JPH03163174A - Heat-insulating coating agent and process for coating with same - Google Patents

Abstract

PURPOSE:To obtain a heat-insulating coating agent which can form a coating layer having a high efficiency of heat reflection a high effect of heat insulation and surface smoothness by mixing at least a binder with a micaceous graphite powder of a particle diameter in a specified range and a solvent. CONSTITUTION:A heat-insulating coating agent is obtained by mixing at least a binder (e.g. a thermosetting resin such as a phenolic resin or an epoxy resin or petroleum- or coal-derived pitch) with a micaceous graphite powder of a particle diameter of 0.1-500mu and a solvent (e.g. water or methanol). this coating agent can form a coating layer having an increased efficiency of heat reflection, a high effect of heat insulation and surface smoothness and excels in heat insulation especially in a temperature range above 2000 deg.C in which heat transmission by radiation is predominant. This agent can be applied desirably to a furnace wall heat-insulating material for high-temperature furnaces.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat-resistant coating agent suitably applied to a furnace wall insulation material of a high-temperature furnace, and a coating method using the same.

[Prior Art and Problems to be Solved by the Invention] Conventionally, in order to improve the heat insulation properties of high-temperature heating furnaces, heat insulating materials for furnace walls, such as carbon fiber felt, have been used. This heat insulating material needs to have high wind resistance and be able to prevent processed materials from entering the heat insulating material. Therefore, a graphite sheet is attached to the surface of the furnace wall heat insulating material. but,
In this method, if the surface of the heat insulating material is not smooth and has a complicated shape such as a curved surface or uneven shape, it is difficult to adhere the graphite sheet to the surface of the heat insulating material in close contact with the surface of the heat insulating material.

In view of the above points, coating agents containing soil graphite or artificial graphite are applied to the surface of the heat insulating material. However, in this method, the surface of the coating layer lacks smoothness and lacks gloss, and the effect of suppressing radiant heat transfer is small.

Further, due to the shape of soil graphite or artificial graphite, a W:t gap occurs between graphite particles in the coating layer, making it difficult to increase heat reflection efficiency and, by extension, heat insulation efficiency. Furthermore, the coating layer formed from the graphite-containing coating agent does not have sufficient mechanical strength, and therefore not only cannot reinforce the heat insulating material, but also peels off from the heat insulating material. Therefore, it is difficult to maintain high heat reflection efficiency and heat insulation efficiency over a long period of time, and the life of the insulation material is also shortened.

An object of the present invention is to provide a heat-insulating coating agent that can improve heat reflection efficiency and wind resistance, and form a coating layer with high heat-insulating efficiency and surface smoothness.

Another object of the present invention is to provide a heat-insulating coating agent that, in addition to the above-mentioned properties, can form a coating layer with excellent mechanical strength, reinforce a heat-insulating material, and extend the life of the heat-insulating material. be.

Furthermore, another object of the present invention is to provide a coating method that can impart the above-mentioned excellent properties.

[Takeshi Sakaki of the Invention] The present invention provides at least a binder and a particle size of 0. 1-5
To provide a heat-insulating coating agent containing 00 μι scale graphite powder and a solvent.

In addition to the above-mentioned certain amount, the present invention also provides fiber length of 0.01 to 1.
．． Provided is a heat-insulating coating agent containing fibers or carbon fibers that can be made into carbon fibers with a diameter of 0 mm and/or powder or carbonaceous powder that can be made into carbon fibers with a particle size of 1 to 200 μm.

Furthermore, the present invention provides a coating method in which each of the above heat-insulating coating agents is applied to the surface of a heat-insulating material and carbonized or graphitized.

Furthermore, the present invention provides a coating in which each of the above-mentioned heat-insulating coating agents is applied to the surface of a heat-insulating material, the coating agent is pressurized with a mold in an uncured state, heat-formed, and then finally carbonized or graphitized. provide a method.

The definitions of terms used in this specification are as follows.

Carbon fiber refers to fiber that has been carbonized or graphitized.

Carbonization treatment refers to fibers that can be made into carbon fibers, for example, 45
It refers to firing treatment at a temperature of about 0 to 1500°C.

