CN115636684A - Preparation method of carbon fiber heat-preservation hard felt - Google Patents

Abstract

The invention provides a method for preparing a carbon fiber thermal insulation hard felt, which comprises the following steps: fully pre-oxidizing pitch fibers to obtain pitch pre-oxidized fibers; chopping the pre-oxidized fibers, mixing them with a dispersant, and putting them in a liquid medium Disperse to obtain a dispersion; or chop the pre-oxidized fiber, mix it with a binder and a dispersant, and disperse it in a liquid medium to obtain a dispersion; filter out the liquid in the dispersion, dry it under pressure, and solidify it. Heat treatment, namely; the pressure of the pressure curing is greater than or equal to 0.1 MPa and less than or equal to 1 MPa.

Description

A kind of preparation method of carbon fiber thermal insulation hard felt

technical field

The invention relates to the field of rigid carbon fiber materials and preparation methods, in particular to a preparation method of carbon fiber thermal insulation hard felt.

Background technique

The low-density rigid carbon fiber material is a low-density carbon/carbon composite material obtained after high-temperature carbonization with carbon fiber as the skeleton and high carbon residue rate precursors such as resin and pitch as the binder. Due to its low density, high porosity, low thermal conductivity and good high temperature stability, it is an excellent thermal insulation material. Carbon fiber insulation hard felt is a low-density rigid carbon fiber material. It is not only suitable for the manufacture of light-weight heat insulation and ablation-resistant heat protection materials, but also widely used as insulation materials for vacuum or non-oxidizing atmosphere high-temperature equipment represented by single crystal growth furnaces and epitaxial growth furnaces. In addition, the activated carbon fiber insulation hard felt can also be made into filter and adsorption materials such as molecular sieves.

Commonly used low-density carbon fiber insulation hard felts can be mainly divided into two categories: lamination curing molding and wet molding. Lamination curing molding mainly uses soft carbon felt impregnation molding process. However, there are disadvantages such as high energy consumption, low interlayer strength, easy cracking, low service life, high binder content, and poor oxidation resistance of carbon fiber hard felt in the production of carbon fiber hard felt by dip molding process. Wet compression molding is mainly to prepare chopped carbon fiber, binder and dispersant into a uniformly dispersed slurry, and use vacuum filtration or pressure filtration molding method to obtain the green body obtained by drying, curing and carbonization. The carbon fiber hard felt obtained by the method has good integrity, is not easy to be delaminated, has a wide range of adjustable density and strong designability. Homogeneous dispersion of chopped carbon fibers and strong bonds between fibers are the key to high performance product quality. The poor dispersibility of carbon fiber in the solution system is mainly due to the small diameter of carbon fiber, large surface area, and easy aggregation. At the same time, there are few active groups on the surface of carbon fiber and low surface activity, which affects its dispersion performance. Therefore, the method of adding an organic solvent and a binder compatible with the organic solvent is often added to the system. However, the effect of adding an organic solvent is relatively simple, which has certain hazards or hidden dangers to the environment and safety, and the liquid bonding system is subject to gravity during carbonization, which can easily lead to a certain impact on the uniformity of product strength and thermal insulation performance.

In view of this, it is necessary to propose a new technical solution to solve the above technical problems.

Contents of the invention

The purpose of the present invention is to provide a low-density rigid carbon fiber material. The method adopts isotropic pitch-based pre-oxidized fiber as raw material fiber. The heat-insulating pitch-based carbon fiber felt is adjusted; the method has simple preparation process, safety and environmental protection, excellent heat insulation effect, strong designability, stable quality, and high cost performance, which can meet large-scale production.

To achieve the above object, the present invention adopts the following technical means:

A preparation method of carbon fiber thermal insulation hard felt, comprising the steps of:

Fully pre-oxidize the pitch fibers to obtain pitch pre-oxidized fibers;

After the pre-oxidized fiber is chopped, mixed with a dispersant, and dispersed in a liquid medium to obtain a dispersion; or

After the pre-oxidized fiber is chopped, mixed with a binder and a dispersant, and dispersed in a liquid medium to obtain a dispersion;

Filtrate the liquid in the dispersion liquid, dry and pressurize and solidify, and then conduct heat treatment to obtain;

The pressure of the pressure curing is greater than or equal to 0.1 MPa and less than or equal to 1 MPa.

