JP2024048872A - Insulation - Google Patents

Abstract

[Problem] To provide a heat insulating material with low replacement costs. [Solution] A heat insulating material that covers the periphery of a heat generating body, comprising a first heat insulating member arranged on the heat generating body side and a second heat insulating member arranged on the opposite side to the heat generating body, the first heat insulating member and the second heat insulating member both containing carbon fiber, and the first heat insulating member and the second heat insulating member are in contact with each other in a separable state. [Selected Figure] Figure 1

Description

The present invention relates to a heat insulating material.

Insulation materials made from carbon fibers have a high heat resistance and excellent insulating properties, so they are widely used as insulation for high-temperature furnaces such as single crystal pulling equipment and ceramic sintering furnaces.

Insulating materials using carbon fibers are widely used in the form of highly porous felt, paper products, etc., to suppress heat transfer through the carbon fibers. Generally, felt is deformable, so it is used as a component that fills empty spaces to fill those spaces, or as an insulating material that surrounds other parts. On the other hand, paper products have high shape retention, so they are processed into a specified shape and used as insulating parts. Felt can also be used as an insulating part with good shape retention by compressing it and then fixing it with a binder.

Insulation materials that use carbon fibers can fall off due to oxidation in the furnace and mechanical friction, resulting in the generation of particles. Such defects can also cause a decrease in the insulation against radiation.

In order to solve these problems, Patent Document 1 discloses a composite carbonaceous insulation material having a carbonaceous insulation member with a bulk density of 0.1 to 0.4 g/cm ³ , a carbonaceous protective layer with a bulk density of 0.3 to 2.0 g/cm ³ , and a pyrolytic carbon coating having a bulk density greater than that of the carbonaceous protective layer, in which the carbonaceous protective layer is joined to at least a portion of the surface of the carbonaceous insulation member to form a joint, and a pyrolytic carbon coating layer is formed on at least the surface of the carbonaceous insulation member among the surfaces of the joint, thereby suppressing wear, deterioration, and powdering of the carbon fibers during use and obtaining a composite carbonaceous insulation material with excellent thermal insulation properties.

JP 2000-327441 A

However, when the insulating material described in Patent Document 1 is used as an insulating material at high temperatures such as in an induction heating furnace, wear and deterioration of the pyrolytic carbon coating layer is unavoidable, and when wear and deterioration of the pyrolytic carbon coating layer progresses, it becomes necessary to replace the entire insulating material even if the carbonaceous protective layer and carbonaceous insulating member are not deteriorated. This poses the problem of high replacement costs for the insulating material.

The present invention was made to solve the above problems, and the object of the present invention is to provide an insulating material with low replacement costs.

The heat insulating material of the present invention is a heat insulating material that covers the periphery of a heating element, and is characterized in that it comprises a first heat insulating member arranged on the heating element side and a second heat insulating member arranged on the opposite side of the heating element, the first heat insulating member and the second heat insulating member both containing carbon fiber, and the first heat insulating member and the second heat insulating member are in contact with each other in a separable state.

In the insulation material of the present invention, the first insulation member and the second insulation member are in contact with each other in a separable state, so even if the first insulation member deteriorates or wears out, only the first insulation member can be replaced. This shortens the time required to replace the insulation material, and also reduces the amount of insulation material to be replaced. This reduces the cost of replacing the insulation material.

In the heat insulating material of the present invention, the surface of the first heat insulating member facing the heating element is preferably a pyrolytic carbon layer containing pyrolytic carbon.
Since the surface of the first heat insulating member facing the heating element is a pyrolytic carbon layer, it exhibits excellent heat insulating properties by blocking heat conduction due to radiation in high temperature ranges, particularly in high temperature ranges exceeding 2000° C. Furthermore, even if reactive gas is generated from the heating element or inside the heating element, it has low reactivity to the reactive gas and is less susceptible to deterioration or wear.

In the heat insulating material of the present invention, the pyrolytic carbon layer preferably has a thickness of 2 μm to 60 μm.
If the thickness of the pyrolytic carbon layer is 2 μm to 60 μm, it is possible to achieve both excellent gas barrier properties and radiant heat barrier properties.

In the heat insulating material of the present invention, the surface of the first heat insulating member facing the heating element is preferably a carbon layer containing carbon-based particles between carbon fibers.
Since the surface of the first heat insulating member facing the heating element is a carbon layer containing carbon-based particles, generation of particles due to deterioration of the carbon fibers can be suppressed.

In the heat insulating material of the present invention, the carbon-based particles and the carbon fibers of the carbon layer are preferably bonded to each other with a carbon-based adhesive.
When the carbon-based particles and carbon fibers constituting the carbon layer are bonded to each other with a carbon-based adhesive, the carbon layer becomes strong.

In the heat insulating material of the present invention, the carbon-based particles are preferably at least one carbon-based particle selected from the group consisting of graphite, carbon black, glassy carbon particles, and particles obtained by pulverizing carbon fibers.
At least one carbon-based particle selected from the group consisting of graphite, carbon black, glassy carbon particles, and crushed carbon fiber particles has few impurities and is the same carbon-based material as the carbon fibers that make up the thermal insulation material, and therefore has high durability in high temperature ranges.

In the heat insulating material of the present invention, the carbon-based particles preferably have an average particle size of 10 nm to 500 μm.
When the average particle size of the carbon-based particles is 10 nm to 500 μm, a thin coating layer can be formed in the gaps between the carbon fibers, and the bonding with the carbon fibers in the heat insulating material can be ensured at a high level. Also, the thickness of the carbon layer, which tends to have a high thermal conductivity, can be prevented from becoming too thick.

In the heat insulating material of the present invention, the carbon layer preferably has a thickness of 10 μm to 1000 μm.
When the thickness of the carbon layer is 1000 μm or less, the deterioration of the heat insulating performance can be suppressed.
When the thickness of the carbon layer is 10 μm or more, the strength of the carbon layer can be sufficiently ensured.

