WO2005023412A2

WO2005023412A2 - Wax microdispersion preparation method

Info

Publication number: WO2005023412A2
Application number: PCT/FR2004/002185
Authority: WO
Inventors: Jean-Christophe Henrion
Original assignee: L'oreal
Priority date: 2003-09-01
Filing date: 2004-08-24
Publication date: 2005-03-17
Also published as: WO2005023412A3

Abstract

The invention relates to a wax microdispersion preparation method. The inventive method consists in: preparing a mixture comprising wax, a surface-active agent and water; heating the mixture; and, subsequently, cooling said mixture, such as to form the desired wax microdispersion. The invention is characterised in that the cooling step is performed by passing the mixture through a heat exchanger.

Description

Method for preparing a microdispersion of wax

The present invention relates to a new process, in particular industrial, for the preparation of aqueous microdispersion of wax particles.

The aqueous microdispersions of wax particles are constituents usually used in the field of cosmetic compositions. Mention may in particular be made of documents EP1201221 and WO02 / 43673 which mention a certain number of their applications. In the document EP1201221, the microdisper- aqueous wax particles sion was prepared by heating at 90 ^C C wax and surfactant, with gentle stirring, followed by addition of water previously heated to 90 ° C, maintaining the agitation. The mixture obtained is then cooled, ethanol is added and a microdispersion of waxes having an average particle diameter of approximately 170 nm is obtained. DE19646878 discloses a process for preparing an oil-in-water emulsion consisting in preparing by phase inversion a first oil-in-water emulsion, having a particle size of 500 nm maximum, then mixing this first emulsion with a second oil-in-water emulsion having a particle size greater than 1 micron and or with a hydrogel comprising a hydrophilic emulsifier and a lipophilic co-emulsifier. The first emulsion is prepared by mixing the constituents, for example wax, surfactant and water, heating to 95 ° C. with stirring and cooling to 20 ° C. It is also known from document WO00 / 33953, a process for preparing dispersion of nanoparticles having an average size of 10-300 nm, in which an organic compound, for example a wax, is mixed in a fluid phase in which it is not soluble, for example an aqueous phase, the mixture is heated above the melting point of the organic compound, then a surfactant is added in order to form a microemulsion which is then cooled, with stirring, up to a temperature below the melting point of the organic compound. However, it is not specified how the cooling step is carried out. Document WO02 / 43673 describes the use in cosmetics of wax nanoparticles having an average particle size of 5-500 nm and a melting point of at least 40 ° C. This document mentions several processes for preparing wax microdispersions, in particular an evaporation process, a GAS process (Gas antisolvent Recrystallization), a PCA process (precipitation with a compressed fluid antisolvent), a PGSS process (particles from saturated solutions in gas); a RESS process (rapid expansion of supercritical solutions). This document also describes a process in which the wax is mixed with a liquid in which it is not miscible, for example water, then the mixture is heated beyond the melting point of the wax; a surfactant is then added and the whole is mixed using an anchor or paddle mixer, so as to emulsify the fluid phase of molten wax, and to form microdispersion. The wax microdispersion obtained is then cooled. This process avoids the use of homogenization high pressure or high speed mixer. However, it is not specified how the cooling step is carried out. This document also describes a process in which the wax is mixed with water and a surfactant, then the mixture is heated beyond the melting point of the wax and stirred using an anchor mixer, so as to form the microdispersion, which is then poured, through a nozzle under a pressure of 20-30 mbar, in a second reactor which comprises water.

However, it can be seen that the methods described in the prior art have drawbacks at the industrial level, or simply cannot be implemented under industrial conditions.

In particular, a process consisting in heating the wax beyond its melting point, in slowly pouring the hot aqueous phase to obtain a phase inversion (the continuous phase of the emulsion passing from the wax to the water), then to be cooled before packaging, does not guarantee the reproducibility of the particle size during the various manufacturing operations.

This is notably due to the fact that certain waxes of natural origin, such as Camauba wax, are made up of a mixture of fatty substances, the proportion of which can be variable depending on the batch. These differences in quality lead to poor reproducibility of the microdispersion preparation process and the obtaining of particles whose diameter can be very variable, from one batch to another. It is common to obtain a particle size distribution, depending on the manufacturing, such that around 20% of the manufacturing does not comply with the specifications initially required.

