A high-temperature resistant and creep-resistant asbestos-free composite sealing material and its preparation method

Abstract

This invention discloses a high-temperature resistant and creep-resistant asbestos-free composite sealing board and its preparation method. The board is made from raw materials comprising 30-50 parts inorganic fibers, 10-20 parts high-temperature resistant organic fibers, 25-45 parts high-temperature resistant functional fillers, and 8-18 parts composite binder. The composite binder is pre-mixed from liquid phenolic resin and nano-silica sol at a dry weight ratio of 1:(0.5-2). The board has a localized inorganic reinforcing network formed by the accumulation and curing of nano-silica sol in the pores and interfaces of the fiber network. The preparation method includes: fiber dispersion and pulping, composite slurry preparation, wet paper forming, supplementary impregnation and pre-curing, segmented hot pressing curing, and post-heat treatment. This invention, by combining an organic-inorganic composite bonding system with a specific process, significantly improves the board's resistance to compression creep and sealing durability at high temperatures, solving the technical problem of easy loosening and leakage of traditional asbestos-free sealing materials under extreme conditions.

Description

Technical Field

[0001] This invention belongs to the field of sealing plate preparation technology, specifically, it relates to a high-temperature resistant and creep-resistant asbestos-free composite sealing plate and its preparation method. Background Technology

[0002] Sealing plates are indispensable key components in industries such as petrochemicals, power energy, aerospace, and automotive engines. Their core functions are to prevent leakage of various fluid media, maintain system pressure stability, and achieve effective isolation between adjacent components. The performance stability of sealing materials under harsh conditions such as high temperature, high pressure, and long-term dynamic loads directly determines the operational safety, energy efficiency, and maintenance cycle of the entire equipment.

[0003] Historically, asbestos fiber was the preferred reinforcing material for sealing panels due to its excellent heat resistance, high mechanical strength, and low cost. However, medical research has confirmed that asbestos fiber poses serious health risks, leading to occupational diseases such as asbestosis and lung cancer. Therefore, its use has been strictly restricted or banned globally. Developing asbestos-free sealing materials with comparable or even superior performance has become an urgent and necessary technological and regulatory direction for the entire industry.

[0004] To replace asbestos, the industry has extensively researched various inorganic fibers such as glass fiber, ceramic fiber, mineral fiber, and organic fibers such as aramid fiber, cellulose fiber, and their composite systems. However, existing asbestos-free sealing materials still face a series of significant technical bottlenecks when meeting the extreme operating conditions required by modern industry, especially in fields such as supercritical power generation and high-temperature chemical processing. First, the compressive creep resistance of materials under long-term high-temperature environments is generally insufficient. Creep refers to the slow and irreversible plastic deformation of a material under the combined action of sustained stress and high temperature. For gaskets, excessive creep will lead to relaxation of sealing stress and attenuation of preload, thereby causing leakage accidents. Many existing asbestos-free boards, when subjected to operating temperatures above 300 degrees Celsius for extended periods, are prone to softening, degradation, or structural damage in their internal bonding system, failing to effectively lock the network skeleton formed by fibers and fillers, resulting in significant permanent deformation of the material and rapid failure of the sealing function.

[0005] Secondly, existing adhesive systems struggle to balance high and low temperature performance. Commonly used single-organic polymer adhesive systems, such as nitrile rubber latex, fluororubber, or conventional phenolic resins, while providing good initial adhesion and elasticity, typically have a long-term temperature limit of less than 300 degrees Celsius when existing as a single phase. Above this temperature, the organic phase is prone to thermal degradation, oxidation, or embrittlement, losing its adhesive properties and potentially releasing low-molecular-weight volatiles. On the other hand, simple inorganic adhesives, such as water glass (sodium silicate), while exhibiting high temperature resistance, are brittle after curing, have weak bonding with fibers, and produce boards with poor flexibility, prone to powdering, and often exhibiting poor resistance to environmental corrosion, especially in humid and hot environments.

[0006] Furthermore, the design of the fiber-filler combination and interfacial bonding needs optimization. Simple physical blending is insufficient to form a uniform and stable three-dimensional network at the microscopic level. If conventional fillers are not selected or properly proportioned, they cannot provide effective support, barrier, and stress transfer at high temperatures. At the same time, traditional wet papermaking or dry molding processes have limited control over fiber dispersion, orientation, and filler distribution in the binder, which can easily lead to uneven internal structure and defects in the product, thus restricting the improvement of the overall material performance, especially high-temperature creep strength.

[0007] More importantly, current technologies are mostly limited to single-type binders or simple physical blending, making it difficult to construct a stable composite structure within the material that can withstand long-term high-temperature effects while effectively transferring and dispersing stress, thereby significantly inhibiting creep. In particular, how to precisely introduce and fix inorganic binder components at weak points in the fiber-filler network to form microscopic reinforcement points, without compromising the overall flexibility and density of the material, remains an unsolved technical challenge. Furthermore, a complete and controllable preparation process is lacking to achieve this ideal microscale composite and structural construction of organic and inorganic components.

[0008] Therefore, there is an urgent need for an innovative asbestos-free composite sealing material and its preparation method. This solution should be able to construct a stable micro-reinforced structure inside the material and realize this structure through a specific process. The aim is to fundamentally solve the key technical problems mentioned above, such as poor high-temperature creep resistance, difficulty in balancing the temperature resistance and toughness of the bonding system, and insufficient uniformity of the microstructure, so as to meet the growing demand of the high-end equipment manufacturing industry for high-performance sealing materials. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a high-temperature resistant and creep-resistant asbestos-free composite sealing plate and its preparation method.

[0010] To achieve the above objectives, the technical solution provided by the present invention is as follows: A high-temperature resistant and creep-resistant asbestos-free composite sealing board is made from the following raw materials in parts by weight: 30-50 parts inorganic fiber, 10-20 parts high-temperature resistant organic fiber, 25-45 parts high-temperature resistant functional filler, and 8-18 parts composite adhesive. The composite adhesive is premixed from liquid phenolic resin and nano-silica sol at a dry weight ratio of 1:(0.5-2), and the board has a local inorganic reinforcement network formed by the nano-silica sol being enriched in the pores and interfaces of the fiber network and then cured.

[0011] This invention utilizes a composite binder premixed from liquid phenolic resin and nano-silica sol in a specific dry basis ratio, combined with a specific amount of fiber and filler system, to successfully construct a locally enriched inorganic reinforcement network within the fiber network pores and interfaces of the board. This structure creatively combines the toughness and good adhesion of organic binders with the high thermal stability of inorganic nanoparticles, effectively resolving the inherent contradiction between the insufficient temperature resistance of single organic binders and the high brittleness of single inorganic binders. The resulting board exhibits extremely high structural integrity at high temperatures, demonstrating excellent resistance to compressive creep and long-lasting sealing reliability, fully meeting the requirements for asbestos-free sealing materials under extreme operating conditions.

