TW201341160A - Method of preparing multi-layer porous membrane and multi-layer porous membrane - Google Patents

Abstract

A method of preparing a multi-layer porous membrane is disclosed. The method includes the following steps: providing the PTFE-containing materials; providing an expanding facility for the expanding procedure of the PTFE-containing materials; executing an expanding step along the mechanical direction for transforming the PTFE-containing materials into porous PTFE membrane material; and executing an expanding step along the tensile direction for transforming the porous PTFE membrane material into the multi-layer porous PTFE membrane. The method provides an improved way of preparing the multi-layer porous membrane with improved porous characteristics. A multi-layer porous PTFE membrane possessing multiple ultraviolet-resistant characteristics is also disclosed.

Description

Multi-layer porous film manufacturing method and multi-layer porous film

The present invention relates to a method for producing a film; and more particularly to a method for producing a multi-layered porous film.

Polytetrafluoroethylene (PTFE) is a plastic material commonly known as Teflon. It has a wide temperature range, insulation, corrosion resistance, water repellency, anti-adhesion, self-lubricity (low friction coefficient) and biocompatibility. Sex and other characteristics, widely used in insulation, waterproof coatings and dust coatings.

Polytetrafluoroethylene film generally refers to polytetrafluoroethylene as raw material. The commonly used processing process includes: mixing, preforming, extrusion, calendering, stretching and other methods to prepare the film, and through subsequent heat setting and cooling, etc. The processing procedure produces a finished polytetrafluoroethylene film. The expanded polyetrafluoroethylene film (also known as ePTFE) obtained by the stretching method is expanded in the process, and the air is simultaneously filled into the space formed by the expansion, thereby imparting a polytetrafluoroethylene film. The porous structural characteristics (also referred to as porosity) make the polytetrafluoroethylene film a porous film. The porous structure of the PTFE membrane, and its unique material properties, make the PTFE membrane an ideal material in various high-tech fields, and more often used in the manufacture of clothing, filtration equipment, Fire equipment, medical equipment, etc.

In the porous film of polytetrafluoroethylene, the porous structure constituting the porous film includes fibril and island-shaped nodes formed by connecting a plurality of fibers to each other. The fibers are arranged along the stretching direction in the stretching process, and are surrounded by fibers and nodes to form a three-dimensional pore structure. The connection between the pores causes a complicated three-dimensional pipeline network to form a layered "hole layer" structure, and based on such characteristics, the PTFE membrane has superior water repellency or gas permeability. Sex.

The stretching process of the porous film of polytetrafluoroethylene can significantly affect the characteristics of the film formation, and the current stretching process of the porous film of polytetrafluoroethylene generally includes a uniaxial stretching step or a biaxial stretching step. , wherein the biaxial stretching step comprises a stretching process in a machine direction direction and a stretching process in a tensile direction, the stretching step being performed at a predetermined fixed magnification, and During the process, the user can adjust the working temperature, stretching rate and stretching ratio of each step according to the requirements to form a final porous polytetrafluoroethylene film product. However, if the above-mentioned PTFE film stretching process has excessive stretching or improper combination of temperature, stretching rate and stretching ratio, it may cause fiber breakage or joint structure in the porous structure. Disintegration significantly reduces the porosity of the film, which in turn affects the weatherability of the PTFE film.

At present, in order to improve the properties of the porous polytetrafluoroethylene film, the porosity of the porous polytetrafluoroethylene film is often adjusted, and most of them are adjusted by the process of stretching the polytetrafluoroethylene film. The working method (such as stretching ratio and stretching times) increases the porosity. However, from a microscopic point of view, the existing methods are still unable to effectively extend the pore size range of the porous polytetrafluoroethylene film structure to the micron-scale nodes. Into a more tiny pore structure.

For example, U.S. Patent No. 3,953,566 describes a method for producing a porous polytetrafluoroethylene material in which a stretching method is used; and in US Patent No. 3962153, a method for producing a polytetrafluoroethylene material by a stretching method is described. . The polytetrafluoroethylene material in the above two patents has an amorphous structure, and then adjusts the porosity of the film by adjusting the temperature parameter and the stretching rate of the process, and the fine structure in the film contains The microstructure of the nodes and the fibers are interlaced, wherein the pores have a pore size of about 0.25 to 0.55 microns. Such a polytetrafluoroethylene material has high porosity and high strength film properties, and is therefore suitable for processing into various types of materials such as film, column or continuous filaments. Further, U.S. Patent No. 4,902,423 discloses a low-density, high-porosity porous polytetrafluoroethylene film produced by a longitudinal stretching and a transverse stretching process.

In addition, in order to increase the thickness and strength of the film, in some processes, two or more layers of polytetrafluoroethylene film are bonded together and then stretched, but this type of method is not only The original pore-related properties of the membrane have been altered, while also increasing the cost of raw materials. Therefore, how to improve the thin film process to obtain a porous film having an ideal pore diameter and a porosity occupation ratio is one of the goals of the art.

Therefore, the present invention has been made in view of the above problems, and provides a method for producing a multi-layer porous film, which improves the absence of the above-described method for producing a porous film; and the multi-layer porous film produced by the method not only improves the polytetrafluoroethylene. The resistance of the film to ultraviolet light makes it less prone to deterioration, and prolongs the service life of the product made of the above-mentioned tetrafluoroethylene film; and can be further applied to various substrate products or textiles which are intended to isolate or mask ultraviolet light. Provides protection against the harmful effects of ultraviolet light on the human body or products.

In order to solve the above-mentioned shortcomings of the prior art, the present invention provides a method for manufacturing a multi-layer porous film, comprising the following steps:

(1) providing a first tetrafluoroethylene polymer material;

(2) immersing the first tetrafluoroethylene polymer material in a high molecular organic solution and removing it to obtain a second tetrafluoroethylene polymer material;

(3) performing a first direction stretching process on the second tetrafluoroethylene polymer material, and converting the second tetrafluoroethylene polymer material into a first porous tetrafluoroethylene polymer film;

(4) immersing the first porous tetrafluoroethylene polymer film in the polymer organic solution, and taking out a second porous tetrafluoroethylene polymer film;

(5) performing at least two second-direction stretching processes on the second porous tetrafluoroethylene polymer film, and converting the second porous tetrafluoroethylene polymer film into a porous four a vinyl fluoride polymer film; wherein the first direction and the second direction are not parallel to each other.

Meanwhile, in order to solve the above-mentioned lack of the prior art, the present invention also provides a multi-layer porous film comprising a porous tetrafluoroethylene polymer film according to the above-mentioned multi-layer A method for producing a porous film is produced.

SUMMARY OF THE INVENTION A primary object of the present invention is to provide a method for producing a multi-layered porous film, by which a film having ultraviolet light resistance and good weather resistance can be obtained.

