JP2016196387A - Heat-insulating coating liquid, heat-insulating material, and composition for heat-insulating coating liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-insulating coating liquid which can be prepared by a simple work and has excellent performance, a heat-insulating material coated therewith, and a composition for producing the heat-insulating coating liquid.SOLUTION: The heat-insulating coating liquid contains 100 pts.mass of water, 10-20 pts.mass of an inorganic binder, 0.2-2 pts.mass of a swelling clay mineral, and 10-200 pts.mass of a radiation scattering material. The radiation scattering material is one or more kinds selected from the group consisting of: ceramic fibers which are composed of fibrous particles containing AlOand having a diameter of 2 μm or less and in which secondary particles formed by aggregation of the fibrous particles have a median diameter of 40 μm or less; a silicon carbide powder having a median diameter of 40 μm or less; a silicon nitride powder having a median diameter of 40 μm or less; a boron nitride powder having a median diameter of 40 μm or less; and an alumina powder having a median diameter of 40 μm or less.SELECTED DRAWING: None

Description

  The present invention relates to a heat insulating coating liquid, a heat insulating material produced using the heat insulating coating liquid, and a composition for producing a heat insulating coating liquid.

  Heating furnaces that can be heated at high temperatures, such as soaking furnaces used in the manufacture of steel materials, heat treatment furnaces, and firing furnaces used in the manufacture of ceramics, have inner walls made of refractory inside the outer walls. Have. The refractory is usually attached to the outer wall of the heating furnace via a fitting.

  As a refractory that forms the inner wall, a block made of ceramic fibers containing silica, alumina, zirconia, or the like is frequently used. Since this block has excellent heat insulation performance, the temperature in the furnace and the rate of temperature rise can be easily controlled by using it on the inner wall of the heating furnace. Moreover, since the said block contains the ceramic fiber with small bulk specific gravity, it is comparatively lightweight. Therefore, the block can be easily attached to the outer wall of the heating furnace.

  However, there is a problem that a block made of ceramic fibers gradually contracts when placed in a high temperature environment of, for example, 1000 ° C. or more for a long period of time. For this reason, when the heating furnace is used for a long period of time, a gap is generated between adjacent blocks, resulting in a decrease in heat insulation performance.

  In addition to blocks containing ceramic fibers, aggregates consist of heat-resistant refractory bricks, chamotte, alumina and chrome based on acid oxide, neutral oxide and basic oxide as defined in JIS R2611. A refractory material such as a plastic refractory material, a castable refractory material containing calcia and alumina as an aggregate, and a refractory material such as a refractory mortar may be used as an inner wall of a heating furnace. However, these refractories also have a problem of gradually shrinking when placed in a high temperature environment for a long time as described above.

  Therefore, in order to suppress the shrinkage of the refractory due to the temperature rise, a technique for providing a heat insulating coating layer on the surface of the refractory has been proposed. For example, Patent Document 1 discloses a non-precipitation refractory mortar containing ceramic powder, clay mineral and colloidal oxide solution and having thixotropic properties. Patent Document 2 discloses a coating material containing inorganic fibers, inorganic particles, an inorganic binder, and an organic binder.

JP 2009-137809 A Japanese Patent No. 4297204

  Since the refractory mortar of Patent Document 1 has a high viscosity, it is difficult to apply to a portion having deep irregularities or a complicated structure such as a joint of a refractory. Therefore, there is a problem that workability when applying the refractory mortar is low. In addition, since it is difficult to reduce the coating thickness of the refractory mortar, there is a problem that the refractory coated with the refractory mortar easily peels off from the outer wall of the heating furnace.

  In order to improve the applicability of the heat insulating coating liquid applied to the refractory, and to reduce the coating thickness, it is effective to use a heat insulating coating liquid having a low viscosity. However, the heat-insulating coating solution having a low viscosity usually contains an organic substance such as an organic binder or an organic solvent like the coating material of Patent Document 2. Therefore, when the heat insulation coating liquid is heated and dried, the organic substance is gasified, and there is a possibility that cracks and the like are generated in the heat insulation coating layer obtained. Such a crack is not preferable because it causes a decrease in heat insulation performance. Moreover, the coating liquid containing an organic substance may be spoiled when stored for a long period of time.

  As described above, from the viewpoints of coatability, coating thickness, heat insulation performance, and storage stability, the heat insulation coating liquid preferably has a low viscosity and does not contain an organic substance. However, it is difficult to disperse the solid content in the solvent over a long period of time with the low-viscosity thermal insulation coating liquid composed only of inorganic substances, and the solid content precipitates relatively early after the solid content is dispersed in the solvent. There is a problem of doing. For this reason, such a heat insulating coating liquid performs a work such as mixing the solvent and the solid content each time it is used, or sufficiently agitating immediately before application to the refractory to re-disperse the solid content in the solvent. It was necessary and the preparatory work before application was complicated.