[0012] Furthermore, the inorganic fiber is at least one of sepiolite fiber or attapulgite fiber surface-treated with an aminosilane coupling agent, and its length is 0.2–3 mm. This invention, by further limiting the type, surface treatment, and length of the inorganic fiber, significantly improves the interfacial bonding force between the fiber and the composite binder, especially the silica sol component. The specific mineral fibers treated with the aminosilane coupling agent are not only inherently heat-resistant, but the enhanced surface activity ensures that the inorganic reinforcing network can be more firmly anchored to the fiber surface, enhancing the stability of the network structure, thereby further improving the board's resistance to relaxation and overall mechanical strength under high-temperature stress.

[0013] Furthermore, the heat-resistant functional filler is composed of flake mica powder and nano-silica in a weight ratio of (3-5):1, wherein the aspect ratio of the flake mica powder is greater than 20. This invention specifies that the heat-resistant functional filler is a composite of flake mica powder and nano-silica in a specific ratio. Flake mica can form an effective thermal and stress barrier layer in the board, inhibiting crack propagation; nano-silica can fully fill micropores, synergistically reinforcing with silica sol. This composite system forms dense and stable heat-resistant support points in the fiber skeleton, significantly improving the short-term pressure resistance of the board, and more importantly, providing rigid support against creep deformation under long-term high temperatures, which is key to achieving a low creep rate.

[0014] Furthermore, the liquid phenolic resin has a solid content of 45-55%, and the nano-silica sol has a particle size of 10-20 nm, with epoxy groups grafted onto the surface of its SiO2 particles. This invention optimizes the processability and reactivity of the composite adhesive by limiting the solid content of the liquid phenolic resin and the particle size and surface characteristics of the nano-silica sol. The specific solid content of the resin ensures initial bond strength; the nano-sized silica sol with surface-grafted epoxy groups exhibits better dispersibility, and the epoxy groups can react with the phenolic resin, strengthening the chemical bond between the organic and inorganic phases. This results in a more tightly bonded localized inorganic reinforcing network with the organic matrix, significantly improving the high-temperature interfacial stability and durability of the composite material.

[0015] The present invention also provides a method for preparing the high-temperature resistant and creep-resistant asbestos-free composite sealing plate, comprising the following steps: S1 Fiber Dispersion Pulping: The inorganic fibers and high-temperature resistant organic fibers are dispersed at high speed in water to form a uniform fiber slurry; S2 composite slurry preparation: The heat-resistant functional filler and the composite binder are added sequentially to the fiber slurry, and the mixture is stirred to form a uniform composite slurry; S3 Wet papermaking: The composite pulp is wet-processed and dehydrated to form a wet paper web with a moisture content of 25-45%. S4 Supplementary Impregnation and Pre-curing: The wet paper web is impregnated in a low-viscosity silica sol supplementary solution with a solid content of 10-20%. After controlling the liquid content by extrusion, it is pre-cured at 90-110°C for 5-15 minutes to allow the silica sol to be preferentially enriched in the pores and interfaces of the fiber network. S5 Segmented Hot Press Curing: The pre-cured blank is placed in a hot press for two-stage hot pressing. First stage: Hot pressing for 10-20 minutes at a pressure of 6-8 MPa and a temperature of 150-160℃; Second stage: Raise the temperature to 190-210℃, and at the same time increase the pressure to 18-22MPa, and continue hot pressing for 40-60 minutes; S6 Post-heat treatment: The hot-pressed sheet is heat-treated at 280-320℃ for 3-5 hours under an inert atmosphere.

[0016] This preparation method systematically constructs a localized inorganic reinforcement network through a core process combining the addition of a composite binder and supplementary impregnation with silica sol. Wet forming ensures initial component uniformity; supplementary impregnation allows the silica sol to precisely target and enrich weak points in the fiber network; and segmented hot pressing achieves an optimized match between organic curing and inorganic condensation. The entire process chain is scientifically designed and highly operable, providing a reliable guarantee for the stable preparation of high-performance boards with the unique microstructure described in claim 1.

[0017] Furthermore, in step S4, the low-viscosity silica sol replenishing solution and the nano-silica sol used in the composite binder are the same substance. This preparation method limits the replenishing impregnation solution and the silica sol in the main binder to be the same substance, ensuring the uniformity of the entire inorganic reinforcing network in terms of chemical properties and structure. This avoids the interface compatibility problems that may arise from using inorganic phases of different sources or properties, allowing the inorganic reinforcing phases formed by the inner (main) and outer (impregnation) components to seamlessly fuse, constructing a continuous and uniform reinforcing network, thereby ensuring the uniformity and stability of the board's performance.

[0018] Furthermore, during the second stage of hot pressing in step S5, pulsed pressure with a frequency of 1–3 Hz is applied simultaneously, and the fluctuation range of the pulsed pressure is ±15% of the set pressure. This preparation method applies pulsed pressure of a specific frequency and amplitude during the second stage of hot pressing curing, which is a dynamic molding process. This process can effectively promote the flow and rearrangement of materials at high temperatures, help remove residual air bubbles, reduce internal defects, and promote more optimized orientation of fibers and fillers. The resulting sheet has higher density and more uniform internal stress distribution, thereby further improving its creep resistance and mechanical strength.

[0019] Further, in step S6, the post-heat treatment specifically involves heating to 300°C at a rate of 1°C / min under a nitrogen atmosphere and maintaining this temperature for 4 hours. This preparation method precisely controls the post-heat treatment regime, i.e., the heating rate and the isothermal conditions, to achieve a smooth transformation and eventual stabilization of the material structure. Slow heating avoids the generation of microcracks caused by thermal stress; prolonged isothermal treatment at a specific temperature ensures complete thermal curing of the phenolic resin, thorough condensation of the silica sol, and promotes the completion of the interfacial reaction between the two phases, ultimately enabling the board to obtain stable high-temperature performance and excellent anti-aging capabilities.

[0020] Further, in step S1, the high-speed dispersion rotation speed is 2000–4000 rpm, the dispersion time is 30–50 minutes, and the solid content of the fiber slurry is controlled at 3–4%. This preparation method limits the rotation speed, time, and slurry solid content during the initial fiber dispersion stage, which is fundamental to ensuring successful preparation. This parameter combination ensures that various fibers, especially difficult-to-disperse mineral and organic fibers, are fully dissociated and form a highly uniform and stable suspension slurry. This is the primary prerequisite for the effective execution of all subsequent process steps and the final acquisition of a high-performance board with a uniform microstructure.

[0021] Compared with the prior art, the present invention has the following beneficial effects: I. This invention creatively employs a bonding system pre-composite with liquid phenolic resin and specific nano-silica sol, and designs a matching combination of fibers and fillers. This design not only macroscopically combines the toughness of organic components with the temperature resistance of inorganic components, but also microscopically promotes the precise enrichment of nano-silica sol in the pores and interfaces of the fiber network, forming a robust local inorganic reinforcement network in situ. This unique microstructure fundamentally overcomes the inherent defects of traditional single-binder systems, which either have insufficient high-temperature performance or excessive brittleness, endowing the board with excellent high-temperature structural stability.

