Method for the preparation of a base formulation for a dermatological sunscreen composition and for the preparation of a dermatological sunscreen composition

Abstract

A process for preparing a base formulation for a dermatological sunscreen composition comprising base formulations comprising oil and water phases and containing a plurality of UV-absorbing substances and at least one amphiphilic substance which forms lamellar structures.

Claims

1. A method for the preparation of a base formulation for a dermatological sunscreen composition comprising the steps of: producing an oil phase by (i) heating and homogenizing at a temperature in the range of 80 C. to 96 C. a mixture comprising a capryl triglyceride and/or a coco glyceride, 1 to 8.5 weight percent of phytosqualane, 3.5 to 19.5 weight percent of alkyl benzoate, an organic bisoctrizole based UV-A/UV-B absorbing substance, and at least one additional organic UV absorbing substance selected from the group consisting of hexyl benzoate, bemotrizinol, cyanuric triamide, ethylhexyl triazone, ethylhexyl salicylate, and combinations thereof and optionally coated titanium dioxide, and (ii) admixing the heated and homogenized mixture of (i) with coated titanium dioxide at a temperature in the range of 70 C. to 82 C., wherein the coated titanium dioxide of (i) and (ii) is present in the oil phase in a concentration of 6.5 to 20.5 weight percent, the organic UV absorbing substances of (i) to the coated titanium dioxide of (i) and (ii) are in a ratio of at least 1:1, and the oil phase is present in the base formulation in an amount of 30 to 50 weight percent; producing a first water phase by heating and homogenizing a mixture comprising 0.5 to 12.5 weight percent of hydrogenated phosphatidylcholine, a polyalcohol, and water at a temperature in the range of 70 C. to 86 C., wherein the heating and homogenization of the hydrogenated phosphatidylcholine forms lamellar structures and the water phase is present in the base formulation in an amount of 30 to 40 weight percent; mixing the oil phase and the first water phase to form a combined product; and homogenizing the combined product to form the base formulation for the dermatological sunscreen composition, wherein the oil phase and the first water phase that comprise the base formulation do not separate and all weight percentages are relative to the total weight of the base formulation.

2. The method of claim 1, wherein the coated titanium dioxide of (i) and (ii) is present in the oil phase in a concentration of 6.5 to 15.5 weight percent.

3. The method of claim 1, wherein the hydrogenated phosphatidylcholine is present in the first water phase in a concentration of 0.5 to 10.5 weight percent.

4. The method of claim 1, wherein the polyalcohol of the first water phase is a glycerol and/or a glycol.

5. The method of claim 4, wherein the glycol is pentylene glycol.

6. The method of claim 1, further comprising: producing a second water phase comprising water and at least one polyalcohol; mixing the base formulation with the second water phase at a temperature of at least 60 C. to form a mixture; and homogenizing the mixture.

7. The method of claim 6, wherein the at least one polyalcohol is a glycerol and/or a glycol.

8. The method of claim 7, wherein the glycol is pentylene glycol.

9. The method of claim 1, wherein the mixture of the first water phase further comprises an anionic polysaccharide that stabilizes the lamellar structures against hydrolysis.

Description

(1) In the sense of the invention, the base formulation is a base formulation comprising an oil phase and a water phase and containing at least one UV-absorbing substance and at least one amphiphilic substance forming lamellar structures, preferably a system of lamellar structures. Lamellar structures form systems which are characterized by a regular, layer-like structure. In the human body, such structures are found as lipid bilayers in the cell membranes.

(2) Topical lamellar systems are usually based on natural models and use phosphatidylcholine, ceramides, sterols and fatty acids as structure-forming elements.

(3) In the sense of the invention, however, lamellar systems can also be formed by many synthetic surfactants if they are present in sufficiently high concentrations and if these amphiphilic substances permit a double layer arrangement due to their molecular structure, i.e. a balanced ratio of hydrophilic and lipophilic molecule parts.

(4) However, the formation of lamellar structures of hydrogenated lipids is not spontaneous, but requires a high energy input in the form of temperature and possibly mechanical energy (e.g. homogenization under pressure and/or stirring) during production, especially during barrier constitution.

(5) In the sense of the invention one produces for the production of an initial formulation for a dermatological sun protection preparation: an oil phase comprising at least one emollient, preferably a triglyceride, and the essential content of UV-absorbing substances, and heats and homogenizes this oil phase in a first step to at least 80 C., preferably at least 90 C., preferably up to a maximum of 96 C.; and in a second step adds at least one UV-absorbing inorganic substance at at least 70 C., preferably at least 75 C., preferably up to a maximum of 82 C.; a water phase comprising the substantial content of amphiphilic substance and heating and homogenizing said water phase to at least 70 C., preferably at least 80 C., preferably up to a maximum of 86 C.;

(6) combines both phases, optionally with the addition of at least one further UV-absorbing substance, and homogenizes the combined product.

(7) In preferred processes, instead of the previously described oil phase, an oil phase comprising at least one emollient, preferably a triglyceride, is produced and this oil phase is heated and homogenized in the first step to at least 80 C., preferably at least 90 C., preferably up to a maximum of 96 C., and at least one UV-absorbing inorganic substance is added in the second step at at least 70 C., preferably at least 75 C., preferably up to a maximum of 82 C., at least one UV-absorbing inorganic substance.

