Ceramic fiber paper and preparation method thereof

Abstract

The invention discloses a ceramic fiber paper, wherein the raw materials of the ceramic fiber paper include Si-O tetracoordinated orthosilicate, fluorine-substituted silicate, vermiculite, aluminum silicate fiber, fluorine-substituted polyolefin, phosphorus-nitrogen flame retardant, and nylon, and the mass ratio of the total mass of the Si-O tetracoordinated orthosilicate, fluorine-substituted silicate, vermiculite, aluminum silicate fiber, fluorine-substituted polyolefin, phosphorus-nitrogen flame retardant, and nylon in the raw materials is 70%-80%. The ceramic fiber paper obtained by the method of the invention has the characteristics of low thermal conductivity and high temperature resistance, the product has a wide range of applications, a simple production process, and excellent thermal insulation performance.

Description

Technical Field

[0001] The invention relates to the technical field of materials, and in particular to ceramic fiber paper and a preparation method thereof. Background Art

[0002] Traditional ceramic fiber paper is aluminum silicate ceramic fiber paper, including ordinary type, standard type, high aluminum type or zirconium-containing ceramic fiber paper, which is made of ordinary ceramic fiber, standard ceramic fiber, high aluminum type ceramic fiber or zirconium-containing ceramic fiber through a vacuum forming wet process. Ceramic fiber paper is widely used in the production process of microcrystalline ceramics and foam ceramics as a special thermal insulation fiber material and demolding thermal insulation pad.

[0003] Aerogel is a porous solid material composed of nano-colloidal particles or polymer molecules with a developed three-dimensional network structure and extremely high porosity. In addition, its excellent properties such as high specific surface area and low thermal conductivity (0.01-0.03W / (mK)) have attracted widespread attention in the field of flame retardancy and thermal insulation. In order to further improve the use of ceramic fiber paper in high-temperature technology, some researchers in the prior art have used aerogel to prepare ceramic fiber paper in order to improve the heat resistance of ceramic fiber. However, studies have found that because aerogel cannot block high-temperature infrared radiation heat transfer, the high-temperature thermal insulation performance of ceramic fiber paper is poor, and the use temperature of ceramic fiber paper cannot exceed 800°C.

[0004] The emergence of vermiculite in materials used in high-temperature fields and its use in materials can help improve the high-temperature resistance of materials and keep them in a good state at no less than 800°C. This is because vermiculite is a secondary mineral whose volume can expand 2-20 times instantly when heated. After the vermiculite expands at high temperatures, its specific surface area and porosity are greatly increased, and its thermal stability and thermal insulation properties are improved. However, when vermiculite expands when heated, it loses water between the layers, causing the brittleness of the product to increase rapidly. In the prior art, vermiculite is often used in thermal insulation coating materials, etc., but not in ceramic fiber paper.

[0005] Ceramic fiber paper not only requires high temperature resistance, but also flexibility and lightness. Although the use of vermiculite in ceramic fiber paper can further improve the high temperature resistance of ceramic fiber paper, how to balance the relationship between the brittleness of ceramic fiber paper and the high temperature resistance of ceramic fiber paper during the thermal expansion of vermiculite is a technical problem that needs to be solved at present. Summary of the invention

[0006] In view of the problems in the prior art, the present invention discloses a ceramic fiber paper and a preparation method thereof. The ceramic fiber paper of the present invention is not only light and thin and flexible, but also has the advantages of better thermal conductivity and thermal insulation performance in low temperature range and high temperature range (>1000°C).

[0007] The present invention is achieved through the following technical solutions:

[0008] The present invention provides a ceramic fiber paper, wherein the raw materials of the ceramic fiber paper include Si-O tetracoordinated orthosilicate, fluorine-substituted silicate, vermiculite, aluminum silicate fiber, fluorine-substituted polyolefin, phosphorus-nitrogen flame retardant and nylon, the mass ratio of the total mass of the Si-O tetracoordinated orthosilicate, fluorine-substituted silicate, vermiculite, aluminum silicate fiber, fluorine-substituted polyolefin, phosphorus-nitrogen flame retardant and nylon in the raw materials is 70%-80%, and the mass ratio of the Si-O tetracoordinated orthosilicate, fluorine-substituted silicate, vermiculite, aluminum silicate fiber, fluorine-substituted polyolefin, phosphorus-nitrogen flame retardant and nylon is (0.01 part-0.2 part): (0.01 part-0.2 part): (0.05 part-0.2 part): (1 part-2 parts): (0.3 part-0.4 part): (0.2 part-0.3 part): (0.2 part-0.3 part).

