JPH08325010A - Alkaline hydrated alumina sol and its production - Google Patents

Abstract

PURPOSE: To produce a sol having excellent stability and superior transparency in an alkali region by allowing an acidic hydrated alumina sol to contact with an anion exchanger in the presence of an alkali in an aqueous phase. CONSTITUTION: In this production, 1×10<-3> to 0.1mol of an alkali per mol of alumina (Al2 O3 ) is added to an acidic hydrated alumina sol which consists of a single kind or plural kinds of crystals having fibrous, spherical, chainlike, platelike or undefined form and a 1 to 500nm average grain size and also has a 1 to 20wt.% alumina concn., to adjust the pH of the resultant liquid suspension to 8 to 11. Then, this liquid suspension is allowed to contact with 1 to 20liter of an anion exchanger such as strongly basic or weakly basic anion exchange resin per kg of alumina (Al2 O3 ) at room temp. to 100 deg.C for 0.5 to 50hr to obtain the objective alkaline hydrated alumina sol having absorbances of <=1.0, <=1.5 and <=2.5 at 800, 560 and 400nm wavelengths, respectively, when the alumina concn. of the sol is 0.5wt.%. This sol can be used not only for producing a catalyst carrier but also in a wide variety of application fields.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alumina hydrate sol in which alumina hydrate fine particles are dispersed, and more particularly to an alumina hydrate sol excellent in stability and transparency in an alkaline region and a method for producing the same. Is.

[0002]

2. Description of the Related Art Conventionally, various kinds of alumina sol and methods for producing alumina sol have been known. For example, JP-A-59-78925 discloses an acidic alumina sol composed of pseudo-boehmite crystals, and JP-A-53-112299 discloses
An acidic alumina sol having a boehmite crystal lattice is disclosed. Although these sols are actually alumina hydrate sols, they are conventionally conventionally called alumina sols. In the present specification, the alumina hydrate sol may be referred to as the alumina sol.

Since the above-mentioned acidic (cationic) alumina sol usually contains an inorganic acid or an organic acid as a stabilizer for particles, there is corrosiveness or an irritating odor due to this acid component and the working environment is deteriorated. There was a problem such as making it happen. Also,
These acidic alumina sols are violently aggregated when mixed with anionic fine particles such as colloidal silica, and thus have been restricted in use in various applications of the alumina sols.

Further, conventionally, it has been attempted to disperse the fine alumina powder in a solvent by pulverizing the powder. However, in order to obtain colloidal particles by these pulverization methods, it is necessary to give a high share for a long time, and if a high share is given, the crystal is likely to be distorted and only a colloidal solution with low stability over time can be obtained. I couldn't do it.

On the other hand, Japanese Patent Publication No. 3-52410 discloses that
A method for producing an alkaline alumina sol composed of alumina monohydrate by calcination of alumina trihydrate, quenching and milling in an alkaline solution is disclosed. According to this method, although the milling time can be shortened and the stability with time can be expected to some extent, the transparency of the alumina sol is not satisfactory because the particle size distribution is very wide. Further, the particle shape of the alumina sol obtained by these pulverization methods is indefinite, it is difficult to specify the particle shape, and its use is limited. Therefore, at present, a stable alkaline alumina hydrate sol having a dispersoid substantially composed of alumina hydrate and excellent transparency is not yet known.

[0006]

It is an object of the present invention to use an alumina hydrate (aluminum hydroxide) fine particle having a sharp particle size distribution as a dispersoid and having excellent stability and transparency in an alkaline region, and an alkaline alumina hydrate sol. It is to provide a manufacturing method.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The alkaline alumina hydrate sol according to the first invention is characterized in that the absorbance of the alumina hydrate sol having an alumina concentration of 0.5% by weight is as follows (a) to (c). To do. (A) Absorbance at a wavelength of 800 nm is 1.0 or less (b) Absorbance at a wavelength of 560 nm is 1.5 or less (c) Absorbance at a wavelength of 400 nm is 2.5 or less Further, the alkaline alumina hydrate sol is The viscosity (η ₂₅ ) of the alumina hydrate sol having an alumina concentration of 5% by weight at 25 ° C. is preferably 100 cp or less.

