CN114606794A - Paper-based material with electromagnetic characteristics distributed in transverse gradient manner and manufacturing method and application thereof - Google Patents

Abstract

The invention relates to a paper-based material with transverse gradient distribution of electromagnetic properties, a manufacturing method and application thereof. The paper base material comprises a plurality of gradient regions, wherein the gradient regions are arranged along the cross-web direction, any one gradient region in the gradient regions consists of 0.1-95 wt% of wave-absorbing fibers and 5-99.9 wt% of wave-transmitting fibers, and the contents of the wave-absorbing fibers or the wave-transmitting fibers in different gradient regions in the gradient regions are different. The paper-based material can regulate and control the electromagnetic characteristics of each area according to the electromagnetic performance requirement.

Description

Paper-based material with electromagnetic characteristics distributed in transverse gradient manner and manufacturing method and application thereof

Technical Field

The invention relates to the technical field of papermaking, in particular to a paper-based material with transverse gradient distribution of electromagnetic properties, a manufacturing method and application thereof.

Background

The high-performance paper-based composite material is special paper prepared from high-performance fibers by a papermaking wet forming technology, and has the characteristics of light weight and high strength. After being prepared into a large-rigidity secondary stress structural member, the composite material is widely applied to the fields of aerospace, rail transit and the like. The electromagnetic function paper-based composite material is one of high-performance paper-based composite materials, namely special paper prepared from electromagnetic function fibers. The electromagnetic function paper-based composite material with the structural design has the advantages of light weight, high strength and flexible design of electromagnetic performance, and can be widely applied to the fields of electromagnetic wave absorption and the like.

Functionally Graded Material (FGM) is a new type of heterogeneous composite material, which is an integrated material that varies continuously from one function (composition) to the other in time or space. The functional gradient material designed by electromagnetic parameter gradient can realize broadband electromagnetic wave absorption. For example, a honeycomb material with the mark of HC-10580 wave-absorbing, which is released by ARC company in America, is cut into a pointed cone shape by a physical method, so that the gradient design of electromagnetic parameters is realized, and the reflectivity is less than or equal to-10 dB within a frequency band of 2-18 GHz. The Laird company in the United states provides a mark RFHC wave-absorbing honeycomb, and realizes electromagnetic parameter gradient design by using a method of gradient dipping wave-absorbing slurry, wherein the reflectivity is less than or equal to-10 dB in a frequency band of 6.8GHz-18 GHz. Therefore, the electromagnetic parameter gradient design of the high-performance paper-based composite material is an important means for realizing the wave absorbing function of the high-performance paper-based composite material.

Chinese patent application CN110890555A relates to a method for preparing a diffusion layer with gradient hydrophilicity or hydrophobicity. The prepared carbon fiber paper is used as a substrate layer, and a gradient microporous layer MPL is prepared on the surface of the substrate layer, wherein the gradient mainly shows that the hydrophilic/hydrophobic gradient is horizontal and vertical. The patent application selects carbon fibers which are not carbonized/graphitized as a matrix to prepare carbon fiber paper, and the neutral energy effect of the carbon fiber paper prepared by using the carbon fibers as the matrix is basically the same as that of the carbon fiber paper with the same specification of Japan Dongli company. The transverse gradient filling material is filled according to a certain proportion. The filling material that this patent application used is more, and is consuming time long, and carbon fiber paper makes through the layering, and then comes the bonding to increase the complexity of technology through adding resin, and in addition, the interlayer bonding strength between the different layers is also lower, and the performance parameter of the carbon fiber paper of producing is unstable controllable. The transverse direction described in this patent refers to the thickness direction of the material and the manufacturing process is a batch-made composite. Unlike the way in which paper is made, continuously produced paper, due to the operation of the equipment, has fibers oriented in the direction of travel along the machine. The paper industry defines the direction along which the machine runs as the longitudinal direction, the direction perpendicular to the longitudinal direction, i.e. parallel to the guide rolls of the machine, as the transverse direction, also called the cross-web direction, and the paper is likewise a three-dimensional material, the cross-section of which is called the thickness direction. The carbon fiber paper of the patent is formed by mechanical mixing and compression molding, and is different from an industrial papermaking process. The patent only refers to gradient change in the thickness direction and the longitudinal direction of the material, and the layered manufacturing, the partition manufacturing, the complex process and the weak interlayer bonding force.

