JP2834400B2 - Gold colloid solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gold colloid which is excellent in light resistance and heat resistance and is stable even when frozen. The gold colloid of the present invention can be applied to the fields of medicine, cosmetics, food and water-based paint.

[0002]

2. Description of the Related Art In the fields of medicines, cosmetics, foods, and paints, dyes have been used for the purpose of improving the identification and taste of products. In particular, red dyes are frequently used. For these uses, tar pigments, natural pigments such as sicon, safflower and raccaic acid, and pigments such as red iron or manganese violet have been used. However, these dyes have poor light fastness and heat resistance, and are often limited in use because of fading or discoloration or problems in safety.

[0003] On the other hand, it has long been known that gold colloid is adsorbed on a solid surface and colored reddish purple, and it has been widely used as a stained glass coloring agent in ancient Europe. Gold colloid is an inert metal, so it is a safe and stable dye, but it has a reddish purple color.
Only when dispersed as fine colloids. Therefore, when gold colloid is used as a colorant, it has been applied by adsorbing or immobilizing it on a carrier.

Conventional methods for producing a colloidal gold solution include a method of reducing a gold salt in an aqueous solution with a reducing agent such as sodium borohydride or sodium citrate, and a method such as thermal reduction and photoreduction. I have. Among these, a reduction method using a reducing agent is industrially used.
Each of the gold colloid solutions obtained by these methods exhibits a red to purple-red color, but has poor stability, and the gold colloid aggregates and precipitates during storage. On the other hand, in order to prepare a stable gold colloid solution, there are known methods such as adding a cationic surfactant during reduction to have an electric repulsion between colloid particles and adding a water-soluble polymer. ing. However, the colloidal gold solution prepared by these methods also has insufficient stability, cannot withstand long-term storage, and causes aggregation and precipitation due to the addition or freezing of an electrolyte. For this reason, the use of colloidal gold as a colorant is limited to a method of enclosing it in glass or adsorbing it on a solid surface, and cannot be used as a solution.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a stable colloidal gold solution.

[0006]

The present inventors Means for Solving the Problems] is stable as long prepared gold colloid solution, extensive research result thought to be safety and stability excellent colorant, citric gold salt in an aqueous solution When reducing with an acid, ascorbic acid or a salt thereof , a colloidal gold solution obtained by adding a nonionic surfactant and ethanol before or after reduction was found to be extremely stable, and the present invention was completed.

Hereinafter, the present invention will be described in detail. In the present invention, a gold salt is converted to citric acid, ascorbic acid or the like in an aqueous solution.
And a gold colloid solution obtained by adding a nonionic surfactant and ethanol before or after reduction when reducing with a salt thereof .

The gold salt used in the present invention includes, for example, chloroauric acid and its salts, and those obtained by dissolving gold powder in aqua regia. Is preferably from 0.0001 to 0.1% by weight, more preferably from 0.001 to 0.01% by weight, based on the total amount of

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

The ascorbate used in the present invention is
Alkali metal salts such as sodium ascorbate and potassium ascorbate. The concentration in the reaction solution is preferably 3 to 5 times the molar concentration of the gold ion, and more preferably 4 to 4 times. Molar concentration.

As the nonionic surfactant used in the present invention, for example, polyoxyethylene (60 mol ) hydrogenated
Hydrogenated castor oil, polyoxyethylene (20 mol) sorbitan laurate, polyoxyethylene (40 mol) nonylphenyl ether, sucrose monolaurate,
Examples thereof include polyglycerin lauroyl ester and polyoxyethylene (10 mol) glyceryl ether monostearate, and those having an HLB (hydrophilic-lipophilic balance) of 10 or more are preferable. The compounding amount is preferably 0.001 to 0.1% by weight, more preferably 0.005 to 0.05% by weight, based on the total amount of the final composition.

The ethanol used in the present invention is a commonly used ethanol, and the production method such as fermentation or synthesis is not particularly limited. The amount is preferably 5 to 30% by weight, more preferably 10 to 30% by weight based on the total amount of the final composition.
-20% by weight.

In the production method of the present invention, a gold salt (gold ion) is reduced with citric acid, ascorbic acid or a salt thereof in an aqueous solution to form a fine colloidal solution of zero-valent gold. Yes, a stable gold colloid solution can be obtained by adding a nonionic surfactant and ethanol before or after the reduction reaction. The nonionic surfactant and ethanol may be added before or after the reduction reaction, or one may be added before the reduction reaction, and the other after the reduction reaction. It is preferable because of its high safety. The conditions of the reduction reaction are not particularly limited, and stirring may be performed at room temperature. However, when the reaction temperature is 70 ° C. or higher, the reaction proceeds rapidly, and the color tone of the obtained gold colloid solution is also bright red. become. Also, by appropriately changing the reaction conditions, a red-violet to blue colloidal gold solution can be obtained.

[0014]

The present invention will be specifically described below with reference to examples. In addition, as an evaluation test of the gold colloid solution of the present invention and a comparative dye, a light resistance test, a heat resistance test, and a freezing test were performed as follows.

1. Light resistance test 20,000 kJ with a cycle weather meter using a carbon arc light source having a light source characteristic similar to sunlight
After irradiating a considerable amount of light, the change in the dye solution was visually judged, and there was no change: ○ slight discoloration / discoloration: Δ marked remarkable discoloration / discoloration and sedimentation: ×.

