JPH0225842B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to basic aluminum sulfate having novel properties and a method for producing the same, and provides a basic aluminum sulfate having a previously unknown fibrous shape and a method for producing the same. Conventionally, as fibrous alumina, those shown in Table 1 are known.

【table】

[Table] All of these are manufactured by spinning, so
Although lengths of several centimeters or more can be obtained, diameters are limited to 2 to 3 microns at most, and extremely thin ones of 1 micron or less cannot be produced. On the other hand, the fibrous basic aluminum sulfate of the present invention is produced directly from a solution by reaction, and therefore is characterized by an extremely thin diameter of generally about 0.1 to 0.5 microns. Moreover, the fiber length is generally 5 to 150 microns, and the aspect ratio reaches several hundred. Its composition has the general formula Al(OH) _a (SO ₄ ) _b・nH ₂ O...(A) (where a+2b=3, 2.32a<2.44, 0.28<b
0.34, On10). In addition, in order to obtain the above general formula (A), first, basic aluminum sulfate is thoroughly washed, then dried using an appropriate means as necessary, and the weight is measured. Next, this is dissolved in acid, and Al and SO ₄ are determined by chemical analysis such as chelate titration. Since the value of b can then be calculated, the value of a is then determined to satisfy the condition of a+2b=3. The reason for using such a method is that it is difficult to quantify OH, and it is customary to set the coefficients in a general formula so as to maintain electrical neutrality. Now, if we calculate the values of a and b as above, we get
The formula weight of Al(OH) _a (SO ₄ ) _b can be calculated. Since this value multiplied by the Al concentration in the sample and subtracted from the initially measured sample weight corresponds to nH ₂ O, n can be determined by simple calculation. In general, the value of n varies considerably depending on the drying state of the basic aluminum sulfate. for example,
When the water is still floating after washing, n=10 to 8, and when the water is no longer floating, n=7 to 6. In addition, if you wash with water and then wash with ethanol, n=2, and if you dry it for 12 hours at 60℃ after washing with ethanol, n
= around 1. If the drying temperature is further increased and the drying time is lengthened, the value of n will gradually become smaller.
When dried at 150°C for 2 hours, n becomes almost 0. This water represented by nH ₂ O has a broad X-ray diffraction pattern of the fibrous basic aluminum sulfate of the present invention, as will be described later, so it has not yet been concluded that this is water of crystallization. However, by analogy with the results of examining the change in crystallinity accompanying drying of the prismatic basic aluminum sulfate shown in Comparative Example 2, the fibrous basic aluminum sulfate of the present invention also has nH ₂ O
We believe that this is not just adhered water, but a type of crystalline water similar to zeolite water. The shape of basic aluminum sulfate represented by formula (A) above is generally fibrous with a diameter of 0.1 to 0.5 microns and a length of 5 to 150 microns, and some of these are composited into bundles. It may also include shape. In powder X-ray diffraction using CuK rays, the fibrous basic aluminum sulfate of the present invention has the following properties:
Only weak and broad diffraction peaks are observed around 2θ angles of 7 to 9 degrees and 18 to 20 degrees, and the crystallinity is extremely low in terms of X-rays. However, for example, when a sample suspended in water is observed under a polarizing microscope, the light is quenched depending on the orientation of the polarizing plate, which suggests that the fibrous basic aluminum sulfate of the present invention is essentially crystalline. Conceivable. Presumably, the fibrous basic aluminum sulfate of the present invention is a collection of very fine crystalline cellulose, and the X-ray diffraction pattern is broad because the cellulose is extremely small. When the fibrous basic aluminum sulfate of the present invention is heated and calcined, it is dehydrated and converted into alumina in the same way as conventional aluminum hydroxide. However, the fibrous shape remains intact. That is, fibrous γ-alumina can be obtained by firing at 1000°C, and fibrous α-alumina can be obtained by firing at 1200°C. however,
The strength of the fiber before gelatinization is not very high, so
Care must be taken not to apply external force that would destroy the shape during firing operations, etc. The fibrous basic aluminum sulfate of the present invention having the above-mentioned properties has, for example, the general formula Al( _OH ) _c
3. Addition time T of sulfate soluble in the basic aluminum salt solution represented by 0.5c1.9) until the molar ratio of SO ₄ /Al reaches the value of (3-c)/2.
