Heat insulation pad and preparation method thereof

Abstract

The invention relates to the technical field of heat insulation pads, in particular to a heat insulation pad and a preparation method thereof. The heat insulation pad is prepared by the method. The method comprises the following steps: uniformly mixing calcined kaolin, glass powder and silica sol to obtain a mixed material liquid; uniformly dip-coating or uniformly blade-coating the mixed material liquid on a high silica cloth to obtain a coated cloth; according to the target thickness H0 of the heat insulation pad, selecting the coating cloth with the required number to be laminated to the thickness H1; h1 is 1.5 to 1.7 times of H0; the laminated coating cloth is subjected to pressing treatment; and then drying treatment and calcination treatment are sequentially carried out, and the heat insulation pad with the target thickness is obtained. The preparation steps are simple, and the heat insulation pad which is low in cost, low in heat conductivity coefficient and capable of meeting the requirement for temperature resistance of 900 DEG C or above can be prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermal insulation pad, in particular to a thermal insulation pad and a preparation method thereof. BACKGROUND

[0002] Carbon ceramic brake pad has been widely used in high-performance braking system due to its excellent high-temperature resistance and friction and wear performance. The entire carbon ceramic brake pad is assembled by a steel back plate, a thermal insulation pad and a carbon ceramic friction block. During extreme braking, the temperature of the carbon ceramic friction block can reach above 1000℃. Accordingly, the thermal insulation pad needs not only to have a low thermal conductivity, but also to have a temperature resistance above 700℃. The traditional glass fiber reinforced resin-based composite thermal insulation pad obviously cannot meet the temperature resistance requirement above 700℃. Although the quartz fiber reinforced SiO2 composite material can meet the temperature resistance requirement above 700℃, its high cost and complex preparation process limit its use to aerospace industry.

[0003] In view of the above, it is necessary to develop a thermal insulation pad and a preparation method thereof to solve the problems in the prior art. SUMMARY

[0004] The present application aims to provide a thermal insulation pad and a preparation method thereof, and the specific technical solutions are as follows: In a first aspect, the present application provides a preparation method of a thermal insulation pad, comprising: Step S1, uniformly mixing calcined kaolin, glass powder and silica sol to obtain a mixed liquid; The calcined kaolin is 1000-4000 mesh calcined kaolin, the glass powder is 1000-4000 mesh glass powder with a melting point of 650-750℃, the mass ratio of the calcined kaolin to the glass powder is 7:3-19:1, and the mass of the silica sol is 100%-200% of the sum of the masses of the calcined kaolin and the glass powder. Step S2, uniformly dip-coating or uniformly blade-coating the mixed liquid on a high-silica cloth to obtain a coated cloth; The mass percentage of silicon dioxide in the high-silica cloth is greater than or equal to 96%. Step S3, selecting the required number of coated cloth layers to a thickness H1 according to the target thickness H0 of the thermal insulation pad; H1 is 1.5-1.7 times of H0. Step S4, pressing the stacked coated cloth; then, sequentially drying and calcining to obtain a thermal insulation pad with a target thickness.

[0005] Optionally, the solid content of the silica sol is 20%-50%.

[0006] Optionally, the pattern on the high-silica cloth comprises any one of plain weave, twill weave and satin weave.

[0007] Optionally, the pattern on the high-silica cloth comprises plain weave.

[0008] Optionally, the thickness of the high-silica cloth is 0.2-2 mm.

[0009] Optionally, on the coated cloth, the coating amount of the mixed solution is 100%-150% of the mass of the high-silica cloth.

[0010] Optionally, the pressure applied in the pressing treatment is 5-30 MPa, and the pressure holding time is 5-15 min.

[0011] Optionally, the drying temperature applied in the drying treatment is 40-80 ℃, and the drying time is 240-480 min.

[0012] Optionally, the calcination temperature applied in the calcination treatment is 800-1100 ℃, and the calcination time is 30-90 min.

[0013] In the second aspect, the application provides a heat insulation pad prepared by the preparation method of the heat insulation pad.

