JPS6045125B2 - Manufacturing method of alumina sol - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing alumina sol.

More specifically, the present invention relates to a method for producing an alumina sol that has low viscosity and excellent stability over time.

Currently, various alumina sols and dispersible alumina powders that are intended to be used by drying the sol into a powder and redispersing it are on the market, but all of these products contain approximately 10% by weight or more. A1 of.

When the sol reaches a concentration of 03, its stability over time decreases significantly and it gels within a few days.

Also, low A1. O. Concentrated sols have the disadvantage that large amounts of medium must be transported or that large amounts of medium must be evaporated during use. Alumina sol is usually produced by peptizing an alumina gel dispersion with an inorganic or organic acid. Conventionally, as a method for producing alumina sol, a dispersion of 1-alumina gel was hydrothermally treated in the presence of an acid with an acid radical/Al (molar ratio) of 0.5 to 2.4 to form a fiber having a boehmite crystal lattice. A method for producing alumina sol (Japanese Patent Publication No. 40-1429), in which an aqueous solution of sodium dialuminate and a water-soluble aluminum salt solution are reacted in a short period of time at a pH of 9 to 10 to produce alumina gel. After aging, a monovalent inorganic acid or an organic acid is added to the alumina gel dispersion so that the acid radical/Al (molar ratio) is 0.15 or more, thereby producing a uniform sol (Japanese Patent Publication No. 1973- No. 84 Publication), 8 Pseudo-boehmite produced by blowing carbon dioxide into a sodium aluminate solution was mixed with acid radical/Al (molar ratio) from 0.05 to
A method of dispersion in a strong monovalent acid of 0.2 (British Patent No. 1)
440194) etc. have been proposed.

However, the alumina sol obtained by method 1 contains Al in the slurry during sol formation, probably because the alumina is fibrous.

If the O3 concentration is about 1% by volume or more, a gel will form during the hydrothermal treatment and it will not be possible to form a sol, and when the dispersible alumina powder obtained by this method is dispersed in water to prepare a liquid sol. , with a low Al2 concentration of approximately 1% by volume or less
Even in the case of adjusting the O3 concentration of the sol, there is a drawback that the dispersibility is poor and the sol cannot be obtained efficiently. In addition, the amount of acid used for solization is also the same as acid radical/. A1 (molar ratio) 0.5-2.
It only teaches the range of 4. The powder for alumina sol obtained by method 2 also has poor redispersibility and Al2O
This method has the disadvantage that an alumina sol having a concentration of up to about 1% by volume can only be prepared, and the stability over time at that concentration is also extremely poor.

In addition, in the Japanese Patent Publication No. 1984-1984, it is stated that in the case of alumina gel produced by this method, the acid radical/A1 (molar ratio) is 0.1.
It is stated that if it is less than 5, the resulting powder will not convert into sol form. The alumina sol produced by method 3 and having an Al2O3 concentration of about 10% by weight or more is stable for only a few days at most.

Furthermore, the British patent specification states that the alumina gel produced by the patented method cannot be converted into a sol using an organic acid. As described above, among the conventionally known methods, there is no known method for producing an alumina sol with excellent stability over time at a high Al2O3 concentration.

Under such circumstances, the present inventors conducted intensive research to produce an alumina sol with significantly superior stability over time, and found that alumina gel obtained from a specific aluminum salt was treated with a specific organic acid, a specific acid group/ It has been found that the above object can be achieved by processing in the presence of Al (molar ratio). That is, the present invention uses general formula Al.

(0H), XyY2 (wherein, X is Cl or NO3, Y
indicates SO4, x+y+22=6, 0〈x〈6,0≦
y x 6, 0≦22 x 6, Y. ．． z is not zero at the same time.
) Alumina gel produced by neutralizing a water-soluble basic aluminum salt represented by
To provide a method for producing an alumina sol having low viscosity and excellent stability over time, which is obtained by hydrothermal treatment in the presence of a monovalent organic acid in an amount such that the molar ratio of A1 is 0.001 to less than 0.005. In carrying out the method of the present invention, the raw material alumina has the general formula Al2(0H), X, Y2 (wherein, X, Y, x, y and z are the same as above. Preferably, An alumina gel obtained by neutralizing a water-soluble basic aluminum salt represented by 1<x<5) with an alkali is used.As the water-soluble basic aluminum salt, basic aluminum chloride, basic aluminum nitrate, etc. ,
Basic aluminum sulfate is mentioned, and basic aluminum chloride is particularly preferably used.