A further object of the present invention is to treat a semi-finished film material with an organic solution in a stretching process, and to swell the semi-finished film product, and then perform a stretching process, thereby achieving the effect of improving the characteristics of the polytetrafluoroethylene film, and further combining The unique physical and chemical properties unique to PTFE materials can fundamentally enhance the resistance of various product manufacturing materials to ultraviolet light.

Another object of the present invention is to provide a multi-layer porous film which has good ultraviolet light-proof ability and can effectively block light, and the multi-layer porous film itself can resist the damage caused by ultraviolet light.

Still another object of the present invention is to provide a method for producing a multi-layer porous film, and a multi-layer porous film obtained by the method, and a method for producing the multi-layer porous film and a multi-layer porous material The film is widely used in various products that are vulnerable to ultraviolet light. It can be protected from ultraviolet light by using various methods to protect the above products.

The method for producing a multi-layer porous film proposed by the present invention has the following advantages as compared with the conventionally known method for producing a multi-layer porous film:

(1) The method for producing a multi-layered porous film according to the present invention can produce a multi-layered porous film having a denser pore structure, a smaller average pore diameter, and a better light-blocking effect.

(2) The method for producing a multi-layered porous film according to the present invention can produce a multi-layered porous film having a more porous structure and a weather resistance which is more resistant to ultraviolet light damage.

(3) The method for producing a multi-layer porous film according to the present invention can control the porosity of a multi-layered porous material and form a multi-layer porous film having a multi-layered property.

Fig. 1A is a schematic view showing the internal pore structure of a stretched porous tetrafluoroethylene polymer film obtained by the method for producing a multi-layered porous film of the present invention.
Fig. 1B is a partially enlarged schematic view showing the internal pore structure of the stretched porous tetrafluoroethylene polymer film obtained by the method for producing a multi-layered porous film of the present invention, showing the pore structure of the L region in Fig. 1A.
1C is a partially enlarged schematic view showing the internal pore structure of the stretched porous tetrafluoroethylene polymer film obtained by the method for producing a multi-layer porous film of the present invention, showing the pores of the L' region in FIG. 1B. structure.
Figure 2 is a graph showing the data of the weather resistance of UVB ultraviolet light obtained from a porous tetrafluoroethylene polymer film obtained by a conventional method.
Fig. 3 is a graph showing the data of the weather resistance of UVB ultraviolet light in the porous tetrafluoroethylene polymer film obtained in Example 1 according to the present invention.
Fig. 4 is a graph showing the data of UVB ultraviolet light weather resistance of a porous tetrafluoroethylene polymer film obtained in Example 2 according to the present invention.

The present invention will be understood by those skilled in the relevant art, and the present invention will be described in the following description. The preferred embodiments are further illustrated. The drawings in the following texts are intended to be illustrative of the features of the present invention and are not required to be fully drawn according to the actual circumstances.

Since the present invention discloses a method for producing a multi-layered porous film, the principle of preparation of the tetrafluoroethylene polymer material used in the method, the characteristics of the tetrafluoroethylene polymer material, the stretching equipment, and the operation of the stretching apparatus The concepts and operating procedures are well known to those of ordinary skill in the relevant art and are therefore not fully described below.

First, the present invention proposes a method of manufacturing a multi-layer porous film comprising the following steps:

(1) providing a first tetrafluoroethylene polymer material;

(2) immersing the first tetrafluoroethylene polymer material in a polymer organic solution, and taking out the immersed tetrafluoroethylene polymer material, which is called a second tetrafluoroethylene polymer material;

(3) performing a first direction stretching process on the second tetrafluoroethylene polymer material, and then stretching the second tetrafluoroethylene polymer material into a porous tetrafluoroethylene polymer film by stretching. It is called a first porous tetrafluoroethylene polymer film;

(4) The first porous tetrafluoroethylene polymer film is immersed in a polymer organic solution and taken out to obtain a porous tetrafluoroethylene polymer film after immersion, which is called second porous tetrafluoroethylene polymerization. Membrane material; and

(5) performing a second porous stretching process on the second porous tetrafluoroethylene polymer film at least twice, and then stretching the second porous tetrafluoroethylene polymer film into a A porous tetrafluoroethylene polymer film; wherein the first direction and the second direction are not parallel to each other or perpendicular to each other.

The definition, principle, measurement method or calculation formula of each measurement parameter of the present invention is briefly described as follows:

Porosity (%) : Generally refers to the proportion of space volume that is not occupied by material molecules in a porous tetrafluoroethylene polymer film or a porous tetrafluoroethylene polymer film of a certain volume. The calculation formula is:

Porosity (%) = (visual density / true density)%

Wherein, the apparent density = the weight of the film formation / the volume of the film formation; and the true density = the initial density of the non-porous tetrafluoroethylene polymer material (literature reference value is 2.15).

Definition of fibers and nodes :

Please refer to FIG. 1A, which is a schematic cross-sectional view of a film or film prepared by using a polytetrafluoroethylene polymer as a material. This cross-sectional structure exhibits a three-dimensional pore structure in the structure of the polytetrafluoroethylene polymer. Please refer to FIG. 1B , which is a partial enlarged view of the polytetrafluoroethylene polymer molding material or the cross-sectional structure region L of the film. It can be seen that in the pore structure, the structure elongated and elongated like a long fiber is called “fiber” 1 , and more The island-like portion where the fibers are staggered or attached is the "node" 2, and the pore size of the pore structure in this structure usually falls on the order of micrometers. It should be noted that the size of the fibers, the nodes and the pore size in the pore structure of the present invention is not particularly limited, and the tetrafluoroethylene polymer material has good ductility in addition to the pore structure observable by electron microscopy. Characteristic, there is also a deeper and smaller pore structure in the expected junction. For example, a partial enlargement of the region L' shown in 1C, the pore size is mostly in the nanometer or smaller than the nanometer. The size, therefore, continues to be microscopic, and in this tiny pore structure, there are also smaller structures of the fibers 1' and 2'. Therefore, the definition of the minimum size of the fiber and the node is limited by the upper limit range that can be detected by the currently used positron quenching spectrometer technology (ie, the smallest size that can be measured by the positron quenching spectrometer technology).

Definition of micropores and nanopores :

Based on the foregoing definition of fibers and nodes, in a porous tetrafluoroethylene polymer film or a porous tetrafluoroethylene polymer film structure, a space surrounded by fibers and nodes may be defined as a "hole", and the hole includes "Micro-holes" and "nano holes". Among them, "micropores" refers to pores that can be detected by general electron microscopy and pore measurement methods. The pore size is usually close to 100 nm or more than 100 nm. In nanopores, the pore diameter is usually less than 50 nm. In addition to the pores that can be ascertained by the methods described above, the Mikon hole also contains tiny nanopores that cannot be viewed by electron microscopy. This tiny nanopore must be detected by the positron quenching spectrometer technique.

