Aqueous dispersion of polymer particles, film-forming composition containing same and uses thereof

Abstract

The present invention concerns an aqueous dispersion of multiphase polymer particles in which the polymer particles comprise at least two separate phases, the internal phase being formed by polymerization in the presence of a crosslinking agent, said dispersion further comprising a surfactant chosen from amino acid derivatives. The invention also concerns a film-forming composition comprising said aqueous dispersion of polymer particles. The invention also relates to a film obtained after application of said film-forming composition. This film dries very quickly, is water resistant, and has good adhesion, elasticity and breaking strength properties. The invention also concerns the use of said film for protecting surfaces of the skin or mucous membranes, wounds, injuries and/or skin disorders.

Claims

1. An aqueous dispersion of multiphase polymer particles in which the polymer particles comprise at least two distinct phases: a first phase formed by a polymer P.sub.1 of soft nature having a glass transition temperature (Tg.sub.1) of less than 20 C., a second phase formed by a polymer P.sub.2 of hard nature having a glass transition temperature (Tg.sub.2) of greater than 60 C., said dispersion comprising a surfactant chosen from amino acid derivatives and in which polymer P.sub.1 is a crosslinked polymer formed by polymerization in the presence of a crosslinking agent, and wherein polymer P.sub.2 comprises at least 95% by weight of until obtained by polymerization of hydrophobic monomers, and wherein the surfactant derived from amino acids is chosen from sarcosinic acid derivatives and glutamic acid derivatives.

2. The aqueous dispersion as claimed in claim 1, wherein the phase formed by polymer P.sub.1 of soft nature is the internal phase of the particle and the phase formed by polymer P.sub.2 of hard nature is the external phase of the particle.

3. The aqueous dispersion as claimed in claim 1, wherein the multiphase polymer particles are substantially spherical and exhibit a diameter of between 15 and 300 nanometers.

4. The aqueous dispersion as claimed in claim 1, wherein polymer P.sub.1 represents from 60% to 90% by weight of the particles and polymer P.sub.2 represents from 10% to 40% by weight of the particles.

5. The aqueous dispersion as claimed in claim 1, wherein polymer P.sub.1 comprises: from 90% to 99.5% by weight of units obtained by polymerization of at least one monomer chosen from group (I) comprising (C.sub.1-C.sub.16)alkyl esters of (meth)acrylic acid, hydroxyalkyl esters of (meth)acrylic acid, vinyl esters of linear or branched carboxylic acids, styrene, alkylstyrenes, haloalkylstyrenes, (meth)acrylamide, acrylonitrile, vinyl chloride, (meth)acrylic acids and their derivatives, monomers comprising acidic or basic functional groups, silanated (meth)acrylic or vinyl monomers, monomers comprising acetoacetoxy groups, and mixtures thereof; and from 0.5% to 10% by weight of units obtained by polymerization of a crosslinking agent.

6. The aqueous dispersion as claimed in claim 5, wherein the crosslinking agent is chosen from group (II) comprising allyl or (C.sub.1-C.sub.16)alkyl esters of monocarboxylic or dicarboxylic acids, conjugated dienes, polyol poly(meth)acrylates, polyvinylbenzenes, polyallyl derivatives, and mixtures thereof.

7. The aqueous dispersion as claimed in claim 1, wherein polymer P.sub.2 comprises from 95% to 99.5% by weight of units obtained by polymerization of at least one monomer chosen from group (I) as defined in claim 5.

8. The aqueous dispersion as claimed in claim 5, wherein the monomers of group (I) of polymer P.sub.1 are chosen from butyl acrylate, methyl methacrylate and mixtures thereof.

9. The aqueous dispersion as claimed in claim 6, wherein the crosslinking agents of group (II) of polymer P.sub.1 are chosen from diallyl maleate, dimethyl maleate, 1,4-butanediol diacrylate and mixtures thereof.

10. The aqueous dispersion as claimed in claim 7, wherein the monomer of group (I) of polymer P.sub.2 is methyl methacrylate.