[0014] The application has at least the following beneficial effects: The preparation method of the heat insulation pad provided by the application not only has simple preparation steps, but also can prepare a heat insulation pad with low cost, low thermal conductivity and temperature resistance of above 900 ℃. The specific principle is as follows: In terms of heat resistance, the main components of the calcined kaolin used in the mixed liquid of the present invention are SiO2 and Al2O3. The nano-particle size of the silicate multi-molecule polymer SiO2·XH2O (X represents the number of water molecules, and its value range is related to the preparation and use environment, generally 1 to 3, and some are even higher and even reach 50.) in the silica sol is easily adsorbed on the surface of the calcined kaolin matrix particles, and the silicate ions interact with the aluminum oxide tetrahedron and silicon oxide tetrahedron in the calcined kaolin to form hydrogen bonds. Adding an appropriate amount of silica sol can make the entire mixed liquid A stable dispersion system is formed, the overall stability of the mixed liquid is improved, and it is beneficial for the mixed liquid to be evenly coated on the high-silica cloth; further, in order to ensure that the particles in the mixed liquid fully penetrate into the fibers of the high-silica cloth, the present invention selects calcined kaolin with a size of 1000-4000 mesh and glass powder with a size of 1000-4000 mesh; if particles with too small a particle size are selected, the dispersion time of the particles in the preparation process of the mixed liquid and the drying time of the moisture of the thermal insulation pad will be increased during the drying process; wherein, the heat-resistant temperature of calcined kaolin is as high as 1700°C; the heat-resistant temperature of silica sol is The temperature also reaches 1200℃; the mass percentage of silicon dioxide in the high silica cloth is greater than or equal to 96%, and it can be used for a long time at 1000℃ and for a short time at 1200℃; the pressing treatment is not only convenient for improving the bonding strength between the coated cloths after lamination, but also can ensure the flatness of the formed thermal insulation pad; as the drying treatment proceeds, the silica sol on the surface of the calcined kaolin matrix particles first loses water and gels to form silica gel, avoiding cracking and delamination during the drying treatment; then, during the calcination treatment, the silica gel further dehydrates and shrinks. The combination creates strong covalent bonds between nano-scale SiO2 particles. Due to the high wettability and high permeability of silica sol, a continuous and stable Si-O-Si three-dimensional spatial network can be formed in the thermal insulation mat, ensuring the strength and thermal stability of the thermal insulation mat. Adding an appropriate amount of glass powder with a melting point of 650-750℃ can melt during the calcination process to form liquid phase sintering. The low-melting-point glass phase penetrates into the gaps between the particles and the high-silica cloth, enhancing the mechanical anchoring effect, improving the bonding strength, further improving the strength of the thermal insulation mat, and ensuring the structural stability of the thermal insulation mat during long-term use. In terms of low thermal conductivity, the raw materials used in the present invention have low thermal conductivity, so that the prepared thermal insulation pad has low thermal conductivity; among them, the thermal conductivity of high silica cloth is 0.035~0.08 W / (m·k), the thermal conductivity of 4000 mesh calcined kaolin is 0.1~0.3 W / (m·k), and the thermal conductivity of silica sol is 0.008~0.02 W / (m·k). DETAILED DESCRIPTION

[0015] The technical solutions in the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art belong to the scope of protection of the present application.

[0016] Embodiment 1 A preparation method of a thermal insulation pad, comprising: Step S1, introducing calcined kaolin, glass powder and silica sol into a stirring tank for stirring and mixing, controlling the stirring speed to be 2000 r / min, and the stirring time to be 30 min, to obtain a mixed liquid; The calcined kaolin is 1000-4000 mesh calcined kaolin; the glass powder is 1000-4000 mesh glass powder, and the melting point of the glass powder is 650℃; the mass ratio of the calcined kaolin to the glass powder is 17:3; the mass of the silica sol is 130% of the sum of the masses of the calcined kaolin and the glass powder; Step S2, uniformly dip-coating the mixed liquid on the high-silica cloth after cutting (the size of the high-silica cloth after cutting is 300 mm x 300 mm, wherein the cutting size is determined by the size of the thermal insulation pad) to obtain a coated cloth; The mass percentage content of silicon dioxide in the high-silica cloth is greater than or equal to 96%; Step S3, according to the target thickness H0 (specifically 1.8±0.1 mm) of the thermal insulation pad, selecting the required number (specifically 6 pieces) of the coated cloth for stacking to a thickness H1; H1 is 1.5-1.7 times (specifically 1.5 times) of H0; Step S4, performing pressing treatment on the stacked coated cloth; then, sequentially performing drying treatment and calcination treatment to obtain a thermal insulation pad with a target thickness.