Chinese patent application CN110820423A relates to a glass fiber filter paper with a gradient structure and a preparation method and application thereof. In the production process, the water-soluble acrylic resin emulsion is applied by accurately controlling the first-aperture glass fiber filtering layer slurry and the second-aperture glass fiber filtering layer slurry, so that the coarse glass fiber layer and the fine glass fiber layer can well form two-layer gradient combination, the formed wet paper is not easy to fall off or layer, and the one-time production of the filter paper is realized. The patent application only realizes the gradient distribution in the thickness direction of the paper by blending the addition amount ratio of two types of coarse and fine fibers, and cannot realize the gradient distribution in the cross-web direction of the paper. The patent is only in the thickness direction of the paper and has no gradient change of the banner.

In summary, up to now, there is no technology that can realize both functional graduation and stable and controllable electromagnetic properties.

Disclosure of Invention

In order to overcome the defects of the prior art, the effects of functional graduating and stable and controllable electromagnetic properties are achieved at the same time. The invention provides a transverse gradient distribution paper base material with electromagnetic characteristics, a manufacturing method and application thereof, wherein the paper base material can realize functional gradient and stable and controllable electromagnetic characteristics. The method has simple process, can prepare the base paper with various electromagnetic parameters, and can flexibly allocate the electromagnetic parameters according to different material requirements.

The purpose of the invention is realized by adopting the following technical scheme.

In one aspect, the invention provides a transverse gradient distribution paper-based material with electromagnetic properties, which comprises a plurality of gradient regions, wherein the gradient regions are arranged along the cross-web direction, any one of the gradient regions consists of 0.1-95 wt% of wave-absorbing fibers and 5-99.9 wt% of wave-transmitting fibers, and the contents of the wave-absorbing fibers or the wave-transmitting fibers in different gradient regions in the gradient regions are different. The paper-based material can regulate and control the electromagnetic characteristics of each area according to the electromagnetic performance requirement.

Preferably, the wave-absorbing fibers are magnetic fibers, dielectric fibers, conductive fibers and the like with an electromagnetic wave loss function, and are selected from one or more of polycrystalline iron fibers, carbon fibers, silicon carbide fibers and basalt fibers; carbon fibers are preferred.

Preferably, the wave-transmitting fiber is an inorganic fiber with good wave-transmitting property, a high-performance synthetic fiber and pulp thereof, is selected from one or more of para-aramid fiber, para-aramid fibrid and meta-aramid fibrid, and is preferably meta-aramid fiber.

Preferably, the plurality of gradient regions is 2 to 15, preferably 15.

Preferably, the plurality of gradient regions are identical gradient regions.

Preferably, the content of the wave-absorbing fibers or wave-transmitting fibers between different gradient regions in the plurality of gradient regions is different, and the content makes the electromagnetic properties of the plurality of gradient regions in a gradient distribution along the cross-web direction (for example, the gradient distribution may be a gradient rise, and may also be a gradient fall).

In another aspect, the present invention provides a method for manufacturing a paper-based material having a transverse gradient distribution of electromagnetic properties, the method comprising the steps of:

(1) respectively preparing slurry suspensions of wave-absorbing fibers and wave-transmitting fibers;

(2) uniformly mixing the slurry suspension of the wave-absorbing fibers and the slurry suspension of the wave-transmitting fibers prepared in the step (1) by using a multistage mixing device, and feeding in a gradient distribution manner along the cross-web direction of a paper machine by using the multistage mixing device to form a plurality of gradient areas;

(3) forming the slurry on a net;

(4) squeezing and drying;

(5) and (6) calendaring and coiling.

