KR102149166B1 - Coating liquid and method for producing refractory material having coating layer - Google Patents

Abstract

It provides a coating solution for refractory materials that can be prepared by a simple operation and has excellent performance, a composition for producing a coating solution, and a refractory material having a coating layer having excellent heat insulation performance and wind resistance. The coating liquid contains 100 parts by mass of moisture, 10 to 20 parts by mass of an inorganic binder, 0.2 to 2 parts by mass of swellable clay mineral, and 10 to 200 parts by mass of a radiation scattering material. The radiation scattering material is a ceramic fiber and/or alumina powder, silica powder, titania powder, chromia powder, yttria powder, zirconia powder with an average fiber length of 100 μm or less composed of fibrous particles containing Al ₂ O ₃ . , Lanthanum oxide powder, ceria powder, silicon carbide powder, silicon carbide aluminum powder, silicon nitride powder, and boron nitride powder, including one or two or more ceramic powders having a median diameter of 60 μm or less. .

Description

Coating liquid and method for producing refractory material having coating layer

The present invention relates to a refractory material having a coating solution for application to a refractory material, a composition for preparing the coating solution, and a coating layer produced using the coating solution.

A heating furnace configured to be heated at a high temperature, such as a crack furnace used for manufacturing steel materials or a heat treatment furnace, or a calcination furnace used for manufacturing ceramics, has an outer wall and an inner wall disposed inside the outer wall. The inner wall is made of refractory material.

The refractory material constituting the inner wall is usually attached to the outer wall of the heating furnace through an attachment bracket. As this type of refractory material, blocks made of ceramic fibers containing silica, alumina, zirconia, and the like are widely used. Since this block has excellent heat insulation performance, it is possible to easily control the temperature in the furnace and the rate of temperature increase by using it for the inner wall of the heating furnace. In addition, the block is relatively lightweight because it contains ceramic fibers having a small bulk specific gravity. 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 shrinks when it is placed in a high temperature environment of 1000°C or higher for a long period of time. Therefore, when the heating furnace is used for a long period of time, a gap is formed between blocks adjacent to each other, resulting in a decrease in thermal insulation performance.

In addition to blocks containing ceramic fibers, heat-resistant refractory bricks containing acidic oxides, neutral oxides and basic oxides as main components specified in JIS R2611, plastic refractories containing chamotte, alumina and chromium as aggregates, calcia and Castable refractories containing alumina as aggregate and refractory materials such as refractory mortar may be used as the inner wall of the heating furnace. However, similarly to the above, these refractories also have a problem of gradually shrinking when left in a high temperature environment for a long period of time. In addition, when the refractory material in the heating furnace for heating the metal comes into contact with a metal or a by-product generated during metal refining, there is a problem that the refractory material may be corroded. In particular, when ferrous oxide (scale) containing an alkaline substance was in contact, it was remarkable.

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

Patent Document 1: Japanese Unexamined Patent Application Publication No. 2009-137809 Patent Document 2: Japanese Patent No. 4297204

Since the refractory mortar of Patent Literature 1 has a high viscosity, it is difficult to apply it to portions having deep irregularities or complex structures, such as joints of refractories. Therefore, there is a problem that the workability when applying the refractory mortar is low. Further, since it is difficult to reduce the application thickness of the refractory mortar, there is a problem that the refractory material to which the refractory mortar is applied is easily peeled from the outer wall of the heating furnace due to its own weight.

In order to improve the applicability of the coating liquid to be applied to the refractory and to reduce the thickness of the coating, it is effective to use a coating liquid having a low viscosity. However, a coating liquid having a low viscosity usually contains a large amount of organic substances such as an organic binder and an organic solvent, like the coating material of Patent Document 2. Therefore, when the coating liquid is heated and dried, the organic binder or the like is gasified, and there is a concern that cracks or the like may occur in the obtained coating layer. Such cracks are not preferable because they cause a decrease in heat insulation performance and the like. In addition, there is a concern that the coating liquid containing an organic binder or an organic solvent may spoil when stored for a long period of time.

As described above, from the viewpoint of coating properties, coating thickness, performance, and storage properties, it is preferable that the coating liquid for refractories has a low viscosity and does not contain an organic binder or the like. By the way, in the low viscosity coating liquid prepared without using an organic binder or an organic solvent, it is difficult to disperse the solid content in the solvent over a long period of time, and there is a problem that the solid content precipitates relatively early after dispersing the solid content in the solvent. Therefore, it is necessary to perform operations such as mixing the solvent and solids each time they are used, or sufficiently stirring and dispersing the solids in the solvent immediately before application to the refractory, making preparation work before application complicated. Was supposed to be done.

The present invention has been made in view of this background, and is intended to provide a coating liquid that can be prepared by a simple operation and exhibits excellent performance by applying it to a refractory material, a composition for producing the coating liquid, and a refractory material having a coating layer. will be.

One aspect of the present invention is a coating liquid for application to refractories,

100 parts by mass of moisture,

10 parts by mass or more of an inorganic binder,

0.2 to 2 parts by mass of a swellable clay mineral,

It contains 10 to 200 parts by mass of radiation scattering material,

The radiation scattering material,

Ceramic fibers having an average fiber length of 100 μm or less and/or consisting of fibrous particles containing Al ₂ O ₃ ,

It is selected from the group consisting of alumina powder, silica powder, titania powder, chromia powder, yttria powder, zirconia powder, lanthanum oxide powder, ceria powder, silicon carbide powder, silicon carbide aluminum powder, silicon nitride powder and boron nitride powder, 60 It is a coating liquid containing one or two or more types of ceramic powders having a median diameter of µm or less.

