JP2011181258A - Heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating device and manufacturing method thereof, equipped with a heat-insulating material endowed with both excellent heat-insulating properties and substantial strength. <P>SOLUTION: The heating device is provided with a heating element, and a base part made of a heat-insulating material and retaining the heating element. The heat-insulating material contains silica fine particles with the mean particle size of 50 nm or less, with a bulk density of 190 to 600 kg/m<SP>3</SP>and a compression strength of 0.65 MPa or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heating device having a heating element and a heat insulating material, and more particularly, to both excellent heat insulating properties and sufficient strength of the heat insulating material.

  Insulating materials manufactured by wet molding of inorganic fibers can be molded into any shape, in addition to being lightweight, yet have sufficient strength and are easy to handle and secondary processing. Has been used for various purposes.

  That is, for example, Patent Document 1 describes an electric heater having an electric heating coil and a plate-like heat insulating material that holds the electric heating coil. This electric heater has a high degree of cleanness, a high heat radiation efficiency, a high degree of design freedom, and has been preferably used in various applications such as a firing furnace for electronic parts.

  On the other hand, conventionally, as a heat insulating material having low heat conductivity and excellent heat insulating performance, silica fine particles, inorganic fibers, and a binder, which are low heat conductive materials, are mixed, pressed, and then machined. There was a heat insulating material obtained (for example, Patent Documents 2 and 3).

JP 2001-27397A Japanese National Patent Publication No. 11-513349 Japanese National Patent Publication No. 10-514959

  However, in recent years, with the emergence of global environmental problems, demands for reducing the environmental burden in the industry are increasing, and in industrial facilities such as heating furnaces, further significant energy saving is urgently required.

  In this regard, for example, in the electric heater described in Patent Document 1, in place of the inorganic fiber heat insulating material, by adopting the silica fine particle heat insulating material as described in Patent Documents 2 and 3, It is also conceivable to save energy by improving the heat insulation of the electric heater.

  However, the silica fine particle heat insulating material is inherently weak in strength, and thus is not necessarily suitable for use as an electric heater. In particular, when a groove for accommodating an electric heating coil is formed in the silica fine particle heat insulating material, the strength of the heat insulating material is further reduced, so that a problem occurs when the electric heater is manufactured or used. .

  Moreover, in the prior art described in Patent Documents 2 and 3, since a binder is used, for example, it is necessary to perform degreasing, and this degreasing has a problem that the strength of the heat insulating material is reduced. In addition, the use of a binder increases the environmental load. Thus, when using a binder, there existed a problem of the increase in the number of processes, required time, and energy accompanying degreasing.

  On the other hand, it is also possible to increase the strength by adjusting the press pressure and increasing the density of the heat insulating material without using a binder. However, in this case, for example, solid heat transfer increases as the density increases, so that there is a problem that the heat insulating performance of the heat insulating material decreases.

  The present invention has been made in view of the above problems, and an object thereof is to provide a heating device having a heat insulating material having both excellent heat insulating properties and sufficient strength, and a method for manufacturing the same. .

A heating device according to an embodiment of the present invention for solving the above-described problem is a heating device including a heating element and a base made of a heat insulating material and holding the heating element, and the heat insulating material includes: It includes silica fine particles having an average particle size of 50 nm or less, a bulk density of 190 to 600 kg / m ³ , and a compressive strength of 0.65 MPa or more. ADVANTAGE OF THE INVENTION According to this invention, the heating apparatus which has the heat insulating material which combined the outstanding heat insulation and sufficient intensity | strength can be provided.

  Moreover, the said heat insulating material is good also as not containing a binder. The heat insulating material may include one or both of an alkaline earth metal and an alkali metal. In this case, the heat insulating material may include 0.1 to 10 parts by weight of one or both of the alkaline earth metal and the alkali metal with respect to 100 parts by weight of the heat insulating material raw material containing the silica fine particles. .

  The heat insulating material may further include a reinforcing fiber. In this case, the heat insulating material may include 50 to 98% by mass of the silica fine particles and 2 to 20% by mass of the reinforcing fiber. Further, the heat insulating material may include one or both of an alkaline earth metal and an alkali metal in addition to the silica fine particles and the reinforcing fiber. In this case, the heat insulating material is 0.1 to 10 parts by weight of one of the alkaline earth metal and the alkali metal or 100 parts by weight of the heat insulating material raw material containing the silica fine particles and the reinforcing fibers. It is good also as including both.

  The heat insulating material may have a thermal conductivity at 600 ° C. of 0.05 W / (m · K) or less. Further, the base portion may have a groove portion that accommodates the heating element.

  A manufacturing method of a heating device according to an embodiment of the present invention for solving the above problem is a manufacturing method of a heating device including a heating element and a base made of a heat insulating material and holding the heating element. The method further comprises the step of producing the heat insulating material by curing a dry pressure molded body containing silica fine particles having an average particle size of 50 nm or less at a relative humidity of 70% or more. ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the heating apparatus which has the heat insulating material which had the outstanding heat insulation and sufficient intensity | strength can be provided.

  Further, the dry pressure-molded body may not contain a binder. In addition, the dry pressure molded body may include one or both of an alkaline earth metal hydroxide and an alkali metal hydroxide. In this case, the dry-type pressure-molded body comprises 0.1 to 10 parts by weight of the alkaline earth metal hydroxide and the alkali metal hydroxide with respect to 100 parts by weight of the heat insulating material raw material containing the silica fine particles. One or both may be included.

  The dry pressure-molded body may further include reinforcing fibers. In this case, the dry pressure-molded body may include 50 to 98% by mass of the silica fine particles and 2 to 20% by mass of the reinforcing fiber. Furthermore, the dry pressure-molded body may include one or both of an alkaline earth metal hydroxide and an alkali metal hydroxide. Further, in this case, the dry pressure-molded body may include 0.1 to 10 parts by weight of the alkaline earth metal hydroxide and 100 parts by weight of the heat insulating material raw material including the silica fine particles and the reinforcing fibers. One or both of the alkali metal hydroxides may be included.

  A heating device according to an embodiment of the present invention for solving the above-described problems is manufactured by any one of the manufacturing methods described above. ADVANTAGE OF THE INVENTION According to this invention, the heating apparatus which has the heat insulating material which combined the outstanding heat insulation and sufficient intensity | strength can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the heating apparatus which has the heat insulating material which combined the outstanding heat insulation and sufficient intensity | strength, and its manufacturing method can be provided.

It is a perspective view which shows the external appearance about an example of the heating apparatus which concerns on one Embodiment of this invention. It is explanatory drawing which shows the member which comprises the heating apparatus shown in FIG. 1 by a side view. It is explanatory drawing which shows the member which comprises the heating apparatus shown in FIG. 1 by planar view. It is explanatory drawing which shows typically the cross section of the heating apparatus which concerns on one Embodiment of this invention. It is explanatory drawing which shows typically the cross section about the other example of the heating apparatus which concerns on one Embodiment of this invention. It is a perspective view which shows the external appearance about the further another example of the heating apparatus which concerns on one Embodiment of this invention. It is a perspective view which shows the external appearance about the further another example of the heating apparatus which concerns on one Embodiment of this invention. It is explanatory drawing which shows the main processes contained in an example of the manufacturing method of the heat insulating material which concerns on one Embodiment of this invention. It is explanatory drawing about the mechanism in which the intensity | strength of a heat insulating material improves by the curing in the manufacturing method of the heat insulating material which concerns on one Embodiment of this invention. In the Example which concerns on one Embodiment of this invention, it is explanatory drawing which shows an example of the result of having examined the compressive strength of the heat insulating material by changing curing conditions. It is explanatory drawing which shows an example of the electron micrograph of the heat insulating material obtained in the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the X-ray-diffraction result of the heat insulating material obtained in the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows the correlation with the peak value in X-ray diffraction, and compressive strength about the heat insulating material obtained in the Example which concerns on one Embodiment of this invention. In the Example which concerns on one Embodiment of this invention, it is explanatory drawing which shows an example of the result of having examined the compressive strength of the heat insulating material by changing the addition amount of calcium hydroxide. In the Example which concerns on one Embodiment of this invention, it is explanatory drawing which shows an example of the result of having examined the compressive strength of the heat insulating material by changing curing time. In the Example which concerns on one Embodiment of this invention, it is explanatory drawing which shows an example of the result of having examined the compressive strength of the heat insulating material by changing curing temperature. It is explanatory drawing which shows the other example of the electron micrograph of the heat insulating material obtained in the Example which concerns on one Embodiment of this invention. In the Example which concerns on one Embodiment of this invention, it is explanatory drawing which shows an example of the result of having examined the compressive strength of the heat insulating material by changing the kind of alkaline-earth metal hydroxide.

