Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Shaping by extrusion
Patent
2000-05-24
2000-12-12
Acquah, Samuel A.
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Shaping by extrusion
528302, 528481, 528502, 528503, 2641761, 2642107, B29C 4788
Patent
active
061594067
ABSTRACT:
The present invention relates to a process for introducing strain-induced crystallization to polyesters. Specifically, amorphous polymer from the melt phase reactor is first extruded through a traditional strand die. However, instead of going directly into a pelletizer/cutter, it is stretched uniaxially at a temperature only slightly higher than Tg. The chain alignment resulting from stretching makes crystallization occur at a considerably higher rate than with traditional thermal crystallization. After this stretching process, the strand is annealed and fed to the pelletizer and chopped. The process of the present invention is advantageous for crystallizing polymers having slow rate of thermal crystallization half time from the glass. Optically clear polymers having at least about 15% crystallinity and a single melting point endotherm are produced.
REFERENCES:
patent: 4064112 (1977-12-01), Rothe et al.
patent: 5292865 (1994-03-01), Kerpes et al.
"Extrusion of Film Tapes" in Plastics Extrusion Technology, Ed. by F. Hensen, Hanser, New York, 1988, p. 299.
Donelson Michael Eugene
Hall Harry Probert
Shelby Marcus David
Weinhold Stephen
Acquah Samuel A.
Eastman Kodak Company
Gwinnell Harry J.
Harding Karen A.
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