Polymer recovery
AssigneesThe Dow Chemical Company, E. I. Du Pont de Nemours and Company
InventorsRichard C. Abel, Jr., Michael E. Rowland, Robert B. Combs, Jerry W. Soape, Stanley W. Smith
Life of this patent
Estimating the term…
Abstract
Methods for devolatilizing polymer solutions have been invented which include, in certain aspects, dissolving a viscous polymer in a solvent forming a polymer-solvent solution, introducing the polymer-solvent solution into a thermal dryer, heating or cooling the polymer-solvent solution in the thermal dryer forming product polymer with solvent removed and separated solvent (which may include other residuals), the separated solvent with other residuals if present vaporizing in the thermal dryer forming a vapor, removing the vapor from the thermal dryer, and discharging product polymer from the thermal dryer.
Claims27
A method for devolatilizing a polymer-solvent solution, characterized by a single iteration of the following sequential steps:
- (A) introducing a polymer-solvent solution having a solvent plus residuals content of less than 80 weight percent into a thermal dryer which has a horizontal shell and a rotating shaft inside the shell, disc elements placed in the shaft at an angle, and stationary counter hooks secured to the shell's interior,
- (B) treating the polymer-solvent solution in the thermal dryer to form product polymer and separated solvent, the separated solvent with residuals therein vaporizing in the thermal dryer to form a vapor containing solvent and residuals,
- (C) removing the vapor containing solvent and residuals from the thermal dryer, and
- (D) discharging from the thermal dryer polymer product having not more than 0.5 percent by weight solvent and residuals.
A method for devolatilizing a polymer having a Mooney viscosity greater than 50, the method comprising
- (A) introducing a polymer-solvent solution into a thermal dryer,
- (B) treating the polymer-solvent solution in the thermal dryer forming polymer product and separated solvent forming product polymer and separated solvent, the product polymer having at most 0.5% by weight solvent, and other residuals, separated solvent with residuals therein vaporizing in the thermal dryer forming a vapor containing solvent and residuals, wherein the polymer-solvent solution has a residence time of less than 50 minutes in said dryer,
- (C) removing the vapor from the thermal dryer using a vacuum in fluid communication with said dryer from 10 mm Hg to 200 mm Hg, and
- (D) discharging product polymer with solvent removed therefrom from the thermal dryer.
A discharge system for use with a thermal dryer to dry a polymer product comprising:
- a single or twin screw conveyor rotatably mounted in a housing, the housing having an interior into which product polymer flows through a housing inlet,
- a direct drive motor at a drive end of the housing connected to the single or twin screw conveyor for rotating it,
- dual mechanical seals at the drive end of the housing for sealing an interface of the single or twin screw conveyor and the housing,
- bearings at the drive end for facilitating rotation of the single or twin screw conveyor, and
- an outlet for the product polymer to flow from the housing.
Dependencies are inferred from the claim text.