JP2003096437A - Ultraviolet light absorbent and/or shielding agent and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ultraviolet light absorbent and/or shielding agent effective not only in the UV-B area but in the UV-A area. SOLUTION: This ultraviolet light absorbent and/or ultraviolet light-shielding agent contains titanium oxide obtained by hydrolyzing a low valent titanium salt (especially a 3 valent titanium salt).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to titanium oxide having an ultraviolet absorbing ability in the UV-A region, a method for producing the same, and an ultraviolet absorbing and / or shielding agent comprising the titanium oxide.

[0002]

Ultraviolet rays from the sun have wavelengths in the range 240 to 400 nm. Ultraviolet rays are divided into three bands according to their wavelength range. That is, it is absorbed by the long wavelength ultraviolet rays (UV-A) of 320 to 400 nm, the ultraviolet rays of 280 to 320 nm (UV-B), and the ozone layer of the earth, and does not reach the surface 240
It is a low wavelength ultraviolet ray (UV-C) of ~ 280 nm. Such radiation not only adversely affects the human body, but various substances that have received radiation have phenomena such as embrittlement, discoloration, decomposition, and destabilization, which are the causes of reducing the value of many commercial products. It was.

Therefore, in order to provide a light resistant (weather resistant) material, a polymer compound such as plastic or rubber,
A compound having an effect of absorbing and blocking ultraviolet rays may be added to the thermal recording sheet and the thermal transfer ink or the liquid crystal display material. Such additives have been used in cosmetics, paints, lenses, filters, films and the like in order to prevent inflammation of the human body and deterioration of products due to ultraviolet rays.

Conventionally, as such additives, for example, salicylate-based, benzophenone-based, benzotriazole-based, cyanoacrylate-based, hydantoin derivatives, hindered amine-based (light stabilizer) organic compounds are known. Due to its absorbing action, the ultraviolet absorbers can be expected to have an immediate ultraviolet-shielding effect, but their use amount is decreasing due to problems such as durability (durability) and safety. Therefore, in recent years, an ultraviolet absorber / shielding agent composed of an inorganic compound having less of these problems has been attracting attention.

The mainstream of the ultraviolet absorbing / screening agent composed of an inorganic compound is that which has two functions of the ultraviolet absorbing ability of the inorganic compound itself and the scattering ability in the ultraviolet wavelength region by controlling the particle size. . As a typical inorganic compound, titanium oxide whose particle size is controlled,
Ultraviolet absorbing / blocking agents which are metal oxides such as zinc oxide and cerium oxide have been proposed (JP-A-49-450, JP-A-5-43682, JP-B-7-2329).
4 publication).

[0006] Zinc oxide has an effective absorption region near UV-A, and is expected to be used as a UV absorber for cosmetics in particular, but it easily reacts with acids and alkalis and has difficulty in chemical stability. . Further, cerium oxide has an effective absorption region near UV-A and is effective for UV-A screening, but its use is limited because it is expensive. On the other hand, titanium oxide has high chemical stability, is relatively inexpensive, and has an effective absorption region near UV-B. However, for UV-A, the particle size is controlled to cause scattering. It is necessary to make up for the shielding effect, and the particle size with which the most effective scattering effect is obtained is said to be fine particles having an average particle size of 0.1 μm or less.

However, such fine particle metal oxides easily aggregate, and require a dispersion step at the time of use, so that the cost is high, which is a limitation in use.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a titanium oxide UV absorbing and / or UV absorbing agent having a sufficient UV absorbing / shielding effect in both UV-A and UV-B UV regions regardless of particle size. The purpose is to provide a shielding agent.

[0009]

The present inventor has conducted extensive studies in view of the above problems of the prior art, and as a result, titanium oxide obtained by adding an alkali to a low-valent titanium salt and hydrolyzing it absorbs ultraviolet rays. The present invention was completed by finding out that it has the ability.

