Preparation method of microporous film material

Abstract

The invention relates to a preparation method of a microporous film material, the method is a dry stretching film technology, any grease for subsequent removal to form pores or any pore-forming microparticles for promoting the formation of micropores are not added into a polymer of the material, and the preparation method comprises the following steps: S1, a pore-free precursor extrusion process; s2, annealing and ripening process; s3, longitudinal stretching with or without a transverse relaxation process; s4, carrying out a transverse stretching non-longitudinal relaxation process; s5, a transverse relaxation process; and S6, a rolling process.

Description

Technical Field

[0001] The present invention relates to a method for preparing a microporous membrane material for moisture permeability and waterproofing or a microporous membrane material for a battery pack separator, in particular, a method for preparing a microporous membrane material for moisture permeability and waterproofing by a uniaxial stretching machine and a microporous membrane material for a battery pack separator. Background Art

[0002] The prior art is directed to novel and / or improved MD and / or TD stretched and optionally calendered membranes, separators, substrate films, microporous membranes, battery pack separators comprising such separators, substrate films or membranes, batteries comprising such separators, and / or methods for making and / or using such membranes, separators, substrate films, microporous membranes, battery pack separators and / or batteries, as disclosed in Taiwan Patent Publication No. TWI762647B, a novel and / or improved method for making microporous membranes having better balanced ideal properties than previous microporous membranes and battery pack separators, and battery pack separators comprising such microporous membranes. The disclosed method includes the following steps: 1.) obtaining a non-porous film precursor; 2.) forming a porous biaxially stretched film precursor from the non-porous film precursor; 3.) performing at least one of (a) calendering, (b) additional machine direction (MD) stretching, (c) additional transverse direction (TD) stretching, and (d) pore filling on the porous biaxially stretched precursor to form a final microporous film. The microporous film or battery separator described in the present case may have an ideal balance of the following properties before any coating is applied: a TD tensile strength greater than 200 or 250 kg / cm2, a puncture strength greater than 200, 250, 300, or 400 gf, and a JIS Gurley greater than 20 or 50 s.

[0003] The prior art is directed to at least one selected microporous membrane produced by a dry stretching process and having substantially circular pores and a ratio of vertical tensile strength to transverse tensile strength in the range of 0.5 to 6.0, as disclosed in Chinese Patent Publication No. CN102892534A, wherein the method for manufacturing the microporous membrane comprises the following steps: extruding a polymer into a non-porous precursor, and biaxially stretching the non-porous precursor, wherein the biaxial stretching comprises vertical stretching and transverse stretching, and the transverse stretching comprises simultaneously controlled vertical relaxation. At least a selected embodiment of the present invention may involve a biaxially oriented porous membrane, and the composite material comprises a biaxially oriented porous membrane, a biaxially oriented microporous membrane, a biaxially oriented perforated membrane, a battery separator, a filter medium, a humidity control medium, a flat sheet membrane, a liquid retention medium, etc., related methods, manufacturing methods, methods of use, etc. Figure 1A flow chart of a prior art method for preparing a microporous film material is shown, illustrating the porous membrane, comprising: at least one layer of a porous polymer film, which is produced by a dry stretching process comprising the following steps: extruding a polymer into at least a single layer of a non-porous precursor 101, and then biaxially stretching the non-porous precursor, wherein the biaxial stretching comprises longitudinal stretching and transverse stretching, wherein the transverse stretching comprises simultaneous controlled longitudinal relaxation 102, and has substantially circular pores, a porosity of approximately 40% to 90%, a ratio of longitudinal tensile strength to transverse tensile strength in the range of approximately 0.5 to 5.0, a Gurley of less than approximately 100, an average flow pore size of at least approximately 0.04 microns, an Aquapore pore size of at least approximately 0.07 microns, and a water pressure resistance of greater than approximately 140 psi.

[0004] Another example is a prior art study on a microporous membrane that has approximately circular pores through a dry stretching process and a ratio of longitudinal tensile strength to transverse tensile strength in the range of 0.5 to 5.0, as disclosed in U.S. Patent Publication No. US20070196638A1, wherein the method for preparing the microporous membrane comprises the following steps: extruding a polymer into a nonporous precursor, and biaxially stretching the nonporous precursor, wherein the biaxial stretching comprises longitudinal stretching and transverse stretching, wherein the transverse stretching comprises simultaneously controlled longitudinal relaxation. Another prior art study on a battery separator membrane, as disclosed in U.S. Patent Publication No. US20080118827A1, comprises a co-extruded microporous membrane having at least two layers made of an extrudable polymer and having: a uniform thickness defined by a standard deviation of <0.80 micrometers (μm); or an interlayer adhesion of a peel strength>60 grams.

