Stochastic Approximation and Nonlinear Regression

A process for producing a thermoplastic resin sheet having a band of color by feeding a molten thermoplastic resin by an extruder into a sheet-forming flat die having a manifold and extruding said molten resin from an extrusion opening of said flat die, which comprises forcing a stream of a colored molten thermoplastic resin through at least one injection port opened into the manifold of the flat die into a main stream of the molten resin extruded from the extruder and fed to the manifold, associating the main stream of the molten thermoplastic resin and the stream of the colored molten thermoplastic resin within the manifold, and extruding the associated streams from the extrusion opening of said flat die.