, low cost, ease of recycling, good photocatalytic activity, strong light scattering power, high tinting strength, high hiding power, good whiteness, strong bleaching power, high refractive index, high chemical inertness, excellent electrical and thermal properties, and non-toxic and harmless to the human body, it is widely used in photosensitive materials, photocatalysts, cosmetics, food packaging materials, ceramic additives, rubber, plastics, leather tanning, high-grade automotive coatings, and antibacterial and UV-resistant finishing of textiles.
[0013] By adopting the above technical solution and using titanium dioxide as a pore-forming additive, not only can the pore structure of the breathable membrane be improved, but the overall performance of the material can also be enhanced. For example, it can increase the material's hardness, strength, and wear resistance, while also improving its lightfastness and weather resistance, making it less prone to aging and discoloration.
[0014] Furthermore, by adjusting the amount and particle size of titanium dioxide added, the pore structure and distribution of the breathable membrane can be precisely controlled. This controllability allows the breathable membrane to meet the specific requirements of various fields for properties such as air permeability, water permeability, and strength.
[0015] Preferably, the weight ratio of the inorganic filler, vinylsilane and water is 1:(0.05-0.1):(2-5).
[0016] Preferably, the vinylsilane is vinyltrimethoxysilane.
[0017] By employing the above technical solution, vinyltrimethoxysilane contains unsaturated double-bonded vinyl functional groups and three hydrolyzable methoxy groups, exhibiting dual reactivity. By controlling the weight ratio of inorganic filler, vinylsilane, and water, vinyltrimethoxysilane hydrolyzes to form silanols, which then bond with hydroxyl groups on the surface of the inorganic filler, thereby grafting active vinyl functional groups onto the inorganic filler surface. During high-temperature melt extrusion, the polyolefin substrate with similar structures and the modified inorganic filler exhibit good compatibility, which is beneficial for obtaining a breathable membrane with uniform overall structure.
[0018] Preferably, the modified inorganic filler is prepared by stirring and mixing the inorganic filler, vinyl silane, polyethylene glycol and water at 100-120°C for 2-5 hours, filtering and drying to obtain the modified inorganic filler.
[0019] By adopting the above technical solution, polyethylene glycol is used in combination with vinyl silane to modify the surface of inorganic fillers. The surface of the modified inorganic fillers is uniformly coated with a silane layer, which is beneficial to further improve the dispersibility and compatibility of the modified inorganic fillers in polyolefin substrates, and to obtain a breathable membrane with a uniform structure.
[0020] Preferably, the polyolefin substrate comprises one or both of metallocene polyethylene and linear low-density polyethylene.
[0021] Preferably, the polyolefin substrate is composed of metallocene polyethylene and linear low-density polyethylene mixed in a weight ratio of 3:2.
[0022] By adopting the above technical solution, a specific ratio of metallocene polyethylene and linear low-density polyethylene is selected for melt blending, resulting in excellent processing performance. The resulting breathable membrane has good overall structural uniformity, and excellent anti-aging and tear resistance.
[0023] Secondly, this application provides a method for preparing a polyolefin breathable microporous film, which adopts the following technical solution:
[0024] A method for preparing a polyolefin breathable microporous film includes the following steps:
[0025] S1: After mixing the polyolefin matrix and the modified inorganic filler, the mixture is extruded and granulated to obtain composite particles;
[0026] S2: After the composite particles are cast and extruded into a film, the film is stretched and heat-set to obtain a polyolefin breathable microporous film.
[0027] The melt temperature during the casting and extrusion of the composite particles is 225–270℃; the film stretch ratio is 1.2–3.5; and the heat setting temperature is 60–85℃.
[0028] By adopting the above technical solution, the polyolefin substrate and modified inorganic filler exhibit good processing performance at 225–270℃, ensuring that the modified inorganic filler is uniformly distributed in the polyolefin substrate and has good compatibility. Then, by processing according to the above stretching ratio and heat setting temperature, a breathable membrane with uniform overall structure, excellent aging resistance, and excellent tear resistance can be obtained.
[0029] In summary, this application has the following beneficial effects:
[0030] 1. Because this application uses a vinyl silane coupling agent to treat the surface of titanium dioxide, it improves the dispersibility and compatibility of titanium dioxide in the polyolefin substrate, which facilitates the uniform distribution in the breathable membrane to form a stable pore structure, and is beneficial to improving the overall uniformity of the breathable membrane.
[0031] 2. In this application, the pore distribution and pore structure in the breathable membrane can be adjusted by changing the amount of titanium dioxide added and the particle size, which is beneficial to expanding the application of breathable membranes in different fields.
[0032] 3. In the preparation method of this application, under specific process conditions, the polyethylene substrate and the modified inorganic filler have good processing performance, and the preparation method is simple and suitable for large-scale production. Detailed Implementation
[0033] The present application will be further described in detail below with reference to the embodiments.