The outer diameter of the pitch fiber is 7-60 μm;

The length of the pitch fiber after being chopped is 0.5-10mm;

The pitch fibers are isotropic pitch fibers.

The mass ratio of the binder to the pre-oxidized fiber in the dispersion is 0.25-1:1;

The mass ratio of the dispersant to the pre-oxidized fiber is 0-0.05:1;

The mass ratio of the liquid medium to the pre-oxidized fiber is 20-100:1.

The dispersant includes at least one of methylcellulose, sodium carboxymethylcellulose, ethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, polyacrylamide or polyvinyl alcohol.

The binder is selected from phenolic resin, asphalt, furan resin, urea-formaldehyde resin, epoxy resin, vinyl ester resin, or polyethylene, polypropylene, ethylene-propylene copolymer, polyamide, polystyrene or acrylic resin a kind of

The binder satisfies Dv50∈(1,10); and

Satisfaction of said binder satisfies Dv97∈(7,36); and

The Dv97/Dv50 of the adhesive is less than 7.

The pressure curing temperature is 150-280°C;

The pressure curing time is 0.5-2 hours.

The temperature of the heat treatment is 1000-2800°C;

The heating rate of the heat treatment is 0.1-50° C./min.

The density of the carbon fiber thermal insulation hard felt is 0.1-0.3g/cm ³ ;

The thermal conductivity of the carbon fiber thermal insulation hard felt is less than or equal to 0.3W/(m·K).

Compared with the prior art, the present invention brings the following technical effects:

The present invention uses non-carbonized isotropic pitch-based preoxidized fiber as raw material, and its surface is rich in functional groups (carboxyl, or hydroxyl, etc.) with a certain degree of hydrophilicity, so that it has better dispersion in water or polar solvents It is beneficial to realize the uniform dispersion of fibers in space.

The method provided by the invention realizes the material density and layered distribution degree by adjusting the pressure, and can obtain the carbon fiber felt with adjustable thickness and density, which is beneficial to meet different application requirements.

The invention further improves the strength, heat preservation and uniformity of the low-density carbon/carbon composite thermal insulation material and improves the comprehensive performance by adjusting the ratio of the isotropic pitch-based preoxidized fiber dispersion liquid and the molding curing and carbonization process conditions.

The preparation technology of rigid carbon fiber thermal insulation hard felt provided by the invention has simple process, safety and environmental protection, excellent thermal insulation effect, strong designability, stable quality, high cost performance, and can meet large-scale production.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the following will briefly introduce the drawings used in the embodiments.

Fig. 1 shows the infrared spectrogram of pitch-based carbon fiber, pitch-based preoxidized fiber and pitch fiber precursor;

Figure 2 shows a schematic diagram of sampling carbon fiber felt test samples.

Detailed ways

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

The present invention provides a kind of preparation method of carbon fiber thermal insulation rigid felt, specifically comprises the following steps:

Fully pre-oxidize the pitch fibers to obtain pitch pre-oxidized fibers; chop the pre-oxidized fibers, mix them with a dispersant, and disperse them in a liquid medium to obtain a dispersion; or chop the pre-oxidized fibers and mix them with A binder and a dispersant are mixed and dispersed in a liquid medium to obtain a dispersion liquid; the liquid in the dispersion liquid is filtered out, dried and solidified under pressure, and then heat-treated to obtain the product.

The invention adopts the pitch preoxidized fiber as a raw material to prepare the carbon fiber thermal insulation hard felt, which can improve the performance of the prepared carbon fiber thermal insulation hard felt. Carbonization of pre-oxidized fibers is usually done by heating the pre-oxidized fibers to 1400-1600°C under vacuum or high-purity inert atmosphere to remove non-carbon elements such as C, H, and N in the pre-oxidized fibers to carbonize the fibers. A series of complex physical and chemical changes will occur during the carbonization process of pre-oxidized fibers. Dehydration and dehydrogenation reactions will occur between molecules, and the main chain, side chains and terminal groups will decompose, releasing H ₂ O, NH ₃ , CO, CO ₂ , Small molecules such as _N2 , and, during carbonization, the diameter and density of fibers will change significantly. It can be seen from Figure 1 that the functional groups of the pre-oxidized fibers are relatively close to the binder pitch raw materials, while the carbonized fibers have gradually removed non-carbon atoms and functional groups, and the surface has become inert.