(unit: time) at an addition rate that satisfies T<-14c+28, preferably T<-14c+28 and T
It can be produced by adding at a rate that satisfies the two equations of 1.40 at the same time. The basic aluminum salt represented by the above formula (B) can be produced by various methods, but the most preferred method is to produce an aluminum salt of a monovalent anion, such as aluminum chloride, aluminum nitrate, aluminum bromide, This is a method of adding an alkali to an aqueous solution of aluminum iodide, aluminum citrate, aluminum acetate, etc., preferably aluminum chloride, aluminum nitrate, especially aluminum chloride. As the alkali, sodium hydroxide, potassium hydroxide, ammonia, etc. are used. Alkali has an OH/Al molar ratio of 0.5 in the solution.
It is good to add it so that it is in the range of 1.9 to 1.9, preferably 1.0 to 1.7. If it is less than the lower limit of the above range, the yield of fibrous basic aluminum sulfate obtained by adding a soluble sulfate in the next operation will be low. If the upper limit is exceeded, basic aluminum sulfate having a prismatic shape and a different composition will be produced as a by-product during the production of fibrous basic aluminum sulfate, which is not preferable. It is preferable to add the alkali gradually while stirring to avoid gelation. If the alkali addition rate is increased, the pH will locally increase and some precipitation may occur. If such a precipitate occurs, stirring for a sufficient period of time will redisperse the precipitate and form a homogeneous solution. Furthermore, even if no precipitation occurs, it is desirable to continue stirring for an appropriate amount of time in order to stabilize the pH of the solution. The basic aluminum salt solution is preferably an aqueous solution as described above, but an organic solvent such as alcohol or acetone may be mixed therein. Soluble sulfates in the basic aluminum salt solution thus obtained, such as sodium sulfate,
Generally, potassium sulfate, ammonium sulfate, etc. are made into an aqueous solution, and the molar ratio of SO ₄ /Al is (3-c)/
2 (where c is the sign in general formula (B)). Especially (3
-c)/2 It is desirable to add 10% or more greater than the value. By doing so, the filterability of the obtained fibrous basic aluminum sulfate is improved, and the precipitate of the basic aluminum sulfate can be easily separated and washed. When the molar ratio of SO ₄ /Al is less than the value of (3-c)/2, the development of fibrous particles is insufficient, amorphous particles are produced as by-products, and filtration performance may deteriorate. What is also important is that when adding soluble sulfate, the addition time T (unit: hours) until the molar ratio of SO ₄ /Al reaches the value of (3-c)/2 is T<
The addition should be carried out at an addition rate that satisfies -14c+28, preferably at a rate that simultaneously satisfies the two equations: T<-14c+28 and T1.40. If T<1.40, radial particles may be produced as a by-product, and in order to selectively obtain only fibrous particles, it is desirable to carry out the process within the range of T1.40.
Note that here the molar ratio of SO ₄ /Al is (3-c)/2
Until the SO ₄ /Al molar ratio reaches (3-
It does not mean that it is essential to add sulfate to a value equal to or greater than c)/2. Even when sulfate is added only to the extent that the molar ratio of SO ₄ /Al is less than the value of (3-c)/2,
If it is added until the molar ratio of SO ₄ /Al reaches a value of (3-c)/2, it is preferable to add at a rate such that the addition time T until reaching that value satisfies T<-14c+28. is T<-14c+28 and T1.40
This means that the addition should be made at a rate that simultaneously satisfies the following two equations. The fact that fibrous basic aluminum sulfate can be efficiently obtained by setting the addition time T within the range defined by such a formula is unexpected from conventional general technical knowledge. This was first discovered by the inventor as a statistical result of repeated experiments. In addition, near the boundary outside this range, not only fibrous materials cannot be obtained efficiently, but also prismatic or radial basic aluminum sulfate is obtained in addition to fibrous materials, and these are mixed. It becomes what it is. Furthermore, within the above range, there is a tendency that the yield generally improves as the value of c (sign in general formula (B)) increases. Also, regarding the temperature of the basic aluminum salt solution when adding soluble sulfate, the temperature should be lower than 50℃,
