A preparation process of ultra-thin ceramic fiber paper composite reinforcement

Abstract

The application discloses a kind of ultra-thin ceramic fiber paper composite preparation processes, its preparation process includes the following steps: S1, first fiber accurate short cutting pretreatment: polycrystalline mullite fiber and alumina fiber are mixed according to mass ratio 6:4, according to fiber bulk density, adjust the frequency of cotton opener frequency converter to 35~45Hz, mixed fiber is short cut into length 2~3mm, specific gravity 120~150mL / g short cut cotton using diamond cutter, quantitative packaging as pulp preparation raw material, the obtained short cut mixed fiber is put into hydraulic pulper according to mass ratio (6-8) : (2-4), add dispersing agent and pH regulator, and carry out first-order dissociation at 200-300rpm speed for 15-25min.The application realizes the stable preparation of ultra-thin ceramic fiber paper with thickness ≤0.2mm, reduces more than 50% than existing products, tensile strength ≥8MPa, is 2-3 times higher than traditional ceramic fiber paper, meets the demand of automatic mounting, high-temperature strength retention rate >85%, thermal runaway protection reliability is high, process continuous mass production, and good compatibility with existing wet papermaking equipment.

Description

Technical Field

[0001] This invention relates to the field of functional composite material preparation technology, specifically to a process for preparing ultrathin ceramic fiber paper composite reinforcement. Background Technology

[0002] Ceramic fiber paper is a lightweight, high-temperature resistant material made from ceramic fibers through a wet forming process. It possesses low thermal conductivity, excellent thermal stability, and chemical stability, and is widely used in high-temperature insulation, thermal insulation sealing, and other fields. With the rapid development of the new energy industry, the thermal runaway protection scenarios for power battery packs place higher demands on the density, flexural strength, and thermal shock resistance of ceramic fiber paper. The thermal safety performance of power battery packs has become a core technical challenge in the industry. As a high-temperature resistant, low-thermal-conductivity inorganic material, ceramic fiber paper is a core protective material for thermal insulation between battery cells and between modules and the housing. Currently, commercially available ceramic fiber paper generally suffers from the following defects: The thickness is usually above 0.5mm, which cannot meet the ultra-thin space design requirements of high energy density battery packs. During the ultra-thinning process, the fibers are easily dispersed unevenly, resulting in insufficient tensile strength of the finished product (usually below 0.3MPa). It is easy to break during battery pack assembly and use. The uneven distribution of binder in conventional wet molding process causes large fluctuations in the thermal insulation performance of the material. After long-term use, the thermal conductivity increases by more than 20%. The existing process has low production efficiency, and the yield of ultra-thin products is less than 60%, which is difficult to meet the needs of large-scale industrial applications. Products obtained by traditional papermaking process generally have problems such as weak fiber bonding, large thickness (≥0.5mm), and low strength (≤3MPa), which cannot meet the requirements of ultra-thinness and high strength between cells. Summary of the Invention

[0003] The purpose of this invention is to provide an ultra-thin ceramic fiber paper composite reinforcement preparation process to solve the problems mentioned in the background art, such as low production efficiency of existing processes, yield of ultra-thin products of less than 60%, difficulty in meeting the needs of large-scale industrial applications, and the problems of weak fiber bonding, large thickness (≥0.5mm), and low strength (≤3MPa) of products obtained by traditional papermaking processes, which cannot meet the requirements of ultra-thinness and high strength between battery cells.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a process for preparing ultrathin ceramic fiber paper composite reinforcement, the process comprising the following steps: S1. First, the fiber is precisely chopped for pretreatment: Polycrystalline mullite fiber and alumina fiber are mixed at a mass ratio of 6:4. The frequency of the cotton opener inverter is adjusted to 35~45Hz according to the fiber bulk density. The mixed fiber is chopped into short cotton with a length of 2~3mm and a specific weight of 120~150mL / g using a diamond cutter. The short cotton is quantitatively packaged as pulping raw material. The obtained short mixed fiber is put into a hydrapulper at a mass ratio of (6-8):(2-4). Dispersant and pH adjuster are added. The first-stage dissociation is carried out at a speed of 200-300rpm for 15-25min to form a first-stage fiber pulp with a mass concentration of 0.8%-1.5%. Then, it is introduced into a refiner for a second-stage flexible dissociation, and the freeness is controlled at 18-25°SR to obtain a composite fiber pulp.