In addition, the current method commonly used to detect holes in a film or film structure is an electron microscope. When an electron microscope is used to observe a tetrafluoroethylene polymer film, the image that can be observed has limitations, and it is impossible to judge the deeper portion of the film. Ultrafine structures (such as the tiny nanopores described above), as well as the fibers, nodes and pore structures that may be present therein. However, the multi-layer porous tetrafluoroethylene polymer film of the present invention has pore and pore layer characteristics which are constructed by fibers and nodes, and can be passed through Nano Transmission X-ray Microtomography (Nano Transmission X-ray Microtomography). NTXM) Further observations, this technique is a method commonly used in the art, and therefore is not described in detail herein. For the detection image of the multi-layer porous tetrafluoroethylene polymer film, the thickness of the relative position in the film is shown by the shade of the color gradation. The number of layers of the multi-layer porous tetrafluoroethylene polymer film can be expressed by different color gradations as the depth changes.

Hole occupation rate (%) :

The space volume ratio of the aforementioned micropores or nanopores in the porous tetrafluoroethylene polymer film or the porous tetrafluoroethylene polymer film is a so-called hole occupation ratio. Among them, the pore occupancy rate caused by micropores is called "micropore occupation rate"; and the porosity occupation rate caused by nanopores is called "nano hole occupation rate".

In order to facilitate the description of the specific embodiment of the present invention, steps (1) to (5) of the above-described method for producing a multi-layered porous film are sequentially described as follows. First, in the step (1) of the method for producing a multi-layer porous film of the present invention, any of the tetrafluoroethylene polymer materials is first provided. The tetrafluoroethylene polymer material includes, but is not limited to, the following materials: a fluoropolymer, a fluoropolymer polymer or various forms of tetrafluoroethylene tree fingers, but the preferred tetrafluoroethylene polymer material in the present invention is four. Fluoroethylene polymer. Furthermore, the tetrafluoroethylene polymer used in the production method of the present invention may be added with other components as needed to adjust or improve the properties of the film, such as titanium dioxide, cerium oxide, carbon black, carbon nanotubes, inorganic oxides, The organic oxide; and when actually added, one additive may be used alone or in combination of two or more additives, and the total additive content is about 15% to 30%.

Next, the coil material is further prepared by using the above-mentioned tetrafluoroethylene polymer material, and the processes, methods and related equipment thereof are well known to those skilled in the art, and therefore will not be described in detail. For example, the present invention can use a common extrusion process in which dispersed tetrafluoroethylene polymer resin particles and a squeezing agent (about 20% or so) are uniformly mixed to prepare a paste mixture and processed by an extruder apparatus. Extrusion of preformed tetrafluoroethylene polymer extrudates, and the extrudates may be in the form of strips, cylinders, prisms, sheets, and the like. The above-mentioned tetrafluoroethylene polymer resin particles refer to a polymer obtained by an emulsion polymerization method, and are condensed in an aqueous dispersion to be separated and dried to form a powder; the composition of the polymer may be tetrafluoroethylene (TFE). A single molecular polymer, or a heteropolymolecular copolymer of tetrafluoroethylene and a small amount of perfluoroalkylvinylether (less than 0.5% by weight) (ie, denatured tetrafluoroethylene, also known as PFA).

In this extrusion process, in order to facilitate the subsequent stretching process to proceed more smoothly, the rheological behavior of the material in the over-exaggeration can be regulated, and the preferred method is to suppress the molecular alignment of the tetrafluoroethylene polymer resin particles during the extrusion process. Conditions, such as reducing the necking ratio of the extruded tube (the range is usually 100:1 or less, preferably 20:1 to 60:1); the ratio of tetrafluoroethylene polymer resin particles/extrusion aid (usually It is 77:23 to 80:20); and adjusts the angle of the die of the extruder (usually about 60 degrees).

The processing is then carried out using the aforementioned extrudates to further produce a tetrafluoroethylene polymer material or coil for the drawing apparatus. At this stage, the extrudate has initially possessed the characteristics of being able to be made into a film, so further the calendering process is carried out by the principle of rolling calendering of the roller device in the stretching device, that is, parallel rolling along the upper and lower rollers in the roller device. The direction (also referred to as "mechanical direction" or "longitudinal") or vertical direction (also known as "anti-tensioning" or "lateral") is used to calender the extrudate into a sheet or film.

After the calendering process is completed, the extrusion process of the extrusion agent is carried out: the process mainly heats the calender obtained by the calendering process, or dissolves with a solvent such as trichloroethane or trichloroethylene. A squeezing agent to facilitate removal of the squeezing agent and further drying. If the process is carried out by heating, the heating temperature may be adjusted or selected according to the type of the extrusion agent used, wherein a preferred temperature of 200 ° C to 300 ° C, especially at 250 ° C, is better; however, if it exceeds At 300 ° C, especially at a temperature of 327 ° C above the melting point of the tetrafluoroethylene polymer, a tendency to sinter occurs.

After the above process, the material of the film or sheet material at this time has a pore characteristic, and the porosity thereof is about 25% to 30%. However, the dry extrudate at this stage is observed under an electron microscope with a magnification of about 6000 times. Generally, a slender "fiber" structure cannot be observed, but after the completion of the extrusion process, the aid is released or dispersed. The remaining voids provide space for subsequent stretching processes to develop and expand the fine fiber network.

In the manufacturing method of the present invention, the technical means used includes a "soaking procedure", which is to firstly apply a tetrafluoroethylene polymer material (which may include a sheet, a coil or a material beforehand) before performing the steps of the stretching process. The semi-finished product is immersed in the organic solution of the specific formulation. The swellability of the organic solution of the specific formulation to the structure of the polytetrafluoroethylene material can make the PTFE material softer and enhance its ductility, so that the four can be adjusted. The structure of the pore structure (fibers and nodes) produced by stretching the fluoroethylene polymer film allows the fibers to be more stably stretched in the stretching process, and the Teflon portion of the joint portion can also be stretched. The process is extended to further form a finer pore structure, and according to this characteristic, a multi-layered pore structure containing a porous layer is further formed until the desired multi-layered porous film semi-finished product or final product is formed.

The organic solution used in the "soaking procedure" of the present invention has the purpose of using an organic solvent to cause the polytetrafluoroethylene material to swell and affect the physical or chemical properties of the tetrafluoroethylene material. However, the present invention The preferred embodiment of the process generally has a heating or high temperature process, and the organic solvent generally has a low boiling point and a high volatilization property. Therefore, in order to overcome this limitation, the present invention preferably uses an organic solution for the soaking process. Therefore, the organic solution component or formulation of the present invention can be adjusted according to the use requirements, for example, adding a polymer or mixing and using different kinds of organic solvents, wherein a polymer organic solution is used, which is a better embodiment of the present invention. The invention adopts a formula of a polymer organic solution, and the components thereof may include: alcohols, ketones, esters, ethers, polymers, and may be used alone or in combination. The above alcohols, ketones, esters, and ethers are preferably organic compounds having a carbon number of from 1 to 10; and the above polymers are selected to include Hydroxypropyl acrylate and polyethylene glycol. Diacrylate, triethylene glycol diacrylate, tripropylene glycol diacrylate, tetraethylene glycol diacrylate, 2-(2-ethoxyethoxy)ethyl acrylate, polyvinyl alcohol and polyvinyl acetate Polyvinyl vinyl acetate may be used singly or in combination, and for the use of the polymer, it is preferred to dissolve the polymer in an organic solvent to form a polymer organic solution.