Another aspect of the present invention is a composition of a coating liquid for application to refractories,

10 parts by mass or more of an inorganic binder,

0.2 to 2 parts by mass of a swellable clay mineral,

It contains 10 to 200 parts by mass of radiation scattering material,

The radiation scattering material,

Ceramic fibers having an average fiber length of 100 μm or less and/or composed of fibrous particles containing Al ₂ O ₃ ,

It is selected from the group consisting of alumina powder, silica powder, titania powder, chromia powder, yttria powder, zirconia powder, lanthanum oxide powder, ceria powder, silicon carbide powder, silicon carbide aluminum powder, silicon nitride powder and boron nitride powder, 60 It is a composition for a coating liquid containing one or two or more ceramic powders having a median diameter of µm or less.

Another aspect of the present invention is a gas composed of a refractory material,

It has a coating layer formed on the substrate,

The coating layer,

10 parts by mass or more of an inorganic binder,

0.2 to 2 parts by mass of a swellable clay mineral,

It contains 10 to 200 parts by mass of radiation scattering material,

The radiation scattering material,

Ceramic fibers having an average fiber length of 100 μm or less and/or consisting of fibrous particles containing Al ₂ O ₃ ,

It is selected from the group consisting of alumina powder, silica powder, titania powder, chromia powder, yttria powder, zirconia powder, lanthanum oxide powder, ceria powder, silicon carbide powder, silicon carbide aluminum powder, silicon nitride powder and boron nitride powder, 60 It is a refractory material having a coating layer containing one or two or more ceramic powders having a median diameter of µm or less.

The coating liquid contains the inorganic binder, the swellable clay mineral (hereinafter referred to as "clay mineral"), and the radiation scattering material in the specific ratio with respect to 100 parts by mass of water. In addition, the radiation scattering material is composed of ceramic fiber and/or ceramic powder whose particle diameter distribution is controlled as described above.

The solvent and binder of the coating solution are composed of inorganic materials. Therefore, the coating liquid can have excellent storage properties and suppress the occurrence of cracks in the coating layer after drying.

In addition, the coating solution can form the coating layer having excellent performance by having the specific composition. In addition, since the coating liquid has a low viscosity, it has excellent coating properties and can reduce the coating thickness.

In addition, 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 operation before application to the refractory can be shortened, and in some cases, there is no need to perform the stirring operation. As a result, the preparation work before application can be greatly simplified.

As described above, the coating solution can be prepared by a simple operation, has excellent coating properties, and can be applied thinner.

In addition, since the refractory material has the coating layer including the inorganic binder in the specific ratio, the clay mineral and the radiation scattering material, it has excellent heat insulation performance and an effect of improving wind resistance or corrosion resistance of refractories. The refractory material having the coating layer can maintain excellent performance over a long period of time in a high temperature environment of, for example, 1000°C or higher.

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

The composition of the coating liquid will be described below.

Inorganic binder: 10 parts by mass or more

The coating liquid contains 10 parts by mass or more of an inorganic binder with respect to 100 parts by mass of moisture. The inorganic binder has a function of firmly adhering the dried coating layer to a substrate made of a refractory material. The coating liquid can suppress problems such as cracking or the like in the coating layer after drying or peeling of the coating layer from the substrate by setting the content of the inorganic binder in the specific range.

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 solution can be prepared by, for example, a method of blending colloidal silica or the like in the coating solution so that the content of colloidal particles is within the specific range. Usually, the median diameter of colloidal particles contained in the inorganic colloidal solution is 100 nm or less. As the inorganic colloidal solution, colloidal silica, colloidal alumina, colloidal zirconia, and 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 deteriorated, and cracks or peeling may occur in the coating layer. As a result, there is a fear that the performance of the refractory material is deteriorated.

In order to improve the adhesion 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 becomes difficult to obtain an effect suitable for cost, and there is a concern that problems such as a decrease in the melting point of the coating layer may occur.

In addition, since the inorganic binder has a high reactivity, if the content of the inorganic binder is excessively large, the coating layer may be deteriorated by reaction with a gas or a radiation scattering material under a high temperature environment, and further, performance may be deteriorated. The reaction with gas or radiation scattering material may occur even when any of particulates derived from colloidal silica, particulates derived from colloidal alumina, and particulates derived from colloidal zirconia is used, but in particular, particulates derived from colloidal silica are used as inorganic binders. It is easy to happen when used as. In order to avoid such a problem, the content of the inorganic binder is preferably 20 parts by mass or less.

Therefore, it is more preferable to set the content of the inorganic binder to 10 to 20 parts by mass from the viewpoint of improving the adhesion between the coating layer and the substrate and suppressing the degradation of the coating layer under high temperature.

-Swellable clay mineral: 0.2 to 2 parts by mass

The coating liquid contains 0.2 to 2 parts by mass of the clay mineral with respect to 100 parts by mass of water. Clay minerals have an effect 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 preparation work before application can be greatly simplified.

As the clay mineral, for example, a clay mineral having swelling properties, such as kaolinite, haloysite, smectite, mica, vermiculite, chlorite, imogolite, allophane, sepiolite, valegilsite and gibsite, can be used. I can.

