WO2019193182A1

WO2019193182A1 - Oil in water emulsion forming a shape memory cream

Info

Publication number: WO2019193182A1
Application number: PCT/EP2019/058703
Authority: WO
Inventors: Cecile MULLER
Original assignee: Sederma
Priority date: 2018-04-06
Filing date: 2019-04-05
Publication date: 2019-10-10
Also published as: FR3079745A1; FR3079745B1

Abstract

The emulsion comprises, in particular, as a rheology modifier, a copolymer of acrylate and/or methacrylate monomers having acrylate and/or methacrylate side chains esterified with a polyalkoxylated C12-C30 fatty alcohol, for example the beheneth-25 acrylate and methacrylate copolymer, one or more emulsifiers, preferably of sorbitan type (poly)alkoxylated and (poly)esterified with a C8-C30 fatty carboxylic acid and/or of sorbitan and/or sorbitol type (poly)esterified with a C8-C30 fatty carboxylic acid, and one or more esters, natural or synthetic, of C12-C30 fatty alcohol in the form of an oil, in precise proportions and pH, for obtaining an original texture similar to an opaque aqueous balm with shape memory.

Description

OIL IN WATER EMULSION FORMING A SHAPE MEMORY CREAM

TECHNICAL FIELD

The subject of the present invention is an oil-in- water (O/W) emulsion forming a shape memory cream and a method for producing this emulsion.

It relates more particularly to the field of cosmetics and dermatology but can be applied to any other field using this type of formula, such as food or paints.

PRIOR ART

A shape memory cream is a low-viscosity cream, most often a transparent gel or a continuous phase-water emulsion (O/W), whose smooth surface shape is deformed after being sampled and then is reformed over time, returning to its original smooth texture as if it had not served (the surface of the pot becoming again flat). When a small force is applied to the cream, at the time of sampling in its pot, by mixing and/or simply via application on the skin, the cream becomes easily spreadable. Then, over time, a film of cream is reformed on the skin fitting the application site with a "filling" and "lifting" effect.

For this purpose, an agent capable of modifying the rheology of the emulsion is used, that is to say an agent capable of modifying the flow or deformation of the formula under the effect of the stresses applied to it.

For a shape memory cream, the rheology modifier must contribute to produce a final formula whose shear strength, and thus the viscosity, can change very strongly between rest and use.

This technical effect can for example be obtained by using a copolymer functionalized by the presence of different side chains capable of interacting with each other under certain conditions. Such interaction, in addition to a certain degree of crosslinking, will give the copolymer a three-dimensional network structure and thus give the formula a high shear rate, and when this network structure is modified by the application of an external force, the shear rate of the formula will greatly decrease.

For example, a copolymer of acrylate and/or methacrylate monomers has been proposed, having acrylate and/or methacrylate side chains which are esterified for example with a polyalkoxylated fatty alcohol (-(0-(CH₂)_n)_n -0C_n H2_n”+l). In aqueous or ionic solution, the anionic acrylate and/or methacrylate chains will repel each other while the long chains of alkoxylated fatty alcohol will associate themselves to form micelles, creating a three- dimensional network under weak reversible bonds, together with the swelling of the emulsion particles themselves.

A copolymer of this type (INCI name: Acrylates/Beheneth-25 Methacrylate Copolymer) is sold for example under the trade name Volarest™ FL by the CRODA company, Aculyn™ 28 Polymer and Aculyn™ 28P Polymer by the DOW CHEMICAL company, Rheostyl™ 90 N and Rheostyl™ 10 SH by the COATEX company, Novethix™ L-10 Polymer by the Lubrizol company, Euro flow 100 by the EOC Surfactants company or Tinovis GTC by the BASF company. This copolymer comprises a mixture of anionic acrylate and methacrylate monomers, with certain of the methacrylates being esterified to form the beheneth-25 fatty side chains, that is to say side chains of the formula -(O-CH2- CH₂)₂₅-0-(CH₂)_2i-CH₃, with n=2 (a polyethoxylated fatty alcohol), n=25 on average and n'=21), and certain of the acrylates and/or methacrylates being in the form of simple esters (C1-4). The proportion of methacrylate monomers having a beheneth-25 side chain is generally less than 10% in weight based on the total weight of the other monomers forming the copolymer.

