Carbon fiber insulation material and its manufacturing method

Abstract

To provide a carbon fiber-based heat insulation material in which a surface layer is formed that curbs degradation, gas permeation, and the like.SOLUTION: A method of manufacturing a carbon fiber-based heat insulation material comprises: a lamination step of laminating a carbon fiber-based heat insulation base material and an adhesive sheet made of thermoset resin having a softening point; a provisional bonding step of provisionally bonding the carbon fiber-based heat insulation base material and the adhesive sheet by heating to a temperature higher than the softening point and softening the thermoset resin; a lamination material preparation step of preparing a lamination material by laminating a carbon-based sheet on the adhesive sheet; a bonding step of, while applying pressure to the lamination material from the carbon fiber-based heat insulation base material side and the carbon-based sheet side, heating the lamination material to a hardening temperature or higher and bonding the lamination material; and a heat processing step of thermally processing the lamination material in an inert atmosphere and carbonizing the thermoset resin. Bulk density of the carbon-based sheet is larger than bulk density of the carbon fiber-based heat insulation base material.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a carbon fiber-based thermal insulation material, and more particularly to a carbon fiber-based thermal insulation material having a surface layer bonded to a carbon fiber-based thermal insulation base layer. [Background technology]

[0002] Carbon fiber insulation materials are used in various applications because they have excellent thermal stability and insulation performance and are lightweight. Such carbon fiber insulation materials include carbon fiber felt made by intertwining carbon fibers, and carbon fiber molded insulation materials made by impregnating carbon fiber felt with a resin material and then carbonizing the resin material. Carbon fiber felt has the advantage of being highly flexible, while carbon fiber molded insulation materials have the advantages of being highly stable in shape and capable of being finely processed.

[0003] The type of heat insulating material to be used is appropriately selected depending on the purpose and application. The latter, the carbon fiber molded heat insulating material, is excellent in thermal stability, heat insulating performance, and shape stability, and is therefore used as a heat insulating material for high-temperature furnaces such as single crystal silicon pulling devices, polycrystalline silicon casting furnaces, sintering furnaces for metals and ceramics, and vacuum deposition furnaces.

[0004] Since such carbon fiber insulation uses fine carbon fibers with diameters of about 5 to 20 μm, there is a risk that the carbon fibers may come off or stick to the hands during handling or installation. If the fallen carbon fibers are released into the furnace atmosphere, it may cause a deterioration in product quality.

[0005] In addition, in manufacturing equipment for single crystal or polycrystalline silicon, SiO gas is generated in a high-temperature furnace, and oxygen gas is mixed into the manufacturing atmosphere as an impurity gas. SiO gas and oxygen gas are highly active (reactive), and when carbon fiber insulation reacts with SiO gas, SiC is generated, and when carbon fiber insulation reacts with oxygen gas, carbon oxides such as carbon monoxide and carbon dioxide are generated. These reactions cause the skeletal structure made of carbon fiber to collapse, and as a result, the insulation function obtained by the skeletal structure forming a large number of spaces is reduced. In addition, this deterioration causes the carbon fiber to pulverize and be released into the furnace atmosphere, resulting in a decrease in product quality.

[0006] In order to solve this problem, a layer that provides a function such as preventing deterioration has been bonded to the surface of the carbon fiber-based insulation material. For example, Patent Document 1 proposes a technology in which a carbonaceous protective layer is bonded to a carbonaceous insulation member to prevent powdering and deterioration of the carbon fiber. In addition, Patent Document 2 proposes a technology in which a carbon-based surface layer is bonded to a carbon fiber-based insulation base material to prevent deterioration of the carbon fiber and gas permeation. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 4361636 [Patent Document 2] JP 2015-174807 A

[0008] The technology of Patent Document 1 is for bulk density of 0.1 to 0.4 g / cm 3 and a carbon fiber structure with a bulk density of 0.3 to 2.0 g / cm 3and a pyrolytic carbon coating layer having a bulk density greater than that of the carbonaceous protective layer, the carbonaceous protective layer being bonded to a portion of the surface of the carbonaceous heat insulating member to form a bonded body, a pyrolytic carbon coating layer being formed on at least the surface of the carbonaceous heat insulating member among the surfaces of the bonded body, and the carbonaceous heat insulating member and the carbonaceous protective layer being bonded via a dense carbonaceous intermediate layer. This technology is said to provide a carbonaceous heat insulating material that is less worn, deteriorated, or pulverized during use and has excellent heat insulating properties.

