JPH0633036A - Selective UV absorbing material - Google Patents

Abstract

(57) [Summary] The present invention relates to a selective ultraviolet absorbing material containing silicon carbide as a main component, and more specifically, the free carbon content in silicon carbide is 0.3 wt% or less, and The present invention relates to a selective ultraviolet absorbing material containing, as a main component, substantially white or transparent silicon carbide having a transition element metal compound content of 0.2 wt% or less. [Effect] The selective ultraviolet absorbing material of the present invention has high transparency in the visible light region and exhibits high absorption performance in the ultraviolet light region due to the above-mentioned effect of silicon carbide. Furthermore, since the main component is silicon carbide, which also has excellent corrosion resistance, cosmetics, clothing, fibers, paints,
It can be widely used as an ultraviolet protection material for containers, parts such as window materials, and building structures, and is industrially useful.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a selective ultraviolet absorbing material containing silicon carbide as a main component and having high transparency in the visible light region.

[0002]

2. Description of the Related Art Various materials are known as ultraviolet absorbing materials, but inorganic materials are superior in corrosion resistance and safety compared to organic materials and are widely used. There is. Among them, titanium oxide and zinc oxide are easy to be highly purified and are widely used in paints, cosmetics, fibers and the like. However, these oxide-based materials are
Corrosion resistance and ultraviolet absorption effect are still insufficient, and improvement is desired. An object of the present invention is to provide a selective ultraviolet absorbing material having excellent corrosion resistance and an ultraviolet absorbing effect in order to solve such a problem.

[0003]

The present inventors have completed the present invention as a result of extensive studies to achieve the above object. That is, the gist of the present invention relates to a selective ultraviolet absorbing material containing silicon carbide as a main component.

The selective ultraviolet absorbing material of the present invention contains silicon carbide as a main component, and the silicon carbide used has a free carbon content of 0.3 wt% or less and a transition element metal compound content of 0. 0.2 wt% or less is preferable, more preferably the free carbon content is 0.1 wt% or less, and the transition element metal compound content is 0.1 wt%.
% Or less. If the free carbon content exceeds 0.3 wt% or the transition element metal compound content exceeds 0.2 wt%, the transparency (transmittance) in the visible light region is poor and it is not suitable for practical use. Furthermore, the absorption capacity in the ultraviolet region is extremely poor,
It impairs the features of the present invention. Further, the silicon carbide in the present invention needs to be substantially white or transparent. In the present invention, the free carbon content and the transition element metal compound content can be measured according to JIS-R-61-244-1980. Such high-purity silicon carbide selectively exhibits the absorption ability in the ultraviolet light region, has little absorption in the visible light region, is practically colorless, and can be widely used as an ultraviolet absorbing material.

The crystal system of silicon carbide is α type, β type, and 2 type.
Polymorphs such as H, 4H, 6H, 8H, 15R, and 3C are not limited, but 2H, 4H, and 2H from the viewpoint of transparency in the visible light region.
6H is preferred. The crystal system is selected from the above, and in the present invention, one kind or a mixture of two or more kinds can be used.

The form of silicon carbide may be, for example, a single crystal processed body, a sintered body, a powder, or the like.
When a processed body or a sintered body is used, the transparency in the visible light region is preferably 50% or more in total transmittance from the practical viewpoint.
It is more preferably at least 65%. If it is less than 50%, the compound or member composed of the ultraviolet absorbing material becomes opaque or colored, which is not preferable in practice. Further, in the case of powder, a plate shape or a spherical shape is desirable, and the particle size is usually 0.01 to 10
It is desirable that the thickness is in the range of 0 μm, preferably 0.1 to 50 μm. When it is less than 0.01 μm, the dispersibility is deteriorated and the ultraviolet ray absorbing effect is lowered, and when it exceeds 100 μm, the shielding area is reduced and the ultraviolet ray absorbing effect is lowered.

The method for producing silicon carbide in the present invention is not particularly limited, but the free carbon content is 0.3 wt% or less and the transition element metal compound content is 0.2 wt%.
In order to obtain a substantially white or transparent material below, the following known method may be used. That is, a method of removing a transition element metal compound from a silicon carbide raw material by acid treatment and heating free carbon may be used. At this time, hydrochloric acid, oxalic acid, nitric acid, hydrofluoric acid, or the like or a mixed acid thereof is used as the acid. The heating may be performed at 15 to 95 ° C.
In addition, a method of heating and sublimating a silicon carbide raw material to grow crystals (for example, magazine “Vacuum”, Volume 30 (1987), P5).
2) and a method of synthesizing silicon and carbon raw materials by a vapor phase method (for example, magazine "Ceramics", Vol. 19 (19
84), P478) and the like.