Typically, an O/W emulsion shape memory cream, known from the state of the art and including this copolymer, will be formed of at least:

- an aqueous phase containing the copolymer, one or more humectants and one or more emulsifiers;

- a fatty phase containing one or more emollients and one or more emulsifiers;

- optionally, active agents distributed in the appropriate phase according to their hydrophilic or hydrophobic nature;

- a pH adjuster, and

- optionally one or more preservatives, antioxidants, antifungals, dyes, perfumes or any other suitable additive;

with the weight of emollient (forming the base of the fatty phase) generally representing about 10% of the final weight of the formula. The emollients used are generally fatty alcohol esters of natural origin (vegetable) or synthetic origin in the form of oils (fats that are fluid at room temperature). These emulsifiers are also selected so as to obtain a "soft" (elastic)“thread forming” cream having a viscosity of about 75000 Cps (10 ³ Pa.s) ± 10%. SUMMARY OF THE INVENTION

The subject matter of the present invention is a new formula for an O/W type emulsion shape memory cream having original characteristics in terms of rigidity and elasticity.

According to a first object, the present invention provides an O/W type emulsion, with shape memory, constituted in weight % relative to the total weight of the emulsion of:

- in the aqueous phase:

o 0.2 to 1% in weight of a copolymer of acrylate and/or methacrylate monomers having acrylate and/or methacrylate side chains being esterified with a polyalkoxylated Cl 2 -C30 fatty alcohol, as rheology modifier;

o 3.00% to 15.00% in weight of one or more humectants;

o 1% to 5% in weight of one or more emulsifiers;

o water

- in the fatty phase:

o 1.00% to 5.00% in weight of one or more esters, natural or synthetic, of C12- C30 fatty alcohol in the form of oil, as emollient;

the water in the aqueous phase being in sufficient weight quantity so that the total weight of the composition be 100% (qsp 100%);

a pH adjuster being present in a weight amount such that the pH of the emulsion being between 6.00 and 7.00; and

optionally one or more water-soluble or liposoluble active agents in the appropriate phase, preservatives, antioxidants, antifungal agents, dyes, perfumes, flakes or other additive.

In the present description, all indicated percentages in weight are relative to the total weight of the emulsion, unless otherwise specified. All indicated physical measurements are taken at room temperature (+/- 20°C). Viscosity measurements are made with a Brookfield DV- I Prime viscometer (SP93 needle, 2.5 rpm speed, lmm, at 25°C).

According to the invention, the term "fatty alcohol" means a C12-C30 alcohol, preferably C16-C26 alcohol, more preferably C18-C22 alcohol.

According to the invention, the term "fatty carboxylic acid" means a C8-C30 carboxylic acid.

The formula according to the invention differs from the state of the art in addition to the choice of the nature of the rheology modifier, the emulsifiers and the emollient, in that it contains only a very small amount of emollient fatty phase, between 1 and 5% relative to the total weight of the composition. Thanks to this particular formula an opaque shape memory cream is obtained, which has no elasticity, and which breaks as if it were hard. Its viscosity is high, at least 100,000 Cps (10³ Pa.s) measured at room temperature. Real pieces can be sampled. The cream has the consistency of a balm but instead of being traditionally greasy/waxy would be watery. It also has the characteristics of a shape memory cream: it regains its smooth surface shape after a piece is taken (after a few hours) and is softened so that it can be applied to the skin on which it will then form a smoothing film fitting the skin relief.

Preferably, according to the invention, the rheological modifier copolymer is a copolymer of acrylates and methacrylates esterified with a polyalkoxylated fatty alcohol having on average from 15 to 35 alkoxy units, more preferably from 20 to 30 alkoxy units.

Also preferably, the copolymer is acrylates and methacrylates copolymer of polyethoxylated and/or polypropoxylated C12-C30 fatty alcohol (the alkoxy units being ethoxylated and/or propoxylated units), preferably polyethoxylated, and more preferably the copolymer is the copolymer of acrylates and methacrylates beheneth 25 as described above, more preferably the Volarest™FL, with a content of methacrylate side chains esterified with the beheneth 25 in weight % with regard to the weight of the non-esterified side chains (acrylates or methacrylates) being less than 10%.

