Heat insulating material and method for producing heat insulating material

Abstract

To provide a heat insulating material capable of preventing generation of particles without deteriorating thermal insulation performance.SOLUTION: There is provided a heat insulating material 10 using carbon fibers 2 which has a coating layer 6 containing a pyrolytic carbon on the surface and an underlying layer 5 containing carbon-based particles 4 between carbon fibers 2 under the coating layer 6, There is provided a method for producing the heat insulating material 10 which comprises an underlying layer formation step of forming an underlying layer 5 by impregnating the surface of molded bodies 3 of carbon fibers 2 with a slurry containing carbon-based particles 4 and a CVD step of forming a coating layer 6 containing a pyrolytic carbon on the underlying layer 5 by a chemical vapor deposition method by putting the molded bodies 3 in a CVD furnace.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a heat insulating material and a method for manufacturing the heat insulating material.

Background Art

[0002] Heat insulating materials using carbon fibers are widely used as heat insulating materials for high-temperature furnaces, such as single crystal pulling apparatuses and ceramic sintering furnaces, because they have a high heat resistance temperature and excellent heat insulating performance.

[0003] Heat insulating materials using carbon fibers are widely used in the form of felts and paper-made products with a high porosity in order to suppress heat transfer by the carbon fibers. Generally, since felts are deformable, they are used as members that fill the empty space and fill the space, or as heat insulating materials that surround other parts. On the other hand, since paper-made products have high shape retention, they are processed into a predetermined shape and used as heat insulating parts. Note that felts can also be used as heat insulating parts with good shape retention by fixing them with a binder after compression.

[0004] Carbon fiber heat insulating materials may cause fiber dropout and generate particles due to oxidation in the furnace, mechanical friction, etc. Further, such problems may cause a decrease in heat insulation against radiation.

[0005] In order to solve such problems, Patent Document 1 discloses a heat insulating material for preventing heat of a heater that heats a crucible in a single crystal pulling apparatus from moving to the outside of a sealed body. The heat insulating material is formed of a base material of a heat insulating material made of a carbon fiber molded body and a film made of pyrolytic carbon, and a thermosetting resin carbide obtained by heating and curing a thermosetting resin and then carbonizing is formed as an intermediate layer between the carbon fiber molded body and the film made of pyrolytic carbon. A heat insulating material for a single crystal pulling apparatus is disclosed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, since the heat insulating material described in Patent Document 1 forms the intermediate layer with a thermosetting resin, the thermosetting resin penetrates into the carbon fiber molded body, and the thickness capable of securing the original heat insulating property becomes small, which may lead to a decrease in heat insulating property.

[0008] The present invention provides a heat insulating material using carbon fibers that can prevent the generation of particles without degrading the heat insulating performance, and a method for manufacturing the heat insulating material.

Means for Solving the Problems

[0009] The heat insulating material of the present invention is a heat insulating material using carbon fibers, which has a coating layer containing pyrolytic carbon on the surface, and has a base layer containing carbon-based particles between the carbon fibers under the coating layer.

[0010] According to the heat insulating material of the present invention, since the coating layer containing dense pyrolytic carbon covers the heat insulating material of carbon fibers, the diffusion of carbon fibers to the outside as particles is suppressed. Further, since the base layer of the heat insulating material contains carbon-based particles, the coating layer containing pyrolytic carbon can be suppressed from penetrating into the main body of the heat insulating material containing carbon fibers, and a decrease in heat insulating performance can be suppressed.

[0011] The heat insulating material of the present invention is preferably in the following embodiments.

[0012] The carbon fibers are exposed on the surface of the base layer.

[0013] When the carbon fibers are exposed on the surface of the base layer, the coating layer directly joins with the carbon fibers, so that the bonding strength between the heat insulating material and the coating layer can be enhanced, and the coating layer can be made difficult to peel off.

[0014] The carbon-based particles and the carbon fibers of the base layer are joined to each other with a carbon-based adhesive.

[0015] Since the carbon-based particles and the carbon fibers are joined to each other with a carbon-based adhesive, delamination of the base layer can be prevented, and a strong bonding force can be imparted to the coating layer.

