Preparation method of high-strength and high-heat-resistance para-aramid nanometer paper

Abstract

The application discloses a preparation method of high-strength and high-heat-resistance para-aramid nanometer paper; the method uses para-aramid short-cut fibers as raw materials, adopts pressurized CO2 to obtain aramid nanometer fiber gel through one-step reaction, then uses water washing and pressing under vacuum suction to obtain aramid paper embryo, and finally obtains para-aramid nanometer paper through drying; the prepared aramid nanometer paper has a thickness of 0.01-0.16 mm and has the characteristics of high strength and high heat resistance; the preparation process is simple, the requirement for equipment is low, and the method is beneficial to industrialized production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of papermaking, and particularly relates to a preparation process of high-strength and high-heat-resistance para-aramid nanometer paper. BACKGROUND

[0002] A para-aramid paper prepared from para-aramid fibers with high chain regularity and strong rigidity has excellent mechanical properties, high-temperature resistance and electrical insulation. At present, the para-aramid paper produced industrially is prepared by mixing short-cut fibers and pulp according to a certain proportion, and then through wet-forming papermaking and hot calendering process. In the process, the para-aramid pulp is prepared by cutting, grinding and fibrillation of para-aramid fibers, and adding a dispersant to improve the dispersibility and stability of the pulp. Since the para-aramid fiber has no melting point, poor compatibility and is difficult to be mechanically processed, the process is complicated and costly. Meanwhile, the interface interaction between the pulp fibers and the short-cut fibers is poor, the structure of the prepared para-aramid paper is loose, the porosity is high, and thus the overall mechanical properties of the paper are reduced.

[0003] Chinese patent CN106567274A discloses a method for preparing a para-aramid nanometer paper only using para-aramid nanofibers as raw materials. First, the nanofiber dispersion liquid is adjusted to a suitable concentration, then formed into a wet paper sheet on a wire, and then the final product is obtained through pressing, drying and high-temperature calendering. Although the prepared para-aramid nanometer paper has high stability and uniformity, the cross-linking degree between the aramid fibers is poor, resulting in poor overall rigidity of the paper and very low tear resistance.

[0004] Chinese patent CN111218841A discloses a nanometer aramid paper-based material, a preparation method and application thereof. After the aramid fibers are completely nanometerized, the fibers are defibrated after being protonated in water to obtain aramid pulp, and then the nanometer aramid paper is obtained through wire-forming, dehydration, drying and hot-pressing. The steps are complicated, time-consuming and the breaking strength of the paper depends on the hot-pressing process.

[0005] Therefore, how to use an efficient and universal method to prepare a high-strength and high-heat-resistance para-aramid nanometer paper and realize its mass production has become one of the problems to be solved in the field. SUMMARY

[0006] The present application aims at the above-mentioned problems, and provides a preparation process of high-strength and high-heat-resistance para-aramid nanometer paper, which is simple in process, excellent in product performance, environmentally friendly and low in cost.

[0007] The preparation process of the high-strength and high-heat-resistance para-aramid nanometer paper comprises the following steps:

[0008] (1) mixing para-aramid short-cut fibers, an alkali solution, water and an organic solvent to obtain an aramid fiber mixture;

[0009] (2) transferring the mixed solution to a CO2 pressurization device, injecting CO2 into the device to a certain pressure, stirring the reaction under the given pressure, and then naturally cooling to room temperature to release pressure, to obtain aramid nanofiber gel;

[0010] (3) placing the aramid nanofiber gel in an alkali-resistant organic filter membrane, and performing water washing and pressing under vacuum suction to obtain a wet paper blank;

[0011] (4) drying the wet paper blank to obtain the para-aramid nanometer paper.

[0012] The diameter and aspect ratio of the para-aramid fiber in the application are not particularly limited, and it does not need to be deeply washed.

[0013] The preferred mode of the above preparation method is as follows:

[0014] In the step 1, the mass ratio of aramid fiber, alkali solution, water and organic solvent is 1: (1-5): (5-20): (20-400).

[0015] In the step 2, the reaction conditions are as follows: the temperature is 40-200℃, the pressure is 2-20MPa, and the time is 1-8h.

[0016] In the step 3, the alkali-resistant organic filter membrane includes polyvinylidene fluoride filter membrane (PVDF), polytetrafluoroethylene filter membrane (PTFE), nylon filter membrane (NY), polypropylene filter membrane (PP) and the like; the vacuum degree of vacuum suction is-0.05~-0.1MPa; the pressing pressure is 0.05~0.15MPa.

