JPH05170425A - Production of composite particle - Google Patents

Abstract

PURPOSE:To inexpensively obtain a high purity composite particle free from stripping of a coating layer by uniformly dispersing a silica particle into an aq. solution of a hydrolyzable metallic salt and forming a metallic compound coated layer on the silica by hydrolysis. CONSTITUTION:The aq. solution of the hydrolyzable salt of metal selected from copper, iron, zirconium, aluminum, chromium and yttrium (e.g. yttrium nitrate) is prepared. The other hand, the silica particle is prepared by dissolving tetraalkyl silicate into alcohol and by using a method such as hydrolyzing with addition of ammonia as a catalyst. And the silica particle is uniformly dispersed in the aq. solution of the hydrolyzable metallic salt. The hydrolyzable metallic salt is hydrolyzed by heating to from the coating layer of the metallic compound such as Y(OH)CO3 layer on the silica particle and the composite particle is obtained. The composite particle obtained is suitably used for a catalyst, an adsorbent, an electronic material or the like.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a catalyst, a catalyst carrier, an adsorbent, a pigment, a filler, a masking agent, a lubricant, a conductive filler (particles), a magnetic material, an optical material, a non-linear optical material, an electronic material, a semiconductor. The present invention relates to the production of composite particles that can be suitably used for a wide range of applications such as sealants, anisotropic conductive materials, column chromatography fillers, cosmetics, spacers, and pharmaceutical drug delivery carriers.

[0002]

2. Description of the Related Art As a method for producing silica-metal compound composite particles, a method is known in which silica particles are dispersed in alcohol, a metal alkoxide is added and hydrolyzed to deposit a metal oxide on the silica particles. There is. But,
In this method, it is difficult to control the hydrolysis rate, and as a result, it is difficult to efficiently deposit the metal compound on the silica particles, and particles of the metal compound alone are produced together with the composite particles.

An electroless plating method is also known, in which metal ions are reduced and deposited on the surface of silica particles to coat the metal, and since an external power source is not required, non-conductive silica particles can be coated. It is an excellent method. However, in this method, the purity of the metal coated on the silica particles is low, and the adhesion of the coating layer (hereinafter sometimes referred to as the shell) is poor, which is a problem in practice.

[0004]

As described above, silica-based
Although metal compound composite particles are a promising material, a method for obtaining those having good performance at low cost and simply has not been found so far.

[0005]

The present invention relates to silica particles in an aqueous solution of a metal salt of hydrolyzable copper, iron, zirconium, aluminum, chromium and yttrium (hereinafter referred to as hydrolyzable metal salt). Is uniformly dispersed, a metal compound coating layer is provided on the silica particles by a hydrolysis reaction, and further reduction treatment is carried out, if necessary, to provide a method for producing the above composite particles.

The present invention will be described in detail below. First, a method for producing composite particles in which the core is silica and the shell is selected from copper compounds, iron compounds, aluminum compounds, zirconium compounds, chromium compounds and yttrium compounds will be described.

A method for producing silica particles is described in J. Co
lloid InterfaceSci. Volume 26, 62
The sol-gel method described on page 69 (1968) is preferred. That is, this is a method in which a tetraalkyl silicate is dissolved in alcohol, ammonia is added as a catalyst, and hydrolysis is performed.

As the tetraalkyl silicate, those having 1 to 5 carbon atoms such as tetramethyl silicate, tetraethyl silicate, tetrapropyl silicate and tetrapentyl silicate are particularly preferable. Of these, tetramethyl silicate is the most rapidly hydrolyzed, completes within 1 minute, and is preferably used for obtaining a particle size of, for example, 0.2 μm or less. Further, the hydrolysis rate differs depending on the type of alcohol used, and methanol is the fastest, and is therefore suitable for obtaining silica particles having a small particle size. On the other hand, butanol and the like are suitable for obtaining silica having a large particle size.

Further, generally, as the alkyl group of the alcohol increases, the monodispersity of the silica particles obtained tends to be impaired, so it is preferable to control by mixing methanol and butanol, for example. Similarly, the particle size of silica particles changes depending on the amount of ammonia as a catalyst, so the addition amount is determined so that the desired particle size is obtained.

It is also possible to employ a hot water heating decomposition method in which water is used in place of the alcohol and the material is hydrolyzed by heating.

By the above method, the particle diameter is usually 5 μm.
The following silica particles are obtained. In order to produce monodisperse silica particles having a particle size of 5 μm or more, for example, silica particles having a diameter of 4 μm are prepared in advance by the above-mentioned method, and this is used as a seed and dispersed in alcohol to hydrolyze the tetraalkylsilicate. Further, grain growth may be further performed. By repeating the above method, spherical silica particles having a large particle size can be obtained.

