Studies on the Oil Additive. II.

Abstract

Authors studied the reaction conditions for preparation of the dialkyl dithiophosphates from 4 moles of alcohol (isopropyl, n- and sec-butyl, iso-amyl, n- and sec-hexyl, 4-methyl, 2-pentyl, cyclohexyl, 1- and 2-octyl, 2-ethylhexyl, or n-lauryl) and 1 mole of P2S5. When the alcohol having an alkyl chain of less than 4 carbon atoms (e.g. isopropyl, isobutyl etc.) is used as starting material, the advisable reaction temperature and time are 57 hr at 5060°C, while in case of alcohols having C5 C8 alkyl chain (e.g. 2-ethyl hexyl, 4-methyl, 2-pentyl etc.), it becomes 3 hr at 100°C respectively. When reaction temperature exceeds the above mentioned range, side reactions occur and both purity and yield of the product decrease. The antioxidation power of the Zn salt of these products was tested by measurements of the induction period for oxygen uptake in liquid paraffin. Induction period decreases according to the following order : 4-methyl-2-pentyl, cyclohexyl, sec-butyl, 2-ethyl hexyl, iso-amyl, n-hexyl, and 2-octyl which denote alkyl radical radical in the dialkyl dithiophos phates. Among them, initial three Zn salts are excellent as antioxidant.