In order to make the fiber bond well with the binder, the pre-oxidized fiber used in the present invention has more functional groups to participate in the reaction than the carbon fiber, and these surface functional groups can form a firm bonding effect with the binder, which can Increase the strength of the prepared carbon fiber thermal insulation hard felt. Moreover, due to the rich functional groups on the surface of the pre-oxidized fiber, the dispersion effect in the solvent is also greatly improved, the dispersibility of the fiber is improved, and the uniformity of the prepared carbon fiber thermal insulation hard felt will also be greatly improved.

The uniformity of filter cake obtained by wet forming of chopped pre-oxidized fiber has been significantly improved. Compared with carbon fiber products, the main problem is that in the subsequent carbonization process, the filter cake will experience a large shrinkage process due to the removal of non-carbon elements and small molecular components. It should be pointed out that in the present invention, the bonding The agent has consolidated the fibers to form a stable felt body. In the subsequent carbonization shrinkage, the shrinkage of the fibers will be limited by the shrinkage of the binder and other fibers. Therefore, the shrinkage of the overall product is different from that of pre-oxidized fibers and traditional pre-oxidized felts ( No binder) changes are not consistent, relatively more slowly. Therefore, this relatively slow process will result in smaller shrinkage, which is conducive to the uniform preparation of carbon fiber insulation rigid felt.

Compared with the inherent idea of using carbon fiber finished products as raw materials to prepare carbon fiber thermal insulation hard felt in this field, the present invention selects pre-oxidized fiber as the starting raw material fiber, and uses carbon fiber preparation technology in the process of preparing carbon fiber thermal insulation hard felt, and realizes Fiber carbonization and fiber felting.

Specifically, the pressure of the pressure curing is greater than or equal to 0.1 MPa and less than or equal to 1 MPa. Excessive pressure will lead to excessive bulk density of the product or the risk of fiber breakage due to excessive pressure, and too small pressure will result in insufficient contact between fibers, resulting in poor mechanical properties of the product.

Specifically, the outer diameter of the pitch fiber is 7-60 μm; it is not easy to completely pre-oxidize it when the fiber diameter is larger; the smaller fiber diameter is likely to cause excessive oxidation of the fiber, thereby losing additional carbon in the subsequent carbonization process Elements form defects, which affect the mechanical properties of carbon fiber mats;

Specifically, the length of the pitch fibers after being chopped is 0.5-10 mm; too short fibers will reduce the mechanical properties of the carbon fiber mat, and too long fibers are not conducive to the dispersion of fibers.

Specifically, the pitch fibers are isotropic pitch fibers. The microcrystalline structure in the isotropic pitch fiber is small in size and disorderly arranged, which is more beneficial to heat preservation (the thermal conductivity of the material itself is small)

Specifically, the mass ratio of the binder to the pre-oxidized fiber in the dispersion is 0.25 to 1:1; if the mass ratio of the binder is too small, it will easily lead to poor bonding effect, thus affecting the quality of the product. Mechanical properties: If the proportion of binder mass is too large, it will easily lead to uneven dispersion of binder, resulting in agglomeration of pyrolysis carbon of binder, resulting in a decrease in thermal insulation performance and uniformity of the product.

Specifically, the mass ratio of the dispersant to the pre-oxidized fiber is 0-0.05:1; a small amount of dispersant can help the dispersion of fiber and binder, and too much dispersant will lead to system viscosity The significant increase is not conducive to the subsequent filtration process.

Specifically, the mass ratio of the liquid medium to the pre-oxidized fiber is 20-100:1. Too little liquid medium is not conducive to the dispersion of fibers and binders, and too much liquid medium will reduce production efficiency and indirectly increase production costs.

Specifically, the dispersant includes at least one of methyl cellulose, sodium carboxymethyl cellulose, ethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, polyacrylamide or polyvinyl alcohol A sort of. The addition of dispersant can improve the surface tension between the binder, fiber and liquid medium, which is beneficial to form a uniform dispersion system among each other, and make the binder and fiber not easy to settle and agglomerate, providing enough for the filtration process after dispersion. time window. Preferably, the above-mentioned dispersant can promote the dispersion of carbon fibers.