11. The aqueous dispersion as claimed in claim 1, wherein polymer P.sub.2 comprises 100% by weight of units obtained by polymerization of hydrophobic monomers.

12. The aqueous dispersion as claimed in claim 1, wherein the surfactant derived from amino acids is chosen from sodium N-lauroylglutamate, disodium N-cocoylglutamate, sodium N-cocoylglutamate, sodium N-lauroylsarcosinate, sodium N-myristoylsarcosinate, sodium N-cocoylsarcosinate, sodium N-oleoylsarcosinate, ammonium N-lauroylsarcosinate and mixtures thereof.

13. The aqueous dispersion as claimed in claim 1, wherein the concentration of the surfactant is between 0.1% and 5% by weight, based on the weight of dry matter of the aqueous dispersion.

14. The aqueous dispersion as claimed in claim 1, wherein the pH of the aqueous dispersion is greater than one unit above the pKa of the surfactant used.

15. The aqueous dispersion as claimed in claim 1, wherein it comprises an active agent chosen from antibacterial agents, antiseptics, antivirals, antifungal agents, painkillers, anti-inflammatories, agents which promote healing, hydrating agents, depigmenting agents, keratolytic agents, restructuring agents, anesthetics and sunscreens.

16. The aqueous dispersion as claimed in claim 15, wherein the active agent is incorporated in an internal phase or in an external phase of the multiphase polymer particles.

17. A film-forming composition comprising, in a physiologically acceptable medium, an aqueous dispersion of multiphase polymer particles as claimed in claim 1.

18. The film-forming composition as claimed in claim 17, wherein it comprises a pharmaceutical agent chosen from antibacterial agents, antiseptics, antivirals, antifungal agents, painkillers, anti-inflammatories, agents which promote healing, hydrating agents, depigmenting agents, keratolytic agents, restructuring agents, anesthetics and sunscreens.

19. A process for protecting surfaces of the skin, mucous membranes, wounds, lesions and/or skin conditions comprising applying the film-forming composition as defined in claim 17 to the surface that is to be protected.

Description

EXAMPLES

(1) The following abbreviations are used in the examples:

(2) MMA: methyl methacrylate

(3) BuA: n-butyl acrylate

(4) BDA: 1,4-butanediol diacrylate

(5) DAM: diallyl maleate

(6) SB: sodium bisulfite

(7) KPS: potassium persulfate

(8) SFS: sodium formaldehydesulfoxylate

(9) APS: ammonium persulfate

(10) Preparation A:

(11) 0.49 g of Na.sub.2HPO.sub.4 is placed in a 250 ml container and demineralized water is added so as to obtain 150 g of aqueous solution.

(12) Preparation B:

(13) 2.8% by weight aqueous solution of the initiator SB (sodium bisulfite).

(14) Preparation C (Surfactant: Sodium N-Lauroylsarcosinate):

(15) 54.2 g of BuA (423 mmol), 23.2 g of MMA (232 mmol), 0.8 g of crosslinking agent BDA (4 mmol) and 17 g of a 10% by weight aqueous solution of sodium N-lauroylsarcosinate (Schill+Seilacher GmbH, Perlastan L30) are introduced into a flat-bottomed glass container (internal diameter 55 mm) equipped with a magnetic stirrer (length 50 mm). The medium is stirred at 600 rpm until emulsified, i.e. for at least 5 minutes.

(16) Preparation D (Surfactant: Sodium Dodecyl Sulfate):

(17) 54.2 g of BuA (423 mmol), 23.2 g of MMA (232 mmol), 0.8 g of crosslinking agent BDA (4 mmol) and 17 g of a 10% by weight aqueous solution of sodium dodecyl sulfate (SDS, Aldrich) are introduced into a flat-bottomed glass container (internal diameter 55 mm) equipped with a magnetic stirrer (length 50 mm). The medium is stirred at 600 rpm until emulsified, i.e. for at least 5 minutes.

