JPH09296130A - Photochromic white pigment and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photochromic white pigment having excellent photochromic property without deteriorating whiteness of the pigment by heating an aqueous suspension in which a white pigment has been dispersed. SOLUTION: This photochromic white pigment is obtained by coating the particle surfaces of an inorganic white pigment with 10-150wt.% of SnO2 to the inorganic white pigment as the substrate, so as to make the degree of discoloration, ΔE1 by formula I (L1 , a1 and b1 are each color tone just before UV irradiation; L2 , a2 and b2 are each color tone directly after UV irradiation) to 4-15, and the degree of restoration by formula II (L3 , a3 and b3 are each color tone when the coating was allowed to stand for 24 hr after the UV irradiation. In order to obtain this photochromic white pigment it is preferable to heat an aqueous suspension in which inorganic white pigment materials (practically titanium dioxide, aluminum oxide, etc.) has been dispersed, adding an aqueous solution of stannic acid or a stannate and an alkali or acid to the suspension to form a coating of stannic dioxide hydrate on the surfaces of the inorganic white pigment particles, then neutralizing, filtering, washing and drying the pigment, and heating the pigment at 100-700 deg.C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a white pigment having excellent photochromic properties and used for cosmetics, paints, resins and the like.

[0002]

2. Description of the Related Art A phenomenon in which a substance changes its color when irradiated with light and returns to its original color when irradiation is stopped is called photochromism, and a substance having that property is called a photochromic substance.

Typical examples of photochromic substances include silver halides and spiropyran compounds, which are used in discolored sunglasses and variable color makeup cosmetics, for example, Japanese Patent Laid-Open No. 56-4931.
2, 56-100709 and the like.

As the photochromic pigment, a pigment obtained by adding iron, chromium, copper, nickel, manganese, cobalt, molybdenum, etc. to titanium oxide is disclosed in, for example, JP-A-63 / 1988.
-132811, WO89 / 12084, JP-A-4-3
64117, 5-17152, 5-51209, 5-1
70440 and the like. In these, anatase type titanium dioxide for fine particles or pigments or plate-like titanium dioxide is used as a substrate, and the above elements are added for the purpose of exhibiting photochromic properties.

However, when the above elements are added, the pigment itself is colored to give a skin color and the like, so that it is difficult to diversify the colors.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to provide a white pigment having a high photochromic effect.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a white inorganic pigment, and to a white inorganic pigment for a substrate,
A photochromic white pigment coated with 10 to 150% by weight of tin dioxide is provided.

The photochromic white pigment of the present invention is
The white inorganic pigment is characterized by being coated with tin dioxide. As a result, the photochromic white pigment of the present invention has both good whiteness and photochromic properties as compared with conventional products, and is therefore suitable for use in cosmetics, paints, resins and the like. The characteristics of the above-mentioned photochromic white pigment of the present invention are attributable to the production method of the present invention described later.

The white inorganic pigment as the base material of the present invention is commercially available titanium dioxide, aluminum oxide, silicon dioxide, zinc oxide, zinc sulfide, barium sulfate, zirconium oxide,
Any alkali metal titanate, muscovite, calcium carbonate, kaolin clay or talc can be used, and two or more kinds of them may be combined. Taking titanium dioxide as an example, to explain it in more detail, there is no limitation on the size of particles, and even particles having a spherical shape, a needle shape, or the like, and further as a crystalline form, anatase type, rutile type, and amorphous type. Quality ones can also be used.

The amount of tin dioxide coated is 10 to 150% by weight, preferably 30 to 100% by weight, based on the white inorganic pigment of the substrate. When the amount is less than 10% by weight, the photochromic property is not sufficiently expressed, and when the amount is more than 150% by weight, fine particles or agglomerated particles which are not coated on the surface of the substrate are generated, and the dispersibility is deteriorated, which is not preferable.

