JP4705347B2 - Method for producing silver core-gold shell fine particles protected with water-insoluble polymer pigment dispersant - Google Patents

Description

  The present invention relates to a method for producing silver core-gold shell fine particles protected with a water-insoluble polymer pigment dispersant.

  Gold fine particles having a particle size of several tens of nanometers or less make use of the unique properties of fine particles not found in bulk gold, chemically stable colorants, color filters, conductive pastes, chemical reaction catalysts, Its application fields such as transparent conductive films are expanding.

  As a method for producing metal fine particles such as gold fine particles, there are a gas phase method and a liquid phase method. Gas phase methods include, for example, gas evaporation method, RAD method, etc. In the gas evaporation method, the metal is evaporated in a vacuum vessel into which an inert gas is introduced, and is coated with a thiol or amine organic compound. Metal fine particles can be obtained. On the other hand, the liquid phase method is a method for obtaining metal fine particles by reducing metal ions by irradiating a metal ion-containing solution with ultraviolet light or adding a reducing agent. In particular, a method using a reducing agent can produce metal fine particles relatively easily without requiring a special apparatus.

In recent years, attempts have been made to produce composite metal fine particles as novel metal fine particles.
For example, a step of preparing a polymer-protected metal colloid in which a first metal is coated with a protective polymer, a step of coordinating a second metal ion to the polymer to form a colloid-complex complex, and the colloid-complex complex There is a method for producing a composite metal colloid comprising a step of removing the protective polymer from the metal. (For example, see Patent Document 1)

  Also, a noble metal such as gold having a particle diameter of 10 nm or less or an alloy colloidal ultrafine particle containing this noble metal as a nucleus, and gold or the like by a reduction method on the surface of the nucleus in the presence of alkylamine, carboxylic acid amide or aminocarboxylate as a dispersant. There is also disclosed a method of obtaining a metal fine particle dispersion by precipitating a noble metal or an alloy containing the noble metal. (For example, see Patent Document 2)

Further, for example, a method for producing a metal colloid solution having a large particle size and a high metal concentration by reducing a metal compound in a raw material metal colloid solution containing a polymer pigment dispersant has been proposed. (For example, see Patent Document 3)
JP 2000-296339 A JP 2004-51997 A JP 2004-75703 A

  Using the above manufacturing method, if composite metal fine particles having a core portion made of inexpensive metal fine particles and a shell portion made of gold fine particles are produced, the fine particles have the same characteristics as gold fine particles and are made of conventional gold alone. It was expected that the amount of gold used would be less than the manufacturing method, and the cost could be reduced.

  However, the method for producing a composite metal colloid as disclosed in Patent Document 1 has a problem in that productivity is poor because a process for producing a colloid-complex complex requires a very long time. Further, in the method for preparing a metal fine particle dispersion as in Patent Document 2, since a large amount of unreacted dispersant remains in the obtained metal fine particle dispersion, it is necessary to wash the reaction liquid after the reaction a plurality of times. It took time to manufacture. Furthermore, in the method for producing a metal colloid solution as described in Patent Document 3, since a metal compound and a reducing agent are introduced into the raw metal colloid solution, the residual ions derived from the metal compound remain in the obtained metal colloid solution. was there.

  The present invention has been made in view of the above problems, and does not require washing multiple times, is simple and productive, is inexpensive, exhibits the same optical characteristics as gold, and is redispersible. A method for producing silver-gold composite metal fine particles is proposed.

That is, the present invention relates to a method for producing silver core-gold shell fine particles protected with a water-insoluble polymer pigment dispersant, wherein (a) the silver fine particles protected with the water-insoluble polymer pigment dispersant are mixed with water. at the interface between compatibility without organic solvent silver fine particle dispersion solution dispersed in the (b) gold ion-containing aqueous solution, subjected to reduction of gold ions, to cause fine particles of gold to be deposited on the silver microparticle surface silver core - gold shell Fine particles are formed, the organic solvent containing the silver core-gold shell fine particles is separated from the aqueous solution, and the organic solvent is taken out .

