MXPA00000308A - Process for the stabilization of oil-in-water emulsions, cosmetic topical composition of oil-in-water emulsion and fabrication process of cosmetic topical composition of oil-in-water emulsion - Google Patents

Abstract

The present invention refers to a process for the stabilization of oil-in-water emulsion which comprises a continuous phase, a discontinuous phase, an emulsifier and physical filters, characterized for the fact that it comprises the stage of contacting said phases with an emulsifier having a hydrophilic portion and a hydrophobic portion in each extremity and at least 10%of said physical filters selected from titanium oxide, zinc oxide and its mixtures. The invention also refers to a process for preparing an oil-in-water emulsion.

Description

"Process for Stabilization of Water Emulsions in Oil, Topical Cosmetic Composition of Water Emulsion in Oil and Process for the Manufacture of Topical Cosmetic Composition of Water Emulsion in Oil".

The present invention relates to a process for the stabilization of water-in-oil emulsions, to a cosmetic water-in-oil emulsion topical composition and to a process for the manufacture of cosmetic water-in-oil emulsion topical composition. Particularly, the invention relates to a process for stabilizing a water-in-oil emulsion, useful for use as sunscreen compositions or any other source emitting ultraviolet radiation or, generically, UV radiation, hereinafter specified and generically called sunscreens.

BACKGROUND OF THE INVENTION Sunscreens in the manner that are used in this invention generally indicate topical compositions that are applied to the skin or hair of people to protect themselves from the evils resulting from exposure to UV radiation. In the case of solar rays, UV radiation is divided into UV-A and UV-B radiation and is located between 290 to 400 nm. It is not necessary to comment on the evils resulting from excessive exposure to UV radiation. Among the best known, we mention the loss of elasticity of the skin, the formation of wrinkles and other signs and loss of softness or wetting. According to researchers, the incidence of these and other even more serious problems has increased due to changes in habits of adults and children who stay longer under the sun and, even, due to the decrease in the ozone layer that allows the passage more free of said radiations. These facts have induced people to look for more effective sunscreens, with a higher Sun Protection Factor (SPF). The Solar Protection Factor (SPF) is a factor that is traditionally understood as defining the protection that will be provided to an individual, according to the time of exposure to UV radiation to which this individual submits. For example, an unprotected individual burns in the sun after 10 minutes. When using a sunscreen with SPF 15, it would take about 15 times longer to burn equivalently.

The efficient sunscreens, in addition to allowing a longer time of exposure to the sun by having a high SPF, are intended to protect UV-A and UV-B from both radiations. There are several types of sunscreens known, all using as their main active ingredient so-called sunscreens that are divided, in a simplified way, into chemical or organic filters and physical or inorganic filters. There are also those that, in addition to using these filters, include other properties such as changing the color so that the user notices their continuity of action, insect repellents, etc. We indicate below examples of the aforementioned sunscreens, revealed by several patents, all gathered here as a reference. US Patent 5,770,183 discloses waterproof solar block compositions with high SPF (30 or more) in the form of water-in-oil emulsions. The high SPF value is obtained by combining physical and chemical filters, such as titanium dioxide and 2-ethoxyethyl p-methoxy cinnamate amyl dimethyl PABA, respectively, and using a silicone emulsifier (cetyl dimethicone copolyol).

