Preparation method of electromagnetic shielding composite paper

Abstract

The invention relates to the technical field of high-performance materials, and particularly discloses a preparation method of electromagnetic shielding composite paper. The preparation method of the electromagnetic shielding composite paper provided by the invention comprises the steps of fiber modification treatment, foam system construction, forming and drying as well as gum dipping and carbonization. According to the method for preparing the electromagnetic shielding composite paper through foam forming, the problem that basalt fibers and carbon fibers are difficult to disperse is solved, the uniformity and porosity of the paper are improved, the fibers are subjected to modification treatment, the modified fibers have good mechanical properties, and the electromagnetic shielding composite paper is prepared. The mechanical strength and the electromagnetic shielding performance of the electromagnetic shielding composite paper are improved.

Description

Technical Field

[0001] The invention relates to the technical field of high-performance materials, and specifically discloses a method for preparing electromagnetic shielding composite paper. Background Art

[0002] With the rapid development of modern electronic technology, the problem of electromagnetic pollution is becoming increasingly serious, and the demand for high-performance electromagnetic shielding materials is becoming more urgent. The insulation performance, high temperature resistance and electrothermal performance of basalt fiber make it have a certain electromagnetic wave attenuation ability, and it has application prospects in the preparation of insulating electromagnetic shielding materials. Carbon fiber, as a conductive fiber, has good electromagnetic shielding performance and mechanical properties, and has occupied an important position in the field of electromagnetic shielding materials.

[0003] Although basalt fiber and carbon fiber have many advantages in the field of electromagnetic shielding, their respective problems cannot be ignored. At present, basalt fiber is mostly used in the field of electromagnetic shielding in the form of fabrics, and carbon fiber is also mostly composited with organic fiber to prepare electromagnetic shielding composite paper. The reason is that modified basalt fiber and modified carbon fiber are difficult to disperse in water, which seriously affects the uniformity of the paper, thus adversely affecting all aspects of performance. The traditional wet forming has low concentration, high water consumption, poor uniformity and high density of the formed product, which makes it difficult for the performance of electromagnetic shielding composite paper to reach the ideal state and cannot meet the growing demand for high-performance electromagnetic shielding materials. Summary of the invention

[0004] The present invention aims to combine the excellent properties of basalt fiber and carbon fiber, overcome the disadvantages of the traditional wet papermaking method, and develop a method for preparing basalt fiber and carbon fiber electromagnetic shielding composite paper.

[0005] The preparation method of the electromagnetic shielding composite paper provided by the present invention adopts the following technical scheme:

[0006] A method for preparing electromagnetic shielding composite paper comprises the following steps: (1) Fiber modification: acid leaching the basalt fiber to obtain modified basalt fiber; The carbon fiber is immersed in a polymer dispersant solution to obtain a modified carbon fiber; (2) Construction of foam system: The modified basalt fiber, the modified carbon fiber, the foaming agent and the binder are placed in water to obtain a mixture, and the mixture is stirred and foamed to prepare a foam-fiber slurry; (3) Forming and drying: dehydrating and drying the foam-fiber slurry to obtain primary electromagnetic shielding composite paper; (4) Impregnation and carbonization: impregnating the primary electromagnetic shielding composite paper with a carbon precursor resin, drying it, and then subjecting it to a high-temperature carbonization treatment to obtain an electromagnetic shielding composite paper.

[0007] The present invention uses modified basalt fiber and modified carbon fiber to form electromagnetic shielding composite paper through a foam forming method. The method of preparing electromagnetic shielding composite paper by foam forming used in the present invention solves the problem that basalt fiber and carbon fiber are difficult to disperse, improves the uniformity and porosity of paper, and the impregnation and drying of the primary electromagnetic shielding composite paper by the carbon precursor resin enhances the bonding force between fibers, ensuring that the electromagnetic shielding composite paper finally prepared has low conductivity and excellent electromagnetic shielding performance.

[0008] Preferably, the preparation of the modified basalt fiber specifically comprises the following steps: degumming the basalt fiber, first ultrasonication, and acid leaching to obtain the modified basalt fiber.

