The Dow Chemical Company

Stuart Farquharson

Joseph P Weller

David P Denton

Sandra V Lange

Jean P Chauvel, Jr

Mary Anne Leugers

Peter T Keillor, Iii

Harry D Ruhl, Jr

Chester R Norman

Gregory A Winter

Terry D Haymon

Leslie J May

A process control method for controlling a polyolefin polymerization process, such as a solution polyethylene process, which includes five steps. The first step is to flow a stream of a solvent into a polyolefin reactor, such as flowing a stream of heptane solvent into the reactor at essentially a constant rate. The second step is to add a principal monomer to the stream of solvent, such as by adding ethylene at a controllable rate to the stream of solvent. The third step is to add a co-monomer to the stream of solvent, such as by adding 1-octene at a controllable rate to the stream of solvent. The fourth step is to determine the concentration of the principal monomer and the concentration of the co-monomer in the stream of solvent by high resolution multi-wavelength vibrational spectroscopy analysis, such as by Fourier transform infrared spectroscopy system having a spectral resolution of 4 wavenumbers which analyzes at 1909 wavenumbers for ethylene, at 1829 wavenumbers for 1-octene and at 2120 wavenumbers for a reference signal. The fifth step is to control the rate of addition of the principal monomer, the rate of addition of the comonomer or preferably the rate of addition of both the principal monomer and the co-monomer according to the determination of the fourth step to obtain the desired concentration of ethylene and 1-octene in the solvent so that, for example, the density of the polyolefin product can be controlled.

Process control method for manufacturing polyolefin

An improvement upon spectroscopic cells of the type that have a single window sealed to each window opening of the cell body. The improvement is: (1) to position an additional window at each such opening, each such window being juxtaposed, spaced apart and biplanar with each original window so that there is a sealed space between each additional window and each original window; and (2) to position at least two passageways through the body of the cell, each such passageway in fluid communication with each of the above formed sealed spaces so that any leakage of a sample past the original seal is vented from the cell via one of the passageways to a detector to be detected. In a highly preferred embodiment of the present invention each such sealed space contains a spacer ring and the body is provided with additional passageways so that a purge fluid, such as nitrogen, can be flowed through the passageways and the sealed space to a flow through detector, such as a thermal conductivity detector, to detect any leakage of a fluid sample past one of the original seals.

Spectroscopic cell system having vented dual windows

A method for the on-line determination of the residence time distribution of a polymer extruder by injecting a quantity of dye, such as Mobay Red 5B, into the feed throat of the extruder and then photometrically monitoring the polymer flowing from the extruder for the dye. The advance of the present invention is to direct a single beam of polychromatic light through the polymer flowing from the extruder, e.g., by using a quartz-halogen light source and an optical fiber, and then to split this single beam of light that has passed through the polymer into two beams, e.g., by the use of a bifurcated optical fiber, each of which resulting beams are then passed through a separate filter to a separate photodetector. The wavelength of maximum transmission of one of the filters is selected to be near the wavelength of maximum light absorption of the dye so that the signal from the photodetector associated with this filter is a function of the concentration of the dye in the polymer flowing from the extruder. The wavelength of maximum transmission of the other filter is selected to be near the wavelength of minimum light adsorption of the dye and the polymer so that the signal from the photodetector associated with this filter is a function of the background light absorption of the polymer flowing from the extruder. The noise level of the dye concentration signal can be a problem due to bubbles and inclusions in the polymer flowing from the extruder and this noise level is substantially reduced by correcting the dye concentration signal with the background signal.

Method for determining the residence time distribution of a polymer

A photometric probe or a photometric cell having separate windows and a metallic probe body or cell body. The window(s) are sealed to the probe or cell body by brazed or frit seals which are less likely to leak after extended use in high temperature and/or high pressure industrial applications than probes and cells having gasket sealed windows. The windows can be made of sapphire, cubic zirconia, diamond, ruby, glass or quartz and, in the case of the probe, can be in the shape of an Attenuated Total Reflectance prism. The probe or cell body can be Kovar alloy or stainless steel.

Photometric cell and probe having windows fusion sealed to a metallic

Growing community of inventors

Freeport, TX, United States of America

Stuart Farquharson