US Patent 5,352,793 shows an example of the use of sunscreens extracted from Pacific corals. US Patent 5,609,854 discloses the stabilization of emulsions of the water-in-oil type for sunscreens using an aluminum salt derived from carboxylic acids with a chain containing Ci-Cs. US Pat. No. 5,417,961 discloses a protector in the form of an emulsion, of the water-in-oil type, with a synergistic effect provided by the addition of polyethylene in a composition with sun and chemical filters and a high sun protection factor. WO 97/42933 shows a sunscreen containing an insect repellent. The patent application WO 97/25971 describes the protectors as oil-in-water emulsions, including the addition of phthalic acid derivatives to increase the sun protection factor. The patent US 5,811,082 describes new particles for incorporating sunscreens, made from waxes with pigments with diameters of at least 10 nm. Generally, the protectors described in these patents have the great disadvantage of the high potential for skin irritation and the appearance of allergic reactions in a large number of users, particularly in children who have the most sensitive skin and hair. These disadvantages are due, mainly, to the fact of incorporating chemical filters and other substances that, when reacting with UV radiation, can generate harmful subcompounds to the skin, to the hair or to both. To overcome these drawbacks, another generation of sunscreens without chemical filters and containing, therefore, exclusively physical filters. To obtain high SPF values in sunscreens containing only physical filters, the most widely used path has been to incorporate high levels of physical filters, generally in the form of dust. Examples of this type of protectors, which only have physical filters, are described in the following patents, also gathered here as a reference. US Patent 5,250,289 describes a sunscreen as a water-in-oil emulsion that uses only titanium dioxide as a filter and a polyglycerol associated with other compounds as emulsifiers. US Pat. No. 5,468,471 discloses sunscreens containing only physical filters, in the form of oil-in-water or water-in-oil emulsions, to obtain, generally, high SPF values, which, for the examples described, are about of 25, maximum.

In US Pat. No. 5,700,451 a gel is described whose physical filter is titanium dioxide of the anatated / amorphous type. A disadvantage of the protectors obtained according to these inventions is the fact that only titanium dioxide is used as a sunscreen, which protects the users only against UV-B rays, when a broad spectrum of protection is desirable for such a product, including, especially, UV-A radiation, which is known to cause more serious damage. US patent 5,543,136, on the other hand, describes a water-in-oil emulsion with two different sunscreens: zinc oxide in the oil phase, intended to protect against UV-A radiation and titanium dioxide in the aqueous phase to protect against UV-B rays, that is, physical filters are contained in different phases. These physical filters are associated with organic agents, such as tridecyl neopentanoate to increase the SPF. According to the examples of concretizations of the invention of said patent, when physical filters are used exclusively without association with the aforementioned organic agents, such as tridecyl neopentanoate to increase the SPF, the SPF value is low, that is, always lower than 14 (see examples VII and IX).

US Pat. No. 5,573,753 already describes a generic process for preparing cosmetic sunscreens using, as physical filters, a dispersion of zinc oxide associated or not with titanium dioxide. An example of this type of dispersion is described in US Pat. No. 5,605,652, since when using exclusively physical filters, the SPF values obtained by that invention do not reach SPF 11 (see example 3). In addition, the emulsions mentioned therein are of the oil-in-water type, which do not have a favorable resistance to water. Some oil-in-water emulsions are described in Example I and in Claim 33, using in the aqueous phase, alkalonamine and polymeric thickeners, through a process that uses high temperatures in claim 35 and, more generically, in the report descriptive. Due to the demand for protectors with low adverse reactions and high SPF values, generally higher than 15, predominantly above 20 and, preferably around or greater than 30, it has been necessary to provide protectors using increasingly high physical filter concentrations. . Another desirable feature in sunscreen is the resistance to water and perspiration, useful for athletes, who perspire too much and for children, who at all times are in contact with water, either in the pool or on the seashore. In this regard, it is known to those skilled in the art that water-in-oil emulsions are useful and resistant to water. Due to the fact that emulsions of the water-in-oil type have longer residence time on the skin or hair and that physical filters are more advantageous with respect to chemicals, there is therefore a clear demand to obtain sunscreen this type, with high SPF, preferably above 15, predominantly above 20 and preferably around or above 30 and protecting both UV-A and UV-B radiation.

Brief Description of the Invention The present invention relates to a process for stabilizing a water-in-oil emulsion comprising a continuous phase, a discontinuous phase, an emulsifier and physical filters, characterized in that it comprises the step of contacting said phases. with an emulsifier having a hydrophilic portion and a hydrophobic portion at each end and with at least 10% of said physical filters selected from titanium dioxide, zinc oxide and mixtures thereof, with particle sizes from 0.05 to 0 , 10 μm.

