Ceramic fiber paper with high tensile strength and method for manufacturing the same

Abstract

This invention relates to the field of inorganic non-metallic materials and high-temperature thermal insulation materials, specifically to a ceramic fiber paper with high tensile strength and its preparation method. The paper comprises the following raw material components by mass percentage: 50%~70% aluminosilicate fiber, the surface of which is modified with a silane coupling agent. This invention optimizes the composite ratio of various ceramic fibers. Aluminosilicate fiber serves as the main skeleton, providing temperature resistance; kaolin fiber fills micropores and improves mid-temperature strength; and modified sepiolite fiber toughens, resists cracking, and improves flexibility. These three components synergistically construct a dense fiber network, achieving 2500~4000 fiber overlap points per square centimeter. The room temperature tensile strength reaches over 5.0 MPa, representing an improvement of over 15% compared to conventional wet-formed products. It also significantly improves flexibility, meeting the application requirements of power batteries and other applications requiring bending installation.

Description

Technical Field

[0001] This invention relates to the field of inorganic non-metallic materials and high-temperature thermal insulation materials, specifically to a ceramic fiber paper with high tensile strength and its preparation method. Background Technology

[0002] Ceramic fiber paper is a high-temperature resistant insulation material widely used in high-temperature equipment insulation gaskets, sealing materials, and other fields. Current ceramic fiber paper manufacturing technologies mainly employ a wet forming process, using aluminosilicate fiber as the main raw material, adding binders, and then proceeding through forming, drying, and curing steps.

[0003] Generally, however, these products typically suffer from low mid-temperature strength and easy pulverization. Their strength decreases significantly above 800℃, and the powder shedding rate is high, making it difficult to meet the requirements of high-end applications such as power batteries for material mechanical properties and dimensional stability. Furthermore, existing products have high and unevenly distributed binder content, a loose fiber network structure, insufficient flexibility, and a large minimum bending radius, limiting their application in situations requiring bending and installation. Therefore, there is a need for a ceramic fiber paper and its preparation method that can achieve high tensile strength, low powder shedding rate, high flexibility, and good mid-temperature stability while reducing binder usage.

[0004] Based on this, the present invention provides a ceramic fiber paper with high tensile strength and a method for preparing the same, in order to solve the technical problems mentioned above. Summary of the Invention

[0005] The purpose of this invention is to provide a ceramic fiber paper with high tensile strength and its preparation method, so as to solve the technical problems of existing ceramic fiber paper, such as high and uneven binder content, loose fiber network structure, significant decrease in strength under medium temperature conditions, high dust loss rate, poor flexibility, and lack of systematic optimization of process parameters.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention proposes a ceramic fiber paper comprising the following raw material components by mass percentage: 50%~70% aluminosilicate fiber, the surface of which is modified with a silane coupling agent to provide temperature resistance as the main skeleton; 15%~25% kaolin fiber, the surface of which is modified with a silane coupling agent to fill micropores and improve intermediate temperature strength; 5%~15% modified sepiolite fiber for toughening, crack resistance, and improved flexibility; 6%~9% inorganic-organic composite binder, wherein the inorganic-organic composite binder comprises inorganic binder and organic binder, the inorganic binder comprising silica sol and water glass, and the organic binder comprising polyvinyl alcohol and acrylate emulsion, the organic binder providing room temperature flexibility, and the inorganic binder transforming into a silica glass phase at high temperature to continue binding the fibers; 0.3%~1% dispersant and 0.2%~1% additives; the number of fiber overlap points per square centimeter is 2500~4000, constructing a dense and uniform fiber network structure.

[0007] Furthermore, the volume ratio of silica sol to water glass in the inorganic binder is 3:1, the volume ratio of polyvinyl alcohol to acrylate emulsion in the organic binder is 2:1, and the mass ratio of the inorganic binder to the organic binder is 4:1. This ratio allows the organic binder to provide flexibility at room temperature, while the inorganic binder forms a silica glass phase network at high temperature, thus ensuring both cold and hot strength.

[0008] Preferably, the silica sol has a solid content of 30% to 40%, the water glass has a modulus of 2.8 to 3.2, the polyvinyl alcohol has a degree of polymerization of 1700 to 2000, and the acrylate emulsion has a solid content of 45% to 55%. These parameters ensure that the binder components have suitable viscosity and reactivity.