  The present invention has been made in view of such a background, and a heat insulating coating liquid that can be prepared by a simple operation and has excellent performance, a heat insulating material applied with the heat insulating coating liquid, and a composition for producing a heat insulating coating liquid. It is something to be offered.

One embodiment of the present invention provides:
100 parts by weight of water,
10 parts by mass or more of an inorganic binder,
0.2-2 parts by weight of a swellable clay mineral;
10 to 200 parts by mass of radiation scattering material,
The radiation scattering material is
Ceramic fibers which are composed of fibrous particles having a diameter of 2 μm or less containing Al ₂ O ₃ and whose median diameter of secondary particles formed by aggregation of the fibrous particles is 40 μm or less;
Silicon carbide powder having a median diameter of 40 μm or less;
Silicon nitride powder having a median diameter of 40 μm or less;
Boron nitride powder having a median diameter of 40 μm or less;
The heat insulating coating liquid is characterized in that it is one or more selected from the group consisting of alumina powder having a median diameter of 60 μm or less.

Another aspect of the present invention is a heat insulating material having a base made of a refractory and a heat insulating coating layer formed on the base,
The said heat insulation coating layer exists in the heat insulating material formed by drying the heat insulation coating liquid of said aspect.

Still another aspect of the present invention is an inorganic binder of 10 parts by mass or more,
0.2-2 parts by weight of a swellable clay mineral;
10 to 200 parts by mass of radiation scattering material,
The radiation scattering material is
Ceramic fibers which are composed of fibrous particles having a diameter of 2 μm or less containing Al ₂ O ₃ and whose median diameter of secondary particles formed by aggregation of the fibrous particles is 40 μm or less;
Silicon carbide powder having a median diameter of 40 μm or less;
Silicon nitride powder having a median diameter of 40 μm or less;
Boron nitride powder having a median diameter of 40 μm or less;
The composition for heat-insulating coating liquid is any one selected from the group consisting of alumina powder having a median diameter of 60 μm or less, or two or more.

  The heat insulating coating liquid (hereinafter referred to as “coating liquid”) has the above-mentioned specific ratio of the inorganic binder, the swellable clay mineral (hereinafter referred to as “clay mineral”) and 100 parts by mass of water. The radiation scattering material is contained. And the said radiation scattering material is comprised from the ceramic fiber and / or ceramic powder by which the particle size distribution was controlled as mentioned above.

  As described above, the coating liquid does not use an organic substance for any of the solvent and the solid content, and is composed only of an inorganic substance. Therefore, the coating liquid has excellent storage stability and can suppress the occurrence of cracks in the heat-insulating coating layer after drying (hereinafter referred to as “coating layer”).

  Moreover, the said coating liquid can form the said coating layer which has the outstanding heat insulation performance in the high temperature environment which becomes 1000 degreeC or more, for example by having the said specific composition. Moreover, since the said coating liquid is low-viscosity, while having the outstanding applicability | painting, it can make application | coating thickness thin.

  Further, the coating liquid can stably disperse the solid content in the solvent over a long period of time. Therefore, the coating liquid can be mixed with water and solids in advance, and further, the stirring work before application to the refractory can be shortened. In some cases, it is not necessary to perform the stirring work. As a result, the preparatory work prior to application can be greatly simplified.

  As described above, the coating liquid can be prepared by a simple operation, is excellent in applicability, heat insulation performance, and storage stability, and can reduce the coating thickness. And since the said heat insulating material has the said coating layer formed by drying the said coating liquid, it has the outstanding heat insulation performance.

  The composition for a coating liquid contains the inorganic binder, the clay mineral, and the radiation scattering material in the specific ratio. Therefore, the coating liquid can be easily prepared by adding water to the composition.

  The composition of the coating solution will be described below. In the following, “median diameter” is a median diameter calculated based on a particle size distribution measured by a laser diffraction scattering method.

-Inorganic binder: 10 mass parts or more The said coating liquid contains 10 mass parts or more of inorganic binders with respect to 100 mass parts of water | moisture content. An inorganic binder has the effect | action which adheres the coating layer after drying firmly to the base | substrate which consists of a refractory. By setting the content of the inorganic binder in the specific range, the coating liquid can suppress problems such as generation of cracks in the coating layer after drying or peeling of the coating layer from the substrate.

