Solid-temperature synergistic regulation method for pore structure of uhmwpe fiber membrane and application

Abstract

The application discloses a solid-temperature synergistic regulation method for pore structure of UHMWPE fiber membrane and application, the method comprises three stages of low-temperature casting, stretching and medium-temperature heat setting, extraction and high-temperature annealing, and pore size and pore structure are synergistically regulated through heat treatment and inorganic particles. The UHMWPE fiber membrane obtained through the method is applied to ion battery separators, super capacitor separators, waterproof and breathable membranes, radiation cooling membranes, soundproof membranes, heat management membranes or seawater desalination membranes. In the forming process of the UHMWPE porous fiber membrane, the pore size and pore structure are synergistically regulated by using solid fillers and three-stage heat treatment, the wide-range accurate regulation of the pore size is realized, and the method is simple and easy to implement and suitable for large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polymer porous film preparation, in particular to a solid-temperature synergistic regulation method for the pore structure of UHMWPE fiber film and application. BACKGROUND

[0002] Ultra-high molecular weight polyethylene (UHMWPE) has excellent mechanical properties, impact resistance, solvent resistance, and low temperature resistance, and is an excellent film material. Currently, the main manufacturing technology for UHMWPE porous film is a wet pore-forming process, which mainly includes the following processes: a high-boiling, low-volatility solvent (pore former) and UHMWPE raw material are melted and plasticized by an extruder and then continuously extruded from a die at high temperature, followed by rapid cooling of the cast sheet, during which the UHMWPE and the pore former undergo phase separation; then the cast sheet is subjected to bidirectional stretching; and after the pore former is extracted with a volatile solvent, the film is dried, thereby preparing a UHMWPE porous film.

[0003] The porous film prepared by this method is mainly used as a battery separator, and the pore size distribution is mainly in the range of 20-50 nm, and the porosity and specific surface area are not large, thus limiting its application in many fields (such as the environment, energy, gas separation, sound absorption, biomedical treatment, and material detection). For example, in order to quickly transport ions while effectively inhibiting the growth of lithium dendrites, the appropriate pore size range for ion battery separators is 20-60 nm; in order to minimize the resistance to the movement of electrolyte ions under the premise that electrode particles do not penetrate the separator, the appropriate pore size range for supercapacitor separators is 80-150 nm; the pore size distribution range for waterproof and breathable membranes in the medical field is 0.1-5 μm; and in order to ensure a high reflectivity to sunlight, the appropriate pore size range for porous membranes used for radiative cooling is 1-10 μm. Moreover, when UHMWPE porous film is used as a supporting base film, it is necessary to fill active substances in the pores of the film or coat active substances on the surface of the film, which requires larger pore sizes and specific surface areas to facilitate the filling or adhesion of active substances on the surface of the film. On the other hand, when UHMWPE porous film is loaded with functional fillers, in order to maximize the effect of the surface active groups of the functional fillers, the functional fillers need to be more distributed on the surface of the pore structure rather than being completely wrapped by UHMWPE. Therefore, how to simply, efficiently, and widely regulate the pore size and porosity of UHMWPE porous film is a key problem for overcoming the limitations of UHMWPE porous film applications.

[0004] The patent application with the publication number CN109834961A proposes a manufacturing method of a high porosity and large specific surface area polyolefin porous membrane, which mainly uses a twice bidirectional stretching method to improve the porosity and specific surface area of the polyolefin porous membrane. However, this method has a limited control on the pore size of the polyolefin porous membrane, and needs two sets of bidirectional stretching devices, which greatly increases the manufacturing cost of the polyolefin porous membrane. Moreover, the pore size and pore structure required by different application fields are different, and a single control method cannot realize wide-range and accurate control of the pore size and pore structure.