Preferably, in the step (1), the wave-absorbing fiber is a magnetic fiber, a dielectric fiber, a conductive fiber and the like with electromagnetic wave loss function, and is selected from one or more of polycrystalline iron fiber, carbon fiber, silicon carbide fiber and basalt fiber; carbon fibers are preferred.

Preferably, in step (1), the wave-transparent fiber is an inorganic fiber with good wave-transparent property, a high-performance synthetic fiber and pulp thereof, and is selected from one or more of para-aramid fiber, para-aramid fibrid and meta-aramid fibrid, and is preferably meta-aramid fiber.

Preferably, in the step (1), the slurry suspension of the wave-absorbing fibers and the wave-transmitting fibers is obtained in a mechanical stirring device, the stirring time is 10-30 min, and the wave-absorbing fibers and the wave-transmitting fibers are uniformly dispersed in water through stirring.

Preferably, in the step (1), the concentration of the slurry suspension of the wave-absorbing fibers and the wave-transmitting fibers is 0.005-0.1% (w/v), and is preferably 0.01%.

Preferably, in the step (2), the multistage mixing device is composed of a plurality of mixing devices, each of which feeds each of the plurality of gradient zones, wherein each of the plurality of mixing devices includes a forming device; mixing the slurry pipe; a proportional valve; a wave-transparent fiber pulp pipe; a wave-absorbing fiber pulp pipe; the wave-transparent fiber pulp pipe is used for conveying the wave-transparent fiber pulp suspension to the forming device through the mixed pulp pipe; the wave-absorbing fiber pulp pipe is used for transmitting the wave-absorbing fiber pulp suspension to the forming device through the mixed pulp pipe; the mixed pulp pipe is used for receiving the wave-transmitting fiber pulp suspension liquid transmitted by the wave-transmitting fiber pulp pipe and the wave-absorbing fiber pulp suspension liquid transmitted by the wave-absorbing fiber pulp pipe, mixing the two suspensions and then transmitting the mixture to the forming device; the mixed pulp pipe, the wave-transmitting fiber pulp pipe and the wave-absorbing fiber pulp pipe are communicated at an angle of 120 degrees; the quantitative valve is arranged on the wave-transmitting fiber pulp pipe or the wave-absorbing fiber pulp pipe and is used for controlling the proportion between the wave-transmitting fiber pulp suspension and the wave-absorbing fiber pulp suspension; a necking is arranged on the mixed pulp pipe, the diameter of the pipeline at the necking is more than or equal to 10mm, preferably 12mm, and the ratio of the diameter of the pipeline at the necking to the diameter of the pipeline of the mixed pulp pipe is less than 0.5, preferably 0.3; the diameters of the mixed pulp pipe, the wave-transmitting fiber pulp pipe and the wave-absorbing fiber pulp pipe are 40 mm.

Preferably, in step (2), the multi-stage mixing device is used for feeding in a gradient distribution along the cross-machine direction to form a plurality of gradient regions.

Preferably, in step (2), the number of gradient regions is 2 to 15, preferably 15.

Preferably, in step (2), the plurality of gradient regions are identical gradient regions.

Preferably, in step (3), the slurry is passed through a wire after being mixed in a partition manner, usually by inclined wire, fourdrinier wire or cylinder wire forming, preferably inclined wire forming.

Preferably, in the step (4), the drying temperature is 90-120 ℃, and preferably 110 ℃.

Preferably, in the step (5), the calendering pressure is 50-400 KN/m, and is preferably 300 kN/m.

