JPS6021886A - Coating material for ceramic fiber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention: For ceramic fibers to be coated on the heat receiving side outer surface of a ceramic fiber insulation material formed into a block shape with 47 to 40% by weight, alumina content of 53 to 60%, fiber diameter of 2 to 3μ This relates to coating materials. More specifically, the present invention can reduce heat shrinkage of ceramic fibers and prevent reactions between ceramic fibers and scale by coating the outer surface of the heat-receiving side of ceramic fiber blocks. The present invention relates to a coating material for ceramic fibers that can impart wind speed resistance to ceramic fibers.

In recent years, insulation using ceramic fiber lining has been widely implemented in order to save energy in heating furnaces, soaking furnaces, tunnel kilns, etc., and remarkable energy saving effects have been obtained. Ceramic fiber insulation materials used for such insulation have a silica content of 47 to 40% by weight,
Ceramic fibers with an alumina content of 53 to 50% and a fiber diameter of 2 to 3 μm are wrapped in a case or the like, or ceramic fiber blankets are stacked in the thickness direction as described in JP-A-53-18609, and mutual contact is made. Commonly used are blocks whose surfaces are bonded together with adhesive and formed into a block shape, such as by bonding such blocks to the opposite wall with adhesive, or by fixing ceramic fiber blocks with studs. It will be constructed.

These ceramic fiber insulation materials have excellent insulation properties, are light, have a small heat storage liquid, are immersed in spalling resistance, and are immersed in various ways compared to traditional fireproof insulation bricks, so they can be used in various furnaces. It is used as an insulation material. However, although ceramic fiber insulation has the above-mentioned excellent properties, it has low strength, flexibility, and
At temperatures above 000°C, the amorphous state crystallizes (mainly produces mullite crystals), so the heating shrinkage becomes thick (,13
At 00°C, it exhibits a linear shrinkage of about 2 to 4%, so voids are created between the blocks, making it impossible to obtain the desired heat insulating effect. In addition, it has poor wind speed resistance, and the ceramic fibers are blown away at a wind speed of 21 J m /gee.

Furthermore, when iron oxide, which is expressed as scale, adheres to this block, fayalite, a low melting point substance, is formed and softens and melts. A coating material for 5y Kufu fiber is being tried.

For example, Japanese Unexamined Patent Publication No. 50-45709 discloses that the surface of a fibrous heat insulating material is coated with a silicic acid glaze to make it ceramic-like. JP-A-52-1
Publication No. 40509 discloses that a metal mesh is fixed on top of a layer of ceramic fibers attached to a casing steel plate, and a monolithic refractory is coated on top of the wire mesh to prevent the layer of ceramic fibers from peeling off due to wind speed or dust. This is disclosed.

JP-A-54-113609 discloses ceramic fibers with improved heat resistance and wind speed resistance by applying a specific glue-like coating material to the interlayers and all or part of the surface of a flaky ceramic fiber laminate. Disclosed. Japanese Unexamined Patent Publication No. 53-128628 discloses a ceramic fiber for spraying, which is made by adding and mixing alumina cement as a binder and is excellent in high-temperature heat insulation properties, wind speed resistance, tensile strength, and bending strength.

However, although these conventional methods can be applied to fibers, the coating material tends to peel off or crack when receiving heat, and the reaction between scale and fibers is not sufficiently prevented. It seems that it cannot be prevented.

Therefore, the coating material for Cera 5y fibers, which can be coated on the heat-receiving surface of ceramic fibers to reduce heat shrinkage of the fibers, provide wind speed resistance, and prevent reaction with scale, has not been developed so far. The reality is that there is no such thing.

According to the inventors' studies, the reason why the coating peels off when receiving heat is that the coating material shrinks when heated, which causes a warping phenomenon and breaks the fibers at the bonded part with the ceramic fiber. Another possible cause is that the strength of the coating material becomes too thick at the stage when the water evaporates, and the hardening of the coating material causes fiber cutting.

Next, it is considered that the cause of cracks is that the coating material shrinks too much and has too much strength.

Summary of the Invention The present invention was made with the aim of solving the above-mentioned problems and improving the conventional coating materials, and was achieved as a result of various research into the composition of coating materials for ceramic phytsumers. be.