[0034] Preparation Example
[0035] Preparation Example 1
[0036] A modified inorganic filler, the raw materials and their corresponding weights (kg) are shown in Table 1 below.
[0037] Table 1
[0038] The above-mentioned modified inorganic filler is prepared by stirring and mixing vinylsilane and water, adjusting the pH of the mixture to 3.5, stirring and mixing for 45 min, then adding inorganic filler, stirring and mixing at 120℃ for 2 h, filtering, drying, and pulverizing to obtain the modified inorganic filler.
[0039] In the preparation examples of this application, the vinylsilane is vinyltrimethoxysilane;
[0040] The inorganic filler is composed of titanium dioxide SFA101 and calcium carbonate OM2-JI mixed in a weight ratio of 13:7; the particle size of the inorganic filler is 2-5 μm, and the particle size distribution is greater than or equal to 85%.
[0041] Preparation Examples 2-3
[0042] A modified inorganic filler differs from Preparation Example 1 in that the raw materials and their corresponding weights (kg) are shown in Table 2 below.
[0043] Table 2
[0044] Preparation Example 4
[0045] A modified inorganic filler, which differs from Preparation Example 1 in that the vinylsilane is vinyltriethoxysilane.
[0046] Preparation Example 5
[0047] A modified inorganic filler, which differs from Preparation Example 1 in that the inorganic filler is composed of titanium dioxide and calcium carbonate mixed in a weight ratio of 1:1.
[0048] Preparation Example 6
[0049] A modified inorganic filler, which differs from Preparation Example 1 in that the inorganic filler is composed of titanium dioxide and calcium carbonate mixed in a weight ratio of 2:5.
[0050] Preparation Example 7
[0051] A modified inorganic filler differs from Preparation Example 1 in that the raw materials and their corresponding weights (kg) are shown in Table 3 below.
[0052] Table 3
[0053] The above-mentioned modified inorganic filler is prepared by stirring and mixing vinylsilane and water, adjusting the pH of the mixture to 3.5, stirring and mixing for 45 min, then adding inorganic filler and polyethylene glycol 2000, stirring and mixing at 120℃ for 2 h, filtering, drying, and pulverizing to obtain the modified inorganic filler.
[0054] Preparation Example 8
[0055] A modified inorganic filler differs from Preparation Example 1 in that an equal weight of methyltrimethoxysilane is used instead of vinylsilane.
[0056] The above-mentioned modified inorganic filler is prepared by stirring methyltrimethoxysilane and water for 45 min, then adding inorganic filler, stirring and mixing at 120℃ for 2 h, filtering, drying, and pulverizing to obtain the modified inorganic filler.
[0057] Performance testing
[0058] The air-permeable microporous membranes prepared in the embodiments and comparative examples of this application were tested for porosity, pore size distribution, tensile strength, anti-aging properties, and water permeability. The testing methods are as follows:
[0059] Porosity and pore size distribution: tested in accordance with GB / T 21650.1-2008 standard.
[0060] Tensile strength: Tested in accordance with GB / T 1040.3-2006 Determination of tensile properties of plastics Part III: Test conditions for films and sheets.
[0061] Anti-aging performance: In accordance with GB / T16585-1996 standard, a light aging test was conducted, with the aging time set to 200h.
[0062] Permeability: The permeability test was conducted using a multiple squeeze permeability test method, with the specific steps as follows:
[0063] Instruments: a 50ml measuring cup, several 2kg pressure blocks, a 1000ml beaker with a base area of 7*25cm, a stopwatch, several filter papers (minimum width greater than 200mm), several sanitary napkins, and several drainage tubes;
[0064] Test solution: 23℃ physiological saline (with a small amount of pigment added), wherein the physiological saline ratio is 9g sodium chloride added per 1000ml distilled water;
[0065] Sampling and sample preparation: The breathable microporous membrane taken must not have wrinkles or defects, and the sample size must be larger than the area of the sanitary napkin used for testing. The bottom film of the sanitary napkin used for testing should be removed.
[0066] Experimental steps:
[0067] (1) Lay the filter paper flat on the platform;
[0068] (2) Lay the microporous membrane to be tested on the filter paper, and then lay the sanitary napkin with the bottom membrane removed;
[0069] (3) Inject 30ml of test solution into the center of the sanitary napkin through the drainage tube;
[0070] (4) After the liquid is completely absorbed, place a 2kg pressure block on the sanitary napkin and start timing at the same time;
[0071] (5) After 2 minutes, lift the block and press it down again. Repeat the above operation every 2 minutes thereafter.
[0072] (6) After lifting the pressure block for the fifth time, stop pressing it down and observe whether there is any leakage on the filter paper. If there is, it is determined that there is leakage in this batch of materials.
