JP2018080094A - Thermal insulation material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal insulation material having excellent heat insulation property, small bulk specific gravity, and hardness enough to allow handling.SOLUTION: The thermal insulation material comprises a heat insulation aggregate having a porous structure containing pores with a pore diameter of 0.01-5 μm, preferably, a fireproof fiber as a reinforcement material, and a binder for binding these and, after firing, exhibits a bulk specific gravity of 0.3-0.5, has a ratio of pores having a pore diameter of 10-30 μm being 40-70 vol.% of the volume of all the pores, the thermal conductivity at 800°C being 0.18 W/(m K) or under, and the thermal conductivity at 1400°C being 0.26 W/(m K) or under.SELECTED DRAWING: None

Description

  The present invention relates to a heat insulating material used for equipment such as an industrial furnace whose inside becomes high temperature during operation, and particularly relates to a heat insulating material excellent in heat insulating properties in a high temperature range of about 1400 ° C.

  Heat-insulating materials are used for energy saving in high-temperature equipment such as industrial furnaces that become hot inside during operation. Especially for equipment used in the temperature range of 800 to 1400 ° C, fire-resistant and heat-insulating bricks, irregular-shaped fireproof Thermal insulation materials such as compositions (castable) and fibrous thermal insulation materials are used. These heat insulating materials are generally desired to have low thermal conductivity and low bulk specific gravity not only in a low temperature range of about 800 ° C. but also in a high temperature range of about 1400 ° C.

  However, general fireproof insulating bricks and irregular refractory compositions have a problem that the bulk specific gravity is 0.4 or more, the heat storage loss is large, and the heat conductivity is large, so that the heat transfer is high. In particular, since the thermal conductivity increases as the temperature increases, the thermal insulation performance may be insufficient when used at higher temperatures. For example, Patent Document 1 discloses a technique for increasing the porosity on the small pore diameter side by adding a flammable pore-providing material or a foaming agent to the material of the refractory heat-insulating brick, thereby reducing the thermal conductivity. Is disclosed.

Further, Patent Document 2 uses a heat-insulating aggregate mainly composed of CaO.6Al ₂ O ₃ instead of a non-porous aggregate as a material for an amorphous refractory composition, and the heat-insulating aggregate has A technique for reducing the thermal conductivity by a porous structure of pore groups having a small pore diameter is disclosed. On the other hand, since a general fibrous heat insulating material has a bulk specific gravity of less than 0.4, it has an advantage that heat storage loss is small and heat conductivity is low.

  In recent years, research and development of materials having a low bulk specific gravity and a low thermal conductivity have been promoted. For example, Patent Document 3 discloses a technique of using nanoparticles, a crystal transition suppressing material, and a radiation scattering material as a heat insulating material. Proposed. Further, as a material capable of reducing the thermal conductivity at higher temperatures, Patent Document 4 discloses a technique for forming a heat insulating material made of a porous sintered body using a highly heat-resistant composition. In Patent Document 4, the size and ratio of the pores of the porous sintered body are adjusted, thereby suppressing the conduction heat transfer and the radiation heat transfer due to the scattering of infrared rays, thereby increasing the thermal conductivity even at high temperatures. It is described that can be suppressed.

JP 2014-062018 A JP 2009-203090 A JP, 2006-040226, A Japanese Patent Laid-Open No. 2006-104682

  The thermal conductivity of the refractory insulating bricks and the irregular refractory compositions described in Patent Document 1 and Patent Document 2 is generally 0.3 W / (m · K) or higher at 800 ° C. and 0.5 W at 1400 ° C. / (M · K) or more. On the other hand, although the heat insulating property of the fibrous heat insulating material is low in the low temperature region, radiation heat transfer increases in the high temperature region, so that the heat insulating performance may be insufficient when used in the high temperature region. That is, the thermal conductivity of the fibrous heat insulating material is generally 0.1 W / (m · K) or more at 800 ° C. and 0.5 W / (m · K) or more at 1400 ° C.

