Rheological measurement process

#The present disclosure generally relates to apparatuses and methods for measuring and controlling the viscosities of liquids.

#Viscosity measurement of liquids is a procedure used in the characterization of many liquid products including polymers and polymer melts. The testing is typically performed off-line on a small scale in a laboratory setting. Samples of the polymer melt are periodically withdrawn from the main process stream during the manufacturing process and carried to the laboratory to be tested and characterized. The test results are then used to tweak and adjust the manufacturing process to obtain a targeted polymer melt quality. Data obtained in this manner is not representative of the ongoing manufacturing process since a significant time delay in obtaining the data exists.

#More recently, efforts have been directed to reducing the response time by measuring polymer melt properties during the manufacturing process itself in order to provide better control over the quality of the polymer melt. Measurement during the manufacturing process, however, requires equipment that is relatively easy to use, maintain, and rugged enough to withstand the operating conditions to which the equipment will be exposed. In order to be effective, the equipment must be responsive, and must avoid disturbing the manufacturing process being monitored.

#Referring now to the figures, which are exemplary embodiments, and wherein the like elements are numbered alike:

#FIG. 1 is a schematic diagram of a continuous reactor for preparing a polymer melt;

#FIG. 2 graphically illustrates a correlation between a pressure of a polymer melt measured at a first location in a conduit and a pressure of the polymer melt measured at a second location in the conduit;

#Referring now to FIG. 1, a schematic diagram of a continuous polymerization apparatus 10 is depicted. Although the continuous polymerization apparatus 10 is shown, it should be understood that the apparatus is exemplary only, and other suitable apparatus may be used, wherein it is generally desirable to determine the real-time liquid properties of a liquid passing through a conduit.

#The illustrated apparatus 10 includes a reactor 12 that contains a polymer melt. More preferably, the polymer melt is a finished polymer that is free from further polymerization and changes in rheological properties. The reactor 12 may comprise one or more interconnected reactors (not shown) for polymerizing monomers to produce a desired polymer. The reactor 12 includes a conduit 14 in fluid communication with a device 20. A metering pump 16, or the like, is connected to conduit 14 to flow the finished polymer melt contained in the reactor 12 at a defined flow rate through conduit 14 to device 20. Device 20 may comprise an extruder, a molding apparatus, another reactor, and the like.

#Pressure probes 30, 34 and at least one temperature sensor 32 are disposed in the conduit 14 downstream from the metering pump 16. The temperature sensor 32 is positioned in the conduit 14 preferably at a location intermediate to the location of pressure probes 30, 34 and provides an output signal corresponding to a temperature of the polymer melt as it flows between the pressure probes 30, 34. Optionally, more than one temperature sensor may be disposed between the pressure probes 30, 34 to provide a temperature average of the polymer melt as it flows between pressure probe 30 and pressure probe 34. The pressure probes 30, 34, provide output signals indicative of the pressure, P1, P2, at the probes respective location. Optionally, more than one pressure probe can be employed to provide redundancy in the melt property calculations, which will facilitate pressure sensor failure detection.