JP2000034465A - Ultraviolet-screening material and its preparation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ultraviolet-screening material capable of inhibiting the photocatalyst function which the conventional ultraviolet-screening materials additionally possess and exhibiting ultraviolet-screening function alone without light-aging the organic base material having been added and dispersed in the ultraviolet-screening material, and to provide a method for preparing the same. SOLUTION: Ultraviolet-screening materials are obtained by coating an ultraviolet-screening functional substance with a clay mineral. A method for preparing the ultraviolet-screening material comprises the steps of (a) dispersing a clay mineral in a dispersion medium to prepare a clay mineral dispersion; (b) mixing an ultraviolet-screening functional substance into the clay mineral dispersion; (c) subjecting the resulting mixture to solid-liquid separation; and (d) heating the solids content obtained in step (c).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet shielding material, and more particularly, to an ultraviolet shielding material comprising a clay mineral coated with an ultraviolet shielding material containing an inorganic compound having an ultraviolet shielding function such as titanium oxide. The present invention relates to an ultraviolet ray shielding material capable of exhibiting only an ultraviolet ray shielding function without causing a photocatalytic function of a substance to be exhibited and without causing photo-aging of an organic substrate to which an ultraviolet ray shielding material is added or dispersed, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, ultraviolet shielding materials have been used for food packaging materials for avoiding decomposition of oil components, furniture protection sheets for preventing discoloration and coloring, greenhouse sheets, ultraviolet shielding fibers, ultraviolet stabilizing paints, ultraviolet cut glass. Application fields are expanding as additives to paper, building materials and the like. Ultraviolet shielding materials are based on the fact that both organic and inorganic materials absorb ultraviolet energy. Therefore, by absorbing the ultraviolet energy, the ultraviolet shielding substance itself changes or emits active oxygen and electrons, and has an action of oxidizing a contacting substance. This property often has a disadvantage that the advantage of the ultraviolet shielding effect is negated. That is, when an ultraviolet ray shielding effect is to be obtained by adding to a plastic film, the film itself is photo-aged and the durability is impaired. In the case of an organic ultraviolet ray shielding material, the substance itself changes into another substance and loses the ultraviolet ray shielding ability, and the effect is not permanent. On the other hand, in the case of an inorganic ultraviolet shielding material, an attempt has been made to suppress the photocatalytic function by coating the surface with an inert substance such as SiO ₂ or Al ₂ O ₃ (for example, Japanese Patent No. 1934945).

[0003] When a general inorganic ultraviolet shielding material is added to a substrate, it is necessary to increase the concealing rate of the substrate to some extent in order to enhance the shielding effect, and at the same time, to improve the transmittance of visible light. Due to the requirements, the particle size of the shielding material must be extremely fine. Therefore, since the particles have a large cohesive force, they are coagulated when added to a base material such as plastic or paint, and it is difficult to uniformly disperse them. The aggregation and dispersion unevenness lower the shielding effect and significantly impair the appearance of the substrate.

As a measure for improving the dispersibility of such an inorganic ultraviolet shielding material, a compound having an ultraviolet shielding function such as titanium oxide is supported on the surface of a flaky clay mineral (for example, see JP-A-9-87141). JP-A-9-5912
9) and intercalation between layers of clay minerals have been attempted.

[0005] However, as a matter of course, a compound having a function of shielding ultraviolet light is exposed on the surface of a surface carrier on a visco-mineral such as titanium oxide. Also, when intercalating between clay mineral layers, titanium oxide is coordinated also in the outermost layer of the clay layer. Therefore, it is inevitable that a compound having an ultraviolet shielding function is exposed on the surface. That is, the problems of cohesiveness and suppression of the photocatalytic function in the inorganic ultraviolet shielding material have not been solved at the same time.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to suppress the photocatalytic function of the above-mentioned conventional ultraviolet shielding material and to cause photo-aging of the organic substrate to which the ultraviolet shielding material is added or dispersed. It is an object of the present invention to provide an ultraviolet ray shielding material capable of exhibiting only an ultraviolet ray shielding function and a method for producing the same.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems of the prior art, and as a result, have found that an ultraviolet ray shielding material containing an inorganic compound having an ultraviolet ray shielding function such as titanium oxide is used. By coating with a clay mineral, the photocatalytic function of the ultraviolet shielding material cannot be exhibited, and only the ultraviolet shielding function can be exhibited without photoaging the organic base material to which the ultraviolet shielding material is added or dispersed. The present invention has been completed.