  Hereinafter, an embodiment of the present invention will be described. Note that the present invention is not limited to this embodiment.

  The heating device according to the present embodiment is a heating device including a heating element and a base made of a heat insulating material and holding the heating element. FIG. 1 is a perspective view showing an appearance of an example of a heating device. FIG. 2 is an explanatory view showing the members constituting the heating device shown in FIG. 1 in a side view. FIG. 3 is an explanatory diagram showing the members constituting the heating device shown in FIG. 1 in plan view. FIG. 4 is an explanatory view schematically showing a cross section of the heating device.

  As shown in FIGS. 1 to 4, the heating device includes a heating element B, a plate-like base A1 made of a heat insulating material and holding the heating element B, and a plate shape made of a heat insulating material and stacked on the base A1. Cover part A2.

  In this example, the heating element B is composed of an electric heating coil. The base A1 and the lid A2 are made of a heat insulating material containing silica fine particles. In addition, this heat insulating material can further contain a reinforcing fiber. This heat insulating material will be described in detail later.

  The base A1 has a groove 1 that accommodates the heating element B. This groove portion 1 is formed in a shape corresponding to the heating element B, and in this example, it is formed as a through-groove hole extending elongated corresponding to the electric heating coil. In the example shown in FIGS. 1 to 4, a plurality of linearly extending groove portions 1 are formed in parallel at a predetermined interval.

  The groove part 1 has the accommodating part 1a opened to the surface of the one side of base A1, and the thermal radiation part 1b opened to the surface of the other side of the said base A1. The opening of the accommodating portion 1a on the surface on one side of the base portion A1 is formed in a size and shape that allows the heating element B to be inserted in the assembly of the heating device. The housing portion 1a is formed with a recess 1c for holding the coil pitch of the electric heating coil.

  The base A1 is formed with a communication recess 1d for guiding and connecting the lead terminals of the electric heating coils fitted in the adjacent grooves 1 respectively. FIG. 3 shows a state in which the lead terminal of the electric heating coil and the lead terminal connecting sleeve 2 are accommodated in the connecting recess 1d.

  On the other hand, as shown in FIGS. 2 and 3, the opening of the heat radiating portion 1b on the surface on the other side of the base A1 is smaller than the opening of the housing portion 1a and is formed in a size and shape that the heating element B cannot pass through. . For this reason, the heating element B is stably held in the accommodating portion 1 a of the groove portion 1.

  As shown in FIG. 4, the lid A2 is stacked on the base A1 so as to close the opening of the accommodating portion 1a of the base A1. That is, the heating device is assembled by housing the heating element B in the groove portion 1 of the base portion A1, and then bonding the base portion A1 and the lid portion A2. The base A1 and the lid A2 can be integrated with, for example, a fastening tool such as a bolt and a nut. In the example shown in FIGS. 1 and 3, a bolt insertion hole 3 is formed in the base A1. Heating by the heating device is performed by causing the heating element B to generate heat and releasing the heat from the opening of the heat radiating portion 1b of the groove portion 1 to the outside.

  In the above-described example, the concave portion 1c that receives the coil portion of the electric heating coil is provided on the inner surface of the housing portion 1a into which the electric heating coil is fitted, and thereby the coil pitch is maintained, but this is not restrictive.

  That is, for example, the concave portion 1c is omitted, and the electric heating coil is fitted in an inner surface of the housing portion 1a formed to have a width matching the diameter of the electric heating coil, and an adhesive material such as refractory mortar is applied, and the electric heating coil is held by the adhesive material. You can also In this case, the application of the adhesive may be performed on the entire inner surface of the housing portion 1a or a part thereof.

  Further, for example, the width of the accommodating portion 1a is formed slightly smaller than the diameter of the electric heating coil, the elastic force of the electric heating coil fitted into the accommodating portion 1a, and the elastic force of the heat insulating material constituting the base A1; The electric heating coil can also be held by.

  Moreover, the inner surface of the accommodating part 1a can be formed in a waveform shape or uneven | corrugated shape (for example, sawtooth shape), and an electrothermal coil can also be hold | maintained by these shapes. In this case, if the holding power of the electric heating coil is obtained, a slight deviation in the coil pitch is allowed. Further, the above-described means for holding the electric heating coil may be appropriately combined.

  The heating device is not particularly limited as long as the heating element B is accommodated in the groove 1 formed in the vicinity of the surface of the heat insulating material constituting the base A1, and is preferably realized as a panel heater using the heating element B, for example. can do.

  The heating element B is not particularly limited as long as it generates heat to such an extent that heating by a heating device is realized, and examples thereof include iron-chromium-aluminum or nickel-chromium metal heating elements. Further, examples of such a metal heating element include a coil shape and a wave shape. In addition, a so-called sheathed heater in which the heating element B is placed in a sheath (pipe) and filled with an insulator can be used.

  FIG. 5 is an explanatory view schematically showing a cross section of another example of the heating device. The heating device shown in FIG. 5 includes a heating element B, a plate-like base A1 having a groove portion 1 made of a heat insulating material and containing the heating element B, and a plate-like lid made of a heat insulating material and stacked on the base A1. Part A2.

  In the example shown in FIGS. 1 to 4 described above, the groove portion 1 is formed as a through groove hole that opens on the surface on one side and the other side of the base A1, but in the example shown in FIG. It is formed as a bottomed slot opening on only one surface of the base A1. The heating element B is fitted into the base A <b> 1 from the opening of the groove 1 and is held by the groove 1. The heating device is assembled by laminating the cover A2 on the base A1 so as to close the opening of the groove 1 in which the heating element B is accommodated.

  In this heating device, heat from the heating element B is released through the surface portion 4 of the base A1 including the bottom of the groove 1. Therefore, the smaller the thickness t of the surface portion 4, the higher the heat dissipation efficiency, which is preferable.

  According to such a heating device (for example, an electric heating coil embedded type panel heater), since the surface portion 4 becomes a planar heating element, the heating device (for example, an electric heating coil open type) shown in FIGS. Although the temperature rise characteristic is lower than that of the panel heater, the radiation efficiency is increased after the temperature rise.

  FIG. 6 is a perspective view showing the appearance of still another example of the heating device. The heating device shown in FIG. 6 includes a heating element B, a cylindrical base A1 made of a heat insulating material and having a groove for receiving the heating element B, and a cylinder made of a heat insulating material and stacked radially outside the base A1. And an outer layer portion A2. Also in this example, the heating element B is composed of an electric heating coil. And the spiral groove part is formed in the internal peripheral surface of base A1, and the heat generating body B is accommodated in the said groove part.

  FIG. 7 is a perspective view showing the appearance of still another example of the heating device. The heating device shown in FIG. 7 includes a heating element B and a semi-cylindrical base A1 made of a heat insulating material and holding the heating element B.

In this example, the heating element B is made of a single heating metal wire (for example, molybdenum disilicide (MoSi ₂ )), and the heating element B is attached to the inner peripheral surface of the base A1 by the staple 5. The semi-cylindrical heating device can be combined with other semi-cylindrical heating devices to form a cylindrical heating device as a whole.