[0009] Preferably, in step (1), the temperature of the first ultrasound is 80°C-100°C, the time of the first ultrasound is 30min-120min, and the power of the first ultrasound is 80W-300W; and / or In step (1), the acid leaching uses an acid solution with a pH of 3-5, and the acid leaching time is 15 min-25 min; preferably, the acid solution is an aqueous solution of hydrochloric acid.

[0010] The present invention limits the modification conditions of basalt fiber to ensure that the modified basalt fiber has good insulation performance and can give the electromagnetic shielding composite paper extremely low conductivity.

[0011] Preferably, the preparation of the modified carbon fiber specifically comprises the following steps: debonding the carbon fiber, placing the debonded carbon fiber in a polymer dispersant solution and performing a second ultrasound treatment to obtain the modified carbon fiber.

[0012] Preferably, in step (1), the polymer dispersant solution is selected from one or both of polyethylene oxide solution and polyacrylamide solution; and / or In step (1), the temperature of the second ultrasound is 20°C-30°C, the time of the second ultrasound is 30min-120min, and the power of the second ultrasound is 80W-300W.

[0013] The invention limits the modification conditions of carbon fibers to ensure that the modified carbon fibers have good mechanical properties and conductive properties, thereby improving the mechanical strength and electromagnetic shielding properties of the electromagnetic shielding composite paper.

[0014] Preferably, in step (2), the mass concentration of the foam-fiber slurry is 0.8%-1.2%.

[0015] The present invention avoids the low mechanical strength of the primary electromagnetic shielding composite paper caused by the low content of the foaming agent and the binder by limiting the mass concentration of the foam-fiber slurry. It can also avoid the high viscosity of the primary electromagnetic shielding composite paper caused by the high content of the foaming agent and the binder, which causes the comprehensive performance of the primary electromagnetic shielding composite paper to decrease.

[0016] Preferably, in step (2), the foaming agent is selected from anionic foaming agents, and the amount of the foaming agent added is 0.04%-0.07% of the total mass of the foam-fiber slurry; the binder is polyvinyl alcohol, and the amount of the binder added is 0.8%-1.1% of the total mass of the foam-fiber slurry.

[0017] Preferably, the foaming agent is selected from sodium dodecylbenzene sulfonate, sodium dodecyl sulfate or sodium fatty alcohol polyoxyethylene ether sulfate.

[0018] The present invention controls the foaming degree of the foam-fiber slurry by limiting the types and addition amounts of the foaming agent and the binder, thereby avoiding the problem that the composite degree of the primary electromagnetic shielding composite paper is low due to the high foaming agent content, thereby reducing the bonding performance of the electromagnetic shielding composite paper; at the same time, it can also avoid the problem that the basalt fiber and the carbon fiber are difficult to disperse due to the poor foaming effect caused by the low foaming agent content.

[0019] Preferably, in step (2), the stirring rate is 1200 rpm-1800 rpm, and the stirring time is 10 min-20 min.

[0020] The present invention effectively improves the foaming effect by limiting the stirring rate and time, thereby improving the dispersion effect of basalt fibers and carbon fibers, and improving the uniformity and porosity of paper.

[0021] Preferably, in step (4), the carbon precursor resin is selected from phenolic resin or silicone resin.

[0022] The present invention effectively improves the bonding between basalt fiber and carbon fiber and improves the physical properties of electromagnetic shielding composite paper by limiting the types of carbon precursor resin.

[0023] Preferably, the diameter of the basalt fiber is 8 μm-16 μm, and the length is 3 mm-9 mm, the diameter of the carbon fiber is 3 μm-11 μm, and the length is 1 mm-5 mm, and the mass ratio of the basalt fiber to the carbon fiber is (1-8):(1-4).

[0024] The present invention limits the length and diameter of basalt fibers to form a stable support structure in the system. At the same time, the present invention limits the length and diameter of carbon fibers, so that carbon fibers can complement basalt fibers, further improving the bonding force of electromagnetic shielding composite paper. At the same time, the present invention limits the ratio of basalt fibers to carbon fibers, thereby ensuring that the electromagnetic shielding composite paper has good electromagnetic shielding performance and low electrical conductivity.

