Insulation

Abstract

The present invention provides an insulating material that minimizes temperature distribution within the furnace and suppresses localized deterioration. [Solution] A cylindrical thermal insulation material in which a thermal insulation sheet containing carbon fiber is wound and laminated in a spiral shape, characterized in that the thickness of the thermal insulation sheet is 0.3 to 2.0 mm.

Description

Technical Field

[0001] The present invention relates to a heat insulating material.

Background Art

[0002] Heat insulating materials using carbon fibers are widely used as heat insulating materials for high-temperature furnaces such as semiconductor manufacturing furnaces and ceramic sintering furnaces because they have a high heat resistance temperature and excellent heat insulating performance.

[0003] The shape of the heat insulating material is appropriately set according to the shape of the heat insulating object. For example, in order to insulate a cylindrical object, a cylindrical heat insulating material is used.

[0004] For example, Patent Documents 1 and 2 disclose methods for manufacturing a cylindrical heat insulating material by winding and laminating carbon fiber felts.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0008] This invention was made to solve the above problems, and aims to provide an insulating material that can reduce the temperature distribution inside the furnace and suppress localized deterioration. [Means for solving the problem]

[0009] The present invention provides a cylindrical thermal insulation material in which a thermal insulation sheet containing carbon fibers is wound and laminated in a spiral shape, characterized in that the thickness of the thermal insulation sheet is 0.3 to 2.0 mm.

[0010] The thickness of the insulating sheets constituting the insulating material of the present invention is thin, ranging from 0.3 to 2.0 mm. Therefore, the number of layers of insulating sheets per unit thickness of the insulating material can be increased, and variations in density in the in-plane direction of the insulating sheets are less likely to be reflected in variations in density in the circumferential direction of the insulating material. As a result, the insulating material has reduced circumferential density variations. When circumferential density variations are reduced, it is possible to suppress the occurrence of localized decreases in insulating performance, which can lead to a larger temperature distribution inside the furnace, and to suppress localized deterioration of the insulating material.

[0011] In the thermal insulation material of the present invention, it is preferable that the thermal insulation sheet contains flaky graphite. Because flake graphite easily reflects heat emitted from a heating element, the presence of flake graphite in an insulating sheet can improve its thermal insulation performance.

[0012] The thermal insulation material of the present invention preferably has a thickness of 5 to 100 mm. If the thickness of the insulation material is within the above range, it is possible to achieve sufficient insulation performance while preventing the heating furnace from becoming excessively large.

[0013] In the heat insulating material of the present invention, the number of layers of the heat insulating sheet is preferably 15 to 300 layers. When the number of layers of the heat insulating sheet is within the above range, the variation in the density in the circumferential direction of the heat insulating material can be particularly suppressed.

[0014] In the heat insulating material of the present invention, the value obtained by dividing the difference between the maximum density and the minimum density when the heat insulating material is divided into 8 parts in the circumferential direction by the average density ((maximum density - minimum density) / average density × 100 (%)) is preferably 5% or less. When the above conditions are satisfied, the variation in the density in the circumferential direction of the heat insulating material is sufficiently reduced, so that the occurrence of heating failure and partial deterioration of the heat insulating material can be particularly suppressed.

Brief Description of Drawings

[0015] [Figure 1] FIG. 1 is a perspective view schematically showing an example of the heat insulating material of the present invention. [Figure 2] FIG. 2 is a partially enlarged view of the heat insulating material shown in FIG. 1 when viewed from above. [Figure 3] FIG. 3 is a perspective view schematically showing an example of the heat insulating sheet constituting the heat insulating material of the present invention. [Figure 4] FIG. 4 is a cross-sectional view schematically showing an example of the heat insulating sheet. [Figure 5] FIG. 5 is an enlarged cross-sectional view schematically showing another example of the heat insulating sheet

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be specifically described. However, the present invention is not limited to the following embodiments, and can be appropriately changed and applied within the range not changing the gist of the present invention.