[0009] The above-mentioned design of the present invention, in which Si-O tetra-coordinated orthosilicate and fluorine-substituted silicate form silica aerogel, and the formed silica aerogel is coated on the surface of vermiculite; the surface of the aluminum silicate fiber is smooth, and the internal solid phase material exists in the form of a continuous skeleton, and the vermiculite coated with silica aerogel will be embedded in the gap between the aluminum silicate fibers, which can reduce the volume of the ceramic fiber paper and improve the heat resistance and thermal insulation performance of the ceramic fiber paper. In the present invention, we also further designed silicate, using Si-O tetra-coordinated orthosilicate and fluorine-substituted silicate to cooperate with each other, wherein Si-O tetra-coordinated orthosilicate has a smaller polarity, and can better form an aerogel with a more suitable porosity and a more uniformly distributed pore structure; and the fluorine-substituted silicate can participate in the formation of aerogel on the one hand, and on the other hand, the fluorine-substituted group in the fluorine-substituted silicate can promote the aerogel to be more evenly coated on the surface of the vermiculite. On this basis, we have further designed fluorine-substituted polyolefins, phosphorus-nitrogen flame retardants and nylon, which can further improve the heat resistance and flexibility of the ceramic fiber paper obtained, so that the ceramic fiber paper obtained can balance the brittleness of ceramic fiber paper and the high temperature resistance of ceramic fiber paper on the basis of being thin. Among them, fluorine-substituted polyolefins can be more easily matched with fluorine-substituted silicates, and the substances are easier to disperse evenly; in addition, the combination of phosphorus-nitrogen flame retardants and nylon can improve the flame retardancy of ceramic fiber paper on the one hand, and improve the hygroscopicity of ceramic fiber paper on the other hand, which is conducive to reducing the brittleness of ceramic fiber paper at high temperature; and the nitrogen and phosphorus in the phosphorus-nitrogen flame retardant have lone pairs of electrons, and the fluorine substituents in the fluorine-substituted polyolefins and fluorine-substituted silicates are electron-withdrawing groups, so that the phosphorus-nitrogen flame retardant can better match the fluorine-substituted polyolefins and fluorine-substituted silicates, which is more conducive to coating on the surface of vermiculite and in the gaps between aluminum silicate fibers, and improving the flexibility of ceramic fiber paper. The combination of the raw materials of the present invention enables the ceramic fiber paper to have good heat resistance, heat insulation and flexibility on the basis of being relatively thin.

[0010] As a further solution, the Si-O tetra-coordinated orthosilicate includes one or more of methyl orthosilicate and ethyl orthosilicate.

[0011] As a further embodiment, the fluorine-substituted silicate includes one or more of fluorine-substituted methyltriethoxysilane and fluorine-substituted dimethyldiethoxysilane.

[0012] As a further embodiment, the fluorine-substituted methyltriethoxysilane is perfluorine-substituted methyltriethoxysilane; and the fluorine-substituted dimethyldiethoxysilane is perfluorine-substituted dimethyldiethoxysilane.

[0013] As a further solution, the vermiculite includes one or more of Lingshou vermiculite from Hebei and Yuli vermiculite from Xinjiang.

[0014] As a further embodiment, the fluorine-substituted polyolefin includes one or more of polyvinylidene fluoride and polytetrafluoroethylene.

[0015] As a further embodiment, the phosphorus-nitrogen flame retardant includes one or more of piperazine pyrophosphate, ammonium polyphosphate, melamine polyphosphate, and pentaerythritol phosphate.

[0016] As a further solution, the components of the aluminum silicate fiber include SiO2 (48%-52%), Al2O3 (43%-49%), and impurities, and the total mass fraction of SiO2, Al2O3 and impurities in the aluminum silicate fiber is 100%.

[0017] As a further embodiment, the impurities include one or more of Fe2O3, CaO, and MgO.

[0018] As a further solution, the length of the aluminum silicate fiber is 2 mm-10 mm. The length of the aluminum silicate fiber is within the range of 2 mm-10 mm, which is more conducive to the dispersion of the aluminum silicate fiber and the consistent orientation of the aluminum silicate fiber, thereby facilitating the acquisition of thin ceramic fiber paper.

[0019] As a further scheme, the raw materials of the ceramic fiber paper include methyl orthosilicate, fluorine-substituted methyltriethoxysilane, vermiculite, aluminum silicate fiber, polyvinylidene fluoride, melamine polyphosphate, and nylon. By mass, the ratio of methyl orthosilicate, fluorine-substituted methyltriethoxysilane, vermiculite, aluminum silicate fiber, polyvinylidene fluoride, melamine polyphosphate, and nylon is (0.08 parts-0.12 parts): (0.08 parts-0.12 parts): (0.09 parts-0.11 parts): (1.3 parts-1.7 parts): (0.34 parts-0.36 parts): (0.24 parts-0.26 parts): (0.24 parts-0.26 parts). Methyl orthosilicate has shorter side chains, which makes it easier to disperse in the slurry. Fluorine-substituted methyl triethoxysilane can be combined with methyl orthosilicate to form a highly ordered and structurally stable silica aerogel, which is more conducive to the thermal insulation performance of ceramic fibers at low temperatures. The combination of polyvinylidene fluoride and melamine polyphosphate makes ceramic fiber paper have suitable flexibility and mechanical strength. In addition, the cyano group in melamine polyphosphate can also improve the heat resistance of ceramic fiber materials.

[0020] As a further solution, the raw material of the ceramic fiber paper also includes an adhesive.

[0021] As a further solution, the adhesive includes one or more of acrylic resin, polyurethane emulsion, colloidal alumina, and aluminum sulfate-ammonia water.

[0022] As a further solution, the mass proportion of the adhesive in the raw materials is 20%-30%.

[0023] As a further solution, the thickness of the ceramic fiber paper is 3 mm-6 mm.

