JPS6278106A - Transparent film and production thereof - Google Patents

Abstract

PURPOSE:To produce a film having excellent transparency and composed of extremely fine alumina particles, by casting a specific alumina dope on a substrate. CONSTITUTION:An aqueous solution of an aluminum salt [e.g. Al2(SO4)3] is added with excess ammonia water, aged by leaving at 5-7 pH for 12-24hr, separated and washed with water to obtain precipitate of aluminum hydroxide. The precipitate is added with 6-20% acetic acid and 100-300% water based on the weight of the precipitate and the mixture is refluxed by heating at 60-90 deg.C for 3-8hr to obtain alumina dope, which is, if necessary, added with a sol or liquid of inorganic oxide fine powder (e.g. SiO2) or an aqueous solution of a water-soluble metallic compound, etc. The dope is cast on a releasable substrate and water is slowly evaporated from the cast film at 20-30 deg.C spending 20-60hr to obtain a transparent film having a thickness of 10-50mu and com posed of fine alumina particles of 3-30nm in diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a transparent film made of alumina particles having an extremely fine particle size and a method for producing the same.

[Technical background of the invention and its problems]

When ultrafine particles with a particle size of 10 Qnm or less are made of a total bending compound or a total bending compound, the specific surface area becomes extremely large, and therefore characteristics different from those of particles in a bulk state are expected.

Conventionally, fine particles having a particle size of, for example, about 20 to 500 nm have been known, and gas evaporation methods, solvent freezing methods, plasma methods, etc. have been used as methods for producing them. however,
The fine particles produced by these methods were not fully satisfactory in terms of particle size uniformity, stability, ease of handling, etc. For example, when fine particles were produced by conventional methods, - Even if fine particles are obtained, since they themselves have high activity, aggregation occurs between each particle, and as a result, only large particles can be obtained. It was difficult to redisperse the clumps into smaller particles.

As a countermeasure to this problem, methods include generating fine particles in a microemulsion and coating the particle surface with an appropriate surfactant, or freezing and condensing the particles obtained by evaporation with an appropriate solvent. is being carried out. However, with these methods, it is difficult to generate a uniform microemulsion and to set the conditions for generating fine particles.
The latter tends to cause secondary aggregation when the solvent is removed, and in both cases it is difficult to remove the surfactant and solvent.

As mentioned above, ultrafine particles, especially those with a particle size of 1100n
It is difficult to produce ultrafine particles with a particle diameter of less than 100 mL, and for this reason, it has been almost impossible to produce films using them. Conventionally known films include, for example, silica or alumina films produced by the sol-gel method using alkoxide hydrolysis, colloidal substances of layered compounds, or colloidal substances and functional groups such as imino groups and vinyl groups. An inorganic film made of a mixture of monomers with
However, these films had problems in terms of transparency because of the large particles they contained.

[Purpose of the invention]

It is an object of the present invention to solve the above-mentioned problems and provide a film that is made of extremely fine alumina particles and has high transparency.

[Summary of the invention]

As a result of intensive research to achieve the above object, the present inventors have found that extremely fine alumina particles can be obtained by appropriately adjusting the aging and decomposition conditions when producing alumina from aluminum salt. Furthermore, they discovered that a film made of ultrafine alumina particles has high transparency, and completed the present invention.

That is, the present invention relates to a transparent film made of fine alumina particles, characterized in that the fine alumina particles have a particle size of 3 to 30 nm, and a method for manufacturing the same.

The fine alumina particles constituting the transparent film of the present invention are produced by producing aluminum hydroxide from an aqueous aluminum salt solution, and then by appropriately selecting the aging and decomposition conditions. Alumina fine particles can be obtained.

Examples of the aluminum salt used here include aluminum sulfate, aluminum chloride, and aluminum nitrate.