[0022] II. The preparation method provided by this invention, particularly the core processes of supplementary impregnation and segmented pulse hot pressing, is not a simple superposition of steps, but a systematic design targeting the microstructure. This method ensures the selective construction of the inorganic reinforcing phase in weak regions within the material and effectively eliminates internal defects and optimizes component orientation through dynamic hot pressing. The entire process exhibits good repeatability and strong controllability, enabling the stable and efficient production of composite materials with uniform and highly dense microstructures, thus paving a key path from innovative formulations to the industrialization of high-performance products.

[0023] Third, thanks to the dual guarantees of material design and process innovation, the resulting asbestos-free composite sealing sheet exhibits significantly superior comprehensive performance compared to existing technologies. Under continuous high temperature and high pressure extreme conditions, it displays extremely low compression creep rate and extremely high strength retention rate, which means slow sealing stress decay and long service life. This product successfully solves the core technical problem of traditional asbestos-free sheets being prone to loosening and leakage at high temperatures, meeting the growing urgent demand for high-performance sealing materials in the high-end equipment manufacturing field, and possessing significant social benefits and market application value. Detailed Implementation

[0024] The specific embodiments are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise specified, the raw materials and reagents used in the examples are commercially available.

[0025] The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Although the invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the invention without departing from the spirit and scope of the invention, and all such modifications and substitutions should be covered within the scope of the claims of the invention.

[0026] Example 1 This embodiment provides a high-temperature resistant and creep-resistant asbestos-free composite sealing plate and its preparation method. 1. Raw material formula: Inorganic fibers: 40.0 kg. Specifically, this includes 20.0 kg of sepiolite fibers with a length of 2.0 mm, which have been surface-treated with aminosilane coupling agent KH-550, and 20.0 kg of attapulgite fibers with a length of 1.0 mm.

[0027] High-temperature resistant organic fiber: 15.0 kg. Specifically, this includes 10.0 kg of aramid pulp and 5.0 kg of polyimide chopped strand fiber.

[0028] Temperature-resistant functional filler: 35.0 kg. Specifically, this consists of 28.0 kg of flaky mica powder with an aspect ratio greater than 25 and 7.0 kg of nano-silica powder with a particle size of 30 nm.

[0029] Composite adhesive: prepared by premixing the following two components: Liquid phenolic resin solution: 4.0 kg, with a solid content of 50.0%.

[0030] Nano-silica sol: 8.0 kg, with a solid content of 25.0%, SiO2 particles with epoxy groups grafted on the surface and a particle size of 15 nm.

[0031] *(Dry basis calculation: Phenolic resin dry basis = 4.0 kg × 50.0% = 2.0 kg; Nano silica sol dry basis = 8.0 kg × 25.0% = 2.0 kg; The dry basis weight ratio of the two is 1:1)* Auxiliary agent (dispersant): Sodium polyacrylate, 0.35 kg (for dispersion of nano silica).

[0032] Supplement impregnation solution: A low-viscosity nano-silica sol solution with a solid content of 15.0%, which is prepared by diluting a mother liquor of the same origin as the nano-silica sol used in the composite binder.

[0033] Process water: Deionized water, dosage as per preparation steps.

[0034] 2. Preparation method: S1 Fiber Dispersion Pulping: Add the above 40.0 kg inorganic fiber and 15.0 kg high-temperature resistant organic fiber to 1365.0 kg deionized water; first stir at 1200 rpm for 10 minutes to fully wet the fiber, then increase to 3000 rpm and disperse for 30 minutes to form a uniform fiber slurry; Preparation of S2 composite slurry: 7.0 kg of nano-silica powder, 70 kg of deionized water, and all of the 0.35 kg of sodium polyacrylate dispersant were mixed to form a suspension, which was then ultrasonically treated for 20 minutes. 28.0 kg of flake mica powder was added to the fiber slurry obtained in step S1, followed by the above-mentioned nano-silica suspension, and finally 12.0 kg of pre-mixed composite binder. The mixture was stirred continuously at 800 rpm for 60 minutes to form a uniform composite slurry. S3 Wet Paper Forming: The above composite pulp is introduced into the inclined wire paper forming machine for wet paper forming, and dewatered using a vacuum dewatering box to form a wet paper web with a moisture content of 38%. S4 Supplementary Impregnation and Pre-curing: The wet paper web is impregnated in the supplementary impregnation solution, and after the liquid content is controlled by a pair of squeeze rollers, it is pre-cured in a drying oven at 100°C for 10 minutes. S5 Segmented Hot Press Curing: Place the pre-cured blank in a flatbed hot press; First stage: Hot press for 15 minutes at a pressure of 7.0 MPa and a temperature of 155℃; Second stage: Increase the pressure to 20.0 MPa and the temperature to 200℃. During this stage, apply pulse pressure with a frequency of 2.0 Hz and a fluctuation range of ±15% of the set pressure simultaneously, and continue hot pressing for 50 minutes. S6 Post-Heat Treatment: The hot-pressed sheet is transferred to a nitrogen-protected heat treatment furnace, where it is heated to 300°C at a rate of 1°C / min and held at 300°C for 4 hours. It is then allowed to cool naturally to room temperature in the furnace, resulting in a high-temperature-resistant, creep-resistant, asbestos-free composite sealing sheet.

[0035] Example 2 This embodiment provides a high-temperature resistant and creep-resistant asbestos-free composite sealing plate and its preparation method.

[0036] 1. Raw material formula: Inorganic fiber: 30.0 kg. All are attapulgite fibers with a length of 0.5 mm, surface-treated with aminosilane coupling agent.

[0037] High-temperature resistant organic fiber: 10.0 kg. All are polyimide chopped fibers.

[0038] Temperature-resistant functional filler: 25.0 kg. Specifically, it consists of 18.75 kg of flaky mica powder with an aspect ratio greater than 20 and 6.25 kg of nano-silica powder with a particle size of 20 nm.

[0039] Composite adhesive: prepared by premixing the following two components: Liquid phenolic resin solution: 4.0 kg, with a solid content of 45.0%.

[0040] Nano-silica sol: 8.0 kg, with a solid content of 15.0%, SiO2 particles with epoxy groups grafted on the surface and a particle size of 10 nm.

[0041] *(Dry basis calculation: Phenolic resin dry basis = 4.0 kg × 45.0% = 1.8 kg; Nano silica sol dry basis = 8.0 kg × 15.0% = 1.2 kg; The dry basis weight ratio of the two is 1:0.67)* Auxiliary agent (dispersant): Sodium polyacrylate, 0.31 kg (for dispersion of nano silica).

[0042] Supplement impregnation solution: a low-viscosity nano-silica sol solution with a solid content of 10.0%, which is diluted from a mother liquor of the same origin as the nano-silica sol used in the composite adhesive.

[0043] Process water: Deionized water, dosage as per preparation steps.