  Moreover, although the heat insulating material of the said patent document 3 has the heat conductivity which was 0.05 W / (m * K) excellent in 800 degreeC, since heat-resistant temperature is about 1200 degreeC, it is about 1400 degreeC. It could not be used at high temperatures. The thermal conductivity of the heat insulating material of Patent Document 4 is 0.21 W / (m · K) at 800 ° C. and 0.25 W / (m · K) at 1400 ° C., and has excellent heat insulating properties even in a high temperature range. ing. However, since the heat insulating material made of the porous sintered body of Patent Document 4 has a bulk specific gravity as large as 0.8, the heat conductivity is higher at 800 ° C. than that of the conventional fiber heat insulating material. If the bulk specific gravity is decreased to reduce the strength, the strength is lowered, and there is a risk of causing problems in terms of handling properties.

  The present invention has been made in view of the above-described conventional problems, and provides a heat insulating material that is excellent in heat insulation even in a high temperature range of about 1400 ° C., has a small bulk specific gravity, and has a strength that can be handled. For the purpose.

  In order to achieve the above object, a heat insulating material according to the present invention is a heat insulating material composed of a heat insulating aggregate having a porous structure, a fireproof fiber as a reinforcing material, and a binder for bonding them, and after firing, The pores having a bulk specific gravity of 0.3 to 0.5 and a pore diameter of 10 to 30 μm occupy 40 to 70% by volume of the total pore volume, and the thermal conductivity at 800 ° C. is 0.18 W / (m · K) The thermal conductivity at 1400 ° C. is 0.26 W / (m · K) or less.

  ADVANTAGE OF THE INVENTION According to this invention, the heat insulating material which is excellent in heat insulation, has a small bulk specific gravity, and has the intensity | strength of the grade which can be handled can be provided.

Hereinafter, embodiments of the heat insulating material of the present invention will be described. The heat insulating material of the embodiment of the present invention is composed of a heat insulating aggregate having a porous structure, a refractory fiber as a reinforcing material, and a binder for bonding them, and has a bulk specific gravity of 0.3 to 0.3 after sintering. The pores having a pore diameter of 10 to 30 μm account for 40 to 70% of the total pore volume. The bulk specific gravity of 0.3 to 0.5 is 300 to 500 kg / m ^{3 in} terms of bulk density. In this way, the refractory fiber has a low rate of heat transfer at low temperatures but a large increase in the thermal conductivity at the time of temperature increase to a high temperature, and the heat conductivity high at low temperature but at the time of the temperature increase to a high temperature. By mixing the heat-insulated aggregate with a small increase rate so that a group of pores having a predetermined bulk specific gravity and a predetermined pore diameter occupy a predetermined rate, the heat conductivity at low temperature is low and the temperature rises to high temperature. It is possible to obtain a heat insulating material having a small increase rate of thermal conductivity at the time of warming.

  In other words, the heat insulating material composed only of the refractory fiber and its binder has a low bulk specific gravity of less than 0.3, so the conductivity at low temperature is low, but the pores formed when these are mixed and sintered Since the hole diameter is about 40 to 80 μm, the radiant heat transfer is increased, and the rate of increase in thermal conductivity at the time of temperature increase from a low temperature to a high temperature is increased. On the other hand, a heat insulating aggregate composed of fine pores having a high heat resistance composition and a heat insulating material composed only of the binder can suppress radiant heat transfer because the pore diameter of the pore group is about 0.01 to 5 μm. Therefore, although the rate of increase in thermal conductivity at the time of temperature increase from low temperature to high temperature can be reduced, the heat conductivity at low temperature is increased. On the other hand, since the heat insulating material of the embodiment of the present invention mixes the heat insulating aggregate, the refractory fiber, and the binder as described above, a wide temperature from a low temperature range of about 800 ° C. to a high temperature range of about 1400 ° C. Thermal conductivity can be kept low over a range.

