The present invention relates to a copolymerized polyester resin which can give film characteristics being suitable for a use as a heat-shrinkable label and which is excellent in the recycling property. According to the present invention, there is provided a copolymerized polyester resin which contains dicarboxylic acid and diol as constituting components, wherein the copolymerized polyester resin contains terephthalic acid as a main component of a dicarboxylic acid component, and contains ethylene glycol as a main component of a diol component, wherein a content of neopentyl glycol is from 18 to 32% by mole and a content of diethylene glycol is from 7 to 15% by mole when a total amount of the whole diol component is taken as 100% by mole, and wherein a molar proportion of each phosphorus compound contained in the copolymerized polyester resin and having a specific structure satisfies the specific inequality (1).

The aim of the present invention is to provide a copolymerized polyester resin for solving the problem of die staining and foreign matter adhesion to the film etc. in the continuous production of the film etc.; and the problem of recycling property of the copolymerized polyester. This copolymerized polyester resin contains dicarboxylic acid and did as constituting components, wherein the copolymerized polyester resin contains terephthalic acid as a main component of a dicarboxylic acid component, and contains ethylene glycol as a main component of a diol component, wherein a content of diethylene glycol is from 7 to 30% by mole and a content of triethylene glycol is from 0.05 to 2% by mole when a total amount of the whole diol component is taken as 100% by mole, wherein a content of a cyclic dimer consisting of terephthalic acid and diethylene glycol is 7000 ppm or less, and wherein a content of a cyclic dimer consisting of terephthalic acid, diethylene glycol and triethylene glycol is 200 ppm or less.

The aim of the present invention is to provide a copolymerized polyester resin for solving the problem of die staining and foreign matter adhesion to the film etc. in the continuous production of the film etc.; and the problem of recycling property of the copolymerized polyester. This copolymerized polyester resin contains dicarboxylic acid and did as constituting components, wherein the copolymerized polyester resin contains terephthalic acid as a main component of a dicarboxylic acid component, and contains ethylene glycol as a main component of a diol component, wherein a content of diethylene glycol is from 7 to 30% by mole and a content of triethylene glycol is from 0.05 to 2% by mole when a total amount of the whole diol component is taken as 100% by mole, wherein a content of a cyclic dimer consisting of terephthalic acid and diethylene glycol is 7000 ppm or less, and wherein a content of a cyclic dimer consisting of terephthalic acid, diethylene glycol and triethylene glycol is 200 ppm or less.

A method for improving L* color of polyethylene terephthalate polymer, the method including bis-hydroxylethyl-eneterephthalate being polycondensed to produce said polyethylene terephthalate polymer in a polyethylene terephthalate manufacturing process, and wherein said process requires an antimony-containing catalyst, the method comprising the steps of: i) adding said antimony-containing catalyst at a temperature in a range of a melting point of said BHET to an upper temperature of 220° C.; and ii) exposing said BHET in a molten state to glycol removal before addition of said antimony-containing catalyst.

A method for improving L* color of polyethylene terephthalate polymer, the method including bis-hydroxylethyl-eneterephthalate being polycondensed to produce said polyethylene terephthalate polymer in a polyethylene terephthalate manufacturing process, and wherein said process requires an antimony-containing catalyst, the method comprising the steps of: i) adding said antimony-containing catalyst at a temperature in a range of a melting point of said BHET to an upper temperature of 220° C.; and ii) exposing said BHET in a molten state to glycol removal before addition of said antimony-containing catalyst.

The present invention provides a polyester resin which is excellent in long-term thermal stability and moldability, comprises a dicarboxylic acid component and a glycol component, wherein 10 mol % or more of a furandicarhoxylic acid is contained as the dicarboxylic acid component and the polyester resin satisfies following requirements (1) to (3); (1) a total metal element content is 150 ppm or less relative to the mass of the polyester resin; (2) a phosphorus element content is 100 ppm or less relative to the mass of the polyester resin; and (3) TODΔ reduced viscosity represented by the following formula is 0.030 dl/g or less;
(TODΔ reduced viscosity)=(reduced viscosity before thermal oxidation test)−(reduced viscosity after thermal oxidation test).

The present invention provides a polyester resin which is excellent in long-term thermal stability and moldability, comprises a dicarboxylic acid component and a glycol component, wherein 10 mol % or more of a furandicarhoxylic acid is contained as the dicarboxylic acid component and the polyester resin satisfies following requirements (1) to (3); (1) a total metal element content is 150 ppm or less relative to the mass of the polyester resin; (2) a phosphorus element content is 100 ppm or less relative to the mass of the polyester resin; and (3) TODΔ reduced viscosity represented by the following formula is 0.030 dl/g or less;
(TODΔ reduced viscosity)=(reduced viscosity before thermal oxidation test)−(reduced viscosity after thermal oxidation test).

A catalyst/initiator system that can be used for polymerizing β-butyrolactone is described. The catalyst/initiator system includes a rare earth metal, a chiral ligand, at least one nucleophilic ligand, optionally at least one solvent ligand, and optionally an alkali based co-catalyst. The chiral ligand can have the structure of Formula A, as shown below: ##STR00001##
wherein Y represents rare earth metal Yttrium, Ph represents Phenyl radical and thf represents tetrahydrofuran solvent ligand.

A catalyst/initiator system that can be used for polymerizing β-butyrolactone is described. The catalyst/initiator system includes a rare earth metal, a chiral ligand, at least one nucleophilic ligand, optionally at least one solvent ligand, and optionally an alkali based co-catalyst. The chiral ligand can have the structure of Formula A, as shown below: ##STR00001##
wherein Y represents rare earth metal Yttrium, Ph represents Phenyl radical and thf represents tetrahydrofuran solvent ligand.

A method includes depolymerizing post-consumer or post-industrial recycled polyethylene terephthalate (rPET) to form bis(2-hydroxyethyl) terephthalate (BHET), and reacting at least a portion of the BHET with a catalyst to form an alcohol. The alcohol includes cyclohexanedimethanol (CHDM) or 1,4-phenylenedimethanol (PDM). Further steps of the method include polymerizing the alcohol in the presence of additional BHET to form a polyester. The polyester may include poly(cyclohexylenedimethylene terephthalate (PCT), polyethylene terephthalate glycol (PETG) copolyester, polycyclohexylene dimethylene terephthalate glycol (PCTG) copolyester, polycyclohexylene dimethylene terephthalate acid (PCTA), or a monomer having repeating units with the structure (I), wherein n is an integer having a value of at least 20.

##STR00001##