Insulating paper for formation cabinet and preparation method thereof

Abstract

The application discloses a kind of insulation paper for formation cabinet and preparation method thereof, insulation paper for formation cabinet includes the following components according to mass percentage: 22~30% meta-aramid short fiber, 20~34% PEN short fiber, 32~41% Co-PET / PET sheath-core type bicomponent short fiber, 5~12% aqueous phosphate modified epoxy resin emulsion, 0.7~1.5% wet strength agent, 0.5~1% dispersant.The insulation paper prepared by the preparation method of the application has good high-temperature resistance, insulation, flame retardance, chemical stability and thickness uniformity, and has certain tensile strength and wear resistance, low impurity content, and is not easy to produce dust.

Description

Technical Field

[0001] This invention relates to the field of paper preparation technology, and more particularly to an insulating paper for chemical forming cabinets and its preparation method. Background Technology

[0002] In the production process of chemical forming cabinets, paper materials are critical consumables for ensuring production safety. They are typically used to wrap heating plates or make positioning bags, and these materials come into direct contact with the high-temperature battery cells. Therefore, these materials need to meet a series of stringent performance requirements, including high temperature resistance, insulation, flame retardancy, and chemical stability, to ensure the safety of personnel and the normal operation of equipment during production. However, the current chemical forming paper industry has some problems in material selection and performance, which pose potential threats to the production process and safety.

[0003] Existing chemical forming paper mostly uses conventional materials such as aramid and polyester. These materials have limited high-temperature resistance and cannot remain stable under long-term operation of high-temperature battery cells, easily leading to deformation and cracking. This directly affects the stability of the heating plate and the safety of the battery cell.

[0004] Existing flame-retardant papers mostly use traditional chlorine-containing or phosphorus-based flame retardants. Although they have a certain flame-retardant effect, these flame retardants are not environmentally friendly and may release harmful substances under high-temperature environments. Furthermore, the flame-retardant effect of some existing materials decreases with long-term exposure to high temperatures and electrolyte corrosion, resulting in short-lasting flame retardancy.

[0005] During the formation process, electrolyte leakage or evaporation may occur in the battery cells. Existing materials often fail to fully consider the reactivity between the material and the electrolyte, resulting in a decline in the performance of paper materials in high-temperature electrolyte environments, affecting insulation and corrosion resistance.

[0006] The thickness of existing chemical forming paper is difficult to control strictly, resulting in poor paper uniformity. This affects the uniformity of contact between the heating plate and the battery cell, further impacting the formation effect of the battery cell. This non-uniformity can also lead to localized overheating and underheating, thereby affecting the stability and lifespan of the battery cell performance.

[0007] The production process of existing materials may result in low ash content and cleanliness failing to meet industry standards due to impurities in raw materials and inadequate control of production processes, which affects the chemical stability and lifespan of the battery cells.

[0008] In practical applications, many chemically formed paper materials have high raw material costs, complicated preparation processes, and lack industrial production capabilities, which means that companies must weigh performance and cost when making selections, making it difficult to find an ideal balance. Summary of the Invention

[0009] In view of this, the present invention proposes an insulating paper for chemical forming cabinets and a method for preparing the same.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: An insulating paper for chemically formed cabinets, by mass percentage, comprises the following components: 22-30% meta-aramid chopped fibers, 20-34% PEN chopped fibers, 32-41% Co-PET / PET core-sheath bicomponent chopped fibers, 5-12% aqueous phosphate-modified epoxy resin emulsion, 0.7-1.5% wet strength agent, and 0.5-1% dispersant.

[0011] Furthermore, the linear density of the meta-aramid chopped fiber is 1.5–2.0D, and the length is 3–6 mm; the length of the PEN chopped fiber is 5–6 mm.

[0012] Furthermore, the melting point of the sheath layer of the Co-PET / PET sheath-core bicomponent chopped fiber is 110℃~160℃, the melting point of the core layer is ≥250℃, and the melting point difference ΔT between the sheath layer and the core layer is ≥90℃; The aqueous phosphate-modified epoxy resin emulsion contains a latent curing system, and the initial reaction temperature of the emulsion, measured by differential scanning calorimetry, is 145℃~165℃.

[0013] Furthermore, the wet strength agent is PAE; the dispersant is PEO.

[0014] This invention also provides a method for preparing insulating paper for chemical forming cabinets, comprising the following steps: Step 1: Meta-aramid staple fibers, PEN staple fibers, and Co-PET / PET core-sheath type bicomponent chopped fibers are dissociated in deionized water, and the total mass concentration of the sizing fiber is adjusted to 0.2%–0.5%; Step 2: Add the slurry to the slurry tank and perform low-shear mixing; Under stirring conditions, the reinforcing agent PAE is added to the slurry to form a uniformly distributed cationic charge layer on the surface of each fiber. As the aqueous phosphate-modified epoxy resin emulsion is slowly added, the aqueous phase of the slurry changes from turbid to clear. The phosphate-modified epoxy resin and PAE are neutralized through interfacial charge and firmly anchored to the fiber matrix. With the addition of dispersant PEO, the slurry exhibits a sterically stable suspension state. Step 3: Transfer the pulp obtained in Step 2 to the wire section of the paper machine; the pulp undergoes rapid solid-liquid separation on the filter screen, and the functional fibers and epoxy emulsion particles fixed on the fiber surface are trapped on the wire surface and deposited to form a wet paper sheet; Step 4: Transfer the wet paper sheet to the drying wire; under the pressure of the drying wire, the wet paper sheet adheres tightly to the high-temperature outer surface of the steam drying cylinder; The wet paper sheets pass through multiple steam drying cylinders in sequence with the dry wire for graded drying. After drying, the fibers begin to bond and form a porous fiber mesh skeleton with initial strength. Step 5: The dried paper is fed into a multi-roll calender; The paper sheet is preheated by the preheating roller, and then enters the gap between two hot press rollers under tension support, which completes the instantaneous compaction of the paper sheet, thereby constructing a dense three-dimensional cross-linked network; The compacted paper sheet travels around the circumferential surface of the cooling and shaping roller, and through rapid cooling, it is finally transformed into finished insulating paper.

[0015] Furthermore, in step one, meta-aramid short fibers, PEN short fibers, and Co-PET / PET core-sheath type bicomponent chopped fibers are fed into a fiber dissociation machine, and deionized water is added for dissociation. The dissociation speed is 2900-3000 rpm, and the dissociation time is 15-25 min.

