JP7198215B2 - Molded heat insulating material with surface layer and method for manufacturing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a molded heat insulating material using carbon fiber, and more particularly to a molded heat insulating material provided with a surface layer for enhancing durability.

BACKGROUND ART Carbon fiber-based heat insulating materials are used in various applications because they are excellent in thermal stability and heat insulating performance and light in weight. Such heat insulating materials include carbon fiber felt formed by entangling carbon fibers, and carbon fiber molded heat insulating materials containing carbon fibers and carbonized resin materials. Carbon fiber felt has an advantage of being excellent in flexibility, and carbon fiber-based molded heat insulating material has an advantage of being excellent in shape stability and capable of fine processing.

Molded insulation materials using carbon fibers include felt-based molded insulation materials that are carbonized by impregnating carbon fiber felt with a resin material and carbonizing carbon fiber, and carbon fiber milled (short) by a wet or dry method. There is a short fiber-based molded heat insulating material that is formed by molding and carbonizing synthetic resin.

Which heat insulating material to use is appropriately selected according to the intended use and application. Carbon fiber molded heat insulating materials are excellent in thermal stability, heat insulation performance, and shape stability. It is used as a heat insulating material for high-temperature furnaces such as hot isostatic pressure furnaces (HIP furnaces) and vacuum deposition furnaces.

However, in a high-temperature furnace, an oxidizing gas such as oxygen gas may be mixed into the manufacturing atmosphere. Oxygen gas has a high activity (reactivity), and carbon fiber-based molded heat insulating material reacts with oxygen gas to produce carbon oxides (carbon monoxide, carbon dioxide, etc.). As a result, the carbon fibers in particular deteriorate, the skeletal structure composed of the carbon fibers collapses, and the heat insulating effect obtained by the skeletal structure forming a large number of spaces decreases. In addition, this deterioration may cause the carbon fibers, in particular, to be pulverized and released into the atmosphere in the furnace, thereby degrading the product quality.

In particular, in heat treatment furnaces and HIP furnaces in which the inside of the furnace is set to near normal pressure or high pressure, or in which argon gas or nitrogen gas is flowed, oxidizing gas easily permeates inside the formed heat insulating material due to air currents and pressure differences, and the above problems occur. will appear prominently.

In order to solve this problem, Patent Document 1 proposes a technique of adhering an expanded graphite sheet obtained by rolling expanded graphite to the surface of a molded heat insulating material.

JP-A-2005-133032

According to this technique, the expanded graphite sheet, which is substantially gas-impermeable, is said to prevent permeation of gas into the interior of the molded insulation material, thereby preventing deterioration of the molded insulation material.

When the inventors of the present invention have studied the technique of Patent Document 1, they have found the following problems. The expanded graphite sheet is formed by rolling expanded graphite into a sheet, and does not contain a binder component that binds the graphite layers together. For this reason, if the expanded graphite sheet is used for a long period of time in a reactive gas atmosphere or in an environment where oxidative wear and tear is likely to occur, deterioration such as dissociation will become noticeable on the surface, and the graphite layer will peel off. However, there is a problem in that the gas permeation prevention function is lost due to the progress of the cracking, and it becomes impossible to extend the life of the molded heat insulating material.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is a molding that can suppress permeation of gas into the inside of a molded heat insulating material for a long period of time without reducing the heat insulating effect or increasing unnecessary costs. The purpose is to provide thermal insulation.

The present invention relating to a molded heat insulating material for solving the above problems is configured as follows.
A carbon fiber-based molded heat insulating material, one expanded graphite sheet laminated on one surface of the carbon fiber-based molded heat insulating material, and a carbon fiber sheet protective layer laminated in contact with the expanded graphite sheet. The carbon fiber sheet protective layer includes a carbon fiber nonwoven fabric sheet in which carbon fibers are entangled and a matrix made of carbonaceous matter covering the carbon fiber surface of the carbon fiber nonwoven fabric sheet, and the carbon fiber molded heat insulating material molded insulation with a surface layer, wherein the expanded graphite sheet and the carbon fiber sheet protective layer are not disposed on the other surface of the molded insulation.

