Sunscreen compositions comprising a mixture of titanium and/or zinc oxide particles, method of preparing the same and use thereof

A sunscreen composition containing a synergic mixture of titanium and/or zinc oxide particles, characterized in that said particles are incorporated in paste-forming oils and/or esters and/or fatty alcohols and/or ethers selected so as to provide a wetting point of the incorporated titanium oxide particles and of the incorporated zinc oxide particles lower than about 5 and a flow point of said incorporatedparticles lower than about 30. The invention also provides a method for preparing said composition and the use thereof for protecting the skin against ultraviolet radiation and for maintaining the monocrystalline dispersion of minerals in the formulation and on the skin.

The subject of the invention is sunscreen compositions based on titanium 
oxide and/or on zinc oxide. It is also targeted at a method for producing 
them and at their cosmetic and therapeutic use in protecting the skin 
against all the effects of ultraviolet radiation A and B. 
It is known to use titanium oxide (TiO.sub.2) and/or zinc oxide (ZnO) as 
agents for reflecting ultraviolet rays. 
By way of examples, Patents EP 91 304 100, GB 87/17662 or WO 89/01438 
describe sunscreen compositions containing titanium oxide as agent for 
protecting against radiation. 
In the same way, Patents EP 535 972 and WO 92/13517 describe sunscreen 
compositions containing zinc oxide as agent for protecting against 
radiation. 
Patents FR 2 591 480 and EP 833 086 describe, for their part, sunscreen 
compositions containing a combination of the two oxides. It appears that 
this combination has a synergic effect on the value of the sun protection 
factor. This combination is consequently shown to be particularly 
advantageous in the production of sunscreen compositions. 
However, the compositions thus obtained might be further improved. This is 
because it would be beneficial to increase their stability and in 
particular the homogeneity of the particle dispersion. Their protective 
power might also be further optimized. 
The aim of the invention is to provide a sunscreen composition based on 
titanium oxide and/or on zinc oxide which is better in quality than those 
already existing as regards: 
their stability with time, 
the homogeneity of their dispersion in the formula and on the skin, 
the non-reagglomeration of the crystals with time, and 
their protective power. 
Success has been achieved, according to the invention, by employing zinc 
oxide particles and/or titanium oxide particles incorporated in 
paste-forming oils and/or esters and/or fatty alcohols and/or ethers 
selected with the aim of producing: 
a wetting point for the incorporated titanium oxide particles and a wetting 
point for the incorporated zinc oxide particles which are less than 
approximately 5, 
a flow point for the incorporated titanium oxide particles and a flow point 
for the incorporated zinc oxide particles which are less than 
approximately 30. 
The amount by weight of petrolatum to be added to a mixture of 9 g of 
particles and 7 g of paste-forming oil in order to produce complete 
wetting of the powders and a fluid paste respectively is called the 
wetting point and the flow point respectively of the incorporated 
particles. 
Incorporation of the TiO.sub.2 particles is understood to mean the 
operation which consists in predispersing, by milling, the said particles 
in a choice of oils and/or of esters and/or of fatty alcohols and/or of 
ethers with hyperdispersing qualities, so that, after milling the 
particles and the oils and/or the esters and/or the fatty alcohols and/or 
the ethers in a triple roll mill or bead mill, a stable white paste is 
obtained which can be directly included in the industrial process. 
Incorporation prevents any reagglomeration of the particles which may be 
responsible for the fall in the photoprotection on the skin of the 
finished product. 
The particles, thus predispersed in this mixture of oils and/or of esters 
and/or of fatty alcohols and/or of ethers, without an emulsifying agent, 
change from the cake and agglomerate state (of more than 100 microns) to 
an ideal monodispersed and monocrystalline form (15 to 30 nm). 
As regards the TiO.sub.2, this ready-for-use paste for the industrial 
process is different from commercial suspensions and titanium oxide 
powders, such as TioVeil (Tioxyde): the white paste is obtained without 
addition of subsidiary surface-active compounds and of organic compounds. 
