JP6924595B2 - Molded insulation and its manufacturing method - Google Patents

Description

The present invention relates to a molded heat insulating material using carbon fibers, and more particularly to a molded heat insulating material having a surface layer formed to enhance durability.

Carbon fiber-based heat insulating materials are used in various applications because they are excellent in thermal stability and heat insulating performance and are lightweight. Such heat insulating materials include carbon fiber felt made by entwining carbon fibers and carbon fiber molded heat insulating material obtained by impregnating carbon fiber felt with a resin material and carbonizing it. The carbon fiber felt has an advantage of being excellent in flexibility, and the carbon fiber molded heat insulating material has an advantage of being excellent in shape stability and capable of fine processing.

Which heat insulating material is used is appropriately selected according to the purpose of use and application. The latter carbon fiber molded heat insulating material has excellent thermal stability, heat insulating performance, and shape stability. Therefore, a single crystal silicon pulling device, a polycrystalline silicon cast furnace, a metal or ceramics sintering furnace, and a vacuum vapor deposition furnace. It is used as a heat insulating material for high temperature furnaces.

However, in a manufacturing apparatus for single crystal or polycrystalline silicon, SiO gas is generated in a high temperature furnace, or oxygen gas is mixed into the manufacturing atmosphere as an impurity gas. SiO gas and oxygen gas are highly active (reactive), and when the carbon fiber molded heat insulating material reacts with SiO gas, SiC is generated, and when the carbon fiber molded heat insulating material reacts with oxygen gas, carbon oxide (carbon monoxide, Carbon dioxide, etc.) is generated. As a result, the carbon fibers are particularly deteriorated, the skeletal structure composed of the carbon fibers is destroyed, and the heat insulating effect obtained by the skeletal structure forming a large number of spaces is lowered. Further, due to this deterioration, carbon fibers may be particularly pulverized and released into the atmosphere inside the furnace, which may deteriorate the product quality.

Further, in an industrial furnace, the pressure inside the furnace may be higher than the atmospheric pressure. In such a case, a flow of atmospheric gas (nitrogen gas or argon gas) in the furnace is generated due to the pressure difference, but when the highly active atmospheric gas permeates the internal space of the molded heat insulating material, the internal structure of the molded heat insulating material deteriorates. As a result, the heat insulation performance deteriorates.

In response to this problem, Patent Document 1 has a coating layer for a heat insulating material which has sufficiently low gas permeability and can impart dust generation prevention, oxidation resistance, mechanical strength and heat insulating performance. Is proposing.

WO2006 / 115102

Patent Document 1 is a coating layer for a heat insulating material in a laminated body for a heat insulating material including a carbonized molded body and a coating layer for the heat insulating material laminated on at least one surface of the carbonized molded body, and has a bulk density. A heat insulating material laminate comprising a carbonized molded body having a gas permeability of 0.08 to 0.8 g / cm ³ and a heat insulating material coating layer having a gas permeability of 8.0 NL / hr · cm ² · mmH _{2 O or less.} It is a technique related to a coating layer for a heat insulating material in.

According to this technique, it is said that it has low gas permeability and can impart excellent dust generation prevention property, oxidation resistance, mechanical strength and heat insulating effect to the laminate for heat insulating material.

However, the heat insulating material has a porosity of about 90%, and a considerable space exists even in the coating layer. Since gas is permeable through this space, it is not possible to sufficiently reduce the gas permeability simply by providing a thin coating layer. Further, if the coating is thickened, the gas permeability can be increased, but in this case, the coating layer is easily peeled off and the durability is lowered.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a molded heat insulating material capable of suppressing the permeation of gas into the molded heat insulating material without sacrificing durability. do.

The method for producing the molded heat insulating material according to the present invention is as follows.
A dense base layer forming liquid containing an aggregate made of carbon and a binder made of a thermosetting resin is impregnated in a region of at least 0.4 mm from at least one surface of the molded heat insulating material, and then fired at 500 ° C. or higher. A surface containing an aggregate containing a component that becomes carbon particles after firing and a binder composed of a thermosetting resin, and a step of forming a dense base layer that carbonizes the thermosetting resin to form a dense base layer. A surface coating layer forming step of impregnating a region of at least 0.1 mm from the surface of the dense base layer with a coating liquid and then firing at 1000 ° C. or higher to carbonize the thermosetting resin to form a surface coating layer. If the provided volume fraction of the aggregate in the dense underlayer after the dense underlying layer forming step is 0.3 to 5% the surface coating layer on the dense underlayer was formed region A method for producing a molded heat insulating material, wherein the body integration rate of the aggregate is 1 to 7%.

