Composition in the Form of a Smooth Paste and Process for Its Preparation

The present invention relates to a composition, in particular a cosmetic of dermatological composition, in the form of a smooth paste which may be used to care for and/or to make up the lips and/or the skin. The invention also relates to a process for the preparation of this composition.

Cosmetic compositions which may be applied to the skin or the lips as a make-up or care product, such as bases for the lips or lipsticks, for example, may be, in a known manner, in the form of a solid stick, for example a lipstick pencil, or in the form of a smooth paste, which can be applied with a brush, for example.

Compositions in stick form generally comprise a large amount of waxes, as well as oils, pigments and/or fillers and, optionally, additives. Compositions in smooth paste form generally contain few or no waxes, which allows them to be taken up and applied easily, given that a large amount of waxes would lead to a composition of high viscosity, and thus one which is difficult to apply.

However, waxes make it possible to impart certain advantageous properties to the compositions comprising them, in particular qualities of creaminess of the composition and qualities of hold and of thickness of the film applied. Thus, it would be desirable to have available compositions in smooth paste form which may comprise large amounts of waxes.

Moreover, it would be advantageous to accentuate some of the cosmetic qualities of compositions in smooth paste form; in particular, it would be desirable to enhance further their softness when they are applied to the lips or the skin, while at the same time imparting a certain level of moisturization and care to the support.

Thus, it would be desirable to be able to incorporate, into compositions in smooth paste form, moisturizing or care ingredients such as, for example, polyhydric alcohols or active agents, in particular in dispersion or in solution in an aqueous phase. Now, it has been observed that polyhydric alcohols, and in particular glycerol, just like the gelled aqueous phases, are generally incompatible with fatty substances. The reason for this is that it has also been observed that a composition comprising fatty substances and glycerol is not in the form of a single homogeneous phase, but in the form of two separate phases, thereby introducing problems of conservation over time.

One of the solutions to overcome this drawback is to incorporate into the composition, in particular when it is in the form of a stick, a surfactant which makes it possible to maintain the composition in the form of a single homogeneous phase. However, the composition obtained may have a certain irritant nature.

It is also possible to choose the fatty substances as a function of the polyhydric alcohol, given that certain specific fatty substances are compatible with certain polyhydric alcohols, for example isoprene-glycol; however, this introduces a great limitation as regards the formulations which may be envisaged.

The aim of the present invention is to overcome these drawbacks, and the invention proposes a composition in smooth paste form which is particularly homogeneous, although it comprises, on the one hand, lipophilic components such as fatty substances and, on the other hand, hydrophilic components such as polyhydric alcohols and/or an aqueous phase.

One subject of the present invention is thus an extruded composition in the form of a smooth paste, comprising a lipophilic component and a hydrophilic component, the said composition being in the form of a single homogeneous phase.

Another subject of the invention is a process for the preparation of the said composition, in which at least part of the process is carried out using a mixer-extruder.

Thus, generally, the process according to the invention makes it possible to obtain a homogeneous composition from two mutually incompatible phases, one of these phases being lipophilic and the other being hydrophilic.

An advantage of the invention is that it allows the preparation of homogeneous compositions of varied formulation, without being restricted by the presence of a certain type of fatty substance.

Moreover, the composition obtained may be stable and homogeneous even if it contains no or essentially no surfactants. As defined herein, the phrase "essentially no surfactants" means an amount of surfactant insufficient to maintain the composition in the form of a single homogeneous phase when one skilled in the art tries to obtain a single homogeneous phase solely by using a surfactant.

The composition according to the present invention is thus a smooth paste the viscosity of which may be measured, in contrast with the solid structure of a pencil or stick, the viscosity of which cannot be measured. The said dynamic viscosity at 25.degree. C. generally ranges from 3 to 35 Pa s, measured with a Contraves TV rotary viscometer equipped with an "MS-r4" rotor at a frequency of 60 Hz.

The composition according to the invention thus comprises at least one lipophilic component, which may be chosen, for example, from the usual constituents of a fatty phase such as waxes, oils, gums and/or fatty substances which are pasty, hydrocarbon-containing and/or silicone-containing, and possibly volatile, alone or as a mixture.