[0005] Therefore, aiming at the above problems, if the cross-scale control of the pore size and pore structure of the UHMWPE porous membrane can be realized through the cooperation of the processing process and the formula design, the matching problem of the pore size and pore structure with the actual application can be effectively solved, so as to break through the application limitation of the UHMWPE porous membrane. SUMMARY

[0006] The purpose of the present application is to overcome the shortcomings of the prior art, and provide a solid-temperature synergistic control method of UHMWPE fiber membrane pore structure, which uses the synergistic method of solid-phase filler and three-stage heat treatment to control the pore size and pore structure during the forming process of the UHMWPE porous fiber membrane, realizes the wide-range and accurate control of the pore size, and is simple and easy to implement and suitable for large-scale industrial production.

[0007] Another purpose of the present application is to provide an application of the UHMWPE fiber membrane pore structure obtained by the above method.

[0008] The technical scheme of the present application is: a solid-temperature synergistic control method of UHMWPE fiber membrane pore structure, comprising the following steps:

[0009] (1) low-temperature casting: uniformly mixing UHMWPE, inorganic filler and pore-forming agent according to the proportion to form slurry, and then extruding the slurry through an extruder and performing low-temperature casting on a casting roller to form a gel film piece;

[0010] (2) stretching and medium-temperature heat setting: stretching the gel film piece to make the gel film piece fiberize by lamellar slip, and then performing medium-temperature heat setting to perfect the molecular chain crystallization, and the inorganic particles will affect the fiber distribution of the gel film piece to form a fiber membrane;

[0011] (3) extraction and high temperature annealing: after the extraction drying of the fiber membrane, high temperature annealing is carried out, and the shrinkage force generated by the shrinkage of the fiber membrane in the extraction process is combined with the high temperature annealing, so that the partially imperfect crystal structure in the fiber membrane is melted and rearranged under the action of two-dimensional stress and heat coupling. The inorganic filler originally wrapped in the molecular chain is extruded and attached to the micropore surface, so as to regulate the pore structure of the fiber membrane.

[0012] According to the pore size and pore structure of the pore structure in the fiber membrane, the specific regulation process includes the following three kinds:

[0013] The first kind is nanometer hole with a pore size of 10nm-100nm: in step (1), the mass fraction of UHMWPE in the raw material of the fiber membrane is 50-95 parts, the mass fraction of inorganic filler is 5-50 parts, the particle size of inorganic filler is 5-50nm, and the casting roller temperature in the low temperature casting process is 10-40℃; in step (2), the temperature of the medium temperature setting is 90-130℃, and the time of the medium temperature setting is 0.1-5min; in step (3), the temperature of the high temperature annealing is 120-140℃, and the time of the high temperature annealing is 0.1-3min;

[0014] The second kind is mesopore with a pore size of 0.1-1μm: in step (1), the mass fraction of UHMWPE in the raw material of the fiber membrane is 15-85 parts, the mass fraction of inorganic filler is 15-85 parts, the particle size of inorganic filler is 40-500nm, and the casting roller temperature in the low temperature casting process is 10-40℃; in step (2), the temperature of the medium temperature setting is 90-130℃, and the time of the medium temperature setting is 0.1-5min; in step (3), the temperature of the high temperature annealing is 130-160℃, and the time of the high temperature annealing is 0.1-5min;

[0015] The third kind is micropore with a pore size of 1-20μm: in step (1), the mass fraction of UHMWPE in the raw material of the fiber membrane is 10-85 parts, the mass fraction of inorganic filler is 15-90 parts, the particle size of inorganic filler is 1-50μm, and the casting roller temperature in the low temperature casting process is 10-40℃; in step (2), the temperature of the medium temperature setting is 90-130℃, and the time of the medium temperature setting is 0.1-5min; in step (3), the temperature of the high temperature annealing is 130-160℃, and the time of the high temperature annealing is 0.1-8min.

[0016] As a preferred solution, the molecular weight of the UHMWPE is 1.5-9 million.

[0017] The content of the porogen in step (1) accounts for 50-90% of the total mass of the formed slurry, and the porogen is a high molecular porogen (such as PVP, PEG, PVA, etc.) or a small molecular porogen (such as vegetable oil, decalin, sodium chloride, potassium carbonate, lithium chloride, ADC foaming agent, etc.).

[0018] The shape of the inorganic filler is one or more of spherical, granular, flaky, fibrous, columnar, hollow tubular, or hollow microspheres.