[0005] S2. Then, add 8-12% of the total fiber mass of the silica sol-silane coupling agent composite bonding system to the pulp, stir evenly, and then pass it through an ultrasonic field for 5-8 minutes to make the binder evenly adhere to the fiber surface. Send the modified pulp into a high-level tank, control the on-line concentration to 0.08-0.12wt%, and use an inclined wire forming device to perform three-stage vacuum gradient dewatering to obtain a wet paper web.

[0006] S3. Finally, the obtained wet paper web is directly introduced into the impregnation tank, and the impregnation of the reinforcing agent solution is assisted by vacuum suction. The reinforcing agent is a mixed solution of silica sol and alumina sol, in which the mass ratio of SiO2 to Al2O3 is 1:0.3-0.8. The impregnation pressure is -0.05 to -0.08 MPa, and the impregnation time is 30-90 s. The impregnated wet paper web is then subjected to three stages of hot-press drying: the first stage temperature is 80-100℃, and the linear pressure is 0.5-1.0 kN / m; the second stage temperature is 120-150℃, and the linear pressure is 1.5-2.5 kN / m; the third stage temperature is 180-220℃, and the linear pressure is 2.0-3.0 kN / m. This yields an ultra-thin ceramic fiber paper substrate, which is then surface functionalized and dried. The dried paper is then fed into a roller hot press for hot pressing to fully cross-link and cure the binder, resulting in a preliminary product. The preliminary product is then longitudinally cut, transversely cut, and inspected to obtain the final product.

[0007] Preferably, the dispersant is sodium polyacrylate, and the addition amount is 0.1%-0.5% of the oven-dry fiber mass; the pH adjuster is acetic acid or ammonia water, which adjusts the pH of the pulp to 6.5-7.5; the secondary flexible dissociation adopts a double-disc refiner with a disc gap of 0.2-0.5 mm and a dissociation number of 1-2 times.

[0008] Preferably, the reinforcing agent solution also contains 0.5%-1.5% boric acid by mass of the solute to form a B-Si-Al ternary copolymer crosslinking network. The rollers used in the three-stage hot pressing are mirror-finished stainless steel rollers, and an air suspension section of 20-40cm is provided between adjacent hot pressing sections to release internal water vapor.

[0009] Preferably, the rollers used in the three-stage hot pressing are mirror-finished stainless steel rollers, and an air suspension section of 20-40cm is provided between adjacent hot pressing sections to release internal water vapor. Each 20kg unit of chopped cotton is a quantitative packaging unit.

[0010] Preferably, the prepared ultrathin ceramic fiber paper has a thickness of 0.1~0.3mm, a tensile strength ≥0.8MPa, a thermal conductivity ≤0.035W / (m·K), and a product yield of ≥92%.

[0011] Preferably, the surface functionalization treatment is carried out by spraying or roller coating, applying a nano-alumina coating with a thickness of 1-5 μm to at least one surface of the obtained paper substrate, and then drying it at a high temperature of 150-200℃ to obtain the corresponding initial product.

[0012] Compared with the prior art, the beneficial effects of the present invention are: the present invention achieves stable preparation of ultra-thin ceramic fiber paper with a thickness of ≤0.2mm, which is more than 50% thinner than existing products, with a tensile strength of ≥8MPa, which is 2-3 times higher than traditional ceramic fiber paper, meeting the requirements of automated mounting, with a high temperature strength retention rate of >85%, high reliability of thermal runaway protection, continuous process that can be mass-produced, good compatibility with existing wet papermaking equipment, and easy industrial transformation.

