Absorbing rubber film, absorbing prepreg and preparation methods thereof

Abstract

The present invention provides a wave-absorbing adhesive film, a wave-absorbing prepreg, and preparation methods thereof. The weight ratio of the resin to the magnetic medium type absorbent in the wave-absorbing adhesive film is 15 to 35:30 to 70, wherein the particle size of the magnetic medium type absorbent is less than or equal to 15 μm. The magnetic medium type absorbent includes a magnetic medium absorbent body and a surface modification layer, and the surface modification layer is a silica coating layer or a phosphorus oxide coating layer. The viscosity of the resin at 60 to 80 °C is less than or equal to 10,000 cps. In this application, targeted designs are carried out on both the resin material and the magnetic medium type absorbent of the wave-absorbing adhesive film. Even when the content of the magnetic medium material is relatively high, or even when it is the main body of the composite material, its uniform dispersion in the resin material is still ensured, ensuring the stable control of the electromagnetic parameters, areal density and thickness of the finally formed wave-absorbing prepreg.

Description

Technical Field

[0001] The present invention relates to the field of microwave absorbing materials, and more particularly to a microwave absorbing adhesive film, a microwave absorbing prepreg, and methods for preparing the same. Background Art

[0002] Microwave absorbing materials can be classified into coating microwave absorbing materials and structural microwave absorbing materials according to the forming process and load-bearing capacity. Coating microwave absorbing materials have the advantages of simple process, low cost, and convenient construction, but they have disadvantages such as poor high-temperature thermal stability, large coating density, and easy shedding. In contrast, structural microwave absorbing materials are usually made by adding absorbers to resin / fiber reinforced composites as carriers, which have both load-bearing capacity and microwave absorbing performance. Under certain conditions, they alleviate the contradiction between thickness and weight, and have the advantages of high temperature resistance and stronger designability, thus attracting more attention at home and abroad.

[0003] In order to achieve better microwave absorbing performance and absorb electromagnetic waves with wider bandwidth and lower frequency, structural microwave absorbing materials often have a large amount of absorber filling. In addition, a multi-layer structure design is often adopted in the structure, such as geometrically gradient structure microwave absorbing materials, resistance gradient structure microwave absorbing materials, and gradient dielectric structure microwave absorbing materials. In a multi-layer structure, the control of the electromagnetic parameters and thickness of each layer of material is the key to realizing the design of microwave absorbing performance. Only when the absorber is evenly and quantitatively distributed in a single-layer material can the stable control of electromagnetic parameters and single-layer thickness be achieved. To achieve uniform distribution of the absorber in the material, the hot-melt resin film method is often used to prepare microwave absorbing prepregs. Compared with the traditional solution impregnation method, the hot-melt resin film method is solvent-free, pollution-free, and has simple preparation and forming processes.

[0004] For example, a patent application with the publication number CN106147129A discloses a microwave absorbing prepreg and a method for preparing the same. In this solution, an absorber and a rheological thixotropic agent are added to epoxy resin to obtain a mixed adhesive solution, and then a film is prepared and hot-pressed and impregnated with reinforcing fibers to prepare a microwave absorbing prepreg. This solution has 3-10 parts by weight of rheological thixotropic agent (including fumed silica, precipitated silica, organic bentonite, asbestos, kaolin, etc.) in the film. This part of the rheological thixotropic agent not only occupies the filling amount of the absorber, but also affects the electromagnetic parameters of the absorber, and ultimately affects the electromagnetic parameters of the prepreg, thereby affecting the design of microwave absorbing performance.

[0005] However, the technique of adding a rheological thixotropic agent is a commonly used technique for increasing the filling amount of the absorber at present. This technique causes a contradiction between the high filling amount of the absorber, the design of microwave absorbing performance of the multi-layer structure, and the stable control of the electromagnetic parameters and single-layer thickness of a single-layer material. Summary of the Invention

[0006] The main object of the present invention is to provide a wave-absorbing adhesive film, a wave-absorbing prepreg, and a preparation method thereof, so as to solve the problem of the contradiction between the high filling amount of the absorber and the control of the single-layer electromagnetic parameters and thickness in the prior art.

[0007] To achieve the above object, according to one aspect of the present invention, there is provided a wave-absorbing adhesive film. The weight ratio of the resin to the magnetic medium type absorber in the wave-absorbing adhesive film is 15-35:30-70, wherein the particle size of the magnetic medium type absorber is less than or equal to 15 μm. The magnetic medium type absorber includes a magnetic medium absorber body and a surface modification layer, and the surface modification layer is a silicon dioxide coating layer or a phosphorus oxide coating layer. The viscosity of the resin at 60-80 °C is less than or equal to 10000 cps.

[0008] Further, the above magnetic medium absorber body is selected from one or more of ferrite, ultrafine metal powder, and carbonyl iron powder. Preferably, the D50 particle size of the magnetic medium type absorber is less than or equal to 4 μm, the D90 particle size is less than or equal to 7 μm, and the D98 particle size is less than or equal to 10 μm.

[0009] Further, the above carbon resin is a hot-melt epoxy resin.

[0010] According to another aspect of the present invention, there is provided a preparation method of any one of the above wave-absorbing adhesive films. The preparation method includes: Step S1, adding the magnetic medium type absorber into the molten resin for mechanical melt blending to obtain a melt blended adhesive liquid; Step S2, preparing the melt blended adhesive liquid into an adhesive film.

[0011] Further, in the above step S1, the magnetic medium type absorber is added to the molten resin in batches, and preferably the magnetic medium type absorber is added to the molten resin 3-5 times.

[0012] Further, the above step S1 includes: adding the magnetic medium type absorber to the molten resin in batches and stirring with a double planetary dispersion mixer to form a melt blended adhesive liquid. Preferably, the stirring speed is 400-800 rpm and the time is 40-60 min; introducing compressed air into the double planetary dispersion mixer to extrude the melt blended adhesive liquid, and a metal mesh is provided at the extrusion outlet, and the aperture of the metal mesh is less than or equal to 30 μm. Preferably, the extrusion time is less than or equal to 10 min, and preferably stirring is continued during the extrusion process.

[0013] Further, the above step S2 includes: coating the melt blended adhesive liquid by the differential speed scraping method to form a wave-absorbing adhesive film. Preferably, during the coating process, the coating speed of the coating roller is controlled to be less than or equal to 5 m / min, and the adjustment roller speed is greater than or equal to 3% of the coating speed. Preferably, the coating temperature is 70-80 °C, and the viscosity of the melt blended adhesive liquid at the coating temperature is less than or equal to 200000 cps.