[0024] The present invention also provides a method for preparing the ceramic fiber paper, the method comprising:

[0025] S1: After uniformly mixing Si-O tetracoordinated orthosilicate, fluorine-substituted silicate, alcohol organic solvent and deionized water into a clear mixed solution, adding acid to adjust the pH range, and then hydrolyzing the mixed solution;

[0026] S2: Add nylon, phosphorus-nitrogen flame retardant and vermiculite to the product after the hydrolysis reaction of S1 according to the mass ratio, and then disperse them evenly;

[0027] S3: quickly and evenly mix the gel catalyst and the product obtained in S2, and then perform alcohol replacement; perform supercritical drying;

[0028] S4: crush the product obtained in S3 to obtain the crushed product, add adhesive, aluminum silicate fiber, and fluorine-substituted polyolefin respectively according to the mass ratio to obtain mixed pulp, adopt wet papermaking to form, and dry. In the method of the present invention, in order to balance the brittleness of ceramic fiber paper and the high temperature resistance of ceramic fiber paper, we add nylon and phosphorus nitrogen flame retardant during the preparation process. On the one hand, nylon and phosphorus nitrogen flame retardant have good structural stability and will not be affected after supercritical drying, so that they can be stably coated on the surface of vermiculite, thereby improving the brittleness of vermiculite; on the other hand, phosphorus nitrogen flame retardant can cooperate with fluorine-substituted silicate and fluorine-substituted polyolefin, which is not only beneficial to the stability of the coating structure, but also can cooperate with fluorine-substituted polyolefin in the gap of aluminum silicate fiber to improve the flexibility of ceramic fiber paper. In addition, the fluorine-substituted polyolefin is mixed with the vermiculite forming a coating structure, which, on the one hand, prevents the influence of supercritical drying on its flexibility, and on the other hand, the fluorine-substituted polyolefin can be more easily dispersed in the adhesive, thereby being evenly dispersed throughout the ceramic fiber paper, including in the gaps between the aluminum silicate fibers, thereby improving the flexibility of the ceramic fiber paper.

[0029] As a further solution, the concentration of the Si-O tetra-coordinated orthosilicate in the mixed solution in S1 is 0.063 g / mL-0.125 g / mL, and the Si-O tetra-coordinated orthosilicate and fluorine-substituted silicate are weighed respectively according to the mass ratio.

[0030] As a further solution, the volume ratio of the alcohol organic solvent to deionized water in S1 is (80-100):(10-20).

[0031] As a further solution, the acid in S1 adjusts the pH range, and the pH range is 2-3.

[0032] As a further solution, the temperature of the hydrolysis reaction in S1 is 45°C-55°C, and the time of the hydrolysis reaction is 18h-22h.

[0033] As a further embodiment, the alcohol organic solvent includes one or more of isopropanol, anhydrous methanol, and anhydrous ethanol.

[0034] As a further embodiment, the acid for acid adjustment includes one or more of hydrochloric acid, nitric acid, and phosphoric acid.

[0035] As a further solution, the ratio of vermiculite, nylon and melamine polyphosphate added to S2 is (0.05 parts-0.2 parts):(0.2 parts-0.3 parts):(0.2 parts-0.3 parts) by mass.

[0036] As a further solution, the uniform dispersion method in S2 includes stirring, and the stirring speed is 800r / min-1200r / min. In the present invention, as long as the dispersion is uniform, the technicians in this field can select different uniform dispersion methods according to the actual situation; when the stirring method is selected, the technicians in this field can also adjust the speed and stirring time according to the actual situation.

[0037] As a further solution, the preparation method of the gel catalyst in S3 includes preparing the gel catalyst using alkali and deionized water, with the alkali:deionized water = 1:(20-40) by mass, and uniformly mixing to obtain a clear solution.

[0038] As a further embodiment, the base includes one or more of aqueous ammonia, sodium bicarbonate, ammonium fluoride or sodium hydroxide.

[0039] As a further embodiment, the ratio of the gel catalyst in S3 to the product obtained in S2 is 1 part:(15 parts-35 parts) by mass.

[0040] As a further solution, the temperature of the alcohol replacement in S3 is 60°C-70°C, and the time of the alcohol replacement is 24h-36h.

[0041] As a further embodiment, the alcohol for alcohol replacement includes one or more of anhydrous methanol or anhydrous ethanol. In the alcohol replacement process, as long as the replaced product can be submerged in the alcohol solution.

[0042] As a further solution, the uniform mixing time in S3 is 5 min to 15 min, during which the sol state is transformed into a gel state.

[0043] As a further solution, the supercritical drying in S3 is ethanol supercritical or carbon dioxide supercritical.

[0044] As a further solution, the specific conditions for the ethanol supercriticality are: ethanol supercritical temperature 250°C-260°C, pre-pressurization 1.5Mpa-2.5MPa, and maintaining the pressure at 10Mpa-12MPa for 1h-2h.

[0045] As a further solution, the specific conditions for the supercritical carbon dioxide are that the supercritical temperature of carbon dioxide is 55°C-65°C and the pressure is 14Mpa-16MPa and maintained for 1h-2h.

[0046] As a further solution, the crushing method in S4 includes ball milling, and the parameters of the ball milling are a rotation speed of 20r / min-40r / min and a time of 5min-15min.

[0047] As a further solution, the D50 of the particles after crushing in S4 is between 0.05 mm and 1.2 mm.

[0048] As a further solution, the wet papermaking in S4 includes a rotary paper machine or a fourdrinier paper machine, and the mixed slurry in S4 is diluted to a solid content of 0.1%-1.3% in the mixed slurry.

[0049] As a further solution, the drying temperature in S4 is 80°C-110°C, and the dryness of the ceramic paper after it leaves the v-roll is 7%-12%. The dryness of the ceramic paper after it leaves the v-roll is the water content in the ceramic paper.

[0050] The characteristics and beneficial effects of the present invention are:

[0051] (1) The ceramic fiber paper obtained by the method of the present invention has the characteristics of low thermal conductivity and high temperature resistance, the product has a wide range of applications, a simple production process, and excellent thermal insulation performance.