The method for producing an alkaline alumina hydrate sol according to the second invention is characterized in that the acidic alumina hydrate sol is brought into contact with an anion exchanger in the presence of an alkali in the aqueous phase. is there. The acidic alumina hydrate sol is preferably an alumina hydrate having a boehmite, pseudo-boehmite, gibbsite, diaspore, bayerite or amorphous crystal form.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be specifically described below. First, the alkaline alumina hydrate sol according to the first invention will be described.

In the first aspect of the invention, the alumina hydrate sol is a highly transparent alkaline alumina hydrate sol having a specific absorbance at a specific wavelength as described above, and alumina hydrate fine particles to be a dispersoid. (Hereinafter sometimes referred to as colloidal particles) is an alumina hydrate having a boehmite, pseudo-boehmite, gibbsite, diaspore, bayerite or amorphous crystal form. This kind of alumina hydrate is inexpensive and is widely used as a material for the chemical industry.

The absorbance of the alumina hydrate sol is measured by a spectrophotometer, and the absorbance at a wavelength of 800 nm for a sol having an alumina concentration of 0.5% by weight is 1.0 or less, preferably 0.5 or less, more preferably The absorbance at a wavelength of 560 nm is 1.5 or less, preferably 1.0 or less, more preferably 0.5 or less, and the absorbance at a wavelength of 400 nm is 2.
5 or less, preferably 2.0 or less, more preferably 1.0
It is the following. When the absorbance at each wavelength is larger than the above range, the transparency becomes poor.

The alkaline alumina hydrate sol of the present invention is 25% of the alumina hydrate sol having an alumina concentration of 5% by weight.
The viscosity (η ₂₅ ) at 0 ° C. is preferably 100 cp or less, preferably 50 cp or less, and more preferably ₂₅ cp or less. When the viscosity (η ₂₅ ) is 100 cp or more,
It is inconvenient in handling such as mixing operation.

In the alkaline hydrate hydrate of the present invention, the zeta potential of the alumina sol having an alumina concentration of 2% by weight and a pH of 10 is preferably -5 mV or higher, and particularly preferably -10 mV or higher. When the zeta potential is -5 mV or less, the dispersion stability may be significantly reduced, and when other anionic fine particles such as colloidal silica are mixed with the alumina sol, aggregation or increase in viscosity may occur. It is not preferable.

The alkaline alumina hydrate sol of the present invention is very stable, and even if an aqueous sol having an alumina concentration adjusted to 1% by weight is treated with a centrifuge at 1000 rpm for 30 minutes, fine particles of alumina hydrate are obtained. Does not settle. On the other hand,
A paste-like semi-solid body obtained by dispersing fine alumina powder in an alkaline aqueous solution (usually, such a semi-solid body is also called a sol) has an alumina concentration adjusted to 1% by weight and centrifuged. It is distinguished from the alkaline alumina hydrate sol of the present invention because it is separated into two layers when treated with a separator at 1000 rpm for 30 minutes.

The alkaline alumina hydrate sol of the present invention has a low viscosity and extremely high dispersion stability, so that the alumina concentration can be increased. Alumina concentration is usually 1
It is adjusted in the range of ˜30% by weight. Further, a highly pure alkaline alumina hydrate sol can be obtained according to the purity of the raw material acidic alumina hydrate sol described below, and other inorganic oxide components may be contained in addition to alumina.
Examples of such an inorganic oxide include silica, titania, iron oxide, zirconia, calcia, magnesia, boron oxide, etc., and the amount of the inorganic oxide is 0.3 mol or less relative to 1 mol of alumina. It may be contained.

The alkaline alumina hydrate sol of the present invention has an extremely small amount of an acid component such as an inorganic acid or an organic acid contained in the sol, so that the electric double layer surrounding the colloidal particles is thick and the dispersion stability is excellent. . The amount of the acid component contained in the sol is 1% by weight or less, preferably 0.5% by weight or less, and more preferably 0.1% by weight or less based on alumina. When the amount of the acid component is 1% by weight or more, the electric double layer surrounding the colloidal particles becomes thin and the dispersion stability decreases. Further, the zeta potential is also lowered, which is not preferable.

Since the alumina hydrate fine particles constituting the alkaline alumina hydrate sol of the present invention are negatively charged, even if mixed with anionic fine particles such as colloidal silica at an arbitrary ratio, aggregation occurs. Never.