[0014] According to another aspect of the present invention, a wave-absorbing prepreg is provided, which includes a resin matrix and a fiber material, and the resin matrix is formed by curing any one of the above wave-absorbing adhesive films.

[0015] Furthermore, the weight ratio of the resin to the fiber material in the above resin matrix is 15-140:15-35, preferably 55-85:15-35. Preferably, the fiber material is selected from one or more of glass fiber, quartz fiber, and aramid fiber.

[0016] According to another aspect of the present invention, a preparation method of the above wave-absorbing prepreg is provided. The preparation method includes: preparing the wave-absorbing prepreg by hot pressing and impregnating the wave-absorbing adhesive film and the fiber material. Preferably, the temperature of the hot pressing and impregnating is 85-115°C, and the melt viscosity of the wave-absorbing adhesive film at the temperature of the hot pressing and impregnating is less than or equal to 50000 cps.

[0017] Applying the technical solution of the present invention, the present application specifically designs the key parameters of the resin material and the magnetic medium type absorbent in the wave-absorbing adhesive film. First, the absorbent is surface-modified, and a silica coating layer or a phosphorus oxide coating layer is coated on its surface, so as to effectively control the agglomeration of particles by using surface groups. Then, the particle size of the magnetic medium type absorbent is controlled to be less than or equal to 15 μm. The wave-absorbing agent within this small particle size range can be better dispersed in the resin material. And because the magnetic medium type absorbent has been modified, the compatibility between the absorbent and the resin is higher, further improving the dispersibility of the absorbent in the resin. In addition, a resin material with a viscosity less than or equal to 10000 cps at 60-80°C is selected to ensure good fluidity of the resin material and make the absorbent easier to disperse. In summary, the present application specifically designs the wave-absorbing adhesive film for both the resin material and the magnetic medium type absorbent. Even when the content of the magnetic medium material is relatively high or even the main body of the composite material, the uniform dispersion of the magnetic medium material in the resin material is still ensured, and the electromagnetic parameters, areal density, and thickness of the finally formed wave-absorbing prepreg are ensured to be stable and controllable. Description of the Drawings

[0018] The specification drawings constituting a part of the present application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0019] Figure 1 The wave-absorbing performance curve of the 2-mm-thick structural wave-absorbing material obtained by optimizing the layup of the wave-absorbing prepreg prepared according to Example 1 of the present invention through CST simulation and the wave-absorbing performance curve of the 2-mm-thick structural wave-absorbing material obtained by testing the flat reflectivity of the actual layup and curing are shown. Detailed Embodiments

[0020] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0021] As described in the background art of the present application, the structural wave-absorbing materials in the prior art often adopt a multi-layer structure design. In this structure, the electromagnetic parameters and the thickness of a single layer are the keys to realizing the wave-absorbing performance design. In order to enable each layer of material to obtain excellent electromagnetic parameters, more wave-absorbing materials are usually required. However, due to the poor dispersibility of the wave-absorbing materials in the prior art and the inability to stably control the thickness, a problem of contradiction between the high filling amount of the absorber and the control of the electromagnetic parameters and thickness of a single layer has been caused. To solve the above problems, the present application provides a wave-absorbing adhesive film, a wave-absorbing prepreg, and preparation methods for both.

[0022] In a typical embodiment of the present application, a wave-absorbing adhesive film is provided. The weight ratio of the resin to the magnetic medium type absorber in the wave-absorbing adhesive film is 15-35:30-70, wherein the particle size of the magnetic medium type absorber is less than or equal to 15 μm. The magnetic medium type absorber includes a magnetic medium absorber body and a surface modification layer, and the surface modification layer is a silica coating layer or a phosphorus oxide coating layer. The viscosity of the resin at 60-80 °C is less than or equal to 10,000 cps.

[0023] To solve the problem of poor dispersion performance of the wave-absorbing agent in the prior art, the present application has carried out targeted design on the key parameters of the resin material and the magnetic medium type absorber in the wave-absorbing adhesive film. First, the absorber is surface-modified by coating a silica coating layer or a phosphorus oxide coating layer on its surface, thereby effectively controlling the agglomeration of particles by using surface groups. Then, the particle size of the magnetic medium type absorber is controlled to be less than or equal to 15 μm. The wave-absorbing agent within this small particle size range can be better dispersed in the resin material. Moreover, due to the modification of the magnetic medium type absorber, the absorber has higher compatibility with the resin, further improving the dispersion of the absorber in the resin. In addition, a resin material with a viscosity less than or equal to 10,000 cps at 60-80 °C is selected to ensure good fluidity of the resin material, making it easier for the absorber to disperse. In summary, the present application has carried out targeted design on both the resin material and the magnetic medium type absorber in the wave-absorbing adhesive film. Even when the content of the magnetic medium material is relatively high and even when it is the main body of the composite material, it still ensures its uniform dispersion in the resin material, ensuring the stable control of the electromagnetic parameters, areal density, and thickness of the finally formed wave-absorbing prepreg.

[0024] The magnetic medium type wave absorber used in this application can be selected from the magnetic medium type wave absorbers in the prior art, or can be modified by silicon coating or phosphating according to the methods in the prior art, and details thereof will not be elaborated herein. In order to obtain excellent wave absorption performance, it is preferred that the magnetic medium absorber body is selected from one or more of ferrite, ultrafine metal powder, and carbonyl iron powder. The above magnetic medium absorber has good electromagnetic parameters and can further improve the wave absorption effect of the wave absorption adhesive film. Further, it is preferred that the D50 particle size of the magnetic medium type absorber is less than or equal to 4 μm, the D90 particle size is less than or equal to 7 μm, and the D98 particle size is less than or equal to 10 μm. The magnetic medium type absorber within the above particle size range has better dispersibility.

[0025] The resin of this application can select various adhesives with a viscosity less than or equal to 10000 cps at 60-80 °C. In order to reduce the preparation operation difficulty of the subsequent prepreg, it is preferred that the above resin is an epoxy resin. The above resin is solid or semi-solid at room temperature and can be softened to a molten state after heating, and the prepreg can be prepared by the dry method. In addition, the above resin contains a latent curing agent, which can be directly cured at high temperature and has good processing performance.

[0026] In another typical embodiment of this application, a preparation method of any one of the above wave absorption adhesive films is provided. The preparation method includes: Step S1, adding the magnetic medium type absorber into the molten resin for mechanical melt blending to obtain a melt blended adhesive liquid; Step S2, preparing the melt blended adhesive liquid into an adhesive film.

