JPH07330417A - Production of refractory heat insulating material - Google Patents

Abstract

PURPOSE:To obtain a refractory heat insulating material by using rock wool which is lightweight and low-cost but has inferior fire resistance as the base material so that the obtd. material can be used for coatings on iron bars or the like to endure at a high temp. as about 1000 deg.C which is produced in normal fires. CONSTITUTION:Before or after rock wool and aq. soln. of alkali silicate are mixed, carbonate or hydrogen carbonate of alkali metal or ammonium is mixed. The mixture is molded and dried by heating. Thus, an inexpensive refractory heat insulating material comprising rock wool having excellent heat insulating property is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a lightweight heat-insulating material having excellent fire resistance and processability, which is used for a fire-resistant heat-insulating molded article such as a steel frame fire-resistant coating material.

[0002]

2. Description of the Related Art Steel materials have the property that the elastic modulus and the yield point sharply decrease at high temperatures (350 to 500 ° C.). Therefore, in a steel-framed structure, if a beam or column is exposed to a high temperature during a fire, it will not be able to support the load and will bend. For this reason, the Building Standards Law stipulates that the exposed parts should be fireproof in steel frame construction.

[0003] Conventionally, the fireproof coating method for steel frames has been carried out mainly by spraying a mixture of rock wool and cement directly onto the steel frames. This is because the work is relatively easy and the cost is low, such as the unevenness of the steel frame and the easy coating of the curved surface. However, this spraying method generates a lot of dust, so the working environment is bad,
There are many drawbacks such as a lot of irregularities on the construction surface and poor appearance, and a problem in performance guarantee due to uneven coating thickness.

[0004] It is also practiced to coat with a lightweight cellular concrete plate, or to form a lath substrate and then coat it with leeche mortar or leeche plaster, but the former is heavy and It can only be used to a certain degree, and the latter has the drawback of being laborious. As another construction method, there is a method of covering the periphery of the steel frame with a forming plate such as a calcium silicate plate. According to this method, the surface after construction shows a smooth and desirable appearance, but the calcium silicate plate has the drawback that it is lightweight but the material is expensive, and the construction is troublesome and inefficient.

In order to solve these problems, a method of attaching a felt of an inorganic fiber has been previously proposed. The felt is lightweight and easy to cut, and its flexibility allows it to be adhered to the steel frame even at the corners and to be adhered efficiently.

[0006]

However, since the density of felt is generally as small as 60 kg / m ³ or less, there is a problem that the heat insulating property at high temperature is inferior. When the density is set to about 200 kg / m ³ , this point is improved, but the flexibility is extremely deteriorated, and the advantages of felt are lost. Further, since the felt generates a considerable amount of dust from its surface and cross section, it becomes necessary to attach a metal foil or a non-woven fabric. In addition, there are many problems such as being unable to stand in front of the steel frame and leaving it outdoors, or peeling inside the felt when it is attached to the steel frame with an adhesive, and measures to solve these problems should be taken. , It will be quite expensive.

A further serious problem is that although felt and board made only of rock wool are inexpensive, they have low fire resistance and are significantly deformed at about 800 ° C., resulting in poor heat insulation performance. Therefore, 30 to 50% of silica-alumina fiber (ceramic fiber) that can withstand 1,200 ° C. is mixed and molded, or a fiber having a high melting point (ceramic fiber) is used as disclosed in JP-A-62-268446. The felt is laminated on the surface layer of rock wool products to improve fire resistance. However, these methods are troublesome and cause another problem that they are expensive because the ceramic fibers are expensive.

[0008]

In view of the above, the present inventor uses rock wool, which is lightweight and inexpensive, but has poor fire resistance, as a base material and withstands a high temperature of about 1,000 ° C. that occurs during a normal fire. The present invention has been completed as a result of intensive research to develop a fireproof heat insulating material. That is, according to the present invention, alkali silicate is used as an inorganic binder in rock wool, to which carbonate or hydrogen carbonate of alkali metal or ammonia is added and heated and dried. By this operation, the alkali silicate adhering to the surface of rock wool is decomposed by the action of carbon dioxide gas to generate a silicate gel having a higher degree of fire resistance than alkali silicate and sodium carbonate having a low reactivity at high temperature. It seems that the fire resistance of rock wool has been greatly improved. Therefore, the obtained refractory has high thermal insulation at high temperature and has high strength, so it is less susceptible to mechanical damage, easy to cut and cut, and less likely to generate dust and inexpensive. It has advantages such as being obtained.

If an organic binder is used as the rock wool binder, it will burn due to the heat of a fire and lose its shape, resulting in poor fire resistance and heat insulation. On the other hand, the inorganic binder has a drawback that the strength is not exhibited unless the addition amount is increased, but it has shape retention at high temperature and the fire resistance is improved as compared with that without addition.