The incorporation of the ZnO particles is of the same nature as that of 
TiO.sub.2 particles. 
It may also be possible to employ zinc oxide particles, such as, for 
example, those of Spectraveil type, sold by Tioxyde, without ever 
combining it with TIOVEIL (TIOXYDE), an acicular titanium oxide 
suspension. 
The combination of the two oxides incorporated in oils and/or esters and/or 
fatty alcohols and/or ethers in accordance with the invention results in a 
synergic effect on the protection factor, whereas the same combination, 
without incorporation, does not give rise to this synergy. 
Advantageously, the titanium oxide particles exhibit a size of less than or 
equal to 20.+-.5 nm and the zinc oxide particles a size of greater than or 
equal to 60.+-.5 nm. 
Use may be made, in particular, of TiO.sub.2 crystals of rutile type, with 
a prismatic and non-acicular morphology, for example: 
T 805, sold by Degussa (alkylsilane treated) and 
MT 100T, sold by Tayca (aluminum hydroxide and stearic acid coated). 
Use may be made, as ZnO particles, of in particular ultrafine particles of 
powdered zinc oxide, of the Z-dimension and Z-dimension HP1 (sunsmart) or 
neutral zinc (H & H) type or optionally of an oily suspension of 
Spectraveil (TIOXYDE) zinc oxide. 
The titanium oxide particles preferably exhibit a mean size of 20 nm and 
the zinc oxide particles a mean size of 60 nm. 
According to an advantageous embodiment of the present invention, the 
paste-forming oils and/or esters and/or fatty alcohols and/or ethers are 
selected from the group comprising decyl oleate, a C.sub.12-15 alkyl 
benzoate, octyl dodecanol, octyl dodecyl neopentanoate, glyceryl oleate 
and propylene glycol, propylene glycol dioctanoate, capric/caprylic 
triglycerides, cetearyl octanoate, octyl palmitate, isoarachidyl 
neopentanoate, dioctyl maleate, dicapryl ether and their mixtures. 
The choice will preferably be made to incorporate the titanium oxide 
particles in a mixture of decyl oleate and of C.sub.12-15 alkyl benzoate 
and the zinc oxide particles in capric/caprylic triglycerides. 
For example, 50% by weight of TiO.sub.2 particles, 30% by weight of Finsolv 
TN and 20% by weight of Cetiol V (HENKEL) will be mixed. 
Advantageously, the titanium oxide is present in the incorporation product 
at a relative concentration by weight of between 20 and 60% and in the 
final formulation of at most 25%. 
More advantageously still, the zinc oxide is present in the incorporation 
product at a relative concentration by weight of between 20 and 60%. The 
final amount in the formulation will be less than 30%. 
According to another preferred embodiment of the composition according to 
the invention, the latter additionally contains pigmental iron oxide 
particles with a size of 1 to 10 .mu.m or in nanometer-range form of Nassy 
Cat type from LACHI Inc. (U.S.A.) &lt;50 nm, their relative proportion by 
weight being between 0.1 and 3%. 
The addition of iron oxide has the effect of coloring the formula in the 
highest factors (PF 30; 40; 50) by introducing yellow and red color in 
order to render transparent the product spread over the skin and not to 
have whiteness incompatible with the use, as well as strongly to protect 
in the I.R. region in particular. 
The method for manufacturing a sunscreen composition according to the 
invention contains a preliminary stage consisting in: 
incorporating titanium oxide particles in at least one paste-forming oil 
and/or ester and/or fatty alcohol and/or ether, in order to obtain 
incorporated titanium oxide particles, and/or 
incorporating zinc oxide particles in at least one paste-forming oil and/or 
ester and/or fatty alcohol and/or ether, in order to obtain incorporated 
zinc oxide particles, optionally 
mixing the incorporated titanium oxide particles and the incorporated zinc 
oxide particles, in order to obtain a paste intended to be incorporated in 
the said composition. 