[0005] Prior art is directed to a packaging film for fresh or fermented food, a packaging material and a packaging container using the film, as disclosed in Chinese patent publication number CN101309952A, wherein the packaging film for fresh or fermented food has an average pore size of 0.01-2 μm and a porosity of 10-80%, wherein the film is made of pure crystalline polymer without adding inorganic or organic compounds for forming pores by a dry stretching method without using organic solvents and solvents to give microporosity. A packaging film that can package fermented foods such as kimchi and fresh foods such as vegetables, wherein through a simple processing process, the packaging film can allow the food to carry out some activities, such as breathing and transpiration, but can inhibit the penetration of liquids such as water and can effectively prevent the loss of taste, so that the food can remain fresh. Another prior art is directed to a method for manufacturing a microporous laminated sheet having a first film layer and a second layer, as disclosed in US patent publication number US06811643B2, wherein the first film layer includes a pore-forming initiator and is bonded to the second layer to form a laminated film. The laminated film is then stretched using at least one transverse stretching machine and at least one longitudinal stretching machine. A method for making a microporous film and a microporous film laminate is provided, as well as an apparatus for stretching the film or the laminated film. Summary of the invention

[0006] The present invention is a method for preparing a microporous film material. The method is a dry-stretching film technology, and the polymer of the material does not contain any grease or any pore-forming particles that are subsequently removed to form pores, and the steps include: S1. Non-porous precursor extrusion process, which uses semi-crystalline thermoplastic polymer to heat and extrude to form a non-porous precursor; S2. Annealing and aging process, which is applied at a lower temperature than the extrusion temperature to cause the non-porous precursor to recrystallize to complete the annealing, and the film roll is removed from the extrusion production line and stored to complete the aging; S3 longitudinal stretching with or without transverse relaxation process, which is room temperature to the melting point of the polymer temperature below the non-porous precursor longitudinal stretching, and with or without applying transverse relaxation to form a longitudinally stretched film; S4. A transverse stretching process without longitudinal relaxation, wherein the longitudinally stretched film is transversely stretched at least once at a temperature above the glass transition point of the polymer and below the melting point, and no longitudinal relaxation is applied, i.e., the longitudinal relaxation rate is 0%, so as to increase the longitudinal production line speed to form a longitudinal / transverse stretched film; S5. A transverse relaxation process, wherein the longitudinal / transverse stretched film is transversely relaxed at least once at a temperature above the glass transition point of the polymer and below the melting point to form a microporous film material; S6. Winding process, the microporous film material is rolled into a coil and then stored. Among them, the semi-crystalline thermoplastic polymer in the non-porous precursor extrusion process is polyolefin. Among them, the semi-crystalline thermoplastic polymer in the non-porous precursor extrusion process is polyethylene or polypropylene. Among them, the aging time in the annealing and aging process is to stand and store for more than 3 days. Furthermore, in the longitudinal stretching process with or without transverse relaxation, the longitudinally stretched film is rolled into a coil and removed from the production line for static storage to complete the secondary aging. Among them, the secondary aging time is to stand and store for more than 3 days. Among them, the longitudinal stretching temperature in the longitudinal stretching process with or without transverse relaxation is 0 to 25°C at ambient temperature for cold stretching (cold stretch), or 10 to 100°C below the melting point temperature of the polymer for hot stretching (hotstretch). Among them, the transverse stretching temperature in the transverse stretching process without longitudinal relaxation is 10 to 100°C below the melting point temperature of the polymer. Wherein, the transverse stretching ratio in the transverse stretching without longitudinal relaxation process is 1.1 to 2.5 times. Wherein, the relaxation ratio in the transverse relaxation process is 2 to 10%. Wherein, the porosity of the microporous film material in the winding process is higher than 50% to 90%. Wherein, the air permeability of the microporous film material in the winding process is less than 4 seconds / 10cc. The present invention has the advantage of reducing equipment investment costs. The pore-forming effect of the porous membrane with biaxial simultaneous stretching can be achieved with a uniaxial stretching device. The preparation method of the microporous film material of the present invention is different from the prior art, and its novelty, progress and practical benefits are unmistakable. Regarding the technology, means and effects adopted by the present invention, a preferred embodiment is now cited and described in detail with the accompanying drawings. It is believed that the above-mentioned purpose, structure and characteristics of the present invention can be understood in depth and in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 : A flow chart showing a method for preparing a microporous film material in the prior art; Figure 2 : A flow chart showing the method for preparing the microporous film material of the present invention; Figure 3 : An electron microscope image showing a microporous film material prepared by the present invention with a transverse stretching ratio of 1.5 times; Figure 4 : An electron microscope image showing a microporous film material prepared by the present invention with a transverse stretching ratio of 1.75 times; Figure 5 : An electron microscope image showing a microporous film material prepared by the present invention with a transverse stretching ratio of 2.0 times; Figure 6 : An electron microscope image showing a microporous film material prepared by the present invention with a transverse stretching ratio of 2.25 times; Figure 7: An electron microscope image showing the microporous film material prepared by the present invention with a transverse stretching ratio of 2.5 times.

