Cosmetic preparation, surface-hydrophobized silica-coated...

Drug – bio-affecting and body treating compositions – Topical sun or radiation screening – or tanning preparations

Reexamination Certificate

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C424S401000, C106S436000

Reexamination Certificate

active

06534044

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a cosmetic material, to surface-hydrophobicized silica-coated metal oxide particles, to a silica-coated metal oxide sol and to a process for their production. More specifically, it relates to a cosmetic material and particularly an ultraviolet-screening cosmetic material, to surface-hydrophobicized silica-coated metal oxide particles suitable for use in the cosmetic material and to a process for their production, as well as to a silica-coated metal oxide sol suitable for use in a cosmetic material and particularly an ultraviolet-screening cosmetic material, having a specified infrared absorption spectrum peak, coated with a dense, practical silica film and having a small primary particle size with satisfactory dispersability. It further relates to a surface-hydrophobicized silica-coated metal oxide sol which is obtained by surface treatment with a hydrophobicizing agent after silica coating, and to a process for its production. Even more specifically, the present invention relates to a cosmetic material with an excellent feel during cosmetic use, a high ultraviolet-screening function, low phototoxicity and excellent storage stability, and to surface-hydrophobicized silica-coated metal oxide particles having a specified infrared absorption spectrum peak, coated with a dense, practical silica film and being surface treated with a hydrophobicizing agent, the surface-hydrophobicized silica-coated metal oxide particles being suited for use as ultraviolet-screening materials, cosmetic products, pigments and the like. The invention still further relates to a cosmetic material containing the silica-coated metal oxide sol and/or surface-hydrophobicized silica-coated metal oxide sol, exhibiting a high ultraviolet-screening function, a high photocatalytic activity-suppressing effect, excellent storage stability and excellent feel and transparency for cosmetic use.
BACKGROUND ART
Many of the ultraviolet-screening cosmetic materials used in recent years have been inorganic-based ultraviolet-screening materials with excellent ultraviolet-screening function and high stability. Such commonly used inorganic-based ultraviolet-screening materials include metal oxide powders of titania and zinc oxide.
When these metal oxide powders are added directly to cosmetic materials, however, problems are known to occur such as a poor feel or adverse effect on the human body or skin due to the photocatalytic activity of the metal oxide particles, and it has therefore been necessary to provide the metal oxide particles with some manner of coating. A coating of an inorganic substance is particularly preferred because it is resistant to chemical change by photocatalytic reaction.
However, although inorganic-coated metal oxide particles have a photocatalytic activity-suppressing effect when added to cosmetic materials, they have been inconvenient in that their dispersion in hydrophobic base materials is insufficient and excellent powder properties are not adequately exhibited, when incorporated into oily cosmetic materials, W/O dispersion cosmetic materials or water-repellent cosmetic materials that are resistant to cosmetic disintegration due to perspiration and moisture.
Also, when particles of a metal oxide such as titania or zinc oxide, which are widely used as highly stable inorganic ultraviolet-screening materials with the excellent ultraviolet-screening function described above, are added directly to cosmetic materials, it is common to coat the surfaces with an inorganic substance with no photocatalytic activity, because of the problems of poor feel during cosmetic use or adverse effect on the human body due to the photocatalytic activity of the metal oxide particles. Metal oxide particles coated with alumina, silica and the like are commercially available, but no product has been known which satisfies both aspects of suppressing the photocatalytic activity by the coating and improving the feel, during use, when added to cosmetics.
The present inventors have disclosed silica-coated metal oxide particles having a silica film wherein the ratio I of the peak intensities of the infrared absorption spectrum at 1150-1250 cm
−1
and 1003-1100 cm
−1
(I=I1/I2: where I1 is the maximum absorption peak intensity in the range of 1150-1250 cm
−1
and I2 is the maximum absorption peak intensity in the range of 1000-1100 cm
−1
) is 0.2 or greater, and the refractive index is 1.435 or greater, a process for their production and a cosmetic material comprising them, and have demonstrated that an ultraviolet-screening cosmetic material with a satisfactory feel during use, a high suppressing effect on photocatalytic activity and excellent storage stability can be obtained by including these silica-coated metal oxide particles coated with a silica film of a thickness between 0.1 and 100 nm and having photocatalytic activity of no more than 60 Pa/min as measured by the tetralin autooxidation method (PCT/JP98/01133).
In recent years, ultraviolet-screening cosmetic materials have needed a satisfactory feel during use and a highly transparent feel or appearance, in addition to the high ultraviolet-screening function. In order to provide a satisfactory feel in use, and a transparent feel or appearance for the metal oxide particles added to cosmetic materials as ultraviolet-screening materials, it has become more desirable to decrease the size of the primary particles and improve the dispersion properties. The aforementioned silica-coated metal oxide particles based on the invention of the present inventors have excellent properties such as suppression of photocatalytic activity and an excellent feel during use, but further improvement in the particle fineness and dispersion properties have been desired to increase the transparency when added to cosmetic materials.
However, because metal oxide powders with small primary particle sizes produce lumps when suspended in solvents, they do not readily undergo high dispersion and require extra steps such as the use of ultrasonic waves for silica coating or prolonged stirring, which constitutes a problem in economic terms.
It is a first object of the present invention to provide a cosmetic material with satisfactory dispersion of metal oxide particles in an oily base, an excellent feel during cosmetic use, a high ultraviolet-screening function, low phototoxicity and excellent storage stability, and to provide surface-hydrophobicized silica-coated metal oxide particles coated with a dense, practical silica film having specific properties and a high contouring property, as well as an economical method for the production thereof.
It is a second object of the invention to provide an economical production method for the above-mentioned silica-coated metal oxide sol, to provide a metal oxide sol coated with a dense, practical silica film to exhibit improved dispersion properties and transparency, and to provide an ultraviolet-screening cosmetic material with a particularly excellent transparent feel or appearance, wherein the silica-coated metal oxide disperses satisfactorily in the cosmetic material.
DISCLOSURE OF THE INVENTION
The present invention which achieves the two aforementioned objects is as follows. Aspects (1) to (21) relate particularly to the first object, while aspects (22) to (48) relate particularly to the second object.
(1) A cosmetic material characterized by comprising surface-hydrophobicized silica-coated metal oxide particles obtained by further treating the surface of silica-coated metal oxide particles with a hydrophobicizing agent.
(2) A cosmetic material comprising surface-hydrophobicized silica-coated metal oxide particles according to (1) above, characterized in that the silica film thickness is 0.1-100 nm.
(3) A cosmetic material according to (1) or (2) above, characterized in that the hydrophobicizing agent is one or more hydrophobicizing agents selected from the group consisting of silicone oils, organic alkoxysilanes and higher fatty acid salts.
(4) A cosmetic material according to an

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