322 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 1.2 . 0••.7_:: .. 0 1 2 3 4 5 6 7 8 9 10 Time At Reaction Condition •,n. .... • Figure 2. Ethoxylation rate (no catalyst). -•- Hyrdoxy Stearic AcH "•- Lactic Acid -z-- Stearic Acid -u- Stearyl Alcohol Reaction Condition 1. Temperature 150 C 2. Initial Pressure 45 psig 3. No Catalyst glycol. This by-product concentration will be increased by having water present in the fatty material before ethoxylation. Published data (9,10) indicates that the concentrations of PEGs are as follows: Hydrophobe NaOH catalyst Moles EO Ethoxylate PEG Cetyl/stearyl alcohol 1.0 5.0 96.0% 4.0% Lauryl alcohol 1.0 10.0 93.3 % 6.7 % Lauryl alcohol 1.0 20.0 91.8% 8.2% Lauryl alcohol 1.0 50.0 88.5 % 11.5 % FATTY ACID ETHOXYLATION Fatty acids when reacted with ethylene oxide produce complex mixtures of hydroxy esters. Unlike the products formed by the ethoxylation of fatty alcohols which are ethers, esters are formed when ethylene oxide is reacted with fatty acids. In addition to the oligomeric species that form during the reaction of a fatty acid with ethylene oxide, there is an added complication. That complication is the formation of diester. ESTER PRODUCTS Mono ester R - C(O) - O - CH2CH2OH Diester R - C(O) - O - CH2CH2OC(O) - R

ETHOXYLATION OF HYDROXY ACIDS 323 12 10 --0.15 KOH .30 KOH No Catalyst O.6 KOH Reaction Condition 1. Temperature 150 C 2. Initial Pressure 45 3. Catalyst level varied 0 0.5 1 1.5 2 2.5 3 3.5 Time At Reaction Condition (•n. .... ) Figure 3. Stearic acid ethoxylation rates. Published data indicate that the ratios of mono- to di- ester are as follows (11): Hydrophobe Moles EO Mono ester Diester PEGS* Stearic acid 9.0 38.9 41. ! 20.0 Oleic acid ! 3.6 59.7 26.8 ! 3.5 As earlier stated, the salient difference between fatty acid ethoxylation and fatty alcohol ethoxylation under base catalysis is that the former has an induction period. During this early stage of the reaction, there is a period of time in which there are negligible amounts of product formed. After that initial induction period, the reaction rate in- creases to about that of the fatty alcohol. As Figure 3 shows, increasing the amount of alkaline catalyst simply shortens the induction period but does not eliminate it. The ethoxylation of fatty acids, like that of fatty alcohols, will not occur without a catalyst. The catalyst can be either acidic or, more typically, alkaline. Alkaline catalysts generally produce fewer by-products. EXPERIMENTAL HYDROGENATED CASTOR ETHOXYLATION--ETHENIFICATION REACTION Hydrogenated castor oil is principally 12-hydroxystearic triglyceride. Hydrogenated castor ethoxylates are items of commerce and are commonly used in several applications, including textile and personal care applications. It was originally thought that these materials ethoxylated almost exclusively on the hydroxyl group. It is now under- * PEGS are polyoxyethylene glycol.