Therefore, after obtaining the above-mentioned tetrafluoroethylene polymer material, the immersion procedure described in the step (2) is continued: the tetrafluoroethylene polymer material is immersed in a polymer organic solution and then taken out, thereby obtaining the swelled four. Fluoroethylene polymer material (ie, a second tetrafluoroethylene polymer material). The temperature range of the solution during soaking depends on the formulation of the particular organic solution, between -50 ° C and 30 ° C, preferably between -20 ° C and 10 ° C.

Next, a stretching process for producing a multi-layered porous film of the present invention is carried out by using a stretching apparatus to obtain a tetrafluoroethylene polymer material (for example, extruding a formed tetrafluorocarbon) after obtaining a tetrafluoroethylene polymer material. Ethylene polymer material) is subjected to a series of stretching processes, as detailed below.

Regarding the stretching process, the present invention does not limit the stretching method used in the stretching process, and the stretching process generally refers to the method of rolling the above material by direct pressing or applying tensile stretching from the side. . The stretching apparatus, the using method and the operating procedure for rolling or stretching the tetrafluoroethylene polymer material to convert the tetrafluoroethylene polymer material into a sheet or film semi-finished product are those skilled in the art. It is well known and will not be described again.

Briefly, the stretching apparatus comprises a series of rollers and heating devices, and the rolling operation of the roller device can provide driving force for driving the stretching of the film; the rolling direction of the roller device can be used to control the direction in which the film is stretched. The rolling speed of the roller device controls the stretching rate, while the heating device provides a heat source for the film to be stretched under a specific temperature environment. In addition, the present invention is not particularly limited to the stretching apparatus, for example, the roller setting direction of the roller device and the film stretching direction are not limited to a single direction; the number of roller devices or heating devices can be selected according to the use requirements. For single or multiple, multi-stage roller design can be used; even devices that regulate and control rolling speed, heating temperature and tensile strength can be installed according to the quality requirements of the production line.

In general, the stretching process can be divided into "uniaxial extension" and "biaxial extension". The biaxial stretching can be further divided into "longitudinal stretching" or "transverse stretching", wherein "longitudinal" in the longitudinal stretching refers to the stretching direction of the first stretching of the film along the stretching device, so The process of stretching parallel to the longitudinal direction is referred to as longitudinal stretching, and such a stretching direction is also referred to as "first direction" in the present invention; and "transverse direction" referred to as transverse stretching means not parallel to The direction of the "longitudinal direction" described above, so that the process of stretching in a direction parallel to the transverse direction is called transverse stretching. Such a direction of stretching is also referred to as "second direction" in the present invention, and can also be regarded as a film. A biasing stretch with different longitudinal strength or shrinkage. Here, the non-parallel relationship refers to a non-parallel relationship in a stereoscopic space, and is not limited to a non-parallel relationship on a single plane.

As mentioned above, the expanded tetrafluoroethylene polymer material has pore characteristics, but at this time, the pores are less and unevenly distributed, and it is necessary to pass through the stretching process to produce pores with uniform and dense pore distribution. structure. The stretching process of different conditions can control the condition of the film formation, the pore size and the uniformity of the pores, so as to enhance the film forming characteristics, such as gas permeability or water resistance, with the subsequent use. For the above purposes, the factors controlling the film formation hole characteristics of the stretching process include: stretching temperature, stretching speed, stretching ratio setting, etc., all of which can affect the properties of film formation.

The draw ratio refers to a magnification of the film area after stretching compared to the film area before the stretching process (for example, the longitudinal stretching process or the transverse stretching process). For example, the stretching ratio of 2 means that the stretching process stretches the film at a stretching ratio of 1:2, so that the film having an original area of 1 unit is stretched into a film having a film area of 2 units, meaning completion The film area of the film after this stretching procedure was twice the film area of the original film before the stretching process. For the convenience of explaining the embodiments of the present invention, the following expressions regarding the stretching ratio are all expressed by a single ratio.

It is worth mentioning that the stretching ratio is one of the key factors affecting the tensile strength of the film, so it must be carefully selected. Although the invention is not limited, the stretching ratio is usually between 3 and 10; preferably In the range of 4 to 8. If the draw ratio is less than 3, or the draw ratio is higher than 10, it is possible to produce a hole having a pore diameter or a porosity which is not as good as expected.

In addition, stretching the film at a specific temperature also stretches the existing fiber structure in the film, wherein the fibers are stretched or stretched along the stretching direction, and the fibers are joined at the joint along with the stretching process. After being stretched, the structure of the joint is produced. Overall, the stretching process results in the formation of a microfibrous structure within the stretched film, and the air is simultaneously charged into the pores of the microfiber structure during stretching. 1A is a schematic view showing the internal pore structure of a stretched porous tetrafluoroethylene polymer film obtained by the method for producing a multi-layer porous film according to the present invention, comprising fiber 1, node 2, and A plurality of fibers 1 and a plurality of nodes 2 constitute a stacked layer structure 30 having a three-dimensional network structure. In fact, the fibers 1 and 2 in the microfibrous structure can be identified by electron microscopy, and such fibers 1 and 2 form a complex network of complex pores, and the pore size surrounded by the fibers 1 and 2 The size of the pores in the film is determined; and the number of nodes affects the overall porosity of the film.

Based on the above characteristics, when the stretching ratio is insufficient, the desired pore size and porosity cannot be obtained; when the stretching ratio is too large, the lateral shrinkage may be increased to shorten the distance between the fibers and reduce the pore diameter and fiber strength. Weakening or even breaking, thus disintegrating the structure between the fibers and the nodes, affecting the overall properties of the film. In addition, if the stretching ratio in a single direction is large, the holes become longer along the stretching direction, so that the holes are elongated; if the stretching ratio in the two directions is large, the holes become longer along the biaxial stretching direction. To make the hole square.

Regressing the manufacturing method of the multi-layer porous film of the present invention, and further subdividing the stretching process of the present invention into three processes: the first process is a longitudinal stretching process (first direction stretching process); and the second The third and third program is the horizontal stretching program (the second direction stretching program), which is described as follows:

In the step (3) of the method for producing a multi-layer porous film according to the present invention, the first process in the drawing process, that is, the longitudinal stretching process, is performed on the swollen tetrafluoroethylene polymer material by a stretching apparatus. The swelled tetrafluoroethylene polymer material is transformed into a porous tetrafluoroethylene polymer film.