A known method can be used to generate aluminum hydroxide from these aluminum salts. That is, by dissolving the above-mentioned aluminum salt in water and then adding excess aqueous ammonia to this solution, aluminum hydroxide can be precipitated. Next, the produced precipitate is aged as it is under a constant pH condition for a certain period of time. In this case, the po is 5 to 7, preferably 5.8 to 6.3. Adjustment of pH is as follows. , when adding ammonia water, the above pH
This is done by adjusting the amount added so that it falls within the range of
In addition, the aging time is 12 to 24 hours, preferably 15 to 2 hours.
0 hours is good.

After aging the precipitate of aluminum hydroxide produced in this way, the precipitate is separated by a method such as centrifugation or filtration, and thoroughly unwashed.Next, acetic acid and water are added to the precipitate, and then heated.・By refluxing, the particle size is reduced to 3
A dope solution consisting of alumina fine particles of ~30n+s can be obtained.

In this case, the amount of acetic acid and water added is 6 to 20% and 100 to 300%, respectively, preferably 10 to 18%, based on the weight of the precipitate. at 60-90℃ for 3-8 hours,
Preferably, the temperature is 65 to 85°C for 3.5 to 6 hours.

Next, the alumina dope solution obtained in this way,
The mixture is uniformly cast on a suitable smooth surface, for example, on a releasable substrate such as a metal plate or glass plate coated with a silicone resin or a polyethylene plate, by a casting method or the like. The amount of casting in this case is not particularly limited, but the thickness of the formed film is 10 to 5o#.
L is preferable.

Thereafter, water is slowly evaporated from the film formed on the substrate at 20 to 30° C. over 20 to 60 hours, whereby a colorless and transparent film made of alumina fine particles can be obtained.

The film of the present invention thus obtained has a 1000
Because it maintains an amorphous structure and is transparent even at temperatures close to °C, for example, rare earth salts that thermally decompose at high temperatures and become colored, such as Pr(NO3) s (green)
, Nd(NO3)s (purple).

Sm (NO3) 3 (yellow), Eu (NO3)
A transparent and colored film can be obtained by adding s or the like to an alumina dope solution, forming it into a film, and then sintering it.

In addition, by adding a polymer or monomer having a functional group to the alumina dope liquid and forming it into a film,
It can also be made into a highly flexible film. The blending amount of this polymer or hexamer is about 30 to 80% based on the weight of alumina in the dope solution. Examples of the polymer or monomer used here include polymers such as polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyethyleneimine, and carboxymethyl cellulose, and monomers constituting them.

Furthermore, a sol or liquid substance of inorganic oxide fine particles or an aqueous solution of a water-soluble metal compound can be added to the alumina dope liquid, and then a transparent composite film can be obtained in the same manner as described above.

Inorganic oxides that can be used as other components of the composite film include 5i02, Cub, MgO, Cab,
Bad.

SrO,5n02, MnO2, Nip, Co
o, TiO2.

Th02, ZnO, PbO, ZrO2, Fe2
03.

v20s etc. can be mentioned.

Examples of methods for preparing these inorganic oxides into fine particle sol or liquid substances are as follows.

(1) 5i02; By adding the Si (OC2Hs) liquid to the alumina dope, it is hydrolyzed by the water in the dope and becomes a sol-like substance.

(2) TiO2; using TiC solution, (1)
Do the same as.

(3) 5n02; Proceed as in (1) using a concentrated solution of 1 g of SnC.

(4) V 20 s; 0.5N hydrochloric acid is added to a 10% NH4VO3 aqueous solution, and the precipitated red precipitate is filtered out and washed with water. Discard the initial solution after washing with water, and collect the filtrate, which is peptized and becomes a red liquid, and use it as a sol solution.

(5) Fe20s; 1stll! Water 700+a
(D) Add 12 mJ of 30% FeCls solution to make an aqueous solution.

(e) ZrO2; Q, 2 mol Zr0C12.8
The H2Q aqueous solution is heated at 90°C for 5 to 6 hours and then cooled to form an aqueous solution.

(?) Th02; Seen ThC.・2H202
An aqueous solution of 5 g dissolved in 300 g of water was heated at 90°C for 5 g.
After ~6 hours, cool to form an aqueous solution.