More preferably, the temperature is 40°C or lower and 10°C or higher, preferably 20°C or higher. By satisfying this temperature condition, basic aluminum sulfate, which is the object of the present invention, can be efficiently obtained. If the liquid temperature is higher than the above upper limit temperature, the fibrous shape will collapse,
Fine spherical particles are produced, and conversely, when the temperature is lower than the lower limit temperature, radial particles tend to be produced. However, after the entire amount of sulfate has been added, even if the liquid temperature becomes low, it is not affected much. Now, according to the conditions described above, a soluble sulfate salt is added to the basic aluminum salt solution. Shortly after starting to add the sulfate, it first begins to become cloudy like a sol, and then the cloudiness gradually increases until it finally becomes a milky white suspension. When this milky white suspension is allowed to stand still, it separates into a white precipitate and a supernatant. This white precipitate is the fibrous basic aluminum sulfate of the present invention, and known means such as centrifugation or filtration can be used to separate it. If necessary, the product is washed with water and/or an organic solvent such as alcohol, and then dried to remove the salt and obtain pure fibrous basic aluminum sulfate. When it is necessary to preserve the fibrous basic aluminum sulfate as a suspended slurry without drying it, it is desirable to disperse it in a non-aqueous solvent. This is because if fibrous basic aluminum sulfate is suspended in water or in a mother liquor for a long time, the fibrous shape tends to change, producing prismatic or tetrahedral particles. In order to disperse fibrous basic aluminum sulfate in a non-aqueous solvent such as hexane, for example, an anionic surfactant is added to an aqueous suspension of fibrous basic aluminum sulfate to make the surface of the fibrous particles lipophilic. , a method of extraction with a non-aqueous solvent, etc. are used. Incidentally, the above series of operations are usually performed at room temperature. The fibrous basic aluminum sulfate of the present invention can not only be effectively used in the field of application of conventionally known basic aluminum sulfate or aluminum hydroxide, but also open up completely new fields of application due to the above-mentioned unique properties. be. For example, it can be made into a sheet and used as a heat-resistant and chemical-resistant filter or a filter-like catalyst carrier. The sheet can be easily produced by a method such as filtering a suspension slurry of the fibrous basic aluminum sulfate of the present invention or fibrous alumina obtained by firing the same. In addition, when used in the production of fiber-reinforced composite materials, such as fiber-reinforced metals (FRM) and fiber-reinforced plastics (FRP), because the fiber diameter is extremely small and the aspect ratio is large,
A far greater reinforcing effect than conventional alumina fibers can be obtained. Furthermore, since alumina is a material with high thermal conductivity, it is extremely effective not only for reinforcement but also for improving thermal conductivity. Although the fibrous basic aluminum sulfate of the present invention is a short fiber, it can also be made into a long fiber by spinning it by a known method. At that time, since it is a fibrous particle, it is easier to spin than ordinary alumina powder and has greater strength. Furthermore, the present invention has great industrial value, as it can be used as a raw material for oriented alumina sintered bodies or as an orientation promoting material when producing oriented sintered bodies by utilizing shape anisotropy. . The present invention will be described below with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Example 1 N/2-AlCl ₃ aqueous solution 400ml in a glass beaker
ml and stirred with a magnetic stirrer, and 200 ml of N/2-NaOH aqueous solution was added thereto at a rate of 1 ml/min using a micro tube pump. At this time, since it is a strong alkali, it is locally
A heterogeneous reaction resulted in a high pH, and a small amount of gel-like precipitate was generated. Therefore, after the addition of N/2-NaOH was completed, stirring was continued for 12 hours. By doing so, a small amount of gel-like precipitate was redispersed, and a colorless and transparent basic aluminum chloride aqueous solution having a composition represented by the general formula Al(OH) _1.50 Cl _1.50 was theoretically obtained. The pH of this solution was 3.86. Incidentally, both the above reaction and the reaction described below were carried out at a liquid temperature of 20°C. While stirring 600 ml of the above basic aluminum chloride aqueous solution, 520 ml of N/4-Na ₂ SO ₄ aqueous solution was added.