[0027] Since the magnetic medium type absorber used in this application not only has a small particle size but also its surface is modified by silicon or phosphorus, even if its content in the wave absorption adhesive film is large, it can ensure a high dispersion degree in the resin material with a low viscosity. This enables the magnetic medium type absorber to be evenly and quantitatively distributed, reducing the scratches on the adhesive film during the subsequent preparation process of the wave absorption adhesive film, and being able to better control the areal density, thereby realizing the stable control of the electromagnetic parameters, areal density, and thickness of the finally formed wave absorption prepreg, providing a guarantee for the preparation of a structurally wave-absorbing material with excellent and controllable performance.

[0028] During the process of preparing the adhesive film, controlling the amount of the magnetic medium type absorber added per unit time can better control the dispersibility of the absorber. It is preferred that the above magnetic medium type absorber is added to the molten resin in batches. By controlling the amount of the absorber added each time, new absorber is added after the absorber in the resin is fully dispersed, further ensuring the dispersibility of the absorber. It is preferred that the magnetic medium type absorber is added to the molten resin in 3-5 times. The above addition times not only ensure that the absorber can be fully dispersed but also shorten the preparation time as much as possible, ensuring the preparation efficiency.

[0029] The mechanical melt blending in step S1 above can be achieved by referring to the common mechanical melt blending in the prior art. In some embodiments, step S1 above includes: adding the magnetic medium absorbent in batches to the molten resin and stirring it with a double planetary dispersion mixer to form a melt blended adhesive solution; introducing compressed air into the double planetary dispersion mixer to extrude the melt blended adhesive solution, and a metal mesh is provided at the extrusion outlet, and the aperture of the metal mesh is less than or equal to 30 μm. The above double planetary dispersion mixer has a good mixing and stirring effect on the mixture with a certain viscosity. Preferably, the stirring speed is 400 - 800 rpm and the time is 40 - 60 min. The above stirring parameters not only ensure the mixing and stirring effect but also ensure the preparation efficiency. At the same time, the basic process is further optimized. A metal mesh with an aperture less than or equal to 30 μm is provided at the outlet, so that the absorbent particles agglomerated due to improper operation or other factors are screened and filtered out, ensuring that there are no absorbents with a particle size greater than 30 μm in the final absorbent film, making the particle size of the melt blended adhesive solution more uniform, and further improving the overall uniformity of the formed film. Further preferably, the extrusion time is less than or equal to 10 min, and continuous stirring is preferably carried out during the extrusion process. Optionally, a relatively fast extrusion is carried out, and continuous stirring is carried out during the extrusion process, so that the absorbent remains in a dispersed state throughout the extrusion process, ensuring that the obtained melt blended adhesive solution has better uniformity and avoiding the oxidation of the molten resin by the oxygen in the compressed air.

[0030] There are various ways to form the absorbent film using the melt blended adhesive solution, such as roll coating, spin coating, spraying, etc. In some embodiments of the present application, step S2 above includes: forming an absorbent film by coating the melt blended adhesive solution using the differential speed scraping and spreading method. Using the differential speed scraping and spreading method to prepare the absorbent film can make the film density more uniform. Preferably, during the coating process, the coating speed of the coating roller is controlled to be less than or equal to 5 m / min, and the adjusting roller speed is greater than or equal to 3% of the coating speed. By increasing the roller rotation speed, the thickness and thickness uniformity of the film are further controlled. Preferably, the coating temperature is 70 - 80 °C, and the viscosity of the melt blended adhesive solution is less than or equal to 200000 cps at the coating temperature. Within the above parameter range, better dispersion of the absorbent can be achieved.

[0031] In another typical embodiment of the present application, a wave-absorbing prepreg is provided, which includes a resin matrix and a fiber material, and the resin matrix is cured from any of the above absorbent films.

[0032] The absorbent film of the present application is formed by using a low-viscosity resin material and a magnetic medium absorbent with a small particle size and surface modification. Even when the content of the magnetic medium material is relatively high, its uniform dispersion in the resin material is still ensured, ensuring the stable control of the electromagnetic parameters, areal density and thickness of the finally formed wave-absorbing prepreg.

[0033] Preferably, the weight ratio of the resin to the fiber material in the above resin matrix is 15-35:15-35, preferably 55-85:15-35. The prepreg within the above weight ratio range has good mechanical properties and wave absorption properties. The fiber materials used in this application include, but are not limited to, one or more of glass fiber, quartz fiber, and aramid fiber. Using the above fibers in combination with the adhesive film to form a wave-absorbing prepreg with high structural stability.

[0034] In another typical embodiment of this application, a preparation method of any of the above wave-absorbing prepregs is provided. The preparation method includes: preparing the wave-absorbing prepreg by hot pressing and impregnating the wave-absorbing adhesive film with the fiber material. Preferably, the impregnating temperature is 85-115°C, and the melt viscosity of the wave-absorbing adhesive film at the impregnating temperature is less than or equal to 50000 cps.

[0035] This application improves the raw materials and preparation method of the wave-absorbing adhesive film to obtain a wave-absorbing adhesive film with a high content and uniform dispersion of the magnetic medium type absorbent. Using this adhesive film to prepare the prepreg can ensure the stable control of the electromagnetic parameters, areal density, and thickness of the prepreg. Further, the impregnating temperature and the melt viscosity of the wave-absorbing adhesive film at the impregnating temperature are optimized to improve the performance of the prepreg.

[0036] The following exemplarily illustrates the preparation methods of the magnetic medium type absorbents coated with silica and phosphorus oxide in this application.

[0037] Preparation method of the magnetic medium type absorbent coated with phosphorus oxide: Take a certain amount of the magnetic medium absorbent body, weigh phosphoric acid, and prepare a mixed solution with an appropriate amount of acetone as the solvent and stir evenly. Add the magnetic medium absorbent body to make the liquid surface completely immerse the iron powder. Slowly stir and turn it for 15 minutes and then let it stand for 1 hour. Repeat 5 times, then transfer the container to a cool and ventilated place to air dry at room temperature for 48 hours, and then put the iron powder into a drying oven and dry it with forced air at 40°C for 8 hours. The thickness of the phosphorus oxide can be controlled by controlling the mass ratio of the magnetic medium absorbent body to phosphoric acid.

[0038] Preparation method of the magnetic medium type absorbent coated with silica: Prepared by atomic layer deposition. Put the taken magnetic medium absorbent body into the reaction kettle, introduce the required amino silane, and keep the temperature at 400°C for 10 minutes; after introducing nitrogen to remove all the amino silane, introduce the same molar amount of oxygen, and keep the temperature at 400°C for 10 minutes; introduce nitrogen to remove the remaining oxygen and reaction products, and complete one cycle to form a single layer of SiO 2 , and perform multiple cycle treatments according to the required coating thickness. The thickness of SiO 2 can be controlled by adjusting the dosage of amino silane.

