Patent Application
20080051492
The inverse emulsions of the present invention comprise a crosslinked polymer obtained by polymerisation of: acrylic and/or methacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and a cationic monomer.
The inverse emulsions of the invention beside possessing high skin and hair compatibility and exhibiting good thickening properties and stability over time, show high thickening power not only in aqueous solutions, but also in oil and water emulsions; these properties makes them particularly suited for the preparation of cosmetic formulations.
With the expression “cosmetic formulations” we mean the products normally used for personal care, such as body and face creams, hair gels and lotions, hair colouring and bleaching creams, sunscreen compositions, make-up products, cleansing, moisturizing and perspiring fluids and other products for similar applications.
By cosmetic product with high compatibility with skin and hair we mean a product that is easily absorbed through a keratinous substrate while making changes in the touch, in moisturization and perspiration, and improving the general sensorial characteristics without altering the physiological pH.
A further essential characteristic of the thickeners employed in cosmetic formulations is that they manifest their thickening capability without negatively altering the other properties of the formulations. It is moreover highly desirable in the cosmetic field to have thickeners in the form of stable emulsion that are able to give stable cosmetic formulations.
With the expression “stable emulsion” we mean an emulsion that in the normal storing conditions (from −10° C. to 40° C.) and for the usual lifetime (180-360 days) does not show phase separation, sediment, formation of floating pellicles and lumps.
With the expression “stable cosmetic product” we mean a cosmetic formulation that in the above said conditions and lifetime does not show phase separation, sediment, formation of floating pellicles and lumps.
In the specialised literature many methods are reported to regulate the rheological properties of different formulations, often including the use of polymers in the form of inverse emulsion (an inverse emulsion is an emulsion containing both an oil-in-water emulsifier and a water-in-oil emulsifier, wherein the aqueous phase is dispersed in the organic phase in very small drops), but the synthetic thickeners for cosmetics of the present invention are never described. It is a fundamental object of the present invention to prepare an inverse emulsion useful for the preparation of cosmetic formulations wherein the weight ratio between the aqueous phase and the organic phase is from 4:1 to 2:1 and containing from 20 to 70% by weight of an acrylic polymer comprising monomeric units deriving from:
wherein R1 is hydrogen or methyl; R2, R3, R4 are, one independently of the others, hydrogen or C1-C4 alkyl; Y is NH or O; A is a C1-C6 alkylene; X is an anion;
The present invention also includes a procedure for the preparation of an inverse emulsion for cosmetic formulations characterised by:
wherein R1 is hydrogen or methyl; R2, R3, R4 are, one independently of the others, hydrogen or C1-C4 alkyl; Y is NH or O; A is a C1-C6 alkylene; X is an anion; iii) acrylic or methacrylic acid. The mixture is further characterized by the fact that 2-acrylamido-2-methylpropanesulfonic acid represents from 1% to 29% molar of the total monomers i), ii) and iii);
In the general formulas for the cationic acrylic monomers, the X is defined as an anion. This counter ion may be any that will not cause the cationic acrylic monomer to be insoluble or otherwise prevent it from being polymerized. For example, X can be a halide such as a chloride or bromide. While the general formula appears to require the anion to have a −1 charge, it is not so limited. For example, it may be a complex or simple anion having a −2 charge subject to the prior stated requirement that the counter ion not prevent the cationic acrylic monomer from being polymerized.
The cationic acrylic monomer of formula I is present in the acrylic polymer of the invention in a molar percentage comprised between 0.1 and 10% on the total sum of monomers i), ii) and iii) and is preferably chosen from acryloyloxyethyl-trimethylammonium chloride and methacryloyloxyethyl-trimethylammonium chloride.
The polyfunctional monomer contains two or more unsaturated reactive groups and it is present in the acrylic polymer in an amount comprised between 0.01 and 1 mmoles per mole of mixture of monomers i), ii) and iii). In some embodiments, the polyfunctional monomer is methylenebisacrylamide.
In the procedure according to the invention it is preferred to use the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid, and to regulate the pH of phase b. with aqueous sodium hydroxide (NaOH).
Among the initiators of radical polymerisation useful for with the present invention are ammonium, potassium or sodium persulfate, and water-soluble organic peroxides. For example hydrogen peroxide and peracetic acid may be so used.
In the inverse emulsions of the invention the organic phase consists of mineral oils containing saturated hydrocarbons or by vegetable oils or by mixture thereof having boiling point from 150 to 300° C. Preferably the organic phase is mineral oil, polydecene, isohexadecane, or a C13-C16 isoparaffin; more preferably it is C13-C16 isoparaffin.