Specifically, the binder is selected from phenolic resin, asphalt, furan resin, urea-formaldehyde resin, epoxy resin, vinyl ester resin, or polyethylene, polypropylene, ethylene-propylene copolymer, polyamide, polystyrene or One of the acrylic resins; the above-mentioned binder is easier to be pulverized by air-flow crushing equipment, and the carbonaceous bonding points formed after the above-mentioned binder is carbonized have strong bonding strength, so that the fibers are tightly bonded knot, thereby improving the mechanical properties of carbon fiber felt.

Specifically, the binder meets Dv50∈(1,10); and the binder meets the binder Dv97∈(7,36); and the binder meets Dv97/Dv50 is less than 7. Dv50 is a parameter used to characterize the particle size distribution, that is, the particle size corresponding to 50% of the volume distribution, and the Dv50 of the particle size of the binder used in the present invention belongs to 1-10 μm. Correspondingly, Dv97 is between 7 and 36 μm. When the particle size of the binder is in the above range, a better effect can be obtained. If the particle size is too large, the number of particles of the binder is too small for a certain quality of the binder, which is not conducive to the formation of a homogeneous system, resulting in poor bonding effect. When the particle size is too small, it is not conducive to the uniform dispersion of the binder .

Specifically, the pressure curing temperature is 150-280° C.; when the temperature is too low, the binder will not melt or solidify; if the temperature is too high, the binder will cure too quickly and fail to fully crosslink or begin to degrade.

Specifically, the pressure curing time is 0.5-2 hours. If the curing time is too short, the binder will not be sufficiently cured or melt and flow to the fiber overlap to infiltrate the interface between fibers. If the curing time is too long, unnecessary energy and time consumption and potential transitional crosslinking will be caused. resulting in poor performance.

Specifically, the temperature of the heat treatment is 1000-2800°C; the purpose of the heat treatment is to remove non-carbon elements in the binder, fiber, and dispersant, and if the temperature is too low, there will be more non-carbon elements If the temperature is too high, the thermal conductivity of the carbon fiber felt will increase, which is not conducive to its use as a thermal insulation felt.

Specifically, the heating rate of the heat treatment is 0.1-50° C./min. If the heating rate is too low, the production efficiency will decrease and the energy consumption cost will increase; if the heating rate is too fast, it will easily lead to the failure of the heating equipment and indirectly increase the production cost.

Specifically, the density of the carbon fiber thermal insulation hard felt is 0.1-0.3g/cm ³ ;

Specifically, the thermal conductivity of the carbon fiber thermal insulation hard felt is less than or equal to 0.3W/(m·K).

The present invention will be further described below in conjunction with specific examples.

Example 1

1. Put 50g of isotropic pitch-based preoxidized fibers with a diameter of 19 μm and a length of 0.5mm into a 3L beaker filled with 1000g of deionized water; then put in 12.5g of isotropic pitch powder, whose particle size Dv50 is 4.9 μm, Dv97 is 12.9μm; then add 2.5g PVP dispersant; under stirring at 400rpm, disperse for 60min to obtain a uniform slurry;

2. Pour the above slurry into mold i for suction filtration, and dry the obtained filter cake in a drying oven at 80°C for 12 hours;

3. Then put the above-mentioned mold i containing fiber filter cake into a hot press, apply a pressure of 0.1Mpa from the top of the mold, and heat the mold, that is, the first heat treatment, and raise the temperature to 280 at a heating rate of 5°C/min. ℃ and keep it warm for 0.5h, make the asphalt powder binder melt and flow, and bond at the overlapping joints of the fibers, and the molten asphalt solidifies after the natural cooling of the mold, and the asphalt fiber mat is obtained by demoulding;

4. The above-mentioned pitch fiber felt is subjected to high-temperature heat treatment, that is, the second heat treatment, and the temperature is raised to 2200° C. at a heating rate of 0.5° C./min to obtain a carbon fiber felt.