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

Radiation scattering material: 10 to 200 parts by mass

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

In a heating furnace in which the temperature inside the furnace becomes a high temperature of 1000° C. or more, heat transfer from the furnace to the outside of the furnace by radiation becomes dominant compared to 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 is possible to effectively reflect or scatter electromagnetic waves such as infrared rays radiated in the furnace. In addition, since the refractory material can reflect or scatter electromagnetic waves radiated in the furnace by the coating layer on the surface, heat transfer to the outside of the furnace can be effectively reduced. As a result, the refractory material has excellent heat insulation performance and the like.

Further, since the refractory material can reduce the electromagnetic waves reaching the gas due to the presence of the coating layer, it is possible to suppress an increase in the temperature of the gas. As a result, the refractory can suppress the contraction of gas due to heating, and furthermore, the contraction of the entire refractory can be suppressed.

When the content of the radiation scattering material is less than 10 parts by mass, since the action of reflecting or scattering electromagnetic waves becomes insufficient, 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 increases, and there is a fear that the coatability may deteriorate. Therefore, in order to make the heat insulating performance and coatability compatible, the content of the radiation scattering material is set to 10 to 200 parts by mass. From the same viewpoint, it is preferable to set the content of the radiation scattering material to 10 to 120 parts by mass, more preferably 10 to 80 parts by mass.

As the radiation scattering material, ceramic fibers and/or one or two or more ceramic powders having a median diameter of 60 μm or less can be used. In addition, the median diameter of the ceramic powder can be calculated based on the particle diameter distribution measured by the laser diffraction scattering method.

The ceramic fiber is composed of fibrous particles containing Al ₂ O ₃ . The ceramic fiber is usually composed of Al ₂ O ₃ and SiO ₂ , but may contain components other than these.

The ceramic fiber can effectively reflect or scatter radiated electromagnetic waves as the content of Al ₂ O ₃ increases. Therefore, ceramic fibers with a large content of Al ₂ O ₃ can improve the performance of the finally obtained refractory. From the viewpoint of improving performance such as thermal insulation properties, 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, even more preferably 65% by mass or more, and 70% by mass or more. It is particularly preferred.

Individual fibrous particles constituting the ceramic fiber usually have a length of one or more times the diameter. The average diameter of the fibrous particles can be 60 μm or less. In this case, it is possible to improve the dispersibility of the ceramic fiber and reduce the coating thickness of the coating liquid. From the viewpoint of industrial availability, it is preferable that the average diameter of the fibrous particles is 12 µm or less.

The average fiber length of the ceramic fibers is 100 μm or less. When the average fiber length exceeds 100 µm, since the content of excessively long fibrous particles increases, ceramic fibers tend to settle during storage. In addition, when the content of excessively long fibrous particles increases, it becomes difficult to reduce the thickness of the coating liquid, and it becomes difficult to reduce the thickness of the coating layer after drying.

Therefore, in order to improve the dispersibility of the ceramic fibers and to reduce the coating thickness of the coating solution, the average fiber length of the ceramic fibers is set to 100 μm or less. From the same viewpoint, the average fiber length of the ceramic fibers is preferably 60 µm or less, and more preferably 40 µm or less.

As the ceramic powder, specifically, alumina (Al ₂ O ₃ ), silica (SiO ₂ ), titania (TiO ₂ ), chromia (Cr ₂ O ₃ ), yttria (Y ₂ O ₃ ), zirconia (ZrO ₂₎ ), lanthanum oxide (La ₂ O ₃ ), ceria (CeO ₂ ), silicon carbide (SiC), aluminum silicon carbide (Al ₄ SiC ₄ ), silicon nitride (Si ₃ N ₄ ) and boron nitride (BN) Any one or two or more types of powders selected can be used. These ceramic powders may be used alone or in combination with ceramic fibers.

The ceramic powder has a particle diameter distribution such that the median diameter is 60 μm or less. By setting the median diameter of the ceramic powder to 60 µm or less, the content of particles having a large particle diameter can be reduced. As a result, while improving the dispersibility of the ceramic powder in water, it is possible to easily reduce the coating thickness of the coating liquid. From the same viewpoint, the median diameter of the ceramic powder is preferably 40 µm or less, more preferably 20 µm or less, and even more preferably 10 µm or less. In addition, 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 be 1 µm or more.

When the coating liquid contains only one of ceramic fibers or alumina powder as a radiation scattering material, the content of Al ₂ O ₃ relative 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 capable of more effectively reflecting or scattering the radiated electromagnetic waves. And, by using the coating liquid, it is possible to further improve the heat insulation performance of the refractory.

When the coating liquid contains two or more types of radiation scattering materials, it is preferable to contain at least ceramic fibers as the radiation scattering material. That is, it is preferable that the coating liquid contains two or more types of radiation scattering materials including ceramic fibers.

All of the ceramic powders have excellent performance as a radiation scattering material. However, when two or more types of ceramic powders are used together, the viscosity of the coating liquid tends to increase, so that there is a concern that problems such as deterioration of coating properties or thickening of coating thickness may occur. On the other hand, when the ceramic fiber is used in combination with the ceramic powder, it is difficult to increase the viscosity of the coating liquid. Therefore, the coating liquid containing two or more types of radiation scattering materials including ceramic fibers can further improve the performance of the refractory material while suppressing an increase in viscosity.

