JP3003935B2 - Molded heat insulating material and its manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a molded heat insulating material suitable as a heat insulating material at the time of a high-temperature heat treatment and a method for producing the same.

[Related Art and Problems to be Solved by the Invention] In recent years, high-temperature heat treatment using a vacuum evaporation furnace, a semiconductor single crystal growth furnace, a ceramic sintering furnace, a C / C composite firing furnace, or the like has been regarded as important. The heat insulating material for high-temperature heat treatment is required to be excellent in heat resistance and heat resistance and not to deteriorate in physical properties at high temperatures. Therefore, the usefulness of the heat insulating material using carbon fiber is increasing.

On the other hand, as a method of manufacturing a carbon fiber heat insulating material, a method of impregnating a carbon fiber felt with a resin capable of being carbonized or graphitized and performing a heat treatment is known. A method of impregnating a carbon fiber felt with a carbonizable or graphitizable resin, laminating and compressing the impregnated felt into a molded product having a desired thickness and bulk density, and then using the molded product as a molded heat insulating material has been proposed. (See Japanese Patent Publication No. 50-30930).

However, in these methods, since carbon fiber felt in which fibers are joined by needle punch is used,
The fibers are multiaxially oriented and the orientation direction is irregular. Therefore, the heat transfer by the fiber cannot be sufficiently restricted,
High thermal conductivity and insufficient insulation. In particular, in the former method, since the bulk density of the heat insulating material is low due to a problem in the production method, the heat insulating property is inferior in combination with the irregular orientation direction of the fibers.

Further, in these methods, the uniformity and workability of the heat insulating material are not sufficient due to uneven fiber and characteristic impregnation of felt. In particular, in the latter method, since the laminate is fastened with the metal band, the uniformity is not sufficient.

Also, in the former method, in order to obtain a heat insulating material having a complicated shape, it is necessary to cut and join an appropriate shape,
Felt loss or the like occurs and the cost increases, and the operation becomes complicated, and it is difficult to produce a heat insulating material having a complicated shape with high productivity.

Furthermore, in the latter method, the bulk density of the molded heat insulating material is governed by the compressive force. Therefore, in the case of a flat shaped heat insulating material, it is easy to perform lamination compression at a relatively high density, but in the case of a cylindrical shaped heat insulating material or the like, a large machine is used to obtain a molded heat insulating material having a large bulk density. Energy is required, and workability and productivity are reduced.

Also, as a method of manufacturing a heat insulating material with excellent uniformity,
It is also known to add 0.05 to 0.2 parts by weight of a binder such as polyvinyl alcohol to 1 part by weight of carbon fiber. Although this method is useful for producing a lightweight sheet-like heat insulating material having a thickness of about 1 mm, it is not suitable for producing a thick heat insulating material. That is, a binder effect cannot be obtained unless thermocompression bonding is performed, and it is difficult to obtain a heat insulating material having sufficient strength. In addition, due to the migration of the binder, only the surface of the heat insulating material is hard, and the inside thereof has a very brittle structure and is non-uniform.

An object of the present invention is to provide a molded heat insulating material in which fibers are oriented in a specific direction, have a desired bulk density, and are excellent in heat insulating properties, uniformity, homogeneity, and workability.

Another object of the present invention is to provide a method for producing a molded heat insulating material having the above-mentioned characteristics with good workability and productivity even in a complicated shape.

[Constitution of the invention] The present invention is a uniform and uniform molded heat insulating material which is integrally formed of carbon fiber and a carbide or graphitized resin, wherein the carbon fiber is perpendicular to the thickness direction of the molded heat insulating material. This problem is solved by a molded heat insulating material which is oriented in the direction in which it is oriented, has a thickness of 3 to 200 mm, and has a bulk density of 0.3 g / cm ³ or less. The shape of the integrally formed heat insulating material may be a hollow cylindrical shape, a ring shape, or a disk shape.