[0016] Furthermore, in step two, a low-shear propulsion agitator is installed in the slurry tank, with a stirring speed of 150-250 rpm, to maintain micro-turbulent circulation of the slurry.

[0017] Furthermore, in step three, the slurry is evenly sprayed onto the wire section of the paper machine through the weir plate; The slurry undergoes rapid solid-liquid separation on a filter screen via gravity dehydration and a vacuum suction box. The moisture content of the wet paper sheet is 65% to 75%.

[0018] Furthermore, in step four, the negative pressure effect generated by the vacuum suction roller is used to smoothly peel the dehydrated wet paper sheet from the forming wire surface and transfer it to the dry wire. The wet paper sheets pass through the first 1 to 6 steam drying cylinders in sequence along with the dry wire, with a drying temperature of 85℃ to 105℃ and a drying time of 4 to 8 seconds for the first stage of drying; The wet paper sheets then pass through 3 to 4 steam drying cylinders in the later stage along with the dry wire, where the drying temperature is 130℃ to 150℃ and the drying time is 2 to 5 seconds, for a second stage of drying.

[0019] Further, in step five, the temperature of the preheating roller is 160℃~180℃, and the preheating time is 0.5~3s; the temperature of the hot pressing roller is 240℃~280℃, and the paper sheet bears an instantaneous linear pressure of 200~400kN / m in the gap between the two hot pressing rollers; the paper sheet stays in the gap for 30~60ms; the surface temperature of the cooling and shaping roller is 20℃~40℃, and the cooling time is 2~4s. The basis weight of the insulating paper is 80-120 g / m², and the thickness range is ≤ ±1.5 μm.

[0020] Compared with existing technologies, the beneficial effects of the present invention are as follows: The insulating paper for the formation cabinet prepared by the present invention has the following excellent properties: (1) high temperature resistance, which can withstand the high temperature of 45 to 85°C during the formation process; (2) insulation performance, which has extremely high resistivity and high insulation level; (3) flame retardant performance, which reaches UL94V-0 level; (4) mechanical strength, which has certain tensile strength and wear resistance; (5) chemical stability, which is resistant to electrolyte corrosion; (6) low ash content / cleanliness, which has low impurity content and is not easy to generate dust; (7) thickness uniformity, which has small thickness tolerance and smooth surface. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Example 1

[0023] An insulating paper for chemical forming cabinets, by mass percentage, comprises the following components: 22% meta-aramid chopped fibers, 34% PEN chopped fibers, 34% Co-PET / PET core-sheath bicomponent chopped fibers, 8% aqueous phosphate-modified epoxy resin emulsion, 1.5% wet strength agent, and 0.5% dispersant.

[0024] The linear density of meta-aramid chopped fibers is 1.8D, and the length is 4mm. The length of PEN (polyethylene naphthalate) chopped fibers is 5mm, and the intrinsic viscosity IV is ≥0.8dL / g.

[0025] The melting point of the sheath layer of Co-PET / PET core-sheath bicomponent short-cut fiber is 110℃~160℃, the melting point of the core layer is ≥250℃, the melting point difference between the sheath layer and the core layer is ΔT≥90℃, and the sheath / core mass ratio is 3∶7.

[0026] The waterborne phosphate-modified epoxy resin emulsion contains a latent curing system. The initial reaction temperature of the emulsion, measured by differential scanning calorimetry, is 145℃~165℃. The solid content of the waterborne phosphate-modified epoxy resin emulsion is 50%, the epoxy equivalent is 250g / eq, and the phosphorus content is ≥3wt%.

[0027] The wet strength agent is PAE (polyamide polyamine epichlorohydrin resin); the dispersant is PEO (polyethylene oxide).

[0028] Meta-aramid chopped fibers, PEN chopped fibers, Co-PET / PET core-sheath bicomponent chopped fibers, waterborne phosphate ester modified epoxy resin emulsions, wet strength agent PAE, and dispersant PEO can all be purchased directly from the market without the need for separate preparation.

[0029] Meta-aramid chopped strands possess a high limiting oxygen index and excellent long-term heat resistance, thus ensuring the flame retardancy and dimensional stability of paper at high temperatures. PEN chopped strands have high modulus, low moisture absorption, and excellent electrolyte resistance; therefore, meta-aramid chopped strands provide the foundation for fire resistance and toughness, while PEN provides the foundation for rigidity and chemical resistance. However, both meta-aramid and PEN chopped strands are non-melting fibers. The sheath (Co-PET) melts at 130℃–160℃, flowing like glue to the fiber intersections to bond the fibers together, while the core (PET) remains solid, supporting the fiber structure.

[0030] In waterborne phosphate-modified epoxy resin emulsions, phosphate groups are directly grafted onto the epoxy resin backbone through chemical bonding. During thermal decomposition, the phosphate groups can generate polymetaphosphoric acid in situ, which acts as a strong dehydrating agent to promote the dehydration and carbonization of the epoxy matrix, forming a dense carbonized layer to ensure compliance with the UL94V-0 standard. The introduction of phosphate groups also greatly enhances the polarity of the resin macromolecules and improves the wettability of the resin on the surfaces of meta-aramid chopped fibers and PEN chopped fibers. The phosphate-modified epoxy resin retains highly active epoxy groups, which can undergo efficient nucleophilic substitution reactions with the nitrogen-containing heterocyclic butyl groups in PEN chopped fibers under hot pressing at 260℃.

