JPH0889788A - Production of colloidal gold solution and colloidal gold solution - Google Patents

Abstract

PURPOSE: To obtain a colloidal gold soln. excellent, in shelf stability and maintaining stability even after freezing or the addition of an electrolyte. CONSTITUTION: An aq. gold salt soln. is reduced with citric acid, its salt, ascorbic acid or its salt and a nonionic surfactant having polyoxyethylene chains and HLB(hydrophile-lipophile balance) of >=12 is incorporated to produce the objective colloidal gold soln. The average polymn. degree (mol) of the polyoxyethylene chains is >=10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a colloidal gold solution which has excellent storage stability and is stable even when frozen or added with an electrolyte. The gold colloid of the present invention can be applied to the fields of medicines, cosmetics, foods, water-based paints, model colloids for colloid chemistry experiments, and the like.

[0002]

2. Description of the Related Art Conventionally, dyes have been used in the fields of medicine, cosmetics, foods and paints for the purpose of improving the identification and taste of products. Especially, the red pigment is frequently used. For these applications, tar pigments, natural pigments such as purple root, safflower and laccaic acid, and inorganic pigments such as red iron oxide or manganese violet have been used.

However, these tar-based dyes and natural dyes have poor light resistance and heat resistance, and may fade or discolor,
Their applications were often limited due to safety issues.

Further, these inorganic pigments cannot be used as an aqueous solution because they have low color saturation and do not dissolve in water.

On the other hand, it has long been known that when gold colloid is adsorbed on a solid surface, it is colored in reddish purple, and it has been used as a coloring agent for stained glass in Europe. Gold colloid is a safe and stable pigment because it is an inert metal, but it exhibits reddish purple color only when it is dispersed as a fine colloid. Therefore, when gold colloid is used as a colorant, it needs to be adsorbed or encapsulated in a carrier.

As a conventional method for producing a gold colloidal solution, a method of reducing a gold salt with a reducing agent such as sodium borohydride or sodium citrate in an aqueous solution, and a method such as thermal reduction and photoreduction are known. . Of these, the reduction method using a reducing agent is industrially used.

Reduction with citric acid or sodium citrate is a long-known method for producing a gold colloid solution,
Citric acid molecules are adsorbed on the surface of the gold colloidal particles produced by this method, and it is said that stability is maintained by the electric repulsive force.

However, its stability is not sufficient, and it easily agglomerates or precipitates due to addition or freezing of the electrolyte, so that it cannot be used industrially.

A method is also known in which a cationic surfactant or a water-soluble polymer is added to a gold salt aqueous solution in advance and then reduced with sodium borohydride or the like. The colloidal gold solution produced by this method also easily aggregates and precipitates by adding an electrolyte or freezing.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a production method for obtaining a stable gold colloid solution and a gold colloid solution obtained by the method.

[0011]

[Means for Solving the Problem] The present inventors believe that if a stable gold colloidal solution can be prepared, it will be a coloring agent excellent in safety and stability. A colloidal gold solution obtained by a production method of adding a nonionic surfactant having a polyoxyethylene chain having an average polymerization mole number of 10 or more and an HLB of 12 or more after reduction with ascorbic acid or a salt thereof. It was found that is extremely stable, and the present invention has been completed.

That is, according to claim 1 of the present invention, after the aqueous solution of a gold salt is reduced with citric acid, ascorbic acid or a salt thereof, it has a polyoxyethylene chain having an average number of moles of polymerization of 10 or more and HLB of 12 or less. The method for producing a gold colloid solution is characterized by adding the above-mentioned nonionic surfactant.

A second aspect of the present invention is a gold colloid solution obtained by the production method according to the first aspect.

The details of the present invention will be described below. Examples of the gold salt used in the present invention include chloroauric acid and salts thereof, and those obtained by dissolving gold powder in aqua regia, and the concentration of gold in the final composition is the amount of gold and the final composition. 0.0001 to 0.01% by weight is preferable, and 0.001 to 0.01% by weight is more preferable.

As the citrate used in the present invention,
Examples thereof include alkali metal salts such as sodium salt and potassium salt of citric acid. The concentration of citric acid or a salt thereof in the reaction solution is preferably 3 to 5 times, and more preferably 4 times the molar concentration of the gold ion.

