Solid state polymerization of porous pills made by compacting polyester prepolymers.

摘要

High molecular weight polyester resins such as polyethylene terephthalate, are sometimes produced from low molecular weight polyester prepolymers having the same composition by solid state polymerization. The low molecular weight polyester prepolymers which are used in such solid state polymerizations are normally prepared by conventional melt polymerizations and are generally in the form of pellets or chips. Solid state polymerization rates can be greatly improved by utilizing polyester prepolymers which are in the form of porous pills. By utilizing polyester prepolymers that are in the form of porous pills, higher molecular weights can be achieved after shorter solid state polymerization times. This invention relates to an improved process for solid state polymerizing porous pills which are made by compacting fine fibers of the polyester prepolymer. The present invention specifically relates to a process for making porous pills by compacting fibers of polyester prepolymer which have a diameter of less than about 841 microns.