That is, the present invention provides the following titanium oxide,
A method for producing the same and an ultraviolet ray absorbing and / or shielding agent comprising the titanium oxide are provided. Item 1. UV by hydrolyzing low-valent titanium salt
-A method for producing titanium oxide having absorption ability. Item 2. Item 2. The method for producing titanium oxide according to Item 1, wherein the low-valent titanium salt is a trivalent titanium salt. Item 3. Item 2. The method for producing titanium oxide according to Item 1, wherein the hydrolyzate obtained by hydrolysis is further calcined. Item 4. UV-A absorbing titanium oxide obtained by hydrolyzing a low-valent titanium salt. Item 5. Item 4. An ultraviolet absorbing and / or shielding agent comprising titanium oxide according to item 4.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the low-valent titanium salt refers to a titanium salt having a valence of 2 to 3.8. Bivalent and 3.8
A valent titanium atom can be obtained by reducing a tetravalent titanium atom under specific conditions. A divalent or trivalent titanium salt is preferable, and a trivalent titanium salt is more preferable. One or more of these can be used. The form of the salt may be a normal salt, an acidic salt, a basic salt, a single salt, a double salt, a complex salt, a hydrous salt (hydrate) or an anhydrous salt. Specific compounds include, but are not limited to, titanium chloride, titanium bromide, titanium sulfate, titanium tetrapropoxide, and the like. Preferred are water-soluble titanium salts, and examples thereof include titanium chloride, titanium sulfate, titanium bromide and the like. More preferred are titanium trichloride and titanium (III) sulfate.

The pH at which the above titanium salt is hydrolyzed is very important, but is not particularly limited as long as the desired titanium oxide is produced. For example, pH of about 4.0 to 10.0, preferably p
It is about H6.0-8.0. Within this range, any of hydrolysis methods such as alkali hydrolysis, neutral hydrolysis and acid hydrolysis can be adopted.

For example, the conditions for alkaline hydrolysis are as follows. Examples of the alkali used include sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, aqueous ammonia, and urea, and one or more of these can be used. Examples of the form of the alkali and titanium salts in the hydrolysis include an aqueous solution and an alcohol solution. It is preferably an aqueous solution.

The concentration of the titanium salt aqueous solution is 2 to 30 as Ti.
The amount is about 4% by weight, preferably about 4 to 20% by weight, more preferably about 5 to 10% by weight.

The concentration of the alkaline aqueous solution is, for example, 2% by weight.
To 10% by weight, preferably 10 to 20% by weight, more preferably 20 to 30% by weight.

The titanium salt is hydrolyzed in an aqueous solution to obtain titanium oxide. Aqueous solution containing titanium salt, for example 40 ~
After heating to about 100 ° C, preferably about 80 to 100 ° C, more preferably about 90 to 100 ° C, gradually add alkali to adjust the pH to about 4.0 to 10.0, preferably about pH 6.0 to 8.0. And hydrolyze. After adjusting the pH, if necessary, 20
To about 100 ° C, preferably about 20 to 50 ° C, for about 1 to 24 hours, preferably about 5 to 20 hours, and more preferably 10
By aging with stirring or standing for about 12 hours, particles of the product are increased, and a precipitate having more excellent UV-A absorption effect and excellent filtration efficiency is obtained.

The precipitate formed by hydrolysis is preferably separated by filtration, washed with water and dried, and if necessary, about 100 to 500 ° C, preferably about 200 to 400 ° C, more preferably about 300 to 400 ° C. Bake at.

When the tetravalent titanium salt is hydrolyzed,
Titanium oxide having a rutile type crystal structure is produced. However, in the present invention, since a 2-3.8 valent titanium salt is hydrolyzed, a crystal is generated while the 2-3.8 valent titanium salt is gradually oxidized during the hydrolysis to a tetravalent titanium salt.
grow up. At this time, titanium atoms having a valence of 2 to 3.8 and titanium atoms having a valence of 4 are temporarily present in the crystal structure. The titanium oxide of the present invention obtained in such a state is different from the rutile type crystal structure produced when a tetravalent titanium salt is used,
Its crystal structure cannot build a perfect rutile type crystal structure,
It has an incomplete crystal structure with structural irregularities. Further, by firing, 2-to 3.8-valent titanium atoms remaining in the crystal structure are completely oxidized to tetra-valent titanium atoms, and by further promoting the formation of structural imperfections, the UV-A absorption action is further improved. Become stronger. Even when a mixture of a 2- to 3.8-valent titanium salt and another titanium salt (for example, a 4-valent titanium salt) is hydrolyzed, the produced titanium oxide has a rutile type crystal structure with an asymmetric structure. , As long as it has a UV-A absorbing action, it is included in the present invention.

The titanium oxide of the present invention thus obtained is in the UV-A region, preferably 350 to 400 nm, more preferably
It has an absorption wavelength between 370 and 400 nm. This is thought to be due to the fact that a new energy level is generated in the energy band of ordinary titanium oxide (about 3.0 eV) due to the structural irregularity of the crystal, and the wavelength in the UV-A region is absorbed. . Furthermore, the titanium oxide of the present invention also has the ability to absorb wavelengths in the UV-B region that ordinary titanium oxide has.

Further, since the titanium oxide of the present invention has an ultraviolet absorbing ability, it can be used regardless of the particle size. In addition to this, it is possible to further provide an ultraviolet shielding effect by adjusting the particle size.

