A limited number of W/0 emulsifiers are available. This is because ionic emulsifiers will not work in the case of W/0 emulsions and, since very low HLB is required. variations using ethylene oxide are not possible. W/0 emulsifiers have HLB values between 3 and 6. However, the type of the alkyl chain is also important. In practire, oleyl derivatives have shown good effects. The most widely used W/O emulsifiers are sorbitan monooleate, sorbitan sequioleate and glycerol monooleate, and with increasing importance, polyglycerol esters.
In addition to oleate, ricinoleates and isostearates have aIso found use.
The methoxy PEG-22 dodecyl glycol copolymer is a high molecular weight W/O emulsifier, which is especially effective in formulations containing mineral oils. It is a saturated ether and is therefore stable against oxidation and hydrolysis.
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