The present invention also provides a slurry containing fibers or carbon fibers that can be converted into carbon fibers, organic fibers, a powdered thermosetting resin that can be carbonized or graphitized, and a cationic resin, and suctioning the slurry. After molding, by the method of manufacturing a molded heat insulating material characterized by firing the obtained molded body,
This is to solve the above-mentioned problem.

The terms used in this specification are defined as follows.

Carbonization refers to baking a carbon-containing substance such as polyacrylonitrile at a temperature of, for example, about 450 to 1500 ° C. Graphitization refers to carbon-containing substances, for example, 1500-30
This refers to baking at a temperature of about 00 ° C., which is included in the concept of graphitization even when the crystal structure is not graphitized.

 Carbon fiber refers to a carbonized or graphitized fiber.

As the carbon fiber constituting the molded heat insulating material of the present invention, for example, various kinds of carbon fibers made of polymer fibers such as polyacrylonitrile, phenol resin, rayon, petroleum pitch, coal pitch, liquid crystal pitch and the like can be used. At least one of these carbon fibers is used. The length of the carbon fiber can be appropriately set within a range that does not impair the bulk density and the like of the molded heat insulating material, but the fiber length is preferably 0.1 to 10 mm. If the fiber length is less than 0.1 mm, it may not be possible to secure the integrity of the molded heat insulating material, and if it exceeds 10 mm, it is difficult to increase the bulk density, and pills, which are aggregates of fibers, are easily generated. , Mechanical strength is reduced. The bulk density of the molded heat insulating material can be easily controlled by adjusting the fiber length of the carbon fiber. As the carbon fiber, an appropriate one such as a fiber diameter of 5 to 20 μm can be used.

Further, the molded heat insulating material is uniform and homogeneous, and is integrated with a carbide or graphitized resin. As the resin, for example, phenol resin, furan resin, xylene resin, urea resin, melamine resin, guanamine resin, epoxy resin,
Examples thereof include thermosetting resins such as diallyl phthalate resin, polyurethane, unsaturated polyester, thermosetting acrylic resin, and polyimide, and one or more of them are used.
Among the above resins, a resol type or novolak type phenol resin is preferable.

Usually, the carbonized or graphitized resin of the resin is made of carbon fiber 1
It is about 0.05 to 5 parts by weight, preferably about 0.1 to 3 parts by weight, based on the weight of the resin. If the amount of the carbide or graphitized resin is less than 0.1 part by weight, the mechanical strength is not sufficient, and if it exceeds 5 parts by weight, the uniformity is reduced.

In addition, in order to enhance the homogeneity of the molded heat insulating material, it is important to uniformly entangle carbon fibers. However,
Since the carbon fibers are rigid, the strength of the entanglement between the carbon fibers is not sufficient. Therefore, it is preferable to add an organic fiber, particularly a fibrillated organic fiber, in order to assist the entanglement of the carbon fiber. Such organic fibers include:
For example, wood pulp, natural fibers such as hemp, semi-synthetic fibers such as rayon, polyester, polyethylene, polypropylene, polystyrene, acrylic resin, polyacrylonitrile, phenol resin, polyurethane, and synthetic fibers such as polyamide are exemplified. Is done. Of these, particularly preferred are fibrillated acrylic fibers.

After firing, the organic fiber is usually contained in an amount of about 0 to 0.5 part by weight based on 1 part by weight of the carbon fiber.

Further, the molded heat insulating material may contain a baked product of another resin, for example, a cationic resin, a polymer coagulant, or an additive such as a yield improver.

The carbon fibers are arranged in a direction orthogonal to the thickness direction of the molded heat insulating material. Since the carbon fibers are blended in the above-mentioned direction, the orientation direction of the carbon fibers is irregular, and the heat insulating property can be made larger than that of a molded heat insulating material having the same bulk density. That is, when the carbon fibers are oriented in the thickness direction of the molded heat insulating material, the voids formed between the carbon fibers match the heat transfer direction from the high-temperature side to the low-temperature side, so that the heat mobility increases. . On the other hand, when the carbon fibers are oriented in a direction perpendicular to the thickness direction of the molded heat insulating material, the movement of heat is restricted by the carbon fibers perpendicular to the heat transfer direction, and the heat mobility can be reduced.