The water-in-oil and the oil-in-water emulsifiers are those normally used for this purpose. Useful water-in-oil emulsifiers include: sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, and sorbitan monooleate. Useful oil-in-water emulsifiers include the linear or branched ethoxylated alcohols. The total amount of emulsifiers in the inverse emulsion of the invention is from 2 to 10% by weight; the ratio between water-in-oil emulsifiers and oil-in-water emulsifiers may range between 2:1 and 1:2.
To initiate the polymerization of the acrylic monomers an aqueous solution of sodium bisulfite may advantageously be used.
The inverse emulsions of the invention may further additionally contain the common additives used in radical polymerisation, by way of example sequestering agents such as sodium diethylenetriaminepentaacetate.
As it was previously observed, the inverse emulsions of the present invention are particularly suited for the treatment of hair and skin, in body and face creams, hair gels and lotions, hair colouring and bleaching creams, sunscreen compositions, make-up products, cleansing, moisturizing and perspiring fluids.
In the following examples the preparation of inverse emulsions according to the invention and of an inverse emulsion according to the prior art, prepared with % of 2-acrylamido-2-methylpropanesulfonic acid higher than 29% (according to WO 2004/113393), are reported. The application tests show the very high thickening power of the emulsions of the present invention, in aqueous solution, in glycols, and in emulsified water and oil systems.
The stability of water and oil emulsion systems comprising the inverse emulsions of the invention was also evaluated; the stability is correlated to the stability of the cosmetic products containing the emulsions of the invention as thickeners.
The examples illustrate the present invention without limiting it, nor the kind of application of the inverse emulsions of the invention.
The following ingredients are loaded into a 1.5 l Pyrex reactor equipped with a steel anchor stirrer:
After a cooling down period, necessary to reach a temperature close to 0° C., the following ingredient are slowly added while stirring:
In the meantime, the organic phase is prepared inside a 500 ml beaker adding under stirring:
The aqueous phase is slowly added into the organic phase and subsequently the mixture is efficiently stirred with a high shear dispersing machine (ULTRA-TURRAX IKA). The emulsion obtained is then reloaded in the reactor and the reaction is ready to be started (reaction phase). The first operation is to insufflate nitrogen directly in the bulk of the product for about 10 minutes. This is a key step, because it enables to lower and control the amount of oxygen dissolved in the emulsion and to adjust the induction times. The second phase takes place only after the emulsion temperature is warmed up to 20° C. After that, 23.9 g of a 1% by weight aqueous solution of sodium metabisulfite is quickly loaded drop-wise through an addition funnel. The third phase is the radical reaction. The reaction proceeds spontaneously raising gradually the temperature to about 60° C. in 50 minutes. The stirring is maintained very fast and cool water re-circulates inside the reactor jacket. After this period of time the emulsion is heated to 60° C. and maintained at this temperature for about one hour to complete the monomers conversion, consuming the residual monomers. Subsequently a cooling down period is required to reach a temperature of 35-40° C. The final step is the addition of 25 g of C12-C16 linear alcohol 8 moles ethoxylated.
The mixture is rapidly stirred till homogeneity is reached; the final emulsion (Emulsion 1) is then unloaded and stored for at least 24 hours before the evaluation of its properties.
The following ingredients are loaded into a 1.5 l Pyrex reactor equipped with a steel anchor stirrer:
After a cooling down period, necessary to reach a temperature close to 0° C., the following ingredient are slowly added while stirring:
In the meantime, the organic phase is prepared inside a 500 ml beaker adding under stirring:
The aqueous phase is slowly added into the organic phase and subsequently the mixture is efficiently stirred with a high shear dispersing machine (ULTRA-TURRAX IKA). The emulsion obtained is then reloaded in the reactor and the reaction is ready to be started (reaction phase). The first operation is to insufflate nitrogen directly in the bulk of the product for about 10 minutes. This is a key step, because it enables to lower and control the amount of oxygen dissolved in the emulsion and to adjust the induction times. The second phase takes place only after the emulsion temperature is warmed up to 20° C. After that, 23.9 g of a 1% by weight aqueous solution of sodium metabisulfite is quickly loaded drop-wise through an addition funnel. The third phase is the radical reaction. The reaction proceeds spontaneously raising gradually the temperature to about 60° C. in 50 minutes. The stirring is maintained very fast and cool water re-circulates inside the reactor jacket. After this period of time the emulsion is heated to 60° C. and maintained at this temperature for about one hour to complete the monomers conversion, consuming the residual monomers. Subsequently a cooling down period is required to reach a temperature of 35-40° C. The final step is the addition of 25 g of C12-C16 linear alcohol 8 moles ethoxylated.