[0039] The following further illustrates the beneficial effects of this application in combination with examples and comparative examples.

[0040] In the embodiments, the so-called double-sided impregnation means that a layer of wave-absorbing adhesive film, a layer of fiber material, and a layer of wave-absorbing adhesive film are stacked in this order, and then hot pressing impregnation is carried out.

[0041] In the embodiments, the so-called single-sided impregnation means that a layer of wave-absorbing adhesive film and a layer of fiber material are stacked in this order, and then hot pressing impregnation is carried out.

[0042] In the embodiments, the parts of each component are all parts by weight.

[0043] Example 1:

[0044] 1) Preparation of the blended adhesive solution: The carbonyl iron powder (coated with surface oxidized phosphorus, coating thickness: 40 nm, self-made) is screened by particle size before each addition to remove agglomerated particles ≥15 μm or other impurities. Using the mechanical melting blending method, 40 parts of the above carbonyl iron powder (as the magnetic absorber) are added to 15 parts of the molten hot-melt epoxy resin (model: YPH160, Kunshan Yubo Composite Materials Co., Ltd.) in 4 portions. The blending temperature is 75 °C, and the viscosity of the molten resin at this temperature is 8000 cps. Using a double planetary dispersion mixer, after stirring at a speed of 600 rpm for 50 min, a molten blended adhesive solution is obtained. Compressed air is introduced into the double planetary dispersion mixer, and the molten blended adhesive solution is extruded through the discharge port. The discharge port is a metal mesh with a diameter ≤30 cm, and the aperture of the metal mesh ≤30 μm to remove the agglomerated particles in the blended adhesive solution. During the discharging process, the planetary dispersion mixer continues to work, and the compressed air pressure is adjusted according to the viscosity of the adhesive solution so that the discharging time is 10 min.

[0045] 2) Preparation of the wave-absorbing adhesive film: The molten blended adhesive solution is added to a coater to prepare the wave-absorbing adhesive film, and the coating method is the differential scraping and spreading method. By controlling the gap between the coating roller and the adjusting roller, the coating speed, and the speed difference between the two rollers, the surface density of the adhesive film is adjusted. Among them, the coating speed is 3 m / min, and the speed of the adjusting roller > 3% of the coating roller speed. The coating temperature is 75 °C, and the viscosity of the blended adhesive solution at the coating temperature is 100000 cps. The average surface density of the adhesive film is 275 g / m 2 , the deviation of the adhesive film surface density is ±8 g / m 2 , the thickness is 0.135 mm, and the thickness error is ±0.01 mm.

[0046] 3) Preparation of the wave-absorbing prepreg: Using the double-sided impregnation method, 110 parts of the wave-absorbing adhesive film and 20 parts of glass fiber material are prepared into the wave-absorbing prepreg by hot pressing impregnation. Among them, the impregnation temperature is 95 °C, the viscosity of the blended adhesive solution at the impregnation temperature is 40000 cps, and the impregnation speed is 2 m / min. The average surface density of the obtained wave-absorbing prepreg is 650 g / m 2 , the density deviation is ±16 g / m 2 .

[0047] Example 2:

[0048] 1) Preparation of the blended adhesive solution: The ultrafine metal powder (coated with silica on the surface, with a coating thickness of 60 nm, self-made) is sieved by particle size before each addition to remove agglomerated particles or other impurities with a size ≥ 15 μm. Using the mechanical melting blending method, 70 parts of the above-mentioned ultrafine metal powder (as the magnetic absorber) are added to 35 parts of molten hot-melt epoxy resin (model: YPH160, Kunshan Yubo Composite Materials Co., Ltd.) in 4 portions. The blending temperature is 80 °C, and the viscosity of the molten resin at this temperature is 10,000 cps. Using a double planetary dispersion mixer, after stirring at 800 rpm for 40 min, a molten blended adhesive solution is obtained. Compressed air is introduced into the double planetary dispersion mixer, and the molten blended adhesive solution is extruded through the discharge port, where the discharge port is a metal mesh with a diameter ≤ 30 μm and a pore size of 50 μm to remove the agglomerated particles in the mixed adhesive solution. During the discharging process, the planetary dispersion mixer continues to work, and the compressed air pressure is adjusted according to the viscosity of the adhesive solution to make the discharging time 10 min.

[0049] 2) Preparation of the wave-absorbing adhesive film: The molten blended adhesive solution is added to a coater to prepare the wave-absorbing adhesive film, and the coating method is the differential scraping and spreading method. The surface density of the adhesive film is adjusted by controlling the gap between the coating roller and the adjustment roller, the coating speed, and the speed difference between the two rollers. Among them, the coating speed is 2 m / min, and the speed of the adjustment roller is > 3% of the coating roller speed. The coating temperature is 80 °C, and the viscosity of the blended adhesive solution at the coating temperature is 200,000 cps. The obtained adhesive film has a surface density of 300 g / m 2 , with a surface density deviation of ±8 g / m 2 , and a wave-absorbing adhesive film with a thickness of 0.15 mm and a thickness deviation of ±0.015 mm.

[0050] 3) Preparation of the wave-absorbing prepreg: Using the single-sided impregnation method, 105 parts of the wave-absorbing adhesive film and 35 parts of quartz fiber material are prepared into the wave-absorbing prepreg by hot pressing impregnation. Among them, the impregnation temperature is 115 °C, the viscosity of the blended adhesive solution at the impregnation temperature is 20,000 cps, and the impregnation speed is 2 m / min. When the surface density of the wave-absorbing prepreg is 400 g / m 2 , the surface density deviation of the wave-absorbing prepreg is ±12 g / m 2 .

[0051] Example 3:

[0052] 1) Preparation of the blended adhesive solution: The ferrite (coated with silica on the surface, coating thickness: 60 nm, self-made) was sieved by particle size before each addition to remove agglomerated particles ≥15 μm or other impurities. Using the mechanical melting blending method, 30 parts of the above ferrite (as the magnetic absorber) were added to 25 parts of the molten hot-melt epoxy resin (model: YPH160, Kunshan Yubo Composite Materials Co., Ltd.) in 4 portions. The blending temperature was 60 °C, and the viscosity of the molten resin at this temperature was 10,000 cps. Using a double planetary dispersion mixer, after stirring at a speed of 400 rpm for 60 min, a molten blended adhesive solution was obtained. Compressed air was introduced into the double planetary dispersion mixer, and the molten blended adhesive solution was extruded through the discharge port, where the discharge port was a metal mesh with a diameter of 50 cm and a pore size of ≤30 μm to remove the agglomerated particles in the mixed adhesive solution. During the discharging process, the planetary dispersion mixer continued to work, and the compressed air pressure was adjusted according to the viscosity of the adhesive solution to make the discharging time 8 min.

