Preparation and application of coagulating bath wet-process uniform porous fiber membrane

Abstract

The invention discloses a preparation method and application of a coagulating bath wet process uniform porous fiber material, and belongs to the technical field of porous materials, the preparation method comprises the following steps: mechanically stirring polymethyl methacrylate and N-methyl pyrrolidone, uniformly mixing, and treating through a defoaming machine to obtain a spinning solution; extruding the spinning solution into a coagulating bath tank through an extrusion process, and carrying out phase separation and curing to obtain a polymethyl methacrylate fiber precursor; the preparation method comprises the following steps: adding a polymethyl methacrylate fiber material into deionized water, and desolvating to obtain the uniform porous fiber material. A polymethyl methacrylate skeleton network constructs a uniform porous structure system with a stable shape, so that the material has rich sunlight reflection capability; in addition, the framework of the polymethyl methacrylate has rich C-C and C-O functional groups, so that the high emissivity is achieved in the atmospheric window wave band.

Description

Technical Field

[0001] The invention belongs to the technical field of porous materials, and in particular relates to the preparation and application of a uniform porous fiber membrane by a coagulation bath wet method. Background Art

[0002] Porous fiber membrane is a material composed of fibers with microporous structure. Its unique structure makes it have excellent air permeability, filtration and adsorption properties. These characteristics make porous fiber membrane widely used in many fields, such as filtration, separation, catalysis and thermal management. In recent years, passive radiation cooling technology, as an emerging thermal management technology, has attracted widespread attention and research. This technology can effectively reduce the absorption of light and heat on the surface of the material through special surface structure and optical design, thereby reducing the increase in surface temperature. This is crucial for equipment and materials working in high temperature environments, and can significantly improve their performance and durability. Applying passive radiation cooling technology to porous fiber membranes can further optimize their thermal management characteristics. The structural characteristics of porous fiber membranes give them unique advantages in heat conduction and thermal isolation, and at the same time, they can achieve precise adjustment of optical properties through structural regulation. Therefore, combined with passive radiation cooling technology, the stability and reliability of porous fiber membranes in high temperature environments can be effectively improved, expanding their application potential in new energy, electronic devices, aerospace and other fields.

[0003] However, despite the broad application prospects of porous fiber membranes in thermal management, there are still some challenges in current technology. For example, the non-radiative heat gain of conventional porous materials is high during radiative cooling. Summary of the invention

[0004] The present invention provides a method for preparing a uniform porous fiber membrane by a coagulation bath wet process and its application, which overcomes the shortcoming of high non-radiative heat gain of conventional porous materials during radiation cooling, and effectively improves the matching degree of the pore structure of polymeric porous materials to the radiation cooling spectrum.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a uniform porous fiber material by a coagulation bath wet process comprises the following steps:

[0007] Step 1: Mechanically stir polymethyl methacrylate and N-methylpyrrolidone, mix them evenly and process them through a defoamer to obtain a uniform and transparent spinning solution;

[0008] Step 2: Extruding the spinning solution into a coagulation bath through an extrusion process for phase separation and solidification to obtain a polymethyl methacrylate fiber precursor;

[0009] Step 3: Add the polymethyl methacrylate fiber material into deionized water for further desolvation to obtain a uniform porous fiber material.

[0010] The invention uses a polymethyl methacrylate matrix and realizes uniform construction of a pore structure in a polymer skeleton through coagulation bath molding, and obtains the pore structure through simple desolvation.

[0011] Furthermore, in step 1, the mass ratio of polymethyl methacrylate to N-methylpyrrolidone is 10-30:80-100.

[0012] Furthermore, in step 1, the mechanical stirring temperature is 50-80° C., and the mechanical stirring time is 4 hours.

[0013] Furthermore, the extrusion process in step 2 is specifically as follows:

[0014] A digital injection pump is selected as the device for extruding the spinning solution, a 10 mL syringe is selected, a needle with an inner diameter of 0.25 mm is selected, an extrusion flow rate is 0.05 mL / min, and the digital injection pump is placed vertically at a distance of 10 cm from the coagulation bath.