[0013] This invention significantly improves the tensile strength of the product by more than 200% compared to existing similar products while reducing the amount of binder used. At the same time, it maintains a thermal conductivity of less than 0.035 W / (m·K), effectively achieving a balance between ultra-thinness, high strength, and low thermal conductivity, and providing better protection for battery packs in new energy sources. Attached Figure Description

[0014] Figure 1 This is a performance comparison table for the present invention. Detailed Implementation

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Example 1:

[0017] Please see Figure 1 A process for preparing ultrathin ceramic fiber paper composite reinforcement includes the following steps: S1. First, the fiber is precisely chopped for pretreatment: Polycrystalline mullite fiber and alumina fiber are mixed at a mass ratio of 6:4. The frequency of the cotton opener inverter is adjusted to 35~45Hz according to the fiber bulk density. The mixed fiber is chopped into short cotton with a length of 2~3mm and a specific gravity of 120~150mL / g using a diamond cutter. The short cotton is quantitatively packaged as pulping raw material. The obtained short mixed fiber is put into the hydrapulper at a mass ratio of (6-8):(2-4). Dispersant and pH adjuster are added, and the pulp is rotated at 200-300rpm. The pulp undergoes primary dissociation for 15-25 minutes to form a primary fiber pulp with a mass concentration of 0.8%-1.5%. It is then introduced into a refiner for secondary flexible dissociation, with the freeness controlled at 18-25°SR to obtain a composite fiber pulp. The dispersant is sodium polyacrylate, added at 0.1%-0.5% of the oven-dry fiber mass. The pH adjuster is acetic acid or ammonia, adjusting the pulp pH to 6.5-7.5. Secondary flexible dissociation is performed using a dual-disc refiner with a disc gap of 0.2-0.5 mm, and the dissociation is performed 1-2 times.

[0018] S2. Then, add 8-12% of the total fiber mass of the silica sol-silane coupling agent composite bonding system to the pulp, stir evenly, and then pass it through an ultrasonic field for 5-8 minutes to make the binder evenly adhere to the fiber surface. The modified pulp is sent to a high-level tank, and the online concentration is controlled at 0.08-0.12wt%. A three-stage vacuum gradient dewatering is performed using an inclined wire forming device to obtain a wet paper web. Boric acid, accounting for 0.5%-1.5% of the solute mass, is also added to the reinforcing agent solution to form a B-Si-Al ternary copolymer crosslinking network. The rollers used for the three-stage hot pressing are mirror stainless steel rollers, and an air suspension section of 20-40cm is set between adjacent hot pressing sections to release internal water vapor. The chopped cotton is packaged in quantitative units of 20kg each.

[0019] S3. Finally, the obtained wet paper web is directly introduced into the impregnation tank, and vacuum suction is used to assist in impregnating the reinforcing agent solution. The reinforcing agent is a mixed solution of silica sol and alumina sol, in which the mass ratio of SiO2 to Al2O3 is 1:0.3-0.8. The impregnation pressure is -0.05 to -0.08 MPa, and the impregnation time is 30-90 s. The impregnated wet paper web is then subjected to three stages of hot-press drying: the first stage temperature is 80-100℃, and the linear pressure is 0.5-1.0 kN / m; the second stage temperature is 120-150℃, and the linear pressure is 1.5-2.5 kN / m; the third stage temperature is 180-220℃, and the linear pressure is 2.0-3.0 kN / m, to obtain ultra-thin ceramic paper. The ceramic fiber paper substrate is surface functionalized and then dried. The dried paper is then fed into a roller hot press for hot pressing to fully cross-link and cure the adhesive, resulting in a preliminary product. The preliminary product is then longitudinally and transversely cut and inspected to obtain the final product. The prepared ultra-thin ceramic fiber paper has a thickness of 0.1~0.3mm, a tensile strength ≥0.8MPa, a thermal conductivity ≤0.035W / (m·K), and a product yield ≥92%. The surface functionalization treatment is carried out by spraying or roller coating, applying a 1-5μm thick nano-alumina coating to at least one surface of the obtained paper substrate, and then drying at a high temperature of 150-200℃ to obtain the corresponding preliminary product.

[0020] Example 2:

[0021] The distinguishing feature from Embodiment 1 is as follows: The preparation process in this embodiment includes the following steps: S1. Precision Fiber Short Cutting Pre-treatment: Mix 60kg of polycrystalline mullite fiber with 40kg of alumina fiber, adjust the frequency of the cotton opener inverter to 35Hz, and use a diamond cutter to cut the mixed fiber into short cotton with a length of 2mm and a specific value of 120mL / g, and package it in quantitative quantities of 20kg.

[0022] S2. Composite dispersion system preparation: Take 20kg of chopped cotton and put it into the preparation tank. Add 160kg of deionized water, then add 60g of polyacrylamide dispersant and 40g of polyethylene oxide retention aid in sequence. Stir at 200rpm for 20min to obtain a uniform fiber slurry with a concentration of 0.25wt%.

