Non-irritating benzoyl peroxide
View Patent ↗A method of making crystalline benzoyl peroxide particles having a particle size no greater than 25 microns and formed by wet milling in the absence of solvents and wherein the crystalline benzoyl peroxide is not irritating to the skin. A method of making a therapeutic or cosmetic composition comprising a water-based gel containing the crystalline benzoyl peroxide.
1. A method of preparing crystalline, solvent-free, benzoyl peroxide particles comprising:
adding water to solid benzoyl peroxide;
milling to break up agglomerates and form an aqueous benzoyl peroxide composition;
adding a dispersion system and mixing;
adjusting the pH to 2.8 to 6.6; and
milling to a particle size not more than 25 microns.
2. The method of claim 1 wherein the pH is adjusted to 5.5 to 6.
3. The method of claim 1 wherein the pH is adjusted by adding an effective amount of sodium hydroxide potassium hydroxide or calcium hydroxide.
4. The method of claim 1 wherein the milling is performed with a rotor mill.
5. The method of claim 1 wherein the temperature is maintained below 30° C.
6. The method of claim 1 wherein the particle size is not greater than 10 microns.
7. The method of claim 1 wherein at least 90% of the particles are less than 3.5 microns in size.
8. The method of claim 1 wherein at least 95% of the particles are less than 3.5 microns in size.
9. The method of claim 1 wherein an average particle size is from 1 to 2 microns.
10. The method of claim 1 wherein the dispersion system comprises at least one selected from the group consisting of suspending agents, gelling aids, buffering agents, and dispersants.
11. The method of claim 1 wherein the water is added to solid benzoyl peroxide in the absence of solvents.
12. A method of making a therapeutic or cosmetic composition comprising preparing crystalline, solvent-free, benzoyl peroxide particles in accordance with claim 1 ; then adding the benzoyl peroxide particles to a water-based gel.
13. The method of claim 12 wherein the particle size is not greater than 10 microns.
14. The method of claim 12 wherein at least 90% of the particles are less than 3.5 microns in size.
15. The method of claim 12 wherein at least 95% of the particles are less than 3.5 microns in size.
16. The method of claim 12 wherein an average particle size is from 1 to 2 microns.
17. The method of claim 12 wherein the water-based gel comprises a dispersing system.
18. The method of claim 17 wherein the dispersion system comprises at least one selected from the group consisting of suspending agents, gelling aids, buffering agents, and dispersants.
19. The method of claim 17 wherein the composition contains about 25 to 65% by weight benzoyl peroxide.