The photochromic white pigment of the present invention is
Preferably, the color change degree ΔE ₁ defined below is 4 to 15,
The restoration degree ΔE ₂ is 4 or more. Discoloration degree _{△ E 1 = {(L 1} -L 2) 2 + (a 1 -a 2) 2 + (b 1
−b ₂ ) ² } ^1/2 restoration ΔE ₂ = {(L ₂ −L ₃ ) ² + (a ₂ −a ₃ ) ² + (b ₂
-B ₃ ) ² } ^1/2 L ₁ , a ₁ , b ₁ : Color tone before UV irradiation L ₂ , a ₂ , b ₂ : Color tone immediately after UV irradiation L ₃ , a ₃ , b ₃ : After UV irradiation, Color tones left in the dark for 24 hours

The photochromic white pigment of the present invention is
Compared to the untreated base pigment shown in the comparative example, ΔE ₁ was 4
It is very large as ˜15 and ΔE ₂ is as high as 4 or more, which is excellent and shows excellent photochromic properties.

Further, the photochromic white pigment obtained in the present invention is further coated with an organic substance such as silicone, a coupling agent, a surfactant, a metal soap, a fatty acid or a hydrate such as alumina, silica or zirconia. May be. By performing such a surface treatment, the dispersibility is improved and the photochromic property can be further improved.

The photochromic white pigment according to the present invention is a titanium dioxide prepared by heating a white inorganic pigment, for example, an aqueous suspension in which titanium dioxide is dispersed, and adding a tin salt or stannate solution and an alkali or an acid. It is manufactured by coating the surface with hydrated tin dioxide, neutralizing, filtering, washing, drying and heating.

The water suspension in which titanium dioxide is dispersed is heated in the range of 40 ° C to the boiling point, preferably 60 ° C to the boiling point. If the temperature is lower than 40 ° C., the precipitation rate of tin dioxide hydrate in the next step is slow, and uniform coating cannot be performed, which is not preferable.

The method of coating the surface of titanium dioxide with a film of tin dioxide hydrate is a method of adding an aqueous solution of tin salt or stannate to the suspension and then adding an alkali or an acid, tin salt or tin. There is a method of adding an aqueous acid salt solution and an alkali or an acid in parallel, and the latter method of parallel addition is more suitable.

The pH at the time of addition may be 2-9,
Since the isoelectric point of tin dioxide hydrate is pH 5.5, it is preferable to maintain pH 2 to 5 or pH 6 to 9, whereby the surface of the substrate particles can be uniformly coated with tin dioxide hydrate. it can.

As the tin salt used in the coating treatment, for example, tin chloride, tin sulfate, tin nitrate or the like can be used. As the stannate, for example, sodium stannate, potassium stannate, etc. can be used.
Among them, tin chloride is preferable.

As the alkali, for example, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, aqueous ammonia, ammonia gas and the like can be used, but sodium hydroxide is preferred.

Examples of the acid include hydrochloric acid, sulfuric acid, nitric acid,
Although acetic acid and the like can be used, hydrochloric acid is preferable.

The amount of tin dioxide hydrate for coating a white pigment such as titanium dioxide is 10 to 190% by weight, preferably 30 to 130% by weight, as SnO _{2 with} respect to the white inorganic pigment of the substrate. Is. When it is less than 10% by weight, the photochromic property is not sufficiently expressed,
If it is more than 190% by weight, fine particles or agglomerated particles which are not coated on the surface of the base particles are generated, and the dispersibility is lowered, which is not preferable.

The neutralization after adding the tin salt or stannate solution and the alkali or acid is preferably carried out at a pH of 6 to 8 in order to bring the pH of the manufactured pigment to near neutral.

The temperature for heat treatment after filtration, washing and drying is 100 to 700 ° C., preferably 300 to 600.
If the temperature is lower than 100 ° C., the proportion of chemically bound water in the coated tin dioxide is high, and if higher than 700 ° C., the crystallinity is high and the crystal lattice is stabilized, so that the photochromic property is high. It is not preferable because it decreases. Also,
The heating time is 15 minutes to 6 hours, preferably 1 to 4 hours. When the heating time is shorter than 15 minutes, the above effect is not obtained, and when the heating time is longer than 6 hours, no further effect can be expected, which is not preferable.

Incidentally, ΔE ₁ and ΔE ₂ are obtained by the following method.