As the inorganic binder, cement, sodium silicate-based binder, silicic acid sol, alumina sol, aluminum phosphate-based binder and the like are usually used. However, cement has the disadvantage that the density becomes large because the strength is low unless about 40% is added to rock wool, and the silica sol and alumina sol must be added in an amount of 20% or more, resulting in a high cost. Aluminum phosphate has the drawback that strength is not obtained unless it is heated to 250 ° C. or higher, and a malodorous gas is generated in the process. Commercially available sodium silicate-based binders are easy to use, but as with other binders, it is difficult to improve the fire resistance of the molded product to 900 ° C or higher even if the addition amount is increased, and the density of the molded product increases. Machinability deteriorates significantly. The alkali silicate, which is the main material of the sodium silicate-based binder, is heated (150 to 200 ° C).
If it is not cured, it will not cure, and its water resistance and fire resistance will be low. In order to improve this drawback, a mixture of a hardener and inorganic fiber powder is the sodium silicate binder. Therefore, the method of use (spray) as in the present invention is difficult and costly.

Therefore, in the present invention, the cost is low and the temperature is 150 ° C.
An alkaline silicate (an aqueous solution) that exerts a binding force at a moderate temperature is used as a binder. Further, as an additive, an alkali metal or ammonia carbonate or hydrogen carbonate which generates carbon dioxide at around 100 ° C. in the presence of water is used.
By mixing these and molding and drying, 1050 ° C
We were able to make an insulating material that can withstand the high temperatures of. The refractory heat insulating material obtained by the present invention is used for coating a steel frame, an iron plate, etc. formed into a plate shape, and is also used for coating pipes, cocks and other metal products exposed to high heat by molding. It is a thing.

Rockwool is natural rock or slag that is melted at high temperature, and the melt is blown off by centrifugal force to form a fibrous form. Heat-resistant inorganic fiber containing silica, lime, alumina, etc. as its main component. (Heat resistant temperature is about 650 to 800 ° C.). At present, various grades are made by blending rock with slag and adjusting the components or changing the production method, but any of them can be used in the present invention.

Alkali silicate has the general formula M ₂ O.mSiO
_{It is represented by 2} · nH ₂ O (M = Na, K, Li), and any commercially available product can be used, but in the case of sodium silicate, the molar ratio of SiO ₂ / Na ₂ O is ₂ to 3.5. Is desirable. . The mixing ratio is about 3 to 30% by weight, and more preferably about 5 to 20% by weight, as a solid content (dry residue) of M ₂ O and SiO ₂ with respect to rock wool. If the amount added is small, the strength and fire resistance of the molded product will be low, and 3
If it is 0% or more, it becomes too hard, the machinability deteriorates, and dust easily occurs.

Examples of the carbonate or hydrogen carbonate include ammonium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate,
Water-soluble substances such as ammonium hydrogencarbonate are mentioned, and they are added in the form of powder or an aqueous solution. The amount of addition is about 3 to 30% in terms of solid content with respect to rock wool, and increases or decreases depending on the composition and amount of alkali silicate.

Next, the manufacturing method will be described. Also in the present invention, a method generally used as a means for producing a mat, a board, or a mold by mixing rock wool and a binder can be applied.

However, if carbonate or hydrogen carbonate is mixed in advance with the alkali silicate solution, a silicate gel is formed and solidified in a short time. When gelled, the adhesive force is lost, and it is difficult to mix it with rock wool uniformly, so it is necessary to devise a method for mixing the two. That is, since it is possible to obtain a material having both excellent strength and fire resistance when the proportion of the two that are in contact with each other and reacting by the molding is small, it is necessary to add the both separately. It is desirable to mold quickly. Therefore, it is necessary to devise the device and the operation.

The rock wool used may be bulk fibers as it is, but if rock wool is granulated in advance to a size of 2 to 30 mm,
Mixing with aqueous solution of alkali silicate, powder of carbonate or hydrogen carbonate is easy and reliable, and compression molding is easy, so equipment and operation are simple, and strength, fire resistance and machinability are good. A molded product can be obtained with good reproducibility.

The thermal insulation performance of the refractory insulation according to the invention is determined by its thickness, but also by its density. The density is adjusted by the pressure during molding, but a high pressure is not preferable because it suppresses decomposition of hydrogen carbonate and the like. When rock granules are used as the raw material, the density of the molded product can be easily adjusted by adjusting the density of the particles. The molding method is as follows. A mold is filled and uniaxially pressed, or a continuous press roller is used. The molding temperature may be about room temperature. Then
In the process of heating and drying, the reaction between the alkali silicate and the carbonate or hydrogen carbonate is completed.