Examples of the ascorbic acid salt used in the present invention include alkali metal salts such as sodium and potassium salts of ascorbic acid. The concentration of ascorbic acid or its salt in the reaction solution is 3 to the molar concentration of gold ion.
It is preferable to use a 5-fold molar concentration, and more preferably a 4-fold molar concentration.

Examples of the nonionic surfactant used in the present invention include polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene (20 mol) sorbitan monooleate and polyoxyethylene (20 mol) sorbitan monostearate. Polyoxyethylene (60 mol) hydrogenated castor oil, polyoxyethylene (10
Hydrogenated castor oil and other polyoxyethylene hydrogenated castor oils, polyoxyethylene (10 moles) oleyl ether, polyoxyethylene (15 moles) cetyl ether and other polyoxyethylene alkyl ethers, polyoxyethylene (10 moles) ) Polyoxyethylene alkyl phenyl ethers such as nonyl phenyl ether and polyoxyethylene (15 mol) octyl phenyl ether having an average number of moles of polyoxyethylene polymerization of 10 or more and an HLB of 12 or more.

The average number of moles of polymerization is less than 10, or HL
When it is less than B12, the stabilizing effect on the gold colloid solution is insufficient.

The blending amount thereof is preferably 0.001 to 0.1% by weight, and more preferably 0.005 to 0.05% by weight, based on the total amount of the final composition.

In the production method of the present invention, an aqueous gold salt (gold ion) solution is reduced with citric acid, ascorbic acid or a salt thereof to obtain a gold colloid solution in which fine particles of 0-valent gold are dispersed. After that, a nonionic surfactant having a polyoxyethylene chain having an average polymerization mole number of 10 or more and having an HLB of 12 or more is added.

The conditions of the reduction reaction are not particularly limited, but the reaction temperature is 70 ° C. or higher, particularly preferably 90.
When the temperature is higher than or equal to ℃, the reaction proceeds rapidly, and the color tone of the obtained gold colloid solution becomes bright red. Further, a red-purple to blue-violet gold colloidal solution can be obtained by appropriately changing the conditions of the reduction reaction.

The nonionic surfactant may be added after citric acid, ascorbic acid or a salt thereof is added, but in order to obtain a gold colloid solution having a bright red color and high stability. Is preferably added immediately after the reduction reaction is completed.

When the reduction reaction is carried out at 70 ° C. or higher, it is particularly preferable that after the reduction reaction is completed, the temperature is cooled to around room temperature and then rapidly added.

When the nonionic surfactant is added before the addition of citric acid, ascorbic acid or salts thereof, the color tone becomes blue to black-purple and precipitation occurs in a short period of time.

[0025]

EXAMPLES The present invention will be specifically described below with reference to examples. As a stability evaluation test of the gold colloid solution of the present invention, a storage stability test, a freezing test, and an electrolyte addition test were conducted as follows.

1. Storage stability test After storage in a constant temperature bath of 30 ° C. for 6 months, the state of the gold colloid solution was observed with the naked eye, and there was no change: ○ ・ Discoloration or precipitation occurred: ×.

2. Freezing test After freezing in a freezer at −80 ° C., the temperature was returned to room temperature and evaluated in the same manner as in the storage stability test.

3. Electrolyte addition test A magnesium sulfate solution was added to the gold colloid solution so that the final concentration was 0.3 mol / liter, and the state after standing for one day was evaluated in the same manner as in the storage stability test.

Example 1 20.59 mg of chloroauric acid tetrahydrate was dissolved in 95 g of water and heated. While refluxing in the boiling state, an aqueous solution of 58.8 mg of sodium citrate dihydrate dissolved in 5 g of water was added thereto, and the mixture was stirred for 10 minutes. After cooling to room temperature, an aqueous solution prepared by dissolving 10 mg of polyoxyethylene (20 mol) sorbitan monooleate (HLB15.0) in 1 g of water was added, stirred for 10 minutes, and filtered to obtain a gold colloid solution of the present invention.

Example 2 10.30 mg of chloroauric acid tetrahydrate was dissolved in 95 g of water to obtain 9
Heated to 0 ° C. Sodium ascorbate 1
An aqueous solution prepared by dissolving 9.8 mg in 5 g of water was added, and the mixture was stirred at 90 ° C for 10 minutes. After cooling to room temperature, an aqueous solution prepared by dissolving 10 mg of polyoxyethylene (20 mol) sorbitan monooleate (HLB15.0) in 1 g of water was added, stirred for 10 minutes, and filtered to obtain a gold colloid solution of the present invention.

