JPS6245192B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a refractory composition, particularly a refractory composition using basic aggregate. Binders have a long history in the field of refractories, and many binders such as water glass, silica sol, alumina sol, basic aluminum chloride, alumina cement, and various phosphates have been developed and put into practical use. Among these, water glass contains alkali metals and exhibits a decrease in bond strength at high temperatures.Although silica sol and alumina sol are used in special fields, they generally have low bond strength over the entire range of low and high temperatures. There is a shortage. In addition, although basic aluminum chloride is an excellent binder, it generates chlorine gas at high temperatures, making it undesirable for work, and alumina cement requires a considerable amount of use when used in medium acid aggregates.
As a result, the molded product contains a large amount of calcium, and a low melting point substance is produced. Regarding phosphate, this binder has been developed in recent years and has excellent strength, but when used as a furnace wall for ladle etc., for example, the phosphoric acid component gets mixed into the molten metal as an impurity. Problems such as these have 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. Furthermore, although basic aggregates such as magnesia clinker have excellent fire resistance, no suitable binder has been found for their use. In view of this current situation, the present inventors have conducted repeated research,
Although basic aluminum lactate was found to be an excellent binder (Japanese Patent Publication No. 61-16745), it was found that fine cracks were generated during drying after forming the refractory. Therefore, in order to solve this problem, we conducted further research and found that aggregates, basic aluminum lactate, oxalic acid, citric acid, tartaric acid or their alkali metal salts, ammonium salts, and silicofluorides were selected. If one or more of these are used together,
The present invention was completed by discovering that it is possible to prevent the occurrence of minute cracks during drying after molding a refractory. The basic aluminum lactate used in the present invention has a composition of Al ₂ O ₃ /lactic acid (molar ratio) of 0.2 to 2.0, and its manufacturing method involves combining a water-soluble aluminum salt with an alkali metal or ammonium carbonate, and a carbonate of an alkali metal or ammonium. It can be produced by reacting a carbonate or the like or reacting an alkali aluminate with carbon dioxide gas and dissolving the precipitated 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 a barium compound, to a mixed solution of aluminum sulfate and lactic acid or aluminum lactate. When using this basic aluminum lactate, it can be used as a solution, or it can be dried and used as a powder. The present invention uses basic aluminum lactate having the above composition and one or more selected from oxalic acid, citric acid, tartaric acid, their alkali metal salts, ammonium salts, and silicofluorides. As the alkali metal salts and ammonium salts of oxalic acid, citric acid, and tartaric acid used in the invention, sodium salts, potassium salts, ammonium salts, etc. of oxalic acid, citric acid, and tartaric acid can be used. In addition, examples of silicofluoride include sodium silicofluoride, potassium silicofluoride, ammonium silicofluoride,
Magnesium silicofluoride, calcium silicofluoride, etc. can be used. As for its usage ratio, it varies depending on the basicity of the basic aluminum lactate used, the type of the above-mentioned compound, the type of substance to be bound, the purpose, etc., but it is approximately 10 to 10 to Al ₂ O ₃ of basic aluminum lactate.
200% by weight is desirable. More preferably, oxalic acid, citric acid, and tartaric acid are used in an amount of 40 to 100% by weight based on the Al ₂ O ₃ of basic aluminum lactate, and their alkali metal salts and ammonium salts are added in an amount of 90 to 180% by weight. For silicofluorides, 15 to 60% by weight is desirable. That is, below the lower limit, it is not possible to expect a greater effect in preventing the generation of microcracks than when using basic aluminum lactate alone, and above the upper limit, hardening occurs when the binder and the material to be bonded are mixed. quick,
This causes a problem of poor workability. The present invention will be further explained below with reference to Examples, but the present invention is not limited thereto. In addition, although the examples of the present invention mainly describe the case of basic aggregates, from the technical content of the present invention, acidic aggregates such as waxite, zircon flour, silica sand, etc., and medium acidic aggregates are also applicable. Of course, it can also be used. In this example, unless otherwise specified, all percentages are by weight. Example 1