2. Heat resistance test After storage in a thermostat at 45 ° C. for 6 months, it was visually judged according to the same standard as in the light resistance test.

3. Freezing test After freezing in a freezer at −80 ° C., the temperature was returned to room temperature, and visually judged according to the same standard as in the light resistance test.

Example 1 Chloroauric acid tetrahydrate (20.59 mg) was added to water (94.93).
g) and heated to 90 ° C. A solution prepared by dissolving sodium citrate dihydrate (58.5 mg) in water (5 g) was added thereto, and the mixture was stirred at 90 ° C. for 10 minutes. After cooling to room temperature, hydrogenated hydrogenated castor oil (11.8 m) was added with ethanol (17.65 g) and polyoxyethylene (60 mol).
g) was added, stirred for 10 minutes, and filtered to obtain a colloidal gold solution of the present invention.

Example 2 Chloroauric acid tetrahydrate (10.30 mg) was added to water (94.97).
g), and polyoxyethylene (60 mol) hydrogenated hydrogenated castor oil (11.8 mg) was added thereto, followed by heating to 90 ° C.
A solution prepared by dissolving sodium ascorbate (19.8 mg) in water (5 g) was added thereto, and the mixture was stirred at 90 ° C. for 10 minutes. After cooling to room temperature, ethanol (17.65 g
), Stirred for 10 minutes, and filtered to obtain a colloidal gold solution of the present invention.

Comparative Example 1 A comparative gold colloid solution was obtained in the same manner as in Example 1 without adding ethanol and polyoxyethylene (60 mol) hydrogenated hydrogenated castor oil.

Comparative Example 2 The same operation as in Example 1 was performed without adding ethanol to obtain a colloidal gold solution for comparison.

Comparative Example 3 The same operation as in Example 1 was carried out without adding hydrogenated hydrogenated castor oil to polyoxyethylene (60 mol) to obtain a gold colloid solution for comparison.

Comparative Example 4 Chloroauric acid tetrahydrate (824 mg) was dissolved in water (100 ml). Water (915 ml) was added to the aqueous solution (25 ml), and a 1% by weight aqueous solution of stearyltrimethylammonium chloride (10 ml) was added with stirring. Further, an aqueous solution (50 ml) of sodium borohydride (75.7 mg / 50 ml) was added and stirred for 10 minutes, followed by filtration to obtain a colloidal gold solution for comparison.

In each of the gold colloid solutions obtained in Examples 1 and 2 and Comparative Examples 1 to 4, gold colloid having a particle size of about 10 to 1000 Å was uniformly dispersed immediately after preparation, and was visually observed. It had a bright red color.

The gold colloid solutions obtained in Examples 1 and 2 and Comparative Examples 1 to 4 and a tar dye, Red No. 106 (0.
(01% by weight aqueous solution) and the natural pigment raccaic acid (0.01% by weight aqueous solution) were evaluated in the above evaluation test. Table 1 shows the results.

[0026]

[Table 1]

As is clear from Table 1, the gold colloid solution of the present invention showed excellent stability in any of the above evaluation tests. The gold colloid solution for comparison was excellent in the light resistance test, but discolored or settled in the heat resistance test and the freezing test, and was judged to be unsuitable for actual use. In addition, existing Red No. 106 and raccaic acid were significantly discolored in the light resistance test.

Comparative Example 4 can be used as a dye if used in an environment where it does not freeze. However, sodium borohydride is used as a reducing agent, and it is dissolved when the solution is used as it is in the food, cosmetics, and pharmaceutical fields. Boron is a safety issue.

Example 3 Chloroauric acid tetrahydrate (205.9 mg) was added to water (68.88).
g) and ethanol (25 g) and polyoxyethylene (20 mol) sorbitan monolaurate (0.1 g).
1 g) and heated to reflux. A solution prepared by dissolving potassium citrate monohydrate (811 mg) in water (5 g) was added thereto, and the mixture was heated under reflux with stirring for 10 minutes. After cooling to room temperature, filtration was performed to obtain a red-purple gold colloid solution of the present invention.

Example 4 Chloroauric acid tetrahydrate (1.03 mg) was dissolved in water (87 g), and ethanol (8 g) was added, followed by heating to 50 ° C.
A solution of ascorbic acid (1.32 mg) in water (5 g) was added thereto, and the mixture was stirred at 50 ° C. for 60 minutes. After cooling to room temperature, polyglycerin lauryl ester (2
mg), stirred for 10 minutes, and filtered to obtain a blue-violet colloidal gold solution of the present invention.

The gold colloid solutions of the present invention obtained in Examples 3 and 4 were all excellent in the above evaluation tests.

[0032]

The colloidal gold solution of the present invention has excellent light resistance and heat resistance, and is stable even when frozen.

Continuation of front page (58) Fields investigated (Int. Cl. ⁶ , DB name) B01J 13/00 B22F 9/00 C22B 11/00 A16K 7/00 D06P 5/00

Claims (1)

(57) [Claims] 1. Citric acid, ascorbic acid or a combination thereof
A colloidal gold solution reduced with a salt of, comprising a nonionic surfactant and ethanol.