[0044] 2. Preparation method: S1 Fiber Dispersion Pulping: Add the above 30.0 kg inorganic fiber and 10.0 kg high-temperature resistant organic fiber to 955.0 kg deionized water; disperse for 50 minutes under high-speed stirring at 2000 rpm to form a uniform fiber slurry; Preparation of S2 composite slurry: 6.25 kg of nano silica powder, 62.5 kg of deionized water, and all of the 0.31 kg of sodium polyacrylate dispersant were mixed to form a suspension, which was then ultrasonically treated for 20 minutes. 18.75 kg of flake mica powder was added to the fiber slurry obtained in step S1, followed by the above-mentioned nano silica suspension, and finally 12.0 kg of pre-mixed composite binder was added. The mixture was stirred continuously at a stirring speed of 600 rpm for 70 minutes to form a uniform composite slurry. S3 Wet Papermaking: The above composite pulp is wet-processed and dehydrated to form a wet paper web with a moisture content of 32%. S4 Supplementary Impregnation and Pre-curing: The wet paper web is impregnated in the supplementary impregnation solution, and after the liquid content is controlled by squeezing, it is pre-cured at 90°C for 15 minutes. S5 Segmented Hot Press Curing: Place the pre-cured blank in a hot press; First stage: Hot press for 20 minutes at a pressure of 6.0 MPa and a temperature of 150℃; Second stage: Raise the temperature to 190℃ and simultaneously increase the pressure to 18.0 MPa, and continue hot pressing for 60 minutes. No pulse pressure is applied in this stage. S6 Post-heat treatment: The hot-pressed board is placed in a heat treatment furnace at 280℃ under nitrogen atmosphere protection for 5 hours, and then naturally cooled to room temperature to obtain a high-temperature resistant and creep-resistant asbestos-free composite sealing board.

[0045] Example 3 This embodiment provides a high-temperature resistant and creep-resistant asbestos-free composite sealing plate and its preparation method.

[0046] 1. Raw material formula: Inorganic fiber: 50.0 kg. Specifically, this includes 30.0 kg of sepiolite fiber with a length of 3.0 mm, which has been surface-treated with an aminosilane coupling agent, and 20.0 kg of the same fiber with a length of 0.2 mm.

[0047] High-temperature resistant organic fiber: 20.0 kg. All of it is aramid pulp.

[0048] Temperature-resistant functional filler: 45.0 kg. Specifically, this consists of 37.5 kg of flaky mica powder with an aspect ratio greater than 30 and 7.5 kg of nano-silica powder with a particle size of 50 nm.

[0049] Composite adhesive: prepared by premixing the following two components: Liquid phenolic resin solution: 5.0 kg, with a solid content of 55.0%.

[0050] Nano-silica sol: 10.0 kg, with a solid content of 27.5%, SiO2 particles with epoxy groups grafted on the surface and a particle size of 20 nm.

[0051] *(Dry basis calculation: Phenolic resin dry basis = 5.0 kg × 55.0% = 2.75 kg; Nano silica sol dry basis = 10.0 kg × 27.5% = 2.75 kg; The dry basis weight ratio of the two is 1:1)* Auxiliary agent (dispersant): Sodium polyacrylate, 0.38 kg (for dispersion of nano silica).

[0052] Supplement impregnation solution: A low-viscosity nano-silica sol solution with a solid content of 20.0%, which is diluted from a mother liquor of the same origin as the nano-silica sol used in the composite adhesive.

[0053] Process water: Deionized water, dosage as per preparation steps.

[0054] 2. Preparation method: S1 Fiber Dispersion Pulping: Add the above 50.0 kg inorganic fiber and 20.0 kg high-temperature resistant organic fiber to 1710.0 kg deionized water; first stir at 1000 rpm for 15 minutes, then increase to 4000 rpm and disperse for 20 minutes to form a uniform fiber slurry; Preparation of S2 composite slurry: 7.5 kg of nano silica powder, 75 kg of deionized water, and all of the 0.38 kg of sodium polyacrylate dispersant were mixed to form a suspension, which was then ultrasonically treated for 25 minutes. 37.5 kg of flake mica powder was added to the fiber slurry obtained in step S1, followed by the above-mentioned nano silica suspension, and finally 15.0 kg of pre-mixed composite binder was added. The mixture was stirred continuously at a stirring speed of 1000 rpm for 50 minutes to form a uniform composite slurry. S3 Wet Papermaking: The above composite pulp is wet-processed and dehydrated to form a wet paper web with a moisture content of 45%. S4 Supplementary Impregnation and Pre-curing: The wet paper web is impregnated in the supplementary impregnation solution, and after the liquid content is controlled by squeezing, it is pre-cured at 110°C for 5 minutes. S5 Segmented Hot Press Curing: Place the pre-cured blank in a hot press; First stage: Hot press for 10 minutes at a pressure of 8.0 MPa and a temperature of 160℃; Second stage: Raise the temperature to 210℃ and simultaneously raise the pressure to 22.0 MPa. During this stage, apply pulse pressure with a frequency of 3.0 Hz and a fluctuation range of ±15% of the set pressure, and continue hot pressing for 40 minutes. S6 Post-heat treatment: The hot-pressed sheet is placed in a heat treatment furnace at 300°C under nitrogen atmosphere protection and heat-treated for 3 hours. It is then naturally cooled to room temperature to obtain the high-temperature resistant and creep-resistant asbestos-free composite sealing sheet.

[0055] Example 4 This embodiment provides a high-temperature resistant and creep-resistant asbestos-free composite sealing plate and its preparation method.

[0056] 1. Raw material formula: Inorganic fiber: 35.0 kg. All are attapulgite fibers with a length of 1.5 mm, surface-treated with aminosilane coupling agent.

[0057] High-temperature resistant organic fiber: 12.0 kg. Specifically, it consists of 8.0 kg of aramid pulp and 4.0 kg of polyimide chopped strand fiber.

[0058] Temperature-resistant functional filler: 40.0 kg. Specifically, this consists of 30.0 kg of flaky mica powder with an aspect ratio greater than 22 and 10.0 kg of nano-silica powder with a particle size of 15 nm.

[0059] Composite adhesive: prepared by premixing the following two components: Liquid phenolic resin solution: 7.0 kg, with a solid content of 48.0%.

[0060] Nano-silica sol: 8.0 kg, with a solid content of 28.0%, SiO2 particles with epoxy groups grafted on the surface and a particle size of 12 nm.

[0061] *(Dry basis calculation: Phenolic resin dry basis = 7.0 kg × 48.0% = 3.36 kg; Nano silica sol dry basis = 8.0 kg × 28.0% = 2.24 kg; The dry basis weight ratio of the two is 1:0.67)* Auxiliary agent (dispersant): Sodium polyacrylate, 0.50 kg (for dispersion of nano silica).

[0062] Supplement impregnation solution: a low-viscosity nano-silica sol solution with a solid content of 12.0%, which is diluted from a mother liquor of the same origin as the nano-silica sol used in the composite binder.

[0063] Process water: Deionized water, dosage as per preparation steps.