[0019] In step (2), the gel film is uniaxially stretched, synchronously biaxially stretched, or asynchronously biaxially stretched, with a stretching ratio of 2-20 times and a stretching temperature of 90-120℃. When the gel film is synchronously biaxially stretched or asynchronously biaxially stretched, the transverse stretching ratio is 2-20 times, and the longitudinal stretching ratio is also 2-20 times.

[0020] The thickness of the UHMWPE fiber membrane is 1-500μm, and the porosity is 40-85%.

[0021] The UHMWPE fiber membrane is a single-layer flat membrane or a multi-layer flat membrane structure, and when the UHMWPE fiber membrane is a multi-layer flat membrane, the molecular weight of UHMWPE in each layer of flat membrane is the same or different.

[0022] The UHMWPE fiber membrane is a single-layer hollow fiber membrane or a coaxial multi-layer hollow fiber membrane.

[0023] When the UHMWPE fiber membrane is a multi-layer flat membrane or a coaxial multi-layer hollow fiber membrane, the content and type of inorganic filler in each layer can be the same or different.

[0024] The application of the UHMWPE fiber membrane with the pore structure obtained by the above-mentioned solid-temperature synergistic regulation method, the UHMWPE fiber membrane is applied to ion battery separators, super capacitor separators, waterproof and breathable membranes, radiation cooling membranes, soundproof membranes, thermal management membranes, or seawater desalination membranes.

[0025] The principle of the solid-temperature synergistic regulation method of the pore structure of the above-mentioned ultra-high molecular weight polyethylene fiber film is that three-stage heat treatment, such as low-temperature casting, stretching and medium-temperature heat setting, extraction and high-temperature annealing, and inorganic particles are used to synergistically regulate the pore size and pore structure. The UHMWPE is mixed with functional fillers and pore-forming agents to form a slurry, which is extruded by an extruder and then cast on a casting roller at low temperature to form a gel film piece, which prevents the formation of large-size spherocrystals and ensures the solid-liquid bicontinuous phase structure of the UHMWPE gel film piece and the stretchability of the gel film piece. Subsequently, in the process of heat stretching, the stacked lamellar crystals are converted into fiber crystals through melt recrystallization under the action of the force field, and the micropores formed between the lamellar crystal clusters due to defects are converted into narrow leaf-shaped pores between the fibers. Then, the UHMWPE molecular chains are crystallized and perfected through the medium-temperature heat setting process. With the extension of the medium-temperature heat setting process, the crystallinity gradually increases, the crystalline region becomes more dense, the proportion of the pore-forming agent dispersed in the amorphous region of the molecular chain increases, the volume of the leaf-shaped dispersed phase increases, the pore size of the fiber film after extraction increases, and the shrinkage rate during the extraction process decreases. At the same time, the inorganic particles also affect the spacing and size between the fibers during the stretching and setting processes, thereby affecting the final pore structure (including pore size and porosity). After extraction and drying, the fiber film is annealed at high temperature. The shrinkage force generated by the shrinkage of the film during the extraction process causes the fiber crystals in the fiber film to crystallize under the action of stress and heat coupling, the imperfect crystals are rearranged along the circumference, the adjacent fibers are merged, the fibers are thickened, the mechanical properties are greatly improved, and the pore size of the film is increased. At the same time, the rearrangement process causes the functional fillers originally wrapped inside the molecular chains to be extruded and attached to the surface of the micropores, which is more conducive to the functional properties of the surface groups of the fillers. In addition, the addition of fillers reduces the relative content of the polymer and hinders the movement of the molecular chains, which effectively reduces the crystallinity of the film before stretching and increases the number of micropores between the crystal frameworks and the amorphous regions, which is beneficial to the formation of more and larger pore structures during the stretching process, ultimately increasing the pore size and porosity of the fiber film.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] In the solid-temperature synergistic regulation method for the pore structure of the UHMWPE fiber membrane, the fiber membrane prepared by using the thermal induced phase separation and solid phase stretching of UHMWPE has the characteristics of high porosity and high mechanical performance, which endows it with wide application prospects. At the same time, the pore structure of the microporous membrane is adjusted by using the solid-temperature synergistic regulation method, so that the pore size of the microporous membrane can be precisely regulated in a large range of nanometer-micrometer, overcoming the difficulty in matching the pore size and pore structure of the existing fiber membrane with the actual application. At the same time, the regulation of the distribution of functional inorganic fillers can maximize the use of the surface groups of the functional inorganic fillers, reduce the addition amount of the functional inorganic fillers, thereby reducing the production cost. Moreover, the regulation method is simple, can be mass-produced, and has a wide range of applications.