To obtain incorporated titanium oxide particles, it will be possible, for 
example, to use dry titanium oxide particles, to incorporate them in an 
oil and/or an ester and/or a fatty alcohol and/or an ether, to roughly mix 
the entire combination and to pass it once to three times through a roll 
mill. The incorporated titanium oxide particles are provided, in this 
case, in the form of a white, homogeneous and glossy paste. 
To obtain incorporated zinc oxide particles, it will be possible to proceed 
in an analogous way. 
According to a preferred embodiment of the method according to the 
invention, the oil and/or the ester and/or the fatty alcohol and/or the 
ether for incorporating the titanium oxide particles and the oil and/or 
the ester and/or the fatty alcohol and/or the ether for incorporating the 
zinc oxide particles are selected independently of one another, in order 
to obtain: 
a wetting point for the incorporated titanium oxide particles and a wetting 
point for the incorporated zinc oxide particles which are less than 
approximately 5, and 
a flow point for the incorporated titanium oxide particles and a flow point 
for the incorporated zinc oxide particles which are less than 
approximately 30. 
The composition is advantageously provided in the form of a water-in-oil 
emulsion, in particular a water-in-oil emulsion in which the oil is 
silicone-based. 
It will be possible to add gelling derivatives of inorganic origin of the 
group of the Montmorillonites of the Bentone type (38;34) (Quaternium 14, 
18 Hectorite) or aerosil sic! (Degussa, for example Aerosil R 972), 
which, judiciously introduced during the industrial process, make it 
possible to optimize the stability of the product. Moreover, they strongly 
potentiate the solar protection in the highest protection factors and 
stabilize the protection factor with time. 
The composition according to the invention is introduced in a vehicle. It 
acts as dispersing diluent and transporter of photoprotective materials 
(metal oxides+inorganic gelling agents) recorded above and it must 
facilitate their distribution over the human skin while having regard for 
the microcrystalline dispersion. 
This vehicle is in this instance, essentially, with a continuous lipophilic 
phase, emulsion or anhydrous excipient. 
The composition according to the invention can be provided in the form of a 
suspension or of a dispersion in solvents or fatty substances, in the form 
of an emulsion, such as a cream or a milk, in the form of an ointment, of 
a gel or of an anhydrous or non-anhydrous solid compound or be packaged as 
an aerosol and be provided in the form of a foam. 
It can contain the adjuvants usual in this type of composition, such as 
thickeners, softeners, moisturizers, surfactants, preservatives, 
sequestrants, antioxidants, antifoaming agents, oils, waxes, lanolin, 
fragrances, propellants, dyes, vitamins or any other ingredient commonly 
used. 
In the case of a composition packaged as an aerosol, use is made of 
conventional propellants, such as alkanes, fluoroalkanes and 
chlorofluoroalkanes, dimethyl ether or nitrous oxide. 
Mention may be made, among the main adjuvants which can be present in the 
compositions of the invention, of solvents, such as water, lower 
monoalcohols or polyols containing 1 to 6 carbon atoms or their mixtures, 
monoalcohols or polyols, ethanol, isopropanol, propylene glycol, glycerol 
and sorbitol; mention may also be made of fatty substances, such as 
mineral, animal, vegetable or synthetic oils or waxes, fatty acids, esters 
of fatty acids, such as triglycerides of fatty acids having from 6 to 12 
carbon atoms, fatty alcohols, petrolatum, paraffin wax, lanolin, 
hydrogenated lanolin, acetylated lanolin or silicone oil. 
However, use may also be made of the powders talc, various earths, kaolins, 
starch, plant or synthetic gums, nylon, smectites and derivatives, 
polyacrylate and derivatives, optionally modified magnesium or aluminum 
silicates, xanthan and derivatives, carboxyvinyl polymer and derivatives 
or alternatively preservatives, such as parabens for example, 
antioxidants, such as B.H.T. for example, fragrances, odor concealers, 
various active extracts or dyes. 
It will be possible to produce an emulsion of the water-in-oil type. It 
contains an aqueous phase, a fatty phase and an emulsifying system. 