  Next, the heat insulating material used for the heating device will be described in detail. First, a method for manufacturing this heat insulating material (hereinafter referred to as “the present method”) will be described. This method is a method for producing a heat insulating material, in which a dry pressure molded body containing silica fine particles having an average particle diameter of 50 nm or less is cured at a relative humidity of 70% or more. Here, an example in which the dry pressure molded body further includes reinforcing fibers will be described.

  FIG. 8 is an explanatory diagram showing main steps included in an example of the present method. In the example shown in FIG. 8, the present method includes a preparation step S1 for preparing a dry pressure molded body, a curing step S2 for curing the dry pressure molded body at a high humidity, and the dry pressure molded body after curing. And drying step S3 for drying.

  In the preparation step S1, a heat insulating material raw material including silica fine particles and reinforcing fibers is prepared. The silica fine particles are not particularly limited as long as the average particle diameter is 50 nm or less, and any one kind can be used alone or two or more kinds can be used in any combination.

  That is, as the silica fine particles, for example, dry silica fine particles (anhydrous silica fine particles) produced by a gas phase method and wet silica fine particles produced by a wet method can be used, and among them, dry silica fine particles are preferably used. Can do. Specifically, for example, fumed silica fine particles produced by a gas phase method can be preferably used, and among them, hydrophilic fumed silica fine particles can be preferably used.

More specifically, the average particle diameter of the silica fine particles can be, for example, 5 nm or more and 50 nm or less. The silica (SiO ₂ ) content of the silica fine particles is preferably 95% by weight or more, for example. The thermal conductivity of the silica fine particles at 25 ° C. is preferably 0.01 W / (m · K) or less, for example. BET specific surface area of the silica fine particles, for example, preferably at ^{50 m} 2 / g or more, more specifically, for example, ^{50 m} 2 / g or more, it can be 400 meters ² / g or less, more preferably Can be 100 m ² / g or more and 300 m ² / g or less.

  The reinforcing fiber is not particularly limited as long as it can reinforce the heat insulating material, and one or both of inorganic fibers and organic fibers can be used.

  The inorganic fiber is not particularly limited as long as it can be used as a reinforcing fiber, and any one kind can be used alone, or two or more kinds can be arbitrarily combined. Specifically, the inorganic fiber is, for example, selected from the group consisting of silica-alumina fiber, silica fiber, alumina fiber, zirconia fiber, alkaline earth metal silicate fiber, glass fiber, rock wool, and basalt fiber. More than seeds can be used. The alkaline earth metal silicate fiber is a biosoluble inorganic fiber. That is, as the inorganic fiber, one or both of a non-biosoluble inorganic fiber and a biosoluble inorganic fiber can be used.

  The thermal conductivity at 400 ° C. of the inorganic fiber is preferably 0.08 W / (m · K) or less, and more preferably 0.04 W / (m · K) or less, for example. As such low thermal conductive inorganic fibers, for example, silica-based fibers such as silica-alumina fibers and silica fibers can be preferably used.

  The fiber length of the inorganic fiber is, for example, preferably 1 mm or more and 10 mm or less, more preferably 1 mm or more and 7 mm or less, and particularly preferably 3 mm or more and 5 mm or less. When the fiber length is less than 1 mm, the inorganic fibers may not be properly oriented, and as a result, the mechanical strength of the heat insulating material may be insufficient. When the fiber length exceeds 10 mm, the powder fluidity at the time of molding is impaired and the moldability is lowered, and the workability may be lowered due to density unevenness.

  For example, the average fiber diameter of the inorganic fibers is preferably 15 μm or less, and more specifically, for example, preferably 5 μm or more and 15 μm or less. When the average fiber diameter exceeds 15 μm, the inorganic fibers may be easily broken, and as a result, the strength of the heat insulating material may be insufficient. Therefore, as an inorganic fiber, for example, a fiber having a fiber length of 1 mm or more and 10 mm or less and an average fiber diameter of 15 μm or less can be preferably used.

  The organic fiber is not particularly limited as long as it can be used as a reinforcing fiber, and any one kind can be used alone, or two or more kinds can be arbitrarily combined. Specifically, as the organic fiber, for example, one or more selected from the group consisting of an aramid fiber, a polyethylene fiber, a polypropylene fiber, and a polyolefin fiber can be used.

  The fiber length of the organic fiber is, for example, preferably 1 mm or more and 10 mm or less, more preferably 2 mm or more and 7 mm or less, and particularly preferably 3 mm or more and 5 mm or less. When the fiber length is less than 1 mm, the organic fibers may not be properly oriented, and as a result, the mechanical strength of the heat insulating material may be insufficient. When the fiber length exceeds 10 mm, the powder fluidity at the time of molding is impaired and the moldability is lowered, and the workability may be lowered due to density unevenness.

  For example, the average fiber diameter of the organic fibers is preferably 15 μm or less, and more specifically, for example, preferably 5 μm or more and 15 μm or less. When the average fiber diameter exceeds 15 μm, the organic fibers may be easily broken, and as a result, the strength of the heat insulating material may be insufficient. Therefore, as an organic fiber, for example, a fiber having a fiber length of 1 mm or more and 10 mm or less and an average fiber diameter of 15 μm or less can be preferably used.

  The dry pressure-molded body can be produced by preparing a dry mixture by mixing the silica fine particles and the reinforcing fibers as described above in a dry method, and then press-molding the dry mixture in a dry method.

  Specifically, for example, a heat insulating material raw material containing a dry powder of silica fine particles and a dry powder of reinforcing fibers is dry-mixed using a predetermined mixing device, and then the obtained dry-type mixture is predetermined molded A dry press-molded body is produced by filling the mold and dry press molding. In addition, by performing mixing and shaping | molding by a dry type, compared with the wet case, management of a raw material and a molded object is easy, and the time which manufacture requires can be shortened effectively.

  The dry pressure-molded body can contain, for example, 50 to 98% by mass of silica fine particles and 2 to 20% by mass of reinforcing fibers, and 65 to 80% by mass of silica fine particles and 5 to 18% by mass of reinforcing fibers. Can be included. When the content of the reinforcing fiber is less than 2% by mass, the strength of the heat insulating material may be insufficient. When the content of the reinforcing fiber exceeds 20% by mass, the powder fluidity at the time of molding is impaired, the moldability is lowered, and the workability may be lowered due to density unevenness.

  Moreover, when a dry-type pressure-molded body contains only silica fine particles and reinforcing fibers, for example, the total of 80 to 98% by mass of silica fine particles and 2 to 20% by mass of reinforcing fibers is 100% by mass. Preferably, 82 to 98% by mass of silica fine particles and 2 to 18% by mass of reinforcing fibers can be included so that the total is 100% by mass, more preferably 85 to 97% by mass. Silica fine particles and 3 to 15% by mass of reinforcing fibers can be contained so that the total becomes 100% by mass. When the content of the reinforcing fiber is less than 2% by mass, the strength of the heat insulating material may be insufficient. When the content of the reinforcing fiber exceeds 20% by mass, the powder fluidity at the time of molding is impaired, the moldability is lowered, and the workability may be lowered due to density unevenness.

  Further, the dry pressure molded body may not contain a binder. That is, in this method, since the strength of the heat insulating material can be effectively improved by the curing treatment described later, it is not necessary to use a binder. In this case, the dry pressure-molded body does not substantially contain a conventionally used binder such as an inorganic binder such as a water glass adhesive or an organic binder such as a resin. Thus, the conventional problems associated with the use of binders can be reliably avoided. In this case, the dry pressure molding is not particularly limited, but can be performed at a temperature of 5 ° C. or more and 60 ° C. or less, for example.