[0025] Preferably, the electromagnetic shielding composite paper has a thickness of 1 mm-2 mm, a tensile strength of ≥85 MPa, an electrical conductivity of ≤10 S / cm, and an electromagnetic shielding efficiency of 30 dB-80 dB at a frequency of 8.2 GHz-12.4 GHz.

[0026] The electromagnetic shielding composite paper prepared by the preparation method provided by the present invention has good physical strength and good electromagnetic shielding efficiency.

[0027] An electromagnetic shielding composite paper is prepared by the above scheme.

[0028] In summary, the present invention includes at least one of the following beneficial technical effects: 1. The method for preparing electromagnetic shielding composite paper by foam forming utilized in the present invention solves the problem that basalt fiber and carbon fiber are difficult to disperse, thereby improving the uniformity and porosity of the paper. The impregnation and drying of the primary electromagnetic shielding composite paper by the carbon precursor resin enhances the bonding force between the fibers, thereby ensuring that the electromagnetic shielding composite paper finally prepared has low conductivity and excellent electromagnetic shielding performance, so that the electromagnetic shielding composite paper provided by the present invention shows excellent application potential in high-end fields such as aerospace, automobile manufacturing, and electronic equipment. 2. In terms of raw material selection of the present invention, basalt fiber can give the electromagnetic shielding composite paper extremely low conductivity, and its electrothermal performance can also convert part of the electromagnetic waves into heat energy and be absorbed. The specification of 3-9mm in length is conducive to forming a stable support structure in the system; carbon fiber can improve the strength and electromagnetic shielding performance of paper, and the length of 1-5mm can synergistically complement with basalt fiber; the diluted phenolic resin improves the bonding force between fibers without affecting the flexibility of the electromagnetic shielding composite paper, and the residual carbon produced after its carbonization further improves the electromagnetic shielding performance of the electromagnetic shielding composite paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a flow chart of the method for preparing electromagnetic shielding composite paper in Example 1;

[0030] Figure 2The following are sample photos and scanning electron microscope images of electromagnetic shielding composite papers prepared in Example 1 and Comparative Example 1, wherein (a) is a sample photo of Example 1; (b) is a sample photo of Comparative Example 1; (c) is a scanning electron microscope image of Example 1; (d) is a scanning electron microscope image of Comparative Example 1;

[0031] Figure 3 The graph shows the variation curve of the electromagnetic wave shielding value of the electromagnetic wave shielding composite paper prepared in Examples 1-3 and Comparative Example 2. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0033] Embodiment 1:

[0034] A method for preparing electromagnetic shielding composite paper comprises the following steps:

[0035] Step (1): 5 g of basalt fiber was calcined in a high-temperature furnace at 300° C. for 2 h to remove the surface adhesive, and then ultrasonicated for 60 min in an environment at 90° C. with an ultrasonic power of 150 W, and then transferred to a hydrochloric acid solution with a pH of 4 and soaked at room temperature for 20 min and then dried to obtain modified basalt fiber;

[0036] 5g of carbon fiber was calcined in a high-temperature furnace at 350°C for 2h to remove the surface adhesive, and the calcined carbon fiber was placed in a mixed aqueous solution of 0.5L polyethylene oxide and polyacrylamide for ultrasonic drying to obtain modified carbon fiber, wherein the mass of polyethylene oxide in the mixed aqueous solution of polyethylene oxide and polyacrylamide was 0.005g, the mass of polyacrylamide was 0.005g, the ultrasonic time was 60min, the temperature was 25°C, and the power was 150W;

[0037] Step (2): transferring the modified basalt fiber and the modified carbon fiber into a foaming container, then adding water to prepare a fiber dispersion with a total concentration of 1% of the modified basalt fiber and the modified carbon fiber, adding polyvinyl alcohol and sodium dodecylbenzene sulfonate to obtain a mixture, wherein the amount of polyvinyl alcohol added is 0.8% of the total mass of the mixture, and the amount of sodium dodecylbenzene sulfonate added is 0.04% of the total mass of the mixture, stirring and foaming, setting the rotation speed to 1500 rpm, and the foaming time to 10 minutes, to obtain a foam-fiber slurry;

