A three-layer electromagnetic-property banner gradient-tunable paper-based material and a method of manufacturing the same

Abstract

The present application relates to a kind of three-layer electromagnetic characteristic banner gradient adjustable paper base material and its manufacturing method.The paper base material of the present application includes face layer, bottom layer and core layer sandwiched between the face layer and the bottom layer, wherein the face layer and the bottom layer are non-electromagnetic characteristic material, selected from synthetic fiber, synthetic pulp, inorganic fiber and cellulose fiber, the core layer is composed of 90-100% by mass of material with electromagnetic characteristics and 0-10% by mass of non-electromagnetic characteristic material, wherein the material with electromagnetic characteristics in the core layer is selected from magnetic fiber, conductive fiber, dielectric fiber and carbon material, and the non-electromagnetic characteristic material in the core layer is selected from synthetic fiber, synthetic pulp, inorganic fiber and cellulose fiber.The paper base material of the present application can overcome the problem that the electromagnetic characteristic material of the prior art is easy to fall off, the surface strength is insufficient, and the processing and manufacturing are affected;At the same time, the problem of low retention rate of electromagnetic characteristic material can be overcome, and waste is caused.

Description

Technical Field

[0001] This invention relates to the field of papermaking technology, specifically to a three-layer electromagnetic property horizontal gradient adjustable paper base material and its manufacturing method. Background Technology

[0002] High-performance paper-based materials are made from high-performance fibers using wet forming technology. They are lightweight and high-strength, and are widely used in aerospace, rail transportation, and other fields. Electromagnetic paper-based materials are a type of high-performance paper-based material, made using fibers, powders, fillers, coatings, etc., with electromagnetic properties. Structurally designed electromagnetic paper-based materials offer advantages such as lightweight, high strength, and flexible electromagnetic property design, and can be used in fields such as electromagnetic wave absorption.

[0003] Electromagnetic property materials can be broadly classified into two categories: coating-type and structural-type. Structural-type materials, such as honeycomb structure electromagnetic property materials, can impart electromagnetic properties and also serve as load-bearing components. Traditional electromagnetic property honeycomb materials primarily consist of a honeycomb structure impregnated with an electromagnetic property coating. The electromagnetic properties mainly originate from the surface of the honeycomb structure. However, the surface electromagnetic property coating is easily affected by environmental temperature, humidity, and physical vibrations, making it prone to cracking and peeling, thus limiting its service life and affecting the electromagnetic performance of the honeycomb material.

[0004] Functionally graded materials (FJCTs) are a novel type of non-uniform composite material, characterized by a continuous change in function over time or space. FJCTs with gradient electromagnetic parameter design can achieve broadband electromagnetic wave absorption. For example, ARC Pharma in the US uses physical methods to cut honeycomb materials into pointed cone shapes to achieve gradient electromagnetic parameter design, resulting in a reflectivity ≤-10dB in the 2–18 GHz frequency band. Laird Pharma in the US uses a gradient impregnation method with electromagnetic property coatings to achieve gradient electromagnetic parameter design, achieving a reflectivity ≤-10dB in the 6.8 GHz–18 GHz frequency band. High-performance paper-based materials, during wet forming, have their electromagnetic properties gradient-designed along the horizontal direction of the paper web. This paper-based material is then used in honeycomb fabrication. This technique greatly enriches the design methods for honeycomb electromagnetic properties, achieving excellent electromagnetic characteristics and avoiding the shortcomings of impregnated electromagnetic property honeycombs.

[0005] Chinese patent application CN110820423A relates to a gradient-structured glass fiber filter paper, its preparation method, and its application. During production, by precisely controlling the difference between the first and second slurry layers, the gradient of the two layers is achieved through a water-soluble acrylic resin emulsion, enabling the one-time production of two-layer gradient filter paper. However, this patent application only achieves a gradient distribution in the paper's thickness direction, and cannot achieve a gradient distribution in the paper's horizontal direction.

[0006] Chinese patent application CN110890555A relates to a method for preparing a gradient hydrophilic or hydrophobic diffusion layer. Using prepared carbon fiber paper as the matrix layer, a gradient microporous layer (MPL) is prepared on its surface. The gradient is mainly manifested in the hydrophilic / hydrophobic gradient in the transverse and longitudinal directions. The transverse direction described in this patent refers to the thickness direction of the material, although a longitudinal gradient of the paper web is also achieved. However, this patent application uses a large amount of filler, is time-consuming, and involves intermittent layering and bonding with resin, making the process extremely complex. It belongs to the field of proton exchange membrane fuel cell component processing technology, which differs from the mechanism of paper-based materials. In the papermaking industry, the direction along the paper machine's running direction is defined as the longitudinal direction of the paper web, and the direction perpendicular to the longitudinal direction, i.e., parallel to the paper machine guide rollers, is defined as the transverse direction of the paper web. Paper-based materials are three-dimensional materials, and their cross-section is called the thickness direction. The carbon fiber paper in this patent is produced through mechanical mixing and molding, unlike the industrial papermaking process.