On the other hand, the invention provides a wave-absorbing sandwich which is prepared from the paper-based material; preferably, the wave-absorbing sandwich is a corrugated plate-shaped sandwich, a diamond-shaped sandwich, a regular hexagonal honeycomb sandwich or other special-shaped honeycomb sandwich;

preferably, the wave-absorbing sandwich method comprises the following steps:

(1) gluing, laminating, pressing and cutting the paper-based material to prepare a sandwich laminated block;

(2) stretching and shaping the sandwich laminated block prepared in the step (1) to prepare a sandwich block;

(3) impregnating the sandwich block prepared in the step (2) with resin and curing, wherein the resin is thermosetting or thermoplastic high molecular polymer, such as phenolic resin, epoxy resin, acrylic resin, polyimide resin and the like;

(4) and (4) slicing the sandwich block dipped and cured in the step (3) to obtain the wave-absorbing sandwich.

Compared with the prior art, the invention provides the transverse gradient distribution paper-based material with the electromagnetic property and the preparation method thereof, the transverse dielectric constant of the paper-based material obtained by the method is in gradient distribution, and the gradient is adjustable; the gradient is characterized in that the paper-based material transverse wave-absorbing fibers are distributed in a gradient manner according to the proportion of the total weight, and the gradient of the transverse dielectric constant is controlled by adjusting the proportion of the wave-absorbing fibers.

Specifically, the present invention has the following advantages:

(1) the manufacturing technology of the invention simplifies the manufacturing process of the wave-absorbing honeycomb structure material, does not need to use various papers with different electromagnetic properties to manufacture the wave-absorbing material, and greatly reduces the production energy consumption and time consumption of the wave-absorbing material;

(2) the paper-based material prepared by the invention has excellent transverse electromagnetic property of gradient distribution, and the reliability and stability of the wave-absorbing material are improved;

(3) the transverse electromagnetic property of the paper-based material manufactured by the invention is adjustable, and the paper-based material can be accurately controlled by a zone control technology, so that the production flexibility of the wave-absorbing material with different electromagnetic property requirements is improved.

Drawings

FIG. 1 is a process flow of a paper-based material made in accordance with the present invention;

FIG. 2 is a flow chart of the loading of the multistage mixing apparatus of the present invention, wherein 1 is a forming apparatus; 2 is a mixed slurry pipe; 3 is a proportional valve; 4 is a wave-transparent fiber pulp pipe; 5 is a wave-absorbing fiber pulp pipe;

FIG. 3 is a schematic view of a single mixing device in a multistage mixing device of the present invention, wherein, slurry A is a wave-absorbing fiber suspension, slurry B is a wave-transparent fiber suspension, slurry C is a mixed slurry, α is 120 °, β is 120 °, S is a constriction, d1 is the diameter of the constriction, d2 is the diameter of the mixed slurry pipe, and 3 is a proportional valve;

FIG. 4 is a structure of base paper;

FIG. 5 is a schematic diagram of the gradient distribution of the electromagnetic properties of the base paper in the transverse direction;

FIG. 6 is a process flow for preparing the wave-absorbing honeycomb;

FIG. 7 is a schematic diagram of a prepared gradient wave-absorbing honeycomb core material;

FIG. 8 is a comparative graph of the experimental effect of the mixing tube.

Detailed Description

The present invention will be further described with reference to the following examples. These examples are intended to help illustrate the content of the invention and not to limit the scope of the invention.

EXAMPLE 1 multistage mixing apparatus of the invention

As shown in fig. 2, the multistage mixing device of the present invention is composed of n mixing devices according to gradient requirements, each gradient region is controlled by a separate mixing device, as shown in fig. 3, wherein a slurry flow is wave-absorbing fiber suspension, a slurry flow is wave-transparent fiber suspension, a quantitative valve is provided for controlling the flow rate of the a slurry flow, and the device has the following design considerations for ensuring uniform mixing: the angle alpha is 120 deg., and the angle beta is 120 deg.. When the angle beta is zero degree, the flow rate of the C pulp flow is increased by increasing the A pulp flow, and when the angle beta is less than 90 degrees, the flow rate of the C pulp flow is reduced by increasing the A pulp flow, and the optimal design angle beta is 120 degrees. Since the mixing takes place immediately after the shaping of the upper wire, the homogeneity of the mixing must be taken into account, while at the same time ensuring a steady and uniform flow C of the mixed stock. In order to ensure the uniform mixing of the pulp, the optimal mixing can be obtained when the alpha angle is 120 degrees, and the random distribution of the wave-absorbing fibers in the final paper-based material can be ensured.