That is, the present invention is an ultraviolet shielding material characterized in that an ultraviolet shielding functional substance is coated with a clay mineral. The present invention is also a method for producing an ultraviolet shielding material,
The following steps: a) a step of preparing a dispersion of the clay mineral by dispersing the clay mineral in a dispersion medium; b) a step of mixing an ultraviolet shielding functional substance with the dispersion of the clay mineral; c) solid-liquid separation of the mixture And d) heating the solids obtained in step c).

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ultraviolet shielding material according to the present invention has a structure in which the surface of an ultraviolet shielding functional material is coated with a clay mineral, and the ultraviolet shielding functional material itself is not exposed on the surface. For this reason, although the ability to absorb ultraviolet light is maintained, the organic base material or the like to which the ultraviolet shielding material is added or dispersed does not come into direct contact, so that these organic base materials and the like are photo-degraded by photocatalysis. There is no. Furthermore, since the clay mineral after coating retains the original swelling property of the clay mineral, the shielding materials do not agglomerate with each other and have excellent dispersibility.

[0010] The ultraviolet shielding material in the present invention includes an inorganic compound having a high ultraviolet absorbing ability and therefore an excellent ultraviolet shielding ability. Specific examples of the inorganic compound include titanium, iron, zinc and tin. And inorganic oxides such as cerium. In the present invention, the inorganic oxides include hydrated oxides such as hydroxides.

Further, the ultraviolet ray shielding material in the present invention includes those in which the above-mentioned inorganic compound is supported on the surface of an inorganic substance such as clay mineral, silica, alumina or glass. The shape of these inorganic substances is preferably plate-like or flake-like. The above clay mineral may be the same as the clay mineral for coating.

The ultraviolet shielding material used in the present invention contains an inorganic compound such as titanium oxide which has a high ultraviolet absorbing ability and an excellent ultraviolet shielding ability as described above. The inorganic compound supported on the inorganic substance can be obtained by a conventionally known method. For example, a titanium salt or a titanium compound is hydrolyzed in an aqueous solution of an inorganic titanium salt or an organic titanium compound in which a core inorganic substance is dispersed, and a titanium hydrolyzate is deposited on the surface of the inorganic substance. Then, solid-liquid separation is performed by means such as filtration and washing to obtain a desired ultraviolet shielding functional substance.

As the clay mineral used for coating the above-mentioned ultraviolet shielding function material, a phyllosilicate having a layered structure is preferable, and specific examples thereof include smectites such as saponite and montmorillonite, vermiculite, and swelling mica. No.

Next, a method for manufacturing the ultraviolet shielding material of the present invention will be described. In the present invention, attention is paid to the fact that there is a temperature region where the bonding force between the ultraviolet ray shielding functional substance and the clay mineral increases without losing the properties such as the inherent swelling properties of the clay mineral, and the ultraviolet ray shielding is performed within the temperature region. By heating a mixture of a functional substance and a clay mineral, an ultraviolet ray shielding material which is firmly bonded to the ultraviolet ray shielding functional substance and the clay mineral is not easily separated is basically obtained.

In the method for producing an ultraviolet shielding material according to the present invention, first, as a step a), a clay mineral is dispersed in a dispersion medium to prepare a clay mineral dispersion. As the dispersion medium at this time, a polar substance such as water or alcohol is used. These may be used alone or as a mixture. The concentration of the clay mineral in the dispersion is not particularly limited, but from the viewpoint of production efficiency is 0.5 to 3.
It is preferably in the range of 0% by weight.

Next, as a step b), an ultraviolet ray shielding material is uniformly mixed with the dispersion. The ultraviolet shielding functional substance may be mixed in a powder form, or may be mixed as a dispersion liquid dispersed in an appropriate dispersion medium. The dispersion medium at this time is preferably the same as the dispersion medium of the clay mineral. The temperature of the mixture is preferably in the range of 10 to 70 ° C., and the stirring time is 0.5 to 70 ° C.
A range of ~ 24 hours is preferred.