[0009] The technology of Patent Document 2 is a technology in which an adhesive sheet in which a carbon fiber nonwoven fabric sheet is impregnated with a binder that carbonizes by heat treatment is used to bond a different carbon-based sheet such as an expanded graphite sheet to a carbon fiber-based heat insulation substrate, and the sheet is baked and carbonized after bonding. This technology is said to provide effects such as preventing gas permeation, suppressing surface deterioration, improving handling, and improving strength without causing poor adhesion or appearance. DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0010] The inventors of the present invention have studied the above technology diligently and found the following problems. In the above Patent Document 1, a dense carbon-forming composition consisting of flake graphite and a binder component that is carbonized by heating is applied to a carbonaceous heat insulation member to bond (adhere) to a carbonaceous protective layer, and then the binder is carbonized. However, it is difficult to sufficiently and uniformly apply the dense carbon-forming composition to a carbonaceous heat insulation member having a low bulk density (many voids), which increases the work time and causes problems such as poor adhesion and poor appearance of the product due to uneven application. In addition, since flake graphite contains a large amount of impurities, there is a problem that the impurities vaporize or decompose when used in a high-temperature environment, causing poor adhesion and deterioration of the product. It is considered that this problem can be solved if carbon particles such as flake graphite, which serve as aggregates, are not used, but if carbon particles are not used, the viscosity of the composition becomes too low, so the composition penetrates into the carbonaceous heat insulation member and does not contribute to adhesion.

[0011] Furthermore, in the above-mentioned Patent Document 2, there are problems such as the fact that the production of the adhesive sheet impregnated with the binder is time-consuming and the binder used in the adhesive sheet is likely to soil the manufacturing environment.

[0012] The present invention has been made to solve the above-mentioned problems, and aims to provide a carbon fiber-based insulation material with a bonded surface layer without increasing the labor required or causing poor adhesion. [Means for solving the problem]

[0013] The present invention, which relates to a method for producing a carbon fiber-based insulation material to solve the above problems, is configured as follows. 1. A method for producing a carbon fiber-based insulation material, comprising: a lamination step of laminating a carbon fiber-based insulation substrate and an adhesive sheet made of a thermosetting resin having a softening point; a temporary adhesion step of heating the substrate to a temperature equal to or higher than the softening point to soften the thermosetting resin and temporarily adhere the carbon fiber-based insulation substrate and the adhesive sheet after the lamination step; a laminate material preparation step of laminating a carbon-based sheet on the adhesive sheet to form a laminate material after the temporary adhesion step; a bonding step of heating the laminate material to a temperature equal to or higher than the hardening temperature of the thermosetting resin while applying pressure to the laminate material from the carbon fiber-based insulation substrate side and the carbon-based sheet side to bond the laminate material; and a heat treatment step of heat-treating the laminate material in an inert atmosphere after the bonding step to carbonize the thermosetting resin, wherein the bulk density of the carbon-based sheet is greater than the bulk density of the carbon fiber-based insulation substrate.

[0014] In the present invention, the carbon fiber-based heat insulation substrate and the carbon-based sheet serving as the surface layer are bonded to each other using an adhesive sheet made of a thermosetting resin having a softening point. The adhesive sheet made of a thermosetting resin having a softening point is not cured, and is extremely flexible and difficult to handle by itself. For this reason, it is usually sold commercially with release films on both sides. And, when one side of the adhesive sheet is not fixed (when one side is not bonded to the release film or other members), the release film on the other side cannot be peeled off. That is, in order to provide a carbon fiber-based heat insulation substrate and a surface layer on both sides of the adhesive sheet, it is necessary to first bond one of them to the other side.

[0015] In the present invention, the carbon fiber-based heat insulation substrate, which has a lower bulk density than the carbon-based sheet, and the adhesive sheet are laminated and temporarily bonded. In the temporary bonding process, the adhesive sheet is heated to a temperature equal to or higher than the softening point of the thermosetting resin, and the adhesive sheet softens and flows, and a part of the adhesive sheet flows into the voids of the carbon fiber-based heat insulation substrate or clings to the carbon fiber. This increases the adhesion between the carbon fiber-based heat insulation substrate and the adhesive sheet, increasing the adhesive strength (temporarily bonded), and the release film on the other side of the adhesive sheet can be peeled off to laminate the carbon-based sheet directly on the adhesive sheet. In addition, the adhesive strength between the carbon fiber-based heat insulation substrate and the adhesive sheet is further strengthened by this temporary bonding step and the subsequent bonding step.

[0016] Because carbon fiber-based insulation substrates have a lower bulk density and more voids than carbon-based sheets, it is difficult to achieve strong adhesion with thermosetting resins; if this temporary adhesion is not performed, the adhesive strength between the carbon fiber-based insulation substrate and the adhesive sheet after carbonization is weak and the substrate will easily peel off.