[0031] An insulating paper for chemical forming cabinets and its preparation method, comprising the following steps: Step 1: Weigh meta-aramid staple fiber, PEN staple fiber, and core-sheath type bicomponent polyester staple fiber according to the preset ratio; put the above fibers into the fiber debonding machine, add deionized water, and debond at 2950 rpm for 15 minutes; use high-frequency hydraulic shear force to debond the fiber bundle into a single suspended state; after debonding, continue to add deionized water to the pulp tank to adjust the total mass concentration of the pulp fiber (i.e., the proportion of oven-dry fiber mass to the total mass of pulp) to 0.35%; Step 2: Weigh out the reinforcing agent PAE, water-based phosphate ester modified epoxy resin emulsion, and dispersant PEO according to the preset ratio; The slurry is added to a slurry tank equipped with a low-shear propulsion agitator, and the speed of the low-shear propulsion agitator is set to 200 rpm to maintain micro-turbulent circulation of the slurry. Under stirring, the reinforcing agent PAE is added to the slurry. Since PAE carries a positive charge, it is anchored to the surface of the negatively charged meta-aramid, PEN and core-sheath polyester fibers through electrostatic attraction. Stirring is maintained for 10 minutes to form a uniformly distributed cationic charge layer on the surface of each fiber. Water-based phosphate-modified epoxy resin emulsion is slowly added dropwise; the epoxy resin particles in the emulsion are strongly induced by the positive charge layer of PAE on the fiber surface, and are precisely adsorbed and uniformly coated on the outer periphery of the fiber, forming a continuous and uniform PAE-epoxy resin composite coating layer on the outer periphery of the fiber; the aqueous phase of the slurry changes from turbid to clear, which indicates that the phosphate-modified epoxy resin and PAE are firmly anchored to the fiber matrix through interfacial charge neutralization. By adding the dispersant PEO, the long chain segments of PEO with ultra-high molecular weight form a steric hindrance layer around the fiber, which effectively counteracts the viscous attraction generated after the fiber is coated with resin, prevents the fiber from flocculating, and the slurry presents a highly dispersed steric hindrance stable suspension state. Step 3: The pulp obtained in Step 2 is evenly sprayed onto the wire section of the paper machine through the weir plate; The slurry undergoes rapid solid-liquid separation on a filter screen via gravity dewatering and a vacuum suction box. Moisture and unabsorbed additives pass through the mesh into the recycling system; functional fibers and epoxy emulsion particles fixed on the fiber surface are trapped on the mesh surface and deposited to form a wet paper sheet with a moisture content of 70%. Step 4: Using the negative pressure effect generated by the vacuum suction roller, the dehydrated wet paper sheet is smoothly peeled off from the forming wire and transferred to a highly permeable single-layer dry wire; under the pressure of the dry wire, the wet paper sheet adheres tightly to the high-temperature outer surface of the steam drying cylinder, so that heat can be conducted between the paper sheet and the cylinder surface; The wet paper sheets pass through eight steam drying cylinders in sequence along with the dry wire. The surface of each group of drying cylinders is coated with a polytetrafluoroethylene anti-stick coating. The temperature of the first five steam drying stages is strictly controlled at 90℃; the air permeability of the dryer is used to allow the moisture to vaporize smoothly, preventing the formation of air bubbles in the resin coating layer due to excessive heating, and ensuring the density of the insulation structure. The paper sheet enters the three steam drying cylinders in the later stage, where the temperature gradient is increased to 140℃. At this point, the Co-PET sheath of the core-sheath bicomponent fiber reaches its melting point and begins to soften, creating heat-melting contact points at the fiber intersections. The fibers begin to bond and form a porous fiber network skeleton with initial strength. As the moisture concentration increases, the nitrogen-containing heterocyclic butyl groups of PAE begin to undergo preliminary covalent bonding with the hydroxyl groups on the fiber surface, and the paper sheet changes from a wet state to a dry state. The paper sheet obtains sufficient dry strength to withstand the winding tension, and its thickness is initially determined. Step 5: The dried paper leaves the dryer through an air jet and is fed into a multi-roll calender; The paper sheet first passes through the preheating roller of a calender at 170°C for 1.5 seconds. During this process, the Co-PET skin of the fiber and the phosphorus-containing epoxy resin are fully softened and in a highly elastic state, while the PAE remains stably distributed. The preheated paper sheet enters the gap between two high-strength hot press rollers under tension support. The surface of the hot press rollers is treated with ultra-mirror polishing. The temperature of the hot press rollers is 260℃. The paper sheet is subjected to an instantaneous linear pressure of 300kN / m in the gap between the two hot press rollers. The paper sheet stays in the gap for 40ms, which realizes instantaneous compaction of the paper sheet. The softened skin material undergoes directional filling, expelling air from the fiber gaps and inducing the molten components to achieve micro-filling and in-situ chemical cross-linking, thereby constructing a high-density and high-flatness insulation structure and building a dense three-dimensional cross-linked network, thus forming a high-density and high-flatness rigid insulation structure. After being compacted, the paper sheet smoothly leaves the metal hot press roller and travels around to the circumferential surface of the cooling and shaping roller. The surface temperature of the cooling and shaping roller is 30°C and the cooling time is 3 seconds. Through rapid cooling, the final product is insulation paper. The final finished insulating paper has a basis weight of 80–120 g / m² and a thickness range of ≤ ±1.5 μm. The longitudinal and transverse thermal shrinkage rates of the finished insulating paper at 150℃ for 30 min are ≤ 0.1%.

[0032] The insulating paper used in the formation cabinet ultimately possesses the following properties: (1) High temperature resistance: It can withstand the high temperatures during the formation process (usually 45-85℃, or even higher). Considering that the formation process generates heat and the heating plate needs to be heated and pressurized, the material will not melt, deform, or release harmful gases due to high temperatures; (2) Insulation performance: It has extremely high resistivity and a high insulation level. Considering the need to prevent the metal heating plate from contacting the battery tabs and causing a short circuit, it can avoid causing a fire or damaging the battery cell; (3) Flame retardant performance: It reaches UL94V-0 level. Considering the risk of thermal runaway in lithium batteries during the formation process, it can withstand the high temperatures. It can effectively prevent the fire from spreading; (4) Mechanical strength, the insulating paper has a certain tensile strength and wear resistance. Considering that during the feeding and hot pressing process of the frequent decomposition, the paper is subjected to mechanical friction and pressure and is not easily damaged; (5) Chemical stability, resistant to electrolyte corrosion. Considering that the battery cell may be mixed during the formation, the material is prevented from not reacting with the electrolyte; (6) Low ash content / cleanliness, low impurity content, not easy to generate dust, prevent dust from polluting the battery cell and affecting the battery performance; (7) Thickness uniformity, small thickness tolerance, flat surface, ensure that the heating plate and the battery cell are in uniform contact, and ensure consistent formation effect. Example 2

[0033] Compared with Example 1, the difference is that: an insulating paper for chemically formed cabinets, by mass percentage, comprises the following components: 34% meta-aramid chopped fibers, 20% PEN chopped fibers, 32.3% Co-PET / PET core-sheath type bicomponent chopped fibers, 12% aqueous phosphate ester modified epoxy resin emulsion, 0.7% wet strength agent, and 1% dispersant.

[0034] Everything else is the same as in Example 1. Example 3

[0035] Compared with Example 1, the difference is that: an insulating paper for chemically formed cabinets, by mass percentage, comprises the following components: 27% meta-aramid chopped fibers, 30.2% PEN chopped fibers, 32% Co-PET / PET core-sheath type bicomponent chopped fibers, 9% aqueous phosphate ester modified epoxy resin emulsion, 1% wet strength agent, and 0.8% dispersant.