[0007] Chinese invention patent CN104404814B discloses a microwave absorbing paper, its preparation method, and its application. This invention involves mixing a fibrous microwave absorbing agent with microwave-transparent fibers and then processing the mixture into a paper with microwave-absorbing properties. This microwave-absorbing paper is then used as a grid material to form a microwave-absorbing core. The microwave-absorbing cores, made from microwave-absorbing papers with varying fibrous microwave absorbing agent contents, are separated by a microwave-transparent layer. Finally, the entire structure is impregnated and cured to obtain the microwave-absorbing material. The microwave-absorbing paper prepared by this invention does not possess gradient electromagnetic properties. Gradient microwave-absorbing core materials are prepared by stacking multiple honeycomb cores, resulting in a complex process. In the single-layer paper-based material prepared by this patent, the microwave-absorbing raw materials are located on the outer surface of the paper, making them prone to detachment during processing and affecting the processing and the environment. When microwave-absorbing and microwave-transparent raw materials are mixed and processed, such as when using micro / nano electromagnetic materials like carbon nanotubes and graphene, the retention of these micro / nano electromagnetic materials during papermaking is difficult to control, leading to the loss and waste of high-cost raw materials.

[0008] Chinese patent application CN114606794A discloses a paper-based material with a transverse gradient distribution of electromagnetic properties, its manufacturing method, and its application. However, this invention prepares a single-layer paper-based material. The electromagnetic property material and the non-electromagnetic property material are mixed through pipelines to achieve the material preparation. The electromagnetic property material still exists on the surface of the paper-based material, which can lead to the problem of shedding. Furthermore, the retention rate is low during the production of micro- and nano-electromagnetic property materials. The patent uses a pipeline mixing method to control the electromagnetic properties of the region. When the amount of electromagnetic property material added is extremely small, it is difficult to accurately measure it in engineering.

[0009] In summary, to date, no technology has achieved both adjustable gradient of the horizontal electromagnetic properties of paper-based materials and a three-layer structure for horizontal gradient electromagnetic properties in paper machine materials. Furthermore, there is currently no technology to achieve a "sandwich" structure for electromagnetically graded paper-based materials, with the core layer being an electromagnetically graded material layer; current technologies still suffer from issues such as electromagnetically graded material shedding and low retention rates. Summary of the Invention

[0010] To overcome the shortcomings of the prior art, this invention proposes a three-layer electromagnetic property horizontal gradient adjustable paper-based material, such as... Figure 2 As shown, the paper-based material consists of a surface layer, a core layer, and a bottom layer along its thickness direction. The surface and bottom layers are non-electromagnetic materials, including but not limited to aramid fibers, aramid pulp, PBO fibers, aramid III pulp, aramid III fibers, polyester fibers, hemp pulp, and wood pulp. The core layer is primarily composed of an electromagnetically variable material with adjustable gradients along the paper's width, including but not limited to carbon fibers, carbon nanotubes, graphene, metal fibers, and magnetic powder. This paper-based material overcomes the problems of existing technologies, such as the easy shedding of electromagnetically variable materials and insufficient surface strength of the paper-based material, which affect the processing of honeycomb core materials. It also overcomes the problem of low retention of electromagnetically variable materials during the wet forming process of gradient paper-based materials in existing technologies, resulting in waste of these materials.

[0011] The objective of this invention is achieved through the following technical solution.

[0012] On one hand, the present invention provides a three-layer electromagnetic property horizontal gradient adjustable paper-based material, the paper-based material comprising a surface layer, a bottom layer and a core layer sandwiched between the surface layer and the bottom layer, wherein the surface layer and the bottom layer are non-electromagnetic materials selected from synthetic fibers, synthetic pulp, inorganic fibers and cellulose fibers, the core layer is composed of 90-100% by mass of an electromagnetic material and 0-10% by mass of a non-electromagnetic material, wherein the electromagnetic material in the core layer is selected from magnetic fibers, conductive fibers, dielectric fibers and carbon materials, and the non-electromagnetic material in the core layer is selected from synthetic fibers, synthetic pulp, inorganic fibers and cellulose fibers.