Graphitization treatment refers to firing treatment at a temperature of, for example, 1,500 to 3,000°C, and even if it does not have a graphite crystal IR structure, if it is treated at the above temperature, it is considered to have been graphitized. To tell.

As the binder contained in the coating agent of the present invention,
Examples include thermosetting resins such as phenolic resins, furan resins, urea resins, melamine resins, unsaturated polyesters, diallyl phthalate resins, epoxy resins, polyurethanes, polyimides, thermosetting acrylic resins, petroleum or coal pitch, etc. Ru. One or more types of these binders can be used. Among these binders, thermosetting resins such as phenol resins and furan resins, which have a large residual carbon content during carbonization or graphitization and have excellent adhesive properties, are preferred.

Unlike the soil graphite and artificial graphite, which are non-scaly, the scaly graphite powder has a scaly shape, and therefore has excellent surface smoothness and hiding properties of the coating layer. In particular, with soil graphite and artificial graphite, gaps occur between graphite particles in the coating layer, whereas in the case of scale graphite powder, graphite powder is arranged in layers within the coating layer, and the gaps between graphite particles are extremely small. Or no gap is created. In addition, in the high temperature range of 2000℃ or higher, the proportion of radiation heat transfer in the thermal conductivity is dominant, but scaly graphite powder has a higher rate of heat transfer than soil graphite or artificial graphite.
Excellent in terms of heat reflectance and non-transmission. Therefore, when scaly graphite powder is used, radiation heat transfer can be suppressed and heat reflection efficiency and heat insulation efficiency can be significantly increased.

The scaly graphite powder used has a particle size of 0.1 to 500 μm, preferably 1 to 300 μm, which does not impair coating properties, dispersion stability, etc. If the particle size of the scaly graphite powder is less than 0.1 μm, the heat reflectance and heat insulation efficiency tend to decrease, and if it exceeds 500 μm, the coating properties and dispersion stability tend to decrease.

The content of scale graphite can be set as appropriate within a range that does not create gaps between graphite particles in the coating layer, but usually 20 to 300 parts by weight, preferably 30 to 30 parts by weight, of scale graphite per 100 parts by weight of the binder. It is 200 parts by weight. If the amount of scaly graphite is less than 20 parts by weight, it is difficult to reduce the thermal conductivity, and if it exceeds 300 parts by weight, it not only tends to reduce the applicability to the insulation material but also tends to peel off from the insulation material. .

It is preferable that the coating agent contains fibers or carbon fibers that can be made into carbon fibers together with the above-mentioned scale-like graphite. When fibers that can be made into carbon fibers or carbon fibers are used in combination, the coating layer can be reinforced and the strength of the heat insulating material can be increased. It also prevents the coating layer from peeling off from the insulation material.
The life of the insulation material can be significantly extended. Examples of fibers that can be made into carbon fibers include fibers made from acrylonitrile, cellulose, rayon, phenol resin, etc., and examples of carbon fibers include carbon fibers made from these fibers. The carbon fibers may be of high strength type, high density type, high elasticity type, general purpose type, etc., and one or more types may be used. In addition,
A mixture of fibers that can be made into carbon fibers and carbon fibers may be used. The above-mentioned fibers that can be made into carbon fibers and carbon fibers may have an appropriate fiber diameter of 5 to 30 μm, for example.

Fibers that can be made into carbon fibers or carbon fibers have a fiber length of 0.
01 to 1.0 mm is used. Fiber length is 0.0
If it is less than 1mm, the reinforcing property etc. will not be sufficient and 1.0m
If it exceeds m, it is difficult to obtain a uniform coating agent. Preferred fibers are milled fibers and milled fiber-like fibers.

The above-mentioned fibers that can be made into carbon fibers and carbon fibers can be used within a range that does not impair properties such as reinforcing properties, and are usually 10 to 150 parts by weight, preferably 25 to 12 parts by weight, based on 100 parts by weight of the binder.
5 parts by weight. If the fiber content is less than 10 parts by weight, it is difficult to ensure sufficient reinforcing properties, and if it exceeds 150 parts by weight, it is difficult to mix uniformly. In addition,
Mixing these carbon fibers helps increase reinforcing properties, but has little effect on thermal conductivity.