As described above, the produced silica particles are uniformly dispersed in an aqueous solution of a hydrolyzable metal salt, and if necessary, a pH controlling agent such as an acid is added, and the particles are hydrolyzed by heating to hydrolyze the surface of the particles. A metal compound, which is a decomposition product, is coated to obtain composite particles. The amount of silica particles used in this case is usually 0.001 to 1000 g / l reaction mixture.

This method is non-commercial from an industrial point of view.
It is always cheap, efficient and safe. Where
Examples of the water-decomposable metal salt include Y (NO₃)₃, Cu
(NO ₃)₂, Fe (NO₃)₃, Cr (NO₃)₃, CrC
l₃And Al (NO₃)₃Nitrates such as FeCl₃of
Chlorides such as Zr (SO_Four)₂, Al₂(SO_Four)₃No
Una sulfate etc. are mentioned. These can be at room temperature or
Easily hydrolyzed by heat. Thereby, for example, Zr
₂(OH)₆SO_Four, Cu (OH)₂・ CuCO₃, Al
(OH)₃, Y (OH) CO₃, Cr (OH)_Four, Fe
(OH)₂, Α-Fe₂O₃, Fe₃O_FourLike oxides
Or silica compounds, which are the core silica particles
The surface is evenly coated.

The amount of these hydrolyzable metal salts used is
0.01 mmol / reaction mixture 1 liter or more is preferable, more preferably 0.1 mmol / reaction mixture 1 liter or more,
Particularly preferred is 1 mmol / reaction mixture 1 liter or more, but the upper limit is generally 100 mmol / reaction mixture 1 liter.

Further, examples of the pH control agent include urea and formamide. The amount of these pH control agents used is usually 100 mol / l or less of the reaction mixture,
It is preferably 10 mol / l or less of the reaction mixture, and particularly preferably 5 mol / l or less of the reaction mixture.

If the shell is a metal hydroxide, it is suitable.
Easily performed by heat treatment at an appropriate temperature in an oxygen atmosphere
It can also be converted to a metal oxide. For example, Y (OH)
CO ₃By holding above 600 ° C for 2 hours
Y₂O₃Can be converted to Zr₂(OH)₆SO_FourIs 80
ZrO by holding at 0 ℃ or more for 2 hours₂Change to
Can be exchanged. Similarly, Al (OH)₃, Cr (OH)_Four, C
u (OH) ・ CuCO₃, Fe (OH)₂About 800 ℃
Above each Al₂O₃, CrO₂, CuO and Cu₂
O, α-Fe₂O₃Can be converted to. In addition, Cu (OH)
CuCO₃And Fe (OH)₂Is due to the addition of alkali
Acid at a relatively low temperature (normal temperature to 100 ° C) as an aqueous dispersion
CuO, Fe₃O_FourIs converted to.

What is important in the above method is to uniformly disperse the core silica particles in the aqueous solution. For example, the dispersed state is poor, and one core particle cannot be formed,
If there are several hundreds of lumps, the metal compound is coated on the lumps, and uniform composite particles cannot be formed. Further, in some cases, the produced composite particles are associated with each other in a solution and aggregated, and cannot be redispersed. In order to improve these drawbacks, it is preferable to use a water-soluble polymer and / or a surfactant as a dispersibility improving agent. The amount of these dispersibility improving agents used is preferably 1 part by weight or more, more preferably 3 to 300 parts by weight, and particularly preferably 5 to 250 parts by weight, based on 100 parts by weight of the silica particles.

Preferred as the water-soluble polymer or surfactant are polyvinylpyrrolidone, polyvinyl alcohol, sodium polycarboxylate, sodium hexametaphosphate, sodium naphthalenesulfonate, sodium dodecylbenzenesulfonate or sodium dodecylsulfate, and particularly preferred. Is polyvinylpyrrolidone or sodium dodecyl sulfate. Ammonia may be added to increase the reaction efficiency. The amount used at that time is usually 100 mol / l or less of the reaction mixture, preferably 50 mol / l or less of the reaction mixture, particularly preferably 10 mol / l or less of the reaction mixture.

The composite particles obtained by these production methods are
It is a redispersible particle having a uniform coating layer.