In the present invention, the expanded graphite sheet and the protective layer of the carbon fiber sheet are laminated in order on the molded carbon fiber heat insulating material. Here, the expanded graphite sheet acts to prevent permeation of gas into the molded insulation. In addition, when the oxidizing gas is generated, the carbon fiber sheet protective layer reacts with the oxidizing gas before the expanded graphite sheet reacts, so early deterioration of the expanded graphite sheet is prevented. As a result, the effect of preventing gas permeation by the expanded graphite sheet can be obtained for a long period of time. That is, the surface layer consisting of the expanded graphite sheet and the carbon fiber sheet protective layer acts to prevent permeation of gas into the molded heat insulating material for a long period of time.

Here, a commercially available carbon fiber-based molded heat insulating material can be used. For example, the above-mentioned felt-based molded heat insulating material and short fiber-based molded heat insulating material can be used. Moreover, a commercially available expanded graphite sheet can be used. Moreover, as the carbon fiber nonwoven fabric sheet, a commercially available one can be used, and for example, a carbon fiber sheet, carbon fiber paper, or carbon fiber felt can be used.

The carbonaceous matrix coats the surface of the carbon fiber and binds the protective layer of the carbon fiber sheet and the expanded graphite sheet. Although the matrix is not particularly limited as long as it is carbonaceous, it is more preferably a carbonized thermosetting resin.

Further, the expanded graphite sheet may be laminated in contact with the carbon fiber-based molded heat insulating material, and a layer for enhancing adhesion may be interposed between the two. When the expanded graphite sheet is laminated in contact with the molded heat insulating material, it is preferable that a carbonized product obtained by carbonizing an adhesive resin such as a thermosetting resin exists in the vicinity of the interface between the two. In addition, since laminating two or more expanded graphite sheets increases the cost, one expanded graphite sheet is used .

On the other hand, the carbon fiber sheet protective layer is in direct contact with the expanded graphite sheet. The carbon fiber sheet protective layer may have a structure in which two or more layers are laminated in order to obtain a desired thickness.

In the above structure, the carbon fiber sheet protective layer preferably has a bulk density of 0.1 to 0.5 g/cm ³ and a thickness of 0.3 to 3 mm.

As the bulk density of the carbon fiber sheet protective layer becomes smaller, the protective effect of the expanded graphite sheet becomes smaller. On the other hand, as the bulk density of the carbon fiber sheet protective layer increases, it becomes difficult to adhere to the expanded graphite sheet. From the balance between the two, the bulk density of the carbon fiber sheet protective layer is preferably 0.1-0.5 g/cm ³ , more preferably 0.2-0.4 g/cm 3 , and 0.2-0.4 g/cm ³ . More preferably, it is 2 to 0.3 g/cm ³ .

Moreover, as the thickness of the protective layer of the carbon fiber sheet becomes smaller, the protective effect of the expanded graphite sheet becomes smaller. On the other hand, when the thickness of the protective layer of the carbon fiber sheet increases, the cost increases accordingly. From the balance between the two, the thickness of the carbon fiber sheet protective layer is preferably 0.3 to 3 mm, more preferably 0.4 to 2.0 mm, and more preferably 0.5 to 1.5 mm. More preferred.

In the above structure, it is preferable that the carbon fibers forming the protective layer of the carbon fiber sheet are isotropic pitch-based carbon fibers.

Isotropic pitch-based carbon fibers are preferable because they are soft and less likely to damage the expanded graphite sheet and have good adhesion to the expanded graphite sheet.

A first aspect of the present invention relating to a method for manufacturing a molded heat insulating material for solving the above problems is constructed as follows.
A resin-impregnated carbon fiber nonwoven fabric sheet manufacturing step of impregnating a carbon fiber nonwoven fabric sheet with a thermosetting resin before thermosetting, and one expanded graphite sheet is attached to one surface and an expanded graphite sheet is attached to the other surface. a lamination step of laminating at least one carbon fiber nonwoven fabric sheet only on the surface of the expanded graphite sheet of the carbon fiber-based molded heat insulating material that has not been laminated to form a laminate; A binding step of heating to a resin thermosetting temperature or higher to bind the carbon fiber nonwoven fabric sheet to the surface of the expanded graphite sheet; and a carbonization step of carbonizing a thermosetting resin.