[0028] The UHMWPE fiber membrane prepared by the solid-temperature synergistic regulation method for the pore structure of the UHMWPE fiber membrane can be applied to ion battery separators, supercapacitor separators, waterproof and breathable membranes, radiation cooling membranes, soundproof membranes, thermal management membranes, or seawater desalination membranes, etc. in multiple technical fields, and has a wide range of applications, which is conducive to wide application. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is the surface structure electron microscope graph of the UHMWPE fiber membrane prepared in Example 2.

[0030] Figure 2 It is the cross-sectional structure electron microscope graph of the UHMWPE fiber membrane prepared in Example 2.

[0031] Figure 3 It is the surface structure electron microscope graph of the UHMWPE fiber membrane prepared in Example 3.

[0032] Figure 4 It is the surface structure electron microscope graph of the radiation cooling layer of the UHMWPE fiber membrane prepared in Example 5.

[0033] Figure 5 It is the surface structure electron microscope graph of the light-heat conversion layer of the UHMWPE fiber membrane prepared in Example 5.

[0034] Figure 6 It is the electron microscope graph of the cross-sectional structure of the UHMWPE fiber membrane prepared in Example 5. DETAILED DESCRIPTION

[0035] The application will be further described in detail below in combination with examples, but the embodiments of the application are not limited thereto.

[0036] Example 1

[0037] The UHMWPE fiber membrane of this embodiment is used as a lithium ion battery separator.

[0038] The raw material thereof uses UHMWPE with a molecular weight of 1.8 million to prepare the fiber skeleton, uses fumed silica (SiO2) with a particle size of 15 nm as the inorganic filler, and uses liquid paraffin as the porogen.

[0039] The preparation method is as follows:

[0040] (1) UHMWPE and SiO2 are weighed according to the mass fraction ratio of 90:10, liquid paraffin is added to form a mixture, the mass of liquid paraffin accounts for 80% of the total mass of the formed mixture, and the mixture is stirred in a stirred tank at 80°C for 5 min;

[0041] Then melt-blending and plasticizing transportation are performed through a double-rotor extruder at 210°C, and a gel film is obtained through an extrusion die head casting, and the casting roller temperature is 15°C;

[0042] (2) The gel film is subjected to biaxial stretching on a synchronous biaxial stretching machine to obtain a fiber film, the stretching ratio is 6×6 (i.e., the transverse stretching ratio and the longitudinal stretching ratio are both 6 times), and the stretching temperature is 100°C; the fiber film obtained by stretching is then heat set at 120°C for 3 min;

[0043] (3) The fiber film after heat setting in step (2) is extracted using n-hexane as an extractant to remove liquid paraffin, and then dried to remove n-hexane;

[0044] (4) The dried fiber film in step (3) is annealed at a high temperature of 150°C for 1 min to obtain a UHMWPE fiber film, which can be used as a lithium ion battery separator.

[0045] Through experiments, the UHMWPE lithium ion battery separator prepared by the above method has a thickness of 5 μm, a tensile strength of 127.5 MPa, an average pore size of 34 nm, a thermal shrinkage rate of 3% after being placed at 120°C for 1 h, and a room temperature lithium ion conductivity of 0.68×10 -3 S / cm, a specific capacity of 142.3 mAh / g when assembled into a battery with lithium iron phosphate as the positive electrode and a metal lithium sheet as the negative electrode, and a capacity retention rate of 94.7% after 100 cycles of charge and discharge. Compared with existing lithium ion battery separators on the market, the performance is greatly improved.

[0046] Example 2

[0047] The UHMWPE fiber film of this example is used as a radiative cooling film.