(18) Preparation E (Sunscreen: Parsol MCX):

(19) 54.2 g of BuA (423 mmol), 23.2 g of MMA (232 mmol), 0.8 g of crosslinking agent BDA (4 mmol), 3.96 g of ethylhexyl methoxycinnamate (Parsol MCX) and 17 g of a 10% by weight aqueous solution of sodium N-lauroylsarcosinate (Schill+Seilacher GmbH, Perlastan L30) are introduced into a flat-bottomed glass container (internal diameter 55 mm) equipped with a magnetic stirrer (length 50 mm) and protected from the light by aluminum foil. The medium is stirred at 600 rpm until emulsified, i.e. for at least 5 minutes.

(20) Preparation F:

(21) 1.36 g of BuA (10.61 mmol), 3.37 g of MMA (33.66 mmol), 0.3 g of crosslinking agent DAM (1.53 mmol) and 0.49 g of preparation B (i.e., 0.136 mmol of initiator SB) are introduced into a flat-bottomed glass container (internal diameter 30 mm) equipped with a magnetic stirrer (length 20 mm). The medium is stirred at 600 rpm until emulsified, i.e. for at least 5 minutes.

(22) Preparation G:

(23) 11.71 g of MMA (117 mmol) and 3.82 g of water are introduced into a flat-bottomed glass container (internal diameter 30 mm) equipped with a magnetic stirrer (length 20 mm). The medium is stirred at 600 rpm until emulsified, i.e. for at least 5 minutes.

(24) Preparation H (Sunscreen: Parsol MCX):

(25) 11.71 g of MMA (117 mmol), 3.61 g of Parsol MCX and 3.82 g of water are introduced into a flat-bottomed glass container (internal diameter 30 mm) equipped with a magnetic stirrer (length 20 mm) and protected from the light by aluminum foil. The medium is stirred at 600 rpm until emulsified, i.e. for at least 5 minutes.

Example 1: (Comparative) Preparation of an Aqueous Dispersion of Monophase Polymer Particles with a Surfactant Derived from Amino Acid

(26) 115 g of preparation A (i.e., 2.65 mmol of Na.sub.2HPO.sub.4) are introduced into a round-bottomed reactor with an internal diameter of 100 mm equipped with an anchor-shaped glass stirrer and degassed beforehand with nitrogen, followed by an introduction under nitrogen of preparation C.

(27) The reaction temperature is adjusted to 70 C. using an external oil bath of adjustable height and the mixture is stirred at 260 rpm under nitrogen. 10 minutes after the end of the addition, 2.62 g of preparation B (i.e., in moles, 0.73 mmol of initiator) are introduced dropwise into the mixture at a fixed rate over five minutes. Then, after stirring for a further ten minutes, 0.34 g of KPS (1.25 mmol) in solution in 7.7 g of demineralized water are added to the mixture via a peristaltic pump over a period of time of 2 minutes. After one hour, the reaction mixture is cooled, still with stirring. The emulsion obtained (referred to as emulsion 1) is collected in a container as soon as the temperature is less than 35 C.

Example 2: Preparation of an Aqueous Dispersion of Multiphase Polymer Particles with a Surfactant Derived from Amino Acid According to the Invention

(28) 150 g of emulsion 1 are placed at 70 C., under nitrogen and with stirring as above, in the reactor described above. The preparation F is then added by means of a peristaltic pump over a period of time of 2 minutes. 0.015 g of KPS (0.055 mmol) dissolved in 0.7 g of demineralized water is then introduced by means of a peristaltic pump over a period of time of 10 minutes. Stirring is maintained at 70 C. for 60 minutes, then 2.20 g of a 1.74% by weight aqueous solution of SFS (i.e., 0.25 mmol of SFS) are added in one minute using a peristaltic pump and then, in parallel, using two peristaltic pumps, the preparation G and 10 g of a 0.5% by weight aqueous solution of ammonium persulfate (i.e., 0.22 mmol of APS) are added over a period of 15 minutes. After addition, the temperature of the reactor is maintained at 70 C. for 30 minutes. After this, the remaining reactive entities are deactivated by adding a mixture of 0.46 g of an aqueous ammonium persulfate solution (15.61% by weight) and 0.32 g of an aqueous SB solution (2.8% by weight). The reaction is thus maintained at 70 C. for 30 minutes. Stirring is then maintained but heating is halted by lowering the oil bath. The emulsion (referred to as emulsion 2) is collected as soon as the temperature is less than 35 C.