[0019]

Embodiments will be described in detail below based on embodiments of the present invention. Example 1 Rock wool granular cotton was treated with a double-roll type defibrating machine (“Seripet” manufactured by Serizawa Seisakusho) provided with a needle cloth on the surface to obtain a granular material having a diameter of 5 to 15 mm. The bulk density of this granular material was 0.08 kg / m ³ . 180 g of a solution obtained by diluting sodium silicate No. 2 product (JIS K1408-1966) three times with water is sprayed and mixed with 300 g of the granular material,
Next, after spraying 20 g of sodium hydrogen carbonate powder and mixing, put it in a mold (180 x 180 mm) and have a thickness of 44 mm.
The resulting product was compressed into a mold, demolded, and dried at 150 ° C. for 120 minutes. The amount of sodium silicate added was 9% based on rockwool as the solid content of Na ₂ O and SiO ₂ . The density of the molded plate was 250 kg / m ³ , and it could be easily cut with a cutter knife, but even when mechanical external force such as normal transportation and stacking work was applied, almost no chipping or cracking occurred. Further, when these two molded plates were adhered with a sodium silicate adhesive, placed in an electric furnace and heated at 1,050 ° C. for 60 minutes, almost no change or abnormality was observed in the appearance and cross section.

Example 2 A fireproof heat insulating plate was prepared in the same manner as in Example 1 except that a concentrated solution of ammonium hydrogen carbonate was used instead of sodium hydrogen carbonate. After spraying and mixing 180 g of a solution of sodium silicate No. 2 diluted 3 times with water, spray 24 g of ammonium hydrogencarbonate dissolved in 70 g of water, put it in a mold and compress it to a thickness of 44 mm, 12 at 150 ° C
Dry for 0 minutes. The obtained one showed similar fire resistance, although the strength was somewhat inferior to that of Example 1.

Comparative Example Molding was carried out in the same manner as in Example 1 except that sodium hydrogen carbonate was omitted. The strength of the obtained molded plate was about the same as that of Example 1, but when heated at 1050 ° C., cracks and voids were generated in the portion having a depth of 15 to 25 mm from the surface, and were missing. There were some parts, and the fire resistance was significantly inferior to that of Example 1.

Example 3 300 g of bulk rock wool was mixed with 100 g of water while being sprayed, and then 20 g of sodium hydrogen carbonate powder was sprayed and mixed. Next, 180 g of the sodium silicate solution used in Example 1 was sprayed and mixed, then placed in a mold and molded and dried in the same manner as in Example 1. The dried product had a slightly lower strength than that obtained in Example 1, and the result of the heating test at 1,050 ° C. was 5 mm from the surface.
Although there were some voids in the area up to the depth, there was no practical problem.

Example 4 (Method of use and evaluation) An inorganic adhesive was applied to the surface of an iron plate having a thickness of 12 mm and a size of 140 × 140 mm, and the inorganic adhesive was obtained in Examples 1, 2 and 3. The molding plate was attached to the entire surface. As a result of testing this refractory-coated iron plate according to the method of JIS-A 1304, the temperature of the iron plate surface when the temperature inside the furnace was raised from 500 ° C to 1010 ° C over 2 hours was 320 ° C to 3 ° C.
The temperature was 50 ° C., and it was estimated to have fireproof performance for 2 hours. In addition, changes such as deformation, breakage and falling of the covering material were hardly observed.

[0024]

As described above, according to the present invention, before or after mixing rock wool and an aqueous solution of alkali silicate, an alkali metal or ammonium carbonate or hydrogen carbonate is mixed and molded, and dried by heating. To produce a refractory heat insulating material.

Therefore, there is an advantage that a fireproof heat insulating material that can withstand a high temperature of 1,050 ° C. can be obtained in large quantities at low cost while using inexpensive rock wool. Moreover, the obtained fireproof heat insulating material is excellent in fire resistance and heat insulation, and has high strength.
It has the advantages of easy machinability and penetrability of the welding pin, and does not generate dust during handling. It can be said to be an ideal fireproof heat insulating material.

Further, it can be molded into a plate shape or a mold, and even if it is coated with a steel frame or other metal products only with this material, sufficient fire resistance can be imparted.

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Claims (3)

[Claims] 1. A refractory heat insulating material, characterized in that before or after mixing rock wool and an aqueous solution of alkali silicate, a carbonate or hydrogen carbonate of an alkali metal or ammonium is mixed, molded and heated and dried. Manufacturing method. 2. Rock wool having an average diameter of 2 to
The method for producing a refractory heat insulating material according to claim 1, wherein a granulated material of 30 mm is used. 3. The method for producing a refractory heat insulating material according to claim 1, wherein the carbonate or hydrogen carbonate is mixed in a powder state.