[0048] The raw material thereof uses UHMWPE with a molecular weight of 1.8 million to prepare the fiber skeleton, uses fumed silica (SiO2) with a particle size of 15 nm as the inorganic filler, and uses liquid paraffin as the porogen.

[0049] The preparation method is as follows:

[0050] (1) UHMWPE and SiO2 are weighed according to the mass fraction ratio of 40:60, liquid paraffin is added to form a mixture, the mass of liquid paraffin accounts for 80% of the total mass of the formed mixture, and the mixture is stirred in a stirred tank at 80°C for 5 min;

[0051] Then melt-blending and plasticizing transportation are carried out through a double-screw extruder at 210°C, and a gel film is obtained by extrusion die casting;

[0052] (2) The gel film is subjected to biaxial stretching on a synchronous biaxial stretching machine to obtain a fiber film, the stretching ratio is 2x2, and the stretching temperature is 100°C; the fiber film obtained by stretching is heat set at 120°C for 5 min;

[0053] (3) The heat set fiber film in step (2) is extracted by using n-hexane as an extractant to remove liquid paraffin, and then dried to remove n-hexane;

[0054] (4) The dried fiber film in step (3) is annealed at a high temperature of 150°C for 2 min to obtain a UHMWPE fiber film, which can be used as a radiation cooling film.

[0055] Through experiments, the surface SEM image of the UHMWPE-based radiation cooling film prepared by the above method is as shown in Figure 1 , the cross-sectional SEM image is as shown in Figure 2 , the thickness is 350μm, the tensile strength is 35MPa, the average pore size is 4.5μm, the porosity is 69.4%, the solar reflectivity is 99.1%, and the atmospheric window infrared emissivity is 92.6%. Compared with existing radiation cooling films on the market, the performance has been greatly improved.

[0056] Example 3

[0057] The UHMWPE fiber film of the present embodiment is used as a supercapacitor separator.

[0058] In the raw materials, UHMWPE with a molecular weight of 1.8 million is used, the functional inorganic filler is fumed aluminum oxide (Al2O3) with a spherical shape and a particle size of 10-15nm, and the porogen is liquid paraffin.

[0059] The preparation method is as follows:

[0060] (1) UHMWPE and Al2O3 are weighed according to the mass fraction ratio of 70:30, liquid paraffin is added to form a mixture, the mass of liquid paraffin accounts for 80% of the total mass of the formed mixture, and the mixture is stirred in a stirred tank at 80°C for 5 min;

[0061] Then melt blend and plasticize transportation through double screw extruder under the condition of 210℃, and get gel film through extrusion die casting;

[0062] (2) Stretch the gel film on the synchronous biaxial stretching machine to get fiber film, the stretching ratio is 6x6, and the stretching temperature is 110℃; heat set the fiber film obtained by stretching at 120℃ for 3min;

[0063] (3) Use n-hexane as extractant to extract the heat set fiber film in step (2) to remove liquid paraffin, and then dry to remove n-hexane;

[0064] (4) Anneal the dried fiber film in step (3) at high temperature of 140℃ for 4min to obtain UHMWPE fiber film which can be used as super capacitor separator;

[0065] Through experiments, the surface SEM diagram of the UHMWPE-based super capacitor separator prepared by the above method is as shown in Figure 3 The thickness is 5μm, the tensile strength is 40MPa, and the average pore size is 0.435μm. Using activated carbon electrode and 1mol / L sodium sulfate solution as electrolyte to test the energy storage performance. The test results show that the CV curve of the super capacitor has approximate rectangular characteristics at 5mv per second scanning speed, the specific capacitance is 16.2F / g at 1A per gram current density, the internal resistance is 0.53Ω, the charge transfer resistance is 0.21Ω, and the capacitance retention rate is almost unchanged after 10000 cycles at 1A / g current density. Compared with the existing super capacitor separator on the market, its performance has been greatly improved.

[0066] Example 4

[0067] The UHMWPE fiber film of the present embodiment is used as a porous sound-absorbing film.