The amount of the clay mineral used for coating the ultraviolet shielding material is preferably 20 to 500 parts by weight per 100 parts by weight of the ultraviolet shielding material. If the amount is less than 20 parts by weight, the unblocked ultraviolet ray shielding functional substance remains, so that the oxidation resolution of the ultraviolet ray shielding material is increased, which is not preferable. If the amount exceeds 500 parts by weight, the excess amount of the clay mineral increases, and the relative amount of the ultraviolet shielding function material in the obtained ultraviolet shielding material decreases, which causes problems such as a decrease in the ultraviolet shielding function. Not preferred.

Next, as step c), the mixture of the clay mineral thus obtained and the ultraviolet shielding material is filtered,
Solid-liquid separation is performed by means such as centrifugal sedimentation to obtain a solid (cake).

Finally, as a step d), the above-obtained cake is heated to obtain an ultraviolet ray shielding material in which a target ultraviolet ray shielding functional substance is coated with a clay mineral. The heating conditions are selected from a temperature range of 60 to 350 ° C. at which the bond between the ultraviolet ray shielding functional substance and the clay mineral becomes strong. At this time, it is preferable to heat the ultraviolet shielding material after the heat treatment so that the loss on drying is measured at a temperature of 105 to 110 ° C. and the loss on drying is in a range of 3 to 15% by weight.

The heating temperature is less than 60 ° C. or the loss on drying is 1
If the content exceeds 5% by weight, the bonding between the ultraviolet ray shielding functional substance and the clay mineral is insufficient, and the titanium oxide in the ultraviolet ray shielding functional substance is exposed due to peeling when dispersed in an organic base material according to the purpose of use. Problem comes out. On the other hand, when the temperature exceeds 350 ° C. or when the loss on drying is less than 3% by weight, the swelling characteristic of clay minerals is lost. In this case, even if the obtained ultraviolet shielding material is dispersed again in water or the like, it does not swell and cannot be dispersed as fine particles. Therefore, in order to form fine particles, it is necessary to rely on mechanical pulverization, and a part of the ultraviolet shielding material is exposed on the fracture surface by the pulverization, which is not preferable.

The ultraviolet shielding material according to the present invention obtained by the method described above has an ultraviolet shielding functional material coated with a clay mineral, and the outermost layer is made of a clay mineral, that is, [clay mineral (C) / Ultraviolet shielding functional material (M) / clay mineral (C)] as the minimum unit. When the amount of the clay mineral is smaller than that of the ultraviolet ray shielding material, the minimum unit such as [(C) / (M) / (C) / (M) / (C)] overlaps. In some cases, it has a different structure.

The ultraviolet shielding material according to the present invention having the above-mentioned structure is heated in a temperature range in which the crystal structure of the clay mineral does not change, so that it retains the swelling characteristic of the clay mineral. For this reason, when the obtained ultraviolet shielding material is dispersed again in a dispersion medium such as water, the dispersion medium easily penetrates between the layers of the outermost clay mineral and the clay mineral of the ultraviolet shielding material having the above structure and swells. I do. When this is subjected to dispersion treatment by ultrasonic vibration or the like, a dispersion of fine particles having a structure consisting of the minimum unit described above is obtained, and if this is dried by an appropriate method such as spray drying, a conventional mechanical pulverization is performed. Without the above, fine particles of the ultraviolet shielding material coated with the clay mineral can be obtained.

[0023]

Example 1 (1) Preparation of UV-shielding functional substance 113 g of titanium tetraisopropoxide (TIP) was added to 1,000 g of an 80% aqueous acetic acid solution, and the mixture was stirred to obtain a TI.
P was hydrolyzed to obtain a sol in which a titanium oxide precursor (abbreviated as p-TiO ₂ ) was dispersed. This sol and a sol 4,000 obtained by dispersing 1.0% by weight of saponite (Smecton SA manufactured by Kunimine Industries Co., Ltd .; hereinafter, abbreviated as SAP) in pure water.
and stirred at 50 ° C. for 1 hour. The solid content was separated from the sol by centrifugal sedimentation to obtain an ultraviolet shielding functional material (a) in which a hydrated oxide of titanium was supported on a cake SAP.

