Surfactant for water-in-oil emulsion

A water-in-oil surfactant consisting of a mixture of compounds of formula (I):

• wherein the compound of formula (I) has an average degree of polymerisation n of between 4 and 6,
• R1, R2 and R3 being, independently of one another, a hydrogen atom or an R4 group derived from at least one carboxylic acid,
• the carboxylic acid being 12-hydroxystearic acid or a mixture of 12-hydroxystearic acid and ricinoleic acid,
• R4 being a group C(═O)—(R5)—CH(OH)—(CH2)5—CH3 or C(═O)—(R5)—CH[(CH2)5—CH3]—O—{C(═O)—(R5)—CH[(CH2)5—CH3]—O}pC(═O)—(R5)—CH[(CH2)5—CH3]—OH where p=0 to 5, R5 being a group (CH2)10 or a mixture of the groups (CH2)10 and (CH2)7—(CH═CH)—CH2, and wherein at least one of the R1, R2 and R3 groups is an R4 group.