[0016] The carbon fibers form a mat or a web.

[0017] When the molded body is in the form of a mat or a web, the carbon fibers are randomly arranged and can be spaced apart from each other, so that the heat insulation property can be enhanced.

[0018] The carbon-based particles are at least one carbon-based particle selected from graphite, carbon black, glassy carbon particles, or mild carbon fibers.

[0019] Carbon-based particles such as graphite, carbon black, glassy carbon particles, or mild carbon fibers have few impurities, are of the same carbon-based as the carbon fibers constituting the heat insulating material and the coating layer, and have low reactivity, so that the generation of decomposition gas can be suppressed.

[0020] The carbon-based particles have an average particle diameter of 10 nm to 500 μm.

[0021] When the average particle diameter of the carbon-based particles is within the above range, a thin base layer can be formed in the gaps between the carbon fibers, and in the heat insulating material, the joining between the carbon fibers and the coating layer can be ensured at a high level. Further, it is possible to prevent the thickness of the base layer, where heat conduction is likely to increase, from becoming too thick.

[0022] The base layer has a thickness of 10 μm to 500 μm.

[0023] When the thickness of the base layer is 500 μm or less, a decrease in heat insulation performance can be suppressed. When the thickness of the base layer is 10 μm or more, penetration of the coating layer into the main body of the heat insulating material can be prevented.

[0024] The manufacturing method of the heat insulating material of the present invention is as follows: A base layer forming step of impregnating a slurry containing carbon-based particles on the surface of a carbon fiber formed body to form a base layer; A CVD step of putting the formed body into a CVD furnace and forming a coating layer containing pyrolytic carbon on the base layer by chemical vapor deposition method.

[0025] According to the manufacturing method of the heat insulating material of the present invention, a coating layer containing pyrolytic carbon is formed on the base layer by the CVD step. Therefore, a coating layer containing dense pyrolytic carbon covers the heat insulating material of carbon fiber, so that the diffusion of carbon fiber to the outside as particles is suppressed. Further, in this manufacturing method, since the base layer contains carbon-based particles in the base layer forming step, it is possible to suppress the coating layer containing pyrolytic carbon from entering the main body of the heat insulating material containing carbon fiber, and to suppress a decrease in heat insulating performance.

[0026] The manufacturing method of the heat insulating material of the present invention is preferably the following aspect.

[0027] In the base layer forming step, the carbon fiber is exposed on the surface.

[0028] By exposing the carbon fiber on the surface of the base layer, the coating layer is directly joined to the carbon fiber, so that the bonding strength between the heat insulating material and the coating layer can be increased, and the coating layer can be made difficult to peel off.

[0029] In the base layer forming step, a solution of a carbon precursor is impregnated on the surface of the formed body simultaneously with or after the impregnation of the slurry, and the carbon-based particles and the carbon fiber are fixed, and the carbon precursor is carbonized to form a carbon-based adhesive that joins the carbon-based particles and the carbon fiber.

[0030] Since the carbon-based particles and the carbon fiber are joined to each other by the carbon-based adhesive, a strong bonding strength can be imparted to the coating layer.

[0031] The carbon fiber forms a mat or a sheeted body.

[0032] When the molded body is in the form of a mat or a sheeted body, the carbon fibers are randomly arranged and can secure a space from each other, so that the heat insulation property can be enhanced.

[0033] The carbon-based particles are at least one carbon-based particle selected from graphite, carbon black, glassy carbon particles, or mild carbon fibers.

[0034] Carbon-based particles such as graphite, carbon black, glassy carbon particles, or mild carbon fibers have few impurities, are of the same carbon system as the carbon fibers and the coating layer constituting the heat insulating material, and have low reactivity, so that the generation of decomposition gas can be suppressed.

[0035] The carbon-based particles have an average particle diameter of 10 nm to 500 μm.