It is sufficient that most of the carbon fibers are oriented in the above-mentioned direction, and it is not necessary that all the carbon fibers are arranged in a direction orthogonal to the thickness direction of the molded heat insulating material.

The molded heat insulating material of the present invention may have an appropriate bulk density, but usually has a bulk density of 0.3 g / cm ³ or less, for example, 0.05 to 0.
It is about 3 g / cm ³ . The bulk density is in the range of carbon fiber / resin carbide or graphitized product = 1 / 0.2 to 1 (parts by weight)
It may be about 0.05 to 0.3 g / cm ³ . The thickness of the molded heat insulating material is usually about 3 to 200 mm.

The shape of the molded heat insulating material of the present invention is not particularly limited, and may be a sheet shape, a hollow cylindrical shape, a ring shape, a disk shape, or the like.

Hereinafter, a method for producing the molded heat insulating material of the present invention will be described.

The method for producing a molded heat insulating material of the present invention comprises preparing a slurry containing fibers or carbon fibers that can be converted into carbon fibers, organic fibers, a powdered thermosetting resin that can be carbonized or graphitized, and a cationic resin. And a baking step of baking the formed body.

In the slurry preparation step, a solvent is used together with the above materials. Examples of the fiber that can be converted into carbon fiber include a fiber used as a material of the carbon fiber and an infusibilized pitch fiber, and at least one fiber is used. Among the above fibers, polyacrylonitrile fibers, phenol resin fibers, rayon, and pitch-based fibers are preferable. As the carbon fiber, those similar to the above can be used. In the present invention, as described above, short fibers can be used as the fibers or carbon fibers that can be converted into carbon fibers, so that scrap yarn generated during fiber production or processing can be effectively used.

The organic fibers are preferably fibrillated organic fibers, and the beating degree of the fibrillated organic fibers is 100 to 4 in a Canadian freeness type beating degree tester.
00 ml is preferred. If the beating degree is less than 100 ml, the suction moldability and the productivity are reduced, and if it exceeds 400 ml, the uniform mixing with short fibers is reduced.

The ratio of the fiber that can be converted into carbon fiber or the ratio of carbon fiber, resin, and organic fiber is set in consideration of the fact that the weight is reduced by carbonization or graphitization. That is, the ratio of the carbon fiber-forming fiber or the carbon fiber to the resin is usually 0.01 to 10 parts by weight, preferably about 0.1 to 3 parts by weight with respect to 1 part by weight of the fiber. The ratio of the fibers that can be converted into carbon fibers or the ratio between the carbon fibers and the organic fibers is usually about 0.01 to 0.5 parts by weight of the organic fibers per 1 part by weight of the fibers.

Examples of the cationic resin include an acrylic resin such as polyamide and polyacrylamide, and a resin containing a nitrogen atom such as polyethyleneimine, and at least one kind is used. With this cationic resin, the thermosetting resin can be fixed to fibers that can be converted into carbon fibers or carbon fibers. The cationic resin can be used in an appropriate amount, but is usually about 0.02 to 2% by weight based on the solid content. The amount of the cationic resin used can be adjusted according to the use ratio of the thermosetting resin and the like.

The cationic resin may be used in combination with a cationized starch, a sulfate band, or the like.

As the solvent used in the slurry preparation step, for example, water, hydrocarbons, alcohols, ethers, esters, ketones, and a mixed solvent thereof can be used. In order to increase the yield of the resin in the suction molding step, the solvent is preferably a solvent having low solubility in the resin and capable of existing in a state where the resin is dispersed in the form of particles, particularly water. The particle size of the resin in the solvent can be set according to the suction molding efficiency and the like, but in order to ensure the compactness and homogeneity of the molded heat insulating material, a fine particle is preferable, and usually, the particle size is 100 mesh or less, preferably 40 μm. Below, the average particle size is about 15 μm.

The amount of the solvent to be used is usually 0.5 to 5% by weight, preferably about 1 to 3% by weight, in the slurry.