A second aspect of the present invention relating to a method for manufacturing a molded heat insulating material for solving the above problems is constructed as follows.
A prepreg manufacturing step of impregnating a carbon fiber structure in which carbon fibers are entangled with a thermosetting resin before thermosetting to form a prepreg, and a resin-impregnated carbon impregnating a carbon fiber nonwoven fabric sheet with the thermosetting resin before thermosetting. a step of preparing a fiber nonwoven fabric sheet, laminating one expanded graphite sheet only on one surface of the prepreg, and further laminating and laminating at least one resin-impregnated carbon fiber nonwoven fabric sheet only on the surface of the expanded graphite sheet. A step of laminating to form a body, and a step of bonding the prepreg, the expanded graphite sheet, and the carbon fiber nonwoven fabric sheet by heating the laminate to a thermosetting temperature of the thermosetting resin or higher while pressing the laminate. and a carbonization step of heat-treating the bonded laminate in an inert gas atmosphere to carbonize the thermosetting resin.

The difference between the above two manufacturing methods is that when laminating the resin-impregnated carbon fiber nonwoven fabric sheets, the molded heat insulating material portion is already carbonized (first manufacturing method of the present invention) or not carbonized (second manufacturing method). of the present invention). By adopting any one of these, it is possible to manufacture the molded heat insulating material with a surface layer according to the present invention by a simple and low-cost method. A carbon fiber structure in which carbon fibers are entangled may be either a felt type or a short fiber type.

As described above, according to the present invention, it is possible to realize a long-life carbon fiber-based molded heat insulating material with a surface layer that can suppress permeation of gas at low cost.

FIG. 1 is a cross-sectional micrograph of the vicinity of the surface of a molded heat insulating material with a surface layer according to the present invention.

FIG. 2 is a micrograph showing the state of the surface of the expanded graphite sheet after durability test 2 of the molded heat insulating material with a surface layer according to Comparative Example 1. FIG.

(Embodiment)
The molded heat insulating material with a surface layer according to the present invention comprises a carbon fiber molded heat insulating material, an expanded graphite sheet laminated on the carbon fiber molded heat insulating material, and a carbon fiber sheet protective layer laminated in contact with the expanded graphite sheet. , is equipped with Here, the carbon fiber sheet protective layer has a carbon fiber non-woven fabric sheet in which carbon fibers are entangled and a matrix made of carbonaceous matter covering the carbon fiber surface of the carbon fiber non-woven fabric sheet. That is, the molded heat insulating material with a surface layer according to the present invention has a structure in which a surface layer composed of an expanded graphite sheet and a carbon fiber sheet protective layer is provided on a carbon fiber type molded heat insulating material. The carbon fiber sheet protective layer is the outermost layer.

In the above configuration, the expanded graphite sheet acts to prevent permeation of gas into the molded heat insulating material. Further, when the oxidizing gas is generated, the protective layer of the carbon fiber sheet reacts with the oxidizing gas before the expanded graphite sheet reacts, so early wear of the expanded graphite sheet is prevented. As a result, the effect of preventing gas permeation by the expanded graphite sheet can be obtained for a long period of time. That is, the two-layered surface layer of the expanded graphite sheet and the carbon fiber sheet protective layer acts to prevent permeation of gas into the molded heat insulating material for a long period of time.

Here, a layer (adhesive layer) may be provided between the carbon fiber-based molded heat insulating material and the expanded graphite sheet to enhance the adhesion between the two. This layer can be made, for example, by carbonizing a carbon fiber nonwoven fabric sheet impregnated with a thermosetting resin. If the two can be firmly adhered even without an adhesive layer, the adhesive layer may not be provided.

Here, the carbon fiber constituting the carbon fiber molded heat insulating material, the adhesive layer, the carbon fiber sheet protective layer, etc. is not particularly limited, and for example, an anisotropic or isotropic pitch derived from coal or petroleum , polyacrylonitrile (PAN)-based, rayon-based, phenol-based, and cellulose-based carbon fibers can be used singly or in combination. Among them, isotropic pitch-based carbon fiber is preferable because it is soft and hardly damages the graphite sheet, and has good adhesion to the graphite sheet.

The microscopic structure of any carbon fiber is not particularly limited, and only those having the same shape (crimped type, straight type, diameter, length, etc.) may be used, or those having different structures may be used. may be mixed. However, since the type of carbon fiber and its microscopic structure affect the physical properties of the molded heat insulating material with a surface layer to be manufactured, they should be appropriately selected according to the application.