(2) Preparation of Ultraviolet Shielding Material The ultraviolet shielding functional material (a) obtained above was dispersed in 8,000 g of the above-mentioned SAP 1.0% by weight dispersion sol and stirred at room temperature for 2 hours. . After stirring, the cake obtained by solid-liquid separation by centrifugal sedimentation is kept at 80 ° C., dried until the loss on drying at 110 ° C. becomes 6%, and the ultraviolet ray having the ultraviolet ray shielding functional substance (a) coated with saponite A shielding material (A) was obtained.

Example 2 (1) Preparation of UV shielding functional substance ₂ g of 15 g / L (TiO ₂ equivalent) titanyl sulfate aqueous solution
30 g of kaolin was added thereto, and the mixture was stirred at 95 ° C. for 2 hours. After cooling to room temperature, solid-liquid separation is performed, and cake-like SA
An ultraviolet ray shielding material (b) in which a hydrated compound of titanium was supported on P was obtained.

(2) Preparation of Ultraviolet Shielding Material The ultraviolet shielding functional material (b) obtained above was dispersed in 6,000 g of the 1.0% by weight dispersion sol of SAP used above and stirred at room temperature for 2 hours. . After stirring, the cake obtained by solid-liquid separation by centrifugal sedimentation is kept at 80 ° C., dried until the loss on drying at 110 ° C. becomes 8%, and the ultraviolet ray having the ultraviolet ray shielding functional substance (b) coated with saponite A shielding material (B) was obtained.

Example 3 (1) Preparation of Ultraviolet Shielding Functional Material A 15% aqueous solution of 2% by weight of TiO _{2 in} titanyl sulfate was added.
Aqueous ammonia was added until the pH reached 8.5, and the mixture was stirred, and then filtered and washed to obtain a cake of hydrous titanium oxide. A cake of 500 g in terms of solid content is prepared by adding 850% of a 20% aqueous hydrogen peroxide solution.
In 0 g, the mixture was stirred at 85 ° C. for 3 hours to obtain a titanic acid aqueous solution. 56 g of montmorillonite (Kunimine Kogyo Co., Ltd. Kunipia F) was added to the aqueous solution, and the mixture was stirred at 95 ° C. for 96 hours. After cooling to room temperature, solid-liquid separation was carried out to obtain an ultraviolet ray shielding functional material (c) in which titanium hydrated oxide was supported on cake-like montmorillonite.

(2) Preparation of Ultraviolet Shielding Material The ultraviolet shielding functional material (c) obtained above was dispersed in the montmorillonite 1.0% by weight dispersion sol 11,20 used above.
0 g, and stirred at room temperature for 2 hours. After stirring, the cake obtained by solid-liquid separation by centrifugal sedimentation is kept at 80 ° C.
Dried until the loss on drying at 110 ° C. is 9%,
An ultraviolet shielding material (C) in which the ultraviolet shielding functional material (c) was covered with montmorillonite was obtained.

Comparative Example 1 The ultraviolet shielding materials (A), (B) and (C) obtained in Examples 1 to 3 were each pulverized to 200 mesh or less and then fired at 500 ° C. for 2 hours. D),
(E) and (F) were obtained. These are all 110
The loss on drying at 0 ° C was 0.2% or less.

COMPARATIVE EXAMPLE 2 In Example 2, instead of drying at 80 ° C.,
After holding for 4 hours, an ultraviolet ray shielding material (G) having a loss on drying at 110 ° C. of 28% was obtained.