  Moreover, the dry-type pressure-molded body can also contain one or both of an alkaline earth metal hydroxide and an alkali metal hydroxide. The alkaline earth metal hydroxide is not particularly limited as long as it can be used as a strong base, and any one kind can be used alone or two or more kinds can be used in any combination. Specifically, as the alkaline earth metal hydroxide, for example, one or more selected from the group consisting of calcium hydroxide, magnesium hydroxide, strontium hydroxide and barium hydroxide can be used. Calcium oxide can be preferably used.

  The alkali metal hydroxide is not particularly limited as long as it can be used as a strong base, and any one kind can be used alone or two or more kinds can be used in any combination. Specifically, as the alkali metal hydroxide, for example, one or more selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide can be used.

  The dry pressure-molded body is, for example, one of 0.1 to 10 parts by weight of an alkaline earth metal hydroxide and an alkali metal hydroxide with respect to 100 parts by weight of a heat insulating material raw material containing silica fine particles and reinforcing fibers. Or both can be included. That is, in this case, the dry pressure molded body can contain 0.1 to 10 parts by weight of an alkaline earth metal hydroxide or an alkali metal hydroxide, and the alkaline earth metal hydroxide and the alkali metal hydroxide. A total of 0.2 to 20 parts by weight of metal hydroxide can also be included. The content of one or both of the alkaline earth metal hydroxide and the alkali metal hydroxide can be, for example, 1 to 7 parts by weight, or 2 to 5 parts by weight.

  The dry pressure-molded body comprises a dry powder of silica fine particles, a dry powder of reinforcing fibers, and a dry powder of one or both of an alkaline earth metal hydroxide and an alkali metal hydroxide. It can be made by mixing and then dry pressing the resulting dry mixture.

  Moreover, the dry pressure-molded product can further contain other components. That is, the dry pressure-molded body can include, for example, a radiation scattering material. The radiation scattering material is not particularly limited as long as it can reduce heat transfer by radiation, and any one kind can be used alone or two or more kinds can be arbitrarily combined.

  Specifically, as the radiation scattering material, for example, one or more selected from the group consisting of silicon carbide, zirconia, and titania can be used. The radiation scattering material preferably has an average particle size of 50 μm or less, more specifically 1 to 50 μm, and a relative refractive index of 1.25 or more for light having a wavelength of 1 μm or more. Is preferred.

  When the radiation scattering material is used, the dry pressure molded body includes, for example, 50 to 93% by mass of silica fine particles, 2 to 20% by mass of reinforcing fiber, and 5 to 40% by mass of the radiation scattering material. More preferably, it may contain 65 to 80% by mass of silica fine particles, 5 to 18% by mass of reinforcing fibers, and 15 to 30% by mass of radiation scattering material.

  In the subsequent curing step S2, the dry pressure molded body prepared in the preparation step S1 is cured at a high humidity of 70% or higher relative humidity. The relative humidity during curing can be, for example, 75% or more, 80% or more, and 85% or more. Furthermore, curing can also be performed at a relative humidity higher than 85%.

  Curing is performed by holding the dry pressure molded body for a predetermined time in the high humidity environment as described above. Specifically, for example, a dry press-molded body is placed in a constant temperature and humidity chamber in which the temperature and humidity are set to predetermined values, or in an autoclave in which the reached temperature is set to a predetermined value, and left for a predetermined time. By doing this, the said dry-type pressure-molded body can be cured at high humidity.

  The temperature at which curing is performed can be arbitrarily set within a range where the effect of the curing can be obtained. Specifically, the curing temperature can be, for example, 40 ° C. or higher, preferably 60 ° C. or higher, more preferably 80 ° C. or higher, and particularly preferably 90 ° C. or higher. By raising the curing temperature, the curing time until the effect is obtained can be shortened. Although the upper limit of curing temperature is not specifically limited, For example, it can be 95 degrees C or less. In addition, when a dry-type pressure-molded body contains an alkaline earth metal hydroxide, the curing temperature may be preferably 100 ° C. or less or less than 100 ° C. Moreover, curing temperature can also be made into less than 40 degreeC, for example.

  Curing can also be performed under pressurized conditions. In this case, the curing temperature can be arbitrarily set as long as the curing effect is obtained. Specifically, the curing temperature under a pressurized condition can be, for example, 100 to 200 ° C, or 120 to 170 ° C. By performing curing under such pressure conditions, it is expected to shorten the curing time until the effect is obtained.

  The time for performing curing can be arbitrarily set within a range in which the effect of the curing can be obtained. Specifically, the curing time can be, for example, 2 hours or more, and preferably 6 hours or more. The effect of curing can be enhanced by lengthening the curing time.

  More specifically, when the dry pressure-molded body contains neither an alkaline earth metal hydroxide nor an alkali metal hydroxide, the curing time is preferably long. Moreover, the alkaline earth metal hydroxide in a relatively small amount (for example, 0.1 to 2 parts by weight with respect to 100 parts by weight of the heat insulating material containing silica fine particles and reinforcing fibers) and When one or both of the alkali metal hydroxides are included, the curing time is preferably 6 hours or more and 100 hours or less. Further, the alkaline earth metal water in a relatively large amount (for example, more than 2 parts by weight and not more than 20 parts by weight with respect to 100 parts by weight of the heat insulating material raw material containing silica fine particles and reinforcing fibers) of the dry pressure molded body. When one or both of the oxide and the alkali metal hydroxide are included, the curing time is preferably 12 hours or less, and more preferably 6 hours or less.

  In addition, the conditions for curing are not limited to the above-described examples, and can be arbitrarily set within a range where the effect of the curing is obtained. That is, the curing conditions can be appropriately adjusted so that, for example, the strength (for example, compressive strength) and the thermal conductivity of the heat insulating material manufactured by this method are within a predetermined range as described later. Moreover, for example, the curing time is not limited to the above example, and can be appropriately determined according to other curing conditions such as temperature and humidity.

  In the subsequent drying step S3, the dry pressure molded body cured in the curing step S2 is dried. That is, in the drying step S3, moisture derived from the steam that has soaked into the dry pressure-formed body during curing is removed. The drying method is not particularly limited as long as unnecessary moisture can be removed from the dry pressure molded body. That is, for example, by holding a dry pressure molded body at a temperature of 100 ° C. or higher, the dry pressure molded body can be efficiently dried.

  In this method, finally, a dry pressure-molded body after curing and drying is obtained as a heat insulating material. According to this method, a heat insulating material having excellent heat insulating performance and strength can be manufactured. That is, according to this method, the strength of the heat insulating material can be effectively improved without increasing the density. Moreover, according to this method, the heat insulating material provided with sufficient intensity | strength can be manufactured, without using a binder.

  FIG. 9 is an explanatory view of a mechanism for improving the strength of the heat insulating material by high humidity curing in this method. Here, as shown in FIG. 9, the description will be made by paying attention to two adjacent silica fine particles P <b> 1 and P <b> 2 among the silica fine particles contained in the dry pressure-formed body. The following can be considered as a mechanism for improving the strength of the heat insulating material by high humidity curing.

  That is, first, as shown in FIG. 9A, extremely fine voids V (for example, ultrafine pores of about several nm) are formed between the silica fine particles P1 and P2 contained in the dry pressure-molded body before curing. ing. Next, when curing is started to hold the dry pressure molded body in a high-humidity atmosphere, as shown in FIG. A cross-linked structure S made of a liquid is formed.

Further, when the dry pressure molded body is kept in a high humidity atmosphere, as shown by arrows in FIG. 9C, silica is eluted from the silica fine particles P1 and P2, and the eluted silica is separated between the silica fine particles P1 and P2. A crosslinked structure S containing is formed. As the elution reaction of silica, the following silicate reaction can be considered: “SiO ₂ + 2H ₂ O → H ₄ SiO ₄ → H ⁺ + H ₃ SiO ₄ ⁻ ”.

  And the crosslinked structure S formed between silica fine particles P1 and P2 is hardened by drying the dry-type pressure-molded body after curing. The formation of such a crosslinked structure S can effectively increase the strength of the heat insulating material. A similar crosslinked structure is formed between the silica fine particles and the reinforcing fibers.