If the molded heat insulating material is formed by laminating and molding a carbon fiber sheet having a fiber felt and a protective carbon layer made of carbon material that coats the carbon fiber surface of the fiber felt, it is mixed as an impurity around the molded heat insulating material. Alternatively, when the active gas (oxygen gas, SiO gas, etc.) generated in the furnace is present, the protective carbon layer covering the surface of the carbon fiber reacts with the active gas prior to the carbon fiber. As a result, the reaction between the carbon fiber and the active gas is suppressed from deterioration.

Here, when the protected carbon layer reacts with oxygen gas, the carbon constituting the protected carbon layer becomes carbon dioxide gas and is removed, and when it reacts with SiO gas, it becomes SiC and remains without being removed. However, in each case, since the skeletal structure composed of carbon fibers is maintained, the heat insulating effect obtained by forming a large number of spaces by the skeletal structure is maintained.

Then, in the present invention, a surface layer composed of a dense base layer and a surface coating layer is formed on the surface of the molded heat insulating material. The dense base layer is formed in a region of at least 0.4 mm from the surface of at least one of the molded heat insulating materials. This layer is formed by the dense base layer forming liquid containing a carbonaceous aggregate and a thermosetting resin permeating into the molded heat insulating material and carbonizing, and a part of the voids between the carbon fibers of the molded heat insulating material is formed. , Filled with aggregates and carbonized thermosetting resin, reducing the diameter of the path through which the gas passes. Therefore, the dense base layer suppresses the intrusion of gas into the molded heat insulating material.

The surface coating layer is formed in a region of at least 0.1 mm from the surface of the dense base layer. This layer is formed by further permeating and carbonizing a surface coating liquid containing an aggregate that becomes carbon particles after heat treatment and a binder made of a thermosetting resin before thermosetting into the dense base layer. , A part of the voids between the carbon fibers is further filled with the aggregate (carbon particles) and the carbonized product of the thermosetting resin, and the diameter of the path through which the gas passes is further reduced. Therefore, the intrusion of gas into the molded heat insulating material is further suppressed.

That is, by sequentially forming the dense base layer and the surface coating layer on the molded heat insulating material, the invasion of gas into the molded heat insulating material is effectively suppressed without causing the layers to peel off.

Here, the aggregate locally fills the path through which the gas passes, and the carbonized product of the thermosetting resin fills the path through which the gas passes so as to cover the surface of the carbon fiber and the surface of the aggregate. The effect of reducing the diameter of the path is great. Further, when the shape of the aggregate is a particle shape such as a spherical shape or an elliptical spherical shape, the effect of reducing the diameter of the path is greater than when the shape is a shape having a high aspect ratio such as a fibrous shape or a needle shape. Also, the effect of carbon particles is greater after the path diameter has been reduced. Therefore, when the dense base layer forming liquid does not contain an aggregate, or when the surface coating liquid does not contain a component that becomes carbon particles after firing as an aggregate, the effect of reducing the passage of gas is sufficient. I can't get it.

The shape of the aggregate used for the dense base layer forming liquid is not particularly limited, and may be in the form of particles, milled (short fibers), or the like. Further, the surface coating liquid may contain carbon components having other shapes such as carbon fiber milled in addition to those that become carbon particles after heat treatment.

Here, the particles contained in the surface coating liquid that become carbon particles after the heat treatment are carbonaceous (graphitic or amorphous) particles already before the heat treatment and resins that are carbonized by the heat treatment (for example, after thermosetting). It means particles of (thermosetting resin).

In order to obtain the effect of the present invention, the volume fraction of the aggregate in the surface coating layer (a region in which the surface coating layer formed on a dense base layer) was restricted to 1% or more, dense underlayer (surface coating layer The volume fraction of aggregate in the case where is not formed or before the surface coating layer is formed) is restricted to 0.3% or more. Further, if the volume fraction of the aggregate is too high, the cost will be high. Therefore, the volume fraction of the aggregate in the surface coating layer should be 7% or less, and the volume fraction of the aggregate in the dense underlying layer should be 5% or less. And. Since the surface coating layer is formed by impregnating and firing the surface coating liquid in the dense base layer, the volume fraction of the aggregate in the surface coating layer is naturally the volume of the aggregate in the dense base layer. Greater than a fraction.

Further, the gas permeation inhibitory action is influenced not only by the diameter of the path through which the gas permeates, but also by the thickness of the region where the diameter of the path is narrow. Therefore, it is essential that the thickness of the impregnated region of the surface coating liquid is 0.1 mm or more, and the thickness of the impregnated region of the dense base layer forming liquid is 0.4 mm or more.