[0036] When the average particle diameter of the carbon-based particles is within the above range, a thin base layer can be formed in the gaps between the carbon fibers, and in the heat insulating material, the joining of the carbon fibers and the coating layer can be ensured at a high level. Further, it is possible to prevent the thickness of the base layer, where heat conduction easily increases, from becoming too thick.

[0037] The base layer has a thickness of 10 μm to 500 μm.

[0038] When the thickness of the base layer is 500 μm or less, a decrease in heat insulation performance can be suppressed. When the thickness of the base layer is 10 μm or more, penetration of the coating layer into the main body of the heat insulating material can be prevented.

Advantages of the Invention

[0039] According to the present invention, there is provided a heat insulating material capable of preventing the generation of particles without degrading the heat insulation performance.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2

Figure 3

Figure 4

MODE FOR CARRYING OUT THE INVENTION

[0041] Hereinafter, embodiments of the present invention will be specifically described. However, the present invention is not limited to the following embodiments, and can be appropriately modified and applied without changing the gist of the present invention.

[0042] FIG. 1 shows the manufacturing process of the heat insulating material according to the embodiment of the present invention. The heat insulating material according to the embodiment is a heat insulating material 10 using carbon fibers 2 as shown in FIG. 1(c), having a coating layer 6 containing pyrolytic carbon on the surface, and having a base layer 5 containing carbon-based particles 4 between the carbon fibers 2 under the coating layer 6.

[0043] The heat insulating material 10 is manufactured by a method for manufacturing a heat insulating material having a base layer forming step of impregnating a slurry containing carbon-based particles 4 on the surface of a molded body 3 (FIG. 1(a)) of carbon fibers 2 to form a base layer 5 (FIG. 1(b)), and a CVD (Chemical Vapor Deposition) step of putting the molded body 3 into a CVD furnace and forming a coating layer 6 (FIG. 1(c)) containing pyrolytic carbon on the base layer 5 by chemical vapor deposition.

[0044] As the molded body 3 of the carbon fiber 2 shown in Fig. 1(a), those having forms such as a mat or a paper-made body can be used. In other words, the carbon fiber 2 can constitute a mat, a paper-made body, etc. When the molded body 3 is in the form of a mat or a paper-made body, the carbon fibers 2 are randomly arranged and can secure a space from each other, so that the heat insulation property can be enhanced.

[0045] An example of the molded body 3, the paper-made body, can be obtained, for example, by dispersing short fibers of the carbon fiber 2 (for example, having a length of 0.1 to 5 mm) in water and then paper-making. The mold used for paper-making may be a flat surface or a curved surface mold of a desired shape. When using a curved surface mold, either an inner mold or an outer mold may be used, but it is desirable to use a suction mold so that the paper-made body does not fall from the mold.

[0046] An example of the molded body 3, the mat, can be obtained, for example, by laminating long fibers of the carbon fiber 2 (for example, having a length of 10 to 10,000 mm) in a sheet shape. The obtained mat is molded into a predetermined shape and the shape is fixed to obtain the molded body 3. As the fixing method, any method such as a binder, sewing with a thread, needle punching, etc. can be used.

[0047] The molded body 3 molded using a paper-made body and a binder can be further processed by cutting to obtain a molded body 3 with higher shape accuracy.

[0048] The bulk density of the molded body is, for example, 0.05 to 0.4 g / cm 3 It is. When the bulk density is 0.05 g / cm 3 or more, it has a certain strength as a heat insulating material and can secure light shielding property, so that heat transfer by radiative heat transfer can be suppressed. Since the thermal conductivity of carbon itself is high, when the bulk density is 0.4 g / cm 3 or less, heat conduction by the carbon fiber can be suppressed.

[0049] The type of carbon fiber 2 to be used is not particularly limited, but those with a thickness of 1 μm to 20 μm can be utilized. When the thickness of the carbon fiber is 20 μm or less, the effect of conductive heat transfer by the carbon fiber itself can be suppressed. When the thickness of the carbon fiber is 1 μm or more, it has excellent light-shielding properties and can suppress radiative heat transfer.