[0013] Preferably, the materials of the surface layer and the bottom layer are selected from one or more of aramid fiber, aramid pulp, poly(p-phenylenebenzodioxazole) fiber, aramid III pulp, aramid III fiber, polyester fiber, cotton fiber, wood fiber, hemp fiber, glass fiber, quartz fiber, Tencel, viscose fiber, nylon fiber and polyvinyl alcohol fiber, and are more preferably aramid III pulp, aramid III fiber, meta-aramid pulp or meta-aramid chopped fiber;

[0014] Preferably, the materials of the top layer and the bottom layer are 50% by weight aramid fiber and 50% by weight aramid pulp, or 50% by weight meta-aramid pulp and 50% by weight chopped meta-aramid fiber.

[0015] Preferably, the quantitative range of the top layer and the bottom layer is 10-60 g / m², and more preferably 20-30 g / m².

[0016] That is, the materials of the top layer and the bottom layer in this application can be the same.

[0017] Preferably, the material with electromagnetic properties in the core layer is selected from one or more of carbon fiber, metal fiber, carbon nanotube, graphene, magnetic powder, etc., and is more preferably selected from carbon fiber and carbon nanotube.

[0018] Preferably, the non-electromagnetic material in the core layer is selected from one or more of aramid fiber, aramid pulp, poly(p-phenylenebenzodioxazole) fiber, aramid III pulp, aramid III fiber, polyester fiber, cotton fiber, wood fiber, hemp fiber, glass fiber, quartz fiber, Tencel, viscose fiber, nylon fiber and polyvinyl alcohol fiber, and is more preferably selected from aramid fiber and aramid pulp.

[0019] Preferably, the quantitative range of the core layer is 0.1-10 g / m², and more preferably 0.1-2 g / m².

[0020] In one specific embodiment, the present invention provides a three-layer electromagnetic property horizontal gradient adjustable paper-based material, comprising a face layer, a bottom layer, and a core layer sandwiched between the face layer and the bottom layer. The face layer and the bottom layer are made of the same material, consisting of 50% aramid fiber and 50% aramid pulp by weight. The core layer is made of 50% carbon fiber and 50% meta-aramid pulp by weight. The basis weight of the face layer and the bottom layer ranges from 20-22 g / m². The basis weight of the core layer ranges from 0.5-2 g / m².

[0021] On the other hand, the present invention provides a method for manufacturing the above-mentioned three-layer electromagnetic property horizontal gradient adjustable paper-based material, the process flow of which is as follows: Figure 1 and 3 As shown, the method includes the following steps:

[0022] (1) Prepare slurry suspensions for the bottom layer, core layer and surface layer respectively;

[0023] (2) The pulp suspensions of the bottom layer, core layer, and top layer prepared in step (1) are diluted by rinsing and then pumped to the distributor for distribution along the horizontal direction of the paper machine. The distribution system includes a top layer conical distributor 1 for distributing the top layer, a core layer conical distributor 2 for distributing the core layer, and a bottom layer conical distributor 3 for distributing the bottom layer. The core layer conical distributor 2 is equipped with a clear water conical distributor 4. The core layer is divided into multiple regions, such as... Figure 4 As shown, each area is equipped with a clean water regulating valve for controlling the clean water flow rate. During slurry application, the surface layer conical slurry distributor 1, the core layer conical slurry distributor 2, and the bottom layer conical slurry distributor 3 are applied simultaneously. The clean water flow rate is adjusted by the clean water regulating valve, causing the clean water conical slurry distributor 4 to release different amounts of clean water to adjust the concentration of the slurry suspension in each area of ​​the core layer, thereby adjusting the electromagnetic properties of each area of ​​the horizontal band. After slurry application, a headbox 5 is used to ensure uniform slurry dispersion. In this invention, each area is adjustable; each area can be different or the same.

[0024] (3) The three layers of pulp are wired onto the wire (i.e., the upper dewatering wire section 6), dewatered, and shaped (to obtain a wet paper web);

[0025] (4) Pressing and drying;

[0026] (5) Hot pressing

[0027] (6) Roll up.

[0028] Preferably, in step (2), the region is either equally divided or non-equally divided, with equally divided regions being preferred. The width of each region is 5–100 mm, more preferably 5–20 mm. The number of regions is selected according to the product requirements.

[0029] Preferably, in step (2), the opening degree of the water regulating valve is 0-100% (this opening degree refers to the valve opening position; 0 means fully closed, and 100% means fully open), preferably 40-80%. By adjusting the opening degree of the water valve, the electromagnetic characteristics of each region can be adjusted.

[0030] Preferably, in step (3), after the three layers of slurry are laid on the web, the dewatering screen is usually made of a slanted screen, a long screen, a clamped screen or a round screen, preferably a long screen.

[0031] Preferably, in step (4), the initial drying temperature is 70-90°C, more preferably 80°C; the middle and later drying temperatures are 110-140°C, more preferably 130°C.