When the a-slurry flow is added to the main slurry flow, it is inevitable to cause cross-flow or large eddies when the flow rate or flow rate increases or decreases at one point in the headbox, which is disadvantageous and to be avoided. Therefore, when the flow rate of the slurry A is adjusted, the total flow rate is kept unchanged or slightly changed as much as possible, and the consistency of the concentrations of the slurry A and the slurry B is ensured during the preparation of the slurry. The ratio of the fluid resistance of the mixing zone into which the a slurry stream is fed to the resistance of the outlet after mixing will affect the consistency of the C slurry stream flow. The smaller the resistance ratio, the smaller the change in total flow. Therefore, in the design, a throttling opening is designed after the mixing device is considered, and the outlet resistance after mixing is increased. The S part of the invention is designed with a necking, and in order to prevent slurry hanging and the like, the arc of the necking is designed, and the manufacturing process is subjected to fine polishing treatment. Theoretically, the smaller the size of the constriction at this point, the better, but the size of the fibers in the fiber suspension and the fluid mechanical properties of the suspension need to be considered, so that the pulp blockage is prevented, and the large-scale turbulence caused by the too fast pulp speed is generated, so that the fibers are flocculated. The invention is optimally designed, the diameter of the pipeline at the necking part is more than or equal to 10mm, the ratio of d1/d2 at the necking part is less than 0.5, preferably, the d1 is 12mm, the d2 is 40mm, and the ratio of d1/d2 is 0.3.

The necking design increases the resistance coefficient after mixing, and when the A slurry flow adjusts the proportional valve 3, the flow rate of the mixed slurry flow C before and after adjustment is approximately equal, and the slurry flows are uniformly mixed.

Example 2

The meta-aramid fiber is used as wave-transmitting fiber, the carbon fiber is used as wave-absorbing fiber, 0.02 wt% of pulp suspension A (wave-transmitting fiber suspension) and 0.02 wt% of pulp suspension B (wave-absorbing fiber suspension) are prepared by using a mechanical stirring device, the proportion of the wave-transmitting fiber and the wave-absorbing fiber in each gradient area is controlled by a mixing device (shown in figure 2), 15 areas and 15 gradients are arranged in the embodiment, and the mass ratio of the wave-absorbing fiber in the areas 1-15 to the total fiber is 0.5%, 1%, 1.5%, 2%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5% and 8% in sequence. According to the preparation flow shown in figure 1, respectively pumping slurry A and slurry B to a mixing device, wherein the mixing device is shown in figure 2, 4 is a wave-transparent fiber slurry pipe and distributes slurry for a manifold, and the number of branch pipes and the gradient proportion are changed according to the gradient requirement of a product; and 5, wave-absorbing fiber pulp pipes are arranged, each fiber pulp pipe is provided with a proportional valve, and the proportion of wave-transmitting fibers and wave-absorbing fibers in each area is controlled by adjusting the proportion of the wave-absorbing fibers. The wave-absorbing fiber and the wave-transmitting fiber are mixed quantitatively in a subarea manner, then are formed by an inclined net, are squeezed, are dried at the temperature of 110 ℃, and are calendered under the linear pressure of 75KN/m to obtain the paper-based material, as shown in figure 4. The paper banner is 120mm, and is divided into 15 zones equally spaced in the banner direction, which are marked as zone 1, zone 2 … zone 15, and the central zone is zone 8, as shown in fig. 5.

The prepared paper base material with gradient change along the paper cross-web direction has relative dielectric constants of 1.2,1.5,1.8,2.0,2.2,2.5,2.8,3.0,3.5,4.0,4.5,5.0,5.5,6.0 and 6.5 from the 1 st zone to the 15 th zone, and the dielectric loss is as follows: 0.005,0.100,0.180,0.200,0.220,0.250,0.280,0.300,0.350,0.400,0.450,0.500,0.550,0.600,0.650.