However, prior to the stretching process, a pre-heat treatment step of the tetrafluoroethylene polymer material may be added as needed to facilitate the stretching process.

First, the swollen tetrafluoroethylene polymer material is subjected to a longitudinal stretching process at a draw ratio of 3 to 50, preferably a draw ratio of 5 to 30, and an optimum draw ratio of 10 to 20. The stretching temperature used in the longitudinal stretching process is 200 ° C to 400 ° C, the preferred stretching temperature is 250 ° C to 350 ° C, and the optimum stretching temperature is 280 ° C to 330 ° C. A porous tetrafluoroethylene polymer film (first porous tetrafluoroethylene polymer film) can be obtained by this longitudinal stretching process.

After obtaining the porous tetrafluoroethylene polymer film, since the temperature is still high, it can be sent to the low temperature tank to cool down, which helps to maintain the structural stability in the membrane, and the temperature control range in the low temperature tank is -50 ° C to 30 ° C, preferably at -20 ° C to 10 ° C.

Prior to entering the second and third procedures in the stretching process (both of which are transverse stretching procedures), the porous tetrafluoroethylene polymer is prepared according to the method (4) of the method for producing a multi-layer porous film of the present invention. After the film is immersed in a specific polymer organic solution and taken out, a swelled porous tetrafluoroethylene polymer film (second porous tetrafluoroethylene polymer film) can be obtained, and the specific polymer organic used therein is obtained. The selection of the solution, as well as the temperature of the solution and the like, the principle is as in the above-mentioned manufacturing method step (2), and will not be described again.

Next, according to the method (5) of the method for producing a multi-layer porous film of the present invention, the step of performing at least two transverse stretching processes on the swollen porous tetrafluoroethylene polymer film by a stretching apparatus (second) The direction stretching process), that is, the second and third procedures in the stretching process, the swelled porous tetrafluoroethylene polymer film is converted into a porous tetrafluoroethylene polymer film.

Wherein, when the first transverse stretching process is performed on the swollen porous tetrafluoroethylene polymer film, the stretching ratio is 2 to 20, the stretching ratio is preferably 3 to 15, and the optimum stretching ratio is 3 to 12. The stretching temperature used in the transverse stretching process is 200 ° C to 400 ° C, the preferred stretching temperature is 250 ° C to 350 ° C, and the optimum stretching temperature is 280 ° C to 330 ° C.

After obtaining the porous tetrafluoroethylene polymer film, since the temperature is still high, it can be sent to the low temperature tank to cool down, which helps to maintain the structural stability in the film, and the temperature control range in the low temperature tank is as described above. Therefore, it will not be repeated.

The porous tetrafluoroethylene polymer film obtained at this stage contains a main fiber structure called a "porous layer", which is composed of a plurality of nodes and fibers, and the nodes are surrounded by fibers. A plurality of "micro-holes" are formed in the space, and the so-called micro-pores here generally refer to holes having a pore diameter of about 100 nm. In the case of the micropores of the present invention, the average pore diameter is greater than 100 nm, and the proportion of the micropores in the overall porous tetrafluoroethylene polymer film causes the porous tetrafluoroethylene to polymerize. The material film has a specific "micropore occupation rate" of 5% to 99%.

Further, from a microscopic point of view, the fibers and nodes in the fiber structure may comprise a finer pore structure, called a "nanoporous layer", which contains finer fibers and nodes. A plurality of nanopores are formed, and the nanopores generally refer to pores having a pore diameter of less than 100 nm.

Continue to return to the stretching process, and perform the third process in the stretching process, that is, the second transverse stretching process, where the stretching ratio is 2 to 20, and the stretching ratio is preferably 3 to 15, and the optimum stretching is performed. The magnification is 3 to 12. The stretching temperature used in this second transverse stretching process is 200 ° C to 400 ° C, the preferred stretching temperature is 250 ° C to 350 ° C, and the optimum stretching temperature is 280 ° C to 330 ° C.

Therefore, the finished product of the porous tetrafluoroethylene polymer film can be obtained after the first and second stretching processes.

Further, from a microscopic point of view, the finished product of the porous tetrafluoroethylene polymer film can be used to determine the characteristics of the nanoporous layer which cannot be observed by an electron microscope via a positron quenching spectrometer technique and an analytical method. The nanoporous layer of the porous tetrafluoroethylene polymer film obtained at this stage has a higher nanopore layer than the porous tetrafluoroethylene polymer film which has been subjected to only one transverse stretching procedure. The nanopore has a larger porosity and a finer nano-scale porous structure, and the tiny pores contained in this nanoporous layer are called "nano pores", and this nanopore diameter is not only one, but can contain pore sizes of various sizes. The pore size is preferably in the range of 0.1 to 50 nm. Such a microscopic level of nano-scale porous structure, which also has the characteristics of fibers and nodes.

However, such a small level of structure can no longer be observed or measured using conventional electron microscopy techniques (average resolution of about 100 nm to 500 nm), and must be passed through "positron annihilation lifetime spectroscopy" (positron annihilation lifetime spectroscopy) The pore-related parameters of the nano-scale porous structure in the porous tetrafluoroethylene polymer film were determined.

The technology of positron quenching spectrometer has been used to study the ultrafine structure and its changes of materials, especially in the field of solid physics research, which can be used to study radiation damage of crystal defects or extremely fine structures. The principle of the present invention for measuring the ultrafine structure of a tetrafluoroethylene polymer film is to use a positron quenching spectrometer technique to detect the free volume of inter-molecular gaps in a plurality of materials in a non-destructive manner. Characteristics. Therefore, the positron quenching spectrometer technology has been widely accepted and used for the analysis of inter-molecular gap structures in polymer materials, and the detection of pores in the range of nanometers (usually between 0.1 nm and 10 nm). Therefore, the present invention also uses a positron annihilation spectrometer technology to detect the pore size, porosity and nanopore occupancy of a tetrafluoroethylene polymer film.

In summary, the nanoporous porous structure of the porous tetrafluoroethylene polymer film produced by the present invention is referred to as a "nanoporous layer", and the nanoporous layer contains a plurality of layers. "Neon Hole", the so-called nano-holes are distinguished by the size distribution. They mainly contain two kinds of tiny holes, including holes with an average pore diameter of 0.1 nm to 5 nm. The Mikon Cave and the hole with an average pore diameter between 5 nm and 50 nm are called "Second Nano Holes". However, if the characteristics of the lamination in the void structure are analyzed, the fibers and nodes of the porous tetrafluoroethylene polymer film are stacked layer structures formed by a 3D network structure, and the porous tetrafluoroethylene polymer film is formed. The stacking standard of the stacked layer structure is "the number of first nanopore layers in the unit thickness", which is calculated by dividing the film thickness by the average pore diameter of the first nanopore, which represents The number of layers of the stacked layer structure. The proportion of these nanopores in the overall porous tetrafluoroethylene polymer film gives the tetrafluoroethylene polymer film a specific "nano-hole occupancy rate" ranging from 90% to 99.9%.