In principle, there are two kinds of production mechanisms of the composite particles of the present invention. One of them is that a hydrolyzed metal ion or a further hydrolyzed complex is adsorbed on silica particles to form a coating layer. It is something to do. The other is
This is a mechanism in which very small hydrolyzed metal compound fine particles are initially formed, and these are adsorbed by silica particles by heteroaggregation, and then the metal compound layer grows on the surface of these particles. In this latter mechanism, the thickness of the coating layer is controlled by the number and particle size of the metal compound particles adsorbed on the silica particles. For example, in order to efficiently adsorb the metal compound fine particles on the silica particles, when the hydrolysis reaction occurs at a pH above the isoelectric point of the metal compound particles, it is preferable to use silica particles having a positive charge as the core. When the reaction proceeds at a pH below the isoelectric point, it is preferable to use silica particles having a negative charge.

The metal compound particles can also be efficiently adsorbed on the silica particles by increasing the heterocoagulation effect by increasing the zeta potential difference between the metal compound fine particles and the silica particles by adding an acid. Examples of the acid here include hydrochloric acid, sulfuric acid, oxalic acid, nitric acid,
Examples thereof include acetic acid and phosphoric acid, and hydrochloric acid or nitric acid is preferably used. The amount of this acid used is usually 100.
Mol / reaction mixture 1 l or less, preferably 10 mol / reaction mixture 1 l or less, particularly preferably 1 mol / reaction mixture 1
It is 1 or less.

The particle size of the composite particles thus obtained is preferably 0.05 to 50 μm, more preferably 0.1 to 20 μm, and particularly preferably 0.2 to 5 μm for the production of silica particles. The ratio of the inner diameter to the outer diameter of the particles is preferably 0.5 to 0.99, but when the shell composition conversion is performed by heat treatment, in order to prevent cracks,
0.7 to 0.99, and more preferably 0.75 to 0.99 are preferable.

By selecting the shell composition from the above metal compounds, various properties can be imparted to the composite particles of the present invention. For example, when abrasion resistance, heat resistance, strength and the like are desired, copper compounds, zirconium compounds, yttrium compounds, aluminum compounds and chromium compounds are preferable, and oxides of these metals are particularly preferable. Specific examples of these compounds include ZrO ₂ , Al ₂ O ₃ and C.
RO _{2 and the} like are particularly preferable, and ZrO ₂ and Al ₂ O ₃ are particularly preferable. If a magnetic material is desired, iron compounds are preferred and magnetite (Fe ₃ O ₄ ) is especially preferred. The shell composition may be selected according to the performance required in this way.

The silica-copper compound or iron compound composite particles thus obtained are heated and reduced, for example, in a hydrogen atmosphere to obtain composite particles in which the core is silica and the shell is metallic copper or metallic iron. be able to.

In the case of producing silica-metal copper composite particles, the silica-copper compound composite particles are, for example, 0.5 at a temperature of 100 ° C. or higher while flowing hydrogen in an electric furnace.
Reduce and manufacture over time. The reduction temperature at this time is preferably 120 ° C. or higher, more preferably 140 ° C. or higher in view of the efficiency of reduction to copper. Even if Cu (OH) ₂ · CuCO ₃ is used as the copper compound that constitutes the shell,
Even uO is converted to metallic copper, but generally Cu
In the case of (OH) ₂ · CuCO ₃ , the temperature is 140 ° C or higher, and C
In the case of uO, the temperature is 130 ° C or higher. The flow rate of hydrogen is generally 10 to 5 when the inner volume of the electric furnace is 2 l.
The amount is 00 ml / min, preferably 50 to 400 ml / min. The purity of metallic copper obtained by the above reduction is 96% by weight or more as a copper content, which is extremely high in purity as compared with about 70% by weight in the electroless plating method.

On the other hand, in the case of producing the silica-metal iron composite particles, the silica-iron compound composite particles obtained previously are flowed with hydrogen in the electric furnace in the same manner, and at least 500 ° C. or higher, preferably 800. 0.5 at temperatures above ℃
The reduction is performed for not less than time, preferably not less than 2 hours. The flow rate of hydrogen is generally 10 to 500 ml / min, preferably 50 to 400 ml / min when the internal volume of the electric furnace is 2 l. When the particle size of the composite particles is relatively small, for example, 0.5 μm or less, the surface energy is high and the composite particles are rapidly oxidized in the air.

The particle size of these silica-metal copper or metal iron composite particles is preferably 0.05 to 45 μm, more preferably 0.1 to 20 μm, and particularly preferably 0.4 to 8 μm.
μm. The ratio of the inner diameter to the outer diameter of the particle is 0.55
0.99 is preferable, and 0.7 to 0.99 is more preferable for preventing distortion and cracks due to shell composition conversion.

These composite particles can be used also as conductive particles and magnetic particles, and high-purity particles which cannot be obtained by the conventional electroless plating method can be obtained.