Among the waxes which may be envisaged, alone or as a mixture, mention may be made of mineral waxes such as microcrystalline waxes, paraffin, petrolatum, petroleum jelly, ozokerite and montan wax; animal waxes such as beeswax, lanolin and derivatives thereof; plant waxes such as candelilla wax, ouricurry wax, carnauba wax, Japan wax, cocoa butter, cork fibre wax or sugar cane wax; hydrogenated oils, fatty esters and glycerides which are solid at 25.degree. C.; synthetic waxes such as polyethylene waxes and the waxes obtained by Fischer-Tropsch synthesis; silicone waxes; mixtures thereof.

Among the oils which may be envisaged, alone or as a mixture, mention may be made of mineral oils such as paraffin oil or liquid petroleum jelly; animal oils such as perhydrosqualene or arara oil; plant oils such as sweet almond oil, calophyllum oil, palm oil, castor oil, avocado oil, jojoba oil, olive oil or cereal germ oil; silicone oils such as polydimethyl-siloxane; esters of lanolic acid, of oleic acid, of lauric acid, of stearic acid or of myristic acid, for example; alcohols such as oleyl alcohol, linoleyl alcohol, linolenyl alcohol, isostearyl alcohol or octyldodecanol; alcohol or polyalcohol acetylgly-cerides, octanoates, decanoates or ricinoleates; volatile oils such as cyclotetradimethylsiloxane, cyclopentadimethylsiloxane, cyclohexadimethylsiloxane and methylhexyldimethylsiloxane, or isoparaffins.

The composition may preferably comprise from 65 to 99% by weight of lipophilic component, which may preferably contain from 8 to 40% by weight of waxes and from 60 to 92% by weight of oils.

By means of the process used to prepare the present composition, it is possible to add a large amount of waxes into the composition, for example at least 10% and more preferably about 15-25% by weight, without incurring any problem of homogeneity or of formation of grains. Thus, the composition obtained having a high wax content is capable of forming a film which is of good hold.

The composition according to the invention also comprises at least one hydrophilic component, which may be a polyhydric alcohol and/or which may be in the form of a gelled aqueous phase.

The polyhydric alcohol may preferably be a compound having 2-8 carbon atoms and 2-6 hydroxyl functions, such as ethylene glycol, isoprene-glycol, glycerol, 1,2-propanediol, diglycerol, erythritol, arabitol, adonitol, sorbitol and dulcitol. The polyhydric alcohol may also be a polyether alcohol with a weight average molecular weight of 150-600, such as polyethylene glycol 300 and polyglycerol 500. A mixture of polyhydric alcohols may also be used.

The gelled aqueous phase may be gelled by the presence of any gelling agent known to those skilled in the art.

As a gelling agent, mention may be made in particular of:

alga extracts such as agar-agar, carrageenans and alginates,

seed extracts such as extracts of carob or of guar,

fruit extracts, in particular pectin,

plant exudates, such as gum arabic, gum tragacanth, karaya gum and ghatti gum,

cellulose derivatives such as carboxymethyl cellulose,

gelling agents of animal origin such as gelatin or caseinates,

exudates of microorganisms such as xanthan gum,

synthetic gelling agents such as acrylic polymer derivatives (Carbomer, Carbopol, Pemulen) or silicates (compounds based on silicon such as Laponite, Lapomer or Veegum).

The gelling agent may preferably be present in the aqueous phase in a proportion of 0.2-10% by weight relative to the aqueous phase.

The hydrophilic component may have a viscosity preferably ranging from 1 to 250 poises, more preferably 30 to 250 poises. As regards the lipophilic component, this may have a viscosity higher or lower than that of the hydrophilic component.

The composition may preferably comprise 1-35% by weight of hydrophilic component, more preferably 3-15% by weight, the hydrophilic component possibly also being in the form of a mixture of gelled aqueous phase and of polyhydric alcohol.

The composition may also comprise any constituent usually used in the field of application envisaged, and in particular antioxidants, fragrances, essential oils, preserving agents, cosmetic active agents, moisturizing agents, vitamins, essential fatty acids, sphingolipids, sunscreens, surfactants, dyes, pigments, pearlescent agents, fillers and polymers.