[0036] Everything else is the same as in Example 1. Example 4

[0037] Compared with Example 1, the difference is that: an insulating paper for chemically formed cabinets, by mass percentage, comprises the following components: 24% meta-aramid chopped fibers, 26% PEN chopped fibers, 41% Co-PET / PET core-sheath type bicomponent chopped fibers, 7% aqueous phosphate ester modified epoxy resin emulsion, 1% wet strength agent, and 1% dispersant.

[0038] Everything else is the same as in Example 1. Example 5

[0039] Compared with Example 1, the difference is that: an insulating paper for chemically formed cabinets, by mass percentage, comprises the following components: 30% meta-aramid chopped fibers, 20% PEN chopped fibers, 37.5% Co-PET / PET core-sheath type bicomponent chopped fibers, 11% water-based phosphate ester modified epoxy resin emulsion, 0.8% wet strength agent, and 0.7% dispersant.

[0040] Everything else is the same as in Example 1.

[0041] Comparative Example 1 An insulating paper for chemical forming cabinets, by weight percentage, comprises the following components: 56% PEN chopped short fibers, 34% Co-PET / PET core-sheath bicomponent chopped short fibers, 8% aqueous phosphate-modified epoxy resin emulsion, 1.5% wet strength agent, and 0.5% dispersant.

[0042] PEN chopped short fibers have a length of 5 mm and an intrinsic viscosity IV ≥ 0.8 dL / g.

[0043] The melting point of the sheath layer of Co-PET / PET core-sheath bicomponent short-cut fiber is 110℃~160℃, the melting point of the core layer is ≥250℃, the melting point difference between the sheath layer and the core layer is ΔT≥90℃, and the sheath / core mass ratio is 3:7.

[0044] The wet strength agent is PAE; the dispersant is PEO.

[0045] An insulating paper for chemical forming cabinets and its preparation method, comprising the following steps: Step 1: Weigh PEN staple fiber and core-sheath type bicomponent polyester staple fiber according to the preset ratio; put the above fibers into the fiber debonding machine, add deionized water, and debond at 2950 rpm for 15 minutes; use high-frequency hydraulic shear force to debond the fiber bundle into a single suspended state; after debonding, continue to add deionized water to the pulp tank to adjust the total mass concentration of the pulp fiber to 0.35%; Step 2: Weigh out the reinforcing agent PAE, water-based phosphate ester modified epoxy resin emulsion, and dispersant PEO according to the preset ratio; The slurry is added to a slurry tank equipped with a low-shear propulsion agitator, and the speed of the low-shear propulsion agitator is set to 200 rpm to maintain micro-turbulent circulation of the slurry. While stirring, add reinforcing agent PAE to the slurry. Since PAE carries a positive charge, it anchors itself to the surface of negatively charged meta-aramid, PEN and core-sheath polyester fibers through electrostatic attraction. Keep stirring for 10 minutes. Slowly add water-based phosphate ester modified epoxy resin emulsion; With the addition of dispersant PEO, the slurry exhibits a highly dispersed, sterically stable suspension state. Step 3: The pulp obtained in Step 2 is evenly sprayed onto the wire section of the paper machine through the weir plate; The slurry undergoes rapid solid-liquid separation on a filter screen via gravity dewatering and a vacuum suction box. Moisture and unabsorbed additives pass through the mesh into the recycling system; functional fibers and epoxy emulsion particles fixed on the fiber surface are trapped on the mesh surface and deposited to form a wet paper sheet with a moisture content of 70%. Step 4: Using the negative pressure effect generated by the vacuum suction roller, the dehydrated wet paper sheet is smoothly peeled off from the forming wire and transferred to a highly permeable single-layer dry wire; under the pressure of the dry wire, the wet paper sheet adheres tightly to the high-temperature outer surface of the steam drying cylinder, so that heat can be conducted between the paper sheet and the cylinder surface; The wet paper sheets pass through eight steam drying cylinders in sequence along with the dry wire. The surface of each group of drying cylinders is coated with a polytetrafluoroethylene anti-stick coating. The temperature of the first five steam drying stages is strictly controlled at 90℃; The paper enters the three steam drying cylinders in the later stage, where the temperature gradient is increased to 140℃. At this time, the Co-PET sheath of the core-sheath type bicomponent fiber reaches the melting point and begins to soften. Heat-melting contact points are generated at the fiber intersections, and the fibers begin to bond and form a porous fiber network skeleton with initial strength. The paper changes from a wet state to a dry state, and the thickness is initially determined. Step 5: The dried paper leaves the dryer through an air jet and is fed into a multi-roll calender; The paper sheet first passes through the preheating rollers of a calender at 160°C for 1.5 seconds. The preheated paper sheet enters the gap between two high-strength hot press rollers under tension support. The surface of the hot press rollers is treated with ultra-mirror polishing. The temperature of the hot press rollers is 180℃. The paper sheet is subjected to an instantaneous linear pressure of 300kN / m in the gap between the two hot press rollers. The paper sheet stays in the gap for 40ms, which realizes the instantaneous compaction of the paper sheet. After being compacted, the paper sheet smoothly detaches from the metal hot press roller and travels around to the circumferential surface of the cooling and shaping roller. The surface temperature of the cooling and shaping roller is 30°C, and the cooling time is 3 seconds. Through rapid cooling, the final product, insulating paper, is obtained.

[0046] Comparative Example 2 An insulating paper for chemically formed cabinets, comprising the following components by weight percentage: 22% meta-aramid chopped fibers, 34% PEN chopped fibers, 34% Co-PET / PET core-sheath bicomponent chopped fibers, 8% bisphenol A type epoxy resin emulsion, 1.5% wet strength agent, and 0.5% dispersant.

[0047] The linear density of meta-aramid chopped fibers is 1.8D, and the length is 4mm. The length of PEN chopped fibers is 5mm, and the intrinsic viscosity IV is ≥0.8dL / g.

[0048] The melting point of the sheath layer of Co-PET / PET core-sheath bicomponent short-cut fiber is 110℃~160℃, the melting point of the core layer is ≥250℃, the melting point difference between the sheath layer and the core layer is ΔT≥90℃, and the sheath / core mass ratio is 3:7.

[0049] The wet strength agent is PAE; the dispersant is PEO.