4 g of the pigment was evenly dispersed in 16 g of nitrocellulose lacquer (Nitron Clear manufactured by Musashi Paint Co., Ltd.), and 76 g of the pigment was placed on art paper (Astor T manufactured by Chuetsu Pulp Co., Ltd.).
After uniformly coating with a μm applicator, it is dried and left at room temperature in a dark place for 12 hours or more to be used as a sample.

The light irradiation conditions are as follows: UV fluorescent lamp FL2
0S ・ BLB and FL20S ・ E (manufactured by Toshiba Lighting & Technology Co., Ltd.) were fixed one by one at an interval of 11 cm, and an ultraviolet intensity integrating meter (SUV-T manufactured by Toray Techno Co., Ltd.) was applied so that the ultraviolet intensity of the sample was ² mW / cm ^2. Adjust the distance to.

The color tone of the unirradiated sample left in the dark is measured with a spectrocolorimeter (CM-2002 manufactured by Minolta Co., Ltd.), and the color tones at this time are L ₁ , a ₁ and b ₁ . Next, ultraviolet rays are irradiated for 30 minutes under the above irradiation conditions, and the color tone of the discolored sample is similarly measured, and the color tones at this time are designated as L ₂ , a ₂ and b ₂ . Further, the color tone after leaving this sample in a dark place at room temperature for 24 hours is similarly measured, and the color tone at this time is L ₃ , a ₃ , and b ₃ .

From the above measured values, the degree of color change ΔE ₁ = {(L _{1
^{-L 2) 2 + (a 1}} -a 2) 2 + (b 1 -b 2) 2} 1/2, restitution _{△ E 2 = {(L 2} -L 3) 2 + (a 2 -a 3 ) ² + (b ₂ -b
₃ ) ² } ^1/2 .

[0029]

The present invention will be described in more detail with reference to the following examples. The following examples are provided for illustrative purposes only, and are not intended to limit the scope of the invention.

Example 1 Rutile titanium dioxide (KR-310 manufactured by Titanium Industry Co., Ltd.,
100 g of a specific surface area of 7 m ² / g) was dispersed in 1 liter of water to obtain an aqueous suspension. This suspension was kept warm at 80 ° C. Separately prepared stannic chloride (SnCl ₄ , 5H ₂ O)
A solution obtained by dissolving 70.0 g in 500 ml of 2N hydrochloric acid and a 30% sodium hydroxide solution were simultaneously added over about 1 hour so that the pH of the suspension was kept at 2-3. After the dropping was completed, the pH of the treated suspension was adjusted to 6, filtered and washed, and the obtained treated pigment cake was dried at 100 ° C.

Then, the dry powder thus obtained is dried in air at 300
It heat-processed at 2 degreeC for 2 hours, and obtained the objective photochromic white pigment. When the discoloration degree ΔE ₁ and the restoration degree ΔE ₂ of this sample were determined, ΔE ₁ was 6.9 and ΔE ₂ was 5.
It was 3.

Examples 2 to 7 Photochromic white pigments were obtained in the same manner as in Example 1 except that the addition amount of stannic chloride and the heat treatment temperature were changed as shown in Table 1. ΔE ₁ and ΔE _{2 of} this sample
I asked. The results are shown in Table 1.

Example 8 In Example 1, instead of rutile type titanium dioxide, anatase type ultrafine particle titanium dioxide (ST manufactured by Titanium Industry Co., Ltd.) was used.
T-65C, specific surface area 60 m ² / g),
A target photochromic white pigment was obtained by the same treatment as in the same example except that 70.0 g of stannic chloride was changed to 232.6 g. ΔE ₁ and E ₂ of this sample were determined. The results are shown in Table 1.

Example 9 The same treatment as in Example 1 was carried out except that aluminum oxide (AKP-30 manufactured by Sumitomo Chemical Co., specific surface area 6 m ² / g) was used in place of rutile titanium dioxide. Then, a desired photochromic white pigment was obtained. ΔE ₁ and ΔE ₂ of this sample were obtained. The results are shown in Table 1.