[0068] In the raw materials, UHMWPE with a molecular weight of 5 million is used, hollow glass microbeads are used as functional inorganic fillers, the average particle size is 20μm, and liquid paraffin is used as a porogen.

[0069] The preparation method is as follows:

[0070] (1) UHMWPE and hollow glass microbeads are weighed according to the mass fraction ratio of 60:40, then liquid paraffin is added to form a mixture, the mass of liquid paraffin accounts for 80% of the total mass of the formed mixture, and the mixture is stirred in the stirred tank at 80℃ for 5min;

[0071] Then melt blend and plasticize transportation through double screw extruder under the condition of 210℃, and get gel film through extrusion die casting;

[0072] (2) The gel film is subjected to biaxial stretching on a simultaneous biaxial stretching machine to obtain a fiber film, the stretching ratio is 4x4, and the stretching temperature is 100°C; the fiber film obtained by stretching is subjected to heat setting at 120°C for 5 min;

[0073] (3) The fiber film subjected to heat setting in step (2) is extracted by using n-hexane as an extractant to remove liquid paraffin, and then dried to remove n-hexane;

[0074] (4) The dried fiber film in step (3) is subjected to annealing treatment at a high temperature of 150°C for 5 min, and the obtained UHMWPE fiber film can be used as a porous sound-absorbing film.

[0075] Through experiments, the UHMWPE-based porous sound-absorbing film prepared by the above method has a thickness of 135 μm, a tensile strength of 22.45 MPa, an average pore size of 5.62 μm, a porosity of 76%, and an acoustic activity of 57% obtained by normalizing the sound absorption coefficients at different frequencies. Compared with existing sound-absorbing films on the market, the performance has been greatly improved.

[0076] Example 5

[0077] The UHMWPE fiber film of the present embodiment is a light-heat conversion-radiation cooling dual-mode integrated UHMWPE porous fiber film. The fiber film has a double-layer structure, one layer is a radiation cooling layer prepared by using UHMWPE as a fiber skeleton and a functional inorganic filler SiO2, and the other layer is a light-heat conversion layer prepared by using UHMWPE as a fiber skeleton and a functional inorganic filler carbon black (CB).

[0078] In the raw materials, UHMWPE with a molecular weight of 1.8 million, SiO2 and CB as functional inorganic fillers, and liquid paraffin as a porogen are used, wherein the particle size of SiO2 is 2-3 μm, and the particle size of CB is 20 nm.

[0079] The preparation method is as follows:

[0080] (1) UHMWPE and SiO2 are weighed according to the mass fraction ratio of 70:30, UHMWPE and CB are weighed according to the mass fraction ratio of 70:30, and liquid paraffin is added respectively to form two kinds of mixture materials. The mass of liquid paraffin in the two kinds of mixture materials accounts for 80% of the total mass of the mixture materials, and the two kinds of mixture materials are respectively stirred in the stirred tank at 80°C for 5 min;

[0081] The two kinds of mixture materials are respectively subjected to melt blending and plasticizing transportation through two double-screw extruders at 210°C, and a double-layer co-extrusion die head is used to obtain a double-layer composite gel film;

[0082] (2) The double-layer composite gel film is stretched on a synchronous biaxial stretching machine to obtain a fiber film, the stretching ratio is 2x2, and the stretching temperature is 100 DEG C; the stretched fiber film is heat set at 130 DEG C for 5 min;

[0083] (3) The fiber film after heat setting in step (2) is extracted by using n-hexane as an extractant to remove liquid paraffin, and then dried to remove n-hexane;

[0084] (4) The dried fiber film in step (3) is annealed at a high temperature of 150 DEG C for 3 min to obtain a light-heat conversion-radiative cooling dual-mode integrated UHMWPE porous film;

[0085] In step (2), the surface SEM of the radiative cooling layer of the light-heat conversion-radiative cooling dual-mode integrated UHMWPE porous film is shown in Figure 4 , the surface SEM of the light-heat conversion layer is shown in Figure 5 , and the cross-sectional SEM of the double-layer film is shown in Figure 6 , the thickness is 330 μm, the tensile strength is 18.7 MPa, the average thickness of the light-heat conversion layer is 43 nm, the pore size of the radiative cooling layer is an average pore size of 3.58 μm, and the porosity is 78%. For the radiative cooling layer, the solar reflectivity is 95.70%, and the atmospheric window infrared emissivity is 92.49%; for the light-heat conversion layer, the solar absorption rate is 95.67%.