In the above case, it is more preferable that the coating liquid contains 30 parts by mass or less of the alumina powder. When alumina powder is used in combination with ceramic fibers, it is easier to increase the viscosity of the coating liquid compared to silicon carbide powder, silicon nitride powder, and boron nitride powder. Therefore, by regulating the content of the alumina powder to 30 parts by mass or less, it is possible to suppress an increase in the viscosity of the coating liquid.

Further, in the above case, it is more preferable that the coating liquid has an Al ₂ O ₃ content of 50 mass% or more with respect to the total solid content. In this case, the coating liquid can form a coating layer capable of more effectively reflecting or scattering the radiated electromagnetic waves. And, by using the coating liquid, it is possible to further improve the heat insulation performance of the refractory.

It is preferable that the coating liquid has a viscosity of 20 Pa·s or less. In this case, the coating liquid may be applied to the gas by spraying. Further, in this case, it may be applied by immersing the gas in the coating liquid. As a result, it is possible to further improve workability in the application of the coating liquid. From the viewpoint of more easily performing application by spray coating or immersion, it is more preferable that the coating liquid has a viscosity of 5 Pa·s or less.

In addition, it is preferable that the coating solution is configured to maintain a state in which the solid content is dispersed in water for more than a day. In this case, by mixing water and solid content in advance, the stirring operation before application to the refractory material can be shortened, and in some cases, it is not necessary to perform the stirring operation. As a result, the preparation work before application can be greatly simplified.

The coating liquid may contain an organic substance as long as it is within a range that does not impair coatability and storage properties. Examples of organic substances that can be included in the coating liquid include colorants, preservatives, and thickeners.

Colorant: 0.5 parts by mass or less

The coating liquid may contain 0.5 parts by mass or less of a colorant based on 100 parts by mass of water. In this case, the color tone of the coating liquid can be adjusted to a color tone different from that of the substrate. Thereby, it is possible to easily discriminate between a portion to which the coating liquid is applied and a portion that is not applied. As a result, it is possible to reduce the unevenness of the coating liquid.

Preservative: 0.5 parts by mass or less

The coating liquid may contain 0.5 parts by mass or less of a preservative based on 100 parts by mass of water. In this case, spoilage of the coating liquid can be prevented over a longer period.

· Thickener: 0.5 parts by mass or less

The coating liquid may contain 0.5 parts by mass or less of a thickener based on 100 parts by mass of water. The thickener is used to fine-tune the viscosity of the coating liquid.

It is preferable that content of a coloring agent, a preservative, and a thickener is 0.5 mass part or less. By limiting the content of these organic substances to the above specific range, the amount of gas generated during drying of the coating liquid can be sufficiently reduced. As a result, it is possible to avoid the occurrence of cracks in the coating layer after drying.

The refractory material may be prepared, for example, by applying the coating solution to a base composed of refractory material and then drying the coating solution to form a coating layer. By using the coating solution to form the coating layer, the thickness of the obtained coating layer can be reduced. In addition, the coating liquid can be applied to the substrate by spraying, since the viscosity can be lowered than conventionally as described above. In addition, the coating liquid can be applied to the surface of the substrate using a brush or spatula, as in the prior art.

The substrate to which the coating liquid is applied is composed of a conventionally known refractory material. Specifically, as the refractory material constituting the base, blocks and molded articles made of ceramic fibers can be employed. As the ceramic fiber constituting the substrate, for example, a refractory ceramic fiber, an alumina fiber, and a biosoluble fiber can be used.

The reflector ceramic fiber contains, for example, Al ₂ O ₃ : 30 to 60 mass%, SiO ₂ : 40 to 60 mass%, and the balance contains a chemical component consisting of ZrO ₂ and/or Cr ₂ O ₃ . It is composed of fibrous particles having. In addition, the fibrous particles constituting the reflector ceramic fiber are amorphous.

The alumina fiber is composed of fibrous particles containing, for example, Al ₂ O ₃ : 60% by mass or more, and the remainder having a chemical component consisting of SiO ₂ . Further, the fibrous particles constituting the alumina fiber contain both a mullite crystal and an alumina crystal.

The biosoluble fiber is composed of, for example, SiO ₂ : 40 to 60% by mass, and the remainder is composed of fibrous particles having a chemical component consisting of MgO and/or CaO. Further, the fibrous particles constituting the biosoluble fiber are amorphous.

In addition, as the refractory material, heat-resistant refractory bricks specified in JIS R2611, plastic refractories containing chamotte, alumina and chromium as aggregates, castable refractories containing calcia and alumina as aggregates, and refractory mortar are used. It is also possible.

The above-described heat-resistant refractory brick, plastic refractory material, castable refractory material, and refractory mortar have a smoother surface than that of a block including ceramic fibers. Therefore, in the case of forming a coating layer using a conventional coating solution, it has been difficult to suppress problems such as low adhesion between the substrate and the coating layer, cracks or the like in the coating layer, or peeling of the coating layer.

On the other hand, the coating liquid can reduce the thickness of the coating layer applied to the surface of the substrate as compared to the conventional one, and as a result, the thickness of the coating layer can be reduced. Therefore, the adhesion of the coating layer to the substrate made of heat-resistant refractory bricks or the like can be improved, thereby suppressing the occurrence of peeling or cracking of the coating layer.

Example

Examples of the coating solution will be described below. In addition, in this example, a coating liquid was produced using the following materials.