[0015] Furthermore, the coagulation solvent in the coagulation bath in step 2 is anhydrous ethanol.

[0016] Furthermore, the temperature of the deionized water in step 3 is 60-80°C.

[0017] Furthermore, the desolvation time in step 3 is 24 h.

[0018] Furthermore, the porous fiber material prepared as described above is applied in the field of radiation cooling.

[0019] Beneficial effects of the present invention:

[0020] 1. The present invention designs a new uniform porous polymer system with low cost and high preparation efficiency. In the system, polymethyl methacrylate as the matrix can not only be miscible with N-methylpyrrolidone, but also the structure can be stably present in the coagulation bath during the coagulation bath molding process, so as to facilitate further desolvation treatment.

[0021] 2. The polymethyl methacrylate skeleton network in the present invention constructs a uniform porous structure system with a stable shape, so that the material itself has a strong ability to reflect sunlight. In addition, since the polymethyl methacrylate skeleton has abundant CC and CO functional groups, it has a strong emissivity in the atmospheric window band.

[0022] 3. The present invention designs a method for preparing a uniform porous fiber material in a coagulation bath. The preparation process is simple, the method is easy to operate, the raw materials are cheap and easy to obtain, and the polymer porous material prepared by the preparation method has excellent radiation cooling characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below in conjunction with the accompanying drawings.

[0024] Figure 1 It is an electron microscope image of the porous fiber material prepared in Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 of the present invention;

[0025] Figure 2 is a reflectivity spectrum diagram of the porous fiber materials prepared in Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 of the present invention;

[0026] Figure 3 1 is an emissivity spectrum diagram of the porous fiber material obtained in Example 1, Example 2, Example 3 and Comparative Example 1 and Comparative Example 2 of the present invention;

[0027] Figure 4 1 is a thermal conductivity diagram of the porous fiber material obtained in Example 1, Example 2, Example 3 and Comparative Example 1 and Comparative Example 2 of the present invention;

[0028] Figure 5 It is a radiation cooling diagram of the porous fiber material obtained in Example 1, Example 2, Example 3 of the present invention and Comparative Example 1, Comparative Example 2. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] A method for preparing a uniform porous fiber material by a coagulation bath wet process comprises the following steps:

[0031] Step 1: Mechanically stir polymethyl methacrylate and N-methylpyrrolidone, mix them evenly and process them through a defoamer to obtain a uniform and transparent spinning solution;

[0032] Step 2: Extruding the spinning solution into a coagulation bath through an extrusion process for phase separation and solidification to obtain a polymethyl methacrylate fiber precursor;

[0033] Step 3: Add the polymethyl methacrylate fiber material into deionized water for further desolvation to obtain a uniform porous fiber material.

[0034] In step 1, the mass ratio of polymethyl methacrylate to N-methylpyrrolidone is 10-30:80-100.

[0035] In step 1, the mechanical stirring temperature is 50-80° C., and the mechanical stirring time is 4 h.

[0036] The extrusion process in step 2 is specifically as follows:

[0037] A digital injection pump is selected as the device for extruding the spinning solution, a 10 mL syringe is selected, a needle with an inner diameter of 0.25 mm is selected, an extrusion flow rate is 0.05 mL / min, and the digital injection pump is placed vertically at a distance of 10 cm from the coagulation bath.

[0038] The coagulation solvent in the coagulation bath in step 2 is anhydrous ethanol.

[0039] Step 3: The temperature of the deionized water is 60-80°C.

[0040] The desolvation time in step 3 is 24 h.