Next, a method for producing the alkaline alumina hydrate sol according to the second invention will be described. The production method of the present invention comprises contacting an acidic alumina hydrate sol containing fine particles of cationic alumina hydrate consisting of a single or a plurality of crystals with an anion exchanger in the presence of an alkali in an aqueous phase. Is.

Examples of the alumina hydrate fine particles include boehmite, pseudo-boehmite, gibbsite, diaspore, bayerite, and amorphous alumina hydrate, and single or plural crystals selected from them. One or two or more of the following aluminas are used as a dispersoid.

The average particle size of the alumina hydrate fine particles in the acidic alumina hydrate sol can be used in the range of 1 to 500 nm, and from the viewpoint of transparency, it is particularly 200 nm.
The following particle sizes are preferable. As such an acidic alumina hydrate sol, a commercially available acidic alumina hydrate sol having a fibrous shape, a spherical shape, a chain shape, a plate shape, or an amorphous shape can be used as it is. When an alumina hydrate sol having a large particle size is used, it may be further refined by a known method before use.

In the method of the present invention, the concentration of the acidic alumina hydrate sol is preferably in the range of 1 to 20% by weight, and the pH of the suspension after addition of alkali is 8 to 8.
A range of 14 is desirable. The contact with the anion exchanger is carried out until the alumina hydrate fine particles become colloidal, but usually 0.5 to 0.5 in the temperature range of room temperature to 100 ° C.
After treatment for ~ 50 hours, it is deflocculated into a colloidal form. When the acidic alumina hydrate sol contains a trace amount of an alkali component such as sodium, it is not necessary to add the alkali again.

Examples of the alkali used in the present invention include hydroxides of alkali metal elements such as sodium hydroxide, potassium hydroxide and lithium hydroxide, and nitrogen compounds such as ammonia and tetramethylammonium hydroxide. These alkalis are used alone or as a mixture. In the production of alkaline alumina hydrate sol, the amount of alkali added is alumina (Al ₂ O ₃ )
1 × 10 ^{−3 to} 0.1 mol, preferably 1 mol.
It is desirable to set it in the range of 5 × 10 ^{−3 to} 0.05 mol.

In the present invention, the anion exchanger can be used as long as it has an anion exchange ability, and in addition to a strongly basic or weakly basic anion exchange resin, a chelate resin, an ion exchange membrane, an ion exchange resin. A filter etc. are illustrated. These anion exchangers may be used alone or in combination. In the case of an anion exchange resin, it is usually alumina (A
1 ₂ O ₃ ) Used at a ratio of 1 to 20 liters per 1 kg.

In the production method of the present invention, the acid which is the stabilizer for the acidic alumina hydrate sol is removed by the anion exchanger and passes through the isoelectric point of alumina, whereby the alumina hydrate fine particles are aggregated. However, on the alkaline side, the alumina hydrate reacts with the alkali to form an aluminum salt, and the aluminate ion of this aluminum salt is removed by the anion exchanger to regenerate the alkali. The reaction with the substance is repeated, and the alumina hydrate fine particles are deflocculated to become colloidal particles (fine particles). In this method, even if the amount of alkali is small relative to the alumina hydrate, the alkali is regenerated and repeatedly acts on the alumina hydrate, so that the alumina hydrate fine particles can be sufficiently deflocculated. Moreover, since the amount of aluminate contained in the obtained alkaline alumina hydrate sol is very small, that is, since the content of the salt in the sol is small, the colloidal particles sufficiently form an electric double layer, High stability.

On the other hand, in the conventional method for producing an alkaline alumina hydrate sol, a large amount of alkali is required to peptize an acidic alumina hydrate sol with an alkali to form colloidal particles, and the isoelectric point of alumina is When passing through the colloidal particles, the colloidal particles agglomerate, and aluminum ions dissolved in the aqueous solution become aluminum hydroxide, so that the colloidal particles are easily bonded to each other. In addition, the large amount of salt produced thins the electric double layer of the particles, and as a result, the particles agglomerate and the dispersibility is low, and only a colloidal solution having poor transparency can be obtained. Further, in order to wash the aluminum salt with an ultrafiltration membrane or the like into colloidal particles, a large amount of water and washing for a long time are required, and the ratio of uniform colloidal particles is very small. Not efficient. Further, as described above, when the alumina hydrate powder is peptized with an alkali, the desired alumina hydrate sol is difficult to obtain because the reactivity with the alkali is very poor.