[0052] (2) The ceramic fiber paper obtained by the present invention is placed in a muffle furnace for heat treatment at 1000°C for more than 1800 seconds, and the material expansion rate is no more than 1%, which proves that the ceramic fiber paper of the present invention not only has better thermal insulation performance but also has a smaller volume expansion rate.

[0053] (3) The ceramic fiber paper of the present invention also has a relatively thin thickness, and on this basis, the relationship between thermal insulation performance, flexibility, and volume expansion rate can be balanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate a ceramic fiber paper in an embodiment of the present invention, the drawings required for use in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention.

[0055] Figure 1 This is the ceramic fiber paper before high temperature treatment in the embodiment of the present invention.

[0056] Figure 2 The ceramic fiber paper is subjected to high temperature treatment according to the embodiment of the present invention.

[0057] Figure 3 This is the side edge of the ceramic fiber paper after high temperature treatment according to the embodiment of the present invention. DETAILED DESCRIPTION

[0058] In order to facilitate the understanding of the ceramic fiber paper of the present invention, the ceramic fiber paper of the present invention will be described in more detail below, and embodiments of the present invention are given, but the scope of the present invention is not limited thereby.

[0059] Embodiment 1:

[0060] After methyl orthosilicate, fluorine-substituted methyltriethoxysilane, anhydrous ethanol and deionized water are uniformly mixed into a clear mixed solution, an acid is added to adjust the pH range to 2-3, and then the mixed solution is subjected to a hydrolysis reaction; wherein the temperature of the hydrolysis reaction is 50°C, and the time of the hydrolysis reaction is 20 hours; the acid solution for acid adjustment is hydrochloric acid; wherein the volume ratio of anhydrous ethanol to deionized water is 8:1, the amount of methyl orthosilicate added is 100g, and the amount of fluorine-substituted methyltriethoxysilane is 100g; the concentration of methyl orthosilicate in the mixed solution is 0.1g / mL.

[0061] S2: Add 250g nylon, 250g melamine polyphosphate and 100g Xinjiang Yuli vermiculite to the product after the hydrolysis reaction of S1, mix and then disperse evenly; mix evenly by stirring.

[0062] S3: the gel catalyst and the product obtained in S2 are quickly and evenly mixed for 10 minutes, and then replaced with anhydrous ethanol; and supercritical drying is performed;

[0063] The gel catalyst was prepared by using ammonia water and deionized water, wherein the mass ratio of ammonia water to deionized water was 1:30.

[0064] The conditions for anhydrous ethanol replacement are a temperature of 65°C, an alcohol replacement time of 30 hours, an alcohol replacement method of immersion, and anhydrous ethanol is used for the alcohol replacement.

[0065] Supercritical drying conditions: supercritical carbon dioxide, supercritical temperature of carbon dioxide 60°C, pressure 15MPa maintained for 1.5h.

[0066] S4: The product obtained in S3 is crushed, and an adhesive of 25% of the total mass of the raw materials, 1500g of 5mm aluminum silicate fiber, and 350g of polyvinylidene fluoride are added to the crushed product to obtain a mixed pulp, which is formed by wet papermaking and dried.

[0067] The ball milling method was adopted, with a rotation speed of 30r / min and a time of 10r / min.

[0068] The D50 of the crushed particles is 0.8 mm.

[0069] The wet papermaking is done by a fourdrinier paper machine, the paper stock concentration after dilution is 0.7%, the drying temperature is 100°C, and the dryness of the paper out of the roller is 10%.

[0070] Embodiment 2:

[0071] The preparation method is as shown in Example 1, but the added amount of methyl orthosilicate in Example 2 is 10 g, and the other parameters are the same as in Example 1.

[0072] Embodiment 3:

[0073] The preparation method is as shown in Example 1, but the added amount of methyl orthosilicate in Example 3 is 200 g, and the other parameters are the same as in Example 1.

[0074] Embodiment 4:

[0075] The preparation method is as shown in Example 1, but the added amount of fluorine-substituted methyltriethoxysilane in Example 4 is 10 g, and the other parameters are the same as in Example 1.

[0076] Embodiment 5:

[0077] The preparation method is as shown in Example 1, but the added amount of fluorine-substituted methyltriethoxysilane in Example 5 is 200 g, and the other parameters are the same as in Example 1.

[0078] Embodiment 6:

[0079] The preparation method is as shown in Example 1, but the added amount of Xinjiang Yuli vermiculite in Example 6 is 50g, and the other parameters are the same as in Example 1.

[0080] Embodiment 7:

[0081] The preparation method is as shown in Example 1, but the added amount of Xinjiang Yuli vermiculite in Example 7 is 200g, and the other parameters are the same as in Example 1.

[0082] Embodiment 8:

[0083] The preparation method is as shown in Example 1, but the added amount of 5 mm aluminum silicate fiber in Example 8 is 1000 g, and the other parameters are the same as in Example 1.

[0084] Embodiment 9:

[0085] The preparation method is as shown in Example 1, but the added amount of 5 mm aluminum silicate fiber in Example 9 is 2000 g, and the other parameters are the same as in Example 1.

[0086] Embodiment 10:

[0087] The preparation method is as shown in Example 1, but the added amount of polyvinylidene fluoride in Example 10 is 300 g, and the other parameters are the same as in Example 1.

[0088] Embodiment 11:

[0089] The preparation method is as shown in Example 1, but the added amount of polyvinylidene fluoride in Example 11 is 400 g, and the other parameters are the same as in Example 1.