Example 3: (Comparative) Preparation of an Aqueous Dispersion of Multiphase Polymer Particles with the Surfactant Sodium Dodecyl Sulfate

(29) The procedure of example 1 is followed but using the preparation D instead of the preparation C. An emulsion 3 is obtained and is converted into emulsion 4 by following the procedure of example 2.

Example 4: Comparison of the Emulsions of Examples 1 to 3

Comparison of the Particle Sizes

(30) Measurements by DLS (Dynamic Light Scattering) were carried out using an ALV/CGS3 goniometer equipped with an ALV/LSE 5004 multi-T correlator and with an HeNe laser at a wavelength of 632.8 nm. The measurements were carried out on samples with a diameter of 10 mm over seven scattering angles ranging from 60 to 120 with an incrementation of 10. The system was maintained at 23 C. Each sample was prepared as follows: 20 ml of Milli-Q water, filtered twice through a syringe filter with a porosity of 0.22 m, are placed in a glass flask. 5 l of emulsion are injected therein using a micropipette. These samples are then analyzed in sequences of 100 seconds for each angle value; the data collected are then processed by cumulant analysis.

(31) In emulsion 1, the particles are spherical and have a mean diameter of approximately 36-38 nm, measured by DLS.

(32) Emulsion 2 has a pH of between 6 and 7 and the dry matter portion is approximately 40%. The dispersed polymer particles are spherical and have a mean diameter of approximately 38-42 nanometers, measured by DLS. The phase of soft nature of the particles, composed of a mixture of butyl acrylate and methyl methacrylate, represents approximately 80% of the total weight of the particles and the phase of hard nature, composed of methyl methacrylate, represents approximately 20% of the total weight of the particles.

(33) In emulsion 4, the particles are spherical and have a mean diameter of approximately 47-49 nm, measured by DLS.

(34) Comparison of the Mechanical Properties of the Thick Films Obtained with Emulsion 1 (Comparative), Emulsion 2 (According to the Invention) and Emulsion 4 (Comparative)

(35) Films with a thickness of approximately 0.7 mm are obtained by evaporating a column of emulsion 2 with a height of approximately 2 mm in a Teflon mold. Dumbbells of DIN 53504S3A shape (working length 12 mm, width 2 mm) corresponding to the standard ISO 527-3 are obtained by punching the sheet with a thickness of approximately 0.7 mm using a hollow punch.

(36) The mechanical measurements are carried out at a drawing rate of 10 mm/min using an Instron tensile testing device equipped with a 500N force sensor and gave the following results:

(37) Dynamic mechanical analysis (DMA) measurements are carried out, starting from rectangular samples with dimensions of 10 mm25 mm cut out from the same film, using a DMA 2980 analyzer (TA Instruments) in the in-tension geometry of films by applying a pretension of 0.01N and operating at 1 Hz. The Tg values are the temperatures at which the dissipation factor tan(delta) passes through a maximum.

(38) These values are measured at the first heating at 3 C./min on films not preheated.

(39) The films obtained with emulsion 1 exhibit the following characteristics: Breaking stress: 0.25 MPa Tg.sub.1=5 C.

(40) The films obtained with emulsion 2 exhibit the following characteristics: Elongational elastic modulus: 48 MPa Yield point: 2.6 MPa Breaking stress: 3.7 MPa Nominal strain at break: 250% The measurement of strain by video extensiometry showed that the strain at break is greater than 150% Tg.sub.1=3 C., Tg.sub.2=70 C.