  As the inorganic binder, fine particles that can be dispersed in water to form an inorganic colloidal solution such as colloidal silica can be used. That is, the coating liquid can be prepared by, for example, a method of blending colloidal silica or the like with the coating liquid such that the content of colloidal particles is in the specific range. Usually, the median diameter of the colloidal particles contained in the inorganic colloidal solution is 100 nm or less. As the inorganic colloid solution, colloidal silica, colloidal alumina, colloidal zirconia, or the like can be used.

  When the content of the inorganic binder is less than 10 parts by mass, the adhesion between the coating layer and the substrate is lowered, and there is a possibility that cracks or peeling occurs in the coating layer. As a result, the heat insulating performance of the heat insulating material may be reduced.

  In order to improve the adhesiveness between the coating layer and the substrate, it is preferable that the content of the inorganic binder is large. However, when the content of the inorganic binder is excessively large, it may be difficult to obtain an effect commensurate with the cost, or the melting point of the coating layer may be lowered.

  In addition, since the inorganic binder has high reactivity, when the content of the inorganic binder is excessively large, the coating layer changes in quality by reacting with the base material, the radiation scattering material, etc. in a high temperature environment, and the heat insulation performance is lowered. There is a fear. The reaction with the base material, radiation scattering material, etc. can occur when any of fine particles derived from colloidal silica, fine particles derived from colloidal alumina, and fine particles derived from colloidal zirconia is used, but is particularly derived from colloidal silica. This is likely to occur when fine particles are used as an inorganic binder. In order to avoid these problems, the content of the inorganic binder is preferably 20 parts by mass or less.

  Therefore, the content of the inorganic binder is more preferably 10 to 20 parts by mass from the viewpoint of improving the adhesiveness between the coating layer and the substrate and suppressing the performance degradation of the coating layer at a high temperature.

Swelling clay mineral: 0.2-2 parts by mass The coating liquid contains 0.2-2 parts by mass of the clay mineral with respect to 100 parts by mass of water. The clay mineral has an action of improving the dispersibility of solid content in water. The coating liquid can stably disperse the clay mineral, the inorganic binder, and the radiation scattering material in water over a long period of time by setting the content of the clay mineral in the specific range. As a result, the preparatory work prior to application can be greatly simplified.

  Examples of the clay mineral include swellable clay minerals such as kaolinite, halloysite, smectite, mica, vermiculite, chlorite, imogolite, allophane, sepiolite, varigilskite, and gibbsite.

  When the content of the clay mineral is less than 0.2 parts by mass, it is difficult to disperse the solid content in water, and the solid content may settle relatively early after the solid content is dispersed in water. is there. On the other hand, when the content of the clay mineral exceeds 2 parts by mass, there is a possibility that problems such as a decrease in coatability due to an increase in the viscosity of the coating liquid and a decrease in heat resistance of the coating layer may occur.

-Radiation scattering material: 10-200 mass parts The coating liquid contains 10-200 mass parts radiation scattering material with respect to 100 mass parts moisture. The radiation scattering material has an action of reflecting or scattering electromagnetic waves such as infrared rays radiated from the furnace.

  In a heating furnace in which the temperature in the furnace is a high temperature of 1000 ° C. or higher, heat transfer from the inside of the furnace to the outside of the furnace by radiation is dominant as compared with heat transfer by convection or conduction. On the other hand, since the coating layer formed by drying the coating liquid contains a radiation scattering material, it can effectively reflect or scatter electromagnetic waves such as infrared rays radiated from the furnace. And since the said heat insulating material can reflect or scatter the electromagnetic waves radiated | emitted from the inside of a furnace with the said coating layer on the surface, it can reduce heat transfer outside a furnace effectively. As a result, the heat insulating material has excellent heat insulating performance.

  Moreover, since the said heat insulating material can reduce the said electromagnetic wave which reaches | attains a base | substrate by presence of the said coating layer, it can suppress the temperature rise of a base | substrate. As a result, the heat insulating material can suppress the shrinkage of the base body due to heating, and as a result, the heat insulating material as a whole can be prevented from shrinking.

  When the content of the radiation scattering material is less than 10 parts by mass, the effect of reflecting or scattering electromagnetic waves becomes insufficient, and it is difficult to improve the heat insulation performance. On the other hand, when the content of the radiation scattering material exceeds 200 parts by mass, the viscosity of the coating liquid becomes high and the applicability may be deteriorated. Therefore, in order to achieve both heat insulation performance and applicability, the content of the radiation scattering material is set to 10 to 200 parts by mass. From the same viewpoint, the content of the radiation scattering material is preferably 10 to 120 parts by mass, and more preferably 10 to 80 parts by mass.