[0073] Five parallel test groups were conducted, with 10 points in each group.
[0074] Example
[0075] Example 1
[0076] A polyolefin breathable microporous membrane, the components of which and their corresponding weights (kg) are shown in Table 4 below.
[0077] Table 4
[0078] The preparation method of the above-mentioned polyolefin breathable microporous film includes the following preparation steps:
[0079] S1: After mixing the polyolefin matrix and the modified inorganic filler, the mixture is extruded and granulated to obtain composite particles;
[0080] S2: The composite particles are cast and extruded to form a melt, which is then extruded into a film. Finally, the film is stretched and heat-set to obtain a polyolefin breathable microporous film.
[0081] The melt temperature is 225℃; the film stretch ratio is 1.2; and the heat setting temperature is 60℃.
[0082] In this embodiment, the polyolefin substrate is composed of metallocene polyethylene and linear low-density polyethylene mixed in a weight ratio of 3:2.
[0083] The melt flow index of metallocene polyethylene is 3.5 g / 10 min, and its density is 0.927.
[0084] The melt index of linear low-density polyethylene is 2.3 g / 10 min, and its density is 0.917.
[0085] The modified inorganic filler used was the modified inorganic filler prepared in Preparation Example 1.
[0086] Examples 2-3
[0087] A polyolefin breathable microporous film, which differs from Example 1 in that the components and their corresponding weights (kg) are shown in Table 5 below.
[0088] Table 5
[0089] The porosity, tensile strength, anti-aging properties and water permeability of the polyolefin breathable microporous films prepared in Examples 1 to 3 of this application were tested, and the test results are shown in Table 6 below.
[0090] Table 6
[0091] Data analysis of Table 6 above shows that the polyolefin breathable microporous films prepared in Examples 1-3 have a porosity as high as 80-88%, a tensile strength as high as 12.70-13.60 N, and did not exhibit yellowing or water seepage after 200 hours of light exposure. This indicates that the polyolefin breathable microporous films prepared in Examples 1-3 of this application have good overall structural uniformity and excellent breathability, mechanical properties, and anti-aging properties.
[0092] Examples 4-9
[0093] A polyolefin breathable microporous membrane, which differs from Example 1 in that the modified inorganic filler is the modified inorganic filler prepared in the preparation examples in Table 7 below.
[0094] Table 7
[0095] The porosity, tensile strength, anti-aging properties and water permeability of the polyolefin breathable microporous films prepared in Examples 4 to 9 of this application were tested, and the test results are shown in Table 8 below.
[0096] Table 8
[0097] Analysis of the data in Table 8 shows that, compared to Example 1, the porosity and tensile strength of Examples 4 and 5 are both reduced. This may be because when the weight ratio of inorganic filler, vinyl silane, and water is 1:0.08:3, the grafting effect of vinyl silane on the surface of the inorganic filler is higher, improving the dispersibility and compatibility of the modified inorganic filler in the polyolefin substrate. Therefore, this not only increases the porosity of the film but also results in a film with higher overall uniformity and thus better mechanical properties.
[0098] Compared to Example 1, Example 6 showed a decrease in both porosity and tensile strength. This indicates that, in the total raw materials for preparing the polyolefin breathable microporous film of this application, the use of vinyltrimethoxysilane to modify the surface of inorganic fillers can improve the uniformity of the overall film structure and mechanical strength.
[0099] Compared to Example 1, the porosity and tensile strength of Examples 7 and 8 were both reduced. This indicates that, in the total raw materials for preparing the polyolefin breathable microporous film of this application, adjusting the amount of titanium dioxide particles added can improve the overall breathability and mechanical strength of the film.
[0100] Compared to Example 1, Example 9 showed an increase in both porosity and tensile strength. This indicates that, in the total raw materials for preparing the polyolefin breathable microporous film of this application, using polyethylene glycol 2000 to modify the surface of the inorganic filler can improve the overall porosity and mechanical strength of the film structure. The reason for this is likely that polyethylene glycol 2000 has good surface activity, which can promote the dispersion and grafting of silanols on the surface of the inorganic filler, further improving the dispersibility and compatibility of the modified inorganic filler and the polyolefin substrate.
[0101] Example 10
[0102] A polyolefin breathable microporous film, which differs from Example 1 in that the polyolefin substrate is composed of a mixture of metallocene polyethylene and linear low-density polyethylene in a weight ratio of 2:3.
[0103] The porosity and tensile strength of the polyolefin breathable microporous film prepared in Example 10 of this application were tested, and the test results are shown in Table 9 below.