The copolymer content in the emulsion according to the invention is preferably from 0.3 to 0.9%, more preferably from 0.5 to 0.75% in weight relative to the total weight of the emulsion.

Preferably according to the invention, the first emulsifier of the aqueous phase is a polyethoxylated emulsifier, preferably a polyethoxylated sorbitan, several of the alcohol sites, preferably all the sites, being ethoxylated and comprising several ethoxyl units, and mono-esterified with the C8-C30 fatty carboxylic acid, preferably in the 6-position on the primary alcohol.

Preferably, according to the invention, the emulsifier is of sorbitan type which is (poly)alkoxylated and (poly) esterified with a C8-C30 fatty carboxylic acid, and/or of sorbitan and/or sorbitol type which is (poly)esterified with a C8-C30 fatty carboxylic acid.

More preferably, the sorbitan type emulsifier which is (poly)alkoxylated and (poly)esterified with a C8-C30 fatty carboxylic acid is the polyoxyethylene sorbitan monostearate having the following formula (1NC1 name: Polysorbate 60):

The content of the first emulsifier is preferably from 1 to 5%, more preferably from 2 to 3% in weight relative to the total weight of the emulsion.

Preferably, the sorbitan and/or sorbitol type emulsifier (poly)esterified with a C8-C30 fatty carboxylic acid is non-alkoxylated, more preferably based on monoesterified sorbityl and/or sorbitan, even more preferably constituted of a mixture of sorbityl stearate and sorbityl laurate. This type of non-alkoxylated emulsifier is used for the stability of the emulsion and contributes to obtaining the shape memory effect.

The content of sorbitan and/or sorbitol type emulsifier (poly)esterified with a C8-C30 fatty carboxylic acid is preferably 1 or 3% in weight relative to the total weight of the emulsion, preferably from 1 to 2% in weight.

Preferably, the formula according to the invention contains the three preferred emulsifiers in the following proportions (in weight % relative to the total weight of the emulsion):

- 0.5 to 3% in weight of polyoxyethylene sorbitan monostearate;

- 0.5 to 1.5% in weight of sorbitan stearate, and

- 0.5 to 1.5% in weight of sorbityl laurate.

Polyoxyethylene sorbitan monostearate (INCI name: Polysorbate 60) is sold under the trademark Tween™ 60 by Croda.

A mixture of sorbitan stearate and sorbityl laurate with substantially equal weight contents is sold under the trade name ARLACEL™ LC by Croda.

Preferably, the humectant(s) used are, according to the invention, chosen from glycol, pentylene glycol and glycerin, more preferably pentylene glycol.

Preferably the humectant content is from 3.00% to 5.00% in weight, preferably 3.00% in weight.

Preferably, according to the invention, the esters of vegetable or synthetic fatty alcohols in the form of oil forming the emollient are polar oils of monoesters, preferably volatile, preferably aromatic, more preferably benzoate monoesters, and even more preferably of C12-C15 alcohols esters. The benzoate monoesters are advantageously volatile oils and therefore are "dry" to the touch, which will contribute to forming a lightweight, non-greasy, non-sticky aqueous cream. A minimum presence of oil, at least 1% by weight is however necessary to form the emulsion and for obtaining the desired shape memory with a good maintening, and necessary for obtaining a pleasant touch (the binder). The amount of oil is preferably between 1 and 3%.

Preferably, the viscosity of the cream is adjusted to at least 110,000 Cps, more preferably at least 120,000 Cps.

According to a preferred example, it is provided an emulsion consisting of:

- 2.5% in weight of Volarest™ FL (INCI name: Acrylates / Beheneth-25 Methacrylate Copolymer), comprising about 0.75% of the shape memory copolymer;

- 1.70% in weight of Arlacel™ LC (INCI name: Sorbitan Stearate (and) Sorbityl Laurate);

- 2.00% in weight of Tween™ 60 (INCI name: Polysorbate 60);

- 3.00% in weight of Crodamol™AB (INCI name: C12-15 Alkyl Benzoate);

- 3.00% in weight of pentylene glycol;

- a pH adjuster in an amount such that the pH of the composition is between 6.10 and 0.5;

- deionized water in sufficient quantity for a total composition weight of 100% (qsp 100%); and

- optionally one or more water-soluble or lipo-soluble active agents in the appropriate phase, preservatives, antioxidants, antifungal agents, dyes, perfumes, glitters or other additive.