[0050] An insulating paper for chemical forming cabinets and its preparation method, comprising the following steps: Step 1: Weigh meta-aramid staple fiber, PEN staple fiber, and core-sheath type bicomponent polyester staple fiber according to the preset ratio; put the above fibers into the fiber debonding machine, add deionized water, and debond at 2950 rpm for 15 minutes; use high-frequency hydraulic shear force to debond the fiber bundle into a single suspended state; after debonding, continue to add deionized water to the pulp tank to adjust the total mass concentration of the pulp fiber to 0.35%; Step 2: Weigh out the reinforcing agent PAE, bisphenol A type epoxy resin emulsion and dispersant PEO according to the preset ratio; The slurry is added to a slurry tank equipped with a low-shear propulsion agitator, and the speed of the low-shear propulsion agitator is set to 200 rpm to maintain micro-turbulent circulation of the slurry. While stirring, add reinforcing agent PAE to the slurry. Since PAE carries a positive charge, it anchors itself to the surface of negatively charged meta-aramid, PEN and core-sheath polyester fibers through electrostatic attraction. Keep stirring for 10 minutes. Slowly add bisphenol A type epoxy resin emulsion; With the addition of dispersant PEO, the slurry exhibits a highly dispersed, sterically stable suspension state. Step 3: The pulp obtained in Step 2 is evenly sprayed onto the wire section of the paper machine through the weir plate; The slurry undergoes rapid solid-liquid separation on a filter screen via gravity dewatering and a vacuum suction box. Moisture and unabsorbed additives pass through the mesh into the recycling system; functional fibers and epoxy emulsion particles fixed on the fiber surface are trapped on the mesh surface and deposited to form a wet paper sheet with a moisture content of 70%. Step 4: Using the negative pressure effect generated by the vacuum suction roller, the dehydrated wet paper sheet is smoothly peeled off from the forming wire and transferred to a highly permeable single-layer dry wire; under the pressure of the dry wire, the wet paper sheet adheres tightly to the high-temperature outer surface of the steam drying cylinder, so that heat can be conducted between the paper sheet and the cylinder surface; The wet paper sheets pass through eight steam drying cylinders in sequence along with the dry wire. The surface of each group of drying cylinders is coated with a polytetrafluoroethylene anti-stick coating. The temperature of the first five steam drying stages is strictly controlled at 90℃; The paper enters the three steam drying cylinders in the later stage, where the temperature gradient is increased to 140℃. At this time, the Co-PET sheath of the core-sheath type bicomponent fiber reaches the melting point and begins to soften. Heat-melting contact points are generated at the fiber intersections, and the fibers begin to bond and form a porous fiber network skeleton with initial strength. The paper changes from a wet state to a dry state, and the thickness is initially determined. Step 5: The dried paper leaves the dryer through an air jet and is fed into a multi-roll calender; The paper sheet first passes through the preheating rollers of a calender at 170°C for 1.5 seconds. The preheated paper sheet enters the gap between two high-strength hot press rollers under tension support. The surface of the hot press rollers is treated with ultra-mirror polishing. The temperature of the hot press rollers is 260℃. The paper sheet is subjected to an instantaneous linear pressure of 300kN / m in the gap between the two hot press rollers. The paper sheet stays in the gap for 40ms, which realizes the instantaneous compaction of the paper sheet. After being compacted, the paper sheet smoothly detaches from the metal hot press roller and travels around to the circumferential surface of the cooling and shaping roller. The surface temperature of the cooling and shaping roller is 30°C, and the cooling time is 3 seconds. Through rapid cooling, the final product, insulating paper, is obtained.

[0051] Comparative Example 3 An insulating paper for chemical forming cabinets, by weight percentage, comprises the following components: 22% meta-aramid chopped fibers, 34% PEN chopped fibers, 34% Co-PET / PET core-sheath bicomponent chopped fibers, 8% aqueous phosphate-modified epoxy resin emulsion, and 2% wet strength agent.

[0052] The linear density of meta-aramid chopped fibers is 1.8D, and the length is 4mm. The length of PEN chopped fibers is 5mm, and the intrinsic viscosity IV is ≥0.8dL / g.

[0053] The melting point of the sheath layer of Co-PET / PET core-sheath bicomponent short-cut fiber is 110℃~160℃, the melting point of the core layer is ≥250℃, the melting point difference between the sheath layer and the core layer is ΔT≥90℃, and the sheath / core mass ratio is 3:7.

[0054] The wet strength agent is PAE.

[0055] An insulating paper for chemical forming cabinets and its preparation method, comprising the following steps: Step 1: Weigh meta-aramid staple fiber, PEN staple fiber, and core-sheath type bicomponent polyester staple fiber according to the preset ratio; put the above fibers into the fiber debonding machine, add deionized water, and debond at 2950 rpm for 15 minutes; use high-frequency hydraulic shear force to debond the fiber bundle into a single suspended state; after debonding, continue to add deionized water to the pulp tank to adjust the total mass concentration of the pulp fiber to 0.35%; Step 2: Weigh out the reinforcing agent PAE and the water-based phosphate ester modified epoxy resin emulsion according to the preset ratio; The slurry is added to a slurry tank equipped with a low-shear propulsion agitator, and the speed of the low-shear propulsion agitator is set to 200 rpm to maintain micro-turbulent circulation of the slurry. While stirring, add reinforcing agent PAE to the slurry. Since PAE carries a positive charge, it anchors itself to the surface of negatively charged meta-aramid, PEN and core-sheath polyester fibers through electrostatic attraction. Keep stirring for 10 minutes. Slowly add water-based phosphate ester modified epoxy resin emulsion; Step 3: The pulp obtained in Step 2 is evenly sprayed onto the wire section of the paper machine through the weir plate; The slurry undergoes rapid solid-liquid separation on a filter screen via gravity dewatering and a vacuum suction box. Moisture and unabsorbed additives pass through the mesh into the recycling system; functional fibers and epoxy emulsion particles fixed on the fiber surface are trapped on the mesh surface and deposited to form a wet paper sheet with a moisture content of 70%. Step 4: Using the negative pressure effect generated by the vacuum suction roller, the dehydrated wet paper sheet is smoothly peeled off from the forming wire and transferred to a highly permeable single-layer dry wire; under the pressure of the dry wire, the wet paper sheet adheres tightly to the high-temperature outer surface of the steam drying cylinder, so that heat can be conducted between the paper sheet and the cylinder surface; The wet paper sheets pass through eight steam drying cylinders in sequence along with the dry wire. The surface of each group of drying cylinders is coated with a polytetrafluoroethylene anti-stick coating. The temperature of the first five steam drying stages is strictly controlled at 90℃; The paper enters the three steam drying cylinders in the later stage, where the temperature gradient is increased to 140℃. At this time, the Co-PET sheath of the core-sheath type bicomponent fiber reaches the melting point and begins to soften. Heat-melting contact points are generated at the fiber intersections, and the fibers begin to bond and form a porous fiber network skeleton with initial strength. The paper changes from a wet state to a dry state, and the thickness is initially determined. Step 5: The dried paper leaves the dryer through an air jet and is fed into a multi-roll calender; The paper sheet first passes through the preheating rollers of a calender at 170°C for 1.5 seconds. The preheated paper sheet enters the gap between two high-strength hot press rollers under tension support. The surface of the hot press rollers is treated with ultra-mirror polishing. The temperature of the hot press rollers is 260℃. The paper sheet is subjected to an instantaneous linear pressure of 300kN / m in the gap between the two hot press rollers. The paper sheet stays in the gap for 40ms, which realizes the instantaneous compaction of the paper sheet. After being compacted, the paper sheet smoothly detaches from the metal hot press roller and travels around to the circumferential surface of the cooling and shaping roller. The surface temperature of the cooling and shaping roller is 30°C, and the cooling time is 3 seconds. Through rapid cooling, the final product, insulating paper, is obtained.