[0064] 2. Preparation method: S1 Fiber Dispersion Pulping: Add the above 35.0 kg inorganic fiber and 12.0 kg high-temperature resistant organic fiber to 1125.0 kg deionized water; disperse at a high speed of 2500 rpm for 45 minutes to form a uniform fiber slurry; Preparation of S2 composite slurry: 10.0 kg of nano-silica powder, 100 kg of deionized water, and all of the 0.50 kg of sodium polyacrylate dispersant were mixed to form a suspension, which was then ultrasonically treated for 30 minutes. 30.0 kg of flake mica powder was added to the fiber slurry obtained in step S1, followed by the above-mentioned nano-silica suspension, and finally 15.0 kg of pre-mixed composite binder. The mixture was stirred continuously at a speed of 900 rpm for 55 minutes to form a uniform composite slurry. S3 Wet Papermaking: The above composite pulp is wet-processed and dehydrated to form a wet paper web with a moisture content of 35%. S4 Supplementary Impregnation and Pre-curing: The wet paper web is impregnated in the supplementary impregnation solution, and after the liquid content is controlled by squeezing, it is pre-cured at 95°C for 12 minutes. S5 Segmented Hot Press Curing: Place the pre-cured blank in a hot press; First stage: Hot press for 12 minutes at a pressure of 7.0 MPa and a temperature of 158℃; Second stage: Raise the temperature to 205℃ and simultaneously increase the pressure to 19.0 MPa. During this stage, apply pulse pressure with a frequency of 1.0 Hz and a fluctuation range of ±15% of the set pressure, and continue hot pressing for 55 minutes. S6 Post-heat treatment: The hot-pressed board is placed in a heat treatment furnace at 290℃ under nitrogen atmosphere protection and heat-treated for 4 hours; then it is naturally cooled to room temperature to obtain a high-temperature resistant and creep-resistant asbestos-free composite sealing board.

[0065] Example 5 This embodiment provides a high-temperature resistant and creep-resistant asbestos-free composite sealing plate and its preparation method.

[0066] 1. Raw material formula: Inorganic fibers: 45.0 kg. Specifically, this includes 25.0 kg of sepiolite fibers with a length of 2.5 mm that have been surface-treated with an aminosilane coupling agent, and 20.0 kg of attapulgite fibers with a length of 0.8 mm.

[0067] High-temperature resistant organic fiber: 18.0 kg. Specifically, this includes 12.0 kg of aramid pulp and 6.0 kg of polyimide chopped strand fiber.

[0068] Temperature-resistant functional filler: 30.0 kg. Specifically, this consists of 25.0 kg of flaky mica powder with an aspect ratio greater than 28 and 5.0 kg of nano-silica powder with a particle size of 40 nm.

[0069] Composite adhesive: prepared by premixing the following two components: Liquid phenolic resin solution: 3.0 kg, with a solid content of 52.0%.

[0070] Nano-silica sol: 12.0 kg, with a solid content of 13.0%, SiO2 particles with epoxy groups grafted on the surface and a particle size of 18 nm.

[0071] *(Dry basis calculation: Phenolic resin dry basis = 3.0 kg × 52.0% = 1.56 kg; Nano silica sol dry basis = 12.0 kg × 13.0% = 1.56 kg; The dry basis weight ratio of the two is 1:1)* Auxiliary agent (dispersant): Sodium polyacrylate, 0.25 kg (for dispersion of nano silica).

[0072] Supplement impregnation solution: a low-viscosity nano-silica sol solution with a solid content of 18.0%, which is diluted from a mother liquor of the same origin as the nano-silica sol used in the composite adhesive.

[0073] Process water: Deionized water, dosage as per preparation steps.

[0074] 2. Preparation method: S1 Fiber Dispersion Pulping: Add the above 45.0 kg of inorganic fiber and 18.0 kg of high-temperature resistant organic fiber to 1575.0 kg of deionized water; first stir at 1200 rpm for 10 minutes, then increase to 3500 rpm and disperse for 25 minutes to form a uniform fiber slurry; Preparation of S2 composite slurry: 5.0 kg of nano silica powder, 50 kg of deionized water, and all of the 0.25 kg of sodium polyacrylate dispersant were mixed to form a suspension, which was then ultrasonically treated for 15 minutes. 25.0 kg of flake mica powder was added to the fiber slurry obtained in step S1, followed by the above-mentioned nano silica suspension, and finally 15.0 kg of pre-mixed composite binder was added. The mixture was stirred continuously at a stirring speed of 700 rpm for 65 minutes to form a uniform composite slurry. S3 Wet Papermaking: The above composite pulp is wet-processed and dehydrated to form a wet paper web with a moisture content of 25%. S4 Supplementary Impregnation and Pre-curing: The wet paper web is impregnated in the supplementary impregnation solution, and after the liquid content is controlled by squeezing, it is pre-cured at 105°C for 8 minutes. S5 Segmented Hot Press Curing: Place the pre-cured blank in a hot press; First stage: Hot press for 18 minutes at a pressure of 7.5 MPa and a temperature of 152℃; Second stage: Raise the temperature to 195℃ and simultaneously increase the pressure to 21.0 MPa, and continue hot pressing for 45 minutes. No pulse pressure is applied in this stage. S6 Post-heat treatment: The hot-pressed board is placed in a heat treatment furnace at 310℃ under nitrogen atmosphere protection and heat-treated for 3.5 hours; then it is naturally cooled to room temperature to obtain a high-temperature resistant and creep-resistant asbestos-free composite sealing board.

[0075] Comparative Example 1 This comparative example aims to examine the effect of replacing the composite adhesive of the present invention, namely the liquid phenolic resin and nano-silica sol composite system, with a single, common organic adhesive on the high-temperature performance of the board.

[0076] 1. Raw material formula: Inorganic fiber: 40.0 kg, same as in Example 1.

[0077] High-temperature resistant organic fiber: 15.0 kg, same as in Example 1.

[0078] Temperature-resistant functional filler: 35.0 kg, same as in Example 1.

[0079] Adhesive: Water-based styrene-butadiene rubber latex, with a solid content of 48% and a dry weight of 12.0 kg (on a dry basis, replacing composite adhesive).

[0080] Auxiliary agent (dispersant): Sodium polyacrylate, 0.35 kg.

[0081] Replenish the impregnation solution: Do not perform this step.

[0082] Process water: Deionized water, dosage as per preparation steps.

[0083] 2. Preparation method: S1 fiber dispersion pulping: Same as in Example 1; Preparation of S2 composite slurry: 7.0 kg of nano silica powder, 70 kg of deionized water, and 0.35 kg of sodium polyacrylate dispersant were mixed to form a suspension, which was then ultrasonically treated for 20 minutes. 28.0 kg of flake mica powder was added to the fiber slurry, followed by the above nano silica suspension, and finally 12.0 kg of water-based styrene-butadiene rubber latex. The mixture was stirred continuously at a speed of 800 rpm for 60 minutes to form a uniform slurry. S3 wet paper forming: Same as in Example 1; S4 Additional Impregnation and Pre-curing: Cancel this step; S5 Segmented Hot Press Curing: Place the wet paper web blank in a hot press. To adapt to the vulcanization temperature of styrene-butadiene rubber, the process is adjusted to: hot press for 60 minutes at a pressure of 10.0 MPa and a temperature of 150℃; S6 Post-heat treatment: The high-temperature heat treatment step is cancelled, and drying is carried out only at 80°C for 2 hours.

[0084] Comparative Example 2 This comparative example aims to examine the impact of eliminating the key "supplementary impregnation" process step of the present invention on the formation of the "local inorganic reinforcement network" inside the board and its final performance.

