JPS6336808B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing elements for microfiltration, ultrafiltration or reverse osmosis, in which alkoxides, organometallic compounds or A metal salt of an inorganic or organic acid is hydrolyzed to produce a sol of oxide or hydroxide particles of the corresponding chemical element, a thickening agent is added to said sol, and the resulting sol is desirably used in a filtration element. A support layer with coarser pores is coated, the thin film deposited on the support layer is then dried, and the thickening agent is removed by heat treatment to cause sintering of the particles of the deposited thin film. do.

(Ceramic by BEYoldas)
Bulletin, 54 No. 3 (1975) 286-290), an alumina gel is prepared by hydrolyzing an aluminum alkoxide with hot water, and the suspension formed is treated with a strong acid, which produces an anion that does not complex with aluminum. A method for deflocculating the material has already been proposed. The resulting sol is dried to form a microporous gel that can be used as a filter medium.

Further, French Patent Publication No. 2150390 proposes a method in which a thickener is added to the sol and coating is performed by a filtration action.

However, it is difficult to produce sols that can be deposited onto microporous supports to form filtration layers, and to obtain particle sizes fine enough to be suitable for use in microfiltration, ultrafiltration and reverse osmosis. It's also difficult.

Furthermore, it is difficult to prevent the gel from cracking and collapsing during the drying and firing process of the gel layer deposited on the support layer.

The object of the present invention is to provide a coating material that can be easily deposited on a support layer by coating and that can prevent coarsening of particles and generation of cracks and collapse of the gel during the drying and baking process of the gel. It is an object of the present invention to provide a method for manufacturing an element for microfiltration, ultrafiltration, or reverse osmosis as described above. Further objects of the present invention include extremely small and uniform pore size, high permeability, thin and uniform thickness, good mechanical durability, back pressure cleaning and high filtration. The object of the present invention is to provide a method for producing an element for microfiltration, ultrafiltration, or reverse osmosis, which has characteristics such as being able to use pressure, having good chemical resistance, and being resistant to the effects of microorganisms and oxygen.

In the production method of the present invention, alkoxide,
A sol of particles of oxides or hydroxides of chemical elements present in organometallic compounds or metal salts of inorganic acids or organic acids is produced by hydrolysis, and the sol of particles is A strong acid, which produces an anion that does not form a complex with the metal ion of the oxide, is added together with a thickener, and the coating is effected by mere contact without filtration.

As mentioned above, by using a strong acid that produces an anion that does not form a complex with the metal of the oxide or hydroxide, the metal of the oxide or hydroxide is not liberated as an ion and forms the oxide or hydroxide. is maintained in a precipitate state.

In addition, since it is a strong acid, even if it is added at a low concentration, the surface charge hardening of the sol particle surface necessary for peptization can be obtained. If a high concentration of acid is used, the capacity occupied by the acid in the sol before firing will be extremely large, and the acid will volatilize during firing, solidifying the final element and making it impossible to obtain porosity.

Preferably, the method has one or more of the following features.

-The thickener is polyvinyl alcohol.

-A strong acid is nitric acid.

- Slow drying at a temperature below the boiling point of water.

- as a microporous solid homogeneous layer in which during heat treatment the organic substances originating from the thickener are removed and at least a portion of the hydroxide particles are decomposed into oxide particles and the said particles are deposited on the support layer; Use a temperature level and duration sufficient to cause sintering.

- Increasing the maximum temperature of heat treatment to obtain a layer with coarser pores.

In addition to nitric acid, other strong acids that function as deflocculants include:
Particularly suitable are hydrochloric acid, perchloric acid, and trichloroacetic acid.

Using the method described above, in particular if the particles are aluminum,
Such microfiltration, ultrafiltration or reverse osmosis elements can be produced from hydroxides or oxides of titanium, zirconium or silicon or mixtures thereof.

As an example, a method for manufacturing a membrane according to the present invention will be shown below.

Example 1 A sol of boehmite (monohydrated alumina) obtained by hydrolysis of aluminum alkoxide, which is commercially available from Condea-Chimie under the trade name "Pural SB", was used. use.

Composition A is made by mixing 18 g of "Pural SB" boehmite, 30-40 g of deionized water, and 1.5 g of a nitric acid solution at a concentration of 10 g of nitric acid to 160 g of water.

Furthermore, a composition B having the following composition is prepared.