[0056] Comparative Example 4 An insulating paper for chemical forming cabinets, by mass percentage, comprises the following components: 22% meta-aramid chopped fibers, 34% PEN chopped fibers, 34% Co-PET / PET core-sheath bicomponent chopped fibers, 8% aqueous phosphate-modified epoxy resin emulsion, 1.5% wet strength agent, and 0.5% dispersant.

[0057] The linear density of meta-aramid chopped fibers is 1.8D, and the length is 4mm. The length of PEN chopped fibers is 5mm, and the intrinsic viscosity IV is ≥0.8dL / g.

[0058] The melting point of the sheath layer of Co-PET / PET core-sheath bicomponent short-cut fiber is 110℃~160℃, the melting point of the core layer is ≥250℃, the melting point difference between the sheath layer and the core layer is ΔT≥90℃, and the sheath / core mass ratio is 3:7.

[0059] The wet strength agent is PAE; the dispersant is PEO.

[0060] An insulating paper for chemical forming cabinets and its preparation method, comprising the following steps: Step 1: Weigh meta-aramid staple fiber, PEN staple fiber, and core-sheath type bicomponent polyester staple fiber according to the preset ratio; put the above fibers into the fiber debonding machine, add deionized water, and debond at 2950 rpm for 15 minutes; use high-frequency hydraulic shear force to debond the fiber bundle into a single suspended state; after debonding, continue to add deionized water to the pulp tank to adjust the total mass concentration of the pulp fiber to 0.35%; Step 2: Weigh out the reinforcing agent PAE, water-based phosphate ester modified epoxy resin emulsion, and dispersant PEO according to the preset ratio; The slurry is added to a slurry tank equipped with a low-shear propulsion agitator, and the speed of the low-shear propulsion agitator is set to 200 rpm to maintain micro-turbulent circulation of the slurry. While stirring, add reinforcing agent PAE to the slurry. Since PAE carries a positive charge, it anchors itself to the surface of negatively charged meta-aramid, PEN and core-sheath polyester fibers through electrostatic attraction. Keep stirring for 10 minutes. Slowly add water-based phosphate ester modified epoxy resin emulsion; With the addition of dispersant PEO, the slurry exhibits a highly dispersed, sterically stable suspension state. Step 3: The pulp obtained in Step 2 is evenly sprayed onto the wire section of the paper machine through the weir plate; The slurry undergoes rapid solid-liquid separation on a filter screen via gravity dewatering and a vacuum suction box. Moisture and unabsorbed additives pass through the mesh into the recycling system; functional fibers and epoxy emulsion particles fixed on the fiber surface are trapped on the mesh surface and deposited to form a wet paper sheet with a moisture content of 70%. Step 4: Using the negative pressure effect generated by the vacuum suction roller, the dehydrated wet paper sheet is smoothly peeled off from the forming wire and transferred to a highly permeable single-layer dry wire; under the pressure of the dry wire, the wet paper sheet adheres tightly to the high-temperature outer surface of the steam drying cylinder, so that heat can be conducted between the paper sheet and the cylinder surface; The wet paper sheets pass through eight steam drying cylinders in sequence along with the dry wire. The surface of each group of drying cylinders is coated with a polytetrafluoroethylene anti-stick coating. The temperature of the first five steam drying stages is strictly controlled at 90℃; The paper enters the three steam drying cylinders in the later stage, where the temperature gradient is increased to 140℃. At this time, the Co-PET sheath of the core-sheath type bicomponent fiber reaches the melting point and begins to soften. Heat-melting contact points are generated at the fiber intersections, and the fibers begin to bond and form a porous fiber network skeleton with initial strength. The paper changes from a wet state to a dry state, and the thickness is initially determined. Step 5: The dried paper leaves the dryer through an air jet and is fed into a multi-roll calender; The paper sheet first passes through the preheating rollers of a calender at 160°C for 1.5 seconds. The preheated paper sheet enters the gap between two high-strength hot press rollers under tension support. The surface of the hot press rollers is treated with ultra-mirror polishing. The temperature of the hot press rollers is 180℃. The paper sheet is subjected to an instantaneous linear pressure of 300kN / m in the gap between the two hot press rollers. The paper sheet stays in the gap for 40ms, which realizes the instantaneous compaction of the paper sheet. After being compacted, the paper sheet smoothly detaches from the metal hot press roller and travels around to the circumferential surface of the cooling and shaping roller. The surface temperature of the cooling and shaping roller is 30°C, and the cooling time is 3 seconds. Through rapid cooling, the final product, insulating paper, is obtained.

[0061] According to GB / T13542 (Series Standards for Films for Electrical Insulation), the samples prepared in Examples 1-5 and Comparative Examples 1-4 were obtained by wire cutting. Each sample was 100mm × 100mm, and a 50mm long baseline segment was marked on both the longitudinal and transverse centerlines. The initial baseline length L0 was measured first. The sample was then placed flat on a smooth tray and kept in a 150℃ constant temperature forced-air drying oven for 30 minutes. After removal and cooling to room temperature under standard conditions, the baseline length L1 was measured again. The shrinkage rate S = (L0 - L1) / L0, and the test results are shown in Tables 1 and 2.