Example 10 In Example 1, instead of rutile type titanium dioxide, muscovite (Kuraray made szolite mica, specific surface area 7 m ² /
Except that g) was used, the same treatment as in the case of the same example was carried out to obtain the desired photochromic white pigment. ΔE ₁ and ΔE ₂ of this sample were obtained. The results are shown in Table 1.

Example 11 In Example 1, zirconium oxide (high-strength zirconia manufactured by Toyo Soda Co., Ltd., specific surface area 17 m ² / g) was used in place of rutile titanium dioxide, and stannic chloride 70.
Except that 0 g was changed to 170.0 g, the same treatment as in the case of the same example was carried out to obtain a desired photochromic white pigment. ΔE ₁ and ΔE ₂ of this sample were obtained. The results are shown in Table 1.

Comparative Example 1 The rutile type titanium dioxide used in Examples 1 to 7 was used at 300 ° C.
And heated. ΔE ₁ and ΔE ₂ of this sample were obtained. The results are shown in Table 1.

Comparative Example 2 The aluminum oxide used in Example 8 was heated at 300 ° C. ΔE ₁ and ΔE ₂ of this sample were obtained. The results are shown in Table 1.

Comparative Example 3 The same process as in Example 1 was carried out except that the heating temperature was set to 900 ° C. in Example 1. ΔE ₁ and ΔE ₂ of this sample were obtained. The results are shown in Table 1.

Comparative Example 4 Stannous chloride (SnCl ₄ ) was added to 1 liter of hot water at 80 ° C.
・ 5H ₂ O) (70.0 g) dissolved in 500 ml of 2N hydrochloric acid and 30% sodium hydroxide were added to the solution.
Simultaneous addition was carried out over about 1 hour so that H was kept at 2-3. After completion of the dropping, the pH of the liquid was adjusted to 6, filtered and washed, and the obtained cake was dried at 100 ° C. 30 g of this dry powder and 100 g of KR-310 used in the examples were mixed and heat-treated in the air at 300 ° C. for 2 hours. ΔE ₁ and ΔE ₂ of this sample were obtained. The results are shown in Table 1.
This sample had very poor dispersibility.

[0041]

[Table 1]

[0042]

INDUSTRIAL APPLICABILITY The present invention uses a white inorganic pigment as a base pigment, and coats tin dioxide to produce a white pigment which does not impair the whiteness and is excellent in photochromic properties, relatively easily. And has industrially high advantages.

Claims (5)

[Claims] 1. The surface of a white inorganic pigment is coated with SnO _{2 in an amount} of 10 to 150% by weight based on the white inorganic pigment of the substrate, and the degree of discoloration ΔE ₁ is 4 to 15 and the degree of restoration ΔE ₂ is 4 or more. Is a photochromic white pigment. Discoloration degree _{△ E 1 = {(L 1} -L 2) 2 + (a 1 -a 2) 2 + (b 1
−b ₂ ) ² } ^1/2 restoration ΔE ₂ = {(L ₂ −L ₃ ) ² + (a ₂ −a ₃ ) ² + (b ₂
-B ₃ ) ² } ^1/2 L ₁ , a ₁ , b ₁ : Color tone before UV irradiation L ₂ , a ₂ , b ₂ : Color tone immediately after UV irradiation L ₃ , a ₃ , b ₃ : After UV irradiation, Color tones left in the dark for 24 hours 2. The white inorganic pigment is titanium dioxide, aluminum oxide, silicon dioxide, zinc oxide, zinc sulfide, barium sulfate, zirconium oxide, alkali metal titanate,
The photochromic white pigment according to claim 1, which is at least one selected from the group consisting of muscovite, calcium carbonate, kaolin clay and talc. 3. An aqueous suspension of a white inorganic pigment dispersed therein is heated, and an aqueous solution of tin salt or stannate and an alkali or an acid are added to coat the surface of the white inorganic pigment with tin dioxide hydrate. The method for producing a photochromic white pigment according to claim 1 or 2, which comprises heating after neutralization, filtration, washing, drying. 4. The method according to claim 3, wherein the tin salt or stannate is added in an amount of 10 to 190% by weight as SnO _{2 with} respect to the white inorganic pigment. 5. The method according to claim 3, wherein the heating temperature is 100 to 700 ° C.