2.0ml/using micro tube pump
It was added at a rate of 1 minute. Approximately 1 hour and 20 minutes after the addition of the N/4-Na ₂ SO ₄ aqueous solution, precipitation began to occur, and by the time the entire amount had been added 4 hours and 20 minutes later, it had become milky white, and when stirring was stopped and the mixture was allowed to stand still. It was separated into a white precipitate and a supernatant. When this milky white suspension was examined using an optical microscope, it was confirmed that numerous fibrous particles with an average length of about 50 μm were formed as shown in FIG. After continuing to stir the fibrous particle suspension obtained by the above method for about 3 hours, suction filtration was performed using No. 5C filter paper to separate the precipitate. The filter cake was sheet-like and had low bulk, and fine crepe wrinkles were formed on the surface. Next, wash the filter cake with about 500 ml of distilled water,
Further washing is performed using ethanol, and finally 60
Drying was carried out at .degree. C. for 24 hours to obtain 3.57 g of a sheet of fibrous basic aluminum sulfate. When the resulting white sheet was examined with a scanning electron microscope, it was found that
It was confirmed that the fibrous particles overlapped each other, making it look like a non-woven fabric. The size of the fibrous particles was approximately within the range of 0.1 to 0.3 μm in width and 40 to 70 μm in length. A scanning electron micrograph taken at 2000x magnification is shown in Figure 2. Further, as a result of chemical analysis, it was found that the sheet-like dry cake contained 24.2% Al and 25.4% SO ₄ . From this, it is thought that the composition of the basic aluminum sulfate obtained in this example is represented by the general formula Al(OH) _2.40 (SO ₄ ) _0.30 ·0.85H ₂ O. In addition, approximately 100 ppm of Na was detected, probably due to insufficient cleaning, but the content of other metal elements was low.
It was less than 100ppm. The yield was calculated to be 48% as the recovery rate of Al. Further, the results of powder X-ray diffraction using CuKα radiation (40 KV, 120 mA) are shown in FIGS. 6 and 7. Figure 6 shows the filter cake in a damp state after washing with distilled water, and Figure 7 shows the filter cake at 60°C after washing with ethanol.
The measurements were taken on each sample after it had been dried for 12 hours. As can be seen in these figures, almost no peak-like peaks were observed in the dry matter;
Even in a wet state, only weak broad diffraction peaks are observed around 2θ angles of 7 to 9 degrees and 18 to 20 degrees. Incidentally, FIG. 8 shows the results obtained by measuring an Al plate under the same conditions, and even when compared with this, the degree of broadening of the diffraction peak of the fibrous basic aluminum sulfate of the present invention can be understood. In addition, the specific surface area was measured using a rapid surface area measuring device SA-1000 manufactured by Shibata Kagaku Kaikai Kogyo.
The sample dried at 60°C for 24 hours after washing with ethanol had an area of 21 m ² /g. From this value of specific surface area,
It was inferred that the fibrous particles with a width of 0.1 to 0.3 μm obtained in this example were an aggregation of extremely thin cellulose with a thickness of about 55 μm. Furthermore, when the fibrous basic aluminum sulfate obtained in this example was fired in an electric furnace, at 1000°C, γ
-Al ₂ O ₃ changes to α-Al ₂ O ₃ at 1200℃,
This was confirmed from a powder X-ray diffraction pattern. As a result of scanning electron microscopy, γ-
It was found that even after changing to Al ₂ O ₃ , the fibrous shape remained almost unbroken. Furthermore, it was found that when the fibrous particles were converted to α-Al ₂ O ₃ by firing at 1200° C. for 30 minutes, the surface of the fibrous particles became uneven, but the fibrous morphology of the particles as a whole was still maintained. _The specific surface area at this time is 70m ₂ ^/
g, α-Al ₂ O ₃ was 19 m ² /g. Example 2 N/2-AlCl ₃ aqueous solution 400ml in a glass beaker
ml and stir with a magnetic stirrer, add 200 ml of N/2-NH ₄ OH aqueous solution,
Addition was made using a microtube pump at a rate of 1 ml/min. After the addition was completed, the mixture was stirred for about 1 hour to obtain a colorless and transparent homogeneous solution, and the pH at this time was 3.77. The basic aluminum chloride thus obtained is theoretically thought to have a composition represented by the general formula Al(OH) _1.50 Cl _1.50 . Incidentally, both the above reaction and the reaction described below were carried out at a liquid temperature of 30°C. While stirring 600 ml of the above basic aluminum chloride aqueous solution, 520 ml of N/4-Na ₂ SO ₄ aqueous solution was added.
