  We explore a nonlinear extension to quantum theory giving rise to
deterministic partial disentanglement between pairs of particles. The extension
is based on a modified Schr\"{o}dinger equation having an added nonlinear term.
To avoid conflicts with the principles of causality and separability, it is
postulated that disentanglement is active only during the time when particles
interact. A butterfly-like effect is found near highly entangled multipartite
vector states.