  As the radiation scattering material, one or more selected from the group consisting of ceramic fiber, silicon carbide powder, silicon nitride powder, boron nitride powder and alumina powder can be used. Hereinafter, silicon carbide powder, silicon nitride powder, boron nitride powder, and alumina powder may be collectively referred to as “ceramic powder”.

The ceramic fiber is composed of fibrous particles containing Al ₂ O _{3 and} having a diameter of 2 μm or less. The ceramic fiber is usually made of Al ₂ O ₃ and SiO ₂ , but may contain other components.

The ceramic fiber can effectively reflect or scatter the radiated electromagnetic wave as the content of Al ₂ O ₃ increases. Therefore, the ceramic fiber having a large content of Al ₂ O ₃ can improve the heat insulating performance of the heat insulating material finally obtained. From the viewpoint of improving the heat insulation performance, the content of Al ₂ O ₃ in the ceramic fiber is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 65% by mass or more. It is preferably 70% by mass or more.

  Ceramic fibers usually contain secondary particles formed by agglomerating fibrous particles. Secondary particles are formed by entanglement of fibrous particles.

  The ceramic fiber has a particle size distribution in which the median diameter of the secondary particles is 40 μm or less. When the median diameter of the secondary particles exceeds 40 μm, the content of the secondary particles having a large particle size increases, so that the ceramic fibers are likely to settle during storage. Further, when the content of secondary particles having a large particle size is increased, it is difficult to reduce the coating thickness of the coating liquid, and it is therefore difficult to reduce the thickness of the coating layer after drying.

  Therefore, in order to improve the dispersibility of the ceramic fiber and reduce the coating thickness of the coating liquid, the median diameter of the secondary particles is set to 40 μm or less. From the same viewpoint, the median diameter of the secondary particles is preferably 20 μm or less.

  Of the above four types of ceramic powders, silicon carbide powder, silicon nitride powder, and boron nitride powder all have a particle size distribution with a median diameter of 40 μm or less. These three kinds of ceramic powders can reduce the content of particles having a large particle size by setting the median diameter to 40 μm or less as in the case of the secondary particles of the ceramic fiber described above. As a result, the dispersibility of the ceramic powder in water can be improved, and the coating thickness of the coating liquid can be easily reduced. From the same viewpoint, the median diameter of the ceramic powder is preferably 10 μm or less. From the viewpoint of avoiding an increase in the viscosity of the coating liquid, it is preferable that the median diameter of the ceramic powder is 1 μm or more.

  Of the four ceramic powders, the alumina powder has a particle size distribution with a median diameter of 60 μm or less. By setting the median diameter of the alumina powder to 60 μm or less, the content of particles having a large particle diameter can be reduced as described above. As a result, the dispersibility of the alumina powder in water can be improved, and the coating thickness of the coating liquid can be easily reduced. From the same viewpoint, the median diameter of the alumina powder is preferably 40 μm or less. Further, from the viewpoint of avoiding an increase in the viscosity of the coating liquid, the median diameter of the alumina powder is preferably 1 μm or more, and more preferably 20 μm or more.

When the coating liquid contains only one of ceramic fiber or alumina powder as a radiation scattering material, the content of Al ₂ O ₃ with respect to the total solid content of the coating liquid is preferably 50% by mass or more. In this case, the coating liquid can form a coating layer that can more effectively reflect or scatter the radiated electromagnetic waves. And the heat insulation performance of the said heat insulating material can be improved more by using the said coating liquid.

  When the coating liquid contains two or more kinds of radiation scattering materials, it is preferable that at least ceramic fibers are included as the radiation scattering materials. That is, it is preferable that the coating liquid contains two or more kinds of radiation scattering materials including ceramic fibers.

  Silicon carbide powder, silicon nitride powder, boron nitride powder and alumina powder all have excellent performance as a radiation scattering material. However, when two or more of these ceramic powders are mixed and used, the viscosity of the coating liquid tends to increase, which may cause problems such as poor applicability or thick coating thickness. On the other hand, ceramic fibers are less likely to increase the viscosity of the coating liquid when mixed with the ceramic powder. Therefore, the coating liquid containing two or more kinds of radiation scattering materials including ceramic fibers can further improve the heat insulating performance of the heat insulating material while suppressing an increase in viscosity.