Here, the surface coating liquid can be configured to impregnate a region thicker than 0.1 mm. For example, the surface coating liquid may be impregnated in a region of at least 0.2 mm from the surface of the dense base layer, or may be impregnated in a region of at least 0.4 mm from the surface of the dense base layer. Further, the surface coating liquid may be impregnated in all the dense base layers. In this case, the finished molded heat insulating material apparently does not have a dense base layer (the surface layer of the molded heat insulating material is not a two-layer structure consisting of a surface coating layer and a dense base layer, but only a surface coating layer). However, in this case, the volume fraction of the aggregate in the dense base layer may be regulated within the above range after the step of forming the dense base layer.

Further, the dense base layer forming liquid can be configured to impregnate a region thicker than 0.4 mm. For example, the dense base layer forming liquid may be impregnated in a region of at least 0.5 mm from the surface of the molded heat insulating material, or may be impregnated in a region of at least 1.0 mm from the surface of the molded heat insulating material. The thicker the impregnated region of the surface coating liquid or the dense base layer forming liquid, the lower the gas permeability, but the higher the cost. Therefore, it is preferable to determine the thickness in a balance between cost and effect.

Further, in the present specification, carbon means a thing in a broad sense, and may be amorphous or graphitic. Further, the particles may have a spherical shape, an elliptical spherical shape, an indefinite shape, or the like, but do not include a short fiber (milled) shape. For example, those having a circular end face (short fibers) and those having an aspect ratio of 9 or more are not considered to be particles. The surface coating liquid may contain a component that becomes carbon particles, and may contain carbon fiber milled or the like as a sub-component as an aggregate component other than this.

The average particle size of the carbon particles (after firing) is preferably 3 to 100 μm, more preferably 5 to 60 μm, and even more preferably 10 to 40 μm.

In the case of a milled form, the average fiber diameter is preferably 5 to 30 μm, more preferably 6 to 20 μm, and even more preferably 7 to 18 μm. The average fiber length (length average fiber length) is preferably 0.04 to 0.8 mm, more preferably 0.1 to 0.6 mm, still more preferably 0.2 to 0. It is 5 mm. The average fiber length Z _L is Z _L = (X ₁ ² + X ₂ ² + X ₃ ² + ... + X _n ² ) / (X ₁ + X ₂ + X ₃ + _{, where X n} is the individual fiber length. ... + X _n ).

The volume fraction of the aggregate in the surface coating layer is more preferably 2 to 7%, still more preferably 3 to 5%. The volume fraction of the aggregate in the dense base layer is more preferably 0.3 to 5%, and further preferably 2 to 4%.

Further, as the binder used for the dense base layer forming liquid and the surface coating liquid, a thermosetting resin such as a phenol resin, a furan resin, a polyimide resin, or an epoxy resin can be used.

The aggregate used for the surface coating liquid more preferably contains cured product particles of a thermosetting resin and carbonized particles of a thermosetting resin, which become amorphous carbon particles after firing, and contains 600 to 1000 phenol resins. It is more preferable to contain carbonized particles obtained by heat treatment at ° C.

Further, the dense base layer forming liquid and the surface coating liquid may contain a solvent that dissolves the binder in addition to the aggregate and the binder. As the solvent, a component (for example, ethanol or methanol) that is volatilized and removed by calcination is used.

The mass ratio of the aggregate in the dense base layer forming liquid or the surface coating liquid is preferably 1 to 20% by mass, more preferably 1 to 10% by mass, and 5 to 10% by mass. Is even more preferable.

The firing temperature of the dense base layer forming step is preferably 500 to 1500 ° C, more preferably 600 to 1000 ° C, and even more preferably 700 to 900 ° C. The firing temperature of the surface coating layer forming step is preferably 1000 to 2500 ° C, more preferably 1500 to 2500 ° C, and even more preferably 2000 to 2500 ° C.

Further, the dense base layer forming liquid and the surface coating liquid may be the same as long as the above regulations are satisfied.

Further, the dense base layer forming step may be a step of impregnating and firing the dense base layer forming liquid twice or more, respectively, and the surface coating layer forming step may be a step of impregnating the surface coating liquid and firing twice or more, respectively. It may be a step to be performed. However, as the number of times of impregnation and firing increases, the cost increases accordingly. Therefore, it is preferable to determine the number of times of impregnation and firing from the balance between cost and effect. It is more preferable to set it once.

The molded heat insulating material produced by the production method according to the present invention is as follows.
In a molded heat insulating material having a fiber felt in which carbon fibers are entangled and a protective carbon layer made of carbonaceous material that coats the carbon fiber surface of the fiber felt, in a region 0.4 mm from at least one surface of the molded heat insulating material. is formed carbonaceous surface layer and the carbonized product of the aggregate and the thermosetting resin is permeated into the interior of the molded insulation, said surface layer, as well as containing carbon particles as the aggregate, the aggregate volume fraction of, Ru 1-7% der, or the surface layer, the surface side of the area, the volume fraction of the aggregates and a small inner side area than the area of the surface The region on the surface side includes a region of at least 0.1 mm from the surface, contains carbon particles as the aggregate, and the volume fraction of the aggregate in this region is 1 to 7%. The volume fraction of the aggregate in the side region is 0.3 to 5% .