The various silica-metal compound composite particles and silica-metal composite particles thus obtained are not limited to these examples. For example, these composite particles may be further coated with the same or another kind of metal compound. 2 shells
It may be composed of more than one layer.

[0030]

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

[Production of Silica Particles] Example-1 A 2-liter four-necked flask was charged with 1 liter of ethanol, 332 ml of 28% ammonia water, and 36.1 ml of water, and 62.4 ml of tetraethyl silicate was added to this mixed solution for 2 hours. It was stirred. Next, 499.2 ml of tetraethyl silicate was added dropwise over 2 hours and then stirred for 3 hours. The process of filtering the obtained silica particles, adding pure water and washing was repeated 3 times. The particle size of the obtained silica particles is 1.6.
was μm.

Example-2 A 2-liter four-necked flask was charged with 900 ml of ethanol, 100 ml of propanol, 215 ml of 28% by weight aqueous ammonia and 521 ml of water, and 60 ml of tetrapentyl silicate was added to this mixed solution and stirred for 3 hours. Then example-
The same washing as 1 was performed. The obtained silica particles were granular and had a particle size of 0.25 μm.

Example-3 The silica particles obtained in Example-1 were used as seed particles and grown in the same manner as in Example-1. That is,
21 in a four-necked flask with 21 liters of ethanol. 332 ml of 28 wt% ammonia water and 36.1 ml of water were charged, and 62.4 ml of tetraethyl silicate was added to this mixed solution to obtain 2
Stir for hours. Next, 499.2 ml of tetraethyl silicate was added dropwise over 2 hours and then stirred for 3 hours. Further, 499.2 ml of tetraethyl silicate was added dropwise over 2 hours, and then the step of stirring for 3 hours was repeated 3 times, then the obtained silica particles were filtered, and the step of washing with pure water was repeated 3 times. It was The silica particles obtained were spherical and the particle size was 5.3 μm.

[Production of Composite Particles] Example-1 Aqueous dispersion of silica particles obtained in Example-1 (concentration 1 g / l)
10 ml, 3% by weight aqueous solution of polyvinylpyrrolidone 0.1
ml, 3.6 mol / l urea aqueous solution 50 ml, distilled water 29.9 m
l and 5 × 1 pre-filtered with 0.2 μm filter
10 ml of a 0 ^-1 mol / l yttrium nitrate aqueous solution was added to 1
Place in a glass container with a 50 ml lid. After thoroughly stirring for 1 minute in an ultrasonic water bath, the mixture was placed in a thermostat set at 90 ° C for 2 hours for hydrolysis. Then, the mixture was cooled to room temperature, the composite particles were settled by centrifugation, the supernatant solution was separated, distilled water was added, and the mixture was placed in an ultrasonic water bath until the particles were completely dispersed. Then, the particles were dried at room temperature. The obtained particles have a mean particle size of 1.68 μm, a ratio of the inner diameter to the particle size of 0.95, and a uniform Y (OH) particle surface.
It was a spherical composite particle coated with a CO ₃ layer.

Examples 2 to 9 Basically the same as Example 1, except that the components used during the hydrolysis and the production conditions were changed as shown in Tables 1 to 3 to obtain Examples 2 to 9. In Tables 1 to 3, PVP is polyvinylpyrrolidone and PVA is polyvinyl alcohol. The results are shown in Tables 1 to 3 together with Example 1.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

Example 10 An aqueous potassium hydroxide solution was added to an aqueous chromium nitrate solution so that the ion ratio was [Cr ³⁺ ] / [OH ⁻ ] = 1. That is, 800 ml of 20 ml of 0.2 mol / l chromium nitrate aqueous solution
0.1 mol / l potassium hydroxide aqueous solution was added dropwise to 1 l of distilled water with stirring, and finally distilled water was added so that the total amount became 1 l. After 12 hours, this solution was filtered through a 0.2 μm filter. In a glass container with a 150 ml lid, 25 ml of the 4 × 10 ^-3 mol / l stock solution obtained above,
Aqueous dispersion of silica particles obtained in Example-2 (concentration 1 g / l)
20 ml, 1 ml of a 3% by weight polyvinylpyrrolidone aqueous solution and 54 ml of distilled water were added. 1 in ultrasonic water bath
After stirring for a minute, the mixture was hydrolyzed in a constant temperature bath at 85 ° C for 6 hours. Then, the mixture was cooled to room temperature, the composite particles were settled by centrifugation, the supernatant solution was separated, distilled water was added, and the mixture was placed in an ultrasonic water bath until the particles were completely dispersed. Then, the particles were dried at room temperature. The obtained particles have an average particle size of 0.35.
It was a spherical composite particle in which the surface of the silica particle having a diameter of μm and the ratio of the inner diameter to the outer diameter of 0.71 was covered with a uniform Cr (OH) ₃ layer.