[0023] S3. In-situ composite reinforcement modification: Add 1.6 kg of silica sol-silane coupling agent composite bonding system to the slurry, stir evenly, and then pass it through an ultrasonic field for 8 min. The ultrasonic frequency is 40 kHz and the power density is 0.8 W / cm3.

[0024] S4. Gradient wet forming: The modified pulp is fed into a high-level tank, and the online concentration is controlled at 0.12wt%. A three-stage vacuum dewatering process is carried out using an inclined wire forming device: the first stage vacuum degree is -0.02MPa, the second stage vacuum degree is -0.04MPa, and the third stage vacuum degree is -0.06MPa, to obtain a wet paper web.

[0025] S5. Segmented Gradient Drying: The wet paper web is fed into a three-stage drying system: the first stage temperature is 80℃, drying for 5 minutes; the second stage temperature is 120℃, drying for 8 minutes; the third stage temperature is 160℃, drying for 3 minutes. The moisture content after drying is 1.5%. Hot Pressing and Shaping Enhancement: The dried paper web is fed into a roller hot press. The hot pressing temperature is 220℃, the linear pressure is 80N / mm, and the hot pressing speed is 5m / min. The finished product is obtained after post-processing.

[0026] Example 3:

[0027] The distinguishing feature from Embodiment 1 and Embodiment 2 is as follows: The preparation process in this embodiment includes the following steps: S1. Precision Fiber Short Cutting Pretreatment: Mix 60kg of polycrystalline mullite fiber with 40kg of alumina fiber, adjust the frequency of the cotton opener inverter to 45Hz, and use a diamond cutter to cut the mixed fiber into short cotton with a length of 3mm and a specific value of 150mL / g, and package it in quantitative quantities of 20kg.

[0028] S2. Composite dispersion system preparation: Take 20kg of chopped cotton and put it into the preparation tank. Add 200kg of deionized water, then add 100g of polyacrylamide dispersant and 80g of polyethylene oxide retention aid in sequence. Stir at 300rpm for 15min to obtain a uniform fiber slurry with a concentration of 0.15wt%.

[0029] S3. In-situ composite reinforcement modification: Add 2.4 kg of silica sol-silane coupling agent composite bonding system to the slurry, stir evenly, and then pass it through an ultrasonic field for 5 min. The ultrasonic frequency is 40 kHz and the power density is 1.0 W / cm3.

[0030] S4. Gradient wet forming: The modified pulp is fed into a high-level tank, and the online concentration is controlled at 0.08wt%. A three-stage vacuum dewatering process is carried out using an inclined wire forming device: the first stage vacuum degree is -0.03MPa, the second stage vacuum degree is -0.05MPa, and the third stage vacuum degree is -0.07MPa, to obtain a wet paper web.

[0031] S5. Segmented Gradient Drying: The wet paper web is fed into a three-stage drying system: the first stage temperature is 100℃, drying for 3 minutes; the second stage temperature is 140℃, drying for 5 minutes; the third stage temperature is 180℃, drying for 2 minutes. The moisture content after drying is 1.0%. Hot Pressing and Shaping Enhancement: The dried paper web is fed into a roller hot press. The hot pressing temperature is 250℃, the linear pressure is 120N / mm, and the hot pressing speed is 3m / min. The finished product is obtained after post-processing.

[0032] Example 4:

[0033] The distinguishing features from Embodiments 1, 2, and 3 are as follows: The preparation process in this embodiment includes the following steps: By using the traditional ceramic fiber paper preparation process: the fiber stub length is 5mm, no ultrasonic modification is performed, and conventional one-step dehydration and drying processes are used, the resulting product has a thickness of 0.5mm, a tensile strength of 0.28MPa, a thermal conductivity of 0.042W / (m·K), and a product yield of 58%.