In the above configuration, the carbon particles can be configured to include amorphous carbon particles. Graphite has a highly developed graphite structure (layer structure), has a larger specific surface area than amorphous carbon, and is more likely to react with active gas, especially at its edges, so it is not as carbon particles as graphite particles. It preferably contains crystalline carbon particles.

Further, in the above configuration, the volume fraction of the carbon particles in the region where the volume fraction of the aggregate is 1 to 7% is preferably 1 to 7%, more preferably 2 to 7%, still more preferably. It shall be 3 to 5%. This configuration is preferable because the path through which the gas passes can be reduced more effectively.

As described above, according to the present invention, it is possible to realize a carbon fiber molded heat insulating material capable of suppressing gas permeation at low cost.

FIG. 1 is a cross-sectional micrograph of the molded heat insulating material according to the present invention. 2A and 2B are cross-sectional micrographs of the molded heat insulating material according to Example 3, FIG. 2A is a molded heat insulating material before processing, and FIG. 2B is a molded heat insulating material after forming a dense base layer. 2 (c) shows the molded heat insulating material after the surface coating layer is formed. FIG. 3 is a diagram schematically showing a gas permeation test apparatus.

(Embodiment)
The molded heat insulating material according to the present invention is a molded heat insulating material having a fiber felt in which carbon fibers are entangled and a protective carbon layer made of carbonaceous material that coats the carbon fiber surface of the fiber felt, and is at least one surface of the molded heat insulating material. A surface layer is formed in which an aggregate of carbon particles and a carbonized product of a thermosetting resin are infiltrated into the molded heat insulating material. This surface layer has a volume fraction of aggregate of 1 to 7% . Alternatively, the surface layer has a region on the surface side and a region on the inner side where the volume fraction of the aggregate is smaller than the region on the surface side. The region on the surface side includes a region of at least 0.1 mm from the surface, contains carbon particles as an aggregate, and the volume fraction of the aggregate in this region is 1 to 7%. The volume fraction of the material is 0.3 to 5% .

Here, the protective carbon layer reacts with the active gas (oxygen gas, SiO gas, etc.) prior to the carbon fibers and acts to suppress the deterioration of the carbon fibers.

The carbon fibers constituting the molded heat insulating material are not particularly limited, and are, for example, anisotropic or isotropic pitch type derived from coal or petroleum, polyacrylonitrile (PAN) type, rayon type, phenol type, and cellulose type. Etc., can be used as a single type or a mixture of a plurality of types.

The microscopic structure of the carbon fiber is not particularly limited, and only those having the same shape (curvature type, linear type, diameter, length, etc.) may be used, or different structures are mixed. You may. However, since the type of carbon fiber and its microscopic structure affect the physical properties of the molded heat insulating material to be manufactured, it is preferable to appropriately select it according to the application.

As the microscopic structure of the molded heat insulating material, it is preferable to use a material in which carbon fibers oriented in random directions are intricately interlaced.

Further, the molded heat insulating material may be cut or the like after the molded heat insulating material is produced by using a long or long molded heat insulating material, or may be cut in advance to the size of the molded heat insulating material.

The protective carbon layer is present so as to cover the entire surface of the carbon fibers or a part of the surface of the carbon fibers, or fill the spaces between the carbon fibers. Further, the protective carbon layer may be carbonaceous, and the compound from which it is derived is not particularly limited. Of these, it is preferable to use a carbonized resin material that can be impregnated in the 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.

Here, only one type of thermosetting resin may be used for producing the molded heat insulating material, or two or more types may be mixed and used. Further, the thermosetting resin may be contained in the fiber felt as it is, or may be diluted with a solvent and contained in the fiber felt. As the solvent, alcohols such as methyl alcohol and ethyl alcohol can be used.

In the configuration of the present embodiment, a surface layer is provided on at least one surface of the molded heat insulating material, and a carbon fiber reinforced carbon composite material sheet is arranged on the surface on the active gas source (heat source) side. Penetration of active gas by airflow is suppressed. Furthermore, this layer also suppresses deterioration and pulverization of carbon fibers. Therefore, the heat insulating effect can be obtained for a long period of time, and the life of the molded heat insulating material can be extended.

The surface layer is formed on the molded insulation as follows.
A dense base layer forming liquid composed of a carbonaceous aggregate, a thermosetting resin, and a solvent is applied to a region 0.4 mm from at least one surface of the molded heat insulating material, and the dense base layer is applied to this region. Infiltrate the forming liquid. At this time, the molded heat insulating material may be applied so as to apply pressure.