[0017] In the step 4, a slight pressure is applied during the drying process, and the paper surface pressure is 0.01~0.5MPa.

[0018] Compared with the prior art, the application has the following beneficial effects:

[0019] The application provides a preparation method of high-strength and high-heat-resistance p-aramid nanometer paper, and only pure p-aramid short fibers are used as raw materials, and the prepared aramid paper has excellent mechanical strength and high-temperature resistance; the p-aramid fibers are prepared into nanometer aramid paper through a nanometerization-sol-gel-film conversion process, wherein the p-aramid short fibers are reacted under the action of pressurized CO2 to obtain aramid nanofiber gel, and then the aramid nanofiber gel is washed, pressed and dried into paper under vacuum suction. Since the p-nanometer aramid fibers are uniformly dispersed and have high crosslinking degree during the CO2 treatment process, the obtained p-aramid nanometer paper has high compactness and stable performance; the high-performance p-aramid nanometer paper is developed and produced by using a new process and a new method, the production process is simple, the efficiency is extremely high, and the production process can be industrialized, which has great practical significance for reducing the production cost of the p-aramid nanometer paper, expanding the application field of the p-aramid nanometer paper and promoting the development of related industries. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 : XRD pattern of the p-aramid nanometer paper and the aramid fibers obtained in example 1 of the application, and the inner interpolation figure from left to right is a gel photo obtained after pressurized CO2 treatment, the corresponding final p-aramid nanometer paper product and thickness.

[0021] Figure 2 : Scanning electron microscope characterization of the target product obtained in example 1 of the application.

[0022] Figure 3 : Stress-strain curve of the target product obtained in example 1 of the application.

[0023] Figure 4 : Thermogravimetric curve of the target product obtained in example 1 of the application. DETAILED DESCRIPTION

[0024] The application will be further described below in combination with specific examples. It should be understood that the examples are only used to illustrate the application but not to limit the scope of the application. In addition, it should be understood that those skilled in the art can make various modifications or changes to the application after reading the content of the application, and these equivalent forms also fall within the scope defined by the appended claims of the application.

[0025] A preparation method of high-strength and high-heat-resistance p-aramid nanometer paper, characterized in that the method comprises the following steps:

[0026] Step 1, p-aramid short fibers, alkali solution, water and organic solution are stirred and mixed to obtain aramid fiber mixed solution, and the mass ratio of aramid, alkali solution, water and organic solvent is 1:(1-5):(5-20):(20-400);

[0027] Step 2, the mixed solution is transferred to a CO2 pressurization device, CO2 is injected into the device to a certain pressure, after stirring the reaction at a given pressure, it is naturally cooled to room temperature and decompressed to obtain aramid nanofiber gel, the reaction temperature is 40-200 DEG C, the pressure is 2-20 MPa, and the time is 1-8h;

[0028] Step 3, the aramid nanofiber gel is placed in an alkali-resistant organic filter membrane, and water washing and pressing are carried out under vacuum suction to obtain a wet paper blank, the vacuum degree of vacuum suction is-0.05~-0.1 MPa, and the pressing pressure is 0.05~0.15 MPa;

[0029] Step 4, the wet paper blank is dried to obtain the aramid nanometer paper, and the paper surface pressure during drying is 0.01~0.5 MPa.

[0030] In the application, the morphology and performance of the para-aramid nanometer paper are determined by the following methods:

[0031] (1) apparent morphology observation

[0032] The apparent morphology of the para-aramid nanometer paper is observed by using a German ZEISS Gemini SEM 300 field emission scanning electron microscope, and the acceleration voltage is 3KV.

[0033] (2) mechanical property test

[0034] The mechanical property test of the para-aramid nanometer paper is carried out by using a CMT4104 type universal electronic testing machine of the United States, the test temperature is room temperature, the sample width is 10mm, the clamping distance is 20mm, and the tensile speed is 1mm / min.

[0035] (3) thermal performance test

[0036] The thermal decomposition performance test of the para-aramid nanometer paper is carried out by using an SDT Q600 type thermal gravimetric analyzer, the protective gas is nitrogen, the gas flow rate is 10mL / min, the temperature interval is 30-800 DEG C, and the heating rate is 10 DEG C / min.