[0038] Step (3): after the foaming is completed, the foam-fiber slurry is transferred to a paper sheet forming device, and after vacuum defoaming is performed at a pressure of 0.1 MPa, the wet paper web is obtained by dehydration; the wet paper web is transferred to a paper sheet drying device, and dried at 90° C. for 60 min to obtain a basalt fiber carbon fiber electromagnetic shielding composite paper;

[0039] Step (4): prepare a 5% dilution with ethanol using phenolic resin, immerse the basalt fiber carbon fiber electromagnetic shielding composite paper in step (3) in the phenolic resin dilution for 60 seconds, wherein the mass ratio of the basalt fiber carbon fiber electromagnetic shielding composite paper to the phenolic resin dilution is 1:10, take out the immersed basalt fiber carbon fiber electromagnetic shielding composite paper, dry it at 160°C for 30 minutes, and then transfer it to an atmosphere tube furnace, introduce N2, and carbonize it at 800°C for 2 hours to obtain the electromagnetic shielding composite paper.

[0040] Embodiment 2:

[0041] A method for preparing electromagnetic shielding composite paper comprises the following steps:

[0042] Step (1): 8 g of basalt fiber was calcined in a high-temperature furnace at 300° C. for 2 h to remove the surface adhesive, and then ultrasonicated for 60 min in an environment at 90° C. with an ultrasonic power of 150 W, and then transferred to a hydrochloric acid solution with a pH of 4 and soaked at room temperature for 20 min and then dried to obtain modified basalt fiber;

[0043] 2g of carbon fiber was calcined in a high-temperature furnace at 350°C for 2h to remove the surface adhesive, and the calcined carbon fiber was placed in a mixed aqueous solution of 0.2L of polyethylene oxide and polyacrylamide for ultrasonic drying to obtain modified carbon fiber, wherein the mass of polyethylene oxide in the mixed aqueous solution of polyethylene oxide and polyacrylamide was 0.002g, the mass of polyacrylamide was 0.002g, the ultrasonic time was 60min, the temperature was 25°C, and the power was 150W;

[0044] Step (2): transferring the modified basalt fiber and the modified carbon fiber into a foaming container, then adding water to prepare a fiber dispersion with a total concentration of 1% of the modified basalt fiber and the modified carbon fiber, adding polyvinyl alcohol and sodium dodecylbenzene sulfonate to obtain a mixture, wherein the amount of polyvinyl alcohol added is 0.8% of the total mass of the mixture, and the amount of sodium dodecylbenzene sulfonate added is 0.04% of the total mass of the mixture, stirring and foaming, setting the rotation speed to 1500 rpm, and the foaming time to 10 minutes, to obtain a foam-fiber slurry;

[0045] Step (3): after the foaming is completed, the foam-fiber slurry is transferred to a paper sheet forming device, and after vacuum defoaming is performed at a pressure of 0.1 MPa, the wet paper web is obtained by dehydration; the wet paper web is transferred to a paper sheet drying device, and dried at 90° C. for 60 min to obtain a basalt fiber carbon fiber electromagnetic shielding composite paper;

[0046] Step (4): prepare a 5% dilution with ethanol using phenolic resin, immerse the basalt fiber carbon fiber electromagnetic shielding composite paper in step (3) in the phenolic resin dilution for 60 seconds, wherein the mass volume ratio of the basalt fiber carbon fiber electromagnetic shielding composite paper to the phenolic resin dilution is 1:10, take out the immersed basalt fiber carbon fiber electromagnetic shielding composite paper, dry it at 160°C for 30 minutes, and then transfer it to an atmosphere tube furnace, introduce N2, and carbonize it at 800°C for 2 hours to obtain the electromagnetic shielding composite paper.