In this type of emulsion, the concentration of emulsifying system is 
between 4 and 35% by weight with respect to the total weight of the 
emulsion; the fatty phase is present in proportions of between 20 and 60% 
by weight and the aqueous phase in proportions of between 20 and 70% by 
weight with respect to the total weight of the emulsion. The emulsifiers 
are those commonly used in this type of emulsion. 
The fatty phase can also contain silicone oils which are soluble in the 
other oils, such as dimethylpolysiloxane, methyl phenyl polysiloxane and 
silicone-glycol copolymers, fatty acids and fatty alcohols. 
With a view to promoting retention of the oils, it is also possible to use 
waxes, such as carnauba wax, candelilla wax, beeswax, microcrystalline 
wax, ozokerite or oleates, myristates, linoleates and stearates of Ca, Mg 
and Al. 
The emulsions of the water-in-oil type can be provided in the form of 
sticks. In this case, the concentration of the aqueous phase in the 
emulsion is generally between 5 and 70% by weight with respect to the 
total weight of the emulsion. 
These water-in-oil emulsions are generally prepared by introducing the 
fatty phase and the emulsifier into a manufacturing vessel. The mixture is 
heated to a temperature of 70-75.degree. C. The oil-soluble ingredients 
are then added, followed by the addition, with stirring, of the water, 
brought beforehand to the same temperature, the water-soluble ingredients 
having been dissolved beforehand in this water; the mixture is stirred 
until an emulsion is obtained which has the desired fineness and then the 
emulsion is allowed to cool to room temperature, optionally with slow 
stirring. 
The fatty gels comprise an oil or wax and a thickener, such as silica. The 
oil/alcohol or water/alcohol gels comprise one or more lower alcohols or 
polyols, such as ethanol, propylene glycol or glycerol, and a thickener, 
such as silica, cellulose derivatives, polyacrylic acid derivatives, guar 
gum, locust bean gum and xanthan gum, in the presence of oil or of water 
respectively. 
The sticks and other solid anhydrous forms are composed of fatty 
substances, such as natural or synthetic waxes and oils, fatty alcohols, 
fatty acid esters and lanolin. 
As regards the water-in-silicone emulsions, they can in particular be 
formulated based: 
on silicone emulsifiers resulting from high molecular weight polymers, 
on dimethyl polysiloxane polymer with polyoxyethylene and/or 
polyoxypropylene chains having a molecular weight of 10,000 to 50,000. 
The dimethyl polysiloxane polymer is often dispersed in volatile silicone. 
This dispersion comprises, for example, from 1 to 20% by volume of polymer 
and from 80 to 99% of volatile silicone. 
Mention may be made, among these emulsifiers, of Dow 322 5C, Q2 5200 and 
their derivatives, for example. 
Among another family of silicone emulsifiers, polyalkyl polyether 
polysiloxanes can be employed, for example the copolyolcetyl dimethicone 
(Abil EM 90) and its derivatives (Abil WE 09 and Abil WS 08) 
(GOLDSCHMIDT), alone or in combination with a nonionic water/oil 
emulsifier of polyglycerol ester type. 
The composition can comprise, in addition, photoprotective agents, 
antioxidants and agents for combating free radicals, and other adjuvants. 
Mention will be made, as antioxidants and agents for combating free 
radicals, of, for example: vitamin E and its acetates, vitamin A and its 
derivatives, .beta.-carotene, retinol, vitamin C and its derivatives, 
glutathione, selenium, various trace elements, B.H.T., B.H.A., flavonoids 
and polyphenols of plant origin for example, or melanin and precursors of 
human, plant, animal or biotechnological origin. 
Mention will furthermore be made, as adjuvants, of: 
all vegetable oils which can be of advantage to the sun formulation by 
absorption of UV radiation (sesame, olive, grapeseed, coconut, and the 
like), 
all film-forming compounds which make possible good persistence to water 
and to sweat of the product with time (P.V.P. derivatives, Pemulen and 
derivatives (Goodrich), silicone wax, water-persistent silicone of DOW 593 
type; Antaron (WP660; V 220); Gantrez E 542S or cellulose derivatives). 
