Continuous Polymer Process

SUMMARY

A better quality polymer results from control of viscosity during its manufacture. One manufacturer, for example, reports material savings amounting to $130,000 per VISCOLINER® per month, due to increased yield. With viscosity measurement typically made between first and second reactor stages, or downstream prior to packaging, increased control over viscosity improves product quality by allowing for better control of molecular weight, degree of branching, and polymer concentration. Similar improvements are being made in the manufacture of polyethylene, polypropylene, polyisobutylene, nylon, polycarbonate, polyester, and polystyrene.

INSTALLATION

Pipeline installation of the VISCOLINER® transducer using standard ANSI flange connections and mounting in an elbow ensures good sample exchange. Steam or hot fluid jackets with insulation ensure minimal heat loss and avoid hardened polymer collection in the sensor area. An RTD, integral with the viscosity sensor, measures the same volume element of process material in real time and also guides sensor removal on shutdown. The transmitter can be mounted in the production area or located in a control room up to 1000’ away from the transducer.

OPERATION

Continuous purging of the transducer dome with nitrogen or dry instrument air excludes moisture and reduces coil failure due to heat cycling. On shutdown, sensors should be removed and cleaned. Check instrument calibration once a year. One customer heat soaks sensors for 24 hours on startup to melt solid polymer plugs. Wedging a slug between the pipe wall and sensor must be avoided. A sensor guard may be installed to protect the probe from solids slugs.

TEST

Covering a range of melt flow index from 0.1 to 200 MFI, the coefficient of determination, R2, for process VISCOLINER® measurement to MFI is 0.988 with standard error less than 1%. The month prior to installing their first VISCOLINER®, one customer produced 88% within control limits using a competitive viscometer; the month following installation of the VISCOLINER®, the customer produced 97.7% within control limits.

TYPICAL OPERATING CONDITIONS

Temperature: 250°F to 500°F

Pressure: Partial Vacuum to 200 psig

Viscosity: 10 to 100,000 cP VISCOLINER®

SPECIFICATION

Temperature: -40°F to 850°F

Pressure: Vacuum to 5000 psig

Viscosity: 0.1 to 1,000,000 cP

Materials of Construction: 316SS 5/12/2005

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