JP2001278680A - Coating material for inorganic fiber reinforced article and coated article using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating material with good applicability for forming a surface layer free from cracking or peeling-off on an inorganic fiber reinforced molded article. SOLUTION: The coating material contains the inorganic fiber of 1-20 wt.%, an inorganic particle of 60-90 wt.%, an inorganic binder of 2-30 wt.% and an organic binder of 0.5-2 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for coating (covering) the surface of a molded article such as a heat insulating material made of ceramic fibers, and a coated inorganic fiber molded article.

[0002]

2. Description of the Related Art There is known an inorganic fibrous molded product obtained by molding an aggregate of inorganic fibers such as silica fiber and silica alumina fiber, and firing the aggregate if necessary. These inorganic fibrous formed bodies are lightweight and have excellent heat insulating properties, and are used as various heat insulating materials and heat-resistant materials.

[0003] However, inorganic fibrous molded articles have a problem of scattering of fiber material. For example, when an inorganic fibrous molded body is used as a material for a furnace for heat-treating electronic components or as a heat insulating material, contamination due to scattering of fibers (the presence of invisible fibers may cause defects for electronic components) Becomes a problem. In addition, the powderiness caused by scattering of fibers is also a problem in fields other than the electronic component field.

As a method for avoiding such a problem of scattering of fibers, there is a technique of coating the surface of a fibrous formed body with a glass layer. For example, Japanese Patent Publication No. 57-135
Japanese Patent Application Publication No. 14 and Japanese Unexamined Patent Application Publication No. 1-219083 describe a technique for coating a glass layer on the surface of a fibrous formed body, although the purpose is different.

[0005]

By using the technique for forming a glass layer as described above, scattering of fibers from a fibrous formed body as a substrate can be suppressed. However, when the fibrous formed body is used as a heat insulating material, there arises a problem that cracks are formed in the coated glass layer or the glass layer is separated.

This is due to the difference in the coefficient of thermal expansion between the fibrous molded article as the base material and the coating layer. That is, when heated, the state of thermal expansion (or thermal shrinkage) between the base material and the coating layer becomes different, and cracks occur in the thin and weak brittle coating layer. It is peeled off from. In addition, since the inorganic fibrous formed body is basically a porous material, there is a problem when it is used where air permeability and airtightness are required. For example, when a gas harmful to the human body or a gas that is harmful to the environment is used or generated in a furnace when used as a heat insulator for a furnace, an inorganic fiber molded body is used as a heat insulator. With only the structure, gas leakage may be a problem.

An object of the present invention is to solve this problem. That is, in the coating material for the inorganic fibrous molded article, (1) function as a coating member for suppressing scattering of fibers;
(3) It can be formed with good workability. (4)
It is a main object of the present invention to solve the problem of having airtightness and non-breathability despite being an inorganic fibrous formed article.

[0008]

In order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that 1 to 20% by weight of inorganic fibers having a fiber length of 1 to 200 μm and 60 to 90% by weight of inorganic particles.
And at least 2 to 30% by weight of one or more inorganic binders selected from colloidal silica, alumina sol, aluminum phosphate, sodium silicate and glass frit, and 0.5 to 2% by weight of an organic binder. The gist of the present invention is that it is a coating material for an inorganic fibrous formed article made of

The silica-alumina fiber is an inorganic fiber composed of a silica component and an alumina component (or containing them as main components). The mullite fiber is a kind of silica-alumina fiber in which a silica component and an alumina component are blended at a specific ratio and have a predetermined crystal structure. It should be noted that a similar relationship exists for silica alumina particles and mullite particles. In the present invention, the fiber length of the inorganic fiber is defined as an average value, and its variation is ± 50.
% Is preferable.

The coating material according to the first aspect of the present invention is in the form of a mortar or a solution having a lower viscosity (a solution is referred to as having a high viscosity but is referred to for convenience). And further dried and, if necessary, baked to obtain a coat layer.

According to a second aspect of the present invention, in the first aspect, the shot content in the inorganic fiber is 5% by weight or less, and the diameter of the inorganic fiber is 0.01 to 5 μm (where the diameter of the inorganic fiber is the fiber length). The gist is that the inorganic particles have a diameter of 0.5 to 10 μm.

According to a third aspect of the present invention, in the first or second aspect, the coating material has a viscosity of 5 × 10 ³ cp to 150 × CP.
It should be 10 ³ cp.

The invention according to claim 4 is the invention according to claims 1 to 3.
The gist of the present invention is an inorganic fibrous molded article obtained by applying the coating material on the surface.