[0090] Embodiment 12:

[0091] The preparation method is as shown in Example 1, but the added amount of melamine polyphosphate in Example 12 is 200 g, and the other parameters are the same as in Example 1.

[0092] Embodiment 13:

[0093] The preparation method is as shown in Example 1, but the added amount of melamine polyphosphate in Example 13 is 300 g, and the other parameters are the same as in Example 1.

[0094] Embodiment 14:

[0095] The preparation method is as shown in Example 1, but the amount of nylon added in Example 14 is 200 g, and the other parameters are the same as in Example 1.

[0096] Embodiment 15:

[0097] The preparation method is as shown in Example 1, but the amount of nylon added in Example 15 is 300 g, and the other parameters are the same as in Example 1.

[0098] Embodiment 16:

[0099] The preparation method is as shown in Example 1, but the Si-O tetracoordinated orthosilicate in Example 16 is ethyl orthosilicate, the fluorine-substituted silicate is fluorine-substituted dimethyldiethoxysilane, the 2 mm aluminum silicate fiber, the fluorine-substituted polyolefin is polytetrafluoroethylene, and the phosphorus-nitrogen flame retardant is ammonium polyphosphate. Other parameters are the same as in Example 1.

[0100] Embodiment 17:

[0101] The preparation method is as shown in Example 1, but in Example 17, 10 mm aluminum silicate fiber is selected, the phosphorus nitrogen flame retardant is pentaerythritol phosphate, and other parameters are the same as in Example 1.

[0102] Embodiment 18:

[0103] The preparation method is as shown in Example 1, but the Si-O tetracoordinated orthosilicate in Example 18 is ethyl orthosilicate, the fluorine-substituted silicate is fluorine-substituted dimethyldiethoxysilane, the fluorine-substituted polyolefin is polytetrafluoroethylene, and the phosphorus-nitrogen flame retardant is piperazine pyrophosphate. Other parameters are the same as in Example 1.

[0104] Comparative Example 1:

[0105] The preparation method is as shown in Example 1, but in Comparative Example 1, no fluorine-substituted polyolefin, phosphorus-nitrogen flame retardant and nylon are added, and other parameters are the same as those in Example 1.

[0106] Comparative Example 2:

[0107] The preparation method is the same as that in Example 1, but in Comparative Example 2, polyethylene with the same mass as polyvinylidene fluoride and tetrabromophthalic anhydride with the same mass as melamine polyphosphate are added, and other parameters are the same as those in Example 1.

[0108] In the embodiments and comparative examples of the present invention, the fluorine-substituted methyltriethoxysilane is perfluorinated methyltriethoxysilane, and the preparation process of perfluorinated methyltriethoxysilane, wherein the yield of perfluorinated methyltriethoxysilane is 98%:

[0109]

[0110] In the embodiments and comparative examples of the present invention, the fluorine-substituted dimethyldiethoxysilane is perfluorine-substituted dimethyldiethoxysilane, and the preparation process of perfluorine-substituted dimethyldiethoxysilane, wherein the yield of perfluorine-substituted dimethyldiethoxysilane is 97%:

[0111]

[0112] We also tested the following ceramic fiber papers:

[0113] Thermal conductivity test: The test is carried out in accordance with the national standard GB10295-88 Determination of steady-state thermal resistance and related characteristics of insulation materials (heat flow meter method). The test equipment is Xiangtan Xiangke brand DRS-3A thermal conductivity tester, which tests the thermal conductivity of each ceramic fiber paper at 1000°C.

[0114] Bending stiffness test: The ceramic fiber papers provided in Examples 1-18 and Comparative Examples 1-4 were tested for bending stiffness using a bending stiffness tester (Japan KATO Company, KES-FB2S model) to characterize their flexibility. The test results are shown in Table 2.

[0115] Results and Analysis

[0116] Table 1 Formulas of the embodiments of the present invention and comparative examples

[0117]

[0118] Table 2 Test results of the embodiments of the present invention and the comparative examples

[0119]

[0120]

[0121] Ceramic fiber paper is successfully obtained by the preparation method of the present invention. Figure 1 As shown. We also compare a series of ceramic fibers obtained by the present invention with the ceramic fibers in the prior art, as shown in Table 1-Table 2. By comparing Example 1-Example 18 with Comparative Example 1-Comparative Example 2, it is found that the ceramic fiber paper obtained by the present invention has better flexibility, thermal insulation performance and volume expansion rate than the ceramic fibers obtained in the prior art on the basis of having a thinner thickness. We believe that it is first because the Si-O tetra-coordinated orthosilicate and fluorine-substituted silicate in the present invention form silica aerogel, and the formed silica aerogel is coated on the surface of vermiculite, and the coated vermiculite is embedded in the gaps between the aluminum silicate fibers. The aluminum silicate fibers exist in the ceramic fiber paper in the form of a continuous skeleton, thereby improving the mechanical strength of the ceramic fibers, and the vermiculite coated with silica aerogel is dispersed in the gaps between the aluminum silicate fibers, thereby improving the thermal insulation performance of the ceramic fibers at low and high temperatures, so that the ceramic fiber paper obtained by the present invention has a wider range of use value. It can be seen that the combination of aluminum silicate fiber and vermiculite coated with silica aerogel improves the thermal insulation performance and mechanical strength of ceramic fiber paper. In addition, in order to promote the formation of silica aerogel to be more evenly coated on the surface of vermiculite, we further designed Si-O tetra-coordinated orthosilicate and fluorine-substituted silicate to form silica aerogel, among which Si-O tetra-coordinated orthosilicate has smaller polarity and can better form aerogel with more suitable porosity and more uniform pore structure; while fluorine-substituted silicate can participate in the formation of aerogel on the one hand, and on the other hand, the fluorine-substituted group in fluorine-substituted silicate can promote aerogel to be more evenly coated on the surface of vermiculite.