[0017] On the other hand, the carbon-based sheet has a higher bulk density than the carbon fiber-based heat insulation substrate, has fewer voids, and has more contact points with the adhesive sheet, so the carbon-based sheet and the adhesive sheet can be firmly bonded by heat curing and carbonization in a pressurized environment without temporary bonding. It is preferable to perform the laminate material preparation step at a temperature lower than the softening point (cooling the laminate after temporary bonding once), because this eliminates the fluidity of the thermosetting resin and enhances the effect of temporary bonding, and the thermosetting resin constituting the adhesive sheet softens again during the temperature rise in the bonding step, which acts to enhance the adhesion between the carbon-based sheet and the adhesive sheet. In addition, during this temperature rise, the temperature may be held at or above the softening point for a certain period of time, as in the temporary bonding step.

[0018] Furthermore, the method of performing multiple heating steps (temporary adhesion step and adhesion step) using an adhesive sheet is simpler than the method of applying and impregnating a binder containing graphite and a binder to a carbon fiber-based heat insulation substrate, or the method of using an adhesive sheet obtained by impregnating a carbon fiber nonwoven fabric sheet with a binder, and does not cause uneven impregnation of the binder or contamination of the manufacturing environment. This reduces the amount of work required, prevents contamination of the manufacturing environment, and prevents poor adhesion and poor appearance due to uneven impregnation.

[0019] Therefore, by adopting the above-mentioned manufacturing method, it is possible to reliably bond a carbon-based sheet to a carbon fiber-based heat insulation substrate in a simple manner without causing contamination of the manufacturing environment. This carbon-based sheet can impart effects such as gas permeation prevention, suppression of surface deterioration, improved handling (prevention of carbon fiber loss or adhesion during handling), and improved strength to the molded heat insulation material.

[0020] Conversely, a method in which a carbon-based sheet and an adhesive sheet are first temporarily bonded together, the temporarily bonded laminate is cooled and then laminated on top of a carbon fiber-based insulation substrate, and then the temperature is maintained at or above the softening point for a certain period of time during the heating step in order to increase the adhesion between the carbon fiber-based insulation substrate and the adhesive sheet is not preferred because this is likely to result in differences in adhesive strength on both sides of the adhesive sheet and is costly.

[0021] Here, the temporary adhesion step is performed at a temperature equal to or higher than the softening point of the thermosetting resin and lower than the curing temperature and the heat resistance temperature of the release film. The temporary adhesion step is preferably performed within a temperature range of the softening point of the thermosetting resin to the softening point + 30°C, more preferably within a temperature range of the softening point to the softening point + 20°C, and even more preferably within a temperature range of the softening point to the softening point + 10°C. From the viewpoint of a balance between cost and sufficient softening, it is preferable to perform the temporary adhesion step within the above temperature range.

[0022] In addition, the preferred heating time in the temporary adhesion step (retention time in the above temperature range) is influenced by the heating temperature (temperature difference from the softening point), but is preferably 2 minutes or more, more preferably 5 minutes or more, and even more preferably 7 minutes or more. If the retention time is too long, the cost will increase, so it is preferably 20 minutes or less, more preferably 15 minutes or less, and even more preferably 10 minutes or less.

[0023] In addition, if pressure is not applied to the laminated material in the adhesion step, the adhesion of the three materials becomes insufficient, and peeling is likely to occur after heat treatment. Preferably, the pressure is 0.01 to 0.20 MPa, more preferably 0.05 to 0.10 MPa. Note that, due to the pressure applied in the adhesion step, a part of the thermosetting resin constituting the adhesive sheet may move to the carbon fiber-based heat insulation substrate side or the carbon-based sheet side, and therefore, the carbonized product of the thermosetting resin due to the heat treatment may also be contained in the carbon fiber-based heat insulation substrate or the carbon-based sheet.

[0024] Even if both the carbon fiber-based heat insulation substrate and the carbon-based sheet have flexibility, the flexibility of the carbon fiber-based heat insulation material may be lost due to the carbonized thermosetting resin constituting the adhesive sheet after the adhesion step or the heat treatment step. Therefore, it is preferable to process the carbon fiber-based heat insulation material into the desired shape before the heat treatment step (for example, during the temporary adhesion step or the adhesion step).

[0025] The shape of the carbon fiber insulating material obtained after the heat treatment is not particularly limited and can be appropriately set according to the intended use, and can be, for example, cylindrical, flat, etc.