More specifically, as the fireproof fiber used for the heat insulating material of the embodiment of the present invention, one having a heat resistant temperature of 1400 ° C. or higher is used. For example, at least one selected from the group consisting of alumina fiber, mullite fiber, CaO · 6Al ₂ O ₃ (calcia aluminate) fiber, and biosoluble fiber is used. These fibers are preferred because they are not carcinogenic and are not designated as specific chemicals. Among these, alumina fibers (for example, Fiber Max 1600 manufactured by ITM Corporation) are more preferable.

The refractory fiber preferably has an average fiber length of 0.5 mm to 30 mm, and more preferably 1 mm to 10 mm. The heat-resistant fiber preferably has an average fiber diameter of 1 μm or more and 10 μm or less, and more preferably 2 μm or more and 8 μm or less. In addition, these average fiber lengths and average fiber diameters are measured by the following methods.
(1) Average fiber length After taking a group of fibers to be measured with an electron microscope, the linear distance from end to end in the longitudinal direction of any 100 fibers on the image obtained by this imaging Was measured, and the value obtained by arithmetically averaging them was defined as the average fiber length. In this measurement, 200 μm or more was excluded because it could not be measured accurately.
(2) Average fiber diameter After taking a group of fibers to be measured with an electron microscope, measure the width of any part of any 200 fibers on the image obtained by this photography. The value obtained by arithmetically averaging the average fiber diameter

As the heat insulating aggregate having a porous structure having a fine pore group used for the heat insulating material, one having a heat resistant temperature of 1400 ° C. or higher and a composition having a high heat resistance is used. The heat insulating aggregate preferably has a pore diameter of 0.01 to 5 μm. For example, spinel ceramics (Thermoscatt (registered trademark) manufactured by Coors Co., Ltd.), and CaO.6Al ₂ O ₃ (calcia aluminum). Nate) One or more selected from the group consisting of ceramics (SLA-92 manufactured by Almatis Co., Ltd.) may be used. The ceramic particles constituting the heat insulating aggregate preferably have a particle size of 0.5 μm or more and 30 μm or less, and more preferably 1 μm or more and 20 μm or less. In addition, said hole diameter is measured with a mercury porosimeter, and a particle size is measured with the laser diffraction type particle size distribution measuring apparatus.

  In the heat insulating material according to the embodiment of the present invention, if the content of the refractory fiber is too small, the bulk specific gravity of the heat insulating material becomes too large to suppress conduction heat transfer. On the other hand, if the content of the refractory fiber is too large, the pore diameter of the pores constituting the heat insulating material becomes too large to suppress the radiant heat transfer, and the effect of suppressing the thermal conductivity at the time of temperature rise cannot be obtained sufficiently. On the other hand, in the heat insulating material of the embodiment of the present invention, if the content ratio of the heat insulating aggregate is too small, the bulk specific gravity of the heat insulating material becomes too small to suppress radiant heat transfer. On the contrary, if the content of the heat insulating aggregate is too large, the bulk specific gravity becomes too large, the conduction heat transfer becomes large, and the effect of suppressing the thermal conductivity at the time of temperature rise cannot be obtained sufficiently.

  A suitable range of the content ratio of the above-mentioned refractory fibers and heat insulating aggregates can be changed mainly depending on the properties of the fibers such as the average diameter of the fibers and the content of shots (non-fiber particles). Therefore, in the heat insulating material of the embodiment of the present invention, the mixing ratio of these refractory fibers and the heat insulating aggregate is adjusted so as to satisfy a predetermined bulk specific gravity and thermal conductivity after sintering. Specifically, the bulk specific gravity after sintering is 0.3 to 0.5, the thermal conductivity at 800 ° C. is 0.18 W / (m · K) or less, and the thermal conductivity at 1400 ° C. is 0. The mixing ratio is adjusted to be .26 W / (m · K) or less.