The prepared paper-based material is processed into a honeycomb according to the process flow of fig. 6, the height direction H of the honeycomb shown in fig. 7 is the cross-web direction of the paper web, and in the honeycomb gradual change layer, the reflectivity can be less than-10 dB in the frequency range of 2-18GHz, wherein the reflectivity reaches the lowest value of-41.9 dB at the frequency of 7.1 GHz.

The wave-absorbing material is a material capable of absorbing electromagnetic waves or reducing the surface reflection of the electromagnetic waves as much as possible, thereby reducing the influence of the electromagnetic waves. The wave-absorbing stealth material develops towards the trend of light, thin, wide and strong, wherein light means light weight, thin means thin thickness, wide means wide frequency band and strong means high strength. The aramid fiber honeycomb material is a known light, thin and strong material, and the honeycomb prepared in the embodiment can meet the condition that the reflectivity is less than-10 dB in the frequency range of 2-18GHz in the honeycomb gradual change layer, wherein the reflectivity reaches the lowest value of-41.9 dB at the frequency of 7.1GHz, and the honeycomb embodies excellent broadband absorption characteristic.

Example 3

The method comprises the steps of respectively using para-aramid fibers as wave-transmitting fibers and carbon fibers as wave-absorbing fibers to prepare 0.01 wt% of slurry suspensions A (wave-transmitting fiber suspensions) and B (wave-absorbing fiber suspensions) by using a mechanical stirring device, wherein the proportion of the wave-transmitting fibers and the wave-absorbing fibers in each gradient area is controlled by a mixing device (shown in figure 2), the mass ratio of the wave-transmitting fibers to the wave-absorbing fibers in the 1-15 areas is 0.5%, 1%, 1.5%, 2%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5% and 8% in the embodiment. According to the preparation flow shown in figure 1, respectively pumping slurry A and slurry B to a mixing device, wherein the mixing device is shown in figure 2, 4 is a wave-transparent fiber slurry pipe and distributes slurry for a manifold, and the number of branch pipes and the gradient proportion are changed according to the gradient requirement of a product; and 5, wave-absorbing fiber pulp pipes are arranged, each fiber pulp pipe is provided with a proportional valve, and the proportion of wave-transmitting fibers and wave-absorbing fibers in each area is controlled by adjusting the proportion of the wave-absorbing fibers. The wave absorbing fiber and the wave transmitting fiber are mixed quantitatively in a subarea mode, then are formed by an inclined net, are pressed and dried at the temperature of 110 ℃, and then are calendered under the line pressure of 75KN/m to obtain the paper base material, as shown in figure 4. The paper banner is 120mm, and is divided into 15 zones equally spaced in the banner direction, which are marked as zone 1, zone 2 … zone 15, and the central zone is zone 8, as shown in fig. 5.

The prepared paper base material with gradient change along the paper cross-web direction has relative dielectric constants of 1.2,1.5,1.8,2.0,2.2,2.5,2.8,3.0,3.5,4.0,4.5,5.0,5.5,6.0 and 6.5 from the 1 st zone to the 15 th zone, and the dielectric loss is as follows: 0.005,0.100,0.180,0.200,0.220,0.250,0.280,0.300,0.350,0.400,0.450,0.500,0.550,0.600,0.650.

The prepared paper base material is processed into honeycomb according to the process flow of fig. 6, and the height direction H of the honeycomb is the cross-web direction of the paper web as shown in fig. 7.

The wave-absorbing material is a material capable of absorbing as much electromagnetic waves as possible, reflecting the electromagnetic waves as little as possible so as to reduce the influence of the electromagnetic waves, and the wave-absorbing stealth material is developed towards the trend of light, thin, wide and strong, the light refers to light weight, the thin refers to thin thickness, the wide refers to wide frequency band, and the strong refers to high strength. The aramid fiber honeycomb material is a known light and thin strong material, and the honeycomb prepared in the embodiment has the advantages that the reflectivity is less than-10 dB in the frequency range of 2-18GHz in the honeycomb gradual change layer, wherein the reflectivity reaches the lowest value of-41.9 dB at the frequency of 7.1GHz, and the honeycomb embodies excellent broadband absorption characteristic.