Furthermore, the coating agent, together with at least flaky graphite,
Preferably, it contains scale-like graphite, fibers or carbon fibers that can be made into carbon fibers, and powder or carbonaceous powder that can be made into carbonaceous material with a particle size of 1 to 200 μm, preferably 1 to 80 μm. When the particle size of the powder is less than 11, the adhesion between the coating layer and the heat insulating material is low, and when it exceeds 200 μm, the applicability and dispersion stability tend to deteriorate.

Examples of the powder include small carbonaceous spheres such as mesocarbon microbeads, coke breeze, and fillers that can be carbonized or graphitized, such as bulk mesophase carbon obtained by making infusible crushed pitch products. 5 coal etc.
It may also be low-temperature calcined coke that is carbonized at a low temperature of about 00°C and pulverized. Among these carbonaceous powders, mesocarbon microbeads are preferred. These mesocarbon microbeads have a true spherical shape and are easily dispersed uniformly in a coating agent containing scaly graphite powder. It also reinforces the coating layer and improves the adhesion between the coating layer and the heat insulating material. Mesocarbon microbeads are made from approximately 400% of coal tar, pitch vacuum distillation residue, etc.
Means spherical bodies with a particle size of about 1 to 80 μm that are heat-treated at ~500° C. and separated from the pitch matrix by using the generated mesophase small spheres as quinoline insoluble matter.

In the coating layer, the scaly graphite powder is oriented in a layered manner, and the adhesion between the coating layer and the heat insulating material tends to decrease. On the other hand, when using powder from the previous generation, the powder fills the voids existing on the surface of the insulation material, increasing the bonding area and further increasing the adhesion due to the anchor effect. No surface cracks or peeling occurs.

These powders can be used alone or in combination of two or more. The content of the powder can be selected within a range that reinforces the coating layer and does not impair the adhesion with the heat insulating material, but it is usually 20 to 300 parts by weight per 100 parts by weight of the binder. is about 50 to 150 parts by weight. If the content of the powder is less than 20 parts by weight, it is difficult to improve the reinforcing properties and adhesion of the coating layer, and if it exceeds 300 parts by weight, the coating properties decrease and the coating layer becomes It becomes easy to peel off.

The coating agent of the present invention further contains a solvent.

Examples of the solvent include water, alcohols such as methanol, ethanol and isopropanol, aliphatic or alicyclic hydrocarbons such as hexane, octane and cyclohexane, aromatic hydrocarbons such as benzene, toluene and xylene, dichloromethane and trichloro. Halogenated hydrocarbons such as methane and ethylene chloride, esters such as ethyl acetate, ethers such as diethyl ether, dioxane and tetrahydrofuran, ketones such as acetone and methyl ethyl ketone, and mixed solvents thereof can be used.

The solvent can be selected depending on the type of binder.

In addition, the amount can be set as appropriate depending on the viscosity of the coating agent within a range that does not impair the coating properties, etc., but it is usually 100%
The amount of the solvent is 100 to 500 parts by weight, preferably 150 to 400 parts by weight.

When the amount of the solvent is less than 100 parts, the viscosity of the coating agent is high, and minute air is likely to be entangled in the coating film, making it difficult to form a coating layer that is uniform and has a smooth surface. Furthermore, when a heat insulating material treated with a coating agent is carbonized or graphitized, minute air expands, the surface of the coating layer becomes a bolus, the surface smoothness is impaired, and the amount of radiant heat transfer becomes dominant, especially at temperatures above 2000℃. It is difficult to reduce the amount of radiant heat transfer. Furthermore, if the amount of solvent exceeds 500 parts by weight, the concentration of the components in the coating agent decreases, and in order to ensure a predetermined coating thickness, it is necessary to increase the number of coatings, resulting in a decrease in workability.

The coating agent of the present invention may contain various additives such as a dispersant, a viscosity modifier, and a filler within a range that does not impair the heat insulation properties.