[0085] 1. Raw material formula: It is exactly the same as Example 1.

[0086] 2. Preparation method: Steps S1 and S2 are exactly the same as in Example 1; S3 wet paper forming: Same as in Example 1; S4 Additional Impregnation and Pre-curing: This step is omitted. The wet paper web is dried directly at 100°C for 10 minutes. Steps S5 and S6 are exactly the same as in Example 1.

[0087] Comparative Example 3 This comparative example aims to examine the effect of replacing the "flaky mica powder / nano silica" composite filler system specific to this invention with a single conventional filler on performance.

[0088] 1. Raw material formula: The inorganic fibers, high-temperature resistant organic fibers, composite binders, auxiliary agents, and supplementary impregnation solutions are all the same as in Example 1.

[0089] Temperature-resistant functional filler: only calcium carbonate powder is used, 35.0 kg, with a particle size D50 of 30 μm.

[0090] 2. Preparation method: It is exactly the same as Example 1.

[0091] Comparative Example 4 This comparative example aims to examine the impact of eliminating the "segmented hot pressing curing" process of the present invention and adopting the traditional one-stage hot pressing on the densification and structure of the board.

[0092] 1. Raw material formula: It is exactly the same as Example 1.

[0093] 2. Preparation method: Steps S1 to S4 are exactly the same as in Example 1; S5 segmented hot pressing curing: changed to single-stage hot pressing; the pre-cured blank is placed in a hot press and directly hot-pressed for 65 minutes under the conditions of pressure 20.0 MPa and temperature 200℃ (the total time is similar to the sum of the two stages in Example 1). Step S6 is exactly the same as in Example 1.

[0094] Comparative Example 5 This comparative example aims to investigate the effect of replacing the high-temperature resistant organic fiber (aramid / polyimide) required by this invention with ordinary cellulose fiber on the high-temperature performance of the board.

[0095] 1. Raw material formula: The inorganic fibers, heat-resistant functional fillers, composite binders, auxiliary additives, and supplementary impregnation solutions are the same as in Example 1.

[0096] Organic fiber: All made from lignocellulose fiber (pulp), 15.0 kg.

[0097] 2. Preparation method: It is exactly the same as Example 1.

[0098] Comparative Example 6 This comparative example aims to examine the necessity of the specific feature in claim 4, "the surface of SiO2 particles is grafted with epoxy groups", and to verify its role in improving interfacial bonding and high-temperature stability.

[0099] 1. Raw material formula: The inorganic fibers, high-temperature resistant organic fibers, temperature-resistant functional fillers, and auxiliary additives are the same as in Example 1.

[0100] Composite adhesive: Prepared by premixing the following two components: Liquid phenolic resin solution: 4.0 kg, with a solid content of 50.0%.

[0101] Nano silica sol: 8.0 kg, with a solid content of 25.0% and a particle size of 15 nm, but the SiO2 particles were not grafted on the surface (i.e., ordinary nano silica sol).

[0102] Supplement impregnation solution: A low-viscosity nano-silica sol solution with a solid content of 15.0%, which is diluted from a mother liquor of the same origin as the ordinary nano-silica sol used in the composite adhesive.

[0103] 2. Preparation method: It is exactly the same as Example 1.

[0104] Comparative Example 7 This comparative example aims to simulate what may be considered the closest prior art solution, namely, a combination of conventional organic binders, conventional fillers, and conventional hot pressing processes, and to directly compare it with the complete solution of the present invention.

[0105] 1. Raw material formula: Inorganic fibers and high-temperature resistant organic fibers: Same as in Example 1.

[0106] Temperature-resistant functional filler: only calcium carbonate powder is used, 35.0 kg, with a particle size D50 of 30 μm.

[0107] Adhesive: Water-based styrene-butadiene rubber latex, with a solid content of 48% and a dry basis weight of 12.0 kg.

[0108] Auxiliary agent (dispersant): Sodium polyacrylate, 0.35 kg.

[0109] Replenish the impregnation solution: Do not perform this step.

[0110] 2. Preparation method: S1 fiber dispersion pulping: Same as in Example 1; S2 slurry preparation: Add 35.0 kg of calcium carbonate powder and 12.0 kg of styrene-butadiene rubber latex to the fiber slurry and stir to mix; S3 wet paper forming: Same as in Example 1; S4 Additional Impregnation and Pre-curing: Cancel this step; S5 hot-press curing: single-stage hot pressing is used, with hot pressing for 60 minutes at a pressure of 10.0 MPa and a temperature of 150℃; S6 Post-heat treatment: The high-temperature heat treatment step is cancelled, and drying is carried out only at 80°C for 2 hours.

[0111] Performance comparison tests were conducted on Examples 1-5 and Comparative Examples 1-7. The test items are as follows: The following test methods are specifically designed to evaluate the key performance of the asbestos-free composite sealing sheets prepared in the embodiments and comparative examples of this invention. All tests follow or refer to relevant national and international standards, and adaptive provisions have been made for the high-temperature operating conditions of the materials of this invention to ensure the scientific validity, comparability, and reproducibility of the test results.

[0112] I. High-Temperature Compressive Strength Residual Rate Test 1. Test Objective: To quantitatively evaluate the ability of a sheet material to retain its mechanical strength after prolonged aging at a specified high temperature. This indicator directly reflects the structural integrity and stress relaxation potential of the material after high-temperature service, and is a core parameter for measuring the high-temperature durability of sealing materials.

[0113] 2. Reference Standards: The test procedures for compressive strength are mainly based on GB / T 20671.1-2020 "Classification System and Test Methods for Non-metallic Gasket Materials", and a high-temperature aging pretreatment step has been added to simulate long-term heat exposure.

[0114] 3. Testing equipment: Universal testing machine (accuracy not lower than grade 1, such as INSTRON 5967 series).

[0115] High-temperature box furnace (maximum working temperature not less than 600℃, temperature control accuracy ±5℃).

[0116] Dryer, vernier caliper (accuracy 0.02mm).

[0117] Constant temperature and humidity chamber (used for sample condition adjustment).

[0118] 4. Sample preparation: Samples were cut from the homogeneous plates prepared in each embodiment and comparative example using a special mold or a precision cutting machine.

[0119] The sample is cylindrical with a diameter of (25.0 ± 0.1) mm and a thickness of (3.0 ± 0.1) mm.

[0120] At least five parallel specimens should be prepared for each sample, and the specimen surfaces should be flat and free of visible defects.

[0121] Before testing, the sample needs to be conditioned in a constant temperature and humidity chamber at a temperature of (23 ± 2)℃ and a relative humidity of (50 ± 5)% for no less than 24 hours.

[0122] 5. Test steps: (1) Initial compressive strength test: Take a set of calibrated samples and measure their actual thickness.

[0123] The material is placed between the upper and lower parallel pressure plates of the universal testing machine and a compressive load is applied at a constant displacement rate of (1.0 ± 0.1) mm / min.

[0124] Record the load-displacement curves continuously until the specimen fractures or the compressive strain reaches 25% (whichever occurs first). Record the peak load (F_max).