The carbon fiber-based molded heat insulating material is not particularly limited, and a commercially available one can be used as appropriate. For example, a laminate of a plurality of carbon fiber sheets having a thickness of about 3 to 15 mm can be used. Also, the length and width are not particularly limited. As for the microscopic structure of the carbon fiber, it is preferable to use a carbon fiber in which randomly oriented carbon fibers intersect intricately.

The expanded graphite sheet is not particularly limited, and commercially available ones can be used as appropriate.

The carbon fiber nonwoven fabric sheet constituting the carbon fiber sheet protective layer is not particularly limited, and for example, a sheet having a thickness of about 0.3 to 3 mm can be used. Also, the length and width are not particularly limited. Moreover, as the microscopic structure of the carbon fiber nonwoven fabric sheet, it is preferable to use one in which carbon fibers oriented in the most dimensional or random directions in the plane direction intersect in a complex manner.

Further, these materials may be cut or the like after the surface layer-attached molded heat insulating material is produced using a long or wide one, or they may be cut in advance to the size of the surface layer-attached molded heat insulating material.

The matrix exists so as to cover the entire surface of the carbon fiber, a part of the surface of the carbon fiber, or to fill the space between the carbon fibers. Moreover, the carbon matrix may be carbonaceous, and the compound from which it is derived is not particularly limited. Among them, a carbonized resin material that can be impregnated into the carbon fiber nonwoven fabric sheet is preferable. When an adhesive layer is provided between the carbon fiber molded heat insulating material and the expanded graphite sheet, the adhesive layer and the thermosetting resin impregnated into the carbon fiber nonwoven fabric sheet are preferably made of the same material. Thermosetting resins such as phenol resins, furan resins, polyimide resins, and epoxy resins are preferable as such resin materials. When a thermosetting resin is used, the expanded graphite sheet and the carbon fiber nonwoven fabric sheet can be easily and strongly bonded by thermosetting.

Here, the thermosetting resin may be used alone or in combination of two or more. The thermosetting resin may be contained in the carbon fiber nonwoven fabric sheet as it is, or may be diluted with a solvent and then contained. Alcohols such as methyl alcohol and ethyl alcohol can be used as the solvent.

Also, the bulk density of the molded heat insulating material is preferably 0.10 to 0.30 g/cm ³ , more preferably 0.12 to 0.20 g/cm ³ , and more preferably 0.13 to 0.16 g. /cm ³ is more preferred. The thickness of the molded heat insulating material may be appropriately set according to the desired heat insulating performance.

Also, the bulk density of the expanded graphite sheet is preferably 0.5 to 1.5 g/cm ³ , more preferably 0.6 to 1.3 g/cm ³ , and more preferably 0.8 to 1.1 g. /cm ³ is more preferred. The thickness of the expanded graphite sheet is preferably 0.1 to 1.5 mm, more preferably 0.2 to 1.0 mm, even more preferably 0.3 to 0.5 mm.

Next, a method for manufacturing the molded heat insulating material will be described.

(First manufacturing method)
(Preparation of molded insulation with expanded graphite sheet attached)
Molded insulation with commercially available graphite sheets bonded thereto can be used. Alternatively, an expanded graphite sheet may be attached to a molded heat insulating material using a thermosetting resin or the like, and then heat-cured and carbonized to bond the two together. At this time, carbon fiber paper or the like impregnated with a thermosetting resin is interposed between the molded heat insulating material and the expanded graphite sheet, or an adhesive liquid such as a thermosetting resin is applied to the surface of the expanded graphite sheet and/or the molded sheet. It may be applied to the surface of the heat insulating material to enhance the adhesion between the two. A well-known method can be adopted for heat curing and carbonization. The thermosetting resin may be used as it is, or may be dissolved in an alcoholic solvent such as methanol or ethanol, and may further contain carbonaceous particles or short fibers.

Here, the shape of the molded heat insulating material is not particularly limited, and may be, for example, rectangular parallelepiped or cylindrical.

(Resin-impregnated carbon fiber non-woven fabric sheet preparation step)
A commercially available carbon fiber nonwoven fabric sheet can be used. A carbon fiber nonwoven fabric sheet is impregnated with a thermosetting resin solution by coating or spraying to form a resin-impregnated carbon fiber nonwoven fabric sheet.

(Lamination step)
A resin-impregnated carbon fiber nonwoven fabric sheet is laminated on the expanded graphite sheet of the molded heat insulating material to which the expanded graphite sheet is adhered to form a laminate. Two or more resin-impregnated carbon fiber nonwoven fabric sheets may be laminated.