The slurry can be prepared by simultaneously stirring and mixing the above materials.However, the fibers that can be converted into carbon fibers or the carbon fibers and the organic fibers, particularly the fibrillated organic fibers, are beaten simultaneously, and then the other materials are added and mixed. Is preferred. By the simultaneous beating, the fibers that can be converted into carbon fibers or the fibers of the carbon fibers are entangled with each other, and a slurry that is homogeneous and has excellent mixing and dispersibility can be obtained. If the fibers that can be converted into carbon fibers or the carbon fibers and the organic fibers are simply mixed and stirred without beating, non-uniform entanglement occurs, a long tail or the like is easily formed, and the dispersibility is not sufficient.

In order to increase the yield by suction molding, it is preferable to add a surfactant having an aggregating action, particularly a polymer flocculant and a retention aid. As the polymer coagulant, for example, an acrylic resin such as polyacrylamide having a molecular weight of 100,000 or more can be used. The amount of the coagulant used is not particularly limited as long as the yield can be improved by coagulation, but is usually about 0.005 to 0.5% by weight based on the solid matter. If the amount of the flocculant is less than 0.005% by weight, it is difficult to obtain a sufficient flocculating effect, and if it exceeds 0.5% by weight, excessive flocculation tends to occur and it is difficult to prepare a homogeneous dispersion.

If necessary, additives such as a dispersant, a stabilizer, a viscosity modifier, and a filler may be added as long as the properties of the molded heat insulating material are not adversely affected.

Next, suction molding is performed in the slurry prepared as described above. This suction molding step will be described with reference to the accompanying drawings.

1 is a schematic longitudinal sectional view showing a suction molding state, FIG. 2 is a schematic sectional view showing a suction mold and a molded body, and FIG. 3 is a schematic sectional perspective view showing a molded body. In the suction molding step, the slurry (1) contained in the slurry tank (2) is suctioned by the suction molding die (3), and solids in the slurry (1) are deposited on the outer surface of the suction molding die (3). It is done by doing.
As shown in FIGS. 1 and 2, the suction mold (3) includes a suction part (4) having a pipe connection part (6) for connecting a pipe (5), and a suction part (4). 4)
And a cylindrical portion (7) formed with a large number of mesh-shaped holes (8) sized to prevent passage of solids in the slurry (1).
And a flange (9) connected to the cylindrical portion (7). Therefore, by suctioning with a suction pump (not shown) through the pipe (5) connected to the pipe connection part (6) of the suction mold (3), the slurry ( The solid content in 1) is deposited by suction to obtain a hollow cylindrical molded body (10) having a hollow portion (11) corresponding to the outer diameter of the cylindrical portion (7) as shown in FIG. it can. At that time, the carbonizable fibers and carbon fibers in the slurry (1) are deposited along the outer surface of the cylindrical portion (7), and thus the carbonizable fibers and carbon fibers of the molded body (10) are converted into the molded body ( It is oriented in the direction dr perpendicular to the thickness direction dt in 10). In addition, at the time of suction molding, the bulk density of the molded body (10) can be easily controlled by adjusting the suction force, the fiber length of the carbonizable fiber or the carbon fiber, and the ratio between the fiber and the resin. In addition, since the molding is performed by suction, the molded body is homogeneous and has excellent uniformity.

FIG. 4 is a perspective view showing another molded body. The molded body (20) has a small thickness, is a ring shape having the same hollow portion (21) as described above, and fibers or carbon fibers that can be converted into carbon fibers are oriented in a direction dr perpendicular to the thickness direction dt. . Since FIG. 4 shows the state at the time of completion of the suction molding, the fibers on the upper end face are oriented in various directions in the figure.
In the suction mold shown in FIG. 2, the molded body (20) having such a shape does not have the hole (8) formed in the cylindrical portion (7), and has an outer cylinder set up on the periphery of the flange (9). A molding die in which a plurality of holes are formed in a flange (9) located between the cylindrical portion (7) and the outer cylinder, that is, a bottom plate, and the height of the cylindrical portion (7) and the outer cylinder is reduced. And can be produced by suction molding. The space between the cylindrical portion and the outer cylinder is used as a suction space, and a number of holes formed in the bottom plate have a size to prevent the passage of solids in the slurry. It communicates with (4). In this case, solids in the slurry can be suction-deposited on the bottom plate, and fibers or carbon fibers that can be converted into carbon fibers are oriented parallel to the suction surface, that is, in a direction dr perpendicular to the thickness direction dt of the molded body (20). Can be.