Example 4

In the embodiment, the mixing device of fig. 3 is adopted, the pipe diameter of d2 is fixed to be 40mm, and the result is shown in fig. 8 by comparing the change of the adjusting flow rate C with the opening degree of the valve 3 under different d1/d2 ratios. The flow of the curve I is the process demand flow, and the assumed target flow is 1; the curve (C) is d1/d2 equal to 0.3, and the flow rate (C) changes along with the change of the opening degree of the valve (3); the curve (C) is d1/d2 equal to 1, and the flow rate C changes along with the change of the opening degree of the valve 3. It can be shown from the figure that the constriction can reduce the influence of valve regulation on the total flow, and an excellent control effect of the mixed flow C is obtained.

Claims (10)

1. A transverse gradient distribution paper-based material with electromagnetic properties comprises a plurality of gradient regions, wherein the gradient regions are arranged along the cross-web direction, any one gradient region in the gradient regions consists of 0.1-95 wt% of wave-absorbing fibers and 5-99.9 wt% of wave-transmitting fibers, and the contents of the wave-absorbing fibers or the wave-transmitting fibers in different gradient regions in the gradient regions are different.

2. The paper-based material according to claim 1, wherein the wave-absorbing fibers are magnetic fibers, dielectric fibers, conductive fibers and the like having an electromagnetic wave loss function, and are selected from one or more of polycrystalline iron fibers, carbon fibers, silicon carbide fibers and basalt fibers; carbon fibers are preferred.

3. The paper-based material according to claim 1 or 2, wherein the wave-transparent fibers are inorganic fibers having good wave-transparency, high-performance synthetic fibers and pulp thereof, and are selected from one or more of para-aramid fibers, para-aramid fibrids and meta-aramid fibrids, and preferably meta-aramid fibers.

4. An electromagnetic properties transverse gradient distribution paper based material according to any of claims 1 to 3, wherein said plurality of gradient zones is 2-15, preferably 15;

preferably, the plurality of gradient regions are identical gradient regions;

preferably, the content of the wave-absorbing fibers or wave-transmitting fibers between different gradient regions in the plurality of gradient regions is different, and the content makes the electromagnetic properties of the plurality of gradient regions in a gradient distribution along the cross-web direction (for example, the gradient distribution may be a gradient rise, and may also be a gradient fall).

5. A method of manufacturing an electromagnetic properties transverse gradient profile paper based material as claimed in any one of claims 1 to 4, the method comprising the steps of:

(1) respectively preparing slurry suspensions of wave-absorbing fibers and wave-transmitting fibers;

(2) uniformly mixing the slurry suspension of the wave-absorbing fibers and the slurry suspension of the wave-transmitting fibers prepared in the step (1) by using a multistage mixing device, and feeding in a gradient distribution manner along the cross-web direction of a paper machine by using the multistage mixing device to form a plurality of gradient areas;

(3) forming the slurry on a net;

(4) squeezing and drying;

(5) and (6) calendaring and coiling.

6. The manufacturing method according to claim 5, wherein in the step (1), the wave-absorbing fiber is a magnetic fiber, a dielectric fiber, a conductive fiber or the like having an electromagnetic wave loss function, and is selected from one or more of a polycrystalline iron fiber, a carbon fiber, a silicon carbide fiber and a basalt fiber; preferably carbon fibers;

preferably, in the step (1), the wave-transparent fiber is inorganic fiber with good wave-transparent property, high-performance synthetic fiber and pulp thereof, is selected from one or more of para-aramid fiber, para-aramid fibrid and meta-aramid fibrid, and is preferably meta-aramid fiber;

preferably, in the step (1), the slurry suspension of the wave-absorbing fibers and the wave-transmitting fibers is obtained in a mechanical stirring device, the stirring time is 10-30 min, and the wave-absorbing fibers and the wave-transmitting fibers are uniformly dispersed in water through stirring;

preferably, in the step (1), the concentration of the slurry suspension of the wave-absorbing fibers and the wave-transmitting fibers is 0.005-0.1% (w/v), and is preferably 0.01%.