In the heat insulating material of the present invention, it is preferable that the first heat insulating member further has a base material made of the carbon fiber and provided on the surface of the carbon layer opposite to the surface on the heating element side.
A substrate made of carbon fibers has gaps between the carbon fibers, and therefore the heat insulating performance can be improved.

In the heat insulating material of the present invention, the substrate is preferably a needle mat of the carbon fiber or a paper product of the carbon fiber.
The carbon fiber needle mat and the carbon fiber paper product are composed of randomly arranged carbon fibers, and therefore can exhibit high thermal insulation properties, making them particularly suitable as a base material constituting the first thermal insulation member.

In the heat insulating material of the present invention, the carbon fibers constituting the substrate preferably have an average fiber length of 2 mm to 8 mm.
When the average fiber length of the carbon fibers constituting the substrate is within the above range, the strength is high and the carbon fibers are less likely to be oriented, so that when used in an induction heating furnace, heat generation due to induction heating can be minimized.

FIG. 1 is a perspective view showing a typical example of the heat insulating material of the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a partially cutaway perspective cross-sectional view that shows a schematic example of a heating device constructed using the heat insulating material of the present invention. FIG. 4 is a partial enlarged view of the area enclosed by the dashed line in FIG. FIG. 5 is a partial enlarged view of the area enclosed by the dashed line in FIG. FIG. 6 is a diagram showing a schematic view of a state in which a deteriorated first heat insulating member is removed. FIG. 7 is a diagram showing a schematic view of a state in which a new first insulating member is inserted.

The following is a detailed description of an embodiment of the present invention. However, the present invention is not limited to the following embodiment, and can be modified as appropriate within the scope of the present invention.

[Thermal insulation]
The insulating material of the present invention is an insulating material that covers the periphery of a heating element, and is characterized in that it comprises a first insulating member arranged on the heating element side and a second insulating member arranged on the opposite side of the heating element, wherein the first insulating member and the second insulating member both contain carbon fiber, and the first insulating member and the second insulating member are in contact with each other in a separable state.

(First heat insulating member)
The first insulating member preferably has a base material made of carbon fibre.
The substrate made of carbon fibers has gaps between the carbon fibers, and therefore the heat insulating performance can be improved.

The average fiber diameter of the carbon fibers is preferably 1 μm to 20 μm.
When the average fiber diameter of the carbon fibers is 20 μm or less, the conductive heat transfer effect of the carbon fibers themselves can be suppressed, and when the average fiber diameter of the carbon fibers is 1 μm or more, the light shielding property is excellent and radiative heat transfer can be suppressed.

The average fiber length of the carbon fibers is preferably 2 mm to 10,000 mm.
The average fiber length of the carbon fibers may be 2 mm to 8 mm, or 10 mm to 10,000 mm.

The carbon fiber can be either pitch-based carbon fiber or PAN-based carbon fiber, and can be either graphitic or carbonaceous carbon fiber.

The substrate is preferably a needle mat of carbon fiber or a paper article of carbon fiber.
The carbon fiber needle mat and the carbon fiber paper product are composed of randomly arranged carbon fibers, and therefore can exhibit high thermal insulation properties, making them particularly suitable as a base material for constituting the first thermal insulation member.

When the substrate is a needle mat of carbon fibers, the average fiber length of the carbon fibers is preferably 10 mm to 10,000 mm.
When the substrate is a carbon fiber paper product, the average fiber length of the carbon fibers is preferably 2 mm to 8 mm.

The first heat insulating member may have a substrate and a carbon layer formed on the surface of the substrate, the carbon layer containing carbon-based particles between carbon fibers.
The carbon fibers constituting the carbon layer are the same as the carbon fibers constituting the first heat insulating member.

The surface of the first heat insulating member facing the heating element may be a carbon layer containing carbon-based particles between carbon fibers.
By forming the surface of the first heat insulating member facing the heating element as a carbon layer containing carbon-based particles, generation of particles due to deterioration of the carbon fibers can be suppressed.
Whether or not the surface of the first heat insulating member facing the heating element is a carbon layer can be confirmed by observing a cross section of the first heat insulating member with a polarizing microscope or the like.

The thickness of the carbon layer is not particularly limited, but is preferably 10 μm to 1000 μm.
When the thickness of the carbon layer is 1000 μm or less, the deterioration of the heat insulating performance can be suppressed.
When the thickness of the carbon layer is 10 μm or more, the generation of particles due to deterioration of the carbon fiber can be sufficiently suppressed.

The surfaces of the first insulating member other than the surface facing the heating element, i.e., the surface opposite the surface facing the heating element, and/or the longitudinal end surfaces may also be carbon layers.

The carbon-based particles are preferably at least one carbon-based particle selected from the group consisting of graphite, carbon black, glassy carbon particles, and pulverized carbon fiber particles.
At least one carbon-based particle selected from the group consisting of graphite, carbon black, glassy carbon particles, and crushed carbon fiber particles has few impurities and is the same carbon-based material as the carbon fibers and pyrolytic carbon layer that make up the thermal insulation material, and therefore has high durability in high temperature ranges.

The glassy carbon particles are obtained by pulverizing non-graphitizable carbon such as phenol resin carbide.
The particles obtained by pulverizing carbon fibers are also called milled carbon fibers. The average fiber length of the milled carbon fibers is preferably, for example, 20 μm to 500 μm.

The carbon-based particles preferably have an average particle size of 10 nm to 500 μm.
When the carbon-based particles have an average particle size of 10 nm to 500 μm, a thin carbon layer can be formed in the gaps between the carbon fibers, and the bonding between the carbon fibers and the pyrolytic carbon layer in the heat insulating material can be ensured at a high level. Also, the carbon layer, which tends to have a high thermal conductivity, can be prevented from becoming too thick.

The carbon-based particles and carbon fibers are preferably bonded to each other with a carbon-based adhesive.
When the carbon-based particles and carbon fibers constituting the carbon layer are bonded to each other with a carbon-based adhesive, the carbon layer becomes strong.

Carbon-based adhesives are organic binders that are carbonized by heating in a non-oxidizing atmosphere. Details will be given later.