[0017] [Heat Insulating Material] The heat insulating material of the present invention is a cylindrical heat insulating material in which a heat insulating sheet containing carbon fibers is wound and laminated in a spiral shape, and the thickness of the heat insulating sheet is 0.3 to 2.0 mm.

[0018] FIG. 1 is a perspective view schematically showing an example of the heat insulating material of the present invention. As shown in FIG. 1, the heat insulating material 1 is cylindrical with an outer diameter R1, an inner diameter R2, and a height h, and a cylindrical space 100 is provided inside.

[0019] The thickness t0 of the heat insulating material 1 is the length that connects the inner surface 1a and the outer surface 1b of the heat insulating material 1 at the shortest distance in a plane orthogonal to the height direction (the direction indicated by the arrow Z in FIG. 1), and is measured at eight positions every 45 degrees of the central angle of the inscribed circle of the inner surface 1a of the heat insulating material 1, and the average value thereof is taken.

[0020] The shape of the heat insulating material may be cylindrical, and it may be cylindrical or rectangular tubular, but a cylindrical shape is preferred.

[0021] The cross-sectional area obtained by cutting the space provided inside the heat insulating material in a direction parallel to a plane orthogonal to the height direction is preferably 20 to 10000 cm 2 ².

[0022] When the shape of the heat insulating material is cylindrical, the inner diameter is preferably 50 to 1000 mm. The inner diameter R2 of the heat insulating material 1 is the diameter of the inscribed circle of the inner surface 1a of the heat insulating material 1 in a plane orthogonal to the height direction, and is the average value of the diameters of the inscribed circles of the inner surfaces of both end faces and the central plane bisecting the heat insulating material 1.

[0023] When the shape of the heat insulating material is cylindrical, the outer diameter is preferably 60 to 1200 mm. The outer diameter R1 of the heat insulating material 1 is the diameter of the inscribed circle of the outer surface 1b of the heat insulating material 1 in a plane orthogonal to the height direction, and is the average value of the diameters of the inscribed circles of the outer surfaces of both end faces and the central plane bisecting the heat insulating material 1.

[0024] The height of the heat insulating material is preferably 150 to 1000 mm. The height is measured at eight points on the inner surface 1a of insulation material 1, at 45-degree intervals between the central angles of the inscribed circle, and the average value is used.

[0025] The density of the insulation material is 0.10 to 0.30 g / cm³. 3 Preferably, it is 0.15 to 0.25 g / cm³. 3 It is preferable that it be so.

[0026] The density of an insulating material can be determined by calculating its volume from its external and internal dimensions, and then dividing its weight by its volume.

[0027] It is preferable that the value obtained by dividing the difference between the maximum density and the minimum density when the insulation material is divided into 8 sections in the circumferential direction by the average density ((maximum density - minimum density) / average density × 100 (%)) is 5% or less. When the above conditions are met, the variation in density in the circumferential direction of the insulation material is sufficiently reduced, which in turn helps to suppress heating failures and localized deterioration of the insulation material. In this specification, the density variation of the thermal insulation material is evaluated by dividing the difference between the maximum and minimum densities when the thermal insulation material is divided into eight sections in the circumferential direction by the average density. Therefore, this value is also referred to as the density variation rate. In other words, it is preferable that the thermal insulation material of the present invention has a density variation rate of 5% or less, as shown by the above formula.

[0028] The density of the thermal insulation material when it is divided into eight sections in the circumferential direction can be determined by dividing the thermal insulation material 1 into eight equal parts in a plane perpendicular to the height direction of the thermal insulation material, using a central angle of 45 degrees for the inscribed circle of the inner surface 1a of the thermal insulation material 1. Furthermore, a rectangular parallelepiped with a volume of 35% or more of each of the eight divided sections is cut out, and the volume and weight of each section are measured. If it is not possible to cut out a rectangular parallelepiped with a volume of 35% or more of each section, the volume of each section is measured using a known three-dimensional measuring machine.

