An object of the present invention is to provide a polyester resin having good producibility and color tone, containing fewer foreign bodies, and showing good adhesion to a metal substrate and curability.

A polyester resin containing 2 to 10 ppm by mass of titanium in terms of metal and 50 to 100 ppm by mass of zinc in terms of metal, in which the number of foreign bodies contained in the polyester resin is 15 or less per 5 g of the polyester resin.

An object of the present invention is to provide a polyester resin having good producibility and color tone, containing fewer foreign bodies, and showing good adhesion to a metal substrate and curability.

A polyester resin containing 2 to 10 ppm by mass of titanium in terms of metal and 50 to 100 ppm by mass of zinc in terms of metal, in which the number of foreign bodies contained in the polyester resin is 15 or less per 5 g of the polyester resin.

A method of forming a polyester from a regenerated composition comprising a regenerated diacid and a catalyst obtained from depolymerization of a polyester in a waste material is disclosed. The method comprises: reacting a diol and the regenerated diacid in the regenerated composition to form one or more compounds including an ester bond; optionally providing additional catalyst; and polymerizing the one or more compounds including an ester bond to form a polyester.

The instant disclosure relates to a polyester composition and method for preparing the same, as well as products comprising the polyester composition and applications thereof. The polyester composition comprises aliphatic polyester, titanium and zirconium, wherein the weight ratio of titanium/zirconium is greater than 0.05. The polyester composition of the present invention has a specific titanium/zirconium weight ratio range, can reduce the process time, and can obtain a biodegradable composition with a lower acid value.

The instant disclosure relates to a polyester composition and method for preparing the same, as well as products comprising the polyester composition and applications thereof. The polyester composition comprises aliphatic polyester, titanium and zirconium, wherein the weight ratio of titanium/zirconium is greater than 0.05. The polyester composition of the present invention has a specific titanium/zirconium weight ratio range, can reduce the process time, and can obtain a biodegradable composition with a lower acid value.

Provided is a copolymer comprising an irregularly arranged structure of a repeating unit of the following Chemical Formula 1 and a repeating unit of the following Chemical Formula 2, and a repeating unit of the following Chemical Formula 3 present at least at one end of the structure:

##STR00001##

and is characterized by having an improved elongation and also having a high weight average molecular weight while maintaining intrinsic properties of a polylactic acid. Also provided are methods of preparing the copolymer.

Provided is a copolymer comprising an irregularly arranged structure of a repeating unit of the following Chemical Formula 1 and a repeating unit of the following Chemical Formula 2, and a repeating unit of the following Chemical Formula 3 present at least at one end of the structure:

##STR00001##

and is characterized by having an improved elongation and also having a high weight average molecular weight while maintaining intrinsic properties of a polylactic acid. Also provided are methods of preparing the copolymer.

A polymer resin includes a copolymer of polyethylene terephthalate (PET). In the process of preparing PET, part of ethylene glycol is replaced with other components to obtain the copolymer of PET.

An aliphatic-aromatic polyester resin comprising principal structural units that includes aliphatic dicarboxylic acid units, aromatic dicarboxylic acid units, and aliphatic diol units and/or alicyclic diol units, wherein an abundance ratio (molar ratio) between the aliphatic dicarboxylic acid units and the aromatic dicarboxylic acid units is 15:85 to 85:15; the aliphatic-aromatic polyester resin has a glass transition temperature of −25° C. or more; and the aliphatic-aromatic polyester resin has branched structures represented by formulae (1) to (4) below:

##STR00001## where Ar.sup.1, Ar.sup.2, and Ar.sup.3 each independently represent an optionally substituted divalent group having 4 to 12 carbon atoms, the optionally substituted divalent group being a divalent aromatic hydrocarbon group or a divalent aromatic heterocyclic group; R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; and n, m, and r are each independently an integer of 2 to 10.

An aliphatic-aromatic polyester resin comprising principal structural units that includes aliphatic dicarboxylic acid units, aromatic dicarboxylic acid units, and aliphatic diol units and/or alicyclic diol units, wherein an abundance ratio (molar ratio) between the aliphatic dicarboxylic acid units and the aromatic dicarboxylic acid units is 15:85 to 85:15; the aliphatic-aromatic polyester resin has a glass transition temperature of −25° C. or more; and the aliphatic-aromatic polyester resin has branched structures represented by formulae (1) to (4) below:

##STR00001## where Ar.sup.1, Ar.sup.2, and Ar.sup.3 each independently represent an optionally substituted divalent group having 4 to 12 carbon atoms, the optionally substituted divalent group being a divalent aromatic hydrocarbon group or a divalent aromatic heterocyclic group; R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; and n, m, and r are each independently an integer of 2 to 10.