[0062] According to GB / T1408.1 (Test methods for electrical strength of insulating materials - Part 1: Test at power frequency), the samples prepared in Examples 1-5 and Comparative Examples 1-4 were obtained by wire cutting. Each sample, measuring 100mm × 100mm, was clamped between a pair of electrodes. The withstand voltage tester was turned on, and the voltage increase rate was set to 0.2kV / s. The voltage was increased uniformly in the air medium until the sample underwent electrical breakdown. The instrument then tripped and locked the peak voltage U. The thickness d was measured near the breakdown point using a thickness gauge. The electrical strength E = U / d. The test results are shown in Tables 1 and 2.

[0063] According to UL94 (Flammability Test for Plastic Materials Used in Equipment Parts), the samples prepared in Examples 1-5 and Comparative Examples 1-4 were obtained by wire cutting. Each 125mm × 13mm strip sample was taken and suspended vertically in the test chamber with the lower end 10mm away from the burner nozzle. The lower end of the sample was ignited with a standard Bunsen burner for 10s and then removed, and the afterflame time t1 was recorded. Immediately after extinguishing, a second ignition was performed for 10s, and the afterflame time t2 and afterburner time t3 were recorded. It was observed whether there were any burning droplets that ignited the degreased cotton below. If t1 + t2 ≤ 50s and there were no droplets, it was classified as V-0. The test results are shown in Tables 1 and 2.

[0064] According to GB / T12914 (Determination of Tensile Strength of Paper and Paperboard), the samples prepared in Examples 1-5 and Comparative Examples 1-4 were obtained by wire cutting. Each long strip sample of 150mm×15mm was taken. The clamping distance of the universal tensile testing machine was adjusted to 100mm, and the sample was clamped vertically and flatly in the upper and lower clamps to ensure that it was not skewed. The tensile speed was set to 20mm / min, and the instrument was started until the sample broke. The maximum tensile force F at the time of breakage was recorded. Tensile strength = F / 15 (width). The test results are shown in Tables 1 and 2.

[0065] According to ASTM D3884 (Taber Abrasion Method), the samples prepared in Examples 1-5 and Comparative Examples 1-4 were obtained by wire cutting. Each disc sample with a diameter of 114 mm was taken, and a 6 mm diameter mounting hole was punched in the center. The sample was then fixed to the rotating base of the Taber abrasion tester. Rubber grinding wheels were selected, and a 500 g weight was loaded onto each wheel arm. The rotation speed was set, and abrasion was started. The machine was stopped and observed every 100 revolutions until the sample surface showed exposed fibers or obvious damage to the resin layer. The number of revolutions at this point was recorded, and the test results are shown in Tables 1 and 2.

[0066] The samples obtained in Examples 1-5 and Comparative Examples 1-4 were all obtained by wire cutting. Each 150mm × 15mm strip sample was prepared, and a standard electrolyte (1M LiPF6, EC∶DMC∶EMC=1∶1∶1) was used to immerse the sample in the electrolyte and store it in a constant temperature environment of 85℃ for 72 hours. The sample was then removed, and residual salt on the surface was cleaned with DMC solvent. The tensile strength was retested using the above tensile strength test method and compared with the initial value before immersion. Strength retention rate = strength after immersion / initial strength. The test results are shown in Tables 1 and 2.

[0067] According to GB / T463 (Determination of Ash Content in Paper and Paperboard), the samples prepared in Examples 1-5 and Comparative Examples 1-4 were obtained by wire cutting. Approximately 3g of each paper sample was taken, torn into small pieces, and placed in a constant-weight crucible with a known mass m0. The samples were slowly heated on an electric furnace to completely carbonize them. The crucible was then transferred to a muffle furnace and calcined at 600°C for at least 2 hours until the carbon was completely eliminated. The crucible was then removed and placed in a desiccator to cool to room temperature. The total mass m1 of the crucible containing ash was weighed. Ash content = (m1-m0) / original weight of the sample. The test results are shown in Tables 1 and 2.

[0068] According to GB / T451.3 (Determination of thickness of paper and paperboard), the samples prepared in Examples 1-5 and Comparative Examples 1-4 were obtained by wire cutting. Strips of test paper with a width of 100 mm were taken along the transverse direction of the paper. A precision contact thickness gauge with a graduation of 0.001 mm was used. A test point was selected every 5 cm along the transverse direction of the test paper, for a total of 10 points. The thickness values ​​of all points were recorded. The range of this set of data, i.e., the deviation between the maximum and minimum values, was calculated. The test results are shown in Tables 1 and 2.

[0069] Table 1. Performance test results of Examples 1-5 performance Example 1 Example 2 Example 3 Example 4 Example 5 150°C heat shrinkage rate 0.08% 0.08% 0.08% 0.08% 0.08% Breakdown voltage (kV / mm) 45.5 45.2 45.3 45.5 45.5 UL94 flame retardant rating V-0 V-0 V-0 V-0 V-0 Tensile strength (kN / mm) 12.5 12.4 12.1 12.4 12.7 Electrolyte retention rate 96% 95% 95% 95% 96% Ash content (%) 0.05 0.05 0.05 0.05 0.05 Thickness range (μm) ±1.1 ±1.1 ±1.1 ±1.1 ±1.1 Table 2 shows the performance test results for Comparative Examples 1-4. performance Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 150°C heat shrinkage rate 0.25% 0.12% 0.15% 0.35% Breakdown voltage (kV / mm) 40.2 38.4 32.1 28.5 UL94 flame retardant rating V-0 V-2 V-1 V-0 Tensile strength (kN / mm) 10.2 9.5 7.8 6.2 Electrolyte retention rate 92% 68% 85% 45% Ash content (%) 0.05 0.06 0.06 0.05 Thickness range (μm) ±1.8 ±1.4 ±8.5 ±3.2 As can be seen from Tables 1 and 2, in Comparative Example 1, when PEN fiber was used to replace the amount of meta-aramid chopped fiber, the heat shrinkage rate at 150℃ increased sharply from 0.08% to 0.25%. This is because meta-aramid chopped fiber has high thermal dimensional stability, while PEN chopped fiber, although heat-resistant, still tends to shrink when approaching its glass transition temperature.