[0029] Figure 2 is a magnified view of a top-down view of the insulation material shown in Figure 1. In Figure 2, the thickness direction of the insulation sheet 10 is indicated by a double-headed arrow t, the thickness of the insulation material 1 is indicated by a double-headed arrow t0, and the thickness of the insulation sheet 10 is indicated by a double-headed arrow t1. The thickness of the insulation sheet is the average value obtained by measuring the thickness at 10 random locations.

[0030] As shown in Figure 2, the thermal insulation material 1 is made up of 15 layers of thermal insulation sheets 10 wound in a spiral pattern. Although not shown in Figure 2, the thermal insulation sheet 10 that makes up the thermal insulation material 1 is a single long sheet, and there are no seams or joints in the thermal insulation sheet 10. Therefore, the part that makes up the inner surface 1a of the thermal insulation material 1 corresponds to one end of the thermal insulation sheet 10, and the part that makes up the outer surface 1b of the thermal insulation material 1 corresponds to the other end of the same thermal insulation sheet 10.

[0031] If the insulation sheet 10 is rolled and laminated starting from the center, then the beginning portion of the insulation sheet 10 forms the inner surface 1a of the insulation material 1, and the end portion of the insulation sheet 10 forms the outer surface 1b of the insulation material 1.

[0032] The inner surface 1a of the insulation material 1 is the surface exposed to the cylindrical space 100, and the outer surface 1b of the insulation material 1 is the surface not exposed to the cylindrical space 100. The inner surface 1a and the outer surface 1b of the insulation material 1 face each other in a plane perpendicular to the height direction Z of the insulation material 1.

[0033] The thickness t1 of the insulation sheet 10 is 0.3 to 2.0 mm. When the thickness of the insulation sheet is 0.3 to 2.0 mm, the number of layers of insulation sheet per unit thickness of the insulation material can be increased, and variations in density in the plane of the insulation sheet are less likely to be reflected in variations in density in the circumferential direction of the insulation material. As a result, the insulation material has reduced variations in density in the circumferential direction. When variations in density in the circumferential direction are reduced, it is possible to suppress the occurrence of localized deterioration of insulation performance, which can lead to a larger temperature distribution inside the furnace, and to suppress localized deterioration of the insulation material.

[0034] If the thickness of the insulation sheet is less than 0.3 mm, defects such as tearing become more likely to occur in the insulation sheet, making the manufacturing process itself difficult. In addition, the mechanical strength of the insulation sheet decreases, increasing the likelihood of damage to the insulation sheet during winding and lamination.

[0035] The thickness t0 of the insulation material 1 is preferably 5 to 100 mm. If the thickness of the insulation material is within the above range, it is possible to achieve sufficient insulation performance while preventing the heating furnace from becoming excessively large.

[0036] The number of layers of the insulation sheet 10 constituting the insulation material 1 is preferably 15 to 300 layers. When the number of layers of insulation sheets is within the above range, variations in the density of the insulation material in the circumferential direction can be particularly suppressed.

[0037] Figure 3 is a schematic perspective view showing an example of an insulating sheet that constitutes the insulating material of the present invention. Since the heat insulating sheet 10 is a flexible sheet, it may be stored in a rolled-up state, for example, as shown in Figure 3.

[0038] (Insulation sheet) The insulation sheet contains carbon fiber.

[0039] The average fiber length of the carbon fibers is preferably between 0.4 mm and 10,000 mm. Furthermore, the average fiber length of the carbon fibers may be between 0.4 mm and 4 mm, or between 10 mm and 10,000 mm. The average fiber length of the carbon fibers is calculated by measuring the longitudinal length of 20 randomly selected carbon fibers using any method and averaging the results.

[0040] The average fiber diameter of the carbon fibers is preferably 1 μm to 30 μm. If the average fiber diameter of the carbon fibers is 30 μm or less, the effect of conductive heat transfer by the carbon fibers themselves can be suppressed. Furthermore, if the average fiber diameter of the carbon fibers is 1 μm or more, excellent light shielding properties are achieved, and radiative heat transfer can be suppressed. The average fiber diameter of carbon fibers is calculated by measuring the fiber diameter of 20 randomly selected carbon fibers using a scanning electron microscope (SEM) and averaging the results.