According to a second object, the present invention provides a method of manufacturing the emulsion according to the first object, characterized in that it comprises the steps of:

- forming an aqueous part A comprising:

o the shape memory copolymer;

o one or more humectants; and

o said at least one emulsifier;

- heating where necessary said part A to homogenize it to a liquid form;

- form a part B comprising the emollient;

- add part B into part A;

- form the emulsion under rapid stirring;

- adjust the pH between 6 and 7 using a pH adjuster; - optionally add one or more water-soluble active agents, preservatives, antioxidants, antifungal agents, dyes or perfumes.

Preferably, according to the method the formation of part A is divided into subsequent formation of two parts Al and A2 which are then rejoined, the method comprising:

- forming the part Al comprising the shape memory copolymer and a first emulsifier;

- If necessary, heat said part Al so as to homogenize it in liquid form;

- forming the part A2 comprising the humectant and a second emulsifier; and

- If necessary, heat said part A2 so as to homogenize it in liquid form.

Preferably, the first emulsifier added to part Al is the sorbitan type emulsifier (poly)alkoxylated and (poly)esterified with a C8-C30 fatty carboxylic acid, as defined above.

Also preferably, the second emulsifier added to part A2 is the sorbitan and/or sorbitol type emulsifier (poly)esterified with a C8-C30 fatty carboxylic acid, as defined above.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be better understood in the light of the following description of a non- limiting example.

For this formula example, the commercial ingredient Volarest™ FL is used as a rheology modifier. It comprises about 30% Beheneth-25 acrylate/methacrylate copolymer in an aqueous matrix.

The commercial ingredients Tween™ 60 and Arlacel™ LC are used as emulsifiers. Their constituents are pure in fluid "paste" form.

The commercial ingredient Crodamol™ AB is used as an emollient. It consists of a pure mixture of Cl 2- 15 alkyl benzoate.

Protocol

Weigh part A and mix. Heat Part A at 75°C in a water bath.

Weigh part B and mix.

Add Part B to Part A and stir for 30 min at 75°C with normal helix agitation (= 500 rpm). Weigh part C and heat it to 75°C in a water bath.

Add part C to parts A + B with vigorous stator stirring (= 1000 rpm)

Adjust the pH to 6.1 +/- 0.5.

The cream obtained is white and opaque, having a high viscosity of 120,000 cps (10 ³ Pa.s). It has a balm like appearance, solid with a flat upper surface in which one can dig with a small spatula to take a "piece" of cream. Unlike the wax-based balm, the initial shape of the cream is re-formed after a few hours at room temperature.

To the touch, the cream is light, fresh (because globally watery) and little sticky. It softens and can be applied and spread easily on the skin by the application of a slight stress. After a while, a real film of cream is formed on the skin covering its irregularities.

The following additional ingredients can be added to this formula:

- one or more preservatives: for example, 0.1% of potassium sorbate is added to part A and/or 0.80% of phenoxyethanol to part B;

- a perfume: for example, 0.10% added at the end of formulation;

- one or more hydrophilic cosmetic active agents: for example, added at the rate of a few% each at the end of the formulation; and/or

one or more lipophilic cosmetic active agents: for example, added at a level of a few% each in the emollient.

Claims

1. O/W type emulsion, with shape memory, constituted in weight % relative to the total weight of the emulsion of:

- in the aqueous phase:

o 3.00% to 15.00% in weight of one or more humectants;

o 1% to 5% in weight of one or more emulsifiers;

o water

- in the fatty phase:

2. Emulsion according to claim 1, characterized it presents a viscosity of at least

100 000 Cps (lO ³ Pa.s) at 25°C.