[0086] Example 6

[0087] The UHMWPE fiber film of the present embodiment is a UHMWPE double-layer composite coaxial hollow fiber film for seawater desalination. The fiber film has a double-layer hollow tubular structure, the inner layer is a hydrophilic layer prepared from UHMWPE and SiO2, which facilitates rapid extraction of seawater; and the outer layer is a light-heat conversion layer prepared from UHMWPE and CB, which can absorb sunlight to rapidly evaporate seawater.

[0088] In the raw materials, UHMWPE with a molecular weight of 1.8 million, SiO2 and CB are used as functional inorganic fillers, and liquid paraffin is used as a porogen.

[0089] The preparation method is as follows:

[0090] (1) UHMWPE and SiO2 are weighed according to a mass fraction ratio of 60:40, UHMWPE and CB are weighed according to a mass fraction ratio of 70:30, and liquid paraffin is added to form two mixtures, respectively. The mass of liquid paraffin in the two mixtures accounts for 80% of the total mass of the mixture, and the two mixtures are stirred in a stirred tank at 80 DEG C for 5 min;

[0091] The two mixtures are respectively melt-blended and plasticized and transported through two twin-screw extruders at 210℃, and a double-layer composite hollow gel film is obtained through a double-layer co-extrusion die;

[0092] (2) The double-layer composite hollow gel fiber is uniaxially stretched on a stretching machine to obtain a fiber film, the stretching ratio is 10, and the stretching temperature is 100℃; the fiber film obtained by stretching is heat-set at 130℃ for 5 minutes;

[0093] (3) The fiber film after heat-setting in step (2) is extracted by using n-hexane as an extractant to remove liquid paraffin, and then dried to remove n-hexane;

[0094] (4) The fiber film after drying in step (3) is annealed at a high temperature of 150℃ for 3 minutes to obtain a UHMWPE double-layer coaxial composite hollow fiber film for seawater desalination;

[0095] Through experiments, the UHMWPE double-layer coaxial composite hollow fiber film for seawater desalination prepared by the above method has a thickness of 60μm, a tensile strength of 200MPa, an average pore size of 2.28μm, and a porosity of 69%. For the hydrophilic layer, the water contact angle is 67.2°; for the light-heat conversion layer, the solar light absorption rate is 96.58%. Compared with the existing seawater desalination film on the market, the performance of the UHMWPE double-layer coaxial composite hollow fiber film is greatly improved.

[0096] As described above, the present application can be well implemented, and the above examples are only preferred embodiments of the present application, but not used to limit the implementation scope of the present application; any equivalent changes and modifications made according to the content of the present application are all covered in the scope of the claims of the present application.

