Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Web – sheet or filament bases; compositions of bandages; or...
Reexamination Certificate
1998-10-05
2001-11-06
Webman, Edward J. (Department: 1617)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Web, sheet or filament bases; compositions of bandages; or...
C424S078200, C514S844000
Reexamination Certificate
active
06312714
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to cosmetic compositions, and, more particularly, to a cosmetic composition for rejuvenating the appearance of skin with substantially no skin irritation.
2. Description of the Prior Art
Cosmetic compositions having an alpha- or beta-hydroxy acid (AHA/BHA) as the active ingredient are well-known in the art. These compositions are useful for treatment of the skin, particularly for anti-aging, improvement in skin tone, reduction of fine line, enhancement of moisture, and development of a smooth skin. Application of such compositions generally results in a younger-looking skin as new cells replace the old. Smith, in Soap/Cosmetics/Chemical Specialties, Sept. 1993, page 54, addressed the question of whether an AHA must be in the acid form to be effective in promoting exfoliation and skin renewal. Various AHA and BHA compounds were examined for their ability to increase cell renewal at different pHs, with similar results observed for all acids tested. As the pH increased, the ability to stimulate cell renewal diminished; in fact, at a pH above 6, very little stimulation of cell turn over was observed with any AHA material. For the acids tested, a maximal stimulation of renewal was observed at a pH of about 3, as shown in Table 1 below.
TABLE 1
Relationship between Cell Renewal,
Irritation & pH for Various Acids Tested
TEST MATERIAL
pH
CELL RENEWAL*
IRRITATION*
4% Lactic acid
3
35
2.8
5
24
2.1
7
13
1.2
4% Glycolic acid
3
34
2.9
5
23
2.1
7
10
1.1
4% Salicylic acid
3
42
3.0
5
28
2.3
7
12
1.2
5% Citric acid
3
18
2.3
5
14
2.1
7
8
1.1
*A higher number indicates improved cell renewal/more irritation
Accordingly, to achieve improvement in skin condition, it has been found necessary for the user to tolerate the skin irritation caused by the acid present in the product. Thus, skin irritation is a major concern to formulators of alpha and beta-hydroxy acid-containing products, particularly at acid loading levels which can deliver faster and more effective skin peeling. More irritation, however, is perceived by the user as being a more effective treatment.
Scott and Yu, in EP 671162, have described an amphoteric composition containing AHAs and their esters and salts for topical application for the treatment of cosmetic conditions and dermatological disorders. The inclusion of an amphoteric compound in the composition provided a stable composition having a pH closer to that of skin.
Usumura, in U.S. Pat. No. 5,512,277, described a method of removing keratotic plugs by applying a keratotic plug remover composition onto the skin, and peeling off the composition after the composition was dried, and, particularly, wherein the active ingredient of the composition was a cationic polymer compound such as polymethacryloylethyl trimethylammonium chloride.
Chaudhuri, in U.S. Pat. No. 5,736,128 also described a cosmetic composition for rejuvenating the appearance of skin with reduced or minimal skin irritation which included an anionic copolymer of methyl vinyl ether-maleic acid as the active ingredient in an aqueous, alcoholic or aqueous-alcoholic solution of 0.5 to 25 wt. % of the copolymer at a pH of 1.5 to 5.
U.S. Pat. No. 5,037,924 described the preparation of terpolymers of maleic anhydride, a C
1
-C
4
alkyl vinyl ether and isobutylene, for use as denture adhesives in the form of their mixed salts. These terpolymers were made by precipitation polymerization in the presence of a cosolvent system of ethyl acetate and cyclohexane. The resultant terpolymer had a low molecular weight of about 30,000 to 400,000, and contained residual ethyl acetate and cyclohexane in the terpolymer.
Accordingly, it is an object of this invention to provide a new and improved cosmetic composition for the rejuvenating the appearance of skin which produces excellent skin compatability with substantially no skin irritation, and with the environmental benefit of a residual solvent-free system.
SUMMARY OF THE INVENTION
What is described herein is a cosmetic composition for rejuvenating the appearance of skin with excellent skin compatability, and substantially no skin irritation, in the form of a lotion, creme, solution or gel, or applied onto a carrier, such as woven and non-wovens, in the form of a skin peelable strip, the active ingredient being 0.5 to 50 wt % of a solvent-free, high molecular weight terpolymer of maleic anhydride-methyl vinyl ether-isobutylene, at a pH of 1.5 to 5.
DETAILED DESCRIPTION OF THE INVENTION
The active ingredient of the cosmetic composition of the invention are solvent-free, fine powders of high molecular weight alternating terpolymers of maleic anhydride (MAN), a C
1
-C
4
alkyl vinyl ether (AVE) and isobutylene (IB), having molecular structure of (A-B)
n
, where A=MAN and B=AVE or IB, and containing preferably about 5 to 25 mole % of isobutylene.
The terpolymers have a molar ratio of maleic anhydride to alkyl vinyl ether to isobutylene of about 0.50:0.45-0.25:0.05-0.25, respectively.
The NMR spectra of these terpolymers show an alternating molecular structure (A-B)
n
as described above, where n is such that the terpolymer has a weight average molecular weight (GPC, water pH 9) in excess of about 1,500,000, and a specific viscosity which is ≧6 (1% in DMF, 25° C.).
The powders are made by a solvent-free process which is carried out by charging the alkyl vinyl ether and isobutylene into a reactor at a mole ratio of isobutylene to alkyl vinyl ether which is substantially greater than that desired in the terpolymer, adding a radical initiator, heating the mixture to a reaction temperature of about 50 to 100° C., and feeding molten maleic anhydride over time into the reactor, wherein the mole ratio of maleic anhydride to the total charge of alkyl vinyl ether and isobutylene is not higher than 1:3. The resulting terpolymers obtained herein are odorless and free of the trace amounts of solvents characteristic of other known processes for making such terpolymers.
Preferably the solvent-free polymerization process is carried out using an excess of alkyl vinyl ether and isobutylene as the reaction medium. Such a polymerization reaction is carried out by precharging an AVE/IB mixture of predetermined composition into the reactor, adding a radical initiator, heating to a reaction temperature of about 50° to 100° C., and feeding molten maleic anhydride into the reactor over time.
The mole ratio of MAN to the total of MVE+IB is not higher than 1:3, preferably less than 1:5. Furthermore, the mole ratio of IB to MVE in precharge is made significantly higher than that desired in the terpolymer, preferably about 1:1 IB:MVE for a terpolymer containing 1:2 IB:MVE and about 1:2 IB:MVE for a terpolymer containing 1:4 IB:MVE.
Generally, an additional amount of MVE is added near the end of the polymerization in order to fully react the MAN reactant.
After stripping the remaining MVE and IB, the product is obtained as a fine, odorless powder, without residual solvent.
REFERENCES:
patent: 5037924 (1991-08-01), Tazi et al.
patent: 5385729 (1995-01-01), Prencipe et al.
patent: 6046291 (2000-04-01), Zhang et al.
Plochocka Krystyna
Prosise William E.
Davis William J.
ISP Investments Inc.
Katz Walter
Maue Marilyn J.
Webman Edward J.
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