The suction direction of the slurry may be any direction, such as the horizontal direction. Further, the suction mold can be appropriately selected according to the desired shape of the molded heat insulating material. For example, in order to obtain a sheet-like molded body such as a flat plate or a corrugated plate, a plate or the like in which a large number of holes are formed may be provided in the suction unit. Further, by providing a peripheral wall, a convex portion, or the like having an appropriate height on a bottom plate located between the cylindrical portion and the outer cylinder, a circumferential slit, a concave portion, or the like can be formed in the molded body.

Note that, as the slurry, a plurality of slurries having different ratios of fibers capable of being converted into carbon fibers or carbon fibers and resin,
By sequentially performing suction molding, it is possible to obtain a molded body whose bulk density varies continuously or stepwise in the thickness direction.

The shape of the molded body may be a hollow cylindrical shape, a ring shape, a disk shape, or the like in addition to the sheet shape.

The molded body is dried and calcined in a calcining step to obtain a molded heat insulating material. Drying of the molded body is, for example,
It can be performed at an appropriate temperature of about 100 to 200 ° C. In the drying step, it is preferable to cure the carbonizable or graphitizable resin. Curing of the carbonizable or graphitizable resin can be performed at a temperature of, for example, about 120 to 250 ° C., and in that case, a curing agent according to the type of the resin, for example, in the case of a novolak type phenol resin which is a preferable resin, Hexamethylenetetramine and the like can be used. In the case of a resole type phenol resin, an acid catalyst and the like can be used.

Then, the molded body is fired in the firing step to obtain an integrated molded heat insulating material. Carbonization and graphitization in the firing step are usually performed under vacuum or in an inert atmosphere,
The carbonization temperature is about 450 ~ 1500 ℃, the graphitization temperature is 1500 ~ 3
It is about 000 ° C. The molded product obtained by the suction molding slightly shrinks due to the above-mentioned firing. Therefore, the size of the formed body may be determined in consideration of the size of the formed heat insulating material as the final product.

The molded heat insulating material obtained as described above has a shape corresponding to the molded body. Referring to FIG. 3, since the carbon fibers are oriented in the direction dr perpendicular to the thickness direction dt of the formed heat insulating material, the hollow portion (11) of the formed heat insulating material obtained through the firing step is removed. The heat insulation efficiency can be increased even on the high temperature side. That is, the heat on the high temperature side moves from the hollow portion (11) of the molded heat insulating material to the outer peripheral surface side, that is, in the thickness direction dt, but since the fibers are oriented in the direction dr perpendicular to the direction of heat transfer, the heat is Movement is restricted by the carbon fiber, and the heat insulation efficiency can be increased. Since the heat insulating efficiency of the molded heat insulating material is high, the thickness can be made smaller than that of the conventional molded heat insulating material having the same bulk density.

The molded heat insulating material of the present invention can be used in various applications such as a heat insulating material for a high-temperature furnace or a vacuum furnace and a cushioning material as a cushioning material for a bottle pusher, depending on its bulk density and shape. For example, molded insulation material to a bulk density of 0.3 g / cm ³ are high temperature insulation,
A molded body having a bulk density of about 0.3 to 0.5 g / cm ³ is excellent in heat resistance and mechanical strength and has appropriate hardness, so that it can be used as a cushion material in addition to a heat insulating material. Further, a molded heat insulating material such as a hollow cylindrical shape can be used for a high-temperature furnace or the like, and a molded heat insulating material such as a disk shape is suitably used as an underlaying member of a molten crucible in a vacuum evaporation furnace.