However, for the cosmetic use for which it is intended, the microdispersion of wax should preferably have a constant particle size (mean diameter by volume, low dispersity), which can be of the order of 150-200 nm; this homogeneity in particle size is directly related to the technical performance of microdispersion, in particular when it is intended for making up the eyelashes. In addition, the microdispersion must preferably remain stable in particle size during its conservation, for example for 2 years at room temperature (20 ° C), and also have a constant water content, not developing undesirable odor or color. and show no bacterial growth.

It therefore appears that there remains a need, for manufacturers, in particular at the industrial level, of microdispersions of wax, to have a process which makes it possible to overcome the drawbacks of the prior art, and in particular making it possible to obtain good reproducibility in the size of the wax particles.

Furthermore, some of the methods proposed by the prior art require the use of special equipment, for example shearing tools such as drills. tor / stator or high pressure homogenizers.

It would therefore be desirable to have a process which does not require the installation of heavy tools intended to emulsify a mixture, while employing a reduced number of reactors, and a short process time, for example by avoiding melting or parboiling of the wax beforehand.

The present invention therefore relates to a process for the preparation of an aqueous microdispersion of wax particles in which:

a mixture comprising the wax, the surfactant and the water is prepared, the said mixture is heated to a temperature above the melting point of the wax,

- Then said mixture is cooled so as to form the desired microdispersion of wax, characterized in that the cooling step is carried out by passing said mixture through a heat exchanger which allows the mixture to cool, from its temperature initial TO at the inlet of the exchanger, greater than the melting point of the wax or of the wax mixture, in particular at least 5 ° C. or even at least 10 ° C. at said melting point, at a temperature T corresponding to T = Tfusion-wax - 3 ° C (melting temperature of the wax minus 3 ° C), temperature of the mixture at the outlet of the exchanger, and this during the transfer time.

This process is particularly advantageous insofar as it can be carried out in standard light equipment, for example of the chemical reactor type such as a tank, equipped with stirring mobile and heated by double jacket.

Furthermore, this process makes it possible to obtain quality microdispersions of wax and having a reproducible particle size profile, regardless of the batch of wax used, the size or the geometry of the reactors used, or even the type of agitation.

In the present invention, the term “aqueous microdispersion of wax particles” is understood to mean an aqueous dispersion of wax particles, in which the size of said wax particles is less than or equal to approximately 1 μm. Wax microdispersions are stable dispersions of colloidal wax particles, and are described in particular in "Microemulsions Theory and Practice", LM Prince Ed., Académie Press (1977) pages 21-32. In particular, these wax microdispersions can be obtained, according to the prior art, by melting the wax in the presence of a surfactant, and optionally part of the water, then progressive addition of hot water with stirring. The intermediate formation of an emulsion of the water-in-oil type is observed, followed by a phase inversion with final production of a microemulsion of the oil-in-water type. On cooling, a stable microdispersion of solid colloidal wax particles is obtained. The method according to the invention therefore consists, in a first step, in preparing a mixture comprising at least one wax, at least one surfactant and water.

In the present application, the term “wax” is intended to mean a lipophilic compound, solid at room temperature (25 ° C.), with reversible solid / liquid state change, having a melting point greater than or equal to 30 ° C. which can go up to 'at 120 ° C. By bringing the wax to the liquid state (melting), it is possible to make it miscible with oils and to form a homogeneous mixture microscopically, but by bringing the temperature of the mixture to room temperature, one recrystallizes the wax in the oils of the mixture.

The melting point of the wax can be measured using a differential scanning calorimeter (D.S.C.), for example the calorimeter sold under the name DSC 30 by the company METLER. A 15 mg sample of product placed in a crucible is subjected to a first temperature rise ranging from 0 ° C to 120 ° C, at the heating rate of 10 ° C / minute, then is cooled from 120 ° C to 0 ° C at a cooling rate of 10 ° C / minute and finally subjected to a second temperature rise from 0 ° C to 120 ° C at a heating rate of 5 ° C / minute. During the second temperature rise, the variation in the difference in power absorbed by the empty crucible and by the crucible containing the product sample is measured as a function of the temperature. The melting point of the compound is the value of the temperature corresponding to the top of the peak of the curve representing the variation of the difference in absorbed power as a function of the temperature.