[0041] Example 1

[0042] A method for preparing a uniform porous fiber material by a coagulation bath wet process comprises the following steps:

[0043] Step 1: dissolve 1.0 g of polymethyl methacrylate in 8.0 g of N-methylpyrrolidone, heat and stir mechanically in a 50° C. oil bath for 4 h until transparent and uniform, remove bubbles with a debubbler to obtain a polymethyl methacrylate spinning solution;

[0044] Step 2: Take 10 mL of spinning solution and put it into the extrusion needle of the digital injection pump. The syringe is 10 mL, the inner diameter of the needle is 0.25 mm, the extrusion flow rate is 0.05 mL / min, and the digital injection pump is placed vertically at a distance of 10 cm from the coagulation bath. The spinning solution is squeezed into the coagulation bath of anhydrous ethanol to obtain a polymethyl methacrylate precursor fiber material;

[0045] Step 3: The polymethyl methacrylate precursor fiber material is placed in deionized water at 60° C. for 24 hours to further remove the organic solvent and obtain a uniform porous fiber material.

[0046] Example 2

[0047] A method for preparing a uniform porous fiber material by a coagulation bath wet process comprises the following steps:

[0048] Step 1: dissolve 2.0 g of polymethyl methacrylate in 9.0 g of N-methylpyrrolidone, heat and stir mechanically in a 70° C. oil bath for 4 h until transparent and uniform, remove bubbles with a debubbler to obtain a polymethyl methacrylate spinning solution;

[0049] Step 2: Take 10 mL of spinning solution and put it into the extrusion needle of the digital injection pump. The syringe is 10 mL, the inner diameter of the needle is 0.25 mm, the extrusion flow rate is 0.05 mL / min, and the digital injection pump is placed vertically at a distance of 10 cm from the coagulation bath. The spinning solution is squeezed into the coagulation bath of anhydrous ethanol to obtain a polymethyl methacrylate precursor fiber material;

[0050] Step 3: The polymethyl methacrylate precursor fiber material is placed in deionized water at 70° C. for 24 hours to further remove the organic solvent and obtain a uniform porous fiber material.

[0051] Example 3

[0052] A method for preparing a uniform porous fiber material by a coagulation bath wet process comprises the following steps:

[0053] Step 1: dissolve 3.0 g of polymethyl methacrylate in 10.0 g of N-methylpyrrolidone, heat and stir mechanically in an 80° C. oil bath for 4 h until transparent and uniform, remove bubbles with a debubbler to obtain a polymethyl methacrylate spinning solution;

[0054] Step 2: Take 10 mL of spinning solution and put it into the extrusion needle of the digital injection pump. The syringe is 10 mL, the inner diameter of the needle is 0.25 mm, the extrusion flow rate is 0.05 mL / min, and the digital injection pump is placed vertically at a distance of 10 cm from the coagulation bath. The spinning solution is squeezed into the coagulation bath of anhydrous ethanol to obtain a polymethyl methacrylate precursor fiber material;

[0055] Step 3: The polymethyl methacrylate precursor fiber material is placed in deionized water at 80° C. for 24 hours to further remove the organic solvent and obtain a uniform porous fiber material.

[0056] Comparative Example 1

[0057] A method for preparing a uniform porous fiber material by a coagulation bath wet method, compared with Example 1, is different in that step 2 of Example 1 "extruding the spinning solution into a coagulation bath of anhydrous ethanol" is changed to "extruding the spinning solution into a coagulation bath of deionized water", and the remaining raw materials, steps and parameters are the same as Example 1.

[0058] Comparative Example 2

[0059] A method for preparing a uniform porous fiber material by a coagulation bath wet process comprises the following steps:

[0060] Step 1: Dissolve 1.0 g of polymethyl methacrylate in 8.0 g of acetone, heat and stir mechanically in a 50° C. oil bath for 4 h until transparent and uniform, remove bubbles with a debubbler to obtain a polymethyl methacrylate spinning solution;

[0061] Step 2: Take 10 mL of spinning solution and put it into the extrusion needle of the digital injection pump. The syringe is 10 mL, the inner diameter of the needle is 0.25 mm, the extrusion flow rate is 0.05 mL / min, and the digital injection pump is placed vertically at a distance of 10 cm from the coagulation bath. The spinning solution is squeezed into the coagulation bath of anhydrous ethanol to obtain a polymethyl methacrylate precursor fiber material;

[0062] Step 3: The polymethyl methacrylate precursor fiber material is placed in deionized water at 60° C. for 24 hours to further remove the organic solvent and obtain a uniform porous fiber material.

