The paper treats the case where blends of polystyrene (PS), poly (dimethylsiloxane) (PDMS) and a diblock copolymer of PS and PDMS are used as model materials. This modelsystem is predicted to be "stable" in discrete blends in simple shear flow. Stable in the sence that the block copolymer can not be removed form the interface during simple shear flow. A hypothesis stating that coalescence of drops may be subdued by "stable" diblock copolymer at the interfaces in 3D flows are tested with a Brabender mixing chamber. For well dispersed systems absence of coalescence would confine the occurrence of bicontinuous structures to a phase inversion point volume or prevent bicontinuous phase structure (IPS) formation all together. Addition of PS-b-PDMS diblock copolymer do contract the volume fraction interval where IPS are found but a relatively broad interval is still observed. The phase inversion volume predicted by theory is outside the observed IPS interval for one of the investigated blend pairs.