[0009] Specifically, the content of the aluminum silicate fiber is 60%~65%, the content of the kaolin fiber is 18%~22%, and the content of the modified sepiolite fiber is 8%~12%. This optimized ratio enables the three fibers to work synergistically, with the aluminum silicate fiber providing the main skeleton, the kaolin fiber filling the micropores, and the modified sepiolite fiber toughening and crack resistance.

[0010] In some embodiments, the product density of the ceramic fiber paper is 180~200 kg / m³. 3 The porosity is 90%~95%, and the thermal conductivity is less than or equal to 0.030 W / (m·K). The thermal conductivity is determined by GB / T10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Protective Hot Plate Method". The number of fiber overlap points per square centimeter is obtained by observation with a scanning electron microscope and statistical analysis using image analysis software.

[0011] As a preferred embodiment, the ceramic fiber paper has a room temperature tensile strength greater than or equal to 5.0 MPa, wherein the room temperature tensile strength is determined by GB / T5486-2008 "Test Methods for Tensile Strength of Inorganic Rigid Thermal Insulation Products"; a tensile strength after treatment at 800℃ for 2 hours is greater than or equal to 4.5 MPa, wherein the high-temperature tensile strength is determined by GB / T30304-2013 "Test Methods for Ceramic Fiber Products for High Temperature Use"; a strength retention rate greater than or equal to 80%; a dust loss rate less than or equal to 1.0%, wherein the dust loss rate is determined by the vibration method, specifically by fixing the sample on a vibration table, vibrating at a frequency of 50 Hz and an amplitude of 5 mm for 10 minutes, collecting the detached powder and weighing it; and a minimum bending radius less than or equal to 15 mm, wherein the minimum bending radius is determined by bending the sample step by step until cracks appear.

[0012] Furthermore, the shear length of the aluminosilicate fiber is 3-6 mm, the shear length of the kaolin fiber is 1-3 mm, the length of the modified sepiolite fiber is 5-10 mm, the average fiber diameter is 2.15-3.0 μm, and the average fiber length is 100-150 μm. These fiber specifications ensure that the fibers are fully dispersed in the slurry and form a dense, overlapping network.

[0013] This invention also provides a method for preparing ceramic fiber paper, comprising the following steps: Step (1): Fiber pretreatment and surface modification: Alumina silicate fiber and kaolin fiber are surface modified by spraying silane coupling agent on the fiber surface to form chemical bonds on the fiber surface, thereby enhancing the interfacial bonding strength between the fiber and the binder and reducing the dust shedding rate. This step solves the problem of weak interfacial bonding and easy detachment between the fiber and the binder in the prior art. Step (2): Fiber grading and dispersion pulping: The modified fiber is mixed with the modified sepiolite fiber, a dispersant is added, and high-speed stirring and ultrasonic-assisted dispersion are carried out to fully disperse the fiber in the pulp and avoid agglomeration, laying the foundation for the formation of a dense fiber network structure. This step solves the problems of uneven fiber dispersion and loose network structure in the prior art. Step (3): Preparation of composite adhesive: Prepare an inorganic-organic composite adhesive, wherein the inorganic adhesive contains silica sol and water glass, and the organic adhesive contains polyvinyl alcohol and acrylate emulsion. The mass ratio of inorganic adhesive to organic adhesive is 4:1. At room temperature, the organic adhesive provides flexibility, and at high temperature, the inorganic adhesive is converted into a silica glass phase to continue bonding the fiber, which solves the problem of decreased strength at medium temperature in the prior art. Step (4): Forming with a homogenizing roller: The composite adhesive prepared in the step of composite adhesive preparation is added to the pulp of the fiber classification and dispersion pulping in the step, and formed by homogenizing roller. The glue content is controlled in stages according to the product thickness. Three homogenizing rollers are used to make the glue spread evenly on the fiber surface to form a continuous coating layer, so as to achieve a high degree of uniform distribution of glue in the paper cross section and plane direction, which solves the problem of uneven distribution of adhesive in the prior art. Step (5): Gradient dewatering and pressing: Gradient vacuum dewatering and pressing are performed on the formed wet paper blank. Two-stage gradient vacuum dewatering is used to avoid cracking on the surface of the wet paper blank. The pressing stage increases the paper density, so that the number of fiber overlap points per square centimeter reaches 2,500 to 4,000, and a dense fiber network structure is constructed. Step (6): Gradient drying and heat setting: Gradient drying and heat setting are carried out on the dehydrated paper blank. The three-stage gradient drying avoids cracking caused by excessive moisture gradient inside and outside the wet paper blank. The high-temperature stage promotes the dehydration and condensation of silica sol to form a silica glass phase inorganic network. Heat setting improves dimensional stability and solves the problem of poor high-temperature dimensional stability in the prior art.

