Patent ID: 8039417

Claim:
A liquid catalyst solution comprising: ethylene glycol and/or 1,4-butanediol; and a polycondensation catalyst comprising one or more titanium atoms, one or more alkaline earth metal atoms, one or more phosphorus atoms, and one or more carbon atoms, said polycondensation catalyst obtained by a process comprising forming a mixture comprising at least one monohydric alcohol, at least one titanium compound, at least one alkaline earth metal compound and at least one acid phosphoric ester compound, and concentrating the mixture, wherein at least part of the carbon atoms are derived from an aliphatic carboxylic acid and/or an aliphatic carboxylate which is derived from an aliphatic carboxylic acid salt of the one or more alkaline earth metal atoms, the content of the titanium atoms T is 4-20% by weight of the polycondensation catalyst, the molar content of the aliphatic carboxylic acid and/or the aliphatic carboxylate (L), the molar content of the alkaline earth metal atoms (M), the weight content of the titanium atoms (T), the molar content of the phosphorus atoms (P), and the weight content of the carbon atoms (C) satisfy expressions (1), (2) and (3): 0.8 ≦L/M≦ 1.8 (1) 0.05 ≦T/C≦ 0.50 (2) 0.5 ≦M/P≦ 3.0 (3); and with the proviso that the at least one titanium compound has not been previously treated with an aromatic polycarboxylic acid, and wherein, when the polycondensation catalyst is dissolved in ethylene glycol, the titanium atoms are present in a concentration of 10,000 ppm to 100,000 ppm.