[0063] The porous fiber materials obtained in Example 1, Example 2, Example 3 and Comparative Example 1 and Comparative Example 2 were observed using a scanning electron microscope. The observation results are as follows: Figure 1 As shown, Figure 1 a is the electron microscope image of the porous fiber material of comparative example 1, Figure 1 b is the electron microscope image of the porous fiber material of comparative example 2, Figure 1 c is the electron microscope image of the porous fiber material in Example 1, Figure 1 d is the electron microscope image of the porous fiber in Example 2, Figure 1 e is the electron microscope image of the porous fiber material in Example 3, Figure 1 It can be seen that in Comparative Example 1, since the solvent of the coagulation bath is deionized water, the solubility difference between deionized water and the polymer spinning solution is too large, resulting in the coagulation bath molding structure being almost non-porous. When the coagulation bath solvent is changed to anhydrous ethanol, since the solubility difference between anhydrous ethanol and the polymer spinning solution is moderate, as shown in Comparative Example 2, Example 1, Example 2 and Example 3, a rich uniform porous structure is presented, and the pore structure becomes smaller as the concentration of the spinning solution increases.

[0064] The reflectivity of the porous fiber materials obtained in Example 1, Example 2, Example 3 and Comparative Example 1 and Comparative Example 2 was analyzed using an ultraviolet-visible-near infrared spectrophotometer (UV3600). The spectrophotometer used polytetrafluoroethylene (PTFE) as the reference, xenon lamp and iodine tungsten lamp as the light source, and a wavelength range of 0.3-2.5um with a step size of 0.001um. Based on the solar spectrum irradiance at wavelength λ, the average reflectivity of the 0.3-2.5um material was determined using the ASTMG173-03 (2012) standard. The test results are shown in Figure 1. Figure 2 As shown by Figure 2It can be seen that the reflectivity of Comparative Example 1 (60.5%) and the reflectivity of Comparative Example 2 (72.4%) show a very serious decline as the wavelength of sunlight increases. However, Example 1 (89.6%), Example 2 (95.5%) and Example 3 (93.5%) all show higher reflectivity characteristics in the entire sunlight band. Compared with the comparative examples, the embodiments show reflectivity characteristics that are significantly higher than those between the comparative examples. This is because according to the Mie scattering principle, when the pore structure matches the wavelength of the sunlight band, the material shows the most excellent reflectivity characteristics.

[0065] The diffuse reflectance and transmittance of the porous fiber materials obtained in Example 1, Example 2, Example 3 and Comparative Example 1 and Comparative Example 2 in the atmospheric transparency window of long-wave infrared (8-13 um) were measured using a Fourier transform infrared spectrometer (America Nicol et IS550) and an integrating sphere (A562-G / Q), respectively. The emissivity = 1 - reflectivity - transmittance. The test results are shown in FIG. Figure 3 As shown, since polymethyl methacrylate has abundant infrared thermal emission functional groups in the atmospheric window, such as CC and CO, all samples have very excellent emissivity, but due to the difference in pore structure, comparative example 1 and comparative example 2 may have a certain transmittance, so the emissivity of comparative example 1 (74.5%) and comparative example 2 (89.9%) are slightly lower than those of example 1 (96.8%), example 2 (98.5%) and example 3 (98.0%). In addition, the high thermal emissivity of the embodiment can transport excess heat outward, providing important support for the field of radiation cooling.