Examples of the inorganic fibrous molded article to be used in the present invention include those obtained by binding an inorganic fiber material with an organic binder, those obtained by molding a mixture of an inorganic fiber material and an inorganic binder, and those molded articles. Includes fired ones. Further, the coating layer includes both a coating layer which is not fired and is simply dried after application of the coating material, and a coating layer which is further baked. Further, the formation of the coat layer may be performed before or after the firing of the inorganic fibrous formed body as the base material.
Further, as the inorganic fibrous molded product, a product obtained by further mixing inorganic particles with an inorganic fiber material, or a product obtained by using an organic binder and an inorganic binder in combination can be employed.

[0015] The invention of claim 5 is the gist of claim 4, wherein the inorganic fiber material constituting the inorganic fibrous formed body and the inorganic fiber material in the coating material are the same.

According to a sixth aspect of the present invention, in the fourth or fifth aspect, the air permeability of the inorganic fibrous formed body is 1.0 × 10 5
It should be at least ⁸ (Pa · s / m ³ ).

According to a seventh aspect of the present invention, there is provided an inorganic material having a surface coated with a coating layer containing 1 to 20% by weight of an inorganic fiber and having an air permeability of 1.0 × 10 ⁸ (Pa · s / m ³ ) or more. The gist is a fibrous formed body.

[0018] The invention of claim 8 is the invention according to claim 7, wherein the coating layer contains 60 to 90% by weight of inorganic particles and one or more selected from colloidal silica, alumina sol, aluminum phosphate, sodium silicate and glass frit. The gist of the present invention is an inorganic fibrous formed article containing at least 2 to 30% by weight of a kind of inorganic binder.

According to claim 7 or claim 8, the inorganic fiber in the coating layer has a fiber length of 1 to 200 μm, a shot content of 5% by weight or less, and a diameter of the inorganic fiber of 0.01 to 5 μm. (The diameter of the inorganic fiber is shorter than the fiber length).

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to obtain a coating material according to the present invention, for example, inorganic particles and an organic binder are mixed, an inorganic binder is added thereto, an inorganic fiber is further added, and water is further added to adjust the viscosity. Obtained by: And
Applying the coating material to an inorganic fibrous molded body as a substrate,
By further drying and firing, a ceramicized coating layer is obtained. In an actual use situation, it is possible to appropriately select a usage method in which the composition is used in a state where it is not fired and is heated by receiving heat during use, or a usage method which is used in a state where it is fired after drying.

The reason why the fiber length of the inorganic fiber material is set to 1 to 200 μm is to satisfy the requirements required for the coating material. The inorganic fiber material reinforces the coat layer obtained by its presence, and makes it difficult for cracks to occur. However, if the fiber length is 1 μm or less, the reinforcing effect is small, and a coating layer having the desired strength cannot be obtained. On the other hand, if the fiber length is 200 μm or more, the fibers are aggregated or entangled when the coating material is applied, so that it is not possible to obtain appropriate dispersibility. That is,
If the fibers are agglomerated or entangled in the coat layer and the proper dispersibility is not obtained, local coarseness and denseness are generated in the material of the coat layer, and cracks are easily generated. Preferably, the length is 200 μm or less.

Further, the reason why the mixing ratio of the inorganic fiber is set to 1 to 20% by weight is to satisfy the applicability (easiness of application) while maintaining the applicability.
This is to obtain the necessary reinforcing effect at the same time. The inorganic fiber material in the coating material is preferably the same as the inorganic fiber material contained in the base material. By doing this,
The coefficient of thermal expansion or the thermal properties of the substrate and the coat layer can be made close to each other, and the problems of cracks and peeling of the coat layer can be further suppressed.

The reason for blending the inorganic particles is to give the coat layer an appropriate strength. The mixing ratio of inorganic particles is 6
If it is 0% by weight or less, the required strength cannot be obtained, and if the compounding ratio is 90% by weight or more, the reinforcing effect of the inorganic fibers is impaired and the strength of the coat layer is insufficient, which is not preferable.

The inorganic binder is necessary for imparting a certain degree of strength to the obtained coat layer, and its mixing ratio is suitably from 2 to 30% by weight. If the compounding ratio of the inorganic binder is smaller than this range, the required strength cannot be obtained, which is not preferable. On the other hand, if it is more than this range, the proportion of the inorganic fibers and inorganic particles that contribute to the reinforcing effect and the high strength is relatively small, and the strength of the coat layer is undesirably reduced.

The organic binder plays an important role in facilitating the application of the coating material and obtaining a coating layer having required physical properties. By making the organic binder 0.5 to 2% by weight, the elongation (good coatability) of the coating material required for good coatability can be obtained, and the water retention required for forming the coat layer. Is obtained.

