According to Seoul-based LG Household & Health Care, when developing cosmetic foams, hydrophobic polymer foams based on acrylonitrile butadiene rubber (or NBR) and styrene-butadiene rubber (SBR) are widely used since they have good wear- and/or oil-resistance. However, they exhibit low workability.
To solve this problem, natural rubber (NR) has been proposed in place of them. NR is said to be highly compatibility with hydrophobic polymers such as polyethylene, polypropylene, polystyrene and polyester. It also has good sensory and mechanical properties, such as wear-resistance.
Then again, nothing is ever as simple as it seems. In sun protection formulas, NR is incompatible with oil-soluble organic UV filters, causing issues with their impregnation into foams. How can this issue be resolved? The present inventors bounced around a combined approach.
Double substrate to impregnate UV cosmetics in hydrophobic polymer foams
U.S. Patent 9744117
Publication date: Aug. 29, 2017
Assignee: LG Household & Health Care, Ltd.
These inventors have discovered that the combination of NR with NBR as a polymer substrate can solve the adsorption problem of oil-soluble organic UV filters. Thus, this invention specifies cosmetics including a foam, NR, a hydrophobic polymer and an organic UV filter.
According to the inventors, this arrangement reduces the amount of UV filter adsorbed to the impregnation material to impart excellent UV protection. It is also less susceptible to whitening and it can be developed in light formulations such as milks, gels and lotions, or creams and foundations.