[0032] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0033] (1) This invention provides a three-layer electromagnetic property horizontal gradient adjustable paper-based material and its manufacturing method. The paper-based material obtained by this method has a three-layer "sandwich" structure, with the core layer being an electromagnetic property layer. By adjusting the water flow rate in each region of the core layer, the gradient distribution of the electromagnetic property material in the core layer can be achieved.

[0034] (2) The manufacturing method of the present invention is to form in one step and prepare electromagnetic gradient paper-based materials in batches, which makes it convenient to flexibly adjust the preparation of the required gradient electromagnetic paper-based materials according to the needs of the gradient electromagnetic honeycomb structure materials.

[0035] (3) This invention not only realizes the online adjustment of the horizontal electromagnetic properties of paper-based materials, but also realizes the designable “sandwich” structure of the paper thickness direction (TD) structure, thus realizing the convenient adjustment and design of the three-dimensional structure of the electromagnetic properties of paper-based materials;

[0036] (4) The horizontal gradient electromagnetic property paper-based material of the present invention is achieved by adjusting the water flow rate of the core layer, which is convenient, quick, has high control precision, and a wide adjustment range.

[0037] (5) The core layer of the electromagnetic property paper-based material of the present invention is an electromagnetic property material. The electromagnetic property material has a high retention rate during the manufacturing process, which reduces the waste of electromagnetic property material and saves costs.

[0038] (6) The electromagnetic property paper-based material of the present invention has the electromagnetic property material in the core layer. During post-processing, transportation, storage and use, there is no problem of electromagnetic property material falling off, which affects the processing, and the working environment for material processing and manufacturing is improved.

[0039] (7) The present invention can realize the manufacturing of ultra-low quantitative electromagnetic characteristic core layers and use them for the preparation of functional structural components.

[0040] (8) The present invention overcomes the problems of electromagnetic property materials being easy to fall off and insufficient surface strength of electromagnetic property paper-based materials in the original technology, which affect the processing and manufacturing of honeycomb core materials; it also overcomes the problem of low retention rate of electromagnetic property materials in the wet forming process of gradient paper-based materials in the original technology, which causes waste of electromagnetic property materials. Attached Figure Description

[0041] Figure 1 This is a process flow diagram of the paper-based material of the present invention;

[0042] Figure 2 This is a schematic diagram of the cross-sectional structure of the paper-based material of the present invention;

[0043] Figure 3 This is a schematic diagram of the vertical surface of the paper-based material wet forming preparation of the present invention, wherein 1 is the surface layer conical pulp distributor, 2 is the core layer conical pulp distributor, 3 is the bottom layer conical pulp distributor, 4 is the core layer clear water conical pulp distributor, 5 is the headbox, 6 is the dewatering wire section, and 7 is the wet paper web;

[0044] Figure 4 This is a top view schematic diagram of the cross-sectional profile of the electromagnetic property gradient control of the core layer of the paper-based material of the present invention, wherein V1, V2, V3...V n The water regulating valves for each zone have corresponding paper-based material gradient regions A1, A2, A3...A n . Detailed Implementation

[0045] The present invention will be further described below with reference to embodiments. These embodiments are intended to help illustrate the content of the present invention and not to limit the scope of the present invention.

[0046] Example 1: A method for manufacturing the electromagnetically variable horizontal gradient paper-based material of the present invention, the process flow of which is as follows: Figure 1 and Figure 3 As shown, the method includes the following steps:

[0047] (1) Prepare slurry suspensions for the bottom layer, core layer and surface layer respectively;

[0048] (2) The pulp suspensions of the bottom layer, core layer, and top layer prepared in step (1) are distributed along the horizontal direction of the paper machine using a pulp distribution system. The pulp distribution system includes a top layer conical distributor 1 for distributing the top layer pulp, a core layer conical distributor 2 for distributing the core layer pulp, and a bottom layer conical distributor 3 for distributing the bottom layer pulp. The core layer conical distributor 2 is equipped with a clear water conical distributor 4, and a clear water regulating valve for controlling the clear water flow rate, such as... Figure 4 As shown, the core layers are A1, A2, A3...A 10 There are 10 zones in total, each equally divided and 15mm wide. Each zone is equipped with a conical distributor for the core layer, and each conical distributor outlet has multiple branch pipes equipped with a clean water regulating valve to control the clean water flow rate, i.e., V1, V2, V3…V… 10 During slurry application, surface conical slurry distributor 1, core conical slurry distributor 2, and bottom conical slurry distributor 3 are applied simultaneously. The flow rate of clean water is adjusted by regulating valves, so that different amounts of clean water are added to different areas of the clean water conical slurry distributor 4 to adjust the concentration of the core slurry suspension, thereby adjusting the electromagnetic properties of each area of ​​the horizontal band. After slurry application, a headbox 5 is used to ensure that the slurry is evenly dispersed.