The invention also relates to a process for preparing a water-in-oil emulsion and also to a resulting emulsion. In this type of water-in-oil emulsion, the continuous phase is defined as the external phase, which is the oil phase, and the discontinuous phase is defined as the internal phase which is the aqueous phase. Detailed description of the invention After deep studies and tests, the present inventors were surprised to find that it is possible to obtain the stabilization of a water-in-oil emulsion, useful to produce protective compositions such as sunscreens with high percentages of physical dust filters, such as the oxide of zinc and titanium dioxide, through the contact of the aqueous and oily phases with a specific emulsifier containing a hydrophilic portion and a hydrophobic portion at each end, resulting in a favorable emulsion for the safety offered to the user and cosmetically pleasing. For the purposes of the present invention, it was found that, generally and preferably, physical filters are used in the form of a powder and even more so physical filters dispersed in oil. Examples of physical filters dispersed in oil are described in US Pat. No. 5,573,753 and US Pat. No. 5,605,652.

The percentage of physical filters defines the solar factor that will be obtained. In general terms, the effects of the water-in-oil emulsion according to the invention with regard to obtaining a high SPF (above 15, predominantly above 20 and preferably around or above 30) they begin to be obtained when the emulsion includes at least 10% of physical filter dust.

Description of the Process for Preparing an Emulsion of the Invention The process is carried out in stages in a reactor where the emulsifier and other components are placed as emollients, antiradical agent and film-forming compound, together with the physical filters, they are heated at a certain temperature and under previous agitation of the propeller, lower at 1,000 rpm, preferably between 450 and 800 rpm, and a stirring of the scraper, lower than 60 rpm, preferably between 5 and 40 rpm. In an auxiliary reactor, the water and other usual components, such as the stabilizing agent, the scavenger and the moisturizer are placed, also under agitation for a certain period, after which the heating starts up to a certain temperature, maintaining the agitation. When the temperature reaches the desired degree, the transfer of the mixture found in the auxiliary reactor to the main reactor begins, under the stirring of the propeller between 450 and 800 rpm. After the total transfer, the mixing is carried out by stirring for a period of time and the process of cooling begins with agitation until reaching a temperature between 35 ° C and 40 ° C. Upon reaching the determined temperature, water and the preservative are added, also under agitation of the propeller, preferably between 450 and 800 rpm.

Optionally, in a last stage of the process, when it is desired to increase the radiation spectrum covered by an emulsion, the Timiron pigment is added, maintaining the agitation for up to 5 more minutes. The cooling is continued, even under the agitation of the scraper between 5 and 40 rpm, until reaching a temperature of preferably between 22 ° C and 35 ° C. This pigment helps to increase the protection spectrum, also protecting agaiinfrared rays. The stabilization of the emulsion results from the association of physical filters with a selected emulsifier and in previously defined percentages, together with a low agitation during the whole process and mainly during the cooling that occurs after the emulsion conversion, being that in this phase the water is transferred slowly to the main reactor, so that it allows the passage of the minimum water possible in a certain period of time. Another advantage of the invention is the fact that the process dispenses the homogenization step. Emulsion The emulsion, object of the present invention, is more advantageous when the physical filters used are in the form of powder and dispersed in oil and the emulsifier used is a specific emulsion that allows the development of emulsions of low viscosity and excellent stability, being an emulsifier copolymer, having a hydrophilic portion and a hydrophobic portion at each end. An example of an emulsion according to the invention is characterized in that it is composed, by weight, of 2.5 to 4.7% by weight of a copolymer emulsifier of the polyethylene glycol family (PEG), preferably PEG 30 Dipolyhydroxystearate; from 2.0 to 15% of a mixture of emollients, such as, for example, cyclomethicone and isohexadecane; 0.1 to 1.0% of a film-forming compound, such as, for example, candelilla wax; from 3.5 to 30.0% of dispersed titanium dioxide; from 3.5 to 17.0% dispersed zinc oxide; from 1.0 to 65.0% demineralized water; 0.1 to 1.0% of a stabilizer, such as sodium chloride; from 0.1 to 0.5% of tetrasodium EDTA in 40% solution, preservatives, from 0.005 to 0.1%, such as 2-Bromo-2-Nitropropane-1,3-Diol. The emulsion offers the advantage, according to the invention, of presenting a stability that allows other compounds to be included without affecting their performance. If desired, an antiradical agent, specifically vitamin E, by weight of 0.1 to 1.5%, from 1.0 to 12.0% of moisturizing agents, such as glycerin and an agent, can be included in the emulsion. protector against infrared radiation, such as the pigment Timiron Super Red, in percentage weight of 0.5 to 1.5%. In derivatized formulas, the film-forming compounds, the ozocerite wax and the copolymer octylacrylamide acrylate polymer can also be included as the neutralizing agent dimethyl stearamine, as the stabilizer magnesium sulfate, in addition to an active compound such as, for example, the alpha bisabolol and octyl palmitate as an emulsifier.