[0122] On this basis, the ceramic fiber paper obtained by the present invention has a thinner thickness (3mm-6mm), and we further add fluorine-substituted polyolefins, phosphorus-nitrogen flame retardants, and nylon, and balance the relationship between the brittleness and thermal insulation performance of the ceramic fiber paper on the basis of maintaining the thinness of the ceramic fiber paper. First, the fluorine-substituted polyolefin can be more easily matched with the fluorine-substituted silicate, and the substances are more easily dispersed evenly, and it is also beneficial to improve the flexibility of the ceramic fiber paper. Second, under the cooperation of the phosphorus-nitrogen flame retardant and nylon, on the one hand, the flame retardancy of the ceramic fiber paper can be improved, and on the other hand, the hygroscopicity of the ceramic fiber paper can be improved, which is beneficial to reduce the brittleness of the ceramic fiber paper at high temperature; third, the nitrogen and phosphorus in the phosphorus-nitrogen flame retardant have lone pairs of electrons, and the fluorine substituents in the fluorine-substituted polyolefin and the fluorine-substituted silicate are electron-withdrawing groups, so that the phosphorus-nitrogen flame retardant can be better matched with the fluorine-substituted polyolefin and the fluorine-substituted silicate, so that it is more conducive to coating on the surface of vermiculite and in the gaps between aluminum silicate fibers, and improving the flexibility of the ceramic fiber paper. It can be seen that through the combination and design of the above-mentioned substances, a thinner ceramic fiber paper can be obtained, and the fiber paper of the present invention also has the characteristics of low thermal conductivity and high temperature resistance, the product has a wide range of applications, and has excellent thermal insulation performance; and the ceramic fiber paper of the present invention also has a small expansion rate, which can be obtained from Figure 2-Figure 3 Verification in.

[0123] On this basis, we further studied the optimization of the raw materials for preparing ceramic fiber paper, so as to further improve the thermal insulation performance and flexibility of ceramic fiber paper. We studied the improvement of the final ceramic fiber performance under different ratios of raw materials, which can be compared through Examples 1 to 15 in Tables 1 and 2.

[0124] We compared Example 1 to Example 5, among which Example 1 has the best flexibility and thermal insulation performance. First, the addition amount of Si-O tetra-coordinated orthosilicate and fluorine-substituted silicate will affect the thickness of the silica aerogel coated on the surface of vermiculite. When the addition amount is less, it may result in the failure to form a uniform and complete coating layer on the surface of vermiculite. In the preparation process S4, the crushed vermiculite product may not be coated with silica aerogel, and the thermal insulation performance of the ceramic fiber paper at low temperature is finally obtained. Reduced; when the addition amount is more, a thicker silica aerogel coating layer may be coated on the surface of the vermiculite. Although it will not affect the thermal insulation performance of the vermiculite at low temperatures, it will not only affect the increase in the thickness of the ceramic fiber paper, but also require more nylon and phosphorus nitrogen flame retardant additions to match the flexibility and flame retardancy of the ceramic fiber paper. On this basis, the ratio of Si-O tetra-coordinated orthosilicate and fluorine-substituted silicate is selected to satisfy the formation of silica aerogel coated on vermiculite on the one hand, and to promote the uniform coating of vermiculite by silica aerogel on the other hand. Therefore, the mass ratio of Si-O tetra-coordinated orthosilicate and fluorine-substituted silicate is (0.08 parts-0.12 parts): (0.08 parts-0.12 parts).

[0125] We also studied the improvement of the amount of vermiculite added to ceramic fiber paper, such as Example 1, Example 6-Example 7 comparison. We found that on the basis of Example 1 having good thermal insulation performance, ceramic fiber paper also has good flexibility. We think that the amount of vermiculite added has a great influence, and the volume expansion of vermiculite can improve the thermal insulation performance of ceramic fiber paper at high temperatures, but the brittleness and expansion rate of ceramic fiber paper will rise. When the amount of vermiculite added is more, although the thermal insulation performance of ceramic fiber paper at high temperatures can be improved, the serious volume expansion rate and the brittleness after the volume expansion of vermiculite rise, all of which can cause the rupture of ceramic fiber paper, causing ceramic fiber paper to lose the ability to insulate, and safety performance declines. Therefore, we further prefer that the amount of vermiculite added is 0.09 parts-0.11 parts.

[0126] Aluminum silicate fiber is mainly used as the skeleton structure of ceramic fiber paper in ceramic fiber paper, and has a certain influence on the flexibility and thermal insulation performance of ceramic fiber paper. We can find that Example 1 has more suitable flexibility and thermal insulation performance by comparing Example 1, Example 8-Example 9. We know that when more aluminum silicate fiber is added, although the thermal insulation performance can be improved, the flexibility of ceramic fiber paper will decrease, and when less aluminum silicate fiber is added, the flexibility increases but the thermal insulation performance decreases. Therefore, we further prefer that the addition amount of aluminum silicate fiber is 1.3-1.7 parts by mass.