After that, the thermosetting resin is carbonized by heat treatment at 500 to 1000 ° C. in an inert atmosphere, so that the surface of the carbon fiber, the surface of the protective carbon layer, and a part of the voids between the carbon fibers are formed into bones. The material and the carbonized material of the thermosetting resin are infiltrated to form a dense base layer.

After that, a surface coating liquid composed of an aggregate made of amorphous carbon, a thermosetting resin, and a solvent is applied or sprayed to a region of at least 0.1 mm from the surface of the dense base layer, and this region. Infiltrate the surface coating liquid.

After that, the thermosetting resin is carbonized by heat treatment at 1000 to 2500 ° C. in an inert atmosphere, so that the aggregate and the carbonized product of the thermosetting resin are further permeated into at least a part of the dense base layer. A surface coating layer is formed. Therefore, the surface layer formed in the molded heat insulating material has a two-layer structure of a dense base layer and a surface coating layer (when the surface coating layer is formed on the entire dense base layer, it has a one-layer structure).

Here, carbonization as used herein means a broad definition including graphitization. For example, especially when heat treatment is performed at a temperature of 2000 ° C. or higher, it is conceivable that the graphite structure of the surface coating layer develops. In the present invention, the aggregate of the dense base layer and the surface coating layer is amorphous and graphite. It may be any of.

As the thermosetting resin used for forming the dense base layer and the surface coating layer, a phenol resin, a furan resin, a polyimide resin, an epoxy resin or the like can be used. As the aggregate used for forming the dense base layer, natural graphite, artificial graphite powder, or milled carbon fiber can be used. As the aggregate used when forming the surface coating layer, a cured product of a thermosetting resin (for example, phenol resin, furan resin, polyimide resin, epoxy resin, etc.) which becomes amorphous carbon particles after firing and / or Carbonized products can be used. It is more preferably a carbonized product of a thermosetting resin, and further preferably a carbonized product obtained by heat-treating a phenol resin at 600 to 1000 ° C. The aggregate in the dense base layer forming liquid and the surface coating liquid is preferably 1 to 20% by mass, more preferably 1 to 10% by mass.

Further, the bulk density of the molded heat insulating material main body portion (the portion where the dense base layer or the surface coating layer is not formed) ^{is preferably 0.07 to 0.3 g / cm 3} , preferably 0.13 to 0.3 g. / more preferably cm is ^3, further preferably 0.16～0.3G / cm ^3.

The bulk density of the dense underlayer is preferably 0.1 to 1.0 g / cm ^3, more preferably from 0.2 to 0.6 g / cm ^3, 0.3-0.6 g It is more preferably / cm ^3. The bulk density of the surface coating layer is preferably 0.2~1.2g / cm ^3, more preferably 0.4~0.9g / cm ^3, 0.6~0.9g It is more preferably / cm ^3.

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

(Formation of a dense base layer)
A molded heat insulating material (DON-1000-H manufactured by Osaka Gas Chemical Co., Ltd., bulk density 0.16 g / cm ³ ) was cut into 100 × 100 × 50. On one surface of this molded heat insulating material having an area of 100 × 100, 99 parts by mass of a liquid resole-type thermosetting phenol resin and 1 part by mass of natural scaly graphite powder (average particle size 30 μm) are mixed. 1.3 g of the dense base layer forming liquid was impregnated by pushing it with a brush.

The molded heat insulating material impregnated with the dense base layer forming liquid was placed in a heat treatment furnace and heat-treated at 800 ° C. for 1 hour in a nitrogen gas atmosphere to carbonize the phenol resin.

After firing, 0.3 g of the above-mentioned dense base layer forming liquid was impregnated in the same manner as above, and then heat treatment was performed. By this treatment, a dense base layer was formed on the surface of the molded heat insulating material. Further, the dense base layer forming liquid was impregnated in a region of about 800 μm.

(Formation of surface coating layer)
6.8 parts by mass of amorphous carbon spherical particles (average particle size 15 μm) and 1.2 parts by mass of carbon fiber milled (S-242 (average fiber length 0.37 mm) manufactured by Osaka Gas Chemical Co., Ltd.) as aggregate , 10% by mass of granular phenol resin as a thermosetting resin and 82 parts by mass of industrial methanol as a solvent were mixed to prepare a surface coating liquid.

A surface coating liquid was applied to the dense base layer so that the thickness of the impregnated region of the liquid was about 400 μm. Then, the thermosetting phenol resin was carbonized by heat treatment at 2000 ° C. for 5 hours in an inert atmosphere to prepare a molded heat insulating material according to Example 1. That is, in this embodiment, a surface layer having a two-layer structure of a dense base layer having a thickness of 400 μm and a surface coating layer having a thickness of 400 μm is formed in the molded heat insulating material.