Furthermore, the present invention relates to a method for producing silver core-gold shell fine particles protected with the water-insoluble polymer pigment dispersant, wherein the silver fine particles protected with the water-insoluble polymer pigment dispersant contain silver ions. the solution has a pigment affinity groups in the main chain and / or side chains and having a plurality of side chains that constitute the solvation portion, nonaqueous further the solvated portion has a hydrophobic structure It is obtained by carrying out a reduction reaction of silver ions in the presence of a conductive polymer pigment dispersant and removing the solvent.

  The silver core-gold shell fine particles obtained by the present invention have a core-shell structure in which silver fine particles are coated with gold fine particles, and the surroundings are surrounded by a water-insoluble polymer pigment dispersant. Since it exhibits optical properties equivalent to those of gold fine particles, it can be expected as a method for producing an inexpensive gold fine particle substitute that can be redispersed.

  Further, since the silver core-gold shell fine particles of the present invention are present in an organic phase, that is, in an organic solvent that is not compatible with water, miscellaneous ions generated as a by-product during the preparation of the gold ion-containing aqueous solution are In other words, it is not necessary to perform the washing process a plurality of times. Furthermore, it is not necessary to add a new dispersant when preparing the silver fine particle dispersion solution, and as a result, a large amount of unreacted dispersant does not remain in the organic phase, so that it is not necessary to perform the washing step a plurality of times. Therefore, the silver core-gold shell fine particles can be easily produced with high productivity.

Hereinafter, the present invention will be described in detail.
The method for producing the silver core-gold shell fine particles protected with the water-insoluble polymer pigment dispersant of the present invention is as follows: (i) The silver fine particles protected with the water-insoluble polymer pigment dispersant are not compatible with water. At the interface between the silver fine particle dispersed solution dispersed in the organic solvent and the (b) gold ion-containing aqueous solution, a reduction reaction of gold ions is performed to deposit the gold fine particles on the surface of the silver fine particles to form silver core-gold shell fine particles. The organic solvent containing the silver core-gold shell fine particles is separated from the aqueous solution, and the organic solvent is taken out .

  The silver fine particles 1 protected with the water-insoluble polymer pigment dispersant have a configuration in which the water-insoluble polymer pigment dispersant 4 surrounds the silver fine particles 2 as shown in FIG. It is obtained by a production method as disclosed in Japanese Patent No. -76800. That is, after dissolving a silver compound in a solvent, silver is reduced in the presence of a water-insoluble polymer pigment dispersant. Thereafter, silver fine particles protected with a water-insoluble polymer pigment dispersant can be obtained by removing the solvent. Examples of the silver compound include silver acetate, silver nitrate, and silver perchlorate.

As the water-insoluble polymer pigment dispersant used here, for example, (1) having a pigment affinity group in the main chain and / or a plurality of side chains, and having a plurality of side chains constituting a solvation part Examples include polymers. Wherein the solvated portion has a hydrophobic structure. Further, those having 2 to 3000 pigment affinity groups in one molecule and 2 to 1000 side chains constituting the solvation part in one molecule and having a number average molecular weight of 2,000 to 1,000,000 are preferably used. . Specifically, it is desirable to have a carboxylic acid and an amine as the pigment affinity group. In addition to (1), (2) a polymer having a plurality of pigment affinity groups consisting of pigment affinity groups in the main chain, and (3) a pigment affinity part consisting of pigment affinity groups at one end of the main chain. It is also possible to use linear polymers having the same.

  Commercially available water-insoluble polymer pigment dispersants include Solsperse series (Avicia), EFKA series (EFKA Chemical), Ajisper series (Ajinomoto).

  In silver fine particles protected with a water-insoluble polymer pigment dispersant, the average particle size of the silver fine particles is preferably 1 to 30 nm. If the thickness is less than 1 nm, the core-shell structured fine particles can no longer serve as the core. If it exceeds 30 nm, the color developability deteriorates, which is not preferable. The water-insoluble polymer pigment dispersant is desirably 300 to 100,000 parts by weight with respect to 100 parts by weight of the silver fine particles. If the amount is less than 300 parts by weight, the dispersion stability of the silver fine particles is poor, and if it exceeds 100000 parts by weight, gold fine particles alone may be produced when reducing the gold ions to produce silver core-gold shell fine particles. There is.