The first insulating member may have a base material and a pyrolytic carbon layer made of pyrolytic carbon formed on the surface of the base material.

The surface of the first heat insulating member facing the heating element may be a pyrolytic carbon layer made of pyrolytic carbon.
By forming a pyrolytic carbon layer on the surface of the first heat insulating member facing the heating element, the gas barrier properties and the radiant heat barrier properties can be improved.
Whether or not the surface of the first heat insulating member facing the heating element is a pyrolytic carbon layer can be confirmed by observing a cross section of the first heat insulating member using a polarizing microscope or the like.

The thickness of the pyrolytic carbon layer is not particularly limited, but is preferably 2 μm to 60 μm.
The thickness of the pyrolytic carbon layer can be confirmed by observing a cut surface of the first heat insulating member using a polarizing microscope or the like.

The surfaces of the first insulating member other than the surface facing the heating element, i.e., the surface opposite the surface facing the heating element, and/or the longitudinal end surfaces may also be pyrolytic carbon layers.

The first insulating member may have both a pyrolytic carbon layer and a carbon layer.
In this case, it is preferable that the pyrolytic carbon layer is disposed on the front surface side.
In other words, it is preferable that a carbon layer is disposed between the substrate and the pyrolytic carbon layer.

The first insulating member may be composed of a substrate made of carbon fiber, or may be composed of the substrate and a pyrolytic carbon layer formed on the surface of the substrate, or may be composed of the substrate and a carbon layer formed on the surface of the substrate, or may be composed of the substrate, a carbon layer formed on the surface of the substrate, and a pyrolytic carbon layer formed on the surface of the carbon layer.

When the first heat insulating member has both a pyrolytic carbon layer and a carbon layer, it is preferable that carbon fibers are exposed on the surface of the carbon layer.
When the carbon fibers are exposed on the surface of the carbon layer, the pyrolytic carbon layer is directly bonded to the carbon fibers, thereby increasing the bonding strength between the carbon layer and the pyrolytic carbon layer and preventing delamination between the carbon layer and the pyrolytic carbon layer.

The thickness of the first heat insulating member is not particularly limited, but is preferably 3 to 50 mm.
The thickness of the first heat insulating member is the shortest distance between the surface of the first heat insulating member on the heating element side and the surface opposite to the surface on the heating element side.

The outer shape of the first heat insulating member is not particularly limited as long as it has a columnar space inside for accommodating the heating element, and examples of the outer shape include columnar shapes such as a cylindrical shape and a rectangular column shape.
The outer shape of the space is not particularly limited, but examples thereof include columnar shapes such as a cylindrical shape and a rectangular column shape.

The cross-sectional shape of the space formed inside the first insulating member in a direction perpendicular to the longitudinal direction is not particularly limited, and may be, for example, a circular shape such as a perfect circle or an ellipse, or a polygonal shape such as a square, pentagon, or hexagon.

The bulk density of the first heat insulating member is not particularly limited, but is preferably 0.05 to 0.4 g/cm ³ .
The bulk density of the first insulating member can be measured by dividing the weight of the first insulating member by the volume determined from the outer dimensions of the first insulating member.

The first heat insulating member does not have to be formed in a cylindrical shape from the beginning.
That is, the first heat insulating member may be an assembly of a plurality of heat insulating members each having a cylindrical shape divided into a plurality of pieces.
The first heat insulating member may be a sheet-like molded body made of carbon fiber and having a generally rectangular shape in plan view, which is deformed so that a columnar space for accommodating the heating element is formed inside.

When the sheet-like molded body is deformed into a cylindrical shape, the portions where the ends of the sheet-like molded body come into contact with each other (contact portions) may be in contact with each other in a separable state, may be bonded to each other with a carbon-based adhesive, or may be sewn together with carbon fiber, etc.

(Second heat insulating member)
The second insulating member includes carbon fiber.
The second heat insulating member preferably has a substantially cylindrical shape that is one size larger than the first heat insulating member.
Moreover, the thickness of the second heat insulating member is preferably greater than the thickness of the first heat insulating member.

The thickness of the second heat insulating member is preferably 6 to 500 mm.
The thickness of the second heat insulating member is the shortest distance between the surface of the second heat insulating member facing the heating element and the surface opposite the surface facing the heating element.

The bulk density of the second heat insulating member is preferably 0.05 to 0.4 g/cm ³ .
The bulk density of the second insulating member can be measured in the same manner as the bulk density of the first insulating member.

The second insulating member may have a similar configuration to the first insulating member.
That is, the second insulation member may have a substrate made of carbon fiber, may have a pyrolytic carbon layer made of pyrolytic carbon on the substrate, may have a carbon layer, or may have a carbon layer and a pyrolytic carbon layer.
Furthermore, the average fiber diameter and average fiber length of the carbon fibers constituting the second insulation member may be the same as the average fiber diameter and average fiber length of the carbon fibers constituting the first insulation member, or may be different from each other.

The external shape of the second insulating member may be any shape capable of covering the periphery of the first insulating member, and may be cylindrical from the start, may be an assembly of multiple insulating members each having a cylindrical shape divided into multiple pieces, or may be a sheet-like molded body that has been deformed into a cylindrical shape.

Hereinafter, an example of the heat insulating material of the present invention will be described with reference to the drawings.
Fig. 1 is a perspective view showing an example of the heat insulating material of the present invention, and Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1.

As shown in FIG. 1 , the thermal insulation material 1 includes a first thermal insulation member 10 and a second thermal insulation member 20 .
The first heat insulating member 10 has a cylindrical space 30 therein for accommodating a heat generating element.
That is, the first heat insulating member 10 is disposed closer to the heat generating element than the second heat insulating member 20 .
The first heat insulating member 10 has a generally cylindrical shape extending in the longitudinal direction (Z direction in FIG. 1 ). The top view shape of the first heat insulating member 10 from the Z direction is annular with respect to a plane parallel to the X direction and the Y direction perpendicular to the longitudinal direction (Z direction).