[0034] In summary, the experimental results of Example 1 demonstrate that, compared with the experimental results of Examples 2, 3, and 4, the ultrathin ceramic fiber paper prepared by this invention has significantly reduced thickness while exhibiting much better mechanical properties, thermal insulation properties, and product yield than products prepared using traditional processes.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for preparing ultrathin ceramic fiber paper composite reinforcement, characterized in that: Its preparation process includes the following steps: S1. First, precise fiber stub cutting pretreatment is required: Polycrystalline mullite fiber and alumina fiber are mixed at a mass ratio of 6:

4. The frequency of the cotton opener inverter is adjusted to 35~45Hz according to the fiber bulk density. The mixed fiber is stubbed into short cotton with a length of 2~3mm and a specific gravity of 120~150mL / g using a diamond cutter. The short cotton is quantitatively packaged as pulping raw material. The obtained short mixed fiber is put into a hydrapulper at a mass ratio of (6-8):(2-4). Dispersant and pH adjuster are added. The first-stage dissociation is carried out at a speed of 200-300rpm for 15-25min to form a primary fiber pulp with a mass concentration of 0.8%-1.5%. Then, it is introduced into a refiner for secondary flexible dissociation, and the freeness is controlled at 18-25°SR to obtain composite fiber pulp. S2. Then, add 8-12% of the total fiber mass of the silica sol-silane coupling agent composite bonding system to the pulp, stir evenly, and then pass it through an ultrasonic field for 5-8 minutes to make the binder evenly adhere to the fiber surface. Send the modified pulp into the high-level tank, control the on-line concentration to 0.08-0.12wt%, and use an inclined wire forming device to perform three-stage vacuum gradient dewatering to obtain a wet paper web. S3. Finally, the obtained wet paper web is directly introduced into the impregnation tank, and the impregnation of the reinforcing agent solution is assisted by vacuum suction. The reinforcing agent is a mixed solution of silica sol and alumina sol, in which the mass ratio of SiO2 to Al2O3 is 1:0.3-0.

8. The impregnation pressure is -0.05 to -0.08 MPa, and the impregnation time is 30-90 s. The impregnated wet paper web is then subjected to three stages of hot-press drying: the first stage temperature is 80-100℃, and the linear pressure is 0.5-1.0 kN / m; the second stage temperature is 120-150℃, and the linear pressure is 1.5-2.5 kN / m; the third stage temperature is 180-220℃, and the linear pressure is 2.0-3.0 kN / m. This yields an ultra-thin ceramic fiber paper substrate, which is then surface functionalized and dried. The dried paper is then fed into a roller hot press for hot pressing to fully cross-link and cure the binder, resulting in a preliminary product. The preliminary product is then longitudinally cut, transversely cut, and inspected to obtain the final product.

2. The preparation process of ultrathin ceramic fiber paper composite reinforcement according to claim 1, characterized in that: The dispersant is sodium polyacrylate, and the addition amount is 0.1%-0.5% of the oven-dry fiber mass; the pH adjuster is acetic acid or ammonia water, which adjusts the pH of the pulp to 6.5-7.5; the secondary flexible dissociation adopts a double-disc refiner with a disc gap of 0.2-0.5 mm and a dissociation number of 1-2 times.

3. The preparation process of ultrathin ceramic fiber paper composite reinforcement according to claim 1, characterized in that: The reinforcing agent solution also contains 0.5%-1.5% boric acid by mass of solute to form a B-Si-Al ternary copolymer crosslinking network. The rollers used in the three-stage hot pressing are mirror stainless steel rollers, and an air suspension section of 20-40cm is set between adjacent hot pressing sections to release internal water vapor.

4. The preparation process of ultrathin ceramic fiber paper composite reinforcement according to claim 1, characterized in that: The rollers used in the three-stage hot pressing are mirror-finished stainless steel rollers, and an air suspension section of 20-40cm is set between adjacent hot pressing sections to release internal water vapor. Each 20kg of chopped cotton is a quantitative packaging unit.

5. The preparation process of ultrathin ceramic fiber paper composite reinforcement according to claim 1, characterized in that: The prepared ultrathin ceramic fiber paper has a thickness of 0.1~0.3mm, a tensile strength ≥0.8MPa, a thermal conductivity ≤0.035W / (m·K), and a product yield ≥92%.

6. The preparation process of ultrathin ceramic fiber paper composite reinforcement according to claim 1, characterized in that: The surface functionalization treatment is carried out by spraying or roller coating, applying a nano-alumina coating with a thickness of 1-5 μm to at least one surface of the obtained paper substrate, and then drying it at a high temperature of 150-200℃ to obtain the corresponding initial product.

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