| 摘要 |
PROBLEM TO BE SOLVED: To provide a polyester readily eluted by alkali, which is a polyester that does not use any heavy metal compound having a true specific gravity of ≥5, is therefore environmentally friendly and shows good color tone and heat resistance, provided that the use of the polyester hardly causes staining of a spinneret at spinning and is excellent in spinning operability represented by spinnability.SOLUTION: The polyester comprises, based on the total acid component, 4.5-6.0 mol% isophthalic acid component containing a metal phosphonate group. The polyester comprises, calculated in terms of titanium element, 3-10 ppm titanium compound that is soluble in a polyester and, calculated in terms of phosphorus element, 5-15 ppm phosphonite or phosphite as a phosphorus compound and is substantially free of any element having a true specific gravity of ≥5. |