Since space 30 is a space for accommodating a heating element (not shown), insulation material 1 is an insulation material that covers the periphery of the heating element.

As shown in Figure 2, the first insulation member 10 has a first main surface 10a which is the surface facing the heating element, a second main surface 10b which is the surface opposite to the surface facing the heating element, and end surfaces 10c which correspond to both ends in the longitudinal direction.
The second main surface 10b, which is the surface opposite to the surface on the heating element side, is also the surface on the second heat insulating member 20 side.

The second heat insulating member 20 has a substantially cylindrical space therein for accommodating the first heat insulating member 10 .
That is, the second heat insulating member 20 is disposed on the opposite side of the first heat insulating member 10 to the heating element.

The second heat insulating member 20 has a generally cylindrical shape extending in the longitudinal direction (Z direction in FIG. 1).
The second insulation member 20 has a first main surface 20a which is the surface facing the heating element, a second main surface 20b which is the surface opposite to the surface facing the heating element, and end surfaces 20c which correspond to both ends in the longitudinal direction.

The first main surface 20a is also the surface on the first heat insulating member 10 side.
The second main surface 20b is also the surface opposite to the surface on the first heat insulating member 10 side.

The second insulating member 20 has an approximately cylindrical shape that is slightly larger than the first insulating member 10.

When the thermal insulation material 1 is used, a heating element is placed in the space 30 shown in FIG.
This will be explained with reference to FIG.

FIG. 3 is a partially cutaway perspective cross-sectional view that shows a schematic example of a heating device constructed using the heat insulating material of the present invention.
The heating device 100 shown in FIG. 3 includes a heat insulating material 1, a crucible 50, and an induction heating coil 70 for heating the crucible 50.
The crucible 50 is heated by the induced current generated by the induction heating coil 70. Therefore, the crucible 50 is a heating element.
The crucible 50 has a cavity 51. Therefore, the heating device 100 can heat the material placed in the cavity 51 by causing the crucible 50 to generate heat using the induction heating coil 70.

The crucible 50 , which is a heating element, is surrounded by a heat insulating material 1 .
The heat insulating material 1 comprises a first heat insulating member 10 arranged on the heating element side, and a second heat insulating member 20 arranged on the opposite side to the heating element.
The space in which the crucible 50 , which is a heating element, is placed is a part or the whole of the space 30 that the thermal insulation material 1 has.
An induction heating coil 70 is wound around the outer circumferential surface of the heat insulating material 1 .

In the heating device 100, the crucible 50, which is the heating element, and the insulating material 1 are in direct contact with each other, but an appropriate gap may be provided between the crucible 50, which is the heating element, and the insulating material 1.

In the thermal insulation material 1, the first thermal insulation member 10 and the second thermal insulation member 20 are in contact with each other in a separable state.
Therefore, even if the heating device 100 is used and the first insulating member 10 deteriorates, only the first insulating member 10 can be easily replaced, thereby reducing replacement costs.

In the heating device 100 shown in FIG. 3, the material constituting the crucible 50 is not particularly limited as long as it is a conductor, but graphite is preferred because of its excellent heat resistance and durability at high temperatures (especially 2000°C or higher).

Heating elements are not limited to those for heating solids and liquids as described above.
For example, the heating element may be a cylinder made of graphite that heats the gas passing through it.
The heating element may be a heater that is heated directly by electrical current, and there may be a gap between the heating element and the insulating material to accommodate the object to be heated.

In the heating device 100 shown in FIG. 3, the first heat insulating member 10 containing carbon fiber is used so as to cover the heating element 50.
In addition, in the heating device 100 shown in Figure 3, it can be said that a second insulating member 20 containing carbon fiber is used so as to cover the periphery of the first insulating member 10 and to be in contact with the first insulating member 10 in a separable state.

FIG. 4 is a partial enlarged view of the area enclosed by the dashed line in FIG.
As shown in FIG. 4 , in the thermal insulation material 1 , the first thermal insulation member 10 is disposed on the heating element 50 side, and the second thermal insulation member 20 is disposed on the opposite side to the heating element 50 .

When the surface of the first insulating member 10 facing the heating element 50 (first main surface 10a) is a pyrolytic carbon layer containing pyrolytic carbon as described below, it reflects the radiant light emitted from the heating element 50 to prevent radiant heat transfer and has excellent gas barrier properties.

In FIG. 4, the heating element 50 and the first insulating member 10 are in close contact with each other, but the distance between the heating element 50 and the first insulating member 10 may be adjusted appropriately to provide a gap. The gap is a part of the space 30 shown in FIG. 2 that remains when a heating element 50 having dimensions smaller than the space 30 is placed in the space 30.

Fig. 5 is a partial enlarged view of the area surrounded by the dashed line in Fig. 2. However, in Fig. 5, configurations other than the first heat insulating member are omitted.
As shown in Figure 5, the first insulation member 10 has a surface (first main surface 10a) that is positioned on the side of the space 30 that accommodates the heating element, a surface (second main surface 10b) that is positioned on the side of the second insulation member 20, and an end surface 10c.
The thickness of the first heat insulating member 10 is the shortest distance between the first main surface 10a and the second main surface 10b, and is the length indicated by the double-headed arrow _d10 in FIG.

As shown in FIG. 5, the first insulating member 10 may have a pyrolytic carbon layer 11, a carbon layer 12, and a substrate 13.

The pyrolytic carbon layer 11 is a layer containing pyrolytic carbon.
5, the surface (first main surface 10a) of the first heat insulating member 10 on the heating element side may be a pyrolytic carbon layer 11a containing pyrolytic carbon. In this case, it can be said that the pyrolytic carbon layer 11a is provided on the first main surface 10a of the first heat insulating member 10.
The surface (second main surface 10b) opposite to the surface on the heating element side of the first heat insulating member 10 may be a pyrolytic carbon layer 11b containing pyrolytic carbon. In this case, it can be said that the pyrolytic carbon layer 11b is provided on the second main surface 10b of the first heat insulating member 10.
Furthermore, the end surface 10c of the first heat insulating member 10 may be a pyrolytic carbon layer 11c containing pyrolytic carbon. In this case, it can be said that the end surface 10c of the first heat insulating member 10 is provided with the pyrolytic carbon layer 11c.