[0014] Preferably, in the fiber pretreatment and surface modification step, the concentration of the silane coupling agent is 2% to 5%, the spraying amount is 0.5% to 2% of the fiber mass, and the stirring time is 15 to 30 minutes. This parameter range ensures that the silane coupling agent fully reacts on the fiber surface to form chemical bonds without being excessively consumed.

[0015] Preferably, in the fiber classification and dispersion pulping step, the stirring speed is 800~1200 rpm, the ultrasonic frequency is 40 kHz and the power is 500~800 W, and the dispersion time is 10~20 minutes. This range of process parameters ensures that the fibers are fully dispersed without excessive breakage.

[0016] Preferably, in the homogenizing roller forming step, three homogenizing rollers are used, the screen speed is 5~15 m / min, the slurry concentration is 0.6%~1.0%, the glue content is controlled at 6.5% when the product thickness is 1.5mm, at 8% when the product thickness is 3.0mm, and at 8.5% when the product thickness is 4.5mm. This segmented control method ensures that products of different thicknesses have suitable bonding strength.

[0017] Specifically, the linear speed of the three homogenizing rollers increases sequentially. The linear speed of the first homogenizing roller is 3-5 m / min, the linear speed of the second homogenizing roller is 6-10 m / min, and the linear speed of the third homogenizing roller is 10-15 m / min. This gradient linear speed design makes the slurry homogenized step by step, and the glue evenly coats the fiber surface layer by layer.

[0018] Preferably, in the step-by-step gradient dewatering and pressing process, the vacuum degree of the first stage of dewatering is -0.04MPa, the vacuum degree of the second stage of dewatering is -0.06MPa, and the linear pressure of the pressing stage is 10~30kN / m. This gradient vacuum degree and pressing pressure ensure that the moisture in the wet paper blank is discharged in a gradient and improve the density.

[0019] Preferably, in the step-by-step gradient drying and heat setting, the first stage drying temperature is 80~100℃ and the time is 15~25 minutes, the second stage drying temperature is 120~150℃ and the time is 20~30 minutes, and the third stage drying temperature is 180~200℃ and the time is 25~35 minutes. This three-stage gradient drying avoids cracking caused by excessive internal and external moisture gradients, and the high-temperature stage promotes the condensation of silica sol to form an inorganic network.

[0020] Furthermore, in the step gradient drying and heat setting process, the heat setting temperature is 200℃, the linear pressure is 20kN / m, and the setting time is 5~10 minutes. Heat setting makes the surface denser and improves dimensional stability.

[0021] Compared with the prior art, the beneficial effects of the present invention are: 1. Through optimization of the composite ratio of various ceramic fibers, aluminosilicate fibers serve as the main skeleton to provide temperature resistance, kaolin fibers fill micropores and improve medium-temperature strength, and modified sepiolite fibers toughen, crack-resistant, and improve flexibility. The three work together to construct a dense fiber network, resulting in 2,500 to 4,000 fiber overlap points per square centimeter and a room temperature tensile strength of over 5.0 MPa, which is more than 15% higher than conventional wet-formed products of the existing technology (tensile strength of about 4.0 to 4.5 MPa). At the same time, the toughening effect of modified sepiolite fibers reduces the minimum bending radius to below 15 mm, which is about 40% lower than existing products (minimum bending radius of about 20 to 25 mm), significantly improving flexibility and meeting the application requirements of power batteries and other applications that require bending installation.