Example 2

1. Put 50g of isotropic pitch-based preoxidized fibers with a diameter of 32 μm and a length of 5 mm into a 10L beaker filled with 5000 g of deionized water; then put 12.5 g of isotropic pitch powder, the particle size Dv50 of which is 3.2 μm , Dv97 is 12.1μm; then add 1g of PEG dispersant; under stirring at 600rpm, disperse for 60min to obtain a uniform slurry;

2. Pour the above slurry into mold i for suction filtration, and dry the obtained filter cake in a drying oven at 80°C for 12 hours;

3. Then put the above-mentioned mold i containing fiber filter cake into a hot press, apply a pressure of 0.5Mpa from the top of the mold, and heat the mold, that is, the first heat treatment, and raise the temperature to 280 at a heating rate of 5°C/min. ℃ and keep warm for 0.5h, so that the isotropic asphalt powder binder melts and flows and sticks at the overlapping joints of the fibers, and the molten asphalt solidifies after the natural cooling of the mold, and the asphalt fiber mat is obtained by demoulding;

4. The above-mentioned pitch fiber felt is subjected to high-temperature heat treatment, that is, the second heat treatment, and the temperature is raised to 1100° C. at a heating rate of 0.1° C./min to obtain a carbon fiber felt.

Example 3

1. Put 50g of isotropic pitch-based preoxidized fibers with a diameter of 11 μm and a length of 10 mm into a 5L beaker filled with 2500 g of deionized water; then put 25 g of phenolic resin powder, the particle size of which is 2.8 μm, Dv97 11.2μm; add 0.5g of PAM dispersant; under stirring at 500rpm, disperse for 120min to obtain a uniform slurry;

2. Pour the above slurry into mold i for suction filtration, and dry the obtained filter cake in a drying oven at 90°C for 10 hours;

3. Then put the above-mentioned mold i containing fiber filter cake into a hot press, apply a pressure of 0.5Mpa from the top of the mold, and heat the mold, that is, the first heat treatment, and raise the temperature to 150 at a heating rate of 5°C/min. ℃ and keep it warm for 2 hours, so that the phenolic resin powder binder melts and flows, then bonds and solidifies at the overlapping joints of the fibers, and then demoulds with the natural cooling of the mold to obtain a pitch fiber mat;

4. The above-mentioned pitch fiber felt is subjected to high-temperature heat treatment, that is, the second heat treatment, and the temperature is raised to 2800° C. at a heating rate of 20° C./min to obtain a carbon fiber felt.

Example 4

1. Put 50g of isotropic pitch-based preoxidized fibers with a diameter of 28 μm and a length of 3 mm into a 5L beaker filled with 2500 g of deionized water; then put 25 g of phenolic resin powder, the particle size Dv50 of the phenolic resin powder is 6.9 μm, Dv97 21.4μm; then add 0.5g CTAB dispersant; under stirring at 400rpm, disperse for 180min to obtain a uniform slurry;

2. Pour the above slurry into mold i for suction filtration, and dry the obtained filter cake in a drying oven at 90°C for 10 hours;

3. Then put the above-mentioned mold i containing fiber filter cake into a hot press, apply a pressure of 0.2Mpa from the top of the mold, and heat the mold, that is, the first heat treatment, and raise the temperature to 150 at a heating rate of 5°C/min. ℃ and keep it warm for 2 hours, so that the phenolic resin powder binder melts and flows, then bonds and solidifies at the overlapping joints of the fibers, and then demoulds with the natural cooling of the mold to obtain a pitch fiber mat;

4. The above-mentioned pitch fiber felt is subjected to high-temperature heat treatment, that is, the second heat treatment, and the temperature is raised to 2800° C. at a heating rate of 30° C./min to obtain a carbon fiber felt.

Example 5

1. Put 50g of isotropic pitch-based preoxidized fibers with a diameter of 60 μm and a length of 1 mm into a 10L beaker with 5000 g of deionized water; 35.2μm; add 0.5g of PAM dispersant; under stirring at 400rpm, disperse for 180min to obtain a uniform slurry;

2. Pour the above slurry into mold i for suction filtration, and dry the obtained filter cake in a drying oven at 90°C for 10 hours;

3. Then put the above-mentioned mold i containing the fiber filter cake into a hot press, apply a pressure of 0.2Mpa from the top of the mold, and heat the mold, that is, the first heat treatment, and raise the temperature to 280 at a heating rate of 5°C/min. ℃ and keep warm for 0.5h, so that the isotropic asphalt powder binder melts and flows and sticks at the overlapping joints of the fibers, and the molten asphalt solidifies after the natural cooling of the mold, and the asphalt fiber mat is obtained by demoulding;

4. The above-mentioned pitch fiber felt is subjected to high-temperature heat treatment, that is, the second heat treatment, and the temperature is raised to 2600° C. at a heating rate of 50° C./min to obtain a carbon fiber felt.