[0104] Table 9
[0105] Data analysis of Table 9 above shows that, compared to Example 1, the porosity of Example 10 is not significantly different, but the tensile strength is significantly reduced. This indicates that, in the total raw materials for preparing the polyolefin breathable microporous film of this application, the polyolefin substrate is composed of metallocene polyethylene and linear low-density polyethylene mixed in a weight ratio of 3:2, which can improve the porosity and mechanical strength of the polyolefin breathable microporous film.
[0106] Comparative Example
[0107] Comparative Example 1
[0108] A polyolefin breathable microporous film, which differs from Example 1 in that the modified inorganic filler is the modified inorganic filler prepared in Preparation Example 8.
[0109] Comparative Example 2
[0110] A polyolefin breathable microporous membrane differs from Example 1 in that it uses equal weights of inorganic filler and maleic anhydride-grafted polyethylene (item number 24724, purchased from Dongguan Xingyuan Chemical Co., Ltd.) to replace the modified inorganic filler, wherein the weight ratio of inorganic filler to maleic anhydride-grafted polyethylene is 1:0.1.
[0111] The porosity, tensile strength, anti-aging properties and water permeability of the polyolefin breathable microporous films prepared in Comparative Examples 1 and 2 of this application were tested, and the test results are shown in Table 10 below.
[0112] Table 10
[0113] Analysis of the data in Table 10 shows that, compared to Example 1, the porosity of Comparative Examples 1 and 2 decreased by 26.14–28.35%, the tensile strength decreased by 25.20–31.82%, and significant yellowing and 3–5 water seepage points appeared after 200 hours of light exposure. This indicates that, in the total raw materials for preparing the polyolefin breathable microporous film of this application, surface modification of the inorganic filler with vinyl silane can improve the air permeability, mechanical strength, aging resistance, and water resistance of the polyolefin breathable microporous film.
[0114] Meanwhile, the pore size distribution and appearance of the polyolefin breathable microporous films prepared in Examples 1-10 and Comparative Examples 1 and 2 of this application were inspected. The results showed that the polyolefin breathable microporous films prepared in Examples 1-10 had a pore size distribution of 0.01-0.06 nm, high whiteness and gloss, and a uniform overall structure. The polyolefin breathable microporous films prepared in Comparative Examples 1 and 2 had a pore size distribution of 0.04-0.26 nm, and their whiteness, gloss, and overall structural uniformity were lower than those in Examples 1-10. Therefore, the polyolefin breathable microporous film of this application has a uniform overall structure, a narrow pore size distribution, high safety and whiteness / gloss, no leakage, high strength, and excellent aging resistance, making it suitable for use in hygiene products and improving the user experience.
[0115] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.
Claims
1. A polyolefin breathable microporous film, characterized in that, It is made by filling modified inorganic fillers into a polyolefin substrate and then forming a film through casting extrusion, stretching, and heat setting. The weight ratio of the polyolefin substrate to the modified inorganic filler is 9:11 to 1:1; The method for preparing the modified inorganic filler includes: stirring and mixing the inorganic filler, vinyl silane and water at 100-120°C for 2-5 hours, filtering, and drying to obtain the modified inorganic filler.
2. The polyolefin breathable microporous membrane according to claim 1, characterized in that, The modified inorganic filler is composed of titanium dioxide and calcium carbonate mixed in a weight ratio of 13:7 to 1:
1.
3. The polyolefin breathable microporous film according to claim 1, characterized in that, The modified inorganic filler has a particle size of 2-5 μm and a particle size distribution of ≥85%.
4. The polyolefin breathable microporous membrane according to claim 1, characterized in that, The weight ratio of the inorganic filler, vinylsilane, and water is 1:(0.05-0.1):(2-5).
5. The polyolefin breathable microporous membrane according to claim 1, characterized in that, The vinylsilane is vinyltrimethoxysilane.
6. The polyolefin breathable microporous film according to claim 1, characterized in that, The modified inorganic filler is prepared by stirring and mixing inorganic filler, vinyl silane, polyethylene glycol and water at 100-120℃ for 2-5 hours, filtering and drying to obtain the modified inorganic filler.
7. The polyolefin breathable microporous membrane according to claim 1, characterized in that, The polyolefin substrate includes one or both of metallocene polyethylene and linear low-density polyethylene.
8. The polyolefin breathable microporous membrane according to claim 7, characterized in that, The polyolefin substrate is composed of metallocene polyethylene and linear low-density polyethylene mixed in a weight ratio of 3:
2.
9. A method for preparing the polyolefin breathable microporous film according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1: After mixing the polyolefin matrix and the modified inorganic filler, the mixture is extruded and granulated to obtain composite particles; S2: After the composite particles are cast and extruded into a film, the film is stretched and heat-set to obtain a polyolefin breathable microporous film. The melt temperature during the casting and extrusion of the composite particles is 225–270℃; the film stretch ratio is 1.2–3.5; and the heat setting temperature is 60–85℃.