  Using silver fine particles protected with a water-insoluble polymer pigment dispersant as described above, (a) silver fine particles protected with a water-insoluble polymer pigment dispersant are dispersed in an organic solvent incompatible with water. A silver fine particle dispersion solution is prepared. Examples of organic solvents that are not compatible with water include organic solvents such as toluene, xylene, and hexane. Even if it is an organic solvent, the organic solvent compatible with water, such as ethanol and methanol, is not preferable. In addition, it is desirable to adjust the solid content concentration of the silver fine particle dispersion solution to be 1 to 50% by weight. The silver concentration is preferably 0.001 to 30% by weight.

  The (b) gold ion-containing aqueous solution of the present invention can be prepared, for example, by dissolving a gold compound in water. Examples of the gold compound include those that generate gold ions when dissolved in water, such as chloroauric acid, gold chloride, gold chloride, gold sulfite, and potassium metal oxide.

(B) The gold molar concentration of the aqueous solution containing gold ions is not particularly limited, but is preferably 1 × 10 ^{−5 to} 0.5 mol / l. When it is less than 1 × 10 ⁻⁵ mol / l, the gold coating of the silver fine particles is not sufficient, and it is difficult to obtain the same optical characteristics as the gold fine particles. On the other hand, when it exceeds 0.5 mol / l, the amount of gold deposited on the surface of the silver fine particles is increased, and the gold fine particles and / or the silver core-gold shell fine particles are easily aggregated, so that it is difficult to obtain desired optical characteristics.

  When reducing gold ions, (b) a silver particle dispersion solution in which silver particles protected with a water-insoluble polymer pigment dispersant are dispersed in an organic solvent incompatible with water and (b) a solution containing gold ions To do. As for the mixing ratio, it is desirable that the metal is contained in each solution in a weight ratio, that is, silver and gold are mixed so that the weight ratio is 1: 0.1-50. If it is less than 0.1, the gold coating of the silver fine particles is not sufficient, and it is difficult to obtain the same optical characteristics as the gold fine particles. On the other hand, when it exceeds 50, the amount of gold deposited on the surface of the silver fine particles is increased, and the gold fine particles and / or the silver core-gold shell fine particles are likely to be aggregated, so that desired optical characteristics are hardly obtained.

  The gold ion can be reduced by a method of adding a reducing agent to the mixed solution. Reducing agents are metal borohydrides such as sodium borohydride and potassium borohydride, lithium aluminum hydride, potassium aluminum hydride, cesium aluminum hydride, beryllium aluminum hydride, magnesium magnesium hydride, calcium aluminum hydride An aluminum hydride salt such as hydrazine compound, citric acid and its salt, succinic acid and its salt, ascorbic acid and its salt and the like can be used. These can be used by dissolving in water or an alcohol such as ethanol or propanol at a concentration of about 0.01 to 0.1 mol / l.

  In addition, the reduction of gold ions involves (a) a silver fine particle dispersion solution in which silver fine particles protected with a water-insoluble polymer pigment dispersant are dispersed in an organic solvent incompatible with water, and (b) a gold ion-containing aqueous solution. Performed at the interface. By reducing the gold ions at the interface between the aqueous phase and the organic phase, gold can be precipitated on the surface of the silver fine particles, and the formation of the gold fine particles as a simple substance is suppressed. Therefore, it is desirable to adjust the addition rate of the reducing agent.

  The resulting silver core-gold shell fine particles 10 have a silver core-gold shell structure in which silver fine particles 2 are coated with gold fine particles 3, as shown in FIG. The composition is surrounded by the agent 4 and is present in an organic phase, that is, in an organic solvent incompatible with water. By separating the organic phase of the mixed solution using, for example, a separatory funnel and removing the organic solvent from the organic phase, silver core-gold shell fine particles protected by a water-insoluble polymer pigment dispersant can be obtained. it can. Here, miscellaneous ions by-produced when preparing the aqueous solution containing gold ions (such as chlorine ions when chloroauric acid is used as the gold compound) remain in the aqueous phase, and thus the washing step needs to be performed multiple times. And there is an advantage that it is not necessary to use a phase transfer agent. Furthermore, since the silver fine particles protected with the water-insoluble polymer pigment dispersant are dispersed in an organic solvent incompatible with water to form a silver fine particle dispersion solution, a new dispersant is added when the silver fine particle dispersion solution is prepared. There is also a feature that it is not necessary to carry out the washing step a plurality of times because there is no need to add, and as a result, a large amount of unreacted dispersant does not remain in the organic phase.