[0049] (3) The three layers of pulp are wired onto the wire (i.e., the upper dewatering wire section 6), dewatered, and shaped (to obtain a wet paper web);

[0050] (4) Pressing and drying;

[0051] (5) Hot pressing

[0052] (6) Roll up.

[0053] In step (2), the opening degree of the water regulating valve V1 is 10%, the opening degree of V2 is 20%, the opening degree of V3 is 30%, the opening degree of V4 is 40%, the opening degree of V5 is 50%, the opening degree of V6 is 60%, the opening degree of V7 is 70%, the opening degree of V8 is 80%, the opening degree of V9 is 90%, and the opening degree of V10 is 100%. By adjusting the opening degree of the above water valves, different electromagnetic characteristics of each area are obtained.

[0054] In step (3), after the three layers of slurry are put into the web, the dewatering web is a long web.

[0055] In step (4), the initial drying temperature is 80°C; the middle and final drying temperatures are 130°C.

[0056] A schematic diagram of the cross-section of the paper-based material obtained from papermaking is shown below. Figure 2 As shown.

[0057] Example 2

[0058] The flow rates of the top, core, and bottom layers of pulp are controlled according to the machine speed and basis weight requirements. The top layer raw materials consist of 50% aramid III pulp and 50% aramid III fiber, with a basis weight of 20 g / m². The bottom layer raw materials also consist of 50% aramid III pulp and 50% aramid III fiber, with a basis weight of 20 g / m². The core layer raw material is carbon nanotubes. In this embodiment, three adjacent zones are controlled, each with a width of 15 mm, resulting in a 45 mm wide gradient electromagnetic property material. By testing the electromagnetic properties of the finished paper in each zone and adjusting the opening of the clear water valve, the on-grid formation concentration of carbon nanotubes is controlled. The real parts of the equivalent dielectric constants (10 GHz) for zones 1, 2, and 3 are 20, 80, and 150, respectively, with a real part fluctuation (cv) of ≤20% for each zone; the dielectric losses (10 GHz) are 1.8, 2.0, and 2.6, respectively, with a dielectric loss fluctuation (cv) of ≤20% for each zone. The retention rate of carbon nanotubes in the core layer is 80%, and the surface strength of paper and paperboard is measured (wax rod method) at 20A.

[0059] During the papermaking process, by adjusting the dilution water flow rate in each zone, multiple sets of paper-based materials with varying electromagnetic properties are prepared. In the honeycomb cutting process, three zones with the above-mentioned gradient electromagnetic properties are cut into one honeycomb, resulting in a honeycomb with three gradient electromagnetic properties in the height direction and a honeycomb density of 32 kg / m³. 3 Cellular reflectivity is less than -12dB in the 2-18GHz frequency range and less than -20dB in the 8-12GHz frequency range.

[0060] Example 3

[0061] The flow rates of the top, core, and bottom layers of pulp are controlled according to the machine speed and quantitative requirements. The top layer raw materials consist of 50% aramid III pulp and 50% aramid III fiber, with a basis weight of 20 g / m². The bottom layer raw materials also consist of 50% aramid III pulp and 50% aramid III fiber, with a basis weight of 20 g / m². The core layer raw material is carbon fiber. In this embodiment, three adjacent zones are controlled, each with a width of 15 mm, resulting in a 45 mm wide gradient electromagnetic property material. The opening of the clear water valve is adjusted by testing the electromagnetic properties of the finished paper in each zone to control the on-grid forming concentration of the carbon fiber. The equivalent dielectric constants (10 GHz) of the first, second, and third zones are 20, 80, and 150 respectively, with a real part fluctuation (cv) of ≤20% for each zone; the dielectric losses (10 GHz) are 0.6, 0.8, and 1.2 respectively, with a dielectric loss fluctuation (cv) of ≤20% for each zone. The retention rate of carbon fiber in the core layer is 99%, and the surface strength of paper and paperboard (wax rod method) is 20A.

[0062] During the papermaking process, by adjusting the dilution water flow rate in each zone, multiple sets of paper-based materials with varying electromagnetic properties are prepared. In the honeycomb cutting process, three zones with the above-mentioned gradient electromagnetic properties are cut into one honeycomb, resulting in a honeycomb with three gradient electromagnetic properties in the height direction and a honeycomb density of 32 kg / m³. 3 Cellular reflectivity is less than -12dB in the 2-18GHz frequency range and less than -20dB in the 8-12GHz frequency range.