The coating agent of the present invention may be applied to a heat insulating material and cured by heating or at room temperature to form a coating layer, but in order to further improve the strength and heat insulation efficiency of the coating layer, it can be applied as follows. Preferably, a coating layer is formed.

That is, the coating method of the present invention includes at least the following:
The method includes a coating step of applying the coating agent to the surface of the heat insulating material, and a carbonization or graphitization treatment step. A preferred coating method includes, between the coating step and the carbonization or graphitization step, a molding and heating step in which the coating agent is pressurized and heated with a mold in an uncured state.

As a coating means in the coating step, conventionally used methods can be used, such as brush coating, spatula coating, and spray coating methods. The thickness of the coating layer is not particularly limited as long as it can ensure heat insulation, but it is usually 0.1 to 5.
mms is preferably about 0.2 to 2.5 mm.

Furthermore, the mold used in the molding and heating step is preferably a mold with a smooth surface, particularly a mold with a mirror finish, in order to impart surface smoothness. The shape of the mold can be selected depending on the shape of the heating furnace to which the molded insulation material is applied. Examples include a pair of flat plates, a pair of male and female molds, and a mold composed of a cylindrical body and a molding member that can press the cylindrical body from the outside. In addition, in the case of a heat insulating material whose surface after applying the coating agent has a shape other than a flat surface, the use of a mold can be omitted.

Pressure conditions in the molding and heating process can be set within a range that allows a smooth surface to be formed on the coating layer, and the heating temperature is set to a temperature that allows curing depending on the type of resin that can be carbonized or graphitized. The temperature is about 170°C.

When pressurizing and heating the insulation material with the coating layer formed, in order to improve the release property from the mold, a release paper is placed between the coating layer and the mold, and silicone oil, etc. is applied to the mold surface. A mold release agent may be applied.

When the insulation material with a coating layer is heated under pressure in a mold, after demolding, the coating layer not only becomes smooth to correspond to the smooth surface of the mold, but also forms a dense and uniformly thick coating layer. Since it is possible to form a coating layer with extremely high heat reaction q1 efficiency, high strength and excellent surface smoothness, it is possible to provide excellent heat insulation properties. In particular, when a mold with a mirror finish is used, the mirror surface of the mold is transferred to the surface of the coating layer, making it possible to improve the mirror finish and greatly improve heat reflection efficiency. Furthermore, since the coating layer is cured by applying heat and pressure, not only the strength of the coating layer is increased, but also the heat insulating material can be reinforced and the mechanical strength can be increased.

The carbonization or graphitization process can be carried out in an inert atmosphere such as nitrogen gas or helium gas or in vacuum.

The coating agent and coating method of the present invention are suitably applied to various materials that require heat insulating properties, particularly to heat insulating materials used in a high temperature range of 2000° C. or higher.

[Effects of the Invention] The heat-insulating coating agent of the present invention can enhance the heat reflection effect, form a coating layer having high heat-insulating efficiency and surface smoothness. In particular, it has excellent heat insulation properties in a temperature range of 2000° C. or higher, where radiation heat transfer is predominant.

In addition, fibers that can be made into carbon fibers with a fiber length of 0.01 to 1.0 mm, or heat-insulating coating agents containing carbon fibers, and powders or carbonaceous powders that can be made into carbon with a particle size of 1 to 1-00μ dust. In addition to the above-mentioned properties, the heat-insulating coating agent containing the above can form a coating layer with excellent mechanical strength, can reinforce the heat-insulating material, and can extend the life of the heat-insulating material.

Furthermore, according to the coating method of the present invention, it is possible to form a coating layer that has excellent surface smoothness, thermal insulation efficiency, and mechanical strength. The life of the material can be extended.

[Example] Hereinafter, the present invention will be explained in more detail based on practical examples.

Example 1 Phenol resin (manufactured by Gunei Chemical Industry ■, trade name PI, 38
20^) 100 parts by weight, graphite scales (manufactured by Nippon Graphite Industries ■,
100 parts by weight of CB-150 (trade name, average particle size 150 μm), 300 parts by weight of methanol, and 50 parts by weight of milled carbon fiber (manufactured by Donac Oki, trade name Dona Carbo S243, fiber length 0.5 mm) were uniformly mixed and dispersed. A coating agent was prepared.