  As a specific method for adjusting the mixing ratio, for example, when the bulk specific gravity after the heat insulating material is sintered is smaller than a desired value, the content ratio of the heat insulating aggregate is mixed more or the pressure applied at the time of compression molding is increased. Or if the bulk specific gravity is greater than the desired value, the opposite may be done. If the heat conductivity at 800 ° C. is too high, the content of the heat insulating aggregate is mixed slightly. If the heat conductivity at 1400 ° C. is too high, the content of the heat insulating aggregate is mixed or compression molded. The pressure that is sometimes applied may be set higher. In addition, the bending strength of the heat insulating material after baking can be made 0.5 MPa or more by setting the bulk specific gravity and the thermal conductivity within the above ranges. Here, the bending strength means that the heat insulating material to be measured is processed into a test piece having a length of 150 mm, a width of 50 mm, and a thickness of 25 mm, and this is supported at a distance between supporting points of 100 mm, and a three-point bending test is performed using an autograph. This is calculated from the maximum load until the failure. In addition, although the conditions for baking are not specifically limited, In general, it is preferable to hold at 1350 to 1420 ° C. for about 3 hours.

  The type of the binder used for the heat insulating material according to the embodiment of the present invention is not particularly limited as long as the heat resistant temperature is 1400 ° C. or higher. For example, colloidal silica can be used. This binder is added so as to have an appropriate content within a range that does not adversely affect the thermal conductivity, bulk specific gravity, and bending strength of the heat insulating material. In general, the content is preferably 3 to 10% by mass. Furthermore, as long as the thermal conductivity, bulk specific gravity, and bending strength of the heat insulating material are not adversely affected, a plurality of types of refractory fibers may be used, or nanoparticles may be further added.

  The form of the heat insulating material according to the embodiment of the present invention may be a molded product or an amorphous product. Or you may use as a composite article which coat | covered and integrated the fiber board and the blanket with the amorphous product of embodiment of this invention. Further, the heat insulating material may not be homogeneous throughout, and the surface layer portion may have a high content of refractory fibers, for example, in order to prevent dusting and ridge line chipping.

  There is no limitation in the manufacturing method of the heat insulating material of these forms, A well-known manufacturing method can be used. For example, in the case of a molded product, it can be prepared by a molding method such as dry press molding, wet molding press molding, vacuum molding, cast molding or the like, and in the case of an indeterminate product, it can be prepared by wet stirring mixing. Further, when the fibrous board or blanket is coated with an irregular shaped product, an appropriate amount of water is added to the irregular shaped product to form a slurry, which is then applied or impregnated by spray coating or the like. As mentioned above, although the heat insulating material of this invention was demonstrated based on embodiment, this invention is not limited by this embodiment.

  Insulating aggregates, refractory fibers, and binders were mixed at various blending ratios to prepare a plurality of insulating material samples, which were evaluated in terms of bending strength and thermal conductivity. Specifically, spinel ceramics (Thermoscatt, average particle diameter of 10 μm) manufactured by Coors Co., Ltd. was used as the heat insulating aggregate. This heat-insulated aggregate has a porosity of 85 to 91 vol%, and pores having a pore diameter of 0.8 to 10 μm occupy 10 to 40 vol% of the total pore volume, and pores having a pore diameter of 0.01 to 0.8 μm are 5 Occupies -10 vol%. As the heat-resistant fiber, mullite fiber (fiber max 1600, average fiber diameter 4 μm, shot content 15%) manufactured by ITM Co., Ltd. was used. Colloidal silica (Snowtex, EN40) manufactured by Nissan Chemical Co., Ltd. and a polymer flocculant were used as the binder.