[0008] Description of Reference Numerals 101: polymer is extruded into at least a single layer of non-porous precursor; 102: biaxial stretching includes longitudinal stretching and transverse stretching, and the transverse stretching includes simultaneously controlled longitudinal relaxation; 201: non-porous precursor extrusion process; 202: annealing and aging process; 203: longitudinal stretching with or without transverse relaxation process; 204: transverse stretching without longitudinal relaxation process; 205: transverse relaxation process; 206: winding process; 207: the process can be repeatedly implemented. DETAILED DESCRIPTION

[0009] The following describes the implementation of the present invention through specific embodiments, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0010] First, please refer to Figure 2 The flow chart of the method for preparing a microporous film material of the present invention is shown. The present invention is a method for preparing a microporous film material. The method is a dry stretching film technology, and the polymer of the material does not add any grease or any pore-forming microparticles that are used for subsequent removal to form pores, and the steps include: 1. a non-porous precursor extrusion process 201, which heats and extrudes a semi-crystalline thermoplastic polymer to form a non-porous precursor; 2. an annealing and aging process 202, which applies a temperature lower than the extrusion temperature to cause the non-porous precursor to recrystallize to complete annealing, and removes the film roll from the extrusion production line and allows it to stand for storage to complete aging; 3. a longitudinal stretching process with or without transverse relaxation 203, which longitudinally stretches the non-porous precursor at a temperature from room temperature to below the melting point of the polymer, and with or without transverse relaxation to form a longitudinally stretched film; 4. a transverse stretching process without longitudinal relaxation 204, which uses a temperature above the glass transition point of the polymer to below the melting point, such as Figure 2 The process in the middle dotted square area can be repeatedly implemented 207, and the longitudinally stretched film is transversely stretched at least once, and no longitudinal relaxation is applied, that is, the longitudinal relaxation rate is 0%, so as to increase the longitudinal production line speed to form a longitudinal / transverse stretched film; 5. Transverse relaxation process 205, with the temperature above the glass transition point of the polymer and below the melting point, such as Figure 2 The process in the middle dotted square area can be repeatedly implemented 207, and the longitudinal / transverse stretched film is transversely relaxed at least once to form a microporous film material; 6. The rolling process 206 is to roll the microporous film material into a roll and store it.

[0011] In the non-porous precursor extrusion process 201, the semi-crystalline thermoplastic polymer is polyolefin. In the non-porous precursor extrusion process 201, the semi-crystalline thermoplastic polymer is polyethylene or polypropylene. In the annealing and aging process 202, the aging time is more than 3 days. Furthermore, in the longitudinal stretching process 203 with or without transverse relaxation, the longitudinally stretched film is rolled into a coil and removed from the production line for static storage to complete the secondary aging. In the secondary aging time, the static storage is more than 3 days.