The coating process of applying this coating agent to one side of a 30 mm thick heat insulating material made of carbon fiber felt with a brush and the drying process were repeated 4 to 5 times until the coating thickness of the coating agent was 0.6 mm. And so. Then, the temperature is 150℃
After curing the coating layer by heating, carbonization treatment was performed at a temperature of 1000° C. for 2 hours in a nitrogen gas atmosphere, and graphitization treatment was performed at a temperature of 2300° C. for 2 hours. Note that the surface of the coating layer after the graphitization treatment was smooth and glossy.

Implementation f! AI 2 Example except that 50 parts by weight of mesocarbon microbeads (manufactured by Osaka Gas, trade name MPB-20, average particle size 401) were used instead of 50 parts by weight of the milled carbon fiber of Example 1. A coating agent was prepared in the same manner as in Example 1.

The coating process of applying this coating agent to one side of the heat insulating material of Example 1 with a brush and the drying process of drying it were repeated 1 to 3 times, and the coating thickness of the coating agent was 0.6 mm, and the same procedure as in Example 1 was carried out. Then, carbonization and graphitization were carried out. Note that the surface of the coating layer after the graphitization treatment was smooth and glossy.

Comparative Example 1 The heat insulating material used in Example 1 was tested without being coated.

Comparative Example 2 A coating agent was prepared in the same manner as in Example 2, except that soil graphite (manufactured by Kuchimoto Graphite Industries, average particle size: 100 μl) was used instead of the scaly graphite of Example 1.

Further, the obtained coating agent was applied to a heat insulating material having a thickness of 30 mm in the same manner as in Example 1, dried, hardened, and subjected to carbonization and graphitization treatment. The coating layer after graphitization did not have sufficient surface smoothness and lacked gloss.

Example 3 Furan resin (manufactured by Hitachi Chemical Oki, trade name Hitafuran 30)
1) 100 parts by weight, scaly graphite (manufactured by Nippon Graphite Industries F#, trade name Cf3-150, average particle size 150 μm), 50 parts by weight, 20 parts of methyl ethyl ketone, and milled carbon fiber (manufactured by Donac ■, trade name Dona Carbo S243, A coating agent was prepared by uniformly mixing and dispersing 100 parts by weight (fiber length: 0.5 mm).

This coating agent was applied to a heat insulating material with a thickness of 30 mm in the same manner as in Example 1 and dried, resulting in a coating film thickness of 0.6+.
After forming and curing a coating layer of 100 nm thick, it was carbonized and graphitized. Note that the surface of the coating layer after the graphitization treatment was smooth and glossy.

Example 4 Instead of 50 parts by weight of scaly graphite in Example 3, 10 parts by weight of scaly graphite
Using 0 parts by weight and replacing milled fiber,
The coating layer was shaped and cured in the same manner as in Example 3, except that 100 parts by weight of the mesocarbon microbeads used in Example 2 were used, and then carbonized and graphitized.

Note that the surface of the coating layer after the graphitization treatment was smooth and glossy.

Example 5 100 parts by weight of furan resin and 5 parts by weight of scaly graphite were prepared in the same manner as in Example 3 without using milled carbon fibers.
A coating agent containing 0ffl parts and 200 parts by weight of methyl ethyl ketone and not containing milled carbon fibers was prepared. Further, in the same manner as in Example 1, this coating agent was applied to a heat insulating material with a thickness of 30 mm, dried to form a coating layer with a coating thickness of 0.6 mm, and after curing, carbonization and graphitization treatments were performed. Note that the surface of the coating layer after the graphitization treatment was smooth and glossy.

The thermal conductivity of the heat insulating materials obtained in Examples 1 to 5, Comparative Example 1, and Comparative Example 2 was determined, and the results shown in FIG. 1 were obtained. In addition, in FIG. 1, Example 1 and implementation VA
There was almost no difference in thermal conductivity between the heat insulating materials of J2 and between the heat insulating materials of Examples 3 to 5.

