Drug – bio-affecting and body treating compositions – Topical sun or radiation screening – or tanning preparations
Reexamination Certificate
2000-04-04
2001-03-06
Dodson, Shelley A. (Department: 1616)
Drug, bio-affecting and body treating compositions
Topical sun or radiation screening, or tanning preparations
C424S060000, C424S078020, C424S078030, C424S078080, C424S400000, C514S937000, C514S938000, C514S939000, C514S943000
Reexamination Certificate
active
06197283
ABSTRACT:
The invention relates to the use of W/O emulsions comprising crosslinked, water-swellable polymers dispersed therein as thickeners in cosmetic or pharmaceutical formulations. It also relates to W/O emulsions and to cosmetic and pharmaceutical formulations.
When formulating cosmetic or pharmaceutical preparations such as skin creams, skin lotions, gels and other cosmetic beauty products, and pharmaceutical skin preparations as well, use is made of crosslinked acrylic acid polymer stabilizers that are known under the CTFA name Carbomer. These polymers are precipitation polymers and constitute free-flowing powders which are neutralized following their incorporation into water by stirring. This neutralization step is necessary to convert the acidic polymers into the carboxylates, which are ultimately responsible for the rise in viscosity and hence the stabilization of the formulation. Disadvantages of these pulverulent polymers are their dustiness and, associated therewith, their poor wettability, which prolongs the period required for homogenization. It is not possible to rule out small amounts of residual solvent from the preparation process.
A nondusting polymer is described in EP 383 057. That patent relates to crosslinked acrylic acid polymers which include nitrile-containing comonomers and are prepared in a water/paraffin emulsion; the water is removed by distillation as an azeotrope. The emulsions described are employed in the printing of textiles, and are unsuitable for use in cosmetic products.
DE 35 22 419 describes the inverse emulsion polymerization of acrylamide with acrylic acid in one process step. The pH is in the alkaline range and is therefore unfavorable for cosmetic purposes, especially for skin applications.
A process for preparing water-soluble or water-swellable polymers in a W/O emulsion is claimed by EP 126 528, which comprises olymerizing the water-soluble monomers in the presence of emulsifiers and with addition of a specific dispersing system consisting of alkanols. The polymers are not intended for cosmetic applications.
Crosslinked acrylic acid polymers in a W/O emulsion are described, furthermore, in EP 297 184 as water absorbents. The degree of crosslinking is not more than 0.5 mol-%; an inverting agent is present. The concentration of emulsifiers is at least 5% of the total dispersion. The polymerization is started by oil-soluble initiators. Examples of the oil component used are olive oil and eucalyptus oil—in other words, oils which are unsaturated, and hence unstable, or have a strong odor.
DE 42 17 673 A1 discloses electrolyte-thickenable surfactant combinations as a base for cosmetic formulations. The surfactants and electrolytes necessary here for the thickening effect are disadvantageous for certain applications.
WO 95/35089 describes compositions which can be applied topically and which comprise a thickener. The thickener is a W/O emulsion with a crosslinked polymer and a volatile oil, such as a silicone or an isoparaffin, as organic phase.
EP 503 853 discloses water-soluble thickeners for cosmetic formulations, comprising a very specific comonomer (AMPS).
It is an object of the present invention to provide polymers which do not have the disadvantages of the powder products and which do permit simple formulation of cosmetic or dermatological preparations: good efficacy, easy wettability, self-inverting, able to be used without an additional neutralizing step, and giving a pH of 6-7. The end product should have a smooth appearance and in the case of skincare products should “break” easily on the skin.
We have found that this object is achieved by the use of W/O emulsions comprising dispersed therein crosslinked, water-swellable polymers consisting of
a) 35-100% by weight of ionic monomers,
b) 0-65% by weight of nonionic monomers,
c) 0.3-1 mol-%, based on a) and b), of at least one at least bifunctional monomer,
where the oil phase consists of one or more fatty acid esters, as thickeners in cosmetic or pharmaceutical formulations.