[0026] Here, the carbon fiber-based heat insulating substrate means a carbon fiber felt (nonwoven fabric) in which carbon fibers are intertwined, or a carbon fiber-based molded heat insulating material having a carbon fiber felt and a carbon matrix that covers and binds the surface of the carbon fibers that constitute the carbon fiber felt. The molded heat insulating material also includes one in which short carbon fibers are molded together with a resin and the resin is carbonized, and one in which carbon fiber felt is laminated or wound into a cylindrical shape multiple times. In other words, the carbon fiber-based heat insulating substrate is made of carbonaceous matter, and no components other than carbon are added. For example, a prepreg in which carbon fiber felt is impregnated with a resin (binder) is an intermediate product for producing a carbon fiber-based heat insulating substrate, but this is not used as a carbon fiber-based heat insulating substrate in the manufacturing method of the present invention.

[0027] The carbon-based sheet has a larger bulk density than the carbon fiber-based heat insulation substrate. In addition, the carbon-based sheet and the carbon fiber-based heat insulation substrate may have different compositions and three-dimensional shapes. For example, the compositions are different when there is a carbon matrix or the mass ratio of the carbon matrix to the carbon fiber is different, when there is a particulate carbon or the blending ratio is different, when one is made of only amorphous carbon and the other contains graphitic carbon, etc. In addition, the three-dimensional shapes are different when there is a difference between a woven fabric and a nonwoven fabric, a difference in thickness, etc.

[0028] The carbon-based sheet is not particularly limited, and may be, for example, an expanded graphite sheet, a carbon fiber cloth, or a sheet made of a carbon fiber reinforced carbon composite material. Here, the expanded graphite refers to a graphite layer that has been expanded by chemical treatment or the like, the carbon fiber cloth refers to a woven fabric (woven cloth) made of carbon fiber, and the carbon fiber reinforced carbon composite material refers to a fiber reinforced composite material having carbon fiber and a carbon matrix, which may further contain carbon particles, milled carbon fiber (short fiber), etc. In addition, it is preferable that the carbon-based sheet is made of carbonaceous material and does not contain any material other than carbon.

[0029] The effects attributable to the surface layer may vary depending on the material of the carbon-based sheet that forms the surface layer. For example, when an expanded graphite sheet is used, effects such as preventing gas permeation are obtained, and when a sheet made of carbon fiber cloth or carbon fiber reinforced carbon composite material is used, effects such as suppressing surface deterioration, improving handling properties, and improving strength are obtained. In other words, the material of the carbon-based sheet may be appropriately selected depending on the use and purpose of the carbon fiber-based insulation material (i.e., the function required of the surface layer).

[0030] In this specification, unless otherwise specified, the term carbon includes graphitic carbon and amorphous carbon.

[0031] The softening point refers to the temperature at which the resin begins to deform when the temperature is increased. Not all thermosetting resins have a softening point, and thermosetting resins without a softening point (such as resins that have been subjected to infusibility treatment or hardening treatment) are not used in the present invention. The softening point of a thermosetting resin can be, for example, a catalog value of a commercially available product, or can be determined according to JIS K 5601-2-2.

[0032] In addition, the catalog value of the softening point of a commercially available thermosetting resin may not be a single specific temperature but may have a range. In this case, a temperature equal to or higher than the softening point means a temperature equal to or higher than the lower limit. The softening step is preferably performed at a temperature equal to or higher than the median value, more preferably equal to or higher than the upper limit value.

[0033] The thermosetting resin is not particularly limited as long as it has a softening point. Phenol resin, furan resin, polyimide resin, epoxy resin, etc. can be used, and among them, phenol resin is preferable.

[0034] The softening point of the thermosetting resin (if there is a range, the lower limit) is preferably 140 to 90°C, more preferably 120 to 90°C, and even more preferably 100 to 90°C. If the softening point is too high, high temperatures must be applied in the temporary adhesion step, which increases costs. If the softening point is too low, the resin softens even when working at room temperature, reducing workability.

[0035] The residual carbon ratio of the thermosetting resin (mass after firing / mass before firing x 100) is preferably 30 to 70%, more preferably 35 to 65%, and even more preferably 40 to 60%. The bulk density of the adhesive sheet after heat treatment is preferably greater than the bulk density of the carbon fiber-based heat insulation substrate.

[0036] The bulk density of the carbon-based sheet is 0.5 to 2.0 g / cm 3 and preferably 1.0 to 1.6 g / cm 3 It is more preferable that the bulk density of the carbon fiber-based heat insulating substrate is 0.05 to 0.25 g / cm. 3 and preferably 0.08 to 0.20 g / cm 3 It is more preferable that:

[0037] In the above configuration, the carbon fiber-based heat insulating substrate may be configured to not contain graphite particles. This configuration can prevent the adverse effects caused by the impurities contained in the graphite particles. More preferably, the carbon fiber-based heat insulating substrate is configured to not contain amorphous carbon particles either. Note that the carbon-based sheet may contain graphite particles, but it is more preferable that the carbon-based sheet is also configured to not contain graphite particles.