・Microparticles derived from colloidal silica as inorganic binder

·Swellable clay mineral smectite

Ceramic fiber A Al ₂ O ₃ content: 65 mass%, SiO ₂ content: 35 mass%, average diameter of fibrous particles: 6 µm, average fiber length: 10 µm

Ceramic fiber B Al ₂ O ₃ content: 65 mass%, SiO ₂ content: 35 mass%, average diameter of fibrous particles: 6 µm, average fiber length: 20 µm

Ceramic fiber C Al ₂ O ₃ content: 65 mass%, SiO ₂ content: 35 mass%, average diameter of fibrous particles: 6 µm, average fiber length: 40 µm

Ceramic fiber D Al ₂ O ₃ content: 65 mass%, SiO ₂ content: 35 mass%, average diameter of fibrous particles: 6 µm, average fiber length: 60 µm

Ceramic fiber E Al ₂ O ₃ content: 65 mass%, SiO ₂ content: 35 mass%, average diameter of fibrous particles: 6 µm, average fiber length: 80 µm

Ceramic fiber F Al ₂ O ₃ content: 65 mass%, SiO ₂ content: 35 mass%, average diameter of fibrous particles: 6 µm, average fiber length: 100 µm

Ceramic fiber G Al ₂ O ₃ content: 70 mass%, SiO ₂ content: 30 mass%, average diameter of fibrous particles: 6 µm, average fiber length: 20 µm

Ceramic fiber H Al ₂ O ₃ content: 50 mass%, SiO ₂ content: 50 mass%, average diameter of fibrous particles: 6 µm, average fiber length: 20 µm

Silicon carbide powder A median diameter: 1㎛

Silicon carbide powder B median diameter: 5 μm

Silicon carbide powder C median diameter: 40㎛

·Alumina powder A median diameter: 1㎛

·Alumina powder B median diameter: 20㎛

·Alumina powder C median diameter: 40㎛

·Medium diameter of silica powder: 40㎛

·Chromia powder median diameter: 40㎛

-Zirconia powder median diameter: 40㎛

In addition, the average fiber length of the ceramic fiber was calculated by the following method. First, a SEM (scanning electron microscope) image of the ceramic fiber before mixing was obtained. Of the fibrous particles reflected on the SEM image, 100 fibrous particles with both ends identifiable were randomly selected. And the value which averaged the length of these fibrous particles was made into the average fiber length.

In addition, the average diameter of the fibrous particles was calculated by the following method. First, a SEM (scanning electron microscope) image of the ceramic fiber before mixing was obtained. Of the fibrous particles projected on the SEM image, ten fibrous particles whose cross-section can be confirmed were randomly selected. The average diameter of the cross-sections of these fibrous particles was used as the average diameter of the fibrous particles.

In addition, the median diameter of the ceramic powder was measured using a laser diffraction/scattering particle diameter distribution measuring device (Horiba Seisakusho Co., Ltd. product, "LA-500").

(Experimental Example 1)

This example is an example of a coating liquid containing one type of ceramic fiber as a radiation scattering material. In this example, as shown in Table 1, 14 types of coating solutions (test agents 1 to 14) were prepared by changing the type and content of ceramic fibers. Then, evaluation was performed on the properties of the obtained coating liquid.

<Production method of test agent>

First, while stirring water, the swellable clay mineral was divided into several times and added, and the swellable clay mineral was dispersed in water. While stirring this solution, an inorganic binder, a radiation scattering agent, a colorant, a preservative, and a thickener were sequentially added, and test agents 1-14 were produced. In addition, the inorganic binder was mixed with the solution in the state of a colloidal silica solution.

<Characteristic evaluation of test agent>

·Viscosity

The viscosity of each test agent at 20°C was measured using a viscometer ("Visco Tester VT-04E" manufactured by Leon Corporation). The results are shown in Table 1. In addition, the meaning of the symbol of the "viscosity" column in Table 1 is 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 5 Pa·s or less.

B: The viscosity of the test agent was more than 5 Pa·s and 20 Pa·s or less.

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 stirred vigorously to disperse the solid content, and then the test agent was allowed to stand in a room temperature environment. And the time until the solid content completely settled was measured. The results are shown in Table 1. In addition, the meaning of the symbols shown in the column of "dispersion stability" in Table 1 is as follows. In addition, "the state in which the solid content has completely settled" refers to a state in which the boundary between the settled solid and the supernatant liquid is clearly observed.

A+: During the evaluation period, the solid content did not settle.

A: The solid content settled in about several days.

B: The solid content settled in about tens of minutes.

C: The solid content settled immediately after standing still.

-: Evaluation was impossible because the viscosity of the test agent was very high.

<Applicability>

As a test piece, a grid having a large number of holes having a square shape of 3 mm long by 3 mm wide was prepared. Application of each test agent was attempted to this test piece using a spray and a spatula, and whether or not spray application was possible was evaluated. Further, the test piece after application was visually observed, and the presence or absence of clogging of the hole portion by the test agent was evaluated. Table 1 shows the evaluation results. In addition, the meaning of the symbols shown in the "coating property" column in Table 1 is as follows.

A+: Spray application of the test agent could be performed. No clogging of the holes occurred in the test piece after spray application, and all of the holes were open.

A: Spray application of the test agent could be performed. Clogging of the test agent occurred in a part of the hole in the test piece after spray application.

B: Spray application of the test agent could not be performed, and application with a spatula was performed. In the test piece after application, clogging of the test agent occurred in almost all holes.

-: Because the viscosity of the test agent was very high, it was impossible to apply the test agent.

