Batch Polymer
Process
SUMMARY
Viscosity changes with molecular weight, degree of branching and concentration of polymer. A continuous process viscometer monitors initiation, propagation, and termination stages of reaction. More reproducible product quality, reduced cycle time with increased output and improved safety result.
INSTALLATION
Methods for viscosity control depend on process and product characteristics. New reactors can be equipped with a 3 inch Class 300 ANSI stud pad (B) to install the transducer. Retrofit jobs usually require mating to existing process connections, i.e., flange nozzles (A). With some vessels, process side extensions on the transducer (C) are necessary to clear the jacket and reactor wall. With mix systems that sweep the reactor wall, notched mixer blades (D) clear the sensor from the blade path. For glass-lined or rated vessels, a pipe extension (E) or lance from a top man-way to below the liquid level has proven effective. Mounting in an elbow and pointing the sensor toward flow in a re-circulation pipeline (F) is another transducer connection method. Again, non-active transducer extensions (C) are useful for pipeline installation in order to avoid stagnant flow areas. The VISCOLINER® transmitter is located in a control room up to 1000' from the transducer.
OPERATION
Instrument zero needs to be set once prior to initial startup. Check instrument calibration once a year. Set zero near process temperature when the sensor has been visually inspected as clean. For solvent acrylics and water borne emulsions, PFA-teflon coating provides film release and flow causes self-cleaning between batches. This avoids build-up on the sensor. Alternatively, water or solvent cleaning with flushing nozzles pointed toward the sensor has proven effective. When producing a high purity, finished product, solvent flush or re-flux are normal procedures for cleaning the reactor and, at the same time, the sensor. Reading solvent viscosity guides the cleaning operation. Continuous purging of the transducer dome with nitrogen or dry, instrument air excludes moisture from the area and eliminates coil failure due to temperatures above 230°C.
TEST
A computer or DCS creates permanent records of viscosity trend and reaction kinetics for an individual batch. Comparing to previous batch records ensures initiation and this prevents monomer emission. Propagation rate can be held reproducible or changed for process development purposes. Viscosity measurement during termination and adjustment directs the operator to bring the lot within product specification with fewer laboratory samples handled. Hazardous waste disposal costs are also reduced. One customer stated, "the operators use the VISCOLINER® to guide them. This alone makes it worth the price. With this kind of acceptance, we re-wrote our specifications in less than 6 months, reduced time between batches and improved our quality. Now, our customers require continuous VISCOLINER® data with each lot sold."
TYPICAL OPERATING CONDITIONS
Temperature: 200°F to 500°F
Pressure: Vacuum to 150 psig
Viscosity: 1 to 100,000 cP
VISCOLINER® SPECIFICATION
Temperature: -40°F to 850°F
Pressure: ATM to 5000 psig
Viscosity: 0.1 to 1,000,000 cP
Materials of Construction: 316SS
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