JPS6158815A - Manufacture of high-purity alumina sol - Google Patents

Abstract

PURPOSE:To obtain high-purity alumina sol by separating and purifying alumina sol which is obtained by neutralizing an aq. soln. of alkali metal aluminate and an aq. soln. of organic hydroxylic acid with the ultrafiltration membrane or the like. CONSTITUTION:Alumina sol is manufactured by netralizing an aq. soln. of alkali metal aluminate and an aq. soln. of organic hydroxylic acid and allowing both the two to react. The alumina sol is purified with the membrane such as both the ultrafiltration membrane wherein the solute is selectively separated by the porous membrane in using the pressure as its driving force and the membrane filter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel method for producing a high-purity alumina sol, more specifically, an aqueous solution of an alkali metal salt of aluminate and an organic sol having at least one hydroxyl group in the molecule. The organic hydroxyl acid or its salt contained as an impurity is separated and removed from the alumina sol obtained by neutralizing the alumina sol with an aqueous solution of hydroxyl acid, so that the particles are fine and do not cause aggregation in a wide pH range. This invention relates to a method for producing high-purity alumina sol that can be stably maintained for a long period of time.

[Conventional technology]

Alumina sol is a heat-resistant binder in the electrical and electronic industries, ceramics, and foundry industries, a compounding base for ointments in cosmetics and pharmaceuticals, aerosol products, texture improvement in the textile industry, anti-pilling, and an emulsifier in paints, pigments, and printing inks. It is useful as a stabilizer, an adhesion improver, a resin, a surface coating agent for paper, a sizing agent, a catalyst carrier in the petroleum industry, etc.

Various methods have been known to produce alumina sol, but Akio Manba, one of the inventors of the present invention, et al. neutralized an aqueous solution of an alkali metal salt of aluminate and an aqueous solution of an organic hydroxyl acid. We discovered a method for producing alumina sol, which has fine particles and can be stably maintained for a long period of time in a wide pH range without causing @ concentration, by reacting, and filed a patent application (Japanese Patent Application No. 58-93453).

[Problem that the invention seeks to solve]

However, although this method is extremely superior to previous methods, it has the drawback that the organic hydroxyl acid and its salt as raw materials are mixed into the alumina sol produced.

However, if these organic hydroxylic acids or their salts are contained in alumina sol, they cause various adverse effects and severely limit the range of applications of alumina sol. for example,
In applications to electrical and electronic industries, organic hydroxylates cause corrosion to metals, making their use in this field difficult.

There are also concerns about negative physiological effects on cosmetics and pharmaceuticals. However, the alumina sol obtained by the above method is
It is a colloidal solution using water as a dispersion medium, and impurities such as organic hydroxyl acids and their salts are dissolved in water. Therefore, it is predicted that alumina sol can be purified by using solid-liquid separation means such as filtration and washing with water. However, the obtained alumina sol particles were very fine, with a particle size of 0.1 μff.
It is impossible to capture such fine particles using normal filtration methods, as they also contain particles of Z or lower. In addition, centrifugation requires ultracentrifugation at tens of thousands of rpm or more, which will be extremely difficult for industrialization. In addition, both filtration and centrifugation produce a filter cake or a centrifugation cake, and the concentration of colloidal particles becomes very thick in this part, and as the concentration of organic hydroxyl acid decreases, aggregation between colloidal particles occurs. There were problems such as falling, and the coffinashi was difficult.

[Failure to solve the problem]

Therefore, the present inventors conducted intensive research on a method for effectively refining alumina sol by capturing even minute particles and suppressing agglomeration between particles, and as a result, completed the present invention.

That is, the present invention provides a membrane that selectively separates stone from an alumina sol obtained by neutralizing an aqueous solution of an alkali metal aluminate salt and an aqueous solution of an organic hydroxyl acid using a porous membrane using pressure as a driving force. The present invention provides a method for producing a high-purity alumina sol, which is characterized by purifying the alumina sol (by a separation method).

In the present invention, the alkali metal aluminate salts include:
Sodium aluminate, potassium aluminate or a mixture thereof can be mentioned, and the composition thereof can be
Preferably, k13203 is in the range of 1.0 to 1.7 (molar ratio) (M represents an alkali metal). , The organic hydroxyl acid has the following general formula (,1) or (
Those represented by n) are preferred.