[0017] The solid content of the silica sol is 30%.

[0018] The pattern on the high-silica cloth includes any one of plain weave, twill weave and satin weave, and specifically is plain weave.

[0019] The thickness of the high-silica cloth is 0.2-2 mm, and specifically is 0.26 mm.

[0020] On the coated cloth, the coating amount of the mixed liquid is 100%-150% (specifically 140%) of the mass of the high-silica cloth.

[0021] The pressing treatment is completed in a flat vulcanizing machine, and the pressure adopted is 5-30 MPa (specifically 10 MPa), and the pressure maintaining time is 5-15 min (specifically 15 min).

[0022] The drying treatment is completed in a blast oven, which adopts a drying temperature of 40℃ and a drying time of 480 min.

[0023] The calcination treatment is completed in a high-temperature furnace, which adopts a calcination temperature of 800-1100℃ (specifically 900℃) and a calcination time of 1 h.

[0024] Example 2: Different from Example 1, the mass ratio of the calcined kaolin and the glass powder in step S1 is 7:3.

[0025] Comparative Example 1: Different from Example 1, the use of calcined kaolin and glass powder is cancelled in step S1.

[0026] Comparative Example 2: Different from Example 1, the use of glass powder is cancelled in step S1.

[0027] Comparative Example 3: Different from Example 1, a high-melting-point glass powder with a melting point of 1200℃ is used in step S1.

[0028] Comparative Example 4: Different from Example 1, an equal amount of water is used to replace the silica sol in step S1.

[0029] The thermal insulation pads prepared in Examples 1-2 and Comparative Examples 2-3 are respectively subjected to thermal conductivity testing, temperature resistance testing and compression strength testing, and the test results are shown in Table 1. Among them, the thermal insulation pads prepared in Comparative Example 1 and Comparative Example 4 both have delamination phenomenon, which are unqualified products, so Table 1 testing is not done.

[0030] The thermal conductivity testing method is as follows: referring to GB / T 10294-2008 “Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials-Guarded Hot Plate Method”.

[0031] The temperature resistance testing method is as follows: cutting a sample block with a thickness of 2.0 mm and a length and width of 100 mm, calcining at 900℃ in air atmosphere for 3 h, and calculating the weight loss rate / % = [(mass before calcination-mass after calcination) / mass before calcination] x 100%.

[0032] The compression strength testing method is as follows: referring to JC / T2406-2017 “Test Method for Compression Properties of Continuous Fiber Reinforced Ceramic Matrix Composites at Room Temperature”, the sample size is length L=25 mm, rectangular cross-section is 10x10 mm, loading direction is along the high-silica cloth normal direction, and loading speed is 0.2 mm / min.

[0033] Table 1 Test results of thermal conductivity and temperature resistance

[0034] From the data in Table 1, compared with Comparative Example 2, the thermal insulation pads prepared by Examples 1-2 of the present application have higher compressive strength although the thermal conductivity is higher. This is because the low-melting-point glass powder used in Examples 1-2 can melt to form liquid-phase sintering in the calcination process, the low-melting-point glass phase penetrates into the gap between the particles and the high-silica cloth, enhances the mechanical anchoring effect, improves the adhesive strength, and further improves the compressive strength of the thermal insulation pad; the low-melting-point glass powder can melt to form liquid-phase sintering in the calcination process, the low-melting-point glass phase penetrates into the gap between the particles and the high-silica cloth, so that the thermal insulation pad has low porosity, high density, and high thermal conductivity. In Comparative Example 2, the use of glass powder is cancelled, and liquid-phase sintering does not occur in the calcination process in step S4, so that there is a certain gap between the particles and the high-silica cloth, resulting in high porosity, low density, and low thermal conductivity of the thermal insulation pad; in addition, the use of glass powder is cancelled, and liquid-phase sintering does not occur in the calcination process in step S4, and the glass phase does not penetrate into the gap between the particles and the high-silica cloth, so that the adhesive strength cannot be improved by the mechanical anchoring effect, resulting in a decrease in the compressive strength of the thermal insulation pad.