Using a micro tube pump, 2.2ml/
It was added at a rate of 1 minute. Approximately 1 hour and 15 minutes after the addition of N/4-Na ₂ SO ₄ began, precipitation began to occur, and by the time the entire amount had been added 4 hours later, the mixture had become milky white. When this milky white suspension was examined using an optical microscope, it was confirmed that countless fibrous particles with an average length of about 70 μm were formed. The suspension of fibrous particles obtained by the above method was filtered, washed and dried in the same manner as in Example 1 to obtain 3.60 g of a sheet of fibrous basic aluminum sulfate. As a result of chemical analysis, the above white sheet-like substance contains
It was found that it contained 24.3% Al and 25.7% SO ₄ . From this, it is thought that the composition of the basic aluminum sulfate obtained in this example is represented by the general formula Al(OH) _2.40 (SO ₄ ) _0.30 ·0.81H ₂ O. The yield was calculated to be 49% as a recovery rate of Al. Regarding this fibrous basic aluminum sulfate,
When the properties were examined using the same method as in Example 1, the properties were similar to those of the fibrous basic aluminum sulfate obtained in Example 1, except that the length of the fibrous particles was in the range of 50 to 100 μm. It was found that it has Example 3 N/2-AlCl ₃ aqueous solution 400ml in a glass beaker
ml and stir with a magnetic stirrer, add 213 ml of N/2-NaOH aqueous solution,
Addition was made using a microtube pump at a rate of 1 ml/min. After the addition was completed, the mixture was stirred for an additional 12 hours, resulting in a colorless and transparent homogeneous solution with a pH of 3.59. The basic aluminum chloride thus obtained is theoretically thought to have a composition represented by the general formula Al(OH) _1.60 Cl _1.40 . Incidentally, both the above reaction and the reaction described below were carried out at a liquid temperature of 30°C. While stirring 613 ml of the above basic aluminum chloride aqueous solution, 500 ml of N/4-Na ₂ SO ₄ aqueous solution was added.
Using a micro tube pump, 2.1ml/
The same fibrous basic aluminum sulfate as in Example 1 was obtained. As in Example 1, the yield was 4.02 g when dried at 60° C. for 24 hours after washing. As a result of chemical analysis, it was found that the fibrous basic aluminum sulfate contained 23.7% Al and 25.5% SO ₄ . From this, it is thought that the composition of the basic aluminum sulfate obtained in this example is represented by the general formula Al(OH) _2.40 (SO ₄ ) _0.30 ·0.95H ₂ O. The yield was calculated to be 53% as the recovery rate of Al. Regarding this fibrous basic aluminum sulfate,
When the properties were examined by the same method as in Example 1, it was found that it had the same properties as the fibrous basic aluminum sulfate obtained in Example 1. Example 4 N/2-Al(NO ₃ ) ₃ aqueous solution in a glass beaker
Add 400 ml of N/2-NH ₄ OH aqueous solution 133 to this and stir with a magnetic stirrer.
1 ml using a micro tube pump
Addition was made at a rate of ml/min. After the addition was completed, the mixture was stirred for about 1 hour to obtain a colorless and transparent homogeneous solution, with a pH of 3.70. The basic aluminum chloride thus obtained is theoretically thought to have a composition represented by the general formula Al(OH) _1.00 (NO ₃ ) _2.00 . Incidentally, both the above reaction and the following reaction were carried out at a liquid temperature of 25°C. While stirring 533 ml of the above basic aluminum nitrate aqueous solution, 700 ml of N/4-Na ₂ SO ₄ aqueous solution was added.
Using a micro tube pump, 1.9ml/
When the mixture was added at a rate of 1.5 min, fibrous basic aluminum sulfate having properties similar to those of Example 1 was obtained. As in Example 1, the yield was 1.93 g when dried at 60°C for 24 hours after washing, and the yield was expressed as the recovery rate of Al.