[0053] 2) Preparation of the wave-absorbing adhesive film: The molten blended adhesive solution was added to a coater to prepare the wave-absorbing adhesive film, and the coating method was the differential scraping and spreading method. The surface density of the adhesive film was adjusted by controlling the gap between the coating roller and the adjusting roller, the coating speed, and the speed difference between the two rollers. Among them, the coating speed was 5 m / min, and the speed of the adjusting roller was >3% of the coating roller speed. The coating temperature was 70 °C, and the viscosity of the blended adhesive solution at the coating temperature was 150,000 cps. The obtained adhesive film had a surface density of 366 g / m 2 , and the deviation of the surface density was ±10 g / m 2 , the thickness was 0.15 mm, and the thickness deviation was ±0.015 mm.

[0054] 3) Preparation of the wave-absorbing prepreg: Using the single-sided impregnation method, 55 parts of the wave-absorbing adhesive film and 15 parts of the aramid fiber material were prepared into the wave-absorbing prepreg by hot pressing impregnation. Among them, the impregnation temperature was 85 °C, the viscosity of the blended adhesive solution at the impregnation temperature was 40,000 cps, and the impregnation speed was 3 m / min. When the surface density of the wave-absorbing prepreg was 466 g / m 2 , the deviation of the surface density of the wave-absorbing prepreg was ±14 g / m 2 .

[0055] Example 4

[0056] 1) Preparation of the blended adhesive solution: The carbonyl iron powder (coated with silica on the surface, coating thickness 60 nm, self-made) is sieved by particle size before each addition process to remove agglomerated particles or other impurities with a size of ≥15 μm. Using the mechanical melt blending method, 50 parts of carbonyl iron powder with a particle size of 10 μm (as a magnetic absorbent, commercially available) are added to 20 parts of molten hot-melt epoxy resin (model: YPH160, Kunshan Yubo Composite Materials Co., Ltd.) in 4 portions. The blending temperature is 75 °C, and the viscosity of the molten resin at this temperature is 8000 cps. Using a double planetary dispersion mixer, after stirring at a speed of 600 rpm for 60 min, a molten blended adhesive solution is obtained. Compressed air is introduced into the double planetary dispersion mixer, and the molten blended adhesive solution is extruded through the discharge port, where the discharge port is a metal mesh with a diameter of 50 cm and the aperture of the metal mesh is ≤30 μm to remove the agglomerated particles in the mixed adhesive solution. During the discharging process, the planetary dispersion mixer continues to work, and the pressure of the compressed air is adjusted according to the viscosity of the adhesive solution so that the discharging time is 10 min.

[0057] 2) Preparation of the wave-absorbing adhesive film: The molten blended adhesive solution is added to a coater to prepare a wave-absorbing adhesive film, and the coating method is the differential scraping and spreading method. The areal density of the adhesive film is adjusted by controlling the gap between the coating roller and the adjusting roller, the coating speed, and the speed difference between the two rollers. Among them, the coating speed is 3 m / min, and the speed of the adjusting roller is >3% of the speed of the coating roller. The coating temperature is 75 °C, and the viscosity of the blended adhesive solution at the coating temperature is 80,000 cps. The obtained adhesive film has an average areal density of 233 g / m 2 , with an areal density deviation of ±6 g / m 2 , and is a wave-absorbing adhesive film with a thickness of 0.13 mm and a thickness deviation of ±0.01 mm.

[0058] 3) Preparation of the wave-absorbing prepreg: Using the double-sided impregnation method, 140 parts of the wave-absorbing adhesive film and 30 parts of quartz fiber material are prepared into a wave-absorbing prepreg by hot pressing impregnation. Among them, the impregnation temperature is 105 °C, the viscosity of the blended adhesive solution at the impregnation temperature is 30,000 cps, and the impregnation speed is 3 m / min. The average areal density of the wave-absorbing prepreg is 566 g / m 2 , with an areal density deviation of ±15 g / m 2 .

[0059] Example 5

[0060] The difference from Example 1 is that in 1), the amount of carbonyl iron powder is 30 parts and the amount of resin is 35 parts; in 2), the average areal density of the adhesive film prepared is 250 g / m 2 , with an areal density deviation of ±7 g / m 2 , and is a wave-absorbing adhesive film with a thickness of 0.135 mm and a thickness deviation of ±0.02 mm; in 3), the average areal density of the wave-absorbing prepreg prepared is 600 g / m 2 , with an areal density deviation of ±15 g / m2 。

[0061] Example 6

[0062] The differences from Example 1 are as follows: 1) The amount of hydroxyl iron powder is 70 parts, and the amount of resin is 15 parts; 2) The average surface density of the adhesive film prepared is 425 g / m 2 , and the surface density deviation is ±12 g / m 2 , and the thickness of the electromagnetic wave absorbing adhesive film is 0.18 mm with a thickness deviation of ±0.016 mm; 3) The average surface density of the electromagnetic wave absorbing prepreg prepared is 950 g / m 2 , and the surface density deviation is ±22 g / m 2 。

[0063] Example 7

[0064] The differences from Example 1 are as follows: 1) The coating layer of carbonyl iron powder is silica coating with a coating layer thickness of 60 nm; 2) The average surface density of the adhesive film prepared is 275 g / m 2 , and the surface density deviation is ±8 g / m 2 , and the thickness of the electromagnetic wave absorbing adhesive film is 0.135 mm with a thickness deviation of ±0.01 mm; 3) The average surface density of the electromagnetic wave absorbing prepreg prepared is 650 g / m 2 , and the surface density deviation is ±16 g / m 2 。

[0065] Example 8

[0066] The differences from Example 1 are as follows: 1) The hot-melt medium-temperature curing epoxy resin is changed to hot-melt epoxy resin (model: YPH160, Kunshan Yubo Composite Materials Co., Ltd.), the blending temperature is 80 °C, and the viscosity of the molten resin at this temperature is 10,000 cps; 2) The average surface density of the adhesive film prepared is 275 g / m2, the surface density deviation is ±8 g / m2, and the thickness of the electromagnetic wave absorbing adhesive film is 0.135 mm with a thickness deviation of ±0.011 mm; 3) The average surface density of the electromagnetic wave absorbing prepreg prepared is 650 g / m2, and the surface density deviation is ±18 g / m2.