R(OH) m (COOH) n (1) R(
OH) m (PO, H2) n (old (in the formula, m
and n represents a number of 1 or more, R represents a saturated or unsaturated aliphatic group having 1 to 10 carbon atoms, and the molecular weight per acid group is 200 or less) Preferred organic hydroxyl acids Specific examples include oxycarboxylic acids such as glycolic acid, lactic acid, glyceric acid, hydroacrylic acid, oxybutyric acid, tartaric acid, malic acid, araponic acid, gluconic acid, and citric acid; 1-hydroxyl f') f7-1. Examples include oxyphosphonic acids such as 1-diphosphonic acid and 2-hydroxypropylphosphonic acid.

Although the neutralization method of the present invention is not particularly limited, it is preferable to drop an aqueous solution of an organic hydroxyl acid into an aqueous solution of an alkali metal aluminate. The concentration of the aqueous solution of alkali metal aluminate is preferably 2 to 40% by weight, and the concentration of the aqueous solution of organic hydroxyl acid is preferably 5 to 50% by weight.The alumina sol thus obtained is purified by a membrane separation method.

In this membrane separation, when the colloid concentration within the membrane increases, the organic hydroxyl acid or its salt is removed and the colloid particles agglomerate, as described above. Therefore, in order to suppress this, it is necessary to maintain the colloidal particle concentration in the membrane at 40% or less as aluminum hydroxide, and furthermore to suppress the viscosity during membrane separation and obtain a certain amount of water permeation. Considering this, it is preferable to maintain the concentration at 5 to 15%.

The porous membrane used in the present invention does not pass aluminum colloid,
Any porous membrane that allows organic hydroxyl acids and their salts to pass through may be used, and if there is no particular restriction on the membrane, membranes called ultrafiltration membranes, membrane filters, etc. are easy to use in industrial applications.

Also, the form of the membrane is not particularly limited, and may be a flat membrane.

Any form of membrane can be used, such as tubular membranes, spiral membranes, and hollow fiber membranes.

The pressure used as the driving force may be any pressure lower than the withstand pressure of the membrane, and the pressure range is not particularly limited. For ultrafiltration membranes and the like, a pressure of 2 to 3 k17/cd is usually used.

When the temperature during membrane separation is lower than the membrane's heat resistance temperature, the higher the temperature, the lower the viscosity of the system and the higher the water permeation rate. Although some commercially available ultrafiltration membranes have heat resistance up to about 80°C, it is preferable to perform membrane separation at about 40°C in consideration of energy saving.

In this case, the colloidal particles of the alumina sol remain within the membrane, and the organic hydroxyl acid and its salt dissolve in water and are removed from the membrane, so that the two can be advantageously separated to obtain a highly pure alumina sol.

〔Example〕

Next, an example will be given and explained.

Example 1 (1) Potassium aluminate aqueous solution (MtOs 1
1.3%, K, 0, 0, 9 with a molar ratio of 1.631270 was placed in a container and kept at 15° C. with stirring. Next, 280 kg of a 27-chickenic acid aqueous solution was gradually added dropwise to this potassium aluminate aqueous solution, and the pH was adjusted to 8.
0 to obtain an alumina sol.

(II) 550 kg of the alumina sol obtained in (+) with a colloidal concentration of 8.5% as aluminum hydroxide and containing 20.5% potassium citrate was mixed with a membrane area of 4.717? , purified using an ultrafiltration membrane with a molecular weight cutoff of 6000.

The average pressure for membrane separation was maintained at L7 at 9/m, and in order to maintain the alumina sol concentration, the membrane separation was performed while continuously supplying water equal to the amount of permeated water. After 9.7 hours of operation, the potassium citrate concentration could be reduced to 1.3. The average amount of water permeated through the membrane is 30A/hr-mLkg/
CIIL, and the amount of water supplied is 2.3 i te% x 7'c.

Example 2 210 kg of alumina sol having a colloidal concentration of 9.2% as aluminum hydroxide and a potassium citrate content of 23.3%, obtained in the same manner as in Example 1 (1), was added to Example 1.
Using the same ultrafiltration membrane as in (11), the average pressure was 1.71.
Purification was performed using 9/Crl. In other words, an alumina sol containing 9.2 g of aluminum hydroxide was concentrated in a membrane until it reached 13.8%, and then water was supplied in an amount equivalent to the amount of permeated water to maintain an aluminum hydroxide concentration of 13.8%. I did some refining. Average permeation flow rate 613/hr, m2
- When water permeated at kgΔ for 20 hours, potassium citrate was reduced to 1.4%.

that's all

Claims (1)

[Claims] 1. Purify the alumina sol obtained by neutralizing an aqueous solution of aluminic acid or an alkali metal salt with an aqueous solution of an organic hydroxyl acid using a membrane separation method that selectively separates solutes using a porous membrane using pressure as a driving force. A method for producing high purity alumina sol.