The alkaline alumina hydrate sol obtained by the above-mentioned production method can be made into an organosol by substituting water as a dispersion medium with an organic solvent by a known method such as a vacuum distillation method or an ultrafiltration method. Is.

As such an organic solvent, alcohols, glycols, esters, ketones, aromatic solvents and the like can be used. Specifically, methanol, ethanol, propanol, ethylene glycol, propylene glycol, glycerin can be used. , Acetone, methyl ethyl ketone, propylene glycol monomethyl ether, ethyl cellosolve, dimethylformamide, N-methyl-
An organic solvent such as 2-pyrrolidone can be exemplified. Further, the surface of the alumina hydrate particles is subjected to a surface treatment by a known method using a silane coupling agent, a titanium coupling agent, a surfactant, a higher fatty acid ester, or a salt thereof, so that xylene, toluene or dimethylethane can be obtained. It is also possible to use a sol having a low polar organic solvent such as, for example, as a dispersion medium.

The alkaline alumina hydrate sol of the present invention is useful not only as a catalyst carrier but also in the following applications.

(1) Since it has a large binder strength, it can be used as a binder for various refractories to obtain a high-strength molded article. For example, when it is used as a binder in the lost wax method for precision casting, it has excellent strength. Can be obtained. Further, when used as a binder for inorganic fibers such as ceramic sheets, inorganic fibers having excellent strength can be obtained.

(2) Since it has little volume change or thermal expansion at high temperature, it can be used for alumina and refractories containing alumina.

(3) Since the colloidal particles have a high hardness, when used as a hard coat film in combination with various abrasives, various cutting tools, or a matrix of resin, alkoxide hydrolyzate such as ethyl silicate, etc. Excellent effect can be obtained. Further, when used as an abrasive, the polishing rate can be adjusted depending on the difference in particle size or crystal form.

(4) Since it has a large Young's modulus, when it is added to a coating composition such as an electromagnetic steel sheet, the tension of the coating can be greatly improved and a low iron loss electromagnetic steel sheet can be obtained. Further, since the content of the acid component remaining in the alumina hydrate sol is small, the corrosion resistance is excellent.

(5) In particular, since the particle size distribution is narrow, the mechanical strength and running stability can be greatly improved when used as a filler for various plastics and rubbers. For example, when it is used as a filler for a polyester film, a biaxially oriented film having high strength, smoothness, and excellent abrasion resistance and slipperiness can be obtained.

(6) Since it is particularly stable in the alkaline region and has high transparency, it is suitable as a surface treatment agent for fibers, papermaking, glass and the like. For example, when used as a surface treatment agent for natural or synthetic fibers or films, an excellent flame retardant effect can be obtained. Further, if used in combination with a nonionic surfactant such as an ethylene adduct of acetylene alcohol and various surfactants and polyhydric alcohols,
Suitable as an antistatic agent.

(7) In addition, it is suitable for use as a filler for an ink jet film, a cosmetic compounding agent, a lubricant, a thickener, an aluminum casting alloy and the like.

[0036]

EXAMPLES The present invention will be described in detail below with reference to preferred examples.

Example 1 Commercially available acidic alumina sol (Cataloid AS-2, manufactured by Catalyst Kasei Kogyo, solid content concentration: 10% by weight, average particle size: 40)
nm, main crystal form: boehmite form, hydrochloric acid content: 0.3% by weight, pH: 3.4) 500 g and pure water 450 g 40
Strongly basic anion exchange resin (manufactured by Mitsubishi Kasei, DAIAION, SA-10A) 250 while stirring at ℃
After gradually adding cc, 50 g of 1 wt% potassium hydroxide
Was added and stirred for 18 hours. Then, after cooling to room temperature, the ion exchange resin was removed to obtain an alkaline alumina colloid aqueous solution. The obtained colloidal aqueous solution was concentrated to obtain a 10% by weight colloidal aqueous solution as an oxide.

The average particle size of the colloidal particles dispersed in this aqueous alumina colloidal solution was 30 nm. The crystal form of the colloidal particles was a boehmite form, which was the same as that before the treatment. The content of hydrochloric acid in the aqueous colloid solution was 0.01% by weight or less. The crystal form was measured by an X-ray diffractometer, and the average particle size was measured by a centrifugal sedimentation particle size distribution analyzer.

