Chemistry of inorganic compounds – Rare earth compound
Reexamination Certificate
2001-05-31
2003-07-08
Bos, Steven (Department: 1754)
Chemistry of inorganic compounds
Rare earth compound
C427S215000
Reexamination Certificate
active
06589496
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for the preparation of metal oxide doped cerium oxide. Further, the present invention relates to such method in which the metal oxide doped cerium oxide or a complex composed of the metal oxide solid doped cerium oxide is coated with another metal oxide or blended with a compatabilizing agent for a cosmetic composition.
2. Description of the Prior Art
As is well known, ultraviolet rays cause degradation of plastic resins, and many kinds of countermeasures are carried out to protect against such degradation. As one countermeasure method, it is widely practiced that a plastic resin is admixed with an ultraviolet shielding agent including an organic ultra-violet ray absorbing agent or an inorganic ultraviolet ray scattering agent. By admixing these agents in plastic resin, the adverse influence of ultraviolet rays is reduced. As the organic ultraviolet ray absorbing agent, salicylic acid type compound, benzophenone type compound, benzotriazole type compound or cyanoacrylate type compound can be mentioned, however, recently, the lack of heat resistance, lack of durability to weather or the safety of decomposed chemicals of these compounds are becoming serious problems. To solve these problems, fine particles of titanium dioxide or fine particles of zinc oxide, which are inorganic ultraviolet ray scattering agents, are developed, however, the lack of dispersability of these agents is a problem and the catalytic activity of these agents are becoming a new problem. Recently, especially regarding titanium dioxide, it is pointed out that the generation of singlet oxygen by its photo catalyst function is causing a new problem.
Ultraviolet rays have an adverse influence also on living bodies. Namely, it is well-known that the so called UV-B ultraviolet ray in the wavelength range of 280 to 320 nm causes cutaneous inflammations such as erythematous blister and the like while the so called UV-A ultraviolet ray in the wavelength range 320 to 400 nm causes tanning of skin by the accelerated formation of melanin. As the countermeasure method against above mentioned adverse influences of the ultraviolet rays, many kinds of sunscreen cosmetic compositions have been developed heretofore. The ultraviolet shielding agents contained in conventional sunscreen cosmetic compositions can be grossly classified into two types including an ultraviolet absorbing agent such as cinnamic acid type, benzopheno ne type or dibenzoylmethane type and an ultraviolet scattering agent such as zinc oxide or titanium dioxide. However, above mentioned ultraviolet absorbing agents have several problems, such as low absorptivity of ultraviolet rays and safety when the admixing amount in a cosmetic composition is too high. Further, in a case of conventional ultraviolet scattering agent, since it is impossible to improve the transparency even if the dispersibility of particles is improved, the admixing use of it not only causes the deterioration of feeling when the cosmetic composition is applied but also the skin look becomes unnatural. Recently, the use of cerium compound as an ultraviolet scattering agent has been proposed, for example, in Japanese Patent Laid Open Publication 6-145645 or Japanese Patent Laid Open Publication 7-207151. However, since cerium oxide has strong catalytic activity, it has a problem that it accelerates the oxidation decomposition of resin or oil and causes color change and generates offensive odor when admixed in cosmetic compound or resin. Thereupon, the development of new cerium compound which has a function as the ultraviolet scattering agent and does not have catalytic activity has been desired. In Japanese Patent Laid Open Publication 9-118610, silica-cerium oxide composite particle is proposed, however, the reduction of catalytic activity of the silica-cerium oxide composite particle is almost accomplished but the ability for ultraviolet ray shielding is not sufficient.
OBJECT OF THE INVENTION
The present invention addresses the above mentioned circumstance, to provide metal oxide doped cerium oxide with strong ultraviolet ray shielding ability, lower catalytic activity and with excellent transparency. Further, this invention provides a composite composition of metal oxide doped cerium oxide coated with metal oxide. Furthermore, this invention also provides a resin composition and a cosmetic composition in which the metal oxide doped cerium oxide or a composite thereof is admixed.
BRIEF SUMMARY OF THE INVENTION
The present invention provides cerium oxide doped with metal ion having larger ion radius than that of tetravalent cerium ion (Ce
4+
) and/or lower valence than Ce
4+
. As concrete examples of metal ions which can be used in this doping, Ca
2+
, Y
3+
, La
3+
, Nd
3+
, Eu
3+
, Tb
3+
, Sm
3+
, Mg
2+
, Sr
2+
, Ba
2+
, Ce
3+
and the like can be mentioned. The desirable cerium oxide concentration in the metal oxide solid doped cerium oxide is 40 to 98 molar %. Further, when the color index of the metal oxide doped cerium oxide is estimated by L*, a* and b* values, the desirable region of L* is larger than 80, the desirable region of |a* | is smaller than 4, and desirable region of |b* | is smaller than 10. Preferably, the average particle size is ultra fine particle of 2 to 4 nanometers (nm).
Further the metal oxide doped cerium oxide of this invention can be prepared by following steps. That is, the metal oxide doped cerium oxide is formed at a temperature lower than 60° C. and at a pH higher than 5 by reacting aqueous solution of cerium salt, aqueous solution of metal ion having larger ion radius than that of Ce
4+
and/or lower valence than Ce
4+
and alkali, then by adding oxidizing agent to the reaction mixture at the temperature lower than 60° C. Furthermore the metal oxide doped cerium oxide of this invention can be prepared by adding and mixing aqueous solution of cerium salt, aqueous solution of metal ion having larger ion radius than that of Ce
4+
and/or lower valence than Ce
4+
, alkali and oxidizing agent simultaneously at the temperature lower than 60° C. at a pH higher than 5.
The present invention also relates to a composite composition of the metal oxide doped cerium oxide coated by one or more kinds of oxide selected from silicon oxide, zirconium oxide, aluminum oxide, iron oxide and titanium dioxide. Further, the present invention relates to a resin composition to which the metal oxide doped cerium oxide or the composite composition thereof is blended. Still further, the present invention relates to a cosmetic composition to which the metal oxide doped cerium oxide or the composite composition thereof is blended. The surface treated metal oxide doped cerium oxide or the composite composition thereof can be blended to the cosmetic composition. The cosmetic composition can also contain an ultraviolet ray absorbing agent and/or an ultraviolet ray scattering agent. As the desirable example of the ultraviolet ray absorbing agent, one or more kinds of compound selected from oxybenzone, octyl methoxycinnamate and 4-tert-butyl-4′-methoxy dibenzoylmethane can be mentioned, and the desirable content of the ultraviolet ray absorbing agent is 0.1 to 40% by weight. As the desirable example of the ultraviolet ray scattering agent, titanium dioxide and/or zinc oxide can be mentioned, and the desirable content of the ultraviolet ray scattering agent is 0.1 to 50% by weight. Above mentioned cosmetic composition is suited to be used as a sunscreen cosmetic composition.
The metal oxide doped cerium oxide of this invention is cerium oxide doped with metal ion having larger ion radius than that of Ce
4+
and/or lower valence metal ion than Ce
4+
. By doping the metal ion, the catalytic activity of cerium oxide can be reduced. Further, by doping the metal ion, the transparency of cerium oxide is improved and the ultraviolet ray shielding effect can be improved. As c
Momose Shigeyoshi
Sato Tsugio
Tahira Kazuyuki
Tofukuji Kota
Yabe Sinryo
Bos Steven
Nippon Dewho Co., Ltd.
Sherman & Shalloway
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