Example 3 Example 3 was repeated except that polyoxyethylene (20 mol) sorbitan monooleate (HLB15.0) was replaced with polyoxyethylene (60 mol) hydrogenated castor oil (HLB14.0). A gold colloidal solution of the present invention was obtained.

Example 4 The procedure of Example 1 was repeated except that polyoxyethylene (20 mol) sorbitan monooleate (HLB15.0) was replaced with polyoxyethylene (10 mol) oleyl ether (HLB13.5). A gold colloidal solution of the invention was obtained.

COMPARATIVE EXAMPLE 1 Polyoxyethylene (20 mol) sorbitan monooleate (HLB15.0) (10 mg) was dissolved in 5 g of water. Instead of adding an aqueous solution, 5 g of ion-exchanged water was added.
A gold colloidal solution for comparison was prepared in the same manner as in Example 1.

Comparative Example 2 Except that polyoxyethylene (20 mol) sorbitan monooleate (HLB15.0) was replaced by stearyl trimethyl ammonium chloride which is a cationic surfactant,
A gold colloidal solution for comparison was prepared in the same manner as in Example 1.

Comparative Example 3 Comparative gold was prepared in the same manner as in Example 1 except that polyoxyethylene (20 mol) sorbitan monooleate (HLB15.0) was replaced with sodium lauryl sulfate as an anionic surfactant. A colloidal solution was prepared.

Comparative Example 4 The procedure of Example 1 was repeated except that polyoxyethylene (20 mol) sorbitan monooleate (HLB15.0) was replaced with polyoxyethylene (6 mol) sorbitan monooleate (HLB10.0). To prepare a gold colloidal solution for comparison.

COMPARATIVE EXAMPLE 5 Polyoxyethylene (20 mol) sorbitan monooleate (HLB15.0) was replaced with polyoxyethylene (20 mol) hydrogenated castor oil (HLB10.5) in the same manner as in Example 1. A gold colloidal solution for comparison was prepared.

Comparative Example 6 Polyoxyethylene (20 mol) sorbitan monooleate (HLB15.0) was added to polyoxyethylene (7.5).
A gold colloidal solution for comparison was prepared in the same manner as in Example 1 except that (mol) nonylphenyl ether (HLB14.0) was used.

Comparative Example 7 20.59 mg of chloroauric acid tetrahydrate was dissolved in 95 g of water,
An aqueous solution prepared by dissolving 10 mg of polyoxyethylene (20 mol) sorbitan monooleate (HLB15.0) in 1 g of water was added and heated. While refluxing in the boiling state, an aqueous solution of 58.8 mg of sodium citrate dihydrate dissolved in 5 g of water was added thereto, and the mixture was stirred for 10 minutes. After cooling to room temperature, the mixture was stirred for 10 minutes and filtered to prepare a gold colloidal solution for comparison.

Comparative Example 8 824 mg of chloroauric acid tetrahydrate was dissolved in 100 ml of water. To 25 ml of this aqueous solution, 915 ml of water was added, and 10 ml of a 1 wt% stearyltrimethylammonium chloride aqueous solution was added with vigorous stirring. In addition, sodium borohydride (75mg / 5
0 ml) 50 ml of an aqueous solution was added, and the mixture was stirred for 10 minutes and filtered to prepare a gold colloidal solution for comparison.

Examples 1 to 4 and Comparative Examples 1, 3 to 6 and 8
In all cases, a bright red gold colloidal solution was obtained. In Comparative Examples 2 and 7, blue colloidal gold solutions were obtained.

Table 1 shows the evaluation test results of the gold colloid solutions obtained in Examples 1 to 4 and Comparative Examples 1 to 8.

[0043]

[Table 1]

[0044]

The colloidal gold solution of the present invention has excellent storage stability and is stable even when frozen or added with an electrolyte.

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Claims (2)

[Claims] 1. An average polymerization mole number of 10 after reducing an aqueous solution of gold salt with citric acid, ascorbic acid or a salt thereof.
It has the above polyoxyethylene chain and has an HLB of 12
A method for producing a gold colloid solution, which comprises adding the nonionic surfactant as described above. 2. A gold colloid solution obtained by the method according to claim 1.