Antifoaming Properties of Diols. IV.

Abstract

The following vicinal diols R1CH (OH) CH (OH) R2 (R1, C10H21C20H41; R2, H, CH3C9H19, R1+R2=C12H25, C14H29, C16H33, C18H37, C20H41) were prepared and their antifoaming powers were determined in order to clarify the relationship between their molecular structure and the antifoaming properties. The ethylene oxide adducts of these diols were also prepared and examined. The antifoaming powers were determined by the Ross and Miles method for the aqueous solution of sodium dodecylbenzene-sulfonate as a foaming agent. These were expressed as functions of immediate reading of foam height (foam production) and reading of foam height after 5min (foam stability), and the concentration of diols.The results of these experiments were shown in Fig.-126. It was found that the antifoaming properties of the vicinal diols were dependent upon their molecular weights and the position of two hydroxyl groups in the molecules.(1) Tetradecanediols, hexadecanediols, and octadecanediols showed excellent foam inhibiting proper-ties; the antifoaming powers of the vicinal diols increased in the order C14_≈_C16_≈_C18>C20>C22>C12>C10>C8_≈_C6.(2) The antifoaming powers of decanediols and dodecanediols were greater when the two hydroxyl groups were located near the center of an alkyl chain, but those of the symmetrical diols were not great. On the other hand, the antifoaming powers of tetradecanediols and hexadecanediols were not affected by the position of two hydroxyl groups (Fig.-26).(3) The introduction of 12 molecules of ethylene oxide to these diols improved their antifoaming powers considerably.