It was 26%. As a result of chemical analysis, the above fibrous basic aluminum sulfate has the general formula Al(OH) _2.40 (SO ₄ ) _0.30 .
It was found that it had a composition expressed by 0.92H ₂ O. Example 5 N/2-AlCl ₃ aqueous solution 400ml in a glass beaker
ml and stirred with a magnetic stirrer, and 80 ml of N/2-KOH aqueous solution was added thereto at a rate of 1 ml/min using a micro tube pump. After the addition was complete, the solution was stirred for an additional 12 hours, resulting in a colorless and transparent homogeneous solution with a pH of 3.60. The basic aluminum chloride thus obtained is theoretically thought to have a composition represented by the general formula Al(OH) _0.60 Cl _2.40 . Incidentally, both the above reaction and the following reaction were carried out at a liquid temperature of 20°C. While stirring 480 ml of the above basic aluminum chloride aqueous solution, 850 ml of N/4-Na ₂ SO ₄ aqueous solution was added.
Using a micro tube pump, 1.8ml/
When the mixture was added at a rate of 1.5 min, fibrous basic aluminum sulfate having properties similar to those of Example 1 was obtained. As in Example 1, the yield is 0.29 g when dried at 60°C for 24 hours after washing, and the yield is expressed as the recovery rate of Al.
It was 3.8%. As a result of chemical analysis, it was found that the fibrous aluminum sulfate had a composition represented by the general formula Al(OH) _2.38 (SO ₄ ) _0.31 ·0.99H ₂ O. Example 6 Experimental operations were carried out under exactly the same conditions as in Example 1 except that an aqueous N/4-(NH ₄ ) ₂ SO ₄ solution was used instead of an aqueous N/4-NaSO ₄ solution. Also here, fibrous aluminum sulfate having properties similar to those in Example 1 was obtained. As in Example 1, the yield when dried at 60°C for 24 hours after washing was 3.56 g, and the yield was expressed as the recovery rate of Al.
It was 47%. As a result of chemical analysis, it was found that the fibrous aluminum sulfate had a composition represented by the general formula Al(OH) _2.42 (SO ₄ ) _0.29 ·0.92H ₂ O. Example 7 While stirring 600 ml of basic aluminum chloride aqueous solution obtained under the same conditions as Example 1, N/4-
Add 260 ml of Na ₂ SO ₄ aqueous solution to a micro tube.
Addition was made using a pump at a rate of 2.0 ml/min. After continuing to stir the milky white suspension obtained here for another 5 hours, absorption filtration was performed using No. 5C filter paper, the precipitate was filtered out, and the precipitate was washed and washed in the same manner as in Example 1. I did drying. At that time, since the filterability was poorer than in Example 1, the filtering and washing operations required a long time. The obtained white sheet was less flexible than that in Example 1, and when examined with a scanning electron microscope, it was found that the outer shape of the fibrous particles was slightly distorted, and some of them appeared to be fused. I found out. magnification
A scanning electron micrograph taken at 2000x is shown in Figure 3. Example 8 In Example 1, the temperature of the basic aluminum chloride aqueous solution was maintained at 50° C. when adding the N/4-Na ₂ SO ₄ aqueous solution, and the experimental operation was performed under exactly the same conditions other than that. Macroscopically, a milky white suspension similar to that in Example 1 was obtained here as well, but when this suspension was examined with an optical microscope, fibrous particles were obtained.
