Abstract: There is provided a method for deionizing a decomposition produced solution resulting from decomposition of a polyester by ethylene glycol. The ester interchange reaction and hydrolysis reaction along with cation removing treatment of a decomposition product resulting from decomposition of a polyester by ethylene glycol are suppressed. Thereby, a method for deionizing the decomposition produced solution with small reductions in yield and purity can be provided.

Abstract: There is provided a method for producing a polyethylene terephthalate for molding which has a low content of cyclic trimer. The present invention is a method for producing a polyethylene terephthalate for molding which comprises (1) a condensation step of condensing bis(2-hydroxyethyl)terephthalate having an ion content of 10 ppm or less and an acid value of 30 mgKOH/g or less to produce an oligomer having an average polymerization degree of 4 to 10, (2) a melt-polymerization step of melt-polymerizing the oligomer to produce a prepolymer having an intrinsic viscosity of 0.50 to 0.65, and (3) a solid-state polymerization step of crystallizing pellets of the prepolymer and then solid-state polymerizing the prepolymer at a temperature of 190 to 230° C. to produce a polyethylene terephthalate having an intrinsic viscosity of not lower than 0.65; and a polyethylene terephthalate for molding which is obtained by the method and has specific properties.

Abstract: A method is disclosed for efficiently obtaining BHET of high purity from an EG (ethylene glycol) solution containing crude BHET (bis(2-hydroxyethyl)terephthalate), especially a decomposition product solution obtained by decomposing a polyester containing PET (polyethylene terephthalate) as a main component, by use of EG, while minimizing by-production of impurity components such as DEG (diethylene glycol), DEG ester and oligomers. The decomposition product solution is subjected to crystallization and solid-liquid separation under specific temperature conditions. Further, in accordance with the invention, a method of purifying BHET is taught which comprises evaporation steps of evaporating low-boiling-point components from the decomposition product solution under specific conditions so as to obtain a melt solution and a molecular distillation step of distilling the obtained melt solution under specific conditions so as to obtain a specific fraction.

Abstract: An aromatic polyester is pre-decomposed by heating together with bis-?-hydroxyethyl terephthalate and/or a low condensate thereof and then, reacted with ethylene glycol to convert the terephthalic acid component of the pre-decomposed product into bis-?-hydroxyethyl terephthalate and/or a low condensate thereof. The thus obtained solution composition, that is, bis-?-hydroxyethyl terephthalate solution composition containing ethylene glycol, bis-?-hydroxyethyl terephthalate and cations and/or anions as impurities is brought into contact with a cation exchanger and/or an anion exchanger to remove cations and anions as impurities to produce bis-?-hydroxyethyl terephthalate having a small content of ions.

Abstract: There is provided a method for producing a polyethylene terephthalate for molding which has a low content of cyclic trimer. The present invention is a method for producing a polyethylene terephthalate for molding which comprises (1) a condensation step of condensing bis(2-hydroxyethyl)terephthalate having an ion content of 10 ppm or less and an acid value of 30 mgKOH/g or less to produce an oligomer having an average polymerization degree of 4 to 10, (2) a melt-polymerization step of melt-polymerizing the oligomer to produce a prepolymer having an intrinsic viscosity of 0.50 to 0.65, and (3) a solid-state polymerization step of crystallizing pellets of the prepolymer and then solid-state polymerizing the prepolymer at a temperature of 190 to 230° C. to produce a polyethylene terephthalate having an intrinsic viscosity of not lower than 0.65; and a polyethylene terephthalate for molding which is obtained by the method and has specific properties.

Abstract: Bis-?-hydroxyethyl terephthalate having an optical density measured in a 10 wt % methanol solution at a measurement wavelength of 380 nm and a cell optical path length of 10 mm of 0.000 to 0.006. The present invention makes it clear that purified BHET having an optical density of 0.006 or less provides high-quality PET having excellent purity, whiteness and transparency.

Abstract: An object of the present invention is to provide a method of obtaining BHET of high purity efficiently from an EG (ethylene glycol) solution containing crude BHET (bis(2-hydroxyethyl)terephthalate), especially a decomposition product solution obtained by decomposing a polyester containing PET (polyethylene terephthalate) as a main component, by use of EG, while minimizing by-production of impurity components such as DEG (diethylene glycol), DEG ester and oligomers.

Abstract: There is provided a method for deionizing a decomposition produced solution resulting from decomposition of a polyester by ethylene glycol.

Abstract: To provide a process for producing a high-purity bis-&bgr;-hydroxyethyl terephthalate from crude terephthalic acid.

Abstract: An aromatic polyester is pre-decomposed by heating together with bis-&bgr;-hydroxyethyl terephthalate and/or a low condensate thereof and then, reacted with ethylene glycol to convert the terephthalic acid component of the pre-decomposed product into bis-&bgr;-hydroxyethyl terephthalate and/or a low condensate thereof.

Abstract: A process for efficiently removing titanium oxide or red oxide from an ethylene glycol solvolysis product of a polyester containing titanium oxide or red oxide. The process comprises the steps of: (1) mixing at least one calcium compound selected from the group consisting of calcium oxide, calcium carbonate and calcium hydroxide with a polyester decomposition product containing titanium oxide which is an ethylene glycol solvolysis product of a polyester containing titanium oxide to agglomerate titanium oxide contained in the polyester decomposition product, or mixing titanium oxide with a polyester decomposition product containing red oxide which is an ethylene glycol solvolysis product of a polyester containing red oxide to agglomerate red oxide contained in the polyester decomposition product; and (2) subjecting the agglomerates to solid-liquid separation to remove titanium oxide or red oxide from the polyester decomposition product.

Abstract: An aromatic polyester is pre-decomposed by heating together with bis-&bgr;-hydroxyethyl terephthalate and/or a low condensate thereof and then, reacted with ethylene glycol to convert the terephthalic acid component of the pre-decomposed product into bis-&bgr;-hydroxyethyl terephthalate and/or a low condensate thereof. The thus obtained solution composition, that is, bis-&bgr;-hydroxyethyl terephthalate solution composition containing ethylene glycol, bis-&bgr;-hydroxyethyl terephthalate and cations and/or anions as impurities is brought into contact with a cation exchanger and/or an anion exchanger to remove cations and anions as impurities to produce bis-&bgr;-hydroxyethyl terephthalate having a small content of ions.

Abstract: To provide a process for producing a high-purity bis-&bgr;-hydroxyethyl terephthalate from crude terephthalic acid.

Abstract: A method of producing a polyester from high-purity bis-&bgr;-hydroxyethyl terephthalate as a raw material containing cations and anions in trace amounts. Polyester production raw materials including bis-&bgr;-hydroxyethyl terephthalate containing cations and anions in a total weight of not more than 50 ppm, ethylene glycol and antimony trioxide and/or germanium dioxide as a polymerization catalyst are heated without substantially distilling off ethylene glycol and then heated under reduced pressure to be polycondensed while ethylene glycol is distilled off.