[0037] Example 1

[0038] Step 1, para-aramid fiber, potassium hydroxide, water and dimethyl sulfoxide are stirred and mixed according to the mass ratio of 1:3:12:330 to obtain an aramid fiber mixed solution;

[0039] Step 2, the mixed solution is transferred to a CO2 pressurization device, CO2 is injected into the device to 20MPa, and the reaction is carried out at 40 DEG C for 4h to obtain aramid nanofiber gel;

[0040] Step 3: Place 60g of aramid nanofiber gel in a PTFE membrane, wash with water under a vacuum of -0.1MPa to remove DMSO and residual potassium hydroxide, and then press under a pressure of 0.15MPa to obtain a wet paper blank.

[0041] Step 4: Dry the wet paper blank at 0.5 MPa and 100 degrees Celsius for 10 minutes to obtain the para-aramid nanopaper.

[0042] According to the test results, the para-aramid nanopaper described in Example 1 has a thickness of 0.16 mm, a tensile strength of 118 MPa, an elongation of 10.9%, and an initial thermal decomposition temperature of 497.75 °C.

[0043] As attached Figure 1 As shown, attached Figure 1 The XRD patterns of the para-aramid nanopaper obtained in Example 1 and the aramid short-cut fibers used are given. The inset images, from left to right, show the gel photograph obtained after pressurized CO2 treatment, the corresponding final para-aramid nanopaper product, and its thickness. (Attached) Figure 2 The attached image shows a SEM image of the para-aramid nanopaper obtained in Example 1. Figure 2 It can be seen that the nano-aramid fibers are uniformly dispersed and highly cross-linked, with very low porosity. Furthermore, the cross-section exhibits a vesicular cross-linked structure, which can significantly improve the mechanical properties of the aramid nanopaper. (From the attached...) Figure 3 The tensile strength of the para-aramid nanopaper obtained in Example 1 was calculated to be 118 MPa, and the elongation at break was 10.9%. Compared with the commercially available Yantai Minshida YT836 para-aramid paper (data disclosed in Chinese Patent CN108824067A), the tensile strength increased by 2.6 times (45 MPa), and the elongation at break increased by 5.5 times (2.0%). (See attached...) Figure 4 It can be seen that the decomposition temperature of the para-aramid nanopaper obtained in Example 1 is 565.16℃.

[0044] Example 2

[0045] Step 1: Mix para-aramid fibers, potassium hydroxide, water and dimethyl sulfoxide in a mass ratio of 1:3:12:330 to obtain an aramid fiber mixture.

[0046] Step 2: Transfer the mixture to a CO2 pressurization device, inject CO2 into the device to 10 MPa, and react at 100°C for 1.5 h to obtain aramid nanofiber gel.

[0047] Step 3: Place 20g of aramid nanofiber gel in a PTFE membrane, wash with water under a vacuum of -0.1MPa to remove DMSO and residual potassium hydroxide, and then press under a pressure of 0.15MPa to obtain a wet paper blank.

[0048] Step 4, drying the wet paper web at 0.5 MPa, 100 degrees for 10 minutes to obtain the para-aramid nanometer paper.

[0049] According to the test results, the thickness of the para-aramid nanometer paper in Example 2 is 0.05 mm.

[0050] Example 3

[0051] Step 1, para-aramid fiber, potassium hydroxide, water and dimethyl sulfoxide are mixed by stirring according to the mass ratio of 1:3:12:330 to obtain an aramid fiber mixed solution;

[0052] Step 2, the mixed solution is transferred to a CO2 pressurization device, CO2 is injected into the device to 5 MPa, and the reaction is carried out at 60℃ for 3h to obtain aramid nanofiber gel;

[0053] Step 3, 10g of aramid nanofiber gel is placed on a PTFE film, and water washing is carried out under vacuum suction of-0.1 MPa, and after removing DMSO and residual potassium hydroxide, it is pressed under the pressure of 0.15 MPa to obtain a wet paper web;

[0054] Step 4, drying the wet paper web at 0.5 MPa, 100 degrees for 10 minutes to obtain the para-aramid nanometer paper.

[0055] According to the test results, the thickness of the para-aramid nanometer paper in Example 2 is 0.03 mm.