Example 6

1. Put 50g of isotropic pitch-based preoxidized fibers with a diameter of 7 μm and a length of 10 mm into a 3L beaker filled with 1500 g of deionized water; then put 20 g of phenolic resin powder, the particle size of which is 1.3 μm, Dv97 9.1 μm; then add 2.5g of PVP dispersant; under stirring at 600rpm, disperse for 60min to obtain a uniform slurry;

2. Pour the above slurry into mold i for suction filtration, and dry the obtained filter cake in a drying oven at 100°C for 6 hours;

3. Then put the above-mentioned mold i containing the fiber filter cake into a hot press, apply a pressure of 1Mpa from the top of the mold, and heat the mold, that is, the first heat treatment, and raise the temperature to 150°C at a heating rate of 5°C/min And keep it warm for 2 hours, make the phenolic resin powder binder melt and flow, bond and solidify at the overlapping joints of the fibers, and release the asphalt fiber mat after cooling naturally with the mold;

4. The above-mentioned pitch fiber felt is subjected to high-temperature heat treatment, that is, the second heat treatment, and the temperature is raised to 2800° C. at a heating rate of 50° C./min to obtain a carbon fiber felt.

Example 7

The difference between this embodiment and embodiment 1 is that no PVP dispersant is added in step 1, and all the other steps are the same as in embodiment 1;

Comparative example 1

The difference between this comparative example and Example 1 is that the fibers used in step 1 are not fully pre-oxidized isotropic pitch-based fibers, and all the other steps are the same as in Example 1;

Comparative example 2

The difference between this comparative example and Example 1 is that the fibers used in step 1 are mesophase pitch-based preoxidized fibers, and all the other steps are the same as in Example 1;

Comparative example 3

The difference between this comparative example and Example 1 is that the fibers used in step 1 are isotropic pitch-based carbon fibers, and all the other steps are the same as in Example 1;

Comparative example 4

The difference between this comparative example and comparative example 3 is that no PVP dispersant is added in step 1, and all the other steps are the same as comparative example 3;

The carbon fiber mats provided by Examples 1-7 and Comparative Examples 1-4 are tested, and the tests include:

1. The sampling method is shown in Figure 2. The number of tests for each sample is not less than 7, so as to calculate the average value and standard deviation of the test results, and obtain the standard deviation through the sampling test of different parts of the prepared sample to judge the uniformity of the sample. sex;

2. The density is calculated by the ratio of the mass to volume of the carbon fiber felt, the mass is measured by an analytical balance, and the volume is calculated by measuring the size with a micrometer;

3. Use the Hot Disk TPS2500s heat flow meter to test the thermal conductivity of the carbon fiber felt in the Z direction, with a diameter of 25mm and a thickness of 2mm;

4. Use CTM2500 universal material testing machine to test the compressive strength of carbon fiber felt in the Z direction. The size of the test sample is 10*10*10mm ³ , and the test rate is 1mm/min;

The test results are shown in Table 1

From the data results shown in Examples 1-7, it can be seen that using a reasonable lower heat treatment temperature, shorter fiber length, and lower molding pressure is conducive to satisfying the rigidity of the carbon fiber felt and highlighting the heat insulation performance of the carbon fiber felt. And the standard deviation of the data shows that the samples prepared by the present invention have higher sample uniformity; in addition, it can be seen from the data that the increase of the molding pressure can obviously improve the volume density of the carbon fiber felt.