  These were weighed so as to have various contents, mixed with water by adding water, and compression-molded with a dehydrating press to produce heat insulating materials of Samples 1 to 6. In addition, about the heat insulating material of the samples 1-3, it adjusted so that the ratio of a bulk specific gravity and the hole diameter of 10-30 micrometers in the pores of all the pores after baking by changing the pressure of the spin-drying | dehydration press at the time of compression molding may differ. . The addition amount of the polymer flocculant was 3 to 10% by mass.

  The heat insulating materials of Samples 1 to 6 described above were calcined while being held at 1350 ° C. for 3 hours, and the volume and distribution of their pore diameters were measured with a mercury porosimeter. Based on this measurement result, the ratio of the volume of pores having a pore diameter of 10 to 30 μm to the total pore volume was calculated. The bulk specific gravity of the heat insulating material was obtained by dividing the weight of the heat insulating material by a volume calculated by measuring with a caliper. The bending strength was measured by bending the heat insulating material of each sample into a rectangular shape having a length of 150 mm, a width of 50 mm, and a thickness of 25 mm, and using an autograph at a span of 100 mm. The thermal conductivity was measured in a temperature range from 800 ° C. to 1400 ° C. by a hot wire method in accordance with JIS R2616. The above various evaluation results are shown in Table 1 below together with the contents of the heat insulating aggregate, the heat insulating fiber, and the binder.

  As can be seen from the results of Table 1 above, the thermal insulation materials of Samples 1 to 3 that satisfy the requirements of the present invention are 0.5 MPa or more that can handle the bending strength regardless of whether the bulk specific gravity is as light as 0.5 or less. The thermal conductivity is 0.18 W / (m · K) or less at 800 ° C. and 0.25 W / (m · K) or less at 1400 ° C., and the temperature range is 800 to 1400 ° C. It had excellent heat insulating properties.

  On the other hand, since the content of the heat insulating aggregate in Sample 4 was smaller than that in Samples 1 to 3, the bulk specific gravity was lower than 0.3 and the ratio of pore diameters of 10 to 30 μm exceeded 70% by volume. The bending strength was lower than those of Samples 1 to 3, and the thermal conductivity at 1400 ° C. was higher than that of Samples 1 to 3. On the other hand, since the contents of the heat insulating aggregates in Samples 5 and 6 were higher than those in Samples 1 to 3, the ratio of pores having a pore diameter of 10 to 30 μm was within the range of 30 to 70% by volume in the heat insulating material of Sample 5. However, the bulk specific gravity exceeded 0.5, and the heat insulating material of Sample 6 was within the range of the bulk specific gravity of 0.3 to 0.5, but the proportion of pores having a pore diameter of 10 to 30 μm was more than 30% by mass. Therefore, the thermal conductivities at 800 ° C. and 1400 ° C. were higher than those of Samples 1 to 3, respectively. Thus, it can be seen that when at least one of the bulk specific gravity and the ratio of pores having a pore diameter of 10 to 30 μm in the total pore volume deviates from the requirements of the present invention, the bending strength and the thermal conductivity become insufficient.

Claims (5)

  A heat insulating material composed of a heat-insulating aggregate having a porous structure, a refractory fiber as a reinforcing material, and a binder for bonding them, and has a bulk specific gravity of 0.3 to 0.5 and a pore diameter of 10 after firing. The pores of ˜30 μm occupy 40 to 70% by volume of the total pores, and the thermal conductivity at 800 ° C. is 0.18 W / (m · K) or less, and the thermal conductivity at 1400 ° C. is 0.26 W / (M · K) or less, a heat insulating material.   The heat insulating material according to claim 1, wherein after the firing, the bending strength is 0.5 MPa or more.   The heat insulating material according to claim 1, wherein the heat insulating aggregate has pores having a pore diameter of 0.01 to 5 μm.   The heat insulating material according to any one of claims 1 to 3, wherein the heat insulating material has a shaped body or an irregular shape.   A composite article, wherein the heat insulating material according to any one of claims 1 to 3 is integrally formed by covering a molded body in an irregular shape.