  In addition, when the dry pressure-molded body contains one or both of an alkaline earth metal hydroxide and an alkali metal hydroxide, the strength improvement as described above can be promoted, and the curing time is effective. Can be shortened. This is because the presence of alkaline earth metal hydroxide or alkali metal hydroxide forms a highly basic environment suitable for silica elution from the silica fine particles P1 and P2 inside the dry pressure molded body. it is conceivable that.

  That is, by using a strong base such as alkaline earth metal hydroxide or alkali metal hydroxide, elution of silica from silica fine particles P1 and P2 during curing is promoted, and as a result, the strength of the heat insulating material can be improved in a short time. It can be achieved. In this case, a crosslinked structure S containing one or both of an alkaline earth metal and an alkali metal in addition to silica is formed between the silica fine particles P1 and P2.

The heat insulating material used for the heating device (hereinafter referred to as “the present heat insulating material”) can be preferably manufactured by such a method. The heat insulating material can be provided with sufficient strength at a relatively low density. That is, this heat insulating material is, for example, a heat insulating material containing silica fine particles having an average particle size of 50 nm or less and reinforcing fibers, having a bulk density of 190 to 600 kg / m ³ and a compressive strength of 0.65 MPa or more. Can do.

The bulk density of this heat insulating material can also be 190-450 kg / m < ³ >, for example, and can also be 190-300 kg / m < ³ >. The compressive strength of this heat insulating material can also be 0.7 MPa or more, for example, and can also be 0.75 MPa or more. In addition, a compressive strength can be measured using a predetermined compression test apparatus, for example, a commercially available universal test apparatus (Tensilon RTC-1150A, Orientec Co., Ltd.). Specifically, for example, a load is applied in a direction perpendicular to the press surface (30 mm × 30 mm) of a test piece processed to dimensions 30 mm × 30 mm × 15 mm, and the load (MPa) when the test piece is broken is compressed. Get as strength. This compressive strength can be evaluated as the compressive strength in the thickness direction (that is, the breaking strength when the pair of surfaces having the largest area extending in the longitudinal direction is compressed) when the heat insulating material is plate-shaped. .

  This heat insulating material can contain 50-98 mass% silica fine particle and 2-20 mass% reinforcement fiber, for example, 65-80 mass% silica fine particle, and 5-18 mass% reinforcement fiber are included. Can be included. When the content of the reinforcing fiber is less than 2% by mass, the strength of the heat insulating material may be insufficient. When the content of the reinforcing fiber exceeds 20% by mass, the powder fluidity at the time of molding is impaired, the moldability is lowered, and the workability may be lowered due to density unevenness.

  Moreover, when this heat insulating material contains only a silica fine particle and a reinforcement fiber, it contains 80-98 mass% silica fine particle and 2-20 mass% reinforcement fiber so that a sum total may be 100 mass%, for example. Preferably, it can contain 82 to 98% by mass of silica fine particles and 2 to 18% by mass of reinforcing fibers so that the total is 100% by mass, more preferably 85 to 97% by mass of silica fine particles. And 3 to 15% by mass of reinforcing fibers can be included so that the total amount becomes 100% by mass. When the content of the reinforcing fiber is less than 2% by mass, the strength of the heat insulating material may be insufficient. When the content of the reinforcing fiber exceeds 20% by mass, the powder fluidity at the time of molding is impaired, the moldability is lowered, and the workability may be lowered due to density unevenness.

  Moreover, this heat insulating material shall not contain a binder. That is, since this heat insulating material can achieve sufficient strength by curing as described above, it is not necessary to use a binder. In this case, the heat insulating material does not substantially contain a conventionally used binder such as an inorganic binder such as a water glass adhesive or an organic binder such as a resin. Thus, the conventional problems associated with the use of binders can be reliably avoided.

  Moreover, this heat insulating material can contain one or both of an alkaline-earth metal and an alkali metal other than a silica particle and a reinforcing fiber. That is, the present heat insulating material can contain a metal derived from one or both of the alkaline earth metal hydroxide and the alkali metal hydroxide used in curing.

  Specifically, this heat insulating material can contain 1 or more types selected from the group which consists of calcium, magnesium, strontium, and barium, for example, and it is preferable to contain calcium especially. Moreover, this heat insulating material can contain 1 or more types selected from the group which consists of sodium, potassium, and lithium, for example.

  This heat insulating material can contain 0.1 to 10 weight part of one or both of an alkaline-earth metal and an alkali metal with respect to 100 weight part of heat insulating material raw materials containing a silica microparticle and a reinforcing fiber, for example. That is, in this case, the heat insulating material can include, for example, 0.1 to 10 parts by weight of an alkaline earth metal or an alkali metal, and the total of the alkaline earth metal and the alkali metal is 0.2 to 20 parts by weight can be included. The content of one or both of the alkaline earth metal and alkali metal can be, for example, 1 to 7 parts by weight, or 2 to 5 parts by weight.

  Moreover, this heat insulating material can also contain another component further. That is, this heat insulating material can also contain a radiation scattering material, for example. The radiation scattering material is not particularly limited as long as it can reduce heat transfer by radiation, and any one kind can be used alone or two or more kinds can be arbitrarily combined.

  Specifically, as the radiation scattering material, for example, one or more selected from the group consisting of silicon carbide, zirconia, and titania can be used. The radiation scattering material preferably has an average particle size of 50 μm or less, more specifically 1 to 50 μm, and a relative refractive index of 1.25 or more for light having a wavelength of 1 μm or more. Is preferred.

  When using a radiation-scattering material, this heat insulating material may contain, for example, 50 to 93% by mass of silica fine particles, 2 to 20% by mass of reinforcing fibers, and 5 to 40% by mass of the radiation-scattering material. More preferably, it can contain 65-80 mass% silica fine particles, 5-18 mass% reinforcing fiber, and 15-30 mass% radiation scattering material.

  Moreover, this heat insulating material can be equipped with the outstanding heat insulation performance. In other words, the present heat insulating material achieves sufficient strength without increasing the density as in the prior art, and therefore it is possible to effectively avoid a decrease in heat insulating performance due to an increase in solid heat transfer. Specifically, the heat insulating material can be a heat insulating material having a thermal conductivity at 600 ° C. of 0.05 W / (m · K) or less. The thermal conductivity at 600 ° C. of the heat insulating material can be preferably 0.04 W / (m · K) or less.

  The heat insulating material has a structure in which primary particles of silica fine particles having an average particle size of 50 nm or less are associated with each other by intermolecular force to form secondary particles, and the secondary particles are scattered between reinforcing fibers. ing. And by using silica fine particles, this heat insulating material retains a nanopore structure smaller than the mean free path of air molecules inside, thereby providing excellent heat insulation performance in a wide temperature range from a low temperature range to a high temperature range. It can be demonstrated.

  Moreover, this heat insulating material shall have a peculiar structure formed by high-humidity curing. That is, this heat insulating material can be made into a heat insulating material including, for example, silica fine particles having an average particle diameter of 50 nm or less and reinforcing fibers, and having a crosslinked structure including silica between the silica fine particles. As described above, this crosslinked structure is formed by capillary condensation of water vapor and includes silica eluted from silica fine particles.

  The crosslinked structure can also contain one or both of an alkaline earth metal and an alkali metal. That is, in this case, as described above, the crosslinked structure is one or both of an alkaline earth metal and an alkali metal derived from one or both of the alkaline earth metal hydroxide and the alkali metal hydroxide used at the time of curing. Includes both.

  Moreover, this heat insulating material can contain a calcium silicate. That is, for example, when this heat insulating material is manufactured through high-humidity curing to which calcium hydroxide is added, the chemistry of the silica component eluted from the silica fine particles and the calcium hydroxide inside the heat insulating material. The reaction can produce calcium silicate. For this reason, this heat insulating material can contain the calcium silicate produced | generated by the high-humidity curing in the crosslinked structure formed between the silica fine particles or other parts.