[0067] Example 9

[0068] The differences from Example 1 are as follows: 1) The hot-melt medium-temperature curing epoxy resin is changed to hot-melt low-temperature curing epoxy resin (model: WP-B1261, Huibo New Materials Technology (Shanghai) Co., Ltd.), the blending temperature is 60 °C, and the viscosity of the molten resin at this temperature is 10,000 cps; 2) The average surface density of the adhesive film prepared is 275 g / m 2 , and the surface density deviation is ±7 g / m 2, an absorbing adhesive film with a thickness of 0.135 mm and a thickness deviation of ±0.011 mm; 3) the average areal density of the absorbing prepreg prepared from the absorbing prepreg is 650 g / m 2 , and the areal density deviation is ±18 g / m 2 .

[0069] Example 10

[0070] The difference from Example 1 is that: 1) the stirring speed in it is 400 rpm; 2) the average areal density of the adhesive film prepared from the adhesive film is 275 g / m 2 , and the areal density deviation is ±12 g / m 2 , an absorbing adhesive film with a thickness of 0.14 mm and a thickness deviation of ±0.015 mm; 3) the average areal density of the absorbing prepreg prepared from the absorbing prepreg is 650 g / m 2 , and the areal density deviation is ±21 g / m 2 .

[0071] Example 11

[0072] The difference from Example 1 is that: 1) the stirring speed in it is 800 rpm; 2) the average areal density of the adhesive film prepared from the adhesive film is 275 g / m 2 , and the areal density deviation is ±7 g / m 2 , an absorbing adhesive film with a thickness of 0.135 mm and a thickness deviation of ±0.009 mm; 3) the average areal density of the absorbing prepreg prepared from the absorbing prepreg is 650 g / m 2 , and the areal density deviation is ±14 g / m 2 .

[0073] Example 12

[0074] The difference from Example 1 is that: 1) the stirring speed in it is 200 rpm; 2) the average areal density of the adhesive film prepared from the adhesive film is 275 g / m 2 , and the areal density deviation is ±14 g / m 2 , an absorbing adhesive film with a thickness of 0.135 mm and a thickness deviation of 0.018 mm; 3) the average areal density of the absorbing prepreg prepared from the absorbing prepreg is 650 g / m 2 , and the areal density deviation is ±26 g / m 2 .

[0075] Example 13

[0076] The difference from Example 1 is that: 2) the aperture of the metal mesh in it is 40 μm; 2) the average areal density of the adhesive film prepared from the adhesive film is 275 g / m 2 , and the areal density deviation is ±13 g / m 2, the absorbent adhesive film with a thickness of 0.135 mm has a thickness deviation of ±0.017 mm; 3) The average areal density of the absorbent prepreg prepared from the absorbent prepreg is 650 g / m 2 , and the areal density deviation is ±27 g / m 2 .

[0077] Example 14

[0078] The difference from Example 1 is that 1) the discharging time in 1) is 20 min; 2) the average areal density of the adhesive film prepared from the adhesive film is 275 g / m 2 , and the areal density deviation is ±14 g / m 2 , the absorbent adhesive film with a thickness of 0.135 mm has a thickness deviation of ±0.018 mm; 3) The average areal density of the absorbent prepreg prepared from the absorbent prepreg is 650 g / m 2 , and the areal density deviation is ±24 g / m 2 .

[0079] Example 15

[0080] 1) Preparation of the blended adhesive liquid: Before each addition of carbonyl iron powder (coated with phosphorus oxide on the surface, coating thickness: 40 nm, self-made), particle size screening is carried out to remove agglomerated particles ≥15 μm or other impurities. Using the mechanical melting blending method, 40 parts of carbonyl iron powder with a particle size of 12 μm (as the magnetic absorbent) are added all at once to 15 parts of molten hot-melt medium-temperature curing epoxy resin. The blending temperature range is 75 °C, and the viscosity of the molten resin at this temperature is 8000 cps. Using a double planetary dispersion mixer, after stirring at a speed of 600 rpm for 50 min, a molten blended adhesive liquid is obtained. Compressed air is introduced into the double planetary dispersion mixer, and the molten blended adhesive liquid is extruded through the discharge port. The discharge port is a metal mesh with a diameter of 50 cm and a pore diameter of 30 μm to remove agglomerated particles in the blended adhesive liquid. During the discharging process, the planetary dispersion mixer continues to work, and the compressed air pressure is adjusted according to the viscosity of the adhesive liquid so that the discharging time is 10 min.

[0081] 2) Preparation of the absorbent adhesive film: The molten blended adhesive liquid is added to a coater to prepare the absorbent adhesive film, and the coating method is the differential scraping and spreading method. The areal density of the adhesive film is adjusted by controlling the gap between the coating roller and the adjusting roller, the coating speed, and the speed difference between the two rollers. The coating speed is 3 m / min, and the speed of the adjusting roller > 3% of the coating roller speed. The coating temperature is 75 °C, and the viscosity of the blended adhesive liquid at the coating temperature is 100000 cps. The average areal density of the adhesive film is 275 g / m 2 , and the areal density deviation of the adhesive film is ±18 g / m 2 , and the thickness is 0.135 mm, and the thickness error is ±0.028 mm.

[0082] 3) Preparation of microwave absorbing prepreg: By using the double-sided impregnation method, 110 parts of microwave absorbing adhesive film and 20 parts of glass fiber material are prepared into microwave absorbing prepreg through hot pressing impregnation. The impregnation temperature is 95°C, the viscosity of the blended adhesive liquid at the impregnation temperature is 40000 cps, and the impregnation speed is 2 m / min. The average surface density of the obtained microwave absorbing prepreg is 650 g / m 2 , and the density deviation is ±32 g / m 2 .

[0083] Comparative Example 1

[0084] 1) Preparation of blended adhesive liquid: By using the mechanical melting blending method, 40 parts of carbonyl iron powder with a particle size of 10 - 20 μm (used as magnetic absorber, coated with phosphorus oxide on the surface, coating thickness: 40 nm, self-made) are added to 15 parts of molten hot-melt medium-temperature curing epoxy resin in 4 times. The blending temperature range is 75°C, and the viscosity of the molten resin at this temperature is 8000 cps. Using a double planetary dispersion mixer, after stirring at a speed of 600 rpm for 50 min, a molten blended adhesive liquid is obtained. Compressed air is introduced into the double planetary dispersion mixer, and the molten blended adhesive liquid is extruded through the discharge port. The discharge port is a metal mesh with a diameter of 50 cm and a pore diameter of 30 μm to remove the agglomerated particles in the mixed adhesive liquid. During the discharging process, the planetary dispersion mixer continues to work, and the compressed air pressure is adjusted according to the viscosity of the adhesive liquid to make the discharging time 10 min.