As is clear from FIG. 1, the heat insulating materials of each example had lower thermal conductivity than the heat insulating materials of Comparative Example 1 and the heat insulating material of Comparative Example 2, and were superior in heat insulation properties. In particular, at a temperature of 2500°C, the heat insulating materials of Examples 1 and 2 coated with a coating agent containing scaly graphite had a thermal conductivity of 0.0. 2Kcal/m-hr・”C
The thermal conductivity of the insulation materials of Examples 3 to 5 is smaller than that of the insulation material of Comparative Example 2 by 0.15 Kcal/m-hr-"C.
It is small, and its insulation properties at high temperatures have improved by about 30%.

Further, the heat insulating materials of Examples 3 to 5 and Comparative Example 1 were subjected to a bending test in which the coated surface was bent on the tensile side, and the bending strength was measured, and the results shown in the table were obtained.

Coating with a surface agent can strengthen the insulation. Further, when coating with the coating agent of Example 3 containing milled carbon fibers, the bending strength was improved by about 60% compared to the coating agent of Example 5 which did not contain milled carbon fibers. Furthermore, when coating with the coating agent of Example 4 containing mesocarbon microbeads, the sprouting strength was improved by about 100% compared to the coating agent of Example 5.

Example 6 50 parts by weight of phenolic resin of Example 1, 50 parts by weight of furan resin of Example 2, 200 parts by weight of scaly graphite of Example 1,
A coating agent was prepared by uniformly mixing and dispersing 50 parts by weight of the milled carbon fiber of Example 1 and 300 parts by weight of methanol.

The obtained coating agent was applied to one side of the heat insulating material used in Example 1 so that the film thickness after drying was 0.6 mm,
While the coating layer was in an uncured state, it was heated under pressure using a mirror-finished hollow mold coated with a release agent to cure the coating agent. Next, carbonization and graphitization treatments were carried out in the same manner as in Example 1.

Example 7 Coating was carried out in the same manner as in Example 6, except that 50 parts by weight of the mesocarbon microbeads of Example 2 were used instead of the milled carbon fibers of Example 6, using a mirror-finished oval mold. The agent was cured. Next, Example 1
Carbonization and graphitization were carried out in the same manner as above.

Examples 8 and 9 The coating agents obtained in Examples 6 and 7 were used in Example 1.
It was applied to one side of the heat insulating material used in Example 1 so that the film thickness after drying was 0.6 mm, and it was cured in the same manner as in Example 1 without being pressurized and heated with a mold, and then subjected to carbonization and graphitization treatment. .

When the thermal conductivity of the heat insulating materials obtained in Examples 6 to 9 was measured, the results shown in FIG. 2 were obtained.

Note that there is almost no difference in thermal conductivity between the insulation materials obtained in Example 6 and Example 7, and there is almost no difference in thermal conductivity between the insulation materials obtained in Example 8 and Example 9. There wasn't.

From these results, the heat insulating materials of Examples 6 and 7, which were pressurized and heated using a hollow mold, had lower thermal conductivity in the high temperature range than the heat insulating materials obtained in Examples 8 and 7, and had a lower thermal conductivity in the high temperature range. She had excellent sex.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are graphs showing the results of an example and a comparative example, respectively.

Claims (1)

[Scope of Claims] 1. A heat-insulating coating agent comprising at least a binder, scaly graphite powder having a particle size of 0.1 to 500 μm, and a solvent. 2. The heat-insulating coating agent according to claim 1, which contains fibers capable of being made into carbon fibers or carbon fibers having a fiber length of 0.01 to 1.0 mm. 3. The heat-insulating coating agent according to claim 1 or 2, which contains carbonizable powder or carbonaceous powder with a particle size of 1 to 200 μm. 4. A coating method comprising applying the heat-insulating coating agent according to any one of claims 1 to 3 onto the surface of a heat-insulating material and subjecting it to carbonization or graphitization treatment. 5. The heat-insulating coating agent according to any one of claims 1 to 3 is applied to the surface of the heat-insulating material, and in an uncured state, the coating agent is pressurized with a mold and heat-formed, and then carbonized or A coating method characterized by graphitization treatment.