Patent ID: 7176274

Claim:
A method of manufacturing a saturated polyester for use in forming plastic containers, the method consisting of the steps of; forming nano-sized silica particles by reacting sodium silicate with water so as to produce soda silicate; passing the soda silicate through a cation exchange resin column; removing sodium oxide adsorbed to said cation exchange resin column so as to form fine silica particles; crystal-growing said fine silica particles to said nano-sized silica particles; adding said nano-sized silica particles to the saturated polyester that is formable into a plastic container in an amount of 20 ppm to 10% by weight based on a weight of the saturated polyester during transesterification or esterification thereof, said nano-sized silica particles having an average particle diameter of between 3 and 100 nanometers; and polycondensing an aromatic dicarboxylic acid and ethylene glycol as starting materials.