(8) In preferred processes, the base formulation contains an oil phase in a proportion of 30 to 50% by weight, preferably 25 to 40% by weight, or 35 to 45% by weight and a water phase in a proportion of 30 to 40% by weight, preferably 25 to 40% by weight, or 35 to 45% by weight.

(9) In a preferred process according to the invention, the base formulation contains an oil phase and a water phase in a ratio of 1:4 to 4:1, preferably from 1:3 to 3:1 and particularly preferably from 1:2 to 2:1.

(10) In a preferred process in accordance with the invention, the initial formulation contains an oil phase in the majority, preferably nearly, and exclusively for special applications, as well as a small proportion of less than 10% by weight, preferably less than 5% by weight, of a water phase.

(11) In preferred processes, the oil phase contains at least one, preferably two, medium-chain triglycerides selected from esterification products of glycerol with capric acid and caprylic acid in a ratio of 1:3, preferably caprylic triglycerides, and coco triglycerides.

(12) In processes according to the invention, the oil phase contains as UV absorber a hexyl benzoate, preferably a 2-[4-(diethylamino)-2-hydroxybenzoyl]-benzoic acid hexyl ester and/or a bemotrizinol, and/or a cyanuric triamide and/or an ethylhexyl triazone, and/or an ethylhexyl salicylate and/or a preferably coated TiO.sub.2.

(13) In the sense of the invention, coated TiO.sub.2 is a TiO.sub.2 powder whose particles have been coated with a silicate layer. This has the advantage that the UV absorption rate is higher compared to uncoated TiO.sub.2 due to the coating and thus a greater protection against UV radiation is given with the same amount of TiO.sub.2.

(14) In preferred processes, the oil phase contains a proportion of phytosqualane of 0.5 to 6.5, preferably up to 8.5 or even up to 10.5 percent by weight.

(15) In preferred processes, the oil phase contains an alkyl benzoate content of 3.5 to 9.5, preferably up to 14.5 or even up to 19.5 percent by weight.

(16) In preferred processes, the oil phase contains a proportion, preferably coated, of TiO.sub.2 of 6.5 to 15.5, preferably up to 18.5 or even up to 20.5 weight percent as physical filter material. Tests have shown that TiO.sub.2, preferably coated, in the form of nanocrystalline powder with an average particle size of less than 30 nm to 25 nm, preferably less than 25 nm to 20 nm, preferably less than 20 nm to 15 nm or less than 15 nm to 10 nm and especially less than 10 nm to 5 nm, is particularly suitable.

(17) In preferred processes, the UV-absorbing substances in the oil phase to the UV-absorbing inorganic substance are in a ratio of at least 1:1, preferably at least 1:2 to 2:1 or also at least 1:1.5 to 1.5:1, particularly preferably at least 1:3 to 3:1, and at most 1:4 to 4:1.

(18) In preferred processes the water phase contains an amphiphilic substance, preferably hydrogenated phosphatidylcholine with 0.5 to 5.5, preferably up to 10.5 or even up to 12.5 weight percent.

(19) Hydrogenated phosphatidylcholine has a particularly suitable fatty acid composition, consisting of saturated C.sub.18 and C.sub.16 acids, which determine the planar structure of a double layer.

(20) In preferred processes, native phosphatidylcholine fractionated by column chromatography from soy lecithin with a high linoleic acid content of 80 to 90% by weight in the fatty acid composition is preferably used, which produces cellular double layers. Such double layers, also known as liposomes, increase the penetration of active substances, especially physical filters.

(21) In preferred processes, it is thus possible to adjust the initial formulation with a high degree of transport of active substances and a very low wash-out effect from the skin steplessly by setting a suitable mixing ratio of oil phase and/or water phase and/or the UV-absorbing and/or UV-absorbing inorganic substances and/or amphiphilic substances contained therein.

(22) In the case of processes according to the invention, the water phase contains glycerol and/or glycol, preferably pentylene glycol.

(23) In the case of preferred processes according to the invention, at least one, preferably anionic, mixed polysaccharide shall be added to the water phase.

(24) In the sense of the invention, the addition of at least one gelling agent, preferably the aforementioned polysaccharide or a carbomer, serves to stabilize the lamellar structures or the lamellar system against consistency changes or lysophosphatidylcholine formation (elimination of fatty acid residues by hydrolysis).

(25) In preferred processes, the oil phase is heated in the first step to a maximum temperature of 83 C., preferably 88 C., preferably 92 C. and particularly preferably 97 C., and or in the second step to a maximum temperature of 76 C., preferably 81 C. and particularly preferably 86 C., and/or the water phase is heated to a maximum temperature of 72 C., preferably 75 C. and particularly preferably 78 C., in the first step.

(26) In preferred processes the other UV absorbing substance is a bisoctrizole based UV-A/UV-B absorber.

(27) In a process according to the invention for the preparation of a dermatological sun protection formulation, a second water phase is produced which contains at least one polyalcohol in addition to water;

(28) and mixes the initial formulation according to the invention with the second water phase at a temperature of at least 60 C. and homogenizes the mixture.

(29) Preferably, the at least one polyalcohol of the second water phase comprises a glycerol and/or a glycol, preferably pentylene glycol.