  In this paper we consider a scenario where the currently observed
hypervelocity stars in our Galaxy have been ejected from the Galactic center as
a result of dynamical interactions with an intermediate-mass black hole (IMBH)
orbiting the central supermassive black hole (SMBH). By performing 3-body
scattering experiments, we calculate the distribution of the ejected stars'
velocities given various parameters of the IMBH-SMBH binary: IMBH mass,
semimajor axis and eccentricity. We also calculate the rates of change of the
BH binary orbital elements due to those stellar ejections. One of our new
findings is that the ejection rate depends (although mildly) on the rotation of
the stellar nucleus (its total angular momentum). We also compare the ejection
velocity distribution with that produced by the Hills mechanism (stellar binary
disruption) and find that the latter produces faster stars on average. Also,
the IMBH mechanism produces an ejection velocity distribution which is
flattened towards the BH binary plane while the Hills mechanism produces a
spherically symmetric one. The results of this paper will allow us in the
future to model the ejection of stars by an evolving BH binary and compare both
models with \textit{Gaia} observations, for a wide variety of environments
(galactic nuclei, globular clusters, the Large Magellanic Clouds, etc.).
