Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Reexamination Certificate
1999-05-07
2001-02-27
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
Reexamination Certificate
active
06194541
ABSTRACT:
BACKGROUND OF THE INVENTION
The instant invention relates to the removal of volatile components from thermoplastic polymers and more specifically to methods and apparatus therefore that use centrifugal force.
Chisholm, U.S. Pat. No. 3,409,712, herein fully incorporated by reference, disclosed a method and apparatus for devolatilization of thermoplastic polymers by melting the polymer and flowing the melted polymer on a rotating disk surface. Chisholm, U.S. Pat. No. 3,424,832, herein fully incorporated by reference, disclosed a method and apparatus for pelletizing a thermoplastic polymer using a rotating chamber or hollow rotor. Hay, II et al., U.S. Pat. No. 4,940,472, herein fully incorporated by reference, disclosed a method and apparatus for devolatilization of thermoplastic polymers by melting the polymer and flowing the melted polymer on a rotating disk surface. Moore et al., U.S. Pat. No. 4,952,672, herein fully incorporated by reference, disclosed a method and apparatus for devolatilization of thermoplastic polymers by melting the polymer and flowing the melted polymer on a rotating disk surface. Baker Perkins Incorporated of Saginaw Michigan offered a centrifugal pelletizer for sale. Modern Plastics, December 1983, page 56. Haw, Master's Thesis, Case Western Reserve University, January 1995, entitled “Mass Transfer of Centrifugally Enhanced Polymer Devolatilization by using Foam Metal Packed Bed”, herein fully incorporated by reference, disclosed a method and apparatus for devolatilization of thermoplastic polymers by melting the polymer and flowing the melted polymer through a open-cell nickel metal foam gas-liquid contactor rotated within a stationary chamber.
The method and apparatus of Haw suffered from several problems. For example, the nickel metal foam tended to collapse under the centrifugal forces to which it was subjected. In addition, the mechanical seal used tended to contaminate the devolatilized polymer with the seal oil. Furthermore, the method and apparatus of Haw did not produce the devolatilized polymer in the form of pellets.
SUMMARY OF THE INVENTION
The instant invention is a method for devolatilization of a thermoplastic polymer containing at least one volatile component which comprises three steps. The first step is to heat the thermoplastic polymer so that the thermoplastic polymer is a heated liquid or molten thermoplastic polymer. The second step is to flow the heated liquid thermoplastic polymer through a packed bed liquid-gas contactor by centrifugal force. The third step is to flow a stripping gas through the packed bed countercurrent to the flow of the heated liquid thermoplastic polymer so that the volatile component volatilizes into the stripping gas from the heated liquid thermoplastic polymer by gas-liquid contacting in the packed bed.
The instant invention is also an apparatus for devolatilization of a thermoplastic polymer containing at least one volatile component, the apparatus comprising three elements. The first element is a rotatable chamber, the rotatable chamber containing a packing for gas-liquid contact processing. The second element is a polymer conduit, the polymer conduit extending into and terminating within the rotatable chamber so that molten thermoplastic polymer can be flowed into the chamber by way of the conduit while the chamber is being rotated so that the molten thermoplastic polymer then flows through the packing by centrifugal force so that the volatile component of the molten thermoplastic polymer volatilizes into the gas phase in the packed bed. The third element is a gas seal between the polymer conduit and the rotatable chamber.
REFERENCES:
patent: 4940472 (1990-07-01), Hay, II et al.
patent: 4952672 (1990-08-01), Moore et al.
Haw, Jimkuo; Mass Transfer of Centrifugally Enhanced Polymer Devolatilization by Using Foam Metal Packed Bed; Jan. 1995; Case Western Reserve University.
Cummings Clark J.
Moore Eugene R.
Quarderer, Jr. George J.
Tirtowidjojo Dan
Boykin Terressa M.
The Dow Chemical Company
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