The waxes capable of being used in the invention can be chosen from waxes, solid and rigid, at room temperature of animal, vegetable, mineral or synthetic origin and their mixtures. Preferably, the waxes used in the composition may have a melting point greater than approximately 45 ° C., and in particular greater than 55 ° C. The wax can also have a hardness ranging from 0.05 MPa to 15 MPa, and preferably ranging from 6 MPa to 15 MPa. The hardness is determined by measuring the compressive force measured at 20 ° C using the texturometer sold under the name TA-TX2i by the company RHEO, equipped with a stainless steel cylinder with a diameter of 2 mm. moving at the measuring speed of 0.1 mm / s, and penetrating into the wax at a penetration depth of 0.3 mm. To perform the hardness measurement, the wax is melted at a temperature equal to the melting point of the wax + 20 ° C. The melted wax is poured into a container 30 mm in diameter and 20 mm deep. The wax is recrystallized at room temperature (25 ° C) for 24 hours, then the wax is stored for at least 1 hour at 20 ° C before performing the hardness measurement. The hardness value is the measured compression force divided by the surface area of the texturometer cylinder in contact with the wax. Mention may in particular be made of hydrocarbon waxes such as beeswax, lanolin wax, and Chinese insect waxes; rice wax, Carnauba wax, Candellila wax, Ouricurry wax, Alfa wax, cork fiber wax, sugar cane wax, Japanese wax and sumac wax ; montan wax, microcrystalline waxes, paraffins and ozokerite; polyethylene waxes, waxes obtained by the Fisher-Tropsch synthesis and waxy copolymers as well as their esters.

Mention may also be made of the waxes obtained by catalytic hydrogenation of animal or vegetable oils having fatty chains, linear or branched, of C8-C32. Among these, mention may in particular be made of hydrogenated jojoba oil, hydrogenated sunflower oil, hydrogenated castor oil, hydrogenated coconut oil and hydrogenated lanolin oil. Mention may also be made of silicone waxes, fluorinated waxes.

Preferably, the wax is a Carnauba wax.

The wax can be present in the initial mixture in an amount of 15-45% by weight relative to the initial mixture, in particular 20-40% by weight, and in particular 25-35% by weight.

The wax or mixture of waxes can be combined with one or more fatty additives (oily and / or pasty). Mention may in particular be made of vegetable oils such as sunflower oil, jojoba oil; mineral oils such as paraffin oil; silicone oils; petrolatum, lanolin; fluorinated oils; hydrocarbon oils with a perfluorinated group; fatty alcohol esters. It is also possible to add standard liposoluble active agents such as UV filters, liposoluble vitamins and liposoluble cosmetic active agents.

The initial mixture also comprises at least one surfactant, which can be chosen, alone or as a mixture, from:

- anionic surfactants, in particular salts of optionally unsaturated fatty acids, having for example 12 to 18 carbon atoms; alkali metal salts or organic base salts of alkyl sulfuric and alkyl sulfonic acids having 12 to 18 carbon atoms or of alkyl aryl sulfonic acids in which the alkyl chain contains 6-18 carbon atoms; ethers-sulfates.

- nonionic surfactants, in particular polyalkoxylated and / or polyglycerolated surfactants, and in particular fatty acids or fatty acid amides; fatty alcohols or alkylphenols; esters of fatty acids and polyols; alkanediols and alkyl ethers of alkanediols. Mention may also be made of the tri-glycerol alkylcarbamates, the oxyethylenated or propoxylated derivatives of lanolin alcohols, of lanolin fatty acids, or of their mixtures.

- cationic surfactants, in particular quaternary ammonium derivatives. Particularly preferred is polyoxyethylene glyceryl monostearate, in particular comprising 30 ethylene oxide units (30 EO).

The surfactant can be present in the initial mixture in an amount of 3-15% by weight relative to the initial mixture, in particular 5-10% by weight, and in particular 6-9% by weight.

It is also possible to introduce liposoluble active ingredients into the microparticulate waxy phase, such as UV filters, liposoluble vitamins, liposoluble cosmetic active agents.

The aqueous phase can also comprise water-soluble cosmetic active agents, such as preservatives.

The aqueous phase or the water may be present in an amount of 40-82% by weight, especially 50-75% by weight, preferably 60-65% by weight, relative to the initial mixture.

In a second stage of the process, the initial mixture is heated to a temperature higher than the melting temperature of the wax or waxes, preferably higher than 8 to 15 ° C, in particular 10-13 ° C, than said melting temperature.

By 'wax melting temperature' is meant the temperature at which the wax is completely melted.

Thus, when using a Carnauba wax with a melting temperature of 88-90 ° C, the initial mixture can be heated to a temperature above

98 ° C, in particular of the order of 99-103 ° C, for example at 100-102 ° C.