The present invention also provides a multi-layered porous film produced by the above-described method for producing a multi-layered porous film, which has a denser pore structure, a smaller average pore diameter, and a better light blocking effect. The multi-layer porous film itself has a complex and tortuous three-dimensional network pore structure, and the present invention provides the indirect pore structure formed by other materials such as polyethylene (PE) or polyvinylidene fluoride (PVDF). The multi-layer porous film has better barrier properties, so that it has better ultraviolet light resistance.

In addition, the multi-layer porous film provided by the present invention has a better nanopore occupation ratio compared to the conventional multi-layer porous film produced by the conventional porous film production method: and a preferred nanopore The occupation ratio causes the pore structure of the fibers and nodes of the multi-layer porous film to be hardly damaged by the irradiation of ultraviolet light, and thus the film quality is not easily deteriorated, thereby further improving the weather resistance of the multi-layer porous film to ultraviolet light. Therefore, the method for producing a multi-layered porous film proposed by the present invention can be made into a multi-layered porous film having weather resistance which is preferably resistant to ultraviolet light damage.

In addition, according to the manufacturing method provided by the present invention, a tetrafluoroethylene polymer film or a multi-layer porous film having different pore diameters and pore occupation ratios can be further used according to various requirements, and is widely used in various fabrics and buildings. Outdoor equipment, outdoor products, or various products that are vulnerable to ultraviolet light are covered or fitted. By using such a combination, the products are protected from ultraviolet light.

The following two examples of the present invention are listed and compared with porous membranes manufactured by conventionally known methods:

Comparative example (conventional method) :

First, the polytetrafluoroethylene resin particles and the additive are uniformly mixed, and after being matured, they are placed in a preliminary molding machine to prepare the above-mentioned mixture, and then extruded from a die to form a strip of tetrafluoroethylene resin material, and pressed into The tetrafluoroethylene polymer material was then fed to an oven to remove the additive at a temperature of 250 °C. Thereafter, a porous tetrafluoroethylene polymer film was obtained by subjecting the ribbon made of the tetrafluoroethylene polymer material to a longitudinal stretching procedure at a draw ratio of 8 in an environment of 320 °C. The temperature was controlled at 320 ° C, and the porous tetrafluoroethylene polymer film was subjected to a transverse stretching process at a stretching ratio of 2 in this high temperature environment, and the final transverse stretching ratio was 2, and the procedure was completed. The obtained porous tetrafluoroethylene polymer film is referred to as sample A.

Example 1 :

First, the polytetrafluoroethylene resin particles and the additive are uniformly mixed, and after being matured, they are placed in a preliminary molding machine to prepare the above-mentioned mixture, and then extruded from a die to form a strip of tetrafluoroethylene resin material, and pressed into The tetrafluoroethylene polymer material was then fed to an oven and the additive was removed at a temperature of 250 °C. Thereafter, the ribbon made of the tetrafluoroethylene polymer material is immersed in a polyvinyl alcohol polymer organic solution at 10 ° C, and then the swollen tetrafluoroethylene polymer material is taken out, and then at 320 ° C. The longitudinal stretching process was carried out at a draw ratio of 8, and then the tetrafluoroethylene polymer material was fed into a low temperature tank having a temperature of -10 ° C to obtain a porous tetrafluoroethylene polymer film. The porous tetrafluoroethylene polymer film is continuously immersed in a polyvinyl alcohol polymer organic solution at -20 ° C, and then the swollen porous tetrafluoroethylene polymer film is taken out, and then swollen at 320 ° C. The porous tetrafluoroethylene polymer film was subjected to a transverse stretching process at a stretching ratio of 1 in this high temperature environment, and then fed into a low temperature tank having a temperature of -20 °C. Then, the tetrafluoroethylene polymer film of this stage is again immersed in a polyvinyl alcohol polymer organic solution at -20 ° C, and then a transverse stretching ratio of 1 stretching ratio is continued at a temperature of 380 ° C. The procedure was such that the final transverse draw ratio was 2 and then fed into a low temperature tank at a temperature of -20 °C. The porous tetrafluoroethylene polymer film (i.e., sa-PTFE ^R ) obtained by this procedure is referred to as sample B.

Example 2

First, the polytetrafluoroethylene resin particles and the additive are uniformly mixed, and after being matured, they are placed in a preliminary molding machine to prepare the above-mentioned mixture, and then extruded from a die to form a strip of tetrafluoroethylene resin material, and pressed into The tetrafluoroethylene polymer material was then fed to an oven to remove the additive at a temperature of 250 °C. Thereafter, the ribbon made of the tetrafluoroethylene polymer material is immersed in a polyvinyl alcohol polymer organic solution at 10 ° C, and then the swollen tetrafluoroethylene polymer material is taken out, and then at 320 ° C. The longitudinal stretching process was carried out at a draw ratio of 8, and then the tetrafluoroethylene polymer material was fed into a low temperature tank having a temperature of -10 ° C to obtain a porous tetrafluoroethylene polymer film. The porous tetrafluoroethylene polymer film is continuously immersed in a polyvinyl alcohol polymer organic solution at -20 ° C, and then the swollen porous tetrafluoroethylene polymer film is taken out, and then swollen at 320 ° C. The porous tetrafluoroethylene polymer film was subjected to a transverse stretching process at a stretching ratio of 3 in this high temperature environment, and then fed into a low temperature tank having a temperature of -20 °C. Then, the tetrafluoroethylene polymer film of this stage is again immersed in a polyvinyl alcohol polymer organic solution at -20 ° C, and then a transverse stretching ratio of 4 is continued at a temperature of 380 ° C. The procedure was such that the final transverse draw ratio was 12 and then fed into a low temperature tank at a temperature of -20 °C. The porous tetrafluoroethylene polymer film (i.e., sa-PTFER) obtained by this procedure is referred to as sample C.

