JPS6350302B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a fire-resistant and heat-resistant molded body. Binders in the refractory field have long been used as agents to form connective tissue that gives refractory raw materials a structural function, such as water glass, silica sol, alumina sol, basic aluminum chloride, alumina cement, and various phosphates. A number of binders have been developed and used to manufacture irregularly shaped refractories and refractory bricks with improved connective tissue. However, because water glass contains alkali metals in these binders, its bonding strength at high temperatures is low, and although silica sol and alumina sol are effective in special fields, they are generally not suitable for low-temperature and total bonding. It has the disadvantage that the bonding strength is insufficient over the area. Basic aluminum chloride is an excellent binder that does not form low-melting substances, but it generates chlorine gas during high-temperature decomposition, making it unfavorable for the working environment. Since it is necessary to use a large amount, the resulting molded product contains a large amount of calcium, which is undesirable because it produces a low melting point substance. Regarding phosphates, this binder has been developed in recent years and has excellent strength, but for example, when used as a furnace wall for ladle etc., phosphoric acid component may be mixed into the molten metal as an impurity. The problem has become apparent. That is, each binder has its advantages and disadvantages, and it is necessary to strictly select the materials to be bound or the intended use, and in some cases, considerable consideration must be given to the stability, workability, etc. of the binder. In addition, attempts have been made to use aluminum salts of organic acids such as formic acid, oxalic acid, and citric acid alone or in combination with other binders, but they are highly acidic and react violently with the substances to be bound. The field of application is limited due to the inability to obtain sufficient bonding strength. In view of this current situation, the present inventors have conducted repeated research,
It was discovered that basic aluminum lactate salt exhibits excellent bond strength.
As a result of further investigation, we found that by using a dry product obtained by reacting an aluminum salt with an alkali metal carbonate or an ammonium carbonate and a basic aluminum lactate salt as a binder, The inventors discovered that it was possible to obtain a molded body with a further improved bonding strength, and based on this knowledge, they completed the present invention. The basic aluminum lactate salt in the present invention has a composition of Al ₂ O ₃ /lactic acid (molar ratio) of 0.2 to 2.0. As for its production method, as described in Japanese Patent Publication No. 61-16745, it is produced and precipitated by reacting a water-soluble aluminum salt with an alkali metal or ammonium carbonate, bicarbonate, etc., or by reacting an alkali aluminate with carbon dioxide gas. It can be produced by dissolving alumina hydrate in lactic acid. Moreover, ammonium hydroxide or sodium hydroxide can also be used in place of the above carbonate. Furthermore, it can also be produced by adding a compound that forms a water-insoluble sulfate, such as a calcium compound or barium compound, to a mixed solution of aluminum sulfate and lactic acid or aluminum lactate. In the present invention, a basic aluminum lactate salt solution having such a composition is dried and used as a powder. That is, the present invention provides a method for producing a molded body, which comprises using a dried product obtained by reacting an aluminum salt with an alkali metal carbonate or an ammonium carbonate and a basic aluminum lactate salt as a binder. Regarding this, an object of the present invention is to provide a molded product which has excellent stability over time and further improved bonding strength compared to the conventional use of a basic aluminum lactate salt alone. That is, when using a dried product obtained by reacting an aluminum salt with an alkali metal carbonate or an ammonium carbonate and a basic aluminum lactate salt as a binder, the reaction is extremely slow at room temperature, and the increase is slow. You can work without stickiness and can obtain excellent molded objects. Additionally, dry or
These react during low-temperature heat treatment at 200-300°C and exhibit excellent bonding strength. Examples of the aluminum salt used in the present invention include inorganic aluminum salts such as aluminum sulfate, basic aluminum sulfate, aluminum chloride, basic aluminum chloride, aluminum nitrate, basic aluminum nitrate, ammonium alum, potassium alum, and soda alum. Examples include organic aluminum salts such as aluminum acetate and potassium aluminum tartrate. Examples of alkali metal carbonates include sodium and potassium carbonates and bicarbonates, and ammonium carbonates include ammonium carbonate and ammonium bicarbonate, but the invention is not limited to these. Therefore, as an example, the method for producing the strength enhancer of the present invention will be explained using aluminum sulfate as the aluminum salt and ammonium bicarbonate as the carbonate. First, an aluminum sulfate solution is prepared. There are no particular restrictions on the concentration of aluminum sulfate as long as it is within a range in which it can be dissolved. On the other hand,