[0041] Carbon fibers can be pitch-based, PAN-based, or rayon-based, and either graphite-based or carbonaceous carbon fibers can be used.

[0042] The heat insulating sheet is preferably made of a carbon fiber needle mat or a carbon fiber papermaking body. Because carbon fiber needle mats and carbon fiber papermaking materials are composed of randomly oriented carbon fibers, they can exhibit high thermal insulation properties and are particularly suitable as thermal insulation sheets for thermal insulation materials.

[0043] When the insulation sheet is made of a carbon fiber needle mat, the average fiber length of the carbon fibers is preferably between 10 mm and 10,000 mm. When the heat insulating sheet is made of carbon fiber paper, the average fiber length of the carbon fibers is preferably 0.4 mm to 4 mm.

[0044] The heat insulating sheet preferably contains flaky graphite. Because flake graphite easily reflects heat emitted from a heating element, the presence of flake graphite in an insulating sheet can improve its thermal insulation performance.

[0045] Scaly graphite is graphite that has a thin, scaly appearance. Specifically, flaky graphite with a thickness of 100 μm or less is defined as flake graphite.

[0046] Flake graphite has a higher reflectivity of synchrotron radiation compared to other carbon-based materials. Therefore, including flake graphite in an insulating sheet can improve its thermal insulation performance.

[0047] Figure 4 is a schematic cross-sectional view showing an example of an insulating sheet. The thermal insulation sheet 10 shown in Figure 4 contains flake graphite 20. However, the carbon fibers that make up the thermal insulation sheet 10 are omitted in Figure 4.

[0048] Because flake graphite easily reflects heat emitted from a heating element, the presence of flake graphite in an insulating sheet can improve its thermal insulation performance.

[0049] Natural graphite can be used as the flaky graphite.

[0050] The average particle size of the flake graphite is preferably 25 to 400 μm. The average particle size of flake graphite can be measured by sieve analysis in accordance with the "Industrial Analysis and Testing Methods for Natural Graphite" described in JIS M 8511 (2014).

[0051] The arrangement (orientation) of flake-like graphite in the thermal insulation sheet is not particularly limited, but it is preferable that it be oriented along the in-plane direction of the thermal insulation sheet. The in-plane direction of the thermal insulation sheet is the direction perpendicular to the thickness direction of the thermal insulation sheet. In the heat insulating sheet 10 shown in Figure 4, the flake-like graphite 20 is oriented along a plane perpendicular to the thickness direction of the heat insulating sheet 10 (the direction indicated by the double-headed arrow t). When the flake-like graphite is oriented in the direction of the plane, it reflects light emitted from the heating element more easily, thereby improving the thermal insulation performance.

[0052] The content of flake graphite is not particularly limited, but it is preferably 5-30% of the weight of the insulation material.

[0053] In a thermal insulation sheet, it is preferable that the carbon fibers and flake graphite are joined via a carbonaceous binder. In this case, it can be said that the thermal insulation sheet contains a carbonaceous binder in addition to the carbon fibers and flake graphite.

[0054] Figure 5 is a schematic, enlarged cross-sectional view showing another example of an insulating sheet. In the heat insulating sheet 10 shown in Figure 5, the flake-like graphite 20 is oriented in a direction perpendicular to the thickness direction of the heat insulating sheet 10 (indicated by the double-headed arrow t in Figure 5). In addition, in the heat insulating sheet 10, the carbon fibers 30 and the flake-shaped graphite 20 are bonded together via the carbonaceous binder 40 contained in the heat insulating sheet 10. This prevents the flake-shaped graphite 20 from falling off. The carbonaceous binder 40 is formed when the organic binder is carbonized by heating in a non-oxidizing atmosphere.

[0055] [Method of manufacturing insulation material] The thermal insulation material can be obtained by winding and laminating precursor sheets containing carbon fibers, and then firing the resulting precursor sheet laminate at approximately 2000°C in a non-oxidizing atmosphere.

