Species modification in macrocyclic polyester oligomers, and compositions prepared thereby

#This invention generally relates to thermoplastics and articles formed therefrom. More particularly, the invention relates to macrocyclic polyester oligomer compositions and methods for modifying physical and chemical properties of the compositions. Even more particularly, this invention relates to macrocyclic-polyester oligomer compositions having relatively low melting temperatures.

#Linear polyesters such as poly(alkylene terephthalate) are generally known and commercially available where the alkylene typically has 2 to 8 carbon atoms. Linear polyesters have many valuable characteristics including strength, toughness, high gloss and solvent resistance. Linear polyesters are conventionally prepared by the reaction of a diol with a dicarboxylic acid or its functional derivative, typically a diacid halide or ester. Linear polyesters may be fabricated into articles of manufacture by a number of known techniques including extrusion, compression molding, and injection molding. Linear polyesters may be produced from macrocyclic polyester oligomers.

#Macrocyclic polyester oligomers (MPOs) have unique properties that make them attractive as matrices for engineering thermoplastic composites. These desirable properties stem from the fact that MPOs exhibit low melt viscosity, allowing them to impregnate a dense fibrous preform easily. Furthermore, certain MPOs melt and polymerize at temperatures well below the melting point of the resulting polymer. Upon melting and in the presence of an appropriate catalyst, polymerization and crystallization can occur virtually isothermally. As a result, the time and expense required to thermally cycle a tool is favorably reduced.

#The drawings are not necessarily to scale, emphasis instead being generally placed upon illustrating the principles of the invention to facilitate its understanding.

#FIG. 1 is a schematic illustration of an embodiment of the invention including a fractional crystallization process.

#Physical properties, for example, the melting temperatures, of a composition comprising MPOs may be modified by modifying the weight percentage of a MPO species, for example, the macrocyclic polyester tetramer. A MPO composition having a low melting temperature can be-polymerized and processed at lower temperature thereby avoiding the need for special equipment not commonly available in polymer processing.

#Definitions

#The following general definitions may be helpful in understanding the various terms and expressions used in this specification.