[0038] In the above configuration, the thickness of the carbon fiber-based heat insulation substrate can be greater than the thickness of the adhesive sheet and the thickness of the carbon-based sheet. The thickness of the carbon fiber-based heat insulation substrate is preferably relatively thick from the viewpoint of ensuring heat insulation function, and the thickness of the adhesive sheet and the carbon-based sheet is preferably relatively thin because the carbon fiber-based heat insulation material becomes bulky if the thickness is too thick. In addition, the relationship between the thickness of the adhesive sheet and the thickness of the carbon-based sheet does not need to be particularly limited, but the thickness of the carbon-based sheet is preferably less than the thickness of the adhesive sheet, and more preferably less than the thickness of the adhesive sheet.

[0039] In the above configuration, the thickness of the adhesive sheet before heating is preferably 0.2 to 5.0 mm. If the thickness of the adhesive sheet is too thin, sufficient adhesive strength may not be obtained, and if it is too thick, the carbon fiber-based heat insulating material becomes bulky, so it is preferable that the thickness is within the above range. More preferably, the thickness of the adhesive sheet is 0.5 to 3.0 mm.

[0040] In the above configuration, the heat treatment step is preferably performed in an inert atmosphere at 1000 to 2500°C. The atmosphere in the heat treatment step is preferably an inert atmosphere so that carbon does not react with oxygen and gasify. In addition, from the viewpoint of carbonization efficiency and cost, the heat treatment temperature is preferably 1000 to 2500°C, and graphitization of carbonaceous matter does not progress easily in this temperature range. In addition, the heat treatment time varies depending on the heat treatment temperature, but is set with attention paid to the fact that if it is too long, the cost will be high, and if it is too short, the carbonization of the binder may be insufficient.

[0041] The carbon fiber constituting the carbon fiber-based heat insulation substrate is not particularly limited, and pitch-based carbon fiber, rayon-based carbon fiber, polyacrylonitrile-based carbon fiber, phenolic resin-based carbon fiber, cellulose-based carbon fiber, etc. can be used. In addition, when the carbon-based sheet contains carbon fiber, the carbon fiber may be the same as above. It is preferable that the carbon fiber constituting the carbon fiber-based heat insulation substrate and the carbon-based sheet is the same type of carbon fiber.

[0042] The carbon fiber-based insulation material obtained by the above-mentioned manufacturing method has the following configuration. A carbon fiber-based insulation material comprising: a carbon fiber-based insulation substrate layer; an adhesive layer in contact with the carbon fiber-based insulation substrate layer, the adhesive layer being made of a thermosetting resin sheet that has been softened, then hardened and further carbonized; and a carbon-based surface layer in contact with the adhesive layer, wherein the bulk density of the carbon-based surface layer is greater than the bulk density of the carbon fiber-based insulation substrate layer. Effect of the Invention

[0043] As described above, according to the present invention, a surface layer can be adhered to a carbon fiber-based insulation substrate by a simple method, and a carbon fiber-based insulation material having functions imparted by the surface layer can be realized. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] (Embodiment) The embodiment for carrying out the present invention will be described below. The carbon fiber-based heat insulation material according to the present invention includes a carbon fiber-based heat insulation substrate layer, an adhesive layer in contact with the carbon fiber-based heat insulation substrate layer, and a carbon-based surface layer in contact with the adhesive layer. The adhesive layer is made of a thermosetting resin sheet that is softened, cured, and carbonized, and the carbon-based surface layer has a bulk density greater than that of the carbon fiber-based heat insulation substrate layer. In addition, the bulk density of the adhesive layer is preferably greater than that of the carbon fiber-based heat insulation substrate layer.

[0045] The carbon fiber-based heat insulation substrate layer may be a carbon fiber felt in which carbon fibers are entangled, or may be a molded heat insulation material having a carbon fiber felt and a carbon matrix made of carbonaceous material that covers and binds the surface of the carbon fibers of the carbon fiber felt. The carbon fiber-based heat insulation substrate layer preferably does not contain graphite particles. In addition, the carbon fiber-based heat insulation substrate layer may be configured to contain the same adhesive carbon as that contained in the adhesive layer in the region on the adhesive layer side. The carbon fiber felt and molded heat insulation material are not particularly limited, and commercially available materials can be used.