[0056] (Method for manufacturing precursor sheets) Precursor sheets can be obtained, for example, by preparing a suspension in which carbon fibers are dispersed in a dispersion medium such as water and forming it into a sheet (papermaking), or by performing a needle punching treatment on an aggregate of carbon fibers.

[0057] The suspension may contain an organic binder. The presence of an organic binder in the suspension improves moldability by fixing the carbon fibers together during papermaking. The organic binder then carbonizes during subsequent heat treatment (in a non-oxidizing atmosphere) to become a carbonaceous binder, thus continuing to bind the carbon fibers together even after heat treatment.

[0058] Examples of organic binders that act as carbonaceous binders include phenolic resins, polyvinyl alcohol (PVA), and pitch.

[0059] If the papermaking method does not include an organic binder in the suspension, or if the carbon fiber aggregate is subjected to needle punching, the precursor sheet may be made to contain the organic binder by applying a slurry containing the organic binder to the resulting precursor sheet.

[0060] The thickness of the precursor sheet is preferably 0.3 to 3.0 mm. If the thickness of the precursor sheet is within the above range, an insulating sheet with a thickness of 0.3 to 2.0 mm can be obtained.

[0061] (Method for manufacturing a precursor sheet laminate) A precursor sheet laminate can be obtained by winding and laminating precursor sheets containing carbon fibers, with a thickness of 0.3 to 3.0 mm, manufactured using the method described above.

[0062] The precursor sheet may be laminated by winding it around a core material, for example.

[0063] The number of winding layers of the precursor sheet is preferably 15 to 300 layers.

[0064] The layers of stacked precursor sheets may be joined via an organic binder applied to the surface of the precursor sheets, or they may be joined by impregnating the precursor sheets with an organic binder. Examples of organic binders include phenolic resin, polyvinyl alcohol (PVA), and pitch. The amount of organic binder can be 5-25% of the weight of the precursor sheet.

[0065] (Firing of the precursor sheet laminate) The thermal insulation material of the present invention can be manufactured by firing the aforementioned precursor sheet laminate at approximately 2000°C in a non-oxidizing atmosphere.

[0066] Non-oxidizing atmospheres include inert and reducing atmospheres.

[0067] An inert atmosphere is an atmosphere whose main component is an inert gas. Examples of inert gases include nitrogen and argon.

[0068] A reducing atmosphere is an atmosphere whose main component is a reducing gas. Examples of reducing gases include hydrogen, carbon monoxide, hydrocarbons, and chlorine.

[0069] The inner diameter, outer diameter, and height of the resulting insulation material may be adjusted by machining.

[0070] This specification discloses the following:

[0071] This disclosure (1) is a cylindrical thermal insulation material in which a thermal insulation sheet containing carbon fiber is wound and laminated in a spiral shape, The aforementioned insulation material is characterized in that the thickness of the insulation sheet is 0.3 to 2.0 mm.

[0072] Disclosure (2) is the thermal insulation material according to Disclosure (1), wherein the thermal insulation sheet contains flaky graphite.

[0073] Disclosure (3) is the thermal insulation material described in Disclosure (1) or (2), having a thickness of 5 to 100 mm.

[0074] Disclosure (4) is an insulating material in any combination of Disclosure (1) to (3), wherein the number of layers of the insulating sheet is 15 to 300.

[0075] Disclosure (5) is an insulating material in any combination with any of Disclosures (1) to (4), wherein the value obtained by dividing the difference between the maximum density and the minimum density when the insulating material is divided into eight parts in the circumferential direction by the average density ((maximum density - minimum density) / average density × 100 (%)) is 5% or less.

[0076] (Examples) The following are examples that more specifically disclose the present invention. However, the present invention is not limited to these examples.