Most of them have a somewhat distorted fibrous morphology, and the diameter
Countless small spherical particles of about 0.1 to 0.2 μm were produced. Furthermore, when observation was performed using a scanning electron microscope in the same manner as in Example 1, it was confirmed that short fibrous particles with a length of about 10 μm and spherical particles with a diameter of about 0.2 μm were mixed. Ta. A scanning electron micrograph taken at 2000x magnification is shown in Figure 4. Example 9 In Example 1, the temperature of the basic aluminum chloride aqueous solution was maintained at 10° C. when adding the N/4-Na ₂ SO ₄ aqueous solution, and the experimental operation was carried out under exactly the same conditions except for that. of basic aluminum chloride aqueous solution at 10℃
The pH was 4.15. Macroscopically, a milky-white suspension similar to that in Example 1 was obtained, but when this suspension was examined with an optical microscope, it was found that the suspension contained fibrous particles with an average length of about 40 μm and diameters of 20 to 20 μm. Particles with a radial morphology of 30 μm were generated. Example 10 In Example 1, the experimental operation was carried out under exactly the same conditions except that the addition rate of the N/4-Na ₂ SO ₄ aqueous solution was 6 ml/min. It took 1 hour and 25 minutes to complete the addition of 520 ml of N/4-Na ₂ SO ₄ aqueous solution. Here, too, a milky white suspension that was macroscopically similar to that in Example 1 was obtained. When this suspension was examined with an optical microscope, it was found that fibrous particles similar to those seen in Example 1 were formed, but with a diameter of
It was found that particles with a radial shape similar to sea urchins of about 50 μm were generated. Further, when observation was carried out using a scanning electron microscope in the same manner as in Example 1, it was confirmed that one end of some of the fibrous particles was fused to form a radial shape. A scanning electron micrograph taken at 2000x magnification is shown in Figure 5. Example 11 In Example 5, the addition rate of the N/4-Na ₂ SO ₄ aqueous solution was set to 5.4 ml/min, and the experimental operation was carried out under the same conditions except that, the same properties as in Example 1 were obtained. A fibrous basic aluminum sulfate was obtained. As in Example 1, the yield is 0.28 g when dried at 60°C for 24 hours after washing, and the yield is expressed as the recovery rate of Al.
It was 3.6%. As a result of chemical analysis, the above fibrous basic aluminum sulfate has the general formula Al(OH) _2.32 (SO ₄ ) _0.34 .
It was found that it had a composition expressed by 0.98H ₂ O. Example 12 In Example 4, an experiment was carried out under the same conditions except that the N/4-Na ₂ SO ₄ aqueous solution was added at a rate of 0.8 ml/min, and the same properties as in Example 1 were obtained. A fibrous basic aluminum sulfate was obtained. As in Example 1, the yield was 2.09 g when dried at 60°C for 24 hours after washing, and the yield was expressed as the recovery rate of Al.
It was 28%. As a result of chemical analysis, the above fibrous basic aluminum sulfate has the general formula Al(OH) _2.43 (SO ₄ ) _0.285 .
It was found that it had a composition expressed as 0.90H ₂ O. Comparative example 1 N/2-AlCl ₃ aqueous solution 400% in a glass beaker
ml and stir with a magnetic stirrer, add 60 ml of N/2-NH ₄ OH aqueous solution,
Addition was made using a microtube pump at a rate of 1 ml/min. After the addition was completed, the mixture was stirred for about 1 hour to obtain a colorless and transparent homogeneous solution, and the pH at this time was 3.66. The basic aluminum chloride thus obtained is theoretically thought to have a composition represented by the general formula Al(OH) _0.45 Cl _2.55 . While stirring 460 ml of the above basic aluminum chloride aqueous solution, 900 ml of N/4-Na ₂ SO ₄ aqueous solution was added.
It was added at a rate of 3.4 ml/min using a micro tube pump, but even after the entire amount was added,
No formation of any precipitate was observed. Therefore, an attempt was made to further add an aqueous N/4-Na ₂ SO ₄ solution, but there was no change, and it was not possible to obtain fibrous basic aluminum sulfate as shown in the Examples. All of the above reactions were carried out at a liquid temperature of 25°C. Comparative Example 2 In Example 1, the experimental operation was carried out under exactly the same conditions except that the addition rate of N/4-Na ₂ SO ₄ was 0.4 ml/min. Again, a milky-white suspension was obtained that was visually similar to Example 1, but when this suspension was examined with an optical microscope, prismatic particles with an average width of 3 μm and a length of about 30 μm were observed. It was found that fibrous particles such as those observed in Example 1 were not generated. This suspension of prismatic particles was filtered, washed and dried in the same manner as in Example 1 to obtain 3.61 g of white powder of prismatic basic aluminum sulfate. As a result of chemical analysis, the above white powder contained 24.9 Al.