The selective ultraviolet absorbing material of the present invention contains the above-mentioned silicon carbide as a main component. The silicon carbide of the present invention has a high transparency in the visible light region and a high absorption performance in the ultraviolet light region. Therefore, the selective ultraviolet absorbing material of the present invention is within a range that does not impair the characteristics of silicon carbide.
An inorganic substance and / or an organic substance other than silicon carbide may be added and combined. In this case, the content of silicon carbide is usually 60 wt% or more, preferably 80 wt% or more.
If it is less than 60 wt%, the ultraviolet ray absorbing ability is not expressed, which is not preferable. Examples of the inorganic material used include Al,
Examples thereof include metal oxides or hydroxides composed of one or more elements such as Si, Zr, Ti, Zn, Mg, Ca, and Y. Examples of the organic substance include polyester, polyethylene, polystyrene, methyl methacrylate resin, Examples thereof include polypropylene, Teflon, silicone resin, vinyl chloride, acrylic resin and the like. In addition, as an aspect of composite, for example, one in which silicon carbide is dispersed in a solid organic substance, powder,
Various forms such as a film, a fiber, a fiber, a thread, and a resin molded body such as a container are possible.

The selective ultraviolet ray absorbing material of the present invention contains, as a main component, silicon carbide having the above-mentioned excellent selective ultraviolet ray absorbing performance, and since this silicon carbide also has excellent corrosion resistance, for example, cosmetics. It can be widely used as a UV protection material for clothing, textiles, paints, containers, parts such as window materials, and building structures.

[0010]

EXAMPLES The present invention will be specifically described below with reference to Examples, Comparative Examples and Test Examples, but the present invention is not limited to these. In the following examples and comparative examples, the free carbon content and the transition element metal compound content were determined according to the method of JIS-R-61-24-21980.

Example 1 α-type silicon carbide obtained by the Acheson method (average particle size = 3.
5 μm, mixing ratio of polymorphs 6H and 4H is 20%: 80%)
Was immersed in a hydrochloric acid aqueous solution to remove the transition element metal compound. Further, heat treatment was carried out at 700 ° C. for 1 hour in an air stream to remove free carbon. The obtained product has a free carbon content of 0.18 wt% and a transition element metal compound content of 0.1.
It was 5 wt%. The silicon carbide powder obtained was kneaded into silicon oil so as to be 10 wt%, a coating film was formed on quartz glass, and a spectrophotometer (Hitachi, U4000) was used.
Type) was used to measure the transmittance at a wavelength of 200 to 700 nm. As a result, the transmittance in the visible light region is high (500 nm
The transmittance was 78.5%), the transmittance in the ultraviolet region was low (the transmittance at 300 nm was 21.3%), and it was found that the selective ultraviolet absorption characteristics were excellent.

Example 2 α-form silicon carbide obtained by the Acheson method (average particle size = 0.
(15μm, mixing ratio of polymorphs 6H and 4H is 40%: 60%)
In the same manner as in Example 1, the transition element metal compound and the free carbon were removed to obtain a silicon carbide powder having a free carbon content of 0.06 wt% and a transition element metal compound content of 0.08 wt%. About this, the transmittance was measured with a spectrophotometer in the same manner as in Example 1. The result is shown in FIG. From Fig. 1, the transmittance in the visible light region is high, and the transmittance in the ultraviolet light region is low,
It has been found that the selective UV absorption property is excellent.

Example 3 β-type silicon carbide (average particle size = 0.02 μm, polymorph C) obtained by high frequency plasma CVD which is a vapor phase method was heat-treated at 600 ° C. for 1 hour in an air stream to obtain free carbon. Is 0.09 wt
%, And the transition element metal compound was 0.05 wt% to obtain a silicon carbide powder. The ultraviolet absorptivity of this was measured with a spectrophotometer in the same manner as in Example 1. As a result, the transmittance in the visible light region is high (the transmittance at 500 nm is 81.7%), and the transmittance in the ultraviolet region is low (the transmittance at 300 nm is 17.5).
%), And was found to have excellent selective UV absorption characteristics.