[0085] 2) Preparation of microwave absorbing adhesive film: The molten blended adhesive liquid is added to a coater to prepare a microwave absorbing adhesive film, and the coating method is the differential scraping and spreading method. The surface density of the adhesive film is adjusted by controlling the gap between the coating roller and the adjusting roller, the coating speed, and the speed difference between the two rollers. The coating speed is 3 m / min, and the speed of the adjusting roller > 3% of the coating roller speed. The coating temperature is 75°C, and the viscosity of the blended adhesive liquid at the coating temperature is 100000 cps. The average surface density of the adhesive film is 275 g / m 2 , the deviation of the adhesive film surface density is ±20 g / m 2 , the thickness is 0.135 mm, and the thickness error is ±0.028 mm.

[0086] 3) Preparation of microwave absorbing prepreg: By using the double-sided impregnation method, 110 parts of microwave absorbing adhesive film and 20 parts of glass fiber material are prepared into microwave absorbing prepreg through hot pressing impregnation. The impregnation temperature is 95°C, the viscosity of the blended adhesive liquid at the impregnation temperature is 40000 cps, and the impregnation speed is 2 m / min. The average surface density of the obtained microwave absorbing prepreg is 650 g / m 2 , and the density deviation is ±32 g / m 2 .

[0087] Comparative Example 2

[0088] 1) Preparation of the blended adhesive solution: Before each addition of carbonyl iron powder, particle size screening is carried out to remove agglomerated particles ≥15μm or other impurities. Using the mechanical melting blending method, 40 parts of the above carbonyl iron powder (as a magnetic absorber, self-made) are added to 15 parts of molten hot-melt medium-temperature curing epoxy resin in 4 portions. The blending temperature range is 75°C, and the viscosity of the molten resin at this temperature is 8000 cps. Using a double planetary dispersion mixer, stir at 600 rpm for 50 min to obtain a molten blended adhesive solution. Compressed air is introduced into the double planetary dispersion mixer, and the molten blended adhesive solution is extruded through the discharge port. The discharge port is a metal mesh with a diameter of 50 cm and a pore size of 30μm to remove agglomerated particles in the mixed adhesive solution. During the discharging process, the planetary dispersion mixer continues to work, and the pressure of the compressed air is adjusted according to the viscosity of the adhesive solution to make the discharging time 10 min.

[0089] 2) Preparation of the wave-absorbing adhesive film: Add the molten blended adhesive solution into a coater to prepare the wave-absorbing adhesive film, and the coating method is the differential scraping and spreading method. Adjust the areal density of the adhesive film by controlling the gap between the coating roller and the adjusting roller, the coating speed, and the speed difference between the two rollers. The coating speed is 3 m / min, and the speed of the adjusting roller > 3% of the coating roller speed. The coating temperature is 75°C, and the viscosity of the blended adhesive solution at the coating temperature is 100000 cps. The average areal density of the adhesive film is 275 g / m 2 , and the deviation of the areal density of the adhesive film is ±18 g / m 2 , the thickness is 0.135 mm, and the thickness error is ±0.26 mm.

[0090] 3) Preparation of the wave-absorbing prepreg: Using the double-sided impregnation method, 110 parts of the wave-absorbing adhesive film and 20 parts of glass fiber material are prepared into the wave-absorbing prepreg by hot pressing impregnation. The impregnation temperature is 95°C, the viscosity of the blended adhesive solution at the impregnation temperature is 40000 cps, and the impregnation speed is 2 m / min. The average areal density of the obtained wave-absorbing prepreg is 650 g / m 2 , and the density deviation is ±29 g / m 2 .

[0091] Comparative Example 3

[0092] 1) Preparation of the blended adhesive solution: Before each addition of carbonyl iron powder (coated with phosphorus oxide on the surface, coating thickness: 40 nm, self-made), particle size screening was carried out to remove agglomerated particles ≥15 μm or other impurities. Using the mechanical melt blending method, 40 parts of carbonyl iron powder with a particle size of 12 μm (as the magnetic absorber) were added to 15 parts of molten bis-maleimide resin in 4 portions. The blending temperature range was 80 °C, and the viscosity of the molten resin at this temperature was 80,000 cps. Using a double planetary dispersion mixer, after stirring at 600 rpm for 50 min, a molten blended adhesive solution was obtained. Compressed air was introduced into the double planetary dispersion mixer, and the molten blended adhesive solution was extruded through the discharge port, where the discharge port was a metal mesh with a diameter of 50 cm and a pore size of 30 μm to remove agglomerated particles in the mixed adhesive solution. During the discharging process, the planetary dispersion mixer continued to work, and the pressure of the compressed air was adjusted according to the viscosity of the adhesive solution so that the discharging time was 10 min.

[0093] 2) Preparation of the microwave-absorbing adhesive film: The molten blended adhesive solution was added to a coater to prepare the microwave-absorbing adhesive film, and the coating method was the differential scraping and spreading method. The surface density of the adhesive film was adjusted by controlling the gap between the coating roller and the adjusting roller, the coating speed, and the speed difference between the two rollers. Among them, the coating speed was 3 m / min, and the speed of the adjusting roller was >3% of the speed of the coating roller. The coating temperature was 80 °C, and the viscosity of the blended adhesive solution at the coating temperature was 300,000 cps. The average surface density of the adhesive film was 650 g / m 2 , and the deviation of the surface density of the adhesive film was ±17 g / m 2 , the thickness was 0.135 mm, and the thickness error was ±0.027 mm.

[0094] 3) Preparation of the microwave-absorbing prepreg: Using the double-sided impregnation method, 110 parts of the microwave-absorbing adhesive film and 20 parts of glass fiber material were prepared into the microwave-absorbing prepreg by hot pressing impregnation. Among them, the impregnation temperature was 120 °C, the viscosity of the blended adhesive solution at the impregnation temperature was 50,000 cps, and the impregnation speed was 2 m / min. The average surface density of the obtained microwave-absorbing prepreg was 650 g / m 2 , and the density deviation was ±33 g / m 2 .

