Styrene maleic anhydride polymers in cosmetics and personal care products
The invention relates generally to pigmented compositions that, upon the application of water and pressure, exhibit a visible change in one or more optical attributes such as color.
1. A method of achieving a color change in a cosmetic composition applied to a human integument comprising:
(1) applying to said human integument a substantially anhydrous cosmetic composition to form a film thereon, wherein said composition comprises:
(a) one or more cosmetic ingredient selected from waxes, gelling agents, emollients, and film forming polymers; and
(b) a pigment grind capable of exhibiting a color change, prepared by dispersing, under shear, pigment particulates in a substantially anhydrous carrier in the presence of a styrene maleic anhydride copolymer; and
(2) applying water to said film and rubbing it until a visible color change is achieved.
2. A method according to claim 1 , wherein the styrene maleic anhydride copolymer comprises the following repeat unit:
wherein, X is selected from —O—, —NH—, or —NR*—, where R* is a C 1-12 hydrocarbon optionally containing from 1-3 heteroatoms selected from oxygen, sulfur, and nitrogen, and “n” and “m” are each independently integers selected to provide a molecular weight between about 2,500 and about 80,000 Daltons.
3. The method according to claim 1 , wherein said pigment grind comprises: from about 20% to about 80% by weight carrier, from about 20% to about 80% by weight pigment, and from about 0.5% to about 20% by weight styrene-maleic anhydride copolymer.
4. The method according to claim 1 , wherein said pigment comprises one or more of titanium dioxide, iron oxide, FD & C lakes, D & C lakes, and carbon black.
5. The method according to claim 1 , wherein said pigment comprises iron oxide.
6. The method according to claim 1 , wherein said styrene maleic anhydride copolymer is composed of from about 25% to about 50% maleic anhydride monomers and from about 50% to about 75% styrene monomers.
7. The method according to claim 2 , wherein said styrene-maleic anhydride copolymer comprises an alternating copolymer.
8. The method according to claim 2 , wherein “n” and “m” are each independently integers selected to provide a molecular weight between about 5,000 and about 10,000 Daltons.
9. The method according to claim 1 , wherein said styrene-maleic anhydride copolymer comprises the following repeat unit:
wherein, X 1 and X 2 are independently selected from —OH, —OZ, —OR—NH 2 , and —NHR*, wherein R and R* are independently a C 1-12 hydrocarbon optionally containing from 1-3 heteroatoms selected from oxygen, sulfur, and nitrogen, and Z is a cation selected from Na + and NH 4 + , where “n” and “m” are each independently integers selected to provide a molecular weight between about 2,500 and about 80,000 Daltons.
10. The method according to claim 9 wherein one of X 1 or X 2 is a group —NH 2 and the other of X 1 or X 2 is —OH.
11. The method according to claim 9 , wherein said styrene-maleic anhydride copolymer comprises alternating copolymer.
12. The method according to claim 9 , wherein “n” and “m” are each independently integers selected to provide a molecular weight between about 5,000 and about 10,000 Daltons.
13. The method according to claim 1 , wherein said shear is applied in a three-roll mill.