  As described above, the heat insulating material can have both excellent heat insulating performance and high strength at a relatively low density. Therefore, this heat insulating material can be preferably used as, for example, a heat insulating material for a general industrial furnace that requires processing or a heat insulating material for a reformer of a fuel cell.

  The heat insulating material used as the base of the heating device can be manufactured as a molded body having an arbitrary shape. That is, when producing a plate-shaped heat insulating material, for example, a dry mixture containing silica fine particles and reinforcing fibers is filled in a plate-shaped mold and dry-press-molded, and the obtained plate-shaped dry-processed material is obtained. The compacted body is cured at high humidity as described above.

  When manufacturing a cylindrical main heat insulating material, for example, first, a plate-shaped or block-shaped main heat insulating material is formed, and then a cylindrical main heat insulating material is formed from the plate-shaped or block-shaped main heat insulating material. Cut out the material.

  Further, for example, a dry mixture containing silica fine particles and reinforcing fibers is pressed against the inner peripheral surface or outer peripheral surface of a cylindrical mold with a predetermined pressure to produce a cylindrical dry pressure molded body. The cylindrical heat insulating material can also be produced by curing the cylindrical dry pressure-formed body at a high humidity as described above.

  Further, for example, a cylindrical core having a smaller diameter is arranged in the hollow portion of the cylindrical mold, and a dry mixture containing silica fine particles and reinforcing fibers is added between the mold and the core. It is possible to produce a cylindrical main heat insulating material by producing a cylindrical dry pressure molded body by pressing and curing the obtained cylindrical dry pressure molded body at high humidity as described above. it can.

  In addition, the shape of this heat insulating material which comprises a base is not restricted to the above-mentioned plate shape or cylindrical shape, It can shape | mold in arbitrary shapes. Moreover, a groove part can be formed in this heat insulating material manufactured previously, or can also be formed at the time of manufacture of this heat insulating material.

  In the heating device according to the present invention, the heat insulating material constituting the base has extremely low thermal conductivity based on silica fine particles, and the heat insulating material has sufficient strength enhanced by high humidity curing, For example, it can be preferably used for heating various industrial heating furnaces and experimental furnaces such as heating furnaces in nuclear facilities.

  Next, specific examples according to the present embodiment will be described.

  [Production of heat insulating material] Anhydrous silica fine particles (hydrophilic fumed silica fine particles) having an average primary particle diameter of about 13 nm and a thermal conductivity (25 ° C.) of 0.01 W / (m · K), and an average fiber diameter A dry pressure-molded body containing 10 μm and heat-resistant glass fibers having an average fiber length of 3 mm was produced.

  That is, 100 parts by weight of a heat insulating material raw material containing 90% by mass of silica fine particles and 10% by mass of glass fiber and 0, 1, 3, 5 or 10 parts by weight of calcium hydroxide (reagent grade 1, Wako Pure Chemical Industries Ltd.) Were introduced into a mixing apparatus and dry-mixed.

And the plate-shaped dry-type molded object of 100 mm x 150 mm x thickness 15mm was produced from the obtained dry mixed powder by dry press molding. Specifically, first, an appropriate amount of the dry mixed powder was filled into a molding die provided with a predetermined deaeration mechanism. Then, dry press molding was performed so that a desired bulk density was obtained. That is, in dry press molding, the press pressure was adjusted so that the bulk density of the dry molded product was 250 kg / m ³ . After molding, the dry pressure molded body was quickly taken out from the mold.

  Next, the dry-type molded body is kept in a constant temperature and humidity chamber at a temperature of 80 ° C. and a relative humidity of 90% for 3 to 400 hours, or by being held in an autoclave at a temperature of 170 ° C. for 6 hours. Went. And the dry-type molded object after curing was dried at 105 degreeC, and the heat insulating material was obtained.

  [Evaluation of Compressive Strength] The compressive strength of each heat insulating material was measured using a universal testing device (Tensilon RTC-1150A, Orientec Co., Ltd.). That is, a load was applied in a direction perpendicular to the press surface (30 mm × 30 mm) of a test piece processed into dimensions 30 mm × 30 mm × 15 mm, and the load when the test piece was broken was defined as compressive strength (MPa).

  In FIG. 10, the manufacturing conditions and compressive strength of each heat insulating material are shown correspondingly. The compressive strength of the cured heat insulating material was significantly increased compared to the compressive strength (0.25 MPa) of the non-cured heat insulating material.

  That is, when calcium hydroxide was not added (0 part by weight) and curing was performed at 80 ° C. and 90 RH%, the compressive strength was improved as the curing time was increased. Specifically, the compressive strength increased to 0.40 MPa by curing for 3 hours and reached 1.08 MPa by curing for 400 hours.

  Moreover, when calcium hydroxide was not added and it was cured in an autoclave (0 parts by weight, A / C), the compressive strength of the heat insulating material cured for 6 hours was 0.97 MPa. Although not shown in FIG. 10, the same increase in compressive strength was confirmed by curing for 6 hours when calcium hydroxide was not added and curing was performed in an autoclave at 120 ° C. or 200 ° C.

  Further, when calcium hydroxide was added, the compressive strength could be increased in a shorter time than when calcium hydroxide was not added. In addition, it was confirmed that the compressive strength could be increased in a shorter time as the amount of calcium hydroxide added increased.

  That is, when 1 part by weight of calcium hydroxide is added and cured at 80 ° C. and 90 RH%, the compressive strength increases to 0.83 MPa by curing for 3 hours and 1.13 MPa by curing for 48 hours. Reached.

  When 3 parts by weight of calcium hydroxide is added and cured at 80 ° C. and 90 RH%, the compressive strength increases to 0.89 MPa by curing for 3 hours and reaches 1.03 MPa by curing for 6 hours. did.

  When 5 parts by weight of calcium hydroxide is added and cured at 80 ° C. and 90 RH%, the compressive strength increases to 0.91 MPa by curing for 3 hours and reaches 1.08 MPa by curing for 6 hours. did.

  When 10 parts by weight of calcium hydroxide was added and cured at 80 ° C. and 90 RH%, the compressive strength reached 0.93 MPa by curing for 3 hours.

  On the other hand, when calcium hydroxide is added and cured in an autoclave (1 to 10 parts by weight, A / C), the degree of increase in compressive strength is lower than when cured at 80 ° C. and 90 RH%. It was.

  [Electron microscope observation] FIG. 11 shows a heat insulating material (FIGS. 11A and 11B) manufactured without adding calcium hydroxide and curing, 3 parts by weight of calcium hydroxide, and 80 ° C., 90 RH. An example of the result of observing each of the heat insulating materials (FIGS. 11C and 11D) produced by curing for 24 hours with% using a scanning electron microscope (SEM) is shown.

  As shown in FIG. 11A, irregularities were clearly observed on the surface of the heat insulating material to which calcium hydroxide was not added and not cured, whereas calcium hydroxide was added as shown in FIG. 11C. The surface of the cured heat insulating material was relatively flat. In the heat insulating material shown in FIG. 11A, each silica fine particle is merely aggregated, whereas in the heat insulating material shown in FIG. 11C, the silica component eluted from the silica fine particles causes a gap between the silica fine particles. It was considered that a crosslinked structure was formed and as a result, the internal structure was densified.

  Further, as shown in FIG. 11B, on the surface of the heat insulating material to which calcium hydroxide was not added and not cured, the boundary of the silica fine particles was observed blurry, whereas as shown in FIG. The boundary of the silica fine particles was clearly observed on the surface of the heat insulating material to which calcium oxide was added and cured. This is thought to be because, in the heat insulating material shown in FIG. 11D, as a result of the formation of a crosslinked structure between the silica fine particles by the silica component eluted from the silica fine particles, the conductivity was increased and the electron beam could be detected with higher sensitivity. It was.