Ex emplos: Preparation of the Emulsion In a reactor of the Balloon Type RE 120B (750 1) the emulsifier, the emollients, the antiradical agent and the film-forming compound are placed together with the physical filters and heated to a temperature of 60 ° C to 80 ° C, under a stirring of the helix between 450 and 700 rpm and the scraper between 5 and 30 rpm. In an auxiliary reactor, the water, the stabilizing agent, the scavenger and the moisturizer are placed, also under agitation of the propeller between 450 and 800 rpm and of the scraper between 5 and 40 rpm. The mixture is stirred for a period of up to 10 minutes and begins its heating up to a temperature between 60 ° C and 80 ° C, maintaining the agitation. When the temperature reaches between 60 ° C and 80 ° C, the transfer of the mixture found in the auxiliary reactor to the main reactor begins, under the stirring of the propeller between 450 and 800 rpm and the scraper between 5 and 40 rpm. . After the total transfer, the mixing is done through the agitation of the propeller between 450 and 800 rpm and the scraper between 5 and 30 rpm for a period of time of up to 4 minutes and the cooling process begins with agitation of the scraper between 5 and 30 rpm, until reaching a temperature between 35 ° C and 40 ° C. When reaching the temperature between 35 ° C and 40 ° C, water and the preservative are added, also under agitation of the propeller between 450 and 800 rpm. Under the agitation of the propeller between 450 and 800 rpm and the scraper between 5 and 40 rpm, in a last stage of the process, the Timiron pigment is added, maintaining the agitation for up to 5 more minutes. The cooling continues, even under the agitation of the scraper between 5 and 40 rpm, until reaching a temperature between 22 ° C and 35 ° C.

Emulsions Example 1 - Infant FPS 34 hydrating blocking emulsion Example 2 - Sunscreen for sensitive skin Example 3 Sunscreen for athletes (with high water resistance) fifteen 25 30

Claims (13)