The mixture can be maintained at this temperature for a period of approximately 10-90 minutes, preferably of the order of 45-75 minutes, especially 55-65 minutes, in order to obtain a homogeneous mixture.

It is possible to stir the mixture during its heating, and / or after, for example using a stirring anchor or paddle mobile.

Said heated mixture is then cooled so as to form the microdispersion of wax, by passing said heated mixture through a heat exchanger.

A heat exchanger is a device, supplied with a circulation of refrigerated fluid, in particular water at 4 ° C. for example, making it possible to remove heat from the liquid which passes through it. It can be characterized by its ability to absorb calories per unit of time, or cooling power, which will depend in particular on its geometry, the constituent material, the technology used (class of device) and the refrigerant ( nature and temperature among others). Among the commercial exchangers that can be used, mention may in particular be made of tubular, mono- or multitubular exchangers, lamella exchangers, plate exchangers, spiral exchangers; these exchangers can be made of glass, metal, enamelled cast iron, Teflon, or any inert material compatible with the constituents of the microdispersion of wax.

In particular, the use of tubular exchanger mounted between two tanks or reactors with stirring makes it possible to obtain adequate cooling of a microdispersion of wax circulating between said two reactors, by gravity.

In all cases, the essential characteristic of the heat exchanger is that it must allow the mixture to cool, from its initial temperature TO at the inlet of the exchanger, higher than the melting point of the wax or the mixture of wax, in particular at least 5 ° C. or even at least 10 ° C. above said melting point, at a temperature T corresponding to T = Tf _US i ₀ n-wax - 3 ° C (melting temperature of the wax minus 3 ° C), temperature of the mixture at the outlet of the exchanger, and this during the transfer time.

Transfer time is understood to mean the time necessary for the mixture to pass through the exchanger. This transfer time is obviously a function of the amount of mixture, the size of the exchanger and the flow rate through the exchanger, but in all cases, it is adjusted so that the cooling is as short as possible. and is preferably between 10 and 100 seconds, in particular between 20 and 60 seconds.

Thus, for example, in the case of Carnauba wax, the exchanger must be such that at the outlet of the heat exchanger, the temperature of the final mixture is preferably less than or equal to about 85 ° C., preferably at 84 ° C.

It has in fact been found that this particular, and especially rapid, cooling of the mixture makes it possible to avoid the formation of agglomerates and to obtain a microdispersion which is stable over time.

For example, when it is desired to cool from 100 ° C to 85 ° C a mixture according to the invention present in an amount of 600g to 1200g, one can use a monotube heat exchanger of 600 cm ² , made of glass, fed against -current with water at 2-6 ° C, especially 4 ° C. Preferably, the transfer flow rate inside the exchanger is adjusted to less than 40 ml / min, in particular of the order of 10-35 ml / min, so that the temperature at the outlet of the exchanger is about 85 ° C.

The mixture is then cooled to room temperature (20 ° C) so as to form the wax microdispersion. Cooling can be done at a speed tesse of 20 to 30 ° C per hour, especially 22 to 27 ° C per hour.

It is possible to add alcohol, for example ethanol, and / or additives, to the microdispersion of wax thus cooled, for example in an amount of 0.8 to 1.2 parts per 9 parts in microdispersion weight already formed.

The particles of the wax microdispersion preferably have mean dimensions of less than 1 μm, in particular between 150 and 400 nm, and even better between 160 and 250 nm.

The microdispersion of wax can be used in all areas of cosmetics, and in particular in makeup compositions such as mascara, eyeliner, lipstick, blush or eyeshadow, foundation, body makeup product , nail polish. One can also envisage an application in the field of care compositions, sun or self-tanning compositions, in particular as a concealer product.

The invention is illustrated in more detail in the following examples.

Example 1

A microdispersion of Carnauba wax was prepared having, in the end, the following composition:

- Carnauba wax 270 g - Polyoxyethylenated glyceryl monostearate (30 EO) (TAGAT S from GOLDSCHMIDT) 67.5 g

- Ethanol 100 g

- Water 562.5 g

The water, the Carnauba wax and the surfactant are charged into a double-jacket reactor A, equipped with a condenser and a mixer, then the mixture is heated with stirring to 100 ° C.

The contents of the reactor, maintained at a temperature of at least 99 ° C., are poured into a second reactor B, passing through a tubular heat exchanger of 600 cm ² , made of glass, supplied with water at 4 ° C. . The transfer rate is such that the temperature of the microdispersion at the exchanger outlet is less than about 85 ° C (flow rate: 30 ml per minute).