Example-11 Aqueous dispersion of silica particles obtained in Example-1 (concentration 1 g / l)
10 ml, 3 wt% polyvinylpyrrolidone aqueous solution 30 ml,
4.4 mol / l urea aqueous solution 10 ml, 0.1 mol / l hydrochloric acid 3
0 ml, 10 ml of distilled water, and 10 ml of a 5 × 10 ^-2 mol / l FeCl ₃ aqueous solution were placed in a pressure-resistant container with a 150 ml stopper and well stirred in an ultrasonic water bath for 1 minute. Then, it was hydrolyzed by placing it in a constant temperature bath set at 100 ° C. for 48 hours. Then, the mixture is cooled to room temperature, the composite particles are sedimented by centrifugation, the supernatant solution is separated, distilled water is added, and the mixture is placed in an ultrasonic water bath until the particles are completely dispersed. The particles were dried at room temperature. The obtained particles were spherical composite particles having an average particle diameter of 1.63 μm and a silica particle surface having a uniform inner particle diameter to outer particle diameter ratio of 0.98 and covered with a uniform α-Fe ₂ O ₃ layer. ..

Examples 12 to 17 Basically the same as Example 11, except that the components used during hydrolysis and the production conditions were changed as shown in Tables 4 to 6 to make Examples 12-17. The shapes and compositions of the resulting particles are shown in Tables 4 to 6 together with Examples 10 to 11.

By heating and oxidizing these spherical silica-metal compound composite particles in air, the composition of the metal compound in the shell could be changed.

[0043]

[Table 4]

[0044]

[Table 5]

[0045]

[Table 6]

Example-18 2 g of the spherical silica-Y (OH) CO ₃ composite particles obtained in Example-1 was placed in a tubular electric furnace and the temperature was raised from room temperature to 30 ° C. while flowing air at 300 ml / min. Heating at 800 / min
Hold at 3 ° C for 3 hours. Then, the temperature was lowered at a rate of 20 ° C./min. The obtained particles have a particle size of 1.66μ.
m, the ratio of the inner diameter to the outer diameter of the particle was 0.96, and the surface of the silica particle was a composite particle coated with a uniform Y ₂ O ₃ layer.

Examples-19 to 24 Basically the same as in Example-18, but the heating conditions are shown in Tables 7 to 7.
Examples 19 to 24 were changed as shown in FIG. The shape and composition of the obtained particles are shown in Tables 7 to 8 together with Example 18.

[0048]

[Table 7]

[0049]

[Table 8]

Example-25 1 g of the spherical silica-α-Fe ₂ O ₂ composite particles obtained in Example-11 was placed in a tubular electric furnace having an internal volume of 2.2 l, and hydrogen was flown at a rate of 50 ml / min. And reduced at 900 ° C. for 3 hours. Then, the temperature was lowered at a rate of 20 ° C./min.
The obtained particles were spherical particles having a particle diameter of 1.62 μm and a ratio of the inner diameter to the outer diameter of the particle of 0.99, and the surfaces of the silica particles were uniformly coated with metallic iron.

Examples-26 to 28 Basically the same as Example-25, except that the reducing conditions were changed as shown in Table 9 to give Examples-26 to 28. The shape and composition of the obtained particles are shown in Table 9 together with Example 25.
It was shown to.

[0052]

[Table 9]

[0053]

INDUSTRIAL APPLICABILITY The method for producing the composite particles of the present invention is extremely suitable for industrialization, which is different from the conventional method of hydrolyzing a metal alkoxide and allows the target particles to be obtained inexpensively and easily. .. Moreover, the resulting composite particles are of high purity and have excellent quality without peeling of the coating layer, and include catalysts, catalyst carriers, adsorbents, pigments, fillers, hiding agents, lubricants, conductive fillers (particles). ), Magnetic materials, optical materials, non-linear optical materials, electronic materials, semiconductor encapsulants, anisotropic conductive materials, column chromatography fillers, cosmetics, spacers, pharmaceutical drug delivery carriers and the like.

Claims (1)

[Claims] 1. Silica particles are uniformly dispersed in an aqueous solution of a hydrolyzable metal salt selected from copper, iron, zirconium, aluminum, chromium and yttrium, and then a metal compound is formed on the silica particles by a hydrolysis reaction. A method for producing composite particles, which comprises providing a coating layer.