The average particle diameter of the obtained silver core-gold shell fine particles is preferably 5 to 100 nm. Particle size is less than 5nm is not sufficient chromogenic too small may develop color particle size too large is not sufficient when more than 100 nm.

  Hereinafter, the present invention will be described in detail with reference to examples.

In a 100 ml beaker, 0.186 g of silver nitrate was dissolved in 50 ml of distilled water to prepare a silver nitrate aqueous solution. In another 300 ml beaker, 100 ml of water,
1.96 g of a polyester-based water-insoluble polymer pigment dispersant having a comb structure having carboxylic acid and amine as a pigment affinity group (Solsperse (trade name) manufactured by Avicia)
The mixture was heated and stirred at 80 ° C. using a magnetic stirrer. Next, the silver nitrate aqueous solution was poured into the 300 ml beaker, heated and stirred for 2 minutes, and then 2.4 g of dibutylamine was added at a dropping rate of 1 g / min. After completion of the dropwise addition, the mixture is further heated and stirred for 30 minutes, and then the supernatant is removed, and the residue is washed 2 to 3 times with distilled water and protected with a water-insoluble polymer pigment dispersant that is a yellow precipitate. Silver fine particles were collected.

Example 1
A silver fine particle dispersion solution was prepared by dispersing 0.12 g of silver fine particles (silver 6 wt%) protected with the above water-insoluble polymer pigment dispersant in 30 ml of toluene. On the other hand, 0.14 g of chloroauric acid (50% by weight of gold) was dissolved in 30 ml of water to prepare an aqueous solution containing gold ions.
After the gold ion-containing aqueous solution and the silver fine particle dispersion were mixed, 1.00 g of dibutylamine was added at a dropping rate of 1 g / min while heating and stirring at 80 ° C. using a magnetic stirrer. After completion of the dropping of the reducing agent, the mixture was further heated and stirred for 30 minutes, and then the organic phase was taken out using a separatory funnel. The organic phase was red, and when the absorbance was measured with an ultraviolet / visible spectrophotometer (UV-VIS), a UV-VIS spectrum as shown in FIG. 3A was obtained.

Example 2
The same operation as in Example 1 was conducted except that the amount of chloroauric acid (50% by weight of gold) added was 0.07 g. The organic phase was red, and the absorbance was measured with an ultraviolet / visible spectrophotometer (UV-VIS). As a result, a UV-VIS spectrum as shown in FIG. 3B was obtained.

Example 3
The same operation as in Example 1 was conducted except that the amount of dibutylamine added was 1.50 g. The organic phase was red, and when the absorbance was measured with an ultraviolet / visible spectrophotometer (UV-VIS), a UV-VIS spectrum as shown in FIG. 3C was obtained.

Comparative Example 1
0.01 g of silver fine particles (6% by weight of silver) protected with the above water-insoluble polymer pigment dispersant was dispersed in 30 ml of toluene to prepare a silver fine particle dispersion solution. When the absorbance was measured with an ultraviolet / visible spectrophotometer (UV-VIS), a UV-VIS spectrum as shown in FIG. 4D was obtained.

Comparative Example 2
In a 100 ml beaker, 0.23 g of chloroauric acid was dissolved in 50 ml of distilled water to prepare an aqueous chloroauric acid solution. In another 300 ml beaker, 1.96 g of a polyester-based water-insoluble polymer pigment dispersant having a comb structure having 100 ml of water, carboxylic acid and amine as pigment affinity groups (Solsperse (trade name) manufactured by Avicia) The mixture was heated and stirred at 80 ° C. using a magnetic stirrer. Next, the aqueous chloroauric acid solution was poured into the 300 ml beaker, heated and stirred for 2 minutes, and then 2.4 g of dibutylamine was added at a dropping rate of 1 g / min. After completion of the dropwise addition, the mixture is further heated and stirred for 30 minutes, and then the supernatant is removed, and the residue is washed 2 to 3 times with distilled water and protected with a water-insoluble polymer pigment dispersant that is a yellow precipitate. Gold fine particles were collected.
A gold fine particle dispersion solution was prepared by dispersing 0.01 g of gold fine particles (6 wt% gold) protected with the above water-insoluble polymer pigment dispersant in 30 ml of toluene. When the absorbance was measured with an ultraviolet / visible spectrophotometer (UV-VIS), a UV-VIS spectrum as shown in FIG. 4 (e) was obtained.

