Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2000-07-31
2002-08-13
Le, Hoa T. (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C427S212000, C427S215000, C427S219000, C428S404000, C524S492000, C524S493000, C524S497000
Reexamination Certificate
active
06432535
ABSTRACT:
The present invention relates to a pigment in thin flakes for cosmetics, resins, etc. More particularly, the present invention relates to a pigment of thin flakes having a high soft focus effect which is a wrinkle-hiding effect for skin, a good spreading effect on the skin, an ultraviolet shielding effect and an appropriate whiteness degree which are requested to cosmetics and also relates to a method for manufacturing the same.
BACKGROUND OF THE INVENTION
Up to now, substances in thin flakes such as natural mica, synthetic mica, mica coated with titanium oxide, talc, sericite and boron nitride have been used as extenders for cosmetics or fillers for resins, etc. However, when they are used for cosmetics, they do not satisfy the characteristics such as a wrinkle-hiding effect, ultraviolet-shielding effect and degree of whiteness which are required together with adhesive property to and spreading property on the skin.
With regard to a pigment having good spreadability to the skin, extenders such as talc having no luster and boron nitride have been commercially available, but some of talc has been confirmed to contain asbestos and, recently, its use as a pigment for cosmetics has been restricted. Pigments consisting of boron nitride are not suitable for a cosmetic use because boron nitride is expensive and, in addition, unreacted boric acid is sometimes contained in its material. Further, bismuth oxychloride in thin flakes, mica coated with titanium oxide, etc. have been used in some cosmetics as pigments having good spreadability because their feel and spreadability on the skin are good. However, bismuth oxychloride has too strong luster and is unnatural for the skin and, as a result, its use as a foundation, etc. has been limited.
With regard to a pigment having an improved spreadability, one where silica particles of 0.05-50 &mgr;m are adhered on the surface of mica or of mica titanium has been proposed (DE 3922178/1989; the Japanese Laid-Open Patent Publication Hei-03/45660, both corresponding to U.S. Pat. No. 5,407,746. This pigment aims improved spreadability due to a ball bearing effect by silica particles but there is a disadvantage that adhesiveness to the skin is weak and adhesion of the silica particles onto the mica surface is insufficient as well. Thus, exfoliation is apt to occur in the stages after manufacture and before use whereby it is difficult to achieve a sufficient spreading effect. Further, the diameter of the adhered silica particles is as big as 0.05-50 &mgr;m and, therefore, the soft focus effect (refer to Naoki Nakamura, et al: the XIVth I.F.S.C.C. Congress, Barcelona, 1986, volume1, pages 51-63) corresponding to a wrinkle-hiding effect can be hardly expected.
With regard to a pigment wherein the above-mentioned pigment in thin flakes coated with silica particles is improved, pigments in which adhesive property of the spherical silica particles is improved using organic silica such as 4-ethyl silicate or sodium silicate have been proposed (WO 92/03119). It is said that such pigments have improved adhesive property and spreading effect to the skin and have a soft focus effect as well. Diameter of the silica particles disclosed here is mentioned to be about 5 &mgr;m or smaller or, preferably, 0.05-3 &mgr;m. Even in such a particle size however, the silica particles are still big and, therefore, specific treatment to provide adhesive properties is necessary (dielectric constant and ion concentration of the dispersion solution are to be specified to achieve adhesive properties). That is inconvenient for manufacturing. Moreover, since the pigments have a low degree of whiteness, there is another problem that, when used in cosmetics, titanium dioxide or the like must be further added for increasing whiteness.
In addition, in the above-mentioned two types of the pigments coated with silica particles, flaky substrates having particle sizes of as big as 1-500 &mgr;m and about 30 &mgr;m (refer to the Examples), respectively are used and, therefore, they are too big especially for foundations and their sliding on the skin is not good.
SUMMARY OF THE INVENTION
The present inventors have carried out an intensive investigation for improvement especially in the pigment for cosmetics with an object of solving the above-mentioned problems and have succeeded in developing a pigment in thin flakes having a wrinkle-hiding effect (soft focus effect), spreading effect (a product exhibiting a low frictional coefficient or MIU), ultraviolet shielding effect and appropriate whiteness.
Thus, the present invention offers a pigment comprising thin flakes, a method for manufacturing the same and the use thereof as cosmetics and as a filler as mentioned in the following [1] to [6].
[1] A pigment comprising thin flakes where spherical silica particles having an average particle size of 20-400 nm are adhered on the surface of a flaky substrate having an average particle size of 0.5-10 &mgr;m and then the said surface of the flaky substrate adhered with spherical silica is further coated with ultrafine particles of titanium dioxide. The ultrafine titanium dioxide serves to form a thin glaze adhering the silica to the substrate; exfoliation of the spherical silica is thus suppressed.
[2] The pigment comprising thin flakes according to [1]. wherein the amount of the spherical silica particles is 30% by weight of less based upon the flaky substrate adhered with the spherical silica.
[3] The pigment comprising thin flakes according to [1] or [2], wherein the amount of the fine particles of titanium dioxide is 1-50% by weight based upon the pigment in thin flakes and the particle size of the fine particles of the said titanium dioxide is 50 nm, preferably 30 nm, or smaller.
[4] A method for the manufacture of the pigment comprising thin flakes according to any of [1]-[3], characterized in that, an aqueous solution of alkali is added to an aqueous suspension of the flaky substrate to make alkaline, a suspension of fine particles of spherical silica is added to the said alkaline suspension with heating and stirring, a part of the predetermined amount of aqueous solution of titanium salt is dropped thereinto to make pH 1.5-2.5 to adhere the spherical silica particles to the surface of the flaky substrate, the residual aqueous solution of titanium salt is added thereto keeping the pH at 1.5-2.5, then pH is raised to 5 and the resulting solid is filtered, washed with water, dried and calcined.
[5] A cosmetic agent containing the pigment comprising thin flakes according to any of [1]-[3].
[6] A use of the pigment comprising thin flakes according to any of [1]-[3] as a filler.
Basically, any of natural and synthetic substances may be used as a material for the flaky substrate which is used in the present invention but, in view of the use as a pigment, a substance having a high safety and a good durability such as heat resistance is preferred. To be more specific, natural mica, synthetic mica, mica titanium (mica in thin flakes which is coated with titanium oxide; this term is used in the same sense throughout the specification), talc, sericite, kaolin and alumina in thin flakes (including that which is coated with titanium oxide) may be exemplified and natural mica, synthetic mica, mica titanium, talc and sericite are preferred. Among them, natural mica, synthetic mica and mica titanium are more preferred.
With regard to the shape of those flaky substrates, the average particle size is recommended to be about 0.5-10 &mgr;m or, preferably, about 2-8 &mgr;m so that the size of the particles maintains a low frictional coefficient (MIU) suitably for use as cosmetics and, at the same time, hardly resulting in aggregation of the powder. When the particles of smaller than 0.5 &mgr;m are used, the product obtained by the present invention may be aggregated and is not preferred. As a result, it goes without saying that improvement in spr
Noguchi Tamio
Watanabe Yukitaka
Le Hoa T.
Merck Patent Geseelschaft mit beschraenkter Haftung
Millen White Zelano & Branigan
LandOfFree
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