[0127] On this basis, in order to further balance the amount of vermiculite added in the present invention, we studied the influence of the amount of fluorine-substituted polyolefin, phosphorus-nitrogen flame retardant, and nylon added. We can compare Example 1, Example 10-Example 11, Example 1-Example 12-Example 13, Example 1, Example 14-Example 15, and we can find that the flexibility and thermal insulation performance of Example 1 are the best. We believe that fluorine-substituted polyolefin, phosphorus-nitrogen flame retardant, and nylon are mainly used to improve the flexibility of ceramic fiber paper, thereby overcoming the problem of increased brittleness of ceramic fiber paper caused by the expansion of vermiculite. We can find that when the amount of any one of fluorine-substituted polyolefin, phosphorus-nitrogen flame retardant, and nylon added is less, the flexibility of ceramic fiber paper is uniformly affected. When the amount of any one of fluorine-substituted polyolefin, phosphorus-nitrogen flame retardant, and nylon added is more, it is not easy to disperse evenly during the preparation process, thereby affecting the improvement effect of ceramic fiber paper, and the flexibility will also be poor. We further prefer that the mass ratio of fluorine-substituted polyolefin, phosphorus-nitrogen flame retardant and nylon is (0.34 parts-0.36 parts):(0.24 parts-0.26 parts):(0.24 parts-0.26 parts).

[0128] Finally, we also studied the matching of different Si-O tetracoordinated orthosilicates, fluorine-substituted silicates, aluminum silicate fibers, fluorine-substituted polyolefins, and phosphorus-nitrogen flame retardants, as shown in Example 1, Example 16-Example 18. We can find that Example 1 has more matching thermal insulation performance and flexibility. We believe that the methyl orthosilicate in Example 1 has shorter side chains, which is beneficial to reduce the entanglement with the side chains of fluorine-substituted methyltriethoxysilane, so that it is more conducive to dispersion in the slurry and to the formation of a silica aerogel with uniform pore structure distribution; and the fluorine-substituted methyltriethoxysilane has more Si-O bonds than the fluorine-substituted dimethyldiethoxysilane in Example 16, and can be more coordinated with methyl orthosilicate to form a highly ordered and structurally stable silica aerogel, which is more conducive to the thermal insulation performance of ceramic fibers at low temperatures. Under the coordination of polyvinylidene fluoride and melamine polyphosphate in Example 1, on the one hand, the ceramic fiber paper has a suitable flexibility, and can also have a certain mechanical strength, so that the ceramic fiber paper will not be easily broken at high temperatures. In addition, the cyano group in melamine polyphosphate can also improve the heat resistance of ceramic fiber materials. In summary, we further prefer that the raw materials of ceramic fiber paper include methyl orthosilicate, fluorine-substituted methyl triethoxy silane, vermiculite, aluminum silicate fiber, polyvinylidene fluoride, melamine polyphosphate, nylon, and by mass, the ratio of methyl orthosilicate, fluorine-substituted methyl triethoxy silane, vermiculite, aluminum silicate fiber, polyvinylidene fluoride, melamine polyphosphate, and nylon is (0.08 parts-0.12 parts): (0.08 parts-0.12 parts): (0.09 parts-0.11 parts): (1.3 parts-1.7 parts): (0.34 parts-0.36 parts): (0.24 parts-0.26 parts): (0.24 parts-0.26 parts).

[0129] In summary, the ceramic fiber paper obtained by the present invention has a thickness of 3mm-6mm and has good thermal insulation performance at both low and high temperatures. In addition, the ceramic fiber paper of the present invention has a small volume expansion rate.

[0130] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A ceramic fiber paper, characterized in that: The raw materials of the ceramic fiber paper include Si-O tetra-coordinated orthosilicate, fluorine-substituted silicate, vermiculite, aluminum silicate fiber, fluorine-substituted polyolefin, phosphorus-nitrogen flame retardant, and nylon. The mass ratio of the total mass of the Si-O tetra-coordinated orthosilicate, fluorine-substituted silicate, vermiculite, aluminum silicate fiber, fluorine-substituted polyolefin, phosphorus-nitrogen flame retardant, and nylon in the raw materials is 70%-80%. In terms of mass, the ratio of the Si-O tetra-coordinated orthosilicate, fluorine-substituted silicate, vermiculite, aluminum silicate fiber, fluorine-substituted polyolefin, phosphorus-nitrogen flame retardant, and nylon is (0.01 part-0.2 part): (0.01 part-0.2 part): (0.05 part-0.2 part): (1 part-2 parts): (0.3 part-0.4 part): (0.2 part-0.3 part): (0.2 part-0.3 part); Among them, the hydrolysis reaction complex of Si-O tetra-coordinated orthosilicate, fluorine-substituted silicate, nylon, and phosphorus-nitrogen flame retardant is coated on the surface of vermiculite.

2. A ceramic fiber paper according to claim 1, characterized in that: The Si-O tetracoordinated orthosilicate includes one or more of methyl orthosilicate and ethyl orthosilicate; The fluorine-substituted silicate includes one or more of fluorine-substituted methyltriethoxysilane and fluorine-substituted dimethyldiethoxysilane; The vermiculite includes one or more of Lingshou vermiculite from Hebei and Yuli vermiculite from Xinjiang; The fluorine-substituted polyolefin includes one or more of polyvinylidene fluoride and polytetrafluoroethylene; The phosphorus-nitrogen flame retardant includes one or more of piperazine pyrophosphate, ammonium polyphosphate, melamine polyphosphate, and pentaerythritol phosphate; The aluminum silicate fiber comprises SiO2 48%-52%, Al2O3 43%-49% and impurities by mass, and the total mass fraction of SiO2, Al2O3 and impurities in the aluminum silicate fiber is 100%; The length of the aluminum silicate fiber is 2 mm-10 mm.