In the case of an alumina gel produced from an aluminum salt other than the above-mentioned water-soluble basic aluminum salt, the organic acid present in the method of the present invention cannot produce an alumina sol with excellent stability over time.

As the alkali, carbonates such as ammonium carbonate and sodium carbonate, bicarbonates such as sodium hydrogen carbonate and ammonium hydrogen carbonate, and aluminates such as sodium aluminate are preferably used, but other alkalis such as ammonium hydroxide and caustic soda are preferably used. etc. can also be used. The gel-forming reaction between the water-soluble basic aluminum salt represented by the above general formula and an alkali is generally carried out at temperatures below 100°C, since if the reaction is carried out at a temperature higher than 100°C, the resulting gel will crystallize and become difficult to peptize. , preferably about 15
It is carried out at a temperature of ~50°C. The alumina gel thus produced is aged if necessary and then washed to remove by-products. In this case, since the filterability deteriorates with repeated washing, it is preferable to wash with a weak alkali such as dilute ammonia water or ammonium carbonate, and finally wash with pure water.

The alumina gel after washing can be made into a dispersion or a cake with an AI2O3 content of several percent to about 7% by weight by ordinary filtration, drying, or a combination of these, but the form depends on the purpose of use. Adjustments will be made as appropriate.

In carrying out the present invention, the alumina gel obtained by alkali neutralization of a water-soluble basic aluminum salt as described above has a molar ratio of organic acid acid group/A1 of 0.001 to 0.
Low viscosity and high Al2O3 concentration are obtained by hydrothermal treatment in the presence of a monovalent organic acid in an amount less than 0.005,
An alumina sol with excellent stability over time can be obtained.

The monovalent organic acids used in the hydrothermal treatment of the present invention include acetic acid, formic acid, etc., and the amount of the acid radicals of the organic acid/mol of A1 based on Al2O3 in the alumina gel slurry. The ratio is 0.001 to less than 0.005,
Preferably it is about 0.002 to 0.004.

If other acids are used, the expected effects of the present invention cannot be obtained, and if the molar ratio of acid radical/AI is less than 0.001, peptization becomes extremely difficult and productivity decreases.
．． 005 or higher, the stability of the alumina sol over time tends to decrease, especially at high Al2O3 concentrations. The organic acid may be added to the alumina gel before hydrothermal treatment, or it may be added during alumina gel production so that an appropriate amount of the organic acid remains after washing, and the latter method has particularly excellent peptizing performance. This method is effective because alumina gel can be obtained.

This hydrothermal treatment is about 120 to 300' C1, preferably about 14
0.5 to 7 hours, preferably 2 to 7 hours at a temperature of 0 to 200°C
It will be held for 4 hours.

When the treatment temperature is lower than about 120'C, high Al2O
It is difficult to form a sol with three concentrations, it takes a long time to peptize, and a temperature higher than about 300° C. requires rapid cooling equipment, a high pressure container, etc., which is not desirable. When the hydrothermal treatment is carried out under the above conditions, the alumina gel slurry gradually peptizes and changes from milky white to translucent, and an alumina sol having an arbitrary alumina concentration up to about 3% can be produced.

The viscosity of the sol obtained by this hydrothermal treatment is extremely low at 25°C when the Al2O3 concentration is 25% by weight, which is approximately 60:)PS (centipoise or less). It is extremely stable, with only an increase in viscosity. As a result of X-ray diffraction and electron microscopic observation, this alumina sol has a boehmite crystal lattice of about 0.
．． It is plate-like or rod-like with a size of 1 to 0.02μ, and is not fibrous.

The alumina sol produced in this way can be used as it is as a dispersion liquid, or it can be dried by means such as spray drying to form an alumina powder, then redispersed in water and converted into a sol, or it can be used as a powder. It can also be used as is.

According to the method of the present invention as described in detail above, it is possible to produce an alumina sol with lower viscosity, higher Al2O3 concentration, and significantly superior stability over time compared to known methods.