[0077] (Example 1) A suspension containing carbon fibers (average fiber diameter: 13 μm, average fiber length: 0.7 mm), flaky graphite (average particle size: 100 μm), and an organic binder (phenol resin) in a ratio of 100:17:25 (by weight, organic binder is calculated on a solid content basis) was molded by a continuous papermaking method to obtain a precursor sheet (thickness 1.0 mm) made of carbon fibers.

[0078] Next, the obtained precursor sheets were wound around a core material with a diameter of 80 mm to create a cylindrical precursor sheet laminate. The precursor sheet laminate had an inner diameter of 80 mm and an outer diameter of 140 mm, with 30 layers. At this time, the precursor sheets were impregnated with an organic binder (phenol resin) at a rate of 10 parts by weight per 100 parts by weight of the precursor sheet before lamination. The material was heated to 2000°C under an inert atmosphere to carbonize the organic binder (phenol resin) contained in the precursor sheet, and the carbon fibers and flake graphite were bonded together with a carbonaceous binder to obtain the thermal insulation material according to Example 1 (thermal insulation sheet thickness 0.9 mm).

[0079] By machining the inner and outer surfaces of the obtained insulation material, an insulation material with an inner diameter of 96.2 mm, an outer diameter of 130 mm, a height of 210 mm, 19 layers of windings, and a thickness of 16.9 mm was obtained.

[0080] (Examples 2-4, Comparative Examples 1-2) Except for changing the thickness of the insulation sheet to that shown in Table 1 and adjusting the number of windings and laminations when manufacturing the insulation material so that the thickness of the insulation material was approximately the same, the insulation materials for Examples 2-4 and Comparative Examples 1-2 were obtained using the same procedure as in Example 1. However, since tears were observed in the insulation sheet for Comparative Example 1, the insulation material was not manufactured by winding and lamination.

[0081] (Density measurement) Each insulation material was divided into eight equal parts in the circumferential direction, and each of these eight parts was processed to a size of 30 mm in length, 10 mm in width, and 210 mm in height to create test specimens for density measurement. The density of each test specimen was measured from its weight and volume based on its external shape, and the density variation rate (= the value obtained by dividing the maximum density - minimum density by the average density ((maximum density - minimum density) / average density × 100 (%))) was calculated. The results are shown in Table 1.

[0082] [Table 1]

[0083] The results in Table 1 show that insulation materials manufactured using insulation sheets with a thickness of 0.3 to 2.0 mm exhibited a low density variation rate (5% or less). On the other hand, when the thickness of the insulation sheet was less than 0.3 mm, as in Comparative Example 1, defects occurred in the insulation sheet itself, making it impossible to manufacture the insulation material. Furthermore, the results from Comparative Example 2 suggest that when the thickness of the insulation sheet exceeds 2.0 mm, the number of layers of insulation sheet per unit thickness decreases, which is why the density variation rate originating from the insulation sheet could not be eliminated. [Explanation of Symbols]

[0084] 1. Insulation 1a Inner surface of the insulation material 1b Outer surface of the insulation material 10 Insulation Sheets 20. Scaly graphite 30 carbon fiber 40 Carbonaceous binders 100 cylindrical space R1 insulation material outer diameter Inner diameter of R2 insulation material t0 Thickness of insulation material Thickness of t1 insulation sheet h Height of insulation

Claims

1. A cylindrical insulating material in which a carbon fiber insulating sheet is wound and laminated in a spiral shape, An insulating material characterized in that the thickness of the insulating sheet is 0.3 to 2.0 mm.

2. The thermal insulation material according to claim 1, wherein the thermal insulation sheet contains flaky graphite.

3. The thermal insulation material according to claim 1 or 2, wherein the thickness is 5 to 100 mm.

4. The thermal insulation material according to claim 1 or 2, wherein the number of layers of the thermal insulation sheet is 15 to 300.

5. The thermal insulation material according to claim 1 or 2, wherein the value obtained by dividing the difference between the maximum density and the minimum density when the thermal insulation material is divided into eight sections in the circumferential direction by the average density ((maximum density - minimum density) / average density × 100 (%)) is 5% or less.

Images