<Cracking after drying>

As a test piece, a glass plate, an alumina plate, a refractory brick and a ceramic fiber block were prepared. The glass plate and the alumina plate have a smooth surface and have a square shape of 5 cm in length and 5 cm in width. Refractory bricks have a rough surface, and each side has a 5cm cube shape. The ceramic fiber block has a large number of gaps on its surface, and has a 5 cm cube shape on one side.

The test agent was applied to the surface of the four test pieces as thin as possible and to cover the entire surface. Then, the test piece was heated and dried at 110° C. for 12 hours.

The surface of the test piece after drying was visually observed, and the presence or absence of cracks in the coating layer was evaluated. The results are shown in Table 1. In addition, the meaning of the symbols shown in the column of "cracks after drying" in Table 1 is as follows.

A+: No cracks occurred in the coating layer after drying.

A: Although cracking occurred in a part of the coating layer after drying, the deterioration of heat insulation performance due to cracking was not observed.

B: Cracks occurred almost all over the coating layer after drying.

-: Because the viscosity of the test agent was very high, it was impossible to apply the test agent.

<Coating layer roughness>

Of the test pieces obtained as described above, the surface of the test piece having a coating layer formed on the alumina plate was visually observed from a diagonal direction to evaluate the roughness of the surface of the coating layer. The results are shown in Table 1. In addition, the meaning of the symbols described in the "surface roughness" column in Table 1 is as follows.

A: The entire surface of the coating layer was smooth.

B: Unevenness was observed in a part of the coating layer.

C: Unevenness was observed on the entire surface of the coating layer.

-: Because the viscosity of the test agent was very high, it was impossible to apply the test agent.

<Coating layer thickness>

Of the test pieces thus obtained, 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 symbols described in the "thickness of the coating layer" column in Table 1 is as follows. In addition, the thickness of the coating layer was measured by the following method.

In advance, the thickness of five locations randomly selected from the alumina plate before applying the coating layer was measured using a vernier caliper. The average value of the thickness of the five locations thus obtained was taken as the average thickness of the alumina plate. Thereafter, a coating layer was formed on the alumina plate by the method described above, and a test piece was produced. In addition, in the test piece, the thickness of the thickest portion and the thinnest portion determined by the naked eye was measured using a vernier caliper. In addition, three locations were randomly selected from the portion excluding the two locations, and the thickness of the test piece was measured using a vernier caliper. The average value of the thickness at five locations obtained by the above was taken as the average thickness of the test piece. Then, a value obtained by subtracting the average thickness of the alumina plate from the average thickness of the test piece was taken as the thickness of the 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.

-: Because the viscosity of the test agent was very high, it was impossible to apply the test agent.

<Cracking after firing>

Of the four test pieces in which the coating layer was formed as described above, three types of an alumina plate, a refractory brick, and a 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, and the presence or absence of cracks in the coating layer was evaluated. The results are shown in Table 1. In addition, the meaning of the symbols shown in the column of "cracking after firing" in Table 1 is as follows.

A+: No cracks occurred in the coating layer after firing.

A: Although cracking occurred in a part of the coating layer after firing, a deterioration in heat insulation performance due to cracking was not observed.

B: Cracks occurred almost all over the coating layer after firing.

-: Because the viscosity of the test agent was very high, it was impossible to apply the test agent.

<Evaluation of insulation performance>

The test agent was applied to the surface of the substrate made of the refractory material as thin as possible and the entire surface of the surface was covered. Thereafter, the substrate was heated at 110° C. for 12 hours to dry the test agent to form a coating layer. In the above, a refractory material having a coating layer was produced. In addition, as the base material, two types of ceramic fiber blocks with a maximum use temperature of 1260°C and castable refractories with a maximum use temperature of 1300°C were used.

Next, by the following method, a high temperature endurance test was conducted in which the refractory was heated for a long time. In the refractory material using the ceramic fiber block, after loading the refractory material into the heating device, the temperature in the device was raised to 1500°C at a temperature increase rate of 150°C/hour, and then the temperature of 1500°C was maintained for 24 hours. After holding for 24 hours, heating was stopped and the refractory was allowed to stand to cool naturally in the apparatus, and the high temperature durability test was completed. In addition, in the case of a refractory material using a castable refractory, a high-temperature endurance test was performed in the same manner as above, except that the temperature increase rate was set to 100°C/hour and the holding time at 1500°C was set to 3 hours.

Next, the dimensions of the refractory material after performing the high-temperature durability test were measured, and the linear shrinkage rate with respect to the dimensions of the refractory material before the high-temperature durability test measured in advance was calculated. The results are shown in the column of "Line Shrinkage" in Table 1. In addition, the symbol "-" in Table 1 indicates that the linear shrinkage is not measured. In addition, for comparison with a refractory material having a coating layer, a high-temperature durability test was performed using a ceramic fiber block and a castable refractory material in which the coating layer was not formed. The linear shrinkage of the ceramic fiber block was 5.4%, and the linear shrinkage of the castable refractory was 4.8%.

(Experimental Example 2)

This example is an example of the coating liquid in which the content of an inorganic binder and a swellable clay mineral were changed. As shown in Table 2, in this example, eight types of coating liquids (Test Agents 15 to 22) in which the content of the inorganic binder and the swellable clay mineral were changed were prepared by the same method as in Experimental Example 1. And, by the same method as Experimental Example 1, evaluation of various properties was performed. The results are shown in Table 2.

