A heat insulation pad and its preparation method

Abstract

This invention relates to the field of thermal insulation pad technology, specifically to a thermal insulation pad and its preparation method. The thermal insulation pad is prepared by this method. The method includes: mixing calcined kaolin, glass powder, and silica sol to obtain a mixed liquid; uniformly impregnating or uniformly coating the mixed liquid onto a high-silica cloth to obtain a coated cloth; stacking the required number of coated cloth sheets to a thickness H1 according to the target thickness H0 of the thermal insulation pad; H1 being 1.5 to 1.7 times H0; pressing the stacked coated cloth; subsequently, drying and calcining are performed sequentially to obtain the thermal insulation pad of the target thickness. This invention not only has simple preparation steps but also enables the preparation of a low-cost thermal insulation pad with low thermal conductivity and meeting temperature resistance requirements above 900℃.

Description

Technical Field

[0001] This invention relates to the field of heat insulation pad technology, specifically to a heat insulation pad and its preparation method. Background Technology

[0002] Carbon-ceramic brake pads are widely used in high-performance braking systems due to their excellent high-temperature resistance and friction and wear resistance. The entire carbon-ceramic brake pad is assembled from a steel backing plate, a heat insulation pad, and a carbon-ceramic friction block. During extreme braking, the temperature of the carbon-ceramic friction block can reach over 1000℃. Correspondingly, the heat insulation pad not only needs a low thermal conductivity but also requires a temperature resistance of over 700℃. Traditional glass fiber reinforced resin matrix composite heat insulation pads obviously cannot meet the temperature resistance requirements above 700℃. Although quartz fiber reinforced SiO2 composite materials can meet the temperature resistance requirements above 700℃, their high cost and complex manufacturing process limit their use to the aerospace industry.

[0003] In summary, there is a need to develop a heat insulation pad and its preparation method to solve the problems existing in the prior art. Summary of the Invention

[0004] The purpose of this invention is to provide a heat insulation pad and its preparation method, the specific technical solution of which is as follows:

[0005] In a first aspect, the present invention provides a method for preparing a heat insulation pad, comprising:

[0006] Step S1: Mix calcined kaolin, glass powder and silica sol to obtain a mixed liquid;

[0007] Wherein, 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; the mass of the silica sol is 100%-200% of the sum of the masses of the calcined kaolin and the glass powder;

[0008] Step S2: Uniformly dip or uniformly coat the mixture onto a high-silica cloth to obtain a coated cloth;

[0009] The silica content in the high-silica cloth is greater than or equal to 96% by mass.

[0010] Step S3: Based on the target thickness H0 of the heat insulation pad, select the required number of coated fabric sheets to stack to a thickness H1; H1 is 1.5 to 1.7 times H0;

[0011] Step S4: Press the laminated coated fabric; then, dry and calcinate it sequentially to obtain a heat insulation pad of the target thickness.

[0012] Optionally, the solid content of the silica sol is 20% to 50%.

[0013] Optionally, the texture on the high-silica fabric may include any one of plain weave, twill weave, and satin weave.

[0014] Optionally, the texture on the high-silica fabric may include a plain weave.

[0015] Optionally, the thickness of the high-silica cloth is 0.2~2mm.

[0016] Optionally, the coating amount of the mixture on the coated cloth is 100% to 150% of the mass of the high-silica cloth.

[0017] Optionally, the pressing process uses a pressure of 5~30MPa and a holding time of 5~15min.

[0018] Optionally, the drying process uses a drying temperature of 40~80℃ and a drying time of 240~480 min.

[0019] Optionally, the calcination treatment uses a calcination temperature of 800~1100℃ and a calcination time of 30~90 min.

[0020] In a second aspect, the present invention provides a heat insulation pad, which is prepared by the aforementioned heat insulation pad preparation method.

[0021] The application of the technical solution of the present invention has at least the following beneficial effects:

[0022] This invention provides a method for preparing a heat insulation pad, which not only has simple preparation steps but also produces a low-cost heat insulation pad with low thermal conductivity and a temperature resistance requirement of over 900℃. The specific principle is as follows:

[0023] Regarding temperature resistance, the calcined kaolin used in this invention has SiO2 and Al2O3 as its main components in the mixed liquid. The silica polymer SiO2·XH2O (where X represents the number of water molecules, and its value ranges depending on the preparation and usage environment, generally 1-3, and sometimes even reaching 50) with nano-sized particles in the silica sol readily adsorbs onto the surface of the calcined kaolin matrix particles. Furthermore, silicate ions interact with the aluminum-oxygen tetrahedra and silicon-oxygen tetrahedra in the calcined kaolin to form hydrogen bonds. Adding an appropriate amount of silica sol can enhance the overall temperature resistance of the mixed liquid. A stable dispersion system is formed, improving the overall stability of the mixture and facilitating uniform coating of the mixture onto the high-silica cloth. Furthermore, to ensure that the particles in the mixture fully penetrate the fibers of the high-silica cloth, this invention uses calcined kaolin with a particle size of 1000-4000 mesh and glass powder with a particle size of 1000-4000 mesh. Using particles with too small a particle size would increase the dispersion time of the particles during the mixture preparation process and the drying time of the heat insulation pad during the drying process. The calcined kaolin has a heat resistance temperature as high as 1700℃; the silica sol has a heat resistance... The temperature reaches 1200℃; the silica content in the high-silica cloth is greater than or equal to 96%, enabling long-term use at 1000℃ and short-term use at 1200℃; the pressing process not only facilitates the improvement of the bonding strength between the coated cloths after lamination, but also ensures the flatness of the formed heat insulation pad; as the drying process proceeds, the silica sol on the surface of the calcined kaolin matrix particles first dehydrates and gels to form silica gel, avoiding cracking and delamination during the drying process; subsequently, during the calcination process, the silica gel further dehydrates and shrinks. The combination of these materials creates strong covalent bonds between nano-sized SiO2 particles. Due to the high wettability and permeability of the silica sol, a continuous and stable Si-O-Si three-dimensional spatial network can be formed in the heat insulation pad, ensuring the strength and thermal stability of the pad. Adding an appropriate amount of glass powder with a melting point of 650-750℃ allows it to melt and form a liquid phase sintering during calcination. 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, and further increasing the strength of the heat insulation pad, ensuring its structural stability during long-term use.

[0024] Regarding low thermal conductivity, the raw materials used in this invention have low thermal conductivity, resulting in a low thermal conductivity insulation pad. Specifically, the thermal conductivity of the high-silica cloth is 0.035~0.08 W / (m·K), the thermal conductivity of the 4000-mesh calcined kaolin is 0.1~0.3 W / (m·K), and the thermal conductivity of the silica sol is 0.008~0.02 W / (m·K). Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art are within the scope of protection of the present invention.

[0026] Example 1:

[0027] A method for preparing a heat insulation pad, comprising:

[0028] Step S1: Calcinated kaolin, glass powder and silica sol are introduced into a stirring tank and stirred until homogeneous. The stirring speed is controlled at 2000 r / min and the stirring time is 30 min to obtain a mixed liquid.

[0029] The calcined kaolin is 1000-4000 mesh calcined kaolin; the glass powder is 1000-4000 mesh glass powder with a melting point of 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.

[0030] Step S2: Uniformly immerse the cut high-silica fabric (the cut high-silica fabric is 300mm×300mm in size, where the cutting size is determined by the size of the heat insulation pad) with the mixed liquid to obtain the coated fabric;

[0031] The silica content in the high-silica cloth is greater than or equal to 96% by mass.

[0032] Step S3: Based on the target thickness H0 of the heat insulation pad (specifically 1.8±0.1mm), select the required number (specifically 6 pieces) of the coated fabric to be stacked to a thickness H1; H1 is 1.5~1.7 times (specifically 1.5 times) H0;

[0033] Step S4: Press the laminated coated fabric; then, dry and calcinate it sequentially to obtain a heat insulation pad of the target thickness.

[0034] The solid content of the silica sol is 30%.

[0035] The texture on the high-silica fabric includes any one of plain weave, twill weave, and satin weave, specifically plain weave.

[0036] The thickness of the high-silica cloth is 0.2~2mm, specifically 0.26mm.

[0037] On the coated fabric, the coating amount of the mixed liquid is 100% to 150% (specifically 140%) of the mass of the high silica cloth.

[0038] The pressing process is completed in a flat vulcanizing machine, with a pressure of 5~30MPa (specifically 10MPa) and a holding time of 5~15min (specifically 15min).

[0039] The drying process is completed in a forced-air drying oven at a temperature of 40°C for 480 minutes.

[0040] The calcination process is completed in a high-temperature furnace, with a calcination temperature of 800~1100℃ (specifically 900℃) and a calcination time of 1 hour.

[0041] Example 2:

[0042] Unlike Example 1, the mass ratio of calcined kaolin to glass powder in step S1 is 7:3.

[0043] Comparative Example 1:

[0044] Unlike Example 1, the use of calcined kaolin and glass powder is omitted in step S1.

[0045] Comparative Example 2:

[0046] Unlike Example 1, the use of glass powder is omitted in step S1.

[0047] Comparative Example 3:

[0048] Unlike Example 1, a high-melting-point glass powder with a melting point of 1200°C is used in step S1.

[0049] Comparative Example 4:

[0050] Unlike Example 1, an equal amount of water was used to replace the silica sol in step S1.

[0051] The thermal insulation pads prepared in Examples 1-2 and Comparative Examples 2-3 were subjected to thermal conductivity tests, temperature resistance tests, and compressive strength tests, respectively. The test results are shown in Table 1. The thermal insulation pads prepared in Comparative Examples 1 and 4 exhibited delamination and were therefore considered substandard products; therefore, the tests shown in Table 1 were not performed.

[0052] The thermal conductivity test method is as follows: refer to GB / T 10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Insulation Materials - Protective Hot Plate Method".

