Plastic and nonmetallic article shaping or treating: processes – Vacuum treatment of work
Patent
1986-02-28
1988-05-17
Thurlow, Jeffery
Plastic and nonmetallic article shaping or treating: processes
Vacuum treatment of work
264102, 264169, 26421123, 26433122, 264349, 264DIG78, 525927, 528270, B29B 784
Patent
active
047449349
ABSTRACT:
A process is provided for reducing black speck formation which occurs during melt processing of oxymethylene polymer compositions containing polyamide stabilizers having a melting or softening point below the melting point of the oxymethylene polymer and for simultaneously removing volatile materials from a molten oxymethylene polymer, according to which from about 0.05 to about 5.0 weight percent based on the weight of the oxymethylene polymer of said polyamide stabilizer and from about 0.05 to about 10.0 weight percent, based on the weight of the oxymethylene polymer, of hindered phenol antioxidant is added while the molten polymer is passed through a rotating disk polymer processor having at least three stages; a first devolatilization stage, then a stabilization stage and then a second devolatilization stage. The molten polymer in the first devolatilization stage is maintained at a temperature above its melting point in the temperature range of from about 160.degree. C. to about 220.degree. and at a vapor space pressure of from about 0.1 to about 500 Torr. The polymer in the stabilization stage is maintained in the molten state at a temperature of from 160.degree. C. to about 220.degree. C. The polymer in the last devolatilization stage is maintained in the molten state at a temperature of from about 160.degree. C. to 220.degree. C. and at a vapor space pressure of from about 0.1 to about 200 Torr.
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Hoechst Celanese Corporation
Thurlow Jeffery
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