There are no particular restrictions on the concentration of the aqueous ammonium bicarbonate solution to be reacted with this as long as it is within the range of dissolution. Regarding the reaction quantitative ratio of aluminum sulfate and ammonium bicarbonate, it is sufficient as long as a precipitate is formed, but in general,
NH ₄ /Al ₂ O ₃ (molar ratio) is 4.0 or more, and the upper limit has no critical significance, but NH ₄ /Al ₂ O ₃
(molar ratio) of 10 or less is desirable from the perspective of imparting strength. That is, as the value significantly exceeds 10, the strength imparting effect decreases as the value increases. Now, the aluminum sulfate aqueous solution and the ammonium bicarbonate aqueous solution prepared as described above are mixed by any method. When mixing, the latter may be added to the former or vice versa, and the addition method may be intermittent or continuous, but the most suitable method is to add ammonium bicarbonate to the aluminum salt aqueous solution. This is a method in which an aqueous solution is added all at once and stirred rapidly, and a homogeneous product with good permeability can be obtained by this method. Next, regarding the reaction temperature,
It only needs to be below the decomposition temperature of ammonium bicarbonate, and the reaction temperature has almost no influence on the effect of imparting strength, but the lower the reaction temperature, the better the overseparability becomes. In addition to the above-mentioned one-liquid reaction, the strength enhancer of the present invention can also be produced by simultaneously blowing ammonia and carbon dioxide into the aluminum salt solution. In addition, when drying the precipitate, it is of course possible to dry it by leaving it as it is or by forced heating, but generally the precipitate can be dried in a slurry state without separating it from the mother liquor. Spray drying is preferred from the viewpoint of ease of use and quality. The drying temperature is preferably below 200℃.
If it exceeds this, the strength imparting performance will be drastically reduced. Next, regarding the basic aluminum lactate salt, it is used in powder form.The reason for using it in powder form is that when a solution is used, the composition of the basic aluminum lactate salt changes due to the reaction with the strength enhancer of the present invention. This is undesirable as it reduces the bonding strength as a binder. Further, the reason why the powder of basic aluminum lactate salt and the strength enhancer of the present invention are mixed in advance is that if they are mixed separately at the time of mixing with the aggregate, the binder will not be sufficiently dispersed and will be in a non-uniform state. This in turn affects the strength reduction of the binder. Next, regarding the amount of the strength enhancer of the present invention to be used, it varies depending on the basicity of the basic aluminum lactate salt used, the type of substance, the type of substance to be bound, the use, etc., but approximately the amount of the basic aluminum lactate salt used is
It is desirable to use 0.5 to 7.5 times the weight of Al ₂ O ₃ . That is, if the basic aluminum lactate salt is added below the lower limit, it cannot be expected to have a large strength improvement effect compared to plain aluminum salt, and even if it is added above the upper limit, no further effect can be expected, depending on the case. On the contrary, it shows a decrease in strength and durability. The method of using the binder for producing molded bodies of the present invention is to mix the binder with aggregates, fillers, etc. in advance, and then add a small amount of water or an organic solvent and, if necessary, a fired mug, an electric melted mug, or water. It is also possible to use glass, calcium hydroxide, calcium carbonate, potassium hydroxide, potassium carbonate, sodium aluminate, and other hardening agents. It can also be used as an adhesive by coating, drying, and heating. In addition, the binder for producing molded bodies of the present invention can be used not only as a binder for refractories, but also for various plate-like materials, such as slate boards, gypsum boards, silica boards, various barlites, vermiculites, etc. It can also be used as a binder for various aggregates such as zeolite, various natural and artificial fibers such as asbestos, rock wool, glass fiber, aluminosilicate fiber, and carbon fiber, various catalysts such as alumina and silica, and coating materials for iron plates, ceramic materials, etc. If necessary, magnesia, dolomite, chromic acid, alumina hydrate, basic aluminum sulfate, water glass,
A curing agent such as sodium aluminate may be used in combination with alumina, asbestos, mica, red iron, talc,
Zircon flower, barium sulfate, titanium oxide,
A filler such as spinel may be used in combination. The present invention will be further explained below with reference to Examples, but the present invention is not limited thereto. It should be noted that all percentages are by weight unless otherwise specified. Example 1 4 kg of aluminum sulfate solution (Al ₂ O ₃ 4.0%) and 12 kg of sodium bicarbonate solution (Na 1.8%) were added to 2 kg of water.
The entire amount was added in about 1 hour while simultaneously adding to the reaction tank containing Kg. Strain the product and filter the cake.
After washing with 10 times the amount of water, spray drying was performed. The analytical values of this dried product are shown in Table 1.