  [X-ray diffraction] X-ray diffraction (XRD) was applied to each of the heat insulating materials added with 3, 5 or 10 parts by weight of calcium hydroxide and cured at 80 ° C. and 90 RH% for 0 to 24 hours or cured in an autoclave for 6 hours. ), The change in the content of calcium hydroxide and the amount of calcium silicate formed with an increase in curing time was analyzed.

In FIG. 12, an example of the XRD measurement result of the heat insulating material manufactured by adding 3 weight part of calcium hydroxide is shown. 12A and 12B show the measurement results of the heat insulating material that was not cured, and FIGS. 12C and 12D show the measurement results of the heat insulating material that was cured for 24 hours. As shown in FIGS. 12A to 12D, the peak of calcium hydroxide (Ca (OH) ₂ ) disappeared due to curing, and a new peak of calcium silicate (CSH) appeared.

FIG. 13 shows the curing time, the XRD peak values of calcium hydroxide (Ca (OH) ₂ ) and calcium silicate (CSH), and the compressive strength in association with each heat insulating material. FIG. 13A shows a heat insulating material added with 3 parts by weight of calcium hydroxide, FIG. 13B shows a heat insulating material added with 5 parts by weight of calcium hydroxide, and FIG. 13C shows a result of heat insulating material added with 10 parts by weight of calcium hydroxide. Respectively.

  As shown in FIGS. 13A to 13C, as the curing time increased, the content of calcium hydroxide decreased, and the compressive strength increased accordingly. That is, the tendency for the compressive strength of a heat insulating material to increase was seen as the consumption of calcium hydroxide increased.

  Moreover, with the increase in curing time, the content of calcium silicate increased due to new generation of calcium silicate. However, after the calcium hydroxide was consumed, the compressive strength tended to decrease although the calcium silicate content increased.

  That is, there is not always a correlation between the calcium silicate content and the increase in the compressive strength of the heat insulating material, but rather the compressive strength tends to decrease as the calcium silicate content increases. It was.

  [Production of heat insulating material] In addition to the silica fine particles and glass fibers used in Example 1 above, a dry pressure-molded body further containing silicon carbide having an average particle diameter of 3 µm was prepared.

  That is, a mixing apparatus comprising 100 parts by weight of a heat insulating material containing 75% by mass of silica fine particles, 5% by mass of glass fiber and 20% by mass of silicon carbide, and 0, 3, 5 or 10 parts by weight of calcium hydroxide. And dry-mixed.

From the obtained dry mixed powder, a plate-shaped dry molded body of 100 mm × 150 mm × thickness 15 mm was produced by dry press molding. In dry press molding, the press pressure was adjusted so that the bulk density of the dry compact was 240, 260, 280, or 300 kg / m ³ .

  Next, high-humidity curing was performed by holding the dry molded body containing calcium hydroxide in a constant temperature and humidity chamber at a temperature of 80 ° C. and a relative humidity of 90% for 8 hours. And the dry-type molded object after curing was dried at 105 degreeC, and the heat insulating material was obtained. Moreover, curing was not performed for the dry pressure-formed body containing no calcium hydroxide.

  [Evaluation of Compressive Strength and Thermal Conductivity] The compressive strength of each heat insulating material was measured in the same manner as in Example 1 above. Moreover, the heat conductivity in 200, 400, or 600 degreeC of each heat insulating material was measured with the period heating method. That is, a temperature wave was propagated in the test body, and the thermal diffusivity was measured from the propagation time. And thermal conductivity was computed from this thermal diffusivity and the specific heat and density measured separately. As the temperature wave, a temperature wave having a temperature amplitude of about 4 ° C. and a period of about 1 hour was used. The time required for the temperature wave to pass through two points in the test body was defined as the propagation time.

  FIG. 14 shows the added amount of calcium hydroxide, the bulk density, the compressive strength, and the thermal conductivity in correspondence. The bulk density was calculated from the weight and volume. That is, the volume was calculated from the actual dimensions of the test specimen, and the value obtained by dividing the weight of the test specimen by the volume was taken as the bulk density of the test specimen.

  As shown in FIG. 14, it was shown that the compressive strength of a heat insulating material increases by the curing to which calcium hydroxide was added. The compressive strength when the bulk density was constant was highest when the amount of calcium hydroxide added was 3 parts by weight. In addition, there was no significant change in thermal conductivity with or without curing.

  [Production of heat insulating material] In the same manner as in Example 2 described above, a dry pressure molded body containing silica fine particles, glass fibers, and silicon carbide was produced. That is, 100 parts by weight of a heat insulating material containing 75% by weight of silica fine particles, 5% by weight of glass fibers and 20% by weight of silicon carbide, and 0 or 3 parts by weight of calcium hydroxide are charged into a mixing device. Dry mixed.

From the obtained dry mixed powder, a plate-shaped dry molded body of 100 mm × 150 mm × thickness 15 mm was produced by dry press molding. In dry press molding, the press pressure was adjusted so that the bulk density of the dry compact was 240, 260, 280, or 300 kg / m ³ .

  Next, high-humidity curing was performed by holding the dry-type compact containing calcium hydroxide in a constant temperature and humidity chamber at a temperature of 80 ° C. and a relative humidity of 90% for 0 to 24 hours. And the dry-type molded object after curing was dried at 105 degreeC, and the heat insulating material was obtained. Moreover, curing was not performed for the dry pressure-formed body containing no calcium hydroxide.

  [Evaluation of Compressive Strength] The compressive strength of each heat insulating material was measured in the same manner as in Example 1 described above. FIG. 15 shows the added amount of calcium hydroxide, the curing time, the bulk density, and the compressive strength.

  As shown in FIG. 15, the compression strength of the cured heat insulating material (calcium hydroxide 3 parts by weight added, curing 1 to 24 hours) is not cured (no calcium hydroxide added or 3 parts by weight added, curing 0 hours). Compared to

  Moreover, when 3 weight part calcium hydroxide was added, the tendency for compressive strength to increase was seen by making curing time increase. In addition, when 3 weight part calcium hydroxide was added and it was not cured, compressive strength fell rather than the case where it did not cure without adding calcium hydroxide.

  [Production of heat insulating material] In the same manner as in Example 2 described above, a dry pressure molded body containing silica fine particles, glass fibers, and silicon carbide was produced. That is, 100 parts by weight of a heat insulating material containing 75% by mass of silica fine particles, 5% by mass of glass fibers and 20% by mass of silicon carbide and 3 parts by weight of calcium hydroxide are put into a mixing apparatus and dry mixed. did.

From the obtained dry mixed powder, a plate-shaped dry molded body of 100 mm × 150 mm × thickness 15 mm was produced by dry press molding. In dry press molding, the press pressure was adjusted so that the bulk density of the dry compact was 240, 260, or 280 kg / m ³ .

  Next, high-humidity curing was performed by holding the dry molded body for 24 hours in a constant temperature and humidity chamber at a temperature of 40, 60, or 80 ° C. and a relative humidity of 90%. And the dry-type molded object after curing was dried at 105 degreeC, and the heat insulating material was obtained. Moreover, the heat insulating material manufactured without adding calcium hydroxide and curing was also prepared.

  [Evaluation of Compressive Strength] The compressive strength of each heat insulating material was measured in the same manner as in Example 1 described above. FIG. 16 shows the curing temperature, bulk density, and compressive strength in correspondence. As shown in FIG. 16, the compressive strength was remarkably increased by curing at a temperature of 40 ° C. or higher. Moreover, the higher the curing temperature, the more significantly the compressive strength increased.

  [Electron Microscope Observation] FIG. 17 shows that a heat insulating material produced by curing without adding calcium hydroxide (FIG. 17A), 3 parts by weight of calcium hydroxide, and 24 ° C. at 90 RH%. An example of the result of having observed with the scanning electron microscope each of the heat insulating material manufactured by time-curing (FIG. 17B) is shown.