[0022] 2. Through the design of an inorganic-organic composite binder system, the inorganic part has an optimized ratio of silica sol to water glass of 3:1, the organic part has a volume ratio of polyvinyl alcohol to acrylate emulsion of 2:1, and the inorganic to organic mass ratio is 4:1. The organic binder provides flexibility at room temperature, while the inorganic binder transforms into a silica glass phase at high temperature to continue bonding the fibers. This solves the problem of significant strength reduction in existing single binder systems under medium temperature conditions. After treatment at 800℃ for 2 hours, the tensile strength reaches over 4.5MPa, with a strength retention rate of over 80%. This is an improvement of approximately 60% and 25 percentage points respectively compared to conventional wet-molded products (tensile strength after treatment at 800℃ is approximately 2.5~3.0MPa, with a strength retention rate of approximately 60~65%), achieving dual protection of strength in both cold and hot states.

[0023] 3. By modifying the fiber surface with a silane coupling agent, the silane coupling agent forms chemical bonds on the fiber surface, enhancing the interfacial bonding strength between the fiber and the binder. Combined with a three-stage homogenizing roller forming process, the adhesive is evenly spread on the fiber surface to form a continuous coating layer, achieving a highly uniform distribution of the adhesive in the paper cross-section and planar direction. The adhesive uniformity index reaches above 85, and the distribution deviation is controlled within 10%. At the same time, the adhesive content is controlled in a low range of 6% to 9%, which is about 30% to 40% lower than existing technology products (adhesive content about 10% to 15%), and the dusting rate is reduced to below 1.0%, which is about 60% to 70% lower than existing technology products (dusting rate about 2.0% to 3.0%).

[0024] 4. Through gradient dewatering and pressing processes, two-stage gradient vacuum dewatering (vacuum degree -0.04MPa / -0.06MPa) avoids cracking on the surface of the wet paper blank. The pressing stage (linear pressure 10~30kN / m) increases the paper density. Combined with gradient drying and heat setting processes, three-stage gradient drying (80~100℃ / 120~150℃ / 180~200℃) avoids cracking caused by excessive internal and external moisture gradients. The high-temperature stage promotes the dehydration and condensation of silica sol to form a silica glass phase inorganic network. Heat pressing (200℃, 20kN / m) improves dimensional stability. After holding at 950℃ for 24 hours, the linear shrinkage rate drops to below 2%, which is about 40~50% lower than existing technology products (linear shrinkage rate of about 3~4%). Attached Figure Description

[0025] Figure 1 This is a flowchart of the preparation method of the high tensile strength ceramic fiber paper of the present invention. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] The present invention will be further described in detail below with reference to embodiments.

[0028] Unless otherwise specified, all raw materials used in the following examples are commercially available products: Aluminosilicate fiber was purchased from Shandong Luyang Energy-Saving Materials Co., Ltd., kaolin fiber was purchased from Suzhou Sinoma Nonmetallic Minerals Industry Design and Research Institute Co., Ltd., and modified sepiolite fiber was purchased from Hunan Xiangtan Sepiolite Technology Co., Ltd.

[0029] The silane coupling agent KH-550 was purchased from Nanjing Shuguang Chemical Group Co., Ltd.

[0030] Silica sol was purchased from Qingdao Yutian Chemical Co., Ltd., water glass was purchased from Zibo Linzi Qilu Chemical Plant, polyvinyl alcohol was purchased from Sichuan Vinylon Plant, and acrylate emulsion was purchased from BASF (China) Co., Ltd.

[0031] The dispersant was sodium carboxymethyl cellulose, purchased from Shandong Yinying Chemical Co., Ltd.

[0032] Example 1, please refer to Figure 1 In this embodiment, a ceramic fiber paper with a thickness of 3.0 mm is prepared using a formula of 60% aluminum silicate fiber, 20% kaolin fiber, 10% modified sepiolite fiber, 9% inorganic-organic composite binder, and 1% dispersant and additives.

[0033] Step 1: Fiber pretreatment and surface modification. Aluminosilicate fibers (shear length 4 mm) and kaolin fibers (shear length 2 mm) were placed in a mixing tank respectively, and a 3.5% concentration of silane coupling agent KH-550 solution was sprayed on them. The spraying amount was 1% of the fiber mass. The mixture was stirred for 20 minutes to allow the silane coupling agent to form chemical bonds on the fiber surface.