The preparation conditions of the colloidal solution thus prepared are shown in Table 1 together with the following Examples 2, 4, 6 and Comparative Example 1. The properties of this colloidal solution and colloidal particles were measured and observed by the following methods, and the results are shown in Tables 2 and 3, respectively.

(1) Average particle size of colloidal particles The colloidal aqueous solution was diluted with pure water and measured using a centrifugal sedimentation type particle size distribution measuring device (CAPA-700 manufactured by Horiba, Ltd.).

(2) Particle size distribution of colloidal particles It was measured by the same measuring device as above. The symbols in Table 3 have the following meanings. ○ ・ ・ ・ Sharp particle size distribution △ ・ ・ ・ Broad particle size distribution × ・ ・ ・ Very broad particle size distribution

(3) Coefficient of variation of colloidal particles (%) It was measured by the same measuring device as above. However, coefficient of variation (%) =
(Standard deviation / average particle diameter) × 100.

(4) Loss on ignition of colloidal particles One sample was prepared by drying an aqueous colloidal solution at 110 ° C. for 20 hours.
The weight loss was determined by firing at 000 ° C for 1 hour.

(5) Crystal form of colloidal particles After the colloidal aqueous solution was dried by a freeze dryer, it was heated to 110 ° C.
The sample dried at 20 ° C. for 20 hours was measured using a high-power X-ray diffractometer (RINT-1400, manufactured by Rigaku Denki) under the conditions of Cu tube, 60 KV and 200 mA, and JCPD
The crystal form was qualified using S software.

(6) Particle shape of colloidal particles A sample obtained by diluting a colloidal solution with distilled water was observed with a transmission electron microscope (H-800 manufactured by Hitachi, Ltd.).

(7) Absorbance of colloidal solution The colloidal solution was diluted with pure water to adjust the concentration of alumina to 0.5.
The weight% of the sample was measured with a spectrophotometer (U-2000, manufactured by Hitachi, Ltd.).

(8) Dispersion stability of colloidal solution A sample having a concentration of alumina of 1% by weight was prepared by diluting the aqueous colloidal solution with pure water at 1000 rpm with a small centrifuge (manufactured by domestic centrifuge, H-18). Centrifugation was performed for 30 minutes. The symbols in Table 2 have the following meanings. ○: Colloidal solution does not settle and separate ×: Colloidal solution does not settle and separate

(9) Change with time of colloidal solution A colloidal aqueous solution was allowed to stand in a constant temperature bath at 70 ° C. for 1 month, and a sample was diluted with pure water, and a centrifugal sedimentation type particle size distribution analyzer (CAPA-700 manufactured by Horiba, Ltd.) was used. ) Was used for the measurement. The symbols in Table 2 have the following meanings. ◯: Within ± 20% of the average particle size immediately after preparation Δ: Within ± 50% of the average particle size immediately after preparation ×: With respect to the average particle size immediately after preparation More than ± 50%

(10) Viscosity of Colloid Solution A colloidal aqueous solution was diluted with distilled water to have an alumina concentration of 5% by weight, and the viscosity was measured at 25 ° C. with an Ostwald viscometer.

(11) Specific surface area of alumina fine particles After the colloidal aqueous solution was dried by a freeze dryer, it was heated to 110 ° C.
The sample dried for 20 hours was measured by a nitrogen adsorption method (BET method) using a specific surface area measuring device (Multisorb 12 manufactured by Yuasa Ionics).

(12) Oil Absorption of Alumina Fine Particles After the colloidal aqueous solution was dried with a freeze dryer, 110
JIS-K510 for samples dried at 20 ° C for 20 hours
It was measured with linseed oil according to 1-21.

(13) Pore Volume of Alumina Fine Particles After the colloidal aqueous solution was dried with a freeze dryer, 110
The sample dried at 20 ° C. for 20 hours was measured using a mercury porosimeter (manufactured by Carlo Erba, Model 2000).

(14) True Specific Gravity of Alumina Fine Particles A colloidal aqueous solution was measured by a density measuring device (DA, manufactured by Kyoto Electronics Industry
-300) was used to measure the specific gravity of the aqueous solution, and the true specific gravity was calculated from the alumina concentration.