[0125] Calculate the initial compressive strength (σ0): σ0 = F_max / A, where A is the initial cross-sectional area of ​​the specimen. Take the arithmetic mean of 5 specimens as the initial compressive strength of the specimen.

[0126] (2) High-temperature aging treatment: Take another set of parallel samples, place them vertically on a heat-resistant support, and put them into a high-temperature box furnace.

[0127] Under a still air atmosphere, the furnace temperature was raised to (500 ± 5)℃ at a rate of (5 ± 1)℃ / min.

[0128] Maintain this temperature at (24.0 ± 0.5) hours.

[0129] After aging is complete, turn off the heating power and allow the sample to cool naturally with the furnace to below 150°C before removing it and immediately transferring it to a desiccator to cool to room temperature.

[0130] (3) Residual strength test: For the sample after high-temperature aging and cooling, its compressive strength is tested under the same conditions and methods as “(1) Initial compressive strength test”, and recorded as residual compressive strength (σ1).

[0131] (4) Calculation: The residual high-temperature compressive strength of each specimen is calculated using the following formula: Residual strength (%) = (σ1 / σ0) × 100%.

[0132] Report the arithmetic mean of the residual rates of this group of samples.

[0133] II. High-Temperature Compression Creep Rate Test 1. Test Objective: To accurately measure the permanent deformation of sheet metal under constant high temperature and constant compressive stress over a long period. Compression creep rate is the most critical indicator for evaluating the stress relaxation resistance of gaskets and predicting their sealing life.

[0134] 2. Reference Standards: Based on the basic principles of ISO 11547:2020 "Marine and marine technology - Gasket materials - High temperature compression creep test method" and the loading framework of ASTM F38 "Gasket materials - Creep relaxation test method".

[0135] 3. Testing equipment: Specialized high-temperature compression creep testing machine: equipped with an independently temperature-controlled tubular or box-type heating furnace (temperature control accuracy ±2℃), a servo hydraulic or mechanical constant pressure loading system (pressure fluctuation <±1%), and a high-precision linear displacement sensor (such as LVDT, with a resolution of not less than 0.001mm).

[0136] Digital thickness gauge (accuracy 0.001mm).

[0137] Install the clamps in the center.

[0138] 4. Sample preparation: The plate was processed into annular specimens with an outer diameter of (25.0 ± 0.1) mm, an inner diameter of (12.5 ± 0.1) mm, and a thickness of (1.60 ± 0.05) mm.

[0139] The two ends of the sample must be parallel, and the surface must be smooth and free of burrs. At least three samples should be prepared for each sample.

[0140] 5. Test steps: (1) Initial thickness measurement: Under an environment of (23 ± 2)℃, the thickness of three points on the sample ring is measured evenly using a thickness gauge, and the arithmetic mean is taken as the initial thickness (t0).

[0141] (2) Sample loading and system preheating: Place the sample between the polished and parallel pressure plates on the upper and lower parts of the testing machine, ensuring alignment. Place the entire apparatus in the heating furnace. Raise the furnace temperature to (300 ± 2)℃ at a rate of (3 ± 0.5)℃ / min. After reaching the temperature, hold for 1 hour to ensure uniform temperature of the sample.

[0142] (3) Loading and Creep Holding: After the heat preservation is completed, an initial compressive stress of (25.0 ± 0.5) MPa is rapidly and smoothly applied to the specimen. The specimen thickness at the moment of completion of loading (which can be converted by a displacement sensor) is recorded as the "instantaneous thickness after loading". Timing is started immediately and maintained at a temperature of (300 ± 2) ℃ and a pressure of (25.0 ± 0.5) MPa for (100.0 ± 0.5) hours. During this period, the system automatically records temperature, pressure and displacement data.

[0143] (4) Unloading and final measurement: After the holding time is over, remove all loads. Control the furnace temperature to cool to below 80°C at a rate not exceeding 5°C / min, remove the sample, and place it in a desiccator to cool to room temperature. Measure the sample thickness at the same three locations as in step (1), and take the arithmetic mean as the final thickness (t1).

[0144] (5) Calculation: The compression creep rate of each sample is calculated using the following formula: Creep rate (%) = [(t0 - t1) / t0] × 100%.

[0145] Note: t0 is the initial thickness at room temperature, and t1 is the final thickness at room temperature. The calculation is for irreversible permanent deformation.

[0146] Report the arithmetic mean of the creep rates of the three samples.

[0147] III. Seal Leakage Rate Test 1. Test Objective: To quantitatively evaluate the sealing performance of the sheet metal as a gasket under simulated temperature and pressure conditions of actual flange connections. This is a direct performance test to evaluate its engineering application value.

[0148] 2. Reference Standard: Strictly follow GB / T 12385-2008 "Test Method for Sealing Performance of Gaskets for Pipe Flanges".

[0149] 3. Testing equipment: A comprehensive gasket sealing performance testing bench (such as the RF type or equivalent equipment) includes: Standard test flange assembly (flange stiffness and sealing surface roughness meet the standards).

[0150] High-precision hydraulic bolt loading system.

[0151] Medium (nitrogen) pressurization and stabilization system.

[0152] High-temperature environment chamber or heating jacket (temperature control accuracy ±5℃).

[0153] High-sensitivity leak detection systems (such as precision mass flow meters with a range of 10^-6 ~ 10^-2 mg / (s·m); or standard bubble leak detectors).

[0154] 4. Sample preparation: The sheet metal was cut or stamped into annular gasket samples with an inner diameter of (34.0 ± 0.1) mm and an outer diameter of (54.0 ± 0.1) mm.

[0155] The sample cross-section is flat and free from defects such as delamination and cracks.

[0156] 5. Test conditions: Test medium: high-purity nitrogen (purity ≥ 99.99%).

[0157] Initial preload stress of the gasket: Based on material properties and standard recommendations, it is uniformly set to (40.0 ± 1.0) MPa.

[0158] Medium pressure: Maintain (3.0 ± 0.05) MPa (gauge pressure).

[0159] Test temperature: Two independent tests were conducted – room temperature (23 ± 5) ℃ and high temperature (300 ± 5) ℃.

[0160] 6. Testing steps: (1) Installation and pre-tightening: Place the gasket sample between the upper and lower flange sealing surfaces. Tighten the bolts evenly in steps according to the standard procedure until the gasket surface reaches the specified initial pre-tightening stress, as confirmed by the hydraulic system or strain measurement. Record the bolt load or displacement.

[0161] (2) System heating and stabilization (high temperature test only): Start the heating system and heat it to (300 ± 5)℃ at a rate not exceeding 5℃ / min, and keep it at this temperature for at least 1 hour to make the temperature of the flange, bolts and gaskets uniform and stable.

[0162] (3) Pressurization and Leakage Detection: Nitrogen gas is introduced into the sealed cavity, and the pressure is slowly increased to the specified test pressure (3.0 MPa).

[0163] After the pressure stabilizes, begin measuring the leakage rate. Using a mass flow meter, read the stabilized flow rate directly downstream of the system; when using a bubble leak detector, apply the leak detection fluid to the outside of the flange and observe and count the bubbles that escape within a specified time.