[0063] Example 4

[0064] The flow rates of the top, core, and bottom layers of pulp are controlled according to the machine speed and basis weight requirements. The top layer raw materials consist of 50% aramid III pulp and 50% aramid III fiber, with a basis weight of 20 g / m². The bottom layer raw materials also consist of 50% aramid III pulp and 50% aramid III fiber, with a basis weight of 20 g / m². The core layer raw material is magnetic powder. In this embodiment, three adjacent zones are controlled, each with a width of 15 mm, resulting in a 45 mm wide gradient electromagnetic property material. The opening of the clear water valve is adjusted by testing the electromagnetic properties of the finished paper in each zone to control the on-grid forming concentration of the magnetic material. The permeability (1 GHz) of zones 1, 2, and 3 are 1.8, 2.3, and 3.8 respectively, with a permeability cv value ≤ 20% for each zone. The retention rate of the core layer magnetic material is 80%, and the surface strength of the paper and paperboard is measured (wax rod method) at 20A.

[0065] During the papermaking process, multiple sets of electromagnetic property paper base materials with varying gradients are prepared by adjusting the dilution water flow rate of each zone. In the honeycomb cutting process, three zones with the above gradient electromagnetic properties are cut into one honeycomb to obtain a honeycomb with three gradient electromagnetic properties in the height direction.

[0066] Example 5

[0067] The flow rates of the top, core, and bottom layers of pulp are controlled according to the machine speed and quantitative requirements. The top layer raw material consists of 50% meta-aramid pulp and 50% meta-aramid chopped fibers, with a basis weight of 20 g / m². The bottom layer raw material also consists of 50% meta-aramid pulp and 50% meta-aramid fibers, with a basis weight of 20 g / m². The core layer raw material is carbon fiber. In this embodiment, three adjacent zones are controlled, each with a width of 15 mm, to obtain a 45 mm wide gradient electromagnetic property material. The opening of the clear water valve is adjusted by testing the electromagnetic properties of the finished paper in each zone to control the on-grid forming concentration of carbon fiber. The equivalent dielectric constant (10 GHz) real part of zones 1, 2, and 3 are 20, 80, and 150 respectively, with a real part fluctuation (cv) of ≤20% for each zone; the dielectric loss (10 GHz) is 0.6, 0.8, and 1.2 respectively, with a dielectric loss fluctuation (cv) of ≤20% for each zone. The retention rate of carbon fiber in the core layer is 99%, and the surface strength of paper and paperboard (wax rod method) is 20A.

[0068] During the papermaking process, by adjusting the dilution water flow rate in each zone, multiple sets of paper-based materials with varying electromagnetic properties are prepared. In the honeycomb cutting process, three zones with the above-mentioned gradient electromagnetic properties are cut into one honeycomb, resulting in a honeycomb with three gradient electromagnetic properties in the height direction and a honeycomb density of 32 kg / m³. 3 Cellular reflectivity is less than -12dB in the 2-18GHz frequency range and less than -20dB in the 8-12GHz frequency range.

[0069] Example 6

[0070] The flow rates of the top, core, and bottom layers of pulp are controlled according to the machine speed and basis weight requirements. The top layer raw materials consist of 50% aramid III pulp and 50% aramid III fiber, with a basis weight of 20 g / m². The bottom layer raw materials consist of 70% aramid III pulp and 30% aramid III fiber, with a basis weight of 20 g / m². The core layer raw material is carbon nanotubes. In this embodiment, three adjacent zones are controlled, each with a width of 15 mm, to obtain a 45 mm wide gradient electromagnetic property material. The opening of the clear water valve is adjusted by testing the electromagnetic properties of the finished paper in each zone to control the on-grid forming concentration of carbon nanotubes. The equivalent dielectric constants (10 GHz) of the first, second, and third zones are 20, 80, and 150 respectively, with a real part fluctuation (cv) of ≤20% for the dielectric constant of each zone; the dielectric losses (10 GHz) are 1.8, 2.0, and 2.6 respectively, with a dielectric loss fluctuation (cv) of ≤20% for each zone. The core layer carbon nanotube retention rate is 90%, and the surface strength of paper and paperboard is measured (wax rod method) at 20A.

[0071] During the papermaking process, by adjusting the dilution water flow rate in each zone, multiple sets of paper-based materials with varying electromagnetic properties are prepared. In the honeycomb cutting process, three zones with the above-mentioned gradient electromagnetic properties are cut into one honeycomb, resulting in a honeycomb with three gradient electromagnetic properties in the height direction and a honeycomb density of 32 kg / m³. 3 Cellular reflectivity is less than -12dB in the 2-18GHz frequency range and less than -20dB in the 8-12GHz frequency range.