%, and SO ₄ was found to be contained at 22.2%. As a result, the composition of the prismatic basic aluminum sulfate obtained in this comparative example has the general formula Al(OH) _2.5
0 (SO ₄ ) _0.25 ·0.83H ₂ O, and was found to be different from the fibrous basic aluminum sulfate obtained in Examples in both properties and composition. Comparative Example 3 N/2-AlCl ₃ aqueous solution 400% in a glass beaker
ml and stir with a magnetic stirrer, add 260 ml of N/2-NH ₄ OH aqueous solution,
Addition was made using a microtube pump at a rate of 1 ml/min. After the addition was completed, the mixture was stirred for an additional hour to obtain a colorless and transparent homogeneous solution with a pH of 4.10. The basic aluminum chloride thus obtained is theoretically thought to have a composition represented by the general formula Al(OH) _1.90 Cl _1.05 . Incidentally, both the above reaction and the reaction described below were carried out at a liquid temperature of 25°C. While stirring 660 ml of the above basic aluminum chloride aqueous solution, 360 ml of N/4-(NH ₄ ) ₂ SO ₄ aqueous solution was added.
using a micro tube pump, 0.93
Addition was made at a rate of ml/min. Again, a milky white suspension was obtained that was visually similar to Example 1, but when this suspension was examined with an optical microscope, prismatic particles with an average width of 3 μm and a length of about 20 μm were observed. It was found that fibrous particles such as those observed in Example 1 were not generated. This suspension of prismatic particles was filtered, washed and dried in the same manner as in Example 1 to obtain 5.50 g of white powder of prismatic basic aluminum sulfate. As a result of chemical analysis, the above white powder contained 24.6 Al.
It was found that it contained 22.3% of _SO4 . As a result, the composition of the prismatic basic aluminum sulfate obtained in this comparative example has the general formula Al(OH) _2.5
0 (SO ₄ ) _0.25 ·0.90H ₂ O, and was found to be different from the fibrous basic aluminum sulfate obtained in the Examples in both properties and composition. In addition, in the above Examples 1 to 12 and Comparative Examples 1 to 3, the rate of addition of the soluble sulfate to the basic aluminum salt solution was such that the molar ratio of SO ₄ /Al was (3-
The addition rate was such that the addition time T until reaching the value of C)/2 (where C is the sign in the general formula Al( _OH ) _c

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is an optical micrograph (magnification: 750 times) of a suspension of fibrous basic aluminum sulfate obtained in Example 1 of the present invention. Figures 2 to 5 are
1 is a scanning electron micrograph (magnification: 2000 times) of a dried sheet of basic aluminum sulfate obtained in Examples 1, 7, 8, and 10 of the present invention, respectively. FIGS. 6 and 7 show the X-ray diffraction diagrams of the fibrous basic aluminum sulfate of the present invention in wet and dry states, respectively;
FIG. 8 is an X-ray diffraction diagram of the Al plate.

Claims (1)

[Claims] 1 General formula Al(OH) _a (SO ₄ ) _b・nH ₂ O (however, a+
2b=3, 2.32a<2.44, 0.28<b0.34, O
Fibrous basic aluminum sulfate represented by n10). 2 Soluble sulfate was added to a basic aluminum salt solution represented by the general formula Al _{( OH} ) _c /Al molar ratio is (3-c)/2 (however,
c is the general formula of basic aluminum salt Al(OH) _c X _d
The general formula Al is characterized by being added at such an addition rate that the addition time T (unit: hours) until it reaches the value of (sign)
(OH) _a (SO ₄ ) _b・nH ₂ O (a+2b=3, 2.32
a<2.44, 0.28<b0.34, On10) A method for producing fibrous basic aluminum sulfate. 3 Soluble sulfate is added at a molar ratio of SO ₄ /Al of (3
-c)/2 (where c is the sign in the general formula Al(OH) _c X _d of the basic aluminum salt). 4. The manufacturing method according to claim 2, wherein the soluble sulfate is added so that the addition time T (unit: hours) also satisfies T1.40. 5. The manufacturing method according to claim 2, wherein the addition of the soluble sulfate is carried out at a temperature of 10°C or higher and lower than 50°C. 6 A patent claim in which the basic aluminum salt solution is obtained by adding an alkaline solution to an aluminum salt solution of a monovalent anion in an amount such that the molar ratio of OH/Al in the solution is in the range of 0.5 to 1.9. The manufacturing method according to item 2.