Method of Making Polybutylene Terephthalate and Compositions and Articles Comprising the Same

A process comprising:

• reacting
• (i) an oligomeric diol component selected from the group consisting of bis(hydroxybutyl)terephthalate, bis(hydroxybutyl)isophthalate, hydroxybutyl-hydroxyethyl terephthalate, hydroxybutyl-hydroxyethyl isophthalate, bis(hydroxypropyl)terephthalate, bis(hydroxypropyl)isophthalate, hydroxybutyl-hydroxypropyl terephthalate, hydroxybutyl-hydroxypropyl isophthalate, hydroxyethyl-hydroxypropyl terephthalate, hydroxyethyl-hydroxypropyl isophthalate, and combinations thereof to a reactor, with
• (i) a polyethylene terephthalate component selected from the group consisting of polyethylene terephthalate and polyethylene terephthalate copolymers and
• (ii) a monomer diol component selected from the group consisting of 1,4-butanediol, ethylene glycol, propylene glycol, and combinations thereof in a reactor under conditions effective to depolymerize the polyethylene terephthalate component to form a first molten mixture,
• the first molten mixture comprising a component selected from the group consisting of oligomers comprising ethylene terephthalate moieties, oligomers comprising ethylene isophthalate moieties, oligomers comprising diethylene glycol terephthalate moieties, oligomers comprising diethylene glycol isophthalate moieties, oligomers comprising trimethylene terephthalate moieties, oligomers comprising trimethylene isophthalate moieties, oligomers comprising butylene terephthalate moieties, oligomers comprising butylene isophthalate moieties, oligomers comprising dibutylene terephthalate moieties, oligomers comprising dibutylene isophthalate moieties, covalently bonded oligomeric moieties comprising at least two of the foregoing moieties, ethylene glycol, propylene glycol, 1,4-butanediol, and combinations thereof;
• adding 1,4-butanediol to the first molten mixture under conditions effective to form a second molten mixture, the second molten mixture comprising a component selected from the group consisting of oligomers comprising ethylene terephthalate moieties, oligomers comprising ethylene isophthalate moieties, oligomers comprising diethylene glycol terephthalate moieties, oligomers comprising diethylene glycol isophthalate moieties, oligomers comprising trimethylene terephthalate moieties, oligomers comprising trimethylene isophthalate moieties, oligomers comprising butylene terephthalate moieties, oligomers containing butylene isophthalate moieties, covalently bonded oligomeric moieties comprising at least two of the foregoing moieties, 1,4-butanediol, propylene glycol, ethylene glycol, and combinations thereof;
• and
• increasing the temperature of the second molten mixture to form the modified polybutylene terephthalate polymer;
• and further comprising
• collecting excess oligomeric diol component during the adding of the 1,4-butanediol under conditions effective to form a second molten mixture;
• and
• returning the collected oligomeric diol component to the reactor during the reacting of the oligomeric diol component, the monomeric diol component, and the polyethylene terephthalate component.