[0046] The carbon fiber of the carbon fiber-based heat insulation substrate layer is not particularly limited, and for example, petroleum pitch-based, polyacrylonitrile (PAN)-based, rayon-based, phenolic resin-based, cellulose-based, and other carbon fibers can be used alone or in combination. The microscopic structure of the carbon fiber is not particularly limited, and only those having the same shape (wound type, straight type, cross-sectional shape, etc.) may be used, or those having different structures may be mixed. However, the type of carbon fiber and its microscopic structure affect the physical properties of the carbon fiber-based heat insulation material to be manufactured, so it is best to select them appropriately depending on the application.

[0047] When a molded insulation material is used as the carbon fiber-based insulation substrate layer, the carbon matrix may be carbonaceous and is not particularly limited. The compound from which the carbon matrix is ​​derived is not particularly limited, but it is preferably derived from a resin material that can be impregnated into the carbon fiber felt. As such a resin material, a thermosetting resin such as a phenol resin, a furan resin, a polyimide resin, or an epoxy resin is preferable. In addition, only one type of thermosetting resin may be used, or two or more types may be mixed and used. In addition, a carbonized material of a thermosetting resin has a characteristic that it is difficult to graphitize by heat treatment (it is difficult to graphitize).

[0048] Carbon fiber felt used as a material for a molded insulation material or as a carbon fiber-based insulation substrate layer as it is can be prepared by a known method, preferably a method that allows carbon fibers to be easily oriented three-dimensionally. Examples of methods for forming fiber felt include a method in which the fibers are opened by a fiber opener, raised by air pressure and piled up, and then needle punched, a method in which the fibers are stirred and mixed in a solution and piled up on a papermaking net, and a method in which the fiber felt is spun by a carding means such as a carding machine and then needle punched.

[0049] The adhesive layer is made of a thermosetting resin that has been softened, cured, and then carbonized. The thermosetting resin is not particularly limited as long as it has a softening point, and may be a phenolic resin, a furan resin, a polyimide resin, an epoxy resin, or the like, among which a phenolic resin is preferred.

[0050] The carbon-based surface layer is adhered to one surface of the carbon fiber-based insulation material (the surface opposite to the carbon fiber-based insulation substrate layer) using an adhesive layer in order to impart functions such as improved handling and gas permeation prevention to the carbon fiber-based insulation material. The carbon-based surface layer is made of carbonaceous matter, and may be made of, for example, expanded graphite, carbon fiber woven fabric, or carbon fiber reinforced carbon composite material, or may further include a carbon matrix similar to that of the carbon fiber-based insulation substrate.

[0051] Here, the bulk density of the carbon fiber-based heat insulation substrate layer is 0.05 to 0.25 g / cm 3 and preferably 0.08 to 0.20 g / cm 3 It is more preferable that the bulk density of the adhesive layer is 0.2 to 1.0 g / cm. 3 and preferably 0.4 to 0.8 g / cm 3 It is more preferable that the bulk density of the carbon-based surface layer is 0.5 to 2.0 g / cm. 3 and preferably 1.0 to 1.6 g / cm 3 It is more preferable that:

[0052] The thickness of the carbon fiber-based heat insulating substrate layer can be appropriately set according to the required heat insulating function, and is not particularly limited, but is preferably 10 to 180 mm. The thickness of the adhesive layer is preferably 0.1 to 1.0 mm, more preferably 0.2 to 0.5 mm. The thickness of the carbon-based surface layer is preferably 0.2 to 2.0 mm.

[0053] Next, a method for producing the carbon fiber-based thermal insulation material according to this embodiment will be described.

[0054] (Layer step) A carbon fiber-based heat insulating substrate (for example, a commercially available carbon fiber-based molded heat insulating material) and an adhesive sheet made of a thermosetting resin (for example, a phenolic resin) having a softening point are laminated together.

[0055] (Temporary adhesion step) The laminate is heated to a temperature equal to or higher than the softening point to soften the thermosetting resin, thereby temporarily bonding the carbon fiber-based heat insulating substrate and the adhesive sheet.

[0056] (Laminated material preparation step) A carbon-based sheet having a bulk density greater than that of the carbon fiber-based heat insulating substrate is laminated on the adhesive sheet to form a laminate material.

[0057] (Adhesion step) The carbon fiber-based heat insulation substrate and the carbon-based sheet are heated while being pressed from the side, and the thermosetting resin is thermally cured to bond the carbon fiber-based heat insulation substrate, the adhesive sheet, and the carbon-based sheet. The heating temperature is equal to or higher than the curing temperature of the thermosetting resin and lower than the carbonization temperature. The pressure is preferably 0.01 to 0.20 MPa.