[0047] Embodiment 3:

[0048] A method for preparing electromagnetic shielding composite paper comprises the following steps:

[0049] Step (1): 8.8 g of basalt fiber was calcined in a high-temperature furnace at 300° C. for 2 h to remove the surface adhesive, and then ultrasonicated for 60 min in an environment at 90° C. with an ultrasonic power of 150 W, and then transferred to a hydrochloric acid solution with a pH of 4 and soaked at room temperature for 20 min and then dried to obtain modified basalt fiber;

[0050] 1.2 g of carbon fiber was calcined in a high-temperature furnace at 350° C. for 2 h to remove the surface adhesive, and the calcined carbon fiber was placed in a mixed aqueous solution of 0.12 L of polyethylene oxide and polyacrylamide for ultrasonic drying to obtain modified carbon fiber, wherein the mass of polyethylene oxide in the mixed aqueous solution of polyethylene oxide and polyacrylamide was 0.0012 g, the mass of polyacrylamide was 0.0012 g, the ultrasonic time was 60 min, the temperature was 25° C., and the power was 150 W;

[0051] Step (2): transferring the modified basalt fiber and the modified carbon fiber into a foaming container, then adding water to prepare a fiber dispersion with a total concentration of 1% of the modified basalt fiber and the modified carbon fiber, adding polyvinyl alcohol and sodium dodecylbenzene sulfonate to obtain a mixture, wherein the amount of polyvinyl alcohol added is 0.8% of the total mass of the mixture, and the amount of sodium dodecylbenzene sulfonate added is 0.04% of the total mass of the mixture, stirring and foaming, setting the rotation speed to 1500 rpm, and the foaming time to 10 minutes, to obtain a foam-fiber slurry;

[0052] Step (3): after the foaming is completed, the foam-fiber slurry is transferred to a paper sheet forming device, and after vacuum defoaming is performed at a pressure of 0.1 MPa, the wet paper web is obtained by dehydration; the wet paper web is transferred to a paper sheet drying device, and dried at 90° C. for 60 min to obtain a basalt fiber carbon fiber electromagnetic shielding composite paper;

[0053] Step (4): prepare a 5% dilution with ethanol using phenolic resin, immerse the basalt fiber carbon fiber electromagnetic shielding composite paper in step (3) in the phenolic resin dilution for 60 seconds, wherein the mass volume ratio of the basalt fiber carbon fiber electromagnetic shielding composite paper to the phenolic resin dilution is 1:10, take out the immersed basalt fiber carbon fiber electromagnetic shielding composite paper, dry it at 160°C for 30 minutes, and then transfer it to an atmosphere tube furnace, introduce N2, and carbonize it at 800°C for 2 hours to obtain the electromagnetic shielding composite paper.

[0054] Embodiment 4:

[0055] A method for preparing electromagnetic shielding composite paper comprises the following steps: Step (1): 8.8 g of basalt fiber was calcined in a high-temperature furnace at 300° C. for 2 h to remove the surface adhesive, and then ultrasonicated for 60 min in an environment at 90° C. with an ultrasonic power of 150 W, and then transferred to a hydrochloric acid solution with a pH of 4 and soaked at room temperature for 20 min and then dried to obtain modified basalt fiber;

[0056] 1.2 g of carbon fiber was calcined in a high-temperature furnace at 350° C. for 2 h to remove the surface adhesive, and the calcined carbon fiber was placed in a mixed aqueous solution of 0.12 L of polyethylene oxide and polyacrylamide for ultrasonic drying to obtain modified carbon fiber, wherein the mass of polyethylene oxide in the mixed aqueous solution of polyethylene oxide and polyacrylamide was 0.0012 g, the mass of polyacrylamide was 0.0012 g, the ultrasonic time was 60 min, the temperature was 25° C., and the power was 150 W;

[0057] Step (2): transferring the modified basalt fiber and the modified carbon fiber into a foaming container, then adding water to prepare a fiber dispersion with a total concentration of 1% of the modified basalt fiber and the modified carbon fiber, adding polyvinyl alcohol and sodium dodecylbenzene sulfonate to obtain a mixture, wherein the amount of polyvinyl alcohol added is 0.8% of the total mass of the mixture, and the amount of sodium dodecylbenzene sulfonate added is 0.04% of the total mass of the mixture, stirring and foaming, setting the rotation speed to 1500 rpm, and the foaming time to 10 minutes, to obtain a foam-fiber slurry;

