Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2002-04-16
2004-02-24
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S548000, C524S543000, C524S552000, C524S700000, C524S726000, C524S808000, C524S812000
Reexamination Certificate
active
06696517
ABSTRACT:
The present invention relates to the use of water-soluble or water-swellable copolymers based on acrylamidoalkylsulfonic acids and cyclic N-vinylcarboxamides or cyclic and linear N-vinylcarboxamides as thickeners in preparations comprising organic solvents.
Water-containing or solvent-containing multicomponent systems, such as solutions, emulsions or suspensions, are frequently adjusted to higher viscosities or thickened because of economic or application reasons or because of the stability. Thus it is possible, for example, by increasing the viscosity of the external or internal phase of the emulsions or suspensions, to significantly prolong the time before the components separate, which signifies increased storage time. In the case of many products, increasing the viscosity also improves their uniform distribution, in particular on uneven surfaces. This is true in particular for hair care compositions, skin care compositions and pharmaceutical ointments on the skin. In the case of many technical products, such as, for example, wallpaper strippers, paint removers or aircraft deicers, the increased viscosity prevents the product from prematurely running off the surface to be treated. The more uniform distribution and prolonged contact time increases the effectiveness. In addition to the application advantages mentioned, the high viscosity of such preparations also offers advantages for the preparation, packaging, bottling and storage, and also for transportation. In particular, the thickening of acidic media is of importance here from a safety viewpoint.
In general, the rheological properties during the preparation or formulation of cosmetic, pharmaceutical or technical preparations are a decisive criterion for the use of these products in practice. The thickeners used should lead, even in the smallest possible amounts and in a wide pH range, to adequate thickening. The principal properties of the products, e.g. including their color, should not be changed.
Numerous thickener systems have been proposed in the specialist literature for setting rheological properties of aqueous or solvent-containing systems.
Known thickeners are, for example, polymers based on polyacrylic acid, e.g. ®Carbopols, carbomers, ammonium polyacrylates or sodium acrylates copolymers. Also suitable are cellulose ethers, cellulose derivatives (e.g. carboxymethylcellulose, hydroxyethylcellulose), gelatins, starch and starch derivatives, sodium alginates, fatty acid polyethylene glycol esters, agar agar, tragacanth or dextrins. Also suitable are polyvinyl alcohols, polyacrylamides, polyvinylpyrrolidone, polyvinyl methyl ether, polyethylene oxides, copolymers of maleic anhydride and vinyl methyl ether, and mixtures thereof.
Use is also made of long-chain polyethers together with fatty acid esters, e.g. polyethylene glycol 6000 distearate, polyethylene glycol-polypropylene glycol monoethers, and reaction products of polyalcohols with fatty acids, e.g. pentaerythritol fatty acid esters.
However, the thickeners mentioned in the prior art are not free from disadvantages.
Thus, for example, the thickeners based on polyacrylic acid have only inadequate thickening ability in the strongly acidic pH range and in the case of compositions with a high content of organic solvents. In addition, the corresponding gels/formulation are sensitive to UV radiation and shearing and in addition impart a sticky feel to the skin.
Cellulose derivatives are very susceptible to bacteria. The formation of “thread-drawing” gels is also undesired.
Fatty acid polyethylene glycol esters tend toward hydrolysis in the presence of water. The insoluble fatty acids formed therein cause undesired clouding.
Thickeners of a natural origin (e.g. agar agar or tragacanth) have a greatly varying composition depending on their origin.
Surprisingly, it has now been found that copolymers based on acrylamidoalkylsulfonic acids and cyclic N-vinylcarboxamides or cyclic and linear N-vinylcarboxamides are highly suitable as thickeners for preparations comprising organic solvents.
The invention therefore provides for the use of copolymers 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 of 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 carbon atoms, preferably 1 to 20 carbon atoms, particularly preferably 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 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, as thickeners in preparations comprising organic solvents.
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, particularly 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 2-acrylamido-2-methylpropanesulfonic acid, preferably the ammonium salts, 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.
In particular, the crosslinking structures are 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. In this connection, the monomers corresponding to the formulae (1), (2) and (3) are preferably dissolved or dispersed in a protic solvent, then one or more crosslinkers c) are added to this solution or dispersion and the 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 formation of clumps may arise over the course of the polymerization. The nature and the amount of solvent should be chosen in such a way that the salt of acrylamidoalkylsulfonic acid corresponding to formula (3), in particular 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 even after the stirrer has been switched off. The polymer produced in the course of the reaction should, on the other hand, be largely insoluble in the chosen solvent or solvent mixture. Largely insoluble is to be understood here as meaning
Klug Peter
Löffler Matthias
Morschhäuser Roman
Clariant GmbH
Hanf Scott E.
Sastri Satya B
Silverman Richard P.
Wu David W.
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