[0070] As can be seen from Tables 1 and 2, in Comparative Example 2, after using ordinary epoxy resin, the flame retardant rating dropped from V-0 to V-2, and the electrolyte retention rate decreased from 96% to 68%. Phosphate ester modification improved the interfacial compatibility and crosslinking density of the resin and fiber. However, the bisphenol A type epoxy resin emulsion had insufficient crosslinking points, resulting in a loose structure and loss of strength.

[0071] As shown in Tables 1 and 2, in Comparative Example 3, the absence of dispersant PEO resulted in an increase in the thickness range from ±1.1 μm to ±8.5 μm, and a corresponding decrease in the breakdown voltage. This is because PEO achieves single-fiber dispersion through the steric hindrance effect generated by the long polymer chains.

[0072] As can be seen from Tables 1 and 2, in Comparative Example 4, after the hot pressing temperature was reduced to 180℃, although the paper was formed, its tensile strength and electrolyte resistance were the lowest, and the breakdown voltage also dropped to 28.5kV / mm. This is because hot pressing at 180℃ can only melt the Co-PET skin to achieve preliminary bonding, and cannot trigger deep chemical cross-linking between PAE and epoxy resin.

[0073] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An insulating paper for a formation tank, characterized by, By mass percentage, it includes the following components: 22-30% meta-aramid chopped fibers, 20-34% PEN chopped fibers, 32-41% Co-PET / PET core-sheath bicomponent chopped fibers, 5-12% aqueous phosphate-modified epoxy resin emulsion, 0.7-1.5% wet strength agent, and 0.5-1% dispersant.

2. The insulation paper for a formation tank according to claim 1, wherein The linear density of the meta-aramid chopped fiber is 1.5–2.0D, and the length is 3–6 mm; the length of the PEN chopped fiber is 5–6 mm.

3. The insulation paper for a formation tank according to claim 1, wherein The melting point of the sheath of the Co-PET / PET sheath-core bicomponent short-cut fiber is 110℃~160℃, the melting point of the core layer is ≥250℃, and the difference in melting points between the sheath and the core layer is ΔT≥90℃. The aqueous phosphate-modified epoxy resin emulsion contains a latent curing system, and the initial reaction temperature of the emulsion, measured by differential scanning calorimetry, is 145℃~165℃.

4. The insulation paper for a formation tank according to claim 1, wherein The wet strength agent is PAE; the dispersant is PEO.

5. A method of producing an insulation paper for a formation tank according to any one of claims 1 to 4, characterized by, Includes the following steps: Step 1: Meta-aramid staple fibers, PEN staple fibers, and Co-PET / PET core-sheath type bicomponent chopped fibers are dissociated in deionized water, and the total mass concentration of the sizing fiber is adjusted to 0.2%–0.5%; Step 2: Add the slurry to the slurry tank and perform low-shear mixing; Under stirring conditions, the reinforcing agent PAE is added to the slurry to form a uniformly distributed cationic charge layer on the surface of each fiber. As the aqueous phosphate-modified epoxy resin emulsion is slowly added, the aqueous phase of the slurry changes from turbid to clear. The phosphate-modified epoxy resin and PAE are neutralized through interfacial charge and firmly anchored to the fiber matrix. With the addition of dispersant PEO, the slurry exhibits a sterically stable suspension state. Step 3: Transfer the pulp obtained in Step 2 to the wire section of the paper machine; The pulp undergoes rapid solid-liquid separation on the filter screen, and the functional fibers and epoxy emulsion particles fixed on the fiber surface are trapped on the screen and deposited to form a wet paper sheet. Step 4: Transfer the wet paper sheet to the drying wire; under the pressure of the drying wire, the wet paper sheet adheres tightly to the high-temperature outer surface of the steam drying cylinder; The wet paper sheets pass through multiple steam drying cylinders in sequence with the dry wire for graded drying. After drying, the fibers begin to bond and form a porous fiber mesh skeleton with initial strength. Step 5: The dried paper is fed into a multi-roll calender; The paper sheet is preheated by the preheating roller, and then enters the gap between two hot press rollers under tension support, which completes the instantaneous compaction of the paper sheet, thereby constructing a dense three-dimensional cross-linked network; The compacted paper sheet travels around the circumferential surface of the cooling and shaping roller, and through rapid cooling, it is finally transformed into finished insulating paper.

6. The method of claim 5, wherein the insulation paper for the formation tank is prepared by adding 0.1 to 0.5 parts by weight of the compound of formula (1) to 100 parts by weight of the base paper. In step one, meta-aramid short fibers, PEN short fibers, and Co-PET / PET core-sheath type bicomponent chopped fibers are fed into a fiber dissociation machine, and deionized water is added for dissociation. The dissociation speed is 2900-3000 rpm, and the dissociation time is 15-25 min.

7. The method for preparing insulating paper for a chemical forming cabinet according to claim 5, characterized in that, In step two, a low-shear propulsion agitator is installed in the slurry tank, with a stirring speed of 150-250 rpm, to maintain micro-turbulent circulation of the slurry.

8. The method for preparing insulating paper for a chemical forming cabinet according to claim 5, characterized in that, In step three, the slurry is evenly sprayed onto the wire section of the paper machine through the weir plate; The slurry undergoes rapid solid-liquid separation on a filter screen via gravity dehydration and a vacuum suction box. The moisture content of the wet paper sheet is 65% to 75%.

9. The method for preparing insulating paper for a chemical forming cabinet according to claim 5, characterized in that, In step four, the negative pressure effect generated by the vacuum suction roller is used to smoothly peel the dehydrated wet paper sheet from the forming wire and transfer it to the dry wire. The wet paper sheets pass through the first 1 to 6 steam drying cylinders in sequence along with the dry wire, with a drying temperature of 85℃ to 105℃ and a drying time of 4 to 8 seconds for the first stage of drying; The wet paper sheets then pass through 3 to 4 steam drying cylinders in the later stage along with the dry wire, where the drying temperature is 130℃ to 150℃ and the drying time is 2 to 5 seconds, for a second stage of drying.

10. The method for preparing insulating paper for a chemical forming cabinet according to claim 5, characterized in that, In step five, the temperature of the preheating roller is 160℃~180℃, and the preheating time is 0.5~3s; the temperature of the hot pressing roller is 240℃~280℃, and the paper sheet bears an instantaneous linear pressure of 200~400kN / m in the gap between the two hot pressing rollers; the paper sheet stays in the gap for 30~60ms; the surface temperature of the cooling and shaping roller is 20℃~40℃, and the cooling time is 2~4s. The basis weight of the insulating paper is 80-120 g / m², and the thickness range is ≤ ±1.5 μm.