Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Cosmetic – antiperspirant – dentifrice
Reexamination Certificate
2002-02-28
2004-01-27
Padmanabhan, Sreeni (Department: 1617)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Cosmetic, antiperspirant, dentifrice
C526S264000, C514S613000
Reexamination Certificate
active
06682750
ABSTRACT:
The present invention relates to surfactant-free cosmetic, pharmaceutical and dermatological compositions comprising crosslinked water-soluble or water-swellable copolymers based on acrylamidoalkylsulfonic acids and cyclic N-vinylcarboxamides and/or linear N-vinylcarboxamides.
Cosmetic skincare compositions primarily have the task of strengthening or restoring the natural function of the skin as a barrier against environmental influences (e.g. dirt, chemicals, microorganisms) and against the loss of endogenous substances (e.g. water, natural fats, electrolytes).
Another aim of skincare is to compensate for the loss of sebum and water from the skin caused by daily washing.
Medicinal formulations for the skin generally comprise one or more medicaments in an effective concentration.
The cosmetic or dermatological compositions currently used are mostly in the form of oil-in-water emulsions or water-in-oil emulsions.
Water-in-oil emulsions comprise a continuous oil phase and permit a fatty film to form on the surface of the skin which prevents transepidermal water loss and protects the skin against external aggressions.
Such emulsions are particularly suitable for protecting the skin and for the treatment of dry skin.
By contrast, oil-in-water emulsions impart to the skin upon application a soft, less greasy and pleasant feel.
The emulsions are generally stabilized by incorporating emulsifying surfactants of the oil-in-water (ONV) type or of the water-in-oil (W/O) type.
In order to achieve adequate stability of the emulsions, such surfactants must, however, in most cases be added in amounts up to 10% by weight, based on the total weight of the emulsions. Emulsions without surfactants generally exhibit inadequate stabilization of the oil components, which leads to coagulation and separation of the oil phases.
A disadvantage of using surfactants is that they can lead to irritation of the skin, the eyes and the scalp or, in individual cases, may even trigger an allergic reaction. Thus, for example, it is known that certain surfactants can trigger photodermatoses upon simultaneous exposure to sunlight. A further disadvantage is that high surfactant concentrations can lead to a rough, sticky or viscous feel of the compositions or make the compositions appear compact and heavy. Moreover, the surfactants have to be chosen depending on the polarity of the oils, meaning that the variety of formulations is limited.
The users of emulsions have therefore continually made efforts to reduce the surfactant content in order to improve the compatibility of the emulsions and to optimize their cosmetic properties.
Over the course of recent years, polymers which permit the formulation of low-surfactant and even surfactant-free emulsions have become established on the market (WO 96/37180 and U.S. Pat. No. 5,736,125). These polymers are hydrophobic modifications of conventional poly(meth)acrylates which have both thickening and also emulsifying/dispersing properties. Examples of commercial products are ®Pemulen TR-1 and TR-2 from BF-Goodrich and ®Aculyn 22 and ®Aculyn 28 from Rohm und Haas.
Since polymers hydrophobically modified in this way are constructed on the basis of (meth)acrylic acid, they subsequently have the disadvantages of poly(meth)acrylates. A significant disadvantage of thickeners based on poly(meth)acrylic acid is the considerable pH dependency of the thickening ability. Thus, an adequate viscosity is generally only brought about if the pH of the formulation is adjusted above pH 6.0 and thus the poly(meth)acrylic acid is present in neutralized form.
DE 44 25 268 describes emulsifier-free, finely disperse oil-in-water preparations which comprise acrylic acid polymers as thickeners, but which are likewise unsuitable for acidic formulations.
Surprisingly, it has now been found that crosslinked copolymers based on acrylamidoalkylsulfonic acid and cyclic N-vinylcarboxamides and/or cyclic N-vinylcarboxamides are highly suitable as thickener, stabilizer, dispersant and lubricant in surfactant-free cosmetic, dermatological and pharmaceutical compositions.
Advantageously, the copolymers exhibit very good thickening properties over a wide pH range, i.e. even at an acidic pH.
The invention thus provides surfactant-free cosmetic, dermatological and pharmaceutical compositions, comprising at least one copolymer consisting essentially of
a1) 1 to 50% by weight of the repeat structural unit of the formula (1)
where n is an integer from 2 to 9, or
a2) 1 to 50% by weight of a mixture of the repeat structural unit of the formula (1) and the repeat structural unit of the formula (2)
where R, R
1
and R
2
may be identical or different and are hydrogen or a linear or branched alkyl or alkenyl group having in each case 1 to 30, preferably 1 to 20, in particular 1 to 12, carbon atoms and
b) 49.99 to 98.99% by weight of the repeat structural unit of the formula (3)
in which R
3
is hydrogen, methyl or ethyl, Z is (C
1
-C
8
)-alkylene, n is an integer from 2 to 9 and X is an ammonium, alkali metal or alkaline earth metal ion and
c) 0.01 to 8% by weight of crosslinking structures which originate from monomers having at least two olefinic double bonds.
The mixing ratio with regard to structural unit a2) can vary within any desired limits.
Preferred copolymers comprise
2 to 30% by weight, particularly preferably 3 to 15% by weight, of the structural units a1) or a2), preferably of the structural unit a2), 69.5 to 97.5% by weight, particularly preferably 84.5 to 96.5% by weight, of the structural unit b) and 0.01 to 5% by weight, particularly preferably 0.2 to 3% by weight, especially preferably 0.5 to 2% by weight, of the structural unit c).
Particularly preferred structural units according to formula (1) are derived from N-vinylpyrrolidone.
Suitable structural units according to formula (3) are preferably ammonium salts of 2-acrylamido-2-methylpropanesulfonic acid, particularly preferably the NH
4
+
salt.
The crosslinking structural units c) are preferably derived from allyl acrylate or allyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyl ether, tetraallyloxyethane or other allyl or vinyl ethers of multifunctional alcohols, tetraethylene glycol diacrylate, triallylamine, trimethylolpropane diallyl ether, methylenebisacrylamide and/or divinylbenzene. Particular preference is given to allyl acrylate, allyl methacrylate, trimethylolpropane triacrylate and/or trimethylolpropane trimethacrylate.
The crosslinking structures are especially preferably derived from monomers of the formula (4)
in which R is hydrogen, methyl or ethyl.
The copolymers are preferably water-soluble or water-swellable copolymers.
The copolymers are preferably prepared by free-radical copolymerization, preferably by precipitation polymerization, particularly preferably in tert-butanol. Preferably, the monomers corresponding to the formulae (1), (2) and (3) are dissolved or dispersed in a protic solvent, then one or more crosslinkers c) are added to this solution or dispersion, and polymerization is started in a known manner by adding a free-radical-forming compound.
The polymerization reaction is preferably carried out in a water-soluble alcohol or a mixture of two or more alcohols having 1 to 6 carbon atoms, preferably in tert-butanol. The water content of the alcohol or alcohol mixture should not exceed 10% by weight since otherwise clumping can arise in the course of the polymerization. The type and amount of solvent should be chosen so that the salt of the acrylamidoalkylsulfonic acid corresponding to formula (3), in particular of 2-acrylamido-2-methylpropanesulfonic acid, is largely soluble or dispersible therein. Largely soluble or dispersible is to be understood as meaning that no solid material settles out of the solution or dispersion when the stirrer is switched off. The polymer which forms in the course of the reaction should, by contrast, be largely insoluble
Hornung Michael
Löffler Matthias
Morschhäuser Roman
Clariant GmbH
Jiang S.
Padmanabhan Sreeni
Silverman Richard P.
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