That is, the coating material for Cera 5y Kufu fiber according to the present invention contains (A) 100 parts by weight of human bone removal-resistant powder containing 70 parts by weight or more of alumina, (5 to 20 parts by weight of silica powder whose crystal form is α-quartz type), and , (C) 5 to 12 parts by weight of boric acid, and (D) 5 to 5 parts by weight of a plasticizer-containing synthetic resin emulsion.
It is characterized in that it consists of 0 parts by weight (as a resin content).

Effects According to the coating material of the present invention, when it is applied to the heat-receiving outer surface of the ceramic fiber insulation material (details will be described later),
The following ceramic finomer protective effects can be obtained.

(1) Heat shrinkage of the heat-receiving outer surface of the ceramic fiber insulation material can be prevented. For example, uncoated ceramic fiber insulation exhibits linear shrinkage of 2 to 4 inches at 1300°C, resulting in large gaps between blocks, but with the coating of the present invention, shrinkage is extremely small. Its linear shrinkage is 0 to 0.5 inch.

(2) Peeling or cracking of the coating material does not occur. Since the coating material of the present invention has little shrinkage, it does not peel off due to the warping phenomenon observed in conventional coating materials upon receiving heat. Furthermore, due to the synergistic effect of the synthetic resin emulsion containing α-quartz silica powder, boric acid, and a plasticizer, fibers in contact with the coating material are not cut, and therefore no peeling phenomenon occurs.

(3) Wind speed resistance can be imparted to the ceramic fiber insulation material. Ceramic fibers without a coating are blown away and disappear under conditions of a wind speed of 2 L) m/sec or higher, but those coated with the present invention are not blown away even under conditions of a wind speed of 50 m/see.

(4) Reaction between fibers and scale can be prevented. Ceramic fibers without coating react with scale, i.e., iron oxide, and soften and melt, resulting in an extremely poor insulation effect and no longer being able to function as a heat insulating material. The coating material of the invention prevents the reaction between the scale and the fibers, so there is no softening and melting phenomenon caused by the reaction between the scale and the fibers, and the scale that has accumulated on the top surface of the coating can be removed by hand. It can be easily brushed off.

The coating material for ceramic fibers according to the present invention consists of the components A to D described above.

In the present invention (including when interpreting the claims), "consisting of" may include, in addition to the four essential components, various auxiliary components as long as the effects of the present invention are achieved. It means that.

Refractory aggregate powder (A) The refractory aggregate powder used in the present invention is a refractory powder containing 70 parts by weight or more of alumina. 30 of this refractory aggregate
As the refractory material other than alumina that accounts for ~ON amount%, refractory materials commonly used in refractories such as magnesia, silica, silicon carbide, silicon nitride, and spinel are used. Here, in the present invention, it is necessary that the amount of alumina in the total refractory control powder is 70 parts by weight or more. This is because if the amount is less than 70 parts by weight, the reaction between the ceramic fibers and the scale cannot be prevented by coating the surfaces of the ceramic fibers.

Silica Powder (B) The silica powder used in the present invention must have an α-quartz crystal form, and amorphous silica such as cristonolite and tridymite cannot be used. This is because, if silica having a crystalline form other than α-quartz type is used, shrinkage of the coating cannot be prevented, resulting in peeling or cracking of the coating material.

The silica powder is added in an amount of 5 to 20 parts by weight per 100 parts by weight of the refractory aggregate powder. If it is less than 5 parts by weight, shrinkage during heating will be large, while if it exceeds 20:lfj parts, cracks will occur in the coating material.

Boric acid (C) "Boric acid" as used in the present invention is a general term for oxygen acids produced by hydration of diboron trioxide, and includes not only typical orthoboric acid but also metaboric acid, tetraboric acid, etc. It is.

The content of boric acid in the coating material of the present invention is as follows:
The amount is 5 to 12 parts by weight relative to 0 parts by weight. If the amount is more than 12 parts by weight, the strength of the coating material upon drying and curing will be too high, leading to fiber breakage, making the formed coating layer easy to peel off, and reducing the effect of preventing reactions with scale. If the amount is less than 5 parts by weight, the strength of the coating material after drying and hardening will be low and sufficient wind speed resistance will not be obtained.