Claims

1. A method for solid-thermal synergistic regulation of the pore structure of UHMWPE fiber membranes, characterized by, The method comprises the following steps: (1) low-temperature casting: UHMWPE is mixed with inorganic fillers and pore-forming agents according to a proportion to form a slurry, the slurry is extruded by an extruder, and then low-temperature casting is performed on a casting roller to form a gel film; (2) stretching and medium-temperature heat setting: the gel film is stretched to cause fiberization of the gel film, and then medium-temperature heat setting is performed, so that molecular chains are crystallized, and inorganic particles affect the fiber distribution of the gel film to form a fiber film; (3) extraction and high-temperature annealing: after the fiber film is extracted and dried, high-temperature annealing is performed, so that, by using the shrinkage force generated by the shrinkage of the fiber film during the extraction process and in combination with high-temperature annealing, part of the imperfect crystal structure in the fiber film is melted and rearranged under the action of two-dimensional stress and heat coupling, and the inorganic fillers originally wrapped in the molecular chains are extruded and attached to the surface of the micropores, so that the pore structure in the fiber film is regulated; According to the pore size and pore structure of the pore structure in the fiber film, the specific regulation process includes the following three kinds: The first kind is nanometer pores with a pore size of 10 nm to 100 nm: in step (1), the mass fraction of UHMWPE in the raw material of the fiber film is 50 to 95 parts, the mass fraction of inorganic fillers is 5 to 50 parts, the particle size of inorganic fillers is 5 to 50 nm, and the temperature of the casting roller during low-temperature casting is 10 to 40℃; in step (2), the temperature of medium-temperature setting is 90 to 130℃, and the time of medium-temperature setting is 0.1 to 5 minutes; in step (3), the temperature of high-temperature annealing is 120 to 140℃, and the time of high-temperature annealing is 0.1 to 3 minutes; The second kind is mesopores with a pore size of 0.1 to 1 μm: in step (1), the mass fraction of UHMWPE in the raw material of the fiber film is 15 to 85 parts, the mass fraction of inorganic fillers is 15 to 85 parts, the particle size of inorganic fillers is 40 to 500 nm, and the temperature of the casting roller during low-temperature casting is 10 to 40℃; in step (2), the temperature of medium-temperature setting is 90 to 130℃, and the time of medium-temperature setting is 0.1 to 5 minutes; in step (3), the temperature of high-temperature annealing is 130 to 160℃, and the time of high-temperature annealing is 0.1 to 5 minutes; The third kind is micropores with a pore size of 1 to 20 μm: in step (1), the mass fraction of UHMWPE in the raw material of the fiber film is 10 to 85 parts, the mass fraction of inorganic fillers is 15 to 90 parts, the particle size of inorganic fillers is 1 to 50 μm, and the temperature of the casting roller during low-temperature casting is 10 to 40℃; in step (2), the temperature of medium-temperature setting is 90 to 130℃, and the time of medium-temperature setting is 0.1 to 5 minutes; in step (3), the temperature of high-temperature annealing is 130 to 160℃, and the time of high-temperature annealing is 0.1 to 8 minutes.

2. The method according to claim 1, wherein the UHMWPE fiber membrane pore structure is solid-temperature synergistically regulated. The molecular weight of the UHMWPE is 1.5 to 9 million.

3. The method according to claim 1, wherein the method is characterized in that, In step (1), the content of the pore-forming agent accounts for 50 to 90% of the total mass of the formed slurry, and the pore-forming agent is a high-molecular pore-forming agent or a small-molecule pore-forming agent.

4. The method according to claim 1, wherein the UHMWPE fiber membrane pore structure is solid-temperature synergistically regulated. The shape of the inorganic filler is one or more of granular, flaky, fibrous, columnar, hollow tubular, or hollow microspheres.

5. The method according to claim 1, wherein the UHMWPE fiber membrane pore structure is solid-temperature synergistically regulated. In the step (2), the gel film is uniaxially stretched, synchronously biaxially stretched, or asynchronously biaxially stretched, the stretching ratio is 2-20 times, and the stretching temperature is 90-120°C.

6. The method according to claim 1, wherein the UHMWPE fiber membrane pore structure is solid-temperature synergistically regulated. The thickness of the UHMWPE fiber membrane is 1-500 μm, and the porosity is 40-85%.

7. The method according to claim 1, wherein the UHMWPE fiber membrane pore structure is solid-temperature synergistically regulated. The UHMWPE fiber membrane is a single-layer flat membrane or a multi-layer flat membrane structure, and when the UHMWPE fiber membrane is a multi-layer flat membrane, the molecular weight of UHMWPE in each layer is the same or different.

8. The method according to claim 1, wherein the UHMWPE fiber membrane pore structure is solid-temperature synergistically regulated. The UHMWPE fiber membrane is a single-layer hollow fiber membrane or a coaxial multi-layer hollow fiber membrane.

9. Application of the UHMWPE fiber membrane with the pore structure obtained by the solid-temperature synergistic regulation method according to any one of claims 1-8, wherein the UHMWPE fiber membrane is applied to an ion battery separator, a super capacitor separator, a waterproof and breathable membrane, a radiative cooling membrane, a soundproof membrane, or a seawater desalination membrane.

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