The carbon layer 12 is a layer containing carbon-based particles between carbon fibers.
As shown in FIG. 5, a carbon layer 12 may be provided between a pyrolytic carbon layer 11 and a substrate 13 .
The carbon layer 12 may have a carbon layer 12a provided on the first main surface 10a side of the first insulation member 10, a carbon layer 12b provided on the second main surface 10b side, and a carbon layer 12c provided on the end surface 10c side.

The carbon layer 12a is provided on the surface of the pyrolytic carbon layer 11a opposite to the surface on the heating element side.
When the pyrolytic carbon layer 11a is not provided, the surface of the first heat insulating member facing the heating element may be a carbon layer 12a.
The carbon layer 12b is provided on the surface of the pyrolytic carbon layer 11b facing the heating element.
When the pyrolytic carbon layer 11b is not provided, the surface 10b of the first heat insulating member opposite to the surface on the heating element side may be the carbon layer 12b.
The carbon layer 12c is provided on the surface of the pyrolytic carbon layer 11c opposite to the end portion in the longitudinal direction of the first heat insulating member.

The substrate 13 is made of carbon fiber.
The substrate 13 is provided on the surface of the carbon layer 12a opposite to the surface on the pyrolytic carbon layer 11a side. It can also be said that the substrate 13 is provided on the surface of the carbon layer 12b opposite to the surface on the pyrolytic carbon layer 11b side.
In addition, when the pyrolytic carbon layer 11 b and the carbon layer 12 b are not provided, the surface 10 b of the first heat insulating member opposite to the surface on the heating element side may be the base material 13 .

The first heat insulating member 10 shown in FIG. 5 is just one example.
The first insulating member constituting the insulating material of the present invention may be the substrate 13 itself, or may be a substrate 13 having a carbon layer 12 provided thereon, or may be a substrate 13 having a pyrolytic carbon layer 11 provided thereon, or may be a substrate 13 having a carbon layer 12 and a pyrolytic carbon layer 11 provided in this order thereon.

When the first heat insulating member has a carbon layer, it is preferable that at least the surface of the first heat insulating member facing the heating element is a carbon layer.
Furthermore, when the first heat insulating member has a pyrolytic carbon layer, it is preferable that at least the surface of the first heat insulating member facing the heating element is a pyrolytic carbon layer.

The first heat insulating member 10 and the second heat insulating member 20 are in contact with each other in a separable state.
Note that being in contact with each other in a separable state refers to a state in which the first insulating member 10 and the second insulating member 20 can be separated from each other without destroying either of them.

For example, when the first heat insulating member 10 and the second heat insulating member 20 are simply in contact with each other, it can be said that they are in contact with each other in a separable state.
On the other hand, if the first insulating member 10 and the second insulating member 20 are bonded together with a carbon-based adhesive and cannot be separated from each other without destroying the first insulating member 10 and/or the second insulating member 20, the first insulating member 10 and the second insulating member 20 do not fall into a state in which they can be separated from each other.

In the insulation material of the present invention, the first insulation member and the second insulation member are in contact with each other in a separable state, making it easy to remove and replace only the first insulation member that has deteriorated.
This will be explained with reference to FIG. 6 and FIG.

Fig. 6 is a schematic diagram showing how a deteriorated first heat insulating member is removed, and Fig. 7 is a schematic diagram showing how a new first heat insulating member is inserted.
In the insulating material of the present invention, the first insulating member and the second insulating member are in contact with each other in a separable state, so that it is easy to separate the first insulating member 10', which has deteriorated, from the second insulating member 20, as shown in Figure 6.
Then, as shown in FIG. 7, by inserting a new first insulating member 10 inside the second insulating member 20, the insulating performance of the insulating material 1 can be restored.

As described above, in the insulation material of the present invention, only the first insulation member, which deteriorates first, can be easily replaced, reducing the labor time required for replacement. Furthermore, since there is no need to prepare a second insulation member for replacement, the material costs required for replacement can also be reduced.

[Method of manufacturing first heat insulating member]
The first heat insulating member constituting the heat insulating material of the present invention can be manufactured, for example, by a molded body preparation step of preparing a molded body of carbon fiber.

(Preparation of Molded Body)
In the molded body preparation step, a molded body of carbon fiber is prepared.

Methods for obtaining carbon fiber molded bodies include the needling method and the papermaking method.

In the case of the needling method, for example, carbon fibers with an average fiber length of 10 mm to 10,000 mm are stacked in a sheet form, and the inorganic fibers are entangled by needling to obtain a molded body made of carbon fibers.

In the case of the papermaking method, for example, a suspension is prepared in which carbon fibers with an average fiber length of 2 mm to 8 mm are dispersed in a dispersion medium such as water, and a mold is used to make a papermaking process, thereby obtaining a molded body made of carbon fibers.

The mold used for papermaking may be flat, or it may be curved to the desired shape.
That is, the green body obtained in the green body preparation step may have a cylindrical shape from the beginning, but at this stage it may not have a cylindrical shape but may have, for example, a generally rectangular shape when viewed from above.
When the shape of the molded body is a substantially rectangular shape in a plan view, it is deformed into a cylindrical shape by a deformation step described later.

In the case of the papermaking method, the suspension may contain an organic binder.
When the suspension contains an organic binder, the carbon fibers are fixed together during papermaking, improving moldability. In addition, the organic binder remains in the carbon fiber molded body and can bind the carbon fibers together, improving the handleability of the molded body at a stage prior to the carbon layer formation step described below.

The organic binder that may be contained in the suspension may be the same as the organic binder that may be used in the carbon layer formation process described below.

The carbon fibers used in the molded body preparation process can preferably be the same as those that make up the first insulating member.

