METHOD FOR PRODUCING POLYBUTYLENE TEREPHTHALATE

PROBLEM TO BE SOLVED: To provide a polybutylene terephthalate (PBT) and a composition comprising the PBT, which are excellent in color tone, hydrolysis resistance, heat stability, transparency and moldability, and are reduced in the content of foreign matter, and thus can be suitably used for a film, a monofilament, a fiber, an electric or electronic part, an automobile part or the like.SOLUTION: The PBT contains titanium and has a titanium content of 33 ppm or less as a titanium atom, and the composition comprises the PBT. In a preferred embodiment, the PBT and the composition comprising the PBT exhibit a temperature-falling crystallization temperature of 170 to 190°C, have a concentration of a terminal vinyl group of 0.1 to 10 μeq/g, exhibit a haze of solution of 10% or less, exhibit an increase of the concentration of a terminal carboxyl group of 0.1 to 30 μeq/g after being heat-treated under specific conditions, and contain foreign particles having a size of 5 μm or larger in an amount of 50 pieces/10 g polymer or less.