It is preferred to use W/O emulsions whose oil phase consists of polyglycerol fatty acid esters, especially fatty acid esters of a polyglycerol mixture, comprising di- and triglycerol, with caprylic and/or capric acid.
The invention additionally provides W/O emulsions comprising dispersed therein crosslinked, water-swellable polymers consisting of
a) 35-100% by weight of ionic monomers,
b) 0-65% by weight of nonionic monomers,
c) 0.3-1 mol-%, based on a) and b), of at least one at least bifunctional monomer, and
where the oil phase consists of one or more polyglycerol fatty acid esters of a polyglycerol mixture comprising diglycerol and triglycerol with fatty acid mixtures comprising caprylic and/or capric acid.
The invention also provides cosmetic or pharmaceutical formulations comprising a W/O emulsion comprising dispersed therein crosslinked, water-swellable polymers consisting of
a) 35-100% by weight of ionic monomers,
b) 0-65% by weight of nonionic monomers,
c) 0.3-1 mol-%, based on a) and b), of at least one at least bifunctional monomer, and
where the oil phase consists of one or more polyglycerol fatty acid esters.
The preferred end use of the W/O emulsions is in cosmetic formulations for skin or hair.
The W/O polymer dispersion described in the present invention is prepared by inverse emulsion polymerization. In the first step, an aqueous monomer solution is emulsified in an oil phase with W/O emulsifiers typical of these systems. The polymerization is started by free-radical initiators. Since the polymers are intended to function as thickeners, they must be in chemically crosslinked form. The crosslinker is preferably added to the monomer solution.
As monomers it is preferred to employ unsaturated C
3
-C
5
carboxylic acids, such as acrylic acid, methacrylic acid, maleic acid (anhydride), fumaric acid (anhydride), itaconic acid or mixtures thereof. They can be homopolymerized or copolymerized with nonionic monomers. Suitable such compounds are unsaturated compounds which can be dissolved with the ionic monomers in water; examples thereof are acrylamide, methacrylamide, vinylpyrrolidone, vinylimidazole, vinylcaprolactam and hydroxyalkyl esters of carboxylic acids, such as hydroxyethyl acrylate. The proportion of ionic monomers in the overall monomer mixture is from 35 to 100%, preferably from 50 to 100%. Particular preference is given to an acrylic acid content of >90%.
From 5 to 80%, preferably from 10 to 50%, of the ionic monomers are in neutralized form. Neutralization can in principle be carried out using all bases which satisfy cosmetic requirements. Use is made preferably of triethanolamine, NaOH and tetrahydroxypropylethylenediamine, for example. Mixtures of bases are also possible.
The concentration of the monomers in the aqueous solution prior to polymerization is from 10 to 60%.
The polymer is crosslinked by copolymerizing the monomers with at least diunsaturated water- or oil-soluble compounds. Suitable such compounds are methylenebisacrylamide, divinylpyrrolidone, allyl (meth)acrylate, triallylamine, ethylene glycol diacrylates (up to 50 EO), (meth)acrylic esters of dihydric or higher polyhydric alcohols, such as trimethylolpropane triacrylate or pentaerythritol tetraacrylate; the alcohol functions can in this case carry up to 50 EO groups and can each have different degrees of ethoxylation. These crosslinkers are present in amounts of from 0.3 to 1 mol-% individually or as a mixture. Water-soluble crosslinkers are preferred.
The oil phase consists of one or more fatty acid esters. These components of the invention have a positive effect on the cosmetic formulation (appearance, sensation on the skin). Examples of such components are fatty acid isopropyl esters, such as isopropyl palmitate or isopropyl myristate, or polyglycerides of fatty acids, especially fatty acid mixtures comprising at least 50% of caprylic and/or capric acid. Preference is given to polyglycerol fatty acid esters based on a polyglycerol mixture comprising essentially mono-, di-, tri- and tetraglycerol, especially di- and
Rubenacker Martin
Schehlmann Volker
Tiefensee Kristin
BASF - Aktiengesellschaft
Dodson Shelley A.
Keil & Weinkauf
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