[0095] Performance testing

[0096] Electromagnetic parameter testing: The waveguide method was used to test the electromagnetic parameters. The microwave-absorbing prepregs prepared in each example and comparative example were cured with a [0 / 90] layup to obtain composites, and the electromagnetic parameters (real part (ε′) and imaginary part (ε") of the dielectric constant, real part (μ′) and imaginary part (μ″) of the magnetic permeability) in the L1 (1.13 GHz - 1.73 GHz), L (1.72 GHz - 2.61 GHz), and S (2.60 GHz - 3.95 GHz) bands were respectively tested.

[0097] Reflectivity simulation: According to the electromagnetic parameters in the L1, L, and S bands, the wave absorption performance of a composite material with a thickness of 2 mm was obtained through CST simulation.

[0098] Reflectivity test: The wave-absorbing prepregs prepared in each example and comparative example were laminated and cured to obtain a composite material with a thickness of 2 mm. The wave absorption performance of the composite material was tested with reference to the reflectivity test method for radar absorbing materials in GJB 2038A-2011. Among them, the sample size was 300*300 mm and the frequency was 1-4 GHz.

[0099] According to the electromagnetic parameters and single-layer thickness of the wave-absorbing prepreg in Example 1, the wave absorption performance (reflectivity) of the structural wave-absorbing material with a thickness of 2 mm in different bands was obtained through CST simulation. Then, the structural wave-absorbing material with a thickness of 2 mm was actually laminated and cured, and a flat plate reflectivity test was carried out. The results are shown in Figure 1 .. The particle size of the magnetic absorbent, the electromagnetic parameters of the prepreg, and the wave absorption performance of the structural wave-absorbing material with a thickness of 2 mm in each example were recorded in Table 1.

[0100] Table 1

[0101]

[0102]

[0103] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0104] In order to solve the problem of poor dispersion performance of the absorbent in the prior art, the present application has carried out targeted design on the key parameters of the resin material and the magnetic medium absorbent in the wave-absorbing adhesive film. First, the absorbent was surface-modified, coated with silicon or phosphide on its surface, so as to effectively control the particle agglomeration by using the surface groups; then, the particle size of the magnetic medium absorbent was controlled to be less than or equal to 15 μm, and the absorbent in this small particle size range could be better dispersed in the resin material. And because the magnetic medium absorbent has been modified, the absorbent has higher compatibility with the resin, further improving the dispersion of the absorbent in the resin. In addition, a resin material with a viscosity less than or equal to 10000 cps at 60-80 °C was selected to ensure good fluidity of the resin material and make the absorbent easier to disperse. To sum up, the present application has carried out targeted design on both the resin material and the magnetic medium absorbent in the wave-absorbing adhesive film. Even when the content of the magnetic medium material is relatively high and even serves as the main body of the composite material, the uniform dispersion of the magnetic medium material in the resin material is still ensured, and the electromagnetic parameters, areal density, and thickness of the finally formed wave-absorbing prepreg are ensured to be stable and controllable.

[0105] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An absorbing adhesive film, characterized in that, the weight ratio of the resin to the magnetic medium absorbent in the absorbing adhesive film is 15-35:30-70, wherein the particle size of the magnetic medium absorbent is less than or equal to 15 μm, the magnetic medium absorbent comprises a magnetic medium absorbent body and a surface modification layer, the surface modification layer is a silica coating layer or a phosphorus oxide coating layer, and the viscosity of the resin at 60-80 °C is less than or equal to 10,000 cps; the magnetic medium absorbent body is selected from one or more of ferrite, ultrafine metal powder, and carbonyl iron powder.

2. The absorbing adhesive film according to claim 1, characterized in that, the D50 particle size of the magnetic medium absorbent is less than or equal to 4 μm, the D90 particle size is less than or equal to 7 μm, and the D98 particle size is less than or equal to 10 μm.

3. The absorbing adhesive film according to claim 1, characterized in that, the resin is a hot-melt epoxy resin.

4. A method for preparing the absorbing adhesive film according to any one of claims 1 to 3, the preparation method comprises: Step S1, adding the magnetic medium absorbent into the molten resin and performing mechanical melt blending to obtain a melt-blended adhesive liquid; Step S2, using the melt-blended adhesive liquid to prepare an adhesive film.

5. The preparation method according to claim 4, characterized in that, in step S1, the magnetic medium absorbent is added to the molten resin in batches.

6. The preparation method according to claim 5, characterized in that, the magnetic medium absorbent is added to the molten resin 3-5 times.

7. The preparation method according to any one of claims 4 to 6, characterized in that, step S1 includes: adding the magnetic medium absorbent to the molten resin in batches and stirring with a double planetary dispersion mixer to form the melt-blended adhesive liquid; introducing compressed air into the double planetary dispersion mixer to extrude the melt-blended adhesive liquid, and a metal mesh is provided at the outlet of the extrusion, and the aperture of the metal mesh is less than or equal to 30 μm.

8. The preparation method according to claim 7, characterized in that, the stirring speed is 400-800 rpm and the time is 40-60 min; and / or, the extrusion time is less than or equal to 10 min; and / or, continuous stirring is performed during the extrusion process.

9. The preparation method according to any one of claims 4 to 6, characterized in that, step S2 includes: using the differential speed scraping method to coat the melt-blended adhesive liquid to form an absorbing adhesive film.

10. The preparation method according to claim 9, characterized in that, during the coating process, the coating speed of the coating roller is controlled to be less than or equal to 5 m / min, and the adjusting roller speed is greater than or equal to 3% of the coating speed; and / or, the coating temperature is 70-80 °C, and the viscosity of the melt-blended adhesive liquid at the coating temperature is less than or equal to 200,000 cps.

11. An absorbing prepreg, comprising a resin matrix and a fiber material, characterized in that, the resin matrix is cured from the absorbing adhesive film according to any one of claims 1 to 3.

12. The microwave absorbing prepreg according to claim 11, characterized in that, the weight ratio of the resin in the resin matrix to the fiber material is 15-140:15-35.

13. The microwave absorbing prepreg according to claim 12, characterized in that, the weight ratio of the resin in the resin matrix to the fiber material is 55-85:15-35.

14. The microwave absorbing prepreg according to claim 11, characterized in that, the fiber material is selected from one or more of glass fiber, quartz fiber, and aramid fiber.

15. A method for preparing the microwave absorbing prepreg according to any one of claims 11 to 14, characterized in that, the preparation method includes: obtaining the microwave absorbing prepreg by hot pressing and impregnating a microwave absorbing adhesive film and a fiber material.

16. The preparation method according to claim 15, characterized in that, the temperature of the hot pressing and impregnating is 85-115°C, and the melt viscosity of the microwave absorbing adhesive film at the temperature of the hot pressing and impregnating is less than or equal to 50000 cps.

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