The mixture is rapidly stirred till homogeneity is reached; the final emulsion (Emulsion 2) is then unloaded and stored for at least 24 hours before the evaluation of its properties.
The following ingredients are loaded into a 1.5 l Pyrex reactor equipped with a steel anchor stirrer:
After a cooling down period, necessary to reach a temperature close to 0° C., the following ingredient are slowly added while stirring:
In the meantime, the organic phase is prepared inside a 500 ml beaker adding under stirring:
The aqueous phase is slowly added into the organic phase and subsequently the mixture is efficiently stirred with a high shear dispersing machine (ULTRA-TURRAX IKA). The emulsion obtained is then reloaded in the reactor and the reaction is ready to be started (reaction phase). The first operation is to insufflate nitrogen directly in the bulk of the product for about 10 minutes. This is a key step, because it enables to lower and control the amount of oxygen dissolved in the emulsion and to adjust the induction times. The second phase takes place only after the emulsion temperature is warmed up to 20° C. After that, 23.9 g of a 1% by weight aqueous solution of sodium metabisulfite is quickly loaded drop-wise through an addition funnel. The third phase is the radical reaction. The reaction proceeds spontaneously raising gradually the temperature to about 60° C. in 50 minutes. The stirring is maintained very fast and cool water re-circulates inside the reactor jacket. After this period of time the emulsion is heated to 60° C. and maintained at this temperature for about one hour to complete the monomers conversion, consuming the residual monomers. Subsequently a cooling down period is required to reach a temperature of 35-40° C. The final step is the addition of 25 g of C12-C16 linear alcohol 8 moles ethoxylated.
The mixture is rapidly stirred till homogeneity is reached; the final emulsion (Emulsion 3) is then unloaded and stored for at least 24 hours before the evaluation of its properties.
The following ingredients are loaded into a 1.5 l Pyrex reactor equipped with a steel anchor stirrer:
After a cooling down period, necessary to reach a temperature close to 0° C., the following ingredient are slowly added while stirring:
In the meantime, the organic phase is prepared inside a 500 ml beaker adding under stirring:
The aqueous phase is slowly added into the organic phase and subsequently the mixture is efficiently stirred with a high shear dispersing machine (ULTRA-TURRAX IKA). The emulsion obtained is then reloaded in the reactor and the reaction is ready to be started (reaction phase). The first operation is to insufflate nitrogen directly in the bulk of the product for about 10 minutes. This is a key step, because it enables to lower and control the amount of oxygen dissolved in the emulsion and to adjust the induction times. The second phase takes place only after the emulsion temperature is warmed up to 20° C. After that, 21.5 g of a 1% by weight aqueous solution of sodium metabisulfite is quickly loaded drop-wise through an addition funnel. The third phase is the radical reaction. The reaction proceeds spontaneously raising gradually the temperature to about 60° C. in 50 minutes. The stirring is maintained very fast and cool water re-circulates inside the reactor jacket. After this period of time the emulsion is heated to 60° C. and maintained at this temperature for about one hour to complete the monomers conversion, consuming the residual monomers. Subsequently a cooling down period is required to reach a temperature of 35-40° C. The final step is the addition of 25 g of C12-C16 linear alcohol 8 moles ethoxylated.
The mixture is rapidly stirred till homogeneity is reached; the final emulsion (Emulsion 4) is then unloaded and stored for at least 24 hours before the evaluation of its properties.
5 oil/water emulsions are prepared with each of the Emulsions 1 and 4 (columns E1 and E4 in the table), having the following composition:
The thickening properties of the Emulsions 1 and 4 are instead evaluated by measuring their Brookfield viscosity at 2% in water, 25° C. and 5 rpm as well as the viscosity of the formulations of Table 1, in the same conditions. The obtained results are reported in Table 2.
The thickening properties of the Emulsions 1 and 4 are also evaluated in glycerine and monopropylene glycol by measuring their Brookfield viscosity at 2%, 25° C. and 5 rpm in the said solvents. The results are reported in Table 3.
It is observed that the Emulsion 1, according to the invention, has better thickening properties than the Emulsion of the prior art, both in water, and in glycols, and in emulsified water and oil systems.
| Number | Date | Country | Kind |
|---|---|---|---|
| IT-VA2006A000049 | Aug 2006 | IT | national |