(Example 2)
Examples were the same as in Example 1 except that a dense base layer forming liquid having a mass mixing ratio of liquid resole-type thermosetting phenol resin and natural scaly graphite powder of 95: 5 was used. A molded heat insulating material according to No. 2 was produced.

(Example 3)
Examples were the same as in Example 1 except that a dense base layer forming liquid having a mass mixing ratio of liquid resole-type thermosetting phenol resin and natural scaly graphite powder of 90:10 was used. The molded heat insulating material according to No. 3 was produced.

(Example 4)
In the same manner as in Example 1, a dense base layer forming liquid using carbon fiber milled (S-242 manufactured by Osaka Gas Chemical Co., Ltd.) was used as an aggregate instead of the natural scaly graphite powder. The molded heat insulating material according to Example 4 was produced.

(Example 5)
Except for the use of a dense base layer forming liquid having a mass mixing ratio of 95: 5 between a liquid resole-type thermosetting phenol resin and carbon fiber milled (S-242 manufactured by Osaka Gas Chemical Co., Ltd.). The molded heat insulating material according to Example 5 was produced in the same manner as in Example 4.

(Example 6)
The molded heat insulating material according to Example 6 was produced in the same manner as in Example 4 except that the dense base layer forming liquid was impregnated and fired only once.

(Example 7)
The molded heat insulating material according to Example 7 was produced in the same manner as in Example 5 except that the dense base layer forming liquid was impregnated and fired only once.

(Example 8)
The molded heat insulating material according to Example 8 was produced in the same manner as in Example 1 except that the dense base layer forming liquid was impregnated and fired only once.

(Example 9)
The molded heat insulating material according to Example 9 was produced in the same manner as in Example 3 except that the dense base layer forming liquid was impregnated and fired only once.

(Example 10)
The molded heat insulating material according to Example 10 was produced in the same manner as in Example 3 except that the surface coating liquid was not impregnated and the subsequent firing was not performed.

(Comparative Example 1)
The DON-1000-H used in Example 1 was used as the molded heat insulating material according to Comparative Example 1.

(Comparative Example 2)
The molded heat insulating material according to Comparative Example 2 was produced in the same manner as in Example 4 except that the surface coating liquid was not impregnated and the subsequent firing was not performed.

(Comparative Example 3)
The molded heat insulating material according to Comparative Example 3 in the same manner as in Example 4 except that the dense base layer forming liquid was impregnated and fired only once, and the surface coating liquid was not impregnated and subsequently fired. Was produced.

(Comparative Example 4)
The molded heat insulating material according to Comparative Example 4 was produced in the same manner as in Example 5 except that the surface coating liquid was not impregnated and the subsequent firing was not performed.

(Comparative Example 5)
The molded heat insulating material according to Comparative Example 5 in the same manner as in Example 5 except that the dense base layer forming liquid was impregnated and fired only once, and the surface coating liquid was not impregnated and subsequently fired. Was produced.

(Comparative Example 6)
The molded heat insulating material according to Comparative Example 6 was produced in the same manner as in Example 1 except that the surface coating liquid was not impregnated and the subsequent firing was not performed.

(Comparative Example 7)
The molded heat insulating material according to Comparative Example 7 in the same manner as in Example 1 except that the dense base layer forming liquid was impregnated and fired only once, and the surface coating liquid was not impregnated and subsequently fired. Was produced.

(Comparative Example 8)
The molded heat insulating material according to Comparative Example 8 in the same manner as in Example 3 except that the dense base layer forming liquid was impregnated and fired only once, and the surface coating liquid was not impregnated and subsequently fired. Was produced.

The gas transmittance of the molded heat insulating materials according to Examples 1 to 10 and Comparative Examples 1 to 8 was measured under the following conditions. The results are shown in Table 1 below.

(Gas permeation test)
In the gas permeation test apparatus 100, as shown in FIG. 3, a cap-shaped container 41 is placed on a flat plate-shaped base 42, whereby a primary side space 20 is formed. The primary side space 20 is provided with a transparent cell 21. Further, a through hole is provided in the central portion of the base 42, and the pipe 35 is connected to the through hole. The space below the table 42 is the secondary space 30. Further, the gas permeation test apparatus 100 includes a pressure gauge 31 that measures the pressure in the primary side space 20 and the secondary side space 30.

Further, an intake pipe 23 for supplying gas to the inside of the primary side space 20 is provided, and exhaust pipes 25 and 33 are connected to the rotary vacuum pump 34 and exhaust the gas inside the primary side space 20 or the secondary side space 20, respectively. Is provided. Valves 22, 24 and 32 are provided on these pipes, respectively.