If the water retention is not appropriate, the inorganic binder such as colloidal silica will soak into the base material when the coating material is applied, and the binding effect necessary to hold the coating layer will not be obtained. Further, when the inorganic binder permeates the base material, the inorganic particles float on the surface, and the inorganic particles are easily scattered contrary to expectations. In other words, it is rather powdery. In addition, by setting the water retention to an appropriate value, a material in which the inorganic binder permeates the base material appropriately, the bonding strength between the base material and the coat layer is increased, and the coat layer is hardly peeled from the base material can be obtained. By setting the amount of the organic binder in the above range, the coating material having the above-described appropriate water retention can be obtained.

In the present invention, the shot content in the inorganic fibers is 5% by weight or less, and the diameter of the inorganic fibers is 0.0% or less.
By setting the particle length to 1 to 5 μm and the particle diameter to 0.5 to 5 μm, together with the fiber length to 1 to 200 μm, the coating property required for the coating material and the strength required for the obtained coating layer are obtained. (Strength that hardly causes cracks and hardly peels).

The above-mentioned shot refers to non-fibers which have not been converted into fibers in the process of producing inorganic fibers. The shot is generated by the fact that the leading end portion of the melted fiber that is flying when the starting material is skipped and fiberized is formed (the leading end portion of the fiber and the trailing portion becomes the fiber) finally remains. You. The shot generated in this way is 100 μm
Many have the above-mentioned diameters and have projections formed at the time of fiber production.

The thickness of the obtained coat layer (the coat layer in the final ceramic state) is 50 μm to 1 m.
m, preferably 50 μm to 500 μm, and the presence of a shot having a diameter of 100 μm or more is not preferable because it causes generation of lumps in the coat layer and unevenness on the surface of the coat layer.

The shot is generated by a typical method for producing inorganic fibers, such as a spinner method, a rotor method, a blowing method, or a modification thereof or a similar method. The use of shots is not preferable because when used as a coating material, the coatability is reduced and the uniformity of the obtained coat layer is impaired. In order to reduce the proportion of shots, the shots may be removed by sieving.

The diameter of the inorganic fiber used for the coating material is set to 0.0
The reason for setting the thickness to 1 to 5 μm is that if it is less than this range, the reinforcing effect is weak, and if it is more than this range, good dispersibility cannot be obtained, and the reinforcing effect as a fiber cannot be obtained in relation to the fiber length. is there.

If the particle diameter of the inorganic particles used in the coating material is 0.5 to 5 μm, it is unfavorable if the particle diameter is less than this range because the particles are bound between the fibers and the effect of reinforcing the coating layer becomes small. This is because the above-mentioned condition does not provide a state in which the fibers are well dispersed among the fibers, so that the effect of reinforcing the coat layer becomes small, and it becomes difficult to apply the coating material.

The viscosity of the coating material is 5 × 10 ³ cp to 1
By setting the content in the range of 50 × 10 ³ cp, it is possible to obtain the ease of application and the appropriate water retention required for the above-mentioned coating material. That is, it is difficult to directly evaluate the ease of application and water retention quantitatively directly, but it is easy to apply by adjusting the compounding amount of the organic binder and water so that the viscosity of the coating material falls within the above range. In addition, a coating material that can form a coating layer having appropriate water retention and required strength can be obtained.
As a coating method, a method using a brush, a spatula, a method using a spray, or any other coating method is used.

Since the inorganic fibrous molded article of the present invention has a coat layer formed on its surface, it has extremely low air permeability, and practically, an almost air-impermeable one can be obtained. The air permeability is 20 when the thickness of the coat layer is 0.5 mm.
× 10 ⁸ (Pa · s / m ³ ).

[0035]

EXAMPLE 1 In this example, 7.5 parts by weight of silica-alumina fibers containing 50% by weight of a silica component and 50% by weight of an alumina component were used as inorganic fibers, and alumina particles were used as inorganic particles.
6.0 parts by weight, 15.5 parts by weight of colloidal silica as an inorganic binder, 0.3 parts by weight and 0.7 parts by weight of polyethylene oxide and methyl cellulose as organic binders, respectively, and the shot content of the inorganic fiber was 3 parts. What was used by weight% or less was used. The average fiber length of the inorganic fibers was 50 μm, the fiber diameter was 2 μm, and the diameter of the inorganic particles was 3 μm.
μm was used.

First, alumina particles, polyethylene oxide and methylcellulose are mixed to form a mortar, then silica alumina fibers are added and kneaded, 50 parts by weight of water is further added, and the viscosity is 8 × 10 ³ cp. A coated material was prepared.

Apart from the above-mentioned coating material, an inorganic fibrous molded article formed by a dehydration molding method from a slurry obtained by mixing silica-alumina fiber and alumina particles each having a silica component and an alumina component in a proportion of 50% by weight and colloidal silica. Prepare

The above coating material is applied to the surface of the inorganic fibrous formed body, dried at 150 ° C. for 2 hours, and then baked at 1000 ° C. for 24 hours to coat the surface. An inorganic fibrous formed body on which a layer was formed was obtained. The inorganic fibrous formed body on which the coat layer is formed,
Even if a heating / cooling cycle of normal temperature → heating at 900 ° C. → normal temperature is applied 20 times, no cracks are generated in the coat layer or peeling from the coat layer from the base material, and no dust is observed from the surface. Was.