(Deformation process)
The outer shape of the molded body prepared in the molded body preparation step does not have to be cylindrical from the beginning.
For example, a molded body (sheet-shaped molded body) having a generally rectangular shape in plan view may be prepared in the molded body preparation step, and then this may be deformed into a cylindrical shape in the deformation step.

The sheet-like molded body may have, for example, a generally rectangular shape in a plan view, having a first end face and a second end face facing each other in the longitudinal direction, a first main face and a second main face facing each other in a thickness direction perpendicular to the longitudinal direction, and a first side face and a second side face facing each other in a width direction perpendicular to the length direction and the thickness direction.
Of the first and second main surfaces, the main surface on the heating element side is preferably a pyrolytic carbon layer.

The distance between the first end face and the second end face of the sheet-shaped molding is the length of the sheet-shaped molding, which corresponds to the length of the inner circumference of the first insulating member.

The distance between the first and second main surfaces of the sheet-shaped body is the thickness of the sheet-shaped body, which corresponds to the thickness of the first insulating member.

The distance between the first and second sides of the sheet-shaped body is the width of the sheet-shaped body and corresponds to the height of the first insulating member.

When the sheet-shaped molded body is deformed to form the first insulating member, the first end face and the second end face of the sheet-shaped molded body may be in contact with each other in a separable state, may be bonded with a carbon-based adhesive, or may be sewn with thread. The thread may be one that burns away when fired, or one that does not burn away when fired.

When manufacturing the first insulating member, a carbon layer formation process for forming a carbon layer and/or a pyrolytic carbon layer formation process for forming a pyrolytic carbon layer may be performed.

(Carbon layer forming process)
In the carbon layer forming step, the surface of the carbon fiber compact is impregnated with a slurry containing carbon-based particles, and then fired to form a carbon layer.

The firing conditions are not particularly limited, but firing is preferably performed at a temperature of 700 to 2100° C. in a non-oxidizing atmosphere for 1 to 12 hours.
The non-oxidizing atmosphere includes an inert atmosphere and a reducing atmosphere.

The inert atmosphere is an atmosphere containing an inert gas as a main component.
The inert gas includes nitrogen, argon, and the like.

The reducing atmosphere is an atmosphere containing a reducing gas as a main component.
The reducing gas includes hydrogen, carbon monoxide, hydrocarbons, chlorine, and the like.

The carbon-based particles used in the carbon layer formation process can be preferably carbon-based particles that can form the first insulating member.

In forming the carbon layer, it is preferable to expose the carbon fibers on the surface.
As a method for exposing the carbon fibers on the surface, there is a method in which the amount of slurry impregnated into the molded body in the carbon layer forming step is slightly reduced from the amount that would normally be impregnated into the molded body.
This results in the formation of portions on the surface of the molded body that are not impregnated with the slurry, exposing the carbon fibers.

The slurry used in the carbon layer forming step may contain an organic binder.
If the slurry contains an organic binder, the carbon-based particles tend to remain near the surface of the compact when the compact is immersed in the slurry, thereby preventing the carbon layer from becoming too thick.

As the organic binder, both an organic binder that is carbonized when heated in a non-oxidizing atmosphere and an organic binder that is decomposed when heated in a non-oxidizing atmosphere and does not leave a residue can be used.
The organic binder may be one that dissolves in a solvent, or one that disperses as fine particles in the solvent.

When the organic binder is an organic binder that is carbonized by heating in a non-oxidizing atmosphere, the carbonized organic binder functions as a carbon-based adhesive and can firmly bond the carbon-based particles and the carbon fibers. In addition, the carbon-based particles that make up the carbon layer that is unevenly distributed on the surface of the molded body can be prevented from falling off the carbon fibers.

Examples of organic binders that carbonize include phenolic resin, polyvinyl alcohol (PVA), and pitch.

When the slurry does not contain an organic binder, it is preferable to immerse the molded body in the slurry and then impregnate the surface of the molded body with an organic binder solution.
This allows the organic binder to function as a carbon-based adhesive, similarly to when the slurry contains an organic binder, and allows the carbon-based particles and the carbon fibers to be firmly bonded together.

In the carbon layer formation process, the compact is first immersed in a slurry that contains carbon-based particles and a solvent but does not contain an organic binder, and then the compact is immersed in an organic binder solution, which reduces the penetration of the organic binder into the compact and prevents a decrease in insulation performance.

(Pyrolytic carbon layer forming process)
In the pyrolytic carbon layer forming step, a pyrolytic carbon layer containing pyrolytic carbon is formed on the surface of the compact.

The method for forming a pyrolytic carbon layer on the surface of the molded body is not particularly limited, but for example, a method for forming a pyrolytic carbon layer by chemical vapor deposition using a CVD furnace can be mentioned.
The process of forming a pyrolytic carbon layer using a CVD furnace is also called a CVD process.

The conditions for the CVD process are not particularly limited.
The raw material gas may be a hydrocarbon gas, such as methane, ethane, propane, or ethylene.

The temperature of the CVD process is preferably, for example, 800 to 2000°C.
If the temperature in the CVD process is 800° C. or higher, the source gas is easily decomposed, and therefore a pyrolytic carbon layer is easily formed.
When the temperature of the CVD process is 2000° C. or less, sublimation of the carbon fibers is suppressed, and deterioration can be prevented.

When the carbon fibers constituting the molded body are carbonaceous, the temperature in the CVD process is desirably 1700° C. or lower.
When carbonaceous carbon fibers are exposed to high temperatures, they change to graphite, causing changes such as an increase in thermal conductivity, etc. Therefore, by carrying out the CVD process at a temperature of 1700° C. or less, it is possible to suppress the change of the carbon fibers to graphite and maintain the thermal insulation properties of the molded body.

The pyrocarbon layer forming step may be performed on the molded body that has been subjected to the carbon layer forming step.
In this case, a carbon layer is formed on the surface of the substrate made of carbon fiber, and a first heat insulating member is obtained in which a pyrolytic carbon layer is formed on the surface of the carbon layer.

[Method of manufacturing second heat insulating member]
The second heat insulating member constituting the heat insulating material of the present invention can be produced, for example, by a method having a molded body preparation step of obtaining a molded body made of carbon fiber.