[0164] During each pressure / temperature stabilization phase, at least five consecutive leakage rate readings were recorded, and the arithmetic mean was taken as the leakage rate under that condition.

[0165] (4) Results are expressed as follows: To facilitate a direct comparison within the patent text, the measured absolute leakage rate values ​​were normalized and evaluated according to the following levels (the smaller the level value, the better the sealing performance): Level 1 (Excellent): Leakage rate ≤ 1.0 × 10 -4 mg / (s·m) (or no visible continuous bubbles under the bubble leak detection method).

[0166] Grade 2 (Good): 1.0 × 10 -4 Leakage rate ≤ 1.0 × 10 -3 mg / (s·m).

[0167] Level 3 (Medium): 1.0 × 10 -3 Leakage rate ≤ 1.0 × 10 -2 mg / (s·m).

[0168] Level 4 (Poor): 1.0 × 10 -2 Leakage rate ≤ 1.0 × 10 -1 mg / (s·m).

[0169] Level 5 (Poor): Leakage rate > 1.0 × 10 -1 mg / (s·m) (or obvious jet-like leakage occurs).

[0170] The test results are shown in the table below: Test sample High-temperature compressive strength residual rate (%) High-temperature compression creep rate (%) 300℃ sealing leakage rating Example 1 86 4.2 1 Example 2 83 4.8 1 Example 3 88 5.1 2 Example 4 85 4.5 1 Example 5 84 4.7 1 Comparative Example 1 41 26.8 5 Comparative Example 2 72 11.7 3 Comparative Example 3 64 15.3 4 Comparative Example 4 79 9.5 2 Comparative Example 5 49 21.4 5 Comparative Example 6 75 13.5 3 Comparative Example 7 38 28.1 5 Analysis of the table data yields the following: The asbestos-free composite sealing sheets prepared in all embodiments of this invention exhibit excellent comprehensive performance, with residual high-temperature compressive strength exceeding 83% and high-temperature compressive creep rate below 5.2%. Furthermore, their sealing performance at 300 degrees Celsius reaches an excellent or good level. These data fully demonstrate that this material possesses extremely high structural stability and sealing retention capability under simulated extreme working conditions, effectively solving the core technical problem of sealing failure caused by creep relaxation in traditional sealing materials at high temperatures.

[0171] Comparative Example 1, serving as a baseline control, directly demonstrates the advantages of the phenolic resin-nano silica sol composite binder system compared to a single conventional organic binder under the simplest conditions. Comparative Examples 2, 4, and 6 respectively verify the independent contributions of the supplementary impregnation process, the segmented hot-pressing process, and the specific chemical feature of grafting epoxy groups onto the silica sol surface to improving high-temperature interface stability and creep resistance. Comparative Examples 3 and 5 further demonstrate that even under the binder system of this invention, the specific selection of composite fillers and high-temperature resistant organic fibers remains an indispensable component in maintaining the overall high-temperature framework. Crucially, the conventional technology combination constructed in Comparative Example 7 performs even worse than other comparative examples that only modify a single feature, fully highlighting the systematic synergistic effect resulting from the creative integration of key features.

[0172] In summary, this invention is not a partial optimization or simple combination of existing technologies, but rather an organic whole formed by constructing an organic-inorganic composite bonding system, introducing targeted reinforcement processes, screening specific functional components, and adapting the processes. This solution solves the technical challenge of high-temperature creep resistance that cannot be overcome by a single technical means, achieving unexpected and significant technological progress, and providing an innovative solution with outstanding creativity and broad application prospects for the high-end sealing field.

[0173] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. It should not be considered that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A high-temperature resistant and creep-resistant asbestos-free composite sealing board, characterized in that, It is made from raw materials containing the following parts by weight: 30-50 parts inorganic fiber, 10-20 parts high-temperature resistant organic fiber, 25-45 parts heat-resistant functional filler, and 8-18 parts composite binder; The composite adhesive is premixed from liquid phenolic resin and nano-silica sol at a dry weight ratio of 1:(0.5-2), and the board has a local inorganic reinforcement network formed by the nano-silica sol being enriched in the pores and interfaces of the fiber network and then cured.

2. The asbestos-free composite sealing plate according to claim 1, characterized in that: The inorganic fiber is at least one of sepiolite fiber or attapulgite fiber that has been surface-treated with an aminosilane coupling agent, and its length is 0.2 to 3 mm.

3. The asbestos-free composite sealing plate according to claim 1, characterized in that: The heat-resistant functional filler is composed of flake mica powder and nano silica in a weight ratio of (3-5):1, wherein the aspect ratio of the flake mica powder is greater than 20.

4. The asbestos-free composite sealing plate according to claim 1, characterized in that: The liquid phenolic resin has a solid content of 45-55%, the nano-silica sol has a particle size of 10-20 nm, and its SiO2 particles have epoxy groups grafted onto their surface.

5. A method for preparing a high-temperature resistant and creep-resistant asbestos-free composite sealing board as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1 Fiber Dispersion Pulping: The inorganic fibers and high-temperature resistant organic fibers are dispersed at high speed in water to form a uniform fiber slurry; S2 composite slurry preparation: The heat-resistant functional filler and the composite binder are added sequentially to the fiber slurry, and the mixture is stirred to form a uniform composite slurry; S3 Wet papermaking: The composite pulp is wet-processed and dehydrated to form a wet paper web with a moisture content of 25-45%. S4 Supplementary Impregnation and Pre-curing: The wet paper web is impregnated in a low-viscosity silica sol supplementary solution with a solid content of 10-20%. After controlling the liquid content by extrusion, it is pre-cured at 90-110°C for 5-15 minutes to allow the silica sol to be preferentially enriched in the pores and interfaces of the fiber network. S5 Segmented Hot Press Curing: The pre-cured blank is placed in a hot press for two-stage hot pressing. First stage: Hot pressing for 10-20 minutes at a pressure of 6-8 MPa and a temperature of 150-160℃; Second stage: Raise the temperature to 190-210℃, and at the same time increase the pressure to 18-22MPa, and continue hot pressing for 40-60 minutes; S6 Post-heat treatment: The hot-pressed sheet is heat-treated at 280-320℃ for 3-5 hours under an inert atmosphere.

6. The preparation method according to claim 5, characterized in that: In step S4, the low-viscosity silica sol replenishment liquid and the nano silica sol used in the composite binder are the same substance.

7. The preparation method according to claim 5, characterized in that: During the second stage of hot pressing in step S5, a pulse pressure with a frequency of 1 to 3 Hz is applied synchronously, and the fluctuation amplitude of the pulse pressure is ±15% of the set pressure.

8. The preparation method according to claim 5, characterized in that: In step S6, the post-heat treatment specifically involves heating to 300°C at a rate of 1°C / min under a nitrogen atmosphere and maintaining the temperature at that rate for 4 hours.

9. The preparation method according to claim 5, characterized in that: In step S1, the high-speed dispersion speed is 2000-4000 rpm, the dispersion time is 30-50 minutes, and the solid content of the fiber slurry is controlled at 3-4%.