The inorganic fibrous molded article obtained in this example is
The gas flow resistance was 20 × 10 ⁸ (Pa · s / m ³ ), and it could be regarded as almost air-impermeable. Here, the ventilation resistance was obtained by measuring by a method according to ASTM C522-87. Further, in this embodiment, it is known that the ventilation resistance when no coat layer is formed is about 1 × 10 ⁶ (Pa · s / m ³ ). In order to lower the airflow resistivity, the thickness of the coat layer may be increased. However, if the coat layer is too thick, it takes time to form the coat layer, and the probability of occurrence of cracks increases. Conversely, if the coat layer is too thin, the effect of reducing the airflow resistivity will be reduced. From these facts, it is appropriate that the thickness of the coat layer is about 50 μm to 1 mm.

Here, first, inorganic particles, an inorganic binder, and an organic binder are mixed, and inorganic fibers are added thereto.
Although the procedure of adding water was adopted, a method of first dispersing inorganic fibers in water, adding inorganic particles thereto, further adding an inorganic binder, stirring, and finally adding an organic binder may be employed.

Example 2 In this example, as the inorganic fibers, 10 parts by weight of silica-alumina fibers containing 50% by weight of a silica component and 50% by weight of an alumina component were used, and alumina particles were used as inorganic particles.
9.0 parts by weight, 10.0 parts by weight of aluminum phosphate as an inorganic binder, 0.3 parts by weight and 0.7 parts by weight of polyethylene oxide and methylcellulose as organic binders are mixed, and the shot content of inorganic fibers is 3 parts.
What was used by weight% or less was used. Other points are the same as those in the first embodiment, and a description thereof will be omitted. In addition, it was confirmed that the obtained coated inorganic fibrous molded article had the same physical properties as in Example 1.

[0042]

According to the present invention, a coat layer which is easy to coat and which does not cause cracks in the obtained coat layer or peel off of the coat layer is formed on the surface of the inorganic fibrous molded article. As a result, an inorganic fibrous formed article having less dusting properties can be obtained. In addition, an inorganic fibrous molded article that can be regarded as practically impermeable can be obtained.

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Claims (9)

[Claims] 1. An inorganic fiber having a fiber length of 1 to 200 μm, 1 to 20% by weight, inorganic particles of 60 to 90% by weight, colloidal silica, alumina sol, aluminum phosphate, sodium silicate, and glass frit. A coating material for an inorganic fibrous molded product, comprising a composition containing at least 2 to 30% by weight of an inorganic binder and 0.5 to 2% by weight of an organic binder. 2. The method according to claim 1, wherein the shot content in the inorganic fiber is 5% by weight or less, and the diameter of the inorganic fiber is 0.01 to 5 μm (provided that the diameter of the inorganic fiber is shorter than the fiber length). ), And the diameter of the inorganic particles is 0.5
A coating material for an inorganic fibrous molded product, which has a thickness of from 10 to 10 μm 3. An apparatus according to claim 1 or claim 2, coating material of the inorganic fibrous molded body, wherein the viscosity of ^{5 × 10 3 cp~150 × 10 3} cp. 4. An inorganic fibrous formed body to which the coating material according to claim 1 is applied. 5. The inorganic fiber molded article according to claim 4, wherein the inorganic fiber material constituting the inorganic fiber molded article and the inorganic fiber material in the coating material are the same. 6. The inorganic fibrous formed body according to claim 4 or 5, wherein the inorganic fiber molded body has a gas flow resistance of 1.0 × 10 ⁸ (Pa · s / m ³ ).
An inorganic fibrous formed article characterized by the above. 7. The surface is coated with a coat layer containing 1 to 20% by weight of inorganic fibers, and has a permeability of 1.0 × 10
An inorganic fibrous molded product having a viscosity of ⁸ (Pa · s / m ³ ) or more. 8. The coating layer according to claim 7, wherein the coating layer contains 60 to 90% by weight of inorganic particles and one or more inorganic binders selected from colloidal silica, alumina sol, aluminum phosphate, sodium silicate, and glass frit. 2 to 30% by weight of an inorganic fibrous formed body. 9. The inorganic fiber in the coat layer according to claim 7, wherein the fiber length of the inorganic fiber is 1 to 200 μm,
An inorganic fiber molded article having a shot content of 5% by weight or less and an inorganic fiber diameter of 0.01 to 5 μm (provided that the diameter of the inorganic fiber is shorter than the fiber length).