(15) Zeta potential of alumina colloidal particles A sample obtained by diluting an aqueous colloidal solution with distilled water to have an alumina concentration of 2% by weight and a pH of 10 was measured by an ultrasonic zeta potential measuring device (ESA-800 manufactured by Matec). It was measured.

Example 2 The same procedure as in Example 1 was repeated except that potassium hydroxide was changed to lithium hydroxide, the amount of pure water was changed to 1450 g, and the amount of ion exchange resin was changed to 500 cc. An aqueous alumina colloid solution was obtained. The obtained colloidal aqueous solution was concentrated to obtain a 10% by weight colloidal aqueous solution as an oxide. The crystal form of the colloidal particles was a boehmite form, which was the same as that before the treatment.

Example 3 While adding propylene glycol monomethyl ether to 200 g of the aqueous alumina colloid solution (solid content concentration: 10% by weight) obtained in Example 2, the solvent was heated and replaced by a rotary evaporator at 90 ° C. to obtain 15 as an oxide. weight%
An alumina colloidal solution containing propylene glycol monomethyl ether as a dispersion medium was obtained. After diluting this colloidal solution as an oxide to 1% by weight with distilled water,
Centrifugation was performed at 1000 rpm for 30 minutes in a small centrifuge, but no precipitation of colloidal particles was observed.

Example 4 Commercially available acidic alumina sol (Cataloid AS-3, manufactured by Catalysts & Chemicals Industries, solid content concentration: 10% by weight, average particle size: 20)
0 nm, main crystal form: boehmite form, acetic acid content: 0.4
% By weight, pH: 6.9) 500 g and pure water 85 g while stirring at room temperature, while adding strongly basic anion exchange resin (manufactured by Mitsubishi Kasei, DAIAION, SA-10A) 350 cc.
Was gradually added, and 40 g of 1% by weight tetramethylammonium hydroxide was added, and after stirring for 20 hours, the ion exchange resin was removed to obtain an aqueous alkaline alumina colloid solution. The obtained colloidal aqueous solution was concentrated to give a 20% by weight colloidal aqueous solution as an oxide. The crystal form of the colloidal particles was a boehmite form, which was the same as that before the treatment.

Example 5 To 200 g of the aqueous alkaline alumina colloid solution (solid content 20% by weight) obtained in Example 4, ethyl alcohol was added, and an ultrafiltration membrane (SIP-1 manufactured by Asahi Kasei Kogyo Co., Ltd.) was added.
20% by weight as an oxide after solvent replacement in 013)
An alumina colloidal solution containing ethyl alcohol as a dispersion medium was obtained. This colloidal solution was diluted with distilled water so as to be 1% by weight as an oxide, and then 10 with a small centrifuge.
After centrifugation at 00 rpm for 30 minutes, no precipitation of colloidal particles was observed.

Example 6 Commercially available acidic alumina sol (Cataloid AS-1, manufactured by Catalyst Kasei Kogyo, solid content concentration: 7.5% by weight, average particle size: 1)
0 nm, main crystal form: boehmite form, acetic acid content: 3% by weight, pH: 4.3) 1000 g and pure water 1940 g with stirring at room temperature, while adding a strong basic anion exchange resin (Mitsubishi Kasei, DAIAION, SA-10A) 100
After gradually adding 0 cc, 1 wt% sodium hydroxide 6
After adding 0 g and continuing stirring for 20 hours, the ion exchange resin was removed to obtain an alkaline alumina colloid aqueous solution. The obtained colloidal aqueous solution is concentrated to form an oxide, which is 5
A colloidal aqueous solution of wt% was prepared. The crystal form of the colloidal particles was a boehmite form, which was the same as that before the treatment.

Example 7 While adding 200 g of ethylene glycol to 500 g of the aqueous alkaline alumina colloid solution (solid content concentration 5% by weight) obtained in Example 6, a rotary evaporator was used to
The solvent was replaced by heating at 0 ° C. to obtain an alumina colloidal solution containing 10% by weight of ethylene glycol as a dispersion medium as an oxide. This colloidal solution was diluted with distilled water so as to be 1% by weight as an oxide, and then 10 with a small centrifuge.
After centrifugation at 00 rpm for 30 minutes, no precipitation of colloidal particles was observed.