[0056] Example 4

[0057] Step 1, para-aramid fiber, potassium hydroxide, water and dimethyl sulfoxide are mixed by stirring according to the mass ratio of 1:3:12:330 to obtain an aramid fiber mixed solution;

[0058] Step 2, the mixed solution is transferred to a CO2 pressurization device, CO2 is injected into the device to 5 MPa, and the reaction is carried out at 60℃ for 3h to obtain aramid nanofiber gel;

[0059] Step 3, 10g of aramid nanofiber gel is placed on a PTFE film, and water washing is carried out under vacuum suction of-0.1 MPa, and after removing DMSO and residual potassium hydroxide, it is pressed under the pressure of 0.15 MPa to obtain a wet paper web;

[0060] Step 4, drying the wet paper web at 0.5 MPa, 100 degrees for 10 minutes to obtain the para-aramid nanometer paper.

[0061] According to the test results, the thickness of the para-aramid nanometer paper in Example 2 is 0.03 mm.

[0062] Example 5

[0063] Step 1, para-aramid fiber, potassium hydroxide, water and dimethyl sulfoxide were mixed by stirring according to the mass ratio of 1:5:20:200 to obtain an aramid fiber mixture;

[0064] Step 2, the mixture was transferred to a CO2 pressurization device, CO2 was injected into the device to 2 MPa, and reacted at 150℃ for 1h to obtain aramid nanofiber gel;

[0065] Step 3, 20g of aramid nanofiber gel was placed in a PTFE membrane, and water washing was carried out under vacuum suction at-0.1MPa, and after removing DMSO and residual potassium hydroxide, it was pressed under a pressure of 0.15MPa to obtain a wet paper blank;

[0066] Step 4, the wet paper blank was dried at 0.5MPa, 100℃ for 10min to obtain the para-aramid nanometer paper.

[0067] According to the test results, the para-aramid nanometer paper in Example 4 has a thickness of 0.058mm and an initial thermal decomposition temperature of 530.56℃.

[0068] Finally, it should be noted that the skilled person in the art should understand that the present application is not limited by the above examples, and the above examples and the description in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements shall fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high-strength, high-heat-resistant para-aramid nanopaper, characterized by, The method comprises the following steps: Step 1, stirring and mixing p-aramid short fibers, an alkali solution, water and an organic solvent to obtain an aramid fiber mixture, wherein the alkali solution is selected from NaOH or KOH solution, the organic solvent is selected from N,N-dimethylformamide or dimethyl sulfoxide, and the mass ratio of the aramid fiber, the alkali solution, the water and the organic solvent is 1:(1-5):(5-20):(20-400); Step 2, transferring the mixture to a CO2 pressurization device, injecting CO2 into the device to a certain pressure, stirring and reacting under the given pressure, naturally cooling to room temperature and unloading pressure to obtain aramid nanofiber gel, wherein the reaction conditions are: temperature is 40-200℃, pressure is 2-20MPa, and time is 1-8h; Step 3, placing the aramid nanofiber gel in an alkali-resistant organic filter membrane, and performing water washing and pressing under vacuum suction to obtain a wet paper blank; Step 4, drying the wet paper blank to obtain the aramid nanometer paper.

2. The method for preparing a high-strength, high-heat-resistant para-aramid nanopaper according to claim 1, characterized in that, In step 3, the alkali-resistant organic filter membrane is selected from one or more of polyvinylidene fluoride filter membrane (PVDF), polytetrafluoroethylene filter membrane (PTFE), nylon filter membrane (NY) and polypropylene filter membrane (PP).

3. The method for preparing a high-strength, high-heat-resistant para-aramid nanopaper according to claim 1, characterized in that, In step 3, the vacuum degree of the vacuum suction is-0.05~-0.1MPa.

4. The method for preparing a high-strength, high-heat-resistant para-aramid nanopaper according to claim 1, characterized in that, In step 3, the pressing pressure is 0.05~0.15MPa.

5. The method according to claim 1, wherein the method is characterized by, In step 4, a slight pressure is applied during the drying process, and the paper surface pressure is 0.01~0.5MPa.

6. The method for preparing a high-strength, high-heat-resistant para-aramid nanopaper according to claim 1, characterized in that, The aramid paper obtained in step 4 has a thickness of 0.01-0.16mm.

7. The product obtained by the method for preparing high-strength and high-heat-resistance p-aramid nanometer paper according to any one of claims 1 to 6.

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