[0053] The temperature resistance test method is as follows: cut a sample block with a thickness of 2.0 mm and a length and width of 100 mm, calcine it in air at 900℃ for 3 hours, and calculate the weight loss rate / % = [(mass before calcination - mass after calcination) / mass before calcination] × 100%.

[0054] The compressive strength test method is as follows: Refer to JC / T2406-2017 "Test method for compressive properties of continuous fiber reinforced ceramic matrix composites at room temperature", the sample size is length L=25 mm, the rectangular cross section is 10×10 mm, the loading direction is along the normal direction of the high silica cloth, and the loading speed is 0.2 mm / min.

[0055] Table 1 Test results of thermal conductivity and temperature resistance

[0056]

[0057] As shown in Table 1, compared to Comparative Example 2, the thermal insulation pads prepared in Examples 1 and 2 of this invention have higher thermal conductivity but also higher compressive strength. This is because the low-melting-point glass powder used in Examples 1 and 2 can melt and form a liquid phase sintering during the calcination process. 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, and further increasing the compressive strength of the thermal insulation pad. The low-melting-point glass powder can melt and form a liquid phase sintering during the calcination process, and the low-melting-point glass phase penetrates into the gaps between the particles and the high-silica cloth, resulting in low porosity, high density, and increased thermal conductivity of the thermal insulation pad. In Comparative Example 2, the use of glass powder was omitted. In step S4, calcination did not produce liquid phase sintering, resulting in a certain gap between the particles and the high-silica cloth. This led to high porosity, low density, and decreased thermal conductivity of the heat insulation pad. Furthermore, the omission of glass powder prevented liquid phase sintering in step S4, and no glass phase penetrated into the gap between the particles and the high-silica cloth. Consequently, the bonding strength could not be improved through mechanical anchoring, resulting in a decrease in the compressive strength of the heat insulation pad.

[0058] Compared to Comparative Example 3, the heat insulation pads prepared in Examples 1 and 2 of this invention not only have a lower thermal conductivity but also a higher compressive strength. This is because Comparative Example 3 uses high-melting-point glass powder with a melting point of 1200°C. Compared to low-melting-point glass powder, it contains less bismuth trioxide (a component with low thermal conductivity) and more aluminum oxide (a component with high thermal conductivity), thus increasing the thermal conductivity. In addition, the high-melting-point glass powder failed to undergo liquid-phase sintering in step S4, and could not penetrate into the gaps between the particles and the high-silica cloth. Consequently, it could not improve the bonding strength through mechanical anchoring, resulting in a decrease in the compressive strength of the heat insulation pad.

[0059] The reason for the delamination phenomenon in the heat insulation pad prepared in Comparative Example 1 is as follows: only silica sol is used in the mixture in step S1, which results in a very low loading on the high silica cloth, causing most of the high silica cloth matrix to be exposed. After lamination and pressing, the adhesion of each layer of high silica cloth is weak, resulting in the delamination phenomenon of the heat insulation pad obtained after drying and calcination.

[0060] The reason for the delamination phenomenon in the heat insulation pad prepared in Comparative Example 4 is as follows: In step S1, an equal amount of water was used to replace the silica sol. During the drying process, the silica sol lost water and gelled to form silica gel, which led to cracking and delamination during the drying process.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a heat insulation pad, characterized in that, include: Step S1: Mix calcined kaolin, glass powder and silica sol to obtain a mixed liquid; Wherein, 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; 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 or uniformly coat the mixture onto a high-silica cloth to obtain a coated cloth; The silica content in the high-silica cloth is greater than or equal to 96% by mass. Step S3: Based on the target thickness H0 of the heat insulation pad, select the required number of coated fabric sheets to stack to a thickness H1; H1 is 1.5 to 1.7 times H0; Step S4: Press the laminated coated fabric; then, dry and calcinate it sequentially to obtain a heat insulation pad of the target thickness.

2. The method for preparing the heat 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 the heat insulation pad according to claim 1, characterized in that, The texture on the high-silica fabric includes any one of plain weave, twill weave, and satin weave.

4. The method for preparing the heat 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 the heat insulation pad according to claim 1, characterized in that, The thickness of the high-silica cloth is 0.2~2mm.

6. The method for preparing the heat insulation pad according to claim 1, characterized in that, The amount of the mixed liquid applied to the coated fabric is 100% to 150% of the mass of the high-silica fabric.

7. The method for preparing the heat insulation pad according to claim 1, characterized in that, The pressing process uses a pressure of 5~30MPa and a holding time of 5~15min.

8. The method for preparing the heat insulation pad according to claim 1, characterized in that, The drying process uses a drying temperature of 40~80℃ and a drying time of 240~480 min.

9. The method for preparing the heat insulation pad according to claim 1, characterized in that, The calcination process is carried out at a temperature of 800~1100℃ for a time of 30~90 min.

10. A heat insulation pad, characterized in that, It is prepared by the method of any one of claims 1 to 9 for the preparation of the heat insulation pad.

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