[0034] Step 2: Fiber grading and dispersion pulping. Modified aluminosilicate fibers, kaolin fibers and modified sepiolite fibers (8mm in length) are mixed, sodium carboxymethyl cellulose is added as a dispersant, and water is added to prepare a slurry with a concentration of 0.8%. The slurry is stirred at 1000 rpm using a high-speed stirrer, and ultrasonic dispersion at a frequency of 40 kHz and a power of 650 W is applied for 15 minutes.

[0035] Step 3: Preparation of Composite Adhesive. Prepare an inorganic-organic composite adhesive. The inorganic adhesive portion consists of a 35% solids content silica sol and a 3.0 modulus water glass mixed at a volume ratio of 3:1. The organic adhesive portion consists of a 1800 degree of polymerization polyvinyl alcohol and a 50% solids content acrylate emulsion mixed at a volume ratio of 2:1. Then, mix the inorganic and organic adhesives at a mass ratio of 4:1 and stir until homogeneous to obtain the composite adhesive.

[0036] Step 4: Forming with homogenizing rollers. Add the composite adhesive prepared in Step 3 to the slurry in Step 2 to make the adhesive content 8%. Form the slurry by passing it through three homogenizing rollers at a screen speed of 10 m / min. The roller surface linear speeds of the three homogenizing rollers are 4 m / min, 8 m / min, and 12 m / min, respectively, so that the adhesive is evenly spread on the fiber surface to form a continuous coating layer.

[0037] Step 5: Gradient dewatering and pressing. The formed wet paper blank is subjected to gradient vacuum dewatering. The vacuum degree of the first stage of dewatering is -0.04MPa, and the vacuum degree of the second stage of dewatering is -0.06MPa. Then it passes through the pressing stage with a linear pressure of 20kN / m to improve the paper density.

[0038] Step 6: Gradient drying and heat setting. The dehydrated paper blank is subjected to three-stage gradient drying: the first stage drying temperature is 90℃ for 20 minutes, the second stage drying temperature is 135℃ for 25 minutes, and the third stage drying temperature is 190℃ for 30 minutes. Then, it is heat-pressed for setting at 200℃, with a linear pressure of 20kN / m and a setting time of 8 minutes to obtain the finished ceramic fiber paper.

[0039] The density of the ceramic fiber paper product prepared in this embodiment is 190 kg / m³, according to testing. 3 The porosity is 92%, with 3200 fiber overlap points per square centimeter, an average fiber diameter of 2.5 μm, and an average fiber length (SV value) of 120 μm. The room temperature tensile strength was 5.2 MPa, determined according to GB / T5486-2008 "Test Methods for Tensile Strength of Inorganic Rigid Thermal Insulation Products". The tensile strength after treatment at 800℃ for 2 hours was 4.6 MPa, with a strength retention rate of 88%, determined according to GB / T30304-2013 "Test Methods for Ceramic Fiber Products for High Temperature Use". The dust loss rate was 0.8% when tested using the vibration method (frequency 50 Hz, amplitude 5 mm, vibration for 10 minutes) according to the enterprise standard. The minimum bending radius was measured to be 12 mm after progressively bending the sample until cracks appeared. The linear shrinkage rate was 1.5% after the sample was kept at 950℃ for 24 hours. According to GB / T10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Protective Hot Plate Method", the thermal conductivity is 0.028 W / (m·K).

[0040] Example 2 differs from Example 1 in that the fiber ratio is adjusted to 63% aluminum silicate fiber, 20% kaolin fiber, and 10% modified sepiolite fiber, and the binder content is reduced to 7%. The remaining raw materials and process parameters are the same as in Example 1.

[0041] The ceramic fiber paper prepared in this embodiment has a room temperature tensile strength of 5.5 MPa, a tensile strength of 4.8 MPa after treatment at 800℃ for 2 hours, a strength retention rate of 87%, a dust loss rate of 0.7%, a minimum bending radius of 13 mm, a linear shrinkage rate of 1.6% after heat treatment at 950℃ for 24 hours, and a thermal conductivity of 0.026 W / (m·K). The results indicate that increasing the aluminosilicate fiber content to 63% further improves the mechanical properties while reducing the amount of binder required.