(Preparation of Molded Body)
The molded body preparation step is preferably the same as the molded body preparation step in the first method for producing a heat insulating member.

The method for producing the first insulating member and the method for producing the second insulating member may be different.
For example, in the first method for producing a heat insulating member, a carbon fiber molded body may be obtained by a papermaking method, and in the second method for producing a heat insulating member, a carbon fiber molded body may be obtained by a needling method.

The method for manufacturing the second insulating member may include a carbon layer forming process, a pyrolytic carbon layer forming process, or a deformation process, similar to the method for manufacturing the first insulating member.

[Method of manufacturing the heat insulating material]
The first and second insulating members obtained by the above procedure can be combined to obtain the insulating member of the present invention.
Specifically, the insulating material of the present invention can be obtained by arranging a first insulating member so as to cover the space for accommodating the heating element, and then arranging a second insulating member so as to cover the outside of the first insulating member.

The heat insulating material of the present invention can be suitably used in heating devices such as heating furnaces.
Furthermore, the heat insulating material of the present invention can be suitably used, for example, as a heat insulating material for keeping a crucible warm (insulating the crucible) in an apparatus for growing single crystals of Si or SiC.

The following items are disclosed in this specification:

The present disclosure (1) is an insulating material that covers the periphery of a heating element, and is characterized in that it comprises a first insulating member arranged on the heating element side and a second insulating member arranged on the opposite side of the heating element, the first insulating member and the second insulating member both containing carbon fiber, and the first insulating member and the second insulating member are in contact with each other in a separable state.

The present disclosure (2) is the insulating material described in the present disclosure (1), in which the surface of the first insulating member facing the heating element is a pyrolytic carbon layer containing pyrolytic carbon.

The present disclosure (3) is the insulating material described in the present disclosure (2), in which the pyrolytic carbon layer has a thickness of 2 μm to 60 μm.

The present disclosure (4) is the insulating material described in the present disclosure (1), in which the surface of the first insulating member facing the heating element is a carbon layer containing carbon-based particles between carbon fibers.

The present disclosure (5) is the insulating material described in the present disclosure (4), in which the carbon-based particles and the carbon fibers of the carbon layer are bonded to each other with a carbon-based adhesive.

The present disclosure (6) is the insulating material according to the present disclosure (4) or (5), in which the carbon-based particles are at least one carbon-based particle selected from the group consisting of graphite, carbon black, glassy carbon particles, and pulverized carbon fiber particles.

The present disclosure (7) is an insulating material according to any one of the present disclosures (4) to (6), in which the carbon-based particles have an average particle size of 10 nm to 500 μm.

The present disclosure (8) is an insulating material according to any one of the present disclosures (4) to (7), in which the carbon layer has a thickness of 10 μm to 1000 μm.

The present disclosure (9) is an insulating material according to any one of the present disclosures (4) to (8), in which the first insulating member further has a base material made of the carbon fiber provided on the surface of the carbon layer opposite the surface on the heating element side.

The present disclosure (10) is the insulating material described in the present disclosure (9), in which the substrate is a needle mat of the carbon fiber or a paper-made body of the carbon fiber.

The present disclosure (11) is the insulating material described in the present disclosure (9) or (10), in which the average fiber length of the carbon fibers constituting the substrate is 2 mm to 8 mm.

(Example)
EXAMPLES Hereinafter, examples that more specifically disclose the present invention will be described, however, the present invention is not limited to these examples.

Example 1
[Manufacture of first heat insulating member]
[Molded body preparation process]
Carbon fibers (average fiber diameter: 13 μm, average fiber length: 3.3 mm) were molded by a papermaking method to obtain a cylindrical molded product (cylindrical shape with an inner diameter of 95 mm, a height of 190 mm, and a thickness of 3 mm) made of carbon fibers.
This compact was heated to 2000° C. in an inert atmosphere to carbonize the organic binder (phenol resin) contained in the compact.

[Carbon layer forming process]
After the surface of the molded body was processed to adjust the shape, a slurry containing an organic binder and carbon-based particles was applied to the entire surface of the sheet-like molded body.
The carbon particles used were graphite particles with an average particle size of 10 μm, and the organic binder was a phenol resin.

The sheet-like molded body coated with the slurry was then placed in a furnace with a reducing atmosphere and heated at 2000°C for 1 hour, forming a carbon layer on the surface of the substrate made of carbon fibers, in which carbon-based particles were arranged between the carbon fibers and the carbon-based particles and carbon fibers were bonded to each other with a carbon-based adhesive.

At this point, the surface of the carbon layer was observed with a polarizing microscope, and it was confirmed that some of the carbon fibers were exposed on the surface. It was also confirmed that the carbon particles and carbon fibers were bonded together by a carbon-based adhesive, which was formed by carbonizing the organic binder in the slurry by heating it in a reducing atmosphere.

[CVD process]
Next, the sheet-like molded body with the carbon layer formed thereon was placed in a CVD furnace, and the furnace was once evacuated to reduce the air pressure inside the furnace. After that, a raw material gas was introduced to form a pyrolytic carbon layer on the surface of the carbon layer, thereby obtaining a cylindrical first insulating member.
The sheet-like molded product was placed on the support pins, and a pyrocarbon layer was formed in a state where the sheet-like molded product was point-supported by the support pins.
Since the sheet-like molded body is supported at points, the pyrolytic carbon layer is simultaneously formed on almost the entire surface of the sheet-like molded body.

In the CVD process, since a carbon layer is formed on the surface of the sheet-like molded body, the raw material gas does not penetrate into the molded body and is deposited on the surface. At this time, the carbon fibers exposed on the surface act as anchors to firmly connect the molded body made of carbon fibers and the pyrolytic carbon layer.
The bulk density of the first heat insulating member was measured and found to be 0.18 g/cm ₃ .

The first insulating member was cut along the thickness direction, and the surface of the cut surface was observed with a polarizing microscope. It was confirmed that a pyrolytic carbon layer with a thickness of 20 μm had formed on the surface of the first insulating member, and that a carbon layer with a thickness of 100 μm had formed directly beneath the pyrolytic carbon layer.