The compositions in accordance with the invention can be useful in 
cosmetics for protecting the skin against the short- or long-term effects 
of UV A and UV B solar radiation. 
They can also be useful in the manufacture of medicaments intended to be 
used in dermatological treatments of complaints such as Benign Estival 
Photodermatosis (B.E.P.). 
I--Incorporation 
1--Method 
The manner of choosing the oil or the ester or the fatty alcohol or the 
ether for incorporating the titanium oxide particles, by measuring the 
wetting point and the flow point, is explained hereinbelow. 
Several paste-forming oils or esters or fatty alcohols or ethers are chosen 
and the points in question are evaluated for each of them or their 
mixtures. 
To do this, 9 g of titanium oxide particles and 7 g of the oil or of the 
ester in question are used. The amount of petrolatum to be added (x grams) 
for the determination of the points is reported in Table I below. 
The following will be taken as reference: 
for the wetting point, 15 g of petrolatum, 
for the flow point, 60 g of petrolatum. 
TABLE I 
__________________________________________________________________________ 
Liquid C.sub.12-15 alkyl 
Octyl dodecyl 
Glyceryl oleate 
Propylene glycol 
Octyl 
Capric/caprylic 
petrolatums g TiO.sub.2 
benzoate 
neopentanoate 
propylene glycol 
dioctanoate 
dodecanol 
triglyceride 
__________________________________________________________________________ 
Wetting point 
2.63 1.73 2.63 2.38 2.24 
3.91 
Coated TiO.sub.2 
Flow point 
30.94 23.37 26.5 30.33 30.38 
31.8 
Coated TiO.sub.2 
__________________________________________________________________________ 
2--Advantage of the incorporation 
a) Advantage of the mechanical oily dispersion and of the choice of the 
ester for incorporating TiO.sub.2 
The sun protection factor of compositions based on TiO.sub.2 particles as a 
function of the nature of the incorporation is measured. The same factor 
for B+A protection against sunstroke for non-incorporated particles is 
also measured. 
TABLE II 
______________________________________ 
Grade of TiO.sub.2 
P.F. (B + A) at 5% 
P.F. (B + A) at 10% 
______________________________________ 
TiO.sub.2, coated 
5 10 
TiO.sub.2, incorporated 
5 10 
liquid petrolatum 
TiO.sub.2, 7 14 
Incorporation 1 
TiO.sub.2, 10 20 
Incorporation 2 
______________________________________ 
Incorporation 1: octyldodecanol 
Incorporation 2: decyl oleate 
Incorporation 1: octyldodecanol 
Incorporation 2: decyl oleate 
These measurements show the advantage of mechanically dispersing the 
TiO.sub.2 in a chosen lipid. The protection is greater than that provided 
by non-incorporated particles. 
Moreover, differences in dispersion and thus in photoprotection between the 
incorporations are observed. Liquid petrolatum is ineffective, fatty 
alcohol is fairly effective and decyl oleate doubles the photoprotection. 
b) Advantage of the dispersion of the metal oxides 
The protection factor of various compositions as a function of the 
incorporation of the TiO.sub.2 and ZnO particles by different 
incorporations is measured 
______________________________________ 
-12.5% TiO.sub.2 + 1.2% ZnO 
.fwdarw. 
PF 15 
nondispersed 
-12.5% TiO.sub.2 + 1.2% ZnO 
.fwdarw. 
PF 35 
in Incorporation 1 
-12.5% TiO.sub.2 + 1.2% ZnO 
.fwdarw. 
PF 70 
in Incorporation 2 
______________________________________ 
in Incorporation 2 
c) Effect of the amount of TiO.sub.2 particles with Incorporation 2 
The protection factor of various compositions as a function of the amount 
of the TiO.sub.2 particles incorporated in decyl oleate is again measured 
______________________________________ 
-8% TiO.sub.2 + 1.2% ZnO 
.fwdarw. 
PF 30 
-10% TiO.sub.2 + 1.2% ZnO 
.fwdarw. 
PF 36 
-12.5% TiO.sub.2 + 1.2% ZnO 
.fwdarw. 