[0042] Example 3: This example prepares a thin ceramic fiber paper with a thickness of 1.5 mm. The same fiber ratio and adhesive formulation as in Example 1 are used, but the glue content is adjusted to 6.5% and the wire speed is adjusted to 12 meters / minute based on the product thickness of 1.5 mm. All other process parameters are the same as in Example 1.

[0043] Testing showed that the thin ceramic fiber paper prepared in this embodiment has a room temperature tensile strength of 5.0 MPa, a tensile strength of 4.5 MPa after treatment at 800℃ for 2 hours, a strength retention rate of 90%, a dust loss rate of 0.6%, a minimum bending radius of 10 mm, a linear shrinkage rate of 1.4% after heat treatment at 950℃ for 24 hours, and a thermal conductivity of 0.025 W / (m·K). This thin product is suitable for applications requiring lightweight and flexible materials, such as thermal insulation layers for power batteries and sealing gaskets for precision equipment.

[0044] Example 4: This example prepares a thick ceramic fiber paper with a thickness of 4.5 mm. The same fiber ratio and adhesive formulation as in Example 1 are used, but the glue content is adjusted to 8.5% and the wire speed is adjusted to 8 meters / minute based on the product thickness of 4.5 mm. All other process parameters are the same as in Example 1.

[0045] Testing showed that the thick ceramic fiber paper prepared in this embodiment has a room temperature tensile strength of 5.3 MPa, a tensile strength of 4.7 MPa after treatment at 800℃ for 2 hours, a strength retention rate of 89%, a dust loss rate of 0.9%, a minimum bending radius of 14 mm, a linear shrinkage rate of 1.7% after heat treatment at 950℃ for 24 hours, and a thermal conductivity of 0.029 W / (m·K). This thick product is suitable for applications requiring high insulation thickness, such as industrial kiln insulation linings and high-temperature pipeline seals.

[0046] Example 5 is a comparative experiment used to verify the beneficial effects of the technical solution of the present invention. Comparative Example 1 and Comparative Example 2 are set up for comparative testing with Example 1.

[0047] Comparative Example 1: A conventional wet molding process using a single aluminosilicate fiber (70%) and a single organic binder, polyvinyl alcohol (15%), was employed. No fiber surface modification was performed, no three-stage homogenizing roller process was used, and no gradient drying process was employed. Only a single-stage drying at 120°C for 30 minutes was used. All other process parameters were the same as in Example 1.

[0048] Comparative Example 2: A composite system of aluminosilicate fiber (60%), kaolin fiber (20%), and modified sepiolite fiber (10%) was used, but only an inorganic binder (silica sol 10%) was used, no organic binder was used, no fiber surface modification was performed, and the three-stage homogenizing roller process was not employed. The remaining process parameters were the same as in Example 1.

[0049] The performance of each sample was tested using the same test method as in Example 1, and the results are shown in Table 1.

[0050] Table 1

[0051] As shown in Table 1, compared to Comparative Example 1, Example 1 exhibits a 15.6% increase in room temperature tensile strength, a 64.3% increase in 800℃ tensile strength, a 26 percentage point increase in strength retention, a 68% reduction in dust loss, a 40% reduction in minimum bending radius, a 60.5% reduction in linear shrinkage, and a 20% reduction in thermal conductivity. This indicates that the synergistic effect of key technologies such as the inorganic-organic composite binder system, fiber surface modification, three-stage homogenization roller forming, gradient drying, and heat setting significantly improves mid-temperature strength, dust loss, and flexibility. Compared to Comparative Example 2, Example 1 shows a 36.8% increase in room temperature tensile strength and a 52% reduction in minimum bending radius, demonstrating the indispensable contribution of the organic binder component to room temperature flexibility. Simultaneously, the three-stage homogenization roller process ensures uniform binder distribution, achieving dual optimization of cold and hot performance, resulting in unexpected technical effects.

[0052] Example 6 investigates the effect of fiber dispersion process parameters on product performance. The fiber ratio and binder formulation are kept the same as in Example 1, but the fiber dispersion process parameters (stirring speed, ultrasonic power, dispersion time) are changed. The number of fiber overlap points, tensile strength, and dust loss rate of the product are tested.