Example 3

First, the polytetrafluoroethylene resin particles and the additive are uniformly mixed, and after being matured, they are placed in a preliminary molding machine to prepare the above-mentioned mixture, and then extruded from a die to form a strip of tetrafluoroethylene resin material, and pressed into The tetrafluoroethylene polymer material was then fed to an oven to remove the additive at a temperature of 250 °C. Thereafter, the ribbon made of the tetrafluoroethylene polymer material is immersed in a polyvinyl acetate polymer organic solution at 10 ° C, and then the swollen tetrafluoroethylene polymer material is taken out, and then at 320 ° C. Next, the longitudinal stretching procedure was carried out at a draw ratio of 8, and then the tetrafluoroethylene polymer material was fed into a low temperature tank having a temperature of -10 ° C to obtain a porous tetrafluoroethylene polymer film. The porous tetrafluoroethylene polymer film is continuously immersed in a polyethylene vinyl acetate polymer organic solution at -20 ° C, and then the swollen porous tetrafluoroethylene polymer film is taken out, and then at 320 ° C, The swollen porous tetrafluoroethylene polymer film was subjected to a transverse stretching process at a stretching ratio of 3 in this high temperature environment, and then fed into a low temperature tank having a temperature of -20 °C. Then, the tetrafluoroethylene polymer film of this stage is again immersed in a polyethylene vinyl acetate polymer organic solution at -20 ° C, and then a transverse stretching ratio of 4 is continued at a temperature of 380 ° C. The procedure was carried out so that the final transverse draw ratio was 12 and then fed into a low temperature tank having a temperature of -20 °C. The porous tetrafluoroethylene polymer film (i.e., sa-PTFER) obtained by this procedure is referred to as sample D.

Example 4

First, the polytetrafluoroethylene resin particles and the additive are uniformly mixed, and after being matured, they are placed in a preliminary molding machine to prepare the above-mentioned mixture, and then extruded from a die to form a strip of tetrafluoroethylene resin material, and pressed into The tetrafluoroethylene polymer material was then fed to an oven to remove the additive at a temperature of 250 °C. Thereafter, the ribbon made of the tetrafluoroethylene polymer material is immersed in a 10 ° C hydroxypropyl acrylate polymer organic solution, and then the swollen tetrafluoroethylene polymer material is taken out, and then at 320 ° C. Next, the longitudinal stretching procedure was carried out at a draw ratio of 8, and then the tetrafluoroethylene polymer material was fed into a low temperature tank having a temperature of -10 ° C to obtain a porous tetrafluoroethylene polymer film. The porous tetrafluoroethylene polymer film is continuously immersed in a hydroxypropyl acrylate polymer organic solution at -20 ° C, and then the swollen porous tetrafluoroethylene polymer film is taken out, and then at 320 ° C, The swollen porous tetrafluoroethylene polymer film was subjected to a transverse stretching process at a stretching ratio of 3 in this high temperature environment, and then fed into a low temperature tank having a temperature of -20 °C. Then, the tetrafluoroethylene polymer film of this stage is again immersed in a hydroxypropyl acrylate polymer organic solution at -20 ° C, and then a transverse stretching ratio of 4 is continued at a temperature of 380 ° C. The procedure was carried out so that the final transverse draw ratio was 12 and then fed into a low temperature tank having a temperature of -20 °C. The porous tetrafluoroethylene polymer film (i.e., sa-PTFER) obtained by this procedure is referred to as sample E.

Please refer to Table 1 for the pore structure characteristics of the porous tetrafluoroethylene polymer film of Sample A, Sample B and Sample C described above. According to the comparison result of the sample A and the sample B, the porosity (82.4%) of the sample B obtained by the secondary transverse stretching process is higher than that obtained by the one transverse stretching process in the case where the final transverse stretching ratio is the same. The porosity of sample A (78.3%); the average pore diameter of the first nanopore of sample B (2.31 nm) is smaller than the average pore diameter of the first nanopore of sample A (3.61 nm); the second nanopore of sample B The average pore diameter (22.10 nm) is smaller than the average pore diameter of the second nanopore of sample A (32.10 nm); and the second nanopore occupancy rate of sample B (90.22%) is higher than the first nanopore of sample A. The rate of accumulation (75.13%). It can be seen that the average pore diameter of the first nanopore of the sample B, the first nanopore occupation ratio and the average pore diameter of the second nanopore are better than that of the sample A, indicating that the pore structure of the sample B is denser than that of the sample A. Sample B is provided with better barrier properties, which in turn enhances its ability to block light, particularly ultraviolet light.

Based on the same criterion, the final transverse draw ratio of sample B is lower than in the case of two transverse stretching procedures, but the final transverse draw ratio is different (ie, according to the comparison between sample B and sample C). Sample C, the pore structure characteristics of the sample B and the sample C were significantly different, and the influence of the transverse stretching ratio on the film formation characteristics of the porous tetrafluoroethylene polymer film was also demonstrated.

In addition, regarding the film formation characteristics and effects of the polymer organic solution used in the immersion procedure on the porous tetrafluoroethylene polymer film, see the pore structure of sample C, sample D and sample E shown in Table 1. Characteristics, showing the immersion procedure of the manufacturing process, the sample C using the polyvinyl alcohol polymer organic solution, compared with the sample D prepared by using the polyvinyl acetate polymer organic solution, and the hydroxypropyl acrylate polymer organic Sample E prepared by the solution has superior pore characteristics.

In order to examine the ultraviolet light weathering characteristics of the pore structure in the porous tetrafluoroethylene polymer film of Sample A, Sample B, Sample C, Sample D and Sample E described above, Sample A, Sample B, Sample C, and Sample described above were used. D and sample E were further irradiated with UVB ultraviolet light having a wavelength of 313 nm for 600 hours (to simulate the actual situation, ultraviolet light was irradiated onto the porous tetrafluoroethylene polymer film), respectively, and sample A was irradiated with UVB ultraviolet light. Sample A' after preparation; sample B' after sample B is irradiated with UVB ultraviolet light; sample C' after sample B is irradiated with UVB ultraviolet light; sample D is irradiated by UVB ultraviolet light D'; and sample E after sample E was irradiated with UVB ultraviolet light. Referring to Table 2, the pore structure characteristics of the above samples are presented. At the same time, from the data presented in Table 2, the average pore diameter of the first nanopore and the average pore diameter of the second nanopore of the sample A, the sample B, the sample C, the sample D and the sample E after ultraviolet light irradiation are both improved, and the The occupancy rate of a nanometer hole is reduced. Conversely, the second nanopore volume occupancy of Sample A, Sample B, Sample C, Sample D, and Sample E after exposure to ultraviolet light increased. The changes in the parameters related to the pore structure characteristics indicate that the pores of the porous tetrafluoroethylene polymer film (the first nanopore and the second nanopore) are damaged after absorbing ultraviolet radiation, and the structure of the nanopores is damaged. Damaged and partially disintegrated.

In order to test the influence of the conventional method and the secondary transverse stretching procedure on the ultraviolet light weather resistance of the pore structure of the porous tetrafluoroethylene polymer film, the change of the sample A after UVB ultraviolet light irradiation was further analyzed (ie, sample A and Sample A' is compared); Sample B is changed after UVB ultraviolet light irradiation (ie, sample B is compared with sample B'), and the data is shown in Table 3.