The above-mentioned molded heat insulating material was cut into a size of 6 cm in length, 6 cm in width, and about 2 cm in thickness to obtain a test piece 10, and was installed in a permeation cell 21 of a gas permeation test apparatus 100. The periphery of the test piece 10 is sealed with silicone rubber 11 so that gas leakage does not occur, and silicone rubber O-rings 12 are installed on the upper and lower surfaces. As a result, the gas inside the primary side space 20 cannot move to the secondary side space 30 unless it passes through the test piece 10 inside the permeation cell 21.

The measurement was performed as follows. First, the valves 24 and 32 are opened, and the pressure is reduced by the vacuum pump 34 until the primary side space 20 and the secondary side space 30 reach a constant vacuum value. Next, the valves 24 and 32 are closed to stop the operation of the vacuum pump 34. Then, the valve 22 is opened to supply nitrogen gas to the primary side space 20 at a constant gas pressure. Nitrogen gas permeates the test piece 10 from the primary side space 20 and moves to the secondary side space 30, whereby the pressure in the secondary side space 30 begins to rise. The pressure rise rate was measured using a pressure gauge 31. From this pressure rise rate, the gas permeability (K) was calculated using the following equations (3) and (4).

K = (Qh) / (ΔPA) ... (3)
Q = {(p _2- p ₁ ) V ₀ } / t ... (4)
Here, K is the nitrogen gas permeability, Q is the air volume, ΔP is the pressure difference between the primary side and the secondary side, A is the permeation area, h is the thickness of the test piece, and p ₁ is the initial pressure on the secondary side. p ₂ is the final pressure on the secondary side, V ₀ is the volume on the secondary side, and t is the measurement time.

_{At this time, since the measurement is performed in the range of the average pressure P m} (the average value of the pressures in the primary side space and the secondary side space) such that the following equation (5) holds _{, the average pressure P m} is about 50 to 110 kPa. The measurement was performed in the above range. The gas permeability shown in Table 2 shows the value when _{P m} = 100 kPa in the approximate straight line by the least squares method when the gas permeability K is plotted at 3 points or more with respect to the _{average pressure P m.}

K = aP _m + b ・ ・ ・ (5)
Here, a and b are constants.

(Measurement of volume fraction)
The volume fraction of the aggregate (total of scaly graphite, amorphous carbon particles, and carbon fiber milled) in the surface coating layer of the molded heat insulating material according to Examples 1 to 10 and Comparative Examples 1 to 8 was determined. First, the apparent density of the aggregate was determined by the n-butanol immersion method. The apparent density here means the density of n-butanol excluding the open pores that permeate the aggregate. The volume of the aggregate was determined by dividing the mass of the aggregate by the apparent density. Each volume fraction was obtained by dividing the volume of aggregate in each layer by the volume of each layer.

From this result, it can be seen that when Examples 1 to 10 and Comparative Example 1 in which the surface coating layer is not formed at all are compared, it is possible to make it difficult for gas to permeate by about 7 times or more.

Further, in Comparative Examples 1, 3, 5, 7, and 8 in which the number of times of impregnation of the liquid is 1 or less, the gas permeability is 1.3 × 10 ⁴ cm ² / s or more, and the gas permeation cannot be sufficiently suppressed. I understand.

Further, in Comparative Examples 2 and 6 in which the volume fraction of the aggregate in the region from the surface to 100 μm was less than 1% even when the liquid was impregnated twice, the gas permeability was 1.4 × 10 ^4. and ^{cm 2 /s,6.5×10 3 cm 2 / s} , it can be seen insufficient.

Further, in Comparative Example 4 in which carbon particles are not contained as aggregate in the region from the surface to 100 μm, the volume fraction of the aggregate in this region is as high as 2.69%, but the gas permeability is 7.8 × 10. It turns out that it is insufficient at ³ cm ^{2 / s.}

These things can be considered as follows. In order to suppress the permeation of gas, it is important to reduce the diameter of the path through which the gas passes. Here, if the number of times of impregnation of the liquid is 1 or less (Comparative Examples 1, 3, 5, 7, 8), the diameter of the path cannot be sufficiently reduced.

In addition, the aggregate locally fills the path through which the gas passes, and the carbonized material of the thermosetting resin fills the path through which the gas passes so as to cover the surface of the carbon fiber and the surface of the aggregate. The effect of reducing the diameter of the carbon fiber is great. Therefore, in Comparative Examples 2 and 6 in which the volume fraction of the aggregate is too small in the region from the surface to 100 μm, which has a particularly large effect of contributing to gas blocking, the gas blocking effect is insufficient.

Further, the carbon fiber milled is easily oriented along the carbon fibers constituting the molded heat insulating material, and the effect of reducing the diameter of the path is smaller than that of the carbon particles. Therefore, in Comparative Example 4 in which carbon particles are not contained in the region from the surface to 100 μm, which has a particularly large effect of contributing to gas blocking, the gas blocking effect is insufficient.