The ultraviolet absorbing and / or shielding agent of the present invention comprises
It can be used for applications where metal oxide UV absorbers / screeners have been used up to now, and also for applications where conventional titanium oxide could not be used because it does not have UV-A absorption ability. For example, paint, printing ink, plastic,
It is useful as an additive for papermaking, synthetic fibers, capacitors, food additives, and cosmetics.

[0022]

INDUSTRIAL APPLICABILITY The titanium oxide of the present invention is a chemically stable compound having an ultraviolet absorbing ability not only in the UV-B region but also in the UV-A region. Therefore, it can be used as a more stable UV-A absorber instead of the conventional UV-A absorber. In addition, since titanium oxide is harmless and has been widely used as a pigment so far,
Alternatively, it is considered that the shielding agent is also highly safe.

[0023]

Example: Titanium trichloride aqueous solution 5.2k adjusted to 6% by weight
Keeping g at 98-100 ℃, 25% sodium hydroxide aqueous solution 4.0k
After dropwise adding g over about 3 hours to adjust the reaction solution pH to 6.5 to 7.0, heating is stopped, and the mixture is aged overnight in the mother liquor at room temperature.
The obtained precipitate was filtered, washed with water, and dried at 80 ° C. Further, this precipitate was crushed, made into a powder, and then calcined at 400 ° C. for 2 hours to obtain the desired pale yellow titanium oxide. The obtained titanium oxide, titanium oxide before firing, and conventional rutile titanium oxide were subjected to X-ray diffraction measurement. The obtained results are shown in FIG. It was confirmed that both the titanium oxide before firing and the titanium oxide after firing had a rutile type crystal structure.

Next, the transmittance of the suspension of calcined titanium oxide and conventional rutile-type titanium oxide in powder form and suspended in castor oil at a wavelength of 250 to 400 nm was measured using a spectrophotometer. The obtained results are shown in FIG.

The titanium oxide of the present invention showed a remarkable ultraviolet ray blocking effect in the range of 250 to 400 nm including the UV-A region, as compared with ordinary titanium oxide. In conventional titanium oxide, an ultraviolet block is confirmed from around 320 nm to around 350 nm, and it is conventionally known that this is an ultraviolet blocking effect. And conventional titanium oxide is 400 nm from around 350 nm.
The UV-shielding effect decreases over nm. In contrast, the titanium oxide of the present invention is 350 nm even at 350 to 400 nm.
It shows a UV blocking effect of 98% or more, though it is less than the above. As described above, the titanium oxide of the present invention exhibits a very high ultraviolet blocking effect even in the ultraviolet region where the conventional ultraviolet shielding effect of titanium oxide is reduced, and therefore, in addition to the ultraviolet shielding effect, it also has an ultraviolet absorbing effect. Is confirmed. And absorption wavelength band (energy band)
Since the difference between the two is caused by the crystal or molecular structure of each compound, in the titanium oxide of the present invention, the conventional rutile is present in the crystal structure in a microscopic portion that does not appear in the X-ray diffraction. It is assumed that there is a structure different from the crystal structure of type titanium oxide, that is, the presence of structural irregularity.

[Brief description of drawings]

FIG. 1 is a graph showing the X-ray diffraction results of titanium oxide before firing, titanium oxide after firing and ordinary rutile type titanium oxide of the present invention. The horizontal axis shows “2θ [°]” and the vertical axis shows “strength”.
[cps] "is shown.

FIG. 2 is a graph showing the spectrophotometer measurement results of titanium oxide after firing of the present invention and conventional titanium oxide at 250 to 400 nm. The horizontal axis shows "wavelength [nm]" and the vertical axis shows "absorption /
Blocking rate [%] ”is shown.

Continued front page    (72) Inventor Akiyo Yoshida             20-14 Wakamiya no Omoto, Otsu-cho, Naruto City, Tokushima Prefecture F-term (reference) 4C083 AB24 CC19 FF01                 4G047 CA02 CB05 CC03

Claims (5)

[Claims] 1. A method for producing titanium oxide having a UV-A absorption ability by hydrolyzing a low-valent titanium salt. 2. The method for producing titanium oxide according to claim 1, wherein the low-valent titanium salt is a trivalent titanium salt. 3. The method for producing titanium oxide according to claim 1, wherein the hydrolyzate obtained by hydrolysis is further calcined. 4. A titanium oxide having a UV-A absorbing ability, which is obtained by hydrolyzing a low-valent titanium salt. 5. An ultraviolet absorbing and / or shielding agent comprising the titanium oxide according to claim 4.