(binding step)
While pressurizing the laminate to a desired thickness using a press, it is heated to a temperature equal to or higher than the curing temperature of the thermosetting resin, held for a predetermined time (for example, 1 to 10 hours), and laminated. bind the body.

(Carbonization step)
The bonded laminate is heated at 1000 to 2500° C. for a predetermined time (for example, 1 to 20 hours) in an inert atmosphere to carbonize the thermosetting resin to obtain a molded heat insulating material with a surface layer. . By this carbonization, the resin-impregnated carbon fiber nonwoven fabric sheet laminated on the expanded graphite sheet becomes a carbon fiber sheet protective layer. Also, when a resin-impregnated carbon fiber nonwoven fabric sheet is placed between the expanded graphite sheet and the molded heat insulating material, this layer becomes an adhesive layer through carbonization.

(Second manufacturing method)
The second manufacturing method differs from the first manufacturing method in that non-carbonized molded heat insulating material is used. Here, the resin-impregnated carbon fiber nonwoven fabric sheet preparation step, the binding step, and the carbonization step are the same as those in the first manufacturing method, and therefore detailed descriptions thereof will be omitted.

(Prepreg manufacturing step)
A carbon fiber structure in which carbon fibers are entangled is impregnated with a thermosetting resin before thermosetting to form a prepreg. As the carbon fiber structure, a felt-based one or a short fiber-based one can be used. Preferably, carbon fibers are three-dimensionally randomly entangled. The thermosetting resin may be the same as that with which the carbon fiber nonwoven fabric sheet is impregnated, and may be impregnated in a state of being dissolved in a solvent.

(Resin-impregnated carbon fiber non-woven fabric sheet preparation step)
A resin-impregnated carbon fiber nonwoven fabric sheet is produced by impregnating a carbon fiber nonwoven fabric sheet with a thermosetting resin before thermosetting in the same manner as in the first manufacturing method.

(Lamination step)
An expanded graphite sheet is laminated on the prepreg, and at least one resin-impregnated carbon fiber nonwoven fabric sheet is laminated on the surface of the expanded graphite sheet to form a laminate. At this time, two or more prepregs may be laminated in order to obtain desired heat insulation performance.

In addition, as in the first manufacturing method, carbon fiber paper impregnated with a thermosetting resin may be interposed between the prepreg and the expanded graphite sheet, or an adhesive liquid such as a thermosetting resin may be added to the expanded graphite. It may be applied to the surface of the sheet and/or the surface of the molded insulation. Further, when a sufficient amount of thermosetting resin is present at the interface with the expanded graphite sheet during pressing in the binding step, such measures need not be taken. Furthermore, as the carbon fiber paper impregnated with the thermosetting resin, the same material as the resin-impregnated carbon fiber nonwoven fabric sheet can be used.

Thereafter, the binding step and the carbonization step are performed in the same manner as in the first manufacturing method. By this carbonization, the prepreg becomes a carbon fiber-based molded heat insulating material, and the resin-impregnated carbon fiber nonwoven fabric sheet becomes a carbon fiber sheet protective layer.

Here, especially when heat treatment is performed at a temperature of 2000 ° C. or higher, a graphite structure such as carbon fiber or matrix may develop. It means a structure made of graphitic carbon and a structure in which both are mixed.

The present invention will be described in more detail based on examples.

(Example 1)
As a molded heat insulating material (not provided with a surface layer), a felt-based molded heat insulating material made of commercially available pitch-based carbon fiber (DON-1000-R manufactured by Osaka Gas Chemicals, shape: thickness 30 mm, width 1 m, length 1 A 0.5 m flat plate, bulk density: 0.13 g/cm ³ ) was used.

30 parts by weight of commercially available carbon paper made of pitch-based carbon fiber (Dona Carbo Paper S-255AH manufactured by Osaka Gas Chemicals, thickness: 2.4 mm, width: 1 m, length: 1.5 m, basis weight: 75 g/m ² ), resol-based phenol A carbon fiber nonwoven fabric sheet impregnated with a thermosetting resin was prepared by uniformly impregnating 70 parts by weight of the resin.