[0053] Comparative Example 3: Stirring speed was 600 rpm, ultrasonic power was 400 W, and dispersion time was 10 minutes. Comparative Example 4: Stirring speed was 1500 rpm, ultrasonic power was 900 W, and dispersion time was 25 minutes. All other process parameters were the same as in Example 1.

[0054] The test results are shown in Table 2.

[0055] Table 2

[0056] As can be seen from Table 2, Comparative Example 3, using a lower stirring speed and ultrasonic power, resulted in insufficient fiber dispersion, with only 1800 overlapping points per cm. 2 This resulted in a 19.2% decrease in tensile strength and an 87.5% increase in powder shedding. Comparative Example 4 used excessively high stirring speeds and ultrasonic power, although the number of fiber overlap points reached 3500 / cm. 2 However, excessive fiber dispersion led to the breakage of some fibers, resulting in a 3.8% decrease in tensile strength and a 50% increase in powder loss. This indicates that the optimal range of process parameters—stirring speed of 800-1200 rpm, ultrasonic power of 500-800 watts, and dispersion time of 10-20 minutes—is the best range for achieving sufficient fiber dispersion without excessive breakage.

[0057] It is understood that the aluminosilicate fibers are not limited to short chopped fibers with a shear length of 3-6 mm, but can also be fibers with a shear length of 2-8 mm, as long as the average fiber length (SV value) is 80-170 μm. The kaolin fibers are not limited to fine short chopped fibers with a shear length of 1-3 mm, but can also be fibers with a shear length of 0.5-4 mm, as long as they can fill micropores and improve intermediate temperature strength. The modified sepiolite fibers are not limited to fibers with a length of 5-10 mm, but can also be fibers with a length of 3-15 mm, as long as they can provide toughening, crack resistance, and improved flexibility. The silane coupling agent is not limited to KH-550, but can also be amino or epoxy silane coupling agents such as KH-560 and KH-570, as long as they can form chemical bonds on the fiber surface. The inorganic binder is not limited to a combination of silica sol and water glass, but can also be a combination of other inorganic sols such as aluminosilicate sol and silica-aluminosilicate sol with water glass, as long as it can be converted into a glassy phase network at high temperatures. The organic binder is not limited to a combination of polyvinyl alcohol and acrylate emulsion, but can also be a combination of polyvinyl alcohol and other organic binders such as polyvinyl butyral and sodium carboxymethyl cellulose, as long as it can provide room temperature flexibility. The homogenizing roller is not limited to three passes, but can also be two or four passes, as long as it can achieve uniform spreading of the adhesive on the fiber surface. The gradient drying is not limited to three stages, but can also be two or four stages, as long as it can achieve gradient moisture removal and promote silica sol condensation. The hot pressing and setting temperature is not limited to 200℃, but can also be 180~220℃, as long as it can improve dimensional stability without causing complete burn-off of the organic binder.

[0058] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0059] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A ceramic fiber paper with high tensile strength, characterized in that, The raw material components comprise the following percentages by weight: The aluminosilicate fiber comprises 50% to 70%, and the surface of the aluminosilicate fiber is modified by a silane coupling agent. The kaolin fiber comprises 15% to 25%, and the surface of the kaolin fiber is modified by a silane coupling agent. Modified sepiolite fiber 5%~15%; The inorganic-organic composite binder comprises 6% to 9%, wherein the inorganic-organic composite binder includes an inorganic binder and an organic binder, the inorganic binder includes silica sol and water glass, the organic binder includes polyvinyl alcohol and acrylate emulsion, the organic binder provides room temperature flexibility, and the inorganic binder transforms into a silica glass phase at high temperature to continue bonding fibers; Dispersant 0.3%~1% and additives 0.2%~1%; The aluminum silicate fiber serves as the main skeleton to provide temperature resistance, the kaolin fiber fills the micropores and improves the medium-temperature strength, and the modified sepiolite fiber toughens, resists cracking and improves flexibility. The number of fiber overlap points per square centimeter is 2,500 to 4,000.

2. The ceramic fiber paper according to claim 1, characterized in that, The inorganic binder has a volume ratio of silica sol to water glass of 3:1, the organic binder has a volume ratio of polyvinyl alcohol to acrylate emulsion of 2:1, and the inorganic binder has a mass ratio of organic binder of 4:

1.