Performance tests Various performances were evaluated for the ultraviolet shielding materials (A) to (G) and the ultraviolet shielding functional substances (a) to (c) obtained in Examples 1 to 3 and Comparative Examples 1 and 2. did. (1) Measurement of Ultraviolet Reflection Spectrum Ultraviolet shielding materials (A) to (C) pulverized to 200 mesh or less, and ultraviolet shielding functional substances (a) to (c)
Was dried at 110 ° C. for 16 hours and pulverized to 200 mesh or less, and the reflectance at each wavelength was measured. Table 1 shows the results. FIG. 1 shows an ultraviolet ray reflection spectrum of the ultraviolet ray shielding material (A), and FIG. 2 shows an ultraviolet ray reflection spectrum of the ultraviolet ray shielding material (a). (Measurement instrument: UV-visible spectrophotometer V-550, manufactured by JASCO Corporation)

[0032]

[Table 1] As is clear from the results shown in Table 1 and FIG. 1, the UV-reflecting ability of the UV-shielding materials (A) to (C) coated with the clay mineral and the UV-shielding functional materials (a) to (c) not coated were measured. It can be seen that there is no significant change.

(2) Measurement of Ultraviolet Transmission Intensity The ultraviolet shielding materials (A) to (C) and the ultraviolet shielding functional substances (a) to (c) used in the above (1) were each converted into TiO ₂ weight relative to liquid paraffin. Disperse in liquid paraffin so that the ratio becomes 0.1,
UV light is applied between two 6 mm quartz plates,
The transmission intensity of light having a wavelength of nm was measured. Table 2 shows the results.

[0034]

[Table 2] As can be seen from the results in Table 2, the difference between the coated body and the uncoated body made of the clay mineral is small. In addition, the blank is the transmission intensity of only liquid paraffin.

(3) Evaluation of swellability and dispersibility 2 g of each of the ultraviolet shielding materials (A) to (F) and the ultraviolet shielding functional substances (a) to (c) used in the above (1) were placed in a measuring cylinder. After tapping, water was added and the mixture was allowed to stand for 48 hours. The increase in the bulk of the solid after standing was measured. Table 3 shows the results.

[0036]

[Table 3] As can be seen from the results in Table 3, the UV-shielding functional substances (a) to (c) which are not coated with the clay mineral have almost no increase in bulk, whereas the UV-shielding materials (A) to (C) have significantly higher bulk. It can be seen that it has increased and swelled. Also, 500
It can be seen that the ultraviolet shielding materials (D) to (F) fired at ℃ did not increase in bulk and lost their swelling properties.

Further, the test product after swelling of the ultraviolet ray shielding material (A) and the ultraviolet ray shielding material (D) was sufficiently dispersed by an ultrasonic transmitter to measure the particle size distribution. FIG. 3 shows the measurement results. As apparent from FIG. 3, the swelled product of the ultraviolet shielding material (A) is easily dispersed in the fine particles having a median diameter of 2.2 μm, whereas the ultraviolet shielding material (D) has a particle size distribution at the time of pulverization. It can be seen that they are the same and are not sufficiently dispersed.

(4) Comparison of photocatalytic functions The ultraviolet shielding materials (A) to (C) and (G) and the ultraviolet shielding functional materials (a) to (c) used in the above (1) are swollen with ion-exchanged water. And dispersed to prepare a slurry.
These slurries were placed on a 100 mm square quartz plate with TiO ₂
, And baked at 500 ° C. for 2 hours to fix the coating. UV shielding material (A)
The coating film of (C) was smooth and transparent. Each of these quartz plates was sealed in a transparent container together with 100 ppm of acetaldehyde, and irradiated with ultraviolet rays for a predetermined time to evaluate the photocatalytic oxidative decomposition function of acetaldehyde. Table 4 shows the residual concentration of acetaldehyde in each transparent container.

[0039]

[Table 4]

FIG. 4 shows the change in the residual amount of acetaldehyde for the blank, the ultraviolet shielding material (B) and the ultraviolet shielding functional material (b). As can be seen from Table 4 and FIG. 4, the ultraviolet shielding materials (A) to (C) show almost the same residual amount as the blank, whereas the ultraviolet shielding functional substances (a) to (c) show the irradiation time. At the same time, the remaining amount sharply decreases. This indicates that the photocatalytic function is effectively suppressed by coating the ultraviolet shielding material with the clay mineral.