[Manufacture of second insulating member]
Carbon fibers (average fiber diameter: 13 μm, average fiber length: 3.3 mm) were molded by a papermaking method to obtain a cylindrical molded product (cylindrical shape with an inner diameter of 101 mm, a height of 190 mm, and a thickness of 10 mm) made of carbon fibers.
This compact was heated to 2000° C. in an inert atmosphere to carbonize the binder contained in the compact, thereby obtaining a cylindrical second heat insulating member.

[Manufacture of heat insulating materials]
The first insulating member was inserted into the space inside the second insulating member to produce the insulating material of Example 1.

Example 2
The heat insulating material of Example 2 was produced in the same manner as in Example 1, except that the carbon layer forming step and the CVD step were not performed.
Therefore, in the heat insulating material according to Example 2, a carbon layer and a pyrolytic carbon layer are not formed in the first heat insulating member.

(Comparative Example 1)
The first insulating member was not manufactured, and in the manufacture of the second insulating member, the cylindrical molded body was molded to have an inner diameter of 95 mm, a height of 190 mm, and a thickness of 13 mm. Except for this, the second insulating member was obtained in the same manner as in Example 1, and the insulating material related to Comparative Example 1 was manufactured.
The second heat insulating member constituting the heat insulating material according to Comparative Example 1 is a molded body made of carbon fiber, and neither a pyrolytic carbon layer nor a carbon layer is provided on the surface.

[Consumption test]
SiC powder was placed in a graphite crucible (cylindrical shape with an outer diameter of 95 mm, an inner diameter of 90 mm, and a height of 190 mm), and with the lid on, the crucible was inserted into the space inside the first or second insulating member constituting the insulating material of Examples 1 and 2 and Comparative Example 1, and heated at 2400°C for 72 hours by high-frequency induction heating in a reducing atmosphere.
After the heating was completed, the crucible was removed from inside the first or second heat insulating member, and the surface of the first or second heat insulating member facing the crucible was visually observed.
In the heat insulating material according to Example 1, the deterioration of the pyrolytic carbon layer was confirmed, but the deterioration of the base material made of carbon fiber was not confirmed. In addition, the deterioration of the second heat insulating member was not confirmed. In the heat insulating material according to Example 2, the deterioration of the base material made of carbon fiber of the first heat insulating member was confirmed, but the deterioration of the second heat insulating member was not confirmed.
In the heat insulating material of Comparative Example 1, it was confirmed that the second heat insulating member was deteriorated.

[Check compatibility]
In the thermal insulation materials according to Examples 1 and 2, when the end of the first thermal insulation member was grasped and pulled in the longitudinal direction while the second thermal insulation member was held and fixed from the outer periphery, the first thermal insulation member could be easily pulled out from the second thermal insulation member. Also, when a new first thermal insulation member was inserted, it was easily inserted.

On the other hand, since the insulation material in Comparative Example 1 is molded as a single piece, it was determined that the entire insulation material needed to be replaced due to deterioration of the insulation components.

From the above, it has been confirmed that the insulation material of the present invention can reduce replacement costs.

1 Thermal insulation material 10 First thermal insulation member 10a Surface (first main surface) of the first thermal insulation member on the heating element side
10b: surface (second main surface) of the first heat insulating member opposite to the surface on the heating element side
10c End surface 10' of first insulating member First insulating member 11 in which deterioration has progressed Pyrolytic carbon layer 11a Pyrolytic carbon layer 11b provided on the first main surface of the first insulating member Pyrolytic carbon layer 11c provided on the second main surface of the first insulating member Pyrolytic carbon layer 12 provided on the end surface of the first insulating member Carbon layer 12a Carbon layer 12b provided on the first main surface side of the first insulating member Carbon layer 12c provided on the second main surface side of the first insulating member Carbon layer 13 provided on the end surface side of the first insulating member Substrate 20 Second insulating member 20a Surface (first main surface) of the second insulating member facing the heating element
20b: surface (second main surface) of the second heat insulating member opposite to the surface on the heating element side
20c End surface of second heat insulating member 30 Space for accommodating heating element 50 Heating element (crucible)
51 Cavity 70 Induction heating coil 100 Heating device

Claims (11)

A heat insulating material that covers the periphery of a heating element,
A first heat insulating member is disposed on the heating element side, and a second heat insulating member is disposed on the opposite side to the heating element,
The first heat insulating member and the second heat insulating member each contain carbon fiber,
An insulating material, characterized in that the first insulating member and the second insulating member are in contact with each other in a separable state. The heat insulating material according to claim 1, wherein the surface of the first heat insulating member facing the heating element is a pyrolytic carbon layer containing pyrolytic carbon. The thermal insulation material according to claim 2, wherein the pyrolytic carbon layer has a thickness of 2 μm to 60 μm. The heat insulating material according to claim 1, wherein the surface of the first heat insulating member facing the heating element is a carbon layer containing carbon-based particles between carbon fibers. The heat insulating material according to claim 4, wherein the carbon-based particles and the carbon fibers of the carbon layer are bonded to each other with a carbon-based adhesive. The heat insulating material according to claim 4, wherein the carbon-based particles are at least one carbon-based particle selected from the group consisting of graphite, carbon black, glassy carbon particles, and crushed carbon fiber particles. The heat insulating material according to claim 4, wherein the carbon-based particles have an average particle size of 10 nm to 500 μm. The insulating material according to claim 4, wherein the carbon layer has a thickness of 10 μm to 1000 μm. The heat insulating material according to claim 4, wherein the first heat insulating member further has a base material made of the carbon fiber provided on the surface of the carbon layer opposite to the surface facing the heating element. The heat insulating material according to claim 9, wherein the substrate is a needle mat of the carbon fiber or a paper body of the carbon fiber. The heat insulating material according to claim 9, wherein the carbon fibers constituting the substrate have an average fiber length of 2 mm to 8 mm.

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