The alumina sol produced by the method of the present invention is particularly useful, for example, as a binder, coating agent, surface modifier, polymer reinforcing agent, catalyst support, hardening agent, stabilizer for cosmetics, pharmaceuticals, aerosol chemicals, paints, printing inks, etc. .

The method of the present invention will be explained in more detail with reference to Examples below, but the method of the present invention is not limited thereto.

Example 1 A1203 4.5% by weight, 0H/A1 (equivalent ratio) 0.4
Add N to 1 (1) part by weight of the basic aluminum nitrate aqueous solution of No. 5.
723 parts by weight of an aqueous ammonium carbonate solution containing 33.5% by weight of H3 was added at 20°C with stirring to produce an alumina gel.

After aging the resulting alumina gel for 1 hour, it was washed and filtered to obtain 46.5 parts by weight of a cake with an Al2O3 content of 9.5% by weight. This cake was dried in an air bath at 90°C to obtain 8.4 parts by weight of a dry gel containing 5% Al2O3.
1 part by weight of this dry gel was mixed with 1.08 parts by weight of water (Al2O
3 (concentration: 25% by weight) to prepare an alumina gel slurry.

The amount of acetic acid shown in Table 1 was added to this slurry, which was then transferred to a glass autoclave and subjected to hydrothermal treatment at a temperature of 150 to 160°C for 2 hours. Table 11 shows the properties of the alumina sol obtained. Example 2 A1.

034.5% by weight, 0H/A1 (equivalent ratio) 0.43 basic aluminum chloride aqueous solution (100 parts by weight) and 10.9% by weight Na2cO3 aqueous solution 75%. The weighing portion was added over 30 minutes while stirring at 20°C to produce alumina gel.

The resulting alumina gel was aged for 1 hour, then washed and filtered through P to obtain 45.8 parts by weight of a cake with an Al2O3 content of 9.64% by weight. This cake was dried in an air bath at 90°C.
Al2O35l. 8.5 parts by weight of dry gel (heel weight %) was obtained. 1 part by weight of the dry gel was mixed with 0.8 parts by weight of water (Al.O.
3 (concentration: 27.5% by weight) to prepare an alumina gel slurry. To this slurry, the amount of formic acid shown in Table 2 was added, and the slurry was transferred to a glass autoclave.
Hydrothermal treatment was carried out at a temperature of 0° C. for 2 hours. As a result, the properties of the alumina sol obtained were as shown in Table 2, and the peptization rate was 90.9%.

Comparative Example 1 To the alumina gel slurry obtained in the same manner as in Example 2, formic acid was added in an amount such that the acid radical/A1 (molar ratio) was 0.0008, and the mixture was transferred into a glass autoclave and was mixed with an alumina gel slurry of 150 to 16
Hydrothermal treatment was carried out at a temperature of 0° C. for 2 hours.

As a result, the Al2O3 concentration of the obtained alumina sol was 1
The peptization rate was 9.1% by weight, and the peptization rate was 69.5%.

Claims (1)

[Claims] 1 General formula Al_2(OH)_xX_yY_z (in the formula,
X represents Cl or NO_3, Y represents SO_4, x+y
+2_z=6, 0<X<6, 0≦y<6, 0≦2_z<
6, y, and z are not zero at the same time. ) Alumina gel obtained by neutralizing a water-soluble basic aluminum salt represented by an alkali with an alkali is mixed with a monovalent organic acid in an amount such that the molar ratio of organic acid acid group/Al is 0.001 to less than 0.005. A method for producing alumina sol, characterized by hydrothermal treatment in the presence of. 2. The method for producing an alumina sol according to claim 1, wherein the water-soluble basic aluminum salt is basic aluminum chloride. 3. The method for producing an alumina sol according to claim 1 or 2, wherein the water-soluble basic aluminum salt is neutralized with an alkali at a temperature of about 15 to 50°C. 4. The method for producing an alumina sol according to any one of claims 1 to 3, wherein the hydrothermal treatment is carried out at a temperature of about 120 to 300°C. 5. The method for producing an alumina sol according to claim 4, wherein the hydrothermal treatment is carried out at a temperature of about 140 to 200°C. 6 Claims 1 to 5 in which the monovalent organic acid is acetic acid
A method for producing an alumina sol according to any of the above.