Comparative Example 3
A mixed solution of the silver fine particle dispersion solution of Comparative Example 1 and the gold fine particle dispersion solution of Comparative Example 2 was prepared. When the absorbance was measured with an ultraviolet / visible spectrophotometer (UV-VIS), a UV-VIS spectrum as shown in (f) of FIG. 4 was obtained.

  As a result, in Examples 1 to 3, an absorption peak was observed at a wavelength of 528 to 530 nm, which was different from the surface plasmon resonance absorption peak position (wavelength; 420 nm) of the silver fine particle of Comparative Example 1, and the gold fine particle of Comparative Example 2 Since the surface plasmon resonance absorption peak position is substantially the same and the wavelength is not shifted to a short wavelength, the examples are not silver-gold alloy fine particles, but silver core-gold shell fine particles in which the surface of silver fine particles is coated with gold. It was found that. In addition, since the spectral structure of Comparative Example 3 in which gold fine particles and silver fine particles are mixed has peaks at wavelengths; 528 nm and 420 nm, it is confirmed that the silver fine particles and the gold fine particles are not coexisting independently. did it.

  By removing toluene, which is a solvent, from the organic phase obtained in Example 1 using an evaporator, a solid material of silver core-gold shell fine particles protected with a water-insoluble polymer pigment dispersant can be obtained. It was. When 0.01 g of this solid was added to 20 ml each of acetone and butyl lactate, they could be redispersed without aggregation or precipitation. When 0.01 g of the solid was added to 20 ml of water, a red precipitate was confirmed.

  From this, it was found that the silver core-gold shell fine particles obtained were protected with a water-insoluble polymer pigment dispersant and redispersible in an organic solvent.

  As a method for producing an alternative to gold fine particles, cost reduction can be expected, and the obtained silver core-gold shell fine particles can be applied to various fields as a colorant for paints and resin compositions.

It is explanatory drawing which shows notionally the silver fine particle protected with the water-insoluble polymer pigment dispersant. It is explanatory drawing which shows notionally the silver core-gold shell microparticles | fine-particles protected with the water-insoluble polymer pigment dispersant. It is a UV-VIS spectrum of the fine particle dispersion solution concerning an Example. It is a UV-VIS spectrum of the fine particle dispersion solution concerning a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silver fine particle protected with water-insoluble polymer pigment dispersant 2 Silver fine particle 3 Gold fine particle 4 Water-insoluble polymer pigment dispersant 10 Silver core-gold shell fine particle protected with water-insoluble polymer pigment dispersant

Claims (2)

A method for producing silver core-gold shell fine particles protected with a water-insoluble polymer pigment dispersant,
(B) At the interface between a silver fine particle dispersion solution in which silver fine particles protected with a water-insoluble polymer pigment dispersant are dispersed in an organic solvent incompatible with water and (b) a gold ion-containing aqueous solution, A reduction reaction is performed to deposit gold fine particles on the surface of the silver fine particles to form silver core-gold shell fine particles, and the organic solvent containing the silver core-gold shell fine particles is separated from the aqueous solution to remove the organic solvent. A method for producing silver core-gold shell fine particles protected with a water-insoluble polymer pigment dispersant, which is characterized by being taken out . Silver fine particles protected with a water-insoluble polymer pigment dispersant have a silver ion-containing solution having a pigment affinity group in a main chain and / or a plurality of side chains, and a plurality of sides constituting a solvation part. having a chain, further wherein the solvated portion in the presence of a water-insoluble polymer pigment dispersant having a hydrophobic structure, performs a reduction reaction of silver ions, according to claim 1, obtained by removing the solvent A method for producing silver core-gold shell fine particles protected with a water-insoluble polymer pigment dispersant.

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