  In the above case, the coating liquid preferably has an alumina powder content of 30 parts by mass or less. Alumina powder, when used in combination with ceramic fibers, tends to increase the viscosity of the coating solution compared to silicon carbide powder, silicon nitride powder and boron nitride powder. Therefore, the increase in the viscosity of the coating liquid can be suppressed by regulating the content of the alumina powder to 30 parts by mass or less.

Further, in the above case, the coating solution is more preferably the content of Al ₂ O ₃ with respect to the total solid content is 50 mass% or more. In this case, the coating liquid can form a coating layer that can more effectively reflect or scatter the radiated electromagnetic waves. And the heat insulation performance of the said heat insulating material can be improved more by using the said coating liquid.

  The coating liquid preferably has a viscosity of 20 Pa · s or less. In this case, the coating liquid can be applied to the substrate by spraying. In this case, the substrate can also be applied by immersing it in a coating solution. As a result, the workability in the coating liquid coating operation can be further improved. From the viewpoint of easier application by spraying and dipping, the coating liquid more preferably has a viscosity of 5 Pa · s or less.

  Moreover, it is preferable that the said coating liquid is comprised so that the state by which the said solid content was disperse | distributed in water can be maintained for more than one day. In this case, by mixing water and solid content in advance, the stirring work before application to the refractory can be shortened, and in some cases, it is not necessary to perform the stirring work. As a result, the preparatory work prior to application can be greatly simplified.

  The said heat insulating material is producible by apply | coating the said coating liquid to the base | substrate comprised from the refractory material, and drying a coating liquid. As described above, since the viscosity of the coating liquid can be lower than that of the conventional coating liquid, it can be applied to the substrate by spraying. In addition, the said coating liquid can also be apply | coated to the surface of a base | substrate using a brush, a spatula, etc. similarly to the past.

  The substrate to which the coating liquid is applied is composed of a conventionally known refractory material. Specifically, as the refractory constituting the base, a block including a ceramic fiber and a molded product can be employed. In addition, as refractories, refractory bricks, chamotte, plastics containing alumina and chrome as aggregates, castable refractories containing calcia and alumina as aggregates, refractory mortar, etc. It is also possible to use it.

  The above-mentioned heat-resistant and refractory bricks, plastic refractories, castable refractories and refractory mortars have a smoother surface than blocks containing ceramic fibers. Therefore, when a coating layer is formed using a conventional coating solution, the adhesion between the substrate and the coating layer is low, and problems such as cracks in the coating layer or peeling of the coating layer are suppressed. It was difficult.

  On the other hand, the coating liquid can reduce the coating thickness on the substrate surface as compared with the conventional one, and as a result, the coating layer can be thin. Therefore, it is possible to improve the adhesion of the coating layer to the base made of heat-resistant fire-resistant brick and the like, and to suppress the occurrence of peeling or cracking of the coating layer.

  Examples of the heat insulating coating solution will be described below. In this example, a coating solution was prepared using the following materials. The median diameters of the secondary particles and the ceramic powder were measured using a laser diffraction / scattering particle size distribution measuring apparatus (“LA-500” manufactured by Horiba, Ltd.).

・ Inorganic binder Fine particles derived from colloidal silica ・ Swelling clay minerals Smectite

Ceramic fiber A Al ₂ O ₃ content: 65 mass%, SiO ₂ content: 35 mass%, diameter of fibrous particles: 2 μm or less, median diameter of secondary particles: 10 μm
Ceramic fiber B Al ₂ O ₃ content: 65 mass%, SiO ₂ content: 35 mass%, diameter of fibrous particles: 2 μm or less, median diameter of secondary particles: 15 μm
Ceramic fiber C Al ₂ O ₃ content: 65 mass%, SiO ₂ content: 35 mass%, diameter of fibrous particles: 2 μm or less, median diameter of secondary particles: 25 μm
Ceramic fiber D Al ₂ O ₃ content: 65 mass%, SiO ₂ content: 35 mass%, diameter of fibrous particles: 2 μm or less, median diameter of secondary particles: 40 μm

Ceramic fiber E Al ₂ O ₃ content: 70% by mass, SiO ₂ content: 30% by mass, diameter of fibrous particles: 2 μm or less, median diameter of secondary particles: 15 μm
Ceramic fiber F Al ₂ O ₃ content: 50 mass%, SiO ₂ content: 50 mass%, diameter of fibrous particles: 2 μm or less, median diameter of secondary particles: 15 μm

・ Silicon carbide powder A Median diameter: 1μm
Silicon carbide powder B median diameter: 5 μm
-Silicon carbide powder C median diameter: 40 μm
・ Alumina powder A Median diameter: 1μm
Alumina powder B median diameter: 20 μm
Alumina powder C median diameter: 40 μm

(Experimental example 1)
This example is an example of a coating liquid containing one kind of ceramic fiber as a radiation scattering material. In this example, as shown in Table 1, 12 types of coating liquids (test agents 1 to 12) were prepared by changing the types and contents of ceramic fibers. Thereafter, the properties of the obtained coating liquid were evaluated.