[Table] 100 parts of the mixed basic aggregate shown in Table 1 above
Al ₂ O ₃ / lactic acid (molar ratio) 0.33, 3 parts of basic aluminum lactate powder of 20.5% Al ₂ O ₃ and 1.0 part of sodium oxalate (dihydrate) were added and mixed, followed by 7 parts of water. was added and kneaded (example of the present invention). For comparison, a case was also conducted in which sodium oxalate (dihydrate) was not added. Pour these into a 20 x 20 x 80 m/m mold,
The mold was removed after 10 hours, and the resulting molded body was dried at 110°C for 24 hours. The dried molded body is heated to 1000℃ in an electric furnace.
The product was fired for 2 hours, taken out from the furnace, and after cooling in air, the curl strength was measured. The surface condition after firing was also observed. These results are shown in Table 2.

[Table] In addition, the fine cracks referred to here are "none" or "none" if there are ¹ or 2 cracks per 4 cm2, and 10
Those with more than 10 points were classified as ``many''. Example 2

[Table] Al ₂ O ₃ / 100 parts of the basic aggregate shown in Table 3 above
4 parts of basic aluminum lactate powder containing lactic acid (molar ratio) 0.5 and Al ₂ O ₃ 22.32%, further 0.5 part of citric acid (monohydrate) were added, and 7 parts of water were added and kneaded.
As a comparative example, 4 parts of aluminum lactate powder with the above composition was added to 100 parts of the above aggregate, and further hydrochloric acid (composition: HCl 17.5%).
3 parts and 4.5 parts of water were added, quickly kneaded, and similarly quickly molded into a mold. The molded body was fired in an electric furnace, and the hot curl strength was measured at 1000°C and 1200°C. These results are shown in Table 4.

【table】 Example 3

[Table] To 100 parts of the mixed aggregate shown in Table 5 above, add 9 parts of a basic aluminum lactate solution containing Al ₂ O ₃ /lactic acid (molar ratio) 0.6 and Al ₂ O ₃ 7.7%, and further add 1 part of ammonium tartrate. The mixture was kneaded (example of the present invention). For comparison, 9 parts of a basic aluminum lactate solution with the above composition was added to 100 parts of the above mixed aggregate.
Further, 1 part of ammonium acetate was added and kneaded. These were poured into a mold of 20 x 20 x 80 m/m, demolded after 24 hours, and the resulting molded product was dried at 110°C for 8 hours. The dried molded body is heated to 800℃ in an electric furnace for 2 hours.
After firing for several hours, each piece was taken out from the furnace and cooled in air, and the curl strength of each piece was measured. These results are shown in Table 6.

【table】 Example 4

[Table] 100 parts of the mixed basic aggregate shown in Table 7 above
5 parts of basic aluminum lactate powder with Al ₂ O ₃ /lactic acid (molar ratio) 0.25 and 17.5% Al ₂ O ₃ and 0.3 part of sodium silicofluoride were added and mixed, and 7.2 parts of water was added and kneaded ( Example of the present invention). Further, as a comparative example, 5 parts of basic aluminum lactate powder of the above composition was added to 100 parts of the above mixed aggregate,
Furthermore, add 0.3 part of aluminum fluoride, mix, and add water.
7.2 parts were added and kneaded. Pour these into a 20 x 20 x 80 m/m mold,
After 24 hours, the mold was removed and the resulting molded body was dried at 110°C for 24 hours. After drying, the molded body is heated at 1000℃ in an electric furnace.
The hot curling strength was measured after being left at 1200°C and 1400°C for 2 hours. In addition, these were air-cooled and their surface conditions were observed. These results are shown in Table 8.

【table】

Claims (1)

[Claims] 1. Aggregate, basic aluminum lactate, and oxalic acid;
1. A method for producing a fire-resistant composition, characterized by using citric acid, tartaric acid, or one or more selected from the group consisting of alkali metal salts, ammonium salts, and silicofluorides. 2. A patent in which the proportion of one or more of oxalic acid, citric acid, tartaric acid, their alkali metal salts and ammonium salts, and silicofluorides is 10 to 200% by weight based on Al ₂ O ₃ of basic aluminum lactate. The method according to claim 1.