7. The manufacturing method according to any one of claims 4 to 6, wherein in step (2), the multistage mixing device is combined from a plurality of mixing devices, each of which feeds each of the plurality of gradient regions, wherein each of the plurality of mixing devices includes a forming device; mixing the slurry pipes; a proportional valve; a wave-transparent fiber pulp pipe; a wave-absorbing fiber pulp pipe; the wave-transparent fiber pulp pipe is used for conveying the wave-transparent fiber pulp suspension to the forming device through the mixed pulp pipe; the wave-absorbing fiber pulp pipe is used for transmitting the wave-absorbing fiber pulp suspension to the forming device through the mixed pulp pipe; the mixed pulp pipe is used for receiving the wave-transmitting fiber pulp suspension liquid transmitted by the wave-transmitting fiber pulp pipe and the wave-absorbing fiber pulp suspension liquid transmitted by the wave-absorbing fiber pulp pipe, mixing the two suspensions and then transmitting the mixture to the forming device; the mixed pulp pipe, the wave-transmitting fiber pulp pipe and the wave-absorbing fiber pulp pipe are communicated with each other at an angle of 120 degrees; the quantitative valve is arranged on the wave-transmitting fiber pulp pipe or the wave-absorbing fiber pulp pipe and is used for controlling the proportion between the wave-transmitting fiber pulp suspension and the wave-absorbing fiber pulp suspension; a necking is arranged on the mixed pulp pipe, the diameter of the pipeline at the necking is more than or equal to 10mm, preferably 12mm, and the ratio of the diameter of the pipeline at the necking to the diameter of the pipeline of the mixed pulp pipe is less than 0.5, preferably 0.3; the diameters of the mixed pulp pipe, the wave-transmitting fiber pulp pipe and the wave-absorbing fiber pulp pipe are 40 mm;

preferably, in step (2), the multi-stage mixing device is used for feeding in a gradient distribution along the cross-web direction of the paper machine so as to form a plurality of gradient areas;

preferably, in step (2), the number of gradient regions is 2 to 15, preferably 15;

preferably, in step (2), the plurality of gradient regions are identical gradient regions.

8. A method according to any one of claims 4 to 7, characterized in that in step (3) the slurry is passed on a wire after being mixed in sections, typically using wire, fourdrinier or cylinder forming, preferably wire forming.

9. The production method according to any one of claims 4 to 8, wherein in the step (4), the temperature of the drying is 90 to 120 ℃, preferably 110 ℃;

preferably, in the step (5), the calendering pressure is 50-400 KN/m, and is preferably 300 kN/m.

10. A wave absorbing sandwich made of the paper based material of any one of claims 1 to 4; preferably, the wave-absorbing sandwich is a corrugated plate-shaped sandwich, a diamond-shaped sandwich, a regular hexagonal honeycomb sandwich or other special-shaped honeycomb sandwich;

preferably, the wave-absorbing sandwich method comprises the following steps:

(1) gluing, laminating, pressing and cutting the electromagnetic characteristic transverse gradient distribution paper-based material according to any one of claims 1 to 4 to prepare a sandwich laminated block;

(2) stretching and shaping the sandwich laminated block prepared in the step (1) to prepare a sandwich block;

(3) impregnating resin into the sandwich block prepared in the step (2), and curing, wherein the resin is a thermosetting or thermoplastic high molecular polymer, such as phenolic resin, epoxy resin, acrylic resin, polyimide resin and the like;

(4) and (4) slicing the sandwich block dipped and cured in the step (3) to obtain the wave-absorbing sandwich.

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