PF 70 
______________________________________ 
d) Effect of the amount of ZnO 
The protection factor of various compositions as a function of the amount 
of the ZnO particles incorporated in Incorporation 2 is once more measured 
______________________________________ 
-10.5% TiO.sub.2 + 1.2% ZnO (Incorporation 2) 
.fwdarw. 
PF 36.4 
-10.5% TiO.sub.2 + 2.4% ZnO (Incorporation 2) 
.fwdarw. 
PF 50 
______________________________________ 
e) Advantage of Fe.sub.2 O.sub.3 
The advantage of the presence of iron oxide is the coloring of the skin, of 
compositions containing high doses of metal oxides (TiO.sub.2 and ZnO), in 
order to make possible immediate transparency after application to the 
skin, for high-factor products. 
In order to measure the color of the skin, a colorimetric test (L, a, b) is 
carried out after application to the bare skin of 2 formulae, with and 
without iron oxides 
EQU 10.5% TiO.sub.2 +2.4% ZnO Formula A 
EQU 10.5% TiO.sub.2 +2.4% ZnO+2% Formula B 
of a mixture of iron oxides 
It appears that the formula B gives the skin a natural color similar to 
untreated skin. 
f) Advantage of the gelling inorganics 
The sun protection factor of a composition containing a gelling agent is 
calculated; the results are as follows: 
______________________________________ 
Formula with 0.3% of Bentone 38 
.fwdarw. 
PF 44 
Formula with 0.8% of Bentone 38 
.fwdarw. 
PF 55 
______________________________________ 
g) UV A Protection 
The UV A protection was calculated by the P.P.D. or "Permanent Pigmentation 
Darkening" method, the inhibition of immediate tanning by short- and 
long-wave UV A radiation of a skin treated with the photoprotective 
formula being evaluated against the tanning of a bare skin, with the 
tanning being read at 2 hours. 
Irradiation is carried out with a Robertson Berger lamp, WG 335 and UG 11 
screened. 
h) Advantage of the ZnO and incorporated TiO.sub.2 combination 
The protection factors of formulations containing either TiO.sub.2 
particles only or ZnO particles only or a mixture of both are measured. 
The results are recorded below: 
______________________________________ 
-10% TiO.sub.2 powder 
.fwdarw. UV A PF 4 
-2.4% ZnO .fwdarw. UV A PF 2.5 
-10% incorporated TiO.sub.2 /% 
.fwdarw. UV A PF 10 
decyl oleate + 2.4 ZnO 
______________________________________ 
The effect of the amount of each powder on the protection factor is 
evaluated below: 
______________________________________ 
-8% TiO.sub.2 /decyl oleate + 1.2% ZnO 
.fwdarw. 
UV A PF 6.5 
-10% TiO.sub.2 /decyl oleate + 1.2% ZnO 
.fwdarw. 
UV A PF 8.2 
-10% TiO.sub.2 /decyl oleate + 2.4% ZnO 
.fwdarw. 
UV A PF 10 
______________________________________ 
II--Stability with time and according to the method 
The procedure for measuring the stability with time of the compositions is 
as follows: 
The formulations based on incorporation or suspension of TiO.sub.2 +ZnO are 
stored at a warmth at 40.degree. C. over periods of 3 months. The UV B+A 
PF at room temperature and then after 1 month and 3 months at 40.degree. 
C. are calculated. 
The results are combined in the following Table III. 
TABLE III 
______________________________________ 
T, 1 month, 
T, 3 months, 
TO 40.degree. C. 
40.degree. C. 
______________________________________ 
FR 12 15 44 .+-. 5 42 .+-. 5 -- 
FR 12 35 - LP 
50 .+-. 5 -- 49 .+-. 5 
______________________________________ 
It is observed that the compositions according to the invention are 
particularly stable. 
The stability over several years is thus evaluated: 1 month at 40.degree. 
C. is equivalent to 1 year at room temperature; the incorporation makes it 
possible to retain the dispersion of the inorganics with time.