[0012] In the longitudinal stretching process 203 with or without transverse relaxation, the longitudinal stretching temperature is 0 to 25°C at ambient temperature for cold stretching, or 10 to 100°C below the melting point of the polymer for hot stretching. In the transverse stretching process 204 without longitudinal relaxation, the transverse stretching temperature is 10 to 100°C below the melting point of the polymer. In the transverse stretching process 204 without longitudinal relaxation, the transverse stretching ratio is 1.1 to 2.5 times. In the transverse relaxation process 205, the relaxation ratio is 2 to 10%. According to the porosity calculation according to ASTM D2873, the porosity of the microporous film material in the winding process 206 is higher than 50% to 90%. According to ASTM D-726, the time required for 100cc of gas to pass through the microporous film material is measured by using a Gurley 4150 gas permeability analyzer as the air permeability (Gurley) value (seconds / 10ccc) of the microporous film material. Five samples are taken from the microporous film material sample to test the air permeability, and the average value is taken as the air permeability of the microporous film material. The sample size is 25.4mm The air permeability of the microporous film material after the winding process 206 was measured by a Gurley gas permeability analyzer and was less than 4 seconds / 10cc.

[0013] In order to enable the review committee to further understand the actual actual product of the present invention, such as Figure 3-7As shown, a method for preparing a microporous film material of the present invention is a dry stretching film technology, and the polymer of the material does not add any grease or any pore-forming microparticles that are used for subsequent removal to form pores, and the steps include: S1. Non-porous precursor extrusion process 201, which heats and extrudes a semi-crystalline thermoplastic polymer to form a non-porous precursor; S2. Annealing and aging process 202, which applies a temperature lower than the extrusion temperature to cause the non-porous precursor to recrystallize to complete annealing, and removes the film roll from the extrusion production line and allows it to be stored to complete aging; S3. Longitudinal stretching with or without transverse relaxation process 203, which longitudinally stretches the non-porous precursor at a temperature from room temperature to below the melting point of the polymer , and with or without transverse relaxation to form a longitudinally stretched film; S4. Transverse stretching without longitudinal relaxation process 204, which transversely stretches the longitudinally stretched film at least once from the glass transition point of the polymer to below the melting point temperature, and does not apply longitudinal relaxation, that is, the longitudinal relaxation rate is 0%, to increase the longitudinal production line speed to form a longitudinal / transverse stretched film, wherein the transverse stretching ratio in the transverse stretching without longitudinal relaxation process 204 is 1.1 to 2.5 times; S5. Transverse relaxation process 205, which transversely relaxes the longitudinal / transverse stretched film at least once from the glass transition point of the polymer to below the melting point temperature to form a microporous film material; S6. Rolling process 206, rolling the microporous film material into a roll and storing it. The microporous film material is observed under an electron microscope at a magnification of 10,000, and the thickness is measured with a thickness meter, the air permeability is measured by a Gurley gas permeability analyzer, and the porosity is calculated according to ASTM D2873. Figure 3 An electron microscope image of the microporous film material prepared by the transverse stretching ratio of 1.5 times of the present invention is shown. In the figure, the microporous film material is manufactured by a transverse stretching ratio of 1.5 times without a longitudinal relaxation process. The bright part is the surface of the microporous film material body, and the dark part is the porous part, showing a uniform micropore size of less than 1 micron. The microporous film material prepared by the transverse stretching ratio of 1.5 times has a thickness of 11.8 microns, an air permeability of 1.5 seconds / 10cc, and a porosity of 60%. Figure 4 The electron microscope image of the microporous film material prepared by the transverse stretching ratio of 1.75 times of the present invention shows that the uniform micropore size is below 1 micron. The thickness of the microporous film material prepared by the transverse stretching ratio of 1.75 times is 11.7 microns, the air permeability is 1.0 sec / 10cc, and the porosity is 64%. Figure 5 The electron microscope image of the microporous film material prepared by the transverse stretching ratio of 2.0 times of the present invention shows that the uniform micropore size is below 1 micron. The thickness of the microporous film material prepared by the transverse stretching ratio of 2.0 times is 11.6 microns, the air permeability is 0.8 seconds / 10cc, and the porosity is 66%.

[0014] Figure 6 The electron microscope image of the microporous film material prepared by the transverse stretching ratio of 2.25 times of the present invention shows that the uniform micropore size is below 1 micron. The thickness of the microporous film material prepared by the transverse stretching ratio of 2.25 times is 11.5 microns, the air permeability is 0.6 seconds / 10cc, and the porosity is 69%. Figure 7 The electron microscope image of the microporous film material prepared by the transverse stretching ratio of 2.5 times of the present invention shows that the uniform micropore size is below 1 micron. The thickness of the microporous film material prepared by the transverse stretching ratio of 2.5 times is 11.3 microns, the air permeability is 0.5 seconds / 10cc, and the porosity is 71%.

