On-line rheological measurement for process control

Abstract

On-line rheological measurements are made on a process flowing material, such as a polymer melt, utilizing a rheometer of the type in which an inlet pump delivers a relatively large volumetric flow of diverted process material from a process main stream to an inlet site located in very close proximity to the entrance of a capillary passage, and a metering pump draws a smaller portion of the volumetric flow of the diverted material from the inlet site through the capillary passage for return to the process main stream. The viscosity of the diverted material is measured as a function of the rate of flow of the material through the capillary passage and the pressure drop between spaced apart locations along the capillary passage. A parallel flow passage has a volumetric flow capacity considerably greater than the volumetric flow capacity of the capillary passage, an inlet placed at the inlet site, in very close proximity with the entrance of the capillary passage, and an outlet placed downstream of the metering pump. A parallel flow pump in the parallel flow passage moves the balance of the volumetric flow of diverted material from the inlet site for return to the process main stream to assure a continuous supply of fresh diverted material at the entrance to the capillary passage.