The thermosetting resin-impregnated carbon fiber nonwoven fabric sheet is placed on the molded heat insulating material, and an expanded graphite sheet of the same width and length (Toyo Tanso Co., Ltd. Permafoil PF-38 shape: thickness 0.38 mm) is placed on it, Further, one sheet of the thermosetting resin-impregnated carbon fiber nonwoven fabric sheet was placed on the expanded graphite sheet to form a laminate. Thereafter, the laminate was held at a surface pressure of 0.05 MPa and a heating temperature of 200° C. for 30 minutes using a hot compression press to thermally cure the thermosetting resin and bond the laminate.

The laminated body after thermosetting is placed in a heat treatment furnace, and heat treatment is performed in an inert atmosphere at 2000 ° C. for 5 hours to carbonize the thermosetting resin, and the surface composed of the expanded graphite sheet and the carbon fiber sheet protective layer. A layered molded insulation was obtained. At this time, the carbon fiber sheet protective layer had a bulk density of 0.24 g/cm ³ and a thickness of 0.6 mm.

(Comparative example 1)
A molded heat insulating material having a graphite sheet adhered thereto was obtained in the same manner as in Example 1, except that the carbon fiber nonwoven fabric sheet impregnated with a thermosetting resin was not laminated on the expanded graphite sheet.

The molded heat insulating materials with a surface layer according to Example 1 and Comparative Example 1 were measured for durability and peelability under the following conditions.

(Durability test 1)
The molded heat insulating materials with the surface layer according to Example 1 and Comparative Example 1 were cut into rectangular parallelepipeds of 50 mm × 50 mm × 30 mm, held in an electric furnace with an air atmosphere set to a temperature of 700 ° C. and an air flow rate of 2 L / min, The peeling state of the surface layer was observed. As a result, although the surface layer of the molded heat insulating material according to Example 1 was worn three hours after the start of the test, no exfoliation was observed in the expanded graphite sheet at this point. On the other hand, in the molded heat insulating material according to Comparative Example 1, exfoliation of the expanded graphite sheet was observed 3 hours after the start of the test.

(Durability test 2)
The molded heat insulating materials with the surface layer according to Example 1 and Comparative Example 1 were cut into rectangular parallelepipeds of 50 mm × 50 mm × 30 mm, and held for 4 hours in an electric furnace with an air atmosphere set to a temperature of 700 ° C. and an air flow rate of 2 L / min. did. When the surface of the heat insulating material after the test was observed with a scanning electron microscope, deterioration of the carbon fiber protective layer was observed in Example 1, but deterioration of the expanded graphite sheet was hardly confirmed. FIG. 2 is a micrograph showing the state of the surface of the expanded graphite sheet after durability test 2 of the molded heat insulating material with a surface layer according to Comparative Example 1. FIG. In Comparative Example 1, as shown in FIG. 2, deterioration such as dissociation was observed in the expanded graphite sheet.

(Durability test 3)
The molded heat insulating materials with the surface layer according to Example 1 and Comparative Example 1 were cut into rectangular parallelepipeds of 50 mm×50 mm×30 mm and held in an air atmosphere electric furnace set at a temperature of 700° C. and an air flow rate of 2 L/min. At this time, the peeling state of the surface layer was observed, and the change in mass of the formed heat insulating material with the surface layer due to oxidation consumption was measured. At this time, the parts other than the surface layer (other than the expanded graphite sheet and the protective layer of the carbon fiber sheet) were protected with a jig so that only the surface layer was exposed to air. As a result, the molded heat insulating material according to Example 1 had a consumption rate (mass reduction rate of the molded heat insulating material with a surface layer) of 18.8% after 6 hours from the start of the test. No delamination was observed. On the other hand, the molded heat insulating material according to Comparative Example 1 had a consumption rate of 26.3% after 6 hours from the start of the test, and peeling of the expanded graphite sheet was observed at this point.

(Peeling test)
A rectangular parallelepiped of 4 cm×4 cm×3 cm was cut out from the molded heat insulating material according to Example 1 to obtain a test piece. Using a two-liquid adhesive, a peel test jig is attached to the upper and lower surfaces of the test piece in the stacking direction (thickness direction), and a tensilon universal material tester (RTC-1210) manufactured by A&D Co., Ltd. is used. , and pulled in the thickness direction at a crosshead speed of 1 mm/min. As a result, the breakage of the molded heat insulating material occurred before the breakage and peeling of the expanded graphite sheet and carbon fiber sheet protective layer. From this, it was confirmed that the adhesive strength between the carbon fiber sheet protective layer and the graphite sheet was higher than that of the molded heat insulating material portion and was sufficient.