<Method for preparing test agent>
First, the swellable clay mineral was added in several portions while stirring water, and the swellable clay mineral was dispersed in water. While stirring this solution, an inorganic binder and a radiation scattering material were sequentially added to prepare test agents 1 to 12. In addition, the inorganic binder was mixed with the said solution in the state of the colloidal silica solution.

<Characteristic evaluation of test agent>
Viscosity Viscosity of each test agent at 20 ° C. was measured using a viscometer (“Bisco Tester VT-04E” manufactured by Lion Co., Ltd.). The results are shown in Table 1. The meanings of the symbols in the “viscosity” column in Table 1 are as follows.

A +: The viscosity of the test agent was 1 Pa · s or less.
A: The viscosity of the test agent was more than 1 Pa · s and not more than 5 Pa · s.
B: The viscosity of the test agent was more than 5 Pa · s and not more than 20 Pa · s.
C: The viscosity of the test agent exceeded 20 Pa · s.
D: Moisture was insufficient and viscosity measurement was impossible.

<Dispersion stability>
Each test agent was vigorously stirred to disperse the solid content, and then the test agent was allowed to stand in a room temperature environment. And time until solid content settled down completely was measured. The results are shown in Table 1. The meanings of the symbols shown in the column of “dispersion stability” in Table 1 are as follows. Further, the “state where the solid content is completely settled” refers to a state where the boundary between the settled solid content and the supernatant liquid is clearly observed.

A +: The solid content did not settle during the evaluation period.
A: The solid content settled in about several days.
B: The solid content settled in about several tens of minutes.
C: The solid content settled immediately after standing.
-: Evaluation was impossible because the viscosity of the test agent was extremely high.

<Applicability>
As a test piece, a grid having a large number of holes each having a square shape of 3 mm in length and 3 mm in width was prepared. Each test agent was applied to the test piece using a spray and a spatula to evaluate whether spray application was possible. Moreover, the test piece after application | coating was observed visually and the presence or absence of the clogging of the hole part by a test agent was evaluated. Table 1 shows the evaluation results. In addition, the meaning of the symbol shown in the column of “Coating property” in Table 1 is as follows.

A +: The test agent could be applied by spraying. No clogging of the holes occurred in the test piece after spray application, and all the holes were open.
A: The test agent was sprayed. Clogging of the test agent occurred in part of the hole in the test piece after spray application.
B: Spraying of the test agent could not be performed, and coating with a spatula was performed. In the test piece after application, clogging of the test agent occurred in almost all the holes.
-: The test agent could not be applied because the viscosity of the test agent was extremely high.

<Crack after drying>
Glass plates, alumina plates, refractory bricks and ceramic fiber blocks were prepared as test pieces. The glass plate and the alumina plate have a smooth surface and have a square shape of 5 cm long × 5 cm wide. The refractory brick has a rough surface and has a cubic shape with a side of 5 cm. The ceramic fiber block has a large number of gaps on the surface and has a cubic shape with a side of 5 cm.

  The test agent was applied to the surfaces of the four test pieces so as to be as thin as possible and to cover the entire surface. Thereafter, the test piece was dried by heating at 110 ° C. for 12 hours.

  The surface of the test piece after drying was visually observed to evaluate the presence or absence of cracks in the coating layer. The results are shown in Table 1. The meanings of the symbols shown in the “crack after drying” column in Table 1 are as follows.

A +: Cracks did not occur in the coating layer after drying.
A: Cracks occurred in a part of the coating layer after drying, but no decrease in heat insulation performance due to the cracks was observed.
B: Cracks occurred on almost the entire surface of the coating layer after drying.
-: The test agent could not be applied because the viscosity of the test agent was extremely high.

<Coarse layer roughness>
Among the test pieces obtained as described above, the surface of the test piece in which the coating layer was formed on the alumina plate was visually observed from an oblique direction to evaluate the roughness of the coating layer surface. The results are shown in Table 1. In addition, the meaning of the symbol described in the column of “Surface roughness” in Table 1 is as follows.

A: The entire surface of the coating layer was smooth.
B: Unevenness was observed in part of the coating layer.
C: Unevenness was observed on the entire surface of the coating layer.
-: The test agent could not be applied because the viscosity of the test agent was extremely high.