(Experimental Example 3)

This example is an example of a coating liquid containing only ceramic powder as the radiation scattering material. As shown in Table 3, in this example, 18 kinds of coating liquids (Test Agents 23 to 39, 41) in which the type and content of ceramic powder were changed were prepared by the same method as in Experimental Example 1. And, by the same method as Experimental Example 1, evaluation of various properties was performed. 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 the radiation scattering material. As shown in Tables 4 and 5, in this example, 26 types of coating liquids (Test Agents 43 to 68) in which the type and content of ceramic powder were changed were prepared by the same method as in Experimental Example 1. And, by the same method as Experimental Example 1, various property evaluations were performed. The results are shown in Tables 4 and 5.

As can be seen 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, has excellent dispersion stability, and can perform spray coating. Could In addition, such a test agent was able to form a coating layer exhibiting excellent adhesion to various test pieces such as glass and brick, and was able to suppress cracking of the coating layer after drying and firing.

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 refractory material having no coating layer or the refractory material using Test Agent 4 not containing the radiation scattering material, and the linear shrinkage rate after the high-temperature durability test I could make it small.

From the above results, it can be understood that 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 a coating layer having excellent performance can be formed. .

(Experimental Example 5)

This example is an example of evaluating the wind resistance of the refractory. The test body used for evaluation was produced by the following method. First, as a substrate, a ceramic fiber block having a flat plate shape having a length of 10 cm, a width of 10 cm, and a thickness of 1 cm was prepared. Test agent 2 (refer to Table 1) was applied to the surface of the substrate as thin as possible and to cover the entire surface of the substrate. After that, the substrate was heated at 110° C. for 12 hours to dry the test agent 2 to form a coating layer. A refractory material (test body A) was produced by the above.

Further, for comparison with Test Sample A, Test Samples B composed of only the gas and Test Samples C to F shown in Table 6 were prepared. Test Samples C to F are refractory materials produced by the same method as Test Sample A, except that the components of the coating liquid were changed as shown in Table 6.

The evaluation of wind resistance was performed by the following method. First, the masses of Test Samples A to F obtained by the above method were measured. Next, compressed air supplied from the compressor was blown out to the center of the plate surface of the test body for 20 seconds. The pressure of the compressed air was set to a pressure of 9 kg/cm 2. Further, the compressed air outlet was disposed at a position 3 cm away from the plate surface of the test body in the thickness direction. The diameter of the outlet was 3 mm. Then, the mass of the test body after blowing the compressed air was measured.

Based on the mass of the test body before and after jetting obtained as described above, the mass reduction rate was calculated based on the mass of the test body before jetting compressed air. That is, the mass reduction ratio R (%) is a value calculated by the following formula.

R=(Wi-Wf)/Wi×100

In addition, in the above formula, Wi is the mass (g) of the test body before blowing the compressed air, and Wf is the mass (g) of the test body after blowing the compressed air.

In Table 6, the mass reduction rate of each test body was shown.

As can be seen from Table 6, the refractory material (Test A) produced using Test Agent 2 in which the content of the inorganic binder, the swellable clay mineral, and the radiation scattering material is within the above specific range is a Test Body B composed of only ceramic fiber blocks, or Compared to the test specimens C, D, and F that did not have at least one of an inorganic binder or a clay mineral, the mass reduction rate could be reduced.

Test body E had a lower mass reduction ratio than test body A. However, since the test body D does not contain a radiation scattering material (ceramic fiber B), it is estimated that heat insulation performance is inferior to the test body A.

(Experimental Example 6)

In this example, a part of the coating liquid shown above (test agents 1, 2, 14, 33, 34, 36, 54, 60, 61, 62, 23, 24, 38, 39, 41) was used to improve corrosion resistance. It shows the results of the evaluation experiment.

<Preparation of refractory test body>

As a refractory material serving as a base, two types of 10 cm square ceramic fiber blocks were prepared. The first ceramic fiber block used in this example contains 50% by mass of Al ₂ O ₃ and SiO ₂ , respectively, and is commercially available with an upper limit of use temperature of 1260°C (manufactured by ITM Co., Ltd.). The second ceramic fiber block has a composition of 70 mass% of Al ₂ O ₃ content and 30 mass% of SiO ₂ content, and is commercially available (manufactured by ITM Co., Ltd.) at an upper limit use temperature of 1600°C.

A coating solution (test agent) was applied to the surface of these ceramic fiber blocks as thin as possible and to cover the entire surface of the surface. Thereafter, by heating at 110° C. for 12 hours to dry the coating solution, a refractory test body having a coating layer having a thickness of 0.3 mm or less on the surface of the ceramic fiber block as a base material was obtained. In addition, the refractory test body using the second ceramic fiber block was used for Test Agents 2 and 540,000 as shown in Table 7 to be described later.

<corrosion test>

As a substance causing corrosion of the refractory, two types of scale were prepared. Scale 1 is a mass ratio of FeO powder: carbon powder = 10:0.5, and scale 2 is a mass ratio of FeO powder: sodium carbonate: carbon powder = 9:1:0.45. Corrosiveness is stronger on the scale 2 than on the scale 1.