[0035] Compared with Comparative Example 3, the thermal insulation pads prepared by Examples 1-2 of the present application not only have lower thermal conductivity, but also have higher compressive strength. This is because in Comparative Example 3, the high-melting-point glass powder with a melting point of 1200°C is used, which contains less bismuth trioxide, a low-thermal-conductivity component, and more aluminum trioxide, a high-thermal-conductivity component, compared with the low-melting-point glass powder, so that the thermal conductivity is increased; in addition, the high-melting-point glass powder cannot form liquid-phase sintering in the calcination process in step S4, and cannot penetrate into the gap between the particles and the high-silica cloth, so that the adhesive strength cannot be improved by the mechanical anchoring effect, resulting in a decrease in the compressive strength of the thermal insulation pad.

[0036] The reason for the delamination of the thermal insulation pad prepared in Comparative Example 1 is as follows: only silica sol is used in the mixed solution in step S1, so that the loading amount of silica sol on the high-silica cloth is very low, resulting in that most of the matrix of the high-silica cloth is exposed, and after lamination and pressing, the adhesive force of each layer of high-silica cloth is weak, resulting in delamination of the thermal insulation pad obtained after drying and calcination.

[0037] The reason for the delamination of the thermal insulation pad prepared in Comparative Example 4 is as follows: an equal amount of water is used to replace silica sol in step S1, and no silica sol is gelated to form silica gel during the drying process, resulting in cracking and delamination during the drying process.

[0038] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A method for preparing a thermal insulation pad, characterized in that: include: Step S1, mixing calcined kaolin, glass powder and silica sol to obtain a mixed liquid; The calcined kaolin is 1000-4000 mesh calcined kaolin; the glass powder is 1000-4000 mesh glass powder with a melting point of 650-750° C.; the mass ratio of the calcined kaolin to the glass powder is 7:3-19:1; the mass of the silica sol is 100%-200% of the sum of the mass of the calcined kaolin and the glass powder; Step S2, uniformly dipping or scraping the mixed liquid onto a high-silica cloth to obtain a coated cloth; Wherein, the mass percentage of silicon dioxide in the high-silica cloth is greater than or equal to 96%; Step S3: According to the target thickness H0 of the thermal insulation pad, a required number of the coating cloths are selected and laminated to a thickness H1; H1 is 1.5 to 1.7 times H0; Step S4: pressing the laminated coated cloth; then, drying and calcining the cloth in sequence to obtain a thermal insulation pad of target thickness.

2. The method for preparing the thermal insulation pad according to claim 1, characterized in that: The solid content of the silica sol is 20% to 50%.

3. The method for preparing a thermal insulation pad according to claim 1, wherein: The texture of the high-silica cloth includes any one of plain, twill and satin.

4. The method for preparing the thermal insulation pad according to claim 3, characterized in that: The texture on the high-silica cloth includes a plain weave.

5. The method for preparing a thermal insulation pad according to claim 1, wherein: The thickness of the high-silica cloth is 0.2-2 mm.

6. The method for preparing a thermal insulation pad according to claim 1, wherein: On the coating cloth, the coating amount of the mixed liquid is 100% to 150% of the mass of the high-silica cloth.

7. The method for preparing a thermal insulation pad according to claim 1, wherein: The pressure used in the pressing process is 5-30 MPa, and the holding time is 5-15 minutes.

8. The method for preparing a thermal insulation pad according to claim 1, wherein: The drying temperature used in the drying process is 40-80° C., and the drying time is 240-480 min.

9. The method for preparing a thermal insulation pad according to claim 1, wherein: The calcination temperature used in the calcination treatment is 800-1100° C., and the calcination time is 30-90 min.

10. A thermal insulation pad, characterized in that: The thermal insulation pad is prepared by the preparation method of any one of claims 1 to 9.

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