[0050] The thickness of the heat insulating material 10 (formed body 3) is preferably 3 mm to 200 mm. When the thickness is 3 mm or more, the ratio of the coating layer 6 and the base layer 5 in the entire thickness can be reduced, and the heat insulating effect can be efficiently exerted.

[0051] The carbon fiber 2 can be either a pitch-based carbon fiber or a PAN-based carbon fiber, and both graphite-based and carbon-based carbon fibers can be used.

[0052] The heat insulating material 10 as a finished product shown in Fig. 1(c) is manufactured through a base layer forming process from Fig. 1(a) to Fig. 1(b) and a CVD process from Fig. 1(b) to Fig. 1(c).

[0053] As shown in Fig. 1(b), in the base layer forming process, a slurry containing carbon-based particles 4 is impregnated on the surface of the formed body 3 to form the base layer 5.

[0054] The carbon-based particles 4 are, for example, at least one carbon-based particle selected from graphite, carbon black, glassy carbon particles, or milled carbon fibers. Carbon-based particles such as graphite, carbon black, glassy carbon particles, or milled carbon fibers have few impurities, are of the same carbon-based as the carbon fiber 2 and the coating layer 6 constituting the heat insulating material 10, and have low reactivity, so the generation of decomposition gas can be suppressed. Glassy carbon particles are those obtained by pulverizing hardly graphitizable carbon such as a carbide of a phenol resin. Milled carbon fibers are those obtained by pulverizing carbon fibers, and for example, the average fiber length is, for example, 20 μm to 500 μm.

[0055] The carbon-based particles 4, for example, have an average particle diameter of 10 nm to 500 μm. When the average particle diameter of the carbon-based particles 4 is within this range, a thin base layer 5 can be formed in the gaps between the carbon fibers 2, and in the finished heat insulating material 10, the joining between the carbon fibers 2 and the coating layer 6 can be ensured at a high level. Further, it is possible to prevent the thickness of the base layer 5, which is likely to have high thermal conductivity, from becoming too thick. The average particle diameter can be measured with a laser diffraction particle size analyzer.

[0056] Most of the components of the slurry containing the carbon-based particles 4 are filtered on the surface of the molded body 3 during impregnation and remain on the surface, and hardly penetrate into the inside of the molded body 3. For this reason, in the subsequent CVD process, the components of the slurry remaining on the surface suppress the intrusion of the source gas into the inside of the molded body 3, and the coating layer 6 can be formed only on the surface of the heat insulating material 10.

[0057] The slurry used in the base layer forming step contains the carbon-based particles 4 and a solvent, and may further contain a binder. If the slurry contains a binder, it is possible to prevent the carbon-based particles 4 unevenly distributed on the surface from falling off.

[0058] The impregnation of the slurry may not be performed once, but may be performed in a plurality of times. For example, a process of impregnating with the carbon-based particles 4 and the solvent in the first time and with the solvent and the binder in the second time can be used. By passing through such a process, the penetration of the binder into the inside of the heat insulating material 10 can be reduced, and the deterioration of the heat insulating performance can be suppressed.

[0059] The type of the binder of the slurry is not particularly limited, and those that dissolve in the solvent, fine particles dispersed in the solvent, etc. can be used.

[0060] For example, as the binder, either a binder that carbonizes when heated or a binder that depolymerizes without residue can be used. If it is a binder that carbonizes, it is possible to prevent the carbon-based particles 4 from falling off even after the formation of the coating layer 6. As the binder that carbonizes, phenol resin, PVA, pitch, etc. can be used. Also, if it is a binder that carbonizes, it is possible to prevent the carbon-based particles 4 from falling off during handling until it is later put into the CVD furnace.

[0061] In the impregnation of the slurry in the base layer formation step, it is desirable to perform it so that the carbon fibers 2 remain on the surface even after impregnation and the remaining carbon fibers 2 are exposed. When the carbon fibers 2 are exposed on the surface of the base layer 5, the coating layer 6 formed in the subsequent CVD process directly joins with the carbon fibers 2, so the bonding strength between the heat insulating material 10 and the coating layer 6 can be strengthened and the coating layer 6 can be made difficult to peel off.