(41) The films obtained with emulsion 4 exhibit the following characteristics: Breaking stress: 0.85 MPa

(42) The mechanical measurements carried out on the films obtained with emulsion 1 show that the films break for a lower stress, of the order of 0.25 MPa, than the films obtained with emulsion 2 according to the invention. Furthermore, for the films obtained with emulsion 1, plastic strain is observed even for low applied stresses.

(43) This example shows that the films produced from monophase particles (emulsion 1) have inferior mechanical properties to those obtained from particles of multiphase structure according to the invention (emulsion 2).

(44) The mechanical measurements carried out on the films obtained with emulsion 4 show that the films break for a lower stress, of the order of 0.85 MPa, than the films obtained with emulsion 2 according to the invention. Furthermore, for the films obtained with emulsion 4, plastic strain is observed even for low applied stresses.

(45) This example also shows that the films produced from multiphase particles have superior mechanical properties when an amino acid derivative, such as sodium N-lauroylsarcosinate, is used as surfactant instead of SDS, as in the prior art.

Example 5: Incorporation of Active Agent after Polymerization (Free in Solution)

(46) A sample of 8 g of emulsion 2 (example 2) is centrifuged at 14 000 rpm (r=0.08 m), i.e. a radial acceleration of 17 500 g, for 1 hour at 40 C. The pellet is retained and the supernatant is removed and replaced with 16.11 ml of ethanol and 9.7 microliters of a 0.07M solution of Parsol MCX (ethylhexyl methoxycinnamate) in ethanol, i.e. an initial concentration of 43.3 micromol/liter. After standing for 24 hours sheltered from light, the emulsion is centrifuged again under the same conditions. The analysis of the supernatant by ultraviolet spectrometry gives, at 308 nm, an absorbance of 0.325. At the same wavelength, standard solutions of 2.78 micromol/liter and 4.48 micromol/liter of Parsol MCX in ethanol have absorbances of 0.317 and 0.345 respectively.

Example 6: Incorporation of Active Agent in the Internal Phase of the Polymer Particles

(47) The procedure of example 1 is followed, except that preparation E is used instead of preparation C and that the reactor and the flasks are protected from light with aluminum foil. The resulting emulsion is subsequently converted according to the procedure of example 2 while protecting the reactor and the flasks from light with aluminum foil.

(48) The size of the particles of the emulsion obtained, measured by light scattering (DLS), is approximately 36-38 nm.

Example 7: Incorporation of Active Agent in the External Phase of the Polymer Particles

(49) The procedure of example 2 is followed, except that preparation H is used instead of preparation G and that the reactor and the flasks are protected from light with aluminum foil.

(50) The final size of the particles, measured by light scattering (DLS), is approximately 40-44 nm.

(51) A film is produced from this emulsion under conditions identical to those of example 4 but sheltered from light.

(52) The Tg values, measured in the same way as in example 4, are:

(53) Tg.sub.1=8 C., Tg.sub.2=55 C.

(54) The mechanical properties, measured in the same way as in example 4, give the following results:

(55) Elongational elastic modulus: 10 MPa

(56) Yield point: 1 MPa

(57) Breaking stress: 2.1 MPa

(58) Nominal strain at break: 250%

Example 8: Comparative Measurement of the Transmittance of the Films Formed from the Emulsions of Examples 2 and 7

(59) The transmittance of the film obtained in example 7 is measured in the visible region at 530 nm and in the UVB region at 308 nm using a Jasco V-530 spectrometer, the film being placed as close as possible to the detector. The same measurement is carried out on a control film devoid of sunscreen produced according to example 2.

(60) The following results are obtained:

(61) TABLE-US-00001 Transmittance Transmittance Film at 308 nm at 530 nm According to example 2 49% 77% According to example 7 0.07% 80%

Example 9: Application of the Film-Forming Composition According to the Invention

(62) The film-forming composition of example 2 is applied with a brush, in a single layer of 150 m, to a clean and dry skin surface of 3 cm.sup.2.

(63) After two minutes, the water is completely evaporated and the skin is covered with a film which is elastic, which adheres to the skin for several hours, which is not tacky and which resists water, in particular several hand washing operations.