From the above, according to the present invention, a surface layer that can suppress deterioration of a molded heat insulating material due to gas for a long period of time by a simple method of providing a surface layer with a two-layer structure of an expanded graphite sheet and a carbon fiber sheet protective layer. It can be seen that layered molded insulation can be achieved.

FIG. 1 shows a cross-sectional photomicrograph of the vicinity of the surface layer of the molded heat insulating material with the surface layer according to Example 1. As shown in FIG. As can be seen from this photograph, on the formed heat insulating material 4 having many gaps between carbon fibers, an adhesive sheet 3 having fewer gaps between carbon fibers than the formed heat insulating material 4, an expanded graphite sheet 2 having a dense structure, and an adhesive sheet 3 are formed. It can be seen that the carbon fiber sheet protective layer 1, which is almost the same as , is laminated in order.

Although the first manufacturing method according to the present invention is used in the above embodiment, the same effect can be obtained by adopting the second manufacturing method.

As described above, according to the present invention, it is possible to realize a molded heat insulating material with a long life surface layer that can suppress the deterioration of the heat insulating performance due to gas without a significant increase in cost. Availability is great.

1 Carbon fiber sheet protective layer 2 Expanded graphite sheet 3 Adhesive sheet 4 Molded heat insulating material

Claims (5)

a carbon fiber-based molded insulation;
an expanded graphite sheet laminated on one surface of the carbon fiber-based molded insulation;
a carbon fiber sheet protective layer laminated in contact with the expanded graphite sheet,
The carbon fiber sheet protective layer includes a carbon fiber nonwoven fabric sheet in which carbon fibers are entangled and a matrix made of carbonaceous material covering the carbon fiber surface of the carbon fiber nonwoven fabric sheet ,
The expanded graphite sheet and the carbon fiber sheet protective layer are not arranged on the other surface of the carbon fiber-based molded heat insulating material,
Molded insulation with surface layer. The carbon fiber sheet protective layer has a bulk density of 0.1 to 0.5 g/cm ³ and a thickness of 0.3 to 3 mm.
The molded heat insulating material with a surface layer according to claim 1, characterized in that: The carbon fibers constituting the carbon fiber sheet protective layer are isotropic pitch-based carbon fibers,
The molded heat insulating material with a surface layer according to claim 1 or 2, characterized in that: A resin-impregnated carbon fiber nonwoven fabric sheet manufacturing step of impregnating the carbon fiber nonwoven fabric sheet with a thermosetting resin before thermosetting;
At least the carbon fiber nonwoven fabric sheet is placed only on the surface of the expanded graphite sheet of the carbon fiber-based molded heat insulating material having one expanded graphite sheet attached to one surface and no expanded graphite sheet attached to the other surface. a lamination step of laminating one to form a laminate;
a bonding step of heating the laminate to a temperature equal to or higher than the thermosetting temperature of the thermosetting resin while pressurizing the laminate to bond the carbon fiber nonwoven fabric sheet to the surface of the expanded graphite sheet;
a carbonization step of heat-treating the bound laminate in an inert gas atmosphere to carbonize the thermosetting resin;
A method of manufacturing a molded insulation with a surface layer comprising: A prepreg manufacturing step of impregnating a carbon fiber structure in which carbon fibers are entangled with a thermosetting resin before thermosetting to form a prepreg;
A resin-impregnated carbon fiber nonwoven fabric sheet manufacturing step of impregnating the carbon fiber nonwoven fabric sheet with a thermosetting resin before thermosetting;
a lamination step of laminating one expanded graphite sheet only on one surface of the prepreg, and further laminating at least one resin-impregnated carbon fiber nonwoven fabric sheet only on the surface of the expanded graphite sheet to form a laminate;
a bonding step of heating the laminate to a temperature equal to or higher than the thermosetting temperature of the thermosetting resin while pressurizing the laminate to bond the prepreg, the expanded graphite sheet, and the carbon fiber nonwoven fabric sheet;
a carbonization step of heat-treating the bound laminate in an inert gas atmosphere to carbonize the thermosetting resin;
A method of manufacturing a molded insulation with a surface layer comprising:

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