[0062] The base layer 5 has, for example, a thickness of 10 μm to 500 μm. When the thickness of the base layer 5 is 500 μm or less, a decrease in heat insulation performance can be suppressed. When the thickness of the base layer 5 is 10 μm or more, it is possible to prevent the coating layer 6 from penetrating into the main body of the heat insulating material 10.

[0063] In addition, in the base layer formation step, a solution of a binder that is a carbon precursor can further be used. The solution of the carbon precursor impregnates the surface of the molded body 3 simultaneously with or after the impregnation of the slurry, and then is dried to fix the carbon-based particles and carbon fibers. After that, by putting it into a furnace in an inert atmosphere and carbonizing the carbon precursor, a carbon-based adhesive that joins the carbon-based particles 4 and the carbon fibers 2 can be formed. The carbonization temperature is not particularly limited, but is, for example, 700 to 1500°C.

[0064] By going through the above steps, the carbon-based particles 4 and the carbon fibers 2 are joined to each other by the carbon-based adhesive, so it is possible to prevent delamination between the base layers and impart a strong bonding force to the coating layer 6.

[0065] As shown in FIGS. 1(b) and 1(c), in the CVD process, a molded body 3 having an underlying layer 5 containing carbon-based particles 4 on its surface is placed in a CVD furnace, heated, and a raw material gas is introduced to form a coating layer 6 on the surface of the molded body 3.

[0066] The CVD conditions are not particularly limited. As the raw material gas, a hydrocarbon gas can be used, for example, methane, ethane, propane, ethylene, etc. The CVD temperature is preferably, for example, 800 to 2000°C. When it is 800°C or higher, the raw material gas can be easily decomposed. When it is 2000°C or lower, sublimation of the carbon fiber 2 can be suppressed and alteration can be prevented. In the case of the carbonaceous carbon fiber 2, it is more preferably 1700°C or lower. When the carbonaceous carbon fiber 2 is exposed to a high temperature, it is altered to a graphitic form, and alterations such as an increase in thermal conductivity occur. By carrying out the CVD at a temperature of 1700°C or lower, the heat insulation property of the molded body 3 of the carbon fiber 2 can be maintained.

[0067] As described above, in the heat insulating material 10 of the embodiment, since the coating layer 6 containing dense pyrolytic carbon covers the heat insulating material 10 of the carbon fiber 2, diffusion of the carbon fiber 2 to the outside as particles is suppressed. Further, in the heat insulating material 10, since the underlying layer 5 contains carbon-based particles 4, entry of the coating layer 6 containing pyrolytic carbon into the main body of the heat insulating material 10 containing the carbon fiber 2 can be suppressed, and a decrease in heat insulation performance can be suppressed.

[0068] As described above, in the method for manufacturing the heat insulating material of the embodiment, by the CVD process, a coating layer 6 containing pyrolytic carbon is formed on the underlying layer 5. Therefore, since the coating layer 6 containing dense pyrolytic carbon covers the heat insulating material 10 of the carbon fiber 2, diffusion of the carbon fiber 2 to the outside as particles is suppressed. Further, in this manufacturing method, since the underlying layer 5 contains carbon-based particles 4 by the underlying layer forming process, entry of the coating layer 6 containing pyrolytic carbon into the main body of the heat insulating material 10 containing the carbon fiber 2 can be suppressed, and a decrease in heat insulation performance can be suppressed.

[0069] (Example) A mat of carbon fiber (50×50×10 mm) was prepared, sprayed with a binder and solidified, and then heated to 1000 °C to carbonize the binder to form a molded body. Figure 2 shows a scanning electron micrograph of the surface of the molded body.

[0070] After processing the surface of the molded body and shaping it, a slurry containing a binder and carbon-based particles was applied to the surface to form a base layer of carbon-based particles on the surface of the molded body. Note that graphite particles with an average particle size of 10 μm were used as the carbon-based particles.

[0071] The molded body with the base layer formed was placed in a furnace with a reducing atmosphere to carbonize the binder. The carbonized binder joins the carbon-based particles together and prevents particle detachment.