[0072] Comparative Example 1

[0073] The pulp flow rate was controlled according to the machine speed and quantitative requirements, so that the non-electromagnetic raw materials were 50% aramid III pulp and 50% aramid III fiber, with a basis weight of 40 g / m², and single-layer papermaking. The electromagnetic raw material was carbon nanotubes. In this comparative example, three adjacent sections were used, each with a width of 15 mm. By controlling the amount of carbon nanotube suspension mixed into each section, a gradient electromagnetic material with a width of 45 mm was obtained. The opening of the mixing tube regulating valve was adjusted by testing the electromagnetic properties of the finished paper in each section, and the amount of carbon nanotubes on the web in each section was controlled. The real part of the equivalent dielectric constant (10 GHz) for sections 1, 2, and 3 was 20, 80, and 150, respectively, with a real part fluctuation (cv) of ≤20% for each section; the dielectric loss (10 GHz) was 1.8, 2.0, and 2.6, respectively, with a dielectric loss fluctuation (cv) of ≤20% for each section. The obtained product had a carbon nanotube retention rate of 40%, and the surface strength of the paper and paperboard was measured (wax rod method) to be 15A.

[0074] During the papermaking process, multiple sets of paper-based materials with varying electromagnetic properties are prepared by adjusting the regulating valves of the mixing pipes in each zone. In the honeycomb cutting process, three zones with the above-mentioned gradient electromagnetic properties are cut into one honeycomb, resulting in a honeycomb with three gradient electromagnetic properties in the height direction and a honeycomb density of 32 kg / m³. 3 The reflectivity of the honeycomb structure is less than -12dB in the 2-18GHz frequency range and less than -20dB in the 8-12GHz frequency range. During the honeycomb processing, the poor surface strength of the paper can lead to insufficient strength and cracking at the honeycomb nodes; carbon nanotubes are prone to detachment, affecting the processing environment, and detachment into the resin solution can affect the stability of the impregnation process.

[0075] Comparative Example 2

[0076] The pulp flow rate was controlled according to the machine speed and basis weight requirements, resulting in a non-electromagnetic material consisting of 50% aramid III pulp and 50% aramid III fiber, with a basis weight of 40 g / m², and single-layer papermaking. The electromagnetic material was carbon fiber. In this comparative example, three adjacent zones were used, each 15 mm wide. By controlling the amount of carbon fiber suspension mixed into the mixing tube in each zone, a 45 mm wide gradient electromagnetic material was obtained. The opening of the mixing tube regulating valve was adjusted based on the electromagnetic properties of the finished paper in each zone, controlling the amount of carbon fiber on the web in each zone. The equivalent dielectric constant (10 GHz) real part for zones 1, 2, and 3 was 20, 80, and 150 respectively, with a real part fluctuation (cv) of ≤20% for each zone; the dielectric loss (10 GHz) was 0.6, 0.8, and 1.2 respectively, with a dielectric loss fluctuation (cv) of ≤20% for each zone. The obtained product had a carbon fiber retention rate of 95%, and the surface strength of the paper and paperboard (wax rod method) was measured at 15A.

[0077] During the papermaking process, multiple sets of paper-based materials with varying electromagnetic properties are prepared by adjusting the regulating valves of the mixing pipes in each zone. In the honeycomb cutting process, three zones with the above-mentioned gradient electromagnetic properties are cut into one honeycomb, resulting in a honeycomb with three gradient electromagnetic properties in the height direction and a honeycomb density of 32 kg / m³. 3 The honeycomb exhibits a reflectivity of less than -12dB in the 2-18GHz frequency range and less than -20dB in the 8-12GHz frequency range. During the honeycomb processing, the poor surface strength of the paper leads to insufficient strength and cracking at the honeycomb nodes; carbon fiber detachment can cause itching when it comes into contact with human skin during processing.

[0078] Comparative Example 3

[0079] The pulp flow rate was controlled according to the machine speed and basis weight requirements, with the non-electromagnetic raw materials consisting of 50% aramid III pulp and 50% aramid III fiber, and a basis weight of 40 g / m², for single-layer papermaking. The electromagnetic raw material was magnetic powder. In this comparative example, three adjacent zones were used, each 15 mm wide. By controlling the amount of magnetic material suspension mixed into the mixing tube in each zone, a 45 mm wide gradient electromagnetic material was obtained. The opening of the mixing tube regulating valve was adjusted based on the electromagnetic properties of the finished paper in each zone, controlling the amount of magnetic material on the web in each zone. The permeability (1 GHz) of zones 1, 2, and 3 were obtained as 1.8, 2.3, and 3.8 respectively, with a permeability cv value ≤20% for each zone. The obtained product had a magnetic material retention rate of 40%, and the surface strength of the paper and paperboard was measured (wax rod method) at 15A.

[0080] During the papermaking process, multiple sets of paper-based materials with varying electromagnetic properties are prepared by adjusting the regulating valves of the mixing pipes in each zone. In the honeycomb cutting process, three zones with these gradient electromagnetic properties are cut into one honeycomb, resulting in a honeycomb with three gradient electromagnetic properties in the height direction. During the honeycomb processing, the poor surface strength of the paper can lead to insufficient strength and cracking at the honeycomb nodes; magnetic powder is prone to falling off, affecting the processing environment, and falling into the resin solution can affect the stability of the impregnation process.