- 30-35 g of polyvinyl alcohol gel (concentration of 12.5 g of alcohol to 100 g of water (trade name Rhodoviol 25/140)) - 12-13 g of nitric acid solution (concentration of 20 g of acid to 150 g of water) Surfactants are optionally added to the composition in order to obtain good peptization and good wetting of the surface on which the film is deposited.

Compositions A and B are then stirred and homogenized;
Obtain a viscous liquid.

This mixture is filled into a porous tube having pores coarser than desired for the ultrafiltration element. Empty the tube after 1 to several minutes. A portion of the mixture remains deposited in a film on the inner wall of the tube.

Next, heat treatment for drying and firing is performed as follows: - Drying at 20°C for 24 hours - Temperature rise from 20°C to 200°C in 1 hour - Temperature rise from 200°C to 300°C in 1.5 hours - 300°C After calcination at 560°C, a filtration layer with a thickness of approximately 5 microns, a pore diameter of 58 angstroms and a water permeability of 5 liters/hour·m ² ·bar at 20°C is obtained.

Depending on the experimental conditions, a thin film with a thickness of 1 to several tens of microns can be obtained, and depending on the maximum firing temperature, a pore diameter of several angstroms to several thousand angstroms can be obtained, with an opening of 5 to 75% of the pore volume of the film volume. Porosity is obtained. This thin film is bonded onto the porous support layer by sintering.

The final firing temperature can be varied as a function of the desired average pore diameter. At a final temperature of 560°C, the average pore diameter is 58 angstroms;
106 angstroms at 1000℃, final temperature 1200
At ℃ it is 1100 angstroms.

In either case, the pore diameter is mostly close to its average value. For example, the total pore volume of pores with diameters in the range of 1/2 to 2 times the average pore diameter reaches 90%.

Example 2 50% of isobutoxide aluminum Al(OC ₄ H ₉ ) ₃
g Mix with 350 g of deionized water. After stirring for 2 hours at 85°C, the following reaction occurs: Al(OC ₄ H ₉ ) ₃ + (2+X)H ₂ O→AlOOH・
XH ₂ O + 3C ₄ H ₉ OH hydroxide (boehmite) precipitates. The precipitate is washed with water in a Buchner funnel. A precipitate is again obtained which still contains a large amount of water.

This precipitate makes up the following composition A: -Non-dried boehmite precipitate 23% by weight -Deionized water 27% by weight - 15% by weight solution of 20g nitric acid in 320g water Furthermore, the following composition B is made: - Alcohol 12.5% 4% by weight per 100g of water proportion of polyvinyl alcohol (Rhodobiol 25/140) - Deionized water 31% by weight Mix and homogenize compositions A and B.

The resulting viscous liquid is filled into a porous tube. 1~
Empty the tube after a few minutes. A portion of the liquid is deposited on the inner wall of the tube onto a film.

Next, the same heat treatment as in Example 1 is performed. 2-3 microns thick, 40 angstroms at 750°C firing temperature, and 40 angstroms at 1050°C firing temperature.
A layer with an average pore diameter of 120 angstroms is obtained.

Claims (1)

[Claims] 1. A method for producing an element for microfiltration, ultrafiltration or reverse osmosis, which comprises hydrolyzing an alkoxide, an organometallic compound, or a metal salt of an inorganic or organic acid, optionally dissolved in an anhydrous organic solvent. to produce a particle sol of the oxide or hydroxide of the corresponding chemical element, add a thickener to the sol, and apply the resulting sol to a filter element with pores coarser than the desired pores. The method involves coating a support layer with Adding to the sol of oxide particles, together with a thickening agent, a strong acid which forms an uncomplexed anion with the ions of the metals of these oxides or hydroxides, and by mere contact without filtration. The method described above, characterized in that coating is performed. 2. The method according to claim 1, wherein the thickener is polyvinyl alcohol. 3. The method according to claim 1 or 2, wherein the strong acid is nitric acid. 4. The method according to any one of claims 1 to 3, characterized in that the drying is performed slowly at a temperature lower than the boiling point of water. 5. In the heat treatment, the organic substances originating from the thickener are removed and the hydroxide particles are at least partially decomposed into oxide particles, which form a microporous solid homogeneous layer that adheres to the support layer. 5. A method according to any of claims 1 to 4, characterized in that temperature levels and durations sufficient to cause sintering are used. 6. The method according to claim 5, characterized in that the maximum temperature of the heat treatment is increased in order to obtain a layer with coarser pores.