Polymerization catalyst for polyesters, polyesters produced with the same and process for producing polyesters

A process for producing polyester, comprising adding a polyester polymerization catalyst comprising at least one kind selected from the group consisting of aluminum and compounds thereof as a first metal-containing component, characterized in that the hydrolytic stability parameter (HS) of polyethylene terephthalate (PET) polymerized by the catalyst satisfies the following formula (4):

• HS<0.10 (4)
• wherein HS is a numerical value calculated in the formula;
• HS=0.245{[IV]f2−1.47−[IV]i−1.47}
• from the intrinsic viscosity ([IV]f2) which is determined after melt-polymerized resin chips of PET having an initial intrinsic viscosity ([IV]i) of approximately 0.65 dl/g are frozen and milled to give powders of 20 meshes or less which are then vacuum-dried at 130° C. for 12 hours, and 1 g of the powder, together with 100 ml pure water, are placed in a beaker and then heated under stirring for 6 hours in a closed system at 130° C. under pressure,
• the polyester comprising one or more of polyvalent carboxylic acids including dicarboxylic acids and ester-forming derivatives thereof and one or more of polyvalent alcohols including glycols, or comprising one or more of hydroxycarboxylic acids and ester-forming derivatives thereof.

A process for producing polyester, comprising adding a polyester polymerization catalyst comprising at least one kind selected from the group consisting of aluminum and compounds thereof as a first metal-containing component, characterized in that the thermal oxidation stability parameter (TOS) of polyethylene terephthalate (PET) polymerized by the catalyst satisfies the following formula (3):

• TOS<0.10 (3)
• wherein TOS is determined using the formula;
• TOS=0.245{[IV]f1−1.47−[IV]i−1.47}
• wherein [IV]i and [IV]f1 refer to IV (dl/g) before and after a heating test respectively, from IV which is determined after melt-polymerized resin chips of PET having an IV of approximately 0.65 dl/g are frozen and milled to give powders of 20 meshes or less which are then vacuum-dried at 130° C. for 12 hours, and 0.3 g of the powders are placed in a glass test tube and vacuum-dried at 70° C. for 12 hours and then heated at 230° C. for 15 minutes in dry air over silica gel,
• the polyester comprising one or more of polyvalent carboxylic acids including dicarboxylic acids and ester-forming derivatives thereof and one or more of polyvalent alcohols including glycols, or comprising one or more of hydroxycarboxylic acids and ester-forming derivatives thereof.

A process for producing polyester, comprising adding a polyester polymerization catalyst comprising at least one kind selected from the group consisting of aluminum and compounds thereof as a first metal-containing component, characterized in that the color delta Lg parameter (ΔLg) and color delta bg parameter (Δbg) of polyethylene terephthalate polymerized by the catalyst satisfy the following formulas (7) and (8) respectively:

• ΔLg>−2.0 (7)
• wherein ΔLg is a value obtained by subtracting the L value of PET produced by using germanium dioxide as a catalyst from the Hunter's L value, measured by a color difference meter, of PET resin chips having an intrinsic viscosity of approximately 0.65 dl/g which were melt-polymerized by a predetermined amount of a catalyst, whereupon said germanium dioxide is added in an amount of 0.03 mol % in terms of germanium atom relative to the acid component in the polyethylene terephthalate formed,
• Δbg<4.5 (8)
• wherein Δbg is a value obtained by subtracting the b value of PET produced by using germanium dioxide as a catalyst from the Hunter's b value, measured by a color difference meter, of PET resin chips having an intrinsic viscosity of approximately 0.65 dl/g which were melt-polymerized by a predetermined amount of a catalyst, whereupon said germanium dioxide is added in an amount of 0.03 mol % in terms of germanium atom relative to the acid component in the polyethylene terephthalate formed,
• the polyester comprising one or more of polyvalent carboxylic acids including dicarboxylic acids and ester-forming derivatives thereof and one or more of polyvalent alcohols including glycols, or comprising one or more of hydroxycarboxylic acids and ester-forming derivatives thereof.