[Table] 100 parts of this dry product and basic aluminum lactate salt powder (Al ₂ O ₃ /lactic acid molar ratio 0.6, Al ₂ O ₃ 32.5%)
200 parts of the mixture were placed in a ball mill and pulverized and mixed for 8 hours. 9 parts of the mixture, 300 parts of the basic aggregate shown in Table 2, and 18 parts of water were added and kneaded, poured into a mold of 20 x 20 x 80 mm, and demolded after 24 hours. For comparison, 9 parts of the basic aluminum lactate powder of the above composition, 300 parts of the basic aggregate shown in Table 2, and 17 parts of water were added and kneaded, molded in the same manner, and demolded after 24 hours. After drying these specimens at 110℃ for 24 hours,
The bending strength was measured, and the cold bending strength after firing at 1000°C for 2 hours was also measured. The results are shown in Table 3.

【table】

[Table] Example 2 Basic aluminum chloride (Cl/Al
4 kg of ammonium bicarbonate solution (NH ₃ 1.8%) at a liquid temperature of 20°C was added to 500 g (mole ratio 0.75, Al ₂ O ₃ 20.0%) with vigorous stirring for about 8 minutes, and after aging for 8 minutes, spraying was performed. It was dried to obtain a dry product. Next, basic aluminum lactate salt powder (Al ₂ O ₃ /lactic acid molar ratio 0.4, Al ₂ O ₃ 27.0%) and the dried product were taken and thoroughly mixed in the proportions shown in Table 4. Four parts of these mixtures were added to calcined bauxite aggregate (particle size composition
2.0~0.5mm 50 parts, 0.5~0.088mm 15 parts, 0.088mm or less
35 parts) Mix with 100 parts and add 6 parts of water to 50mmφ×150
The mold was placed in a molding cylinder of 1.5 mm in diameter, and removed from the mold by three strokes with a sand rammer. After drying at 110° C. for 24 hours, the compressive strength was measured. The results are shown in Table 4.

[Table] Example 3 Charge ratio of aluminum sulfate and sodium carbonate
4.5 (Na/Al ₂ O ₃ molar ratio), put 500 g of aluminum sulfate solution (Al ₂ O ₃ 10%) in a micro speed mixer, and add sodium carbonate solution (Na2.0
%) 2537g was added at once. After thorough mixing, the product was filtered and further washed with 5200 g of washing water. Separately _, aluminum sulfate solution ( _{Al 2 O 3} 10
%) and 500g of sodium carbonate solution (Na2.0%)
3382g, and then add aluminum sulfate solution (Al ₂ O ₃ 10%) to a charging ratio of 9.5 (Na/Al ₂ O ₃ molar ratio).
of sodium carbonate solution (Na2.0%)
5355g was reacted in the same manner as above, and the product was approximately
Excessive washing was performed with 10 times the amount of water. These washed products were dried in a flash dryer. As in Example 1, 4.5 parts of these dried products were added to 300 parts of the basic aggregate shown in Table 2, and basic aluminum lactate salt powder (Al ₂ O ₃ /lactic acid molar ratio 0.33,
4.5 parts of Al ₂ O ₃ (23.9%) and 20 parts of water were added, mixed well, and vibration molded in a mold of 20 x 20 x 80 mm. After demolding
It was dried at 110°C for 24 hours and its bending strength was measured. The results are shown in Table 5.

[Table] Example 4 Ammonium bicarbonate aqueous solution (NH ₃ 1.5%) 3000g
aluminum chloride (Cl/Al molar ratio 3,
388 g of Al ₂ O ₃ (11.6%) was gradually added with stirring. The product was overwashed and 2 g of the dried product (55.2% Al ₂ O ₃ ) was mixed with basic aluminum lactate salt powder (Al ₂ O ₃ /lactic acid molar ratio 0.6, Al ₂ O ₃ 32.5%).
7 g was uniformly mixed and added as a binder for an alumina fiber molded body. Addition of this product resulted in less loosening of the fiber after firing the fiber molded product than when using basic aluminum lactate alone. Example 5 Dry product obtained from the reaction of the aluminum sulfate aqueous solution and sodium bicarbonate aqueous solution in Example 1 and basic aluminum lactate salt powder (Al ₂ O ₃ /lactic acid molar ratio 0.8, Al ₂ O ₃ 34.6%) were mixed as shown in Table 6, the total amount of Al ₂ O ₃ was kept constant, and the second
It was mixed with 300 parts of the aggregate shown above and molded. The mold was removed 24 hours after pouring into the mold, and the green strength was measured.The dry strength after drying at 110℃ for 24 hours was measured.
And the cold strength of this was measured after firing at 1000°C for 2 hours. The results are shown in Table 6.

【table】

Claims (1)

[Claims] 1. A method for producing a molded body, which comprises using a dried product obtained by reacting an aluminum salt with an alkali metal carbonate or an ammonium carbonate and a basic aluminum lactate salt as a binder.