[Effects of the Invention] As described above, according to the molded heat insulating material of the present invention, the carbon fibers are oriented in a direction orthogonal to the thickness direction of the uniform and uniform molded heat insulating material, and thus exhibit high heat insulating properties. . Also, since it is integrally formed of carbon fiber and resin carbide or graphitized material, by adjusting the ratio of the two, it has a desired bulk density, and is excellent in uniformity, homogeneity and workability. .

According to the method for producing a molded heat insulating material of the present invention, a slurry containing a powdery thermosetting resin and a cationic resin that can be carbonized or graphitized and organic fibers and organic fibers is prepared,
After the suction molding, the molded body is baked, so that the bulk density can be easily controlled by adjusting the length and the suction force of the carbon fiber, etc., without going through the resin impregnation step, and the carbon fiber, etc. Are oriented in a direction perpendicular to the thickness direction of the molded heat insulating material, so that a molded heat insulating material having excellent heat insulating properties can be obtained. In addition, since suction molding is performed, a molded heat insulating material having excellent uniformity, homogeneity, and workability and having a complicated shape can be manufactured with good workability and productivity. Furthermore, since short fibers can be used as carbon fibers or the like, waste threads can be effectively used.

EXAMPLES Hereinafter, the present invention will be described in more detail based on examples.

Raw cotton chop of carbon fiber (fiber diameter 13μm, length 3m
m) 65 parts by weight of polyacrylonitrile fiber (fiber diameter 7
μm, 100 mm length) 5 parts by weight, powdered novolak type phenolic resin 30 parts by weight, hexamethylenetetramine, polyacrylamide (manufactured by Arakawa Chemical Co., Ltd., trade name: Polystron 705) 0.1 part by weight to 10,000 parts by weight of water After the addition and stirring and mixing, 0.01 parts by weight of a polyacrylamide-based polymer flocculant (trade name: Pacoll 292, manufactured by Allied Colloid Co., Ltd.) was added to prepare a slurry.

Then, using a suction mold connected to a suction pump through a pipe, by suction molding, an outer diameter of 540 mm,
A hollow cylindrical molded body having an inner diameter of 420 mm, a thickness of 60 mm, and a height of 630 mm was obtained. The molded body was dried at a temperature of 110 ° C. and fired at a maximum temperature of 2000 ° C. in a graphitization furnace to obtain a molded heat insulating material. The bulk density of the resulting molded heat insulating material is 0.15 g / cm ^3,
It was homogeneous. Further, the carbon fibers of the molded heat insulating material were oriented in a direction substantially perpendicular to the thickness direction.

[Brief description of the drawings]

1 is a schematic longitudinal sectional view showing a suction molding state, FIG. 2 is a schematic sectional view showing a suction mold and a molded body, FIG. 3 is a schematic sectional perspective view showing a molded body, and FIG. It is a perspective view which shows a molded object. (1) Slurry (3) Suction mold (10)
(20) …… Mold

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiki Middle East 5-1, Hiranocho, Higashi-ku, Osaka-shi, Osaka Inside Osaka Gas Co., Ltd.

Claims (4)

(57) [Claims] 1. A molded heat insulating material which is integrally formed of carbon fiber and resin carbide or graphitized material, wherein said carbon fiber is oriented in a direction orthogonal to a thickness direction of the formed heat insulating material. A molded heat insulating material having a thickness of 3 to 200 mm and a bulk density of 0.3 g / cm ³ or less. 2. The shape of the integrally formed heat insulating material is as follows:
2. The molded heat insulating material according to claim 1, wherein the heat insulating material has a hollow cylindrical shape, a ring shape, or a disk shape. 3. A slurry containing a carbon fiber or a carbon fiber, an organic fiber, a powdery thermosetting resin capable of being carbonized or graphitized, and a cationic resin is prepared, and the slurry is suctioned. A method for producing a molded heat insulating material, which comprises, after molding, firing the obtained molded body. 4. The method according to claim 3, wherein the hollow cylindrical, ring-shaped or disk-shaped formed body is fired.