[0015] The present invention is a method for preparing a microporous film material. The present invention has the advantage of reducing equipment investment costs. The pore-forming effect of a porous film by biaxial simultaneous stretching can be achieved with a uniaxial stretching device, and the preparation method of the transverse stretching without longitudinal relaxation process is different from the prior art. Therefore, the deficiencies of the prior art can be effectively improved, and the use has considerable practicality.

[0016] In summary, the specific structure disclosed in the embodiment of the present invention can indeed achieve the pore-forming effect of a porous membrane by biaxial simultaneous stretching using a uniaxial stretching device.

[0017] However, the above is only a preferred embodiment of the present invention, and cannot be used to limit the scope of protection of the present invention. That is, all equivalent changes and modifications made according to the scope of the patent application of the present invention and the contents of the specification should fall within the scope of protection of the patent of the present invention.

Claims

1. A method for preparing a microporous film material, It is characterized in that The method is a dry-type film stretching method, and does not add any grease or any pore-forming particles that promote microporous formation to the polymer of the material for subsequent removal to form pores, and the steps include: S1. Non-porous precursor extrusion process, which uses semi-crystalline thermoplastic polymer to heat and extrude to form a non-porous precursor; S2. Annealing and aging process, which is applied below the extrusion temperature to make the non-porous precursor recrystallize to complete the annealing, and the film roll is removed from the extrusion production line and stored to complete the aging; S3 longitudinal stretching with or without transverse relaxation process, which is room temperature to the melting point of the polymer temperature below the non-porous precursor longitudinal stretching, and with or without applying transverse relaxation to form a longitudinally stretched film; S4. A transverse stretching process without longitudinal relaxation, wherein the longitudinally stretched film is transversely stretched at least once at a temperature above the glass transition point of the polymer and below the melting point, while no longitudinal relaxation is applied, i.e., the longitudinal relaxation rate is 0%, to form a longitudinal / transverse stretched film; S5. A transverse relaxation process, wherein the longitudinal / transverse stretched film is transversely relaxed at least once at a temperature above the glass transition point and below the melting point of the polymer to form a microporous film material; S6. A winding process, wherein the microporous film material is rolled into a roll and stored.

2. The method for preparing a microporous film material according to claim 1, It is characterized in that The semi-crystalline thermoplastic polymer used in the non-porous precursor extrusion process is polyolefin.

3. The method for preparing a microporous film material according to claim 1, It is characterized in that The semi-crystalline thermoplastic polymer used in the non-porous precursor extrusion process is polyethylene or polypropylene.

4. The method for preparing a microporous film material according to claim 1, It is characterized in that The aging time in the annealing and aging process is to keep it static for more than 3 days.

5. The method for preparing a microporous film material according to claim 1, It is characterized in that Furthermore, the longitudinally stretched film formed in the longitudinal stretching process with or without transverse relaxation is rolled into a coil and removed from the production line for static storage to complete secondary aging.

6. The method for preparing a microporous film material according to claim 5, It is characterized in that The secondary ripening time is to keep it still for more than 3 days.

7. The method for preparing a microporous film material according to claim 1, It is characterized in that The longitudinal stretching temperature in the process with or without transverse relaxation is 0 to 25°C at ambient temperature for cold stretching, or 10 to 100°C below the melting point of the polymer for hot stretching.

8. The method for preparing a microporous film material according to claim 1, It is characterized in that In the transverse stretching without longitudinal relaxation process, the transverse stretching temperature is 10 to 100°C below the melting point of the polymer.

9. The method for preparing a microporous film material according to claim 1, It is characterized in that The transverse stretching ratio in the transverse stretching without longitudinal relaxation process is 1.1 to 2.5 times.

10. The method for preparing a microporous film material according to claim 1, It is characterized in that The relaxation ratio in the transverse relaxation process is 2 to 10%.

11. The method for preparing a microporous film material according to claim 1, It is characterized in that The porosity of the microporous film material in the winding process is higher than 50% to 90%.

12. The method for preparing a microporous film material according to claim 1, It is characterized in that The air permeability of the microporous film material in the winding process is less than 4 seconds / 10 cc.

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