Apparatus and method for molding of polyester articles directly from a melt

A process for the continuous production of molded polyester articles which comprises:

• a) reacting polyester homopolymer or copolymer precursors in a reactor under conditions sufficient to produce a stream of molten polyester homopolymer or copolymer;
• b) mixing the stream of molten polyester with a stream of a gas which is substantially inert to the polyester under a pressure of from about 1000 to about 3000 psig to thereby form a mixture;
• c) reducing the pressure of the mixure to subatmospheric pressure thereby causing the mixture to foam, and thereafter separating the gas in the mixture from the polyester by means of a vacuum;
• d) blending the degassed polyester with an acetaldehyde reducing agent to form a blend;
• e) forming a solid molded article from the blend without solidifying the polyester prior to forming the solid molded article.

A process for the continuous production of molded polyester articles which comprises:

• A) reacting polyester homopolymer or copolymer precursors in a reactor under conditions sufficient to produce a stream of molten polyester homopolymer or copolymer;
• B) providing an extruder, said extruder comprising
• a) a cylindrical barrel having a plurality of serially connected zones along the interior of the barrel;
• at least one screw shaft along the interior of the barrel through said zones;
• and means for turning the shaft;
• b) a molten thermoplastic polymer inlet and a gas injection port at a first mixing zone of the barrel;
• said first mixing zone having means for mixing a molten thermoplastic polymer and a gas therein under a pressure of from about 1000 to about 3000 psig to thereby form a mixture;
• c) means for causing a flow of the mixture through a pressure reduction zone to a degassing zone;
• d) a degassing zone capable of being maintained at subatmospheric pressure and having a vacuum gas vent capable of removing gas from the polymer and conveying degassed polymer to a second mixing zone;
• e) a second mixing zone having an inlet port, capable of mixing and conveying the polymer to an outlet of the barrel;
• f) pumping means at the outlet of the barrel for pumping the polymer to a molding device;
• C) continuously flowing the stream of molten polyester into the first mixing zone of the extruder without solidifying the polyester prior to entry into the extruder and mixing the stream of molten polyester with an injected stream of a gas which is substantially inert to the polyester to thereby form a mixture under a pressure of from about 1000 to about 3000 psig;
• D) flowing the mixture through a pressure reduction zone to a degassing zone;
• E) degassing the mixture in the degassing zone which is maintained at subatmospheric pressure and removing the gas from the polymer by means of vacuum gas vent;
• F) mixing the degassed polymer with an acetaldehyde reducing agent in a second mixing zone;
• G) conveying the polymer to an outlet of the barrel and pumping the polymer out of the barrel to a molding device;
• and
• H) continuously forming molded articles from the polymer.