Sunscreen with coated microfine particles

Details Sunscreen with coated microfine particles Sunscreen with coated microfine particles

1994-11-16

1997-03-11

Dodson, Shelley A.

Drug, bio-affecting and body treating compositions

Topical sun or radiation screening, or tanning preparations

106425, 106428, 423609, 423622, A61K 742

Patent

active

056098529

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to coated particles for use in cosmetic and toiletry formulations.
The present invention provides metal oxide particles having a dye lake precipitated onto their surface in a dye lake:metal oxide ratio of between 10:90 and 80:20.
It has been found that water soluble dyes can be used to colour metal oxide particles by a process known as laking. A dye lake is an insoluble precipitate formed by reaction of a metal ion with a water-soluble dye, which can be precipitated onto the surface of a substrate. In the present invention the said metal oxide particles act as the substrate onto which the dye lake can precipitate.
Dyes which act in this respect include azo dyes, triphenylmethane dyes, anthraquinone dyes, indigoid dyes, quinoline dyes, pyrazole dyes, xanthene dyes, fluoran dyes and azine dyes, examples of which are included in Table 1.


TABLE 1 ______________________________________ Colour Index Dye Chemical Type No. ______________________________________ D & C Red no.6 Monoazo 15850 D & C Orange no.4 Monoazo 15510 FD & C Red no.4 Monoazo 14700 Acid Red 27 Monoazo 16185 D & C Red no.33 Monoazo 17200 FD & C Red no.40 Monoazo 16035 FD & C Yellow no.6 Monoazo 15985 Acid Yellow 23 Monoazo 19140 D & C Yellow no.10 Quinoline 47005 FD & C Yellow no.5 Pyrazole 19140 Basic Violet 10 Xanthene 45170 D & C Yellow no.8 Xanthene 45350 D & C Red no.30 Indigoid 73360 FD & C Blue no.1 Triphenylmethane 42090 FD & C Green no.3 Triphenylmethane 42053 D & C Red no.21 Fluoran 45380:2 D & C Red no.27 Fluoran 35410:1 D & C Orange no.5 Fluoran 45370:1 D & C Orange no.10 Fluoran 45425:1 D & C Yellow no.7 Fluoran 45350:1 Acid Blue 74 Indigoid 73015 ______________________________________
The metal oxide particles of the present invention preferably comprise titanium dioxide, zinc oxide, or mixtures thereof. The titanium dioxide particles preferably have a primary particle size of less than 100 nm and the zinc oxide particles preferably have a primary particle size of less than 500 nm.
One aspect of the present invention provides titanium dioxide particles having a mean primary particle size of less than 100 nm and having a dye lake precipitated onto their surface in a dye lake:titanium dioxide ratio of between 10:90 and 80:20. Preferably the ratio is between 20:80 and 70:30.
A further aspect of the present invention provides zinc oxide particles having a mean primary particle size of less than 500 nm and having a dye precipitated onto their surface in a dye lake:zinc oxide ratio of between 10:90 and 80:20. Preferably the ratio is between 20:80 and 70:30.
The advantage of precipitating a dye lake onto metal oxide particles is that the resulting coloured particles are transparent or translucent to visible light but offer a high degree of opacity to ultra violet light. This feature is useful in the cosmetic and toiletry industries.
The art of making dye lakes is exemplified in U.S. Pat. No. 833,602 issued in 1906 and UK Patent 1,467,548 filed 16 July 1975 and is discussed in the article "A Review of the Literature on Color Lakes", American Dyestuff Reporter, Vol. 35, No. 23, Nov. 1946.
The metal oxide particles of the present invention may be formed by the precipitation of insoluble salts from a solution of dye added to a slurry of metal oxide particles with stirring. Precipitation may be facilitated by addition of a soluble salt of an alkaline earth metal or a soluble salt of a transition metal to the metal oxide slurry at the start of the process. Preferred facilitators are soluble salts of calcium, barium, strontium, manganese, aluminium, zinc, copper, iron, titanium, gallium and magnesium. The pH conditions may be any commonly used in lake formation, and may be varied by any conventional pH modifier.
The metal oxide particles of the present invention are separated by filtration of the mixture, with subsequent washing, drying and grinding to a size suitable for use in cosmetic and toiletry formulations.
The above pr

REFERENCES:
patent: 4323554 (1982-04-01), Bernhard
patent: 4847071 (1989-07-01), Bissett et al.
patent: 5143723 (1992-09-01), Calvo et al.

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