[0072] Figure 3 shows a scanning electron micrograph of the surface of the molded body with the base layer formed. The gaps between the carbon fiber molded bodies are filled with carbon-based particles. Also, part of the carbon fibers is exposed on the surface.

[0073] The molded body with the base layer formed was placed in a CVD furnace to form a coating layer on the surface. The molded body was placed on a support pin and the coating layer was formed in a state of being point-supported by the support pin. Since the molded body is point-supported, a coating layer of pyrolytic carbon can be formed simultaneously on almost the entire surface of the molded body.

[0074] In the CVD furnace, after evacuating once to reduce the pressure inside the furnace, the raw material gas was introduced to form a coating layer of pyrolytic carbon layer.

[0075] Since a base layer is formed on the surface of the molded body, in the CVD process, the raw material gas does not penetrate into the inside of the molded body and deposits on the surface. At this time, the carbon fibers exposed on the surface serve as an anchor, and the carbon fiber molded body and the coating layer can be firmly connected.

[0076] FIG. 4 shows a cross-sectional view of the heat insulating material obtained in the example. Since a coating layer with a thickness of about 50 μm is formed on the surface and further has an underlying layer with a thickness of about 100 μm directly below, the coating layer is formed only in the surface layer portion without the pyrolytic carbon invading between the carbon fibers in the main body of the heat insulating material.

Explanation of reference numerals

[0077] 2 Carbon fiber 3 Formed body 4 Carbon-based particles 5 Underlying layer 6 Coating layer 10 Heat insulating material

Claims

1. A heat insulating material using carbon fibers, which has a coating layer containing pyrolytic carbon on the surface and has a base layer containing carbon-based particles between the carbon fibers under the coating layer.

2. The heat insulating material according to claim 1, wherein the carbon fibers are exposed on the surface of the base layer.

3. The heat insulating material according to claim 1 or 2, wherein the carbon-based particles and the carbon fibers in the base layer are joined to each other with a carbon-based adhesive.

4. The heat insulating material according to any one of claims 1 to 3, wherein the carbon fibers form a mat or a paper.

5. The heat insulating material according to any one of claims 1 to 4, wherein the carbon-based particles are at least one carbon-based particle selected from graphite, carbon black, glassy carbon particles or milled carbon fibers.

6. The heat insulating material according to any one of claims 1 to 5, wherein the carbon-based particles have an average particle diameter of 10 nm to 500 μm.

7. The heat insulating material according to any one of claims 1 to 6, wherein the base layer has a thickness of 10 μm to 500 μm.

8. A base layer forming step of impregnating a slurry containing carbon-based particles on the surface of a molded body of carbon fibers to form a base layer, and a CVD step of putting the molded body into a CVD furnace and forming a coating layer containing pyrolytic carbon on the base layer by chemical vapor deposition method, A method for manufacturing a heat insulating material having.

9. The method for manufacturing a heat insulating material according to claim 8, wherein in the base layer forming step, the carbon fibers are exposed on the surface.

10. In the base layer forming step, a solution of a carbon precursor is impregnated on the surface of the molded body simultaneously with or after the impregnation of the slurry, and while fixing the carbon-based particles and the carbon fibers, and carbonizing the carbon precursor, A method for manufacturing a heat insulating material according to claim 8 or 9, wherein a carbon-based adhesive for joining the carbon-based particles and the carbon fibers is formed.

11. The method for manufacturing a heat insulating material according to any one of claims 8 to 10, wherein the carbon fibers form a mat or a paper.

12. The method for manufacturing a heat insulating material according to any one of claims 8 to 11, wherein the carbon-based particles are at least one carbon-based particle selected from graphite, carbon black, glassy carbon particles or milled carbon fibers.

13. The method for manufacturing a heat insulating material according to any one of claims 8 to 12, wherein the carbon-based particles have an average particle diameter of 10 nm to 500 μm.

14. The method for manufacturing a heat insulating material according to any one of claims 8 to 13, wherein the base layer has a thickness of 10 μm to 500 μm.

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