<Thickness of coating layer>
Among the test pieces obtained as described above, the thickness of the coating layer formed on the alumina plate was measured. The results are shown in Table 1. In addition, the meaning of the symbol described in the column of “the thickness of the coating layer” in Table 1 is as follows. Moreover, the thickness of the coating layer was measured by the following method.

  In advance, the thickness of five points randomly selected on the alumina plate before applying the coating layer was measured using a caliper. The average value of the five thicknesses thus obtained was defined as the average thickness of the alumina plate. Then, the coating layer was formed on the alumina board by the above-mentioned method, and the test piece was produced. And in the said test piece, the thickness of the thickest part and the thinnest part judged visually was measured using calipers. Furthermore, three places were selected at random from the portion excluding the two places, and the thickness of the test piece was measured using a caliper. The average value of the five thicknesses obtained as described above was taken as the average thickness of the test piece. And the value which deducted the average thickness of the alumina board from the average thickness of the test piece was made into the thickness of a coating layer.

A +: The thickness of the coating layer was 0.1 mm or less.
A: The thickness of the coating layer was more than 0.1 mm and 0.3 mm or less.
B: The thickness of the coating layer was more than 0.3 mm and 1 mm or less.
C: The thickness of the coating layer was more than 1 mm and 3 mm or less.
D: The thickness of the coating layer exceeded 3 mm.
-: The test agent could not be applied because the viscosity of the test agent was extremely high.

<Crack after firing>
Of the four types of test pieces having the coating layer formed as described above, three types of alumina plate, refractory brick, and ceramic fiber block were heated at 1500 ° C. for 3 hours to fire the coating layer.

  The surface of the test piece after firing was visually observed to evaluate the presence or absence of cracks in the coating layer. The results are shown in Table 1. In addition, the meaning of the symbol shown in the “crack after firing” column in Table 1 is as follows.

A +: No cracks occurred in the coating layer after firing.
A: Cracks occurred in a part of the coating layer after firing, but no decrease in heat insulation performance due to cracks was observed.
B: Cracks occurred on almost the entire surface of the coating layer after firing.
-: The test agent could not be applied because the viscosity of the test agent was extremely high.

<Evaluation of thermal insulation performance>
The test agent was applied to the surface of the substrate made of refractory so as to be as thin as possible and to cover the entire surface. Thereafter, the refractory material was heated at 110 ° C. for 12 hours to dry the test agent, thereby forming a coating layer. The heat insulating material was created by the above. As the substrate, two types of ceramic fiber block having a maximum use temperature of 1260 ° C. and a castable refractory having a maximum use temperature of 1300 ° C. were used.

  Next, the high temperature durability test which heats the said heat insulating material for a long time by the following method was done. In the heat insulating material using the ceramic fiber block, after the heat insulating material is charged into the heating device, the temperature in the device is increased to 1500 ° C. at a temperature increasing rate of 150 ° C./hour, and then the temperature of 1500 ° C. is increased. Hold for 24 hours. After holding for 24 hours, heating was stopped and the heat insulating material was allowed to cool naturally in the apparatus, completing the high temperature durability test. Moreover, in the heat insulating material using a castable refractory, a high temperature durability test was conducted in the same manner as described above except that the temperature rising rate was 100 ° C./hour and the holding time at 1500 ° C. was 3 hours.

  Next, the dimension of the heat insulating material after performing the high temperature durability test was measured, and the linear shrinkage ratio with respect to the dimension of the heat insulating material measured in advance before the high temperature durability test was calculated. The result is shown in the column of “Linear shrinkage” in Table 1. In addition, the code | symbol "-" in Table 1 shows that the linear shrinkage rate is not measured. In addition, for comparison with a heat insulating material having a coating layer, a high temperature durability test was conducted using a ceramic fiber block and a castable refractory in which no coating layer was provided. The linear shrinkage rate of the ceramic fiber block was 5.4%, and the linear shrinkage rate of the castable refractory was 4.8%.

(Experimental example 2)
This example is an example of a coating liquid in which the contents of the inorganic binder and the swellable clay mineral are changed. As shown in Table 2, in this example, eight types of coating liquids (test agents 13 to 20) in which the contents of the inorganic binder and the swellable clay mineral were changed were prepared in the same manner as in Experimental Example 1. Various characteristics were evaluated in the same manner as in Experimental Example 1. The results are shown in Table 2.