  As shown in FIGS. 17A and 17B, compared with the surface of the heat insulating material cured without adding calcium hydroxide (FIG. 17A), the surface of the heat insulating material cured by adding calcium hydroxide (FIG. 17B) is more It was smoothed. This is considered to be because, in the heat insulating material shown in FIG. 17B, the elution of the silica component from the silica fine particles was promoted by the addition of calcium hydroxide, and as a result, the internal structure was further densified.

  [Production of heat insulating material] In the same manner as in Example 2 described above, a dry pressure molded body containing silica fine particles, glass fibers, and silicon carbide was produced. That is, a mixing apparatus comprising 100 parts by weight of a heat insulating material containing 75% by weight of silica fine particles, 5% by weight of glass fibers and 20% by weight of silicon carbide, and 0 or 3 parts by weight of calcium hydroxide or magnesium hydroxide. And dry-mixed.

From the obtained dry mixed powder, a plate-shaped dry molded body of 100 mm × 150 mm × thickness 15 mm was produced by dry press molding. In dry press molding, the press pressure was adjusted so that the bulk density of the dry compact was 240, 260, or 280 kg / m ³ .

  Next, high-humidity curing was performed by holding the dry molded body for 24 hours in a constant temperature and humidity chamber at a temperature of 80 ° C. and a relative humidity of 90%. And the dry-type molded object after curing was dried at 105 degreeC, and the heat insulating material was obtained. Moreover, the heat insulating material manufactured without adding a hydroxide and curing was also prepared.

  [Evaluation of Compressive Strength] The compressive strength of each heat insulating material was measured in the same manner as in Example 1 described above. In FIG. 18, the kind of added hydroxide, bulk density, and compressive strength are shown correspondingly.

  As shown in FIG. 18, the compressive strength was remarkably increased by curing without adding hydroxide, and the compressive strength was increased more remarkably by adding calcium hydroxide and curing. Moreover, compressive strength increased also by adding magnesium hydroxide and curing compared with the case where a hydroxide is not added and it is not cured.

  In the same manner as in the above-described embodiment, a plate-shaped dry pressure molded body containing silica fine particles, glass fibers, and silicon carbide is produced, and the dry pressure molded body is subjected to high humidity curing, thereby producing a plate. A heat insulating material was obtained.

  Next, a heating apparatus as shown in FIGS. 1 to 4 was manufactured using this heat insulating material. That is, the base A1 was produced by forming a plurality of groove portions 1 made of through-grooves having the accommodating portion 1a and the heat radiating portion 1b in parallel at predetermined intervals on a plate-like heat insulating material.

  Then, a heating element B made of an electric heating coil is fitted into the housing part 1a of the base part A1, and a cover part A2 made of another plate-like heat insulating material is laminated on the base part A1 so as to close the opening of the housing part 1a. did. The base A1 and the lid A2 were integrated by tightening with bolts and nuts. Thus, the heating device according to the present invention was manufactured.

  On the other hand, a plate-like dry pressure molded body that is not subjected to high-humidity curing in which a similar groove portion 1 is formed is used as the base A1, and a heating element B made of an electric heating coil is fitted into the groove portion 1, and another plate-shaped A control apparatus was produced in the same manner using the dry pressure molded body as the lid A2.

  However, in the process of manufacturing this control device, crack formation or breakage was observed in a part of the dry pressure molded body used as the base A1. Furthermore, in order to confirm the handling property of the control device, when both ends of the control device were grasped by hand and lifted, crack formation or chipping of the end portion was observed. This was thought to be because the strength of the dry pressure-molded body was reduced by further forming the groove portion 1 in the dry pressure-molded body of silica fine particles that were inherently low in strength.

  On the other hand, in the process of manufacturing the heating device according to the present invention and the confirmation of handling properties, no problems occurred in the heat insulating material used as the base A1. That is, the heat insulating material according to the present invention has sufficient strength while maintaining low thermal conductivity based on silica fine particles because the strength is improved by high-humidity curing in the production process. It was preferably usable.

  A1 base part, A2 lid part, outer layer part, B heating element, S cross-linking structure, 1 groove part, 1a accommodating part, 1b heat radiation part, 1c concave part. 1d communication recess, 2 lead terminal connecting sleeve, 3 bolt insertion hole, 4 surface portion, 5 staple, S1 preparation step, S2 curing step, S3 drying step.

Claims (19)

A heating element;
A base made of a heat insulating material and holding the heating element;
A heating device comprising:
The heat insulating material is
Silica fine particles having an average particle diameter of 50 nm or less,
The bulk density is 190 to 600 kg / m ³ ,
The heating apparatus characterized by having a compressive strength of 0.65 MPa or more. The heating device according to claim 1, wherein the heat insulating material does not include a binder. The said heat insulating material contains one or both of an alkaline-earth metal and an alkali metal. The heating apparatus described in Claim 1 or 2 characterized by the above-mentioned. The said heat insulating material contains one or both of the said alkaline-earth metal and the said alkali metal of 0.1-10 weight part with respect to 100 weight part of heat insulating material raw materials containing the said silica particle. 3. The heating apparatus described in 3. The heating device according to claim 1, wherein the heat insulating material further includes a reinforcing fiber. The heating device according to claim 5, wherein the heat insulating material includes 50 to 98 mass% of the silica fine particles and 2 to 20 mass% of the reinforcing fibers. The heating device according to claim 5 or 6, wherein the heat insulating material includes one or both of an alkaline earth metal and an alkali metal in addition to the silica fine particles and the reinforcing fiber. The heat insulating material includes 0.1 to 10 parts by weight of one or both of the alkaline earth metal and the alkali metal with respect to 100 parts by weight of the heat insulating material raw material including the silica fine particles and the reinforcing fibers. The heating apparatus according to claim 7, wherein the heating apparatus is characterized. The heating device according to claim 1, wherein the heat insulating material has a thermal conductivity at 600 ° C. of 0.05 W / (m · K) or less. The heating device according to any one of claims 1 to 9, wherein the base has a groove for accommodating the heating element. A heating element;
A base made of a heat insulating material and holding the heating element;
A method of manufacturing a heating device comprising:
A method for producing a heating device, comprising: a step of producing the heat insulating material by curing a dry pressure-molded body containing silica fine particles having an average particle size of 50 nm or less at a relative humidity of 70% or more. The method for manufacturing a heating apparatus according to claim 11, wherein the dry pressure-molded body does not contain a binder. The method for manufacturing a heating apparatus according to claim 11 or 12, wherein the dry pressure-molded body includes one or both of an alkaline earth metal hydroxide and an alkali metal hydroxide. The dry pressure-molded body is one or both of 0.1 to 10 parts by weight of the alkaline earth metal hydroxide and the alkali metal hydroxide with respect to 100 parts by weight of the heat insulating material raw material containing the silica fine particles. The method for manufacturing a heating device according to claim 13, comprising: The method for manufacturing a heating apparatus according to claim 11, wherein the dry pressure-molded body further includes a reinforcing fiber. The method for manufacturing a heating apparatus according to claim 15, wherein the dry pressure-molded body includes 50 to 98% by mass of the silica fine particles and 2 to 20% by mass of the reinforcing fibers. The method for producing a heating apparatus according to claim 15 or 16, wherein the dry pressure-molded body contains one or both of an alkaline earth metal hydroxide and an alkali metal hydroxide. The dry-type pressure-molded body comprises 0.1 to 10 parts by weight of the alkaline earth metal hydroxide and the alkali metal hydroxide based on 100 parts by weight of the heat insulating material raw material containing the silica fine particles and the reinforcing fibers. One or both of things are included. The manufacturing method of the heating apparatus described in Claim 17 characterized by the above-mentioned. A heating apparatus manufactured by the manufacturing method according to claim 11.