This scale is spread thinly on the surface of the refractory test body so as to be in a circular state of 2 to 3 cm in diameter. For comparison, a test specimen having scales directly placed on the surface of the two types of ceramic fiber blocks without a coating layer was also prepared. After the refractory test body on which the scale was placed was inserted into the heating device, the temperature in the device was raised to 1400°C at a rate of 150°C/hour, and then, the temperature of 1500°C was maintained for 3 hours. Thereafter, the refractory test body was taken out of the heating device, and the state of erosion was evaluated by visual observation and cross-sectional observation. The results are shown in Table 7. In addition, the meaning of the symbols shown in the "corrosion resistance" column in Table 7 is as follows.

A: Visual and cross-sectional observation showed no erosion to the gas.

B: Although it cannot be judged with the naked eye, erosion of the gas was observed by sectional observation.

C: It was found that there was a depression in a portion with a scale, and there was erosion to the gas with the naked eye without observing the cross section.

As shown in Table 7, it can be seen that forming a coating layer by coating the coating liquid of this example on the surface of the refractory as a base material has an effect of improving the corrosion resistance of the refractory. At least, in the case of a ceramic fiber block having an upper limit of use temperature of 1260°C, for Scale 1, the coating layer by all the coating liquids tested showed an excellent effect of improving corrosion resistance. Further, from the results of Scale 2, when the alumina (Al ₂ O ₃ ) content was 50% by mass or more as a solid content in the coating liquid at least, there was a tendency that a higher effect of improving corrosion resistance was obtained.

(Experimental Example 7)

This example shows the result of conducting an experiment to evaluate another effect of improving corrosion resistance using some of the coating solutions (test agents 2, 14, 36, 38, 39, 41) shown above.

<Preparation of refractory test body>

As a refractory material serving as a base, a ceramic fiber block having a maximum use temperature of 1260°C and a 10 cm square was prepared as in Experimental Example 6, and a pit to receive molten aluminum to be described later was provided on the surface thereof. A coating solution (test agent) was applied to the surface of the ceramic fiber block, as thin as possible, and the entire surface of the surface was covered as in the case of Experimental Example 6. Thereafter, by heating at 110° C. for 12 hours to dry the coating solution, a refractory test body having a coating layer having a thickness of 0.3 mm or less on the surface of the ceramic fiber block as a base material was obtained.

<corrosion test>

As a material causing corrosion of refractory, an aluminum alloy molten metal was assumed, and an aluminum alloy ingot (10 g) of ADC12 was prepared. After placing the aluminum alloy ingot in the pit of the ceramic fiber block and inserting it into the heating device, the temperature in the device was raised to 800°C at a heating rate of 150°C/hour to melt the aluminum alloy, and then the temperature of 800°C was increased. Hold for 10 hours. Thereafter, the refractory test body was taken out of the heating device, and the state of corrosion was evaluated by visual observation and cross-sectional observation. For comparison, the same test was carried out for a test specimen in which an aluminum alloy ingot was placed directly in a pit of a ceramic fiber block having no coating layer. The results are shown in Table 8. In addition, the meaning of the symbols shown in the "corrosion resistance" column in Table 8 is as follows.

A: Visual and cross-sectional observation showed no erosion to the gas.

B: Although it cannot be confirmed with the naked eye, erosion of the gas was observed by sectional observation.

As shown in Table 8, it can be seen that the ability to form a coating layer by coating the coating liquid of this example on the surface of the refractory as a base material has an effect of improving the corrosion resistance of the refractory.

Claims (10)

As a coating liquid for application to refractories,
100 parts by mass of moisture,
10 to 60 parts by mass of an inorganic binder, and
0.2 to 2 parts by mass of a swellable clay mineral,
It contains 10 to 120 parts by mass of radiation scattering material,
The radiation scattering material,
As a ceramic fiber composed of fibrous particles containing Al ₂ O ₃ , ceramic fiber having an average fiber length of 100 μm or less and/or,
It is selected from the group consisting of alumina powder, silica powder, titania powder, chromia powder, yttria powder, zirconia powder, lanthanum oxide powder, ceria powder, silicon carbide powder, silicon carbide aluminum powder, silicon nitride powder and boron nitride powder, 60 It contains one or two or more kinds of ceramic powder having a median diameter of ㎛ or less,
The swellable clay mineral is selected from the group consisting of kaolinite, haloysite, smectite, mica, vermiculite, chlorite, imogolite, allophane, sepiolite, valegilsite and gibsite. The coating liquid according to claim 1, wherein the coating liquid contains only any one of the group consisting of the ceramic fiber and the ceramic powder as the radiation scattering material. The coating solution according to claim 2, wherein the coating solution contains only one of the ceramic fibers or the alumina powder as the radiation scattering material, and the content of Al ₂ O ₃ relative to the total solid content of the coating solution is 50% by mass or more. . The coating liquid according to claim 1, wherein the radiation scattering material comprises the ceramic fiber and at least one ceramic powder. The coating liquid according to claim 4, wherein the content of the alumina powder is 30 parts by mass or less. The coating liquid according to claim 4 or 5, wherein the coating liquid has an Al ₂ O ₃ content of 50 mass% or more with respect to the total solid content. The coating liquid according to any one of claims 1 to 5, wherein the coating liquid has a viscosity of 20 Pa·s or less. The coating liquid according to any one of claims 1 to 5, wherein the coating liquid is configured to maintain a state in which the solid content is dispersed in water for one or more days. delete Preparing a coating solution according to any one of claims 1 to 5,
Applying the coating solution on a substrate composed of refractory material, and
Including the step of forming a coating layer on the substrate by drying the coating solution,
Method for producing a refractory material having a coating layer.