3. The ceramic fiber paper according to claim 1, characterized in that: The raw materials of the ceramic fiber paper include methyl orthosilicate, fluorine-substituted methyltriethoxysilane, vermiculite, aluminum silicate fiber, polyvinylidene fluoride, melamine polyphosphate and nylon. By mass, the ratio of methyl orthosilicate, fluorine-substituted methyltriethoxysilane, vermiculite, aluminum silicate fiber, polyvinylidene fluoride, melamine polyphosphate and nylon is (0.08 part-0.12 part): (0.08 part-0.12 part): (0.09 part-0.11 part): (1.3 parts-1.7 parts): (0.34 parts-0.36 parts): (0.24 parts-0.26 parts): (0.24 parts-0.26 parts).

4. The ceramic fiber paper according to claim 1, characterized in that: The raw materials of the ceramic fiber paper also include an adhesive; the mass proportion of the adhesive in the raw materials is 20%-30%.

5. The ceramic fiber paper according to claim 4, characterized in that: The adhesive includes one or more of acrylic resin, polyurethane emulsion, colloidal aluminum oxide, and aluminum sulfate-ammonia water.

6. The ceramic fiber paper according to claim 1, characterized in that: The thickness of the ceramic fiber paper is 3mm-6mm.

7. The method for preparing the ceramic fiber paper according to any one of claims 1 to 6, comprising: S1: After uniformly mixing Si-O tetracoordinated orthosilicate, fluorine-substituted silicate, alcohol organic solvent and deionized water into a clear mixed solution, adding acid to adjust the pH range, and then hydrolyzing the mixed solution; S2: Add nylon, phosphorus-nitrogen flame retardant and vermiculite to the product after the hydrolysis reaction of S1 according to the mass ratio, and then disperse them evenly; S3: quickly and evenly mix the gel catalyst and the product obtained in S2, and then perform alcohol replacement; and perform supercritical drying; S4: The product obtained in S3 is crushed, and the crushed product is respectively added with adhesive, aluminum silicate fiber, and fluorine-substituted polyolefin according to the mass ratio to obtain mixed pulp, and wet papermaking is adopted for forming, and the mixed pulp is dried.

8. The preparation method according to claim 7, characterized in that: The concentration of the Si-O tetra-coordinated orthosilicate in the mixed solution in S1 is 0.063 g / mL-0.125 g / mL, and the Si-O tetra-coordinated orthosilicate and the fluorine-substituted silicate are weighed respectively according to the mass ratio; The volume ratio of the alcohol organic solvent to deionized water in S1 is (6-12):(2-4); The acid in S1 adjusts the pH range, and the pH range is 2-3; The temperature of the hydrolysis reaction in S1 is 45°C-55°C, and the time of the hydrolysis reaction is 18h-22h.

9. The preparation method according to claim 7, characterized in that: The alcohol organic solvent includes one or more of isopropanol, anhydrous methanol and anhydrous ethanol.

10. The preparation method according to claim 7, characterized in that: The acid for acid adjustment includes one or more of hydrochloric acid, nitric acid and phosphoric acid.

11. The preparation method according to claim 7, characterized in that: In terms of mass, the ratio of vermiculite, nylon and melamine polyphosphate added to S2 is (0.05 parts-0.2 parts): (0.2 parts-0.3 parts): (0.2 parts-0.3 parts); The uniform dispersing method in S2 includes stirring, and the stirring speed is 800r / min-1200r / min.

12. The preparation method according to claim 7, characterized in that: The preparation method of the gel catalyst in S3 comprises preparing the gel catalyst using alkali and deionized water, wherein the alkali:deionized water is 1:(20-40) by mass, and uniformly mixing to obtain a clear solution; The ratio of the gel catalyst in S3 to the product obtained in S2 is 1 part:(15 parts-35 parts) by mass; The temperature of alcohol replacement in S3 is 60°C-70°C, and the time of alcohol replacement is 24h-36h; The uniform mixing time in S3 is 5 min to 15 min; The supercritical drying in S3 is ethanol supercritical or carbon dioxide supercritical.

13. The preparation method according to claim 12, characterized in that: The base includes one or more of ammonia water, sodium bicarbonate, ammonium fluoride or sodium hydroxide.

14. The preparation method according to claim 7, characterized in that: The alcohol for alcohol replacement includes one or more of anhydrous methanol or anhydrous ethanol.

15. The preparation method according to claim 12, characterized in that: The specific conditions for the ethanol supercriticality are: ethanol supercritical temperature 250° C.-260° C., pre-pressurization 1.5 MPa-2.5 MPa, and maintaining the pressure at 10 MPa-12 MPa for 1 h-2 h.

16. The preparation method according to claim 12, characterized in that: The specific conditions of the carbon dioxide supercriticality are that the carbon dioxide supercritical temperature is 55° C.-65° C. and the pressure is 14 MPa-16 MPa and maintained for 1 h-2 h.

17. The preparation method according to claim 7, characterized in that: The crushing method in S4 includes ball milling, and the parameters of the ball milling are a rotation speed of 20r / min-40r / min and a time of 5min-15min; The D50 of the particles after crushing in S4 is between 0.05 mm and 1.2 mm; The wet papermaking in S4 includes a cylinder paper machine or a fourdrinier paper machine, and the mixed slurry in S4 is diluted to a solid content of 0.1%-1.3% in the mixed slurry; The drying temperature in S4 is 80° C.-110° C., and the dryness of the ceramic paper out of the roller is 7%-12%.

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