[0058] (Heat treatment step) The laminated material after bonding is heat-treated to carbonize the thermosetting resin. The heat treatment atmosphere is preferably an inert atmosphere. The treatment temperature is preferably 1000 to 2500°C.

[0059] This manufacturing method provides a carbon fiber-based thermal insulation material comprising a carbon fiber-based thermal insulation substrate layer, an adhesive layer in contact with the carbon fiber-based thermal insulation substrate layer, the adhesive layer being formed by thermally curing and carbonizing a softened thermosetting resin, and a carbon-based surface layer in contact with the adhesive layer. In other words, the carbon fiber-based thermal insulation substrate becomes the carbon fiber-based thermal insulation substrate layer, the adhesive sheet becomes the adhesive layer, and the carbon-based sheet becomes the carbon-based surface layer.

[0060] (Example) The present invention will be described in more detail with reference to examples. Note that steps for which no particular temperature is specified were carried out at room temperature (25° C.).

[0061] Example 1 (Layer step) Molded insulation material as a carbon fiber-based insulation base material (Osaka Gas Chemicals' DonaCarbo RI DON-1000, flat plate shape with a thickness of 30 mm, width of 1 m, and length of 1.5 m, bulk density of 0.13 g / cm 3) and a phenolic resin adhesive sheet (manufactured by Sumitomo Bakelite, 0.8 mm thick, with release films on both sides). The release film on one side of the adhesive sheet was peeled off, and the adhesive sheet was placed on the molded insulation material so that it was in contact with the other side. The softening point of this phenolic resin is 100°C, the hardening temperature is 180°C, and the residual carbon rate is 40%.

[0062] (Temporary adhesion step) The laminate was then heated in an air atmosphere at 100°C for 10 minutes to soften the phenolic resin constituting the adhesive sheet, temporarily bonding the carbon fiber-based heat insulation substrate and the adhesive sheet. The release film on the other side of the adhesive sheet maintained its original state without being deformed by the heating.

[0063] (Laminated material preparation step) The release film on the other side of the adhesive sheet was peeled off, and an expanded graphite sheet (Permafoil PF-38, manufactured by Toyo Tanso, thickness 0.38 mm, width 1 m, length 1.5 m, bulk density 1.0 g / cm) was placed on top of the adhesive sheet as a carbon-based sheet. 3 ) was placed on the plate to obtain a laminated material.

[0064] (Adhesion step) After this, the laminated material was heated at 200°C for 30 minutes while applying a surface pressure of 0.05 MPa from the carbon fiber-based insulation substrate side and the carbon-based sheet side using a heated compression press to thermally cure the phenolic resin that constitutes the adhesive sheet, thereby bonding the carbon fiber-based insulation substrate, adhesive sheet and carbon-based sheet together.

[0065] (Heat treatment step) The laminated material after bonding was heat treated at 2000° C. for 5 hours in an inert atmosphere to carbonize the heat-cured phenolic resin, thereby producing a carbon fiber-based insulation material with a surface layer according to Example 1.

[0066] Comparative Example 1 In the lamination step, temporary adhesion step, and laminate material preparation step, adhesive was applied to the surface of the carbon fiber-based insulation substrate at a rate of 500 g / m without using an adhesive sheet. 2A carbon fiber-based heat insulating material according to Comparative Example 1 was produced in the same manner as in Example 1, except that the carbon fiber-based heat insulating material was uniformly coated and impregnated so that the thickness of the carbon fiber-based heat insulating material was 100 μm, and a carbon-based sheet was placed on the carbon fiber-based heat insulating material to obtain a laminated material. As the adhesive, a mixture of 60 parts by mass of resol-based phenolic resin, 15 parts by mass of natural graphite particles (average particle size 30 μm), 5 parts by mass of milled carbon fiber (Dona Carbo Milled SG-241 manufactured by Osaka Gas Chemicals, fiber diameter 13 μm, average fiber length 0.13 mm), and 20 parts by mass of methanol as a solvent was used. Note that the methanol was volatilized by heating in the adhesion step. The lamination step was completed in about 30 minutes.

[0067] Comparative Example 2 An attempt was made to temporarily bond the carbon fiber-based insulation substrate, adhesive sheet, and carbon-based sheet at the same time by laminating an adhesive sheet on the carbon fiber-based insulation substrate and then laminating a carbon-based sheet on top of that; however, it was not possible to peel the release film from the adhesive sheet on the carbon fiber-based insulation substrate, and it was not possible to produce a carbon fiber-based insulation material.