3. Emulsion according to claim 1 or 2, characterized in that the acrylates and/or

methacrylates side chains are esterified with a polyalcoxylated C12-C30 fatty alcohol having 15 to 35 alcoxy units.

4. Emulsion according to anyone of preceding claims, characterized in that the

copolymer is a polyethoxylated and/or polypropoxylated C12-C30 fatty alcohol acrylate and metacrylate copolymer.

5. Emulsion according to claim 4, characterized in that the copolymer is a beheneth-25 acrylate and methacrylate copolymer.

6. Emulsion according to anyone of preceding claims, characterized in that it comprises a sorbitan type emulsifier which is (poly)alcoxylated and (poly)esterified by a C8- C30 fatty carboxylic acid, and/or a sorbitan and/or sorbitol type emulsifier which is (poly)esterified with a C8-C30 fatty carboxylic acid.

7. Emulsion according to claim 6, characterized in that said sorbitan type emulsifier which is (poly)alcoxylated and (poly)esterified by a C8-C30 fatty carboxylic acid is a sorbitan type emulsifier which is monoesterified by a polyethoxylated C8-C30 fatty carboxylic acid.

8. Emulsion according to claim 7, characterized in that said emulsifier is the

polyoxyethylene sorbitan monostearate (Polysorbate 60).

9. Emulsion according to claims 6 to 8, characterized in that said sorbitan and/or

sorbitol type emulsifier which is (poly)esterified with a C8-C30 fatty carboxylic acid is a monoesterified sorbityl and/or sorbitan based emulsifier.

10. Emulsion according to claim 9, characterized in that said emulsifier is a mixture of sorbitan stearate and sorbityl laurate.

11. Emulsion according to anyone of claims 1 to 10, characterized in that the emollient is an aromatic monoester.

12. Emulsion according to claim 11, characterized in that the emollient is a fatty alcohol benzoate monoester.

13. Emulsion according to claim 12, characterized in that the emollient is a Cl 2- 15 alkyl benzoate.

14. Emulsion according to anyone of claims 1 to 13, characterized in that the oil content is 3% in weight.

15. Emulsion according to claim 1 consisting of: - 2.5% in weight of Volarest™ FL (INCI name: Acrylates / Beheneth-25 Methacrylate Copolymer), comprising about 0.75% of said rheology modifiying copolymer;

- 2.00% in weight of Tween™ 60 (INCI name: Polysorbate 60);

- 3.00% in weight of Crodamol™AB (INCI name: C12-15 Alkyl Benzoate);

- 3.00% in weight of pentylene glycol;

- a pH adjuster in an amount such that the pH of the composition is between 6.10 ± 0.5;

- deionized water in sufficient quantity for a total composition weight of 100%; and

16. A method of manufacturing the shape memory emulsion according to anyone of claims 1 to 15, characterized in that it comprises the steps of:

- forming an aqueous part A comprising:

o said rheology modifying copolymer;

o one or more humectants; and

o said at least one emulsifier;

- heating where necessary said part A to homogenize it to a liquid form;

- form a part B comprising the emollient;

- add part B into part A;

- form the emulsion under rapid stirring;

- adjust the pH between 6 and 7 using a pH adjuster;

- optionally add one or more water-soluble or lipo-soluble active agents in the

appropriate phase, preservatives, antioxidants, antifungal agents, dyes, perfumes, glitters or other additive.

17. Method according to claim 16, characterized in that the formation of part A is

divided into the subsequent formation of two parts A1 and 2 that are thereafter rejoined, the method comprising:

Forming part A1 comprising the shape memory copolymer and a first emulsifier; Heating where necessary said part A1 to homogenize it in liquid form;

Forming part A2 comprising the humectant and a second emulsifier; and Heating where necessary said part A2 to homogenize it in liquid form.

18. Method according to claim 17, characterized in that said first emulsifier added to part Al is the sorbitan type emulsifier which is (poly)alcoxylated and

(poly)esterified by a C8-C30 fatty carboxylic acid.

19. Method according to claim 17 or 18, characterized in that said second emulsifier added to part A2 is the sorbitan and/or sorbitol type emulsifier which is (poly)esterified by a C8-C30 fatty carboxylic acid.