, also known as Fibre Grade PET chips or Filament Grade PET chips are widely used in various industries. These chips have various properties, including intrinsic viscosity, melt specific resistance, electrostatic adhesion, heat resistance and formability.The present invention aims at producing an amorphous polyester chip with low moisture content and a fine particle content. The chip preferably has a moisture content of 300 ppm or less and a fine particle content of 500 ppm or less.Intrinsic Viscosity (IV) is a key quality control test for PET resins. Low IV can result in a brittle or thicker sheet and a high scrap rate at the thermoforming stage of the process.The optimum IV for a polyester resin is determined by the number of polymerized monomer units making up a polymer chaiand the molecular weight distribution of those monomers. A narrower molecular weight distribution can lead to better IV stability during processing than a wide molecular weight distribution.
The IV of a polyester resin can be determined by measuring the IV of a solution of the resin in a 60/40 (wt. %) phenol/1,1,2,2-tetrachloroethane solution using a glass capillary viscometer. Polyester Chips (also called Poly(ether)imides) have excellent heat and chemical resistance, good dimensional stability as well as high tensile and flexural strength. These characteristics make them suitable for a wide variety of engineering applications.The amorphous polyester chips of the present invention are produced by melting polycondensation of a starting material monomer under reduced pressure, pelletizing the produced polyester and drying the obtained chip by a particular drying process (drying step) to be mentioned below. In the method, a specific amount of at least one kind selected from an antimony compound, a germanium compound and a titanium compound is used as a polymerization catalyst.
Moreover, a specific amount of an alkali metal compound, an alkaline earth metal compound and a phosphorus compound is preferably contained in the amorphous polyester chip. Addition of the specific amounts of these compounds enables production of an amorphous polyester chip that shows low melt specific resistance and superior electrostatic adhesion during subsequent film forming by a electrostatic adhesion casting method.Electrostatic adhesion is the clinging of solids to one another in an electric field. It has been a neglected mechanism of materials adhesion in the past, but it is regaining attention in many contexts.In this study, we synthesized poly(cation-adj-p) hydrogels containing adjacent cationic and aromatic sequences. We found that these polymers exhibited excellent electrostatic interactions in saline water.
The polymer chains are condensed and coacervated to provide multiple electrostatic interactions at the interface, which are more stable than a single interaction. This type of supramolecular structure may also contribute to the strong adhesion in these hydrogels, especially in a high ionic-strength environment.Polyester Chips are characterized by having low moisture content, small fine particle content, and a crude by-product content of not more than 2 wt %. In addition, they have a phosphorus compound content of at least 0.5 mol % and have an oligomer weight percentage not more than 1.2 wt %.Moreover, they have an intrinsic viscosity of at least 0.70 to 0.85 dl/g. This enables a subsequently formed product with superior mechanical strength to be obtained from the chips.The molded article thus obtained is excellent in transparency and dimensional stability, free from chalking or variation in internal volume and excellent in heat resistance. These are the properties of a saturated crystalline polyester resin, which can be easily shaped into desired forms by blow molding and the like.