These inorganic oxide sol or liquid substances are mixed and used in an amount of 0.1 to 5z based on the weight of alumina in the alumina dope.

In addition, when using an aqueous solution of a water-soluble metal compound as another component of the composite film, this water-soluble metal compound may be added to
Toshiteha, Ni (used as a 10% by weight aqueous solution)
NO3) 2 , co(NO3) 2 .

1nc12, MnCl2, RhC
l3, RuC13+IrCl3, C
u(NO3)2, ZrQCJ12, NaNO3
.

KNO3* Fe(NO3) 2 1 Pb
(803) 2.

Examples include Fe(NO3) 3 and LiNO3.

This water-soluble metal is used by mixing it in an amount of 0.1 to 5z relative to the weight of alumina in the alumina dope.

After forming the film, the film of the present invention has a
By heating and sintering at a temperature of 0° C. for 10 to 24 hours, a porous film having micropores with a diameter of 50 to 2° n11 can be obtained. This porous film can be used as a gas separation membrane, a conductive membrane, and a separation membrane with catalytic action.

When the film of the present invention is a composite film consisting of alumina and an inorganic oxide or a water-soluble metal compound, the composite film is thermally decomposed in air or in a reducing atmosphere to produce aluminum [Embodiments of the invention]: , the present invention will be further explained in detail with reference to examples.

Example 50 g of aluminum chloride was dissolved in 200 g of water, and the solution was dissolved in 100 g of 6N ammonia water over 3 hours with stirring.
was added to form a precipitate of aluminum hydroxide. The pH after addition was adjusted to 6. Then, after aging for 24 hours at room temperature, the precipitate was separated by centrifugation. Washed with 1 liter of water. To 10 g of this precipitate, add 20 wJ of water and 2 liters of acetic acid.
- was added thereto, and after sufficient stirring, the mixture was heated and refluxed at 80° C. for 5 hours to obtain a dope solution consisting of fine alumina particles having a particle size of 5 to 10 n+s. This dope solution was cast onto a glass plate to a thickness of 30 mm, and then dried at 20 DEG C. for 80 hours to obtain a transparent film.

This film was further sintered at 500 to 900°C to obtain a colorless transparent film having micropores with a diameter of 40 to 100 pores. The gas permeability coefficient P(X 109 ) of this film at 20°C is: H2: 1.5°He: 0.8. CH4-;-1,3,N2;0
．． 4. 02; 0.8°CO□; 3.6.

Reference Example Alumina dope solution prepared in Example and 0.1M old CN
03) After mixing the two aqueous solutions at a volume ratio of 2:1, the mixture was cast onto a glass plate to form a green transparent film. This film was slowly dried until its moisture content was 20 to 30%, then heated to 400°C, and then reduced in a hydrogen stream at 450°C for 2 hours to form a film with a diameter of 45A. An amorphous alumina-supported nickel catalyst containing 1 fine particles was obtained. When this catalyst was used to reduce cyclooctadiene and 4-tert-butyl-methylenecyclohexene, the reactivity and selectivity to monoenes and cyclohexane was superior to that of the Raney N catalyst.

〔Effect of the invention〕

As described above, according to the production method of the present invention, it is possible to easily produce ultrafine alumina particles with a particle size of 3 to 3 mm, which was previously impossible to produce. A highly transparent film can be obtained using this method. Furthermore, the transparent film of the present invention is
By heating and sintering it under certain conditions, it can be made into a porous film having gas separation ability, etc., and its industrial value is extremely large.

Claims (2)

[Claims] (1) A transparent film made of alumina fine particles,
A transparent film characterized in that the alumina fine particles have a particle size of 3 to 30 nm. (2) Alumina obtained by adding ammonia water to an aqueous aluminum salt solution, leaving it to ripen for a certain period of time, separating and washing the resulting precipitate, then adding acetic acid and water to the precipitate, and heating and refluxing for a certain period of time. A method for producing a transparent film, comprising casting a dope solution onto a substrate.