[0058] Step (3): after the foaming is completed, the foam-fiber slurry is transferred to a paper sheet forming device, and after vacuum defoaming is performed at a pressure of 0.1 MPa, the wet paper web is obtained by dehydration; the wet paper web is transferred to a paper sheet drying device, and dried at 90° C. for 60 min to obtain a basalt fiber carbon fiber electromagnetic shielding composite paper;

[0059] Step (4): prepare a 5% dilution with ethanol using the silicone resin, immerse the basalt fiber carbon fiber electromagnetic shielding composite paper in step (3) in the silicone resin dilution for 60 seconds, wherein the mass volume ratio of the basalt fiber carbon fiber electromagnetic shielding composite paper to the silicone resin dilution is 1:10, take out the immersed basalt fiber carbon fiber electromagnetic shielding composite paper, dry it at 160°C for 30 minutes, and then transfer it to an atmosphere tube furnace, introduce N2, and carbonize it at 800°C for 2 hours to obtain the electromagnetic shielding composite paper.

[0060] Comparative Example 1:

[0061] A method for wet-process preparation of electromagnetic shielding composite paper comprises the following steps: Step (1): 5 g of basalt fiber was calcined in a high-temperature furnace at 300° C. for 2 h to remove the surface adhesive, and then ultrasonicated for 60 min in an environment at 90° C. with an ultrasonic power of 150 W, and then transferred to a hydrochloric acid solution with a pH of 4 and soaked at room temperature for 20 min and then dried to obtain modified basalt fiber;

[0062] 5g of carbon fiber was calcined in a high-temperature furnace at 350°C for 2h to remove the surface adhesive, and the calcined carbon fiber was placed in a mixed aqueous solution of 0.5L polyethylene oxide and polyacrylamide for ultrasonic drying to obtain modified carbon fiber, wherein the mass of polyethylene oxide in the mixed aqueous solution of polyethylene oxide and polyacrylamide was 0.005g, the mass of polyacrylamide was 0.005g, the ultrasonic time was 60min, the temperature was 25°C, and the power was 150W;

[0063] Step (2): transferring the modified basalt fiber and the modified carbon fiber into a foaming container, then adding water to prepare a fiber dispersion liquid with a total concentration of the modified basalt fiber and the modified carbon fiber of 0.5%, adding polyvinyl alcohol to obtain a mixture, wherein the amount of polyvinyl alcohol added is 0.8% of the total mass of the mixture, stirring and dispersing, setting the rotation speed to 1500 rpm, and stirring for 10 minutes to obtain a fiber dispersion liquid;

[0064] Step (3): after the stirring is completed, the fiber dispersion is transferred to a paper sheet forming device, and after vacuum dehydration is performed at a pressure of 0.1 MPa, a wet paper web is obtained by dehydration; the wet paper web is transferred to a paper sheet drying device, and dried at 90° C. for 60 min to obtain a basalt fiber carbon fiber composite paper;

[0065] Step (4): prepare a phenolic resin with ethanol into a 5% dilution, immerse the basalt fiber carbon fiber composite paper in step (3) in the phenolic resin dilution for 60 seconds, wherein the mass volume ratio of the basalt fiber carbon fiber composite paper to the phenolic resin dilution is 1:10, take out the immersed basalt fiber carbon fiber composite paper, dry it at 160°C for 30 minutes, and then transfer it to an atmosphere tube furnace, introduce N2, and carbonize it at 800°C for 2 hours to obtain an electromagnetic shielding composite paper.