Depending on the nature of these additional constituents, they will be added to the lipophilic component or to the hydrophilic component during the preparation of the composition. A person skilled in the art will know how to select these possible additional constituents, as well as their amount, such that the advantageous properties of the composition according to the invention are not, or are substantially not, altered by the addition envisaged.

The composition according to the invention may be in the form of a make-up product for the skin, in particular in the form of a foundation, a blusher, an eyeshadow, a mascara, an eyeliner, a lip composition or a base for the lips, or alternatively in the form of a care product for the skin or an antisun or self-tanning product, or even in the form of a hair product.

The composition according to the invention makes it possible to obtain a film which spreads easily and uniformly, and which has a certain softness. The film obtained has a light texture and remains comfortable to wear throughout the day. It is also of good hold. The composition obtained also has good emollient properties when applied to the skin.

The composition according to the invention may advantageously be prepared using a mixer-extruder. A mixer-extruder is generally composed of several parts that can be heated at different temperatures.

It is possible, for example, to prepare a premix comprising at least some of the various constituents of the composition, including at least a portion of those having a high melting point, to heat this premix to a temperature at which it melts, and then to add the rest of the constituents, in one or more portions, and to blend the mixture obtained in a mixer-extruder, during at least part of its period of cooling to room temperature.

For example, it is possible to add all the components with a high melting point in a first part A, and then to add, in a part B or in different parts B, C, D, etc., the remaining components. It is also possible, for example, to add in a first part A, some of the high melting point components, then in a part B, or in parts B, C, D, etc., the other high melting point components, and then to add in one or several parts, J, K, L, etc., the remaining components.

It is also possible to introduce all of the constituents into the top of the mixer-extruder, under hot or cold conditions, then optionally to increase the temperature of the said mixture so as to obtain a homogeneous mixture, while at the same time blending, and to continue the blending for at least part of the period of cooling to room temperature.

It has, indeed, been observed that this process makes it possible to obtain a composition in the form of a smooth and homogeneous paste, although it contains a hydrophilic component and a lipophilic component.

The heating step may be carried out according to any known technique and, in particular, directly in the extruder.

The various steps of the process may be performed in one or more extruders arranged one after the other, and preferably in a single twin-screw extruder.

It has, indeed, been observed that the composition obtained after extrusion is particularly soft and affords a certain silky sensation when it is applied to the skin, while at the same time avoiding the appearance and sensation of an oily grease.

The conditions under which the extrusion may be carried out are described in patent application FR94/00756, the disclosure of which is specifically incorporated into the present application by way of reference.

The invention is illustrated in greater detail in the concrete examples which follow, without any limitation being implied.

A lip composition in smooth paste form and having the following composition was prepared:

The hydrophilic and lipophilic phases were introduced separately into a twin-screw extruder, at an inlet temperature of about 85.degree.-95.degree. C. and an outlet temperature of 30.degree. C. The screw speed was set at about 400 revolutions/minute.

A smooth paste of viscosity equal to 13 Pa s was obtained at the outlet, in the form of a single, stable and homogeneous phase, and which could be taken up for application using a brush. This composition made it possible to obtain a homogeneous film which spread easily and was very soft. The film obtained also had a light texture and was comfortable to wear throughout the day.

A lip composition in smooth paste form and having the following composition was prepared:

The composition was prepared according to Example 1. A homogeneous composition which has good cosmetic properties was obtained.

A treating base for the lips, in smooth paste form and having the following composition, was prepared according to Example 1:

The composition was in the form of a single homogeneous phase and had good cosmetic properties, a certain level of softness on application and good moisturizing properties.

A composition was prepared according to Example 1, comprising:

A composition in the form of a single, stable and homogeneous phase was obtained. It allowed a homogeneous film which spreads easily to be obtained.

A composition was prepared according to Example 1, comprising:

A composition in the form of a single, stable and homogeneous phase which has good cosmetic properties was obtained.

A lip composition in standard smooth paste form and having the following composition was prepared:

The various ingredients were mixed together at 100.degree. C. using a Moritz-type stirrer. A heterogeneous mixture which was in two phases was obtained. It was not possible to obtain a homogeneous dispersion with this process. If the wax content was increased, for example to 8%, it was still not possible to obtain a homogeneous mixture.