[0066] The porous fiber materials obtained in Example 1, Example 2, Example 3 and Comparative Example 1 and Comparative Example 2 were respectively woven into membranes of 3 cm*3 cm*0.25 mm in size, and the thermal conductivity of the porous fiber membranes was measured using a Hot Disk thermal conductivity meter (TPS2500S). The results are as follows: Figure 4 As shown by Figure 4 It can be seen that in Comparative Example 1, since there is almost no porous structure, it presents a thermal conductivity similar to that of the solid material itself (155 mWm -1 K -1 ); In Comparative Example 2, acetone can be used as a solvent to separate from the material to a certain extent, resulting in a certain pore structure in the material skeleton, thus showing certain thermal insulation properties (94mWm - 1 K -1 ). However, for Example 1 (55mWm -1 K -1 )、Example 2 (65mWm -1 K-1 ) and Example 3 (70mWm -1 K -1 ), the rich and uniform pore structure formed after solidification of the embodiment can effectively inhibit the heat conduction of heat, and at the same time, due to the increase of the material skeleton density, the thermal conductivity is gradually increased. Therefore, the increase of the non-radiative heat gain of the material is effectively inhibited, and the poor effect of the material in radiation cooling is avoided.

[0067] The porous fiber materials obtained in Example 1, Example 2, Example 3 and Comparative Example 1 and Comparative Example 2 were subjected to radiation cooling experiments. The cooling test was conducted by preparing a simple heat-insulating box and covering the heat-insulating foam box with a layer of aluminum foil. An A8 channel K-type thermocouple was used to simultaneously record the temperature of the cooling material and the ambient temperature, and the data was connected to the software data, and recorded every 30 seconds. The data was collected using computer software Picolog. The test results are shown in the figure. Figure 5 As shown by Figure 5 It can be seen that by comparing the ambient temperatures, it is found that all samples show radiation cooling characteristics, among which comparative example 1 cools down by 4.5°C, comparative example 2 cools down by 6.4°C, example 1 cools down by 10.5°C, example 2 cools down by 8.4°C, and example 3 cools down by 10.0°C.

[0068] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0069] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a uniform porous fiber material by a coagulation bath wet process, characterized in that: The steps include: Step 1: Mechanically stir polymethyl methacrylate and N-methylpyrrolidone, mix them evenly and process them through a defoamer to obtain a uniform and transparent spinning solution; Step 2: Extruding the spinning solution into a coagulation bath through an extrusion process for phase separation and solidification to obtain a polymethyl methacrylate fiber precursor; Step 3: Add the polymethyl methacrylate fiber material into deionized water for desolvation to obtain a uniform porous fiber material.

2. The method for preparing a uniform porous fiber material by a coagulation bath wet process according to claim 1, characterized in that: In step 1, the mass ratio of polymethyl methacrylate to N-methylpyrrolidone is 10-30:80-100.

3. The method for preparing a uniform porous fiber material by a coagulation bath wet process according to claim 1, characterized in that: In step 1, the mechanical stirring temperature is 50-80° C., and the mechanical stirring time is 4 h.

4. The method for preparing a uniform porous fiber material by a coagulation bath wet process according to claim 1, characterized in that: The extrusion process in step 2 is specifically as follows: A digital injection pump is selected as the device for extruding the spinning solution, a 10 mL syringe is selected, a needle with an inner diameter of 0.25 mm is selected, an extrusion flow rate is 0.05 mL / min, and the digital injection pump is placed vertically at a distance of 10 cm from the coagulation bath.

5. The method for preparing a uniform porous fiber material by a coagulation bath wet process according to claim 1, characterized in that: The coagulation solvent in the coagulation bath in step 2 is anhydrous ethanol.

6. The method for preparing a uniform porous fiber material by a coagulation bath wet process according to claim 1, characterized in that: Step 3: The temperature of the deionized water is 60-80°C.

7. The method for preparing a uniform porous fiber material by a coagulation bath wet process according to claim 1, characterized in that: The desolvation time in step 3 is 24 h.

8. A method for preparing a uniform porous fiber material by a coagulation bath wet process according to any one of claims 1 to 7, characterized in that: The prepared porous fiber material is applied in the field of radiation cooling.

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