(Experimental example 3)
This example is an example of a coating liquid containing only ceramic powder as a radiation scattering material. As shown in Table 3, in this example, 15 types of coating liquids (test agents 21 to 35) in which the type and content of the ceramic powder were changed were produced by the same method as in Experimental Example 1. Various characteristics were evaluated in the same manner as in Experimental Example 1. The results are shown in Table 3.

(Experimental example 4)
This example is an example of a coating liquid containing both ceramic fibers and ceramic powder as a radiation scattering material. As shown in Tables 4 and 5, in this example, 26 types of coating liquids (test agents 36 to 61) in which the type and content of the ceramic powder were changed were produced in the same manner as in Experimental Example 1. Various characteristics were evaluated in the same manner as in Experimental Example 1. The results are shown in Tables 4 and 5.

  As is known from the above experimental examples 1 to 4, the test agent in which the content of the inorganic binder, the swellable clay mineral and the radiation scattering material is within the above specific range has a low viscosity and an excellent dispersion stability. And spray coating could be performed. In addition, such a test agent can form a coating layer exhibiting excellent adhesion to various test pieces such as glass and brick, and can suppress cracking of the coating layer after drying and firing. It was.

  In addition, the test agent in which the content of the swellable clay mineral and the radiation scattering material is within the above specific range is compared with the heat insulating material using the refractory having no coating layer and the test agent 4 not containing the radiation scattering material. In addition, the linear shrinkage rate after the high temperature durability test could be reduced.

  From the above results, the test agent in which the content of the inorganic binder, the swellable clay mineral and the radiation scattering material is within the above specific range can be prepared by a simple operation and can form a coating layer having excellent performance. Understandable.

Claims (10)

100 parts by weight of water,
10 parts by mass or more of an inorganic binder,
0.2-2 parts by weight of a swellable clay mineral;
10 to 200 parts by mass of radiation scattering material,
The radiation scattering material is
Ceramic fibers which are composed of fibrous particles having a diameter of 2 μm or less containing Al ₂ O ₃ and whose median diameter of secondary particles formed by aggregation of the fibrous particles is 40 μm or less;
Silicon carbide powder having a median diameter of 40 μm or less;
Silicon nitride powder having a median diameter of 40 μm or less;
Boron nitride powder having a median diameter of 40 μm or less;
A heat insulating coating liquid characterized by being one or more selected from the group consisting of alumina powder having a median diameter of 60 μm or less.   The heat insulation coating liquid contains only one kind of the radiation scattering material among the ceramic fiber, the silicon carbide powder, the silicon nitride powder, the boron nitride powder, and the alumina powder. Item 2. A thermal barrier coating solution according to item 1. The heat insulation coating liquid contains only one of the ceramic fiber or the alumina powder as the radiation scattering material, and the content of Al ₂ O ₃ with respect to the total solid content of the heat insulation coating liquid is 50% by mass or more. The thermal insulation coating liquid according to claim 2, wherein the thermal insulation coating liquid is present.   The heat insulation coating liquid according to claim 1, wherein the heat insulation coating liquid contains two or more kinds of the radiation scattering materials containing the ceramic fiber.   The heat insulation coating liquid according to claim 4, wherein the heat insulation coating liquid has an alumina powder content of 30 parts by mass or less. The heat insulating coating liquid according to claim 4 or 5, wherein the heat insulating coating liquid has an Al ₂ O ₃ content of 50% by mass or more based on the total solid content.   The said heat insulation coating liquid has a viscosity of 20 Pa * s or less, The heat insulation coating liquid of any one of Claims 1-6 characterized by the above-mentioned.   The heat insulation coating liquid according to any one of claims 1 to 7, wherein the heat insulation coating liquid is configured to maintain a state in which the solid content is dispersed in water for one day or more. . A heat insulating material having a base made of a refractory and a heat insulating coating layer formed on the base,
The said heat insulation coating layer dries the heat insulation coating liquid as described in any one of Claims 1-8, The heat insulating material characterized by the above-mentioned. 10 parts by mass or more of an inorganic binder,
0.2-2 parts by weight of a swellable clay mineral;
10 to 200 parts by mass of radiation scattering material,
The radiation scattering material is
Ceramic fibers which are composed of fibrous particles having a diameter of 2 μm or less containing Al ₂ O ₃ and whose median diameter of secondary particles formed by aggregation of the fibrous particles is 40 μm or less;
Silicon carbide powder having a median diameter of 40 μm or less;
Silicon nitride powder having a median diameter of 40 μm or less;
Boron nitride powder having a median diameter of 40 μm or less;
A composition for heat insulation coating liquid, wherein the composition is any one selected from the group consisting of alumina powder having a median diameter of 60 μm or less.