On the other hand, Examples 1 to 1 in which the number of times of impregnation of the liquid is 2 or 3 times, the volume fraction of the aggregate in the region from the surface to 100 μm is 1% or more, and carbon particles are contained in this region. At 10, the gas permeability ^{can be sufficiently reduced to 1.9 × 10 3} cm ² / s or less.

FIG. 1 shows a cross-sectional micrograph of the molded heat insulating material according to Example 1 in the vicinity of the surface layer. As can be seen from this photograph, the sheets 1 and 2 having few air gaps between fibers and the sheet 3 having relatively large air gaps between fibers are joined without peeling. Among the sheets having few voids between fibers, the surface coating layer 1 and the dense base layer 2 are formed from the surface side, and the sheet having relatively many voids between fibers is the molded heat insulating material main body 3.

2A and 2B are cross-sectional micrographs of the molded heat insulating material according to Example 3, FIG. 2A is a molded heat insulating material before processing, and FIG. 2B is a molded heat insulating material after forming a dense base layer. 2 (c) shows the molded heat insulating material after the surface coating layer is formed. As can be seen from this photograph, in the molded heat insulating material before processing, a large number of carbon fibers exist while retaining a large number of voids (voids between the fibers), and the inner (back) fibers are seen from the voids. It can be seen that there are many regions that are voids to the back (regions where fibers and the like do not exist within the focusing range). It can be seen that after the formation of the dense base layer, the number of voids is reduced to the back, and after the formation of the surface coating layer, many particulate matter filling the voids can be seen.

In this way, the particulate matter locally fills (closes) the voids between the carbon fibers, so that the path diameter through which the gas passes becomes extremely small, and the gas permeability becomes small.

In the above embodiment, the carbon fibers constituting the molded heat insulating material have an average diameter of 13 μm, but the thickness is not limited to this. However, since the diameter of the fiber affects the heat insulating performance and bulk density of the molded heat insulating material to be manufactured, the diameter and the like may be selected according to the desired heat insulating performance and bulk density.

As described above, according to the present invention, it is possible to realize a molded heat insulating material capable of suppressing a decrease in heat insulating performance due to gas without increasing the cost, and therefore its industrial applicability is great.

1 Surface coating layer 2 Dense base layer 3 Molded heat insulating material Main body 10 Test piece 11 Sealing 12 O-ring 20 Primary side space 21 Permeation cell 22 Valve 23 Intake pipe 24 Valve 25 Exhaust pipe 30 Secondary side space 31 Pressure gauge 32 Valve 33 Exhaust pipe 34 Rotary type vacuum pump 35 Piping 41 Container 42 units 100 Gas permeation tester

Claims (4)

A dense base layer forming liquid containing an aggregate made of carbon and a binder made of a thermosetting resin is impregnated in a region of at least 0.4 mm from at least one surface of the molded heat insulating material, and then fired at 500 ° C. or higher. Then, the thermosetting resin is carbonized to form a dense base layer, and a dense base layer forming step.
A surface coating liquid containing an aggregate containing a component that becomes carbon particles after firing and a binder made of a thermosetting resin is impregnated in a region of at least 0.1 mm from the surface of the dense base layer, and then at 1000 ° C. The surface coating layer forming step of firing as described above to carbonize the thermosetting resin to form a surface coating layer,
With
The volume fraction of the aggregate in the dense base layer after the dense base layer forming step is 0.3 to 5%.
The volume fraction of the aggregate in the region where the surface coating layer is formed on the dense base layer is 1 to 7%.
Manufacturing method of molded insulation. In a molded heat insulating material having a fiber felt in which carbon fibers are entangled and a protective carbon layer made of carbonaceous material that coats the carbon fiber surface of the fiber felt.
In a region 0.4 mm from the surface of at least one of the molded heat insulating materials, a surface layer in which a carbonaceous aggregate and a carbonized product of a thermosetting resin are permeated into the molded heat insulating material is formed.
Said surface layer, as well as containing carbon particles as the aggregate, the volume fraction of the aggregates, Ru 1-7% der, or,
The surface layer has a region on the surface side and a region on the inner side where the volume fraction of the aggregate is smaller than the region on the surface side.
The region on the surface side includes a region of at least 0.1 mm from the surface, contains carbon particles as the aggregate, and the volume fraction of the aggregate in this region is 1 to 7%.
The volume fraction of the aggregate in the inner region is 0.3 to 5%.
Molded heat insulating material characterized by that. The carbon particles include amorphous carbon particles.
The molded heat insulating material according to claim 2. Region volume fraction of the aggregate is 1 to 7%, the volume fraction of the carbon particles is 1 to 7%
The molded heat insulating material according to claim 2 or 3.

Images