While maintaining gentle stirring, the final mixture is then cooled from 85 ° C to 20-25 ° C, at a cooling rate of 25 ° C / hour. Ethanol is then added at room temperature, and a microdispersion of wax particles having an average particle diameter of about 174 nm is obtained.

Claims

1. Process for the preparation of an aqueous microdispersion of wax particles in which:

a mixture comprising the wax, the surfactant and the water is prepared,

- said mixture is heated to a temperature above the melting point of the wax,

- Then said mixture is cooled so as to form the microdispersion of the desired wax, characterized in that the cooling step is carried out by passing said mixture through a heat exchanger which allows the mixture to cool, from its temperature initial TO at the inlet of the exchanger, greater than the melting point of the wax or of the wax mixture, in particular at least 5 ° C. or even at least 10 ° C. at said melting point, at a temperature T corresponding to T = Tf _US ion-wax - 3 ° C (melting temperature of the wax minus 3 ° C), temperature of the mixture at the outlet of the exchanger, and this during the transfer time.

2. Method according to claim 1, in which the wax, alone or as a mixture, is chosen from hydrocarbon waxes such as beeswax, lanolin wax, and Chinese insect waxes; rice wax, Carnauba wax, Candellila wax, Ouricurry wax, Alfa wax, cork fiber wax, sugar cane wax, Japanese wax and sumac wax ; montan wax, microcrystalline waxes, paraffins and ozokerite; polyethylene waxes, waxes obtained by the Fisher-Tropsch synthesis and waxy copolymers and their esters; waxes obtained by catalytic hydrogenation of animal or vegetable oils having fatty chains, linear or branched, in C8-C32; hydrogenated jojoba oil, hydrogenated sunflower oil, hydrogenated castor oil, hydrogenated coconut oil and hydrogenated lanolin oil; silicone waxes and fluorinated waxes.

3. Method according to one of the preceding claims, wherein the wax is a Carnauba wax.

4. Method according to one of the preceding claims, wherein the wax is present in the initial mixture in an amount of 15-45% by weight relative to the initial mixture, in particular 20-40% by weight, and in particular 25- 35% by weight.

5. Method according to one of the preceding claims, in which the surfactant is chosen, alone or as a mixture, from:

- anionic surfactants, in particular salts of optionally unsaturated fatty acids, having for example 12 to 18 carbon atoms; alkaline salts or salts organic bases of alkyl-sulfuric and alkylsulfonic acids having 12 to 18 carbon atoms or of alkyl-arylsulfonic acids in which the alkyl chain contains 6-18 carbon atoms; ethers-sulfates.

- nonionic surfactants, in particular polyalkoxylated and or polyglycerolated surfactants, and in particular fatty acids or fatty acid amides; fatty alcohols or alkylphenols; esters of fatty acids and polyols; alkanediols and alkyl ethers of alkanediols. Mention may also be made of the tri-glycerol alkylcarbamates, the oxyethylenated or propoxylated derivatives of lanolin alcohols, of lanolin fatty acids, or of their mixtures. - cationic surfactants, in particular quaternary ammonium derivatives.

6. Method according to one of the preceding claims, in which the surfactant is present in the initial mixture in an amount of 3-15% by weight relative to the initial mixture, in particular 5-10% by weight, and in particular 6- 9% by weight.

7. Method according to one of the preceding claims, wherein the amount of water present in the initial mixture represents 40-82%, in particular 50-75% by weight, preferably 60-65% by weight, of the initial mixture .

8. Method according to one of the preceding claims, in which the initial mixture is heated to a temperature higher than 8 to 15 ° C, in particular 10-13 ° C, than the melting temperature of the wax.

9. Method according to one of the preceding claims, in which said heat exchanger is chosen from tubular, mono- or multitubular exchangers, lamella exchangers, plate exchangers, spiral exchangers; which can be made of glass, metal, enameled cast iron, Teflon, or any inert material compatible with the constituents of the microdispersion of wax.

10. Method according to one of the preceding claims, in which the transfer time is between 10 and 100 seconds, in particular between 20 and 60 seconds.

11. Method according to one of the preceding claims, in which alcohol, for example ethanol, and / or additives is added to the cooled wax microdispersion, for example in an amount of 0.8 to 1, 2 parts per 9 parts by weight of microdispersion already formed.

12. Method according to one of the preceding claims, in which the particles of the wax microdispersion have average dimensions of less than 1 μm, in particular between 150 and 400 nm, and even better between 160 and 250 nm.