[0066] Comparative Example 2:

[0067] A method for preparing electromagnetic shielding composite paper comprises the following steps:

[0068] Step (1): 10 g of basalt fiber was calcined in a high-temperature furnace at 300° C. for 2 h to remove the surface adhesive, and then ultrasonicated for 60 min in an environment at 90° C. with an ultrasonic power of 150 W, and then transferred to a hydrochloric acid solution with a pH of 4 and soaked at room temperature for 20 min and then dried to obtain modified basalt fiber;

[0069] Step (2): transferring the modified basalt fiber into a foaming container, then adding water to prepare a fiber dispersion having a modified basalt fiber concentration of 1%, adding polyvinyl alcohol and sodium dodecylbenzene sulfonate to obtain a mixture, wherein the amount of polyvinyl alcohol added is 0.8% of the total mass of the mixture, and the amount of sodium dodecylbenzene sulfonate added is 0.04% of the total mass of the mixture, stirring and foaming, setting the rotation speed to 1500 rpm, and the foaming time to 10 minutes, to obtain a foam-fiber slurry;

[0070] Step (3): after the foaming is completed, the foam-fiber slurry is transferred to a paper sheet forming device, and after vacuum defoaming is performed under a pressure of 0.1 MPa, the wet paper web is obtained by dehydration; the wet paper web is transferred to a paper sheet drying device, and dried at 90° C. for 60 min to obtain basalt fiber paper;

[0071] Step (4): prepare a phenolic resin diluent with ethanol at a concentration of 5%, immerse the basalt fiber paper in step (3) in the phenolic resin diluent for 60 seconds, wherein the mass volume ratio of the basalt fiber paper to the phenolic resin diluent is 1:10, take out the immersed basalt fiber paper, dry it at 160°C for 30 minutes, transfer it to an atmosphere tube furnace, introduce N2, and carbonize it at 800°C for 2 hours to obtain an electromagnetic shielding composite paper.

[0072] The electromagnetic shielding composite paper provided in Examples 1-3 and Comparative Examples 1-2 is prepared according to GB / T The thickness, grammage, porosity, tensile index, dielectric breakdown strength and conductivity described in 30142-2013 were tested, and the test results are shown in Table 1, wherein the tensile index test method comprises the following steps: cutting the electromagnetic shielding composite paper into long strips of paper samples with a width of 20 mm and a length of 100 mm, and using an electronic universal testing machine to perform a tensile test at a speed of 20 mm / min to obtain the maximum tensile force that the sample can withstand, and dividing it by the cross-sectional area to obtain the tensile strength index; the dielectric breakdown strength test method comprises the following steps: using a voltage breakdown tester, using gradually increasing DC / AC power, measuring the voltage at which the electromagnetic shielding composite paper breaks down, measuring multiple times and taking an average value to obtain the breakdown voltage of the electromagnetic shielding composite paper, and dividing it by the thickness to obtain the dielectric breakdown strength; the conductivity test method comprises the following steps: using a four-probe tester to measure the resistivity of the electromagnetic shielding composite paper, measuring multiple times and taking an average value, and taking the inverse to obtain the conductivity. Table 1 Physical properties test table of electromagnetic shielding composite paper in Examples 1-3 and Comparative Examples 1-2

[0073] It can be seen from Table 1 that the electromagnetic shielding composite paper provided by Examples 1-3 of the present invention has a good tensile index, while the electromagnetic shielding composite paper provided by Comparative Examples 1-2 has a lower tensile index. It can be seen that the preparation method provided by the present invention effectively improves the dispersion of basalt fiber and carbon fiber, enables the basalt fiber and carbon fiber to be evenly mixed, and ultimately improves the prepared electromagnetic shielding composite paper to have good uniformity and porosity.

[0074] contrast Figure 2 (a) Figure 2 (b) Figure 2 (c) and Figure 2 (d) It can be seen that the electromagnetic shielding composite paper provided in Example 1 of the present invention has good bonding performance, and the basalt fiber and the carbon fiber therein can be tightly combined together, while the basalt fiber and the carbon fiber in the electromagnetic shielding composite paper provided in Comparative Example 1 cannot be effectively combined. Therefore, it can be seen that the electromagnetic shielding composite paper provided by the present invention has good bonding performance.