Comparative Example 1 Commercially available acidic alumina sol (manufactured by Catalysts & Chemicals Industry Co., Ltd., Cataloid AS-2, solid content concentration: 10% by weight, average particle size: 40)
nm, main crystal form: boehmite form, hydrochloric acid content: 0.3% by weight, pH: 3.4) 500 g and pure water 375 g 40
While stirring at 4 ° C, add 4 wt% potassium hydroxide to this.
5 g was gradually added, and after stirring for 10 hours, the mixture was cooled to room temperature. Subsequently, while adding pure water, an ultrafiltration membrane (SIP-1013 manufactured by Asahi Kasei Kogyo) has an electric conductivity of 3 m.
After washing to S / cm, the solution was concentrated to give a 10 wt% colloidal solution as an oxide. The crystal form of the colloidal particles was a boehmite form, which was the same as that before the treatment. When this solution was allowed to stand for a while, precipitation of agglomerated alumina colloid particles was observed, and a stable colloid aqueous solution could not be obtained.

[0062]

[Table 1] Preparation of colloidal solution Mixing condition Mixing ratio Solid concentration of alkali pH (* 1) Type Addition ratio (* 2) (* 3) (* 4) Example 1 5 KOH 0.18 × 10 ^-1 5.0 11.3 Example 2 10 LiOH 0.40 × 10 ^-1 2.5 11.0 Example 4 7 TMAH 0.89 × 10 ^-2 8.0 11.1 Example 6 10 NaOH 0.37 × 10 ^-1 2.5 11.4 Comparative Example 1-KOH 0.18 5.0 12.9 (* 1) Mixing ratio = Ion exchange resin (cc) / Al ₂ O ₃ (g) (* 2) Addition ratio = Alkali equivalent / Al equivalent (* 3) Acid alumina sol solid content concentration (wt%) (* 4 ) PH of alkaline alumina sol

[0063]

TABLE 2 Co B A de soluble liquid sexual shaped solids Absorbance dispersion time ζ potential pH Viscosity Concentration 8 00nm 5 60nm 4 00nm stability Stability (wt%) (mV) ( cp) Example 1 20 0.1 0.4 1.0 ○ ○ -15 10.2 2 Example 2 25 0.1 0.4 0.9 ○ ○ -14 9.4 2 Example 4 20 0.5 1.0 1.8 ○ ○ -19 9.1 16 Example 6 30 0.0 0.2 0.5 ○ ○ -13 9.6 23 Comparative Example 1 20 1.1 1.4 2.2 × ×-9 10.5 22

[0064]

[Table 3] Properties of colloidal particles Average particle size fluctuation ratio table Weight Pore oil absorption True specific gravity particle Particle size distribution coefficient Area reduction Volumetric shape ( nm ) ( % ) ( m ² / g ) ( % ) ( ml / g ) ( ml / g ) Example 1 30 ○ 50 60 8.0 0.1 30 3.3 Plate-shaped Example 2 40 ○ 50 60 7.7 0.1 30 3.3 Plate-shaped Example 4 180 ○ 33 320 7.8 0.5 98 3.3 Fiber-shaped Example 6 20 ○ 50 360 8.6 0.3 32 3.3 Feather type Comparative example 1 320 × 50 130 7.6 0.1 32 3.3 Plate type

[0065]

EFFECT OF THE INVENTION The alkaline alumina hydrate sol according to the first aspect of the present invention is stable in the alkaline range of pH 9 to 13, has a low viscosity, and has a specific absorbance characteristic. Various uses can be applied.

In the method for producing an alkaline alumina hydrate sol according to the second aspect of the invention, since alkali is regenerated and acts on the alumina hydrate repeatedly, even if the amount of alkali added to the alumina hydrate is small, the The pulverization of Japanese fine particles can be sufficiently performed, and it is economical as a manufacturing process. In addition, an alkaline alumina hydrate sol having high dispersion stability can be prepared, which is an excellent production method.

Claims (2)

[Claims] 1. An alkaline alumina hydrate sol characterized in that the absorbance of the alumina hydrate sol having an alumina concentration of 0.5% by weight is (a) to (c) below. (A) Absorbance at a wavelength of 800 nm is 1.0 or less (b) Absorbance at a wavelength of 560 nm is 1.5 or less (c) Absorbance at a wavelength of 400 nm is 2.5 or less 2. A method for producing an alkaline alumina hydrate sol, which comprises bringing the acidic alumina hydrate sol into contact with an anion exchanger in the presence of an alkali in an aqueous phase.