Synthetic Resin Emulsion (D) In the coating material composition of the present invention, it is the plasticizer-containing synthetic resin emulsion that primarily behaves as a binder. [Plasticizer-containing synthetic resin emulsion] as used in the present invention means a synthetic resin emulsion containing a plasticizer for the synthetic resin, and includes cases where the plasticizer is included in the synthetic resin and water in the emulsion. This includes both cases where the two are contained in an emulsified form in the phase and cases where the two coexist.

Here, as the "synthetic resin", any resin that can form a resin phase that binds the powder chain components from an emulsion state can be used. From the viewpoint of economy and decomposition products during thermal decomposition, polyvinyl acetate, ethylene-vinyl acetate copolymer, etc. are generally suitable.

These synthetic resins need to be made soft after drying by a plasticizer. As a plasticizer,
Preference is given to using phthalic acid esters, such as dibutyl phthalate, dimethyl phthalate, diethyl phthalate. The amount of plasticizer used is such that the minimum film forming temperature of the resin emulsion is 50" per 100 parts by weight of the resin content of the synthetic resin emulsion.
It is preferable that the amount is 10 to 50 parts by weight when it is C or higher, and 2 to 10 parts by weight when the minimum film forming temperature of the resin emulsion is less than z'c. If the amount of plasticizer used exceeds the upper limit of this range, the synthetic resin film formed during water loss and drying will be too soft, reducing the wind speed resistance of the coating material. On the other hand, when the amount of plasticizer used is less than the above-mentioned lower limit, the softness of the synthetic resin film is insufficient, and ceramic fibers are likely to break when the coating material dries.

The resin content of the synthetic resin emulsion in the coating material composition of the present invention is required to be 5 to 50 parts by weight. When the amount is less than 5 parts by weight, the strength of the coating material becomes too large when it dries, making it easy to cut the ceramic phyno 9-, and causing peeling of the coating material. On the other hand, if it exceeds 1 part by weight, the amount of synthetic resin burned and lost during high-temperature use will increase, resulting in excessive porosity of the coating material and reducing the effectiveness of preventing the reaction between school and ceramic fibers. do.

Production of coating material composition The coating material for ceramic phytsmer of the present invention is as follows:
It can be produced by mixing the above components in a conventional mixer. When the synthetic resin does not contain a plasticizer, the plasticizer can be dissolved in an organic solvent and then emulsified, if necessary, or emulsified and mixed into the synthetic resin emulsion. During mixing, appropriate heating may be performed, and auxiliary components may be added as necessary.

The solid content concentration of the coating material composition of the present invention is usually a value regulated by the water supplied from the synthetic resin emulsion used to provide a predetermined synthetic resin content, but water (and This can be adjusted by adding emulsifiers or by evaporating water.

Construction of the coating material This coating material is made of ceramic fins (silica content: 3147-40% by weight, alumina 53-60qb).
The heat-receiving outer surface of the heat insulating material (with a fiber diameter of about 2 to 3 μm) may be sprayed with a spray gun, or applied with a trowel, roller, brush, etc., and dried. As mentioned above, various advantages can be obtained depending on the coating layer formed.

Experimental Examples Examples 1 to 2 After mixing the formulations shown in Table 1, they were sprayed onto the heat-receiving outer surface of a ceramic fiber heat insulating material installed on the wall of a heating furnace using a commercially available spray gun. After 6 months of operation, there is almost no shrinkage between the ceramic fiber insulation blocks, no change due to wind speed, and no peeling cracks in the coating material and no deposits on the coating surface. The scale was in such a state that it could be easily wiped off by hand.

Examples 3 to 4 After mixing the formulations shown in Table 1, they were applied with a brush to the heat-receiving outer surface of a ceramic fiber heat insulating material installed on the wall of a soaking furnace. After 3 months of use, the coated ceramic fiber insulation showed no shrinkage on the working surface, as in Example 1.2, no peeling or cracking occurred in the coating, and no scale adhering to the surface. could be blown off with compressed air.

Comparative Example Similar construction was carried out using the formulations shown in Table 1. The results were as shown in the table.

Claims (1)

[Claims] 100 parts by weight of refractory aggregate powder containing 70 parts by weight or more of alumina, and 5 to 2 parts by weight of silica powder whose crystal form is α-quartz type.
A coating material for ceramic fibers, characterized in that it consists of 0 parts by weight, 5 to 12 parts by weight of boronic acid, and 5 to 50 parts by weight of a plasticizer-containing synthetic resin emulsion (as a resin component).