[0068] Comparative Example 3 An attempt was made to produce a carbon fiber-based insulation material according to Comparative Example 2 in the same manner as in Example 1, except that the lamination order of the carbon fiber-based insulation substrate and the carbon-based sheet to the adhesive sheet was reversed (the target for temporary adhesion to the adhesive sheet was the carbon-based sheet, not the carbon fiber-based insulation substrate). However, after firing, the adhesive sheet and the carbon fiber-based insulation substrate peeled off, and it was not possible to produce a carbon fiber-based insulation material with a surface layer.

[0069] These results show that in order to produce a carbon fiber-based insulation material with a surface layer using an adhesive sheet made of a thermosetting resin, temporary adhesion between the carbon fiber-based insulation substrate and the adhesive sheet is essential.

[0070] (Judgment of workability) The working time was almost the same in Example 1 and Comparative Example 1. However, the heating time in Example 1 was longer than that in Comparative Example 1, and the time required for lamination was shorter by more than 20 minutes in Example 1. In other words, the work could be carried out more easily in Example 1.

[0071] (Peel test) The carbon fiber insulation materials according to the above Example 1 and Comparative Example 1 were cut into test pieces with a width of 30 mm, a length of 30 mm, and a thickness of 30 mm. The test pieces were peeled (90° peeled) in a direction perpendicular to the lamination direction of each layer of the carbon fiber insulation material at a crosshead speed of 50 mm / min. As a result, in all test pieces, the carbon fiber insulation substrate was destroyed before peeling between the layers occurred. The thickness was adjusted by cutting the carbon fiber insulation substrate layer to reduce the thickness.

[0072] The fact that the carbon fiber-based heat insulating substrate was destroyed in the peel test means that the adhesion between the layers was strong. In other words, the adhesion between the layers of the heat insulating material in both Example 1 and Comparative Example 1 was excellent.

[0073] (Durability test) The surface-layered molded heat insulating materials of Example 1 and Comparative Example 1 were cut into test pieces with a width of 50 mm, a length of 50 mm, and a thickness of 30 mm. The test pieces were placed in an electric furnace and oxidation durability evaluation was performed under conditions of a temperature of 700 ° C and an air volume of 2 L / min. At this time, an alumina jig (outer dimensions: width 60 mm, length 60 mm, thickness 30 mm, inner dimensions: width 50 mm, length 50 mm, thickness 30 mm) was attached to the test piece so that only the surface layer was exposed, so that the wear progressed only from the carbon-based sheet side. The oxidation wear rate (weight loss rate) after 3 hours was about 10% in Example 1 and about 11% in Comparative Example 1, and it was confirmed that the durability performance of the heat insulating materials was excellent in both cases and that the durability performance was enhanced by the expanded graphite sheet.

[0074] From the above, it is evident that the present invention makes it possible to form a strong surface layer without any defects in appearance on a carbon fiber-based insulation material using a simple method. [Industrial Applicability]

[0075] As described above, according to the present invention, a surface layer can be firmly adhered to a carbon fiber-based insulation material by a simple method, and the functionality of a surface layer can be imparted to the carbon fiber-based insulation material, so that the present invention has great industrial applicability.

Claims

1. A lamination step of laminating a carbon fiber-based heat insulation substrate and an adhesive sheet made of a thermosetting resin having a softening point; After the lamination step, a temporary bonding step of heating to a temperature equal to or higher than the softening point to soften the thermosetting resin and temporarily bonding the carbon fiber-based heat insulation substrate and the adhesive sheet; After the temporary adhesion step, a laminated material preparation step is performed in which a carbon-based sheet is laminated on the adhesive sheet to form a laminated material; After the laminated material preparation step, a bonding step of heating the laminated material to a temperature equal to or higher than the curing temperature of the thermosetting resin while applying pressure to the laminated material from the carbon fiber-based heat insulation substrate side and the carbon-based sheet side; A heat treatment step of heat treating the laminated material in an inert atmosphere after the bonding step to carbonize the thermosetting resin, A method for producing a carbon fiber-based insulation material, wherein the bulk density of the carbon-based sheet is greater than the bulk density of the carbon fiber-based insulation substrate.

2. The laminate preparation step is carried out at a temperature lower than the softening point; A method for producing the carbon fiber insulation material according to claim 1.

3. The carbon fiber-based insulation substrate does not contain graphite particles.

3. The method for producing the carbon fiber-based insulation material according to claim 1 or 2.

4. The thickness of the carbon fiber-based heat insulation substrate is greater than the thickness of the adhesive sheet and the thickness of the carbon-based sheet; A method for producing a carbon fiber-based insulation material according to claim 1, 2 or 3.

5. The thickness of the adhesive sheet is 0.2 to 5.0 mm. A method for producing a carbon fiber-based thermal insulation material according to any one of claims 1 to 4.