Surfactants greatly influence degreasing velocity. To explain the differences due to surfactant type, we analyzed the remaining oil film thickness (
T) and the emulsion characteristics induced by the surfactants involved It became clear that
T had a strong relationship to the average oil globule diameter
r∞ in the oil emulsion, which had been formed at a low concentration.
T and (
dT/dt)are summarized as follows: T=r
∞/R, dT/dt
(initial)=-C
1*r
a(T-r
∞)/√r
∞, dT/dt
(end)=-C
2*√r
∞.
R: Water wetting area ratio,
ra: Substantial oil globule diameter of highly concentrated emulsion in boundary film. The degreasing velocity (
dT/dt) in all surfactants was decided by
ra and
r∞ size. These sizes characteristically depended on the surfactant type and oil concentration. The ideal surfactant for high-speed degreasing, should therefore form an oil globule distribution at the smallest size<0.1 and
r∞=2,
ra>30μm.
Little possibility existed; however, that (
dT/dt) was controllable by using the specific globule size alone, which had the slowest movement velocity, only when degreasing by the surfactant ABS, etc., had nearly been completed.
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