From the data shown in Example 1 and Example 7, it can be seen that the addition of dispersant is conducive to the uniformity of the carbon fiber felt made;

From the data of Example 1 and Comparative Example 1, it can be seen that when the incompletely preoxidized isotropic pitch-based preoxidized fiber is selected as raw material, it is unfavorable for the preparation of low-density carbon fiber felt;

From the data of Example 1 and Comparative Example 2, it can be seen that when the mesophase pitch-based preoxidized fiber is selected as raw material, its carbon fiber felt shows a higher thermal conductivity, which is not conducive to the preparation of carbon fiber felt with excellent thermal insulation properties;

From the data of Example 1 and Comparative Example 3, it can be seen that compared with pitch-based carbon fibers, selecting isotropic pitch-based preoxidized fibers as raw materials is obviously beneficial to the uniformity of the prepared carbon fiber felt;

From the data of Example 7 and Comparative Example 3, it can be seen that when isotropic pitch-based preoxidized fibers are selected as raw materials, even if no dispersant is added to assist dispersion, the uniformity of the prepared carbon fiber mat is still better than that of pitch carbon fibers. And the carbon fiber mat prepared when using dispersant;

From the data of Example 7 and Comparative Example 4, it can be seen that when no dispersant is used, the uniformity of the carbon fiber mat prepared by using isotropic pitch-based preoxidized fiber as raw material is obviously better than that prepared by using pitch carbon fiber as raw material. carbon fiber felt.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention, those skilled in the art can make the above-mentioned The embodiments are subject to changes, modifications, substitutions and variations.

Claims (9)

1. a preparation method of carbon fiber thermal insulation hard felt, is characterized in that, comprises the steps: Fully pre-oxidize the pitch fibers to obtain pitch pre-oxidized fibers; After the pre-oxidized fiber is chopped, mixed with a dispersant, and dispersed in a liquid medium to obtain a dispersion; or After the pre-oxidized fiber is chopped, mixed with a binder and a dispersant, and dispersed in a liquid medium to obtain a dispersion; Filtrate the liquid in the dispersion liquid, dry and pressurize and solidify, and then conduct heat treatment to obtain; The pressure of the pressure curing is greater than or equal to 0.1 MPa and less than or equal to 1 MPa. 2. the preparation method of carbon fiber thermal insulation hard felt as claimed in claim 1, is characterized in that: The outer diameter of the pitch fiber is 7-60 μm; The length of the pitch fiber after being chopped is 0.5-10mm; The pitch fibers are isotropic pitch fibers. 3. the preparation method of carbon fiber thermal insulation hard felt as claimed in claim 1, is characterized in that: The mass ratio of the binder to the pre-oxidized fiber in the dispersion is 0.25-1:1; The mass ratio of the dispersant to the pre-oxidized fiber is 0-0.05:1; The mass ratio of the liquid medium to the pre-oxidized fiber is 20-100:1. 4. the preparation method of carbon fiber thermal insulation hard felt as claimed in claim 1, is characterized in that: The dispersant includes at least one of methylcellulose, sodium carboxymethylcellulose, ethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, polyacrylamide or polyvinyl alcohol. 5. the preparation method of carbon fiber thermal insulation hard felt as claimed in claim 1, is characterized in that: The binder is selected from phenolic resin, asphalt, furan resin, urea-formaldehyde resin, epoxy resin, vinyl ester resin, or polyethylene, polypropylene, ethylene-propylene copolymer, polyamide, polystyrene or acrylic resin kind of. 6. the preparation method of carbon fiber thermal insulation hard felt as claimed in claim 1, is characterized in that: The binder satisfies Dv50∈(1,10); and Satisfaction of said binder satisfies Dv97∈(7,36); and The Dv97/Dv50 of the adhesive is less than 7. 7. The preparation method of carbon fiber thermal insulation hard felt as claimed in claim 1, is characterized in that: The pressure curing temperature is 150-280°C; The pressure curing time is 0.5-2 hours. 8. The preparation method of carbon fiber thermal insulation hard felt as claimed in claim 1, is characterized in that: The temperature of the heat treatment is 1000-2800°C; The heating rate of the heat treatment is 0.1-50° C./min. 9. The preparation method of the carbon fiber thermal insulation hard felt according to any one of claims 1 to 8, characterized in that: The density of the carbon fiber thermal insulation hard felt is 0.1-0.3g/cm ³ ; The thermal conductivity of the carbon fiber thermal insulation hard felt is less than or equal to 0.3W/(m·K).

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