3. The ceramic fiber paper according to claim 2, characterized in that... : The solid content of the silica sol is 30%~40%; The modulus of the water glass is 2.8 to 3.2; The degree of polymerization of the polyvinyl alcohol is 1700~2000; The solid content of the acrylate emulsion is 45% to 55%.

4. The ceramic fiber paper according to claim 1, characterized in that... : The content of the aluminum silicate fiber is 60%~65%; The kaolin fiber content is 18%~22%; The modified sepiolite fiber content is 8%~12%.

5. The ceramic fiber paper according to claim 1, characterized in that... : The density of the ceramic fiber paper product is 180~200 kg / m³. 3 The porosity is 90%~95% and the thermal conductivity is less than or equal to 0.030W / (m·K).

6. The ceramic fiber paper according to claim 5, characterized in that... : The ceramic fiber paper has a room temperature tensile strength greater than or equal to 5.0 MPa, a tensile strength greater than or equal to 4.5 MPa after being treated at 800℃ for 2 hours, a strength retention rate greater than or equal to 80%, a dust loss rate less than or equal to 1.0%, and a minimum bending radius less than or equal to 15 mm.

7. The ceramic fiber paper according to claim 1, characterized in that... : The shear length of the aluminum silicate fiber is 3-6 mm, the shear length of the kaolin fiber is 1-3 mm, the length of the modified sepiolite fiber is 5-10 mm, the average fiber diameter is 2.15-3.0 μm, and the average fiber length is 100-150 μm.

8. A method for preparing ceramic fiber paper with high tensile strength, comprising the following steps: Step (1): Fiber pretreatment and surface modification: Alumina silicate fiber and kaolin fiber are subjected to surface modification treatment. The surface modification treatment uses silane coupling agent with a concentration of 2%~5%, a spraying amount of 0.5%~2% of the fiber mass, and a stirring time of 15~30 minutes. Step (2): Fiber grading, dispersion and pulping: Mix the modified fiber with the modified sepiolite fiber, add a dispersant, and carry out high-speed stirring and ultrasonic-assisted dispersion. The stirring speed is 800~1200 rpm, the ultrasonic frequency is 40 kHz and the power is 500~800 watts, and the dispersion time is 10~20 minutes. Step (3): Preparation of composite adhesive: Prepare an inorganic-organic composite adhesive, wherein the inorganic adhesive contains silica sol and water glass, and the organic adhesive contains polyvinyl alcohol and acrylate emulsion, with a mass ratio of inorganic adhesive to organic adhesive of 4:1; Step (4): Forming with a homogenizing roller: Add the composite adhesive prepared in step (3) to the slurry in step (2), and form it by homogenizing roller. Control the glue content in stages according to the product thickness. Use three homogenizing rollers, with a screen speed of 5~15 m / min and a slurry concentration of 0.6%~1.0%. When the product thickness is 1.5mm, the glue content should be controlled at 6.5%; When the product thickness is 3.0mm, the glue content should be controlled at 8%; When the product thickness is 4.5mm, the glue content should be controlled at 8.5%; The linear velocities of the three homogenizing rollers increase sequentially: the linear velocity of the first homogenizing roller is 3-5 m / min, the linear velocity of the second homogenizing roller is 6-10 m / min, and the linear velocity of the third homogenizing roller is 10-15 m / min. Step (5): Gradient dewatering and pressing: Gradient vacuum dewatering and pressing are performed on the formed wet paper blank. The vacuum degree of the first stage of dewatering is -0.04MPa, the vacuum degree of the second stage of dewatering is -0.06MPa, and the linear pressure of the pressing stage is 10~30kN / m. Step (6): Gradient drying and heat setting: The dehydrated paper blank is subjected to gradient drying and heat setting. The first stage of drying temperature is 80~100℃ and the time is 15~25 minutes. The second stage of drying temperature is 120~150℃ and the time is 20~30 minutes. The third stage of drying temperature is 180~200℃ and the time is 25~35 minutes.

9. The preparation method according to claim 8, characterized in that... In step (6), the hot pressing temperature is 200℃, the linear pressure is 20kN / m, and the setting time is 5~10 minutes.

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