It can be seen from the data in Table 3 that, in the case where the final transverse stretching ratio is the same, the first nanopore pore diameter increase rate of the sample B, the first nanopore volume occupancy rate reduction rate, the second nanopore pore diameter increase rate, The increase rate of the second nanopore occupancy rate is lower than that of the sample A, indicating that the damage of the sample B obtained by the secondary transverse stretching procedure is lower than that of the sample A obtained by one transverse stretching procedure. This means that sample B has superior UV weather resistance.

Please refer to FIG. 2 and FIG. 3 at the same time: FIG. 2 is a data diagram of the weather resistance of the porous tetrafluoroethylene polymer film prepared by the conventional method measured by the positron quenching spectrometer technique, that is, sample A and Sample A' has a change in pore size of the first nanopore measured under various detection conditions (depth); and FIG. 3 is a porous method prepared according to the present invention as measured by the positron quenching spectrometer technique. The data sheet of the UVF ultraviolet light resistance of the tetrafluoroethylene polymer film, that is, the pore size change of the first nanopore measured by the sample B and the sample B' under various detection conditions (depth). Figure 2 and Figure 3 show the average pore size distribution of the first nanopore in the surface of the porous tetrafluoroethylene polymer film, showing that the average pore size of the first nanopore in the surface layer of sample A is generally higher than that of sample B, and sample A and sample The pore structure in the B surface layer is damaged by ultraviolet light. However, the comparison results from FIG. 2 and FIG. 3 can further explain that the barrier property of sample B to ultraviolet light damage is better than that of sample A, so that sample B reflects less susceptible to ultraviolet light damage when the detection depth is higher. characteristic.

In order to examine the effect of the final stretching ratio of the longitudinal stretching of the porous tetrafluoroethylene polymer film on the weather resistance of the ultraviolet light through two longitudinal stretching procedures, the change of the sample B after UVB ultraviolet light irradiation was further analyzed (ie, Sample B is compared with sample B'; the change of sample C after UVB irradiation (ie, sample C is compared with sample C'), see Table 4 for data. It can be seen from the data of Table 4 that the final transverse stretching ratio of the sample B is lower than that of the sample after two transverse stretching procedures, but the final transverse stretching ratio is different (that is, according to the comparison between the sample B and the sample C). C, the pore structure characteristics of the sample B and the sample C are significantly different, and the influence of the transverse stretching ratio on the ultraviolet weather resistance of the porous tetrafluoroethylene polymer film is explained. Taking Example 1 and Example 2 of the present invention as an example, Sample C has superior ultraviolet light weather resistance.

Please also refer to Figure 3 and Figure 4 above. Figure 4 is a graph showing the weather resistance of the porous tetrafluoroethylene polymer film obtained according to the present invention, which is measured by the positron quenching spectrometer technique, for UVB ultraviolet light, that is, sample C and sample C' The change in the pore size of the nanopore measured under various detection conditions (depth). Figure 3 and Figure 4 show the average pore size distribution of the first nanopore in the surface of the porous tetrafluoroethylene polymer film, showing that the pore structure in the surface of sample B and sample C is damaged by ultraviolet light, and sample B and sample The average pore size of the nanopore of the surface layer of C is affected by the final transverse stretching ratio. For example, the comparison results from FIG. 3 and FIG. 4 further illustrate that the barrier property of the sample C for ultraviolet light damage is better than that of the sample B, so that the sample C is at a shallower depth of detection (ie, the depth is less than about 2 micrometers). In the case of the case, it began to reflect the characteristics that are less susceptible to UV light damage, indicating that Sample C has superior UV weather resistance.

In order to examine the influence of the pore structure of the porous tetrafluoroethylene polymer film on the weather resistance of the ultraviolet light through the soaking procedure of different kinds of polymer organic solutions, the sample C, the sample D and the sample E are further analyzed, after being irradiated by UVB ultraviolet light. The change in presentation (ie, sample B compared to sample B'; sample C compared to sample C'; sample D compared to sample D'; sample D compared to sample D', data still with sample C, sample D See sample E and data, see Table 5. As can be seen from the data in Table 5, the increase rate of the first nanopore pore size of the sample C and the increase rate of the second nanopore pore diameter are smaller than that of the sample D and the sample E; Compared with the sample D and the sample E, the reduction rate of the mesopores and the second nanopore rate are smaller, indicating that the sample C has better ultraviolet light resistance.

100. . . Multi-layer porous film

30. . . Stacked layer structure

L, L’. . . region

1, 1’. . . fiber

2, 2’. . . Node

100. . . Multi-layer porous film

30. . . Stacked layer structure

1. . . fiber

2. . . Node

Claims (8)

A method for manufacturing a multi-layer porous film, comprising the following steps:
(1) providing a first tetrafluoroethylene polymer material;
(2) immersing the first tetrafluoroethylene polymer material in a polymer organic solution and removing it to obtain a second tetrafluoroethylene polymer material;
(3) performing a first direction stretching process on the second tetrafluoroethylene polymer material, and converting the second tetrafluoroethylene polymer material into a first porous tetrafluoroethylene polymer film;
(4) immersing the first porous tetrafluoroethylene polymer film in the polymer organic solution, and taking out a second porous tetrafluoroethylene polymer film; and (5) the second The porous tetrafluoroethylene polymer film is subjected to at least two second-direction stretching processes, and the second porous tetrafluoroethylene polymer film is converted into a porous tetrafluoroethylene polymer film;
The first direction and the second direction are not parallel to each other. The method for producing a multi-layered porous film according to the first aspect of the invention, wherein the first direction and the second direction are perpendicular to each other. The method for producing a multi-layered porous film according to the first aspect of the invention, wherein the second tetrafluoroethylene polymer material has a stretching ratio of from 3 to 50 in the first direction stretching process. The method for producing a multi-layer porous film according to the first aspect of the invention, wherein the second porous tetrafluoroethylene polymer film has a stretching ratio of 2 in the second direction stretching process of 2 To 20. A multi-layer porous film comprising a porous tetrafluoroethylene polymer film, the porous tetrafluoroethylene polymer film being a multi-layer porous film according to any one of claims 1-4 Made by the manufacturing method. The multi-layer porous film according to claim 5, wherein the porous tetrafluoroethylene polymer film comprises a porous layer composed of a plurality of nodes and a plurality of fibers, and the like The nodes form a plurality of micropores with the space formed by the fibers, the pores of the micropores are larger than 100 nm, and the micropores of the micropores occupy a ratio of 5% to 99%. The multi-layer porous film according to claim 6, wherein the porous tetrafluoroethylene polymer film further comprises a nanoporous layer, the nanoporous layer comprising a plurality of first nanopores and A plurality of second nanopores, and the nanopores of the first nanopores and the second nanopores occupy a nanopore ratio of 90% to 99.9%. The multi-layer porous film according to claim 7, wherein the first nano-hole has a pore diameter of from 0.1 nm to 5 nm, and the second nano-hole has a pore diameter of 5 nm. Up to 50 nm.