Claims

1. Process for stabilizing a water-in-oil emulsion comprising a continuous phase, a discontinuous phase, an emulsifier and physical filters, characterized in that it comprises the step of contacting said phases with an emulsifier having a hydrophilic portion and a hydrophobic portion in each extremity and with at least 10% of said physical filters selected from titanium dioxide, zinc oxide and their mixtures. Process for stabilizing a water-in-oil emulsion according to claim 1, characterized in that the emulsifier is a copolymer emulsifier of the polyethylene glycol (PEG) family. 3. Process for preparing a water-in-oil emulsion, characterized in that it comprises: a) in a first stage, mixing in a reactor the emulsifier, emollients and a film-forming compound, together with physical filters and heating the mixture at a temperature of 60 ° C to 80 ° C, under agitation; b) in a second stage, mixing in an auxiliary reactor the water, the stabilizing agent and a sequestrant, also under agitation, for a period of up to 10 minutes, starting its heating up to a temperature of 60 ° C to 80 ° C; c) when the temperature reaches between 60 ° C and 80 ° C, the transfer of the mixture obtained in (b) which is in the auxiliary reactor for the main reactor begins, under agitation; d) after the total transfer, the mixing is carried out by stirring for a period of time of up to 4 minutes and the cooling process begins with agitation until reaching a temperature between 35 ° C and 40 ° C e) when reaching the temperature between 35 ° C and 40 ° C, water and a preservative are added, also under agitation, following the agitation and the cooling until reaching a temperature between 22 ° C and 35 ° C. Process according to claim 3, characterized in that the mixture of step (a) also comprises an antiradical agent, preferably vitamin E. 5. Process according to claim 3, characterized by the fact that that the mixture of step (b) also comprises a moisturizer. 6. Process according to claim 3, characterized in that optionally include a stage (f) to add a protective compound against infrared radiation, such as the pigment Timiron, under agitation of the propeller, less than 1000 rpm and the scraper , lower than 60 rpm, maintaining the agitation for up to 5 more minutes and continuing the cooling, even under the agitation of the scraper, lower than 60 rpm, until reaching a temperature between 22 ° C and 35 ° C. Process according to any of claims 3 to 6, characterized in that in step (a) a stirring of the helix, less than 1000 rpm and the scraper, less than 60 rpm is performed; in step (b) there is agitation of the propeller, less than 1000 rpm and the scraper, less than 60 rpm; in step (c) there is agitation of the propeller, less than 1000 rpm and the scraper, lower than 60 rpm; in step (d), a stirring of the propeller is performed, less than 1000 rpm and the scraper, less than 60 rpm and during cooling, a stirring of the scraper, less than 60 rpm and in step (e) a stirring of the propeller, lower than 1000 rpm. 8. Water-in-oil emulsion comprising a continuous phase, a discontinuous phase, an emulsifier and physical filters, characterized in that the emulsifier has a hydrophilic portion and a hydrophobic portion at each end and at least 10% of the cited selected physical filters of titanium dioxide, zinc oxide and mixtures thereof. Water-in-oil emulsion according to claim 8, characterized in that it contains the physical filters in a single phase, preferably in the oil phase. 10. Water-in-oil emulsion characterized by being composed, by weight, of 2.5 to 4.7% by weight of a copolymer emulsifier of the polyethylene glycol (PEG) family, preferably PEG 30 Dipolyhydroxystearate; from 2.0 to 15% of a mixture of emollients, such as, for example, cyclomethicone and isohexadecane; 0.1 to 1.0% of a film-forming compound, such as, for example, candelilla wax; from 3.5 to 30.0% of dispersed titanium dioxide; from 3.5 to 17.0% dispersed zinc oxide; from 1.0 to 65.0% demineralized water; 0.1 to 1.0% of a stabilizer, such as sodium chloride; from 0.1 to 0.5% of tetrasodium EDTA in 40% solution, preservatives, from 0.005 to 0.1%, such as 2-Bromo-2-Nitropropane-l, 3-Diol. 11. Water-in-oil type emulsion according to claim 10, characterized in that it optionally contains, by percentage weight, 0.1 to 1.5% of antiradical agent, specifically vitamin E, of 1.0 to 12.0% of moisturizing agents, such as glycerin and from 0.5 to 1.5% of pigment, specifically the pigment Timiron Super Red. 1

2. Water-in-oil emulsion according to claim 10 or 11, characterized by the fact that it can also include as film-forming compounds, ozocerite wax and the copolymer octylacrylamide acrylate polymer and as its neutralizer dimethyl stearamine, as stabilizer magnesium sulfate, as active compound alpha bisabolol and octyl palmitate as emulsifier. Process according to claim 1, characterized in that said physical filters have particles of sizes varying between 0.05 and 0.10 μm.