Claims

1. A three-layer electromagnetic property horizontal gradient adjustable paper-based material, the paper-based material comprising a surface layer, a bottom layer, and a core layer sandwiched between the surface layer and the bottom layer, wherein, The surface layer and the bottom layer are made of 50% aramid III fiber and 50% aramid III pulp by weight, or 50% meta-aramid pulp and 50% meta-aramid chopped fibers by weight; the basis weight of the surface layer and the bottom layer is 20-30 g / m²; the core layer is composed of 100% electromagnetically active material, wherein the electromagnetically active material in the core layer is selected from carbon fiber and carbon nanotubes, and the basis weight of the core layer is 0.1-10 g / m²; the manufacturing method of the paper-based material includes the following steps: (1) Prepare slurry suspensions for the bottom layer, core layer, and surface layer respectively; (2) After diluting the slurry suspensions of the bottom layer, core layer and top layer prepared in step (1), the slurry is pumped to the slurry distributor and distributed along the horizontal direction of the paper machine. The slurry distribution system includes a top layer conical slurry distributor 1 for distributing the top layer, a core layer conical slurry distributor 2 for distributing the core layer, and a bottom layer conical slurry distributor 3 for distributing the bottom layer. The core layer conical slurry distributor 2 is equipped with a clear water conical slurry distributor 4. The core layer is divided into multiple areas, and each area is equipped with a clear water regulating valve for controlling the flow rate of clear water. During slurry distribution, the top layer conical slurry distributor 1, the core layer conical slurry distributor 2 and the bottom layer conical slurry distributor 3 are distributed simultaneously, and the flow rate of clear water is adjusted by the clear water regulating valve so that the clear water conical slurry distributor 4 releases different amounts of clear water to adjust the concentration of the slurry suspension in each area of ​​the core layer, thereby adjusting the electromagnetic characteristics of each area of ​​the horizontal direction. After slurry distribution, the headbox 5 is used to make the slurry disperse evenly. (3) Place the three layers of slurry onto a wire mesh, dehydrate, and form. (4) Pressing and drying; (5) Hot pressing (6) Roll up.

2. The paper-based material according to claim 1, wherein, The quantitative range of the core layer is 0.1-2 g / m².

3. A method for preparing a paper-based material according to claim 1 or 2, the method comprising the following steps: (1) Prepare slurry suspensions for the bottom layer, core layer, and surface layer respectively; (2) After diluting the slurry suspensions of the bottom layer, core layer and top layer prepared in step (1), the slurry is pumped to the slurry distributor and distributed along the horizontal direction of the paper machine. The slurry distribution system includes a top layer conical slurry distributor 1 for distributing the top layer, a core layer conical slurry distributor 2 for distributing the core layer, and a bottom layer conical slurry distributor 3 for distributing the bottom layer. The core layer conical slurry distributor 2 is equipped with a clear water conical slurry distributor 4. The core layer is divided into multiple areas, and each area is equipped with a clear water regulating valve for controlling the flow rate of clear water. During slurry distribution, the top layer conical slurry distributor 1, the core layer conical slurry distributor 2 and the bottom layer conical slurry distributor 3 are distributed simultaneously, and the flow rate of clear water is adjusted by the clear water regulating valve so that the clear water conical slurry distributor 4 releases different amounts of clear water to adjust the concentration of the slurry suspension in each area of ​​the core layer, thereby adjusting the electromagnetic characteristics of each area of ​​the horizontal direction. After slurry distribution, the headbox 5 is used to make the slurry disperse evenly. (3) Place the three layers of slurry onto a wire mesh, dehydrate, and form. (4) Pressing and drying; (5) Hot pressing (6) Roll up.

4. The preparation method according to claim 3, wherein, In step (2), the region is divided into equal parts, and the width of each region is 5~100mm.

5. The preparation method according to claim 3, wherein, In step (2), the region is divided into equal parts, and the width of each region is 5~20mm.

6. The preparation method according to any one of claims 3 to 5, wherein, In step (2), the opening degree of the water regulating valve is 40~80%.

7. The preparation method according to any one of claims 3 to 5, wherein, In step (3), after the three layers of slurry are put into the web, the dewatering web is done using a slanted web, a long web, a clamped web, or a round web.

8. The preparation method according to any one of claims 3 to 5, wherein, In step (4), the initial drying temperature is 70~90℃; the middle and later drying temperatures are 110~140℃.

9. The preparation method according to any one of claims 3 to 5, wherein, In step (4), the initial drying temperature is 80°C; the middle and final drying temperatures are 130°C.

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