Further, comparing the ultraviolet shielding material (B) and the corresponding ultraviolet shielding material (G), the ultraviolet shielding material (G) has a higher oxidation resolution than the ultraviolet shielding material (B). . For this reason, if sufficient heating is not performed after coating with the clay mineral, the bond between the ultraviolet shielding functional material and the clay mineral is insufficient, and when dispersed in water, etc., both are separated and some titanium oxide This indicates that an exposed surface such as an object has occurred.

As is evident from the results of the performance tests described above, even if the ultraviolet shielding material according to the present invention is coated with a clay mineral, there is no significant difference in the reflection and transmission of ultraviolet light, and the function as the ultraviolet shielding material is impaired. You can see that it is not. On the other hand, the oxidative decomposition function as a photocatalyst is significantly reduced, indicating that the coating with the visco-mineral is sufficiently performed.

[0043]

According to the present invention, after sufficiently mixing the ultraviolet ray shielding functional material and the sheet-like clay mineral, the solid-liquid separation is performed.
By a very simple operation of heating at a relatively low temperature, it is possible to coat the ultraviolet shielding functional substance with a clay mineral.

The ultraviolet shielding material according to the present invention obtained in this way does not impair the ability to absorb ultraviolet light even when coated with a clay mineral, and thus has a sufficient function as an ultraviolet shielding material. On the other hand, since the oxidative decomposition function as a photocatalyst is significantly reduced, the organic base material does not deteriorate by light even when added to an organic base material. Further, when the ultraviolet shielding material according to the present invention is dispersed in a dispersion medium such as water, it easily swells, and a dispersion liquid of fine particles having a uniform particle size can be obtained without taking any means such as mechanical pulverization. Therefore, there is no problem that a part of the ultraviolet shielding material is exposed by mechanical pulverization for forming fine particles.

The ultraviolet shielding material according to the present invention having the above characteristics can be used for various applications. For example, if the fine particles of the ultraviolet shielding material according to the present invention are kneaded and stretched into a film, the fine particles of the ultraviolet shielding material are uniformly dispersed, the concealing ratio is high and the ultraviolet shielding function is excellent, and A film free from degradation by the photocatalyst is obtained.

[Brief description of the drawings]

FIG. 1 shows an ultraviolet reflection spectrum of an ultraviolet shielding material (A) obtained in Example 1.

FIG. 2 shows an ultraviolet reflection spectrum of the ultraviolet shielding functional material (a) obtained in Example 1.

FIG. 3 shows the particle size distribution of the ultraviolet shielding material (A) obtained in Example 1 and the ultraviolet shielding material (D) obtained in Comparative Example 1 after swelling and dispersion.

FIG. 4 shows the oxidative resolution as a photocatalytic function of the ultraviolet shielding material (B) and the ultraviolet shielding functional substance (b) obtained in Example 2.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) A61K 7/40 A61K 7/40 (C08K 9/02 3:22)

Claims (9)

[Claims] 1. An ultraviolet shielding material comprising an ultraviolet shielding functional material coated with a clay mineral. 2. The ultraviolet shielding material according to claim 1, wherein the clay mineral is a phyllosilicate. 3. The ultraviolet shielding material includes an inorganic compound having an ultraviolet shielding function.
Or the ultraviolet shielding material according to 2. 4. The ultraviolet shielding material according to claim 3, wherein the inorganic compound having an ultraviolet shielding function is titanium oxide. 5. A method for producing an ultraviolet ray shielding material, comprising the following steps: a) a step of dispersing a clay mineral in a dispersion medium to prepare a dispersion of the clay mineral; Mixing the mixture with a dispersion, c) separating the mixture into a solid and a liquid, and d) heating the solid obtained in the step c). 6. The heating temperature in the step d) is 60 to 350.
The method for producing an ultraviolet shielding material according to claim 5, wherein the temperature is in the range of ° C. 7. The method according to claim 5, wherein the clay mineral is a phyllosilicate. 8. The ultraviolet ray shielding material includes an inorganic compound having an ultraviolet ray shielding function.
8. The method for producing an ultraviolet shielding material according to any one of Items 1 to 7. 9. The method according to claim 8, wherein the inorganic compound having an ultraviolet shielding function is a titanium oxide.