[0075] Depend on Figure 3It can be seen that the ratio of basalt fiber to carbon fiber in the electromagnetic shielding composite paper provided in Example 1 of the present invention is 1:1, and it has an electromagnetic shielding effectiveness of not less than 70dB in the entire X-band, while the content of carbon fiber in the electromagnetic shielding composite paper provided in Example 2 only accounts for 25% of the total fiber mass, and it also has an electromagnetic shielding effectiveness of more than 65dB, and because the amount of basalt fiber added is relatively large, Example 2 also has low conductivity characteristics. No carbon fiber is added to the composite paper of Comparative Example 2, and after impregnation and carbonization, it has an electromagnetic shielding effectiveness of not less than 25dB in the X-band, which reflects that the impregnation and carbonization process of the present invention has the effect of enhancing the electromagnetic shielding effectiveness of the electromagnetic shielding composite paper.

[0076] The above are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, all equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing electromagnetic shielding composite paper, characterized in that: The following steps are involved: (1) Fiber modification: acid leaching the basalt fiber to obtain modified basalt fiber; The carbon fiber is immersed in a polymer dispersant solution to obtain a modified carbon fiber; (2) Construction of foam system: The modified basalt fiber, the modified carbon fiber, the foaming agent and the binder are placed in water to obtain a mixture, and the mixture is stirred and foamed to prepare a foam-fiber slurry; (3) Forming and drying: dehydrating and drying the foam-fiber slurry to obtain a primary electromagnetic shielding composite paper; (4) Impregnation and carbonization: The primary electromagnetic shielding composite paper is impregnated with a carbon precursor resin, and then dried and subjected to a high-temperature carbonization treatment to obtain an electromagnetic shielding composite paper.

2. The method for preparing an electromagnetic shielding composite paper according to claim 1, characterized in that: The preparation of the modified basalt fiber specifically comprises the following steps: degumming the basalt fiber, first ultrasonication, and acid leaching to obtain the modified basalt fiber.

3. The method for preparing an electromagnetic shielding composite paper according to claim 2, characterized in that: In step (1), the temperature of the first ultrasound is 80°C-100°C, the time of the first ultrasound is 30min-120min, and the power of the first ultrasound is 80W-300W; In step (1), the acid leaching uses an acid solution with a pH of 3-5, and the acid leaching time is 15 min-25 min.

4. The method for preparing an electromagnetic shielding composite paper according to claim 1, characterized in that: The preparation of the modified carbon fiber specifically comprises the following steps: removing glue from the carbon fiber, placing the carbon fiber after the glue removal in a polymer dispersant solution and performing a second ultrasonic treatment to obtain the modified carbon fiber.

5. The method for preparing an electromagnetic shielding composite paper according to claim 4, characterized in that: In step (1), the polymer dispersant solution is selected from one or both of polyethylene oxide solution and polyacrylamide solution; and / or In step (1), the temperature of the second ultrasound is 20°C-30°C, the time of the second ultrasound is 30min-120min, and the power of the second ultrasound is 80W-300W.

6. The method for preparing an electromagnetic shielding composite paper according to claim 1, characterized in that: In step (2), the mass concentration of the foam-fiber slurry is 0.8%-1.2%.

7. The method for preparing an electromagnetic shielding composite paper according to claim 1, characterized in that: In step (2), the foaming agent is selected from anionic foaming agents, and the amount of the foaming agent added is 0.04%-0.07% of the total mass of the mixture; the binder is polyvinyl alcohol, and the amount of the binder added is 0.8%-1.1% of the total mass of the mixture.

8. The method for preparing an electromagnetic shielding composite paper according to claim 1, characterized in that: In step (4), the carbon precursor resin is selected from phenolic resin or silicone resin.

9. The method for preparing an electromagnetic shielding composite paper according to claim 1, characterized in that: The diameter of the basalt fiber is 8 μm-16 μm, and the length is 3 mm-9 mm. The diameter of the carbon fiber is 3 μm-11 μm, and the length is 1 mm-5 mm. The mass ratio of the basalt fiber to the carbon fiber is 8:1-1:

4.

10. The method for preparing an electromagnetic shielding composite paper according to claim 1, characterized in that: The electromagnetic shielding composite paper has a thickness of 1 mm to 2 mm, a tensile strength of ≥85 MPa, an electrical conductivity of ≤10 S / cm, and an electromagnetic shielding efficiency of 30 dB to 80 dB at a frequency of 8.2 GHz to 12.4 GHz.

Images