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| Curable solid polyester resins |
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| Apparatus for controlling a plastic extruder |
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| Severable multilayer thermoplastic film |
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Apparatus for forming crystalline polymer pellets
| Details |
Inventors: Stouffer, Jan M.; Blanchard, Elwood N.; Leffew, Kenneth W.;
Assignee: E. I. Du Pont de Nemours and Company (Wilmington, DE)
Primary Examiner: Vargot; Mathieu D.
Assistant Examiner:
Attorney, Agent or Firm:
This invention relates to a process and apparatus for forming a polyester polymer into particles. More particularly, this invention relates to a process and apparatus for forming crystalline, uniform pellets from an amorphous polyester melt. The polyester pellets have utility, for example, as feedstock for a process for producing higher molecular weight polyesters. |
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DETAILED DESCRIPTION This invention provides an apparatus for producing pellets of a polymer from its polymer melt, comprising: (a) a pellet former comprising a rotatable container having a plurality of outlets, defining corresponding openings 0.
5 to 5 mm in diameter, for metering a polymer melt onto the surface of a conveyor; (b) a conveyor comprising a surface, which is adapted for movement relative to the outlets of the pellet former, for receiving the polymer melt, from the pellet former, in the form of a plurality of droplets or crystallizing pellets, said conveyor being adapted for conveying the pellets through a crystallization section; and (c) a crystallization section extending from the point at which the pellets are received onto the surface of the conveyor, extending along at least a portion of the conveyor to a point downstream; the crystallization section further comprising means for controlling the surface temperature of the conveyor within a predetermined temperature range above 50.
degree.
C.
as the surface passes through the crystallization section.
In commercial practice, the crystallization section may further comprise a temperature controller for controlling the temperature of the surface within the crystallization section, such that the pellets are subjected to a surface within a predetermined temperature range for a predetermined period of time.
The above-described apparatus may have a variety of uses, including the production of pellets of a polyester polymer having a glass transition temperature (T.
sub.
g) greater than about 25.
degree.
C.
One such process comprises: (a) metering a polymer melt of the polyester polymer through a multitude of outlets in a rotatable container, each outlet defining an orifice 0.
5 to 5 mm in diameter, thereby forming a plurality of molten droplets; (b) collecting the molten droplets, immediately after being formed, on a solid moving surface, the solid moving surface being maintained within a predetermined temperature range within a heating zone, whereby the pellets are maintained in contact with the solid moving surface, within the heating zone, for a predetermined period of time
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Nonmetallic Processes 