Example 4 Silicon carbide single crystal obtained by the Acheson method (free carbon content 0.02 wt%, transition element metal compound content = 0.01)
wt%) and processed into a 20 mm square and 0.39 mm thick flat plate, and the transmittance was measured with a spectrophotometer in the same manner as in Example 1. The result is shown in FIG. From FIG. 1, it was found that the transmittance in the visible light region was high, the transmittance in the ultraviolet light region was low, and the selective ultraviolet absorption characteristics were excellent.

Example 5 5 wt% of the silicon carbide powder obtained in Example 2 was kneaded into a polypropylene resin to prepare a film having a thickness of 68 μm, and the ultraviolet absorptivity was measured by a spectrophotometer in the same manner as in Example 1. As a result, the transmittance in the visible light region is high (500n
It was found that the transmittance of m was 72.3%), the transmittance in the ultraviolet region was low (the transmittance of 300 nm was 15.4%), and the selective ultraviolet absorption characteristics were excellent.

Comparative Example 1 α-type silicon carbide obtained by the Acheson method (average particle size = 3.
5 μm, mixing ratio of polymorphs 6H and 4H is 20%: 80%,
Free carbon amount = 0.25 wt%, transition element metal compound content = 0.75 wt%) was kneaded in the same manner as in Example 1 so that the silicon carbide powder obtained was 10 wt% in silicon oil, and fused into quartz glass. A coating film was formed and the transmittance was measured with a spectrophotometer in the same manner as in Example 1. The result is shown in FIG. From FIG. 1, it was found that the transmittance in the visible light region was low, the transmittance in the ultraviolet light region was higher than those in Examples 2 and 4, and the selective ultraviolet absorption characteristics were inferior.

Comparative Example 2 β-type silicon carbide (average particle size = 0.02 μm, polymorph C, free carbon 0.41 wt%, transition element metal compound 0) obtained by high-frequency plasma CVD which is a vapor phase method. .05 wt
%) Silicon carbide powder was obtained. For this, the transmittance was measured with a spectrophotometer in the same manner as in Example 1. The result is shown in FIG. From FIG. 1, it was found that the transmittance in the visible light region was low, the transmittance in the ultraviolet light region was higher than those in Examples 2 and 4, and the selective ultraviolet absorption characteristics were inferior.

Test Example Using the silicon carbide obtained in Examples 2 and 4 and titanium dioxide, which is a typical conventional ultraviolet absorbing material, the corrosion resistance of the powder and the processed body was evaluated as follows. . In the case of powder, the corrosion resistance is evaluated by 13 wt% of powder.
It was suspended in the sulfuric acid aqueous solution for 1 hour and judged by qualitative analysis of the eluted Ti and Si ions. In the case of the processed body, the surface of the processed body was mirror-polished and then immersed in concentrated sulfuric acid for 12 hours to qualitatively judge the cloudiness of the surface. Titanium dioxide, if powdered, has an anatase crystal form and an average particle size of 0.2 μm.
In the case of the processed product, a single crystal having a rutile crystal form was processed into a 20 mm square and a thickness of 0.39 mm. As the product of the present invention, the powder and the processed product obtained in Examples 2 and 4 were used.

As a result, in the silicon carbide powder of Example 2, S
i was not detected, and Ti was detected in the titanium dioxide powder. The surface of the silicon carbide processed body of Example 4 was not fogged, and the surface of the titanium dioxide processed body was fogged. Therefore, it has been revealed that the silicon carbide in the present invention exhibits excellent corrosion resistance as compared with the conventional typical titanium dioxide.

[0020]

The selective ultraviolet absorbing material of the present invention has high transparency in the visible light region and high absorption performance in the ultraviolet light region due to the effect of silicon carbide described above. Furthermore, since the main component is silicon carbide, which also has excellent corrosion resistance, cosmetics, clothing, fibers,
It can be widely used as paint, containers, parts such as window materials, and UV protection materials for building structures, and is industrially useful.

[Brief description of drawings]

FIG. 1 is a diagram showing measurement results of spectrophotometers in Examples 2 and 4 and Comparative Examples 1 and 2.

Claims (2)

[Claims] 1. A selective ultraviolet absorbing material containing silicon carbide as a main component. 2. The free carbon content in silicon carbide is 0.3 w.
t% or less, and the transition element metal compound content is 0.
The selective ultraviolet absorbing material according to claim 1, which contains 2 wt% or less of substantially white or transparent silicon carbide as a main component.