Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-05-15
2004-02-10
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S264000, C526S265000, C526S271000, C526S274000, C526S287000, C526S288000, C526S291000, C526S303100, C526S307100, C526S307500, C526S317100, C526S330000, C526S342000
Reexamination Certificate
active
06689856
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to water-soluble polymers comprising a water-soluble backbone and side units with a lower critical solution temperature (LCST) having a specific precipitation temperature in water.
The invention also relates to the preparation process for the synthesis of these polymers.
Finally, the invention relates to aqueous compositions containing these polymers and to the use of these polymers and compositions, especially in cosmetics.
2. Discussion of the Background
The technical field of the invention may be defined as that of water-soluble polymers comprising a water-soluble backbone and side units with an LCST. It is known that these polymers have, in aqueous solution, gelling properties stimulated by an increase in the temperature.
This novel Theological behaviour is particularly advantageous in cosmetics and pharmaceuticals, since it makes it possible to obtain aqueous systems that are fluid at room temperature and gels at the temperature of the human body, that is to say fluid compositions (emulsions, dispersions, lotions, etc.) that gel when applied.
This type of application of the heat-induced gelling power is described in the case of aqueous solutions and emulsions in patents WO-95/24430 (University of Washington, Hoffman), U.S. Pat. No. 5,939,485 (Medlogic Global Corporation, Bromberg), WO-97/00275 (Gel Sciences, Inc, Bromberg) and WO-98/48768 (Medlogic Global Corporation, Bromberg).
Various synthetic processes have been used to obtain polymers of this novel type; these processes are as follows:
I) Reaction for grafting chains with an LCST onto water-soluble macromolecules, using a coupling agent such as dicyclohexylcarbodiimide or 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride. The polymers obtained have a “comb” structure. This synthetic route is described by Hourdet (Hourdet D., L'Alloret F., Audebert R., Polymer, 1997, 38 (10), 2535-2547), in patents EP 583 814, EP 629 649 (Schlumberger Dowell, Maroy), WO-95/24430 (University of Washington, Hoffman).
This synthetic route is difficult to transfer to the industrial scale for reasons of cost (coupling agent and reaction in relatively dilute medium) and of toxicity (coupling agent).
II) Copolymerization of a macromonomer with an LCST and of a water-soluble monomer in homogeneous medium (water or organic solvent) or in emulsion.
This synthetic route in homogeneous medium is described by Hourdet (Hourdet D., L'Alloret F., Audebert R., Polymer, 1997, 38 (10), 2535-2547), in patents EP 583 814, EP 629 649 (Schlumberger Dowell, Maroy), WO-95/24430 (University of Washington, Hoffman). The reverse-emulsion polymerization process is described in patent WO-00/35961 (Rhodia, Yeung). The polymers obtained have a “comb” structure.
Industrially, the synthetic process in homogeneous medium requires the use of large amounts of water or of solvent, the content of active material in the reaction medium generally being less than 10%. The polymer is obtained either as an aqueous solution at a content of less than 10%, which limits its use in terms of formulation; or as an organic solvent and, in this case, must undergo a recovery phase, for example by precipitation.
For the emulsion polymerization, the contents of active materials are larger. However, the recovery of the polymer requires the introduction of large amounts of salt (Na
2
CO
3
or NaOH) in order to obtain the polymer in solid form; or alternatively leads to an aqueous system containing, after inversion of the phases, the polymer and surfactants.
III) Coupling reaction between water-soluble blocks and blocks with an LCST.
This synthetic route, described in patent WO-95/24430 (University of Washington, Hoffman), leads to multiblock polymers. It requires the use of hydrophilic blocks and blocks with an LCST that are functionalized, thus inducing a multi-step process, namely synthesis of the two types of blocks, followed by a coupling reaction.
IV) Free-radical polymerization of water-soluble monomers in the presence of oxyalkylenated derivatives.
This synthetic route, performed in aqueous medium, for example in patents U.S. Pat. No. 5,939,485, WO-97/00275 and WO-98/48768 and in reverse emulsion in patent WO-00/35961, is based on reactions for transferring radicals to the oxyalkylenated chains and leads to compounds of complex structure whose properties in aqueous medium are difficult to control.
V) Free-radical polymerization of a macromonomer bearing chains of C
m
(OE)
n
type and of a monomer bearing at least one unsaturated function.
Patent application EP-1 069 142 (Clariant) describes any water-soluble polymer obtained by free-radical polymerization of a hydrocarbon-based monomer that may contain oxygen, nitrogen, sulphur, phosphorus, chlorine and/or fluorine atoms, and of a macromonomer comprising an oxyalkylenated unit and a hydrophobic unit of C
m
H
2m+1
type, in which m is an integer between 0 and 30. According to claim 4, the number m is preferably between 10 and 22. Claims 8 and 9 relate to polymers having in aqueous solution, above a critical temperature, a constant viscosity or else heat-induced thickening power. In this case, the macromonomers used contain a unit with an LCST in water.
When the number m is greater than 6, the grafts of these “comb” polymers are alkylethoxylated surfactants, these compounds being known to have in water a cloud point by raising the temperature. The corresponding grafted polymers are, below this cloud point, of associative nature since they bear hydrophobic alkyl units. They thus have gelling properties below the cloud point of their grafts (see comparative example 1, pages 14 and 15 of EP-A-1,069,142). Moreover, these polymers containing alkylethoxylated grafts are liable to interact with the surfactants present in the medium, and particularly with amphiphiles of the same chemical nature; this sensitivity to surfactants limits the flexibility of these systems in terms of formulation. It should moreover be noted that the heat-induced gelling properties given in the examples are observed above 90° C.
Example 17 describes a polymer bearing polyoxyethylenated grafts (m=0); however, its rheological behaviour in aqueous medium as a function of the temperature is not described.
Claim
11
specifies the preferred synthetic process, based on a free-radical polymerization by precipitation from tert-butanol.
SUMMARY OF THE INVENTION
In conclusion, this patent application describes a synthetic route that is simple to carry out industrially, using a non-toxic solvent that is suitable for cosmetic applications and for which the polymer/solvent ratio is greater than in the case of processes performed in homogeneous medium. The heat-induced gelling polymers described in this patent application bear heat-sensitive chains containing oxyalkylenated units; however, all the polymers described have a gelpoint of greater than 90° C., which is relatively unsuitable for cosmetic applications.
There is thus a need for water-soluble polymers comprising a water-soluble backbone bearing units with an LCST, which, inter alia:
are suitable for cosmetic uses, with a precipitation temperature of the units at 1% in water that is in a cosmetically advantageous range;
whose synthetic process can be extrapolated to the industrial scale while at the same time allowing good control of the structure of the macromolecules, and thus of their properties in solution and in film form.
The present invention satisfies these needs.
This aim and others are achieved, in accordance with the invention, by means of a water-soluble polymer comprising a water-soluble backbone and side units having in water a lower critical solution temperature, LCST, the polymer being able to be obtained by free-radical precipitation polymerization of:
a) one or more water-soluble monomers (Ia) and, optionally, of one or more hydrophobic monomers (Ib) in a small amount relative to the monomers (Ia), the said monomers (Ia) and (Ib) bearing at least one unsaturated function that can be polymerized to fo
L'Oreal
Pezzuto Helen L.
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